ANODIZATION APPARATUS

Abstract

According to one embodiment, a anodization apparatus includes: a first process tank used for an anodization process on a first portion of a substrate; a second process tank provided inside of the first process tank and used for the anodization process on a second portion of the substrate; a first electrolyte supply unit configured to supply a first electrolyte to the first process tank; a second electrolyte supply unit configured to supply a second electrolyte to the second process tank; a retainer configured to retain the substrate; a first electrode provided above the first process tank and/or the second process tank; and a second electrode provided below the first process tank and the second process tank.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-051370, filed Mar. 23, 2020; and No. 2020-126485, filed Jul. 27, 2020, the entire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an anodization apparatus.

BACKGROUND

A technology of forming porous layers on a silicon surface by anodization is known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an anodization apparatus according to a first embodiment.

FIG. 2 is a perspective view of an anodization process unit of the anodization apparatus according to the first embodiment.

FIG. 3 is a cross-sectional view of the anodization process unit of the anodization apparatus according to the first embodiment.

FIG. 4 is a graph showing a result of concentration monitoring of an electrolyte during an anodization process in the anodization apparatus according to the first embodiment.

FIG. 5 is a diagram of a semiconductor substrate subjected to the anodization process using the anodization apparatus according to the first embodiment.

FIG. 6 is a diagram showing a method of manufacturing a semiconductor memory device using the semiconductor substrate subjected to the anodization process using the anodization apparatus according to the first embodiment.

FIG. 7 is a perspective view of an anodization process unit of an anodization apparatus according to a first example of a second embodiment.

FIG. 8 is a cross-sectional view of the anodization process unit of the anodization apparatus according to the first example of the second embodiment.

FIG. 9 is a block diagram of an anodization apparatus according to a second example of the second embodiment.

FIG. 10 is a perspective view of an anodization process unit of an anodization apparatus according to a second example of the second embodiment.

FIG. 11 is a cross-sectional view of the anodization process unit of the anodization apparatus according to the second example of the second embodiment.

FIG. 12 is a perspective view of an anodization process unit of an anodization apparatus according to a third example of the second embodiment.

FIG. 13 is a cross-sectional view of the anodization process unit of the anodization apparatus according to the third example of the second embodiment.

FIG. 14 is a flowchart of an anodization process in an anodization apparatus according to a first example of a third embodiment.

FIG. 15 is a flowchart of an anodization process in an anodization apparatus according to a second example of the third embodiment.

FIG. 16 is a flowchart of an anodization process in an anodization apparatus according to a third example of the third embodiment.

FIG. 17 is a of an anodization process in an anodization apparatus according to a fourth example of the third embodiment.

FIG. 18 is a flowchart of an anodization process in an anodization apparatus according to a fifth example of the third embodiment.

FIG. 19 is a flowchart of an anodization process in an anodization apparatus according to a sixth example of the third embodiment.

FIG. 20 is a block diagram of an anodization apparatus according to a first example of a fourth embodiment.

FIG. 21 is a block diagram of an anodization apparatus according to a second example of the fourth embodiment.

FIG. 22 is a block diagram of an anodization apparatus according to a third example of the fourth embodiment.

FIG. 23 is a block diagram of an anodization apparatus according to a fourth example of the fourth embodiment.

FIG. 24 is a block diagram of an anodization apparatus according to a first example of a fifth embodiment.

FIG. 25 is a cross-sectional view of an anodization process unit of the anodization apparatus according to the first example of the fifth embodiment.

FIG. 26 is a top view of a retainer and a fixing unit of the anodization process unit of the anodization apparatus according to the first example of the fifth embodiment.

FIG. 27 is a cross-sectional view of an anodization process unit of an anodization apparatus according to a second example of the fifth embodiment.

FIG. 28 is a block diagram of an anodization apparatus according to a third example of the fifth embodiment.

FIG. 29 is a cross-sectional view of an anodization process unit of the anodization apparatus according to the third example of the fifth embodiment.

FIG. 30 is a cross-sectional view of an anodization process unit of an anodization apparatus according to a fourth example of the fifth embodiment.

FIG. 31 is a block diagram of an anodization apparatus according to a sixth embodiment.

FIG. 32 is a block diagram of an anodization apparatus according to a first example of a seventh embodiment.

FIG. 33 is a cross-sectional view of an anodization process unit of the anodization apparatus according to the first example of the seventh embodiment.

FIG. 34 is a cross-sectional view of an anodization process unit of an anodization apparatus according to a second example of the seventh embodiment.

FIG. 35 is a block diagram of an anodization apparatus according to a third example of the seventh embodiment.

FIG. 36 is a cross-sectional view of an anodization process unit of the anodization apparatus according to the third example of the seventh embodiment.

FIG. 37 is a cross-sectional view of an anodization process unit of an anodization apparatus according to a fourth example of the seventh embodiment.

FIG. 38 is a block diagram of an anodization apparatus according to a first example of an eighth embodiment.

FIG. 39 is a block diagram of an anodization apparatus according to a second example of the eighth embodiment.

FIG. 40 is a block diagram of an anodization apparatus according to a third example of the eighth embodiment.

FIG. 41 is a block diagram of an anodization apparatus according to a fourth example of the eighth embodiment.

FIG. 42 is a cross-sectional view of an anodization process unit of an anodization apparatus according to a first example of a ninth embodiment.

FIG. 43 is a top view of a retainer and a fixing unit of the anodization process unit of the anodization apparatus according to the first example of the ninth embodiment.

FIG. 44 is an enlarged view of a region RA shown in FIG. 43.

FIG. 45 is an enlarged view of the region RA shown in FIG. 43.

FIG. 46 is a cross-sectional view of a retainer and a fixing unit of an anodization apparatus according to a second example of the ninth embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, an anodization apparatus comprising: a first process tank used for an anodization process on a first portion of a substrate; a second process tank provided inside of the first process tank and used for the anodization process on a second portion of the substrate; a first electrolyte supply unit configured to supply a first electrolyte to the first process tank; a second electrolyte supply unit configured to supply a second electrolyte to the second process tank; a retainer configured to retain the substrate; a first electrode provided above the first process tank and/or the second process tank; and a second electrode provided below the first process tank and the second process tank.

Hereinafter, embodiments will be described with reference to the accompanying drawings. In the following description, structural elements that have approximately the same function and configuration will be assigned the same reference symbol, and a repeat description will be given only where necessary. The embodiments to be described below are shown as an example of a device or a method for embodying the technical idea of the embodiments, and are not intended to limit the material, shape, structure, arrangement, etc. of components to those described below. The technical idea of the embodiments may be variously modified in the claims.

1. FIRST EMBODIMENT

An anodization apparatus according to a first embodiment will be described.

1.1 Overall Configuration

An example of an overall configuration of an anodization apparatus will be described with reference to FIG. 1. FIG. 1 is a block diagram of an anodization apparatus.

As shown in FIG. 1, an anodization apparatus 1 includes an anodization process unit 10, an electrolyte A supply unit 11, an electrolyte B supply unit 12, a current supply unit 13, and a control circuit 14.

The anodization process unit 10 includes process tanks and electrodes (anode and cathode) corresponding to each process tank, and performs an anodization process on a semiconductor substrate surface. The configuration of the anodization process unit 10 will be described later.

The electrolyte A supply unit 11 supplies an electrolyte A to the process tank provided in the anodization process unit 10. The electrolyte A supply unit 11 has a mechanism (not shown; for example, a pump, etc.) for adjusting a liquid pressure of the electrolyte A supplied to the process tank. The electrolyte A is a process liquid used for the anodization process. As the electrolyte A, a liquid containing a hydrofluoric acid (HF) is used, for example. The electrolyte A supply unit 11 of the present embodiment does not have a function of circulating a liquid (the electrolyte A) between the anodization process unit 10 and an electrolyte A mixing tank 20. In other words, the electrolyte A supply unit 11 supplies unused (new) electrolyte A to the anodization process unit 10.

The electrolyte A supply unit 11 includes an electrolyte mixing tank 20, a supply control unit 21, a plurality of liquid supply units 22 (in the example shown in FIG. 1, three liquid supply units 22a through 22c), and a concentration monitor 23.

The electrolyte A mixing tank 20 is a tank for producing the electrolyte A by mixing multiple liquids. The electrolyte A supply unit 11 produces the electrolyte A by mixing three liquids A to C as ingredients, for example. The three liquids A to C may be, for example, an HF solution, DIW (deionized water), and alcohol. The liquids used for producing the electrolyte A are not limited to three kinds. Moreover, an ingredient other than a liquid may be used to produce the electrolyte A. The produced electrolyte A is supplied to the process tank in the anodization process unit 10 through a pipe 17.

The supply control unit 21 controls an amount of each of the liquids A to C supplied to the electrolyte A mixing tank 20 through the control of the control circuit 14. For example, the supply control unit 21 includes valves and flow meters provided in respective supply lines of the liquids.

Each of the liquid supply units 22a through 22c is coupled to the electrolyte A mixing tank 20 via the respective supply lines (pipes). The liquid supply units 22a through 22c respectively supply the liquids A to C to the electrolyte A mixing tank 20 through the supply lines. The liquid supply units 22a through 22c may have a mechanism for compressing and transferring the liquids A to C from their respective containers, for example.

The concentration sensor 23 monitors a concentration (for example, an F concentration) of the electrolyte A in the electrolyte A mixing tank 20, and transmits the result to the control circuit 14. The control circuit 14 controls the supply control unit 21 based on the result of the concentration monitoring, and adjusts the concentration of the electrolyte A.

The electrolyte B supply unit 12 supplies an electrolyte B to a process tank that is different from the process tank which is provided in the anodization process unit 10 and to which the electrolyte A is supplied. The electrolyte B supply unit 12 has a mechanism (not shown; for example, a pump, etc.) for adjusting a liquid pressure of the electrolyte B supplied to the process tank. The electrolyte B is a process liquid used for the anodization process. The electrolyte B may be the same as or different from the electrolyte A. In the following, an example where the electrolyte B has a concentration (F concentration) differing from that of the electrolyte A is given. As the electrolyte B, a liquid containing HF is used. The electrolyte B supply unit 12 of the present embodiment has a function of circulating the electrolyte B between the anodization process unit 10 and the electrolyte B mixing tank 30. In other words, the electrolyte B supply unit 12 adjusts the components of a liquid recovered from the anodization process unit 10, and supplies the adjusted liquid once again to the anodization process unit 10.

The electrolyte B supply unit 12 includes an electrolyte B mixing tank 30, a supply control unit 31, a plurality of liquid supply units 32 (in the example shown in FIG. 1, three liquid supply units 32a through 32c), and a concentration monitor 33.

The electrolyte B mixing tank 30 is a tank for producing the electrolyte B by mixing multiple liquids. The electrolyte B supply unit 12 is capable of producing the electrolyte B and performing concentration adjustment by mixing the liquid recovered from the anodization processing unit 10 via the pipe 16 with the three liquids D to F. The three liquids D to F may be, for example, an HF solution, DIW, and alcohol. The liquids used for producing the electrolyte B are not limited to three kinds. Moreover, an ingredient other than a liquid may be used to produce the electrolyte B. The produced electrolyte B is supplied to one of the process tanks in the anodization process unit 10 through a pipe 15. The electrolyte B mixing tank 30 has an overflow pipe for draining when a liquid in the tank overflows, for example.

The supply control unit 31 controls an amount of each of the liquids D to F supplied to the electrolyte B mixing tank 30 through the control of the control circuit 14. For example, the supply control unit 31 includes valves and flow meters provided in respective supply lines of the liquids.

The liquid supply units 32a through 32c are coupled to the electrolyte B mixing tank 30 via respective supply lines. The liquid supply units 32a through 32c respectively supply the liquids D to F to the electrolyte B mixing tank 30 through the supply lines. The liquid supply units 32a through 32c may have a mechanism for compressing and transferring the liquids D to F from their respective containers, for example.

The concentration sensor 33 monitors a concentration (for example, an F concentration) of the electrolyte B in the electrolyte B mixing tank 30, and transmits the result to the control circuit 14. The control circuit 14 controls the supply control unit 31 based on the result of the concentration monitoring, and adjusts the concentration of the electrolyte B.

The current supply unit 13 supplies a current to an electrode provided in the anodization process unit 10 through the control of the control circuit 14.

The control circuit 14 controls the entire anodization apparatus 1.

1.2 Detailed Configuration of Anodization Process Unit

Next, an example of the detailed configuration of the anodization process unit 10 will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view of the anodization process unit 10. FIG. 3 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A and B. The example shown in FIGS. 2 and 3 shows the anodization process unit 10 having two upper electrodes coupled to respective current sources, and two process tanks. In the following, this configuration may be referred to as a “divided electrode-multiple power sources-divided process tank”.

As shown in FIG. 2, the anodization process unit 10 includes the process tanks 101 and 103, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107. The insulator 105 may be omitted. In this case, an air gap may be provided between the upper electrode 104 and the upper electrode 106, for example. In other words, any configuration will do as long as the upper electrode 104 and the upper electrode 106 are not electrically coupled.

The process tank 101 has a cylindrical shape, for example. The inner diameter of the process tank 101 is approximately the same as the inner diameter of the semiconductor substrate 1000 which is a target of anodization. It should be noted that the cross section of the cylindrical process tank 101 is not necessarily a perfect circle, and it may be a somewhat deformed circle. Furthermore, the process tank 101 may have a recess or projection on its side surface. If the cross section of the process tank 101 is not a perfect circle, the diameter of the approximate circle of the inner side of the process tank 101 is regarded as an inner diameter. In the following, the example where the semiconductor substrate 1000 is a single crystal silicon (Si) substrate will be described. The bottom surface of the process tank 101 is in contact with the lower electrode 107. When the anodization process is performed, the upper edge of the process tank 101 is located in the vicinity of the surface of the semiconductor substrate 1000. In other words, the upper edge of the process tank 101 is not in contact with the lower surface (the surface to be anodized) of the semiconductor substrate 1000. The process tank 101 is made of an insulating material having a resistance to the electrolytes A and B. The pipes 15 and 18 are coupled to the process tank 101. The pipe 15 is a liquid supply line to the process tank 101. The pipe 18 is a liquid drain line from the process tank 101.

The vat 102 is provided to recover an overflow liquid from the upper edge of the process tank 101. The vat 102 has a cylindrical shape, for example. The inner diameter of the vat 102 is larger than the outer diameters of the process tank 101, the upper electrode 104, and the semiconductor substrate 1000. The vat 102 is arranged concentrically with the process tank 101, for example. The bottom surface of the vat 102 is in contact with the outer periphery of the upper edge or the vicinity of the upper edge of the process tank 101. The upper edge of the vat is located higher than the upper edge of the process tank 101. The vat 102 may be made of an insulating material having a resistance to the electrolytes A and B, for example. The vat 102 may be made of the same material as the process tank 101. The pipe 16 is coupled to the vat 102. The pipe 16 is a liquid drain line from the vat 102.

The process tank 103 has a cylindrical shape, for example. The inner diameter of the process tank 103 is smaller than the inner diameter of the process tank 101. It should be noted that the cross section of the cylindrical process tank 103 is not necessarily a perfect circle, and it may be a somewhat deformed circle. Furthermore, the process tank 103 may have a recess or projection on its side surface. If the cross section of the process tank 103 is not a perfect circle, the diameter of the approximate circle of the inner side of the process tank 103 is regarded as an inner diameter. The process tank 103 is arranged in such a manner that its lower surface is in contact with the lower electrode 107, and is concentric with the process tank 101. The height of the upper edge of the process tank 103 is approximately the same as the height of the process tank 101. The upper edge of the process tank 103 is not in contact with the lower surface of the semiconductor substrate 1000, similarly to the process tank 101. The process tank 103 may be made of an insulating material having a resistance to the electrolytes A and B, for example. The process tank 103 may be made of the same material as the process tank 101. The pipes 17 and 19 are coupled to the process tank 103. The pipe 17 is a liquid supply line to the process tank 103. The pipe 19 is a liquid drain line from the process line 103.

The upper electrode 104 functions as an anode in the anodization process using the process tank 101. Accordingly, the upper electrode 104 is opposed to the process tank 101. The upper electrode 106 functions as an anode in the anodization process using the process tank 103. Accordingly, the upper electrode 106 is opposed to the process tank 103. Above the process tanks 101 and 103, the insulator 105 and the upper electrode 104 are concentrically arranged with respect to the upper electrode 106. In other words, the upper electrodes 106 and 104 are concentrically arranged, and the insulator 105 is arranged between the upper electrodes 106 and 104. For this reason, the upper electrodes 106 and 104 are not electrically coupled.

The outer diameter of the upper electrode 106 is approximately the same as the outer diameter of the process tank 103. The outer diameter of the upper electrode 104 is approximately the same as the outer diameter of the process tank 101. In other words, the outer diameter of the upper electrode 104 is approximately the same as the outer diameter of the semiconductor substrate 1000. The inner diameter of the upper electrode 104 is approximately the same as the outer diameter of the process tank 103.

In the present embodiment, different currents are respectively supplied to the upper electrodes 104 and 106 from the current supply unit 13. More specifically, the current supply unit 13 includes current sources 40 and 41. The current source 40 is coupled to the upper electrode 104 and the lower electrode 107, and supplies a desired amount of current to the upper electrode 104 when the anodization process is performed. The current source 41 is coupled to the upper electrode 106 and the lower electrode 107, and supplies a desired amount of current to the upper electrode 106 when the anodization process is performed.

The lower electrode 107 is opposed to the upper electrodes 104 and 106, and functions as a cathode in the anodization process. The upper electrodes 104 and 106, and the lower electrode 107 are made of conductive materials.

A plurality of each of the pipes 15 through 19 may be provided in the process tanks 101 and 103 and the vat 102.

As shown in FIG. 3, the anodization process unit 10 includes a retainer 108. By the retainer 108, the semiconductor substrate 1000 is arranged in such a manner that its upper surface is in contact with the bottom surfaces of the upper electrodes 104 and 106, and its lower surface (the surface to be anodized) faces downward (namely, faces the process tanks 101 and 103). A gap GP1 is provided between the upper edge of the process tank 101 and the semiconductor substrate 1000. A gap GP2 is provided between the upper edge of the process tank 103 and the semiconductor substrate 1000.

In the present embodiment, when the electrolytes A and B are concurrently supplied to the anodization process unit 10, the liquid pressure of the electrolyte A supplied to the process tank 103 is set higher than the liquid pressure of the electrolyte B supplied to the process tank 101 (the liquid pressure of the electrolyte A>the liquid pressure of the electrolyte B). When the anodization process is performed, the pipes 18 and 19 are turned to a closed state. The electrolyte A thereby flows from the process tank 103 into the process tank 101 via the gap GP2. At this time, since the liquid pressure of the electrolyte A is higher than that of the electrolyte B, the electrolyte B does not flow into the process tank 103 from the process tank 101. The excess electrolyte B (the electrolyte B mixed with the electrolyte A) from the process tank 101 flows into the vat 102 through the gap GP1.

In the example shown in FIG. 3, the outer diameter of the process tank 101 is smaller than the inner diameter of the semiconductor substrate 1000. For this reason, the gap GP1 is provided between the upper edge of the process tank 101 and the semiconductor substrate 1000 in the example; however, the embodiment is not limited thereto. For example, the inner diameter of the process tank 101 may be larger than the outer diameter of the semiconductor substrate 1000 including the retainer 108, and the upper edge of the process tank may be located higher than the surface to be anodized (lower surface) of the semiconductor substrate 1000. In this case, the gap GP1 is provided between the inner side of the upper edge of the process tank 101 and the retainer 108 (and the outer diameter of the semiconductor substrate 1000).

1.3 Example of Electrolyte Concentration Adjustment

Next, an example of electrolyte concentration adjustment will be described with reference to FIG. 4. FIG. 4 is a graph showing a monitoring result of the concentration sensor 33 in the electrolyte B supply unit 12.

As shown in FIG. 4, first, at time to, the electrolyte B supply unit 12 produces the electrolyte B of a predetermined adjustment target concentration in the electrolyte B mixing tank 30. Then, the electrolyte B supply unit 12 supplies the produced electrolyte B to the process tank 101.

At time t1, the anodization process is started. During time t0 through t6, the anodization process is performed. During this period, the electrolyte B is circulated between the process tank 101 and the electrolyte B mixing tank 30.

During time t1 through t2, the concentration of the electrolyte B gradually decreases due to anodization.

At time t2, when the concentration of the electrolyte B decreases to a predetermined lower limit concentration at which the anodization process is possible, the electrolyte B supply unit 12 adds at least one of the liquids D to F to the electrolyte B mixing tank 30 and starts the concentration adjustment of the electrolyte B.

During the period from time t2 to t3, the electrolyte B supply unit 12 performs concentration adjustment of the electrolyte B.

At time t3, when the concentration of the electrolyte B reaches an adjustment target concentration, the electrolyte B supply unit 12 stops the concentration adjustment of the electrolyte B.

During time t3 through t4, the concentration of the electrolyte B is gradually decreased by the anodization process.

At time t4, when the concentration of the electrolyte B decreases to the adjustment target concentration, the electrolyte B supply unit 12 starts the concentration adjustment of the electrolyte B once again.

During the period from time t4 to t5, the electrolyte B supply unit 12 performs the concentration adjustment of the electrolyte B.

At time t5, when the concentration of the electrolyte B reaches the adjustment target concentration, the electrolyte B supply unit 12 stops the concentration adjustment of the electrolyte B.

At time t6, the anodization process is finished. In the example shown in FIG. 4, the electrolyte B supply unit 12 performs the adjustment of concentration of the electrolyte B once again after the anodization process is finished at time t6 so as to be ready for the next process; however, the embodiment is not limited to this example. The electrolyte B may be drained.

1.4 Post-Anodization State of Semiconductor Substrate Surface

Next, the state of the semiconductor substrate surface 1000 will be described with reference to FIG. 5. The example of FIG. 5 shows the surface and the cross section of the semiconductor substrate 1000 after being subjected to the anodization process.

As shown in FIG. 5, through using the anodization apparatus 1 of the present embodiment, porous layers (for example, porous Si layers) having different characteristics are formed in a concentric manner on the surface (the surface to be anodized) of the semiconductor substrate 1000.

More specifically, in the surface center portion of the semiconductor substrate 1000, a porous layer 1100 corresponding to the upper electrode 106 and the process tank 103 (the electrolyte A) is formed. In the surface outer peripheral portion of the semiconductor substrate 1000, a porous layer 1200 corresponding to the upper electrode 104 and the process tank 101 (the electrolyte B) is formed. The porous layers 1100 and 1200 have different anodization process conditions. More specifically, as the anodization process conditions, for example, an amount of current supplied to each of the upper electrodes 104 and 106 (an amount of current per unit area of each of the upper electrodes 104 and 106) and/or the concentrations of the electrolytes A and B, etc. are different. It is thereby possible for the anodization apparatus 1 to form porous layers 1100 and 1200 that vary in film quality (mechanical strength). The porous layers 1100 and 1200 vary in at least one of, for example, a hardness, an average grain size of the porous layer, a density, or a thickness of the porous layer. For example, the hardness of the porous layer 1100 may be higher or lower than the porous layer 1200. For example, the hardness can be measured by a Vickers hardness scale. The average grain size can be measured by a gas adsorption method.

1.5 Specific Example of Manufacturing Method of Semiconductor Apparatus Using Anodized Semiconductor Substrate

Next, a specific example of a manufacturing method of a semiconductor apparatus using the anodized semiconductor substrate 1000 will be described with reference to FIG. 6. FIG. 6 is a flowchart showing an example of the method of bonding semiconductor substrates. As one semiconductor apparatus manufacturing method, there is a method of forming a semiconductor apparatus by bonding a first (semiconductor) substrate in which a device layer 1 is formed with a second (semiconductor) substrate in which a device layer 2 is formed. In the device layers 1 and 2, various types of circuits including an element such as a transistor, etc., are provided, for example. In this case, after the first substrate and the second substrate, namely the device layer 1 and the device layer 2, are bonded together, the first substrate is removed. In the example shown in FIG. 6, the case in which a semiconductor substrate having the porous layers formed as the first substrate through using the anodization apparatus 1 according to the present embodiment will be described.

As shown in FIG. 6, first, an anodization process is performed on a first substrate 1000a using the anodization apparatus 1 of the present embodiment, thereby forming the porous layers 1100 and 1200 on the surface (a).

Next, the device layer 1 is formed on the surface on which the porous layers 1100 and 1200 are formed in the first substrate (b). The device layer 2 is formed in the second substrate 1000b (c).

Next, the first substrate 1000a and the second substrate 1000b are bonded in such a manner that the device layer 1 and the device layer 2 face each other and are electrically coupled (d).

Next, the first substrate 1000a and the device layer 1 (the second substrate 1000b) are peeled off each other using the porous layers 1100 and 1200 as peeling layers (e). The peeled first substrate 1000a is polished on its surface to remove remaining porous layers 1100 and 1200 (f). The polished first substrate 1000a can be thus reused.

Next, the porous layers 1100 and 1200 on the second substrate surface are removed (g). Thus, the second substrate 1000b in which the device layers 1 and 2 are provided is formed.

Herein, the porous layers 1100 and 1200 have such a hardness that peeling of the porous layers from the first substrate 1000a or breakage of the porous layers does not occur in the process of manufacturing the device layer 1 and the process (d) of bonding the first substrate 1000a and the second substrate 1000b. Furthermore, the porous layers 1100 and 1200 have such a hardness that the porous layers 1100 and 1200 function as peeling layers in the peeling process (e) of the first substrate 1000a and the second substrate 1000b. For example, in order to prevent the peeling in the manufacturing process and the peeling process of the device layer 1, it is desirable that the hardness of the porous layer 1200 (the outer peripheral portion) be higher than the hardness of the porous layer 1100 (the center portion).

1.6 Advantageous Effects of Present Embodiment

For example, as a method of bonding semiconductor substrates which is one of the semiconductor substrate manufacturing methods, if a semiconductor substrate having no porous layers is used, it is difficult to peel the semiconductor substrate off a device layer formed thereon, since the mechanical strength of the semiconductor substrate is high. Accordingly, the semiconductor substrate that becomes unnecessary is removed by grinding in most cases. In this case, the semiconductor substrate removed by grinding is discarded and cannot be reused. If a single layer of porous layer is provided between the semiconductor substrate and the device layer, since the mechanical strength of the porous layer is low, peeling or breakage of the porous layer is likely to occur in the process of manufacturing the device layer or the process of bonding the semiconductor substrate.

In contrast, with the configuration according to the present embodiment, the anodization apparatus 1 is capable of supplying the electrolytes A and B having different concentrations to the central portion and the outer peripheral portion of the semiconductor substrate surface, respectively. The anodization apparatus 1 has two upper electrodes 106 and 104 respectively corresponding to the central portion and the outer peripheral portion of the semiconductor substrate surface, and is capable of supplying different amounts of current to the portions respectively. Accordingly, the anodization apparatus 1 can form porous layers 1100 and 1200 having different film qualities in the center portion and the outer peripheral portion of the semiconductor substrate surface.

Through forming the porous layers 1100 and 1200 having different film qualities in the center portion and the outer peripheral portion of the semiconductor substrate surface using the anodization apparatus 1 of the present embodiment, it is possible to form porous layers 1100 and 1200 that function as peeling layers in the process of the semiconductor substrate peeling in a semiconductor substrate bonding method, without causing an occurrence of peeling of the layers during the process of manufacturing a device layer or the process of bonding semiconductor substrates. It is thereby possible to reuse the semiconductor substrate separated at the location of the porous layers.

2. SECOND EMBODIMENT

Next, a second embodiment will be described. In the second embodiment, three configuration examples of the anodization apparatus 1 differing from the first embodiment will be described. Hereinafter, the description will focus mainly on matters different from those of the first embodiment.

2.1 First Example

First, an anodization apparatus 1 according to the first example will be described. In the first example, the upper electrode of the anodization process unit 10 is not divided. The overall configuration of the anodization apparatus 1 in the first example is the same as that shown in FIG. 1 of the first embodiment.

Next, an example of the detailed configuration of the anodization process unit 10 will be described with reference to FIGS. 7 and 8. FIG. 7 is a perspective view of the anodization process unit 10. FIG. 8 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A and B. The example shown in FIGS. 7 and 8 shows the anodization process unit 10 having a single upper electrode coupled to a single current supply source, and two process tanks. In the following, this configuration may be referred to as a “common electrode-single power source-divided process tank”.

As shown in FIGS. 7 and 8, the anodization process unit 10 includes the process tanks 101 and 103, the vat 102, the upper electrode 104, the lower electrode 107, and the retainer 108. In other words, the anodization process unit 10 of the present example has a configuration in which the upper electrode is not divided, compared to the first embodiment shown in FIGS. 2 and 3.

The upper electrode 104 functions as an anode in the anodization process using the process tanks 101 and 103. Accordingly, the upper electrode 104 is opposed to the process tanks 101 and 103. The outer diameter of the upper electrode 104 is approximately the same as the outer diameter of the process tank 101. In other words, the outer diameter of the upper electrode 104 is approximately the same as the outer diameter of the process tank 1000. The upper edge of the upper electrode 104 is located higher than the upper edge of the vat 102.

In the present embodiment, the current supply unit 13 includes a current source 40. The current source 40 is coupled to the upper electrode 104 and the lower electrode 107, and supplies a desired amount of current to the upper electrode 104 when an anodization process is performed.

The other configurations, namely the configurations relating to the process tanks 101 and 103, the vat 102, etc., are the same as those in the first embodiment shown in FIGS. 2 and 3.

2.2 Second Example

Next, an anodization apparatus 1 according to the second example will be described. In the second example, the process tank 103 of the anodization process unit 10 is omitted.

First, an example of an overall configuration of the anodization apparatus 1 will be described with reference to FIG. 9. FIG. 9 is a block diagram of the anodization apparatus 1.

As shown in FIG. 9, in the anodization apparatus 1 of the present example, the electrolyte B supply unit 12 is omitted. Furthermore, similarly to the electrolyte B supply unit 12 shown in FIG. 1 of the first embodiment, the electrolyte A supply unit 11 has a circulation mechanism for circulating the electrolyte A between the electrolyte A mixing tank 20 and the anodization process unit 10. More specifically, in the electrolyte A mixing tank 20, the electrolyte A can be produced by mixing a liquid recovered from the anodization process unit 10 via the pipe 16 with the three liquids A to C, and the concentration of the electrolyte A can be adjusted. The produced electrolyte A is supplied to the anodization process unit 10 through a pipe 15. The electrolyte A mixing tank 20 has an overflow pipe for draining when a liquid in the tank overflows, for example. The electrolyte A supply unit 11 does not necessarily have the mechanism for circulating the electrolyte A. In other words, the configuration may be the same as that of the first embodiment shown in FIG. 1.

Next, an example of the detailed configuration of the anodization process unit 10 will be described with reference to FIGS. 10 and 11. FIG. 10 is a perspective view of the anodization process unit 10. FIG. 11 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolyte A. The example shown in FIGS. 10 and 11 shows the anodization process unit 10 having two upper electrodes 104 and 106 coupled to a single current source, and a single process tank 101. In the following, this configuration may be referred to as a “divided electrode-single power sources-common process tank”.

As shown in FIGS. 10 and 11, the anodization process unit 10 includes the process tank 101, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108. In other words, the anodization process unit 10 of the present example has a configuration in which the process tank 103 is omitted, compared to the first embodiment shown in FIGS. 2 and 3. In addition, the pipes 17 and 19 coupled to the process tank 103 are also omitted in the present example.

The upper electrode 104 functions as an anode when the porous layer 1200 is formed in the anodization process. The upper electrode 106 functions as an anode when the porous layer 1100 is formed in the anodization process.

In the present example, the upper electrode 104 is coupled to the current source 40 via a switch SW1. The upper electrode 106 is coupled to the current source 40 via a switch SW2.

As shown in FIG. 11, there is no gap GP2, as the process tank 103 is omitted in the present example. When the anodization process is performed, the pipe 18 is in a closed state. For this reason, the excess electrolyte A from the process tank 101 flows into the vat 102 through the gap GP1.

The other configurations, namely the configurations relating to the process tank 101, the vat 102, the upper electrodes 104 and 106, etc., are the same as those in the first embodiment shown in FIGS. 2 and 3.

2.3 Third Example

Next, an anodization apparatus 1 according to the third example will be described. In the third example, differing from the second example of the second embodiment, a current source is provided in each of the upper electrodes 104 and 106. The overall configuration of the anodization apparatus 1 in the third example is the same as the second example of the second embodiment shown in FIG. 9.

Next, an example of the detailed configuration of the anodization process unit 10 will be described with reference to FIGS. 12 and 13. FIG. 12 is a perspective view of the anodization process unit 10. FIG. 13 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolyte A. The example shown in FIGS. 12 and 13 shows the anodization process unit 10 having two upper electrodes respectively coupled to current sources, and a single process tank. In the following, this configuration may be referred to as a “divided electrode-multiple power sources-common process tank”.

As shown in FIGS. 12 and 13, the configuration of the anodization process unit 10 is the same as that of the second example of the second embodiment as shown in FIGS. 10 and 11.

In the example, similarly to FIGS. 2 and 3 of the first embodiment, the upper electrode 104 is coupled to the current source 40. The upper electrode 106 is coupled to the current source 41.

2.4 Advantageous Effects of Present Embodiment

The configuration of the present embodiment can attain the same effect as the first embodiment.

3. THIRD EMBODIMENT

Next, the third embodiment will be described. In the third embodiment, six examples of the anodization method using the anodization apparatus 1 will be described. Hereinafter, the explanation will focus mainly on matters which differ from the first and second embodiments.

3.1 First Example

First, an anodization method according to the first example is described with reference to FIG. 14. FIG. 14 is a flowchart showing the anodization method according to the first example. The first example is an example where the porous layer 1100 and the porous layer 1200 are formed at different timings through using the anodization apparatus 1 described in the first embodiment or the first example of the second embodiment.

As shown in FIG. 14, the semiconductor substrate 1000 is carried into the anodization apparatus 1 (step S10), and is fixed by the retainer 108.

Then, the electrolyte A supply unit 11 produces the electrolyte A and supplies it to the process tank 103 (step S11).

Next, the control circuit 14 performs an anodization process on the central portion of the semiconductor substrate 1000 (step S12). In other words, the control circuit 14 forms the porous layer 1100. More specifically, in the case of the anodization apparatus 1 of the first embodiment for example, a current is supplied from the current source 41 to the upper electrode 106, and the anodization process is performed. More specifically, in the case of the anodization apparatus 1 of the first example of the second embodiment for example, a current is supplied from the current source 40 to the upper electrode 104. At this time, the electrolyte B is not supplied to the process tank 101. For this reason, the porous layer 1100 is formed but the porous layer 1200 is not formed.

Next, the control circuit 14 causes the process tank 103 to drain the electrolyte A via the pipe 19 (step S13).

Then, the electrolyte B supply unit 12 produces the electrolyte. B and supplies it to the process tank 101 (step S14).

Next, the control circuit 14 performs an anodization process on the outer peripheral portion of the semiconductor substrate 1000 (step S15). In other words, the control circuit 14 forms the porous layer 1200. More specifically, in the case of the anodization apparatus 1 of the first embodiment for example, a current is supplied from the current source 40 to the upper electrode 104, and the anodization process is performed. More specifically, in the case of the anodization apparatus 1 of the first example of the second embodiment for example, a current is supplied from the current source 40 to the upper electrode 104. At this time, the electrolyte A is not supplied to the process tank 103. For this reason, the porous layer 1200 is formed but the porous layer 1100 is not formed.

Next, the control circuit 14 causes the process tank 101 to drain the electrolyte B via the pipe 18 (step S16).

The semiconductor substrate 1000 is then carried out of the anodization apparatus 1 (step S17), and the anodization process is finished.

In the present example, the case of forming the porous layer 1200 after forming the porous layer 1100 is described; however, the porous layer 1200 may be formed first and then the porous layer 1100 may be formed.

3.2 Second Example

Next, an anodization method according to the second example will be described with reference to FIG. 15. FIG. 15 is a flowchart showing the anodization method according to the second example. The second example is an example where the porous layer 1100 and the porous layer 1200 are formed in a batch through using the anodization apparatus 1 described in the first embodiment or the first example of the second embodiment.

As shown in FIG. 15, the semiconductor substrate 1000 is carried into the anodization apparatus 1 (step S10), and is fixed by the retainer 108.

Then, the electrolyte A supply unit 11 produces the electrolyte A and supplies it to the process tank 103. Then, the electrolyte B supply unit 12 produces the electrolyte B and supplies it to the process tank 101 (step S21).

Next, the control circuit 14 performs an anodization process on the semiconductor substrate 1000 (step S22). In other words, the control circuit 14 forms the porous layers 1100 and 1200. More specifically, in the case of the anodization apparatus 1 of the first embodiment for example, a current is supplied from the current source 40 to the upper electrode 104, and a current is supplied from the current source 41 to the upper electrode 106. More specifically, in the case of the anodization apparatus 1 of the first example of the second embodiment for example, a current is supplied from the current source 40 to the upper electrode 104. Thus, the porous layer 1100 and the porous layer 1200 are formed in a batch.

Next, the control circuit 14 causes the process tank 103 to drain the electrolyte A via the pipe 19. The control circuit 14 causes the process tank 101 to drain the electrolyte B via the pipe 18 (step S23).

The semiconductor substrate 1000 is then carried out of the anodization apparatus 1 (step S17), and the anodization process is finished.

3.3 Third Example

Next, an anodization method according to the third example will be described with reference to FIG. 16. FIG. 16 is a flowchart showing the anodization method according to the third example. The third example is an example where the porous layer 1100 and the porous layer 1200 are formed at different timings through using the anodization apparatus 1 described in the second example of the second embodiment.

As shown in FIG. 16, the semiconductor substrate 1000 is carried into the anodization apparatus 1 (step S10), and is fixed by the retainer 108.

Then, the electrolyte A supply unit 11 produces the electrolyte A and supplies it to the process tank 101 (step S31).

Next, the control circuit 14 turns either one of the switch SW1 or SW2 to an on state, and performs an anodization process (step S32). When the control circuit 14 turns the switch SW2 to an on state, a current is supplied from the current source 40 to the upper electrode 106, and the porous layer 1100 is formed. Alternately, when the control circuit 14 turns the switch SW1 to an on state, a current is supplied from the current source 40 to the upper electrode 104, and the porous layer 1200 is formed.

Next, the control circuit 14 turns another one of the switch SW1 or SW2 not turned to an on state in previous step S32 to an on state, and performs an anodization process (step S33). Either one of the porous layer 1100 or the porous layer 1200 not formed in previous step S32 is thereby formed.

Next, the control circuit 14 causes the process tank 101 to drain the electrolyte A via the pipe 18 (step S34).

The semiconductor substrate 1000 is then carried out of the anodization apparatus 1 (step S17), and the anodization process is finished.

In the present example, the order of forming the porous layer 1100 and the porous layer 1200 can be determined as appropriate.

3.4 Fourth Example

Next, an anodization method according to the fourth example will be described with reference to FIG. 17. FIG. 17 is a flowchart showing the anodization method according to the fourth example. The fourth example is an example where the porous layer 1100 and the porous layer 1200 are formed at different timings through using the anodization apparatus 1 described in the third example of the second embodiment.

As shown in FIG. 17, the semiconductor substrate 1000 is carried into the anodization apparatus 1 (step S10), and is fixed by the retainer 108.

Then, the electrolyte A supply unit 11 produces the electrolyte A and supplies it to the process tank 101 (step S41).

Next, the control circuit 14 causes either one of the current source 40 or 41 to supply a current to its corresponding upper electrode, and performs an anodization process on either one of the center portion or the outer peripheral portion of the semiconductor substrate 1000 (step S42). When a current is supplied from the current source 41 to the upper electrode 106, the porous layer 1100 is formed. Alternately, when a current is supplied from the current source 40 to the upper electrode 104, the porous layer 1200 is formed.

Next, the control circuit 14 causes another one of the current source 40 or 41 not used in previous step S42 to supply a current to its corresponding upper electrode, and performs an anodization process on the central portion or the outer peripheral portion of the semiconductor substrate 1000 that has not yet been anodized (step S43). Either one of the porous layer 1100 or the porous layer 1200 not formed in previous step S42 is thereby formed.

Next, the control circuit 14 causes the process tank 101 to drain the electrolyte A via the pipe 18 (step S44).

The semiconductor substrate 1000 is then carried out of the anodization apparatus 1 (step S17), and the anodization process is finished.

In the present example, the order of forming the porous layer 1100 and the porous layer 1200 can be determined as appropriate.

3.5 Fifth Example

Next, an anodization method according to the fifth example will be described with reference to FIG. 18. FIG. 18 is a flowchart showing the anodization method according to the fifth example. The fifth example is an example where the porous layer 1100 and the porous layer 1200 are formed in a batch through using the anodization apparatus 1 described in the third example of the second embodiment.

As shown in FIG. 18, the semiconductor substrate 1000 is carried into the anodization apparatus 1 (step S10), and is fixed by the retainer 108.

Then, the electrolyte A supply unit 11 produces the electrolyte A and supplies it to the process tank 101 (step S51).

Next, the control circuit 14 causes the current sources 40 and 41 to supply different amounts of current to the corresponding upper electrode 104 and 106 respectively, and performs an anodization process (step S52). Thus, the porous layer 1100 and the porous layer 1200 are formed in a batch.

Next, the control circuit 14 causes the process tank 101 to drain the electrolyte A via the pipe 18 (step S53).

The semiconductor substrate 1000 is then carried out of the anodization apparatus 1 (step S17), and the anodization process is finished.

3.6 Sixth Example

Next, an anodization method according to the sixth example will be described with reference to FIG. 19. FIG. 19 is a flowchart showing the anodization method according to the sixth example. The sixth example is an example where the porous layer 1100 and the porous layer 1200 are formed in a batch through using the anodization apparatus 1 described in the first embodiment.

As shown in FIG. 19, the semiconductor substrate 1000 is carried into the anodization apparatus 1 (step S10), and is fixed by the retainer 108.

Then, the electrolyte B supply unit 12 produces the electrolyte B and supplies it to the process tank 101. The electrolyte A supply unit 11 produces the electrolyte A having a concentration different from that of the electrolyte B, and supplies it to the process tank 103 (step S61).

Next, the control circuit 14 causes the current sources 40 and 41 to supply different amounts of current to the corresponding upper electrodes 104 and 106 respectively, and performs an anodization process (step S62). In other words, in the present example, the control circuit 14 performs an anodization process under different conditions of the electrolyte concentration and an amount of current. Thus, the porous layer 1100 and the porous layer 1200 are formed in a batch.

Next, the control circuit 14 causes the process tank 103 to drain the electrolyte A via the pipe 19. The control circuit 14 causes the process tank 101 to drain the electrolyte B via the pipe 18 (step S63).

The semiconductor substrate 1000 is then carried out of the anodization apparatus 1 (step S17), and the anodization process is finished.

3.7 Advantageous Effects of Present Embodiment

The first through sixth examples of the present embodiment can be performed in the anodization apparatus 1 described in the first and second embodiments.

4. FOURTH EMBODIMENT

Next, the fourth embodiment will be described. In the fourth embodiment, four configuration examples of the electrolyte A supply unit 11 and the electrolyte B supply unit 12 differing from the first embodiment will be described. Hereinafter, the description will focus mainly on matters different from those of the first to third embodiments.

4.1 First Example

First, an anodization apparatus 1 according to the first example will be described with reference to FIG. 20. FIG. 20 is a block diagram of the anodization apparatus 1. Differing from the first embodiment, the first example describes a case in which the electrolyte B supply unit 12 does not have a circulation mechanism.

As shown in FIG. 20, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit 13, the control circuit 14, and the concentration sensor 50.

The configuration of the electrolyte A supply unit 11 is similar to that of the electrolyte A supply unit 11 of the first embodiment shown in FIG. 1.

Similarly to the electrolyte A supply unit 11, the electrolyte B supply unit 12 does not have a circulation mechanism, and it supplies unused electrolyte B to the anodization process unit 10. In other words, the electrolyte B supply unit 12 produces the electrolyte B by mixing three liquids D to F in the electrolyte B mixing tank 30.

The pipe 16 is not coupled to the electrolyte B mixing tank 30, and the liquid used in the anodization process unit 10 (in other words, the liquid recovered from the vat 102) is drained as a waste liquid.

The concentration sensor 50 monitors a concentration of the waste liquid (a mixture of the electrolyte A and the electrolyte B) in the pipe 16, and transmits the monitoring result to the control circuit 14. For example, in the anodization apparatus 1 of the present example, the supply of new electrolytes A and B and the drain of the electrolytes A and B are repeated for every anodization process. However, if it is determined from a result of the concentration monitoring of the waste liquid in the concentration sensor 50 that the electrolytes A and B in the process tanks 101 and 103 are determined to be reusable in the next anodization process, the electrolytes A and B in the process tanks 101 and 103 can be reused entirely or partially. If the electrolyte is partially reused, a shortfall of each of the electrolytes A and B is supplied from each of the electrolyte A supply unit 11 and the electrolyte B supply unit 12.

4.2 Second Example

Next, an anodization apparatus 1 according to the second example will be described with reference to FIG. 21. FIG. 21 is a block diagram of the anodization apparatus 1. The second example describes a case in which the electrolyte A supply unit 11 and the electrolyte B supply unit 12 have a mechanism for circulating the electrolytes.

As shown in FIG. 21, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit 13, and the control circuit 14.

The configuration of the electrolyte B supply unit 12 is similar to that of the electrolyte B supply unit 12 of the first embodiment shown in FIG. 1. In other words, the electrolyte B is recovered from the process tank 101 via the pipe 16.

The electrolyte A supply unit 11 can, via the pipe 16, similarly to the electrolyte B supply unit 12, adjust components of the liquid (the mixture of the electrolytes A and B) recovered from the vat 102 in the anodization process unit 10, and supply the adjusted liquid to the process tank 103 of the anodization process unit 10 once again.

4.3 Third Example

Next, an anodization apparatus 1 according to the third example will be described with reference to FIG. 22. FIG. 22 is a block diagram of the anodization apparatus 1. Differing from the second example, the third example describes a case in which the electrolyte A supply unit 11 recovers the electrolyte A from the process tank 103 via the pipe 19.

As shown in FIG. 22, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit 13, and the control circuit 14.

The electrolyte A mixing tank 20 of the electrolyte A supply unit 11 in the present example is coupled to the process tank 103 of the anodization process unit 10 via the pipe 19. In other words, the electrolyte A supply unit 11 can adjust components of the liquid recovered from the process tank 103, and supply the adjusted liquid once again to the process tank 103 of the anodization process unit 10. The other configurations are similar to those of the second example of the fourth embodiment shown in FIG. 21.

4.4 Fourth Example

Next, an anodization apparatus 1 according to the fourth example will be described with reference to FIG. 23. FIG. 23 is a block diagram of the anodization apparatus 1. Differing from the first embodiment, the fourth example describes a case in which the electrolyte A supply unit 11 has a circulation mechanism, and the electrolyte B supply unit 12 does not have a circulation mechanism.

As shown in FIG. 23, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte. B supply unit 12, the current supply unit 13, and the control circuit 14.

The electrolyte A mixing tank 20 of the electrolyte A supply unit 11 in the present example can, via the pipe 16, similarly to the second example of the fourth embodiment shown in FIG. 21, adjust components of the liquid (the mixture of the electrolytes A and B) recovered from the vat 102 in the anodization process unit 10, and supply the adjusted liquid to the process tank 103 of the anodization process unit 10 once again.

Similarly to the first example of the fourth embodiment shown in FIG. 20, the electrolyte B supply unit 12 does not have a circulation mechanism and it supplies unused electrolyte B to the anodization process unit 10. In other words, the electrolyte B supply unit 12 produces the electrolyte B by mixing three liquids D to F in the electrolyte B mixing tank 30.

4.5 Advantageous Effects of Present Embodiment

According to the configuration of the present embodiment, it is possible to obtain effects similar to those of the first to third embodiments.

The anodization process unit 10 described in each of the first and second examples of the second embodiment is applicable to the first through fourth examples of the present embodiment. The anodization method described in each of the first, second, and sixth examples of the third embodiment can be performed in the first through fourth examples of the present embodiment.

5. FIFTH EMBODIMENT

Next, the fifth embodiment will be described. In the fifth embodiment, four configuration examples of the anodization apparatus 1 differing from the first through fourth embodiments will be described. The anodization apparatus 1 of the present embodiment has a mechanism for supplying an electrolyte between the upper electrode and the upper surface (the surface not to be anodized) of the semiconductor substrate 1000. Hereinafter, the description will focus mainly on matters different from those of the first to fourth embodiments.

5.1 First Example

5.1.1 Overall Configuration

First, an example of an overall configuration of the anodization apparatus 1 of the first example will be described with reference to FIG. 24. FIG. 24 is a block diagram of the anodization apparatus. The configurations of the electrolyte A supply unit 11 and the electrolyte B supply unit 12 are similar to those of the first embodiment. For this reason, in the example of FIG. 24, the details of the components of the electrolyte A supply unit 11 and the electrolyte B supply unit 12 are omitted.

As shown in FIG. 24, the anodization apparatus 1 includes an anodization process unit 10, an electrolyte A supply unit 11, an electrolyte B supply unit 12, an electrolyte C supply unit 61, a current supply unit 13, and a control circuit 14.

The anodization process unit 10 includes a plurality of process tanks and a plurality of electrodes, and performs an anodization process on a semiconductor substrate surface. The configuration of the anodization process unit 10 will be described later.

The configurations of the electrolyte A supply unit 11, the electrolyte B supply unit 12, and the current supply unit 13 are similar to those of the first embodiment shown in FIG. 1.

The electrolyte C supply unit 61 supplies an electrolyte C to the process tank provided between the upper electrode in the anodization process unit 10 and the upper surface (the surface not to be anodized) of the semiconductor substrate 1000. The electrolyte C supply unit 61 has a mechanism (not shown; for example, a pump, etc.) for adjusting a liquid pressure of the electrolyte C supplied to the process tank. As the electrolyte C, a solution that almost does not react to the semiconductor substrate 1000 when the anodization process is performed (namely, a solution that does not solve Si) is used, for example. To suppress metal contamination of the semiconductor substrate 1000, it is preferable that the electrolyte C does not contain any metal elements. The electrolyte C supply unit 61 of the present embodiment has a function of circulating the electrolyte C between the anodization process unit 10 and an electrolyte C mixing tank 70. In other words, the electrolyte C supply unit 61 adjusts components of the liquid recovered from the anodization process unit 10 via the pipe 64, and supplies the adjusted liquid once again to the anodization process unit 10.

The electrolyte C supply unit 61 includes an electrolyte C mixing tank 70, a supply control unit 71, a plurality of liquid supply units 72 (in the example shown in FIG. 24, three liquid supply units 72a through 72c), and a concentration monitor 73.

The electrolyte C mixing tank 70 is a tank for producing the electrolyte C by mixing multiple liquids therein. The electrolyte C supply unit 61 produces the electrolyte C by mixing three liquids G to I as ingredients, for example. The liquids used for producing the electrolyte C are not limited to three kinds. An ingredient other than a liquid may be used to produce the electrolyte C. For example, the electrolyte C may be a diluted HF solution that almost does not react to the semiconductor substrate 1000 when the anodization process is performed, a diluted HCl solution, or a water-insoluble organic electrolyte. For example, as the ingredients, which is a water-insoluble electrolyte, of the electrolyte C, at least one of acetonitrile, propylene carbonate, or dimethylformamide may be selected. As the ingredients, which is a source of fluorides, of the electrolyte C, at least one of anhydrous HF, tetrafluoroborate, or lithium fluoroborate is used. The produced electrolyte C is supplied to the process tank in the anodization process unit 10 through a pipe 63. The electrolyte C mixing tank 70 has an overflow pipe for draining when a liquid in the tank overflows, for example.

The supply control unit 71 controls an amount of each of the liquids G to I supplied to the electrolyte C mixing tank 70 through the control of the control circuit 14. For example, the supply control unit 71 includes valves and flow meters provided in respective supply lines of the liquids.

The liquid supply units 72a through 72c are respectively coupled to the electrolyte C mixing tank 70 via the respective supply lines (pipes). The liquid supply units 72a through 72c supply the liquids G to I respectively to the electrolyte C mixing tank 70 through the supply lines. The liquid supply units 72a through 72c may have a mechanism for compressing and transferring the liquids G to I from their respective containers, for example.

The concentration sensor 73 monitors a concentration of the electrolyte C in the electrolyte C mixing tank 70, and transmits the monitoring result to the control circuit 14. The control circuit 14 controls the supply control unit 71 based on the result of the concentration monitoring, and adjusts the concentration of the electrolyte C. The concentration sensor 73 may measure a resistance value of the electrolyte C.

The control circuit 14 controls the entire anodization apparatus 1. More specifically, the control circuit 14 controls the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, and the current supply unit 13.

5.1.2 Detailed Configuration of Anodization Process Unit

Next, an example of the detailed configuration of the anodization process unit 10 will be described with reference to FIG. 25. FIG. 25 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A to C. The example of FIG. 25 shows a case where the anodization apparatus 1 has a “divided electrode-multiple power sources-divided process tank” configuration, similar to the first embodiment.

As shown in FIG. 25, the anodization process unit 10 includes the process tanks 101, 103, and 111, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108. The configurations of the process tanks 101 and 103, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107, are the same as those in the first embodiment shown in FIG. 2. In the example, similarly to the first embodiment, the upper electrode 104 is coupled to the current source 40. The upper electrode 106 is coupled to the current source 41.

The process tank 111 has a cylindrical shape, for example. The upper edge of the process tank 111 is located at the lower surfaces of the upper electrodes 104 and 106. When the anodization process is performed, the lower edge of the process tank 111 is located at the upper surface (the surface not to be anodized) of the semiconductor substrate 1000. The outer periphery of the process tank 111 is surrounded by the side surfaces of the retainer 108. In other words, the area surrounded by the lower surfaces of the upper electrodes 104 and 106, the upper surface of the semiconductor substrate 1000, and the side surfaces of the retainer 108 corresponds to the process tank 111. In other words, the process tank 111 is provided between the upper electrodes 104 and 106 and the process tanks 101 and 103. The pipes 63 and 64 are coupled to the process tank 111. The pipe 63 is a liquid supply line to the process tank 111. The pipe 64 is a liquid drain line from the process tank ill. In the present embodiment, the pipe 63 is coupled to the liquid supply line of the electrolyte C mixing tank 70. The pipe 64 is coupled to the liquid recovery line of the electrolyte C mixing tank 70. A plurality of each of the pipe 63 and the pipe 64 may be provided. Furthermore, a waste liquid drain pipe for draining the liquid in the process tank 111 as a waste liquid may be coupled to the process tank ill.

The retainer 108 of the present embodiment has a cylindrical shape, for example. The inner surface of the retainer 108 in the vicinity of the upper edge is in contact with the upper electrode 104. In the examples of the first and second embodiments, an L-shaped hook, which is in contact with the lower surface of the semiconductor substrate 1000, is provided at the lower edge of the retainer 108. In this case, the semiconductor substrate 1000 is fixed by being interposed between the upper electrode and the hook. In contrast, in the present example, the hook in contact with the lower surface of the semiconductor substrate 1000 is omitted. The retainer 108 includes a fixing unit 113. The fixing unit 113 is provided on the side surface of the retainer 108. When the anodization process is performed, the semiconductor substrate 1000 is pressed against the fixing unit 113 from the lower surface by the liquid pressures of the electrolytes A and B. The retainer 108 and the fixing unit 113 are made of an insulating material having a resistance to the electrolyte C. For example, for the retainer 108 and the fixing unit 113, an elastic material may be used to improve sealing with the semiconductor substrate 1000. The cross-sectional shape of the fixing unit 113 can be discretionarily determined. For example, the cross-sectional shape of the fixing unit 113 may be semicircular or rectangular.

In the present embodiment, the liquid pressure of each of the electrolytes A and B is set higher than the liquid pressure of the electrolyte C. For this reason, when the anodization process is performed, the upper surface of the semiconductor substrate 1000 is pressed against the fixing unit 113 by the liquid pressures of the electrolytes A and B.

No fixing unit 113 is provided between the lower surface (the surface to be anodized) of the semiconductor substrate 1000 and the lower electrode 107. In other words, the lower surface of the semiconductor substrate 1000 is not in contact with the retainer 108. For this reason, when the anodization process is performed, an area not to be anodized (hereinafter, may be referred to as “edge-cut area”) is not provided on the outer periphery of the lower surface of the semiconductor substrate 1000. For this reason, the porous layers 1100 and 1200 are formed entirely on the lower surface of the semiconductor substrate 1000.

5.1.3 Configuration of Contact Portion

Next, an example of the configuration of the fixing unit 113 will be described with reference to FIG. 26. FIG. 26 is a top view of the fixing unit 113.

As shown in FIG. 26, the fixing unit 113 of the present embodiment has a ring shape. When the anodization process is performed, the entire outer periphery (edge) of the semiconductor substrate 1000 is in contact with the fixing unit 113. Thus, exudation of a liquid from the process tank 101 to the process tank 111 can be suppressed.

5.2 Second Example

Next, the second example will be described. In the second example, the configuration of the anodization process unit 10 differing from the first example will be described with reference to FIG. 27. FIG. 27 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A to C. The example of FIG. 27 shows a case where the anodization apparatus 1 has a “common electrode-single power source-divided process tank” configuration, similar to the first example of the second embodiment.

The overall configuration of the anodization apparatus 1 in the present example is the same as the first example of the fifth embodiment shown in FIG. 24.

As shown in FIG. 27, the anodization process unit 10 includes the process tanks 101, 103, and 111, the vat 102, the upper electrode 104, the lower electrode 107, and the retainer 108.

The process tanks 101 and 103, the vat 102, the upper electrode 104, and the lower electrode 107, are the same as those in the first example of the second embodiment shown in FIG. 8. Similarly to the first example of the second embodiment, the upper electrode 104 is coupled to the current supply unit 13 (the current source 40).

In the present example, the area surrounded by the lower surface of the upper electrode 104, the upper surface of the semiconductor substrate 1000, and the side surfaces of the retainer 108 corresponds to the process tank 111. In other words, the process tank 111 is provided between the upper electrode 104 and the process tanks 101 and 103.

5.3 Third Example

Next, the third example will be described. In the third example, the configuration of the anodization apparatus 1 differing from the first and second examples will be described with reference to FIGS. 28 and 29. FIG. 28 is a block diagram of the anodization apparatus. FIG. 29 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A and C. The example of FIG. 29 shows a case where the anodization apparatus 1 has a “divided electrode-single power source-common process tank” configuration, similar to the second example of the second embodiment.

As shown in FIG. 28, in the anodization apparatus 1 of the present example, the electrolyte B supply unit 12 and the pipes 16 and 17 are omitted from the configuration of the first example of the fifth embodiment (FIG. 24). The electrolyte A mixing tank 20 of the electrolyte A supply unit 11 is coupled to the process tank 101 of the anodization process unit 10 via the pipe 15.

As shown in FIG. 29, the anodization process unit 10 includes the process tanks 101 and 111, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108.

The process tank 101, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107 are the same as those in the second example of the second embodiment shown in FIG. 11. Similarly to the second example of the second embodiment, in the present example, the upper electrode 104 is coupled to the current source 40 via the switch SW1. The upper electrode 106 is coupled to the current source 40 via the switch SW2.

In the present example, the area surrounded by the lower surfaces of the upper electrodes 104 and 106, the upper surface of the semiconductor substrate 1000, and the side surfaces of the retainer 108 corresponds to the process tank 111. In other words, the process tank ill is provided between the upper electrodes 104 and 106 and the process tank 101.

5.4 Fourth Example

Next, the fourth example will be described. In the fourth example, the configuration of the anodization process unit 10 differing from the third example will be described with reference to FIG. 30. FIG. 30 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A to C. The example of FIG. 30 shows a case where the anodization apparatus 1 has a “divided electrode-multiple power sources-common process tank” configuration, similar to the third example of the second embodiment.

The overall configuration of the anodization apparatus 1 in the present example is the same as the third example of the fifth embodiment shown in FIG. 28.

As shown in FIG. 30, the anodization process unit 10 includes the process tanks 101 and 111, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108.

The process tank 101, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107 are the same as those in the third example of the second embodiment shown in FIG. 13. Similarly to the third example of the second embodiment, the upper electrode 104 is coupled to the current source 40. The upper electrode 106 is coupled to the current source 41.

The configuration of the process tank 111 is similar to that of the third example of the fifth embodiment shown in FIG. 29.

5.5 Advantageous Effects of Present Embodiment

According to the configuration of the present embodiment, it is possible to obtain effects similar to those of the first to fourth embodiments.

Furthermore, according to the configuration of the present embodiment, the anodization apparatus supplies an electrolyte between the upper electrode and the semiconductor substrate. It is thereby possible to suppress the size of area where the upper electrode and the semiconductor substrate are in contact. Thus, it is possible to reduce metal contamination of the semiconductor substrate caused by the upper electrode.

Furthermore, according to the configuration of the present embodiment, conduction failure between the upper electrode and the semiconductor substrate can be suppressed through supplying an electrolyte between the upper electrode and the semiconductor substrate.

6. SIXTH EMBODIMENT

Next, the sixth embodiment will be described. In the sixth embodiment, a configuration of the electrolyte C supply unit 61 differing from the first example of the fifth embodiment will be described.

6.1 Overall Configuration

An overall configuration of the anodization apparatus 1 will be described with reference to FIG. 31. FIG. 31 is a block diagram of the anodization apparatus 1.

As shown in FIG. 31, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, the current supply unit 13, the control circuit 14, and a concentration sensor 91.

The anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit 13, and the control circuit 14 are similar to those of the first example of the fifth embodiment shown in FIG. 24.

The electrolyte C supply unit 61 does not have a circulation mechanism, and supplies unused electrolyte C to the anodization process unit 10. In other words, the electrolyte C supply unit 61 produces the electrolyte C in the electrolyte C mixing tank 70 by mixing three liquids G to I.

The pipe 64 is not coupled to the electrolyte C mixing tank 70, and the liquid used in the process tank 111 is drained as a waste liquid.

The concentration sensor 91 monitors a concentration of the waste liquid in the pipe 64, and transmits the monitoring result to the control circuit 14. For example, in the anodization apparatus 1 of the present example, the supply of a new electrolyte C and the drain of the electrolyte C are repeated for every anodization process. However, if it is determined from a result of the monitoring in the concentration sensor 91 that the electrolyte C in the process tank 111 is determined to be reusable in the next anodization process, the anodization apparatus 1 can reuse the electrolyte C in the process tank 111 entirely or partially. If the electrolyte is partially reused, a shortfall of the electrolyte C is supplied from the electrolyte C supply unit 61.

6.2 Advantageous Effects of Present Embodiment

The present embodiment is applicable to the fifth embodiment.

7. SEVENTH EMBODIMENT

Next, the seventh embodiment will be described. In the seventh embodiment, four examples where two types of electrolyte are supplied between the upper electrode and the upper surface of the semiconductor substrate will be described. Hereinafter, the description will focus mainly on matters different from those of the fifth and sixth embodiments.

7.1 First Example

7.1.1 Overall Configuration

First, an overall configuration of the anodization apparatus 1 in the first example will be described with reference to FIG. 32. FIG. 32 is a block diagram of an anodization apparatus. In the example of FIG. 32, the details of the components of the electrolyte A supply unit 11 and the electrolyte B supply unit 12 are omitted.

As shown in FIG. 32, the anodization apparatus 1 includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, an electrolyte D supply unit 62, the current supply unit 13, and the control circuit 14.

The anodization process unit 10 has two process tanks between the upper electrode and the semiconductor substrate 1000. The details of the anodization process unit 10 will be described later.

The configurations of the electrolyte A supply unit 11, the electrolyte B supply unit 12, and the current supply unit 13 are similar to those of the first embodiment shown in FIG. 1.

The configuration of the electrolyte C supply unit 61 is similar to that of the first example of the fifth embodiment shown in FIG. 24. The electrolyte C mixing tank 70 is coupled to the anodization process unit 10 via the pipes 65 and 66. In other words, the electrolyte C supply unit 61 supplies the electrolyte C to the anodization process unit 10 via the pipe 65, and recovers a liquid from the anodization process unit 10 via the pipe 66.

The electrolyte D supply unit 62 supplies an electrolyte D to the process tank provided between the upper electrode in the anodization process unit 10 and the upper surface (the surface not to be anodized) of the semiconductor substrate 1000. The electrolyte D supply unit 62 has a mechanism (not shown; for example, a pump, etc.) for adjusting a liquid pressure of the electrolyte D supplied to the process tank. As the electrolyte D, a solution that almost does not react to the semiconductor substrate 1000 when the anodization process is performed is used, for example. To suppress metal contamination of the semiconductor substrate 1000, it is preferable if the electrolyte D does not contain any metal elements. The electrolyte D may be the same as or differ from the electrolyte C. In the following, the case where the electrolyte D has a concentration (resistance value) different from that of the electrolyte C will be described. The resistance value of the electrolyte D may be higher or lower than the resistance value of the electrolyte C. The resistance values of the electrolytes C and D are adjusted in consideration of the material of the upper electrodes 104 and 106, the effects on the anodization process (influence on the electric field) based on a combination of the electrolytes A to D, and the like. The electrolyte D supply unit 62 of the present embodiment has a function of circulating the electrolyte D between the anodization process unit 10 and an electrolyte D mixing tank 80. In other words, the electrolyte D supply unit 62 adjusts components of the liquid recovered from the anodization process unit 10, and supplies the adjusted liquid once again to the anodization process unit 10.

The electrolyte D supply unit 62 includes an electrolyte D mixing tank 80, a supply control unit 81, a plurality of liquid supply units 82 (in the example shown in FIG. 24, three liquid supply units 82a through 82c), and a concentration monitor 83.

The electrolyte D mixing tank 80 is a tank for producing the electrolyte D by mixing multiple liquids. The electrolyte D supply unit 62 is capable of producing the electrolyte D from the liquid recovered by mixing the anodization process unit 10 through the pipe 64 with the three liquids J to L, and performing concentration adjustment. The liquids used for producing the electrolyte D are not limited to three kinds. An ingredient other than a liquid may be used to produce the electrolyte D. Similarly to the electrolyte C, the electrolyte ID may be, for example, a diluted HF solution that almost does not react to the semiconductor substrate 1000 when the anodization process is performed, a diluted HCl solution, or a non-soluble organic electrolyte. For example, as the ingredients, which is a water-insoluble electrolyte, of the electrolyte D, at least one of acetonitrile propylene carbonate, or dimethylformamide may be selected. As the ingredients, which is a source of fluorides, of the electrolyte D, at least one of anhydrous HF tetrafluoroborate, or lithium fluoroborate may be selected. The produced electrolyte D is supplied to one of the process tanks in the anodization process unit 10 through the pipe 63. The electrolyte D mixing tank 80 has an overflow pipe for draining when a liquid in the tank overflows, for example.

The supply control unit 81 controls an amount of each of the liquids J to L supplied to the electrolyte D mixing tank 80 through the control of the control circuit 14. For example, the supply control unit 81 includes valves and flow meters provided in respective supply lines of the liquids.

The liquid supply units 82a through 82c are respectively coupled to the electrolyte D mixing tank 80 via the respective supply lines. The liquid supply units 82a through 82c supply the liquids J to L respectively to the electrolyte D mixing tank 80 through the supply lines. The liquid supply units 82a through 82c may have a mechanism for compressing and transferring the liquids J to L from their respective containers, for example.

The concentration sensor 83 monitors a concentration of the electrolyte D in the electrolyte D mixing tank 80, and transmits the monitoring result to the control circuit 14. The control circuit 14 controls the supply control unit 81 based on the result of the concentration monitoring, and adjusts the concentration of the electrolyte D. The concentration sensor 83 may measure a resistance value of the electrolyte D.

The control circuit 14 controls the entire anodization apparatus 1. More specifically, the control circuit 14 controls the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, the electrolyte D supply unit 62, and the current supply unit 13.

7.1.2 Detailed Configuration of Anodization Process Unit

Next, an example of the detailed configuration of the anodization process unit 10 will be described with reference to FIG. 33. FIG. 33 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A to D. The example of FIG. 33 shows a case where the anodization apparatus 1 has a “divided electrode-multiple power sources-divided process tank” configuration, similar to the first embodiment.

As shown in FIG. 33, the anodization process unit 10 includes the process tanks 101, 103, 111, and 112, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108. The configurations of the process tanks 101 and 103, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107, are the same as those in the first embodiment shown in FIG. 2. In the example, similarly to the first embodiment, the upper electrode 104 is coupled to the current source 40. The upper electrode 106 is coupled to the current source 41.

In the present example, the upper edge of the process tank 111 is located at the lower surface of the upper electrode 104. The area surrounded by the lower surface of the upper electrode 104, the upper surface of the semiconductor substrate 1000, the side surfaces of the retainer 108, and the side surface of the process tank 112 corresponds to the process tank 111. In other words, the process tank 111 is provided between the upper electrode 104 and the process tank 101.

The process tank 112 has a cylindrical shape, for example. The process tank 112 is arranged concentrically with the process tank 111, for example. The inner diameter of the process tank 112 is smaller than the inner diameter of the process tank 111. For example, the inner diameter of the process tank 112 is approximately the same as the upper electrode 106. The process tank 112 corresponds to the forming of the porous layer 1100. The upper edge of the process tank 112 is in contact with the lower surface of the upper electrode 106. The lower edge of the process tank 112 is located in the vicinity of the upper surface of the semiconductor substrate 1000, and is not in contact with the upper surface of the semiconductor substrate 1000. The area surrounded by the lower surface of the upper electrode 106, the upper surface of the semiconductor substrate 1000, and the side surfaces of the process tank 112 corresponds to the process tank 112. In other words, the process tank 112 is provided between the upper electrode 106 and the process tank 103. A gap GP3 is provided between the lower edge of the process tank 112 and the semiconductor substrate 1000. The side surfaces of the process tank 112 are made of an insulating material having a resistance to the electrolytes C and D. The process tank 112 may be made of the same material as the retainer 108. The pipes 65 and 66 are coupled to the process tank 103. The pipe 65 is a liquid supply line to the process tank 112. The pipe 66 is a liquid drain line from the process tank 112. In the present embodiment, the pipe 65 is coupled to the liquid supply line of the electrolyte C mixing tank 70. The pipe 66 is coupled to the liquid recovery line of the electrolyte C mixing tank 70. A plurality of the pipes 65 and 66 may be provided. Furthermore, a waste liquid drain pipe for draining the liquid in the process tank 112 as a waste liquid may be coupled to the process tank 112.

In the present embodiment, the liquid pressure of each of the electrolytes A and B is set higher than the liquid pressures of the electrolytes C and D (the liquid pressure the electrolytes A+B>the liquid pressure of the electrolytes C+D). For this reason, when the anodization process is performed, the upper surface of the semiconductor substrate 1000 is pressed against the fixing unit 113 by the liquid pressure of the electrolytes A and B.

The liquid pressure of the electrolyte C is set higher than the liquid pressure of the electrolyte D (the liquid pressure of the electrolyte C>the liquid pressure of the electrolyte D). The electrolyte C thereby flows from the process tank 112 into the process tank 111 via the gap GP3 when the anodization process is performed. For example, when the electrolytes A to D are supplied, the liquid pressures of the electrolytes A to D may be in the relationship of A>B>C>D.

7.2 Second Example

Next, the second example will be described. In the second example, the configuration of the anodization process unit 10 differing from the first example will be described with reference to FIG. 34. FIG. 34 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A to D. The example of FIG. 34 shows a case where the anodization apparatus 1 has a “common electrode-single power source-divided process tank” configuration, similar to the first example of the second embodiment.

The overall configuration of the anodization apparatus 1 in the present example is the same as the first example of the seventh embodiment shown in FIG. 32.

As shown in FIG. 34, the anodization process unit 10 includes the process tanks 101, 103, 111, and 112, the vat 102, the upper electrode 104, the lower electrode 107, and the retainer 108.

The process tanks 101 and 103, the vat 102, the upper electrode 104, and the lower electrode 107, are the same as those in the first example of the second embodiment shown in FIG. 8. Similarly to the first example of the second embodiment, a current is supplied from the current supply unit 13 (the current source 40) to the upper electrode 104.

In the present example, the inner diameter of the process tank 111 is approximately the same as the inner diameter of the process tank 103. In other words, the process tank 111 is provided between the area opposed to the process tank 101 of the upper electrode 104, and the process tank 101. The process tank 112 is provided between the area opposed to the process tank 103 of the upper electrode 104, and the process tank 103.

7.3 Third Example

Next, the third example will be described. In the third example, the configuration of the anodization apparatus 1 differing from the first and second examples will be described with reference to FIGS. 35 and 36. FIG. 35 is a block diagram of the anodization apparatus. FIG. 36 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A, C, and D. The example of FIG. 36 shows a case where the anodization apparatus 1 has a “divided electrode-single power source-common process tank” configuration, similar to the second example of the second embodiment.

As shown in FIG. 35, in the anodization apparatus 1 of the present example, the electrolyte B supply unit 12 and the pipes 16 and 17 are omitted from the configuration of the first example of the seventh embodiment (FIG. 32). The electrolyte A mixing tank 20 of the electrolyte A supply unit 11 is coupled to the process tank 101 via the pipe 15.

As shown in FIG. 36, the anodization process unit 10 includes the process tanks 101, 111, and 112, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108.

The process tank 101, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107 are the same as those in the second example of the second embodiment shown in FIG. 11. Similarly to the second example of the second embodiment, in the present example, the upper electrode 104 is coupled to the current source 40 via the switch SW1. The upper electrode 106 is coupled to the current source 40 via the switch. SW2.

In the present example, the upper edge of the process tank 111 is located at the lower surface of the upper electrode 104. The area surrounded by the lower surface of the upper electrode 104, the upper surface of the semiconductor substrate 1000, the side surfaces of the retainer 108, and the side surface of the process tank 112 corresponds to the process tank 111. The upper edge of the process tank 112 is located at the lower surface of the upper electrode 106. The area surrounded by the lower surface of the upper electrode 106, the upper surface of the semiconductor substrate 1000, and the side surfaces of the process tank 112 corresponds to the process tank 112. In other words, the process tank 111 is provided between the upper electrode 104 and the area opposed to the upper electrode 104 of the process tank 101. The process tank 112 is provided between the upper electrode 106 and the area opposed to the upper electrode 106 of the process tank 101.

7.4 Fourth Example

Next, the fourth example will be described. In the fourth example, the configuration of the anodization process unit 10 differing from the third example will be described with reference to FIG. 37. FIG. 37 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A, C, and D. The example of FIG. 37 shows a case where the anodization apparatus 1 has a “divided electrodes-multiple power sources-common process tank” configuration, similar to the third example of the second embodiment.

The overall configuration of the anodization apparatus 1 in the present example is the same as the third example of the seventh embodiment shown in FIG. 35.

As shown in FIG. 37, the anodization process unit 10 includes the process tanks 101, 111, and 112, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108.

The process tank 101, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107, are the same as those in the third example of the second embodiment shown in FIG. 13. Similarly to the third example of the second embodiment, the upper electrode 104 is coupled to the current source 40. The upper electrode 106 is coupled to the current source 41.

The configurations of the process tanks 111 and 112 are similar to those of the third example of the seventh embodiment shown in FIG. 36.

7.5 Advantageous Effects of Present Embodiment

The configuration of the present embodiment can attain the same effect as the sixth embodiment.

Furthermore, with the configuration according to the present embodiment, it is possible to supply the electrolytes C and D having different resistance values respectively to the center portion and the outer peripheral portion of the upper surface of the semiconductor substrate, between the upper electrode group and the semiconductor substrate. Furthermore, in the first, third, and fourth examples, it is possible to respectively supply the electrolytes C and D in accordance with an amount of current supplied to each of the upper electrodes 104 and 106. It is thereby possible to improve the controllability in the forming of the porous layers 1100 and 1200 in the anodization process. Furthermore, the range of voltage control in the upper electrodes can be widened.

Furthermore, power consumption can be reduced through adjusting the resistance values of the electrolytes C and D.

8. EIGHTH EMBODIMENT

Next, the eighth embodiment will be described. In the eighth embodiment, four configuration examples of the electrolyte C supply unit 61 and the electrolyte D supply unit 62 differing from the first example of the seventh embodiment will be described. Hereinafter, the description will focus mainly on matters different from those of the first example of the seventh embodiment.

8.1 First Example

First, an anodization apparatus 1 according to the first example will be described with reference to FIG. 38. FIG. 38 is a block diagram of the anodization apparatus 1. In the first example, differing from the seventh embodiment, the case in which the electrolyte C supply unit 61 and the electrolyte D supply unit 62 do not have a circulation mechanism is described.

As shown in FIG. 38, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, the electrolyte D supply unit 62, the current supply unit 13, the control circuit 14, and concentration sensors 91 and 92.

The anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit 13, and the control circuit 14 are similar to those of the first example of the seventh embodiment shown in FIG. 32.

The electrolyte C supply unit 61 does not have a circulation mechanism, and supplies unused electrolyte C to the anodization process unit 10. In other words, the electrolyte C supply unit 61 produces the electrolyte C in the electrolyte C mixing tank 70 by mixing three liquids G to I.

Similarly to the electrolyte C supply unit 61, the electrolyte D supply unit 62 does not have a circulation mechanism, and supplies unused electrolyte D to the anodization process unit 10. In other words, the electrolyte D supply unit 62 produces the electrolyte D in the electrolyte D mixing tank 80 by mixing three liquids J to L.

The pipe 64 is not coupled to the electrolyte D mixing tank 80, and the liquid used in the process tank 111 is drained as a waste liquid.

The pipe 66 is not coupled to the electrolyte C mixing tank 70, and the liquid used in the process tank 112 is drained as a waste liquid.

The concentration sensor 91 monitors a concentration of the waste liquid in the pipe 66, and transmits the result to the control circuit 14. The concentration sensor 92 monitors a concentration of the waste liquid in the pipe 64, and transmits the result to the control circuit 14. For example, in the anodization apparatus 1 of the present example, the supply of new electrolytes C and D and the draining of the electrolytes C and D are repeated for every anodization process. However, if it is determined from a result of the monitoring in the concentration sensor 91 that the electrolyte C in the process tank 112 is determined to be reusable in the next anodization process, the anodization apparatus 1 can reuse the electrolyte C in the process tank 112 entirely or partially. Similarly, if it is determined from a result of the monitoring in the concentration sensor 92 that the electrolyte D in the process tank 111 is determined to be reusable in the next anodization process, the anodization apparatus 1 can reuse the electrolyte D in the process tank 111 entirely or partially. If the electrolyte is partially reused, a shortfall of each of the electrolytes C and D is supplied from each of the electrolyte C supply unit 61 and the electrolyte D supply unit 62.

8.2 Second Example

Next, an anodization apparatus 1 according to the second example will be described with reference to FIG. 39. FIG. 39 is a block diagram of the anodization apparatus 1. In the second example, the case in which the electrolyte C supply unit 61 and the electrolyte D supply unit 62 circulate the liquid from the process tank 111 is described.

As shown in FIG. 39, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, the electrolyte D supply unit 62, the current supply unit 13, and the control circuit 14.

The anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit and 13, and the control circuit 14 are similar to those of the first example of the seventh embodiment shown in FIG. 32.

The electrolyte C supply unit 61 is similar to that of the first example of the seventh embodiment shown in FIG. 32. In the present example, the electrolyte C supply unit 61 recovers a liquid from the process tank 111 via the pipe 64. The electrolyte C supply unit 61 is capable of producing the electrolyte C by mixing the liquid (a mixed liquid of the electrolytes C and D) recovered from the process tank 111 via the pipe 64 with the three liquids G to I, and of adjusting the concentration of the electrolyte C through the mixing process. Although the pipe 66 is not shown in the present example, the pipe 66 may be omitted or used as a waste liquid drain line of the process tank 112.

The electrolyte D supply unit 62 is similar to that of the first example of the seventh embodiment shown in FIG. 32. The electrolyte D supply unit 62 recovers a liquid from the process tank 111 via the pipe 64, similarly to the electrolyte C supply unit 61.

8.3 Third Example

Next, an anodization apparatus 1 according to the third example will be described with reference to FIG. 40. FIG. 40 is a block diagram of the anodization apparatus 1. In the third example, the case in which the electrolyte C supply unit 61 does not have a circulation mechanism and the electrolyte D supply unit 62 has a circulation mechanism is described.

As shown in FIG. 40, the anodization apparatus 1 of the present example includes the anodization process unit 10, an electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, the electrolyte D supply unit 62, the current supply unit 13, the control circuit 14, and the concentration sensor 91.

The anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte D supply unit 62, the current supply unit 13, and the control circuit 14 are similar to those of the first example of the seventh embodiment shown in FIG. 32.

The electrolyte C supply unit 61 and the concentration sensor 91 are similar to those of the first example of the eighth embodiment shown in FIG. 38.

8.4 Fourth Example

Next, an anodization apparatus 1 according to the fourth example will be described with reference to FIG. 41. FIG. 41 is a block diagram of the anodization apparatus 1. In the fourth example, the case in which the electrolyte C supply unit 61 has a circulation mechanism and the electrolyte D supply unit 62 does not have a circulation mechanism is described.

As shown in FIG. 41, the anodization apparatus 1 of the present example includes the anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the electrolyte C supply unit 61, the electrolyte D supply unit 62, the current supply unit 13, and the control circuit 14.

The anodization process unit 10, the electrolyte A supply unit 11, the electrolyte B supply unit 12, the current supply unit 13, and the control circuit 14 are similar to those of the first example of the seventh embodiment shown in FIG. 32.

The electrolyte C supply unit 61 is similar to that of the second example of the eighth embodiment shown in FIG. 39. In the present example, the electrolyte C supply unit 61 recovers a liquid from the process tank 111 via the pipe 64. In the present example, the electrolyte C supply unit 61 recovers a liquid (a mixed liquid of the electrolyte C and the electrolyte D) from the process tank 111 via the pipe 64; however, the electrolyte C supply unit 61 may recover a liquid (the electrolyte C) from the process tank 112 via the pipe 66. In this case, for example the pipe 64 coupled to the process tank 111 may be used as a waste liquid drain line of the process tank 111.

The electrolyte D supply unit 62 is similar to that of the first example of the eighth embodiment shown in FIG. 38. In the case where the electrolyte C supply unit 61 recovers a liquid (the electrolyte C) from the process tank 112 via the pipe 66, namely a case where the pipe 66 is used as the liquid recovery line, the anodization apparatus 1 may have a concentration sensor 92 explained in the first example of the sixth embodiment. If it is determined from a result of the monitoring in the concentration sensor 92 that the electrolyte D in the process tank 111 is determined to be reusable in the next anodization process, the anodization apparatus 1 can reuse the electrolyte D in the process tank 111 entirely or partially.

8.5 Advantageous Effects of Present Embodiment

The present embodiment is applicable to the seventh embodiment.

9. NINTH EMBODIMENT

Next, the ninth embodiment will be described. In the ninth embodiment, two configuration examples of the retainer 108 differing from the fifth through seventh embodiments will be described. Hereinafter, the description will focus mainly on matters different from those of the fifth and seventh embodiments.

9.1 First Example

First, the first example is described. In the first example, the case where the retainer 108 has two vertically arranged fixing units 113a and 113b will be described with reference to FIGS. 42 through 45. FIG. 42 is a cross-sectional view of the anodization process unit 10 in a state of being supplied with the electrolytes A to C. FIG. 43 is a top view of the fixing unit 113a. FIGS. 44 and 45 are enlarged views of the region RA shown in FIG. 42. FIG. 44 shows the locations of the fixing units 113a and 113b when the semiconductor substrate 1000 is set in the anodization apparatus 1. FIG. 45 shows the locations of the fixing units 113a and 113b when the anodization process is performed.

As shown in FIG. 42, the anodization process unit 10 includes the process tanks 101, 103, and 111, the vat 102, the upper electrodes 104 and 106, the insulator 105, the lower electrode 107, and the retainer 108. The process tanks 101, 103, and 111, the vat 102, the upper electrodes 104 and 106, the insulator 105, and the lower electrode 107, are the same as those in the first example of the seventh embodiment. The configuration of the anodization process unit 10 may be any of the configurations described in the fifth through seventh embodiments.

The retainer 108 includes a plurality of the fixing unit 113a and a plurality of the fixing unit 113b. The cross-sectional shapes of the fixing units 113a and 113b may be a triangle. The shape of the fixing units 113a and 113b is discretionarily determined. The cross-sectional shapes of the fixing units 113a and 113b are preferably in a shape capable of holding the semiconductor substrate 1000 and having less area in contact with the semiconductor substrate 1000.

The fixing units 113a and 113b are located at different heights on the side surfaces of the retainer 108. For example, the fixing unit 113a is located further up on the edge side of the retainer 108 (the side closer to the upper electrode 104) than the fixing 113b. The fixing units 113a and 113b are movable so that they are in a state of projecting toward the inner surface of the retainer 108 (hereinafter “projecting state”) and a state of being retracted inside of the retainer 108 (hereinafter “retracting state”).

As shown in FIG. 43, three fixing units 113a are located, for example, at places rotated by 120 degrees with respect to the center of the retainer 108. The example of FIG. 43 shows a case when the fixing unit 113a is in the projecting state. The fixing unit 113a has a rectangular shape, for example, when viewed from the top. Thus, the fixing unit 113a may have a conical or pyramidal shape, for example. The number of the fixing unit 113a can be discretionarily determined. When the anodization process is performed, at least three fixing units 113a should be provided to fix the semiconductor substrate 1000.

The same is applicable to the fixing unit 113b. The shape, the number, and the arrangement of the fixing unit 113b may differ from those of the fixing unit 113a.

Next, the operations of the fixing units 113a and 113b will be described.

As shown in FIG. 44, when the semiconductor substrate 1000 is set in the inside of the retainer 108 for example, the fixing unit 113a is set to a retracting state, and the fixing unit 113b is set to a projecting state. Thus, when the semiconductor substrate 1000 is set from the top of the retainer 108, the fixing unit 113b holds the lower surface of the semiconductor substrate 1000 to stop the semiconductor substrate 1000 from falling. As shown in FIG. 45, for example, the fixing unit 113a is set to a projecting state and the fixing unit 113b is set to a retracting state when the anodization process is performed. Thus, the semiconductor substrate 1000 is pressed against the fixing unit 113a from the bottom, and the location can be fixed.

9.2 Second Example

Next, the second example will be described. In the second example, the case where an elastic material is used for the retainer 108 is described with reference to FIG. 46. FIG. 46 is a conceptual diagram of the arrangement of the retainer 108 and the semiconductor substrate 1000.

As shown in FIG. 46, in the case of using an elastic material for the retainer 108, when the tip of the semiconductor substrate 1000 is pressed against the retainer 108, the sealing between the retainer 108 and the semiconductor substrate 1000 is improved. The retainer 108 may be in contact entirely or partially with the outer periphery of the semiconductor substrate 1000.

9.3 Advantageous Effects of Present Embodiment

The configuration of the present embodiment is applicable to the fifth through eighth embodiments.

The first and second examples of the present embodiment may be combined.

10. MODIFICATIONS

An anodization apparatus according to above embodiments includes: a first process tank (101) used for an anodization process on a first portion (1200) of a substrate (1000); a second process tank (103) provided inside of the first process tank and used for the anodization process on a second portion (1100) of the substrate; a first electrolyte supply unit (12) configured to supply a first electrolyte (B) to the first process tank; a second electrolyte supply unit (11) configured to supply a second electrolyte (A) to the second process tank; a retainer (108) configured to retain the substrate; a first electrode (104) provided above the first process tank and/or the second process tank; and a second electrode (107) provided below the first process tank and the second process tank.

Through applying the foregoing embodiments, it is possible to form a plurality of porous layers having different film qualities on the substrate surface.

The embodiments are not limited to the above-described aspects, but can be modified in various ways.

For example, in the foregoing embodiments, the anodization apparatus that forms two porous layers having different film qualities in the center portion and the outer peripheral portion of the semiconductor substrate surface has been described; however, the anodization apparatus may form porous layers having three or more different types of film quality. More specifically, in the anodization apparatus 1, three or more upper electrodes may be provided in a concentric manner for example, or three or more process tanks may be provided in a concentric manner.

The state of being “coupled” in the foregoing embodiments includes a state of being coupled with something else indirectly interposed.

The expression “approximately the same” in the foregoing embodiments includes errors to the extent that the formation of porous layers when the anodization process is performed is not affected.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

1. An anodization apparatus comprising:

a first process tank used for an anodization process on a first portion of a substrate;

a second process tank provided inside of the first process tank and used for the anodization process on a second portion of the substrate;

a first electrolyte supply unit configured to supply a first electrolyte to the first process tank;

a second electrolyte supply unit configured to supply a second electrolyte to the second process tank;

a holding part configured to hold the substrate;

a first electrode provided above the first process tank and/or the second process tank; and

a second electrode provided below the first process tank and the second process tank.

2. The anodization apparatus according to claim 1, further comprising a third electrode provided inside the first electrode,

wherein the first electrode is opposed to the first process tank and the third electrode is opposed to the second process tank.

3. The anodization apparatus according to claim 1, wherein

the first electrolyte supply unit is configured to produce the first electrolyte using at least a first liquid,

the first electrolyte supply unit includes: a first mixing tank configured to store the first electrolyte; a first concentration sensor configured to monitor a concentration of the first electrolyte in the first mixing tank; and a first supply controller configured to control a supply of the first liquid to the first mixing tank based on the first concentration sensor.

4. The anodization apparatus according to claim 3, wherein

the first electrolyte supply unit is configured to produce the first electrolyte using a second liquid recovered from the first process tank.

5. The anodization apparatus according to claim 1, wherein

the second electrolyte supply unit is configured to produce the second electrolyte using at least a third liquid,

the second electrolyte supply unit includes: a second mixing tank capable of storing the second electrolyte: a second concentration sensor configured to monitor a concentration of the second electrolyte in the second mixing tank; and a second supply controller configured to control a supply of the third liquid to the second mixing tank based on the second concentration sensor.

6. The anodization apparatus according to claim 5, wherein

the second electrolyte supply unit is configured to use a fourth liquid recovered from the first process tank to produce the second electrolyte.

7. The anodization apparatus according to claim 5, wherein

the second electrolyte supply unit is configured to produce the second electrolyte using a fifth liquid recovered from the second process tank.

8. The anodization apparatus according to claim 1, wherein

the first and second process tanks have a cylindrical shape, and an inner diameter of the second process tank is smaller than that of the first process tank.

9. The anodization apparatus according to claim 2, further comprising:

a first current source configured to supply a first current to the first electrode; and

a second current source configured to supply a second current to the third electrode.

10. The anodization apparatus according to claim 2, further comprising:

a third current source;

a first switch configured to electrically couple the third current source to the first electrode; and

a second switch configured to electrically couple the third current source to the third electrode.

11. The anodization apparatus according to claim 1, further comprising:

a third process tank provided between the first process tank and the first electrode, and/or between the second process tank and the first electrode; and

a third electrolyte supply unit configured to supply a third electrolyte to the third process tank.

12. The anodization apparatus according to claim 11, wherein

the third electrolyte supply unit is configured to produce the third electrolyte using at least a sixth liquid,

the third electrolyte supply unit includes: a third mixing tank configured to store the third electrolyte; a third concentration sensor configured to monitor a concentration of the third electrolyte in the third mixing tank; and a third supply controller configured to control a supply of the sixth liquid to the third mixing tank based on a result of the third concentration sensor.

13. The anodization apparatus according to claim 12, wherein

the third electrolyte supply unit is configured to produce the third electrolyte using a seventh liquid recovered from the third process tank.

14. The anodization apparatus according to claim 2, further comprising:

a third process tank provided between the second process tank and the first electrode;

a fourth process tank provided between the first process tank and the third electrode;

a third electrolyte supply unit configured to supply a third electrolyte to the third process tank; and

a fourth electrolyte supply unit configured to supply a fourth electrolyte to the fourth process tank.

15. The anodization apparatus according to claim 14, wherein

the third electrolyte supply unit is configured to produce the third electrolyte using at least a sixth liquid,

the third electrolyte supply unit includes: a third mixing tank configured to store the third electrolyte; a third concentration sensor configured to monitor a concentration of the third electrolyte in the third mixing tank; and a third supply controller configured to control a supply of the sixth liquid to the third mixing tank based on the third concentration sensor.

16. The anodization apparatus according to claim 15, wherein

the third electrolyte supply unit is configured to produce the third electrolyte using a seventh liquid recovered from the third process tank.

17. An anodization apparatus comprising:

a first process tank used for an anodization process on a substrate;

a first electrolyte supply unit configured to supply a first electrolyte to the first process tank;

a holding part configured to hold the substrate;

a first electrode provided above the first process tank;

a second electrode provided inside the first electrode; and

a third electrode opposed to the first and second electrodes and provided below the first process tank.

18. The anodization apparatus according to claim 17, further comprising:

a third process tank provided between the first process tank and the first electrode, and between the first process tank and the second electrode; and

a third electrolyte supply unit configured to supply a third electrolyte to the third process tank.

19. The anodization apparatus according to claim 17, further comprising:

a third process tank provided between the first process tank and the first electrode;

a fourth process tank provided between the first process tank and the second electrode;

a third electrolyte supply unit configured to supply a third electrolyte to the third process tank; and

a fourth electrolyte supply unit configured to supply a fourth electrolyte to the fourth process tank.