Wafer mounting stage

Abstract

A wafer mounting stand 10 comprises: a ceramic plate 20 which includes a wafer mounting surface 21 on the upper surface thereof; a gas passage 52 through which gas can pass in the vertical direction of the ceramic plate 20; a conductive base plate 30 which is joined to the lower surface of the ceramic plate 20 and is utilized as a plasma generation electrode; and a gas supply path 34 which is provided inside of the base plate 30 and communicates with the gas passage 52. The wafer mounting stand 10 also comprises an electric field adjusting conductor 60. The electric field adjusting conductor 60 is provided so as to extend, from the lower surface of the ceramic plate 20 or a position below the lower surface to an area in front of the wafer mounting surface 21 in the vertical direction in the vicinity of the gas passage 52, and is electrically connected to the base plate 30.

Description

[Technical Field]

[0001] The present invention relates to a wafer mounting table. [Background Art]

[0002] Conventionally, a wafer mounting table is used in semiconductor manufacturing equipment. For example, the wafer mounting table in Patent Document 1 includes a ceramic plate having a wafer mounting surface on an upper surface thereof, a gas passage allowing gas to pass through the ceramic plate in a vertical direction, a conductive base plate joined to a lower surface of the ceramic plate, and a gas supply path provided inside the base plate. The gas passage is formed of a porous plug arranged in a through hole formed in the ceramic plate. In such a wafer mounting table, a high-frequency voltage is applied between the base plate and an upper electrode provided above a wafer to generate plasma above the wafer, and the plasma processes the wafer. At this time, helium gas is introduced into the gas supply path from outside. Then, the helium gas is supplied from the gas supply path through the gas passage to the lower surface side of the wafer, improving the thermal conductivity between the wafer and the ceramic plate. Since the helium gas passes through the pores of the porous plug, arc discharge on the lower surface side of the wafer can be suppressed compared to a case where no porous plug is provided. If there is no porous plug, electrons generated along with ionization of helium will accelerate and collide with other helium atoms, resulting in arc discharge; however, when a porous plug is provided, electrons strike the porous plug before colliding with other helium atoms, thus arc discharge is suppressed. Arc discharge occurring on the lower surface side of the wafer is undesirable because it deteriorates the wafer and renders it unusable as a device. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Laid-Open Publication No. 2019-29384 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] However, there was a need to develop a new structure for these wafer mounting platforms that could suppress discharge within the gas passage.

[0005] This invention was made to solve the above-mentioned problems, and its main objective is to provide a new structure that suppresses discharge within the gas passage. [Means for solving the problem]

[0006] [1] The wafer mounting stage of the present invention is A ceramic plate having a wafer mounting surface on its upper surface, A gas passage through which gas can pass in the vertical direction of the ceramic plate, A conductive base plate is bonded to the lower surface of the ceramic plate and used as a plasma generating electrode, A gas supply passage is provided inside the base plate and communicates with the gas passage, An electric field adjusting conductor is provided, extending vertically in the vicinity of the gas passage from the lower surface of the ceramic plate or a position below it to the front of the wafer mounting surface, and electrically connected to the base plate, It is something that is provided.

[0007] This wafer mounting platform, equipped with an electric field adjustment conductor, allows the direction of the electric field during plasma generation (the direction perpendicular to the equipotential lines) to be adjusted to the horizontal or a direction close to it. As a result, the direction in which electrons generated by the ionization of gas molecules are accelerated becomes horizontal or a direction close to it. Therefore, if the length of the gas passage in the horizontal or near-horizontal direction is short, even if the vertical length inside the gas passage is increased, the distance over which electrons are accelerated will not increase, and discharge is less likely to occur even if the accelerated electrons collide with other gas molecules. Consequently, compared to the case without an electric field adjustment conductor, discharge within the gas passage can be suppressed even if the vertical length inside the gas passage is increased.

[0008] In this specification, the present invention may be described using terms such as up and down, left and right, front and back, but up and down, left and right, and front and back are merely relative positional relationships. Therefore, if the orientation of the wafer mounting stage is changed, up and down may become left and right, or left and right may become up and down, but such cases are also included within the technical scope of the present invention.

[0009] [2] In the wafer mounting stage described above (the wafer mounting stage described in [1] above), the ceramic plate may have at least one electrode, the gas passage may be provided so as to pass through electrode through holes provided in each of the at least one electrode so that each of the at least one electrode is not exposed to the inner surface of the gas passage, and the electric field adjusting conductor may be provided in a state that is electrically insulated from each of the at least one electrode. In this way, the direction of the electric field generated by the electrodes in the ceramic plate can be made to be horizontal or close to horizontal.

[0010] [3] In the wafer mounting stand described above (the wafer mounting stand described in [1] or [2] above), the ceramic plate may have a ceramic plate through-hole that penetrates the ceramic plate in the vertical direction, the gas passage may be provided inside or around the plug placed in the ceramic plate through-hole, and the electric field adjusting conductor may be provided inside the plug. This makes it easier to form the gas passage and electric field adjusting conductor compared to providing the gas passage and electric field adjusting conductor directly in the ceramic plate itself.

[0011] [4] In the wafer mounting stage described above (the wafer mounting stage described in [1] or [2] above), the gas passage and the electric field adjusting conductor may be provided in the ceramic plate. This allows the gas passage and electric field adjusting conductor to be incorporated into the manufacturing of the ceramic plate.

[0012] [5] In the wafer mounting stage described above (the wafer mounting stage described in any of [1] to [4] above), the gas passage may be provided linearly in the vertical or diagonal direction. This allows the gas to flow more easily than when a spiral passage is used as the gas passage or when micropores inside a porous material are utilized, thereby increasing the gas flow rate.

[0013] [6] In the wafer mounting stage described above (the wafer mounting stage described in any of [1] to [5] above), the electric field adjusting conductor may be a flexible conductive wire. The electric field adjusting conductor may be a highly rigid needle-shaped member, but a flexible conductive wire is preferable considering misalignment during manufacturing and deformation during use.

[0014] [7] In the wafer mounting stage described above (the wafer mounting stage described in any of [1] to [6] above), the lower part of the electric field adjusting conductor may be provided in direct contact with the base plate, or it may be electrically connected to the base plate by a conductive elastic body disposed between the base plate and the lower end of the electric field adjusting conductor, which maintains communication between the gas supply path and the gas passage, or it may be electrically connected to the base plate via a conductive film provided on the lower surface of the ceramic plate, which maintains communication between the gas supply path and the gas passage. [Brief explanation of the drawing]

[0015] [Figure 1] Plan view of wafer mounting platform 10. [Figure 2] Cross-sectional view AA in Figure 1. [Figure 3] A magnified view of a portion of Figure 2. [Figure 4] A magnified cross-sectional view of a comparative form. [Figure 5] Manufacturing process diagram for wafer mounting platform 10. [Figure 6] Partially enlarged cross-sectional view of another embodiment. [Figure 7] Partially enlarged cross-sectional view of another embodiment. [Figure 8]Partial enlarged cross-sectional view of another embodiment. [Figure 9] Partial enlarged cross-sectional view of another embodiment. [Figure 10] Partial enlarged cross-sectional view of another embodiment. [Figure 11] Partial enlarged cross-sectional view of another embodiment. [Figure 12] Partial enlarged cross-sectional view of another embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0016] Preferred embodiments of the present invention will be described with reference to the drawings. Figure 1 is a plan view of a wafer mounting table 10, Figure 2 is a cross-sectional view taken along line A-A of Figure 1, and Figure 3 is a partial enlarged view of Figure 2. In Figures 2 and 3, the seal band 21a, the circular small protrusions 21b and the reference surface 21c on the wafer mounting surface 21 are omitted for convenience.

[0017] The wafer mounting table 10 includes a ceramic plate 20, a gas passage 52, a base plate 30, a metal bonding layer 40, and an electric field adjusting conductor 60.

[0018] The ceramic plate 20 is a ceramic disc (for example, 300 mm in diameter and 5 mm thick) made of an alumina sintered body or an aluminum nitride sintered body. The upper surface of the ceramic plate 20 is the wafer mounting surface 21. The ceramic plate 20 has an electrostatic electrode 22 and a bias electrode 23 built into it. The electrostatic electrode 22 is located close to the wafer mounting surface 21 (for example, 0.05 to 0.2 mm from the wafer mounting surface 21), and the bias electrode 23 is located far from the wafer mounting surface 21. As shown in Figure 1, a seal band 21a is formed along the outer edge of the wafer mounting surface 21 of the ceramic plate 20, and a plurality of small circular protrusions 21b are formed on the entire surface. The seal band 21a and the small circular protrusions 21b are of the same height, for example, several μm to several tens of μm. The electrostatic electrode 22 is, for example, a planar mesh electrode, to which a DC voltage can be applied. When a DC voltage is applied to the electrostatic electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a and the upper surface of the circular protrusion 21b) by electrostatic attraction force, and when the application of the DC voltage is removed, the attraction and fixation of the wafer W to the wafer mounting surface 21 is released. The part of the wafer mounting surface 21 that does not have the seal band 21a or the circular protrusion 21b is called the reference surface 21c. The bias electrode 23 is, for example, a planar mesh electrode, to which a high frequency bias is applied to attract ions to the wafer W. The bias electrode 23 is a type of plasma generating electrode (RF electrode).

[0019] The gas passage 52 is a passage through which gas can pass in the vertical direction of the ceramic plate 20. Here, the gas passage 52 is provided inside the plug 50 fixed in the plug placement hole 24. The plug placement hole 24 penetrates the ceramic plate 20 in the vertical direction and is provided to communicate with the gas supply passage 34 of the base plate 30. The plug placement hole 24 penetrates the electrostatic electrode 22 and the bias electrode 23 in the vertical direction, but the electrostatic electrode 22 and the bias electrode 23 are not exposed on the inner circumferential surface of the plug placement hole 24. The plug placement hole 24 is a tapered hole having an inverted frustoconical space in which the area of ​​the upper opening is larger than the area of ​​the lower opening. In a plan view, the plug placement hole 24 is provided at multiple locations on the ceramic plate 20 (for example, at multiple locations provided at equal intervals along the circumferential direction). The plug 50 is a dense ceramic (for example, the same material as the ceramic plate 20) in the shape of an inverted frustoconical placed in the plug placement hole 24. The plug 50 is provided with a gas passage 52 that runs linearly through the plug 50 from its bottom surface to its top surface in the vertical direction. The vertical length L inside the gas passage 52 is the same as the thickness of the ceramic plate 20. Multiple gas passages 52 (for example, 6) are provided along the circumference on the top surface of the plug 50 in a plan view. The diameter (horizontal length) of the gas passage 52 is preferably set to 0.5 mm or less, more preferably to 0.2 mm or less, in order to suppress arc discharge. In this embodiment, the equipotential lines EL are oriented vertically or diagonally, rather than horizontally, as shown in Figure 3. Arc discharge occurs when electrons generated as gas (e.g., helium gas) is ionized in the gas passage 52 are accelerated in the direction of the electric field lines (a direction perpendicular to the equipotential lines EL, approximately horizontal in this embodiment) and collide with other helium. However, if the horizontal length, i.e., the diameter, of the gas passage 52 is 0.5 mm or less (preferably 0.2 mm or less), such arc discharge can be suppressed.

[0020] The base plate 30 is a conductive disc with good thermal conductivity (a disc with the same diameter as or larger than the ceramic plate 20). Inside the base plate 30, a refrigerant channel 32 through which a refrigerant (for example, an electrically insulating liquid such as a fluorine-based inert liquid) circulates and a gas supply channel 34 for supplying gas to a gas passage 52 are formed. The refrigerant channel 32 is formed in a single continuous line from the inlet to the outlet across the entire surface of the base plate 30 in a plan view. Examples of materials for the base plate 30 include metals and composite materials. Examples of metals include Mo. Examples of composite materials include metal-ceramic composites. Examples of metal-ceramic composites include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti, and materials in which Al and / or Si are impregnated into a porous SiC body. Materials containing Si, SiC, and Ti are called SiSiCTi, materials impregnated with Al in a porous SiC body are called AlSiC, and materials impregnated with Si in a porous SiC body are called SiSiC. For the base plate 30, it is preferable to select a material with a thermal expansion coefficient similar to that of the ceramic plate 20. The base plate 30 is used as a source electrode (a type of plasma generating electrode (RF electrode)) to which a source high frequency is applied for plasma generation. For example, the bias high frequency is several hundred kHz, and the source high frequency is several tens to several hundred MHz.

[0021] The gas supply passage 34 comprises a ring portion 34b that is concentric with the base plate 30 in a plan view, and an introduction portion 34a that introduces gas into the ring portion 34b from the lower surface of the base plate 30. The ring portion 34b communicates with the gas passage 52 through a through hole 42 in the metal bonding layer 40. The introduction portion 34a may be, for example, a single portion. The gas introduced into the introduction portion 34a is distributed to each gas passage 52 through the ring portion 34b.

[0022] The metal bonding layer 40 joins the lower surface of the ceramic plate 20 to the upper surface of the base plate 30. The metal bonding layer 40 is formed, for example, by TCB (Thermal Compression Bonding). TCB is a known method in which a metal bonding material is sandwiched between two members to be joined, and the two members are pressed together while heated to a temperature below the solidus temperature of the metal bonding material. The metal bonding layer 40 may also be a layer formed of solder or metal brazing material. The metal bonding layer 40 has through holes 42. The through holes 42 are provided at a position that connects the gas passage 52 and the gas supply passage 34.

[0023] The electric field adjusting conductor 60 is a needle-shaped metal member provided inside the plug 50, extending vertically near the gas passage 52. The electrostatic electrode 22 has an electrostatic electrode through-hole 22a at a position facing the plug 50, and the bias electrode 23 has a bias electrode through-hole 23a at a position facing the plug 50. The electric field adjusting conductor 60 is embedded in the ceramic plate 20, electrically insulated from the electrostatic electrode 22 and bias electrode 23, inside the electrostatic electrode through-hole 22a and inside the bias electrode through-hole 23a. The upper part of the electric field adjusting conductor 60 is inserted into a bottomed hole provided on the lower surface of the plug 50, and the lower part of the electric field adjusting conductor 60 is in direct contact with the base plate 30. The lower part of the electric field adjusting conductor 60 may be joined to the base plate 30 by solder or brazing material while inserted into a hole provided in the base plate 30, or it may be screwed into a hole provided in the base plate 30. The upper end of the electric field adjusting conductor 60 reaches the front of the wafer mounting surface 21. The upper end of the electric field adjusting conductor 60 is positioned so as to maintain the dielectric strength between the electric field adjusting conductor 60 and the wafer W. In this way, the electric field adjusting conductor 60 is provided so as to extend vertically from below the lower surface of the ceramic plate 20 to the front of the wafer mounting surface 21 near the gas passage 52 and is electrically connected to the base plate 30. Therefore, the electric field adjusting conductor 60 is at the same potential as the base plate 30. For example, the electric field adjusting conductor 60 is provided at a position 0.3 to 2.0 mm away from the gas passage 52.

[0024] Next, an example of using the wafer mounting stand 10 configured in this way will be described. First, with the wafer mounting stand 10 installed in a chamber (not shown), the wafer W is placed on the wafer mounting surface 21. Then, the pressure inside the chamber is reduced using a vacuum pump to adjust to a predetermined vacuum level, and a DC voltage is applied to the electrostatic electrode 22 of the ceramic plate 20 to generate electrostatic adsorption force, thereby adsorbing and fixing the wafer W to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a and the upper surface of the circular protrusion 21b). Next, the inside of the chamber is made into a reaction gas atmosphere at a predetermined pressure (for example, several tens to several hundreds of Pa), and in this state, a source high-frequency voltage is applied between an upper electrode (not shown) provided on the ceiling of the chamber and the base plate 30, and a bias high-frequency voltage is applied between the upper electrode and the bias electrode 23 to generate plasma. The surface of the wafer W is treated with the generated plasma. A refrigerant is circulated in the refrigerant flow path 32 of the base plate 30. Backside gas is introduced from a gas cylinder (not shown) into the gas supply path 34. A thermal conductive gas (such as helium) is used as the backside gas. The backside gas is supplied and sealed into the space between the back surface of the wafer W and the reference surface 21c of the wafer mounting surface 21 through the gas supply passage 34, the through hole 42, and the gas passage 52. The presence of this backside gas allows for efficient heat conduction between the wafer W and the ceramic plate 20.

[0025] The wafer mounting stage 10 is equipped with an electric field adjusting conductor 60, which allows the direction of the electric field during plasma generation (the direction perpendicular to the equipotential line EL) to be adjusted to the horizontal or a direction close to it. An example of the equipotential line EL in this embodiment is shown in Figure 3. As a result, the direction in which electrons generated by the ionization of gas molecules are accelerated becomes the horizontal or a direction close to it. Therefore, if the length of the gas passage 52 in the horizontal or a direction close to it is short, even if the vertical length L inside the gas passage 52 is increased, the distance over which electrons are accelerated will not increase, and discharge is less likely to occur even if the accelerated electrons collide with other gas molecules. In contrast, if there is no electric field adjusting conductor 60, as shown in the comparative configuration in Figure 4, the horizontal equipotential line EL exists throughout the entire vertical direction of the gas passage 52. In this case, the direction of the electric field is the vertical direction. Therefore, if the vertical length L inside the gas passage 52 is increased, the distance over which electrons are accelerated also increases, and because the accelerated electrons have high energy, they are more likely to collide with other gas molecules and cause discharge. Therefore, if there is no electric field adjusting conductor 60, instead of a gas passage 52 that extends linearly in the vertical direction, a spiral passage (with a short internal vertical length (e.g., 0.5 mm or less)) is used to suppress discharge within the passage. According to this embodiment, compared to the case where there is no electric field adjusting conductor 60, discharge within the gas passage 52 can be suppressed even if the internal vertical length L of the gas passage 52 is increased.

[0026] Next, a manufacturing example of the wafer mounting table 10 will be described based on Figure 5. Figure 5 is a manufacturing process diagram of the wafer mounting table 10. First, a ceramic plate 20, a base plate 30, and a metal bonding material 90 are prepared (Figure 5A). The ceramic plate 20 has built-in electrostatic electrodes 22 and bias electrodes 23 and is provided with plug placement holes 24. The base plate 30 is provided with a refrigerant flow path 32 and a gas supply path 34. However, the upper part of the ring portion 34b is open at this stage. Also, a hole is provided at a predetermined position in the ring portion 34b for inserting the lower part of the electric field adjusting conductor 60. The metal bonding material 90 is provided with a through hole 92 at a position opposite to the plug placement hole 24.

[0027] Next, a metal bonding material 90 is sandwiched between the lower surface of the ceramic plate 20 and the upper surface of the base plate 30 to form a laminate. The laminate is then pressed and bonded at a temperature below the solidus temperature of the metal bonding material 90 (for example, between a temperature 20°C below the solidus temperature and the solidus temperature), and then returned to room temperature (TCB). As a result, the metal bonding material 90 and the through holes 92 become the metal bonding layer 40 and the through holes 42, respectively. In addition, the upper part of the ring portion 34b is covered by the metal bonding layer 40 except for the position facing the through holes 42. As a result, a bonded body 94 is obtained in which the ceramic plate 20 and the base plate 30 are bonded by the metal bonding layer 40 (Figure 5B). Note that Al-Mg-based bonding materials or Al-Si-Mg-based bonding materials can be used as the metal bonding material 90. It is preferable to use a metal bonding material 90 with a thickness of approximately 100 μm.

[0028] Next, an electric field adjusting conductor 60 and a frustoconical plug 50 are prepared (Figure 5B). The plug 50 has multiple gas passages 52 and a bottomed hole 54 on its lower surface. This bottomed hole 54 is for inserting the upper part of the electric field adjusting conductor 60 and is located at the center of a circle formed by the multiple gas passages 52 in a plan view. First, the electric field adjusting conductor 60 is inserted into the hole in the ring portion 34b and fixed by brazing or the like. Next, the plug 50 is inserted into the plug placement hole 24 and fixed with adhesive. At this time, the plug 50 is positioned so that the electric field adjusting conductor 60 is inserted into the bottomed hole 54. After that, the wafer mounting stage 10 is obtained by processing the upper surface of the ceramic plate 20 (forming a seal band 21a and small circular protrusions 21b) (Figure 5C).

[0029] As described above, the wafer mounting stage 10 is equipped with an electric field adjusting conductor 60, which allows the direction of the electric field during plasma generation (the direction perpendicular to the equipotential line EL) to be adjusted to the horizontal or a direction close to it. As a result, the direction in which electrons generated by the ionization of gas molecules are accelerated becomes the horizontal or a direction close to it. Therefore, if the length of the gas passage 52 in the horizontal or near-horizontal direction is short, even if the vertical length L inside the gas passage 52 is increased, the distance over which electrons are accelerated will not increase, and discharge is less likely to occur even if the accelerated electrons collide with other gas molecules. Consequently, compared to the case without the electric field adjusting conductor 60, discharge within the gas passage 52 can be suppressed even if the vertical length L inside the gas passage 52 is increased.

[0030] Furthermore, the ceramic plate 20 has an electrostatic electrode 22 and a bias electrode 23. The gas passage 52 passes through an electrostatic electrode through-hole 22a so that the electrostatic electrode 22 is not exposed to the inner surface of the gas passage 52, and passes through a bias electrode through-hole 23a so that the bias electrode 23 is not exposed to the inner surface of the gas passage 52. The electric field adjusting conductor 60 is provided in a state where it is electrically insulated from the electrostatic electrode 22 and the bias electrode 23, respectively. Therefore, the direction of the electric field generated by the electrostatic electrode 22 and the bias electrode 23 in the ceramic plate 20 can be made horizontal or close to horizontal.

[0031] Furthermore, the ceramic plate 20 has a plug placement hole 24 (ceramic plate through hole) that penetrates the ceramic plate 20 in the vertical direction. The gas passage 52 and the electric field adjusting conductor 60 are provided inside the plug 50 placed in the plug placement hole 24. Therefore, it may be easier to form the gas passage 52 and the electric field adjusting conductor 60 compared to when the gas passage 52 and the electric field adjusting conductor 60 are directly provided in the ceramic plate 20 itself.

[0032] Furthermore, the gas passages 52 are arranged linearly in the vertical direction. This allows gas to flow more easily and increases the gas flow rate compared to using spiral passages or micropores inside a porous material. As a result, the number of gas passages 52 can be reduced. This reduces manufacturing costs. In addition, although the gas passages 52 become temperature singularities in the wafer W, reducing their number reduces the number of temperature singularities and improves heat uniformity.

[0033] It goes without saying that the present invention is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present invention.

[0034] In the embodiment described above, a gas passage 52 extending linearly in the vertical direction is provided inside the plug 50, but a gas passage 152 shown in Figure 6 may be used instead of the gas passage 52. In Figure 6, the same reference numerals are used for the same components as in the embodiment described above. The gas passage 152 extends linearly in an oblique direction around the plug 50. Specifically, the gas passage 152 is formed by a groove provided on the outer circumferential surface of the plug 50 and the inner circumferential surface of the plug placement hole 24. As shown in Figure 7, multiple gas passages 152 are provided at approximately equal intervals along the outer circumference of the plug 50 (a circle centered on the electric field adjusting conductor 60) in a plan view. The vertical length L inside the gas passage 52 (Figure 3) was the same as the thickness of the ceramic plate 20, but the vertical length L inside the gas passage 152 (Figure 6) is shorter than the thickness of the ceramic plate 20. The same effects as in the embodiment described above can be obtained even if this is done. Note that the gas passage 152 may be provided inside the plug 50 instead of around it. Alternatively, the gas passage 152 may be formed by longitudinal grooves provided on the outer circumferential surface of the plug 50 and the inner circumferential surface of the plug placement hole 24.

[0035] In the embodiment described above, a gas passage 52 and an electric field adjusting conductor 60 are provided in the plug 50 placed in the plug placement hole 24 of the ceramic plate 20. However, instead of these, a gas passage 252 and an electric field adjusting conductor 260 as shown in Figure 8 may be used. In Figure 8, the same components as in the embodiment described above are denoted by the same reference numerals. The gas passage 252 is provided in the ceramic plate 20 and extends linearly in the vertical direction. The gas passage 252 communicates with the gas supply passage 34 and the through hole 42, and as shown in Figure 9, a plurality of gas passages are provided at approximately equal intervals along a circle centered on the electric field adjusting conductor 260 in a plan view. The upper part of the electric field adjusting conductor 260 is inserted into a bottomed hole provided on the lower surface of the ceramic plate 20, and the lower part of the electric field adjusting conductor 260 is in direct contact with the base plate 30. The same effects as in the embodiment described above can be obtained even in this way. Furthermore, the gas passage 252 and the electric field adjusting conductor 260 (or the hole into which the electric field adjusting conductor 260 is inserted) can be fabricated when manufacturing the ceramic plate 20. The gas passage 252 may also be provided in a straight line at an angle within the ceramic plate 20.

[0036] In the embodiment described above, the electric field adjusting conductor 60 erected on the base plate 30 was inserted into the bottomed hole 54 of the plug 50, but instead, the structure shown in Figure 10 may be adopted. In Figure 10, the same components as in the embodiment described above are denoted by the same reference numerals. The electric field adjusting conductor 360 is a via provided inside the plug 50. For example, a conductive paste, which is a precursor of the electric field adjusting conductor 360, may be embedded in a ceramic molded body, which is a precursor of the plug 50, so that when the ceramic molded body is fired to obtain the plug 50, the electric field adjusting conductor 360 is formed at the same time. A metal spring 370 is placed in a compressed state between the lower end of the electric field adjusting conductor 360 and the bottom surface of the gas supply passage 34 (ring portion 34b) of the base plate 30. The electric field adjusting conductor 360 is electrically connected to the base plate 30 via the metal spring 370. The metal spring 370 maintains communication between the gas supply passage 34 and the gas passage 52. The same effects as in the embodiment described above can be obtained even in this way. Figure 10 illustrates a metal spring 370, but it is not limited to the metal spring 370 as long as it is a conductive elastic member that allows gas to pass through in the vertical direction. For example, it may be a metal mesh or a block of metal fibers that can expand and contract in the vertical direction. Such a structure is particularly useful when a resin adhesive layer is used instead of the metal bonding layer 40. In addition, the electric field adjusting conductor 360 and metal spring 370 shown in Figure 10 may be used instead of the electric field adjusting conductors 60 and 260 shown in Figures 6 and 8.

[0037] Alternatively, instead of the metal spring 370 shown in Figure 10, a conductive film 372 may be provided to cover the lower surface of the plug 50 and a portion of the lower surface of the ceramic plate 20 (around the plug placement hole 24), as shown in Figure 11. In Figure 11, the same reference numerals are used for the same components as in the above-described embodiment. The conductive film 372 is formed, for example, by sputtering. A through-hole 372a is provided in the conductive film 372 at a position facing the gas passage 52. Therefore, the conductive film 372 maintains communication between the gas supply passage 34 and the gas passage 52. The electric field adjusting conductor 360 is electrically connected to the base plate 30 via the conductive film 372 and the metal bonding layer 40. The same effects as in the above-described embodiment can be obtained in this way as well. Instead of the electric field adjusting conductors 60 and 260 in Figures 6 and 8, the electric field adjusting conductor 360 and the conductive film 372 in Figure 11 may be used.

[0038] In the embodiment described above, the electrostatic electrode 22 and the bias electrode 23 were embedded in the ceramic plate 20, but at least one of the electrostatic electrode 22, the bias electrode 23, and the heater electrode capable of heating the wafer W may be embedded in the ceramic plate 20. Alternatively, these electrodes may not be embedded in the ceramic plate 20. Figure 12 shows an example of a structure in which electrodes are not embedded in the ceramic plate 20. In Figure 12, the same reference numerals are used for the same components as in the embodiment described above. Figure 12 also shows the equipotential line EL. In Figure 12, by providing the electric field adjusting conductor 60, the direction of the electric field during plasma generation (the direction perpendicular to the equipotential line EL) can be adjusted to a direction close to horizontal. As a result, the direction in which electrons generated by the ionization of gas molecules are accelerated becomes a direction close to horizontal. Therefore, compared to the case without the electric field adjusting conductor 60, discharge in the gas passage 52 can be suppressed even if the vertical length inside the gas passage 52 is increased.

[0039] In the embodiments described above, a flexible conductive wire may be used as the electric field adjusting conductor 60. This allows for greater absorption of positional deviations during manufacturing and deformation during use compared to the case where a highly rigid needle-shaped member is used as the electric field adjusting conductor 60. The same applies to the electric field adjusting conductor 260 in Figure 8 and the electric field adjusting conductors 360 in Figures 10 and 11.

[0040] In the embodiments described above, the plug 50 is provided with multiple gas passages 52 extending linearly in the vertical direction. However, instead of multiple gas passages 52, a single helical passage may be used, or a porous material may be used as the plug 50, utilizing the micropores inside the porous material as gas passages. In these cases, discharge within the gas passages can be more easily suppressed, but the gas will flow less easily compared to the embodiments described above.

[0041] In the embodiment described above, the ceramic plate 20 and the base plate 30 were joined with a metal bonding layer 40, but a resin adhesive layer may be used instead of the metal bonding layer 40.

[0042] In the embodiments described above, the gas supply passage 34 is exemplified as having an introduction portion 34a and a ring portion 34b, but it is not limited to this. For example, a base plate through-hole that penetrates the base plate 30 in the vertical direction and communicates with the gas passage 52 may be used as the gas supply passage.

[0043] In the embodiment described above, the internal space of the plug placement hole 24 was made into an inverted frustoconical space, but it may also be a cylindrical space. In this case, the plug 50 is also cylindrical in shape. [Industrial applicability]

[0044] This invention can be used in wafer mounting stages used in semiconductor manufacturing equipment, such as ceramic heaters, electrostatic chuck heaters, and electrostatic chucks. [Explanation of Symbols]

[0045] 10 Wafer mounting platform, 20 Ceramic plate, 21 Wafer mounting surface, 21a Seal band, 21b Small circular protrusion, 21c Reference surface, 22 Electrostatic electrode, 22a Electrostatic electrode through hole, 23 Bias electrode, 23a Bias electrode through hole, 24 Plug placement hole, 30 Base plate, 32 Refrigerant flow path, 34 Gas supply path, 34a Inlet section, 34b Ring section, 40 Metal bonding layer, 42 Through hole, 50 Plug, 52 Gas passage, 54 Bottomed hole, 60 Electric field adjustment conductor, 90 Metal bonding material, 92 Through hole, 94 Bonded body, 152 Gas passage, 252 Gas passage, 260 Electric field adjustment conductor, 360 Electric field adjustment conductor, 370 Metal spring, 372 Conductive film, 372a Through hole.

Claims

1. A ceramic plate having a wafer mounting surface on its upper surface, A gas passage through which gas can pass in the vertical direction of the ceramic plate, A conductive base plate is bonded to the lower surface of the ceramic plate and used as a plasma generating electrode, A gas supply passage is provided inside the base plate and communicates with the gas passage, An electric field adjusting conductor is provided, extending vertically in the vicinity of the gas passage from the lower surface of the ceramic plate or a position below it to the front of the wafer mounting surface, and electrically connected to the base plate, Equipped with, The ceramic plate has a through-hole that penetrates the ceramic plate vertically, the gas passage is provided inside or around the plug positioned in the through-hole, and the electric field adjusting conductor is provided inside the plug. Wafer mounting stand.

2. A ceramic plate having a wafer mounting surface on its upper surface, A gas passage through which gas can pass in the vertical direction of the ceramic plate, A conductive base plate is bonded to the lower surface of the ceramic plate and used as a plasma generating electrode, A gas supply passage is provided inside the base plate and communicates with the gas passage, An electric field adjusting conductor is provided, extending vertically in the vicinity of the gas passage from the lower surface of the ceramic plate or a position below it to the front of the wafer mounting surface, and electrically connected to the base plate, Equipped with, The electric field adjusting conductor is a flexible conductive wire and is not in contact with the side surface of the gas passage. Wafer mounting stand.

3. A ceramic plate having a wafer mounting surface on its upper surface, A gas passage through which gas can pass in the vertical direction of the ceramic plate, A conductive base plate is bonded to the lower surface of the ceramic plate and used as a plasma generating electrode, A gas supply passage is provided inside the base plate and communicates with the gas passage, An electric field adjusting conductor is provided, extending vertically in the vicinity of the gas passage from the lower surface of the ceramic plate or a position below it to the front of the wafer mounting surface, and electrically connected to the base plate, Equipped with, The lower part of the electric field adjusting conductor is electrically connected to the base plate by a conductive elastic body disposed between the base plate and the lower end of the electric field adjusting conductor, which maintains communication between the gas supply path and the gas passage, or it is electrically connected to the base plate via a conductive film provided on the lower surface of the ceramic plate, which maintains communication between the gas supply path and the gas passage. Wafer mounting stand.

4. The gas passage and the electric field adjusting conductor are embedded in the ceramic plate. The wafer mounting platform according to claim 2 or 3.

5. The gas passage is provided linearly in the vertical or diagonal direction of the ceramic plate. A wafer mounting platform according to any one of claims 1 to 3.

6. The electric field adjusting conductor is a flexible conductive wire. The wafer mounting platform according to claim 1.

7. The lower part of the electric field adjusting conductor is provided so as to be in direct contact with the base plate, or is electrically connected to the base plate by a conductive elastic body disposed between the base plate and the lower end of the electric field adjusting conductor, which maintains communication between the gas supply path and the gas passage, or is electrically connected to the base plate via a conductive film provided on the lower surface of the ceramic plate, which maintains communication between the gas supply path and the gas passage. A wafer mounting platform according to claim 1 or 2.

8. The ceramic plate has at least one electrode, The gas passage is provided such that each of the at least one electrode passes through an electrode through-hole provided in each of the at least one electrode, so that each of the at least one electrode is not exposed to the inner surface of the gas passage. The electric field adjusting conductor is provided in a state where it is electrically insulated from each of the at least one electrode. A wafer mounting platform according to any one of claims 1 to 3.

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