Electrostatic chuck cleaning equipment and cleaning method

Abstract

The invention relates to electrostatic chuck cleaning equipment which comprises a preheating platform, a dry ice generation module, a gas-solid mixing acceleration device and an ionized gas generation device. Wherein the dry ice generation module is used for solidifying liquid COs into dry ice particles; an included angle of 10-45 degrees is formed between a spraying shaft of the gas-solid mixing acceleration device and the plane of the electrostatic chuck, and the mixture of the dry ice particles and the compressed air is accelerated to supersonic speed; a spraying shaft of the ionized gas generating device is parallel to the plane of the electrostatic chuck, the high-frequency and high-voltage electrode ionizes high-purity argon, and the output ion density is larger than or equal to 10 ions / cm. The invention further provides a cleaning method of the electrostatic chuck cleaning equipment, particles on the surface of an electrostatic chuck are cleaned and removed through the synergistic effect of combination of dry ice particle micro-explosion shock waves and particle charges neutralized by ionization argon flow, and the electrostatic chuck cleaning equipment has the beneficial effects that the removal rate is high, the flatness of the surface after cleaning is good, and the failure rate of repeated use is low.

Description

Technical Field

[0001] This invention belongs to the field of precision maintenance technology for semiconductor manufacturing equipment, specifically relating to an electrostatic chuck cleaning device and cleaning method. Background Technology

[0002] Electrostatic chucks suffer the following damage during plasma processing: Particle detachment from the ceramic matrix: High-frequency plasma bombardment causes microcracks in the surface AlN / Al2O3 ceramic, with detached particles ranging from 0.1 to 10 μm in size (SEM analysis data); Charged adsorption effect: Particles carry static charges in the plasma environment (surface potential can reach ±200V) and are strongly adsorbed onto the chuck surface by Coulomb forces. This damage severely affects the performance of the electrostatic chuck, necessitating regular cleaning and maintenance of its surface.

[0003] Traditional cleaning methods have the following limitations: 1. Wet cleaning, which uses ultrasonic waves and solvents, can easily cause liquid to seep into the electrode layer, leading to short circuits and a general failure rate of >18%. 2. The purely physical method of mechanical brushing can easily cause scratches on the surface of the electrostatic chuck, and the Ra value may increase from 0.05 μm to 0.2 μm; 3. Gas purging has limited cleaning effectiveness, with a removal rate of <40% for charged particles.

[0004] Therefore, there is an urgent need to design and develop a high-efficiency cleaning device for electrostatic chucks to remove and maintain the surface contaminants of electrostatic chucks. Summary of the Invention

[0005] The purpose of this invention is to provide a device and method for cleaning particulate contamination on the surface of an electrostatic chuck (ESC) based on the synergistic effect of dry ice particle impact and ionized gas. This method is applicable to the online maintenance of ceramic-based electrostatic chucks such as aluminum nitride (AlN) and alumina (Al2O3).

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, this application provides an electrostatic chuck cleaning device, comprising: a preheating platform with a built-in heater; a dry ice generation module for solidifying liquid CO2 into dry ice particles, and also including a centrifugal particle size classifier; a gas-solid mixing acceleration device: the jet shaft is at an angle of 10~45° to the plane of the electrostatic chuck, accelerating the mixture of dry ice particles and compressed air to supersonic speeds; and an ionization gas generating device: the jet shaft is parallel to the plane of the electrostatic chuck, and high-frequency high-voltage electrodes ionize high-purity argon gas, outputting an ion density ≥10. 9 ions / cm³.

[0007] Secondly, this application provides an electrostatic chuck cleaning method, comprising the following steps: Provide an electrostatic chuck cleaning apparatus as described in the first aspect of this application; S1. Preprocessing: The electrostatic chuck is placed on a preheating platform and heated to 120~150 ℃ by an infrared heater; S2. Collaborative cleaning: The mixture of dry ice particles and compressed air is sprayed at an angle of 10 to 45 degrees to the plane of the electrostatic chuck, and the surface of the electrostatic chuck is scanned in a spiral path. The ionized gas jet axis is parallel to the plane of the electrostatic chuck, and the ionized argon gas flow covers the jet, maintaining an ion density of 10. 9 ~10¹ 0 ions / cm³; S3. In-situ cleaning: Microwave radiation treatment: The electrostatic chuck is placed in microwave radiation, and the condensate is rapidly evaporated by continuous microwave radiation, followed by purging with high-purity nitrogen.

[0008] In some possible implementations, the dry ice particles have a particle size of 20-60 μm.

[0009] In some possible implementations, the dry ice particles have a particle size of 45-55 μm.

[0010] In some possible implementations, the coefficient of variation (CV) of the dry ice particle size distribution is <5%.

[0011] In some possible implementations, the impact velocity of the dry ice particles is preferably 400-500 m / s.

[0012] In some possible implementations, the gas-solid mixing mass ratio is 1:5 to 1:15, preferably 1:10 to 1:15.

[0013] In some possible implementations, the dry ice particle flow rate is 10~30 g / s.

[0014] In some possible implementations, the argon flow rate is 10-20 L / min.

[0015] In some possible implementations, the surface potential of the output ions is -5 to 5 V. Beneficial effects

[0016] The synergistic effect of combining the micro-explosion shock wave of dry ice particles with the neutralization of particle charge by ionized argon gas flow is used to clean and remove particles from the surface of the electrostatic chuck. This method has the advantages of high cleaning rate, good surface smoothness after cleaning, and low failure rate after repeated use. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only a part of the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the functional modules of an electrostatic chuck cleaning device.

[0019] Figure 2 This is a schematic diagram of the cleaning platform structure in an electrostatic chuck cleaning device.

[0020] Figure label: 1: Preheating platform; 2: Injector port of the ionized gas generator; 3: Inlet for injecting a mixture of dry ice pellets and compressed air; 4: The angle between the direction of the dry ice particle and compressed air mixture injection and the plane of the electrostatic chuck; 5: Exhaust port; 6: Electrostatic chuck. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and not to limit the scope of the invention. Specific conditions not specified in the examples shall be carried out under conventional conditions or the manufacturer's recommended conditions. If the manufacturers of the reagents or instruments used are not specified, they can be conventional products that are commercially available or purchased.

[0022] It should be noted that the following embodiments are examples of this application and are used only to illustrate this application, and are not intended to limit this application. Other combinations and various modifications within the scope of this application are possible without departing from the spirit or scope of this application.

[0023] The electrostatic chuck cleaning equipment and cleaning method provided in this application will be described in detail below.

[0024] <Electrostatic suction cup cleaning equipment> This embodiment provides an electrostatic chuck cleaning device, which includes a preheating platform, a dry ice generation module, a gas-solid mixing acceleration device, and an ionized gas generation device.

[0025] The preheating platform has a built-in infrared heater that can preheat the electrostatic chuck it carries to 120~150 ℃, preventing condensation.

[0026] The dry ice generation module includes a liquid CO2 storage tank, an expansion valve directly connected to it, a snowflake dry ice granulator with a screen aperture of 20±3 μm to convert liquid CO2 into dry ice particles, and a centrifugal particle size classifier to output dry ice particles with uniform particle size. The coefficient of variation (CV) of the dry ice particle size distribution is <5%.

[0027] Dry ice particles (solid CO2) undergo a sublimation phase transition upon impact with a surface, resulting in instantaneous volume expansion. ΔV / V0 = (ρ s / ρ g ) - 1 ≈ 845 times: ρ s Density of solid CO2 (1560 kg / m³). ρ g Density of gaseous CO2 (1.84 kg / m³).

[0028] This expansion creates a micro-explosion effect, and the shock wave pressure calculated by the dry ice particle phase transition impact dynamics model is: P = K·ρ·v² K: Material constant (0.6 for ceramics); ρ: Density of dry ice particles; v: Impact speed.

[0029] In this embodiment, the impact velocity of the dry ice particles is greater than 340 m / s. The shock wave generated by the sublimation phase change of the dry ice particles upon impact with the electrostatic chuck surface removes particles detached from the electrostatic chuck surface. The jet axis of the gas-solid mixture forms an angle of 10° to 45° with the plane of the electrostatic chuck. This small angle of incidence (10° to 45°) facilitates the detachment of particles from the electrostatic chuck surface in the reflected shock wave, preventing them from rebounding and adsorbing back onto the surface, thus improving the removal rate.

[0030] To ensure precise cleaning, the dry ice particle size range is 25~60 μm, the dry ice particle flow rate is 10~30 g / s, and the gas-solid mixing mass ratio is 1:5~1:15.

[0031] To achieve better removal results, the angle between the jet axis of the gas-solid mixture and the plane of the electrostatic chuck is preferably 15~25°; the impact velocity of the dry ice particles is preferably 400~500 m / s; the particle size range of the dry ice particles is preferably 45~55 μm; and the mass ratio of the gas-solid mixture is preferably 1:10~1:15.

[0032] In this embodiment, the ionization gas generator ionizes argon gas through a 10 kHz high-frequency, 8 kV high-voltage electrode. The argon gas flow rate is 10~20 L / min, and the output ion density is ≥10. 9The ions / cm³ ion surface potential is -5~5 V. The ionized gas jet axis is parallel to the plane of the electrostatic chuck. The ions in the jet ionized argon gas flow can neutralize the charge on the charged particles, preventing the dust removed by the dry ice shock wave from being electrostatically adsorbed back onto the surface of the electrostatic chuck.

[0033] <Electrostatic Chuck Cleaning Method> The electrostatic chuck cleaning method provided in this embodiment includes the following specific steps: S1. Pretreatment: Place the electrostatic chuck on the preheating platform and heat it to 120~150 ℃ using an infrared heater; S2. Collaborative cleaning: The dry ice particle and compressed air mixture is sprayed at an angle of 10-45° to the plane of the electrostatic chuck, and the spray path is used to scan the area to be cleaned on the surface of the electrostatic chuck. The dry ice particle size is 25-60 μm, preferably 45-55 μm; the coefficient of variation (CV) of the dry ice particle size distribution is <5%; the average impact velocity of the dry ice particles is greater than 340 m / s, preferably 400-500 m / s; the gas-solid mixing mass ratio is 1:5-1:15, preferably 1:10-1:15; and the dry ice particle flow rate is 10-30 g / s.

[0034] The ionized gas jet axis is parallel to the plane of the electrostatic chuck, and ionized argon gas covers the area to be cleaned, maintaining an ion density of 10. 9 ~10¹ 0 ions / cm³; argon flow rate is 10~20 L / min, and the surface potential of the output ions is -5~5 V.

[0035] S3. In-situ cleaning: Microwave radiation treatment: The electrostatic chuck is placed in microwave radiation and continuously irradiated for 15~45s to rapidly evaporate the condensate. Then, high-purity nitrogen is used to purge the water vapor, providing an inert environment to prevent oxidation of the ceramic surface of the electrostatic chuck and restore the insulating properties of the dielectric layer. Example

[0036] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that the embodiments are merely illustrative of the present invention and should not be construed as specific limitations thereof.

[0037] In this embodiment, the raw materials are all commercially available bulk industrial products, and the manufacturers include BASF, Wanhua Chemical, Asahikawa Chemical, Huafeng, etc.

[0038] Example 1

[0039] This embodiment utilizes the electrostatic chuck cleaning equipment and method of the present invention to clean electrostatic chucks contaminated with ceramic particles on their surface, and includes the following steps: S1. Preprocessing: Place the electrostatic chuck to be cleaned on the preheating platform and heat it to 120 ℃ using an infrared heater.

[0040] S2. Collaborative cleaning: The mixture of dry ice particles and compressed air is sprayed at a 15° angle to the plane of the electrostatic chuck, and the surface of the electrostatic chuck is scanned in a spiral path. The dry ice particle size is 55 μm, the coefficient of variation (CV) of the dry ice particle size distribution is 3.7%, the average impact velocity of the dry ice particles is 424 m / s, the mass ratio of compressed air to dry ice particles is 1:10, and the dry ice particle flow rate is 15 g / s. The ionized gas jet axis is parallel to the plane of the electrostatic chuck, and the ionized argon gas flow covers the jet, maintaining an ion density of 10. 9 ~10¹ 0 ions / cm³; argon flow rate is 10 L / min, and the surface potential of the output ions is -5~5 V.

[0041] S3. In-situ cleaning: Microwave radiation treatment: The electrostatic chuck is placed in microwave radiation and continuously irradiated for 45 seconds to rapidly evaporate the condensate. Then, high-purity nitrogen is used to purge the water vapor, providing an inert environment to prevent oxidation of the ceramic surface of the electrostatic chuck and restore the insulating properties of the dielectric layer. Example 2

[0042] The cleaning method in Example 2 is the same as that in Example 1, except that the direction of the dry ice particle and compressed air mixture is at a 45° angle to the plane of the electrostatic chuck. Example 3

[0043] The cleaning method in Example 3 is the same as that in Example 1, except that the dry ice particles have a diameter of 25 μm. Example 4

[0044] The cleaning method in Example 4 is the same as that in Example 1, except that the mass ratio of compressed air to dry ice particles is 1:5. Example 5

[0045] The cleaning method in Example 5 is the same as that in Example 1, except that the argon flow rate is 5 L / min. Example 6

[0046] The cleaning method in Example 6 is the same as that in Example 1, except that the surface potential of the output ions is -2 to 2V.

[0047] Comparative Example 1 The cleaning method of Comparative Example 1 is similar to that of Example 1, except that the direction of the dry ice particle and compressed air mixture is at a 90° angle to the plane of the electrostatic chuck.

[0048] Comparative Example 2 The cleaning method of Comparative Example 2 is similar to that of Example 1, except that ionized argon gas flow was not used to cover the surface of the electrostatic chuck in step S2.

[0049] Comparative Example 3 The cleaning method of Comparative Example 3 is similar to that of Example 1, except that the dry ice particle and compressed air mixture was not used to spray the surface of the electrostatic chuck in step S3.

[0050] Comparative Example 4 The cleaning method of Comparative Example 4 is similar to that of Example 1, except that the microwave radiation treatment in step S3 was not used.

[0051] Comparative Example 5 Comparative Example 5 uses a traditional wet cleaning method, which involves ultrasonic cleaning and solvent wiping. The alumina ceramic surface of the electrostatic chuck to be cleaned is immersed in isopropanol solvent, wiped with hydrochloric acid and hydrogen peroxide, and then subjected to ultrasonic treatment.

[0052] The embodiments and comparative examples involving electrostatic chuck cleaning methods are evaluated using the following methods.

[0053] Clearance rate evaluation The number of particles with a diameter > 0.5 μm was detected before and after cleaning with an electrostatic chuck using an SP2 scanner. The number of particles before cleaning was N1, and the number of particles after cleaning was N2. The removal rate was C = (N1 - N2) / N1.

[0054] Surface flatness evaluation The flatness of the surface of the unused electrostatic chuck and the surface of the cleaned electrostatic chuck were tested using a laser interferometer. The test wavelength was 632.8 nm. The flatness of the surface of the unused electrostatic chuck was P0, and the flatness of the surface of the cleaned electrostatic chuck was P2. ΔP = P2 - P1.

[0055] Failure rate evaluation The cleaned electrostatic chuck was used for adsorption and desorption tests on wafers. The tests were repeated 1000 times, and the number of short circuits and other faults was recorded, as well as the failure rate.

[0056] The evaluation results of the cleaning effect of the electrostatic chuck in the examples and comparative examples are shown in Table 1.

[0057] Table 1

[0058] It should be noted that, based on the explanations and descriptions in the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and alterations to the present invention should also be within the scope of protection of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the invention.

Claims

1. An electrostatic chuck cleaning device, characterized in that, include: Preheating platform: Built-in heater; Dry ice generation module: solidifies liquid CO2 into dry ice particles, and also includes a centrifugal particle size classifier; Gas-solid mixing acceleration device: The jet shaft is at an angle of 10~45° to the plane of the electrostatic chuck, which accelerates the mixture of dry ice particles and compressed air to supersonic speed; Ionized gas generator: The jet shaft is parallel to the plane of the electrostatic chuck, and high-frequency high-voltage electrodes ionize high-purity argon gas, with an output ion density ≥10. 9 ions / cm³.

2. A method for cleaning with an electrostatic chuck, characterized in that, Includes the following steps: Provide an electrostatic chuck cleaning device as described in claim 1; S1. Preprocessing: The electrostatic chuck is placed on a preheating platform and heated to 120~150 ℃ by an infrared heater; S2. Collaborative Cleaning: The mixture of dry ice particles and compressed air is sprayed at an angle of 10 to 45 degrees to the plane of the electrostatic chuck, and the surface of the electrostatic chuck is scanned in a spiral path. The ionized gas jet axis is parallel to the plane of the electrostatic chuck, and the ionized argon gas flow covers the jet, maintaining an ion density of 10. 9 ~10¹ 0 ions / cm³; S3. In-situ cleaning: Microwave radiation treatment: The electrostatic chuck is placed in microwave radiation, and the condensate is rapidly evaporated by continuous microwave radiation, followed by purging with high-purity nitrogen.

3. The electrostatic chuck cleaning method according to claim 2, characterized in that, The dry ice particles have a particle size of 20~60 μm.

4. The electrostatic chuck cleaning method according to claim 2, characterized in that, The dry ice particles have a particle size of 45~55 μm.

5. The electrostatic chuck cleaning method according to claim 2, characterized in that, The coefficient of variation (CV) for the dry ice particle size distribution is less than 5%.

6. The electrostatic chuck cleaning method according to claim 2, characterized in that, The preferred impact velocity of dry ice particles is 400~500 m / s.

7. The electrostatic chuck cleaning method according to claim 2, characterized in that, The gas-solid mixing mass ratio is 1:5 to 1:15, preferably 1:10 to 1:

15.

8. The electrostatic chuck cleaning method according to claim 2, characterized in that, The dry ice particle flow rate is 10~30 g / s.

9. The electrostatic chuck cleaning method according to claim 2, characterized in that, The argon flow rate is 10~20 L / min.

10. The electrostatic chuck cleaning method according to claim 2, characterized in that, The surface potential of the output ions is -5 to 5 V.

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