Components for semiconductor manufacturing equipment

Abstract

The wafer mounting stage 10 includes a ceramic plate 20 having a wafer mounting surface 21 on its upper surface and incorporating electrostatic electrodes 22, a base plate 50 provided on the lower surface of the ceramic plate 20 and incorporating a refrigerant flow path 52, and a gas passage 24 provided so as to extend from the lower surface of the base plate 50 to the wafer mounting surface 21. Further, first to fourth internal electrodes 31 to 34 are provided. Each of the internal electrodes 31 to 34 is provided inside the ceramic plate 20 so as to surround the gas passage 24 below the electrostatic electrodes 22 and not to be exposed on the inner wall of the gas passage 24, and is electrically connected to the electrostatic electrodes 22. The base plate 50 also serves as a bias electrode. The bias electrode is provided electrically independently of the electrostatic electrodes 22, and a bias voltage is applied when generating plasma above the wafer mounting surface 21.

Description

Technical Field

[0001] The present invention relates to a member for a semiconductor manufacturing apparatus.

Background Art

[0002] Conventionally, a member for a semiconductor manufacturing apparatus has been known, which includes a ceramic plate having a wafer placement surface on its upper surface and incorporating electrodes, a base plate provided on the lower surface of the ceramic plate, and a gas passage provided so as to reach from the lower surface of the base plate to the wafer placement surface of the ceramic plate. In Patent Document 1, in such a member for a semiconductor manufacturing apparatus, a cylindrical shield electrode portion is provided around the gas passage in the ceramic plate. The cylindrical shield electrode portion has a function of shielding so that the influence of the electric field generated around the electrostatic electrode does not reach the internal space of the gas passage when a DC voltage is applied to the electrostatic electrode. Thereby, the occurrence of abnormal discharge in the gas passage is prevented or reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, when the shielding by the shield electrode portion is not sufficient, the occurrence of abnormal discharge in the gas passage may not be prevented.

[0005] The present invention has been made to solve the above-described problems, and the main object is to prevent or reduce the occurrence of abnormal discharge in a passage based on a principle different from the conventional one.

Means for Solving the Problems

[0006] [1] The member for a semiconductor manufacturing apparatus of the present invention includes a ceramic plate having a wafer placement surface on the upper surface and incorporating an electrostatic electrode, a base plate provided on the lower surface of the ceramic plate and incorporating a refrigerant flow path, a passage provided so as to reach the wafer placement surface of the ceramic plate from the lower surface of the base plate, at least one internal electrode provided inside the ceramic plate so as to surround the passage below the electrostatic electrode and not expose to the inner wall of the passage, and electrically connected to the electrostatic electrode, a bias electrode provided electrically independently of the electrostatic electrode at the same height as or lower than the lowermost internal electrode among the at least one internal electrode, and to which a bias voltage is applied when generating plasma above the wafer placement surface, and is equipped with the above.

[0007] In this member for a semiconductor manufacturing apparatus, at least one internal electrode electrically connected to the electrostatic electrode is provided inside the ceramic plate so as to surround the passage below the electrostatic electrode and not expose to the inner wall of the passage. When a DC voltage is applied to the electrostatic electrode and a bias voltage is applied to the bias electrode, a potential gradient is generated in the vertical direction in the internal space of the passage. In the present invention, since at least one internal electrode is provided below the electrostatic electrode, the vertical distance in which the potential gradient is generated becomes shorter compared to the case where no internal electrode is provided. As a result, even if electrons ionized from atoms or molecules of the heat transfer gas are accelerated by the potential gradient, they are not sufficiently accelerated and do not have sufficient energy, so it is possible to avoid reaching arc discharge. Therefore, it is possible to prevent or reduce the occurrence of abnormal discharge in the passage by a principle different from the conventional principle of shielding the influence of the electric field generated around the electrostatic electrode.

[0008] In addition, in this specification, "upper" and "lower" do not represent absolute positional relationships, but rather relative positional relationships. Therefore, depending on the orientation of the member for a semiconductor manufacturing apparatus, "upper" and "lower" can become "lower" and "upper", or "left" and "right", or "front" and "rear". Further, examples of the "passage" include a gas passage and a lift pin hole. Also, when there is only one "internal electrode", that "internal electrode" becomes the "lowermost internal electrode".

[0009] [2] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus described in [1] above), the base plate may also serve as the bias electrode. By doing so, it becomes unnecessary to provide a bias electrode separately from the base plate.

[0010] [3] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus described in [1] above), the bias electrode may be incorporated in the ceramic plate.

[0011] [4] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus described in [3] above), the bias electrode may be provided below the lowermost internal electrode.

[0012] [5] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus described in [3] above), the bias electrode is provided at the same height as the lowermost internal electrode and may be provided around the lowermost internal electrode. Square

[0013] [6] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus according to any one of [1] to [3] above), the at least one internal electrode may be a ring-shaped electrode surrounding the periphery of the passage, or may be an electrode having the same shape as the electrostatic electrode and having a through-hole through which the passage passes. When the internal electrode is a ring-shaped electrode, the amount of the electrode material used can be reduced. When the internal electrode has the same shape as the electrostatic electrode, since the internal electrode has a relatively large area, the degree of freedom in designing the wiring for electrically connecting the internal electrode and the electrostatic electrode is increased. Note that "the same shape" means that the shapes (for example, circular or rectangular) may be the same and the sizes may be the same or different.

[0014] [7] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus according to any one of [1] to [4] above), the passage may be connected to a source of a heat-conductive gas. In this case, in the internal space of the passage, atoms or molecules of the heat-conductive gas are ionized to generate electrons, and a phenomenon in which the electrons collide with other atoms or molecules is likely to occur. Therefore, the significance of applying the present invention is high.

[0015] [8] In the member for a semiconductor manufacturing apparatus of the present invention (the member for a semiconductor manufacturing apparatus according to any one of [1] to [5] above), the base plate may also serve as a source electrode to which a source voltage is applied when generating plasma above the wafer placement surface. By doing so, it becomes unnecessary to provide a source electrode separately from the base plate.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0017] Preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the wafer mounting table 10, FIG. 2 is a perspective view with a cross-sectional view of the wafer mounting table 10, FIG. 3 is a partial cross-sectional view of the wafer mounting table 10, and FIG. 4 is a perspective view showing the positional relationship of the electrostatic electrode 22 and the first to fourth internal electrodes 31 to 34. In FIGS. 2 and 3, the seal band 21a and the circular protrusions 21b are omitted. Also, in FIG. 2, the first to fourth internal electrodes 31 to 34 are omitted, and in FIG. 3, the electrode terminals 26, the power supply member 58, and the power supply member arrangement holes 54 are omitted.

[0018] The wafer mounting table 10 is an example of a member for a semiconductor manufacturing apparatus of the present invention. As shown in FIG. 2, it includes a ceramic plate 20, a base plate 50, a bonding layer 60, a power supply member arrangement hole 54, and a gas passage 24.

[0019] The ceramic plate 20 is a ceramic disk (for example, 300 mm in diameter and 5 mm in thickness) such as an alumina sintered body or a aluminum nitride sintered body. The upper surface of the ceramic plate 20 serves as a wafer placement surface 21. The ceramic plate 20 incorporates an electrostatic electrode 22. As shown in FIG. 1, a seal band 21a is formed along the outer edge on the wafer placement surface 21, and a plurality of circular small protrusions 21b are formed on the entire inner surface of the seal band 21a. The seal band 21a and the circular small protrusions 21b are of the same height, and the height is, for example, several μm to several tens of μm. The electrostatic electrode 22 is a circular mesh planar electrode and is connected to a DC power supply 70 via a power supply member 58. When a DC voltage is applied to this electrostatic electrode 22, the wafer W is adsorbed and fixed to the wafer placement surface 21 (specifically, the upper surface of the seal band 21a and the upper surface of the circular small protrusions 21b) by an electrostatic adsorption force, and when the application of the DC voltage is released, the adsorption and fixation of the wafer W to the wafer placement surface 21 is released.

[0020] Inside the ceramic plate 20, as shown in FIGS. 3 and 4, first to fourth internal electrodes 31 to 34 are provided in order from the top, and the fourth internal electrode 34 is located at the lowermost position. The first to fourth internal electrodes 31 to 34 are all provided below the electrostatic electrode 22. The first to fourth internal electrodes 31 to 34 are provided inside the ceramic plate 20 so as to surround the gas passage 24 and not to be exposed on the inner wall of the gas passage 24. The first to fourth internal electrodes 31 to 34 are circular mesh planar electrodes having the same shape as the electrostatic electrode 22, and the size is substantially the same as that of the electrostatic electrode 22. The electrostatic electrode 22 and the first internal electrode 31 are electrically connected by a first via 41 extending in the vertical direction, the first internal electrode 31 and the second internal electrode 32 are electrically connected by a second via 42 extending in the vertical direction, the second internal electrode 32 and the third internal electrode 33 are electrically connected by a third via 43 extending in the vertical direction, and the third internal electrode 33 and the fourth internal electrode 34 are electrically connected by a fourth via 44 extending in the vertical direction. Therefore, the first to fourth internal electrodes 31 to 34 have the same potential as the electrostatic electrode 22. The first to fourth vias 41 to 44 are not aligned in a straight line but are offset when viewed in the vertical direction. As shown in FIG. 3, the distance D1 between the electrostatic electrode 22 and the first internal electrode 31, the distance D2 between the first internal electrode 31 and the second internal electrode 32, the distance D3 between the second internal electrode 32 and the third internal electrode 33, the distance D4 between the third internal electrode 33 and the fourth internal electrode 34, and the distance Db between the fourth internal electrode 34 and the lower surface of the ceramic plate 20 are preferably not less than 1 times the distance d between the wafer mounting surface 21 and the electrostatic electrode 22.

[0021] The base plate 50 is a disk (for example, a disk having the same diameter as or a larger diameter than the ceramic plate 20 and a thickness of 25 mm) with good electrical conductivity and thermal conductivity, and is electrically independent of the electrostatic electrode 22 and the first to fourth internal electrodes 31 to 34. Inside the base plate 50, a refrigerant flow path 52 through which a refrigerant circulates is provided. The refrigerant flowing through the refrigerant flow path 52 is preferably a liquid and preferably has electrical insulation properties. Examples of the electrically insulating liquid include fluorine-based inert liquids. As shown in FIG. 1, the refrigerant flow path 52 is formed in a spiral shape in one stroke from one end (inlet 52in) to the other end (outlet 52out) over the entire base plate 50 in a plan view. At the inlet 52in and the outlet 52out of the refrigerant flow path 52, a supply port and a recovery port of an external refrigerant device (not shown) are respectively connected. The refrigerant supplied from the supply port of the external refrigerant device to the inlet 52in of the refrigerant flow path 52 returns from the outlet 52out of the refrigerant flow path 52 to the recovery port of the external refrigerant device after passing through the refrigerant flow path 52, and after being temperature-adjusted, is again supplied from the supply port to the inlet 52in of the refrigerant flow path 52. The base plate 50 is connected to a source power supply 72 and a bias power supply 74. The source power supply 72 is a power supply that generates a source RF for generating plasma above the wafer mounting surface 21. The bias power supply 74 is a power supply that generates a bias RF for attracting ions to the wafer W. The bias RF has a lower frequency and a larger amplitude than the source RF. The bias RF may be a sine wave (where plus and minus appear alternately) or a rectangular wave (where a negative rectangle appears periodically), but a rectangular wave is preferred for performing etching sharply. The frequency of the source RF is, for example, several tens to several hundreds of MHz, and the frequency of the bias RF is, for example, several hundreds of kHz.

[0022] Examples of the material of the base plate 50 include a metal material, a composite material of metal and ceramic, etc. Examples of the metal material include Al, Ti, Mo, or their alloys. Examples of the composite material of metal and ceramic include a metal matrix composite (MMC), a ceramic matrix composite (CMC), etc. Specific examples of such composite materials include a material containing Si, SiC, and Ti (also referred to as SiSiCTi), a material obtained by impregnating a porous SiC body with Al and / or Si, a composite material of Al2O3 and TiC, etc. As the material of the base plate 50, it is preferable to select a material having a coefficient of thermal expansion close to that of the material of the ceramic plate 20.

[0023] The bonding layer 60 is a metal bonding layer here, and bonds the lower surface of the ceramic plate 20 and the upper surface of the base plate 50. The metal bonding layer may be, for example, a layer formed of solder or a metal brazing material. The metal bonding layer 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 in a state of being heated to a temperature below the solidus temperature of the metal bonding material. Note that the bonding layer 60 may be a resin adhesive layer. Examples of the material of the resin adhesive layer include insulating resins such as epoxy resin, acrylic resin, and silicone resin, and those obtained by adding a filler to the insulating resin.

[0024] As shown in FIG. 2, the power supply member placement hole 54 is a substantially cylindrical hole that vertically penetrates the base plate 50 and the bonding layer 60, and is provided so as not to penetrate the refrigerant flow path 52. An insulating tube 56 is housed in the power supply member placement hole 54. The insulating tube 56 is fixed to the power supply member placement hole 54 with an adhesive. At the upper bottom of the power supply member placement hole 54, an electrode terminal 26 electrically connected to the electrostatic electrode 22 is exposed. A power supply member 58 is electrically connected to the electrode terminal 26. The power supply member 58 is formed by connecting an upper metal terminal 58a and a lower metal terminal 58b with a flexible metal wire 58c, and the upper metal terminal 58a is joined to the electrode terminal 26. The lower metal terminal 58b is exposed from the lower opening of the insulating tube 56 and is connected to a DC power supply 70 for electrostatic adsorption. Note that the power supply member 58 may be a metal rod.

[0025] As shown in FIG. 2, the gas passage 24 is a substantially cylindrical hole that vertically penetrates the base plate 50, the bonding layer 60, and the ceramic plate 20, and is provided so as not to penetrate the refrigerant flow path 52. The gas passage 24 is connected to a He gas supply source 76. The gas passage 24 is provided so as to extend from the lower surface of the base plate 50 to the wafer placement surface 21. An insulating tube 57 is housed in a portion of the gas passage 24 that penetrates the base plate 50 and the bonding layer 60. The insulating tube 57 is fixed to the gas passage 24 with an adhesive. As shown in FIG. 3, the gas passage 24 vertically penetrates the electrostatic electrode 22 and the first to fourth internal electrodes 31 to 34. Through holes 22a, 31a to 34a having a diameter larger than the diameter of the gas passage 24 are provided in portions of the electrostatic electrode 22 through which the gas passage 24 passes and in portions of the first to fourth internal electrodes 31 to 34 through which the gas passage 24 passes. Therefore, the electrostatic electrode 22 and the first to fourth internal electrodes 31 to 34 are not exposed on the inner wall of the gas passage 24. The length L between the gas passage 24 and the through hole 22a of the electrostatic electrode 22 is preferably at least twice the distance d between the wafer placement surface 21 and the electrostatic electrode 22. The length between the gas passage 24 and the through holes 31a to 34a of the first to fourth internal electrodes 31 to 34 is also preferably at least twice the distance d.

[0026] Next, a method for manufacturing the ceramic plate 20 of the wafer stage 10 will be briefly described. The ceramic plate 20 can be obtained, for example, by producing six formed sheets, processing each formed sheet and then laminating them for hot press firing, and then performing shape processing (such as drilling). For example, the first formed sheet from the top is used as it is without processing. For the second formed sheet from the top, a conductive paste is printed on the upper surface so as to have the same shape as the electrostatic electrode 22, and a via filled with the conductive paste is provided at the position of the first via 41 . For the third to fifth formed sheets from the top, a conductive paste is printed on the upper surface so as to have the same shape as the first to third internal electrodes 31 to 33, respectively, and vias filled with the conductive paste are provided at the positions of the second to fourth vias 42 to 44. For the sixth formed sheet from the top, a conductive paste is printed on the upper surface so as to have the same shape as the fourth internal electrode 34. Each formed sheet can be produced by tape casting or mold casting. Then, these six sheets are laminated and hot press fired, and then shape processing (such as drilling) is performed. Note that the gas passage 24 may be formed before the hot press firing or after the hot press firing.

[0027] Next, an example of using the wafer stage 10 configured in this way will be described. First, with the wafer stage 10 installed in a chamber (not shown), the wafer W is placed on the wafer placement surface 21. Then, the inside of the chamber is evacuated by a vacuum pump and adjusted to a predetermined degree of vacuum. A DC voltage is applied to the electrostatic electrode 22 of the ceramic plate 20 to generate an electrostatic adsorption force, and the wafer W is adsorbed and fixed to the wafer placement surface 21. Also, He gas is supplied from the He gas supply source 76 to the gas passage 24. The He gas fills the space surrounded by the seal band 21a, the circular protrusion 21b, and the wafer W. Thereby, the heat conduction between the wafer W and the wafer placement surface 21 is improved. Next, the inside of the chamber is set to a reaction gas atmosphere at a predetermined pressure (for example, several tens to several hundreds of Pa). In this state, a source voltage from the source power supply 72 and a bias voltage from the bias power supply 74 are applied to the base plate 50. Then, plasma is generated between an upper electrode (not shown) provided on the ceiling portion inside the chamber and the wafer placement surface 21 of the wafer stage 10. The surface of the wafer W is processed by the generated plasma. A refrigerant is circulated in the refrigerant flow path 52 of the base plate 50 in a timely manner.

[0028] Here, in the internal space of the gas passage 24, with the application of a DC voltage to the electrostatic electrode 22 and the application of a bias voltage to the base plate 50 which is a bias electrode, a potential gradient from plus to minus occurs in the vertical direction. In the present embodiment, first to fourth internal electrodes 31 to 34 having the same potential as the electrostatic electrode 22 are provided inside the ceramic plate 20. Therefore, no potential gradient occurs in the vertical direction between the electrostatic electrode 22 and the fourth internal electrode 34 in the internal space of the gas passage 24. On the other hand, a potential gradient from plus to minus occurs between the fourth internal electrode 34 and the base plate 50 which is a bias electrode, but the length in the vertical direction in which the potential gradient occurs is about the same as the distance between the fourth internal electrode 34 and the base plate 50 and is short. Therefore, even if an electron generated as a He atom is ionized in the internal space of the gas passage 24 accelerates and hits another He atom, the accelerating distance is short, so the electron does not reach a high energy and abnormal discharge does not occur even if it hits another He atom.

[0029] On the other hand, when the first to fourth internal electrodes 31 to 34 are not provided inside the ceramic plate 20, the vertical length in the internal space of the gas passage 24 where a potential gradient occurs is longer than that in this embodiment. Therefore, assuming that electrons generated as He atoms are ionized accelerate in the internal space of the gas passage 24 and hit other He atoms, since the acceleration distance is long, the electrons reach high energy, and the phenomenon that the electrons hit other He atoms causing those He atoms to be ionized and further electrons are generated easily occurs repeatedly, and abnormal discharge is likely to occur.

[0030] In the wafer mounting stage 10 described in detail above, the first to fourth internal electrodes 31 to 34 electrically connected to the electrostatic electrode 22 are provided inside the ceramic plate 20 below the electrostatic electrode 22 so as to surround the gas passage 24 and not expose to the inner wall of the gas passage 24. When a DC voltage is applied when the electrostatic electrode 22 adsorbs the wafer W on the wafer mounting surface 21, the electrostatic electrode 22 has a positive potential. The base plate 50 which is a bias electrode has a negative potential periodically when a bias voltage is applied to draw in ions in the plasma. Therefore, in the internal space of the gas passage 24, a potential with a gradient from positive to negative is generated in the vertical direction. When a heat conductive gas such as He gas exists in the gas passage 24, electrons ionized from He atoms are accelerated by the electric field, collide with other non-ionized He atoms, and may ultimately lead to arc discharge. In this embodiment, since the first to fourth internal electrodes 31 to 34 are provided below the electrostatic electrode 22, the vertical distance in which the potential gradient occurs becomes shorter. As a result, even if electrons are generated from He atoms, they are not sufficiently accelerated by the potential gradient and do not have sufficient energy, so it is possible to avoid leading to arc discharge. Therefore, the occurrence of abnormal discharge in the gas passage 24 can be prevented or reduced.

[0031] Further, the base plate 50 also serves as a bias electrode. Therefore, there is no need to provide a bias electrode separately from the base plate 50.

[0032] Furthermore, the first to fourth internal electrodes 31 to 34 have the same shape (circular planar electrodes) as the electrostatic electrode 22 and have a relatively large area, so the degree of design freedom of the first to fourth vias 41 to 44 is increased. Note that the sizes of the first to fourth internal electrodes 31 to 34 may be the same as, slightly larger than, or slightly smaller than that of the electrostatic electrode 22.

[0033] Moreover, the gas passage 24 is connected to the He gas supply source 76. Therefore, in the internal space of the gas passage 24, a phenomenon in which He atoms are ionized to generate electrons and the electrons collide with other He atoms is likely to occur, and the significance of applying the present invention is high.

[0034] Also, the base plate 50 also serves as a source electrode. Therefore, it is not necessary to provide a source electrode separately from the base plate 50.

[0035] Furthermore, when viewed in the vertical direction, the first to fourth vias 41 to 44 are not arranged in a straight line but are offset. In this case, compared with the case where the first to fourth vias 41 to 44 are arranged in a straight line in the vertical direction, when the ceramic plate 20 is manufactured by firing, the possibility of cracks occurring at the locations where the first to fourth vias 41 to 44 are provided due to the difference in thermal expansion between the ceramic and the metal is reduced, which is more preferable. That is, in the present embodiment, since the first to fourth vias 41 to 44 are offset when viewed in the vertical direction, the difference in thermal expansion during firing is reduced, and cracks are less likely to occur at the locations where the first to fourth vias 41 to 44 are provided.

[0036] Note that the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[0037] In the above-described embodiment, the base plate 50 is also used as a bias electrode, but the bias electrode may be incorporated in the ceramic plate 20.

[0038] For example, FIG. 5 shows an example in which a bias electrode 35 is provided instead of the fourth internal electrode 34 of the above-described embodiment. In FIG. 5, the same reference numerals are given to the same components as those in the above-described embodiment. The bias electrode 35 is not electrically connected to the electrostatic electrode 22 or the first to third internal electrodes 31 to 33, but is connected to a bias power supply 74. A through hole 35a having a diameter larger than the diameter of the gas passage 24 is provided in a portion of the bias electrode 35 through which the gas passage 24 passes. Therefore, the bias electrode 35 is not exposed on the inner wall of the gas passage 24. The length between the gas passage 24 and the through hole 35a of the bias electrode 35 is preferably at least twice the distance d between the wafer mounting surface 21 and the electrostatic electrode 22. The distance between the bias electrode 35 and the lower surface of the ceramic plate 20 is preferably at least one time the distance d. In the case of FIG. 5, since the first to third internal electrodes 31 to 33 having the same potential as the electrostatic electrode 22 are provided below the electrostatic electrode 22, the vertical distance in which a potential gradient occurs is shorter than the case where the first to third internal electrodes 31 to 33 are not provided. Therefore, the occurrence of abnormal discharge in the gas passage 24 can be prevented or reduced.

[0039] Figures 6 and 7 show an example in which a ring-shaped fourth internal electrode 134 is employed instead of the fourth internal electrode 34 of the above-described embodiment, and a bias electrode 135 is incorporated in the ceramic plate 20 so as to surround the fourth internal electrode 134. In Figures 6 and 7, the same components as those of the above-described embodiment are denoted by the same reference numerals. The fourth internal electrode 134 is provided so as to surround the gas passage 24. A through-hole 134a having a diameter larger than the diameter of the gas passage 24 is provided in a portion of the fourth internal electrode 134 through which the gas passage 24 passes. Therefore, the fourth internal electrode 134 is not exposed on the inner wall of the gas passage 24. The fourth internal electrode 134 is electrically connected to the third internal electrode 33 via a via 144. Therefore, the fourth internal electrode 134 has the same potential as the electrostatic electrode 22. The bias electrode 135 is provided in the same plane as the fourth internal electrode 134, is not electrically connected to the electrostatic electrode 22 nor to the first to fourth internal electrodes 31 to 33, 134, and is connected to a bias power supply 74. The bias electrode 135 has a through-hole 135a provided at a distance from the fourth internal electrode 134. The distance between the third internal electrode 33 and the fourth internal electrode 134 (or the bias electrode 135) is preferably at least one time the distance d between the wafer mounting surface 21 and the electrostatic electrode 22. The length between the gas passage 24 and the through-hole 134a of the fourth internal electrode 134 and the distance between the outer edge of the fourth internal electrode 134 and the inner edge of the through-hole 135a are preferably at least two times the distance d. In the case of Figures 6 and 7, since the first to fourth internal electrodes 31 to 33, 134 having the same potential as the electrostatic electrode 22 are provided below the electrostatic electrode 22, the vertical distance in which a potential gradient occurs is shorter than in the case where the first to fourth internal electrodes 31 to 33, 134 are not present. Therefore, it is possible to prevent or reduce the occurrence of abnormal discharge in the gas passage 24.

[0040] When the bias electrode is built in the ceramic plate 20, an outer bias electrode that is electrically independent of the bias electrode may be provided on the outer peripheral portion of the bias electrode. FIG. 8 shows an example in which an outer bias electrode 136 is provided on the outer peripheral portion of the bias electrode 135 in FIG. 7. In FIG. 8, the same components as those in FIG. 7 are denoted by the same reference numerals. Also, in FIG. 8, the electrostatic electrode 22, the first and second internal electrodes 31, 32, etc. are omitted. The outer bias electrode 136 is a ring-shaped electrode provided in the same plane as the circular bias electrode 135, and is not electrically connected to the electrostatic electrode 22, the first to fourth internal electrodes 31 to 33, 134, or the bias electrode 135. The distance between the inner edge of the outer bias electrode 136 and the outer edge of the bias electrode 135 is preferably at least twice the distance d. In FIG. 8, different bias voltages can be applied to the bias electrode 135 and the outer bias electrode 136, respectively. Therefore, the degree of ion drawing can be changed between the central side and the outer peripheral side of the wafer W. When the focus ring is placed on the step provided along the outer periphery of the ceramic plate 20, the degree of ion drawing can also be changed between the focus ring and the wafer W.

[0041] In the above-described embodiment, the first to fourth internal electrodes 31 to 34 are made to have the same shape as the electrostatic electrode 22. However, the first to fourth internal electrodes 31 to 34 may be ring-shaped electrodes surrounding the gas passage 24. An example thereof is shown in FIG. 9. In FIG. 9, the same reference numerals are given to the same components as those in the above-described embodiment. The first internal electrode 31 is a ring-shaped electrode and is formed in the same plane in a number corresponding to the number of gas passages 24 (see FIG. 1). All the first internal electrodes 31 are electrically connected by a wiring 31b, and one of the first internal electrodes 31 is connected to the electrostatic electrode 22 via a first via 41. The second internal electrode 32 is a ring-shaped electrode and is formed in the same plane in a number corresponding to the number of gas passages 24. All the second internal electrodes 32 are electrically connected by a wiring 32b, and one of the second internal electrodes 32 is connected to the first internal electrode 31 via a second via 42. The third internal electrode 33 is a ring-shaped electrode and is formed in the same plane in a number corresponding to the number of gas passages 24. All the third internal electrodes 33 are electrically connected by a wiring 33b, and one of the third internal electrodes 33 is connected to the second internal electrode 32 via a third via 43. The fourth internal electrode 34 is a ring-shaped electrode and is formed in the same plane in a number corresponding to the number of gas passages 24. All the fourth internal electrodes 34 are electrically connected by a wiring 34b, and one of the fourth internal electrodes 34 is connected to the third internal electrode 33 via a fourth via 44. Therefore, all the first to fourth internal electrodes 31 to 34 have the same potential as the electrostatic electrode 22. Even in this case, the same effects as those in the above-described embodiment can be obtained. Note that instead of providing the first via 41 on the first internal electrode 31, it may be provided on the wiring 31b. This also applies to the second to fourth vias 42 to 44. Also, the wiring 31b may be omitted and the first via 41 may be provided on each of the first internal electrodes 31. This also applies to the second to fourth vias 42 to 44. Further, a part of the first to fourth internal electrodes 31 to 34 may be ring-shaped electrodes and the rest may be electrodes having the same shape as the electrostatic electrode 22.

[0042] In the above-described embodiment, the first to fourth internal electrodes 31 to 34 are provided inside the ceramic plate 20, but the number of internal electrodes may be at least one. For example, only the fourth internal electrode 34 may be provided inside the ceramic plate 20.

[0043] In the above-described embodiment, the electrostatic electrode 22 is incorporated in the ceramic plate 20, but it is not particularly limited thereto. For example, in addition to the electrostatic electrode 22, a heater electrode (resistance heating element) may be incorporated.

[0044] In the above-described embodiment, a porous plug (a plug that allows gas flow in the vertical direction) may be provided at a location where a potential distribution occurs in the gas passage 24. Further, instead of the porous plug, a dense plug having a zigzag or spiral passage (a passage that allows gas flow in the vertical direction) may be employed. By doing so, it becomes easier to prevent abnormal discharge from occurring at a location where a potential distribution occurs.

[0045] In the above-described embodiment, the case where three gas passages 24 are provided is exemplified, but the number of gas passages 24 is not particularly limited thereto and may be any number. Further, the gas passage 24 is a passage that penetrates the wafer mounting table 10 in the vertical direction, but it is not particularly limited thereto. For example, a gas channel structure may be employed instead of the gas passage 24. As the gas channel structure, a ring-shaped passage provided inside the base plate 50 and concentric with the base plate 50 in plan view, a gas introduction passage for introducing gas from the lower surface of the base plate 50 to the ring-shaped passage, and a plurality of gas distribution passages extending upward from the ring-shaped passage and opening to the wafer mounting surface 21 may be employed. The number of gas introduction passages is less than the number of gas distribution passages and may be, for example, one. Such a gas channel structure also corresponds to the "passage" of the present invention.

[0046] In the above-described embodiment, a lift pin hole may be provided separately from the gas passage 24. The lift pin hole penetrates the wafer stage 10 in the vertical direction and is a hole for inserting a lift pin that moves the wafer W up and down with respect to the wafer placement surface 21. When the wafer W is supported by, for example, three lift pins, the lift pin holes are provided at three locations. The configuration of the lift pin hole and its surroundings is the same as that of the gas passage 24 and its surroundings. The lift pin hole is provided so as to extend from the lower surface of the ceramic plate 20 to the wafer placement surface 21. Therefore, He gas also enters the lift pin hole, but similar to the gas passage 24, the occurrence of abnormal discharge in the lift pin hole can be prevented or reduced. Such a lift pin hole also corresponds to the "passage" of the present invention.

[0047] In the above-described embodiment, the DC power supply 70 is connected to the electrostatic electrode 22, but instead, the DC power supply 70 may be connected to any one of the first to fourth internal electrodes 31 to 34.

Industrial Applicability

[0048] The member for a semiconductor manufacturing apparatus of the present invention can be used, for example, in the field of processing wafers with plasma or the like.

Explanation of Reference Numerals

[0049] 10 Wafer stage, 20 Ceramic plate, 21 Wafer placement surface, 21a Seal band, 21b Circular protrusion, 22 Electrostatic electrode, 22a Through hole, 24 Gas passage, 26 Electrode terminal, 31 - 34 First - fourth internal electrodes, 31a - 34a Through holes, 31b - 34b Wires, 35 Bias electrode, 35a Through hole, 41 - 44 First - fourth vias, 50 Base plate, 52 Refrigerant flow path, 52in Inlet, 52out Outlet, 54 Power supply member placement hole, 56, 57 Insulating tubes, 58 Power supply member, 58a Upper metal terminal, 58b Lower metal terminal, 58c Metal wire, 60 Bonding layer, 70 DC power supply, 72 Source power supply, 74 Bias power supply, 76 He gas supply source, 134 Fourth internal electrode, 134a Through hole, 135 Bias electrode, 135a Through hole, 136 Outer bias electrode, 144 Fourth via.

Claims

1. A ceramic plate having a wafer placement surface on the upper surface and incorporating an electrostatic electrode, A base plate provided on the lower surface of the ceramic plate and incorporating a refrigerant flow path, A passage provided so as to reach the wafer placement surface of the ceramic plate from the lower surface of the base plate, A plurality of internal electrodes provided in multiple stages in the vertical direction inside the ceramic plate, located around the passage below the electrostatic electrode and not exposed on the inner wall of the passage, and electrically connected to the electrostatic electrode, A bias electrode provided at the same height as or below the lowermost internal electrode among the plurality of internal electrodes, and electrically independent of the electrostatic electrode, to which a bias voltage is applied when generating plasma above the wafer placement surface, A member for a semiconductor manufacturing apparatus comprising the above.

2. The base plate also serves as the bias electrode provided below the lowermost internal electrode, The member for a semiconductor manufacturing apparatus according to Claim 1.

3. The bias electrode is incorporated in the ceramic plate, The member for a semiconductor manufacturing apparatus according to Claim 1.

4. The bias electrode is provided below the lowermost internal electrode, The member for a semiconductor manufacturing apparatus according to Claim 3.

5. The bias electrode is provided at the same height as the lowermost internal electrode and is provided around the lowermost internal electrode, The member for a semiconductor manufacturing apparatus according to Claim 3.

6. At least one of the plurality of internal electrodes is a ring-shaped electrode surrounding the passage or an electrode having the same shape as the electrostatic electrode and having a through-hole through which the passage passes, 、 The member for a semiconductor manufacturing apparatus according to any one of Claims 1 to 3.

7. The passage is connected to a supply source of heat-conducting gas, The member for a semiconductor manufacturing apparatus according to any one of Claims 1 to 3.

8. The base plate also serves as a source electrode to which a source voltage is applied when generating plasma above the wafer placement surface, The member for a semiconductor manufacturing apparatus according to any one of Claims 1 to 3.

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