Plasma Processing Apparatus and Plasma Processing Method

Abstract

There is disclosed a plasma processing apparatus wherein a sample placed on the top surface of the sample table located within the processing chamber contained in a vacuum vessel is processed with plasma formed in the processing chamber, comprising a set of ducts cut within the sample table through which cooling medium flows; a film-shaped heater whose heating elements are concentrically embedded in the dielectric film serving as the top surface of the sample table; plural temperature controllers which set up the temperature of the cooling medium flowing through the ducts at different values, respectively; and a control unit which switches over the circulations through the ducts of the cooling medium supplied from the plural temperature controllers.

Description

BACKGROUND OF THE INVENTION

This invention relates to a plasma processing apparatus and a plasma processing method, for etching a disc-shaped sample such as a semiconductor wafer in a processing chamber with plasma formed in the processing chamber contained in a vacuum vessel, and more particularly to a plasma processing apparatus and a plasma processing method, that can continuously process the film, which is the object of treatment, deposited on the top surface of the sample under different conditions while the temperature of the sample supported fixedly on the top surface of the sample table is being controlled.

Recently, further reduction in the sizes of circuit patterns formed on a semiconductor wafer has become an everlasting requirement with the demand of increasing the scale of integration of semiconductor elements. Accordingly, more and more strict precision has been required in fabricating such fine circuit patterns. Under these circumstances, it is very important to manage the temperature of the wafer (semiconductor wafer) under etching process.

In etching a wafer with plasma, for example, it is customary to apply a bias voltage to the wafer so that anisotropic patterns may be formed by bombarding the wafer with ions accelerated by the electric field resulted from the application of the bias voltage. During this etching process, the wafer absorbs heat and its temperature rises.

The temperature rise in the wafer influences the effect of etching. For example, in the etching of poly-silicon that serves as electrodes for semiconductor devices, the final line width obtained is largely affected by the re-adhesion of reactive products and/or the deposition of adhesive radicals, on the side walls of the etched patterns during etching process, and the degree of adhesion of these substances varies with the wafer temperature. Consequently, without the proper management of temperature in a wafer during etching process, etching will not be uniform within the treated surface of the wafer and also the reproducibility of uniform wafers will be poor. Further, since there is a tendency that the density of distributed reactive products is lower near the periphery of the wafer than around the center of the wafer, it is necessary to positively control the temperature distribution in the wafer in order to obtain uniform line width (CD) within the treated surface of the wafer.

In order to provide such control of temperature distribution as described above, it is required to control the distribution of the temperature in the wafer supporting surface of the sample table for supporting the semiconductor wafer as a sample thereon, in such a manner that the temperature distribution over the wafer surface may be as desired. To meet this requirement, techniques have been proposed for controlling the temperature of and its distribution in, the material with which the internal and the sample supporting surface, of the sample table for supporting the semiconductor wafer thereon are formed. Such techniques are disclosed in, for example, JP-A-2006-140455, JP-A-2007-067036, and JP-A-2007-300119.

JP-A-2006-140455 and JP-A-2007-067036 disclose a plasma processing apparatus wherein a sheet-like member of dielectric material for directly supporting the sample thereon is placed on the sample table; the sheet-like member has a heater for heating the wafer and an electrode for attracting the wafer to the sheet-like member by electrostatic force, embedded therein; and a disc-like metal member forming the internal of the sample table has concentric ducts through which heat exchange medium flows cut therein so that the temperature of the sample table may be controlled as desired through the heat exchange between the disc-like metal member and the heat exchange medium flowing through the ducts cut in the disc-like metal member. According to the conventional art, the temperature of and its distribution in, the sample table or the wafer placed thereon are controlled as desired by suitably controlling the extent to which the heater generates heat and the heat exchange medium is cooled. On the other hand, JP-A-2007-300119 discloses a plasma processing apparatus having a sample table in the form of a disc, in which cooling fluid ducts and a heater are provided so that the temperature of and its distribution in, the sample is controlled as in JP-A-2006-140455 and JP-A-2007-067036.

SUMMARY OF THE INVENTION

The related art described above came to suffer a problem since there was insufficient consideration regarding the following points. With the demands for the microscopic patterning of circuits, an increasing number of materials came to be used as films on the wafer in the surface of which fine circuit patterns are formed, and processing must be performed continuously on plural types of films or under plural working conditions. Therefore, the range of temperatures at which the wafer must be maintained came to be broadened and the high precision in temperature control must also be attained.

In the adjustment of temperature of the disc-like member by the cooling medium flowing through the disc-like member provided in the sample table, since the heat capacities of the cooling medium and the disc-like member are much larger than that of the wafer, the temperature of or its distribution in, the wafer can be stabilized. However, if the heater is located nearer to the wafer than to the cooling medium ducts, response in heat transfer is indeed high enough, but temperature distribution in the wafer supporting surface or the wafer seems to become uneven to a great extent due to the unevenness in the local generation of heat (i.e. heat generation distribution) by the heater. Because of this tendency, if the range of attainable temperatures is expanded by increasing the heat generated by the heater, the temperature value of and the unevenness of temperature distribution in, the wafer become greater with the elevation of temperature resulting from the increase in heating amount. This is a problem to be overcome.

On the other hand, if the range of change in the temperature of the cooling medium flowing within the sample table is expanded, the unevenness of temperature distribution in the wafer can indeed be reduced but the operational response will be much slower, as compared with the case where heaters are used. In the case of a multi-step process where the wafer, once transferred into the processing chamber and placed fixedly on the sample table, is subjected to successive processing steps under different processing conditions without being transferred out of the processing chamber, the time required for the change in the processing condition prolongs with the increase in the number of the processing steps. This causes a low throughput leading to an impairment of manufacturing efficiency, resulting in a problem.

The conventional related art mentioned above has not taken this problem into consideration, and it has been difficult with the conventional related art to perform processing with high precision and high productivity.

The object of this invention is to provide a plasma processing apparatus and a plasma processing method, that can provide a high productivity.

The object of this invention can be attained with, for example, a plasma processing apparatus wherein a sample placed on the top surface of the sample table located within the processing chamber contained in a vacuum vessel is processed with plasma formed in the processing chamber, comprising a set of ducts cut within the sample table through which cooling medium flows; a film-shaped heater whose heating elements are concentrically embedded in the dielectric film serving as the top surface of the sample table; plural temperature controllers for setting up the temperature of the cooling medium flowing through the ducts at different values, respectively; and a control unit for switching over from the circulation through the ducts of the cooling medium fed out of one of the plural temperature controllers to the circulation through the ducts of the cooling medium fed out of another temperature controller.

The object of this invention can also be attained by, for example, switching the above mentioned circulations in each interval between the two successive processes for treating films of different types. The object of this invention can further be attained by, for example, making up the film-shaped heater with plural heater elements which can be independently controlled in heating. The object of this invention can still further be attained by, for example, providing the sample table with plural independent sets of concentric ducts and switching the circulations of cooling media fed out of plural temperature controllers through the plural independent sets of concentric ducts.

The object of this invention can be attained by using a plasma processing method, for example, wherein the film in the top surface of a sample placed on the sample table located within the processing chamber contained in a vacuum vessel and having a film-shaped heater whose heating elements are concentrically embedded in the dielectric film serving as the top surface of the sample table, is processed with plasma formed in the processing chamber, and wherein the circulations through the concentric ducts, cut within the sample table, of the cooling medium fed out of the plural temperature controllers which can set up at different values the temperatures of the cooling media fed through the concentric ducts, are switched over while the wafer is being heated by the film-shaped heater.

The object of this invention can also be attained by using a plasma processing method, for example, wherein the above mentioned circulations are switched over in each interval between the two successive processes for treating films of different types. The object of this invention can further be attained by using a plasma processing method, for example, wherein the sample is processed while the temperature distribution in the wafer is controlled by operating the film-shaped heater made up with plural heater elements laid out concentrically in the dielectric film. The object of this invention can still further be attained by using a plasma processing method, for example, wherein the sample table is furnished with plural independent sets of concentric ducts, and the circulations of cooling media fed out of plural temperature controllers are switched over between the plural independent sets of concentric ducts and the plural temperature controllers.

Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows in plan view the structure of a vacuum processing apparatus provided with a plasma processing apparatus as an embodiment of this invention;

FIG. 2 shows in vertical cross section the structure of the processing unit shown in FIG. 1;

FIG. 3 schematically shows in vertical cross section the structure of the sample table used in the processing unit shown in FIG. 2;

FIG. 4 graphically shows an example of how the plasma processing performed with the apparatus shown in FIG. 2 proceeds with time; and

FIG. 5 graphically shows another example of how the plasma processing performed with the apparatus shown in FIG. 2 proceeds with time.

DETAILED DESCRIPTION OF THE EMBODIMENT

An embodiment of this invention will be described in detail below in reference to the attached drawings.

Embodiment 1

The embodiment of this invention will be described in reference to FIGS. 1 through 5.

FIG. 1 schematically shows in plan view the structure of a vacuum processing apparatus provided with a plasma processing apparatus as an embodiment of this invention. In FIG. 1, the vacuum processing apparatus 100 can be split into two blocks, front block and rear block. The front block shown as the lower part of the vacuum processing apparatus 100 shown in FIG. 1 is the atmospheric pressure block 101 in which a wafer as a sample to be processed is introduced and conveyed under the atmospheric pressure.

The rear block shown as the upper part of the vacuum processing apparatus 100 shown in FIG. 1 is the processing block 102. The processing block 102 comprises processing units 103, 103′, 104 and 104′, each of which has a processing chamber wherein a wafer conveyed from the atmospheric pressure block 101 is brought in and processed in a vacuum environment; a vacuum transfer vessel 112 whose internal is maintained in a vacuum condition and via which the wafer is transferred into the processing chamber; and plural lock chambers 113, 113′ for communicating between the vacuum transfer vessel 112 and the atmospheric pressure block 101. These units can be maintained at reduced pressures or in a high vacuum condition and therefore the processing block 102 may be called a vacuum block.

On the other hand, the atmospheric pressure block 101 includes a roughly parallelepiped casing 108 with a transfer robot (not shown) installed therein. The casing 108 has plural cassette tables (only three of them are shown) 109 attached to the front wall of the casing 108, onto which wafer cassettes conveyed through the openings cut in the front wall of the casing 108 are placed, each wafer cassette containing a wafer to be processed or to be cleaned. On the rightmost one of the cassette tables 109 is placed a dummy cassette 110 for a dummy wafer used to clean the internal of processing unit 103, 103′, 104 or 104′.

The transfer robot in the casing 108 functions to carry in or out wafers between the wafer cassettes and the lock chambers 113, 113′. The atmospheric pressure block 101 also has a position registration section 118 which is communicated with the casing 108, and the transfer robot takes the wafer out of the wafer cassette and then transfers it into the position registration section 118. The transferred wafer is subjected to positioning in the position registration section 118 in such a manner that the positioned state remains the same as when the wafer is placed on the sample table in the lock chamber 113 or 113′. The lock chamber 113 connects between the atmospheric pressure block 101 and the transfer chamber in the vacuum transfer vessel 112 serving as a transfer unit. The pressure within the lock chamber 113 can be increased or decreased with a wafer contained therein, and the lock chamber 113 is connected with a gas exhaust unit and a gas supply unit, both for controlling the pressure within the lock chamber 113.

For proper operation, the lock chamber 113 is provided in front or rear with gate valves to hermetically close the lock chamber 113. The lock chamber 113 further includes a wafer supporting table within and the wafer supporting table is provided with a means for immobilizing the wafer while the pressure in the lock chamber 113 is being increased or decreased. Namely, the lock chamber 113 is so designed as to be provided with a sealing means which withstands the difference between the pressures inside and outside the chamber while the wafer is being placed within the chamber.

In this embodiment, the processing units 103, 103′ of the processing block 102 are etching process units having etching chambers in which wafers transferred from wafer cassettes to the processing block 102 are etched, whereas the processing units 104, 104′ of the processing block 102 are ashing process units for ashing the wafers. Further, these processing units are detachably connected with the side walls of the vacuum transfer vessel 112 serving as the transfer unit and having a shape of roughly regular polygon (hexagon in this case shown) in plan. The vacuum transfer vessel 112 includes a transfer chamber whose internal can be kept at high vacuum. These processing units 103, 103′, 104, 104′ are disposed in right-left symmetry with respect to a plane perpendicular to the sheet of the drawing (FIG. 1), intersecting the sheet of the drawing in the vertical direction, and passing through the center of the vacuum transfer vessel 112. Hereafter, it is to be understood that the description regarding the processing units 103, 104 is applicable to the processing units 103′, 104′ unless otherwise indicated.

Moreover, the processing block 102 includes a control unit 107 located between the processing units 103 and 104 and especially adjacent to the side wall of the vacuum chamber, the control unit 107 including mass flow controllers for controlling the supply of processing gas or liquid necessary for processing in the units or processing chambers within the units. The mass flow controllers included in the control unit 107 are provided for the adjacent processing units 103 and 104, respectively. One mass flow controller is disposed upon the other so that the supply paths for processing gas or liquid fed to the respective processing units may be shortened and that the resistance of the processing fluid through its conducting path may be lessened.

The transfer unit has in its transfer chamber the robot arm (not shown) which transfers a wafer between the lock chambers 113, 113′ and the processing chambers in the processing units 103 and 104, whose internals are kept at a reduced pressure. In this embodiment, as described above, regarding the processing units 103 and 104, two etching process units and two ashing process units are disposed around and in contact with the side walls of the polygonal vacuum transfer vessel 112. The two etching process units 103 are connected with the two rearmost side walls of the vacuum transfer vessel 112 whereas the two ashing process units 104 are connected with those side walls of the vacuum transfer vessel 112 which are adjacent to the side walls to which the two etching process units 103 are connected. The lock chambers 113 are connected with the remaining side walls of the vacuum transfer vessel 112. Namely, this embodiment involves two etching process chambers and two ashing process chambers.

Under the processing block 102 are located rectangular beds 106, 106′, 106″, 106′″, corresponding to the respective processing units, which accommodate therein various utility units such as reservoirs for gases necessary for different processes, reservoirs for cooling medium, exhaust mechanisms, and power supply sources. Each of the processing units 103 and 104 is divided into two sections vertically, i.e. the upper section including the processing chamber therein and the lower section including the utilities for the processing chamber. Also, the processing units 103 and 104 include the processing chamber sections and the beds 106 and 106″ serving as the upper sections, and they, each as a single unit, are detachably connected with the vacuum transfer vessel 112 or the transfer unit.

The beds 106, 106″ for the processing units 103, 104 are in the form of a rough parallelepiped which incorporates therein utilities, controllers, heat exchanges that are all necessary parts in the upper process chamber sections. The utilities include, for example, an evacuation pump for evacuating the processing chambers, a power source for supplying electric power, a reservoir of gas fed into the processing chamber incorporating therein a sample table for fixedly supporting a wafer as a sample thereon, a reservoir of cooling medium for cooling the sample table, and a heat exchange for refrigerating cycle wherein the cooling medium is circulated and subjected to heat exchange. The beds 106, 106″ contain these utilities, and the bottom surfaces of the beds are connected with the upper flat surfaces of supporting pillars.

The process chamber sections of the processing units 103, 104 are connected with the vacuum transfer vessel 112 through its side walls via dedicated gate valves. A supporting frame (not shown) is located beneath the vacuum transfer vessel 112 to support the vessel at a predetermined height. The utilities within the beds 106, 106″ corresponding to these process chamber sections are connected with pipes for gas or fluid, or wiring conductors for a power source or controllers in the spaces beneath the vacuum transfer vessel 112. Interface sections necessary for driving the utilities contained in the beds 106, 106″ are provided on the side surfaces of the beds 106, 106″. The side surfaces of the beds 106, 106″ are located in the space between the bottom surface of the frame or the vacuum transfer vessel 112 and the floor.

As described above, according to this embodiment, the processing units 103, 104 constitute a single combined unit consisting mainly of the corresponding beds 106, 106″ and the superposed process chamber sections (including evacuating apparatuses for evacuating the processing chambers). This single combined unit is connected detachably with the vacuum processing apparatus 100 or the vacuum transfer vessel 112.

The lock chambers 113, 113′ are located in rear of the atmospheric pressure block 101 and between the block 101 and the processing block 102, and spaced apart from the beds. In rear of the casing 108 in the atmospheric pressure block 101 are located supply conduits for the piping for the gas and cooling medium fed to the processing block 102, wiring conductors from the power sources and so on, and other piping. In general, the vacuum processing apparatus 100 is usually placed in a clean room, i.e. a room in which air is purified. Further, if plural processing apparatuses are installed in a clean room, the reservoirs for various gases and cooling medium fed into the plural processing apparatuses and the power sources for energizing the plural processing apparatuses are usually placed together, from the standpoint of improving the efficiency of layout, on a floor different from that of the clean room, and connected with the plural processing apparatuses via pipes and cables for circulation and supply.

According to this embodiment, a connection interface 116 for the supply lines such as gas and coolant pipes coming from a different floor and the power cables from power sources, is formed in integration with and along the rear surface of, the casing 108. Also, those supply lines which are connected with other supply lines in the connection interface 116 and which serve as the supply lines for utilities supplied to the processing block 102, include gas and coolant pipes and power cables from the connection interface 116. Those supply lines are laid out beneath the lock chambers 113, 113′ and beneath the central part of the bottom surface of the vacuum transfer vessel 112, and connected with the respective beds via the connection interface 116 provided for the bed 106.

Namely, in integration with and along the rear surface of the casing 108 are provided a detecting unit for detecting the working conditions of the supply lines connected with the processing block 102 at the connection interface 116, and a display section 117 having a display unit for displaying the output of the detecting unit so as to enable a user to monitor the working conditions of various devices. Further, an adjusting unit may be provided for adjusting the supply through the supply lines or for receiving such instructions as to adjust the supply.

Moreover, a gap or space is provided between the rear surface of the casing 108 and the processing units 104, 104′ in the processing block 102. The gap is so provided as to enable the user to step in it and work on the processing units 104, 104′, the vacuum transfer vessel 112, or the lock chambers 113, 113′, or also to enable the user to check, adjust and service the connection interface 116 and the display section 117 on the rear surface of the casing 108. Furthermore, units for displaying the information on the operating conditions of the devices connected to the supply lines and adjusting the devices, are laid out in a concentrated manner so that the pre-start work for the operation of the plasma processing apparatus is facilitated with the result that the net working rate of the apparatus can be improved.

Also, according to this embodiment, the supply lines for utilities necessary for the respective units in the processing block 102 are located together. Since the supply lines such as fluid supply pipes and electric cables coming from another location such as a floor below the floor on which the vacuum processing apparatus 100 is placed, are collected together on the rear surface of the casing 108 in the atmospheric pressure block 101, the work of mounting, connecting and dismounting the supply lines can be facilitated in installing the vacuum processing apparatus 100 on a floor, servicing the same and replacing the parts thereof. Accordingly, working efficiency can be improved.

Further, pipes and cables are placed in the space beneath the vacuum transfer vessel 112 and the lock chamber 113 and between the beds corresponding to the respective processing units. Thus, the space in which a serviceman mounts, connects or dismounts the pipes and the cables is secured, whereby the work of mounting, connecting and dismounting the supply lines can be facilitated and the operating efficiency of the apparatus can also be improved. Still further, since the connections of supply lines for utilities are made in the space inside the apparatus, i.e. beneath the vacuum transfer vessel 112 and between the beds, the volume of the space for working within can be saved so that the footprint of the apparatus can be saved as compared with the case where the fluid supply pipes, electric cables and their coupling sections are provided around the apparatus. This makes it possible to install a greater number of apparatuses in a predetermined floor area.

The top portions of the beds have flat surfaces, on which a user or a serviceman can access or service various units such as the process chamber section, the vacuum transfer vessel 112, etc., or replace parts easily. Namely, the space over the beds is used as maintenance space and this also contributes to the reduction of the floor area required for the installation of a vacuum processing apparatus as a whole and further to the improvement in the efficiency of servicing the apparatus.

The processing chambers in the processing units 103, 104 contain supporting tables on which wafers transferred into the chambers are placed and the supporting tables are provided with mechanisms for controlling the temperatures of the tables. For example, a sample table 103a of roughly cylindrical shape is disposed in the processing chamber in the processing unit 103 and concentric ducts through which heat exchange medium composed mainly of water flows are cut within the sample table 103a.

The concentric ducts are connected with circulation ducts 119 for heat exchange medium to flow through. The heat exchange medium is fed into the concentric ducts in the sample table via the circulation duct 119 after its temperature has been adjusted by a temperature controller 105a or 105b to a suitable value at which processing is performed. The heat exchange medium flowing out of the sample table 103a returns to the temperature controllers 105a, 105b via the circulation duct 119 to complete a circulation. A circulation duct selector 120 is located between the temperature controllers 105a, 105b, and the circulation duct selector 120 sets up the flow paths between the temperature controllers 105a, 105b and between the circulation duct 119 and the temperature controller 105a or 105b. The circulation duct selector 120 changes over the flow of the heat exchange medium toward the sample table 103a via the circulation duct 119 between the temperature controller 105a and the temperature controller 105b.

In this embodiment, the two temperature controllers 105a or 105b and the circulation duct selector 120 are contained in a housing 115 of roughly parallelepiped shape disposed adjacent to the rear side (upper position in FIG. 1) wall of the bed 106 having a roughly parallelepiped shape, corresponding to the processing unit 103. The housing 115 is disposed on the floor on which the vacuum processing apparatus is disposed, but it may also be disposed beneath the floor, i.e. in the ceiling of the room located beneath the floor.

FIG. 2 shows in vertical cross section the structure of the processing unit shown in FIG. 1. In FIG. 2, the processing unit 103 as the vacuum processing apparatus 100 according to the embodiment of this invention is conceptually divided into two blocks, i.e. upper and lower blocks. The upper block includes the process chamber section in which the sample to be processed is placed for processing and the bed 106 containing a power source for supplying necessary power for the process chamber section and the reservoir for cooling medium. For example, the upper block is provided with a processing chamber 201 which serves as the space within a vacuum vessel whose internal pressure is to be reduced by evacuation, the vacuum vessel being made of electrically conductive material such as aluminum selected depending on the associated process specification, and the sample table 103a of roughly cylindrical shape disposed in the processing chamber 201.

In the processing unit 103, concentric ducts 203 for temperature-controlled cooling fluid as heat exchange medium to flow through, are cut within the disc-shaped base member 202 serving as the sample table 103a so as to control the temperature of the sample table 103a; the circulation ducts 119 serving as pipe lines for the cooling medium are connected with the concentric ducts; and the two temperature controllers 105a, 105b connected with the circulation ducts 119 to control the temperature of the cooling medium and the circulation duct selector 120 connected with the circulation ducts 119 via cooling medium pipe lines, are contained in the housing 115. The concentric ducts 203 serves as a means for controlling the temperature of the sample table 103a, and the temperature of the sample table 103a can be properly controlled by enabling such a temperature control means.

In the processing chamber 201 is provided a gas supply unit for supplying process gas containing chlorine into the upper region of the processing chamber 201 from the position opposite to the wafer supporting surface (i.e. upper surface) of the sample table 103a, on which a disc-shaped wafer 205 to be processed as a sample is placed. The process gas is poured from the gas supply unit toward the wafer 205 placed on the sample table 103a.

In the process chamber section are provided the processing chamber 201; an electric field supply unit for supplying electric field in the form of electromagnetic waves and a magnetic field supply unit for supplying magnetic field, into the processing chamber 201; the gas supply unit for supplying process gas into the processing chamber 201; an upper and a lower vessel walls 212, 218 for constituting a vacuum vessel that hermetically encloses the processing chamber 201; and an evacuating unit disposed under the lower vessel wall 218 for discharging the particles of the gas or plasma out of the processing chamber 201 and for reducing the internal pressure of the processing chamber 201 and maintaining the internal at a predetermined level of vacuum. The evacuating unit is communicated with an exhaust opening 219 which is an opening cut in the bottom center of the lower vessel wall 218 enclosing a vacuum chamber 214 that defines the space beneath the sample table 103a. The evacuating unit discharges process gas, plasma and reactive products in the processing chamber 201 into the external thereof via the gap around the circumference of the sample table 103a, the vacuum chamber 214 and the exhaust opening 219.

Above the process chamber section are provided a magnetron 207 serving as the electric field supply unit for supplying electric field into the processing chamber 201; an upper waveguide 208a serving as a channel for guiding microwaves generated by the magnetron in the horizontal direction (as indicated by a horizontal arrow); and a lower waveguide 208b communicated with the upper waveguide 208a. The microwaves propagating through the upper waveguide 208a in the direction indicated by the horizontal arrow enter the lower waveguide 208b, proceed through it in the direction indicated by a vertical arrow, and reach the processing chamber 201 below. Namely, the lower waveguide 208b serves as a coupling member that couples the waveguide 208a having an electromagnetic wave source with the processing chamber 201 below.

The microwaves entering the lower waveguide 208b develop an intense electric field in the approximately horizontal direction in the space occupying the upper region of the processing chamber 201 and the lower region of the lower waveguide 208b, by means of a slot antenna. The lower part of the lower waveguide 208b is provided with a disc-shaped dielectric window pane 209 made of insulating material such as, for example, quartz. The electromagnetic waves that develop the high-intensity electric field are propagated through the dielectric window pane 209 into the cylindrical processing chamber 201 below.

In this embodiment, gas intake ports 210 are provided which are communicated with a space beneath the dielectric window pane 209, and process gas is supplied into the space via the gas intake ports 210 after its flow rate has been controlled by the mass flow controller (MFC) disposed in the control unit 107 shown in FIG. 1. The process gas entering the space is then diffused into the processing chamber 201 through the plural perforations of a gas diffusing plate 211 located below. The gas diffusing plate 211, just like the dielectric window pane 209, may be made of dielectric material such as, for example, quartz or semiconductor material such as, for example, silicon, but the material must be the one through which the electromagnetic waves traveling via the waveguides 208a, 208b can pass into the processing chamber 201.

As described above, the dielectric window pane 209 and the gas diffusing plate 211 constitute the upper wall (ceiling) of the processing chamber 201, and the gas diffusing plate 211 serves as the inner wall of the processing chamber 201 which is exposed to the plasma formed in the processing chamber 201. The processing chamber 201 is communicated with the evacuating unit such as, for example, a vacuum pump (not shown), and the pressure in the processing chamber 201 is reduced to develop a predetermined level of vacuum while the reactive products are being produced by the plasma generated from the supplied process gas. A solenoid coil 213 is provided around the upper vessel wall 212 of the processing chamber 201 to develop magnetic field in the processing chamber 201. The process gas fed into the processing chamber 201 is turned into plasma due to its interaction with the combined effect of the electric field created in the process chamber due to the electromagnetic waves travelling through the dielectric window pane 209 and the gas diffusing plate 211 into the chamber 201 and the magnetic field created in the processing chamber 201 by the solenoid coil 213. Thus, plasma is formed in the space above the sample table 103a in the processing chamber 201 inside the upper vessel wall 212.

The sample table 103a is located under the gas diffusing plate 211 serving as the ceiling of the processing chamber 201, and, as a result, a wafer 205 supported on the sample table 103a and the gas diffusing plate 211 face each other. The disc-shaped base member 202 of electrically conductive material is included in the sample table 103a and connected electrically with a high-frequency power source 215. The electric power supplied from the high-frequency power source 215 creates a high-frequency bias voltage in and near the surface of the wafer 205 placed on the base member 202 or a dielectric film 217 disposed on the upper circular surface of the base member 202. At least one electrostatic attracting electrode is provided on the inner side of the dielectric film 217 and connected electrically with a variable direct current source 216.

The wafer 205 is attracted onto and supported fixedly on the sample table 103a (dielectric film 217) due to the electrostatic force developed between the dielectric film 217 (or electrode) and the electric charges accumulated on the surface of the wafer 205 as a result of interaction among the electrostatic attracting electrode, the dielectric film 217, the wafer 205 and the plasma. The electrostatic attracting electrode may be the same as the electrode to which power from the high-frequency power source 215 is supplied.

Ions contained in the plasma generated above the sample table 103a are accelerated by the bias voltage developed by the high-frequency power supplied to the base member 202 and bombard the surface of the wafer 205. Accordingly, radicals are formed in the wafer surface, the formed radicals react on the substance of the wafer surface, and, as a result, the wafer is processed (etched in this embodiment). The reaction between the substance in the wafer surface and the plasma give rise to reaction products above the wafer 205 in the processing chamber 201.

The thus generated reaction products, the plasma and the gas unused for processing are moved down through the gap around the periphery of the sample table 103a into the vacuum chamber 214 and discharged out of the processing chamber 201 through the exhaust opening 219 cut in the bottom center of the lower vessel wall 218 by the suction force developed by means of an exhaust unit such as, for example, a vacuum pump (not shown).

In this embodiment, the exhaust opening 219 is provided with a shutter valve which opens or closes the exhaust opening 219 through rotating operation. The shutter valve can vary the aperture of the exhaust opening 219 depending on the degree of rotation, so as to control the exhaust rate. The upper and lower vessel walls 212, 218 constituting the processing chamber 201 and the vacuum chamber 214 are both grounded through any suitable means.

In this embodiment, a sample table ring 204 of dielectric material is provided surrounding the upper and outer periphery of the sample table 103a so that when the wafer 205 is placed on the sample table, the outer periphery of the wafer 205 is surrounded by the sample table ring 204. The dielectric sample table ring 204 serves to prevent current from flowing from the direct current source for the electrostatic attracting electrode to the plasma in the processing chamber 201. The sample table ring 204 may be made of insulating material for this purpose.

The sample table ring 204 may also be provided with any means for protecting the sample table 103a or the base member 202 serving as an electrode from the bombardment of ions in the generated plasma. For example, the sample table ring 204 may be covered with any protective material which hardly affects the processing of the wafer 205, or made of ceramic such as, for example, alumina which is hardly etched by the bombarding ions and also free from adverse effect on the processing.

Since the wafer 205 is processed by the bombarding ions in the plasma, the temperature of the wafer 205 is elevated during the processing. Therefore, the cooling medium whose temperature is controlled by the temperature controller 105a or 105b is passed through the concentric ducts 203 cut within the sample table 103a. The cooling medium leaving the concentric ducts 203 is circulated back to one of the temperature controllers 105a, 105b so that the temperature of the upper surface of the sample table 103a or the wafer 205 may be adjusted to a desired value during the processing.

In order to improve the efficiency of heat transfer between the wafer 205 and the sample table 103a or the base member 202 and to thereby adjust the temperature of and its distribution in, the wafer 205 as desired, heat transfer gas (e.g. He) is supplied from a heat transfer gas source 222 into the gap between the bottom surface of the wafer 205 and the upper surface of the dielectric film 217 serving as the sample supporting surface. Accordingly, the temperature of and its distribution in, the wafer 205 having heat capacity much smaller than heat capacity of sample table 103a can approach the temperature of and its distribution in, the sample table 103a.

The cooling medium is supplied from one of the temperature controllers 105a, 105b via the circulation duct 119 into the concentric ducts laid out as described above within the base member 202 of the sample table 103a, exchanges heat with the base member 202 while flowing through the concentric ducts 203, and leaves the base member 202 to return to one of the temperature controllers 105a, 105b. The cooling medium whose temperature has been controlled again in the temperature controller 105a or 105b, flows again through the circulation duct 119 to restart its circulation. Thus, the temperature of and its distribution in, the base member 202 can be controlled as desired.

The temperature controllers 105a, 105b are disposed in rear of the bed 106 placed on the floor on which the vacuum processing apparatus 100 is placed. Namely, in this embodiment, they are disposed within the housing 115 having a roughly parallelepiped shape and serving also as a platform for a user to use in climbing up on the bed 106. This layout of parts not only facilitates the use's work such as maintenance but also improves the efficiency of parts layout, so that the footprint of the vacuum processing apparatus 100 can be saved and, in addition, that the efficiency of operating the vacuum processing apparatus 100 can be improved. The housing 115 used for climbing up on the base 106 is reinforced by lining its internal surfaces with planks or the like. The housing 115 may be formed as a bed section 103b. Thus, the platform serving also as the housing 115 can be attached to or detached from the bed section 103b or the vacuum processing apparatus 100, and when the housing is the bed section 103b, it can be attached to and detached from the apparatus proper.

In the processing of the wafer 205 in the processing unit 103, the internal of the processing chamber 201 is depressurized to a preset pressure of, for example, 0.0133 Pa. Now, the wafer 205 is placed on the dielectric film 217, serving as the sample supporting surface, disposed on the sample table 103a, and attracted onto the sample supporting surface for immovable support by means of an electrostatic attracting means. Then, the temperature control means including the concentric ducts 203 for guiding cooling medium within the sample table 103a is driven, and heat transfer gas such as, for example, He, whose flow rate is controlled, is supplied into the gap between the wafer 205 and the dielectric film 217. Accordingly, the wafer 205 can be maintained at the temperature close to a desired temperature value. With the wafer 205 fixedly supported on the dielectric film 217, process gas such as, for example, chlorine is poured toward the wafer 205 by means of a process gas supply means. Plasma is formed in the processing chamber 201 by ionizing the process gas by the electromagnetic waves supplied into the processing chamber 201. The processing (i.e. etching in this embodiment) of the wafer 205 is started by using the plasma. When a predetermined process has been completed, the wafer 205 is carried out of the processing chamber 201 and a series of processing steps performed in the processing unit 103 are completed.

According to this embodiment, the sample table 103a consists of the base member 202 made of titanium having a roughly circular disc-shape, in which the concentric ducts 203 for guiding cooling medium within the sample table 103a is provided, and the dielectric film 217 which is formed over the surface of the disc-shaped base member 202 by the thermal spray of alumina or yttria. The concentric ducts 203 are coupled via the circulation ducts 110 to the temperature controllers 105a, 105b, which respectively cool down the cooling medium to different temperatures. Accordingly, by selecting a desired path of cooling medium, i.e. one of the circulation ducts 119, by the circulation duct selector 120 provided in association with the temperature controllers 105a, 105b, the temperature of and its distribution in the base member 202 and therefore the temperature of and its distribution in the wafer 205 fixedly supported on the base member 202 can be controlled. The temperature values at which the temperature controllers 105a, 105b set the cooling medium are controlled by the signal outputted from a control device (not shown) that controls the vacuum processing apparatus 100.

The structure of the sample table 103a as the embodiment of this invention will now be described in detail in reference to FIG. 3. FIG. 3 schematically shows in vertical cross section the structure of the sample table 103a shown in FIG. 2. In FIG. 3 is omitted the sample table ring 204 provided around the outer periphery of the disc-shaped dielectric film 217 disposed on the base member 202.

In FIG. 3, the dielectric film 217 in its principal portion is in the laminated structure consisting of at least more than one film layer. In this embodiment, the dielectric film 217 comprises two dielectric films of alumina or yttria, i.e. lower film 217a and upper film 217b adjacent to each other. Three film-like heaters whose operations are independently controlled, i.e. an inner heater 322, an intermediate heater 320 and an outer heater 321, are embedded in the lower dielectric film 217a. They are laid out concentrically; the inner heater 322 is circular and the intermediate and outer heaters are of ring shape. The top plane surfaces of these three heaters are even with one another.

Two electrostatic attracting electrodes, i.e. a circular one in the center and a ring-shaped one surrounding the circular one, can be embedded in the upper dielectric film 217b. In this embodiment, as shown in FIG. 3, the two electrostatic attracting electrodes are an inner electrode 341 located in the center and an outer electrode 342 surrounding the inner electrode 341. The inner electrode 341 and the outer electrode 342 are connected respectively with variable direct current sources 216a, 216b for power supply. In this embodiment, the inner electrode 341 and the outer electrode 342 are kept at positive and negative potentials, respectively. Therefore, the sample table 103a according to this embodiment functions as an electrostatic chuck of dipole type so that the wafer can be freely put on or taken off the sample table irrespective of whether or not there exists plasma around the sample table.

The inner, intermediate and outer heaters 322, 321 and 320 are connected via respective filters with separate power sources, which energize the heaters to perform heating operations. In FIG. 3, connection with power source is shown only for the outer heater 320. Namely, a power source 328 is connected via a coil 327 serving as a filter with the outer heater 320 by means of a connector 323 inserted in a tube 324 of insulating material penetrating the outer peripheral portion of the base member 202.

The base member 202 is electrically connected with a high-frequency power source 215 for applying a bias voltage to the wafer 205. The bias voltage causes ions in the plasma to bombard the top surface of the wafer 205 to perform anisotropic etching. During the etching process, the wafer 205 is heated and the heat causes the elevation of the wafer temperature, which adversely affects etching precision to a large extent. To avoid the elevation of the wafer temperature, therefore, the wafer 205 must be cooled down. For this purpose, a through-hole 330 is bored in the sample table 103a at the center, and heat transfer gas such as, for example, He is fed through the through-hole 330 so that the heat transfer between the wafer 295 and the dielectric film 217b can be secured to avoid unwanted elevation of the wafer temperature. It should here be noted that grooves (not shown nor described in detail) for spreading He gas through them are cut in the upper surface of the dielectric film 217b and that the layout pattern of the grooves is optimized such that the He gas introduced via the upper opening of the through-hole 330 into the grooves may reach the periphery of the wafer 205 with minimum pressure loss possible.

In this embodiment, the temperature of the wafer 205 during etching process is detected by using the output of the sensor that detects the temperature of the base member 202, the distribution of which is previously known to have a close correlation to that of the temperature in the wafer 205. To be concrete, holes 334 are bored in the base member 202 at positions apart by certain radial distances from the center of the base member 202, the bottoms of the holes 334 not reaching the undersurfaces of the inner heater 323, the intermediate heater 321 and the outer heater 320, and sheathed thermocouples 333 are placed fixedly in the holes 334 by means of springs 335 and fixing means 336 attached to the undersurface of the base member 202. In FIG. 3 is shown only the sheathed thermocouple 333 located under the intermediate heater 321. When such a sheathed thermocouple is used as a temperature sensor, the quality of contact of the tip of the thermocouple with the base member 202 largely affects the result of temperature detection. In this embodiment, however, the urging force of the spring 335 can provide secure contact between the thermocouple 333 and the base member 202 so that the result of the temperature detection can be highly reliable.

The result of the temperature detection is outputted to a control unit 337, which detects the temperature of and its distribution in the base member 202 on the basis of the inputted result. Consequently, on the basis of this result are controlled the operations, i.e. degree and duration of heating, of the inner heater 322, the intermediate heater 321 and the outer heater 320 which are connected with the control unit 337 in a communicable manner. It is to be noted that the sheathed thermocouple may be replaced by a platinum resistor, a fluorescent thermometer, a radiation thermometer, etc. Further, if foreign material deposition on the rear surface of the base member 202 is negligible, the tip of the temperature sensor can be in direct contact with the rear surface of the base member 202.

Although only one power supply unit for heating is shown in FIG. 3, it will be needless to say that two such units are actually necessary. In this embodiment, power supply for the heater may be from an AC or a DC source.

The patterns of the inner heater 322, the intermediate heater 321 and the outer heater 320 are laid out in the region of the sample table corresponding to that region of the wafer 205 in which the temperature of and its distribution in the wafer 205 in the circumferential or radial direction are to be controlled. In fabricating such heater patterns, the thermal spray technique can be used to advantage. Namely, in order to fabricate heater patterns by thermal spray, pattern masks have only to be prepared. Therefore, no specific limitation is imposed on the pattern to be employed. For example, the power supply terminals of the heaters can be located at any desired positions. On the other hand, if sheathed heaters are used, embedded in the base member 202, the rigidity of the sheath prevents itself from being bent in a very small curvature, making it unrealistic to design a complicated heater pattern. The change in the heater pattern causes the change in the overall length of the heater and therefore the change in the heater resistance. In case of fabricating the heater by thermal spray, the heater resistance can be easily optimized by controlling the thickness and the resistivity of heater material.

In this embodiment, multiple heaters 329 of concentric layout may be disposed on top of the base member 202 in addition to the concentric film heaters embedded in the dielectric film 217b. The heaters 329 are disposed between the concentric ducts 203 cut in the base member 202 and the top surface of the base member 202. The temperature of and its distribution in the base member 202 and the temperature response can be improved by the combined effects of the heating by the heaters 329 and the cooling with the cooling medium flowing through the ducts 203.

As shown in FIG. 2, the concentric ducts 203 of the base member 202 is coupled to the circulation ducts 119a, 119b which are coupled to the temperature controllers 105a and 105b via the circulation duct selector 120, respectively. In this embodiment, the temperature controller 105a adjusts the temperature of the cooling medium to a low value and the temperature controller 105 adjusts the temperature of the cooling medium to a high value, and the circulation duct 119a acts as a duct on the return side and the circulation duct 119b acts as a duct on the supply side.

The circulation duct selector 120 is provided with control valves 345, 346, 347 and 348 each acting as a mass flow controller which are provided on the respective paths of the cooling medium disposed therein. These control valves are operated based on instruction signals 337a from the control unit 337 to thereby close/open the respective paths of the control valves or adjust flow rates of the cooling medium of the respective paths of the control valves, whereby the supply of the cooling medium to the duct 203 from the temperature controllers 105a, 105b can be changed therebetween. FIG. 3 shows an example where the cooling medium passing through the temperature controller 105b circulates through the ducts of the base member 202.

With respect to the cooling medium which temperature is adjusted by the temperature controller 105a, each of the control valve 345 on the supply side and the control valve 347 on the return side is made off (closed). Ducts 338, 339 for respectively coupling the temperature controller 105a with the control valves 345, 347 are coupled to each other via a bypass valve 342. Thus, the cooling medium, which temperature is adjusted by the temperature controller 105a, also flows through the ducts circulating via the bypass valve 342 and so is always set to a set temperature accurately.

As to the cooling medium, which temperature is adjusted by the temperature controller 105b, since each of the control valve 346 on the supply side and the control valve 348 on the return side is made on (opened) or is adjusted its flow rate, the cooling medium can circulate so as to return to the temperature controller 105b via the ducts 203 and 119a from the duct 119b. Further, like the temperature controller 105a, ducts 340, 341 for respectively coupling the temperature controller 105b with the control valves 346, 348 are coupled to each other via a bypass valve 343. Thus, the cooling medium, which temperature is adjusted by the temperature controller 105b, also flows through the ducts circulating via the bypass valve 343 and so is always set to a set temperature accurately.

In this manner, the control unit 337 controls the opening/closing or adjusts the flow rate of each of a pair of the control valves 345, 347 and a pair of the control valves 346, 348 to thereby switch the circulation path of the cooling medium to the duct 203 between the path via the temperature controller 105a and the path via the temperature controller 105. As a result, the temperature of the base member 202, that is, the temperature of the sample table 103a and also the temperature of the wafer 205 placed thereon can be adjusted. In this embodiment, a coupling duct 344 is provided between the temperature controllers 105a and 105b so that the cooling medium can be communicated therebetween. In the figure, numerals 349a, 349b depict coupling portions of the circulation ducts 119a, 119b, respectively.

Even if there arises a difference in a returning amount of the cooling medium between the temperature controllers 105a and 105b depending on the switching timings of the respective control valves 345, 346, 347 and 348, the excessive returning amount of the cooling medium at one of the temperature controllers 105a and 105b flows into the other temperature controller through the duct 344. Thus, such an unbalance of the returning amount of the cooling medium can be eliminated in a short time and so the amount of the cooling medium in each of the temperature controllers 105a and 105b is restored quickly. Further, since each of the respective control valves 345, 346, 347 and 348 is controllable so as to be able to adjust the flow rates on the discharge side and return side, such a phenomenon as water hammering can be prevented from occurring. Furthermore, since the temperature changing speed can be controlled based on the flow rate of the cooling medium, the temperature increasing speed can be enhanced to thereby shorten the processing time.

The flow of the process associated with the vacuum processing apparatus according to this embodiment will be described in reference to FIGS. 4 and 5. FIG. 4 graphically shows the flow of the plasma processing according to the embodiment of this invention shown in FIG. 2. In FIG. 4 are shown how the temperature of the wafer 205 (or the sample supporting surface) and the temperature of the surface of the change with time in the case where the films of different types or different compositions formed on top of the wafer 205 are continuously processed in the processing unit 103 without bringing the wafer 205 out of the processing chamber. In a typical example of this type of process, the films 1 and 2 shown in FIG. 4 are those which are used as a gate and a wiring line (metal), respectively.

In this embodiment, the temperature controllers 105a, 105b can adjust the temperature of the cooling medium passing through them to different temperature values. For example, the temperature controller 105a adjusts the temperature of the cooling medium to 20° C. while the temperature controller 105b adjusts the temperature of the cooling medium to 80° C. The temperature difference of 60° C. is selected such that it is greater than the maximum value ΔTh of the temperature difference attainable in the top surface of the dielectric film 217 by means of the outer heater 320, the intermediate heater 321 and the inner heater 322 embedded in the dielectric film 217 of the sample table 103a.

In this embodiment, the maximum value ΔTs of the temperature difference actually developed in the dielectric film 217 by these heaters is set smaller by a preset value than ΔTh. Accordingly, when the cooling medium whose temperature has been adjusted by the temperature controller 105a is fed into the sample table, the range of temperatures Ts1 attainable in the top surface of the dielectric film 217 or the wafer 205 will be between the first temperature value greater by a preset value δ than the temperature Tc1 of the cooling medium immediately out of the temperature controller 105a and the second temperature value greater by ΔTs than the first temperature value, since the temperature at the top surface of the base member 202 becomes approximately equal to that of the cooling medium flowing through the base member 202 as the heat capacity of the base member 202 is much smaller than that of the cooling medium. When the cooling medium whose temperature has been adjusted by the temperature controller 105b is fed into the sample table, the range of temperatures Ts2 will be between the third temperature value greater by the preset value δ than the temperature Tc2 of the cooling medium immediately out of the temperature controller 105b and the fourth temperature value greater by ΔTs than the third temperature value.

According to this embodiment, the temperature of and its distribution in the top surface of the dielectric film 217 or the wafer 205 are controlled as desired by controlling the operations of the outer heater 320, the intermediate heater 321 and the inner heater 322 through the use of the result obtained by the temperature sensors such as, for example, sheathed thermocouples 333, on the basis of the temperature of and its distribution in the sample table 103a that are controlled by the cooling medium whose temperature is controlled by the temperature controllers 105a, 105b (or the concentric film heater 329) and which flows through the concentric ducts 203 cut within the base member 202 of the sample table 103a. In FIG. 4, in the “film 1 processing” that is the etching process for the first film, the temperature Ts1 of and its distribution in each of plural different dielectric films 217 are set up by energizing the heaters while the temperature in the surface of the base member 202 is kept at Tc1 by feeding cooling medium from the temperature controller 105a into the base member 202.

After the “film 1 processing” has been completed, the “film 2 processing” that is the etching process for the second film of different type or composition is performed. At this time, if the required lowest temperature of the wafer 205 is higher than the highest value Ts1, Tc1 must be replaced with Tc2 by switching the cooling medium out of the temperature controller 105a over to the cooling medium out of the temperature controller 105b. Namely, the circulation duct selector 120 changes the flow path of the cooling medium on the supply side in a manner that the flow path on the discharge (return) side is maintained so as to return the cooling medium discharged out of the concentric ducts 203 of the base member 202 to the temperature controller 105a via the discharge (return) side circulation duct 119a, and thereafter changes over the circulation ducts 119 on the supply side in such a manner that the cooling medium supplied at 80° C. from the temperature controller 105b is fed through the concentric ducts 203 cut within the base member 202 via the supply side circulation duct 119b. At this time, when the control unit makes decision that the cooling medium filling the cooling medium channel from the supply side exit up to the return side entrance, of the circulation duct selector 120 is the cooling medium all supplied from the temperature controller 105b, the circulation duct selector 120 operates the pair of the control valves 345, 347 and the pair of the control valves 346, 348 based on the control signal from the control unit 337 to change over the circulation ducts 119 in such a manner that the cooling medium discharged out of the concentric ducts 203 returns via the circulation duct 119 to the temperature controller 105b. Thus, the cooling medium is circulated between the temperature controller 105b and the concentric ducts 203 cut in the base member 202.

Such duct changeover operations by the circulation duct selector 120 are performed according to the instructions transmitted from the control unit 337 on the basis of the process conditions such as types and compositions of films formed on the wafer 205 obtained through communication apparatuses prior to processing and the data obtained by sensors (including the sheathed thermocouple 333) located at various points in the vacuum processing apparatus 100 or the processing units 103, for detecting various operating conditions at the points. In order to improve the effect of such duct changeover operations, a reservoir for storing a preselected quantity of cooling medium may be provided between the temperature controllers 105a and 105b, or between the circulation duct selector 120 and the temperature controllers 105a, 105b. The capacity of the reservoir will be large enough if it contains a quantity of cooling medium that can fill the concentric ducts 203 and the circulation dusts 119.

Consequently, the temperature in the surface of the base member 202 is changed to and kept at, Tc2. Then, the “film 2 processing” is performed by changing the temperature Ts2 of and its distribution in the wafer 205 to desired values and keeping the values, in accordance with plural different steps.

In the example shown in FIG. 4, the supply and circulation of cooling medium is changed over between the two temperature controllers 105a and 105b which can supply cooling media of different temperatures, so as to set up different temperatures and different temperature distributions in the base member 202 in accordance with the processing steps for plural films of different types or compositions. FIG. 5, on the other hand, shows an example wherein the supply and circulation of cooling medium is changed over between the two temperature controllers 105a and 105b in accordance with the plural process steps for a single film. FIG. 5 graphically shows an example of how the plasma processing performed with the apparatus shown in FIG. 2 proceeds with time. FIG. 5 shows the changes in the temperature of the wafer 205 (or sample supporting surface) and the temperature in the surface of the base member 202 in the case where all films in the top surface of the wafer 205 are continuously processed in the processing unit 103 without being transferred out of the processing unit 103.

In FIG. 5, the process 1 and the process 2 are the etching processes performed on any film under different process conditions. Before and after these processes, the transition of temperature in the wafer 205 occurs due to the changeover of the cooling media fed into the concentric ducts 203 and circulated through the coolant channel and due to the operation of the heater embedded in the dielectric film 217.

In this example shown in FIG. 5, the process 1 is performed while the cooling medium whose temperature is set to 20° C. by the temperature controller 105a is being supplied, whereas the process 2 is performed after the cooling medium with its temperature kept at 20° C. by the temperature controller 105a has been switched to the cooling medium whose temperature is set to 80° C. by the temperature controller 105b. In the transition period before the process 1, the transition of temperature in the base member 202 does not occur. Due to the operations of the inner heater 322, the intermediate heater 321 and the outer heater 320, the temperature of and its distribution in the top surface of the dielectric film 217 or the wafer 205 are set up while the cooling medium is being supplied from the temperature controller 105a (TCU1). In the transition period after the process 1, on the other hand, the switching of the cooling medium supply and circulation through the concentric ducts 203 and the circulation ducts 119 takes place due to the operation of the circulation duct selector 120 as shown in the example in FIG. 4. Namely, the cooling medium being presently supplied from the temperature controller 105a (TCU1) to the base member 202 is switched to the cooling medium to be supplied from the temperature controller 105b (TCU2) so that the transition of temperature in the surface of the base member 202 occurs.

Thereafter, in the process 2, the temperature of and its distribution in the top surface of the dielectric film 217 or the wafer 205 are set up due to the operation of the inner heater 322, the intermediate heater 321 and the outer heater 320 while the cooling medium from the temperature controller 105b (TCU2) is being supplied to the base member 202. After the process 2, the switching of the cooling medium supply and circulation through the concentric ducts 203 and the circulation ducts 119 takes place again due to the operation of the circulation duct selector 120. As a result, the cooling medium being presently supplied from the temperature controller 105b (TCU2) to the base member 202 is switched to the cooling medium to be supplied from the temperature controller 105a (TCU1 so that the transition of temperature in the surface of the base member 202 occurs.

The processing is placed in a transition state (transitions 1, 2, 3) between the respective processes in order to set the temperature of the base member 202 or the sample table 103a to a value suitable for the next process. Among these transition states, in each of the transitions 2 and 3 accompanied with the switching of the temperature controllers 105a, 105b, the control unit 337 instructs the switching of the control valves 345 to 348 to thereby switch the temperature controllers in the similar manner as FIG. 4.

The switching operations in FIGS. 4 and 5 will be explained in detail. As shown in FIG. 5, in each of the transitions 2 and 3, the flow rate of the cooling medium supplied to the duct 203 from the circulation duct selector is once set to 0 at the initial stage of the transition. The flow rate is restored to the constant value after closing all the control valves 345 to 348. On the other hand, since the electric power supplied to (or heat generated from) the inner heater 322, the intermediate heater 321 and the outer heater 320 is interrupted or reduced abruptly earlier than the operation of the control valves 345 to 348, the temperatures of the areas corresponding to the respective heaters 320 to 322 reduces once. Then, the respective heaters are kept in the off state or the reduced power state until the control valves 345 to 348 are switched. Thereafter, when the control valves 345 to 348 are switched, the flow path of the cooling medium flowing into the base member 202 is changed between the temperature controllers 105a and 105b, so that the cooling medium flows into the duct 203 from the switched one of the temperature controllers 105a and 105b to change the temperature of the base member 202, whereby the temperature of the base member 202 approaches the temperature of the cooling medium thus applied from the switched one of the temperature controllers. During this operation, the respective heaters 320 to 322 are subjected to the PID control so as to attain the predetermined target temperatures thereof set for the next process, based on the temperature values of the inner heater area, the intermediate heater area and the outer heater area of the base member 202 or the sample table 103a detected based on the output from the detection device shown in FIG. 3.

Since the temperature of the cooling medium whose supply and circulation paths are switched, is previously set up, the temperature of the base member 202 which is made of metal such as, for example, titanium having a large heat transfer coefficient, can be changed (or make transition) to another level in a very short time. Accordingly, if the temperature of the wafer 205 or the dielectric film 217 needs to be changed in excess of the range of temperature differences attainable in the dielectric film 217 by means of heaters, the efficiency of processing can be improved by performing the processing wherein the temperature of the base member 202 is changed by switching to the circulation of the cooling medium whose temperature is previously set up to attain such temperature differences in excess of the range while heating by heaters is still used. Further, since the temperature in the base member 202 of metal is controlled by the cooling medium passing through the concentric ducts 203 cut in the base member 202, the unevenness in temperature distribution throughout the base member 202 is relatively small. Accordingly, even when the temperature in the wafer 205 is largely changed by means of the heaters, the unevenness in temperature distribution throughout the wafer can be rendered small so that the temperature distribution in the radial or circumferential direction of the wafer 205 can be controlled with high precision. Thus, the manufacturing yield can be improved.

In the embodiment described above, the two temperature controllers 105a, 105b are used to set up the temperatures of cooling medium, but more than two temperature controllers may be employed to embody this invention. Further in the above described embodiment, the concentric ducts 202 cut in the base member 202 are fed with the cooling medium having a single temperature value supplied from a single temperature controller at a time, but it will be needless to say that in another embodiment of this invention, more than one independent set of concentric ducts may be cut in the base member 202 and that the respective independent sets of concentric ducts may be fed with the cooling media whose temperatures are different from one another, so as to set up different temperature distributions in the central and peripheral areas of the base member 202. In still another embodiment, each set of concentric ducts mentioned above may be provided with more than two temperature controllers and more than one circulation duct selector so as to feed the set of concentric ducts with more than two flows of cooling medium having more than two temperature values.

This embodiment requires the complicated control at the switching timing of the cooling medium circulation path as compared with the related art. However, in the process of the film 2 of FIG. 4 or the process 2 of FIG. 5 for performing the high-temperature control, since the temperature difference between the cooling medium (or the temperature of the base member 202) and the respective heater portions to be controlled becomes small, an amount of the electric power supplied to (or an amount of heat generated from) the respective heaters can be made small. Further, since the temperature of the cooling medium can be changed at the time of the temperature increase or reduction, an amount of the electric power supplied the heaters can be reduced or the switching speed can be enhanced advantageously.

According to the investigation of the inventors of the present invention, it was found that the temperature difference between the respective heater areas and the base member 202 (the cooling medium in the duct 203) influences to each other with and is in proportional to the control error (the degradation of the control accuracy) of the temperatures at the heater areas of the wafer 205 or the surface temperature of the base member 202 or the dielectric film 217. This is because, although a large amount of electric power is required in order to maintain the temperature of the wafer 205 at a high value and to enlarge the temperature difference from the base member 202, the control error (the degradation of control accuracy) of the temperatures becomes larger as the electric power increases. Further, since, among the receptive processing apparatuses, there are heating or cooling variances within the dielectric films 217 on the base members 202 due to the variance of the resistance value densities of the heaters 320 to 322, the partial shortage of the cooling ability of the cooling medium of the base member 202, the partial shortage of the cooling ability due to the structural reason such as the wafer insertion portion and the feeding portion disposed within the sample table 103a or the base member 202. Such the heating or cooling variances become large as the electric power increases. The variation can be reduced by adjusting the resistance values of the heaters, for example, but the reduction of the variance is limited to some extent in the case of the improving the accuracy of the temperature adjustment requirement according to the micro-fabrication of devices.

The function to be realized finally in the aforesaid embodiment is to uniformize the etching result on the wafer surface. To this end, according to the embodiment, the plasma distribution set to be uniform as possible is realized by adjusting the magnetic field generated by the solenoid coil 214. Further, in the case of forming different kinds of films continuously, the electric power applied to the respective heaters 320 to 322 is adjusted for each of these films so as to change the temperature distribution in the radial direction of the wafer 205 for each film to thereby adjust the optimum temperature and the adhesion degree of reactive products at the outer peripheral portion of the wafer. In general, the density of the reactive products is lower at the outer peripheral portion of the wafer as compared with that at the center portion of the wafer. Thus, the uniform etching result can be obtained by reducing the temperature at the outer peripheral portion of the wafer to reduce the adhesion degree of reactive products thereat. However, for each wafer, the degree of the uniform etching result is influenced by the variance of the temperature at the outer peripheral portion of the wafer and such the influence becomes remarkable particularly in the case of micro-fabricating a semiconductor device with a line width of 32 nm or less. Further, when a semiconductor device is configured to have more layers and the materials of the respective layers are varied, the difference of the optimum etching temperatures becomes larger among these respective layers. In this case, it becomes difficult to process the semiconductor device in a single processing chamber and so a plurality of the processing chamber are required, which disadvantageously results in the reduction of the etching speed and the increase of the cost of the equipments.

According to the embodiment, since the temperature variance on the entire surface (processed surface) of a wafer 205 can be suppressed, a shift amount of the line with (CD) on the major surface of a wafer can be reduced at the time of performing the etching process.

Further, according to the embodiment, even in the case where the difference of the optimum etching temperatures is large due to the multilayer of the device structure and the variation of materials of the respective layers, such various kinds of the semiconductor devices can be processed by the single processing chamber without employing a plurality of the processing chambers. Thus, since the etching speed can be enhanced, the productivity of the semiconductor devices can be enhanced and the cost of the semiconductor device processing equipment can be reduced.

It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.

Claims

1. A plasma processing apparatus wherein a sample placed on the top surface of the sample table located within the processing chamber contained in a vacuum vessel is processed with plasma formed in the processing chamber, comprising

a set of ducts cut within the sample table through which cooling medium flows;

a film-shaped heater whose heating elements are concentrically embedded in the dielectric film serving as the top surface of the sample table;

plural temperature controllers which set up the temperature of the cooling medium flowing through the ducts at different values, respectively; and

a control unit for switching over from the circulation through the ducts of the cooling medium fed out of one of the plural temperature controllers to the circulation through the ducts of the cooling medium fed out of another temperature controller.

2. A plasma processing apparatus as claimed in claim 1, wherein the switchover of the circulations takes place in each interval between the two successive processes for treating films of different types.

3. A plasma processing apparatus as claimed in claim 1, wherein the film-shaped heater embedded in the dielectric film is made up with plural heater elements which can be independently controlled in heating.

4. A plasma processing apparatus as claimed in claim 1, wherein the sample table is provided with plural independent sets of concentric ducts and the circulations of cooling medium are switched over between the plural temperature controllers and the plural independent sets of concentric ducts.

5. A plasma processing method wherein the film in the top surface of a sample placed on the sample table located within the processing chamber contained in a vacuum vessel and provided with a film-shaped heater whose heating elements are concentrically embedded in the dielectric film serving as the top surface of the sample table, is processed with plasma formed in the processing chamber, and wherein the circulations through the concentric ducts, cut within the sample table, of the cooling medium fed out of the plural temperature controllers which can set up the temperature of the cooling medium fed through the concentric ducts at different values, are switched over while the wafer is being heated by the film-shaped heater.

6. A plasma processing method as claimed in claim 5, wherein the circulations are switched over in each interval between the two successive processes for treating films of different types.

7. A plasma processing apparatus as claimed in claim 5, wherein the sample is processed while the temperature distribution in the wafer is controlled by operating the film-shaped heater made up with plural heater elements laid out concentrically in the dielectric film.

8. A plasma processing apparatus as claimed in claim 5, wherein plural independent sets of concentric ducts are cut within the sample table, and the circulations of cooling medium fed out of the plural temperature controllers are switched over between the plural independent sets of concentric ducts and the plural temperature controllers.