Wafer carrying table and use method thereof

Abstract

A wafer mounting table 10 is provided with a ceramic plate 20, a heat diffusion plate 30, a first adhesive layer 40, a cooling plate 50, and a second adhesive layer 60. The upper surface of the ceramic plate (20) is provided with a wafer carrying surface (22), and the ceramic plate (20) is internally provided with electrodes (24, 26). The heat diffusion plate 30 is arranged on the lower surface of the ceramic plate 20. The first adhesive layer (40) adheres the ceramic plate (20) and the heat diffusion plate (30) to each other. The cooling plate (50) is provided on the lower surface of the heat diffusion plate (30), and has a refrigerant flow path (52) therein. The second adhesive layer (60) is provided between the heat diffusion plate (30) and the cooling plate (50). The second adhesive layer (60) has an adhesive section (62) that adheres the heat diffusion plate (30) and the cooling plate (50) to each other, and a cavity section (64) that is a gap provided between the heat diffusion plate (30) and the cooling plate (50).

Description

TECHNICAL FIELD The present application relates to a wafer mounting table and a method for using the same. BACKGROUND In the past, a wafer mounting table has been known, which includes a ceramic plate having a wafer mounting surface on an upper surface and an electrode built therein, and a cooling plate provided on a lower surface of the ceramic plate and having a refrigerant flow path inside. In this wafer mounting table, as described in Patent Literature 1, a cylindrical recess is formed on an upper surface of the cooling plate, and a heat transfer gas such as He is introduced into a gap (cavity) formed by the recess with the ceramic plate mounted on the cooling plate. In addition, it is described that when etching a wafer, if the thermal resistance between the ceramic plate and the cooling plate is large, the temperature of the ceramic plate rises and it is difficult to set the temperature to a desired temperature, but in order to solve this problem, the pressure of the heat transfer gas supplied to the cavity is adjusted. PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-136552 SUMMARY However, in Patent Literature 1, it is necessary to form a recess on the upper surface of the cooling plate, and therefore, the manufacturing process of the wafer mounting table becomes complicated. In addition, a temperature difference is easily generated between the upper portion of the recess in the ceramic plate and the upper portion of the outer edge portion of the recess, and therefore, a thermal stress is easily applied to the ceramic plate. The present application has been made to solve the above problems, and has as its main object to easily manufacture a cavity between a ceramic plate and a cooling plate, and to hardly apply a thermal stress to the ceramic plate.

[0001] The wafer mounting table of the present application includes: a ceramic plate having a wafer mounting surface on an upper surface and an electrode built therein; a heat diffusion plate provided on a lower surface of the ceramic plate; a first adhesive layer that adheres the ceramic plate and the heat diffusion plate; a cooling plate provided on a lower surface of the heat diffusion plate and having a refrigerant flow path inside; and a second adhesive layer provided between the heat diffusion plate and the cooling plate, and having an adhesive portion that adheres the heat diffusion plate and the cooling plate, and a gap (cavity) provided between the heat diffusion plate and the cooling plate. The wafer mounting table has a second adhesive layer in which an adhesive portion and a hollow portion are present. Since the hollow portion is provided in the second adhesive layer as such, it is not necessary to form a recess (hollow portion) on the upper surface of the cooling plate as in the past, and the hollow portion can be easily manufactured. In addition, since the thermal resistance of the adhesive portion and the hollow portion in the second adhesive layer differs in the vertical direction, a temperature difference is easily generated in the portion directly above the adhesive portion and the portion directly above the hollow portion in the ceramic plate, but here, the heat spreading plate is disposed on the upper surface of the second adhesive layer. Due to the presence of the heat spreading plate, the temperature difference between the portion directly above the adhesive portion and the portion directly above the hollow portion in the ceramic plate is moderated. Therefore, thermal stress is not easily applied to the ceramic plate. Note that in this specification, up and down, left and right, front and back, and the like are used to describe the present application, but up and down, left and right, and front and back are merely relative positional relationships. Therefore, in the case where the orientation of the wafer mounting table is changed, up and down may become left and right, or left and right may become up and down, but such cases are also included in the technical scope of the present application.

[0002] The wafer mounting table of the present application (the wafer mounting table described in [1] above) can have a communication path that communicates with the hollow portion from the lower surface or side surface of the cooling plate. Due to this, for example, the hollow portion can be switched between a state in which the thermal conductivity is high and a state in which the thermal conductivity is low by means of the communication path. For example, in the case where it is desired to cool the wafer efficiently (in the case where the wafer is processed using plasma, etc.), the hollow portion is set to the state in which the thermal conductivity is high, and thus the cooling of the wafer by the coolant is promoted. In addition, in the case where it is not desired to cool the wafer (in the case where plasma is not generated, etc.), the hollow portion is set to the state in which the thermal conductivity is low, and thus the cooling of the wafer by the coolant is suppressed. In addition, for example, if a heat-conducting gas such as He gas is filled in the hollow portion, the hollow portion can be made to be in the state in which the thermal conductivity is high, and if the hollow portion is set to a vacuum, the hollow portion can be made to be in the state in which the thermal conductivity is low.

[0003] In the wafer mounting table of the present application (the wafer mounting table described in [1] or [2] above), the thickness of the heat spreading plate can be thicker than the thickness between the top surface of the coolant flow path in the cooling plate and the upper surface of the cooling plate. Due to this, heat spreading in the horizontal direction in the heat spreading plate can be sufficiently performed, and thus it is easier to moderate the temperature difference between the portion directly above the adhesive portion and the portion directly above the hollow portion in the ceramic plate.

[0004] In the wafer mounting table (the wafer mounting table described in any one of [1] to [3] above) of the present application, the thermal conductivity of the heat diffusion plate can be higher than the thermal conductivity between the top surface of the refrigerant flow path in the cooling plate and the upper surface of the cooling plate. Thereby, the heat diffusion in the horizontal direction in the heat diffusion plate can be sufficiently performed, and thus, the temperature difference between the portion directly above the bonding portion in the ceramic plate and the portion directly above the hollow portion can be more easily moderated.

[0005] In the wafer mounting table (the wafer mounting table described in any one of [1] to [4] above) of the present application, the thickness of the first bonding layer can be thinner than the thickness of the second bonding layer. Thereby, when the thermal conductivity of the hollow portion of the second bonding layer is changed, the influence of the first bonding layer on the change can be suppressed.

[0006] In the wafer mounting table (the wafer mounting table described in any one of [1] to [5] above) of the present application, the thermal resistance in the vertical direction of the first bonding layer can be lower than the thermal resistance in the vertical direction of the bonding portion in the second bonding layer. Thereby, when the thermal conductivity of the hollow portion of the second bonding layer is changed, the influence of the first bonding layer on the change can be suppressed.

[0007] In the wafer mounting table (the wafer mounting table described in any one of [1] to [6] above) of the present application, the proportion of the bonding area of the bonding portion in plan view with respect to the entire area of the second bonding layer can be 10% or more and 50% or less. If the proportion is 10% or more, the heat diffusion plate and the cooling plate can be bonded with sufficient strength. If the proportion is 50% or less, the proportion of the hollow portion in the second bonding layer becomes a sufficient size, and thus, the difference in the heat discharge of the refrigerant when the hollow portion is in the state where the thermal conductivity is high and when the hollow portion is in the state where the thermal conductivity is low can be sufficiently made large.

[0008] In the wafer mounting table (the wafer mounting table described in any one of [1] to [7] above) of the present application, the hollow portion can be switchable between the state where the thermal conductivity is high and the state where the thermal conductivity is low.

[0009] In the method for using the wafer boat (the wafer boat described in [1] or [2] above) of the present application, in a case where it is desired to promote cooling of the wafer placed on the wafer placing surface, the hollow portion can be set to a state of high thermal conductivity, and in a case where it is desired to suppress cooling of the wafer placed on the wafer placing surface, the hollow portion can be set to a state of low thermal conductivity. In the case where the hollow portion is set to a state of low thermal conductivity, the second adhesive layer hinders heat movement between the heat spreading plate and the cooling plate, as compared with the case where the hollow portion is set to a state of high thermal conductivity. Therefore, if the hollow portion is set to a state of high thermal conductivity, cooling of the wafer by the coolant can be promoted, and if the hollow portion is set to a state of low thermal conductivity, cooling of the wafer by the coolant can be suppressed.

[0010] In the method for using the wafer boat (the wafer boat described in [9] above) of the present application, in a case where it is desired to promote cooling of the wafer placed on the wafer placing surface, a heat-conducting gas can be filled in the hollow portion, thereby setting the hollow portion to a state of high thermal conductivity, and in a case where it is desired to suppress cooling of the wafer placed on the wafer placing surface, the hollow portion can be set to a vacuum state, thereby setting the hollow portion to a state of low thermal conductivity. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a perspective view of the wafer boat 10. Figure 2 is an A-A sectional view of Figure 1 Figure 3 is a sectional view when the second adhesive layer 60 is horizontally cut from above. Figure 4 is an explanatory diagram showing a use example of the wafer boat 10 at the time of plasma on. Figure 5 is an explanatory diagram showing a use example of the wafer boat 10 at the time of plasma off. Figure 6 is a graph showing a relationship between time in a process of processing the wafer W and temperature of the wafer W. Figure 7 is a sectional view when the second adhesive layer 160 is horizontally cut from above. DETAILED DESCRIPTION Next, preferred embodiments of the present application will be described with reference to the drawings. Figure 1 is a perspective view of the wafer boat 10, Figure 2 is an A-A sectional view of Figure 1 Figure 3 is a sectional view when the second adhesive layer 60 of the wafer boat 10 is horizontally cut from above.​​ The wafer boat 10 is a member used for CVD, etching, and the like of the wafer W using plasma. The wafer boat 10 includes a ceramic plate 20, a heat diffusion plate 30, a first adhesive layer 40, a cooling plate 50, and a second adhesive layer 60. The ceramic plate 20 is a circular plate member having a step along the outer periphery. The ceramic plate 20 is formed of a ceramic material represented by alumina, aluminum nitride, or the like, and has a circular wafer mounting surface 22 on the upper surface. The wafer W is mounted on the wafer mounting surface 22. Although not shown, a seal band is formed along the outer edge of the upper surface of the ceramic plate 20 on the wafer mounting surface 22, and a plurality of flat circular small projections are formed on the entire surface inside the seal band. The seal band and the circular small projections are the same height, and the height is, for example, several μm to several tens of μm. The electrostatic electrode 24 and the heater electrode 26 are implanted in the ceramic plate 20. The electrostatic electrode 24 is a planar mesh electrode implanted in a region of the ceramic plate 20 corresponding to substantially the entire upper surface, and is capable of applying a direct current voltage. When a direct current voltage is applied to the electrostatic electrode 24, the wafer W is adsorbed and fixed to the wafer mounting surface 22 (specifically, the upper surface of the seal band and the upper surface of the circular small projections) by electrostatic attraction, and when the application of the direct current voltage is released, the adsorption and fixation of the wafer W to the wafer mounting surface 22 is released. The electrostatic electrode 24 is also connected to a high-frequency (RF) power source. The heater electrode 26 is a resistance heating element formed in one stroke from one end to the other end in a region of the ceramic plate 20 corresponding to substantially the entire upper surface. The heater electrode 26 is capable of supplying electric power from a heater power source not shown. The heat diffusion plate 30 is provided on the lower surface of the ceramic plate 20. Specifically, the heat diffusion plate 30 is adhered to the lower surface of the ceramic plate 20 with the first adhesive layer 40. The heat diffusion plate 30 is a solid circular plate member formed of a metal represented by aluminum, an aluminum alloy, or the like. The thickness of the heat diffusion plate 30 is thicker than the thickness of the cooling plate upper layer portion 50a described later, and is preferably 1 to 10 mm, for example, 3 mm. The thermal conductivity of the heat diffusion plate 30 is preferably 50 to 300 W / mK, for example, 180 W / mK. In the present embodiment, the first adhesive layer 40 is a circular and solid resin adhesive layer. The resin adhesive layer is obtained, for example, by sandwiching an adhesive sheet in which both surfaces are coated with an organic adhesive between the lower surface of the ceramic plate 20 and the upper surface of the heat diffusion plate 30 and curing them. The thickness of the first adhesive layer 40 is preferably 0.01 to 1 mm, for example, 0.075 mm. The thermal conductivity of the first adhesive layer 40 is preferably 0.1 to 5 W / mK, for example, 0.2 W / mK. As the resin of the resin adhesive layer, an acrylic resin, a silicone resin, an epoxy resin, or the like can be used. In addition, the resin can contain a filler. A cooling plate 50 is provided to the lower surface of the heat diffusion plate 30. Specifically, the cooling plate 50 is adhered to the lower surface of the heat diffusion plate 30 with the second adhesive layer 60. The cooling plate 50 is a round plate member formed of a metal represented by aluminum, an aluminum alloy, or the like. The cooling plate 50 can be formed of the same material as the heat diffusion plate 30. The cooling plate 50 has a refrigerant flow path 52 inside, through which a refrigerant circulates. The refrigerant flow path 52 is formed in one stroke from one end (an inlet) to the other end (an outlet) in a region corresponding to substantially the entire upper surface of the ceramic plate 20. The refrigerant flow path 52 can be formed, for example, in a spiral shape in plan view, or can be formed in a zigzag shape. The refrigerant is supplied to one end (an inlet) of the refrigerant flow path 52 from a refrigerant circulation device not shown, passes through the refrigerant flow path 52, and is discharged from the other end (an outlet) of the refrigerant flow path 52 to return to the refrigerant circulation device. The refrigerant circulation device can adjust the refrigerant to a desired temperature. The refrigerant is preferably a liquid, and is preferably an electrically insulating liquid. As the electrically insulating liquid, for example, a fluorine-based inactive liquid or the like can be given. The thermal conductivity of the cooling plate 50 is preferably 50 to 300 W / mK, for example, 180 W / mK. The top surface of the refrigerant flow path 52 in the cooling plate 50 and the upper surface of the cooling plate 50 are referred to as a cooling plate upper layer portion 50a. The thickness of the cooling plate upper layer portion 50a is thinner than the thickness of the heat diffusion plate 30, and is preferably 0.5 to 5 mm, for example, 1 mm. The thermal conductivity of the cooling plate upper layer portion 50a is the same as the thermal conductivity of the cooling plate 50. Alternatively, the thermal conductivities can be different. The second adhesive layer 60 is a resin adhesive layer provided between the lower surface of the heat diffusion plate 30 and the upper surface of the cooling plate 50. The resin adhesive layer is obtained, for example, by sandwiching an adhesive sheet on which an organic adhesive is applied on both surfaces between the lower surface of the heat diffusion plate 30 and the upper surface of the cooling plate 50 and curing it. In the second adhesive layer 60, there are an adhesive portion 62 that adheres the heat diffusion plate 30 and the cooling plate 50, and a gap, that is, a hollow portion 64, provided between the heat diffusion plate 30 and the cooling plate 50. Specifically, the adhesive portion 62 and the hollow portion 64 exist in the planar direction of the second adhesive layer 60. The adhesive portion 62 is formed of a resin, and the hollow portion 64 is formed of a space. Figure 3 In the illustrated embodiment, the second adhesive layer 60 is obtained by punching a spiral passage in a circular adhesive sheet having the same outer diameter as the diameter of the heat diffusion plate 30, and the spiral passage is the hollow portion 64, and the portions other than the spiral passage are the adhesive portion 62. For forming the hollow portion 64, it is only necessary to arrange the adhesive sheet in which the spiral passage is punched between the heat diffusion plate 30 and the cooling plate 50. Therefore, compared to forming a recess in the upper surface of the cooling plate 50 as in the past, the hollow portion 64 can be easily formed. As the resin of the resin adhesive layer, an acrylic resin, a silicone resin, an epoxy resin, or the like can be used. Alternatively, the resin can contain a filler. The second adhesive layer 60 (the adhesive portion 62) has a thickness that is thicker than the thickness of the first adhesive layer 40. In other words, the first adhesive layer 40 has a thickness that is thinner than the thickness of the second adhesive layer 60. In addition, the thermal resistance in the up-and-down direction of the adhesive portion 62 in the second adhesive layer 60 is greater than the thermal resistance in the up-and-down direction of the first adhesive layer 40. In other words, the thermal resistance in the up-and-down direction of the first adhesive layer 40 is smaller than the thermal resistance in the up-and-down direction of the adhesive portion 62. When the thermal resistance is set as R (m 2 ·K / W), the thickness is set as t (m), and the thermal conductivity is set as λ (W / mK), R = t / λ. Therefore, for example, in the case where the first adhesive layer 40 and the adhesive portion 62 are formed of materials having the same thermal conductivity, by making the thickness of the first adhesive layer 40 thinner than the thickness of the adhesive portion 62, the thermal resistance in the up-and-down direction of the first adhesive layer 40 is made smaller than the thermal resistance in the up-and-down direction of the adhesive portion 62. The thickness of the second adhesive layer 60 is preferably 0.05 to 2 mm, for example, 0.125 mm. The thermal conductivity of the second adhesive layer 60 (the same as the thermal conductivity of the adhesive portion 62) is preferably 0.1 to 2 W / mK, for example, 0.2 W / mK. In addition, the thermal resistance in the up-and-down direction of the adhesive portion of the second adhesive layer 60 is preferably 0.025 to 20 m 2 ·K / W. On the other hand, the thermal resistance in the up-and-down direction of the first adhesive layer 40 is preferably 0.002 to 10 m 2 ·K / W. The ratio of the adhesive area of the adhesive portion 62 when viewed from the second adhesive layer 60 to the entire area of the second adhesive layer 60 (the total area of the adhesive portion 62 and the hollow portion 64, which is the same as the area of the lower surface of the heat-diffusing plate 30) is preferably 10% or more and 50% or less. The cooling plate 50 is provided with a communication path 54 that communicates with the hollow portion 64. The communication path 54 penetrates the cooling plate 50 in the up-and-down direction and is open at the lower surface of the cooling plate 50. The hollow portion 64 is connected to the fluid switching mechanism 70 via the communication path 54. The fluid switching mechanism 70 is capable of switching the supply and discharge of fluid with respect to the hollow portion 64. The fluid switching mechanism 70 is configured to make the hollow portion 64 a vacuum atmosphere (a state in which the thermal conductivity is low) by discharging the gas in the hollow portion 64 via the communication path 54 and then closing the hollow portion 64, or to make the hollow portion 64 a state in which the thermal conductivity is high by introducing a heat-conducting gas such as He gas (the thermal conductivity is 0.2 W / mK) into the hollow portion 64 in a vacuum atmosphere and then closing the hollow portion 64. The communication path 54 is not limited to Figure 2 the form shown in the drawing, and can be open from the side surface of the cooling plate 50. Next, an example of using the wafer stage 10 will be described. The wafer stage 10 is fixed inside a semiconductor process chamber (not shown). A wafer W is placed on the wafer placement surface 22. In this state, a DC voltage is applied to the electrostatic electrode 24 to cause the wafer W to adhere to the wafer placement surface 22. At the same time, a coolant is circulated through the coolant flow path 52. In addition, the heater electrode 26 is powered to heat the heater electrode 26, thereby heating the wafer W. Then, the interior of the chamber is set to a predetermined vacuum atmosphere, and while supplying process gas from a spray head provided at the top of the chamber, an RF voltage is applied to the electrostatic electrode 24. As a result, plasma is generated between the wafer W and the spray head. Then, CVD film deposition or etching is performed on the wafer W using this plasma. Depending on the situation, an appropriate switch is made between a state in which thermally conductive gas is sealed in the cavity 64 to make it have high thermal conductivity and a state in which the cavity 64 is set to a vacuum atmosphere to make it have low thermal conductivity. For example, such as Figure 4 As shown, when plasma is generated above the wafer W (when the plasma is turned on), the wafer W contains heat input from the plasma. Therefore, this corresponds to a situation where it is desirable to promote cooling of the wafer W placed on the wafer mounting surface 22 (a situation with high cooling demand). In this case, cooling is required by using a coolant flowing through the coolant flow path 52 to bring the temperature of the wafer W to a predetermined temperature. Therefore, the fluid switching mechanism 70 is adjusted so that a heat-conducting gas is sealed within the cavity 64. Accordingly, the thermal conductivity between the heat diffusion plate 30 and the cooling plate 50 increases (the thermal resistance in the vertical direction decreases), thus enabling the wafer W to be cooled smoothly. If the wafer W is below a predetermined temperature, adjustment is made by using the heater electrode 26 to bring the wafer W to the predetermined temperature. On the other hand, such as Figure 5As shown, in the case where the plasma is not generated (when the plasma is turned off), there is no heat input from the plasma in the wafer W. Therefore, a case where cooling of the wafer W placed on the wafer placement surface 22 is intended to be suppressed (a case where the cooling demand is low) is equivalent. In this case, it is less necessary to cool the wafer W in such a manner that the temperature of the wafer W reaches a prescribed temperature by the coolant flowing in the coolant flow path 52. Therefore, the fluid switching mechanism 70 is adjusted in such a manner that the hollow portion 64 becomes a vacuum atmosphere. By this, the thermal conductivity between the heat diffusion plate 30 and the cooling plate 50 is reduced (the thermal resistance in the upward and downward directions is increased), so the temperature of the wafer W does not excessively decrease due to the coolant. In this case, the heater electrode 26 is also used to finely adjust the wafer W to reach the prescribed temperature, but the amount of heat generated by the heater electrode 26 is less than in the case where the second adhesive layer 60 is replaced by the adhesive layer provided in the first adhesive layer 60. The amount of heat generated by the heater electrode 26 is the same as, for example, the case where the plasma is generated. In addition, in this case, the thermal conductivity of the adhesive portion 62 and the thermal conductivity of the hollow portion 64 in the vacuum atmosphere are greatly different, so a temperature difference is generally easily generated in the portion directly above the adhesive portion 62 and the portion directly above the hollow portion 64 in the ceramic plate 20, but here, since the heat diffusion plate 30 is disposed on the lower surface of the ceramic plate 20, the above-mentioned temperature difference in the ceramic plate can be suppressed. In the wafer placement table 10 described above, the second adhesive layer 60 in which the adhesive portion 62 and the hollow portion 64 are present is provided. Since the hollow portion 64 is provided in the second adhesive layer 60 as such, the hollow portion 64 can be easily manufactured compared to the case where the recess (hollow portion) is formed on the upper surface of the cooling plate 50. In addition, since the thermal conductivity of the adhesive portion 62 and the hollow portion 64 in the second adhesive layer 60 is different, a temperature difference is easily generated in the portion directly above the adhesive portion 62 and the portion directly above the hollow portion 64 in the ceramic plate 20, but here, the heat diffusion plate 30 is disposed on the upper surface of the second adhesive layer 60. Due to the presence of the heat diffusion plate 30, the temperature difference between the portion directly above the adhesive portion 62 and the portion directly above the hollow portion 64 in the ceramic plate 20 is moderated. Therefore, the thermal stress is less likely to be applied to the ceramic plate 20. Further, the wafer mounting table 10 is provided with a communication path 54 that communicates from the lower surface of the cooling plate 50 to the hollow portion 64. Therefore, the hollow portion 64 can be switched between the state of high thermal conductivity and the state of low thermal conductivity by means of the communication path 54. For example, in a case where the wafer W is to be cooled efficiently (in a case where the wafer W is processed by plasma, etc.), the hollow portion 64 is set to the state of high thermal conductivity, so that the cooling of the wafer W by the refrigerant is promoted. Further, in a case where the wafer W is not to be cooled (in a case where plasma is not generated, etc.), the hollow portion 64 is set to the state of low thermal conductivity, so that the cooling of the wafer W by the refrigerant is suppressed. Further, for example, if a thermal conductive gas such as He gas is filled in the hollow portion 64, the hollow portion 64 can be made to be in the state of high thermal conductivity, and if the hollow portion 64 is set to a vacuum atmosphere, the hollow portion 64 can be made to be in the state of low thermal conductivity. Further, the thickness of the heat diffusion plate 30 is thicker than the thickness of the cooling plate upper portion 50a. Thereby, the heat diffusion in the horizontal direction in the heat diffusion plate 30 can be sufficiently performed, so that the temperature difference between the portion directly above the bonding portion 62 and the portion directly above the hollow portion 64 in the ceramic plate 20 is more easily moderated. Further, the thermal conductivity of the heat diffusion plate 30 is higher than the thermal conductivity of the cooling plate upper portion 50a. Thereby, the heat diffusion in the horizontal direction in the heat diffusion plate 30 can be sufficiently performed, so that the temperature difference between the portion directly above the bonding portion 62 and the portion directly above the hollow portion 64 in the ceramic plate 20 is more easily moderated. Further, the thickness of the first bonding layer 40 is thinner than the thickness of the second bonding layer 60. Thereby, when the thermal conductivity of the hollow portion 64 of the second bonding layer 60 is changed, the influence of the change can be suppressed by the first bonding layer 40. Further, the thermal resistance in the vertical direction of the first bonding layer 40 is lower than the thermal resistance in the vertical direction of the bonding portion 62 in the second bonding layer 60. Thereby, when the thermal conductivity of the hollow portion 64 of the second bonding layer 60 is changed, the influence of the change can be suppressed by the first bonding layer 40. Further, the proportion of the total bonding area of the plurality of bonding portions 62 with respect to the entire area of the second bonding layer 60 (here, the same as the area of the lower surface of the heat diffusion plate 30) when the second bonding layer 60 is viewed from above is preferably 10% or more and 50% or less. If the proportion is 10% or more, the heat diffusion plate 30 and the cooling plate 50 can be bonded with sufficient strength. If the proportion is 50% or less, the occupancy rate of the hollow portion 64 in the second bonding layer 60 becomes a sufficient size, so that the difference in heat release of the refrigerant when the hollow portion 64 is made to be in the state of high thermal conductivity and when the hollow portion 64 is made to be in the state of low thermal conductivity can be sufficiently made large. Further, since the second adhesive layer 60 has the adhesive portion 62 in addition to the hollow portion 64, the adhesive portion 62 functions as a pillar, and the height of the hollow portion 64 is less likely to be deviated when the entire hollow portion 64 is observed. In contrast, in the patent document 1, since the hollow portion does not have a pillar, the height of the hollow portion is likely to be deviated when the entire hollow portion is observed. Further, in a case where it is desired to promote cooling of the wafer W placed on the wafer placement surface 22, the hollow portion 64 can be set to a state where the thermal conductivity is high, and in a case where it is desired to suppress cooling of the wafer W placed on the wafer placement surface 22, the hollow portion 64 can be set to a state where the thermal conductivity is low. In the case where the hollow portion 64 is set to a state where the thermal conductivity is low, the second adhesive layer 60 hinders heat transfer between the heat spreader 30 and the cooling plate 50, as compared with the case where the hollow portion 64 is set to a state where the thermal conductivity is high. Therefore, if the hollow portion 64 is set to a state where the thermal conductivity is high, cooling of the wafer W by the coolant is promoted, and if the hollow portion 64 is set to a state where the thermal conductivity is low, cooling of the wafer W by the coolant is suppressed. Note that the present application is not limited to the above-described embodiments, and can be implemented in various forms as long as they belong to the technical scope of the present application. In the above-described embodiments, an example is given in which the hollow portion 64 is switched between being sealed with a heat-conducting gas and being set to a vacuum atmosphere in accordance with the on-off of the plasma, but this is not particularly limited. For example, in a process of processing the wafer W, the temperature of the wafer W is repeatedly raised and lowered, but the hollow portion 64 can be set to a vacuum atmosphere at the timing of temperature rise. Figure 6 is a graph showing the relationship between time and the temperature of the wafer W in a process of processing the wafer W. In this case, the hollow portion 64 is set to a vacuum atmosphere at the start of the process, the hollow portion 64 is maintained in a vacuum atmosphere until the temperature of the wafer W rises to Tl, and at the timing at which the temperature of the wafer W reaches Tl, a heat-conducting gas is supplied to the hollow portion 64 and sealed therein. Then, the temperature of the wafer W is maintained at Tl for a predetermined time, and then lowered to T2 (< Tl), and thereafter, the state where the heat-conducting gas is sealed in the hollow portion 64 is maintained during the time when the temperature is maintained at T2. Thereafter, the hollow portion 64 is set to a vacuum atmosphere, and the hollow portion 64 is maintained in a vacuum atmosphere until the temperature of the wafer W rises from T2 to Tl. In Figure 6 In the thick line portion (temperature rise interval) of the broken line graph of, the hollow portion 64 is set to a vacuum atmosphere. According to this, when the wafer W is warmed up, heat is less likely to be taken away by the coolant flow path 52, and thus the wafer W can be quickly warmed up. In the above embodiment, the second adhesive layer 60 is configured such that the spiral-shaped passages are the hollow portions 64 and the portions other than the spiral-shaped passages are the adhesive portions 62, but the second adhesive layer is not particularly limited thereto. For example, instead of the spiral-shaped passages, zigzag-shaped passages can be used as the hollow portions 64. Alternatively, the second adhesive layer 160 shown in FIG. 16 can be used, in which the adhesive portions 162 are configured from a ring-shaped adhesive portion 162a having the same outer diameter as the diameter of the heat-diffusing plate 30 and a plurality of circular adhesive portions 162b scattered in the inner side region of the ring-shaped adhesive portion 162a, and the hollow portions 164 are configured as the portions other than the plurality of circular adhesive portions 162b in the inner side region of the ring-shaped adhesive portion 162a. However, in view of ease of manufacture, it is preferable that the second adhesive layer 60 be configured such that the spiral-shaped passages are the hollow portions 64 and the portions other than the spiral-shaped passages are the adhesive portions 62. Figure 7 The second adhesive layer 160 shown in FIG. 16 can be used, in which the adhesive portions 162 are configured from a ring-shaped adhesive portion 162a having the same outer diameter as the diameter of the heat-diffusing plate 30 and a plurality of circular adhesive portions 162b scattered in the inner side region of the ring-shaped adhesive portion 162a, and the hollow portions 164 are configured as the portions other than the plurality of circular adhesive portions 162b in the inner side region of the ring-shaped adhesive portion 162a. However, in view of ease of manufacture, it is preferable that the second adhesive layer 60 be configured such that the spiral-shaped passages are the hollow portions 64 and the portions other than the spiral-shaped passages are the adhesive portions 62. Figure 3 The second adhesive layer 60. In the above embodiment, the hollow portions 64 are configured to supply gas, but can supply liquid instead of gas. As the liquid, the same liquid as the refrigerant flowing through the refrigerant flow path 52 can be used, for example. In the above embodiment, the thermal conductivity of the hollow portions 64 in the state in which the thermally conductive gas is enclosed in the hollow portions 64 can be the same as the thermal conductivity of the first adhesive layer 40, can be higher than the thermal conductivity of the first adhesive layer 40, or can be lower than the thermal conductivity of the first adhesive layer 40. In the above embodiment, one communication passage 54 is provided in the cooling plate 50, but is not particularly limited thereto. For example, two communication passages 54 can be provided that communicate with the hollow portions 64 from the lower surface of the cooling plate 50, one of which is configured as an inlet for the fluid and the other of which is configured as an outlet for the fluid. In the above embodiment, the first adhesive layer 40 and the second adhesive layer 60 are configured as resin adhesive layers, but one or both of the first adhesive layer 40 and the second adhesive layer 60 can be configured as a metal bonding layer. The metal bonding layer is formed using, for example, welding, soldering, diffusion bonding, TCB (Thermal compression bonding), or the like. TCB refers to a known method in which a metal bonding material is interposed between two components to be bonded, and the two components are press-bonded in a state in which the temperature is below the solidus temperature of the metal bonding material. In the above embodiment, the cooling plate 50 is exemplified as a circular plate member formed of metal, but is not particularly limited thereto. For example, the cooling plate 50 can be a circular plate member formed of a composite material of metal and ceramic. As the composite material of metal and ceramic, metal matrix composites (MMCs), ceramic matrix composites (CMCs), or the like can be given. As specific examples of the composite material, materials containing Si, SiC, and Ti, materials obtained by impregnating Al and / or Si in a SiC porous body, composite materials of Al2O3 and TiC, or the like can be given. In the above-described embodiments, the electrostatic electrode 24 and the heater electrode 26 are exemplified as the electrodes built in the ceramic plate 20, but the present application is not particularly limited thereto. For example, the electrodes built in the ceramic plate 20 can be either one of the electrostatic electrode 24 and the heater electrode 26, and an RF electrode that applies a high-frequency voltage can be built in addition to the above-described electrodes 24 and 26. In the above-described embodiments, in the wafer boat 10, a lift pin hole through which a lift pin for lifting the wafer W from the wafer loading surface 22 is inserted can be formed, and a gas hole through which a backside gas is supplied to the back surface of the wafer W can be formed. In the above-described embodiments, the heater electrode 26 is provided in a region of the ceramic plate 20 corresponding to substantially the entire upper surface, but the region of the ceramic plate 20 corresponding to substantially the entire upper surface can be divided into a plurality of sections, and the heater electrode can be provided in each section. Industrial Applicability The present application can be applied to an apparatus that performs plasma processing on, for example, a wafer. Explanation of Symbols 10 wafer boat, 20 ceramic plate, 22 wafer loading surface, 24 electrostatic electrode, 26 heater electrode, 30 heat-diffusing plate, 40 first adhesive layer, 50 cooling plate, 50a upper layer portion of cooling plate, 52 refrigerant flow path, 54 communication path, 60 second adhesive layer, 62 adhesive portion, 64 hollow portion, 70 fluid switching mechanism, 160 second adhesive layer, 162 adhesive portion, 162a annular adhesive portion, 162b circular adhesive portion, 164 hollow portion, W wafer.

Claims

1. A wafer mounting stage, wherein, have: A ceramic plate having a wafer mounting surface on its upper surface and containing electrodes; A heat diffusion plate is disposed on the lower surface of the ceramic plate; A first adhesive layer bonds the ceramic plate and the heat diffusion plate together. A cooling plate is disposed on the lower surface of the heat diffusion plate and has a refrigerant flow path inside; as well as The second adhesive layer is disposed between the heat diffusion plate and the cooling plate, and has an adhesive portion that bonds the heat diffusion plate and the cooling plate together, as well as a gap or void portion disposed between the heat diffusion plate and the cooling plate.

2. The wafer stage according to claim 1, wherein, The cooling plate has a connecting passage that connects the lower surface or side surface of the cooling plate to the cavity.

3. The wafer stage according to claim 1 or 2, wherein, The thickness of the heat diffusion plate is greater than the thickness between the top surface of the refrigerant flow path in the cooling plate and the upper surface of the cooling plate.

4. The wafer stage according to claim 1 or 2, wherein, The thermal conductivity of the heat diffuser plate is higher than that between the top surface of the refrigerant flow path in the cooling plate and the upper surface of the cooling plate.

5. The wafer stage according to claim 1 or 2, wherein, The thickness of the first adhesive layer is thinner than the thickness of the second adhesive layer.

6. The wafer stage according to claim 1 or 2, wherein, The thermal resistance in the vertical direction of the first adhesive layer is lower than the thermal resistance in the vertical direction of the adhesive portion in the second adhesive layer.

7. The wafer stage according to claim 1 or 2, wherein, When viewed from above, the bonding area of ​​the adhesive portion is more than 10% and less than 50% of the total area of ​​the second adhesive layer.

8. The wafer stage according to claim 1 or 2, wherein, The cavity can switch between a low thermal resistance state and a high thermal resistance state.

9. A method of using a wafer carrier stage, which is the method of using the wafer carrier stage according to claim 1 or 2, wherein, When it is desired to promote the cooling of the wafer placed on the wafer mounting surface, the void portion is set to a state with high thermal conductivity. When it is desired to suppress the cooling of the wafer placed on the wafer mounting surface, the void portion is set to a state with low thermal conductivity.

10. The method of using the wafer stage according to claim 9, wherein, When it is desired to promote the cooling of the wafer placed on the wafer mounting surface, a thermally conductive gas is filled into the cavity, thereby setting the cavity to a state of high thermal conductivity. In order to suppress the cooling of the wafer placed on the wafer mounting surface, the cavity is set to a vacuum state, thereby setting the cavity to a state with low thermal conductivity.

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