Aluminum alloy corrosion-resistant composite coating as well as preparation method and application thereof

Abstract

The invention belongs to the field of semiconductors, and particularly relates to an aluminum alloy corrosion-resistant composite coating and a preparation method and application thereof. The composite coating comprises an AlF3 coating and an Al2O3 coating, the AlF3 coating is prepared by adopting an electrochemical method, and the Al2O3 coating is prepared by adopting an atomic layer deposition method. The electrochemical aluminum fluoride layer prepared by adopting the electrochemical method has relatively high breakdown voltage resistance; the aluminum oxide coating prepared by adopting an atomic layer deposition (ALD) method is relatively compact and can effectively isolate corrosion of halogen elements (such as F and Cl). The composite coating prepared by the method can meet the use conditions of the aluminum alloy in PECVD (Plasma Enhanced Chemical Vapor Deposition) and PEALD equipment.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and particularly relates to an aluminum alloy corrosion-resistant composite coating, a preparation method thereof, and an application thereof. Background Art

[0002] In the prior art, many aluminum alloy parts with different grades in the chambers of PECVD, PEALD and other equipment will be eroded by F ions during the process. For the 1-series aluminum alloy used for heating plates, the existing solution is to grow a fluorination layer in situ by gas dissociation in high-temperature environments with aluminum alloy parts in PECVD, PEALD and other equipment as a protective layer against F-ion erosion or to prepare an electrochemically fluorinated film by an electrochemical fluorination method. However, the mechanical strength of the 1-series aluminum alloy is insufficient and cannot meet specific requirements.

[0003] The mechanical strength of the 7-series or other alloys meets the requirements. However, due to the relatively large number of impurities in the 7-series aluminum alloy and the relatively little use and research on it, if it is necessary to use the 7-series or other grades of aluminum alloy to improve the mechanical properties in the same environment, there is no stable coating protection solution. Summary of the Invention

[0004] The purpose of the present invention is to provide an aluminum alloy corrosion-resistant composite coating, a preparation method thereof, and an application thereof.

[0005] In the first aspect of the present invention, a composite coating is provided. The composite coating includes an AlF3 coating and an Al2O3 coating. The AlF3 coating is prepared by an electrochemical method, and the Al2O3 coating is prepared by an atomic layer deposition method.

[0006] In one or more embodiments, the composite coating has one or more of the following characteristics:

[0007] The thickness of the AlF3 coating is 5-20 μm;

[0008] The thickness of the Al2O3 coating is 150-700 nm;

[0009] The breakdown voltage resistance of the composite coating is 450-1000 V.

[0010] In the second aspect of the present invention, an aluminum alloy part is provided. The aluminum alloy part is an aluminum alloy with a composite coating on its surface. An AlF3 coating is provided on the surface of the aluminum alloy, and an Al2O3 coating is provided on the AlF3 coating. The AlF3 coating is prepared by an electrochemical method, and the Al2O3 coating is prepared by an atomic layer deposition method.

[0011] In one or more embodiments, the aluminum alloy is selected from one or more of 1-series aluminum alloy, 3-series aluminum alloy, 5-series aluminum alloy, 6-series aluminum alloy and 7-series aluminum alloy.

[0012] In a third aspect of the present invention, there is provided a semiconductor device including the aluminum alloy component described in the second aspect of the present invention.

[0013] In a fourth aspect of the present invention, there is provided a method for preparing the aluminum alloy component described in the second aspect of the present invention, the method including the steps of:

[0014] (1) Preparing an AlF3 coating on the surface of the aluminum alloy by an electrochemical method;

[0015] (2) Preparing an Al2O3 coating on the surface of the AlF3 coating by an atomic layer deposition method.

[0016] In one or more embodiments, the step (1) includes: providing an electrolyte with a solute of a fluoride salt, the fluoride salt including ammonium fluoride and optionally other fluoride salts, connecting the aluminum alloy as an anode to a power source, and preparing an electrochemically fluorinated film on the surface of the aluminum alloy by electrochemical fluorination, the concentration of fluoride ions in the electrolyte being 30 - 170 g / L.

[0017] In one or more embodiments, step (1) has one or more of the following characteristics:

[0018] The other fluoride salt is selected from one or two of potassium fluoride and sodium fluoride;

[0019] The solvent of the electrolyte is selected from one or two of ethanol and ethylene glycol;

[0020] The power source is a micro-arc power source;

[0021] The aluminum alloy is selected from 1xxx series aluminum alloy, 3xxx series aluminum alloy, 5xxx series aluminum alloy, 6xxx series aluminum alloy, and 7xxx series aluminum alloy;

[0022] The cathode is stainless steel, titanium alloy, or graphite;

[0023] The temperature of the electrolyte is 0 - 15 °C;

[0024] The conductivity of the electrolyte is 4 - 8 mS / cm;

[0025] The time of the electrochemical fluorination is 120 - 480 min;

[0026] The current density of the electrochemical fluorination is 8 - 30 A / dm 2 ;

[0027] The negative current density of the electrochemical fluorination is 0 - 10 A / dm 2 ;

[0028] The frequency of the electrochemical fluorination is 50 - 1500 HZ;

[0029] The duty cycle of the electrochemically fluorinated is 5-70%.

[0030] In one or more embodiments, step (2) has one or more of the following features:

[0031] The deposition temperature of the atomic layer deposition method is 250-350 °C;

[0032] The deposition pressure of the atomic layer deposition method is ≤10 torr;

[0033] The precursors of the atomic layer deposition method are trimethylaluminum and water.

[0034] In the fifth aspect of the present invention, a method for improving the breakdown voltage resistance and / or halogen element erosion resistance of aluminum alloy parts is provided. The method includes the steps of: preparing an AlF3 coating and an Al2O3 coating on the aluminum alloy surface by using the method described in the fourth aspect of the present invention.

[0035] The present invention has the following beneficial effects:

[0036] (1) The electrochemically fluorinated aluminum layer prepared by the electrochemical method of the present invention has a relatively high breakdown voltage resistance; the alumina coating prepared by the atomic layer deposition method (ALD) is relatively dense and can effectively isolate the erosion of halogen elements (such as F, Cl). The composite coating prepared in the above way can meet the use conditions of aluminum alloy in PECVD and PEALD equipment.

[0037] (2) The inventors found that after only preparing an electrochemically fluorinated film on the surface of the aluminum alloy, excellent breakdown voltage resistance can be ensured, but the aluminum alloy containing only the electrochemically fluorinated film will have a second phase precipitation at the interface between the film layer and the substrate, resulting in defects and unable to effectively block the erosion of halogen elements; after only preparing an ALD-deposited alumina film on the surface of the aluminum alloy, it has excellent resistance to halogen element (F, Cl) erosion, but the breakdown voltage resistance does not meet the requirements.

[0038] (3) In the present invention, the 7-series aluminum alloy is first electrochemically fluorinated and then ALD-deposited with alumina. The aluminum alloy containing the composite coating prepared in this way meets both the requirements of breakdown voltage resistance and halogen element erosion resistance, and the performance of the 7-series aluminum alloy after preparing the composite coating is similar to that of the 1-series aluminum alloy after preparing the composite coating, proving that the method for preparing the composite coating of the present invention will not affect the performance of the composite coating due to the complexity of the substrate (1-series, 7-series) composition. Description of the Drawings

[0039] Figure 1It is a schematic diagram of a device for preparing an electrochemically fluorinated film on the surface of an aluminum alloy in one or more embodiments of the present invention; wherein, A - aluminum alloy, B - electrolyte, C - micro-arc power supply, D - chiller, E - anode, F - cathode.

[0040] Figure 2 It is a schematic diagram of the device for the breakdown voltage resistance test in Test Example 1.

[0041] Figure 3 It is a schematic diagram of the hydrochloric acid corrosion resistance test method in Test Example 2; wherein, 1 - hydrochloric acid, 2 - test tube, 3 - adhesive, 4 - aluminum alloy test block.

[0042] Figure 4 It is a graph showing the fluorine corrosion resistance test results of different aluminum alloy test blocks in Test Example 3. Detailed implementation manners

[0043] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0044] The theories or mechanisms described and disclosed herein, whether right or wrong, shall not in any way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0045] In this article, terms such as "comprising", "including", "containing" and similar expressions cover the meanings of "consisting essentially of" and "consisting of". For example, when it is disclosed herein that "A comprises B and C", it should be considered that "A consists essentially of B and C" and "A consists of B and C" have been disclosed herein.

[0046] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of simplicity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0047] In this article, unless otherwise specified, the percentage refers to the mass percentage and the ratio refers to the mass ratio.

[0048] In this article, when describing embodiments or examples, it should be understood that it is not used to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0049] In this text, for the sake of brevity in description, not all possible combinations of all technical features in each implementation or embodiment are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0050] Composite Coating and Its Preparation Method

[0051] The composite coating of the present invention can effectively isolate the erosion of halogen elements (such as F, Cl), and has a relatively high breakdown voltage resistance. Therefore, the present application provides a composite coating, and the composite coating includes an AlF3 coating and an Al2O3 coating. Preferably, the composite coating is composed of an AlF3 coating and an Al2O3 coating, and does not contain other components. Preferably, the AlF3 coating of the composite coating is in direct contact with the aluminum alloy.

[0052] In some embodiments, the AlF3 coating is prepared by an electrochemical method. The electrochemical method is as described in any of the embodiments in step (1) of the method of the present invention.

[0053] In some embodiments, the Al2O3 coating is prepared by an atomic layer deposition method (ALD method). The atomic layer deposition method is as described in any of the embodiments in step (2) of the method of the present invention.

[0054] In some embodiments, the thickness of the AlF3 coating is 5 - 20 μm, such as 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, and preferably 5 - 7 μm, 7 - 10 μm, 7 - 15 μm.

[0055] In some embodiments, the thickness of the Al2O3 coating is 150 - 700 nm, such as 150 nm, 200 nm, 250 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, and preferably 350 - 500 nm, 500 - 700 nm.

[0056] In some embodiments, the breakdown voltage resistance of the composite coating is 450 - 1000 V, such as 450 V, 500 V, 550 V, 600 V, 650 V, 700 V, 750 V, 800 V, 810 V, 820 V, 830 V, 840 V, 850 V, 860 V, 900 V, 950 V, and preferably 650 - 1000 V, 700 - 950 V, 750 - 900 V, 800 - 850 V.

[0057] Aluminum Alloy Part, Semiconductor Equipment

[0058] The aluminum alloy part with a composite coating of the present invention can effectively isolate the erosion of halogen elements (such as F, Cl), and has a relatively high breakdown voltage. The present invention also provides an aluminum alloy part, which is an aluminum alloy with a composite coating on its surface. An AlF3 coating is provided on the surface of the aluminum alloy, and an Al2O3 coating is provided on the AlF3 coating. In some embodiments, the composite coating of the aluminum alloy part is the composite coating of the present invention.

[0059] In some embodiments, the AlF3 coating is prepared by an electrochemical method. The electrochemical method is as described in any of the embodiments in step (1) of the method of the present invention.

[0060] In some embodiments, the Al2O3 coating is prepared by an atomic layer deposition method (ALD method). The atomic layer deposition method is as described in any of the embodiments in step (2) of the method of the present invention.

[0061] In some embodiments, the aluminum alloy is selected from one or more of 1-series aluminum alloys (such as 1050 aluminum alloy), 3-series aluminum alloys, 5-series aluminum alloys, 6-series aluminum alloys, and 7-series aluminum alloys (such as 7075 aluminum alloy). The 7-series aluminum alloy has better mechanical properties than the 1-series, 3-series, and 6-series. Preferably, the aluminum alloy is a 7-series aluminum alloy.

[0062] In some embodiments, the aluminum alloy part is a component inside a semiconductor device cavity. In some embodiments, the semiconductor device is PECVD or PEALD. In some embodiments, the components inside the semiconductor device cavity are selected from heating plate components, shower plate components, and cavity components.

[0063] The present invention also provides a semiconductor device including the aluminum alloy part of the present invention. Preferably, the semiconductor device is PECVD or PEALD.

[0064] Method for Preparing Aluminum Alloy Part

[0065] The present invention provides a method for preparing the aluminum alloy part of the present invention, and the method includes the steps:

[0066] (1) Prepare an AlF3 coating on the surface of the aluminum alloy;

[0067] (2) Prepare an Al2O3 coating on the surface of the AlF3 coating.

[0068] In some embodiments, the AlF3 coating is prepared by an electrochemical method.

[0069] In some embodiments, the Al2O3 coating is prepared by atomic layer deposition. Atomic layer deposition (ALD) is a vacuum coating process in which a substance is deposited layer by layer on the surface of a substrate in the form of a single atomic layer. It is well known to those skilled in the art that the density of the film layer prepared by the ALD method is undoubtedly high.

[0070] In some embodiments, step (1) includes: providing an electrolyte with a fluoride salt as the solute, the fluoride salt including ammonium fluoride and optionally other fluoride salts, connecting an aluminum alloy as the anode to a power source, and preparing an electrochemically fluorinated film on the surface of the aluminum alloy through electrochemical fluorination. The concentration of fluoride ions in the electrolyte is 30 - 170 g / L, such as 40 g / L, 50 g / L, 60 g / L, 70 g / L, 90 g / L, 94 g / L, 100 g / L, 120 g / L, 150 g / L, preferably 30 - 100 g / L, 90 - 150 g / L.

[0071] In some embodiments, the other fluoride salts are selected from one or both of potassium fluoride and sodium fluoride.

[0072] In some embodiments, the solvent of the electrolyte is selected from one or both of ethanol and ethylene glycol. Preferably, the purity of ethanol and ethylene glycol is ≥99%.

[0073] In some embodiments, the power source is a micro-arc power source.

[0074] In some embodiments, the aluminum alloy is selected from 1xxx series aluminum alloys (such as 1050 aluminum alloy), 3xxx series aluminum alloys, 5xxx series aluminum alloys, 6xxx series aluminum alloys, and 7xxx series aluminum alloys (such as 7075 aluminum alloy), preferably 7xxx series aluminum alloys.

[0075] In some embodiments, the cathode is stainless steel, titanium alloy, or graphite; preferably stainless steel.

[0076] In some embodiments, the temperature of the electrolyte is 0 - 15 °C, such as 2 °C, 5 °C, 8 °C, 10 °C, 13 °C, preferably 5 - 10 °C, 10 - 15 °C.

[0077] In some embodiments, the conductivity of the electrolyte is 4 - 8 mS / cm, such as 4.5 mS / cm, 4.8 mS / cm, 5.2 mS / cm, 5.3 mS / cm, 5.5 mS / cm, 6 mS / cm, 6.5 mS / cm, 7 mS / cm, preferably 4 - 6 mS / cm, 5.2 - 8 mS / cm.

[0078] In some embodiments, the time of the electrochemical fluorination is 120 - 480 min, such as 150 min, 180 min, 200 min, 240 min, 300 min, 360 min, 400 min, preferably 120 - 180 min, 180 - 240 min.

[0079] In some embodiments, the current density of the electrochemical fluorination is 8 - 30 A / dm 2 , such as 10 A / dm 2 , 12 A / dm 2 , 15 A / dm 2 , 18 A / dm 2 , 25 A / dm 2 , 28 A / dm 2 , preferably 8 - 10 A / dm 2 , 10 - 20 A / dm 2 .

[0080] In some embodiments, the negative current density of the electrochemical fluorination is 0 - 10 A / dm 2 , such as 0.1 A / dm 2 , 0.5 A / dm 2 , 1 A / dm 2 , 3 A / dm 2 , 5 A / dm 2 , 8 A / dm 2 , preferably 0.1 - 8 A / dm 2 , 0.1 - 5 A / dm 2 , 0.1 - 1 A / dm 2 .

[0081] In some embodiments, the frequency of the electrochemical fluorination is 50 - 1500 HZ, such as 100 HZ, 150 HZ, 200 HZ, 500 HZ, 700 HZ, 1000 HZ, 1200 HZ, preferably 100 - 500 HZ.

[0082] In some embodiments, the duty cycle of the electrochemical fluorination is 5 - 70%, such as 10%, 15%, 18%, 20%, 30%, 35%, 40%, 50%, 60%, preferably 5 - 18%, 18 - 30%.

[0083] In some embodiments, the method further comprises the step of: pretreating the aluminum alloy and then placing it on the anode of the power supply. Preferably, the pretreatment includes one or more of grinding and polishing, removing grease and floating ash, ultrasonic removal of chemical residues, and drying to remove water vapor residues.

[0084] In some embodiments, in step (2), the deposition temperature of the atomic layer deposition method is 250 - 350 °C, such as 250 °C, 280 °C, 300 °C, 320 °C, 350 °C, and preferably 250 - 300 °C, 300 - 350 °C.

[0085] In some embodiments, in step (2), the deposition pressure of the atomic layer deposition method is ≤ 10 torr, such as 1 torr, 2 torr, 5 torr, 6 torr, 7 torr, 9 torr, and preferably 1 - 6 torr, 2 - 5 torr, 3 - 6 torr.

[0086] The atomic layer deposition method conventional in the art can be used to prepare an Al2O3 film with a specific thickness. In some embodiments, in step (2), the precursors of the atomic layer deposition method are trimethylaluminum and water. The flow rate of trimethylaluminum is 100 - 300 sccm, such as 100 - 180 sccm, 180 - 300 sccm. The introduction time of trimethylaluminum is 2 - 7 s, such as 2 - 5 s. The flow rate of water is 200 - 400 sccm, such as 200 - 250 sccm, 250 - 400 sccm, 250 - 300 sccm. The introduction time of water is 0.1 - 0.5 s, such as 0.1 - 0.3 s, 0.1 - 0.2 s. In some embodiments, trimethylaluminum is introduced first, and then water is introduced to complete one deposition. Those skilled in the art can select the number of depositions according to the thickness of the Al2O3 film to be prepared. Herein, using the one - deposition method defined herein, a total of 2000 - 4000 depositions can be carried out, such as 2500 times, 3000 times, 3500 times. Preferably, after the preparation of the composite coating is completed, the aluminum alloy part is cleaned and dried. The cleaning is carried out for 5 - 10 min. The drying is carried out at 80 - 120 °C, such as 80 - 100 °C, 100 - 120 °C. The drying is carried out for 1 - 4 h, such as 1 - 2 h, 2 - 4 h.

[0087] Prepared by the method of the present invention

[0088] The present invention also provides a method for improving the breakdown voltage resistance and / or halogen element erosion resistance of an aluminum alloy part, the method comprising the steps of: using the method of the present invention to prepare an AlF3 coating and an Al2O3 coating on the surface of the aluminum alloy. Halogen refers to F, Cl, Br, and I; preferably, the halogen is one or two of F and Cl.

[0089] The following further elaborates the present invention with specific examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, percentages and parts are calculated by weight.

[0090] The thickness of the composite coating on the aluminum alloy surface was measured using an eddy current thickness gauge. The test principle of the eddy current thickness gauge is as follows: a high-frequency alternating current signal generates an electromagnetic field in the probe coil. When the probe approaches a conductor, eddy currents are formed therein. The closer the probe is to the conductive substrate, the greater the eddy currents and the greater the reflection impedance. This feedback action quantity characterizes the distance between the probe and the conductive substrate, that is, the thickness of the non-conductive coating (AlF3 and Al2O3) on the conductive substrate (i.e., aluminum alloy).

[0091] Example 1 (1-series alloy, electrochemical fluorination film + ALD alumina film)

[0092] I. Pretreatment

[0093] A 1050 aluminum alloy specimen with dimensions of 50 mm * 50 mm * 5 mm was provided and polished uniformly using 400# sandpaper throughout.

[0094] After polishing, it was degreased and cleaned for 10 min, then washed with hot water at 50 °C after degreasing, and dried after washing.

[0095] II. Preparation of the electrochemical fluorination film

[0096] The specimen was placed in the fluorination solution, and the composition of the fluorination solution was: 100 g of ammonium fluoride, 50 g of potassium fluoride, and 60 g of sodium fluoride were dissolved in a solvent of 500 mL of ethanol (purity 99.7%) and 1500 mL of ethylene glycol (purity 99.7%). The conductivity of the electrolyte was 5.32 mS / cm.

[0097] The pretreated aluminum alloy was placed at the anode of the micro-arc power supply, and the cathode plate material was stainless steel. The parameters of the electrochemical fluorination process were: the current density was 10 A / dm 2 , the negative current density was 0.1 A / dm 2 , the frequency was 100 HZ, the duty cycle was 18%, the electrolyte temperature was controlled at 10 °C by a chiller, and the growth time was 180 min. Electrolysis was carried out under a constant current condition.

[0098] After the aluminum alloy with the electrochemical fluorination film was prepared, it was ultrasonically cleaned with pure water, purged with CDA, and dried in an oven. An electrochemical fluorination film AlF3 with a thickness of 7 μm was prepared on the surface of the aluminum alloy specimen using the method of this example.

[0099] III. Preparation of the Al2O3 film

[0100] Place the test block with the prepared electrochemically fluorinated film in the ALD equipment. After evacuating the air (the pressure is controlled below 6 torr), raise the chamber temperature to 300 °C. The flow rate of TMA (trimethylaluminum) is 180 sccm, and the introduction time is 2 s. Then introduce water, the flow rate of water is 250 sccm, and the introduction time of water is 0.1 s to form 1 deposition. Repeat the same deposition process 3000 times. Further deposit a 500-nm Al2O3 film on the surface of the 1050 aluminum alloy test block with an electrochemically fluorinated film AlF3 on the surface.

[0101] IV. Post-treatment

[0102] After the composite coating is prepared, perform ultrasonic pure water cleaning (40 - 130 KHZ) for 10 min, and dry it at 100 °C for 2 h after cleaning.

[0103] Example 2 (7-series alloy, electrochemically fluorinated film + ALD alumina film)

[0104] Adopt the same method as in Example 1, with the only difference being that 7075 aluminum alloy is used to replace 1050 aluminum alloy.

[0105] Comparative Example 1 (1-series alloy, electrochemically fluorinated film)

[0106] Repeat the methods of Step 1 (pretreatment) and Step 2 (preparation of electrochemically fluorinated film) in Example 1 to obtain AlF3 with a thickness of 7 μm on the surface of the 1050 aluminum alloy test block.

[0107] Comparative Example 2 (1-series alloy, ALD alumina film)

[0108] Repeat the methods of Step 1 (pretreatment) and Step 3 (preparation of Al2O3 film) in Example 1 to directly prepare an Al2O3 film with a thickness of 500 nm on the surface of the pretreated 1050 aluminum alloy test block.

[0109] Comparative Example 3 (7-series alloy, electrochemically fluorinated film)

[0110] Adopt the same method as in Comparative Example 1, with the only difference being that 7075 aluminum alloy is used to replace 1-series aluminum alloy.

[0111] Comparative Example 4 (7-series alloy, ALD alumina film)

[0112] Adopt the same method as in Comparative Example 2, with the only difference being that 7075 aluminum alloy is used to replace 1-series aluminum alloy.

[0113] Comparative Example 5 (1-series alloy, ALD alumina film + electrochemically fluorinated film)

[0114] Repeat the method of "Step 3: Prepare the Al2O3 film" in Example 1 to prepare a 500-nm ALD alumina film on 1050 and 7075 aluminum alloys, and then attempt to prepare an electrochemically fluorinated film on the obtained alumina film.

[0115] It was found experimentally that an electrochemically fluorinated film could not be prepared on the surface of the alumina film. The electrochemically fluorinated film could only be directly prepared on the surfaces of 1050 and 7075 aluminum alloys, but not on the surface of the alumina film.

[0116] Test Example 1 (Breakdown Voltage Resistance Test)

[0117] Step 1: Connect the aluminum alloy test blocks with coatings prepared in the examples and comparative examples to a breakdown voltage tester (Huayi Electronics SE 7440) through cables respectively to form a circuit, see Figure 2 .

[0118] Step 2: Start the tester. After the test is completed, the device will automatically shut down and display the corresponding data results. The breakdown voltage resistances of the aluminum alloy test blocks with coatings are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] By comparing Example 1 with Comparative Examples 1-2 and Example 2 with Comparative Examples 3-4, it can be seen that the breakdown voltage resistance of the aluminum alloy containing the composite coating of the present invention is significantly improved compared with that of the aluminum alloy containing only the ALD coating and the aluminum alloy containing only the electrochemically fluorinated film. The contents and types of impurities in the 1-series aluminum alloy and the 7-series aluminum alloy are different, resulting in different breakdown voltage resistances of the composite coatings prepared in Example 1 and Example 2.

[0123] Test Example 2 (Hydrochloric Acid BT Test)

[0124] Step 1: Respectively take the aluminum alloy test blocks with coatings prepared in the examples and comparative examples, and select a test area in the area more than 10 mm away from the edge. Seal one end of the test tube to the test area and use an adhesive for tube sealing. The sealing should ensure waterproof, acid-resistant and no leakage. The material of the test tube described above is a glass tube with a diameter of 15 mm and a length of at least 25 mm, and the end face is cut flat, see Figure 3 .

[0125] Step 2: Use hydrochloric acid with a weight concentration of 5%, which is prepared freshly before use.

[0126] Step 3: Pour the prepared hydrochloric acid into the test tube bonded to the aluminum alloy test block, and the height of the hydrochloric acid is at least 15 mm. At the same time, start the timer.

[0127] Step 4: No bubbles are generated during the process of hydrochloric acid corroding the film layer. When hydrochloric acid comes into contact with the bare aluminum, obvious hydrogen bubbles will be generated. The failure characteristic is that more than 3 bubbles continuously appear within 1 second in the fluorinated film test area. After the above characteristics appear, turn off the timer and record the duration. The failure times of each aluminum alloy specimen are shown in Table 2.

[0128] Table 2: Hydrochloric acid corrosion resistance time of aluminum alloy specimens with coatings

[0129] Time Example 1 7.5h Example 2 7.2h Comparative Example 1 3.2h Comparative Example 2 1.5h Comparative Example 3 1.6h Comparative Example 4 15 min

[0130] By comparing Example 1 with Comparative Examples 1-2, and Example 2 with Comparative Examples 3-4, it can be seen that the hydrochloric acid corrosion resistance of the aluminum alloy with the composite coating of the present invention is greatly improved compared with the aluminum alloy with only the ALD coating and the aluminum alloy with only the electrochemical fluorinated film.

[0131] Test Example 3 (Fluorine corrosion resistance test)

[0132] Take the aluminum alloy specimens with coatings prepared in Example 1-2, Comparative Example 1, and Comparative Example 3 respectively, and place them in the vacuum chamber of the PECVD equipment. The temperature in the chamber is raised to 400 °C. After the temperature is stabilized, 4000 sccm of NF3 and 8000 sccm of Ar are introduced and dissociated under the action of plasma. The chamber pressure is controlled at 6 torr to continuously fluorinate the aluminum alloy specimens.

[0133] Figure 4 The abscissa is the number of wafers run (pieces), and the ordinate is the film thickness (μm). When the number of wafers run reaches 25000 pieces, the film thickness of the specimens corresponding to Comparative Examples 1 and 3 is still continuously increasing, while the film thickness of the specimens in Example 1-2 tends to be flat and no longer continues to increase.

Claims

1. A composite coating, characterized in that: The composite coating comprises an AlF3 coating and an Al2O3 coating, wherein the AlF3 coating is prepared by an electrochemical method, and the Al2O3 coating is prepared by an atomic layer deposition method.

2. The composite coating according to claim 1, characterized in that The composite coating has one or more of the following characteristics: The thickness of the AlF3 coating is 5-20 μm; The thickness of the Al2O3 coating is 150-700nm; The composite coating has a breakdown voltage of 450-1000V.

3. An aluminum alloy part, characterized in that: The aluminum alloy part is an aluminum alloy with a composite coating on the surface, the aluminum alloy surface is provided with an AlF3 coating, an Al2O3 coating is provided on the AlF3 coating, the AlF3 coating is prepared by an electrochemical method, and the Al2O3 coating is prepared by an atomic layer deposition method.

4. The aluminum alloy part according to claim 3, characterized in that: The aluminum alloy is selected from one or more of 1 series aluminum alloy, 3 series aluminum alloy, 5 series aluminum alloy, 6 series aluminum alloy and 7 series aluminum alloy.

5. A semiconductor device comprising the aluminum alloy member according to claim 3 or 4.

6. A method for preparing the aluminum alloy part according to claim 3 or 4, characterized in that: The method comprises the steps of: (1) Preparing AlF3 coating on the surface of aluminum alloy by electrochemical method; (2) preparing an Al2O3 coating on the surface of the AlF3 coating by an atomic layer deposition method.

7. The method according to claim 6, characterized in that The step (1) comprises: providing an electrolyte whose solute is a fluoride salt, wherein the fluoride salt comprises ammonium fluoride and optionally other fluoride salts, connecting an aluminum alloy as an anode to a power source, and preparing an electrochemical fluoridation film on the surface of the aluminum alloy by electrochemical fluoridation, wherein the concentration of fluoride ions in the electrolyte is 30-170 g / L.

8. The method according to claim 6, characterized in that Step (1) has one or more of the following characteristics: The other fluoride salt is selected from one or both of potassium fluoride and sodium fluoride; The solvent of the electrolyte is selected from one or both of ethanol and ethylene glycol; The power supply is a micro-arc power supply; The aluminum alloy is selected from 1 series aluminum alloy, 3 series aluminum alloy, 5 series aluminum alloy, 6 series aluminum alloy and 7 series aluminum alloy; The cathode is made of stainless steel, titanium alloy or graphite; The temperature of the electrolyte is 0-15°C; The conductivity of the electrolyte is 4-8mS / cm; The electrochemical fluorination time is 120-480 min; The current density of the electrochemical fluorination is 8-30A / dm 2 ; The negative current density of the electrochemical fluorination is 0-10A / dm 2 ; The frequency of the electrochemical fluorination is 50-1500HZ; The duty cycle of the electrochemical fluorination is 5-70%.

9. The method according to claim 6, characterized in that Step (2) has one or more of the following characteristics: The deposition temperature of the atomic layer deposition method is 250-350°C; The deposition pressure of the atomic layer deposition method is ≤10 torr; The precursors of the atomic layer deposition method are trimethylaluminum and water.

10. A method for improving the breakdown voltage and / or halogen corrosion resistance of an aluminum alloy part, characterized in that: The method comprises the steps of: preparing an AlF3 coating and an Al2O3 coating on the surface of the aluminum alloy using the method described in any one of claims 5-9.

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