Anti-metal contamination liner plate of ion implanter and preparation method thereof

Abstract

The application discloses an anti-metal contamination inner lining plate of an ion implanter and a preparation method thereof, and relates to the technical field of ion implantation equipment. The anti-metal contamination inner lining plate comprises an aluminum alloy base body, an intermediate barrier layer formed on the surface of the aluminum alloy base body through an anodic oxidation process, and a silicon coating layer covering the surface of the intermediate barrier layer. The intermediate barrier layer has conductivity, the surface resistivity thereof is less than or equal to 0.1 ohm cm, and the thickness of the intermediate barrier layer is 0.5-5 micrometers. The inner lining plate provided by the application can not only maintain the structural strength and heat conduction performance of the aluminum alloy base body, but also prevent metal particle contamination caused by ion beam sputtering, can ensure that the inner lining plate has good conductivity, avoids charge accumulation and static sparking, and can also realize secondary protection after the silicon coating layer is broken down, so that metal contamination in the whole life cycle is avoided.

Description

Technical Field

[0001] This invention relates to the field of ion implantation equipment technology, and more specifically, to an anti-metal contamination liner for an ion implanter and its preparation method. Background Technology

[0002] In semiconductor manufacturing processes, ion implantation is an important doping method. Ion implantation chambers typically contain liners to protect the chamber walls, guide the beam, or collect sputtered products. Existing liners mainly use the following types: traditional aluminum alloy liners, liners with protective coatings, and removable shielding plates.

[0003] Traditional aluminum alloy substrates offer advantages such as light weight, ease of processing, and good thermal conductivity. However, under prolonged high-energy ion beam bombardment, the aluminum alloy surface is highly susceptible to sputtering, producing tiny aluminum particles or aluminum-containing compound particles. If these metal particles settle on the wafer surface, they cause metal contamination, severely impacting the device's electrical performance (such as increased leakage current) and yield.

[0004] Existing liners with protective coatings have the problem of easy coating peeling. Once the coating is partially damaged due to long-term bombardment, the exposed aluminum alloy substrate will still be sputtered, reintroducing metal contamination.

[0005] For solutions using removable shielding plates, the shielding plates themselves are still mostly made of metal (such as aluminum alloy), which will still cause metal contamination after sputtering; and they need to be disassembled and cleaned frequently, resulting in long equipment downtime and high maintenance costs; in addition, secondary pollution may be caused during the cleaning process.

[0006] Therefore, how to provide an inner liner that can both utilize the processing and thermal conductivity advantages of aluminum alloy substrates and fundamentally avoid metal contamination caused by sputtering is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide an anti-metal contamination liner plate for an ion implanter, its preparation method and application. The liner plate provided by the present invention can maintain the structural strength and thermal conductivity of the aluminum alloy substrate, prevent metal particle contamination caused by ion beam sputtering, ensure that the liner plate has good conductivity, avoid charge accumulation and electrostatic arcing, and also achieve secondary protection after the silicon coating is broken down, ensuring no metal contamination throughout the entire life cycle.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides an anti-metal contamination liner for an ion implanter, comprising: Aluminum alloy substrate; An intermediate barrier layer is formed on the surface of the aluminum alloy substrate by anodizing. The intermediate barrier layer is conductive and has a surface resistivity of ≤0.1Ω. cm, with a thickness of 0.5~5μm; A silicon coating that covers the surface of the intermediate barrier layer.

[0009] Furthermore, the silicon coating is deposited on the surface of the intermediate barrier layer by a spraying process, and its thickness is 0.05~0.15mm.

[0010] It should be noted that the intermediate barrier layer in this invention is conductive because: (a) The film is extremely thin (<5μm), allowing electrons to tunnel through; (b) The film contains impurities such as water of crystallization and chromate ions, forming conductive channels; (c) Unlike ordinary sulfuric acid anodizing (film thickness 10-25 μm, insulation), the thin-layer structure of the present invention ensures conductivity.

[0011] In a second aspect, the present invention provides a method for preparing an anti-metal contamination liner plate for an ion implanter as described above, comprising the following steps: (1) Substrate pretreatment: The aluminum alloy substrate is machined and formed into the required inner lining plate shape, and then cleaned. (2) The cleaned aluminum alloy substrate is subjected to alkaline degreasing treatment; (3) The aluminum alloy substrate after alkaline degreasing is subjected to pickling and activation treatment to obtain the pickled and activated aluminum alloy substrate; (4) Preparation of intermediate barrier layer: Using the aluminum alloy substrate after pickling and activation in step (3) as the anode, a multi-step conductive anodizing treatment is carried out under the conditions of current density of 1~5A / dm² and oxidation voltage of 10~30V to prepare an intermediate barrier layer on the aluminum alloy substrate. After cleaning and drying, it is ready. (5) The aluminum alloy substrate after the intermediate barrier layer is prepared is preheated; (6) Spraying silicon coating: High-purity silicon powder is sprayed multiple times on the surface of the intermediate barrier layer after preheating using plasma spraying equipment to form a silicon coating.

[0012] Further, in step (1), the cleaning includes ultrasonic cleaning with acetone for 5-15 minutes, rinsing with deionized water, and drying; In step (2), during the alkaline degreasing treatment, the degreasing solution contains sodium hydroxide with a mass concentration of 5-8 wt% and sodium carbonate with a mass concentration of 3-5 wt%, the treatment time is 3-5 min, and the treatment temperature is 50-60℃. In step (3), the activation treatment is performed by using dilute nitric acid with a mass concentration of 5-10wt% at room temperature for 1-2 minutes.

[0013] Further, in step (4), the multi-step conductive anodizing process includes: a first stage of treatment at 5-15V for 2-5 minutes, a second stage of treatment at 15-25V for 5-10 minutes, and a third stage of treatment at 10-15V for 2-3 minutes; The electrolyte contains chromic acid at a concentration of 6-10 g / L, sodium dichromate at a concentration of 10-15 g / L, and sodium fluoride at a concentration of 1-5 g / L. The processing temperature is 20~30℃.

[0014] The multi-step conductive anodizing process includes a first stage that forms an extremely thin initial oxide layer with a thickness of less than 0.5 μm to ensure conductivity; a second stage that increases the film thickness and density while maintaining conductivity; and a third stage that appropriately reduces the voltage to seal any excessively large pores while retaining a moderate microporous structure to improve adhesion to the silicon coating.

[0015] In this invention, when performing conductive anodizing, the cathode plate can be made of a material that does not react with the electrolyte, such as lead plate or graphite.

[0016] Furthermore, in step (6), the high-purity silicon powder has a purity greater than 99.99%, a particle size of 20~60μm, and a morphology of spherical or near-spherical, which is beneficial to its flowability.

[0017] Furthermore, in step (6), The number of spraying passes is 4 to 10, the thickness of each pass is 10 to 25 μm, the spraying power is 30 to 50 kW, the argon flow rate is 40 to 60 L / min, the hydrogen flow rate is 8 to 12 L / min, the powder feeding rate is 20 to 40 g / min, the spraying distance is 100 to 150 mm, and the spray gun moving speed is 500 to 1000 mm / s.

[0018] Furthermore, in step (6), after each coat is sprayed, the coating is left to stand for 20-40 seconds for interlayer cooling. Preferably, high-pressure, low-temperature inert gas can be introduced for cooling.

[0019] Furthermore, after the coating reaches the required thickness, allow it to cool naturally to room temperature. Gently brush off any loose powder from the surface with a soft brush, and then blow the surface with compressed air (pressure 0.2-0.3 MPa).

[0020] In a third aspect, the present invention provides an ion implantation chamber, including the anti-metal contamination liner of the ion implanter described above.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The inner lining plate provided by the present invention has a dual protection mechanism, which can completely eliminate the risk of metal contamination. When the outer silicon coating is intact, the ion beam sputtering product is silicon particles, which will not cause metal contamination. Even if the outer silicon coating is bombarded for a long time and partially consumed, the ion beam will bombard the middle barrier layer. The middle barrier layer is formed by anodizing the surface of the aluminum alloy substrate. It is an alumina ceramic layer. The product of sputtering the alumina is Al2O3 particles or aluminum oxide, which are stable ceramic phases. They will not form deep-level impurities in silicon and are not "metal contamination" in semiconductor processes. Compared with the prior art where the coating breaks down and directly exposes the aluminum alloy substrate (producing aluminum particle contamination), the present invention achieves true metal contamination-free throughout the entire life cycle.

[0022] (2) The intermediate barrier layer of the present invention is conductive and its surface resistivity is ≤0.1Ω. The cm ensures that the charge generated by the ion beam bombardment can be conducted to the aluminum alloy substrate through the intermediate barrier layer; the aluminum alloy substrate is grounded through the mounting surface (the side of the aluminum alloy substrate away from the intermediate barrier layer), which can promptly conduct away the accumulated charge; effectively avoiding electrostatic arcing (arc discharge) caused by charge accumulation, and ensuring process stability.

[0023] (3) In this invention, the intermediate barrier layer and the aluminum alloy substrate are an integrated in-situ growth structure with no clear physical interface. The thermal expansion coefficient is gradient transition, which eliminates the abrupt heterogeneous interface between the coating and the substrate. This can reduce the internal stress caused by the mismatch of thermal expansion coefficients. The silicon coating is sprayed on the surface of the intermediate barrier layer. Both are ceramic materials with good chemical compatibility. The bonding strength is significantly higher than that of the scheme of directly spraying on the metal surface. (4) In this invention, the process is mature and the cost is controllable. The anodizing process can be carried out at room temperature without the need for refrigeration equipment and the energy consumption is low. The cost of silicon powder raw materials is much lower than that of rare earth oxides (such as yttrium oxide) and high-purity silicon carbide materials. The plasma spraying process is mature and suitable for industrial mass production. The overall manufacturing cost is controllable. Detailed Implementation

[0024] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] Unless otherwise specified, all materials and reagents used in this invention are available from commercially available products in the field.

[0027] Example 1 A method for preparing a metal-contamination-resistant inner liner for an ion implanter includes the following steps: Step 1: Matrix Pretreatment The substrate made of 6061 aluminum alloy is machined and shaped into the desired inner lining plate shape. Acetone ultrasonic cleaning for 10 minutes to remove surface oil; Rinse with deionized water and dry.

[0028] Step 2: Alkaline degreasing After drying, the aluminum alloy substrate is treated with a degreasing solution containing 6 wt% sodium hydroxide and 4 wt% sodium carbonate at 55°C for 4 minutes to remove the natural oxide layer and residual oil on the surface.

[0029] Step 3: Acid washing and activation The degreased aluminum alloy substrate was treated with 8wt% dilute nitric acid at room temperature for 1.5 minutes to neutralize the residual alkali and activate the surface.

[0030] Step 4: Conductive Anodizing Treatment Using an activated aluminum alloy substrate as the anode and graphite as the cathode, an electrolytic oxidation process was performed in an electrolytic cell containing an electrolyte solution. The electrolyte solution included 8 g / L chromic acid, 12 g / L sodium dichromate, 2 g / L sodium fluoride, and the remainder being deionized water. The temperature was controlled at 25℃±2℃, and the anodic current density was 3 A / dm². The voltage control included: first, treatment at 8V for 3 minutes, then at 18V for 10 minutes, and finally at 10V for 2 minutes. This formed a conductive anodic oxide film with a thickness of approximately 2 μm, i.e., an intermediate barrier layer. Clean thoroughly with deionized water; then dry completely.

[0031] Step 5: Preheating After drying with hot air at 80℃ for 10 minutes, proceed to the next step immediately. Step Six: Silicon Coating Spraying Atmospheric plasma spraying equipment was used, with high-purity silicon powder (purity greater than 99.99%, particle size 20-40μm) as the spraying material. Under the conditions of 40kW power, argon flow rate (main gas) 50L / min, hydrogen flow rate (auxiliary gas) 10L / min, powder feed rate 30g / min, spraying distance 120 mm, and spray gun moving speed 800 mm / s, grid path scanning spraying was used, and a total of 10 coats were applied, each coat with a thickness of about 10μm. A silicon coating with a thickness of 0.1mm ± 0.02mm was obtained. After each coat, wait 30 seconds to avoid the accumulation of thermal stress.

[0032] Step 7: Post-processing After spraying, allow it to cool naturally to room temperature, then gently brush off any loose powder with a soft brush, and finally blow the surface with compressed air (pressure 0.2-0.3 MPa).

[0033] A metal-resistant liner plate A for an ion implanter was prepared.

[0034] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that: In step four, no conductive treatment is performed; the material is directly immersed in the electrolyte for 30 minutes to prepare an intermediate barrier layer with a thickness of approximately 10 μm.

[0035] With everything else remaining unchanged, the inner lining plate B was prepared in this comparative example.

[0036] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that: Steps two through five are omitted, and the silicon coating is directly sprayed onto the surface of the aluminum alloy substrate, i.e., the intermediate barrier layer is omitted. The inner lining plate C was prepared in this comparative example.

[0037] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that: In step four, constant voltage conductive oxidation is used, which means that the voltage control includes: directly processing at 18V for 15 minutes; the rest remains unchanged. The inner lining plate D was prepared in this comparative example.

[0038] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that: In step four, voltage control includes: first processing at 8V for 5 minutes, then processing at 18V for 10 minutes, with the rest remaining unchanged; The inner lining plate E was prepared in this comparative example.

[0039] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that: Step five is omitted, and the rest remains unchanged; the inner lining plate F is prepared in this comparative example.

[0040] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that: In step six, when spraying the silicon coating, the spraying distance is 80 mm and the spray gun moving speed is 400 mm / s; Everything else remains the same; the inner lining plate G was prepared in this comparative example.

[0041] The performance of the prepared liner plate (AG) was tested, including: 1. Combined with strength testing The scratch test method is used to test the bonding strength between the silicon coating and the intermediate barrier layer or between the silicon coating and the aluminum alloy substrate. The standard critical load requirement is ≥25N.

[0042] 2. Resistant to ion sputtering contamination, simulated ion beam bombardment (bombardment conditions: energy 500 eV, dose 1 × 10⁻⁶). 16 ions / cm 2 The amount of aluminum precipitated was then detected by ICP-MS; ≤1×10⁻⁶ -3 μg / cm 2 No obvious metal contamination; 3. Visual inspection: Silicon coating standard: uniform, dense, without peeling or cracks; Intermediate barrier layer standard: slightly transparent iridescent.

[0043] The test results are shown in Table 1 below: Table 1:

[0044] In summary, the anodizing process can form a conductive intermediate barrier layer between the aluminum alloy substrate and the silicon coating. This can effectively conduct away the charge generated by ion beam bombardment, avoiding electrostatic arcing caused by charge accumulation. It can also improve the bonding strength between the layer and the aluminum alloy substrate and the silicon coating, extending the service life of the inner liner. In addition, it can effectively reduce metal contamination during ion implantation and ensure process stability.

[0045] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A metal-contamination-resistant inner liner for an ion implanter, characterized in that, include: Aluminum alloy substrate; An intermediate barrier layer is formed on the surface of the aluminum alloy substrate by anodizing. The intermediate barrier layer is conductive and has a surface resistivity of ≤0.1Ω. cm, with a thickness of 0.5~5μm; A silicon coating that covers the surface of the intermediate barrier layer; The method for preparing the anti-metal contamination lining panel includes the following steps: (1) Substrate pretreatment: The aluminum alloy substrate is machined and formed into the required inner lining plate shape, and then cleaned. (2) The cleaned aluminum alloy substrate is subjected to alkaline degreasing treatment; (3) The aluminum alloy substrate after alkaline degreasing is subjected to pickling and activation treatment to obtain the pickled and activated aluminum alloy substrate; (4) Preparation of intermediate barrier layer: Using the aluminum alloy substrate after acid pickling and activation in step (3) as the anode, perform multi-step conductive anodizing treatment at a current density of 1~5 A / dm² to prepare an intermediate barrier layer on the aluminum alloy substrate. After cleaning and drying, it is ready. The multi-step conductive anodizing process includes: a first stage of treatment at 5-8V for 2-5 minutes, a second stage of treatment at 18-25V for 5-10 minutes, and a third stage of treatment at 10-15V for 2-3 minutes. The electrolyte contains chromic acid at a concentration of 6-10 g / L, sodium dichromate at a concentration of 10-15 g / L, and sodium fluoride at a concentration of 1-5 g / L. The processing temperature is 20~30℃; (5) The aluminum alloy substrate after the intermediate barrier layer is prepared is preheated; (6) Spraying silicon coating: High-purity silicon powder is sprayed multiple times on the surface of the intermediate barrier layer after preheating using plasma spraying equipment to form a silicon coating. The number of spraying passes is 4 to 10, the thickness of each spray is 10 to 25 μm, the spraying power is 30 to 50 kW, the argon flow rate is 40 to 60 L / min, the hydrogen flow rate is 8 to 12 L / min, the powder feeding rate is 20 to 40 g / min, the spraying distance is 100 to 150 mm, and the spray gun moving speed is 500 to 1000 mm / s.

2. The anti-metal contamination liner of the ion implanter according to claim 1, characterized in that, The silicon coating is deposited on the surface of the intermediate barrier layer by a spraying process, and the thickness of the silicon coating is 0.05~0.15mm.

3. The anti-metal contamination liner of the ion implanter according to claim 1, characterized in that, In step (1), the cleaning includes ultrasonic cleaning with acetone for 5-15 minutes, rinsing with deionized water, and drying. In step (2), during the alkaline degreasing treatment, the degreasing solution contains sodium hydroxide with a mass concentration of 5-8% and sodium carbonate with a mass concentration of 3-5%, the treatment time is 3-5 minutes, and the treatment temperature is 50-60℃. In step (3), during the acid washing and activation treatment, dilute nitric acid with a mass concentration of 5-10% is used to treat at room temperature for 1-2 minutes.

4. The anti-metal contamination liner of the ion implanter according to claim 1, characterized in that, In step (6), the high-purity silicon powder has a purity greater than 99.99% and a particle size of 20~60μm.

5. The anti-metal contamination liner of the ion implanter according to claim 1, characterized in that, In step (6), after each coat is sprayed, the coating is left to stand for 20 to 40 seconds for interlayer cooling.

6. An ion implantation chamber, characterized in that, The anti-metal contamination liner of the ion implanter as described in any one of claims 1 to 5.

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