Substrate mounting apparatus and control method of substrate temperature

- NGK Insulators, Ltd.

A substrate mounting apparatus, comprises a ceramic base having a substrate mounting surface, and a jointing layer, which is formed on an opposite surface to the substrate mounting surface of the ceramic base, and has jointing materials differing in a thermal conductivity by in-plane regions and arranged in the regions.

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Description
CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. P2004-191106, filed on Jun. 29, 2004; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate mounting apparatus and a control method of substrate temperature.

2. Description of the Related Art

In a semiconductor manufacturing process and a liquid crystal display manufacturing process, a substrate mounting apparatus such as a susceptor, an electrostatic chuck, or a ceramic heater with a heating element is used to mount a substrate such as a silicon wafer or a glass substrate.

In semiconductor manufacturing processes, temperature distribution in a substrate surface causes in-plane variation of the substrate in quality of formed thin films and in etching characteristics. Therefore, the substrate surface having uniform temperature distribution is desired. However, the temperature distribution in the substrate surface is significantly affected by not only temperature distribution of the substrate mounting apparatus such as a ceramic heater, but also use environment such as heat input distribution due to plasma.

Therefore, even if temperature distribution in the substrate mounting surface of the substrate mounting apparatus itself is controlled to be uniform, it is difficult to obtain uniform temperature distribution in the actual substrate surface due to external factors. Accordingly, to optimize the temperature distribution of the substrate, optimization of plasma conditions and adjustments of shape and material arranged around the substrate mounting apparatus are carried out.

An electrostatic chuck having a substrate mounting surface, which is controlled for an unevenness by location based on heat input distribution due to plasma has been proposed (Japanese patent application laid-open Hei 7-18438). In addition, a multi-zone heater, in which ceramic base constituting a substrate mounting surface is divided into multiple zones, heating elements are buried in the respective zones, and control heating values of heating elements respectively has been proposed (Japanese patent application laid-open 2001-52843).

However, there is a limited effective control range for conventional optimization of the temperature distribution of the substrate through optimization of plasma conditions, adjustments of shape and material arranged around the substrate mounting apparatus, and control of the unevenness of the substrate mounting surface.

On the other hand, according to a technique of burying optimal heating elements for respective zones with consideration of expected plasma irradiation conditions, heater design is great burden and cost of a substrate mounting apparatus is high. Moreover, after manufacturing a substrate mounting apparatus, since it is difficult to correct the substrate mounting apparatus in accordance with changes in use environments, it does not have general versatility. Furthermore, in the case of a required substrate temperature being relatively low, since substrates need to be cooled rather than being heated by a heater, control of the temperature distribution of a substrate surface is desired using a mechanism without a heater.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a substrate mounting apparatus and a control method of substrate temperature, which can control temperature distribution of a substrate and are simple and versatile.

A substrate mounting apparatus according to an embodiment of the present invention comprises a ceramic base having a substrate mounting surface, and a jointing layer, which is formed on an opposite surface to the substrate mounting surface of the ceramic base, and has jointing materials differing in a thermal conductivity by in-plane regions and arranged in the regions.

According to the substrate mounting apparatus, the temperature distribution of a substrate mounted on the substrate mounting surface can be controlled with simple structure.

According to a control method of substrate temperature of an embodiment of the present invention comprises controlling temperature distribution of a substrate mounted on a ceramic base by controlling in-plane thermal conductivity distribution of a jointing layer formed on an opposite surface to a substrate mounting surface of the ceramic base.

According to the control method of substrate temperature, the temperature distribution of a substrate mounted on the substrate mounting surface can be controlled with a simple and versatile way.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1A is a cross-section view of a substrate mounting apparatus according to an embodiment of the present invention, and FIG. 1B is a plane view of a jointing layer thereof;

FIGS. 2A and 2B are plane views showing distributions of jointing materials in jointing layers according to an embodiment of the present invention;

FIGS. 3A and 3B are cross-sectional views showing a substrate mounting apparatus according to another embodiment of the present invention;

FIGS. 4A is a cross-sectional view taken along line 4a-4a of FIG. 4B of a substrate mounting apparatus according to another embodiment of the present invention, and FIG. 4B is a plane view thereof;

FIG. 5 is a graph showing simulation results of temperature distribution in a substrate mounting surface of a substrate mounting apparatus using aluminum nitride as a ceramic base according to an embodiment of the present invention;

FIG. 6 is a graph showing simulation results of temperature distribution in a substrate mounting surface of a substrate mounting apparatus using alumina as a ceramic base according to an embodiment of the present invention;

FIG. 7 shows an apparatus for an evaluation of substrate mounting apparatuses according to a first and a second working examples of the present invention; and

FIG. 8 is a graph showing measurement results of temperature distribution of a substrate mounted on a mounting apparatus according to the first and the second working example of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1A shows a cross-section of a substrate mounting apparatus 1 according to an embodiment of the present invention. The substrate mounting apparatus 1 comprises a ceramic base 10 and a jointing layer 20. The ceramic base 10 has a substrate mounting surface 10a. Specifically, one surface of the platy ceramic base 10 is a substrate mounting surface 10a. The jointing layer 20 is formed on the other surface of the ceramic base 10, i.e., the opposite surface to the substrate mounting surface 10a. The jointing layer 20 is divided into multiple regions in its plane.

More specifically, the jointing layer 20 is divided into multiple regions in the same plane extending direction as the substrate mounting surface 10a extending direction. Jointing materials differing in a thermal conductivity by the in-plane regions are arranged in respective regions. It is preferable that the substrate mounting apparatus 1 comprises a base plate 30 joined to the ceramic base 10 with the jointing layer 20 interposed between the base plate 30 and the ceramic base 10, as shown in FIG. 1A. The base plate 30 is a platy pedestal.

According to the substrate mounting apparatus 1, the in-plane thermal conductivity distribution of the jointing layer 20 arranged on the opposite surface to the substrate mounting surface 10a of the ceramic base 10 can be controlled. Therefore, cooling efficiency due to heat transfer from a substrate mounted on the substrate mounting surface 10a to the ceramic base 10 and the jointing layer 20 can be changed by location. Accordingly, the in-plane temperature distribution of the substrate mounted on the ceramic base 10 can be controlled.

Moreover, joining of the base plate 30 to the ceramic base 10 with the jointing layer 20 allows thermal conduction to the base plate 30 from the substrate via the jointing layer 20, thereby radiating heat. Therefore, the substrate can be cooled more effectively. As a result, an effect of a temperature control function by controlling the in-plane thermal conductivity distribution of the jointing layer 20 can enhance.

FIG. 1B shows a plane view of the jointing layer 20. The jointing layer 20 is divided into two regions, which are a central part and an peripheral part in a plane. In other words, a plurality of regions are the central part and the peripheral part in a plane. A first jointing material 20B is arranged in the central part. A second jointing material 20A differing in a thermal conductivity from the first jointing material is arranged in the peripheral part. This allows control of the in-plane thermal conductivity distribution of the jointing layer 20.

When using the substrate mounting apparatus 1 in a plasma processing apparatus such as a plasma CVD apparatus or a plasma dry etching apparatus, the temperature distribution in the substrate surface is a higher temperature in the peripheral part of the substrate than in the central part. This is attributed to the fact that a temperature in the peripheral part of the substrate surface tends to be higher than that in the central part of the substrate surface due to influence of plasma intensity distribution and apparatus structure. Accordingly, when using the substrate mounting apparatus 1 in such an environment, a jointing material having a low thermal conductivity is arranged as the first jointing material 20B in the central part of the jointing layer 20. A jointing material having a higher thermal conductivity than that of the first jointing material 20B is arranged as the second jointing material 20A in the peripheral part of the jointing layer 20.

According to arranging a jointing material having a high thermal conductivity in the peripheral part, the peripheral part of the substrate where the substrate temperature tends to be easily high, can be effectively cooled. Therefore, an excessive temperature rising can be prevented. Moreover, according to arranging a jointing material having a low thermal conductivity in the central part, cooling the substrate can be suppressed in the central part of the substrate where the substrate temperature tends to be easily low. As a result, uneven temperature distribution of the substrate surface due to the plasma intensity distribution and apparatus structure can be corrected, providing a uniform temperature distribution of the substrate surface.

In FIGS. 1A and 1B, the jointing layer 20 is divided into two regions, which are the central part and the peripheral part, and the first jointing material 20B and the second jointing material 20A differing in a thermal conductivity are arranged in the central part and the peripheral part, respectively, however, the jointing layer may be divided into three regions as shown in FIG. 2A. More specifically, the jointing layer may be divided into a central part, a peripheral part, and an intermediate part between the central part and the peripheral part. Then the first jointing material 20B may be arranged in the central part, the second jointing material 20A may be arranged in the peripheral part, and the third jointing material 20C may be arranged in the intermediate part. For example, jointing materials may be arranged in such a manner that the further inward the region, the lower the thermal conductivity. In other words, a jointing material having a low thermal conductivity may be arranged as the first jointing material 20B, a jointing material having a higher thermal conductivity than the first jointing material 20B may be arranged as the third jointing material 20C, and a jointing material having a higher thermal conductivity than the third jointing material 20C may be arranged as the second jointing material 20A. Alternatively, the number of divided regions may be increased as necessary.

Note that the temperature distribution in the substrate surface is not limited to a distribution having low temperature in the central part of the substrate and high temperature in the peripheral part thereof, and may be a variety of distributions due to use conditions and apparatus structure. Therefore, it is desired to control the in-plane thermal conductivity distribution of the jointing layer in accordance with the temperature distribution in the substrate surface.

Moreover, a form of dividing regions for the jointing layer 20 is not limited to concentrically dividing from the center. A variety of dividing forms may be used based on the necessary temperature control conditions. For example, when the substrate mounting apparatus has through-holes for lift pins and a purge gas, the temperatures of the substrate surface corresponding to regions where through-holes are formed, may be locally high or low. In this case, to correct local changes in temperature, jointing materials having a different thermal conductivity from that of surrounding regions may be arranged in the regions of the jointing layer corresponding to the through-holes, as shown in FIG. 2B.

For example, when the jointing layer has the first jointing material 20B in the central part and the second jointing material 20A in the peripheral part, the third jointing material 20D differing in a thermal conductivity from the first jointing material 20B may be arranged in the regions corresponding to the through-holes in the first jointing material 20B in the central part. In addition, when a temperature of a part of the substrate tends to easily drop due to influence of an exhaust port or other components in a semiconductor manufacturing apparatus in which the substrate mounting apparatus 1 is arranged, jointing materials having a low thermal conductivity may be arranged in regions of the jointing layer 20 corresponding to regions where the temperature tends to easily drop.

According to such controlling method of the in-plane thermal conductivity distribution of the jointing materials in the jointing layer 20, the temperature distribution in the substrate surface can be controlled with a simple way. Moreover, the jointing layer 20 can be easily removed by using an organic jointing material.

Therefore, modification of thermal conductivity distribution in the jointing layer 20 can be easily provided according to changes in use environment for the substrate mounting apparatus 1. Therefore, the substrate mounting apparatus 1 has high versatility.

FIGS. 3A and 3B show substrate mounting apparatus 2 and 3 according to other embodiments. As shown in FIG. 3A, it is preferable that the substrate mounting apparatus 2 includes an electrostatic chuck electrode 40 buried in the ceramic base 10 and thereby having an electrostatic chuck function. The substrate mounting apparatus 2 can improve heat transfer efficiency from the substrate mounting apparatus 2 to a substrate by closely fixing the substrate to a mounting surface of the ceramic base 10 using the electrostatic chuck function. Therefore, accurate control of the temperature distribution of the substrate is possible.

In addition, as shown in FIG. 3B, a substrate mounting apparatus 3 including a resistance heating element 50 and electrostatic chuck electrode 40 buried in the ceramic base 10 may be provided. Alternatively, burying only resistance heating element 50 in the ceramic base 10 without burying the electrostatic chuck electrode 40 is possible. The substrate mounting apparatus 3 having the resistance heating element 50 can serve as a heater. Therefore, the substrate mounting apparatus 3 can raise substrate temperature. Furthermore, using a multi-zone heater, which can set temperatures of respective regions as the resistance heating elements 50, allows control of temperature over a wider range.

Furthermore, as shown in FIG. 3B, a base plate 30a may include a cooling unit. The base plate 30a includes a coolant flow channel 60 through which coolant 10 circulates as a cooling unit. A substrate mounting apparatus having such a cooling unit may be used for, for example, a radio frequency plasma processing apparatus or the like to lower the substrate temperature heightened through plasma irradiation.

Moreover, a substrate mounting apparatus can improve in-plane temperature distribution control function by combining a means controlling in-plane temperature distribution of a substrate. As shown in FIGS. 4A and 4B, for example, the ceramic base 10 may have multiple protrusions on a substrate mounting surface 10a. Moreover, protrusions are formed such that contact area of each of the protrusions with a mounted substrate can differ for every region. In other words, contact areas of the protrusions with the substrate differ by location. This allows further control of in-plane temperature distribution of the substrate. Note that those contact areas correspond to areas of top surface of respective protrusions.

In the case of using a substrate mounting apparatus 4 in a plasma processing apparatus, when the surface temperature of the central part of the substrate is low and that of the peripheral part thereof is high, protrusions 70C each having a small contact area with the substrate are formed in the central part of the substrate mounting surface 10a of the ceramic base 10, as shown in FIGS. 4A and 4B, for example. Protrusions 70B each having a larger contact area than each protrusion 70C are formed surrounding the protrusions 70C. Protrusions 70A each having a larger contact area with the substrate than protrusion 70B are formed in the periphery of the protrusions 70B. In other words, the peripheral part of the substrate mounting surface 10a has larger contact areas than the central part thereof. Since the contact areas of the protrusions 70C in the central part of the substrate mounting surface 10a with a substrate are small, cooling effects due to heat transfer can be suppressed. Since the contact areas of the protrusions 70A in the peripheral part of the substrate mounting surface 10a with the substrate are large, cooling effects due to heat transfer can be advanced. As a result, uneven temperature distribution of the substrate due to plasma intensity distribution and the apparatus structure can be corrected.

Here, the substrate mounting surface 10a is concentrically divided into three regions, and protrusions 70A,70B and 70C each having a predetermined contact area, are formed in respective regions. However, dividing form of the substrate mounting surface may change into a various forms according to temperature of the substrate surface, use conditions or the like. For example, protrusions each having a large contact area with a substrate may be formed in the central part of the substrate mounting surface, while protrusions each having a small contact area with the substrate may be formed in the peripheral part. This structure is opposite to that in FIG. 4B. In other words, the contact area in the central part of the substrate mounting surface is larger than that in the peripheral part thereof.

In this manner, controlling the contact area distribution of the protrusions on the substrate mounting surface 10a in addition to controlling the in-plane temperature distribution of the jointing layer 20 can be carried out. This can fine adjust the temperature distribution of the substrate. Therefore, a desired accurate temperature distribution can be provided.

Next, materials of the substrate mounting apparatus are described. The ceramic base 10 may be made of a variety of ceramics. For example, oxide ceramics such as alumina (Al2O3), nitride ceramics such as aluminum nitride (AlN) silicon nitride (Si3N4), boron nitride (BN), or sialon, or carbide ceramics such as silicon carbide (SiC) may be used as a dense sintered body. Aluminum nitride can be preferably used, since it has high corrosion resistance and a high thermal conductivity.

Note that the shape of the ceramic base 10 may be selected from a variety of shapes according to the size and the shape of substrates to be mounted. The shape of the substrate mounting surface is not limited to circular form, and alternatively, it may be rectangle or polygon.

Moreover, the material of the base plate 30 is not limited either. It is preferable that the base plate 30 is made of metallic material or composite material including metal and ceramics, which has a relatively high thermal conductivity, for example. The base plate 30 may be made of, for example, Al, Cu, brass, SUS or the like.

The ceramic material included in the composite material is not limited. A porous ceramic or the like having the same or different as from the ceramic base 10 may be used. For example, alumina, aluminum nitride, silicon carbide, silicon nitride, sialon, or the like may be used. Meanwhile, it is preferable that a metal filled in the porous ceramic material has high corrosion resistance and is easy to fill. For example, alumina, alloy of alumina and silicon, or the like may be used. Furthermore, it is preferable that the base plate 30 has a cooling unit such as a coolant flow channel 60.

An organic jointing material or an inorganic jointing material such as inorganic glass may be used as the jointing material constituting the jointing layer 20. However, it is preferable to use an organic jointing material as the jointing material. It is further preferable to use a jointing material having a low jointing temperature. According to this, the difference in thermal expansion between the base plate 30 and the ceramic base 10 decreases.

In the substrate mounting apparatus 1, the jointing layer 20 is divided into multiple regions in a plane. Jointing materials differing in a thermal conductivity by regions are used. For example, jointing materials differing in composition may be used in respective regions. Alternatively, a jointing material made of an organic base material such as a resin base material including filler may be used. In other words a jointing material may include a resin base material and filler added to the resin base material. Then, a desired thermal conductivity may be provided by controlling the content of the filler. For example, it is preferable to use a resin such as polyimide resin, silicone resin, or acrylic resin as a base material and add filler such as alumina, aluminum nitride, titanium boride, or aluminum thereto. In particular, it is preferable to use acrylic resin as a base material.

The thermal conductivity of the jointing material is not limited. For example, in the case of arranging a jointing material having a high thermal conductivity in one region and a jointing material having a low thermal conductivity in the other region, the high thermal conductivity may be about 1.1 to about 100 times the low thermal conductivity. Alternatively, a jointing material having more than 100 times the low thermal conductivity may be used as necessary.

Note that to facilitate handling in a manufacturing process, a sheet of an organic jointing material or an adhesive sheet, which is an organic adhesive is applied to both sides of an organic resin sheet may be used as the jointing layer 20.

When using the ceramic base 10 having the electrostatic chuck electrodes 40 buried therein as shown in FIG. 3A, Coulomb's force between the electrostatic chuck electrode 40 and a substrate, or Johnsen-Rahbeck force between a surface of the ceramic base 10 and the substrate may be used as an electrostatic chucking mechanism. In the case of using Coulomb's force, it is preferable that the resistivity of the ceramic base 10, more specifically, the resistivity of the dielectric layer between the substrate mounting surface and the electrostatic chuck electrode 40 is equal to or greater than about 1014 Ω·cm at a working temperature and a thickness of the dielectric layer is equal to or less than about 0.5 mm. On the other hand, in the case of using Johnsen-Rahbeck force, it is preferable that the resistivity of the dielectric layer is about 107 Ω·cm to about 1012 Ω·cm at a working temperature and a thickness of the dielectric layer is about 0.2 mm to about 5 mm.

The electrostatic chuck electrode 40 may be made of a refractory conductive material such as molybdenum (Mo), tungsten (W), molybdenum carbide (MoC), or tungsten carbide (WC), and form thereof is not limited. For example, the electrostatic chuck electrode 40 may be a filmy electrode formed by printing, drying, and sintering a metallic paste, or a predetermined patterned electrode formed by etching a metallic thin film, which is formed by physical deposition such as sputtering or ion beam deposition or chemical deposition such as CVD. Alternatively, a bulk metal such as wire mesh (mesh bulk metal) may be used as the electrostatic chuck electrode 40.

In the case of forming the ceramic base 10 having resistance heating element 50 buried therein as shown in FIG. 3B, the resistance heating element 50 may be made of a refractory conductive material such as molybdenum (Mo), tungsten (W), molybdenum carbide (MoC), or tungsten carbide (WC). Other than refractory conductive materials, Ni, TiN, TiC, TaC, NbC, HfC, HfB2, ZrB2, carbon or the like may be used. The resistance heating element 50 may be a variety of forms such as a linear form, a ribbon form, a mesh form, a coil spring form, a sheet form, or a printed form.

Next, a manufacturing method for the substrate mounting apparatuses 1 to 4 is described. First, the ceramic base 10 and the base plate 30 are formed. To form the ceramic base 10, a ceramic raw powder such as aluminum nitride and a sintering aid such as yttria (Y2O3), silica (SiO2) or alumina (Al2O3) are prepared in a predetermined compounding ratio, and then mixed using a pot mill or ball mill.

Such mixing may be carried out using a wet process or a dry process. When using the wet process, drying is carried out after mixing, providing the mixed raw powder. Afterwards, the mixed raw powder as is or a granulated powder prepared by adding a binder and then granulating is formed into a disc-shaped compact, for example. A method for forming the compact is not limited, and a variety of forming methods are available. For example, a metal mold forming method, a cold isostatic pressing (CIP) method, or a slip casting method may be used.

Afterwards, the compact is sintered by a hot pressing method, atmospheric sintering method or the like to obtain a sintered body. In the case of aluminum nitride, sintering is carried out at about 1700° C. to about 1900° C. In the case of alumina, sintering is carried out at around 1600° C. In the case of sialon, sintering is carried out at about 1700° C. to about 1800° C. In the case of silicon carbide, sintering is carried out at about 2000° C. to about 2200° C.

Note that in the case of burying the electrostatic chuck electrode 40 and the resistance heating element 50 in the ceramic base 10, the electrostatic chuck electrode 40 and the resistance heating element 50 may be buried in a compact. In the case of the electrostatic chuck electrode 40, for example, planar electrode made of a metallic bulk having holes or mesh electrode (wire mesh) may be buried in the raw powder. In the case of burying the resistance heating element 50, a metallic bulk processed into a predetermined form such as a coil form or a spiral form may be buried in the same manner as the electrostatic chuck electrode 40. It is preferable that the electrostatic chuck electrode 40 and the resistance heating element 50 are made of a refractory conductive material such as molybdenum or tungsten.

Alternatively, the electrostatic chuck electrode 40 may be made of a filmy electrode formed by printing, drying, and sintering a metallic paste. In this case, in a forming a compact process, a green sheet layered body may be formed. For example, the green sheet layered body may be formed by preparing two disc-shaped green sheets, printing metallic paste for electrode on one surface of one green sheet, and stacking the other green sheet on the printed electrode. The green sheet layered body is then sintered. The base plate 30 is made of a composite material or metal. A coolant flow channel 60 may be formed in the base plate 30a as necessary.

Next, the ceramic base 10 and the base plate 30 are joined via the jointing layer 20. First, multiple jointing materials differing in a thermal conductivity are arranged on the backside of the ceramic base 10 (the opposite surface to the substrate mounting surface 10a). Jointing materials are arranged by patterning jointing materials on the surface of the ceramic base 10 or the surface of the base plate 30 through printing. Alternatively, multiple sheets of jointing materials may be arranged at predetermined positions between the ceramic base 10 and the base plate 30. Afterwards, the jointing materials are heated in vacuum or in the air up to a curing temperature, and a certain pressure is applied, thereby joining the ceramic base 10 and the base plate 30.

Such substrate mounting apparatus may be used as a susceptor, an electrostatic chuck, a ceramic heater or the like to be used in a semiconductor manufacturing process or a liquid crystal display manufacturing process.

EXAMPLES

Simulation of temperature distribution in a substrate mounting surface is carried out for verification of effectiveness of the present invention and working examples of the present invention are described.

Simulation

The jointing layer 20 arranged between the ceramic base 10 and the base plate 30 is divided into multiple regions in a plane, and simulation of temperature distribution of the ceramic base 10 surface (substrate mounting surface 10a) in the case of arranging jointing materials differing in a thermal conductivity by regions is carried out using the finite element method. Note that the surface temperature of the ceramic base 10 rises due to heat input from plasma when the substrate mounting apparatus is arranged in a plasma processing apparatus, however, in this simulation, assuming that temperature uniformly rises in a plane.

The object for this simulation is the substrate mounting apparatus 2 shown in FIG. 3A. It has the ceramic base 10 in which the electrostatic chuck electrode 40 is buried, and the base plate 30 joined to the ceramic base 10 via the jointing layer 20. Moreover, the jointing layer 20 is divided into two regions, which are a central part and a peripheral part. Then jointing materials differing in a thermal conductivity are arranged in the central part and the peripheral part, respectively. Specifically, the first jointing material 20B is arranged in the central part, and the second jointing material 20A is arranged in the peripheral part. Table 1 shows sizes, materials and thermal conductivities of respective constructional members used for this simulation.

TABLE 1 CONSTRUCTIONAL THERMAL CONDUCTIVITY MEMBER SIZE MATERIAL [W/mK] CERAMIC BASE DIAMETER: 200 mm AlN 90 THICKNESS: 5 mm Al2O3 30 JOINTING LAYER DIAMETER: 200 mm ACRYLIC NO. 1 1.4 THICKNESS: 0.23 mm RESIN NO. 2 0.6 NO. 3 0.1 BASE PLATE DIAMETER: 200 mm Al 180 THICKNESS: 15 mm

Tables 2 and 3 show thermal conductivities and diameters of the jointing layer, and heat input power. The size of the first jointing material 20B in the central part is assumed to be 60 mm, 120 mm, and 140 mm in diameter. Note that it is assumed that the temperature at the bottom surface of the base plate 30 is 20° C., and the energy (heat input power) from plasma inputting to the ceramic base 10 is 300 W, 500 W, and 700 W.

Table 2 and FIG. 5 show simulation results in the case of using aluminum nitride as the ceramic base. Table 3 and FIG. 6 show simulation results in the case of using alumina as the ceramic base. Tables 2 and 3 and FIGS. 5 and 6 show temperature differences ΔT between the center and the end of the substrate mounting surface as the temperature distribution in the substrate mounting surface. In FIGS. 5 and 6, a vertical axis represents a temperature difference ΔT, and a horizontal axis represents a distance from the center of the substrate mounting surface.

TABLE 2 DIAMETER OF HEAT INPUT TEMPERATURE DISTRIBUTION IN CORRESPON- JOINTING LAYER JOINTING LAYER CENTRAL PART POWER SUBSTRATE MOUNTING SURFACE DENCE LINE (PERIPHERAL PART) (CENTRAL PART) [mm] [W] (TEMPERATURE DIFFERENCE ΔT (° C.)) IN FIG. 5 NO. 1 NO. 2 60 300 1.5 101 THERMAL THERMAL 500 2.4 102 CONDUCTIVITY: CONDUCTIVITY: 700 3.4 103 1.4 [W/mK] 0.6 [W/mK] 120 300 1.9 104 500 3.2 105 700 4.5 106 140 300 1.9 107 500 3.2 108 700 4.5 109

TABLE 3 DIAMETER OF HEAT INPUT TEMPERATURE DISTRIBUTION IN CORRESPON- JOINTING LAYER JOINTING LAYER CENTRAL PART POWER SUBSTRATE MOUNTING SURFACE DENCE LINE (PERIPHERAL PART) (CENTRAL PART) [mm] [W] (TEMPERATURE DIFFERENCE ΔT (° C.)) IN FIG. 6 NO. 1 NO. 2 60 300 1.9 201 THERMAL THERMAL 500 3.1 202 CONDUCTIVITY: CONDUCTIVITY: 700 4.4 203 1.4 [W/mK] 0.6 [W/mK] 120 300 2.1 204 500 3.5 205 700 4.8 206 140 300 2.1 207 500 3.4 208 700 4.8 209 NO. 1 NO. 3 60 300 10 210 THERMAL THERMAL 500 17 211 CONDUCTIVITY: CONDUCTIVITY: 700 — — 1.4 [W/mK] 0.1 [W/mK] 120 300 17 212 500 29 213 700 — — 140 300 18 214 500 30 215 700 — —

As shown in Tables 2 and 3 and FIGS. 5 and 6, in the case of heat input power from plasma to the substrate mounting surface 10a of the ceramic base 10 is uniform in a plane, the jointing layer arranged between the ceramic base 10 and the base plate 30 is divided into a central part and an peripheral part, and the first jointing material 20B having a low thermal conductivity is arranged in the central part while the second jointing material 20A having a higher thermal conductivity than the first jointing material 20B is arranged in the peripheral part. This structure can provide temperature distribution having a lower temperature in the peripheral part than that in the central part of the substrate mounting surface 10a. Note that in the case of jointing layers made of a single jointing material not shown in the graph, temperature distribution in the substrate mounting surface of the ceramic base is nearly even.

As a result, it is confirmed that in the case of substrate temperatures being not uniform due to the structure of the substrate mounting apparatus 2 when it is actually used in a plasma processing apparatus, changing the thermal conductivity of the jointing materials in the jointing layer by location allows provision of uniform temperature distribution of a substrate. Moreover, it is also confirmed that control of the temperature distribution of the substrate is possible by dividing the jointing layer into multiple regions in a plane and arranging jointing materials having different predetermined thermal conductivities in the respective regions. Furthermore, it is confirmed that easy and effective control of temperature distribution in the substrate mounting surface of the ceramic base is possible by controlling sizes and shapes of divided regions of the jointing layer and thermal conductivities of jointing materials.

For example, in the case of the thermal conductivity of the jointing material in the central part of the jointing layer being at least double that of the jointing material in the peripheral part, a temperature difference between the central part and the peripheral part of the substrate mounting surface of the ceramic base is controlled to be about 0° C. to about 5° C. Furthermore, changing setting of a thermal conductivity and in-plane distribution of jointing materials allows flexible temperature control. In the case of the thermal conductivity of the jointing material in the central part of the jointing layer being at least ten times that of the jointing material in the peripheral part, temperature difference between the central part and the peripheral part of the substrate mounting surface of the ceramic base is controlled to be about 0° C. to about 30° C.

Working Examples 1 and 2

As working examples 1 and 2, a substrate mounting apparatus shown in FIG. 7 is formed. The substrate mounting apparatus includes the ceramic base 10 in which the electrostatic chuck electrode 40 is buried, the base plate 30a having the coolant flow channel 60, and the jointing layer 20 arranged between the ceramic base 10 and the base plate 30a. Cooling water flows as a coolant in the coolant flow channel 60. The jointing layer 20 is divided into a central part and a peripheral part in a plane, and jointing materials differing in a thermal conductivity are arranged in the central part and the peripheral part, respectively.

Specifically, the ceramic base 10 is formed under the following conditions. First, an acrylic resin binder is added to AIN powder obtained through reductive nitriding, and they are granulated through spray granulation to form granules. These granules are formed using a metal mold by applying pressure in a uniaxial direction. When forming a compact, Mo bulk electrode, which is planar mesh electrode, are buried in the compact. The compact is sintered by hot pressing method, thereby providing an integrated sintered body. Note that the pressure applied when hot pressing is 200 Kg/cm2, a sintering temperature is risen at a rate of 10° C./hour up to the maximum sintering temperature of 1900° C., and the maximum sintering temperature is then maintained for one hour. As a result, a disc-shaped ceramic base 10 made of AIN having a thickness of 5 mm is formed. The volume resistivity of the ceramic base 10 is 1×10 Ω·cm at room temperature. Note that the substrate mounting surface of the ceramic base 10 is formed to be flat without forming protrusions.

On the other hand, an alumina plate is processed to have a diameter of approximately 240 mm and a thickness of 30 mm, and the coolant flow channel 60 is then formed therein by process. In this manner, the base plate 30a is formed.

In the substrate mounting apparatus according to working example 1, a circular acrylic sheet having a thermal conductivity of 1.4 W/mK and a diameter of 60 mm and a ring-shaped acrylic sheet having a thermal conductivity of 0.6 W/mK, an inner diameter of 60 mm, and an outer diameter of 200 mm are arranged between the ceramic base 10 made of aluminum nitride and base plate 30a, and a pressure of 200 psi (1.38×106 Pa) is then applied from above and below at 100° C. in vacuum, thereby joining the ceramic base 10 and the base plate 30a.

In the substrate mounting apparatus according to working example 2, a circular acrylic sheet having a thermal conductivity of 1.4 W/mK and a diameter of 140 mm and a ring-shaped sheet having a thermal conductivity of 0.6 W/mK, an inner diameter of 140 mm, and an outer diameter of 200 mm are arranged between the ceramic base 10 made of aluminum nitride and the base plate 30a, and a pressure of 200 psi (1.38×106 Pa) is then applied from above and below at 100° C. in vacuum, thereby joining the ceramic base 10 and the base plate 30a.

As shown in FIG. 7, the substrate mounting apparatus according to working examples 1 and 2 is arranged in a vacuum chamber 100 having a lamp heater 120. Moreover, a Si substrate 80 having terminals of a thermocouple 90 soldered with Al, is mounted on the substrate mounting surface of the ceramic base 10.

The temperature of cooling water flowing through the coolant flow channel 60 in the base plate 30a is 20° C. Heat input from plasma to the Si substrate 80, which is generated when using the substrate mounting apparatus in a plasma processing apparatus, is simulated. Specifically, the Si substrate 80 is heated using the lamp heater 120 after setting a pressure of 1 Pa or less in the vacuum chamber 100. When the lamp heater 120 outputs power of 300W and 700W, temperatures of the center and the end of the Si substrate 80 are measured, respectively. Measurement results are shown in Table 4 and FIG. 8. Table 4 and FIG. 8 show temperature differences ΔTs between the center and the end of the Si substrate 80 as the temperature distribution in the Si substrate 80. In FIG. 8, a vertical axis represents a temperature difference ΔTs, and a horizontal axis represents a distance from the center of the Si substrate 80.

TABLE 4 JOINTING LAYER JOINTING LAYER (CENTRAL PART) OUTPUT MEASUREMENT SIMULATION (PERIPHERAL PART) MATERIAL/ POWER OF RESULT RESULT MATERIAL/ THERMAL LAMP TEMPERATURE CORRESPON- TEMPERATURE CORRESPON- WORKING THERMAL CONDUCTIVITY/ HEATER DIFFERENCE DENCE LINE DIFFERENCE DENCE LINE EXAMPLE CONDUCTIVITY DIAMETER [W] ΔTs (° C.) IN FIG. 8 ΔTs (° C.) IN FIG. 8 WORKING ACRYLIC RESIN/ ACRYLIC 60 300 1.8 301 1.5 302 EXAMPLE 1.4 W/mK RESIN/ 700 3.8 303 3.4 304 1 0.6 W/mK WORKING 140 300 2.2 305 1.9 306 EXAMPLE 700 4.9 307 4.5 308 2

Since heat input from the lamp heater 120 to the Si substrate 80 is controlled to be almost uniform, the jointing layer made of a single jointing material can provide an even temperature distribution of the substrate. Meanwhile, it is confirmed that in the case of dividing the jointing layer 20 in a plane between the ceramic base 10 and the base plate 30a into a central part and a peripheral part, and arranging a jointing material having a lower thermal conductivity in the central part while arranging a jointing material having a higher thermal conductivity in the peripheral part, a temperature distribution having a lower temperature in the peripheral part than in the central part of the substrate mounting surface of the ceramic base 10 can be provided.

Furthermore, it is also confirmed that the simulation results and actual measurement results are consistent and that the control method of substrate temperature, which is controlling in-plane thermal conductivity distribution in the jointing layer, is extremely effective in actual as the simulation.

Although the inventions have been described above by reference to certain embodiments of the inventions, the inventions are not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings.

Claims

1. A substrate mounting apparatus, comprising:

a ceramic base having a substrate mounting surface; and
a jointing layer, which is formed on an opposite surface to the substrate mounting surface of the ceramic base, and has jointing materials differing in a thermal conductivity by in-plane regions and arranged in the regions.

2. The substrate mounting apparatus according to claim 1, further comprising a pedestal joined to the ceramic base with the jointing layer interposed between the pedestal and the ceramic base.

3. The substrate mounting apparatus according to claim 1, wherein

the regions are a central part and a peripheral part;
a first jointing material is arranged in the central part; and
a second jointing material differing in the thermal conductivity from the first jointing material is arranged in the peripheral part.

4. The substrate mounting apparatus according to claim 3, wherein the second jointing material has a higher thermal conductivity than a thermal conductivity of the first jointing material.

5. The substrate mounting apparatus according to claim 1, wherein the jointing materials include a resin base material and filler

6. The substrate mounting apparatus according to claim 1, further comprising an electrostatic chuck electrode buried in the ceramic base.

7. The substrate mounting apparatus according to claim 1, further comprising a resistance heating element buried in the ceramic base.

8. The substrate mounting apparatus according to claim 2, wherein the pedestal includes a cooling unit.

9. The substrate mounting apparatus according to claim 1, wherein

the ceramic base has protrusions on the substrate mounting surface, and
contact area of each of the protrusions with a mounted substrate differs by the regions.

10. The substrate mounting apparatus according to claim 9, wherein the contact area is larger in a peripheral part than in a central part of the substrate mounting surface.

11. The substrate mounting apparatus according to claim 9, wherein the contact area is larger in a central part than in a peripheral part of the substrate mounting surface.

12. A control method of substrate temperature, comprising:

controlling temperature distribution of a substrate mounted on a ceramic base by controlling in-plane thermal conductivity distribution of a jointing layer formed on an opposite surface to a substrate mounting surface of the ceramic base.

13. The control method according to claim 12, wherein controlling the in-plane thermal conductivity distribution of the jointing layer by arranging a first jointing material in a central part of the jointing layer and a second jointing material differing in a thermal conductivity from the first jointing material in a peripheral part of the jointing layer.

14. The control method according to claim 12, wherein controlling the temperature distribution of the substrate by controlling contact areas of respective protrusions formed on the substrate mounting surface with the substrate by location.

Patent History
Publication number: 20060021705
Type: Application
Filed: Jun 23, 2005
Publication Date: Feb 2, 2006
Applicant: NGK Insulators, Ltd. (Nagoya-City)
Inventors: Yasuyoshi Imai (Nagoya-shi), Tetsuya Kawajiri (Handa-shi), Tomoyuki Fujii (Nagoya-shi)
Application Number: 11/165,573
Classifications
Current U.S. Class: 156/345.520
International Classification: C23F 1/00 (20060101);