electrostatic chuck

Abstract

The present invention provides an electrostatic chuck capable of suppressing the occurrence of abnormal discharges in the gas flow path. The electrostatic chuck comprises a first ceramic plate, an electrostatic chuck electrode embedded in the first plate, and a high-frequency bias electrode provided on the first plate at a position below the electrostatic chuck electrode. The first plate is provided with a gas flow path that extends along the thickness direction of the first plate and through which gas supplied between the wafer and the first main surface passes. The first distance L1, which is the distance between the gas flow path and the electrostatic chuck electrode, and the second distance L2, which is the distance between the gas flow path and the high-frequency bias electrode, satisfy the following equation A in relation to the third distance L3, which is the distance between the electrostatic chuck electrode and the high-frequency bias electrode. Formula A: 0.4271×L3+3

Description

Technical Field

[0001] The present disclosure relates to an electrostatic chuck.

Background Art

[0002] In a semiconductor manufacturing apparatus, for example, when performing processes such as film formation and etching on a wafer, a susceptor is used to support the wafer. As the susceptor, there is known an electrostatic chuck including a ceramic first plate having an electrostatic chuck electrode for chucking the wafer by electrostatic adsorption, and a second plate, for example made of metal, for supporting the first plate (see, for example, Patent Document 1).

[0003] A high-frequency power source for a source is connected to the second plate to generate plasma between the second plate and an upper electrode installed on the ceiling in the vacuum chamber. Further, for example, a high-frequency bias electrode is incorporated in the first plate below the electrostatic chuck electrode. A high-frequency power source for bias is connected to the high-frequency bias electrode. By supplying a bias high-frequency having a lower frequency and a larger amplitude than the high-frequency for the source to the high-frequency bias electrode, ions in the plasma can be drawn into the wafer adsorbed on the first plate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a wafer is adsorbed, a DC voltage is applied to the electrostatic chuck electrode embedded in the first plate, so the electrostatic chuck electrode has a positive potential. On the other hand, a high frequency for biasing is applied to the high frequency bias electrode embedded in the first plate, so the high frequency bias electrode has a negative potential on average. Therefore, inside the first plate, an electric field with a gradient from positive to negative is generated in the thickness direction of the first plate due to the application of a DC voltage to the electrostatic chuck electrode and the application of a high frequency to the high frequency bias electrode.

[0006] Here, the first plate has through-holes that penetrate the thickness direction, serving as gas channels for supplying a thermally conductive inert gas, such as helium gas, to the space between the wafer and the first plate. The electrostatic chuck is used when the gas channel is filled with helium gas. If a corona discharge occurs in the gas channel, dielectric breakdown occurs in the gas present in the gas channel. As a result, electrons are emitted into the gas channel, and these emitted electrons are accelerated by the aforementioned electric field gradient and collide with the helium in the gas, causing helium ionization. If this helium ionization is repeated, there is a risk that it will eventually progress to abnormal discharges such as arc discharge in the gas channel. If an arc discharge occurs in the gas channel, traces of it will remain on the wafer supported by the first plate. Therefore, there is a problem that the yield of wafers processed using the electrostatic chuck decreases.

[0007] One of the objectives of this disclosure is to provide an electrostatic chuck that can suppress the occurrence of abnormal discharges such as arc discharges in a gas flow path. [Means for solving the problem]

[0008] An electrostatic chuck according to this disclosure has the function of generating a high-frequency plasma between itself and an upper electrode positioned above it. The electrostatic chuck according to this disclosure comprises a first ceramic plate including a first main surface for supporting a wafer and a second main surface positioned spaced apart from the first main surface in the thickness direction; an electrostatic chuck electrode extending planarly along a plane parallel to the first main surface and embedded in the first plate; and a high-frequency bias electrode extending planarly along a plane parallel to the first main surface and provided on the first plate at a position below the electrostatic chuck electrode. In the electrostatic chuck according to a first embodiment of this disclosure, the first plate is provided with a gas channel extending from the second main surface to the first main surface along the thickness direction of the first plate, through which a gas supplied between the wafer and the first main surface passes. Furthermore, a first distance L1, which is the distance between the gas channel and the electrostatic chuck electrode, and a second distance L2, which is the distance between the gas channel and the high-frequency bias electrode, satisfy the following equation A in relation to a third distance L3, which is the distance between the electrostatic chuck electrode and the high-frequency bias electrode.

[0009] Formula A: 0.4271×L3+3 <L1,L2 [Effects of the Invention]

[0010] According to the electrostatic chuck described herein, it is possible to suppress the occurrence of abnormal discharges such as arc discharges in the gas flow path. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a plan view of the electrostatic chuck. [Figure 2] Figure 2 is a cross-sectional view of the electrostatic chuck shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing a magnified portion of the electrostatic chuck shown in Figure 2. [Figure 4] Figure 4 is a cross-sectional view showing a magnified portion of a modified example of the electrostatic chuck shown in Figure 1. [Figure 5] Figure 5 is a cross-sectional view showing a magnified portion of a modified example of the electrostatic chuck shown in Figure 4. [Modes for carrying out the invention]

[0012] [Summary of the Embodiment] First, embodiments of electrostatic chucks according to this disclosure are listed and described.

[0013] An electrostatic chuck according to a first aspect of this disclosure has the function of generating high-frequency plasma between itself and an upper electrode positioned above it. The electrostatic chuck according to a first aspect of this disclosure includes a first ceramic plate including a first main surface for supporting a wafer and a second main surface positioned spaced apart from the first main surface in the thickness direction; an electrostatic chuck electrode extending planarly along a plane parallel to the first main surface and embedded in the first plate; and a high-frequency bias electrode extending planarly along a plane parallel to the first main surface and provided on the first plate at a position below the electrostatic chuck electrode. In the electrostatic chuck according to a first aspect of this disclosure, the first plate is provided with a gas channel extending from the second main surface to the first main surface along the thickness direction of the first plate, through which a gas supplied between the wafer and the first main surface passes. Furthermore, a first distance L1, which is the distance between the gas channel and the electrostatic chuck electrode, and a second distance L2, which is the distance between the gas channel and the high-frequency bias electrode, satisfy the following equation A in relation to a third distance L3, which is the distance between the electrostatic chuck electrode and the high-frequency bias electrode.

[0014] Formula A: 0.4271×L3+3 <L1,L2

[0015] According to the electrostatic chuck of the first embodiment, the positions of the gas channel, electrostatic chuck electrode, and high-frequency bias electrode are designed such that when the electrostatic chuck is in use, the electric field generated in the gas channel is adjusted, and even if electrons released due to dielectric breakdown of the gas in the event of corona discharge in the gas channel are accelerated by the gradient of the electric field and gain kinetic energy, this kinetic energy will be less than the ionization energy of the gas. As a result, repeated ionization of the gas in the gas channel is suppressed, and therefore abnormal discharges can be prevented.

[0016] As the electrostatic chuck according to the second aspect of the present disclosure, the electrostatic chuck according to the first aspect described above can be configured such that the first distance L1 and the second distance L2 satisfy the following formula B in relation to the third distance L3.

[0017] Formula B: L1, L2 < 0.4271 × L3 + 6

[0018] According to the electrostatic chuck according to the second aspect, by restricting the magnitudes of the first distance L1 and the second distance L2, it is possible to suppress a decrease in the area in a plan view of the electrostatic chuck electrode and the high-frequency bias electrode. As a result, after the electrostatic chuck electrode and the high-frequency bias electrode each function well, it is possible to suppress the occurrence of abnormal discharge in the gas flow path.

[0019] As the electrostatic chuck according to the third aspect of the present disclosure, the electrostatic chuck according to the first aspect or the second aspect described above can be configured such that only a part of the first plate is interposed between the gas flow path and the electrostatic chuck electrode.

[0020] As the electrostatic chuck according to the fourth aspect of the present disclosure, the electrostatic chuck according to any one of the first aspect to the third aspect described above can be configured such that the high-frequency bias electrode is built in the first plate and only a part of the first plate is interposed between the gas flow path and the high-frequency bias electrode.

[0021] As the electrostatic chuck according to the fifth aspect of the present disclosure, the electrostatic chuck according to any one of the first aspect to the third aspect described above can be configured such that the high-frequency bias electrode is built in the first plate, a through hole penetrating in the thickness direction is formed as the gas flow path in the first plate, and an insulating member having insulating properties and including an internal cavity is inserted in a part on the lower end side which is the second main surface side in the through hole, so that the internal cavity of the insulating member is used as the gas flow path.

[0022] As an electrostatic chuck according to the sixth aspect of this disclosure, the electrostatic chuck according to the fifth aspect described above can be configured such that the upper end of the insulating member is located above the high-frequency bias electrode inside the first plate, and only a portion of the first plate and a portion of the insulating member are interposed between the gas flow path and the high-frequency bias electrode.

[0023] As an electrostatic chuck according to the seventh aspect of this disclosure, the electrostatic chuck according to the fifth aspect described above can be configured such that the upper end of the insulating member is located below the high-frequency bias electrode inside the first plate, and only a portion of the first plate is interposed between the gas flow path and the high-frequency bias electrode.

[0024] As an electrostatic chuck according to the eighth aspect of this disclosure, an electrostatic chuck according to any one of the first to third aspects described above further comprises a second plate which is bonded to the second main surface of the first plate and supports the first plate from below, is conductive, and is used as a high-frequency source electrode, and the second plate can also be configured to serve as a high-frequency bias electrode.

[0025] As an electrostatic chuck according to the ninth aspect of this disclosure, an electrostatic chuck according to any one of the first to eighth aspects described above can be configured such that the third distance L3 is smaller than the first distance L1 and the second distance L2.

[0026] As an electrostatic chuck according to the tenth aspect of this disclosure, an electrostatic chuck according to any one of the first to ninth aspects described above can be configured such that the third distance L3 is 10 mm or less.

[0027] [Specific examples of embodiments] Next, a specific embodiment and a modified example of an electrostatic chuck according to this disclosure will be described with reference to the drawings. In the drawings, identical or corresponding parts are given the same reference numerals.

[0028] Figure 1 is a plan view of the electrostatic chuck 1. Figure 2 is a cross-sectional view of the electrostatic chuck 1. Figure 3 is an enlarged cross-sectional view showing a portion of the electrostatic chuck 1 shown in Figure 2.

[0029] In the following explanation, viewing an object along its thickness direction will be referred to as a "plan view." Furthermore, the shape of an object viewed along its thickness direction will be referred to as its "plan view shape."

[0030] <Overview of electrostatic chucks> Referring to Figures 1 and 2, the electrostatic chuck 1 is installed inside the vacuum chamber of the semiconductor manufacturing apparatus as a stand for supporting the wafer. The inside of the vacuum chamber is maintained in a vacuum or reduced-pressure atmosphere. For example, film deposition processes, such as forming thin films on wafers by chemical vapor deposition (CVD) or physical vapor deposition (PVD), and wafer etching processes are performed inside the vacuum chamber.

[0031] The electrostatic chuck 1 has an electrostatic adsorption function that chucking of wafers by electrostatic adsorption when various processes are performed on wafers in semiconductor manufacturing equipment. The electrostatic chuck 1 also has a plasma generation function that generates high-frequency plasma between itself and an upper electrode installed on the ceiling of a vacuum chamber. The electrostatic chuck 1 may also have a heater function that heats the wafer to a desired temperature.

[0032] The electrostatic chuck 1 comprises at least a first plate 2 that supports the wafer from below, a second plate 3 that supports the first plate 2 from below, an electrostatic chuck electrode 5 embedded in the first plate 2, and a high-frequency bias electrode 6 embedded in the first plate 2.

[0033] <Explanation of the first plate> Referring to Figures 1 and 2, the first plate 2 is a ceramic plate containing, for example, one of the following as its main component: aluminum nitride (AlN), aluminum oxide (Al2O3), silicon carbide (SiC), and silicon nitride (Si3N4). Preferably, the first plate 2 is made of aluminum nitride, which has high thermal conductivity, as its main component. The "main component" refers to the component with the highest content among the contained components, and the content of the main component is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

[0034] The first plate 2 may contain components derived from sintering aids, as long as it contains the above-mentioned materials as its main components. Examples of sintering aids include rare earth metal oxides. The first plate 2 is formed, for example, by a ceramic sintered body obtained by firing ceramic powder, but it may be formed by other methods. For example, the first plate 2 may be formed by stacking and firing multiple green sheets, which are made by kneading ceramic powder and a binder into sheets.

[0035] The first plate 2 has a pair of main surfaces, a first main surface 20 and a second main surface 21, which are spaced apart in the thickness direction. The first main surface 20 and the second main surface 21 are parallel or approximately parallel. In this disclosure, "approximately parallel" includes cases where one is slightly inclined within tolerance relative to the other, or where at least one is slightly distorted and not flat. In this disclosure, in the thickness direction of the first plate 2, the side with the first main surface 20 is defined as the upper side, and the side with the second main surface 21 is defined as the lower side. The first main surface 20 is the surface that supports the wafer, and the second main surface 21 is the surface to which the second plate 3 is joined.

[0036] The plan view shape of the first plate 2 is, for example, circular. The circle does not necessarily have to be a perfect circle; for example, it may be an incomplete circle with a portion missing, such as an orientation flat. The diameter of the first plate 2 is, for example, between 150 mm and 450 mm. The thickness of the first plate 2 is, for example, between 10 mm and 60 mm. Note that the plan view shape of the first plate 2 is not limited to a circle.

[0037] The first main surface 20 of the first plate 2 includes a wafer support region for supporting the wafer. The first main surface 20 may be formed so that its entire surface is a wafer support region. An annular support base, known as a seal band, may be provided in the wafer support region of the first main surface 20. The plan view shape of the annular support base is, for example, a ring shape, but is not limited to a ring shape. The annular support base is provided, for example, on the outer edge of the first plate 2 or inward from the outer edge, extending parallel to the outer edge of the first plate 2. The height of the annular support base, that is, the length that the annular support base protrudes from the first main surface 20, is about a few micrometers to several hundred micrometers. The width of the annular support base is about 1 mm to 50 mm. When the wafer is placed on the annular support base, a space enclosed by the annular support base is formed between the wafer and the first plate 2. By supplying a highly thermally conductive inert gas (hereinafter referred to as "heat transfer gas"), such as helium gas, into this space, heat conduction between the wafer and the first plate 2 can be efficiently performed.

[0038] The wafer support region of the first main surface 20 may be provided with multiple protrusions, for example, cylindrical or frustoconical. The multiple protrusions are provided in the wafer support region within the area enclosed by the annular support base, for example, at equal intervals from one another. The height of the multiple protrusions is the same as or approximately the same as the height of the annular support base. The wafer is placed not only on the annular support base but also on the multiple protrusions. This ensures that the entire wafer is evenly supported. The diameter of the protrusions is approximately 0.5 mm to 5 mm.

[0039] Various electrodes are incorporated into the first plate 2. For example, an electrostatic chuck electrode 5 is incorporated into the first plate 2. The electrostatic chuck electrode 5 is an electrode for chucking a wafer supported on the first main surface 20 of the first plate 2 by electrostatic adsorption. Also, for example, a high-frequency bias electrode 6 is incorporated into the first plate 2. The high-frequency bias electrode 6 is an electrode for attracting ions from a high-frequency plasma generated above the wafer to the wafer chucked to the first plate 2. Also, for example, a heater electrode may be incorporated into the first plate 2. The heater electrode is an electrode for heating the first plate 2 so that the temperature of the wafer adsorbed on the first plate 2 reaches a desired temperature.

[0040] The first plate 2 may have through holes and recesses. A through hole is a hole that penetrates the first plate 2 in the thickness direction. A recess is a depression with a bottom that is recessed from the second main surface 21 toward the first main surface 20. For example, a through hole 23 is formed in the first plate 2 for supplying heat transfer gas to the space surrounded by an annular support between the wafer and the first plate 2. Also, for example, a through hole is formed in the first plate 2 for inserting a lift pin used when lifting the wafer from the first plate 2 after a process such as film deposition on the wafer is completed. Also, for example, recesses 24 and 25 are formed in the first plate 2 into which power supply members that are electrically connected to various electrodes built into the first plate 2 are inserted.

[0041] Referring to Figures 2 and 3, the through-hole 23 extends along the thickness direction from the second main surface 21 to the first main surface 20 of the first plate 2. The cross-sectional shape of the through-hole 23 is, for example, circular. The through-hole 23 is formed in the first plate 2 to provide a gas channel 26 through which heat transfer gas supplied between the wafer and the first main surface 20 passes. The through-hole 23 includes a small-diameter portion 23A located on the first main surface 20 side of the first plate 2 and a large-diameter portion 23B located on the second main surface 21 side of the first plate 2. The through-hole 23 has a structure in which the small-diameter portion 23A and the large-diameter portion 23B are connected along the thickness direction of the first plate 2.

[0042] An insulating member 7, including an internal cavity 70, is inserted into the large-diameter portion 23B, which is a part of the lower end of the through-hole 23. Therefore, in the large-diameter portion 23B of the through-hole 23, the internal cavity 70 of the insulating member 7 becomes a gas passage 26. The internal cavity 70 of the insulating member 7 is in communication with the small-diameter portion 23A, and as a result, a gas passage 26 is provided in the first plate 2 that extends along the thickness direction from the second main surface 21 to the first main surface 20 of the first plate 2. When the insulating member 7 is inserted into the large-diameter portion 23B of the through-hole 23, the following effects are obtained with respect to the bonding layer 4 that joins the first plate 2 and the second plate 3. When the bonding layer 4 is made of resin, the insertion of the insulating member 7 into the first plate 2 prevents the bonding layer 4 from being exposed to corrosive gases, etc., thus suppressing a decrease in the bonding strength of the first plate 2 and the second plate 3. As a result, the lifespan of the electrostatic chuck 1 can be extended. When the bonding layer 4 is made of metal, inserting the insulating member 7 into the first plate 2 extends the lifespan of the electrostatic chuck 1 described above, and also insulates the bonding layer 4 from the gas flow path 26, thereby preventing discharge from occurring in the bonding layer 4.

[0043] The diameter of the through hole 23 is not particularly limited. The diameter d3 of the small diameter portion 23A is, for example, 0.2 mm or more and 1.0 mm or less. The diameter d4 of the large diameter portion 23B is, for example, 2.0 mm or more and 8.0 mm or less.

[0044] Furthermore, the through-hole 23 may be entirely a small-diameter portion 23A, that is, a hole that penetrates the first plate 2 in the thickness direction with a diameter equal to the diameter d3 of the small-diameter portion 23A. In this case, the insulating member 7 is not inserted into a portion of the lower end of the through-hole 23, and only the through-hole 23 having a uniform diameter d3 along the thickness direction of the first plate 2 becomes the gas passage 26.

[0045] The number of through-holes 23 formed as gas passages 26 in the first plate 2 is at least one. The number of through-holes 23 may be one or multiple.

[0046] Referring to Figure 2, each recess 24 and 25 is a depression having a bottom that curves inward from the second main surface 21 toward the first main surface 20 of the first plate 2. Recesses 24 and 25 have different depths. At the bottom of one recess 24, a portion of a terminal 12 embedded in the first plate 2 is exposed so as to contact, for example, the electrostatic chuck electrode 5. At the bottom of the other recess 25, a portion of a terminal 13 embedded in the first plate 2 is exposed so as to contact, for example, the high-frequency bias electrode 6. The terminals 12 and 13 are formed from metals with low coefficients of thermal expansion, such as molybdenum (Mo) and tungsten (W). A power supply member 10 for wafer adsorption is inserted into recess 24, and the upper end of the power supply member 10 is joined to the exposed portion of the terminal 12, for example, by brazing material. This electrically connects the power supply member 10 to the electrostatic chuck electrode 5 via the terminal 12. A power supply member 11 for bias is inserted into recess 25, and the upper end of the power supply member 11 is joined to the exposed portion of the terminal 13, for example, by brazing material. As a result, the power supply member 11 is electrically connected to the high-frequency bias electrode 6 via the terminal 13. Each power supply member 10, 11 may be directly connected to the corresponding electrodes 5, 6, or they may be connected to each electrode 5, 6 with a buffer member made of Kovar or the like sandwiched in between.

[0047] Each power supply member 10, 11 can be formed from a metal or alloy that has high corrosion resistance to the atmosphere during use of the electrostatic chuck 1. Examples of materials for forming each power supply member 10, 11 include nickel (Ni), gold (Au), platinum (Pt), silver (Ag), and alloys thereof. Each power supply member 10, 11 may have a rod-like shape with a circular cross-section. Each power supply member 10, 11 may also have a shape in which a columnar upper part and a columnar lower part are connected by a plurality of flexible metal wires. Each power supply member 10, 11 is electrically connected to the corresponding power supply.

[0048] <Explanation of electrostatic chuck electrodes> Referring to Figures 2 and 3, the electrostatic chuck electrode 5 extends planarly within the first plate 2 along a virtual plane parallel or approximately parallel to the first main surface 20. The electrostatic chuck electrode 5 is, for example, a unipolar type, but may also be a bipolar type. The electrostatic chuck electrode 5 can be formed from a material mainly composed of conductive materials such as high-melting-point metals, alloys of high-melting-point metals, or carbides of high-melting-point metals. Examples of high-melting-point metals include molybdenum (Mo), tungsten (W), niobium (Nb), and tantalum (Ta).

[0049] The electrostatic chuck electrode 5 is formed from, for example, a thin plate, a thin plate with numerous through-holes such as perforated metal or expanded metal, or a mesh made by intersecting multiple wires. The plan view shape of the electrostatic chuck electrode 5 is, for example, circular. In plan view, the electrostatic chuck electrode 5 is, for example, concentric with the first plate 2.

[0050] A DC voltage is applied to the electrostatic chuck electrode 5 from the power supply for wafer adsorption via the power supply member 10. This generates an electrostatic attraction force between the electrostatic chuck electrode 5 and the wafer supported by the first plate 2, and the wafer is chucking the first plate 2 by electrostatic attraction. On the other hand, when the DC voltage is no longer applied to the electrostatic chuck electrode 5, the wafer is released from being chucked by the first plate 2.

[0051] An opening 50 is formed in the electrostatic chuck electrode 5 to allow the through hole 23 formed in the first plate 2 to pass through. The plan view shape of the opening 50 is, for example, circular to match the cross-sectional shape of the through hole 23. The diameter d1 of the opening 50 is larger than the diameter d3 of the small-diameter portion 23A that passes through the opening 50 in the through hole 23, and the opening 50 encloses the small-diameter portion 23A inside in a plan view. In other words, the periphery of the opening 50 is located around the periphery of the small-diameter portion 23A in a plan view. The opening 50 is, for example, concentric with the through hole 23 in a plan view. In the first plate 2, the through hole 23 penetrates the electrostatic chuck electrode 5 as the small-diameter portion 23A passes through the opening 50 of the electrostatic chuck electrode 5.

[0052] The diameter d1 of the opening 50 is not particularly limited. For example, the diameter d1 of the opening 50 is 2.0 mm or more and 10 mm or less.

[0053] The electrostatic chuck electrode 5 surrounds the small-diameter portion 23A, which is the gas flow path 26, but only a portion of the first plate 2 is interposed between the electrostatic chuck electrode 5 and the small-diameter portion 23A. In other words, only the first plate 2 exists between the periphery of the opening 50 and the periphery of the small-diameter portion 23A, and there are no other members such as conductive materials between them.

[0054] The electrostatic chuck electrode 5 is positioned at a first distance L1 from the small-diameter portion 23A, which is the gas flow path 26. The first distance L1 is the distance between the gas flow path 26 and the electrostatic chuck electrode 5, and is a horizontal distance along a direction perpendicular to the thickness direction of the first plate 2. The first distance L1 is determined as the shortest distance between the periphery of the small-diameter portion 23A of the through hole 23 and the periphery of the opening 50. In this embodiment, the first distance L1 is half the difference between the diameter d1 of the opening 50 and the diameter d3 of the small-diameter portion 23A.

[0055] The electrostatic chuck electrode 5 may also have openings formed therein for passing power supply members and various other components.

[0056] <Explanation of high-frequency bias electrodes> Referring to Figures 2 and 3, the high-frequency bias electrode 6 extends planarly within the first plate 2 along a virtual plane parallel or approximately parallel to the first main surface 20. The high-frequency bias electrode 6 is the electrode to which the high frequency for biasing is supplied. The high-frequency bias electrode 6 is formed using conductive materials such as high-melting-point metals, alloys of high-melting-point metals, and carbides of high-melting-point metals. Examples of high-melting-point metals include molybdenum (Mo), tungsten (W), niobium (Nb), and tantalum (Ta).

[0057] The high-frequency bias electrode 6 is formed, for example, from a thin plate made of the material described above, a thin plate with many small through holes such as a punching plate, or from a mesh. The plan view shape of the high-frequency bias electrode 6 is, for example, circular. In plan view, the high-frequency bias electrode 6 is, for example, concentric with the first plate 2.

[0058] The high-frequency bias electrode 6 is supplied with bias high-frequency power from a bias high-frequency power supply via a power supply member 11. The bias high-frequency power has a lower frequency and larger amplitude than the source high-frequency power supplied from the source high-frequency power supply to the second plate 3, which functions as a high-frequency source electrode. The frequency of the source high-frequency power is, for example, several tens to several hundreds of MHz, while the frequency of the bias high-frequency power is, for example, several hundred kHz.

[0059] The high-frequency bias electrode 6 is positioned at a different height from the electrostatic chuck electrode 5 in the thickness direction of the first plate 2. Specifically, the electrostatic chuck electrode 5 is positioned near the first main surface 20, while the high-frequency bias electrode 6 is positioned further from the first main surface 20 than the electrostatic chuck electrode 5. In other words, within the first plate 2, the high-frequency bias electrode 6 is positioned below the electrostatic chuck electrode 5, with a third distance L3 between them. The third distance L3 is the distance between the electrostatic chuck electrode 5 and the high-frequency bias electrode 6, and the third distance L3 is the vertical distance along the thickness direction of the first plate 2.

[0060] The high-frequency bias electrode 6 may be positioned above the upper end of the insulating member 7, as shown in Figure 3, or below the upper end of the insulating member 7, as shown in Figure 4. As shown in Figure 3, if the high-frequency bias electrode 6 is positioned above the upper end of the insulating member 7 inside the first plate 2, corrosion of the resin liquid adhesive or adhesive sheet joining the first plate 2 and the insulating member 7 can be suppressed.

[0061] The high-frequency bias electrode 6 has an opening 60 formed therein for passing through a through hole 23 formed in the first plate 2. The plan view shape of the opening 60 is, for example, circular, to match the cross-sectional shape of the through hole 23. The diameter d2 of the opening 60 is larger than the diameter of the portion of the through hole 23 through which the opening 60 passes. As shown in Figure 3, when the high-frequency bias electrode 6 is positioned above the upper end of the insulating member 7, the diameter d2 of the opening 60 is larger than the diameter d3 of the small-diameter portion 23A that passes through the opening 60 in the through hole 23, and the opening 60 encloses the small-diameter portion 23A inside in a plan view. In other words, the periphery of the opening 60 is located around the periphery of the small-diameter portion 23A in a plan view. On the other hand, as shown in Figure 4, when the high-frequency bias electrode 6 is positioned below the upper end of the insulating member 7, the diameter d2 of the opening 60 is larger than the diameter d4 of the large-diameter portion 23B that passes through the opening 60 in the through hole 23, and the opening 60 encloses the large-diameter portion 23B inside in a plan view. In other words, in a plan view, the periphery of the opening 60 is located around the periphery of the large-diameter portion 23B. In a plan view, the opening 60 is concentric with, for example, the through-hole 23. In the first plate 2, the through-hole 23 penetrates the high-frequency bias electrode 6 by passing through the opening 60 of the high-frequency bias electrode 6 with either the small-diameter portion 23A or the large-diameter portion 23B.

[0062] The diameter d2 of the opening 60 is not particularly limited. For example, the diameter d2 of the opening 60 is 2.0 mm or more and 10 mm or less.

[0063] As shown in Figure 3, when the high-frequency bias electrode 6 is positioned above the upper end of the insulating member 7, it surrounds the small-diameter portion 23A, which is the gas flow path 26. However, only a portion of the first plate 2 is interposed between the high-frequency bias electrode 6 and the small-diameter portion 23A. In other words, only the first plate 2 exists between the periphery of the opening 60 and the periphery of the small-diameter portion 23A, and there are no other members, such as conductive members, between them.

[0064] The high-frequency bias electrode 6 is positioned at a second distance L2 from the small-diameter portion 23A, which is the gas flow path 26. The second distance L2 is the distance between the gas flow path 26 and the high-frequency bias electrode 6, and is a horizontal distance along a direction perpendicular to the thickness direction of the first plate 2. The second distance L2 is determined as the shortest distance between the periphery of the small-diameter portion 23A of the through hole 23 and the periphery of the opening 60. In this embodiment, the second distance L2 is half the difference between the diameter d2 of the opening 60 and the diameter d3 of the small-diameter portion 23A.

[0065] On the other hand, when the high-frequency bias electrode 6 is positioned below the upper end of the insulating member 7, as shown in Figure 4, the high-frequency bias electrode 6 surrounds the internal cavity 70 of the insulating member 7, which is the gas flow path 26. Only a portion of the insulating member 7 and a portion of the first plate 2 are interposed between the high-frequency bias electrode 6 and the internal cavity 70. In other words, only the insulating member 7 and the first plate 2 exist between the periphery of the opening 60 and the periphery of the internal cavity 70, and no other members such as conductive members exist between them.

[0066] In this case, the second distance L2, which is the distance between the gas flow path 26 and the high-frequency bias electrode 6, is the shortest distance between the periphery of the internal cavity 70 of the insulating member 7 and the periphery of the opening 60. In the example in Figure 4, the second distance L2 is half the difference between the diameter d2 of the opening 60 and the diameter d5 of the internal cavity 70 of the insulating member 7.

[0067] The high-frequency bias electrode 6 may also have openings formed therein for passing power supply members and various other components.

[0068] <Explanation of the second plate> Referring to Figures 2 and 3, the second plate 3 is a plate with good thermal conductivity. The second plate 3 is formed from, for example, a metallic material or a composite material of metal and ceramic. Examples of metallic materials include aluminum (Al), titanium (Ti), molybdenum (Mo), or alloys thereof. Examples of metal-ceramic composite materials include metal matrix composites (MMC) and ceramic matrix composites (CMC). Examples of such composite materials include materials containing silicon (Si), silicon carbide (SiC), and titanium (Ti) (SiSiCTi), materials in which at least one of aluminum (Al) and silicon (Si) is impregnated into a porous body of silicon carbide (SiC), and composite materials of aluminum oxide (Al2O3) and titanium carbide (TiC). Preferably, the second plate 3 is formed using a material with a coefficient of thermal expansion similar to the material contained as the main component in the first plate 2.

[0069] The second plate 3 is conductive. The conductive second plate 3 is connected to a high-frequency power supply for the source and functions as an RF electrode for generating plasma between itself and the upper electrode installed on the ceiling of the vacuum chamber.

[0070] The second plate 3 has a pair of main surfaces, a first main surface 30 and a second main surface 31, which are spaced apart in the thickness direction. The first main surface 30 and the second main surface 31 are parallel or approximately parallel. In this disclosure, in the thickness direction of the second plate 3, the side with the first main surface 30 is defined as the upper side, and the side with the second main surface 31 is defined as the lower side.

[0071] The plan view shape of the second plate 3 is, for example, circular. The circle does not necessarily have to be a perfect circle; for example, it may be an incomplete circle with a portion missing, such as an orientation flat. The diameter of the second plate 3 is larger than the diameter of the first plate 2, but may be the same as the diameter of the first plate 2. The thickness of the second plate 3 is, for example, 10 mm or more and 60 mm or less. Note that the plan view shape of the second plate 3 is not limited to a circle.

[0072] A refrigerant flow path 32 may be provided inside the second plate 3 through which the refrigerant circulates. The refrigerant flowing through the refrigerant flow path 32 is, for example, a liquid, and preferably an insulating liquid. An example of an insulating liquid is a fluorine-based inert liquid. The refrigerant flow path 32 is formed in a spiral shape, for example, in a plan view, extending across the entire second plate 3 from an inlet 33 at one end to an outlet 34 at the other end in a single continuous line. The inlet 33 and outlet 34 of the refrigerant flow path 32 are connected to the supply port and recovery port of an external refrigerant device, respectively. The refrigerant supplied from the external refrigerant device to the inlet 33 of the refrigerant flow path 32 passes through the refrigerant flow path 32, is discharged from the outlet 34 of the refrigerant flow path 32, returns to the external refrigerant device to be temperature-adjusted, and is then supplied again to the inlet 33 of the refrigerant flow path 32.

[0073] The second plate 3 may have through holes that penetrate through the thickness direction. For example, a through hole 35 is formed in the second plate 3 for supplying heat transfer gas to the space surrounded by an annular support between the wafer and the first plate 2. Also, for example, a plurality of through holes 36, 37 are formed in the second plate 3 into which power supply members 10, 11 that are electrically connected to electrodes such as an electrostatic chuck electrode 5 and a high-frequency bias electrode 6 built into the first plate 2 are inserted. Furthermore, for example, a through hole is formed in the second plate 3 into which a lift pin for lifting the wafer from the first plate 2 is inserted.

[0074] Each through-hole 35-37 extends along the thickness direction from the second main surface 31 to the first main surface 30 of the second plate 3. The cross-sectional shape of each through-hole 35-37 is, for example, circular. Each through-hole 35-37 is formed in the second plate 3 at a position that avoids the refrigerant flow path 32. Through-hole 35 is formed in the second plate 3 at a position that connects to the through-hole 23 of the first plate 2. Through-holes 36 and 37 are formed in the second plate 3 at positions that connect to the recesses 24 and 25 of the first plate 2, respectively.

[0075] The diameter of the through-hole 35 in the second plate 3 is equal to the diameter d4 of the large-diameter portion 23B of the through-hole 23 in the first plate 2. The through-hole 35 in the second plate 3 communicates with the through-hole 23 in the first plate 2. In the second plate 3, an insulating member 7 is provided in the through-hole 35. The insulating member 7 has, for example, a cylindrical shape. The insulating member 7 has insulating properties. The insulating member 7 is formed using, for example, the same material as the material forming the first plate 2.

[0076] The internal cavity 70 of the insulating member 7 extends from the upper end of the insulating member 7 along the axial direction of the insulating member 7. The cross-sectional shape of the internal cavity 70 is, for example, circular. In a plan view, the internal cavity 70 is located, for example, in the center of the insulating member 7. The internal cavity 70 of the insulating member 7 is a passage through which the heat transfer gas passes and communicates with the small diameter portion 23A of the through hole 23 of the first plate 2. Heat transfer gas is supplied to the internal cavity 70 of the insulating member 7 from a heat transfer gas supply source through a gas supply path. The heat transfer gas is supplied from the internal cavity 70 of the insulating member 7 through the small diameter portion 23A of the through hole 23 of the first plate 2 into the space between the wafer and the first plate 2.

[0077] The outer diameter of the insulating member 7 is equal to or smaller than the diameter of the through hole 35 in the second plate 3. The inner diameter of the insulating member 7 is equal to or larger than the diameter of the large-diameter portion 23B of the through hole 23 in the first plate 2. The upper end of the insulating member 7 is fitted into the large-diameter portion 23B, which is part of the through hole 23 in the first plate 2, and is joined to the first plate 2 inside the large-diameter portion 23B using, for example, a liquid adhesive or adhesive sheet made of resin. This fixes the insulating member 7 to the first plate 2. The insulating member 7 may be further fixed to the second plate 3 by interposing, for example, a liquid adhesive made of resin, between the outer circumferential surface of the insulating member 7 and the inner circumferential surface of the through hole 35 in the second plate 3.

[0078] The diameters of the through-holes 36 and 37 in the second plate 3 are larger than the diameters of the corresponding recesses 24 and 25 in the first plate 2. The corresponding power supply members 10 and 11 are inserted into the through-holes 36 and 37 in the second plate 3. The power supply member 10 is electrically connected to the electrostatic chuck electrode 5 by inserting the upper end of the power supply member 10 into the recess 24 of the first plate through the through-hole 36 of the second plate 3. Also, the power supply member 11 is electrically connected to the high-frequency bias electrode 6 by inserting the upper end of the power supply member 11 into the recess 25 of the first plate through the through-hole 37 of the second plate 3.

[0079] Insulating members 8 and 9 are placed inside each of the through holes 36 and 37 of the second plate 3. Each insulating member 8 and 9 has, for example, a cylindrical shape. Each insulating member 8 and 9 has insulating properties. Each insulating member 8 and 9 is formed using, for example, the same material as the material forming the first plate 2.

[0080] The internal spaces 80 and 90 of each insulating member 8 and 9 extend along the axial direction from one end, the upper end, to the other end, the lower end. The internal spaces 80 and 90 of each insulating member 8 and 9 serve as the housing spaces for the power supply members 10 and 11. By surrounding the power supply members 10 and 11 with each insulating member 8 and 9, the power supply members 10 and 11 are electrically insulated from the second plate 3.

[0081] The outer diameter of each insulating member 8, 9 is equal to or smaller than the diameter of the through holes 36, 37 in the second plate 3. The inner diameter of each insulating member 8, 9 is larger than the diameters of the recesses 24, 25 in the first plate 2 and the diameters of the power supply members 10, 11. The upper ends of each insulating member 8, 9 are joined to the first plate 2 using, for example, a liquid adhesive or adhesive sheet made of resin. This fixes each insulating member 8, 9 to the first plate 2. Each insulating member 8, 9 may be further fixed to the second plate 3 by interposing, for example, a liquid adhesive made of resin, between the outer circumferential surface of each insulating member 8, 9 and the inner circumferential surface of the through holes 36, 37 in the second plate 3.

[0082] Referring to Figures 2 and 3, the second plate 3 is joined to the first plate 2 by a bonding layer 4. The bonding layer 4 is interposed between the second main surface 21 of the first plate 2 and the first main surface 30 of the second plate 3, connecting them together. This fixes the first plate 2 on the second plate 3.

[0083] The bonding layer 4 can be formed using, for example, a liquid adhesive made of resin or an adhesive sheet made of resin. The adhesive sheet is a sheet-like or film-like adhesive that has adhesive properties on either of the pair of main surfaces that are spaced apart in the thickness direction. The resin may be thermoplastic or thermosetting. Examples of resins include silicone resin, acrylic resin, polyimide resin, and epoxy resin. The bonding layer 4 may also be a metal bonding layer formed by, for example, solder, Al-Mg-based bonding material, or Al-Si-Mg-based bonding material. The metal bonding layer can be formed by TCB (Thermal Compression Bonding).

[0084] <Regarding the relationship between distances L1, L2, and L3> In the electrostatic chuck 1 of this disclosure, the positions of the gas channel 26, the electrostatic chuck electrode 5, and the high-frequency bias electrode 6 are suitably designed to suppress the occurrence of abnormal discharges such as arc discharge in the gas channel 26. Specifically, when a wafer is chucking the first plate 2 by electrostatic adsorption, a DC voltage is applied to the electrostatic chuck electrode 5 embedded in the first plate 2, so the electrostatic chuck electrode 5 has a positive potential. On the other hand, a high frequency for biasing is applied to the high-frequency bias electrode 6 embedded in the first plate 2, so the high-frequency bias electrode 6 has an average negative potential. Therefore, inside the first plate 2, an electric field with a gradient from positive to negative is generated in the thickness direction of the first plate 2 when a DC voltage is applied to the electrostatic chuck electrode 5 and a high frequency is applied to the high-frequency bias electrode 6. Here, the gas channel 26 of the first plate 2 is filled with helium gas supplied as a heat transfer gas to the space between the wafer and the first plate 2. If a corona discharge occurs in the gas channel 26, dielectric breakdown occurs in the helium gas present in the gas channel 26. As a result, electrons are emitted into the gas channel 26, and these emitted electrons are accelerated by the electric field gradient described above as they move through the gas channel 26. When they collide with helium in the helium gas, helium ionization occurs. If this helium ionization is repeated, there is a risk that the gas channel 26 will eventually transition to abnormal discharges such as arc discharges.

[0085] For accelerated electrons to collide with helium and cause helium ionization, the electrons must possess sufficient kinetic energy to cause helium ionization immediately before colliding with helium. Therefore, in the electrostatic chuck 1 of this disclosure, the positions of the gas channel 26, electrostatic chuck electrode 5, and high-frequency bias electrode 6 are designed so that even if electrons gain kinetic energy through acceleration, the kinetic energy will be less than the ionization energy of helium, thereby adjusting the electric field generated in the gas channel 26. This suppresses the occurrence of abnormal discharges such as arc discharges in the gas channel 26.

[0086] Specifically, the kinetic energy U [eV] of an electron just before it collides with helium is given by U = m × v 2 It is expressed as / 2, and from this equation, the velocity v [m / s] of the electron just before collision with helium is expressed by the following equation 1.

[0087] Equation 1:v=(2U / m) 1 / 2

[0088] Furthermore, assuming that the electron moves through the gas channel 26 in uniformly accelerated linear motion due to the electric field gradient described above, the velocity v of the electron just before collision with helium is, since the initial velocity is 0, v 2 It is expressed as = 2 × a × L, and from this equation, the acceleration a is expressed by the following equation 2.

[0089] Formula 2: a=v 2 / 2L

[0090] Furthermore, the force F exerted by an electron in an electric field is given by F = q × E, where q is the charge and E is the electric field strength [V / mm]. This is in equilibrium with m × a according to the equation of motion. That is, F = q × E = m × a, and from this equation, the electric field strength E can be expressed by the following equation 3.

[0091] Equation 3: E=m×v 2 / (2q × L)

[0092] Here, assuming that the ionization energy of helium at the temperature (-48°C ± 2°C) is 25 [eV], the velocity v of an electron when it has this energy is 2.94E+6 [m / s], and that the distance L [mm] the electron travels through the gas channel 26 before collision is equal to the mean free path λ of the electron, then using equations 1 to 3, the electric field strength E can be expressed by the following equation 4.

[0093] Equation 4: E=24.6 / λ

[0094] The mean free path λ of electrons changes with the pressure of the helium gas. According to the inventors, the relationship between the electric field strength that ionizes helium as electrons are accelerated and the helium gas pressure P[Torr] is expressed by the following equation 5.

[0095] Equation 5: E=39.367×P

[0096] Here, increasing the helium gas pressure P reduces the mean free path λ of the electrons, so that the kinetic energy of the electrons before collision with helium in the gas channel 26 does not reach the ionization energy of helium. Therefore, ionization of helium occurs due to collisions with electrons, and the risk of abnormal discharge occurring in the gas channel 26 is eliminated. For this reason, when the helium gas pressure is 15 [Torr] or less, the electric field generated in the gas channel 26 is adjusted, and the positions of the gas channel 26, electrostatic chuck electrode 5, and high-frequency bias electrode 6 are designed so that even if electrons are accelerated and gain kinetic energy, that kinetic energy will be less than the ionization energy of helium. This suppresses the occurrence of abnormal discharge in the gas channel 26.

[0097] Specifically, the positions of the gas flow path 26, the electrostatic chuck electrode 5, and the high-frequency bias electrode 6, that is, the first distance L1, the second distance L2, and the third distance L3, are adjusted so that the electric field strength E is 590 [V / mm] or less. As a result of diligent research by the inventors, the relationship between the first distance L1, the second distance L2, and the third distance L3 at which the electric field strength E is 590 [V / mm] or less is expressed by the following equation 6.

[0098] Formula 6: 0.4271×L3+3 <L1,L2

[0099] Thus, by satisfying Equation 6 in relation to the first distance L1 and the second distance L2 and the third distance L3, it is possible to suppress the occurrence of abnormal discharges such as arc discharges in the gas flow path 26. Therefore, since it is suppressed that traces of abnormal discharges remain on the wafer supported by the first plate 2, it is possible to suppress a decrease in the yield of wafers that have undergone various processing using the electrostatic chuck 1.

[0100] It is preferable that the first distance L1 and the second distance L2 satisfy the following equation 7 in relation to the third distance L3. As the values ​​of the first distance L1 and the second distance L2 increase, the electric field strength E decreases, but as the values ​​increase, the area of ​​the electrostatic chuck electrode 5 and the high-frequency bias electrode 6 in a plan view decreases. By satisfying the relationship in equation 7 for the first distance L1, the second distance L2, and the third distance L3, it is possible to suppress the decrease of the electrostatic chuck electrode 5 and the high-frequency bias electrode 6 while suppressing the occurrence of abnormal discharge in the gas flow path 26.

[0101] Formula 7: L1,L2<0.4271×L3+6

[0102] The electric field strength E decreases as the value of the third distance L3 increases. Therefore, it is preferable that the third distance L3 is smaller than the first distance L1 and the second distance L2. However, the third distance L3 does not necessarily have to be smaller than the first distance L1 and the second distance L2.

[0103] The first distance L1 may be greater than the second distance L2, equal to the second distance L2, or less than the second distance L2.

[0104] The first distance L1 and the second distance L2 are not particularly limited, but from the viewpoint of reducing the electric field strength E and effectively suppressing the occurrence of abnormal discharge in the gas flow path 26, they are preferably 2.0 mm or more, and more preferably 3.0 mm or more. The first distance L1 and the second distance L2 are not particularly limited, but from the viewpoint of suppressing the reduction in the area of ​​the electrostatic chuck electrode 5 and the high-frequency bias electrode 6 in a plan view, they are preferably 7.0 mm or less, and more preferably 5.0 mm or less. In other words, the first distance L1 and the second distance L2 are preferably 2.0 mm or more and 7.0 mm or less, and more preferably 3.0 mm or more and 5.0 mm or less.

[0105] The third distance L3 is not particularly limited, but from the viewpoint of ensuring sufficient insulation between the electrostatic chuck electrode 5 and the high-frequency bias electrode 6, it is preferably 1.0 mm or more, and more preferably 2.0 mm or more. The third distance L3 is not particularly limited, but from the viewpoint of reducing the electric field strength E and effectively suppressing the occurrence of abnormal discharge in the gas flow path 26, it is preferably 10.0 mm or less, more preferably 5.0 mm or less, and more preferably 3.0 mm or less. In other words, the third distance L3 is preferably 1.0 mm or more and 10.0 mm or less, more preferably 2.0 mm or more and 5.0 mm or less, and more preferably 2.0 mm or more and 3.0 mm or less.

[0106] <Explanation of variations> The electrostatic chuck 1 according to one embodiment of the present disclosure has been described above. However, various modifications are possible for the implementation of the electrostatic chuck in accordance with the present disclosure, as long as they do not depart from the spirit of the present disclosure. For example, the modifications described below are possible. The modifications described below can be combined as appropriate.

[0107] In the electrostatic chuck 1 according to the embodiment described above, the first plate 2 has a built-in high-frequency bias electrode 6. However, as shown in the modified example in Figure 5, the first plate 2 does not have a built-in high-frequency bias electrode 6, and the second plate 3, which is used as a high-frequency source electrode, may also serve as the high-frequency bias electrode 6. In this modified example, the second plate 3 is supplied with source high-frequency from a source high-frequency power supply and bias high-frequency from a bias high-frequency power supply. In this modified example, ions in the plasma can be efficiently drawn into the wafer using the bias high-frequency.

[0108] In this modified example, as shown in Figure 5, the second distance L2, which is the distance between the gas flow path 26 and the high-frequency bias electrode 6, is the shortest distance between the periphery of the internal cavity 70 of the insulating member 7 and the periphery of the through hole 35 in the second plate 3 into which the insulating member 7 is inserted. In Figure 5, the second distance L2 is half the difference between the diameter d2 of the opening 60 and the diameter d5 of the internal cavity 70 of the insulating member 7.

[0109] Furthermore, in this modified example, as shown in Figure 5, the third distance L3, which is the distance between the electrostatic chuck electrode 5 and the high-frequency bias electrode, is the vertical distance between the electrostatic chuck electrode 5 and the first main surface 30 of the second plate 3 (the height from the first main surface 30 of the second plate 3 to the electrostatic chuck electrode 5).

[0110] In this modified example, the first distance L1 and the second distance L2 satisfy Equation 6 in relation to the third distance L3, thereby suppressing the occurrence of abnormal discharges such as arc discharges in the gas flow path 26. Therefore, since traces of abnormal discharges are suppressed on the wafer supported by the first plate 2, a decrease in the yield of wafers that have undergone various processing using the electrostatic chuck 1 can be suppressed.

[0111] The embodiments and modifications disclosed herein are illustrative in all respects and should be understood not to be restrictive in any way. The scope of the invention is defined by the claims and not by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of Symbols]

[0112] 1: Electrostatic chuck, 2: First plate, 3: Second plate, 4: Bonding layer, 5: Electrostatic chuck electrode, 6: High-frequency bias electrode, 7: Insulating member, 8: Insulating member, 9: Insulating member, 10: Power supply member, 11: Power supply member, 20: First main surface of the first plate, 21: Second main surface of the first plate, 23: Through hole, 23A: Small diameter section, 23B: Large diameter section, 24: Recess, 25: Recess, 26: Gas flow path, 30: First main surface of the second plate, 31: Second main surface of the second plate, 32: Refrigerant flow path, 33: Inlet of refrigerant flow path, 34: Outlet of refrigerant flow path, 35: Through hole, 36: Through hole, 37: Through hole, 50: Opening of electrostatic chuck electrode, 60: Opening of high-frequency bias electrode, 70: Internal cavity of insulating member, 80: Internal space of insulating member, 90: Internal space of insulating member

Claims

1. An electrostatic chuck having the function of generating high-frequency plasma between itself and an upper electrode positioned above it, A ceramic first plate including a first main surface for supporting a wafer and a second main surface positioned at a distance from the first main surface in the thickness direction, It extends in a planar manner along a plane parallel to the first main surface, and the electrostatic chuck electrode embedded in the first plate, A high-frequency bias electrode embedded in the first plate extends in a planar manner along a plane parallel to the first main surface and is positioned below the electrostatic chuck electrode at a distance from it. Equipped with, The first plate is provided with a gas channel that extends from the second main surface to the first main surface along the thickness direction, and through which the gas supplied between the wafer and the first main surface passes. An electrostatic chuck such that the first distance L1, which is the distance between the gas flow path and the electrostatic chuck electrode, and the second distance L2, which is the distance between the gas flow path and the high-frequency bias electrode, satisfy the following equation 1 in relation to the third distance L3, which is the distance between the electrostatic chuck electrode and the high-frequency bias electrode; 0.4271×L3+3<L1, L2≦7.0mm...Formula 1.

2. An electrostatic chuck having the function of generating high-frequency plasma between itself and an upper electrode positioned above it, A ceramic first plate including a first main surface for supporting a wafer and a second main surface positioned at a distance from the first main surface in the thickness direction, It extends in a planar manner along a plane parallel to the first main surface, and the electrostatic chuck electrode embedded in the first plate, A high-frequency bias electrode embedded in the first plate extends in a planar manner along a plane parallel to the first main surface and is positioned below the electrostatic chuck electrode at a distance from it. Equipped with, The first plate is provided with a gas channel that extends from the second main surface to the first main surface along the thickness direction, and through which the gas supplied between the wafer and the first main surface passes. An electrostatic chuck such that the first distance L1, which is the distance between the gas flow path and the electrostatic chuck electrode, and the second distance L2, which is the distance between the gas flow path and the high-frequency bias electrode, satisfy the following equations 1 and 2 in relation to the third distance L3, which is the distance between the electrostatic chuck electrode and the high-frequency bias electrode; 0.4271×L3+3<L1,L2...Formula 1 L1, L2<0.4271×L3+6...Formula 2.

3. The electrostatic chuck according to claim 1 or claim 2, wherein only a portion of the first plate is interposed between the gas flow path and the electrostatic chuck electrode.

4. The high-frequency bias electrode is built into the first plate, The electrostatic chuck according to claim 1 or claim 2, wherein only a portion of the first plate is interposed between the gas flow path and the high-frequency bias electrode.

5. The high-frequency bias electrode is built into the first plate, The first plate has through holes formed therein that penetrate in the thickness direction to serve as gas passages. The electrostatic chuck according to claim 1 or claim 2, wherein in the through hole, an insulating member having insulating properties and including an internal cavity is inserted into a portion of the lower end side which is the second main surface side, so that the internal cavity of the insulating member serves as the gas passage.

6. The upper end of the insulating member is located above the high-frequency bias electrode within the first plate. The electrostatic chuck according to claim 5, wherein only a portion of the first plate and a portion of the insulating member are interposed between the gas flow path and the high-frequency bias electrode.

7. The upper end of the insulating member is located below the high-frequency bias electrode within the first plate. The electrostatic chuck according to claim 5, wherein only a portion of the first plate is interposed between the gas flow path and the high-frequency bias electrode.

8. The device further comprises a second plate which is bonded to the second main surface of the first plate and supports the first plate from below, is conductive, and is used as a high-frequency source electrode. The electrostatic chuck according to claim 1 or claim 2, wherein the second plate also serves as the high-frequency bias electrode.

9. The electrostatic chuck according to claim 1 or claim 2, wherein the third distance L3 is smaller than the first distance L1 and the second distance L2.

10. The electrostatic chuck according to claim 1 or claim 2, wherein the third distance L3 is 10 mm or less.

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