Preparation method of chromium oxide multilayer film with low transmissivity and low reflectivity

Abstract

The invention discloses a preparation method of a chromium oxide multilayer film with low transmissivity and low reflectivity, and relates to the technical field of functional material preparation, and the preparation method specifically comprises the following steps: step 1, carrying out ultrasonic cleaning on the surface of an S O < 2 > substrate: step 2, carrying out sputtering cleaning on the surface of a high-purity chromium target material; and step 3, in an atmosphere with uniform and stable gas distribution, sputtering and depositing a layer of chromium and a layer of chromium oxide on the surface of the Si O2 substrate by using a high-purity chromium target material through magnetron sputtering equipment to obtain the chromium and chromium oxide double-layer film. According to the method, ultrahigh vacuum magnetron sputtering equipment is matched with written automatic working steps, and the chromium and chromium oxide double-layer film with the chromium film thickness being 50 nm and the chromium oxide film thickness being 25 nm is prepared; the surface of the chromium and chromium oxide double-layer film has relatively large and uniform roughness, so that the chromium and chromium oxide double-layer film has low transmissivity of 1.39% and low reflectivity of 7.66%.

Description

Technical Field

[0001] The invention relates to the technical field of functional material preparation, and in particular to a method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity. Background Art

[0002] In the development of laser protection lens film, the balance between high reflectivity and low transmittance is a critical design requirement. The core task of laser protection lenses is to block laser radiation and prevent laser from penetrating the film layer to cause damage to the eyes, skin or sensitive equipment. If the transmittance of the film layer is too high, the laser energy will pass through the lens into areas that should not be touched (such as eyes or equipment). If the reflectivity is too high, the reflected laser may be reflected back to the equipment, laser source or operator, causing potential safety hazards. Therefore, ensuring the balance between the two is a crucial task in the design of laser protection lenses. The balance between high reflectivity and low transmittance of laser protection lenses usually needs to be achieved through a multilayer film structure. In the multilayer film design, the thickness, material selection and refractive index of each layer need to be accurately calculated, and the interaction between different film layers plays a decisive role in the final optical performance. At the same time, since laser irradiation generates a lot of heat, this will affect the long-term stability and performance of the film layer. Therefore, the thermal stability of the film layer needs to be highly compatible with the optical performance. In the preparation process of the film layer, if the film is uneven on the surface of the lens or the adhesion is insufficient, it may cause bubbles, cracks or shedding in the film layer, affecting the optical effect. Therefore, uniformity and adhesion are very important considerations.

[0003] Magnetron sputtering technology has been widely used in the preparation of high-purity single metal films or nitride oxide films, as well as other multi-material films with precisely controlled proportions, and has played an important role in the preparation of nanoscale films and micrometer-scale films. The basic process is to apply negative pressure between the target and the substrate in an ultra-high vacuum environment, so that the positive ions ionized by the working gas are accelerated to collide with the cathode target, so that the target atoms are sputtered and fly onto the substrate. The target atoms flying onto the substrate are affected by factors such as atomic energy, substrate defects, and substrate temperature to form crystalline / amorphous films. Magnetron sputtering technology has the advantages of high deposition rate, high film uniformity, controllable film composition and structure, applicability to a variety of materials, controllable substrate temperature, low cost and environmental protection. Therefore, using magnetron sputtering technology, people have successfully prepared many high-quality optical films, but the preparation of films for specific optical devices is indeed a complicated process.

[0004] Chromium oxide films have a series of significant advantages in physical properties, so they play an important role in many applications. Chromium oxide is a wide bandgap semiconductor with an optical bandgap of approximately 3.0eV to 3.5eV. Therefore, chromium oxide films show strong light absorption in the visible light band and have moderate reflectivity. Chromium oxide films have high thermal stability and can work stably at high temperatures. Its thermal expansion coefficient is low, which is more compatible with the thermal expansion characteristics of most substrates, which enables chromium oxide films to maintain stable physical properties in environments with large temperature fluctuations. Chromium oxide films have good chemical stability, can remain stable in acidic or alkaline environments, and have strong oxidation resistance. Chromium oxide films have strong adhesion to many common substrates (such as glass, metal, ceramics, etc.), especially when using magnetron sputtering or evaporation coating processes, the chromium oxide film layer can usually firmly adhere to the surface of the substrate to form a stable protective layer.

[0005] Existing methods for preparing oxides, such as thermal oxidation, CVD, ALD, electrochemical oxidation, and sol-gel methods, all have their own advantages and can prepare high-quality oxide films, but they also have the following defects, such as insufficient uniformity, generation of impurities, slow deposition rate, and high process requirements. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity. The use of ultra-high vacuum magnetron sputtering equipment in conjunction with a process menu can greatly reduce the difficulty of the process, ensure uniformity within 3%, and achieve a higher deposition rate.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity comprises the following steps:

[0009] Step 1: Ultrasonic cleaning of the SiO2 substrate surface:

[0010] Step 2: sputtering and cleaning the surface of the high-purity chromium target;

[0011] Step 3: In an atmosphere with uniform and stable gas distribution, a layer of chromium and a layer of chromium oxide are sputtered and deposited on the surface of the SiO2 substrate using a high-purity chromium target by a magnetron sputtering device to obtain a double-layer film of chromium and chromium oxide;

[0012] Step three includes the following steps:

[0013] S1. Calibrate the thickness of the chromium film and the chromium oxide film prepared under different oxygen content conditions;

[0014] S2. Testing the thickness of the chromium film and the chromium oxide film prepared under different oxygen content conditions, calculating the corresponding deposition rate, and calculating the sputtering time required for preparing the chromium film and the chromium oxide film;

[0015] S3, sputtering to prepare double-layer films of chromium and chromium oxide with different proportions according to the sputtering time;

[0016] S4. The transmittance and reflectivity of the sputtered double-layer film are tested under visible light conditions with different incident angles, and finally qualified chromium and chromium oxide double-layer films are obtained.

[0017] As a further solution of the present invention: the thickness of the chromium film of the double-layer film is 45-55nm, and the thickness of the chromium oxide film is 20-30nm.

[0018] As a further solution of the present invention: the thickness of the chromium film of the double-layer film is 50nm, the thickness of the chromium oxide film is 25nm, the low transmittance of the double-layer film is 1.39%, and the low reflectivity is 7.66%.

[0019] As a further solution of the present invention: the magnetron sputtering equipment adopts MS I-100 series 8-inch ultra-high vacuum magnetron sputtering equipment, which is used to program automatic process steps to prepare multiple double-layer films of chromium oxide layers with the same structure but different oxygen contents.

[0020] As a further solution of the present invention: the atmosphere uses argon as an auxiliary sputtering gas and oxygen as a reactive sputtering gas.

[0021] As a further solution of the present invention: the sputtering power of the chromium film is 200W DC, and the sputtering power of the chromium oxide film is 300W DC.

[0022] As a further solution of the present invention: the thin film sputtering gas pressure is 1.2Pa-1.9Pa, the thin film sputtering target substrate distance with an oxygen content of 10%-90% is 20cm-25cm.

[0023] As a further solution of the present invention: the sputtering gas argon flow rate of the chromium film is 20sccm; the sputtering gas argon flow rate of the chromium oxide film with an oxygen content of 10%-90% is 2sccm-18sccm, and the oxygen flow rate is 18sccm-2sccm.

[0024] As a further solution of the present invention: before the sputtering deposition process begins, the magnetron sputtering equipment needs to reach a value higher than 1×10 -7 Background vacuum value in mbar.

[0025] As a further solution of the present invention: before the sputtering deposition process starts, the high-purity SiO2 substrate needs to be placed in anhydrous ethanol for ultrasonic cleaning for 3 minutes, and then the substrate is taken out and high-purity nitrogen is blown on the surface of the substrate to clean the residual ethanol and impurities on the surface of the substrate.

[0026] Beneficial effects of the present invention:

[0027] The present invention cooperates with ultra-high vacuum magnetron sputtering equipment and programmed automatic process steps, selects the optimal film sputtering gas pressure of 1.2 Pa, the thin film sputtering target substrate distance of 20 cm, the sputtering gas argon flow rate of the chromium film of 20 sccm, the sputtering gas argon flow rate of the chromium oxide film of 6 sccm, the oxygen flow rate of 14 sccm and other process parameters, and prepares a chromium and chromium oxide double-layer film with a chromium film thickness of 50 nm and a chromium oxide film thickness of 25 nm; the surface of the chromium and chromium oxide double-layer film has a large and uniform roughness, so that it has a low transmittance of 1.39% and a low reflectivity of 7.66%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 is a double-layer membrane data diagram of Example 3 of the present invention;

[0030] Figure 2 is a line graph of transmittance and reflectance of the double-layer film of Example 3 of the present invention;

[0031] Figure 3 is a thickness diagram of the double-layer film of Example 3 of the present invention;

[0032] Figure 4 is a roughness map of the double-layer film of Example 3 of the present invention;

[0033] Figure 5 is a 3D image of the surface morphology of the double-layer film of Example 3 of the present invention;

[0034] Figure 6 It is a simplified schematic diagram of a wafer feeding device;

[0035] Figure 7 It is a schematic diagram of the overall structure of the cleaning device of the present invention;

[0036] Figure 8 It is a schematic diagram of the internal structure of the cleaning device of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The present invention is a method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity;

[0039] Example 1

[0040] (1) Use cleaning equipment, see Figure 7-8 As shown, a 10cm×10cm high-purity SiO2 substrate to be used is placed in anhydrous ethanol. The substrate uses double-sided polished silicon dioxide. After ultrasonic cleaning for 3 minutes, high-purity nitrogen is used to blow away impurities on the surface of the substrate to obtain a clean SiO2 substrate.

[0041] The cleaning device comprises a multi-axis moving mechanism 1, the cleaning box 2 is provided with the multi-axis moving mechanism 1, the multi-axis moving mechanism 1 is provided with a driving motor 11, a suction cup is installed on the output shaft of the driving motor 11, and a plurality of cleaning brushes 12 are installed on the outer peripheral surface of the suction cup;

[0042] Hot air blowers 21 are fixedly installed on both sides of the inner wall of the cleaning box 2. The hot air blowers 21 are connected to the hot air pipe 25 through a pipeline. The hot air pipe 25 is square and fits the inner wall of the cleaning box 2. A plurality of heat dissipation holes are evenly opened on the hot air pipe 25.

[0043] Rotating motors 23 are fixedly mounted on both sides of the cleaning box 2, and telescopic cylinders 24 are fixedly mounted on the output shafts of the rotating motors 23. The piston rods of the telescopic cylinders 24 extend into the cleaning box 2 and are connected to mechanical fixtures 28.

[0044] A lifting cylinder 22 is fixedly installed at the bottom of the cleaning box 2, and a motor is fixedly installed on the piston rod of the lifting cylinder 22. The output shaft of the motor extends into the cleaning box 2 and is fixedly installed with a vacuum suction cup 27.

[0045] The substrate is placed on the vacuum suction cup 27, and the telescopic cylinder 24 is started to move synchronously, and then the substrate is pushed to the center through the mechanical clamp 28, and then the vacuum suction cup 27 sucks it. At this time, the multi-axis moving mechanism 1 is started to drive the cleaning brush 12 to contact the surface of the substrate to clean its surface; the vacuum suction cup 27 releases the substrate, and then the mechanical clamp 28 is started to turn the substrate over and clean the other side; both sides are cleaned well for subsequent cleaning;

[0046] Then the vacuum chuck 27 is lowered and placed on a plurality of springs 26, which are suspended in the air, so as to facilitate cleaning of both sides of the substrate. Anhydrous ethanol is added, and the ultrasonic device on the cleaning box 2 is started to clean it. Since anhydrous ethanol will generate vibration, it will drive the spring 26 to vibrate, thereby accelerating the cleaning efficiency;

[0047] After cleaning is completed, the vacuum suction cup 27 lifts it up, clamps it through the mechanical clamp 28, drives it to rotate, improves the air drying efficiency, and blows it dry through the hot air blower 21. Finally, it is sucked by the suction cup and placed in the ultra-high vacuum magnetron sputtering equipment by the multi-axis moving mechanism 1; the entire equipment forms an automated operation.

[0048] (2) Using MS I-100 series 8-inch ultra-high vacuum magnetron sputtering equipment, see patent number CN2023232490117, patent name is a patent application for a wafer sampling device, see Figure 6 As shown in the simple schematic diagram, when the equipment is in use, the operator first places the chip into the injection chamber, and then uses the transfer robot in the transfer chamber to send the chip to the process chamber for reaction.

[0049] The magnetron sputtering equipment has a sampling chamber and a process chamber. The process chamber is kept in a high vacuum state, and the vacuum state of the sampling chamber is broken to wait for sampling. The sampling chamber is equipped with 6 8-inch sample trays. After the vacuum of the sampling chamber is broken, the sample tray is taken out, and then the cleaned substrate is fixed to the sample tray with high-temperature tape, and then the sample is placed in the sampling chamber of the equipment, and then the observation window of the sampling chamber is closed and the door is opened quickly to start the vacuum system of the sampling chamber; because the dual-chamber magnetron sputtering equipment used in this scheme keeps the vacuum degree of the two chambers consistent before each sample is sputtered and withdrawn, the dual-chamber magnetron sputtering equipment has higher efficiency than the single-chamber magnetron sputtering equipment.

[0050] (3) Before the start of sputtering, the target-substrate distance is set to 25 cm, that is, the sample stage is raised to the set height. The set height of the sample stage and the distance between the target surface must be completed before the process chamber is evacuated, that is, when the process chamber is in a vacuum state, the rubber ring sealing door of the process chamber is opened, the pneumatic baffle of the cathode target head is opened, and then a steel ruler is used to measure the straight-line distance between the target surface and the sample stage in the vertical direction perpendicular to the center of the target surface. Then, the sample stage is raised and lowered until the straight-line distance is 25 cm to obtain the target target-substrate distance. Since the dual-chamber magnetron sputtering equipment used in this scheme utilizes a front-opening door design, it is very convenient to adjust the target-substrate distance, so it saves a lot of time and energy in adjusting experimental parameters compared to other sputtering equipment.

[0051] (4) Before the start of sputtering, the high-purity chromium target is pre-cleaned. The target uses 4N grade 4-inch metal chromium. The argon gas inlet flow rate is set to 20sccm, the sputtering pressure is set to 2Pa, the sputtering power is set to DC 200W, and the sputtering time is set to 5 minutes to complete the pre-cleaning step of the target. The target pre-cleaning step should be completed when the process chamber is in a high vacuum state and the sample is in the sample inlet chamber. At this time, there is no sample on the sample stage, but the sample stage baffle is still closed before cleaning to protect the sample stage heating plate from the particles generated by pre-sputtering and maintain a good thermal conductivity. Then set the molecular pump plug valve to the specified opening, the specified opening of this step is 15%, and then open the electromagnetic diaphragm valve between the flowmeter and the cavity, and then set the gas mass flowmeter The inlet flow rate is 20sccm. Then observe the air pressure value of the capacitance film vacuum gauge and wait for the air pressure to stabilize at 2Pa. Then turn on the DC power supply connected to the target, set the target power, the target power of this step is 200W, turn on the power output and count for 5 minutes. After the timing is over, turn off the power output, turn off the flow meter flow, set the molecular pump plug valve opening to 100%, and wait for the vacuum value of the process chamber to return to a high vacuum state.

[0052] (5) The thickness of the chromium film and the chromium oxide film prepared under different oxygen content conditions were calibrated according to the following experimental sequence:

[0053] 1. For high-purity chromium film calibration, set the argon gas inlet flow rate to 20 sccm, the sputtering pressure to 1.9 Pa, the sputtering power to DC 200 W, and the sputtering time to 10 minutes;

[0054] 2. (Oxygen content 10%) chromium oxide film calibration, set the argon gas inlet flow rate to 18 sccm, set the oxygen gas inlet flow rate to 2 sccm, set the sputtering pressure to 1.9 Pa, set the sputtering power to DC 300 W, and set the sputtering time to 30 minutes; after the calibration is completed, pre-clean the target according to the parameters of step (2);

[0055] 3. (Oxygen content 30%) chromium oxide film calibration, set the argon gas inlet flow rate to 14 sccm, set the oxygen gas inlet flow rate to 6 sccm, set the sputtering pressure to 1.9 Pa, set the sputtering power to DC 300 W, and set the sputtering time to 30 minutes; after the calibration is completed, pre-clean the target according to the parameters of step (2);

[0056] 4. (Oxygen content 50%) chromium oxide film calibration, set the argon gas inlet flow rate to 10sccm, set the oxygen gas inlet flow rate to 10sccm, set the sputtering pressure to 1.9Pa, set the sputtering power to DC 300W, and set the sputtering time to 30 minutes; after the calibration is completed, pre-clean the target according to the parameters of step (2);

[0057] 5. (oxygen content 70%) chromium oxide film calibration, set the argon gas inlet flow rate to 6 sccm, set the oxygen gas inlet flow rate to 14 sccm, set the sputtering pressure to 1.9 Pa, set the sputtering power to DC 300 W, and set the sputtering time to 30 minutes; after the calibration is completed, pre-clean the target according to the parameters of step (2);

[0058] 6. (oxygen content 90%) chromium oxide film calibration, set the argon gas inlet flow rate to 2 sccm, set the oxygen gas inlet flow rate to 18 sccm, set the sputtering pressure to 1.9 Pa, set the sputtering power to DC 300 W, and set the sputtering time to 30 minutes; after the calibration is completed, pre-clean the target according to the parameters of step (2);

[0059] In the above calibration, there is no need to pre-clean the target material between step 1 and step 2, but the target material needs to be pre-cleaned according to step (4) between steps 2, 3, 4, 5, and 6.

[0060] (6) The thickness of the chromium film and the chromium oxide film prepared under different oxygen content conditions were tested, and the corresponding deposition rate was calculated. Then, the required sputtering time was calculated based on 50 nanometers for the chromium film and 25 nanometers for the chromium oxide film.

[0061] After calculating the sputtering time required for each ratio, the automatic process menu function of the magnetron sputtering equipment is used to program the automatic process steps, and the next 6 double-layer films with different ratios are completed by the automatic process steps. The specific setting steps are as follows:

[0062] 1. Establishing layer recipes: First, set up 6 layer recipes according to the 6 experimental parameters obtained in step (5) and step (6). In addition to the power, gas flow, gas pressure, sputtering time, and sputtering target-substrate distance involved in the above steps, it can also include power type, power output mode, sample stage speed, gas intake speed, molecular pump plug valve opening speed, gas pressure stabilization time, etc. Then name these 6 layer recipes as process 1, process 2, process 3, process 4, process 5, and process 6, respectively.

[0063] 2. Create a master recipe, each of which contains two layer recipes. The first layer of the first master recipe is process 1, and the second layer is process 2; the first layer of the second master recipe is process 1, and the second layer is process 3; the first layer of the third master recipe is process 1, and the second layer is process 4; the first layer of the fourth master recipe is process 1, and the second layer is process 5; the first layer of the fifth master recipe is process 1, and the second layer is process 6. Then name these five master recipes as recipe 1, recipe 2, recipe 3, recipe 4, and recipe 5.

[0064] 3. Establish the connection sequence of the master recipes. After establishing 5 master recipes, edit the sample injection and sample withdrawal logic of these 5 master recipes. First, edit the number of injection chamber layers corresponding to the 5 master recipes. Recipe 1, Recipe 2, Recipe 3, Recipe 4, and Recipe 5 correspond to the 1st, 2nd, 3rd, 4th, and 5th layers of the injection chamber respectively. Then edit the sample injection and sample withdrawal logic of the 5 master recipes, and set each recipe to execute sample withdrawal after running 2 processes. Finally, set the exit order of the 5 recipes, set Recipe 1, Recipe 2, Recipe 3, Recipe 4, and Recipe 5 to run in sequence, and finally end.

[0065] According to the automatic sputtering process edited in the above steps, five double-layer films of chromium oxide layers with the same structure but different oxygen contents were finally prepared, namely 50nmCr+25nmx%Cr2O3 (x=10, 30, 50, 70, 90).

[0066] (7) The sputtered double-layer film is taken out from the equipment and subjected to thickness test and roughness test.

[0067] (8) The transmittance and reflectivity of the sputtered double-layer film are tested under visible light conditions at different incident angles.

[0068] In the prior art, fully manual operations are usually used to prepare the same batch of oxide films, and the same films and optical properties can be obtained in the end. However, since the sample introduction and withdrawal, adjustment of air pressure and power, and pre-cleaning in the film preparation process are all manual, there are time differences and errors in human reactions in this process, which makes the experiment take 7-10 days to complete. Later, the process menu for adjusting the process pressure and power was edited separately, which saved some operating time, but people still need to stay in the machine because they have to wait for the next step. In summary, the existing preparation process is difficult and time-consuming;

[0069] In this embodiment, the dual-chamber magnetron sputtering equipment is combined with the preparation process in this scheme, which not only connects the steps of sample introduction and withdrawal, pre-cleaning and sputtering, but also connects the steps corresponding to the 6-layer samples, and conducts preliminary tests. At the same time, the step has better stability and higher completion rate, and the process time can be compressed to 1.5 days, which greatly reduces the process difficulty and time.

[0070] Implementation Case 2

[0071] The only difference between implementation example 2 and implementation example 1 is that the distance between the sputtering target and the substrate is 20 cm.

[0072] In this embodiment, the compactness and crystalline structure of the film are improved by adjusting the target-substrate distance, thereby improving the optical properties and the optical band gap. Therefore, compared with the target-substrate distance in embodiment 1, the distance between the plasma and the substrate is smaller, the energy lost is less, the energy of the deposited atoms reaching the substrate is higher, and the film compactness is better.

[0073] Implementation Case 3

[0074] The only difference between implementation example 3 and implementation example 2 is that the sputtering gas pressure is 1.2Pa.

[0075] In this embodiment, the density of the film and the crystalline structure of the film can be improved by adjusting the sputtering gas pressure, thereby improving the optical properties and the optical band gap. Therefore, compared with Embodiment 2, Embodiment 3 has a lower gas pressure, a larger mean free path of the plasma, fewer collisions, higher energy of the deposited atoms reaching the substrate, and better film density.

[0076] The double-layer membrane obtained in Example 3 was subjected to various performance tests. Figures 1 to 5 As shown:

[0077] Combination Figure 1 and Figure 2 It can be seen that the transmittance of the double-layer film tends to decrease with the increase of the incident angle. The transmittance of the double-layer film basically remains within 3.5% with the increase of the oxygen content of the chromium oxide film, and the minimum value is 1.39%. The reflectivity of the double-layer film tends to increase with the increase of the incident angle. The reflectivity of the double-layer film changes greatly with the increase of the oxygen content of the chromium oxide film. When the incident angle is 50 degrees, the minimum value of the reflectivity is 6.50%. From the perspective of the comprehensive balance of transmittance and reflectivity, the 50nmCr+25nm70%Cr2O3 double-layer film can obtain a transmittance of 1.39% and a reflectivity of 7.66% at an incident angle of 50 degrees;

[0078] Combination Figure 3 From the atomic force microscopy (AFM) image in FIG, it is known that the thickness of the 50nmCr+25nm70%Cr2O3 double-layer film is 76.86nm. Considering that there is a nanometer-level error in the thickness test of the AFM equipment, it can be considered that the thickness of the double-layer film is basically 75nm.

[0079] Combination Figure 4 and Figure 5 It can be seen that the roughness of the double-layer film is Rq = 3.29nm, Ra = 2.638nm, which is greater than that of ordinary single metal films (<0.5nm). At the same time, it can be seen from the 3D distribution diagram of AFM that the particle distribution on the surface of the double-layer film is relatively uniform, making the reflectivity and transmittance of the overall film surface relatively good.

[0080] Therefore, in this embodiment 3, with the cooperation of ultra-high vacuum magnetron sputtering equipment, the optimal film sputtering gas pressure of 1.2 Pa, the thin film sputtering target substrate distance of 20 cm, the sputtering gas argon flow rate of the chromium film of 20 sccm, the sputtering gas argon flow rate of the chromium oxide film of 6 sccm, the oxygen flow rate of 14 sccm and other process parameters are selected to prepare a double-layer film with a chromium film thickness of 50 nm and a chromium oxide film thickness of 25 nm, whose transmittance is 1.39% and reflectivity is 7.66%.

[0081] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity, characterized in that: The following steps are involved: Step 1: Ultrasonic cleaning of the SiO2 substrate surface: Step 2: sputtering and cleaning the surface of the high-purity chromium target; Step 3: In an atmosphere with uniform and stable gas distribution, a layer of chromium and a layer of chromium oxide are sputtered and deposited on the surface of the SiO2 substrate using a high-purity chromium target by a magnetron sputtering device; A double-layer film of chromium and chromium oxide is obtained; Step three includes the following steps: S1. Calibrate the thickness of the chromium film and the chromium oxide film prepared under different oxygen content conditions; S2. Testing the thickness of the chromium film and the chromium oxide film prepared under different oxygen content conditions, calculating the corresponding deposition rate, and calculating the sputtering time required for preparing the chromium film and the chromium oxide film; S3, sputtering to prepare double-layer thin films of chromium and chromium oxide in different proportions according to the sputtering time; S4. The transmittance and reflectivity of the sputtered double-layer film are tested under visible light conditions with different incident angles, and finally qualified chromium and chromium oxide double-layer films are obtained.

2. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: The thickness of the chromium film of the double-layer film is 45-55 nm, and the thickness of the chromium oxide film is 20-30 nm.

3. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 2, characterized in that: The thickness of the chromium film of the double-layer film is 50 nm, and the thickness of the chromium oxide film is 25 nm. The low transmittance of the double-layer film is 1.39%, and the low reflectivity is 7.66%.

4. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: The magnetron sputtering device adopts an ultra-high vacuum magnetron sputtering device, which is used to program automatic process steps to prepare multiple double-layer films of chromium oxide layers with the same structure and different oxygen contents.

5. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: The atmosphere used argon as an auxiliary sputtering gas and oxygen as a reactive sputtering gas.

6. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: The sputtering power of the chromium film is 200W DC, and the sputtering power of the chromium oxide film is 300W DC.

7. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: The thin film sputtering gas pressure is 1.2Pa-1.9Pa, and the thin film sputtering target substrate distance with an oxygen content of 10%-90% is 20cm-25cm.

8. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: The sputtering gas argon flow rate of the chromium film is 20 sccm; the sputtering gas argon flow rate of the chromium oxide film with an oxygen content of 10%-90% is 2 sccm-18 sccm, and the oxygen flow rate is 18 sccm-2 sccm.

9. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: Before the sputtering deposition process begins, the magnetron sputtering equipment reaches a value higher than 1×10 -7 Background vacuum value in mbar.

10. The method for preparing a chromium oxide multilayer film with low transmittance and low reflectivity according to claim 1, characterized in that: Before the sputtering deposition process begins, the high-purity SiO2 substrate is placed in anhydrous ethanol for ultrasonic cleaning for 3 minutes, and then the substrate is taken out and high-purity nitrogen is blown on the substrate surface to clean the residual ethanol and impurities on the substrate surface.

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