Patent ID: 12211671

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.FIG.1is a vertical cross-sectional view (cross-sectional view taken along a plane including the central axis of the wafer placement table10) of a wafer placement table10installed in a chamber94,FIG.2is a plan view of the wafer placement table10, andFIG.3is an enlarged cross-sectional view illustrating the vicinity of a power supply terminal hole36.

The wafer placement table10is used to perform CVD or etching on a wafer W utilizing plasma, and fixed to an installation plate96provided inside the chamber94for semiconductor process. The wafer placement table10includes a ceramic substrate20, a cooling substrate30, and a metal bonding layer40.

The ceramic substrate20includes an outer peripheral section24having an annular focus ring placement surface24aon the outer periphery of a central section22having a circular wafer placement surface22a. Hereinafter the focus ring may be abbreviated as “FR”. A wafer W is placed on the wafer placement surface22a, and a focus ring12is placed on the FR placement surface24a. The ceramic substrate20is composed of a ceramic material represented by alumina, or aluminum nitride. The FR placement surface24ais lower by one step than the wafer placement surface22a.

A wafer attraction electrode26is incorporated in the central section22of the ceramic substrate20at a position close to the wafer placement surface22a. The wafer attraction electrode26is composed of a material containing W, Mo, WC or MoC, for example. The wafer attraction electrode26is a disk-shaped or mesh-shaped monopole electrostatic attraction electrode. The layer, above the wafer attraction electrode26, of the ceramic substrate20functions as a dielectric layer. A wafer attraction DC power supply52is coupled to the wafer attraction electrode26via a power supply terminal54. The power supply terminal54is provided from the lower surface of the ceramic substrate20to the wafer attraction electrode26through an insulation pipe55disposed in a through-hole vertically penetrating the cooling substrate30and the metal bonding layer40. A low pass filter (LPF)53is provided between the wafer attraction DC power supply52and the wafer attraction electrode26.

The cooling substrate30is a disk member composed of a brittle conductive material. The cooling substrate30internally includes a refrigerant flow path32through which a refrigerant can be circulated. As illustrated inFIG.2, the refrigerant flow path32is provided from one end (inlet) to the other end (outlet) in a one-stroke pattern to cover the entire surface of the ceramic substrate20in a plan view. The one end and the other end of the refrigerant flow path32are respectively connected to a refrigerant supply path and a refrigerant discharge path which are provided in the installation plate96and not illustrated. The refrigerant discharged through the refrigerant discharge path undergoes temperature control, then is returned to the refrigerant supply path again. The refrigerant flowing through the refrigerant flow path32is preferably liquid, and preferably has an electrical insulating property. As an electrically insulative liquid, for example, a fluorine-based inert liquid may be mentioned. As a brittle conductive material, a composite material of metal and ceramic may be mentioned. As a composite material of metal and ceramic, a metal matrix composite (MMC) and a ceramic matrix composite (CMC) may be mentioned. Specific examples of such a composite material include a material containing Si, SiC and Ti, a material obtained by impregnating SiC porous body with Al and/or Si, and a composite material of Al2O3and TiC. A material containing Si, SiC and Ti is called SiSiCTi, a material obtained by impregnating SiC porous body with Al is called AlSiC, and a material obtained by impregnating SiC porous body with Si is called SiSiC. As the conductive material used for the cooling substrate30, AlSiC and SiSiCTi having a thermal expansion coefficient closer to that of alumina are preferable. The cooling substrate30is coupled to an RF power supply62via a power supply terminal64. A high pass filter (HPF)63is disposed between the cooling substrate30and the RF power supply62. The cooling substrate30has a flange34near its lower surface. The flange34is used to clamp the wafer placement table10to the installation plate96.

The cooling substrate30is provided with the power supply terminal hole36. The power supply terminal hole36penetrates the cooling substrate30vertically, and intersects with the refrigerant flow path32. The power supply terminal hole36stores the power supply terminal54for applying a voltage to the wafer attraction electrode26. The power supply terminal54is a rod-shaped member extending vertically. The upper end of the power supply terminal54is bonded to the lower surface of the wafer attraction electrode26. The lower end of the power supply terminal54reaches the lower opening of the power supply terminal hole36, and is in contact with the cone-shaped upper end of a power supply rod56provided in the chamber94. The power supply rod56is urged from a lower position to an upper position by a spring which is not illustrated. Thus, the upper end of the power supply rod56is in elastic contact with the lower end of the power supply terminal54. In the power supply terminal hole36, the insulation pipe55is disposed to support the power supply terminal54by allowing the power supply terminal54to pass through the insulation pipe55. The upper end of the insulation pipe55is bonded and fixed to the ceramic substrate20. The lateral surface of the insulation pipe55is provided with a convex section55awhich is in contact with the inner wall of the power supply terminal hole36. The convex section55ais provided to project in a radially outward direction. Two convex sections55amay be provided, for example, in a diameter direction, three or more convex sections55amay be provided in a radial manner, or the convex sections55amay be provided in a ring shape on the entire circumference of the insulation pipe55.

The metal bonding layer40bonds the lower surface of the ceramic substrate20and the upper surface of the cooling substrate30. The metal bonding layer40may be a layer composed of solder or a metal brazing material, for example. The metal bonding layer40is formed by TCB (Thermal compression bonding), for example. TCB is a publicly known method, by which a metal bonding material is inserted between two members to be bonded, and the two members are pressure-bonded in a state of heated to a temperature lower than or equal to the solidus temperature of the metal bonding material. The power supply terminal hole36also penetrates the metal bonding layer40vertically.

The lateral surface of the outer peripheral section24of the ceramic substrate20, the outer periphery of the metal bonding layer40and the lateral surface of the cooling substrate30are covered with an insulating film42. As the insulating film42, for example, a thermal spray film such as alumina and yttria may be mentioned.

The wafer placement table10is mounted on the installation plate96provided inside the chamber94with seal rings76,77interposed between the wafer placement table10and the installation plate96. The seal rings76,77are made of metal or resin. The seal ring76is disposed slightly inward of the outer edge of the cooling substrate30. The seal ring77is disposed to surround the lower opening edge of the power supply terminal hole36to prevent the refrigerant from leaking outwardly of the seal ring77.

The outer peripheral area of the wafer placement table10is attached to the installation plate96using a clamping member70. The clamping member70is an annular member with a substantially inverted L-shaped cross section, and has an inner peripheral stepped surface70a. With the inner peripheral stepped surface70aof the clamping member70placed on the flange34of the cooling substrate30of the wafer placement table10, bolts72are each inserted through the upper surface of the clamping member70and screwed into a screw hole provided on the upper surface of the installation plate96. The bolts72are attached to multiple sites (for example, eight sites or 12 sites) provided at regular intervals in the circumferential direction of the clamping member70. The clamping member70and the bolts72may be produced with an insulating material, or produced with a conductive material (such as metal).

The power supply rod56is inserted from the lower surface of the installation plate96into a through-hole97of the installation plate96, provided at a position opposed to the power supply terminal hole36. The through-hole97has a large diameter section at the upper half, and a small diameter section at the lower half. The inner wall of the small diameter section of the through-hole97is provided with a ring groove, into which an O-ring78is fitted. The O-ring78is pressed and deformed in a radial direction by the power supply rod56to prevent the refrigerant in the power supply terminal hole36from leaking down through the through-hole97. The one end and the other end of the refrigerant flow path32are respectively connected via a seal ring disposed between the cooling substrate30and the installation plate96to the refrigerant supply path and the refrigerant discharge path which are provided in the installation plate96and not illustrated. These seal rings prevent the refrigerant from leaking outward.

Next, a manufacturing example of the wafer placement table10will be described usingFIGS.4A to4G.FIGS.4A to4Gare manufacturing process views of the wafer placement table10. First, a disk-shaped ceramic sintered body120, from which the ceramic substrate20is made, is produced by hot-press firing of a molded body of ceramic powder (FIG.4A). The wafer attraction electrode26is incorporated in the ceramic sintered body120. Next, a hole27is formed from the lower surface of the ceramic sintered body120to the wafer attraction electrode26(FIG.4B), and the power supply terminal54is inserted into the hole27to bond the power supply terminal54to the wafer attraction electrode26(FIG.4C).

Concurrently, two disk members131,133are produced (FIG.4D). Then a groove132, which eventually serves as the refrigerant flow path32, is formed in the lower surface of the upper disk member131. A through-hole136a, which eventually serves as the power supply terminal hole36, is formed in part of the groove132. In addition, a through-hole136b, which eventually serves as the power supply terminal hole36, is formed in the lower disk member133. When the ceramic sintered body120is made of alumina, the disk members131,133are preferably made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina is approximately the same as the thermal expansion coefficients of SiSiCTi and AlSiC.

A disk member made of SiSiCTi can be produced as follows, for example. First, silicon carbide, metal Si and metal Ti are mixed to produce a powder mixture. Next, a disk-shaped molded body is produced by applying uniaxial pressure molding to the obtained powder mixture, and hot-press sintering is applied to the molded body in an inert atmosphere to obtain a disk member made of SiSiCTi.

Subsequently, a first metal bonding material is disposed on the upper surface of the lower disk member133. A vertically penetrating hole is provided at a position of the first metal bonding material, the position being opposed to the through-hole136b. Next, the upper disk member131is disposed on the first metal bonding material, and a second metal bonding material is disposed on the upper surface of the disk member131. A vertically penetrating hole is provided at a position of the second metal bonding material, the position being opposed to the through-hole136a. Then the ceramic sintered body120is placed on the second metal bonding material while the power supply terminal54of the ceramic sintered body120is being inserted into the through-holes136a,136bof the disk members131,133. Thus, a layered body is obtained, in which the disk member133, the first metal bonding material, the disk member131, the second metal bonding material and the ceramic sintered body120are layered in that order from the bottom. A bonded body110is obtained (FIG.4F) by pressurizing the layered body while heating it (TCB).

The bonded body110is such that the ceramic sintered body120is bonded to the upper surface of a circular block130from which the cooling substrate30is produced, with the metal bonding layer40interposed between the circular block130and the ceramic sintered body120. The circular block130is a layered structure body such that the upper disk member131and the lower disk member133are bonded with a metal bonding layer interposed therebetween. The circular block130internally has the refrigerant flow path32and the power supply terminal hole36. In addition, the power supply terminal54is stored in the power supply terminal hole36.

TCB is performed, for example, in the following manner. Specifically, the layered body is pressurized and bonded at a temperature lower than or equal to the solidus temperature of the metal bonding material (for example, more than or equal to a temperature obtained by subtracting 20° C. from the solidus temperature and less than or equal to the solidus temperature), and subsequently, the temperature is returned to room temperature. Consequently, the metal bonding material becomes a metal bonding layer. As the metal bonding material in this case, an Al—Mg based bonding material and an Al—Si—Mg based bonding material may be used. For example, when TCB is performed using an Al—Si—Mg based bonding material, the layered body is pressurized in a state of heated in a vacuum atmosphere. A metal bonding material with a thickness of approximately 100 μm is preferably used.

Subsequently, the outer periphery of the ceramic sintered body120is ground to form a step, thus the ceramic substrate20including the central section22and the outer peripheral section24is produced. In addition, the outer periphery of the circular block130is ground to form a step, thus the cooling substrate30including the flange34is produced. In addition, the insulation pipe55is inserted through the lower opening of the power supply terminal hole36. The power supply terminal54is inserted into the insulation pipe55. The upper end of the insulation pipe55is bonded to the ceramic substrate20. Furthermore, the insulating film42is formed by using ceramic powder to thermally spray the lateral surface of the outer peripheral section24of the ceramic substrate20, the periphery of the metal bonding layer40and the lateral surface of the cooling substrate30(FIG.4G). Consequently, the wafer placement table10is obtained.

Next, an example of use of the wafer placement table10will be described with reference toFIG.1. As described above, the outer peripheral area of the wafer placement table10is fixed to the installation plate96of the chamber94by the clamping member70. The upper end of the power supply rod56is in elastic contact with the lower surface of the power supply terminal54. The seal rings76,77are disposed between the installation plate96and the wafer placement table10. Electrically insulative liquid is supplied to the refrigerant flow path32as a refrigerant. The refrigerant passes through the refrigerant flow path32, and on the way also passes through the power supply terminal hole36. On the ceiling surface of the chamber94, a shower head95is disposed which injects a process gas through a large number of gas injection holes to the inside of the chamber94. The installation plate96is composed of an insulating material such as alumina, for example.

The focus ring12is placed on the FR placement surface24aof the wafer placement table10, and a disk-shaped wafer W is placed on the wafer placement surface22a. The focus ring12includes a step along the inner periphery of the upper end so as not to interfere with the wafer W. In this state, a DC voltage of the wafer attraction DC power supply52is applied to the wafer attraction electrode26to cause the wafer placement surface22ato attract the wafer W. The inside of the chamber94is set to have a predetermined vacuum atmosphere (or a predetermined reduced pressure atmosphere), and an RF voltage from the RF power supply62is applied to the cooling substrate30while supplying a process gas from the shower head95. Then a plasma is generated between the wafer W and the shower head95. The plasma is utilized to perform CVD film formation or etching on the wafer W. Although the focus ring12is also worn out along with plasma treatment of the wafer W, the focus ring12is replaced after several wafers W are treated because the focus ring12is thicker than the wafer W.

When the wafer W is treated with a high-power plasma, it is necessary to cool the wafer W efficiently. In the wafer placement table10, as the bonding layer between the ceramic substrate20and the cooling substrate30, the metal bonding layer40having a high thermal conductivity is used instead of a resin layer having a low thermal conductivity. Thus, the capability to remove heat from the wafer W (heat removal capability) is high. In addition, the thermal expansion difference between the ceramic substrate20and the cooling substrate30is small, thus even when the stress relaxation performance of the metal bonding layer40is low, a problem is unlikely to occur.

In the wafer placement table10described above, the power supply terminal hole36intersects with the refrigerant flow path32. Therefore, the refrigerant flow path32does not need to be provided so as to avoid the power supply terminal hole36. Therefore, temperature singularity is prevented from occurring at the portion of the wafer W, immediately above the power supply terminal hole36.

Also, electrically insulative liquid is supplied to the refrigerant flow path32as a refrigerant. Thus, the power supply terminal54and the cooling substrate30having electrical conductivity are insulated by the electrically insulative liquid.

Furthermore, in the power supply terminal hole36, the insulation pipe55is disposed to support the power supply terminal54by allowing the power supply terminal54to pass through the insulation pipe55. Since the power supply terminal54is supported by the insulation pipe55, the power supply terminal54can be prevented from being pressed and damaged by the flow of refrigerant. In addition, the voltage resistance across the cooling substrate30and the power supply terminal54can be increased.

Furthermore, the upper end of the insulation pipe55is fixed to the ceramic substrate20, and the lateral surface of the insulation pipe55is provided with the convex section55awhich is in contact with the inner wall of the power supply terminal hole36. Thus, the convex section55acan regulate the movement of the insulation pipe55supporting the power supply terminal54with in the power supply terminal hole36. Thus, the power supply terminal54can be prevented from being pressed and damaged by the flow of refrigerant reliably. Note that the convex section55amay be disposed close to the inner wall of the power supply terminal hole36without being in contact therewith.

The present invention is not limited to the above-described embodiment, and can be carried out by various modes as long as they belong to the technical scope of the invention.

In the embodiment described above, in the power supply terminal hole36, the insulation pipe55is disposed to support the power supply terminal54by allowing the power supply terminal54to pass through the insulation pipe55; however, the insulation pipe55may be omitted as illustrated inFIG.5. Even in this way, the power supply terminal54and the cooling substrate30having electrical conductivity are insulated by electrically insulative liquid.

In the embodiment described above, the insulation pipe55having the convex section55aon the lateral surface is used; however, the insulation pipe55having no convex section55aon the lateral surface may be used. Even in this way, the power supply terminal54is supported by the insulation pipe55, thus the power supply terminal54can be prevented from being pressed and damaged by the flow of refrigerant.

In the embodiment described above, as illustrated inFIGS.4A to4G, the cooling substrate30has a layered structure in which the two disk members131,133are bonded. However, without being particularly limited to this, for example, as in the wafer placement table210illustrated inFIG.6, a cooling substrate230with a single-layered structure may be used. InFIG.6, the same components as in the above-described embodiment are labeled with the same symbol. The cooling substrate230has a refrigerant flow path groove282opened in the upper surface. The refrigerant flow path232is formed by covering the upper opening of the refrigerant flow path groove282with the metal bonding layer40. A power supply terminal hole236is provided inside the refrigerant flow path232(the refrigerant flow path groove282). When the wafer placement table210is manufactured, the refrigerant flow path groove282and the power supply terminal hole236are formed in one disk member, and subsequently, the ceramic substrate20may be bonded to the disk member by TCB using a metal bonding material. Since the cooling substrate230has a single-layered structure, the manufacturing cost (material cost and production cost) of the cooling substrate230can be reduced as compared to a layered structure.

Alternatively, as in the wafer placement table310illustrated inFIG.7, a cooling substrate330with a single-layered structure may be used. InFIG.7, the same components as in the above-described embodiment are labeled with the same symbol. The cooling substrate330has a refrigerant flow path groove382opened in the lower surface. A refrigerant flow path332is formed by covering the lower opening of the refrigerant flow path groove382with the installation plate96and the seal ring76. Note that the seal ring77may be omitted. A power supply terminal hole336is provided inside the refrigerant flow path332(refrigerant flow path groove382). When the wafer placement table310is manufactured, the refrigerant flow path groove382and the power supply terminal hole336are formed in one disk member, and subsequently, the ceramic substrate20may be bonded to the disk member by TCB using a metal bonding material. Since the cooling substrate330has a single-layered structure, the manufacturing cost (material cost and production cost) of the cooling substrate330can be reduced as compared to a layered structure. Note that a sealing member to divide adjacent portions of the refrigerant flow path groove382may be disposed between the lower surface of the cooling substrate330and the upper surface of the installation plate96.

In the embodiment described above, as illustrated inFIG.2, the power supply terminal hole36is provided between the one end (inlet) and the other end (outlet) of the refrigerant flow path32; however, the power supply terminal hole36may be provided at the one or the other end of the refrigerant flow path32.

In the embodiment described above, the refrigerant flow path32provided in the cooling substrate30has one line (one system). However, without being particularly limited to this, for example, the refrigerant flow path32may have two or more lines, and one line may be provided with the power supply terminal hole36to intersect with the line, and other lines may not be provided with the power supply terminal hole36. An example thereof is illustrated inFIG.8.FIG.8is a plan view of another example of the wafer placement table10, and the same components as in the above-described embodiment are labeled with the same symbol. The refrigerant flow path432has a first line432aand a second line432b. The first line432aand the second line432bdo not intersect with each other, and are provided from one end (inlet) to the other end (outlet) in a one-stroke pattern in a plan view respectively. Note that the one end (inlet) and the other end (outlet) are provided at different positions in a plan view. The refrigerant is individually supplied and discharged to and from the first line432aand the second line432b. Although the second line432bis provided with the power supply terminal hole36, the first line432ais not provided with the power supply terminal hole36. When the power supply terminal hole36is provided at the second line432b, as illustrated inFIG.8, the power supply terminal hole36may be provided at one end (or the other end) of the second line432b, or provided between the one end and the other end of the second line432b. Alternatively, the second line432bmay not be provided with the power supply terminal hole36, and the first line432amay be provided with the power supply terminal hole36. Alternatively, when a plurality of power supply terminals are present, and each of the plurality of power supply terminals is individually stored in a power supply terminal hole, part of the plurality of power supply terminals may be provided in the first line432a, and the remaining part may be provided in the second line432b. Alternatively, a line is provided for each power supply terminal hole36, and a refrigerant may be individually supplied and discharged to and from each line.

In the embodiment described above, a hole may be provided which penetrates the wafer placement table10from the lower surface of the cooling substrate30to the wafer placement surface22a. As such a hole, a gas supply hole for supplying a thermally conductive gas (for example, He gas) to the back surface of the wafer W, and a lift pin hole for inserting a lift pin to lift or lower the wafer W with respect to the wafer placement surface22amay be mentioned. The thermally conductive gas is supplied to the space formed by the wafer W and a large number of small protrusions (to support the wafer W) which are provided on the wafer placement surface22aand not illustrated. For example, when the wafer W is supported by three lift pins, lift pin holes are provided at three sites.

In the embodiment described above, the cooling substrate30is produced with a brittle conductive material; however, the cooling substrate30may be produced with another brittle material (for example, an alumina material). Alternatively, the cooling substrate30may be produced with metal such as aluminum or aluminum alloy.

In the embodiment described above, the wafer attraction electrode26is incorporated in the central section22of the ceramic substrate20; however, instead of or in addition to this, an RF electrode for plasma generation may be incorporated, or a heater electrode (resistance heating element) may be incorporated. The wafer attraction electrode26may be used along with an RF electrode. In addition, a focus ring (FR) attraction electrode may be incorporated, or an RF electrode or a heater electrode may be incorporated in the outer peripheral section24of the ceramic substrate20.

In the embodiment described above, the ceramic sintered body120ofFIG.4Ais produced by hot-press firing of a molded body of ceramic powder, and the molded body may be produced by layering multiple tape molded bodies, or produced by a mold cast method, or produced by compacting ceramic powder.

In the embodiment described above, the ceramic substrate20and the cooling substrate30are bonded by the metal bonding layer40; however, a resin bonding layer may be used instead of the metal bonding layer40.

The application claims the benefit of Japanese Patent Application No. 2022-072511 filed Apr. 26, 2022, which is hereby incorporated by reference herein in its entirety.