Wafer mounting table and method for using same

Abstract

A wafer mounting table 10 comprises a ceramic plate 20, a thermal diffusion plate 30, a first adhesive layer 40, a cooling plate 50, and a second adhesive layer 60. The ceramic plate 20 has a wafer mounting surface 22 on the top surface thereof, and built-in electrodes 24, 26. The thermal diffusion plate 30 is provided on the bottom surface of the ceramic plate 20. The first adhesive layer 40 bonds the ceramic plate 20 and the thermal diffusion plate 30. The cooling plate 50 is provided on the bottom surface of the thermal diffusion plate 30, and has a refrigerant channel 52 inside. The second adhesive plate 60 is provided between the thermal diffusion plate 30 and the cooling plate 50. The second adhesive layer 60 has: an adhesive portion 62 that bonds the thermal diffusion plate 30 and the cooling plate 50; and a cavity portion 64, which is a gap provided between the thermal diffusion plate 30 and the cooling plate 50.

Description

Wafer mounting table and method of using same

[0001] The present invention relates to a wafer stage and a method for using the same.

[0002] Conventionally, a wafer mounting table has been known that includes a ceramic plate having a wafer mounting surface on its upper surface and a built-in electrode, and a cooling plate provided on the lower surface of the ceramic plate and having a coolant flow path therein. Patent Document 1 (JP-A-2005-102626) describes a method for forming a cylindrical recess in the upper surface of the cooling plate, and introducing a heat transfer gas such as He into a gap (cavity) formed by the recess when the ceramic plate is placed on the cooling plate. Furthermore, Patent Document 1 (JP-A-2005-102626) describes a method for adjusting the pressure of the heat transfer gas supplied to the cavity during wafer etching, which can cause the temperature of the ceramic plate to rise if the thermal resistance between the ceramic plate and the cooling plate is high, making it difficult to achieve the desired temperature.

[0003] Japanese Patent Application Laid-Open No. 2016-136552

[0004] However, in Patent Document 1, it is necessary to form a recess in the upper surface of the cooling plate, which makes the manufacturing process of the wafer mounting table complicated.In addition, a temperature difference is likely to occur between the upper part of the recess and the upper part of the outer edge of the recess in the ceramic plate, which makes the ceramic plate susceptible to thermal stress.

[0005] The present invention has been made to solve these problems, and its main object is to make it possible to easily manufacture a cavity between the ceramic plate and the cooling plate and to make it difficult for thermal stress to be applied to the ceramic plate.

[0006] [1] The wafer mounting table of the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a heat diffusion plate provided on the underside of the ceramic plate; a first adhesive layer bonding the ceramic plate to the heat diffusion plate; a cooling plate provided on the underside of the heat diffusion plate and having a refrigerant flow path therein; and a second adhesive layer provided between the heat diffusion plate and the cooling plate, the second adhesive layer having an adhesive portion bonding the heat diffusion plate to the cooling plate and a cavity portion which is a gap provided between the heat diffusion plate and the cooling plate.

[0007] This wafer mounting table includes a second adhesive layer having an adhesive portion and a cavity. Because the cavity is provided in the second adhesive layer, it is not necessary to form a recess (cavity) in the upper surface of the cooling plate as in conventional cooling plates, and the cavity can be easily manufactured. Furthermore, because there is a difference in thermal resistance between the adhesive portion and the cavity in the vertical direction of the second adhesive layer, a temperature difference is likely to occur between the portion of the ceramic plate directly above the adhesive portion and the portion directly above the cavity. However, in this case, a thermal diffusion plate is disposed on the upper surface of the second adhesive layer. The presence of this thermal diffusion plate reduces the temperature difference between the portion of the ceramic plate directly above the adhesive portion and the portion directly above the cavity. Therefore, thermal stress is less likely to be applied to the ceramic plate.

[0008] Although the present invention is sometimes described using terms such as up / down, left / right, front / back, etc., these terms merely refer to relative positional relationships. Therefore, when the orientation of the wafer table is changed, up / down may become left / right, or left / right may become up / down, and such cases are also within the technical scope of the present invention.

[0009] [2] The wafer stage of the present invention (the wafer stage described in [1] above) may include a communication passage that connects the lower surface or side surface of the cooling plate to the cavity. This allows the cavity to be switched between a high thermal conductivity state and a low thermal conductivity state via the communication passage. For example, when efficiently cooling the wafer (e.g., when processing the wafer with plasma), the cavity can be set to a high thermal conductivity state to promote cooling of the wafer by the refrigerant. When not cooling the wafer (e.g., when plasma is not being generated), the cavity can be set to a low thermal conductivity state to suppress cooling of the wafer by the refrigerant. Furthermore, for example, filling the cavity with a thermally conductive gas such as He gas can create a high thermal conductivity state, and creating a vacuum in the cavity can create a low thermal conductivity state.

[0010] [3] In the wafer stage of the present invention (the wafer stage described in [1] or [2] above), the thickness of the thermal diffusion plate may be greater than the thickness of the cooling plate between the ceiling surface of the refrigerant flow path and the upper surface of the cooling plate. This allows sufficient horizontal heat diffusion in the thermal diffusion plate, making it easier to reduce the temperature difference between the portion of the ceramic plate directly above the adhesive portion and the portion of the cavity.

[0011] [4] In the wafer stage of the present invention (the wafer stage according to any one of [1] to [3] above), the thermal conductivity of the thermal diffusion plate may be higher than the thermal conductivity of the cooling plate between the ceiling surface of the refrigerant flow path and the upper surface of the cooling plate. This allows sufficient horizontal heat diffusion in the thermal diffusion plate, making it easier to reduce the temperature difference between the portion of the ceramic plate directly above the adhesive portion and the portion of the cavity.

[0012] [5] In the wafer stage of the present invention (the wafer stage described in any one of [1] to [4] above), the thickness of the first adhesive layer may be thinner than the thickness of the second adhesive layer. This prevents the first adhesive layer from interfering with the effect of a change in the thermal conductivity of the cavity of the second adhesive layer.

[0013] [6] In the wafer stage of the present invention (the wafer stage described in any one of [1] to [5] above), the thermal resistance of the first adhesive layer in the vertical direction may be lower than the thermal resistance of the adhesive portion of the second adhesive layer in the vertical direction. This makes it possible to prevent the first adhesive layer from interfering with the effect of a change in the thermal conductivity of the cavity portion of the second adhesive layer.

[0014] [7] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [6] above), the ratio of the adhesive area of ​​the adhesive portion to the total area of ​​the second adhesive layer in a plan view may be 10% or more and 50% or less. If this ratio is 10% or more, the thermal diffusion plate and the cooling plate can be bonded with sufficient strength. If this ratio is 50% or less, the occupancy rate of the cavity in the second adhesive layer is sufficiently large, and the difference in heat transfer by the refrigerant between when the cavity is in a high thermal conductivity state and when it is in a low thermal conductivity state can be sufficiently large.

[0015] [8] In the wafer mounting table of the present invention (the wafer mounting table according to any one of [1] to [7] above), the cavity may be switchable between a high thermal conductivity state and a low thermal conductivity state.

[0016] [9] In a method of using the wafer mounting table of the present invention (the wafer mounting table described in [1] or [2] above), the cavity may be set to a high thermal conductivity state if it is desired to promote cooling of a wafer mounted on the wafer mounting surface, or may be set to a low thermal conductivity state if it is desired to suppress cooling of a wafer mounted on the wafer mounting surface. When the cavity is set to a low thermal conductivity state, the second adhesive layer inhibits heat transfer between the thermal diffusion plate and the cooling plate compared to when the cavity is set to a high thermal conductivity state. Therefore, setting the cavity to a high thermal conductivity state can promote cooling of the wafer by the refrigerant, and setting the cavity to a low thermal conductivity state can suppress cooling of the wafer by the refrigerant.

[0017]

[10] In the method of using the wafer mounting table of the present invention (the method of using the wafer mounting table described in [9] above), if it is desired to promote cooling of the wafer mounted on the wafer mounting surface, the cavity may be filled with a heat-conducting gas to set the cavity to a state of high thermal conductivity, and if it is desired to suppress cooling of the wafer mounted on the wafer mounting surface, the cavity may be evacuated to set the cavity to a state of low thermal conductivity.

[0018] A perspective view of the wafer mounting table 10. A cross-sectional view taken along the line A-A in FIG. 1. A cross-sectional view of the second adhesive layer 60 cut horizontally as viewed from above. An explanatory diagram showing an example of using the wafer mounting table 10 when the plasma is on. An explanatory diagram showing an example of using the wafer mounting table 10 when the plasma is off. A graph showing the relationship between time during a process of processing a wafer W and the temperature of the wafer W. A cross-sectional view of the second adhesive layer 160 cut horizontally as viewed from above.

[0019] Next, preferred embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of a wafer mounting table 10, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 3 is a cross-sectional view of a horizontal cross section of a second adhesive layer 60 of the wafer mounting table 10 as viewed from above.

[0020] The wafer mounting table 10 is used to perform CVD, etching, or the like on a wafer W using plasma. The wafer mounting table 10 includes a ceramic plate 20, a thermal diffusion plate 30, a first adhesive layer 40, a cooling plate 50, and a second adhesive layer 60.

[0021] The ceramic plate 20 is a circular plate member having a step along its outer periphery. The ceramic plate 20 is formed of a ceramic material such as alumina or aluminum nitride, and has a circular wafer mounting surface 22 on its upper surface. A wafer W is mounted on the wafer mounting surface 22. Although not shown, a seal band is formed on the wafer mounting surface 22 along the outer edge of the upper surface of the ceramic plate 20, and a plurality of small, flat circular protrusions are formed on the entire inner surface of the seal band. The seal band and the small circular protrusions have the same height, which is, for example, several μm to several tens of μm. An electrostatic electrode 24 and a heater electrode 26 are embedded in the ceramic plate 20.

[0022] The electrostatic electrode 24 is a planar mesh electrode embedded in an area corresponding to almost the entire upper surface of the ceramic plate 20, and is capable of applying a DC voltage. When a DC voltage is applied to the electrostatic electrode 24, the wafer W is attracted and fixed to the wafer mounting surface 22 (specifically, the upper surface of the seal band and the upper surfaces of the small circular protrusions) by electrostatic attraction. When the application of the DC voltage is released, the wafer W is released from the wafer mounting surface 22. The electrostatic electrode 24 is also connected to a radio frequency (RF) power source. The heater electrode 26 is a resistance heating element formed in a single stroke from one end to the other end in an area corresponding to almost the entire upper surface of the ceramic plate 20. The heater electrode 26 can be supplied with power from a heater power source (not shown).

[0023] The thermal diffusion plate 30 is provided on the underside of the ceramic plate 20. Specifically, the thermal diffusion plate 30 is bonded to the underside of the ceramic plate 20 via a first adhesive layer 40. The thermal diffusion plate 30 is a solid disk member made of a metal such as aluminum or an aluminum alloy. The thickness of the thermal diffusion plate 30 is thicker than the thickness of the upper layer 50a of the cooling plate (described later), and is preferably 1 to 10 mm, for example, 3 mm. The thermal conductivity of the thermal diffusion plate 30 is preferably 50 to 300 W / mK, for example, 180 W / mK.

[0024] In this embodiment, the first adhesive layer 40 is a circular, solid resin adhesive layer. The resin adhesive layer is formed, for example, by sandwiching an adhesive sheet, with an organic adhesive applied to both sides, between the lower surface of the ceramic plate 20 and the upper surface of the thermal diffusion plate 30 and curing it. 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. Resins such as acrylic resin, silicone resin, and epoxy resin can be used as the resin for the resin adhesive layer. Furthermore, the resin may contain a filler.

[0025] The cooling plate 50 is provided on the underside of the thermal diffusion plate 30. Specifically, the cooling plate 50 is bonded to the underside of the thermal diffusion plate 30 via a second adhesive layer 60. The cooling plate 50 is a circular plate member made of a metal such as aluminum or an aluminum alloy. The cooling plate 50 may be made of the same material as the thermal diffusion plate 30. The cooling plate 50 includes a refrigerant flow path 52 through which a refrigerant can circulate. The refrigerant flow path 52 is formed in a single stroke from one end (inlet) to the other end (outlet) over an area corresponding to substantially the entire upper surface of the ceramic plate 20. The refrigerant flow path 52 may be formed, for example, in a spiral or zigzag shape in plan view. The refrigerant is supplied to one end (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 (outlet) of the refrigerant flow path 52 and returns 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. Examples of electrically insulating liquids include fluorine-based inert liquids. The thermal conductivity of the cooling plate 50 is preferably 50 to 300 W / mK, and is, for example, 180 W / mK.

[0026] The portion of the cooling plate 50 between the ceiling surface of the refrigerant flow path 52 and the top surface of the cooling plate 50 is referred to as the cooling plate upper layer 50a. The thickness of the cooling plate upper layer 50a is thinner than the thickness of the thermal diffusion plate 30, and is preferably 0.5 to 5 mm, for example 1 mm. The thermal conductivity of the cooling plate upper layer 50a is the same as that of the cooling plate 50. Alternatively, the thermal conductivities of the two may be different.

[0027] The second adhesive layer 60 is a resin adhesive layer provided between the lower surface of the thermal diffusion plate 30 and the upper surface of the cooling plate 50. The resin adhesive layer is formed, for example, by sandwiching an adhesive sheet, with an organic adhesive applied to both sides, between the lower surface of the thermal diffusion plate 30 and the upper surface of the cooling plate 50 and then curing the adhesive sheet. The second adhesive layer 60 includes an adhesive portion 62 that bonds the thermal diffusion plate 30 and the cooling plate 50 together, and a cavity 64 that defines a gap between the thermal diffusion plate 30 and the cooling plate 50. Specifically, the adhesive portion 62 and the cavity 64 exist in the planar direction of the second adhesive layer 60. In the embodiment shown in FIG. 3 , the second adhesive layer 60 is formed by punching a spiral passage into a circular adhesive sheet whose outer diameter is the same as the diameter of the thermal diffusion plate 30. The spiral passage constitutes the cavity 64, and the portion other than the spiral passage constitutes the adhesive portion 62. The cavity 64 can be formed by simply placing the adhesive sheet with the spiral passage punched between the thermal diffusion plate 30 and the cooling plate 50. Therefore, the cavity 64 can be formed more easily than by forming a recess in the top surface of the cooling plate 50 as in the conventional method. The resin for the resin adhesive layer can be an acrylic resin, a silicone resin, an epoxy resin, or the like. The resin may also contain a filler.

[0028] The thickness of the second adhesive layer 60 (adhesive portion 62) is thicker than the thickness of the first adhesive layer 40. In other words, the thickness of the first adhesive layer 40 is thinner than the thickness of the second adhesive layer 60. Furthermore, the thermal resistance in the vertical direction of the adhesive portion 62 in the second adhesive layer 60 is greater than the thermal resistance in the vertical direction of the first adhesive layer 40. In other words, the thermal resistance in the vertical direction of the first adhesive layer 40 is smaller than the thermal resistance in the vertical direction of the adhesive portion 62. The thermal resistance is expressed as R(m 2When the thermal conductivity is λ (W / mK), the thickness is t (m), and the thermal conductivity is λ (W / mK), R=t / λ. Therefore, for example, if the first adhesive layer 40 and the adhesive portion 62 are formed of materials with 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 of the first adhesive layer 40 in the vertical direction becomes smaller than the thermal resistance of the adhesive portion 62 in the vertical direction. 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. Furthermore, the thermal resistance of the adhesive portion of the second adhesive layer 60 in the vertical direction is 0.025 to 20 mK. 2 On the other hand, the thermal resistance of the first adhesive layer 40 in the vertical direction is preferably 0.002 to 10 m 2 -K / W is preferred.

[0029] When the second adhesive layer 60 is viewed in a plane, the ratio of the adhesive area of ​​the adhesive portion 62 to the total area of ​​the second adhesive layer 60 (the combined area of ​​the adhesive portion 62 and the hollow portion 64, which is the same as the area of ​​the underside of the thermal diffusion plate 30 in this case) is preferably 10% or more and 50% or less.

[0030] The cooling plate 50 is provided with a communication passage 54 that communicates with the cavity 64. The communication passage 54 penetrates the cooling plate 50 in the vertical direction and opens to the underside of the cooling plate 50. The cavity 64 is connected to a fluid switching mechanism 70 via the communication passage 54. The fluid switching mechanism 70 can switch between supplying and discharging fluid to the cavity 64. The fluid switching mechanism 70 can create a vacuum atmosphere (low thermal conductivity) in the cavity 64 by discharging gas from the cavity 64 through the communication passage 54 and then closing the cavity 64, or create a high thermal conductivity state in the cavity 64 by introducing a thermally conductive gas such as He gas (thermal conductivity of 0.2 W / m·K) into the vacuum-environed cavity 64 and then closing the cavity 64. The communication passage 54 is not limited to the configuration shown in FIG. 2 and may open from a side surface of the cooling plate 50.

[0031] Next, an example of how the wafer mounting table 10 is used will be described. The wafer mounting table 10 is fixed inside a semiconductor process chamber (not shown). A wafer W is mounted on the wafer mounting surface 22. In this state, a DC voltage is applied to the electrostatic electrode 24 to attract the wafer W to the wafer mounting surface 22. At the same time, a coolant is circulated through the coolant flow path 52. Power is supplied to the heater electrode 26 to generate heat and heat the wafer W. The interior of the chamber is then set to a predetermined vacuum atmosphere, and an RF voltage is applied to the electrostatic electrode 24 while a process gas is supplied from a shower head installed on the ceiling of the chamber. This generates plasma between the wafer W and the shower head. This plasma is then used to perform CVD film formation or etching on the wafer W. Depending on the situation, the cavity 64 can be filled with a thermally conductive gas to achieve a high thermal conductivity, or the cavity 64 can be placed in a vacuum atmosphere to achieve a low thermal conductivity.

[0032] For example, as shown in FIG. 4 , when plasma is generated above the wafer W (when plasma is on), heat is input to the wafer W from the plasma. This corresponds to a case where accelerated cooling of the wafer W placed on the wafer placement surface 22 is desired (when cooling demands are high). In this case, the wafer W needs to be cooled to a predetermined temperature by the coolant flowing through the coolant flow path 52. Therefore, the fluid switching mechanism 70 is adjusted so that a heat-conducting gas is sealed in the cavity 64. This increases the thermal conductivity between the thermal diffusion plate 30 and the cooling plate 50 (reducing the thermal resistance in the vertical direction), allowing the wafer W to be cooled smoothly. If the wafer W falls below a predetermined temperature, the heater electrode 26 adjusts the wafer W to the predetermined temperature.

[0033] On the other hand, as shown in FIG. 5 , when plasma is not generated (plasma-off), no heat is input to the wafer W from the plasma. This corresponds to a case where cooling of the wafer W placed on the wafer mounting surface 22 needs to be suppressed (when cooling demands are low). In this case, there is little need to cool the wafer W to a predetermined temperature using the coolant flowing through the coolant flow path 52. Therefore, the fluid switching mechanism 70 is adjusted to create a vacuum atmosphere in the cavity 64. This reduces the thermal conductivity between the thermal diffusion plate 30 and the cooling plate 50 (increasing the thermal resistance in the vertical direction), preventing the temperature of the wafer W from being excessively lowered by the coolant. In this case, the heater electrode 26 is still finely adjusted to maintain the predetermined temperature, but the heat generation amount of the heater electrode 26 is less than that when a solid adhesive layer is provided instead of the second adhesive layer 60. The heat generation amount of the heater electrode 26 is, for example, approximately the same as when plasma is generated. In addition, in this case, since the thermal conductivity of the adhesive portion 62 is significantly different from that of the hollow portion 64, which is a vacuum atmosphere, a temperature difference is likely to occur between the portion of the ceramic plate 20 directly above the adhesive portion 62 and the portion directly above the hollow portion 64. However, in this case, since the heat diffusion plate 30 is placed on the underside of the ceramic plate 20, it is possible to suppress such a temperature difference from occurring in the ceramic plate.

[0034] The wafer mounting table 10 described above includes a second adhesive layer 60 having an adhesive portion 62 and a cavity 64. The cavity 64 provided in the second adhesive layer 60 makes it easier to form the cavity 64 than by forming a recess (cavity) in the upper surface of the cooling plate 50. Furthermore, because the adhesive portion 62 and the cavity 64 of the second adhesive layer 60 have different thermal conductivities, a temperature difference is likely to occur between the portion of the ceramic plate 20 directly above the adhesive portion 62 and the portion of the cavity 64. However, in this embodiment, a thermal diffusion plate 30 is disposed on the upper surface of the second adhesive layer 60. The presence of the thermal diffusion plate 30 reduces the temperature difference between the portion of the ceramic plate 20 directly above the adhesive portion 62 and the portion of the cavity 64. Therefore, thermal stress is less likely to be applied to the ceramic plate 20.

[0035] The wafer mounting table 10 also includes a communication passage 54 that connects the underside of the cooling plate 50 to the cavity 64. Therefore, the cavity 64 can be switched between a high thermal conductivity state and a low thermal conductivity state via the communication passage 54. For example, when it is desired to efficiently cool the wafer W (e.g., when processing the wafer W with plasma), the cavity 64 is set to a high thermal conductivity state to promote cooling of the wafer W by the coolant. When it is not desired to cool the wafer W (e.g., when plasma is not being generated), the cavity 64 is set to a low thermal conductivity state to suppress cooling of the wafer W by the coolant. Furthermore, for example, filling the cavity 64 with a thermally conductive gas such as He gas can bring the cavity 64 to a high thermal conductivity state, and creating a vacuum atmosphere in the cavity 64 can bring the cavity 64 to a low thermal conductivity state.

[0036] Furthermore, the thickness of the thermal diffusion plate 30 is greater than the thickness of the cooling plate upper layer 50a, which allows sufficient horizontal heat diffusion in the thermal diffusion plate 30, making it easier to reduce the temperature difference between the portion of the ceramic plate 20 directly above the adhesive portion 62 and the portion of the cavity 64 directly above.

[0037] Furthermore, the thermal conductivity of the thermal diffusion plate 30 is higher than that of the cooling plate upper layer 50a, which allows sufficient horizontal heat diffusion in the thermal diffusion plate 30, making it easier to reduce the temperature difference between the portion of the ceramic plate 20 directly above the adhesive portion 62 and the portion of the cavity 64.

[0038] The thickness of the first adhesive layer 40 is thinner than the thickness of the second adhesive layer 60. This makes it possible to prevent the first adhesive layer 40 from interfering with the effect of a change in the thermal conductivity of the cavity 64 of the second adhesive layer 60.

[0039] Furthermore, the thermal resistance in the vertical direction of the first adhesive layer 40 is lower than the thermal resistance in the vertical direction of the adhesive portion 62 of the second adhesive layer 60. This makes it possible to prevent the first adhesive layer 40 from interfering with the effect of a change in the thermal conductivity of the cavity portion 64 of the second adhesive layer 60.

[0040] Furthermore, the ratio of the total adhesive area of ​​the multiple adhesive portions 62 to the total area of ​​the second adhesive layer 60 (here, the same as the area of ​​the underside of the thermal diffusion plate 30) when viewed from above is preferably 10% or more and 50% or less. If this ratio is 10% or more, the thermal diffusion plate 30 and the cooling plate 50 can be bonded with sufficient strength. If this ratio is 50% or less, the occupancy rate of the cavities 64 in the second adhesive layer 60 is sufficiently large, and the difference in heat transfer by the refrigerant when the cavities 64 are in a high thermal conductivity state and when they are in a low thermal conductivity state can be sufficiently large.

[0041] Furthermore, since the second adhesive layer 60 has the adhesive portion 62 in addition to the cavity portion 64, the adhesive portion 62 acts as a support, and the height of the cavity portion 64 is less likely to vary when viewed as a whole. In contrast, in Patent Document 1, since there are no supports in the cavity portion, the height of the cavity portion is likely to vary when viewed as a whole.

[0042] In addition, the cavity 64 may be set to a high thermal conductivity state when it is desired to promote cooling of the wafer W placed on the wafer placement surface 22, and may be set to a low thermal conductivity state when it is desired to suppress cooling of the wafer W placed on the wafer placement surface 22. When the cavity 64 is set to a low thermal conductivity state, the second adhesive layer 60 inhibits heat transfer between the thermal diffusion plate 30 and the cooling plate 50 more than when the cavity 64 is set to a high thermal conductivity state. Therefore, when the cavity 64 is set to a high thermal conductivity state, it is possible to promote cooling of the wafer W by the refrigerant, and when the cavity 64 is set to a low thermal conductivity state, it is possible to suppress cooling of the wafer W by the refrigerant.

[0043] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0044] In the above-described embodiment, an example has been described in which the cavity 64 is alternately filled with a thermally conductive gas or maintained in a vacuum atmosphere depending on whether the plasma is turned on or off. However, this is not intended to be limiting. For example, in a process for processing a wafer W, the temperature of the wafer W is repeatedly increased and decreased. The cavity 64 may be placed in a vacuum atmosphere at the timing of the temperature increase. FIG. 6 is a graph showing the relationship between time and the temperature of the wafer W in a process for processing a wafer W. In this case, the cavity 64 is placed in a vacuum atmosphere at the start of the process and maintained in this vacuum atmosphere until the temperature of the wafer W rises to T1. When the temperature of the wafer W reaches T1, a thermally conductive gas is supplied and sealed into the cavity 64. The temperature of the wafer W is then maintained at T1 for a predetermined time, and then lowered to T2 (<T1). The state in which the thermally conductive gas is sealed in the cavity 64 is maintained until the temperature T2 is maintained for a predetermined time. The cavity 64 is then placed in a vacuum atmosphere, and the vacuum atmosphere is maintained until the temperature of the wafer W rises from T2 to T1. 6, the cavity 64 is set to a vacuum atmosphere in the thick line portion (heating section). This makes it difficult for heat to be absorbed by the coolant flow path 52 when the temperature of the wafer W is raised, so that the temperature of the wafer W can be raised quickly.

[0045] In the above-described embodiment, the spiral passage in the second adhesive layer 60 is defined as the cavity 64, and the portion other than the spiral passage is defined as the adhesive portion 62. However, the second adhesive layer is not limited to this. For example, a zigzag passage may be used as the cavity 64 instead of the spiral passage. Alternatively, as in the second adhesive layer 160 shown in FIG. 7 , the adhesive portion 162 may be configured with an annular adhesive portion 162a whose outer diameter is the same as the diameter of the thermal diffusion plate 30 and multiple circular adhesive portions 162b scattered within the annular adhesive portion 162a, and the cavity 164 may be the portion of the inner region of the annular adhesive portion 162a excluding the multiple circular adhesive portions 162b. However, considering ease of manufacturing, the second adhesive layer 60 shown in FIG. 3 is preferable.

[0046] In the above-described embodiment, gas can be supplied to the cavity 64. However, a liquid can be supplied instead of gas. The liquid can be, for example, the same refrigerant as that flowing through the refrigerant flow path 52.

[0047] In the above-described embodiment, when the cavity 64 is filled with a thermally conductive gas, the thermal conductivity of the cavity 64 may be the same as the thermal conductivity of the first adhesive layer 40, may be higher than the thermal conductivity of the first adhesive layer 40, or may be lower than the thermal conductivity of the first adhesive layer 40.

[0048] In the above-described embodiment, one communication passage 54 is provided in the cooling plate 50, but this is not particularly limited. For example, two communication passages 54 may be provided that communicate from the lower surface of the cooling plate 50 to the cavity 64, with one serving as an inlet for the fluid and the other as an outlet for the fluid.

[0049] In the above-described embodiment, the first adhesive layer 40 and the second adhesive layer 60 are resin adhesive layers, but one or both of the first adhesive layer 40 and the second adhesive layer 60 may be metal bonding layers. The metal bonding layer is formed by, for example, welding, brazing, diffusion bonding, thermal compression bonding (TCB), etc. TCB refers to a known method in which a metal bonding material is sandwiched between two members to be joined and the two members are pressure-bonded while being heated to a temperature below the solidus temperature of the metal bonding material.

[0050] In the above-described embodiment, the cooling plate 50 is illustrated as a disk member made of metal, but is not limited thereto. For example, the cooling plate 50 may be a disk member made of a composite material of metal and ceramic. Examples of composite materials of metal and ceramic include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti, materials in which porous SiC is impregnated with Al and / or Si, and composite materials of Al2O3 and TiC.

[0051] In the above-described embodiment, the electrostatic electrode 24 and the heater electrode 26 are exemplified as electrodes built into the ceramic plate 20, but the present invention is not limited to this. For example, the electrode built into the ceramic plate 20 may be either the electrostatic electrode 24 or the heater electrode 26, or an RF electrode for applying a high-frequency voltage may be built into the ceramic plate 20 in addition to the electrodes 24 and 26.

[0052] In the above-described embodiment, the wafer mounting table 10 may be formed with lift pin holes through which lift pins for lifting the wafer W from the wafer mounting surface 22 can be inserted, or may be formed with gas holes through which backside gas can be supplied to the back surface of the wafer W.

[0053] In the above-described embodiment, the heater electrode 26 is provided in an area corresponding to almost the entire upper surface of the ceramic plate 20, but the area corresponding to almost the entire upper surface of the ceramic plate 20 may be divided into multiple zones, and a heater electrode may be provided in each zone.

[0054] The present invention can be used, for example, in an apparatus for plasma processing a wafer.

[0055] 10 wafer mounting table, 20 ceramic plate, 22 wafer mounting surface, 24 electrostatic electrode, 26 heater electrode, 30 heat diffusion plate, 40 first adhesive layer, 50 cooling plate, 50a cooling plate upper layer portion, 52 refrigerant flow path, 54 communication path, 60 second adhesive layer, 62 adhesive portion, 64 cavity portion, 70 fluid switching mechanism, 160 second adhesive layer, 162 adhesive portion, 162a annular adhesive portion, 162b circular adhesive portion, 164 cavity portion, W wafer.

Claims

1. A wafer mounting table comprising: a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a heat diffusion plate provided on the underside of the ceramic plate; a first adhesive layer bonding the ceramic plate to the heat diffusion plate; a cooling plate provided on the underside of the heat diffusion plate and having a refrigerant flow path therein; and a second adhesive layer provided between the heat diffusion plate and the cooling plate, the second adhesive layer having an adhesive portion bonding the heat diffusion plate to the cooling plate and a hollow portion which is a gap provided between the heat diffusion plate and the cooling plate.

2. The wafer mounting table according to claim 1, wherein the cooling plate is provided with a communication passage that communicates from a lower surface or a side surface of the cooling plate to the cavity.

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

4. The wafer mounting table according to claim 1 or 2, wherein the thermal conductivity of the heat diffusion plate is higher than the thermal conductivity of the cooling plate between a ceiling surface of the refrigerant flow path and an upper surface of the cooling plate.

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

6. The wafer mounting table 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 of the second adhesive layer.

7. The wafer mounting table according to claim 1 or 2, wherein a ratio of an adhesive area of ​​the adhesive portion to a total area of ​​the second adhesive layer in a plan view is 10% or more and 50% or less.

8. The wafer mounting table according to claim 1 or 2, wherein the cavity is switchable between a low thermal resistance state and a high thermal resistance state.

9. A method of using the wafer mounting table according to claim 1 or 2, comprising setting the cavity to a high thermal conductivity state when it is desired to promote cooling of a wafer mounted on the wafer mounting surface, and setting the cavity to a low thermal conductivity state when it is desired to suppress cooling of a wafer mounted on the wafer mounting surface.

10. A method of using a wafer mounting table as described in claim 9, comprising the steps of: when it is desired to promote cooling of a wafer mounted on said wafer mounting surface, filling said cavity with a heat conductive gas to set said cavity to a state of high thermal conductivity; and when it is desired to suppress cooling of a wafer mounted on said wafer mounting surface, setting said cavity to a state of low thermal conductivity by placing said cavity in a vacuum state.

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