JP2010073752A - Plasma processing apparatus, and substrate placing table - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus preventing temperature lowering of an outer peripheral part of an object to be processed to attain uniform plasma processing in placing a substrate to be processed on a placing table to plasma-process the substrate by heat. <P>SOLUTION: The plasma processing apparatus includes the substrate placing table 5 on which the substrate W to be processed is placed in a processing vessel. The table 5 has a placing table body 51 larger in diameter than the substrate W, a heater 56 installed in the body 51 to heat the substrate and a cover 54 covering the surface of the body 51. The cover 54 is constructed such that the thickness d1 of a substrate placed area 54a is thinner than the thickness d2 of an outer area 54d outside of the area 54a and the quantity of heat per unit area supplied from the body 51 to the outer area 54d exceeds the quantity of heat supplied to the area 54a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus for performing plasma processing on a substrate to be processed such as a semiconductor wafer, and a substrate mounting table for mounting the substrate to be processed in a processing container of the plasma processing apparatus.

  In the manufacturing process of a semiconductor device, a semiconductor wafer as a substrate to be processed (hereinafter simply referred to as a wafer) is placed on a wafer mounting table in a processing container, and the wafer is heated by a heater provided in the mounting table main body. In addition, there is a plasma process in which plasma is generated in a processing container and oxidation, nitridation, film formation, etching, and the like are performed on a wafer.

  As a plasma processing apparatus for performing such plasma processing, a parallel plate type has been conventionally used, but recently, as a plasma processing apparatus capable of forming a high-density plasma at a lower electron temperature, 2. Description of the Related Art An RLSA (Radial Line Slot Antenna) microwave plasma processing apparatus that generates plasma by introducing microwaves into a processing container via a planar antenna having a large number of slots has attracted attention (for example, Patent Document 1).

  In such a microwave plasma processing apparatus, for example, when a wafer mounting table made of AlN is exposed to plasma, metal atoms in the wafer mounting table may contaminate and contaminate a semiconductor wafer as a substrate to be processed. A technique is used in which the main body of the wafer mounting table is covered with a quartz cover so that contamination does not reach the semiconductor wafer (for example, Patent Document 2).

However, when a process involving heating is performed in such a plasma processing apparatus, the temperature of the outer peripheral portion of the wafer tends to be lowered. For example, the silicon oxidation process is performed while heating the wafer to about 400 ° C., but the temperature tends to be low at the outer periphery of the wafer, the oxidation rate at that part is slow, and the uniformity of the oxidation process is deteriorated.
JP 2000-294550 A JP 2007-266595 A

  The present invention has been made in view of such circumstances, and the temperature of the outer peripheral portion of the object to be processed is reduced when the substrate to be processed is placed on the mounting table and plasma processing is performed while heating. An object of the present invention is to provide a plasma processing apparatus capable of preventing and performing uniform plasma processing and a substrate mounting table used in such a plasma processing apparatus.

  In order to solve the above problems, according to a first aspect of the present invention, a processing container that can be held in a vacuum and accommodates a substrate to be processed, a substrate mounting table for mounting the substrate to be processed in the processing container, A processing gas supply mechanism for supplying a processing gas into the processing container; and a plasma generation mechanism for generating a plasma of the processing gas in the processing container, wherein the substrate mounting table has a larger diameter than the substrate to be processed. A mounting body, a heating element provided in the mounting base body for heating the mounted substrate to be processed, and a substrate mounting area for covering the surface of the mounting table body and mounting the processing substrate. And the cover has a larger amount of heat per unit area supplied to the outer region than the substrate placement region than the amount of heat per unit area supplied to the substrate placement region. A profile characterized by To provide a Zuma processing apparatus.

  In the first aspect, the plasma generation mechanism includes a planar antenna having a plurality of slots, and a microwave introduction unit that guides microwaves into the processing container via the planar antenna. The processing gas can be turned into plasma by waves. The substrate mounting table may further include a high frequency bias applying unit that applies a high frequency bias for drawing ions in the plasma.

  In a second aspect of the present invention, in a plasma processing apparatus for performing plasma processing on a substrate to be processed in a processing container held in a vacuum, a substrate mounting table for mounting the substrate to be processed in the processing container The mounting table main body having a diameter larger than that of the substrate to be processed, the heating element provided in the mounting table main body for heating the mounted processing substrate, and the surface of the mounting table main body are covered. And a cover having a substrate placement area for placing the object to be processed, wherein the cover places the substrate placement more than the amount of heat per unit area supplied to the substrate placement area from the placement table main body. Provided is a substrate mounting table configured to increase the amount of heat per unit area supplied to a region outside the region.

  In the first and second aspects, the cover may be configured such that the thickness of the substrate placement area is greater than the thickness of the outer area outside the substrate placement area. Moreover, it can be set as the structure by which the clearance gap is formed between the outer side area | region outside the said board | substrate mounting area | region of the said cover, and the said mounting base main body. In this case, the temperature of the substrate to be processed can be controlled by adjusting the distance of the gap. Further, the temperature of the substrate to be processed can be controlled by adjusting the thickness of the substrate placement area and the thickness of the outer area of the cover. Furthermore, the mounting table main body is preferably made of AlN, and the cover is preferably made of quartz.

  According to the present invention, in the substrate mounting table provided with a cover so as to cover the surface of the mounting table main body, the cover is more than the amount of heat per unit area supplied from the mounting table main body to the mounting surface. Since the amount of heat per unit area supplied to the outer region from the mounting surface is increased, sufficient heat is supplied to the outer periphery of the substrate to be processed, and the temperature of the outer periphery of the substrate to be processed is decreased. Can be suppressed, and uniform plasma treatment can be performed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a plasma processing apparatus according to an embodiment of the present invention. The plasma processing apparatus 100 generates plasma by introducing microwaves such as microwaves into a processing chamber using an RLSA (Radial Line Slot Antenna) which is a planar antenna having a plurality of slots. It is configured as a plasma processing apparatus capable of generating microwave plasma with high density and low electron temperature. The plasma processing apparatus 100 can perform processing with plasma having a plasma density of 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a low electron temperature of 0.7 to 2 eV.

  The plasma processing apparatus 100 is hermetically configured and has a substantially cylindrical chamber (processing container) 1 that is grounded and into which a semiconductor wafer (hereinafter simply referred to as a wafer) W, which is a substrate to be processed, is carried. The chamber 1 is made of a metal material such as aluminum or stainless steel, and includes a housing part 2 constituting a lower part thereof and a cylindrical wall part 3 disposed thereon. However, the chamber 1 may be integrated. In addition, a microwave introduction part 26 for introducing a microwave into the processing space is provided on the upper portion of the chamber 1 so as to be openable and closable. At the time of processing, the microwave introduction portion 26 is engaged with the upper end portion of the cylindrical wall portion 3 while being hermetically sealed, and the lower end of the cylindrical wall portion 3 is hermetically sealed with the upper end of the housing portion 2. Engaged. A cooling water flow path 3a is formed in the cylindrical wall portion 3 so as to prevent a decrease in sealing performance and particle generation due to a displacement of the engaging portion due to thermal expansion.

  A circular opening 10 is formed in a substantially central portion of the bottom wall 2a of the housing portion 2. The bottom wall 2a communicates with the opening 10 and protrudes downward to uniformly exhaust the inside of the chamber 1. An exhaust chamber 11 is provided continuously.

  A wafer mounting table (substrate mounting table) 5 for horizontally mounting a wafer W as a substrate to be processed is supported in the housing portion 2 by a cylindrical support member 4 extending upward from the bottom center of the exhaust chamber 11. It is provided in the state that was done. The wafer mounting table 5 has a mounting table main body 51 made of AlN having a diameter larger than that of the wafer W. The mounting table main body 51 is covered with a cover 54, and has a mounting surface 54 a on which the wafer W is mounted on the upper surface of the cover 54. In addition, three (only two are shown) elevating pins 52 for elevating the wafer W are inserted into the mounting table main body 51. Further, a resistance heating type heater 56 is embedded in the mounting table main body 51, and an electrode 57 is embedded in the surface side of the mounting table main body 51. The detailed configuration of the wafer mounting table 5 will be described later.

  A heater power source 6 is connected to the heater 56 via a power supply line 6a passing through the support member 4. When the heater power is supplied from the heater power source 6 to the heater 56, the heater 56 generates heat and the wafer is loaded. The wafer W mounted on the mounting table 5 is heated. A filter box 45 having a noise filter for blocking high frequency noise to the heater power supply 6 is interposed in the power supply line 6a. The temperature of the wafer mounting table 5 is measured by a thermocouple (not shown) inserted in the wafer mounting table 5, and the output of the heater power supply 6 is controlled based on the temperature signal from the thermocouple. Temperature control is possible in the range up to 900 ° C.

  As a material of the electrode 57, for example, a refractory metal material such as molybdenum or tungsten can be suitably used. The electrode 57 is formed in, for example, a mesh shape, a lattice shape, or a spiral shape. The electrode 57 is connected to a high-frequency power supply 44 for applying a bias via a power supply line 42 passing through the support member 4. By supplying high-frequency power from the high-frequency power supply 44 to the electrode 57, the mounting table main body 51. A high frequency bias is applied to the wafer W, and a high frequency bias is also applied to the wafer W thereon via the mounting table main body 51 so that ion species in the plasma can be drawn into the wafer W. The power supply line 42 is provided with a matching box 43 having a matching circuit for matching the plasma impedance with the high frequency power supply 44.

  The filter box 45 and the matching box 43 are connected as a unit by a shield box 46 and attached to the lower side of the bottom wall of the exhaust chamber 11. The shield box 46 is made of a conductive material such as aluminum or stainless steel, and has a function of blocking leakage of microwaves.

  Sealing members 9a, 9b, 9c such as O-rings are provided on the upper and lower engaging portions of the cylindrical wall portion 3, so that the airtight state of the engaging portions is maintained. These sealing members 9a, 9b, 9c are made of, for example, a fluorine rubber material.

  As shown in the enlarged view of FIG. 2, a plurality of gas supply paths 12 are formed in an arbitrary position (for example, four equal positions) in the housing portion 2 in the vertical direction. A gas supply device 16 is connected to the gas supply path 12 via a gas supply pipe 16a (see FIG. 1). A predetermined processing gas or the like is supplied from the gas supply device 16 into the chamber 1 as will be described later. Supplied.

  The gas supply path 12 is connected to an annular passage 13, which is a processing gas supply communication path, formed in a contact surface portion between the upper portion of the housing portion 2 and the lower portion of the cylindrical wall portion 3. A plurality of gas passages 14 connected to the annular passage 13 are formed in the cylindrical wall portion 3. In addition, gas inlets 15a are uniformly provided at a plurality of locations (for example, 32 locations) along the inner peripheral surface at the upper end of the cylindrical wall portion 3, and gas extending horizontally from these gas inlets 15a. An introduction path 15b is provided. The gas introduction path 15 b communicates with a gas passage 14 formed in the vertical direction in the cylindrical wall portion 3.

  The annular passage 13 is configured by a gap between a step portion 18 and a step portion 19 which will be described later at a contact surface portion between the upper portion of the housing portion 2 and the lower portion of the cylindrical wall portion 3. The annular passage 13 communicates horizontally and annularly so as to surround the processing space above the wafer W.

  The annular passage 13 is connected to the gas supply device 16 via the gas supply path 12. The annular passage 13 has a function as gas distribution means for supplying gas to the gas passages 14 evenly distributed, and has a function of preventing the processing gas from being biased and supplied to the specific gas inlet 15a. Have.

  Then, the gas from the gas supply device 16 is supplied into the chamber 1 through the gas supply ports 15, the annular passages 13, and the gas passages 14 through the gas inlets 15 a provided in 32 places. ing. Thus, since the gas is uniformly introduced from the 32 gas inlets 15a, the uniformity of the plasma in the chamber 1 can be increased.

  At the lower end portion of the inner peripheral surface of the cylindrical wall portion 3, a projecting portion 17 is formed in an annular shape that hangs downward in a hook shape (skirt shape). The projecting portion 17 is provided so as to cover the boundary (contact surface portion) between the cylindrical wall portion 3 and the housing portion 2, and the plasma directly acts on the seal member 9b made of a material that easily deteriorates when exposed to the plasma. It plays a role in preventing it.

  The step portion 18 is formed at the upper end of the housing portion 2, the step portion 19 is provided at the upper end of the cylindrical wall portion 3, and the annular passage 13 is formed by combining these step portions 18 and 19. The height of the step portion 19 is larger than the height of the step portion 18, and therefore, in a state where the lower end of the cylindrical wall portion 3 and the upper end of the housing portion 2 are engaged, the side on which the seal member 9 b is provided. Then, the projecting surface of the step portion 19 and the non-projecting surface of the step portion 18 are in contact with each other. On the side where the seal member 9a is provided, the non-projecting surface of the step portion 19 and the projecting surface of the step portion 18 are provided. Is in a non-contact state. By doing in this way, it can be set as the state which contact | abutted reliably the protrusion surface of the step part 19, and the non-protrusion surface of the step part 18, and can seal between these reliably by the sealing member 9b. That is, the seal member 9b functions as a main seal portion. The seal portion 9a is interposed between the non-projecting surface of the stepped portion 19 and the protruding surface of the stepped portion 18 in a non-contact state, thereby maintaining an airtightness that prevents gas from leaking to the outside. It has a function as a part.

  As shown in FIG. 1, a cylindrical liner 49 made of quartz is provided on the inner periphery of the chamber 1. The liner 49 includes an upper liner 49 a that mainly covers the inner surface of the cylindrical wall portion 3, and a lower liner 49 b that continues to the upper liner 49 a and mainly covers the inner surface of the housing portion 2. The upper liner 49 a and the lower liner 49 b have functions of preventing metal contamination due to the chamber constituent material and preventing abnormal discharge due to high-frequency power between the wafer mounting table 5 and the side wall of the chamber 1. From the standpoint of reliably preventing abnormal discharge, the thickness of the lower liner 49b closer to the wafer mounting table 5 is made thicker than that of the upper liner 49a, and the lower liner 49b is located at a lower position than the wafer mounting table 5 in the exhaust chamber 11. It is provided so as to cover partway. Further, a quartz baffle plate 30 having a large number of exhaust holes 30a is provided in an annular shape on the outer peripheral side of the wafer mounting table 5 in order to exhaust the chamber 1 uniformly. The upper liner 49a and the lower liner 49b may be integrated.

  An exhaust pipe 23 is connected to the side surface of the exhaust chamber 11, and an exhaust device 24 including a high-speed vacuum pump is connected to the exhaust pipe 23. Then, by operating the exhaust device 24, the gas in the chamber 1 is uniformly discharged into the space 11 a of the exhaust chamber 11 and exhausted through the exhaust pipe 23. Thereby, the inside of the chamber 1 can be depressurized at a high speed to a predetermined degree of vacuum, for example, 0.133 Pa.

  On the side wall of the housing portion 2, a loading / unloading port for loading / unloading the wafer W and a gate valve for opening / closing the loading / unloading port (not shown) are provided.

  The upper part of the chamber 1 is an opening, and the microwave introduction part 26 can be airtightly arranged so as to close the opening. The microwave introduction unit 26 can be opened and closed by an opening / closing mechanism (not shown).

  The microwave introduction unit 26 includes a lid frame 27, a transmission plate 28, a planar antenna 31, and a slow wave material 33 in order from the wafer mounting table 5 side. These are covered with a conductive cover member 34 made of, for example, stainless steel (SUS), aluminum, an aluminum alloy, etc., and an O-ring is interposed by an annular presser ring 35 having an L-shape in cross section through a support member 36. It is fixed to the lid frame 27. When the microwave introduction portion 26 is closed, the upper end of the chamber 1 and the lid frame 27 are sealed by the seal member 9c and supported by the lid frame 27 via a transmission plate 28 as will be described later. It has become a state. A cooling water flow path 27b is formed on the outer peripheral surface of the lid frame 27 to prevent a decrease in sealing performance due to the occurrence of misalignment of the joining portion due to thermal expansion and the generation of particles due to plasma contact.

The transmission plate 28 is made of a dielectric material such as quartz, Al ₂ O ₃ , AlN, sapphire, SiN, or the like, and functions as a microwave introduction window that transmits microwaves and introduces them into the processing space in the chamber 1. The lower surface of the transmission plate 28 (on the wafer mounting table 5 side) is not limited to a flat shape, and in order to stabilize the plasma by uniformizing the microwave, for example, a recess or a groove may be formed. The outer peripheral portion of the transmission plate 28 is supported in an airtight state via the seal member 29 by the upper surface of the protrusion 27a that protrudes toward the space in the chamber 1 on the inner peripheral surface of the lid frame 27 arranged in an annular shape. ing. Therefore, it becomes possible to keep the inside of the chamber 1 airtight with the microwave introduction part 26 closed.

  The planar antenna 31 has a disk shape and is locked to the inner peripheral surface of the cover member 34 at a position above the transmission plate 28. The planar antenna 31 is made of, for example, a copper plate, an aluminum plate, a nickel plate, or a brass plate whose surface is gold or silver plated, and a number of microwave radiation holes (slots) 32 for radiating electromagnetic waves such as microwaves are predetermined. It is the structure formed by penetrating in this pattern.

  For example, as shown in FIG. 3, the slots 32 form a pair, and typically, the pairs of slots 32 are arranged in a “T” shape, and a plurality of these pairs are concentrically arranged. Has been placed. The lengths and arrangement intervals of the slots 32 are determined according to the wavelength (λg) of the microwave. For example, the intervals of the microwave radiation holes 32 are arranged to be λg / 4 to λg. In FIG. 2, the interval between adjacent slots 32 formed concentrically is indicated by Δr. Further, the slot 32 may have another shape such as a circular shape or an arc shape. Furthermore, the arrangement form of the slots 32 is not particularly limited, and the slots 32 may be arranged concentrically, for example, spirally or radially.

  The slow wave material 33 has a dielectric constant larger than that of the vacuum, and is provided on the upper surface of the planar antenna 31. The slow wave material 33 is made of, for example, a fluorine resin such as quartz, ceramics, polytetrafluoroethylene, or a polyimide resin. Since the wavelength of the microwave becomes longer in vacuum, the wavelength of the microwave is reduced. It has the function of adjusting plasma by shortening. The planar antenna 31 and the transmission plate 28 and the slow wave member 33 and the planar antenna 31 may be in close contact with each other or may be separated from each other, but they are preferably in close contact.

  The cover member 34 is formed with a cooling water flow path 34a, and the cover member 34, the slow wave material 33, the planar antenna 31, the transmission plate 28, and the lid frame 27 are cooled by allowing the cooling water to flow therethrough. It is like that. Thereby, it is possible to prevent deformation and breakage and to generate stable plasma. The cover member 34 is grounded.

  An opening 34b is formed at the center of the upper wall of the cover member 34, and a waveguide 37 is connected to the opening 34b. A microwave generator 39 is connected to the end of the waveguide 37 via a matching circuit 38. Thereby, for example, a microwave having a frequency of 2.45 GHz generated by the microwave generator 39 is propagated to the planar antenna 31 through the waveguide 37. As the microwave frequency, 8.35 GHz, 1.98 GHz, or the like can be used.

  The waveguide 37 is connected to a coaxial waveguide 37a having a circular cross section extending upward from the opening 34b of the cover member 34, and an upper end portion of the coaxial waveguide 37a via a mode converter 40. And a rectangular waveguide 37b extending in the horizontal direction. The mode converter 40 between the rectangular waveguide 37b and the coaxial waveguide 37a has a function of converting the microwave propagating in the TE mode in the rectangular waveguide 37b into the TEM mode. An inner conductor 41 extends in the center of the coaxial waveguide 37a, and the inner conductor 41 is connected and fixed to the center of the planar antenna 31 at the lower end thereof. As a result, the microwave is efficiently and uniformly propagated radially and uniformly to the planar antenna 31 via the inner conductor 41 of the coaxial waveguide 37a.

  The inside of the lid frame 27 is formed so as to face the plasma generation region in the chamber 1, and its surface is sputtered by being exposed to strong plasma, which causes contamination and consumption. For this reason, a silicon film 48 as a protective film is coated on the surface of the protrusion 27a of the aluminum lid frame 27 that functions as a counter electrode with respect to the wafer mounting table. That is, the silicon film 48 protects the surface of the lid frame 27 from the oxidizing action and sputtering action by plasma, and prevents the aluminum and the like constituting the lid frame 27 from being generated as contamination. The silicon film 48 may be crystalline or amorphous. In addition, since the silicon film 48 is conductive, a high-frequency current path that flows from the wafer mounting table 5 to the lid frame 27 that is the counter electrode across the plasma processing space is efficiently formed to cause a short circuit or abnormality in other parts. It also has a function of suppressing discharge.

  The silicon film 48 can be formed by a thin film forming technique such as a PVD method (physical vapor deposition method) and a CVD method (chemical vapor deposition method), a plasma spraying method, or the like, and among them, a thick film should be formed relatively inexpensively. Therefore, the plasma spraying method is preferable.

  Each component of the microwave plasma processing apparatus 100 is connected to and controlled by the control unit 60. As shown in FIG. 4, the control unit 60 includes a process controller 61 including a microprocessor, a user interface 62 connected to the process controller, and a storage unit 63.

  In the plasma processing apparatus 100, the process controller 61 is configured so that each component, for example, the heater power supply 6, has a desired process condition such as temperature, pressure, gas flow rate, microwave output, and high frequency power for bias application. The gas supply device 16, the exhaust device 24, the microwave generator 39, the high frequency power supply 44, and the like are controlled.

  The user interface 62 includes a keyboard on which an operator inputs commands to manage the plasma processing apparatus 100, a display for visualizing and displaying the operating status of the plasma processing apparatus 100, and the like. In addition, the storage unit 63 executes processing on each component of the plasma processing apparatus 100 in accordance with a control program for realizing various processes executed by the plasma processing apparatus 100 under the control of the process controller 61 and processing conditions. A program for processing, that is, a processing recipe is stored.

  Control programs and processing recipes are stored in a storage medium in the storage unit 63. The storage medium may be a hard disk or semiconductor memory, or may be portable such as a CDROM, DVD, flash memory or the like. Further, instead of storing in a storage medium, a processing recipe or the like may be appropriately transmitted from another device, for example, via a dedicated line.

  If necessary, an arbitrary processing recipe is called from the storage unit 63 according to an instruction from the user interface 62 and is executed by the process controller 61, so that the plasma processing apparatus 100 can control the process controller 61 under the control of the process controller 61. Desired processing is performed.

Next, the wafer mounting table 5 will be described in detail.
FIG. 5 is an enlarged cross-sectional view of the wafer mounting table 5. As described above, the wafer mounting table 5 is provided in the housing portion 2 in a state of being supported by the cylindrical support member 4 extending upward from the bottom center of the exhaust chamber 11. The mounting table main body 51 of the wafer mounting table 5 is made of AlN, which is a ceramic material having good thermal conductivity, and three insertion holes 53 (only two are shown) through which the lifting pins 52 are inserted are vertically arranged. It is formed through. The cover 54 is made of high-purity quartz and is provided so as to cover the upper surface and side surfaces of the mounting table main body 51.

  At the center of the upper surface of the mounting table main body 51, a countersink part 51a is formed which forms a groove into which the cover 54 is fitted in an area corresponding to the mounting area of the wafer W. And the convex part 54c which protrudes below is formed in the center part of the cover 54 so that the counterbore part 51a may be fitted. A concave portion 54b is formed on the upper surface of the cover 54 opposite to the convex portion 54c, and a bottom portion of the concave portion 54b serves as a wafer placement region (substrate placement region) 54a on which the wafer W is placed. As described above, the convex portion 54 c of the cover 54 is fitted to the countersink portion 51 a, so that the cover 54 is not displaced from the mounting table main body 51.

  The cover 54 is configured such that the thickness d1 of the central wafer placement area 54a is thicker than the thickness d2 of the outer area 54d outside the wafer placement area 54a. Thus, the amount of heat per unit area supplied to the outer region 54d outside the wafer mounting region 54a is larger than the amount of heat per unit area supplied from the mounting table main body 51 to the wafer mounting region 54a. It is configured. The temperature of the wafer W is controlled by adjusting the thickness d1 of the wafer placement area 54a and the thickness d2 of the outer area 54d.

  Note that the cover 54 has a side surface portion 51 e that covers the side surface of the mounting table main body 51, thereby preventing contamination from the side surface of the mounting table main body 51.

  The elevating pin 52 inserted through the insertion hole 53 is fixed to the pin support member 58. That is, the lift pins 52 are configured as fixed pins. A vertically extending rod 59 is connected to the pin support member 58, and the lift pin 52 is lifted and lowered via the pin support member 58 by lifting and lowering the lift rod 59 by an actuator (not shown). Yes. In addition, 59a is a bellows provided so that the raising / lowering rod 59 can be raised / lowered in an airtight state.

  The wafer mounting table 5 may be configured such that the wafer W is simply mounted on the wafer mounting area 54 a at the center of the cover 54 described above.

Next, the operation of the plasma processing apparatus 100 configured as described above will be described.
First, the wafer W is loaded into the chamber 1 and placed on the susceptor 5. Then, a predetermined processing gas is introduced from the gas supply device 16 into the chamber 1 at a predetermined flow rate through the gas inlet 15a. When performing oxidation treatment of silicon, which is a typical example, an oxidizing gas such as O ₂ , N ₂ O, NO, NO ₂ , and CO ₂ and a rare gas such as Ar, Kr, and He are used as necessary. The plasma treatment may be a nitriding treatment or a film forming treatment. In the case of the nitriding treatment, a nitriding gas such as N ₂ or NH ₃ and a rare gas as required are used. In the case of the film forming treatment, An appropriate film forming gas such as Si ₂ H ₆ and N ₂ or NH ₃ is used.

  Next, the microwave from the microwave generator 39 is guided to the waveguide 37 through the matching circuit 38, and is sequentially passed through the rectangular waveguide 37b, the mode converter 40, and the coaxial waveguide 37a. It is supplied to the planar antenna 31 via 41 and radiated from the slot of the planar antenna 31 into the chamber 1 via the transmission plate 28.

  The microwave propagates in the TE mode in the rectangular waveguide 37b, and the TE mode microwave is converted into the TEM mode by the mode converter 40 and propagates in the coaxial waveguide 37a toward the planar antenna 31. It will be done. An electromagnetic field is formed in the chamber 1 by the microwave radiated from the planar antenna 31 to the chamber 1 through the transmission plate 28, and the processing gas is turned into plasma.

At this time, if necessary, high frequency power having a predetermined frequency and power is supplied from the high frequency power supply 44 to the electrode 57 of the mounting table body 51 to apply a high frequency bias to the mounting table body 51, and further, the mounting table body A high frequency bias is also applied to the wafer W thereon via 51. Thereby, while maintaining the low electron temperature of the plasma, the action of drawing the ion species in the plasma into the wafer W is exhibited, the processing rate of the plasma processing can be increased, and the in-plane uniformity of the plasma processing can be increased. The frequency of the high frequency power for applying the high frequency bias is preferably, for example, in the range of 100 kHz to 60 MHz, and more preferably in the range of 400 kHz to 13.56 MHz. The power of the high frequency power is preferably in the range of, for example, 0.2 to 2.3 W / cm ² as the power density per unit area of the wafer W. Moreover, as high frequency power itself, the range of 200-2000W is preferable.

  The plasma thus formed is allowed to act on the wafer W that is the substrate to be processed, and a predetermined plasma process is performed on the wafer W heated to a predetermined temperature by the heater 56. For example, when a silicon portion (polysilicon or silicon substrate) existing on the wafer W is oxidized, plasma of the oxidizing gas or the like is applied to the wafer W heated to 200 to 600 ° C., for example, 400 ° C. Make it work.

The plasma thus formed has a high density of about 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a wafer by radiating microwaves from a large number of slot holes 32 of the planar antenna member 31. In the vicinity of W, low electron temperature plasma of about 1.5 eV or less is obtained. Therefore, by causing this plasma to act on the wafer W, processing that suppresses plasma damage is possible.

  In such plasma processing, heat (radiant heat) from the mounting table main body 51 heated by the heater 56 is supplied to the wafer W through the cover 54. Conventionally, the temperature of the outer peripheral portion of the wafer W is low. Tended to be. On the other hand, in the present embodiment, the thickness d1 of the wafer placement area 54a of the cover 54 is made thicker than the thickness d2 of the outer area 54d outside the wafer placement area 54a. The amount of heat per unit area supplied to the outer region 54d from the mounting surface 54 is larger than the amount of heat per unit area supplied from the mounting surface 54a to the mounting surface 54a, thereby reducing the temperature of the outer periphery of the wafer W. Can be suppressed.

  Conventionally, the thickness of the cover 54 is uniform, and in the region where the heater 56 is present, the amount of heat per unit area given to the surface of the cover 54 is considered to be almost uniform, but nevertheless, the wafer The temperature of the outer peripheral portion of W tended to decrease. This is presumably because even if the same amount of heat is applied, the outer peripheral portion of the cover 54 is exposed to the processing space, and therefore the outer peripheral portion radiates more heat. For this reason, in the present embodiment, the temperature drop at the outer peripheral portion of the wafer W is suppressed by supplying a larger amount of heat to the outer region 54d than the wafer placement region 54a. That is, as the cover 54 is thinner, the amount of heat transferred from the lower mounting table main body 51 to the upper surface of the cover 54 increases, so that per unit area supplied to the upper surface of the wafer mounting region 54a having a relatively thick thickness d1. The amount of heat per unit area supplied to the upper surface of the outer region 54d having a relatively small thickness d2 is larger than the amount of heat of the wafer W, and the amount of heat supplied to the outer peripheral portion of the wafer W increases. The temperature drop at the outer periphery is suppressed. As a result, the plasma processing rate on the outer periphery of the wafer W can be increased, and uniform plasma processing can be realized. In this case, the temperature of the outer peripheral portion of the wafer W can be relatively increased by increasing the difference between the thickness d1 and the thickness d2. Further, by appropriately adjusting the thickness d1 of the wafer placement region 54a and the thickness itself of the outer region d2, the temperature of the wafer W itself can be controlled, and the plasma processing rate can be controlled.

  That is, by utilizing the transmittance of the heat ray with respect to the quartz cover 54, the thickness of the outer region 54d of the cover 54 is relatively reduced to increase the amount of heat to the outer region 54d, thereby lowering the temperature of the outer peripheral portion of the wafer W. The temperature of the wafer W itself is controlled by changing the thickness of the cover 54 itself and adjusting the amount of heat rays reaching the wafer W, thereby controlling the plasma processing rate. To control.

  In the above example, the recess 54c is formed in the cover 54 by forming the countersunk portion 51a in the mounting table main body 51 for alignment of the wafer W, and the mounting surface 54a is provided there. As shown in FIG. 6, the upper surface of the mounting table main body 51 may be flat, or the upper surface of the cover 54 may be flat as shown in FIG. In this case, the positioning of the wafer W can be performed by providing an outer wall on the outer side of the wafer W or by providing a plurality of guide pins (all not shown).

  Next, simulation results that have led to the configuration of the present embodiment will be described. Here, for the sake of simplicity, the temperature of the center and edge of the wafer when various cover shapes are used, considering only heat conduction and not considering heat radiation, general-purpose steady heat conduction analysis software. It was calculated | required by simulation by 3GA (made by Palsso Tech) which is.

  No. which is a reference. 1, as shown in FIG. 8, the thickness of the cover 54 was made uniform as 1.5 mm. No. 2, as shown in FIG. 9, in order to increase the heat capacity of the outer region 54 d outside the wafer placement region 54 a of the cover 54, the thickness of that portion was increased to 4 mm. Furthermore, no. 3, as shown in FIG. 10, in order to increase the heat capacity outside the wafer placement region 54 a, the thickness of the side surface portion 54 e continuing to the outer region 54 d is increased by 10 mm (total 11.5 mm). This is intended to increase the temperature of the outer portion of the wafer W by forming a portion with a large heat capacity outside the wafer placement region 54a and storing heat in that portion.

As a result, No. which is a reference. Center temperature _{T C} of the wafer W mounted on the 1, wafer placing area 54a is 402.8 ° C., the wafer W of the edge temperature _{T E} is a 381.8 ° C., these differences Δt is 21 ° C. It was No. 2, T _C = 398.1 ° C., T _E = 374.5 ° C., Δt = 23.6 ° C., No. 2 3, T _C = 393 ° C., T _E = 368 ° C., Δt = 25 ° C., and conversely, the temperature decrease at the outer periphery of the wafer W was severe. This is presumably because by increasing the thickness of the outer region 54d and the side surface portion 54e, they function as a heat sink, and the heat supply to the outer region 54d rather than the wafer mounting region 54a is rather reduced.

Therefore, conversely, the wafer mounting area 54a of the cover 54 is thickened. 4 and 5 were simulated. No. As shown in FIG. 11, the thickness d1 of the wafer mounting area 54a is made as thick as 3.5 mm, and the thickness d2 of the outer area 54d is kept at 1.5 mm. As shown in FIG. 12, d1 is 2.5 mm and d2 is 1.5 mm as shown in FIG. As a result, no. 4, T _C = 346.6 ° C., T _E = 334.3 ° C., Δt = 12.3 ° C., No. 4 In Example 5, T _C = 372.16 ° C., T _E = 357.7 ° C., Δt = 14.4 ° C., and Δt was successfully reduced. However, no. In 4 _{T C} is as low as 346.6 ° C., No. _{T C} although the 5 d1 returned to 2.5mm becomes still lower result 372.16 ° C.. Therefore, no. 6, as shown in FIG. 13, simulation was performed with d1 being 2 mm and d2 being 1 mm. As a result, T _C = 386.7 ° C., T _E = 373.7 ° C., Δt = 13 ° _C. Can be within the allowable range. Furthermore, the temperature can be controlled more strictly by adjusting the thickness of the cover 54. However, it is considered to be a limit due to processing problems.

  Thus, by reducing the thickness d2 of the outer region 54d by a predetermined amount from the thickness d1 of the wafer placement region 54a of the cover 54, the temperature drop of the wafer edge portion can be suppressed. Then, by adjusting the thickness of the wafer mounting area 54a and the thickness of the outer area 54d as appropriate, the temperature of the wafer W is appropriately controlled while suppressing the temperature decrease at the outer periphery of the wafer W, thereby performing more uniform plasma processing. It was confirmed that it could be done.

Next, the results of actual plasma processing using the wafer mounting table according to the present embodiment will be described in comparison with a comparative example.
Here, in the plasma processing apparatus of FIG. 1, a silicon nitride film was formed using the wafer mounting table according to the present embodiment shown in FIG. 14 and the wafer mounting table according to the comparative example shown in FIG. The conditions in this case were as follows: the pressure in the chamber was 6.7 Pa, the power of the high frequency bias was 3 kW, N ₂ gas was 600 mL / min (sccm), Ar gas was 100 mL / min (sccm), and Si ₂ H ₆ gas was 4 mL. The film was supplied at a flow rate of / min (sccm) and the temperature of the mounting table body was set to 500 ° C. FIG. 16 shows the relationship between the position on the wafer and the film formation rate at that time. As shown in this figure, in the case of the comparative example, the film formation rate decreases at the edge of the wafer, whereas when the wafer mounting table according to this embodiment is used, the film formation rate at the wafer edge decreases. Was confirmed to be suppressed. Further, the uniformity of the film forming rate (1σ) at this time was 5.5% in the comparative example, but 3.3% in the present embodiment. It was confirmed that the uniformity of the film rate (plasma treatment) was high.

Next, another embodiment of the present invention will be described.
FIG. 17 is an enlarged cross-sectional view showing a wafer mounting table 5 ′ used in a plasma processing apparatus according to another embodiment of the present invention. Since the basic structure of the wafer mounting table 5 'is the same as that of the wafer mounting table 5 shown in FIG. 5, the same parts are denoted by the same reference numerals and description thereof is omitted. The wafer mounting table 5 ′ of the present embodiment has a mounting table main body 51 ′ made of AlN having a flat upper surface and a high purity quartz cover 54 ′ provided so as to cover the surface. Yes.

  The cover 54 'has a wafer placement area 54a' at the center of the upper surface thereof. Further, the upper surface of the cover 54 'has a planar shape, and a plurality of guide pins 70 for positioning the wafer W in the wafer placement area 54a' are provided thereon.

  A step is formed between the wafer mounting area 54a ′ of the cover 54 ′ and the outer area 54d ′ outside the cover 54 ′. Due to the step, the wafer mounting area 54a ′ of the cover 54 ′ and the mounting table main body 51 ′ are formed. A gap 71 is formed between the two. Therefore, heat is directly transmitted from the mounting table main body 51 ′ where there is no gap to the outer region 54 d ′, but heat is transferred from the mounting table main body 51 to the wafer mounting region 54 a ′ via the gap 71. , Inevitably less heat is transferred. Therefore, the amount of heat per unit area supplied to the outer region 54d ′ is larger than the amount of heat per unit area supplied from the mounting table main body 51 ′ to the wafer mounting region 54a ′. For this reason, also in the present embodiment, the amount of heat supplied to the outer peripheral portion of the wafer W increases, and as a result, the temperature decrease of the outer peripheral portion of the wafer W can be suppressed, and uniform plasma processing can be performed. In this case, the temperature of the wafer W itself can be controlled by adjusting the distance G of the gap 71 as appropriate, and the temperature of the wafer W itself is controlled in addition to suppressing the temperature drop at the outer periphery of the wafer W. And the plasma treatment rate can be controlled.

  However, if the distance G of the gap 71 is too large, the temperature of the wafer W may not be set to a desired temperature. Therefore, when the temperature control of the wafer W cannot be sufficiently performed even if the distance G of the gap 71 is increased to an allowable range, the gap 71 is provided between the wafer placement area 54a ′ and the placement table main body 51 ′. Further, as in the previous embodiment, the thickness d1 and d2 itself are adjusted, for example, the thickness d2 of the outer region 54d ′ is made thinner than the thickness d1 of the wafer mounting region 54a ′. By controlling, the temperature adjustment margin can be further increased, and the temperature can be controlled so as to perform a uniform plasma process and, in addition to that, to realize a desired plasma process rate. The temperature adjustment margin can be further increased by providing a gap between the wafer placement area 54a 'and the placement table main body 51' and adjusting the gap and the gap 71.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, an apparatus that applies a high-frequency bias to the wafer mounting table has been described as an example, but the present invention is not limited to an apparatus that applies a high-frequency bias. In the above embodiment, the plasma processing apparatus has been described by taking an RLSA type plasma processing apparatus as an example, but other plasma processing apparatuses such as a remote plasma system, an ICP system, an ECR system, a surface reflected wave system, a magnetron system, etc. It may be. Furthermore, the silicon oxidation process has been described as an example of the plasma process, but the present invention is not limited to this, and other various plasma processes such as a nitriding process, an oxynitriding process, a film forming process, and an etching process are targeted. Can do. Furthermore, the substrate to be processed is not limited to a semiconductor wafer, but can be another substrate such as an FPD glass substrate.

1 is a schematic cross-sectional view showing a schematic configuration of a plasma processing apparatus according to an embodiment of the present invention. Sectional drawing which expands and shows the chamber wall part of the apparatus of FIG. The figure which shows the structure of the planar antenna member used for the plasma apparatus of FIG. The block diagram which shows schematic structure of the control part of the apparatus of FIG. Sectional drawing which expands and shows the wafer mounting base used for the plasma processing apparatus of FIG. The expanded sectional view which shows the modification of a wafer mounting base. The expanded sectional view which shows the other modification of a wafer mounting base. No. which simulated wafer temperature. FIG. 2 is a schematic view showing one wafer mounting table. No. which simulated wafer temperature. Schematic which shows 2 wafer mounting bases. No. which simulated wafer temperature. Schematic which shows the wafer mounting base of 3. FIG. No. which simulated wafer temperature. 4 is a schematic diagram showing a wafer mounting table of No. 4; No. which simulated wafer temperature. FIG. 6 is a schematic view showing a wafer mounting table of 5. No. which simulated wafer temperature. Schematic which shows the wafer mounting base of 6. FIG. The schematic diagram which shows the wafer mounting base which concerns on embodiment of this invention which actually formed the silicon nitride film as a plasma processing. The schematic diagram which shows the wafer mounting base which concerns on the comparative example which actually formed the silicon nitride film as a plasma processing. The graph which shows the relationship between the position on a wafer at the time of forming a silicon nitride film using the wafer mounting base of FIG. 14 and FIG. 15, and a film-forming rate. Sectional drawing which expands and shows the wafer mounting base used for the plasma processing apparatus of other embodiment of this invention.

Explanation of symbols

1; chamber (processing vessel)
2; housing part 3; cylindrical wall part 4; support member 5; wafer mounting table 6; heater power supply 15; gas introduction path 15a; gas introduction port 16; gas supply unit 24; ; Microwave introduction part 31; Planar antenna 32; Slot hole 37; Waveguide 39; Microwave generator 43; Matching box 44; High-frequency power source 51, 51 '; Mounting base body 51a; ; Insertion hole 54, 54 '; Cover 54a, 54a'; Wafer mounting area 54b; Recess 54c; Protrusion 54d, 54d '; Outer area 56; Heater 57; Electrode member 71; Gap 100; Plasma processing apparatus d1, d2 Thickness G; distance W; semiconductor wafer (substrate to be processed)

Claims (14)

A processing container capable of being held in a vacuum and containing a substrate to be processed;
A substrate mounting table for mounting a substrate to be processed in the processing container;
A processing gas supply mechanism for supplying a processing gas into the processing container;
A plasma generation mechanism for generating plasma of a processing gas in the processing container,
The substrate mounting table is
A mounting table body larger in diameter than the substrate to be processed;
A heating element provided in the mounting table main body for heating the substrate to be processed, and
Covering the surface of the mounting table main body, having a substrate mounting area for mounting the substrate to be processed,
The cover is configured such that the amount of heat per unit area supplied to the outer region from the substrate placement region is larger than the amount of heat per unit area supplied to the substrate placement region. A plasma processing apparatus.   2. The plasma processing apparatus according to claim 1, wherein the cover has a thickness of the substrate placement area thicker than a thickness of an outer area outside the substrate placement area.   The plasma processing apparatus according to claim 1, wherein a gap is formed between the substrate placement area of the cover and the placement table main body.   The plasma processing apparatus according to claim 3, wherein the temperature of the substrate to be processed is controlled by adjusting the distance of the gap.   5. The temperature of the substrate to be processed is controlled by adjusting a thickness of the substrate placement region of the cover and a thickness of the outer region. 6. Plasma processing equipment.   The plasma processing apparatus according to claim 1, wherein the mounting table main body is made of AlN, and the cover is made of quartz.   The plasma generation mechanism includes a planar antenna having a plurality of slots, and a microwave introduction means for guiding a microwave into the processing container via the planar antenna, and the processing gas is converted into plasma by the introduced microwave. The plasma processing apparatus according to any one of claims 1 to 6, wherein   The plasma processing apparatus according to claim 7, further comprising a high-frequency bias applying unit that applies a high-frequency bias for drawing ions in the plasma to the substrate mounting table. In a plasma processing apparatus for performing plasma processing on a substrate to be processed in a processing container held in a vacuum, a substrate mounting table for mounting the substrate to be processed in the processing container,
A mounting table body larger in diameter than the substrate to be processed;
A heating element provided in the mounting table main body for heating the substrate to be processed, and
Covering the surface of the mounting table main body, having a substrate mounting area for mounting the object to be processed,
The cover is configured such that the amount of heat per unit area supplied to the outer region from the substrate placement region is larger than the amount of heat per unit area supplied from the mounting table body to the substrate placement region. A substrate mounting table.   The substrate mounting table according to claim 9, wherein the cover has a thickness of the substrate mounting region that is thicker than a thickness of an outer region outside the substrate mounting region.   The substrate mounting table according to claim 9 or 10, wherein a gap is formed between the substrate mounting region of the cover and the mounting table main body.   The substrate mounting table according to claim 11, wherein the temperature of the substrate to be processed is controlled by adjusting the distance of the gap.   13. The temperature of the substrate to be processed is controlled by adjusting a thickness of the substrate placement region of the cover and a thickness of the outer region. 13. Substrate mounting table.   The substrate mounting table according to any one of claims 9 to 13, wherein the mounting table main body is made of AlN, and the cover is made of quartz.