JP7645996B2 - Wafer placement table - Google Patents

Description

The present invention relates to a wafer mounting table.

Conventionally, a wafer mounting table is known that includes a ceramic substrate having a wafer mounting surface and an electrode built therein, a cooling substrate having a refrigerant flow path, and a bonding layer that bonds the ceramic substrate and the cooling substrate. For example, Patent Documents 1 and 2 describe that in such a wafer mounting table, a cooling substrate made of a metal matrix composite material having a linear thermal expansion coefficient similar to that of the ceramic substrate is used. Also, they describe that the wafer mounting table is provided with terminal holes through which power supply terminals for supplying power to the electrodes are inserted, gas holes for supplying He gas to the back surface of the wafer, and lift pin holes through which lift pins for lifting the wafer from the wafer mounting surface are inserted.

Patent No. 5666748 Patent No. 5666749

However, because the heat dissipation capacity is poor around terminal holes, gas holes, and lift pin holes, the areas directly above these holes can become hot spots, where the temperature is higher than other areas of the wafer. Also, there can be other areas with poor heat dissipation capacity besides the areas around these holes, and hot spots can occur directly above these areas.

The present invention has been made to solve these problems, and its main objective is to prevent hot spots from occurring on the wafer.

[1] The wafer mounting table of the present invention comprises:
a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
The cooling substrate has, as a refrigerant flow path, a wide area refrigerant flow path formed over the entire area corresponding to the wafer mounting surface, and a local refrigerant flow path formed in a specific local area and to which refrigerant is supplied independently of the wide area refrigerant flow path.

This wafer mounting table is provided with a wide-area refrigerant flow path formed over the entire area corresponding to the wafer mounting surface, and a local refrigerant flow path formed in a predetermined local area to which the refrigerant is supplied independently of the wide-area refrigerant flow path. The predetermined local area is an area that is prone to become a hot spot, for example, a peripheral area of a terminal hole, a gas hole, or a lift pin hole. The diameter of the local area may be, for example, 1/5 or less of the diameter of the wafer mounting surface, or 1/10 or less. The center of the local area may be offset from the center of the wafer mounting surface. In the present invention, a local refrigerant flow path is provided to supply the refrigerant to such a local area independently of the wide-area refrigerant flow path, so that the local area can be cooled in a focused manner. Therefore, the occurrence of hot spots on the wafer can be suppressed.

In this specification, "up" and "down" do not represent absolute positional relationships, but rather relative positional relationships. Therefore, depending on the orientation of the wafer placement table, "up" and "down" can become "left" and "right," "front" and "back," or "down" and "up."

[2] In the wafer mounting table of the present invention (the wafer mounting table described in [1] above), the local refrigerant flow path may be supplied with a refrigerant having a lower temperature than the wide-area refrigerant flow path. In this way, the low-temperature refrigerant promotes heat removal from the local area.

[3] In the wafer mounting table of the present invention (the wafer mounting table described in [1] or [2] above), the refrigerant may be supplied to the local refrigerant flow path at a higher flow rate than the wide area refrigerant flow path. In this way, the high flow rate of refrigerant promotes heat removal from the local area.

[4] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [3] above), the volume ratio of the refrigerant flow path in the local region of the cooling substrate may be greater than the volume ratio of the refrigerant flow path in a region outside the local region. In this way, the refrigerant flow paths are arranged at high density in the local region, promoting heat removal from the local region. In addition to cases where only a local refrigerant flow path is formed in the local region, not only a local refrigerant flow path but also a wide-area refrigerant flow path may be formed. In such cases, the volume ratio of the refrigerant flow path in the local region may be the total volume ratio of the local refrigerant flow path and the wide-area refrigerant flow path in the local region. On the other hand, since a local refrigerant flow path is not formed in a region outside the local region, the volume ratio of the refrigerant flow path in a region outside the local region may be the volume ratio of the wide-area refrigerant flow path in the region outside the local region.

[5] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [4] above), the local refrigerant flow path may be provided with a heat exchange promotion structure that promotes heat exchange between the refrigerant flowing through the local refrigerant flow path and the wafer placed on the wafer mounting surface. In this way, the heat exchange promotion structure improves the heat transfer coefficient in the local refrigerant flow path and promotes heat removal from a local region. The heat exchange promotion structure may be a fin provided on the inner surface of the local refrigerant flow path, or may be a narrow portion where the flow path narrows midway through the local refrigerant flow path.

[6] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [5] above), the local refrigerant flow path may be supplied with a refrigerant having a higher thermal conductivity than the wide area refrigerant flow path. In this way, the refrigerant having a higher thermal conductivity promotes heat removal from the local area.

[7] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [6] above), the local refrigerant flow path may be supplied with a refrigerant having a larger specific heat capacity than the wide area refrigerant flow path. In this way, the temperature rise of the refrigerant is suppressed, and heat removal from the local area is promoted.

[8] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [7] above), the wide area refrigerant flow path and the local refrigerant flow path may be formed on the same plane parallel to the wafer mounting surface. In this way, both flow paths can be formed more simply than when they are formed in multiple stages, one above the other below a plane parallel to the wafer mounting surface.

[9] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [8] above), the wide area refrigerant flow path and the local refrigerant flow path may be formed in multiple stages, one above the other below a plane parallel to the wafer mounting surface. This allows for greater freedom in the arrangement of both flow paths than if they were formed on the same plane. When formed in multiple stages, the local refrigerant flow path may be formed above the wide area refrigerant flow path.

[10] The wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [9] above) may have a plurality of holes penetrating the cooling substrate in the vertical direction, and the local region may be a peripheral region of at least one of the plurality of holes. Generally, the region directly above such a hole on the wafer is prone to becoming a hot spot. Therefore, there is great significance in applying the present invention.

[11] The wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [10]) has a plurality of holes penetrating the cooling substrate in the vertical direction, and the local region is a peripheral region of at least one of the plurality of holes, and the hole may be at least one of a power supply member insertion hole provided in the wafer mounting table from the electrode downward and through which a power supply member that supplies power to the electrode is inserted, a lift pin hole that penetrates the wafer mounting table in the vertical direction and through which a lift pin is inserted, a gas hole that penetrates the wafer mounting surface in the vertical direction and supplies gas to the wafer mounting surface, and a temperature measurement hole that penetrates the cooling substrate in the vertical direction and through which a temperature measurement member is inserted. In general, the areas directly above the power supply member insertion hole, lift pin hole, gas hole, and temperature measurement hole in the wafer are prone to become hot spots. Therefore, it is highly significant to apply the present invention.

FIG. 2 is a vertical cross-sectional view of the wafer mounting table 10 installed in the chamber 94. FIG. 4 is a cross-sectional view of the wafer mounting table 10 taken along a horizontal plane passing through the wide area coolant flow path 32 and the hole coolant flow path 36. FIG. FIG. 4 is an enlarged cross-sectional view showing a vertical cross section around a lift pin hole 44; 5A to 5C are diagrams showing the manufacturing process of the wafer mounting table 10. FIG. 11 is an enlarged cross-sectional view showing a vertical cross section of another example of the hole coolant flow passage 36. 13 is an enlarged cross-sectional view showing a horizontal cross section of another example of the hole coolant flow passage 36. FIG. FIG. 11 is an enlarged cross-sectional view showing a vertical cross section of another example of the hole coolant flow passage 36. FIG. 4 is a horizontal cross-sectional view showing another example of the wafer mounting table 10. 13 is an enlarged cross-sectional view showing a horizontal cross section of another example of the hole coolant flow passage 36. FIG. FIG. 4 is a vertical cross-sectional view showing another example of the wafer mounting table 10. 12 is a cross-sectional view of the wafer mounting table 10 of FIG. 11 cut along a horizontal plane passing through the wide-area refrigerant flow path 32. 12 is a cross-sectional view of the wafer mounting table 10 of FIG. 11 cut along a horizontal plane passing through a hole coolant flow path 36. FIG.

A preferred embodiment of the present invention will be described below with reference to the drawings. In the embodiment, the predetermined local region is the peripheral region of at least one of the holes penetrating the cooling substrate in the vertical direction, and the local refrigerant flow path is a hole refrigerant flow path provided in the peripheral region of the hole. FIG. 1 is a vertical cross-sectional view of a wafer mounting table 10 installed in a chamber 94 (a cross-sectional view when cut along a plane including the central axis of the wafer mounting table 10), FIG. 2 is a plan view of the wafer mounting table 10, FIG. 3 is a cross-sectional view when the wafer mounting table 10 is cut along a horizontal plane passing through the wide-area refrigerant flow path 32 and the hole refrigerant flow path 36, and FIG. 4 is an enlarged cross-sectional view showing a vertical cross section around a lift pin hole 44.

The wafer mounting table 10 is used to perform CVD, etching, etc. on a wafer W using plasma, and is fixed to a mounting plate 96 provided inside a semiconductor process chamber 94. The wafer mounting table 10 includes a ceramic base material 20, a cooling base material 30, and a metal bonding layer 40.

The ceramic substrate 20 has a central portion 22 having a circular wafer mounting surface 22a, and an outer peripheral portion 24 having an annular focus ring mounting surface 24a on the outer periphery thereof. Hereinafter, the focus ring may be abbreviated as "FR". A wafer W is mounted on the wafer mounting surface 22a, and a focus ring 78 is mounted on the FR mounting surface 24a. The ceramic substrate 20 is formed of a ceramic material such as alumina or aluminum nitride. The FR mounting surface 24a is one step lower than the wafer mounting surface 22a.

The central portion 22 of the ceramic substrate 20 incorporates a wafer adsorption electrode 26 on the side closer to the wafer mounting surface 22a. The wafer adsorption electrode 26 is formed of a material containing, for example, W, Mo, WC, MoC, etc. The wafer adsorption electrode 26 is a disk-shaped or mesh-shaped monopolar electrostatic adsorption electrode. The layer of the ceramic substrate 20 above the wafer adsorption electrode 26 functions as a dielectric layer. A wafer adsorption DC power source 52 is connected to the wafer adsorption electrode 26 via a power supply terminal 54 (corresponding to the power supply member of the present invention). The power supply terminal 54 is inserted into a terminal hole 51 provided between the lower surface of the wafer adsorption electrode 26 and the lower surface of the cooling substrate 30 of the wafer mounting table 10. The power supply terminal 54 is provided so as to pass through an insulating tube 55 arranged in a through hole of the terminal hole 51 that vertically penetrates the cooling substrate 30 and the metal bonding layer 40, and reach the wafer adsorption electrode 26 from the lower surface of the ceramic substrate 20. A low pass filter (LPF) 53 is provided between the wafer attracting DC power supply 52 and the wafer attracting electrode 26 .

As shown in FIG. 2, the wafer mounting surface 22a has a seal band 22b formed along the outer edge, and a number of small protrusions 22c formed over the entire surface. The seal band 22b and the number of small protrusions 22c are formed on a reference surface 22d of the wafer mounting surface 22a. In this embodiment, the small protrusions 22c are flat cylindrical protrusions. The top surface of the seal band 22b and the top surfaces of the number of small protrusions 22c are located on the same plane. The heights of the seal band 22b and the small protrusions 22c (i.e., the distances from the reference surface 22d to these top surfaces) are several μm to several tens of μm. The wafer W is placed on the wafer mounting surface 22a in contact with the top surface of the seal band 22b and the top surfaces of the number of small protrusions 22c.

The cooling substrate 30 is a disk member made of a metal matrix composite material (also called metal matrix composite (MMC)). The cooling substrate 30 cools the ceramic substrate 20 and has a refrigerant flow path (wide-area refrigerant flow path 32 and hole refrigerant flow path 36) through which the refrigerant can circulate. The wide-area refrigerant flow path 32 is connected to a wide-area refrigerant supply device 33, and a refrigerant is supplied from the wide-area refrigerant supply device 33. The hole refrigerant flow path 36 is connected to a hole refrigerant supply device 37, and a refrigerant is supplied from the hole refrigerant supply device 37 independently of the wide-area refrigerant flow path 32. The wide-area refrigerant supply device 33 may be configured to supply the refrigerant discharged from the wide-area refrigerant flow path 32 to the refrigerant flow path 32 again after adjusting the temperature. The same applies to the hole refrigerant supply device 37. The refrigerant flowing through the wide-area refrigerant flow path 32 and the hole refrigerant flow path 36 is preferably a liquid, and is preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids. Examples of MMC include materials containing Si, SiC, and Ti, and materials in which a porous SiC body is impregnated with Al and/or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which a porous SiC body is impregnated with Al is called AlSiC, and a material in which a porous SiC body is impregnated with Si is called SiSiC. When the ceramic substrate 20 is an alumina substrate, the MMC used for the cooling substrate 30 is preferably AlSiC or SiSiCTi, which have a thermal expansion coefficient close to that of alumina. The cooling substrate 30 is connected to an RF power source 62 via a power supply terminal 64. A high-pass filter (HPF) 63 is disposed between the cooling substrate 30 and the RF power source 62. The cooling substrate 30 has a flange portion 34 on the lower surface side, which is used to clamp the wafer stage 10 to a mounting plate 96.

The metal bonding layer 40 bonds the lower surface of the ceramic substrate 20 to the upper surface of the cooling substrate 30. The metal bonding layer 40 may be, for example, a layer formed of solder or a metal brazing material. The metal bonding layer 40 is formed, for example, by TCB (thermal compression bonding). TCB refers to a known method in which a metal bonding material is sandwiched between two members to be bonded, and the two members are pressure-bonded while being heated to a temperature below the solidus temperature of the metal bonding material.

The side of the outer periphery 24 of the ceramic substrate 20, the outer periphery of the metal bonding layer 40, and the side of the cooling substrate 30 are covered with an insulating film 42. Examples of the insulating film 42 include a thermally sprayed film of alumina, yttria, or the like.

The wafer mounting table 10 has a plurality of holes penetrating the wafer mounting table 10 in the vertical direction. As shown in FIG. 2, such holes include a plurality of gas holes 44 opening on the reference surface 22d of the wafer mounting surface 22a and a lift pin hole 48 for inserting a lift pin 49 for moving the wafer W up and down relative to the wafer mounting surface 22a. A plurality of gas holes 44 are provided at appropriate positions on the reference surface 22d when the wafer mounting surface 22a is viewed in plan. A thermally conductive gas such as He gas is supplied to the gas holes 44 from an external gas supply source 46 (see FIG. 1). When the thermally conductive gas is supplied to the gas holes 44 with the wafer W placed on the wafer mounting surface 22a, the space surrounded by the wafer W, the seal band 22b, the small protrusions 22c, and the reference surface 22d is filled with the thermally conductive gas. The thermally conductive gas has a higher thermal conductivity than a vacuum, and therefore plays a role in improving the thermal conduction between the wafer W and the ceramic base material 20. The lift pin holes 48 are provided in a number equal to each other along the concentric circles of the wafer mounting surface 22a when the wafer mounting surface 22a is viewed in plan view. In this embodiment, the gas holes 44 and the lift pin holes 48 are provided in numbers of three each, alternately and equally spaced along the concentric circles of the wafer mounting surface 22a when the wafer mounting surface 22a is viewed in plan view.

The wide-area refrigerant flow path 32 and the hole refrigerant flow path 36 provided inside the cooling substrate 30 are formed on the same plane parallel to the wafer mounting surface 22a of the cooling substrate 30. In other words, they are formed at a position where both the wide-area refrigerant flow path 32 and the hole refrigerant flow path 36 appear in any cross section obtained by cutting the cooling substrate 30 on a plane parallel to the wafer mounting surface 22a. As shown in FIG. 3, when a cross section cut on a horizontal plane passing through the wide-area refrigerant flow path 32 and the hole refrigerant flow path 36 is viewed from above, the wide-area refrigerant flow path 32 is formed in a single stroke from the inlet 32p to the outlet 32q over the entire area of the cooling substrate 30 corresponding to the wafer mounting surface 22a. In this embodiment, the wide-area refrigerant flow path 32 is formed in a spiral shape. The wide-area refrigerant supply device 33 is connected to the inlet 32p and the outlet 32q of the wide-area refrigerant flow path 32. The hole coolant flow passages 36 are formed in an annular shape in the peripheral area (area surrounded by two-dot chain lines in Figs. 2 and 3) of each gas hole 44 and each lift pin hole 48 so as to surround the entire circumference of each hole. Each hole coolant flow passage 36 branches at an inlet 36p and merges at an outlet 36q on the opposite side of the ring. All the hole coolant flow passages 36 are connected in series via a connecting flow passage 38, and auxiliary flow passages 39 are connected to both ends. The hole coolant flow passages 36, the connecting flow passage 38, and the auxiliary flow passage 39 are formed in a C-shape as a whole. The hole coolant supply device 37 is connected to an inlet 39p provided in the upstream auxiliary flow passage 39 and an outlet 39q provided in the downstream auxiliary flow passage 39, and is connected to all the hole coolant flow passages 36 via the auxiliary flow passage 39 and the connecting flow passage 38.

The wafer mounting table 10 is attached to a mounting plate 96 provided inside the chamber 94 using a clamp member 70. The clamp member 70 is an annular member with a cross section of a substantially inverted L-shape and has an inner peripheral step surface 70a. The wafer mounting table 10 and the mounting plate 96 are integrated by the clamp member 70. With the inner peripheral step surface 70a of the clamp member 70 placed on the flange portion 34 of the cooling substrate 30 of the wafer mounting table 10, a bolt 72 is inserted from the upper surface of the clamp member 70 and screwed into a screw hole provided on the upper surface of the mounting plate 96. The bolt 72 is attached to a plurality of locations (e.g., 8 locations or 12 locations) that are equally spaced along the circumferential direction of the clamp member 70. The clamp member 70 and the bolt 72 may be made of an insulating material or a conductive material (such as a metal).

Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 5. FIG. 5 is a manufacturing process diagram of the wafer mounting table 10. First, a disk-shaped ceramic sintered body 120, which is the base of the ceramic base material 20, is produced by hot-pressing and sintering a ceramic powder compact (FIG. 5A). The ceramic sintered body 120 has a built-in wafer adsorption electrode 26. Next, a terminal hole upper portion 151a is formed between the lower surface of the ceramic sintered body 120 and the wafer adsorption electrode 26, and a gas hole upper portion 144a and a lift pin hole upper portion 148a that penetrate the ceramic sintered body 120 in the vertical direction are opened at predetermined positions (FIG. 5B). Then, a power supply terminal 54 is inserted into the terminal hole upper portion 151a to join the power supply terminal 54 and the wafer adsorption electrode 26 (FIG. 5C).

In parallel with this, two MMC disk members 131, 136 are prepared (FIG. 5D). Then, multiple holes penetrating in the vertical direction are drilled in both MMC disk members 131, 136 (FIG. 5E). Specifically, the upper MMC disk member 131 is drilled with a terminal hole intermediate portion 151b, a gas hole intermediate portion 144b, and a lift pin hole intermediate portion 148b. The lower MMC disk member 136 is drilled with a terminal hole lower portion 151c, a gas hole lower portion 144c, and a lift pin hole lower portion 148c. The lower surface of the upper MMC disk member 131 is also formed with a groove 132 that will eventually become the wide area refrigerant flow path 32, a groove 137 that will become the hole refrigerant flow path 36, a groove (not shown) that will become the connecting flow path 38, and a groove (not shown) that will become the auxiliary flow path 39 (FIG. 5E). When the ceramic sintered body 120 is made of alumina, the MMC disk members 131, 136 are preferably made of SiSiCTi or AlSiC, since the thermal expansion coefficient of alumina is approximately the same as that of SiSiCTi or AlSiC.

A SiSiCTi disk member can be produced, for example, as follows. First, silicon carbide, metallic Si, and metallic Ti are mixed to produce a powder mixture. Next, the resulting powder mixture is uniaxially pressed to produce a disk-shaped compact, which is then hot-press sintered in an inert atmosphere to obtain a SiSiCTi disk member.

Next, a metal bonding material is placed between the lower surface of the upper MMC disk member 131 and the upper surface of the lower MMC disk member 136, and a metal bonding material is placed on the upper surface of the upper MMC disk member 131. Each metal bonding material has a through hole at a position opposite each hole. Then, the power supply terminal 54 of the ceramic sintered body 120 is inserted into the terminal hole intermediate part 151b and the terminal hole lower part 151c, and the ceramic sintered body 120 is placed on the metal bonding material placed on the upper surface of the upper MMC disk member 131. This results in a laminate in which the lower MMC disk member 136, the metal bonding material, the upper MMC disk member 131, the metal bonding material, and the ceramic sintered body 120 are laminated in this order from below. The laminate is heated and pressurized (TCB) to obtain the bonded body 110 (Figure 5F). The bonded body 110 is a ceramic sintered body 120 bonded to the upper surface of the MMC block 130, which is the base of the cooling substrate 30, via a metal bonding layer 40. The MMC block 130 is a structure in which an upper MMC disk member 131 and a lower MMC disk member 136 are bonded to each other via a metal bonding layer 135. The MMC block 130 has a wide refrigerant flow path 32, a hole refrigerant flow path 36, a connecting flow path 38 (not shown), an auxiliary flow path 39 (not shown), a terminal hole 51, a gas hole 44, and a lift pin hole 48 inside. The terminal hole 51 is a hole in which the terminal hole upper part 151a, the terminal hole intermediate part 151b, and the terminal hole lower part 151c are connected to each other, and the gas hole 44 is a hole in which the gas hole upper part 144a, the gas hole intermediate part 144b, and the gas hole lower part 144c are connected to each other. The lift pin hole 48 is a hole in which a lift pin hole upper portion 148a, a lift pin hole middle portion 148b, and a lift pin hole lower portion 148c are connected to each other.

TCB is performed, for example, as follows. That is, the laminate is pressed and bonded at a temperature below the solidus temperature of the metal bonding material (for example, at a temperature equal to or higher than the solidus temperature minus 20°C and below the solidus temperature), and then returned to room temperature. This causes the metal bonding material to become a metal bonding layer. The metal bonding material used here can be an Al-Mg based bonding material or an Al-Si-Mg based bonding material. For example, when TCB is performed using an Al-Si-Mg based bonding material, the laminate is pressed while heated in a vacuum atmosphere. It is preferable to use a metal bonding material with a thickness of around 100 μm.

Next, the ceramic sintered body 120 is cut to form a step on the outer periphery, resulting in a ceramic substrate 20 with a central portion 22 and an outer periphery 24. The MMC block 130 is cut to form a step on the outer periphery, resulting in a cooling substrate 30 with a flange portion 34. An insulating tube 55 is placed in the terminal hole 51, through which the power supply terminal 54 is inserted, from the underside of the ceramic substrate 20 to the underside of the cooling substrate 30. Furthermore, the insulating film 42 is formed by spraying the side of the outer periphery 24 of the ceramic substrate 20, the periphery of the metal bonding layer 40, and the side of the cooling substrate 30 with ceramic powder (FIG. 5G). The seal band 22b and the small protrusions 22c are formed, for example, by blasting. This results in a wafer mounting table 10.

Although the cooling substrate 30 in Figure 1 is described as an integral component, it may have a structure in which two components are joined with a metal joining layer as shown in Figure 5G, or a structure in which three or more components are joined with a metal joining layer.

Next, an example of how the wafer mounting table 10 is used will be described with reference to Figure 1. As described above, the wafer mounting table 10 is fixed to the mounting plate 96 of the chamber 94 by the clamp members 70. A shower head 98 is disposed on the ceiling surface of the chamber 94, which ejects process gas into the chamber 94 from multiple gas injection holes.

A focus ring 78 is placed on the FR mounting surface 24a of the wafer mounting table 10, and a disk-shaped wafer W is placed on the wafer mounting surface 22a. The focus ring 78 has a step along the inner circumference of the upper end so as not to interfere with the wafer W. In this state, a DC voltage from the wafer adsorption DC power supply 52 is applied to the wafer adsorption electrode 26 to adsorb the wafer W to the wafer mounting surface 22a. Then, the inside of the chamber 94 is set to a predetermined vacuum atmosphere (or reduced pressure atmosphere), and an RF voltage from the RF power supply 62 is applied to the cooling substrate 30 while supplying a process gas from the shower head 98. Then, plasma is generated between the wafer W and the shower head 98. Then, the plasma is used to perform CVD film formation or etching on the wafer W. The focus ring 78 is also worn out as the wafer W is plasma-processed, but since the focus ring 78 is thicker than the wafer W, the focus ring 78 is replaced after processing multiple wafers W.

When processing the wafer W with high-power plasma, it is necessary to efficiently cool the wafer W. In the wafer mounting table 10, a metal bonding layer 40 with high thermal conductivity is used as the bonding layer between the ceramic substrate 20 and the cooling substrate 30, instead of a resin layer with low thermal conductivity. Therefore, the ability to draw heat from the wafer W (heat extraction ability) is high. In addition, since the thermal expansion difference between the ceramic substrate 20 and the cooling substrate 30 is small, even if the stress relaxation of the metal bonding layer 40 is low, problems are unlikely to occur. Furthermore, since a hole coolant flow path 36 to which a coolant is supplied independently of the wide-area coolant flow path 32 is formed in the peripheral area of each gas hole 44 and each lift pin hole 48, the periphery of the hole coolant flow path 36 can be cooled by temperature control independent of the periphery of the wide-area coolant flow path 32.

In the wafer mounting table 10 of the present embodiment described above, a hole coolant flow path 36 is provided in the peripheral area of at least one of the holes (in this embodiment, three gas holes 44 and three lift pin holes 48) that penetrates the cooling substrate 30 in the vertical direction, to which a coolant is supplied independently of the wide area coolant flow path 32. Generally, the area directly above such holes in the wafer W is prone to become a hot spot, but in this embodiment, the hole coolant flow path 36 is formed in the peripheral area of such holes, and since it can be cooled by temperature control independent of the area outside the peripheral area of the holes, it is possible to cool this area in a focused manner. For example, if a coolant with a lower temperature than the wide area coolant flow path 32 (for example, 10°C or more lower than the wide area coolant flow path 32) is supplied to the hole coolant flow path 36, the low-temperature coolant promotes heat removal from the peripheral area of the holes. In addition, if a coolant is supplied to the hole coolant flow path 36 at a higher flow rate than the wide area coolant flow path 32, the temperature rise of the coolant is small, and heat removal from the peripheral area of the holes is promoted. Furthermore, if the hole coolant flow passage 36 is supplied with a coolant having a higher flow rate than the wide area coolant flow passage 32, the high flow rate coolant promotes heat removal from the area around the hole. If the hole coolant flow passage 36 is supplied with a coolant having a higher thermal conductivity than the wide area coolant flow passage 32, the high thermal conductivity coolant promotes heat removal from the area around the hole. If the hole coolant flow passage 36 is supplied with a coolant having a higher specific heat than the wide area coolant flow passage 32, the temperature rise of the coolant is small, and heat removal from the area around the hole is promoted. If the hole coolant flow passage 36 is supplied with a coolant having a lower viscosity than the wide area coolant flow passage 32, the coolant is more likely to become turbulent, and heat removal from the area around the hole is promoted. Therefore, it is possible to suppress the occurrence of hot spots on the wafer W. Furthermore, if the volume ratio of the refrigerant flow path (hole refrigerant flow path 36) in the area surrounding the hole is made larger than the volume ratio of the refrigerant flow path (wide-area refrigerant flow path 32) in the area outside the area surrounding the hole, the refrigerant flow paths are arranged at high density in the area surrounding the hole, thereby promoting heat removal from the area surrounding the hole.

In addition, since the wide area refrigerant flow path 32 and the hole refrigerant flow path 36 are formed on the same plane parallel to the wafer mounting surface 22a, it is possible to form both flow paths more simply by forming the grooves 132 and 137 together in one MMC disk member 131 as shown in Figure 5E, rather than forming them in multiple stages, one on the upper side and the other on the lower side, across a plane parallel to the wafer mounting surface 22a.

It goes without saying that the present invention is in no way limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present invention.

In the above-described embodiment, the hole refrigerant flow passage 36 may have a heat exchange promotion structure. For example, as shown in the enlarged cross-sectional view of FIG. 6, fins 36a may be provided as a heat exchange promotion structure on the inner surface of the hole refrigerant flow passage 36 in the peripheral region of the gas hole 44. The refrigerant flowing through the hole refrigerant flow passage 36 provided with the fins 36a is more likely to become turbulent than when the fins 36a are not provided. Therefore, heat removal from the peripheral region of the gas hole 44 is promoted. The number and length of the fins 36a may be appropriately set according to the desired amount of heat removal. A similar structure may be adopted for the hole refrigerant flow passage 36 passing through the peripheral region of the lift pin hole 48. Alternatively, as shown in the enlarged cross-sectional view of FIG. 7, a narrow portion 36b in which the flow passage is narrowed may be provided as a heat exchange promotion structure in the middle of the hole refrigerant flow passage 36 in the peripheral region of the gas hole 44. The refrigerant flowing through the hole refrigerant flow passage 36 provided with the narrow portion 36b is more likely to become turbulent because the flow rate becomes faster in the narrow portion 36b. Therefore, the heat removal from the peripheral area of the gas hole 44 is promoted. The hole coolant flow passage 36 passing through the peripheral area of the lift pin hole 48 may have a similar structure. In addition, the wall surface (which may be the side surface or the upper and lower surfaces) of the hole coolant flow passage 36 may have a rougher surface than the wide area coolant flow passage 32 or may have irregularities on the wall surface as a heat exchange promotion structure. The coolant flowing through the hole coolant flow passage 36 having a rough surface or an irregular wall surface is more likely to become turbulent than when the wall surface is smooth. Therefore, the heat removal from the peripheral area of the hole is promoted. In addition, the hole coolant flow passage 36 may be made to meander to serve as a heat exchange promotion structure. By making the hole coolant flow passage 36 meander, the flow is more likely to become turbulent. Therefore, the heat removal from the peripheral area of the hole is promoted.

In the above-described embodiment, as shown in the enlarged cross-sectional view of FIG. 8, the distance d1 from the wafer W to the ceiling surface of the hole coolant flow path 36 in the peripheral area of the gas hole 44 may be shorter than the distance d2 from the wafer W to the ceiling surface of the wide area coolant flow path 32. In this way, the coolant flowing through the hole coolant flow path 36 has a smaller thermal resistance between the coolant and the wafer W than the coolant flowing through the wide area coolant flow path 32. Therefore, heat removal from the peripheral area of the gas hole 44 is promoted. In FIG. 8, the vertical length of the hole coolant flow path 36 is longer than the wide area coolant flow path 32, but it may be the same length as the wide area coolant flow path 32. A similar structure may be adopted for the peripheral area of the lift pin hole 48.

In the above-mentioned embodiment, all of the multiple hole refrigerant flow paths 36 are connected by the connecting flow paths 38, but all or some of them may not be connected by the connecting flow paths 38. For example, as shown in FIG. 9, all of the multiple hole refrigerant flow paths 36 may be independent and the connecting flow paths 38 may not be used. In this case, a refrigerant supply device may be connected individually to each hole refrigerant flow path 36. In addition, in this case, an auxiliary flow path 39 may be connected to at least one of the upstream side (inlet 36p) and downstream side (outlet 36q) of each hole refrigerant flow path 36. Alternatively, the multiple hole refrigerant flow paths 36 may be divided into multiple groups, and only the group containing two or more hole refrigerant flow paths 36 may have the hole refrigerant flow paths 36 connected to the connecting flow paths 38. In this case, a refrigerant supply device may be connected individually to each group, and the auxiliary flow path 39 may be connected to at least one of the upstream side and downstream side of each group. In the above-mentioned embodiment, at least one of the auxiliary flow paths 39 may be omitted.

In the above embodiment, the hole refrigerant flow passage 36 in the peripheral region of the gas hole 44 is formed in an annular shape so as to surround the entire circumference of the gas hole 44, branched at the inlet 36p, and merged at the outlet 36q on the opposite side of the ring, but as long as it is formed in the peripheral region of the gas hole 44, its shape and the arrangement of the inlet and outlet are not particularly limited. For example, as shown in FIG. 10, it may be formed in a C-shape so as to surround the periphery of the gas hole 44. In FIG. 10, it is formed without branching from the inlet 36p at one end of the C-shape to the outlet 36q at the other end. In addition, the hole refrigerant flow passage 36 in the peripheral region of the gas hole 44 may be formed in an annular shape, the arrangement of the inlet 36p and the outlet 36q may be the same as in FIG. 10, and it may be formed without branching from the inlet 36p to the outlet 36q. In addition, the hole refrigerant flow passage 36 in the peripheral region of the gas hole 44 may be formed in a spiral shape so as to surround the periphery of the gas hole 44. The hole coolant flow passage 36 in the peripheral region of the gas hole 44 may be formed to surround at least half of the circumference of the hole. A similar structure may be adopted for the peripheral region of the lift pin hole 48.

In the above embodiment, the wide area refrigerant flow path 32 and the hole refrigerant flow path 36 are formed on the same plane, but they may be formed in multiple stages so that one is on the upper side and the other is on the lower side across a plane parallel to the wafer mounting surface 22a. For example, as shown in FIG. 11, the hole refrigerant flow path 36 may be formed in multiple stages (two stages in FIG. 11) so that the hole refrigerant flow path 36 is on the upper side and the wide area refrigerant flow path 32 is on the lower side. In this way, the freedom of arrangement of both flow paths can be increased compared to forming both flow paths on the same plane. For example, the wide area refrigerant flow path 32 can also be arranged in the peripheral area of the hole to further promote heat removal from the peripheral area of the hole. In addition, since the hole refrigerant flow path 36 is arranged on the upper side, as explained in FIG. 8, the distance d1 from the wafer W to the ceiling surface of the hole refrigerant flow path 36 is shorter than the distance d2 from the wafer W to the ceiling surface of the wide area refrigerant flow path 32, and heat removal from the peripheral area of the hole is promoted. In the wafer mounting table 10 of Fig. 11, when a cross section cut by a horizontal plane passing through the wide-area refrigerant flow path 32 is viewed from above, the wide-area refrigerant flow path 32 is formed in a single stroke from the inlet 32p to the outlet 32q over the entire area of the cooling substrate 30 corresponding to the wafer mounting surface 22a, as shown in Fig. 12. Here, the wide-area refrigerant flow path 32 is also arranged in the peripheral area of the gas hole 44 and the peripheral area of the lift pin hole 48. In the wafer mounting table 10 of Fig. 11, the hole refrigerant flow path 36 is formed in a shape when a cross section cut by a horizontal plane passing through the hole refrigerant flow path 36 is viewed from above, as shown in Fig. 13, which is the same shape as the cross section of the hole refrigerant flow path 36 of the above-mentioned embodiment in Fig. 3 when viewed from above. In this way, if the wide-area refrigerant flow path 32 is also arranged in the peripheral area of the gas hole 44 and the peripheral area of the lift pin hole 48, the volume ratio of the refrigerant flow path in the peripheral area of the hole can be increased by the amount of the wide-area refrigerant flow path 32 arranged in the peripheral area of the hole. In this case, it is preferable that the volume ratio of the coolant flow path in the area around the hole is greater than the volume ratio of the coolant flow path in the area outside the area around the hole, which further promotes heat removal from the area around the hole.

In the above-described embodiment, the hole refrigerant flow passage 36 is provided in the peripheral areas of all the gas holes 44 and all the lift pin holes 48, but is not limited to this. For example, the hole refrigerant flow passage 36 may be provided in the peripheral areas of some of these holes (e.g., areas that are particularly prone to becoming hot spots). Alternatively or in addition to these, the hole refrigerant flow passage may be provided in the peripheral areas of holes that penetrate the cooling substrate 30 in the vertical direction, such as the terminal hole 51 and the temperature measurement hole (not shown). The temperature measurement hole is a hole through which a temperature measurement member such as a thermocouple is inserted. Note that the hole refrigerant flow passage in the peripheral area of the terminal hole 51 and the hole refrigerant flow passage in the peripheral area of the temperature measurement hole may adopt each aspect described for the hole refrigerant flow passage 36.

In the above-described embodiment, the hole refrigerant flow passage 36 is provided in the peripheral area of the hole that penetrates the cooling substrate in the vertical direction, such as the gas hole 44 and the lift pin hole 48, but the present invention is not limited to this, and a local refrigerant flow passage may be provided in a specific local area that is prone to become a hot spot. For example, a local refrigerant flow passage may be provided in an area where the heat extraction capacity tends to be locally inferior to the surrounding area, such as near the refrigerant outlet where the refrigerant temperature is high. A local refrigerant flow passage may also be provided in an area where the heat extraction capacity tends to be locally inferior to the surrounding area due to a difference in structure or material from the surrounding area.

In the above-described embodiment, the cooling substrate 30 is made of MMC, but is not limited to this. The cooling substrate 30 may be made of metal (e.g., aluminum, titanium, molybdenum, tungsten, and alloys thereof). The cooling substrate 30 may also be made of ceramic matrix composite material (CMC). Both MMC and CMC are composite materials of metal and ceramic. Examples of CMC include materials containing Si, SiC, and Ti, and materials in which a porous SiC body is impregnated with Al and/or Si.

In the above-described embodiment, the ceramic substrate 20 and the cooling substrate 30 are bonded via a metal bonding layer 40 that has good thermal conductivity and is highly effective in the invention, but this is not particularly limited. For example, a resin bonding layer may be used instead of the metal bonding layer 40.

In the above-described embodiment, the wide-area refrigerant flow path 32 has a spiral shape when viewed in a plane, but is not limited to this. For example, the wide-area refrigerant flow path 32 may have a zigzag shape when viewed in a plane. Specifically, an inlet and an outlet may be provided at two points near the outer periphery that are point-symmetrical with respect to the center of the cooling substrate 30 in a planar view, and the wide-area refrigerant flow path 32 may be formed so that it is zigzag in a single stroke from the inlet to the outlet.

In the above-described embodiment, the wafer adsorption electrode 26 is built into the center portion 22 of the ceramic substrate 20, but instead of or in addition to this, an RF electrode for generating plasma or a heater electrode (resistance heating element) may be built into the ceramic substrate 20. Also, a focus ring (FR) adsorption electrode may be built into the outer periphery 24 of the ceramic substrate 20, or an RF electrode or a heater electrode may be built into the outer periphery 24 of the ceramic substrate 20.

In the above-described embodiment, the ceramic sintered body 120 in FIG. 5A was produced by hot-press sintering a ceramic powder compact, but the compact in this case may also be produced by stacking multiple tape compacts, by a mold casting method, or by compressing ceramic powder.

This application claims priority from Japanese Patent Application No. 2022-30790, filed on March 1, 2022, the entire contents of which are incorporated herein by reference.

The wafer mounting table of the present invention is used, for example, in semiconductor manufacturing equipment.

10 wafer mounting table, 20 ceramic substrate, 22 center portion, 22a wafer mounting surface, 22b seal band, 22c small protrusion, 22d reference surface, 24 outer periphery, 24a focus ring mounting surface, 26 wafer suction electrode, 30 cooling substrate, 32 wide area coolant flow path, 32p inlet, 32q outlet, 33 wide area coolant supply device, 34 flange portion, 36 hole coolant flow path, 36a fin, 36b narrow portion, 36p inlet, 36q outlet, 37 hole coolant supply device, 38 connection flow path, 39 auxiliary flow path, 39p inlet, 39q outlet, 40 metal bonding layer, 42 insulating film, 44 gas hole, 46 gas supply source, 48 lift pin hole, 51 terminal hole, 52 wafer suction DC power source, 53 low pass filter (LPF), 54 power supply terminal, 55 insulating tube, 62 RF power supply, 63 high pass filter (HPF), 64 power supply terminal, 70 clamp member, 70a inner peripheral step surface, 72 bolt, 78 focus ring, 94 chamber, 96 mounting plate, 98 shower head, 110 bonded body, 120 ceramic sintered body, 130 MMC block, 131 MMC disk member, 132 groove, 135 metal bonding layer, 136 MMC disk member, 137 groove, 144a gas hole upper portion, 144b gas hole middle portion, 144c gas hole lower portion, 148a lift pin hole upper portion, 148b lift pin hole middle portion, 148c lift pin hole lower portion, 151a terminal hole upper portion, 151b terminal hole middle portion, 151c terminal hole lower portion, d1, d2 distance, W wafer.

Claims (14)

a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
The local refrigerant flow path is supplied with the refrigerant having a lower temperature than the wide area refrigerant flow path.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
The refrigerant is supplied to the local refrigerant flow path at a higher flow rate than the wide area refrigerant flow path.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
In the cooling material, a volume ratio of the coolant flow path in the local region is greater than a volume ratio of the coolant flow path in a region outside the local region.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
The local refrigerant flow path is supplied with the refrigerant having a higher thermal conductivity than the wide area refrigerant flow path.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
The local refrigerant flow path is supplied with the refrigerant having a larger specific heat than the wide area refrigerant flow path.
Wafer placement stage. the local refrigerant flow path is provided with a heat exchange promotion structure that promotes heat exchange between the refrigerant flowing through the local refrigerant flow path and the wafer placed on the wafer placement surface.
The wafer mounting table according to any one of claims 1 to 5. the wide area refrigerant flow path and the local refrigerant flow path are formed on the same plane parallel to the wafer mounting surface;
The wafer mounting table according to any one of claims 1 to 5. the wide area refrigerant flow path and the local refrigerant flow path are formed in multiple stages, one on the upper side and the other on the lower side, with a plane parallel to the wafer mounting surface in between;
The wafer mounting table according to any one of claims 1 to 5. A plurality of holes are provided through the cooling substrate in the vertical direction,
The local region is a peripheral region of at least one hole among the plurality of holes.
The wafer mounting table according to any one of claims 1 to 5. A plurality of holes are provided through the cooling substrate in the vertical direction,
the local region is a peripheral region of at least one hole among the plurality of holes,
The hole is at least one of a power supply member insertion hole that is provided in the wafer mounting table from the electrode downward and through which a power supply member that supplies power to the electrode is inserted, a lift pin hole that penetrates the wafer mounting table in the vertical direction and through which a lift pin is inserted, a gas hole that penetrates the wafer mounting surface in the vertical direction and supplies gas to the wafer mounting surface, and a temperature measurement hole that penetrates the cooling substrate in the vertical direction and through which a temperature measurement member is inserted.
The wafer mounting table according to any one of claims 1 to 5. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
A plurality of holes are provided through the cooling substrate in the vertical direction,
the local region is a peripheral region of at least one hole among the plurality of holes,
The local refrigerant flow path includes a plurality of hole refrigerant flow paths provided in a peripheral region of the hole, and the plurality of hole refrigerant flow paths are provided independently without being connected to each other.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
A wafer mounting table comprising :
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
A plurality of holes are provided through the cooling substrate in the vertical direction,
the local region is a peripheral region of at least one hole among the plurality of holes,
the holes include lift pin holes penetrating the wafer mounting table in the vertical direction and through which lift pins are inserted, and gas holes penetrating the wafer mounting surface in the vertical direction and through which gas is supplied to the wafer mounting surface; and the local refrigerant flow paths are formed in peripheral areas of each of the lift pin holes and each of the gas holes, and the hole refrigerant flow paths are all connected in series via a connection flow path.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
the wide area refrigerant flow path and the local refrigerant flow path are formed on the same plane parallel to the wafer mounting surface,
the wide-area refrigerant flow path is formed in a spiral shape, and the local refrigerant flow path is formed in a region on the outer circumferential side of an innermost flow path of the wide-area refrigerant flow path and on the inner circumferential side of an outermost flow path of the wide-area refrigerant flow path.
Wafer placement stage. a ceramic substrate having a wafer mounting surface on an upper surface thereof and incorporating an electrode;
a cooling substrate bonded to a lower surface of the ceramic substrate and configured to cool the ceramic substrate;
Equipped with
the cooling base material has, as coolant flow paths, a wide-area coolant flow path formed over an entire area corresponding to the wafer mounting surface, and a local coolant flow path formed in a predetermined local area, to which a coolant is supplied independently of the wide-area coolant flow path;
the wide area refrigerant flow path and the local refrigerant flow path are formed on the same plane parallel to the wafer mounting surface,
the wide-area refrigerant flow path is formed in a spiral shape, and the local refrigerant flow path is formed in a region on the outer circumferential side of an innermost flow path of the wide-area refrigerant flow path and on the inner circumferential side of an outermost flow path of the wide-area refrigerant flow path,
The local refrigerant flow path is provided in a plurality of parts, and the plurality of local refrigerant flow paths are connected in series via a connecting flow path to form a C-shape as a whole.
Wafer placement stage.

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