Low infrared reflection film and preparation method thereof

Abstract

The invention belongs to the technical field of functional thin film materials, and discloses a preparation method of a low-infrared-reflection thin film, which comprises the following steps: putting a substrate and a target material into a sputtering cavity, introducing argon, and cleaning the target material; then mixed gas of argon, hydrogen and oxygen is introduced, the air pressure in the sputtering cavity is adjusted, a power source is turned on, magnetron sputtering is conducted, and the low-infrared-reflection film is obtained; by controlling the molar ratio of zinc oxide to aluminum oxide in the zinc-aluminum oxide target and the working atmosphere during magnetron sputtering, the visible light reflectivity of the obtained film at the wave band of 750-1300nm is relatively low; in addition, the invention further discloses the low-infrared-reflection film which is prepared through the preparation method of the low-infrared-reflection film.

Description

Technical Field

[0001] This application relates to the technical field of functional thin film materials, and particularly relates to a low infrared reflection thin film and a preparation method thereof. Background Art

[0002] With the continuous progress of technology, the performance requirements for optical thin films are getting higher and higher. Due to its good electrical conductivity and optical transparency, transparent conductive oxide (TCO) thin films have been widely used in fields such as solar cells, flat panel displays, and touch screens. In some specific application scenarios, such as infrared detection and thermal imaging, TCO thin films are required to have a low infrared reflectivity. On the one hand, an infrared low-reflection TCO thin film can improve the performance of infrared detection and thermal imaging devices; reducing the infrared reflectivity can reduce background noise, improve the contrast and clarity of signals, thereby improving the detection accuracy and resolution of the devices. On the other hand, in the field of solar cells, a low-reflection TCO thin film can improve the absorption efficiency of solar cells for sunlight, thereby improving the conversion efficiency of solar cells. However, the TCO thin films on the market have a high reflectivity in the infrared band and are difficult to meet the requirements of these application scenarios.

[0003] The problem to be solved by this solution: how to reduce the infrared reflectivity of TCO thin films. Summary of the Invention

[0004] The purpose of this application is to propose a low infrared reflection thin film and a preparation method thereof. By controlling the molar ratio between zinc oxide and aluminum oxide in the zinc oxide-aluminum target and the working atmosphere during magnetron sputtering, the obtained thin film has a low visible light reflectivity in the 300-1300 nm band.

[0005] To achieve the above purpose, this application discloses a preparation method of a low infrared reflection thin film. The preparation method includes the following steps:

[0006] Step 1: Place the substrate and the target in the sputtering chamber, introduce argon gas, and clean the target.

[0007] Step 2: Introduce a mixed gas of argon, hydrogen, and oxygen, adjust the gas pressure in the sputtering chamber, turn on the power supply for magnetron sputtering, and obtain a low infrared reflection thin film.

[0008] Among them, in Step 1, the target is a zinc oxide-aluminum target with a molar ratio of zinc oxide to aluminum oxide of 98-99:1-2.

[0009] In the mixed gas of Step 2, the volume ratio of argon, hydrogen, and oxygen is 98.4-100:0-1.5:0-0.6, and does not include 0 and 100.

[0010] Zinc oxide is a wide-bandgap semiconductor material with a hexagonal wurtzite structure. Its bandgap is approximately 3.3 eV, providing the basic semiconductor properties for the thin film and endowing it with certain optical and electrical characteristics. However, pure ZnO thin films usually have a relatively high resistivity, while appropriate doping with Al 2 O 3 can make the crystal structure of the ZnO thin film more regular, reduce defects and dislocations, improve the crystallization quality of the thin film, make the grain growth more uniform, increase the density of the thin film, and thus improve the stability and durability of the thin film.

[0011] Argon is an inert gas. In the preparation of thin films, it can prevent unnecessary chemical reactions between the thin film material and oxygen, nitrogen, etc. in the air, ensure the stability of the thin film composition and structure, and facilitate the formation of the ideal microstructure required for a low reflectivity. Appropriate oxygen can also change the crystal structure and optical constants of the thin film, affect the stoichiometry of the thin film, change the absorption and scattering characteristics of the thin film for light of a specific wavelength, and reduce the reflectivity. Hydrogen can react with other gases or surface atoms of the thin film, promote the diffusion and migration of atoms during the thin film growth process, make the thin film crystallization more perfect, reduce defects and stress, and optimize the microstructure of the thin film, thereby reducing the scattering and reflection of light.

[0012] Preferably, in step 2, the air pressure is 0.55 - 0.65 Pa, and the sputtering power of magnetron sputtering is 4 - 8 kW;

[0013] Appropriately increasing the power is beneficial to the growth and enlargement of grains, reducing the number of grain boundaries, reducing the scattering of light at the grain boundaries, and lowering the reflectivity. However, if the power is too high, it may lead to excessive grain growth, resulting in abnormally large grains, which instead reduces the surface flatness of the thin film and increases the reflectivity.

[0014] Preferably, in step 1, the substrate material is one of glass, quartz glass, sapphire, silicon, polyimide PI, or polyethylene terephthalate PET;

[0015] And the substrate needs to be cleaned before use. The specific cleaning operation is as follows: successively use deionized water, acetone, and ethanol for ultrasonic treatment, and then blow dry with nitrogen.

[0016] Preferably, the cleaning operation of the target in step 1 is as follows: introduce argon, adjust the chamber air pressure to 0.6 Pa and the target-substrate distance to 80 mm, turn on the RF power supply with a sputtering power of 4 - 8 kW to clean the surface of the target, clean it twice, with each cleaning time of 30 min and an interval time of 5 min.

[0017] Preferably, in step 2, the target-substrate distance is 80 - 120 mm, the substrate temperature is 25 - 200 °C, and the substrate rotation speed is 3 - 6 rad / min.

[0018] Preferably, the thickness of the low-infrared reflection thin film is 95-105 nm.

[0019] In addition, a low-infrared reflection thin film prepared by the above-mentioned preparation method of the low-infrared reflection thin film is also disclosed.

[0020] The beneficial effects of this application are:

[0021] This application provides a low-infrared reflection thin film and a preparation method thereof. By controlling the molar ratio between zinc oxide and aluminum oxide in the zinc oxide-aluminum target and the working atmosphere during magnetron sputtering, the obtained thin film has a relatively high infrared light transmittance in the wavelength range of 750-1300 nm. Detailed implementation manners

[0022] In the description of this application, it should be noted that for those not specifying specific conditions in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0023] Example 1

[0024] A low-infrared reflection thin film, and its preparation method is as follows:

[0025] Step 1: Put the soda-lime glass substrate (containing 71.0% SiO 2 , 13.1% CaO and 15.9% Na 2 O) that has been ultrasonically cleaned successively with deionized water, acetone, and absolute ethanol and dried with nitrogen, and a zinc oxide-aluminum target with a molar ratio of zinc oxide to aluminum oxide of 98.5:1.5 into the sputtering chamber, introduce argon, and adjust the chamber pressure to 0.6 Pa and the target-substrate distance between the zinc oxide-aluminum target and the soda-lime glass substrate to 80 mm. Turn on the radio frequency power supply with a sputtering power of 6 kW to clean the surface of the target. Clean it twice, with each cleaning time of 30 min and an interval time of 5 min;

[0026] Step 2: Introduce a mixed gas with a volume ratio of argon, hydrogen, and oxygen of 99:0.7:0.3, adjust the pressure in the sputtering chamber to 0.6 Pa, adjust the target-substrate distance to 100 mm, the temperature of the soda-lime glass substrate to 100 °C, and the rotation speed to 4 rad / min. Set the sputtering power to 6 kW, turn on the power supply for magnetron sputtering, and stop sputtering when the thickness of the thin film reaches 100 nm. Put it into the waiting chamber to cool down to 30 °C to obtain the low-infrared reflection thin film.

[0027] Example 2

[0028] Step 1: Put the soda-lime glass substrate (containing 71.0% SiO2 , 13.1% CaO and 15.9% Na 2 O), and a zinc aluminum target with a molar ratio of zinc oxide to aluminum oxide of 98.5:1.5 is placed in the sputtering chamber. Argon is introduced, and the chamber pressure is adjusted to 0.6 Pa, and the target-substrate distance between the zinc aluminum target and the soda-lime glass substrate is 80 mm. A radio frequency power supply with a sputtering power of 6 kW is turned on to clean the surface of the target. The cleaning is carried out 2 times, with each cleaning time of 30 min and an interval time of 5 min;

[0029] Step 2: A mixed gas with a volume ratio of argon, hydrogen, and oxygen of 99:0.7:0.3 is introduced. The pressure in the sputtering chamber is adjusted to 0.55 Pa, and the target-substrate distance is adjusted to 80 mm, the temperature of the soda-lime glass substrate is 25 °C, and the rotation speed is 3 rad / min. The sputtering power is set to 6 kW, and the power supply is turned on for magnetron sputtering. Sputtering is stopped when the film thickness reaches 95 nm, and it is placed in the waiting chamber to cool down to 30 °C to obtain a low infrared reflection film.

[0030] Example 3

[0031] Step 1: A soda-lime glass substrate (containing 71.0% SiO 2 , 13.1% CaO and 15.9% Na 2 O) that has been ultrasonically cleaned successively with deionized water, acetone, and absolute ethanol and dried with nitrogen, and a zinc aluminum target with a molar ratio of zinc oxide to aluminum oxide of 98.5:1.5 are placed in the sputtering chamber. Argon is introduced, and the chamber pressure is adjusted to 0.6 Pa, and the target-substrate distance between the zinc aluminum target and the soda-lime glass substrate is 80 mm. A radio frequency power supply with a sputtering power of 6 kW is turned on to clean the surface of the target. The cleaning is carried out 2 times, with each cleaning time of 30 min and an interval time of 5 min;

[0032] Step 2: A mixed gas with a volume ratio of argon, hydrogen, and oxygen of 99:0.7:0.3 is introduced. The pressure in the sputtering chamber is adjusted to 0.65 Pa, and the target-substrate distance is adjusted to 120 mm, the temperature of the soda-lime glass substrate is 200 °C, and the rotation speed is 6 rad / min. The sputtering power is set to 6 kW, and the power supply is turned on for magnetron sputtering. Sputtering is stopped when the film thickness reaches 95 nm, and it is placed in the waiting chamber to cool down to 30 °C to obtain a low infrared reflection film.

[0033] Example 4

[0034] It is basically the same as Example 1, except that the molar ratio of zinc oxide to aluminum oxide in the zinc aluminum target is 98:2.

[0035] Example 5

[0036] Basically the same as Example 1, except that the molar ratio of zinc oxide to aluminum oxide in the zinc aluminum oxide target is 99:1.

[0037] Example 6

[0038] Basically the same as Example 1, except that in Step 2, the volume ratio of argon, hydrogen, and oxygen in the mixed gas is 98.4:1.5:0.1.

[0039] Example 7

[0040] Basically the same as Example 1, except that in Step 2, the volume ratio of argon, hydrogen, and oxygen in the mixed gas is 99.3:0.1:0.6.

[0041] Example 8

[0042] Basically the same as Example 1, except that in Step 2, the volume ratio of argon, hydrogen, and oxygen in the mixed gas is 99.9:0.05:0.05.

[0043] Example 9

[0044] Basically the same as Example 1, except that in Step 2, the sputtering power is 4 kW.

[0045] Example 10

[0046] Basically the same as Example 1, except that in Step 2, the sputtering power is 8 kW.

[0047] Example 11

[0048] Basically the same as Example 1, except that in Step 2, the sputtering power is 3 kW.

[0049] Example 12

[0050] Basically the same as Example 1, except that in Step 2, the sputtering power is 9 kW.

[0051] Comparative Example 1

[0052] Basically the same as Example 1, except that the molar ratio of zinc oxide to aluminum oxide in the zinc aluminum oxide target is 97.5:2.5.

[0053] Comparative Example 2

[0054] Basically the same as Example 1, except that the molar ratio of zinc oxide to aluminum oxide in the zinc aluminum oxide target is 99.5:0.5.

[0055] Comparative Example 3

[0056] Basically the same as Example 1, except that in Step 2, the mixed gas consists of argon and hydrogen, and the volume ratio of argon to hydrogen is 99:1.

[0057] Comparative Example 4

[0058] It is basically the same as Example 1, except that in Step 2, the mixed gas consists of argon and oxygen, and the volume ratio of argon to oxygen is 99:1.

[0059] Comparative Example 5

[0060] It is basically the same as Example 1, except that in Step 2, the mixed gas does not contain hydrogen and oxygen and consists entirely of argon.

[0061] Performance Test:

[0062] Transmittance of external red light (wavelength 750 - 1300 nm): Tested using an ultraviolet spectrophotometer;

[0063] Carrier concentration: Obtained by testing using a Hall effect tester;

[0064] Carrier mobility: Obtained by testing using a Hall effect tester;

[0065] Resistivity: Obtained by testing using a Hall effect tester;

[0066] After testing, the performance of the low-infrared reflection films prepared in the examples and comparative examples is shown in Table 1:

[0067] Table 1

[0068]

[0069] Conclusion Analysis:

[0070] 1. From Examples 1 - 3 and combined with the data in Table 1, it can be seen that changes in process parameters during the preparation process will also affect the performance of the film. Thus, it can be known that the process parameters of Example 1 are the optimal process parameters.

[0071] 2. From Example 1 and Examples 4 - 5, it can be seen that when changing the composition of the target during sputtering, it will also affect the composition of the film, resulting in changes in the crystal structure and surface appearance of the film, thereby changing the performance of the film;

[0072] Furthermore, from Example 1 and Examples 6 - 8, it can be seen that when the volume ratio of the three gases changes in the mixed gas composed of argon, hydrogen, and oxygen, it will also change the performance of the film;

[0073] In summary, when the molar ratio of zinc oxide to aluminum oxide in the zinc oxide aluminum target is 98.5:1.5 and the volume ratio of argon, hydrogen, and oxygen in the mixed gas is 99:0.7:0.3, the performance of the prepared film is the best.

[0074] 3. As can be seen from Example 1 and Examples 9-10, when the sputtering power of the target changes during sputtering, due to the change in power, the growth of grains in the thin film is affected to varying degrees, resulting in changes in the properties of the thin film.

[0075] Further observing Examples 11-12, it can be seen that when the sputtering power changes further, it will lead to abnormal grain growth, resulting in poor thin film properties.

[0076] 4. As can be seen from Example 1 and Comparative Examples 1-2, under the same process conditions, only by further changing the composition of the aluminum zinc oxide target, the properties of the thin film will also change greatly. Thus, under these process conditions, not all aluminum zinc oxide targets with different compositions can have the same effect.

[0077] 5. As can be seen from Example 1 and Comparative Examples 3-5, since the presence of hydrogen and oxygen in the mixed gas will affect the crystal structure in the thin film, when the mixed gas lacks oxygen, hydrogen, or both, the properties of the thin film prepared under these process conditions will also be poor.

[0078] The above embodiments are preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present application shall be equivalent replacement methods and are all included in the protection scope of the present application.

Claims

1. A method for preparing a low infrared reflection film, characterized in that: The preparation method comprises the following steps: Step 1: Place the substrate and the zinc oxide aluminum target into the sputtering chamber, introduce argon gas, and clean the target; Step 2: introducing a mixed gas of argon, hydrogen and oxygen, adjusting the gas pressure in the sputtering chamber, the target-substrate distance, the substrate temperature and the substrate rotation speed, turning on the power supply for magnetron sputtering, and obtaining a low infrared reflection film; Wherein, the molar ratio of zinc oxide to aluminum oxide in the zinc oxide aluminum target in step 1 is 98-99:1-2; The volume ratio of argon, hydrogen and oxygen in the mixed gas in step 2 is 98.4-100:0-1.5:0-0.6, and does not include 0 and 100.

2. The preparation method according to claim 1, characterized in that: In the step 2, the gas pressure is 0.55-0.65 Pa, and the sputtering power of the magnetron sputtering is 4-8 kW.

3. The preparation method according to claim 1, characterized in that: In step 1, the substrate is selected from one of glass, quartz, sapphire, silicon, polyimide PI or polyethylene terephthalate PET; The substrate needs to be cleaned before use. The specific cleaning operation is: ultrasonic cleaning with deionized water, acetone, and anhydrous ethanol in sequence, and then drying with nitrogen.

4. The preparation method according to claim 1, characterized in that: The target cleaning operation in step 1 is as follows: introducing argon gas, adjusting the chamber pressure to 0.6 Pa and the target-substrate distance to 80 mm, turning on the RF power supply with a sputtering power of 4 to 8 kW to clean the target surface, and cleaning twice, each cleaning time is 30 minutes, and the interval time is 5 minutes.

5. The preparation method according to claim 1, characterized in that: The target-substrate distance in step 2 is 80-120 mm, the substrate temperature is 25-200° C., and the substrate rotation speed is 3-6 rad / min.

6. The preparation method according to claim 1, characterized in that: The thickness of the low infrared reflection film is 95-105 nm.

7. A low infrared reflection film, characterized in that: The low infrared reflection film is prepared by the preparation method of any one of claims 1 to 6.

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