An electrostatic chuck

Abstract

The present invention discloses an electrostatic chuck, belonging to the field of semiconductor technology, which includes a ceramic plate and a base. The ceramic plate is connected to the base through an adhesive layer. The base is provided with a first through hole and a first porous member for the inflow of cooling gas. The first porous member is arranged between the first through hole and the adhesive layer. The ceramic plate is provided with a porous assembly and a second through hole. The porous assembly is located between the second through hole and the adhesive layer. The second through hole communicates with the outside. The porous assembly is located above the first porous member. By providing the first through hole, the first porous member, the porous assembly and the second through hole, it enters between the electrostatic chuck and the adsorbent adsorbed on the electrostatic chuck, and through the electrostatic chuck, smoother air permeability can be obtained; by providing the second porous member and the third porous member and arranging them at intervals, the cooling gas can obtain a longer channel, and the channel is multi-folded, which can better suppress arc discharge.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly relates to an electrostatic chuck. Background Art

[0002] An electrostatic chuck is composed of a ceramic plate bonded to a base. An electrode layer is sandwiched in the ceramic layer. After passing an electric current, an electrostatic adsorption force is generated to adsorb a wafer. An inert gas passage exists in the electrostatic chuck base for passing an inert gas between the wafer and the ceramic plate to control the wafer temperature.

[0003] The electrostatic chuck is used in etching, sputtering, ion implantation, and chemical vapor deposition devices. It is used to adsorb a wafer. During the wafer processing, the wafer will increase in temperature, and the temperature needs to be controlled by the inert gas on the back of the wafer. Therefore, the electrostatic chuck basically has a gas passage. The function of the gas passage is to lead the gas in the base to the ceramic surface through the gas path, so there is a through passage in the ceramic plate and the base.

[0004] When processing the wafer, since both the wafer and the base are charged, an arc discharge phenomenon may occur due to the phenomenon that two electrodes are maintained in conduction by gaseous charged particles, such as electrons or ions, under a certain voltage. The arc discharge is likely to occur at the pore passage. Therefore, in order to avoid the arc discharge phenomenon, a porous ceramic is provided at the pore to increase the electrical resistance performance.

[0005] In the pore porous ceramic structure in the prior patents, the arc discharge phenomenon is improved by using this structure, but there is still a possibility of discharge, and the air permeability is affected.

[0006] In summary, it is crucial to prepare a porous structure with better anti-arc discharge function and smoother air permeability. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an electrostatic chuck with better anti-arc discharge function and smoother air permeability.

[0008] To solve the above technical problem, the technical solution of the present invention is as follows:

[0009] An electrostatic chuck includes a ceramic plate and a base. The ceramic plate is connected to the base through an adhesive layer. The base is provided with a first through hole for the inflow of cooling gas and a first porous member. The first porous member is arranged between the first through hole and the adhesive layer. The ceramic plate is provided with a porous assembly and a second through hole. The porous assembly is located between the second through hole and the adhesive layer. The second through hole communicates with the outside. The porous assembly is located above the first porous member.

[0010] Preferably, the porous component includes a second porous member and a third porous member, a gap is provided between the second porous member and the third porous member, a first positioning hole for cooperating with the second porous member and the third porous member is provided in the ceramic plate, and the first positioning hole communicates with the second through hole.

[0011] Preferably, a second positioning hole for cooperating with the first porous member is provided on the base, one end of the second positioning hole communicates with the first through hole, and the other end of the second positioning hole communicates with the first positioning hole.

[0012] Preferably, the longitudinal section of the second through hole is an isosceles trapezoid, and the length of the upper base of the isosceles trapezoid is less than the length of the lower base.

[0013] Preferably, the second porous member includes a first low-porosity block and a first high-porosity block, a first limiting through hole for cooperating with the first high-porosity block is provided in the first low-porosity block, the third porous member includes a second low-porosity block and a second high-porosity block, a second limiting through hole for cooperating with the second high-porosity block is provided in the second low-porosity block, and the positions of the first high-porosity block and the second high-porosity block in the vertical direction are staggered from each other.

[0014] Preferably, the first low-porosity block is disc-shaped, the diameter of the first low-porosity block is 1 mm to 5 mm, the thickness of the first low-porosity block is 0.1 mm to 1 mm, the second low-porosity block is disc-shaped, the diameter of the second low-porosity block is 1 mm to 5 mm, and the thickness of the second low-porosity block is 0.1 mm to 1 mm.

[0015] Preferably, the porosity of both the first low-porosity block and the second low-porosity block is 0% to 10%, and the porosity of both the first high-porosity block and the second high-porosity block is 10% to 30%.

[0016] Preferably, the closest distance between the side wall of the first limiting through hole and the outer side wall of the first low-porosity block is 100 to 300 microns, and the closest distance between the side wall of the second limiting through hole and the outer side wall of the second low-porosity block is 100 to 300 microns.

[0017] Preferably, the first limiting through hole includes a first straight side wall in the front-rear direction, the difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block is 1 / 4 to 1 / 3 of the diameter of the first low-porosity block, the second limiting through hole includes a second straight side wall in the front-rear direction, and the difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block is 1 / 4 to 1 / 3 of the diameter of the second low-porosity block.

[0018] Preferably, the second porous member is made of a ceramic material, and the second porous member is made of a magnetic material.

[0019] Adopting the above technical solution, the following beneficial effects are achieved:

[0020] By providing the first through hole, the first porous member, the porous assembly, and the second through hole, the cooling gas sequentially passes through the first through hole, the first porous member, the porous assembly, and the second through hole and enters between the electrostatic chuck and the adsorbate adsorbed on the electrostatic chuck. Through the electrostatic chuck, smoother air permeability can be obtained;

[0021] By providing the second porous member and the third porous member, two sets of the second porous member and the third porous member can be provided and arranged at intervals, enabling the cooling gas to obtain a longer channel, and the channel is multi-folded, which can better suppress arc discharge;

[0022] By providing the second through hole, the longitudinal section of the second through hole is an isosceles trapezoid with the length of the upper base less than that of the lower base, which can better discharge the cooling gas;

[0023] The second porous member is made of a magnetic material, which can decompose the arc into more smaller arcs and reduce the influence of the arc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic cross-sectional structure view of an electrostatic chuck according to the present invention;

[0025] Figure 2 is an enlarged structure view of the third porous member of the present invention;

[0026] Figure 3 is an enlarged structure view of the second porous member of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following further describes the specific embodiments of the present invention with reference to the drawings. It should be noted here that the description of these embodiments is for helping to understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] As Figures 1 to 3 shown, Figure 1 is a schematic cross-sectional structure view of an electrostatic chuck according to the present invention, Figure 2 is an enlarged structure view of the third porous member of the present invention, Figure 3Schematic enlarged view of the second porous component of the present invention, including a ceramic plate 1 and a base 2. The ceramic plate 1 is connected to the base 2 through an adhesive layer. The base 2 is provided with a first through hole 3 for the inflow of cooling gas and a first porous component 4. Generally, He gas is used as the cooling gas. The first porous component 4 is arranged between the first through hole 3 and the adhesive layer. The ceramic plate 1 is provided with a porous assembly and a second through hole 11. The porous assembly is located between the second through hole 11 and the adhesive layer. The second through hole 11 communicates with the outside. The porous assembly is located above the first porous component 4;

[0029] The cooling gas enters from the first through hole 3 on the base 2, sequentially passes through the first porous component 4 and the porous assembly, and is discharged from the second through hole 11. There are adhesive layer holes on the adhesive layer to allow the cooling gas to pass through, facilitating the passage of the cooling gas;

[0030] The porous assembly includes a second porous component and a third porous component. There is a gap between the second porous component and the third porous component. The gap between the second porous component and the third porous component facilitates the passage of the cooling gas, forming a horizontal channel. The ceramic plate 1 is provided with a first positioning hole 10 that cooperates with the second porous component and the third porous component. The first positioning hole 10 communicates with the second through hole 11, facilitating the passage of the cooling gas;

[0031] The second porous component and the third porous component allow the cooling gas to pass through. The second porous component and the third porous component are installed in the first positioning hole 10 in the ceramic plate 1. The first positioning hole 10 communicates with the second through hole 11, facilitating the passage of the cooling gas;

[0032] The base 2 is provided with a second positioning hole that cooperates with the first porous component 4. One end of the second positioning hole communicates with the first through hole 3, and the other end of the second positioning hole communicates with the first positioning hole 10, so that the first positioning hole 10, the second positioning hole, and the first through hole 3 are all sequentially connected, allowing the cooling gas to enter from the first through hole 3 and then flow out from the second through hole 11;

[0033] The longitudinal section of the second through hole 11 is an isosceles trapezoid. The length of the upper base of the isosceles trapezoid is less than the length of the lower base. An electrostatic chuck can be used to adsorb the wafer 9. Setting the second through hole 11 to be larger at the lower part and smaller at the upper part can allow the cooling gas to be discharged more smoothly between the ceramic plate 1 and the wafer 9, achieving the effect of reducing the temperature;

[0034] The second porous component includes a first low-porosity block 7 and a first high-porosity block 8. The first low-porosity block 7 is provided with a first limiting through hole that cooperates with the first high-porosity block 8. The third porous component includes a second low-porosity block 5 and a second high-porosity block 6. The second low-porosity block 5 is provided with a second limiting through hole that cooperates with the second high-porosity block 6. The positions of the first high-porosity block 8 and the second high-porosity block 6 are staggered in the vertical direction;

[0035] The electrostatic chuck introduces an inert gas such as He gas between the ceramic plate 1 and the adsorbed object such as the wafer 9 to control the temperature of the wafer 9. The inert gas passage penetrates through the base and the ceramic plate 1, and the gas path is filled with inert gas during ventilation. Under normal circumstances, the gas is non-conductive, but under high pressure, the gas is ionized, forming a sufficient number of free electrons and positive ions in the gas. Therefore, compared with other places, arc discharge is more likely to occur at the pores;

[0036] The positions of the first high-porosity block 8 and the second high-porosity block 6 are staggered in the vertical direction. The inert gas first enters the first positioning hole 10, and then passes through the first high-porosity block 8 and the second high-porosity block 6 to enter between the ceramic plate 1 and the adsorbed object. Since the positions of the first high-porosity block 8 and the second high-porosity block 6 are staggered in the vertical direction, the path of the gas changes from a straight line to a curve. If the second porous member is located above the third porous member, the inert gas first enters the first positioning hole 10, then passes through the second high-porosity block 6 to enter between the second porous member and the third porous member, and then turns to one side of the first high-porosity block 8. The positions of the first high-porosity block 8 and the second high-porosity block 6 are staggered in the vertical direction, making the gas path of the inert gas become a curve, which can extend the distance that the current flows through, prevent the electrons from accelerating, and reduce the probability of arc discharge occurring in the gas path. In order to reduce the probability of arc discharge to a greater extent, two second porous members and two third porous members can be provided, and the second porous members and the third porous members are alternately arranged in the first positioning hole 10. The positions of the first high-porosity block 8 and the second high-porosity block 6 are staggered in the vertical direction, causing the path of the He gas to bend multiple times, making the gas path of the inert gas become a curve, which can extend the distance that the current flows through, prevent the electrons from accelerating, and reduce the probability of arc discharge occurring in the gas path;

[0037] The first low-porosity block 7 is disc-shaped, with a diameter of 1 mm. Since it is arranged in the first positioning hole 10 for the flow of He gas, its size should not be too large. The thickness of the first low-porosity block 7 is 0.1 mm to ensure the smooth flow of He gas. The second low-porosity block 5 is disc-shaped, with a diameter of 1 mm and a thickness of 0.1 mm;

[0038] In other embodiments of this embodiment, the first low-porosity block 7 is disc-shaped, with a diameter of 5 mm and a thickness of 1 mm. The second low-porosity block 5 is disc-shaped, with a diameter of 5 mm and a thickness of 1 mm;

[0039] The porosity of both the first low-porosity block 7 and the second low-porosity block 5 is 0%, and the porosity of both the first high-porosity block 8 and the second high-porosity block 6 is 10%. Since the porosity of both the first low-porosity block 7 and the second low-porosity block 5 is 0%, the cooling gas, helium gas, cannot pass through the first low-porosity block 7 and the second low-porosity block 5. Therefore, the helium gas passes through the first high-porosity block 8 and the second high-porosity block 6. The first high-porosity block 8 and the second high-porosity block 6 are staggered from each other in the vertical direction. The cooling gas, helium gas, can first pass through the first high-porosity block 8 on one side, then enter the gap between the second porous member and the third porous member, and further pass through the second high-porosity block 6 on the other side, making the path of the cooling gas, helium gas, bent, which can better suppress arc discharge. In order to suppress arc discharge to a greater extent, two second porous members and two third porous members can be provided, and the two second porous members and the two third porous members are arranged alternately. The two second porous members are separated by the third porous member, and the two third porous members are separated by the second porous member. There is a certain distance between the second porous member and the third porous member to facilitate the passage of the cooling gas;

[0040] In other embodiments of this embodiment, the porosity of both the first low-porosity block 7 and the second low-porosity block 5 can be 10%, and the porosity of both the first high-porosity block 8 and the second high-porosity block 6 can be 30%. The porosity of the first high-porosity block 8 is higher than that of the first low-porosity block 7, and the porosity of the second high-porosity block 6 is higher than that of the second low-porosity block 5. Therefore, during use, most of the cooling gas passes through the first high-porosity block 8 and the second high-porosity block 6. When the cooling gas passes through the second porous member and the third porous member, most of the cold gas passes through the first high-porosity block 8 and the second high-porosity block 6, forming a bent channel to suppress the generation of arcs;

[0041] The closest distance between the side wall of the first limiting through-hole and the outer side wall of the first low-porosity block 7 is 100 microns, and the closest distance between the side wall of the second limiting through-hole and the outer side wall of the second low-porosity block 5 is 100 microns, which can ensure the structural stability of the first low-porosity block 7 and the second low-porosity block 5. The first high-porosity block 8 is embedded in the first limiting through-hole, and the second high-porosity block 6 is embedded in the second limiting through-hole. At the same time, the closest distance between the first high-porosity block 8 and the outer side wall of the first low-porosity block 7 is 100 microns, and the closest distance between the second high-porosity block 6 and the outer side wall of the second low-porosity block 5 is 100 microns, which can make the first high-porosity block 8 and the second high-porosity block 6 stagger a large distance left and right, so that the cooling gas can obtain a larger lateral path and a better bent path to suppress the generation of arcs;

[0042] In other embodiments of this embodiment, the closest distance between the side wall of the first limiting through hole and the outer side wall of the first low-porosity block 7 is 300 microns, and the closest distance between the side wall of the second limiting through hole and the outer side wall of the second low-porosity block 5 is 300 microns, which can ensure the structural stability of the first low-porosity block 7 and the second low-porosity block 5. The first high-porosity block 8 is embedded in the first limiting through hole, and the second high-porosity block 6 is embedded in the second limiting through hole. At the same time, the closest distance between the first high-porosity block 8 and the outer side wall of the first low-porosity block 7 is 100 microns, and the closest distance between the second high-porosity block 6 and the outer side wall of the second low-porosity block 5 is 300 microns, which can make the first high-porosity block 8 and the second high-porosity block 6 stagger a large distance left and right, so that the cooling gas can obtain a larger lateral path and a better bending path, and suppress the generation of arcs;

[0043] Both the first high-porosity block 8 and the second high-porosity block 6 can be semi-circular structures. The arc part of the semi-circular first high-porosity block 8 faces the outer side wall of the first low-porosity block 7, and the straight segment of the semi-circular first high-porosity block 8 is located in the middle of the first low-porosity block 7. The arc part of the semi-circular second high-porosity block 6 faces the outer side wall of the second low-porosity block 5, and the straight segment of the semi-circular second high-porosity block 6 is located in the middle of the second low-porosity block 5, which can ensure the passage of the cooling gas and stagger the first high-porosity block 8 and the second high-porosity block 6 to a greater extent, obtain a bent cooling gas flow channel, and suppress the generation of arcs;

[0044] The first limiting through hole includes a first straight side wall in the front-back direction. The difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block 7 and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block 7 is 1 / 4 of the diameter of the first low-porosity block 7. The second limiting through hole includes a second straight side wall in the front-back direction. The difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block 5 and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block 5 is 1 / 4 of the diameter of the second low-porosity block 5;

[0045] If the first straight side wall passes through the center of the first low-porosity block 7, the difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block 7 and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block 7 is zero. At this time, a larger first high-porosity block 8 can be obtained, but it will inevitably cause the distance between the first high-porosity block 8 and the second high-porosity block 6 to be too close in the lateral direction, and a bent curve of a longer cooling gas flow path cannot be formed. If the difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block 7 and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block 7 is too large, the first high-porosity block 8 will be too small, thus affecting the passage of the cooling gas through the first high-porosity block 8. Therefore, the difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block 7 and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block 7 is 1 / 4 of the diameter of the first low-porosity block 7;

[0046] If the second straight side wall passes through the center of the second low-porosity block 5, the difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block 5 and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block 5 is zero. At this time, a larger second high-porosity block 6 can be obtained, but it will inevitably cause the distance between the second high-porosity block 6 and the first high-porosity block 8 to be too close in the lateral direction, and a bent curve of a longer cooling gas flow path cannot be formed, affecting its effect of suppressing the electric arc. If the difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block 5 and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block 5 is too large, the second high-porosity block 6 will be too small, thus affecting the passage of the cooling gas through the second high-porosity block 6. Therefore, the difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block 5 and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block 5 is 1 / 4 of the diameter of the first low-porosity block 7;

[0047] In other embodiments of this embodiment, the first limiting through-hole includes a first straight side wall in the front-back direction. The difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block 7 and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block 7 is 1 / 3 of the diameter of the first low-porosity block 7. The second limiting through-hole includes a second straight side wall in the front-back direction. The difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block 5 and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block 5 is 1 / 3 of the diameter of the second low-porosity block 5;

[0048] If the first straight side wall passes through the center of the first low-porosity block 7, the difference between the maximum distance between the first straight side wall and the outer side wall on the left of the first low-porosity block 7 and the maximum distance between the first straight side wall and the outer side wall on the right of the first low-porosity block 7 is zero. At this time, a larger first high-porosity block 8 can be obtained, but it will inevitably cause the distance between the first high-porosity block 8 and the second high-porosity block 6 to be too close in the transverse direction, and a bending curve of a longer cooling gas flow path cannot be formed. If the difference between the maximum distance between the first straight side wall and the outer side wall on the left of the first low-porosity block 7 and the maximum distance between the first straight side wall and the outer side wall on the right of the first low-porosity block 7 is too large, the first high-porosity block 8 will be too small, thereby affecting the passage of the cooling gas through the first high-porosity block 8. Therefore, the difference between the maximum distance between the first straight side wall and the outer side wall on the left of the first low-porosity block 7 and the maximum distance between the first straight side wall and the outer side wall on the right of the first low-porosity block 7 is 1 / 3 of the diameter of the first low-porosity block 7;

[0049] If the second straight side wall passes through the center of the second low-porosity block 5, the difference between the maximum distance between the second straight side wall and the outer side wall on the left of the second low-porosity block 5 and the maximum distance between the second straight side wall and the outer side wall on the right of the second low-porosity block 5 is zero. At this time, a larger second high-porosity block 6 can be obtained, but it will inevitably cause the distance between the second high-porosity block 6 and the first high-porosity block 8 to be too close in the transverse direction, and a bending curve of a longer cooling gas flow path cannot be formed, affecting its effect of suppressing the arc. If the difference between the maximum distance between the second straight side wall and the outer side wall on the left of the second low-porosity block 5 and the maximum distance between the second straight side wall and the outer side wall on the right of the second low-porosity block 5 is too large, the second high-porosity block 6 will be too small, thereby affecting the passage of the cooling gas through the second high-porosity block 6. Therefore, the difference between the maximum distance between the second straight side wall and the outer side wall on the left of the second low-porosity block 5 and the maximum distance between the second straight side wall and the outer side wall on the right of the second low-porosity block 5 is 1 / 3 of the diameter of the first low-porosity block 7;

[0050] The second porous member is made of a ceramic material, the second porous member is made of a magnetic material, the magnetic material is a metallic magnetic material. By alternately arranging the ceramic material of the second porous member and the magnetic material of the second porous member, due to the presence of the metallic magnetic material, the arc discharge distance is shortened, the arc is divided into several short arcs, and the near-cathode effect of the alternating current arc and the near-pole voltage drop of the direct current arc are used to achieve the purpose of extinguishing the arc;

[0051] By providing the first through hole 3, the first porous member 4, the porous assembly and the second through hole 11, the cooling gas sequentially passes through the first through hole 3, the first porous member 4, the porous assembly and the second through hole 11, and enters between the electrostatic chuck and the adsorbent adsorbed on the electrostatic chuck. Through the electrostatic chuck, smoother air permeability can be obtained, so that the cooling gas of the electrostatic chuck can play a cooling role;

[0052] By providing the second porous member and the third porous member, two sets of the second porous member and the third porous member can be provided and arranged at intervals, enabling the cooling gas to have a longer channel, and the channel is multi-folded, which can better suppress arc discharge;

[0053] By providing the second through hole 11, the longitudinal section of the second through hole 11 is an isosceles trapezoid with the length of the upper base less than that of the lower base, which can better discharge the cooling gas;

[0054] The second porous member is made of a magnetic material, which can decompose the arc into more smaller arcs and reduce the influence of the arc.

[0055] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions and variations to these embodiments still fall within the protection scope of the present invention.

Claims

1. An electrostatic chuck, characterized in that: It includes a ceramic plate and a base. The ceramic plate is connected to the base through an adhesive layer. The base is provided with a first through hole for the inflow of cooling gas and a first porous member. The first porous member is arranged between the first through hole and the adhesive layer. The ceramic plate is provided with a porous assembly and a second through hole. The porous assembly is located between the second through hole and the adhesive layer. The second through hole communicates with the outside. The porous assembly is located above the first porous member; The porous assembly includes a second porous member and a third porous member. A gap is provided between the second porous member and the third porous member. The ceramic plate is provided with a first positioning hole that cooperates with the second porous member and the third porous member. The first positioning hole communicates with the second through hole; The second porous member includes a first low-porosity block and a first high-porosity block. The first low-porosity block is provided with a first limiting through hole that cooperates with the first high-porosity block. The third porous member includes a second low-porosity block and a second high-porosity block. The second low-porosity block is provided with a second limiting through hole that cooperates with the second high-porosity block. The positions of the first high-porosity block and the second high-porosity block in the up-down direction are offset from each other.

2. The electrostatic chuck according to claim 1, wherein: The base is provided with a second positioning hole that cooperates with the first porous member. One end of the second positioning hole communicates with the first through hole, and the other end of the second positioning hole communicates with the first positioning hole.

3. The electrostatic chuck according to claim 2, wherein: The longitudinal section of the second through hole is an isosceles trapezoid, and the length of the upper base of the isosceles trapezoid is less than the length of the lower base.

4. The electrostatic chuck according to claim 3, characterized in that: The first low-porosity block is disc-shaped, with a diameter of 1 mm to 5 mm and a thickness of 0.1 mm to 1 mm. The second low-porosity block is disc-shaped, with a diameter of 1 mm to 5 mm and a thickness of 0.1 mm to 1 mm.

5. The electrostatic chuck according to claim 4, wherein: The porosity of both the first low-porosity block and the second low-porosity block is 0% to 10%, and the porosity of both the first high-porosity block and the second high-porosity block is 10% to 30%.

6. The electrostatic chuck according to claim 5, wherein: The closest distance between the side wall of the first limiting through hole and the outer side wall of the first low-porosity block is 100 to 300 microns, and the closest distance between the side wall of the second limiting through hole and the outer side wall of the second low-porosity block is 100 to 300 microns.

7. The electrostatic chuck according to claim 6, wherein: The first limiting through hole includes a first straight side wall in the front-back direction. The difference between the maximum distance between the first straight side wall and the left outer side wall of the first low-porosity block and the maximum distance between the first straight side wall and the right outer side wall of the first low-porosity block is 1 / 4 to 1 / 3 of the diameter of the first low-porosity block. The second limiting through hole includes a second straight side wall in the front-back direction. The difference between the maximum distance between the second straight side wall and the left outer side wall of the second low-porosity block and the maximum distance between the second straight side wall and the right outer side wall of the second low-porosity block is 1 / 4 to 1 / 3 of the diameter of the second low-porosity block.

8. The electrostatic chuck according to claim 7, wherein: The second porous member is made of ceramic material, and the second porous member is made of magnetic material.

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