Method for manufacturing an electrostatic chuck

Abstract

The application relates to a manufacturing method of an electrostatic chuck, which comprises the following steps: step one, preparing aluminum nitride casting slurry; preparing an electrostatic chuck green body, which is provided with a mounting groove; step two, laying an electrostatic electrode plate and a first copper wire at the bottom of the mounting groove, then injecting the aluminum nitride casting slurry which can immerse the electrostatic electrode plate, and forming a first aluminum nitride partition plate after drying and solidification; step three, setting a first metal plate on the first aluminum nitride partition plate; step four, preparing a first base material and a second base material; step five, setting the first base material and the second base material on the first metal plate; step six, setting a second metal plate and a second copper wire on the upper end of the first base material, and setting a third metal plate and a third copper wire on the upper end of the second base material; step seven, injecting aluminum nitride casting slurry into the mounting groove; step eight, sending the aluminum nitride casting slurry into a kiln for firing after drying and solidification; and step nine, cooling to obtain the electrostatic chuck after firing.

Description

Technical Field

[0001] This invention relates to the field of wafer clamping equipment technology, and in particular to a method for manufacturing an electrostatic chuck. Background Technology

[0002] In wafer fabrication, clamping devices are required for fixation, and electrostatic chucks are a commonly used type of wafer clamping device. Existing electrostatic chuck structures, such as the one disclosed in Chinese Patent Application Publication No. CN101419929A, include a base with an insulating layer on top. Multiple helium gas distribution channels are located on the base, and multiple helium gas holes communicating with these channels are located on the insulating layer. These helium gas holes are distributed circumferentially around the center of the insulating layer, or uniformly in a honeycomb pattern. This promotes sufficient and uniform contact between helium gas and the wafer and the electrostatic chuck, increasing the thermal conductivity of the electrostatic chuck to the wafer and fully meeting the temperature uniformity requirements of the wafer. The multiple helium gas holes can utilize dual-zone or multi-zone helium gas systems to separately control the temperature of the wafer center and edge, or to achieve multi-zone temperature control of the wafer. During operation, the aforementioned electrostatic chuck introduces helium gas into the helium gas holes to cool the wafer (the wafer requires strict temperature control during cleaning, etching, and photolithography processes). However, in actual production, helium is relatively expensive (the price of industrial helium is generally over 200 yuan, and the higher the purity of helium, the more expensive it is), and the energy required for helium pressurization and recovery is high, resulting in higher costs. Summary of the Invention

[0003] Therefore, in view of the above problems, the present invention proposes a method for manufacturing an electrostatic chuck. The electrostatic chuck manufactured by this method has good cooling effect and low cost.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for manufacturing an electrostatic chuck includes the following steps;

[0006] Step 1: Prepare aluminum nitride casting slurry;

[0007] A portion of aluminum nitride casting slurry is injected into a mold, dried and cured to form an electrostatic chuck green ceramic blank. The electrostatic chuck green ceramic blank is cylindrical, and an installation groove is provided on the upper bottom surface of the electrostatic chuck green ceramic blank.

[0008] Remaining aluminum nitride casting slurry is reserved;

[0009] Step 2: Prepare the first matrix material. Heat the elemental silicon material to the melt and then uniformly dope it with a five-valent element. Cool to form a columnar first matrix material. The number of electrons in the first matrix material is greater than the number of holes. Both ends of the first matrix material are coated with graphite coating for later use.

[0010] To prepare the second matrix material, elemental silicon material is heated to a molten state and then uniformly doped with trivalent elements. After cooling, a columnar second matrix material is formed. The number of electrons in the second matrix material is less than the number of holes. Both ends of the second matrix material are coated with graphite coating for later use.

[0011] Step 3: Lay an electrostatic electrode plate and a first copper wire connecting the electrostatic electrode plate at the bottom of the mounting groove, and then inject aluminum nitride casting slurry into the mounting groove so that the aluminum nitride casting slurry immerses the electrostatic electrode plate. After the aluminum nitride casting slurry injected in this step is dried and cured, it forms the first aluminum nitride partition.

[0012] Step 4: Continue to inject aluminum nitride casting paste onto the first aluminum nitride separator, and then place the first metal plate on the aluminum nitride casting paste injected in this step. The upper surface of the first metal plate is exposed above the surface of the aluminum nitride casting paste. The electrostatic electrode plate and the first copper wire do not contact the first metal plate. Use a multimeter to test the insulation between the first copper wire and the first metal plate, and then proceed to step 5.

[0013] Step 5: After the aluminum nitride casting slurry injected in Step 3 has dried and cured; the lower end of the first substrate material is placed on the first metal plate, and the graphite coating on the lower end of the first substrate material is in full contact with the first metal plate; the lower end of the second substrate material is placed on the first metal plate, and the graphite coating on the lower end of the second substrate material is in full contact with the first metal plate.

[0014] The first matrix material and the second matrix material are not in contact;

[0015] Step 6: A second metal plate is disposed on the graphite coating at the upper end of the first substrate material, and a second copper wire is connected to the second metal plate; a third metal plate is disposed on the graphite coating at the upper end of the second substrate material, and a third copper wire is connected to the third metal plate.

[0016] The second metal plate and the third metal plate are not in contact;

[0017] Step 7: Inject aluminum nitride casting slurry into the mounting groove so that the aluminum nitride casting slurry covers the second metal plate and the third metal plate;

[0018] The first, second, and third copper wires all pass through the aluminum nitride casting paste; the insulation between the first and second copper wires is tested with a multimeter, and the insulation between the first and third copper wires is also tested, then proceed to step eight;

[0019] Step 8: After the aluminum nitride casting slurry has dried and solidified, remove the electrostatic chuck green ceramic blank from the mold and send it into the kiln for firing.

[0020] Step 9: After firing, allow it to cool naturally to the current ambient temperature to obtain the electrostatic chuck;

[0021] The first, second, and third copper wires of the electrostatic chuck are insulated and encapsulated.

[0022] Furthermore, in step three, a thermistor ceramic and a fourth copper wire connecting the thermistor ceramic are also provided on the first aluminum nitride separator.

[0023] In step seven, the fourth copper wire also passes through the aluminum nitride casting paste, and a multimeter is used to test the insulation between the fourth copper wire and the first copper wire, the insulation between the fourth copper wire and the second copper wire, and the insulation between the fourth copper wire and the third copper wire.

[0024] Furthermore, step nine also includes polishing the outer surface of the electrostatic chuck on the side closest to the electrostatic electrode plate.

[0025] Furthermore, step nine also includes installing heat dissipation fins on the electrostatic chuck at the slot opening of the mounting groove.

[0026] Furthermore, a cooling fan is installed at the slot opening of the mounting groove on the electrostatic chuck.

[0027] Furthermore, in steps one, three, and seven, after the aluminum nitride casting slurry is injected, air bubbles in the aluminum nitride casting slurry are removed by an ultrasonic defoaming device.

[0028] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0029] The electrostatic chuck manufactured using this method is a one-piece molded aluminum nitride ceramic chuck (compared to assembled structures, this one-piece structure improves production efficiency, reduces costs, and offers better insulation and strength). It boasts advantages such as high thermal conductivity, low coefficient of thermal expansion, resistance to cracking, and good machine strength, along with excellent cooling performance and low operating costs. During use, the electrostatic electrode plate generates static electricity through the first copper wire, causing the wafer to be electrostatically attracted to the chuck surface. When wafer cooling is required, the second copper wire is connected to the positive terminal, and the third copper wire to the negative terminal. Due to the thermoelectric effect, the first metal plate absorbs heat, while the second and third metal plates generate heat. The heat absorbed by the first metal plate cools the wafer, while the heat generated by the second and third metal plates is quickly dissipated through heat sink fins and / or a cooling fan. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure for forming an electrostatic chuck green ceramic blank on the mold in step one.

[0031] Figure 2This is a schematic diagram of the structure in step three, in which an electrostatic electrode plate, a first aluminum nitride partition plate, and a first copper wire are installed in the mounting groove of the electrostatic chuck green ceramic blank (mold hidden).

[0032] Figure 3 This is a schematic diagram of the structure in step four where the first metal plate is installed on the first aluminum nitride separator.

[0033] Figure 4 This is a schematic diagram of the structure in step five, where a first substrate material and a second substrate material are placed on the first metal plate.

[0034] Figure 5 This is a schematic diagram of the structure of the electrostatic chuck green ceramic blank obtained in step eight.

[0035] Figure 6 This is a schematic diagram of the structure of an electrostatic chuck with heat-dissipating fins and a cooling fan. Detailed Implementation

[0036] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0037] refer to Figures 1-6 This embodiment provides a method for manufacturing an electrostatic chuck, including the following steps;

[0038] Step 1: Preparation of aluminum nitride casting slurry; The preparation process of aluminum nitride casting slurry is a conventional technique in this field, such as the aluminum nitride casting slurry preparation process disclosed in the application filed by Fujian Huaqing Electronic Materials Technology Co., Ltd. on July 2, 2021, for a method of preparing an aluminum nitride ceramic heating element, which includes:

[0039] (1) One-time ball milling: In a ball mill, aluminum nitride powder and 5 wt% yttrium oxide powder are added and continuously ground, and trioleic acid glyceride is gradually added until the aluminum nitride powder is saturated and adsorbed; a one-time ball milling slurry with a solid mass fraction of more than 40% is obtained.

[0040] (2) Secondary ball milling: A mixed solution of PVB binder and polyethylene oxide is added to the ball mill slurry prepared in the primary ball mill. The volume ratio of PVB binder to polyethylene oxide is 0.9 to 1.8. The volume ratio of the mixed solution to the primary ball mill slurry prepared in step one is 0.55 to 0.6. The ball mill continues to grind until the particle size of aluminum nitride powder reaches 2 to 3 μm, thus obtaining aluminum nitride casting slurry.

[0041] A portion of aluminum nitride casting slurry is injected into mold 100, dried and cured to form an electrostatic chuck green ceramic blank 1. The electrostatic chuck green ceramic blank 1 is cylindrical, and an installation groove 10 is provided on the upper bottom surface of the electrostatic chuck green ceramic blank 1.

[0042] The remaining aluminum nitride casting slurry is reserved.

[0043] Step 2: Prepare the first matrix material 6. Heat the elemental silicon material to melt and then uniformly dope it with a 5-valent element. Cool to form a columnar first matrix material 6. The number of electrons in the first matrix material 6 is greater than the number of holes. Both ends of the first matrix material 6 are coated with graphite coating (not shown in the figure) for later use.

[0044] The pentavalent element is any one or a combination of phosphorus, arsenic, bismuth, and antimony.

[0045] To prepare the second matrix material 7, elemental silicon material is heated to melt and then uniformly doped with trivalent elements. After cooling, a columnar second matrix material 7 is formed. The number of electrons in the second matrix material 7 is less than the number of holes. Both ends of the second matrix material 7 are coated with graphite coating (not shown in the figure) for later use.

[0046] The trivalent element is any one or a combination of boron, indium, and gallium.

[0047] Step 3: Lay an electrostatic electrode plate 2 and a first copper wire 3 connecting the electrostatic electrode plate 2 at the bottom of the mounting groove 10, and then inject aluminum nitride casting slurry into the mounting groove 10 so that the aluminum nitride casting slurry submerges the electrostatic electrode plate 2. Use an ultrasonic defoaming device to remove air bubbles from the aluminum nitride casting slurry.

[0048] After the aluminum nitride casting slurry injected in this step is dried and cured, the first aluminum nitride partition 4 is formed.

[0049] The first aluminum nitride partition 4 is also provided with a thermistor ceramic 14 and a fourth copper wire 15 connecting the thermistor ceramic 14; the thermistor ceramic 14 is used to detect temperature.

[0050] Step 4: Continue injecting aluminum nitride casting slurry onto the first aluminum nitride separator 4. Remove air bubbles from the aluminum nitride casting slurry using an ultrasonic degassing device. Then, place the first metal plate 5 on the aluminum nitride casting slurry injected in this step, with the upper surface of the first metal plate 5 exposed above the surface of the aluminum nitride casting slurry. The electrostatic electrode plate 2 and the first copper wire 3 should not be in contact with the first metal plate 5. Use a multimeter to check the insulation between the first copper wire 3 and the first metal plate 5. If the insulation is not detected, proceed to step 5. Otherwise, remove the first metal plate 5, inject aluminum nitride casting slurry again, and then reposition and adjust the position of the first metal plate 5 so that the insulation between the first copper wire 3 and the first metal plate 5 is checked by a multimeter. This prevents the electrostatic electrode plate 2 and the first copper wire 3 from contacting the first metal plate 5 and causing a short circuit.

[0051] Step 5: After the aluminum nitride casting slurry injected in Step 3 has dried and cured, the lower end of the first substrate material 6 is placed on the first metal plate 5, and the graphite coating (not shown in the figure) at the lower end of the first substrate material 6 is in full contact with the first metal plate 5; the lower end of the second substrate material 7 is placed on the first metal plate 5, and the graphite coating (not shown in the figure) at the lower end of the second substrate material 7 is in full contact with the first metal plate 5.

[0052] The first matrix material 6 and the second matrix material 7 are not in contact.

[0053] Step 6: A second metal plate 8 is disposed on the graphite coating (not shown in the figure) at the upper end of the first substrate material 6, and a second copper wire 9 is connected to the second metal plate 8; a third metal plate 11 is disposed on the graphite coating (not shown in the figure) at the upper end of the second substrate material 7, and a third copper wire 12 is connected to the third metal plate 11.

[0054] The second metal plate 11 and the third metal plate 12 are not in contact.

[0055] Step 7: Inject aluminum nitride casting slurry into the mounting groove 10, and remove the air bubbles in the aluminum nitride casting slurry using an ultrasonic defoaming device, so that the aluminum nitride casting slurry covers the second metal plate 8 and the third metal plate 11.

[0056] The first copper wire 3, the second copper wire 9, the third copper wire 12, and the fourth copper wire 15 pass through the aluminum nitride casting paste; the insulation between the first copper wire 3 and the second copper wire 9, the insulation between the first copper wire 3 and the third copper wire 12, the insulation between the fourth copper wire 15 and the first copper wire 3, the insulation between the fourth copper wire 15 and the second copper wire 9, and the insulation between the fourth copper wire 15 and the third copper wire 12 are tested with a multimeter, then proceed to step eight;

[0057] Step 8: After the aluminum nitride casting slurry has dried and solidified, remove the electrostatic chuck green ceramic blank 1 from the mold 100 and send it into the kiln for firing.

[0058] Under high pressure conditions of 1000MPa to 6000MPa in the kiln, the raw ceramic slabs are heated to a sintering temperature of 950℃ to 1000℃ and held for 3 to 5 hours.

[0059] Since the melting temperature of the first matrix material 6 and the second matrix material 7 is 1410℃, and the melting temperature of copper is 1083.4℃, they will not melt during firing in the kiln.

[0060] Step 9: After firing, allow it to cool naturally to the current ambient temperature to obtain the electrostatic chuck;

[0061] The first copper wire 3, the second copper wire 9, the third copper wire 12, and the fourth copper wire 15 of the electrostatic chuck are insulated and encapsulated.

[0062] Furthermore, the outer surface of the electrostatic chuck near the electrostatic electrode plate 2 is polished.

[0063] Furthermore, a heat dissipation fin 16 and a cooling fan 17 are installed on the electrostatic chuck at the slot opening of the mounting slot 10. The heat dissipation fin 16 is located between the slot opening of the mounting slot 10 and the cooling fan 17.

[0064] In use, the electrostatic electrode plate 2 generates static electricity through the first copper wire 1, which allows the wafer to be electrostatically attracted to the surface of the electrostatic chuck.

[0065] The temperature near the electrostatic electrode plate 2 is detected by the thermistor ceramic 14. When the wafer needs to be cooled, the positive terminal of the power supply (external power supply) is connected to the second copper wire 9, and the negative terminal of the power supply (external power supply) is connected to the third copper wire 12. Due to the thermoelectric effect (the thermoelectric effect is a well-known technology and will not be described in detail here), the first metal sheet 5 absorbs heat, while the second metal sheet 9 and the third metal sheet 12 generate heat. The heat absorbed by the first metal sheet 5 cools the wafer. The heat generated by the second metal sheet 9 and the third metal sheet 12 can be quickly removed by the heat sink fins 16 and the cooling fan 17 (the cooling fan is started by an external controller).

[0066] The temperature on one side of the electrostatic electrode plate 2 can be detected by the thermistor ceramic 14, thereby adjusting the voltage across the second copper wire 9 and the third copper wire 12 connected to the external power supply, and thus controlling the rate at which the first metal sheet 5 absorbs heat.

[0067] The electrostatic chuck produced by this method has good cooling effect and low operating cost.

[0068] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for manufacturing an electrostatic chuck, characterized in that, Includes the following steps; Step 1: Prepare aluminum nitride casting slurry; A portion of aluminum nitride casting slurry is injected into a mold, dried and cured to form an electrostatic chuck green ceramic blank. The electrostatic chuck green ceramic blank is cylindrical, and an installation groove is provided on the upper bottom surface of the electrostatic chuck green ceramic blank. Remaining aluminum nitride casting slurry is reserved; Step 2: Prepare the first matrix material. Heat the elemental silicon material to the melt and then uniformly dope it with a five-valent element. Cool to form a columnar first matrix material. The number of electrons in the first matrix material is greater than the number of holes. Both ends of the first matrix material are coated with graphite coating for later use. To prepare the second matrix material, elemental silicon material is heated to a molten state and then uniformly doped with trivalent elements. After cooling, a columnar second matrix material is formed. The number of electrons in the second matrix material is less than the number of holes. Both ends of the second matrix material are coated with graphite coating for later use. Step 3: Lay an electrostatic electrode plate and a first copper wire connecting the electrostatic electrode plate at the bottom of the installation groove, and then inject aluminum nitride casting slurry into the installation groove so that the aluminum nitride casting slurry immerses the electrostatic electrode plate. After the aluminum nitride casting slurry injected in this step is dried and cured, it forms the first aluminum nitride partition. Step 4: Continue to inject aluminum nitride casting paste onto the first aluminum nitride separator, and then place the first metal plate on the aluminum nitride casting paste injected in this step. The upper surface of the first metal plate is exposed above the surface of the aluminum nitride casting paste. The electrostatic electrode plate and the first copper wire do not contact the first metal plate. Use a multimeter to test the insulation between the first copper wire and the first metal plate, and then proceed to step 5. Step 5: After the aluminum nitride casting slurry injected in Step 3 has dried and cured; the lower end of the first substrate material is placed on the first metal plate, and the graphite coating on the lower end of the first substrate material is in full contact with the first metal plate; the lower end of the second substrate material is placed on the first metal plate, and the graphite coating on the lower end of the second substrate material is in full contact with the first metal plate. The first matrix material and the second matrix material are not in contact; Step 6: A second metal plate is disposed on the graphite coating at the upper end of the first substrate material, and a second copper wire is connected to the second metal plate; a third metal plate is disposed on the graphite coating at the upper end of the second substrate material, and a third copper wire is connected to the third metal plate. The second metal plate and the third metal plate are not in contact; Step 7: Inject aluminum nitride casting slurry into the mounting groove so that the aluminum nitride casting slurry covers the second metal plate and the third metal plate; The first, second, and third copper wires all pass through the aluminum nitride casting paste; the insulation between the first and second copper wires is tested with a multimeter, and the insulation between the first and third copper wires is also tested, then proceed to step eight; Step 8: After the aluminum nitride casting slurry has dried and solidified, remove the electrostatic chuck green ceramic blank from the mold and send it into the kiln for firing. Step 9: After firing, allow it to cool naturally to the current ambient temperature to obtain the electrostatic chuck; The first, second, and third copper wires of the electrostatic chuck are insulated and encapsulated.

2. The method for manufacturing an electrostatic chuck according to claim 1, characterized in that: In step three, the first aluminum nitride separator is also provided with a thermistor ceramic and a fourth copper wire connecting the thermistor ceramic; In step seven, the fourth copper wire also passes through the aluminum nitride casting paste, and a multimeter is used to test the insulation between the fourth copper wire and the first copper wire, the insulation between the fourth copper wire and the second copper wire, and the insulation between the fourth copper wire and the third copper wire.

3. The method for manufacturing an electrostatic chuck according to claim 1, characterized in that: Step nine also includes polishing the outer surface of the electrostatic chuck on the side closest to the electrostatic electrode plate.

4. The method for manufacturing an electrostatic chuck according to claim 1, characterized in that: Step nine also includes installing heat dissipation fins on the electrostatic chuck at the slot opening of the mounting groove.

5. The method for manufacturing an electrostatic chuck according to claim 4, characterized in that: It also includes a cooling fan installed at the slot opening of the mounting groove on the electrostatic chuck.

6. The method for manufacturing an electrostatic chuck according to claim 1, characterized in that: In steps one, three, and seven, after the aluminum nitride casting slurry is injected, air bubbles in the aluminum nitride casting slurry are removed by an ultrasonic defoaming device.

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