CN1188160A - Making of optical anti-reflection film by diamond-like and diamond compound film - Google Patents

Abstract

The diamond composite film belongs to the field of thin film technology, and it is formed by chemical vapor deposition on the diamond-like film made by high-frequency plasma method and then by microwave plasma method. Coated on silicon solar cells and infrared detectors, it has optical anti-reflection effect. The invention solves the problems of photoelectric conversion effect and poor light transmittance of such optoelectronic devices, and has better passivation effect, especially widens the spectral response wavelength range of silicon solar cells, and the transmittance increase rate is close to the theoretical value of 40%. , It solves the light-transmitting material for infrared detectors, especially Hgde devices, and improves the average transmittance.

Description

Diamond-like carbon and diamond composite film as a new type of optical anti-reflection film

The invention is a diamond-like and diamond composite film coated on a photoelectric device, especially used as an optical anti-reflection film on a silicon solar cell and an infrared detector, and belongs to the field of thin film technology.

As we all know, diamond has properties that cannot be achieved by ordinary materials, such as good chemical stability, high hardness, corrosion resistance, excellent insulation and optical transparency, etc. For this reason, the study of diamond films. Since the end of the 1970s, it has been paid attention to by scientific and technological workers in various countries, and has been successful in film preparation. So far, it has been used in certain applications, especially in the use of germanium and other materials as additives due to the wide range of light transmission. Permeable membrane.

The anti-reflection coatings of silicon solar cells have been SiO, TiOx, Al ₂ O ₃ , etc. in the past, but they all have the problems of anti-reflection and photoelectric conversion efficiency. The present inventor once used diamond-like film to be coated on solar cell and HgCdTe infrared detector for the first time, has obtained quite good effect (patent number: 92108354.8), but diamond-like film has corrosion resistance, chemical stability, hardness after all. , wear resistance and even light transmittance are not as good as diamond films, especially in some special occasions, such as aerospace, marine engineering and harsh environments, which show some shortcomings of diamond-like films. For photodetectors, In order to improve the photodetection rate in the infrared band or improve its different anti-reflection effects, such as HgCdTe infrared detectors in the 8-14 μm band, suitable materials can be selected for anti-reflection wavelengths, wide range, wear resistance, corrosion resistance, insulation Excellent film material, the purpose of the present invention is to overcome the above-mentioned deficiencies, and use the composite film of diamond film and diamond-like film as the anti-reflection film of photoelectric devices, especially coated on the film used in poor environmental conditions (such as in space) In solar cells, instead of SiO, TiOx and single diamond-like films, etc. For some optoelectronic devices, the composition of volatile materials, such as III-V, IV-VI and II-VI compound semiconductors, diamond composite films are particularly critical, both It can solve the problem of excellent anti-reflection effect of various wavelengths, and can ensure that the components are not volatile, maintain a certain stoichiometric ratio, and improve its stability, life and reliability against the erosion of harsh external environments.

According to the present invention, the diamond-like film has stated in the patent No. 92108354.8: mainly use a high-frequency 13.56MHz sputtering instrument, rely on plasma chemical vapor deposition, and the raw material is methane (or the organic solvent ethanol carried by hydrogen), hydrogen and argon as Raw materials, and the optoelectronic device of the required deposited film material as the substrate, maintain the pressure between 10 ^-3 ~ 10 ^-2 Torr, and apply a certain DC bias voltage -100 ~ -400V between the two electrodes, wait After glow discharge, adjust the DC reverse bias voltage and deposit the film on the substrate. Some parameters involved in the process roughly include: high frequency power, substrate temperature, reverse bias voltage, adjustment of the proportion of each component in the mixed gas, etc.

It should be particularly pointed out that when the above-mentioned diamond-like film is prepared, the substrate on which the lower electrode is placed can be cooled by water, so that the overflow of volatile components of the substrate material or the composition decomposition can be prevented. It is suitable for the play of some easily decomposable components such as P, As, Hg, S, In, Sb, Se, Te, etc. of optoelectronic devices composed of III-V, IV-VI, and II-VI materials.

If the diamond film is re-deposited on the diamond-like film, the above-mentioned photoelectric device should be placed in a microwave plasma device, and the atmosphere CH ₄ : H ₂ =1.5-3% mixed gas is introduced into the growth system, and the gas flow rate is 50-100 sccm ( sccm-standard milliliter per minute), the absorbed power of the microwave plasma method is 300-600V, and the substrate temperature must be controlled at 200-500°C. The thickness of the diamond that continues to grow on the diamond-like carbon is 100-1000nm. Especially it can be grown on solar cells and II-VI, III-V, IV-VI optoelectronic devices containing volatile components, especially for anti-reflection coatings of infrared optoelectronic devices, it can not only protect materials, passivate the surface, There is also an optical anti-reflection effect. The microwave source power involved in the diamond film production process is 2.45GHz, and the output power is continuously adjustable from tens of watts to 1000 watts. The diameter range of the quartz tube can be adjusted according to the size of the waveguide transmission into the quartz chamber, except for hydrogen growth Diamond can also be replaced by alcohol, methane or other alkanes. Pay attention to the control of growth conditions. Generally, a uniform composite film of diamond and diamond-like carbon can be grown, and it has obvious optical anti-reflection effect on optoelectronic devices.

In order to facilitate the understanding of the present invention, the technical process of the diamond composite film and the implementation effect after being coated on the photoelectric device are illustrated in conjunction with accompanying drawings 1 and 2.

The diagram of the experimental device for the new type of optical anti-reflection coating made of diamond-like carbon and diamond composite film is shown in the attached drawing of the specification. Figure (1) is the general diagram of the experimental device; Figure (2) is the longitudinal section of the A-A' axis. In the figure 1-magnetron (2.45GHz) 2-anode ammeter 3-circulator 4-incident power meter 5-reflection power meter 6-air load 7-four-screw adjuster 8-rectangular waveguide 9-cut-off waveguide 10-quartz Reaction tube 11-reaction gas inlet 12-flat optical glass 13-optical thermometer 14-plasma region 15-substrate 16-plasma region 17-seal joint 18-short-circuit piston 19-cooling water (the microwave source is represented in the dotted line box ).

Embodiment, utilize the microwave source shown in Fig. 1 (marked as dotted line part), it is the magnetron 1 of 2.45GHz by frequency, anode ammeter 2, incident power meter 4, reflected power meter 5, air load 6 and four-screw adjuster 7, the output power of the microwave source is adjustable and continuous, and the maximum power can reach 1000W. The microwave generated by the microwave source composed of a square frame is made of brass, and the size is 110×55mm ² The rectangular waveguide 8, the cut-off waveguide 9 short-circuit the piston 18, so that the microwave is transmitted in the TE10 mode Φ39mm (or adjusted as required) in the quartz reaction tube 10 (or reaction chamber, deposition chamber), the quartz reaction tube 10 is placed horizontally, using Alcohol and hydrogen are reactants. Control the flow of hydrogen gas with a gas flow meter, and the bubbler bottle with alcohol is placed in the ice-water mixture to form the air intake unit 20. The hydrogen flow rate through the bubbler bottle is 2 sccm (standard milliliters/minute), and the reaction gas inlet 11 , into the deposition chamber, while controlling the total flow of hydrogen to be 102 sccm (standard milliliters per minute), a decompression system is connected at the rear of the reaction chamber as a pumping unit 21 to maintain the pressure of the reaction chamber at 2.0kPa～7.0kPa, and the deposition power Generally, it is 300-450W. In order to know the temperature in the reaction chamber, a photoelectric thermometer 13 is used to detect through the flat optical glass 12 . The substrate is taken at a temperature of 200-500°C, and a 100nm diamond-like film has been deposited on its surface by high-frequency plasma chemical vapor deposition (patent No. 92108354.8). Substrate 15 (silicon wafer with crystal orientation [111], silicon solar cell, II-VI, III-V, IV-VI compound semiconductor optoelectronic material) can be placed on the quartz boat 14, so that it is completely immersed in microwave The plasma region 16 generated after the excitation is introduced. The thickness of the film can be made from 0.1mm to 1mm.

The above-mentioned diamond-like and diamond composite films are tested, and the film makes the short-circuit current transmission rate of silicon solar cells ≥ 38%. And it is close to the theoretical value of 40%. The present invention is also applied to the II-VI group HgCdTe as an anti-reflection coating. The wavelength is 4-14 μm, and the transmittance is increased by more than 16% on average, and the transmittance at 8 μm is increased by more than 22%. Diamond Composite films have better passivation conditions than pure diamond-like films.

As an optical anti-reflection film, diamond composite film has both passivation and good anti-reflection effect. It is a film with wide application and strong practicability.

Claims (4)

1, a kind of diamond film that makes with high frequency plasma body method vapour deposition diamond-film-like and microwave plasma, be deposited on photoelectric device surfaces such as germanium, make the diamond compound film with antireflection, feature of the present invention is to make the diamond compound film with the anti-reflection and passivation effect of light on silicon solar cell and infrared eye surface.

2,, it is characterized in that the effect of the anti-reflection and passivation of on the infrared eye that II-VI, IV-VI, III-V compound material are made tool optics according to the diamond compound film of claim 1.

3,, it is characterized in that having the anti-reflection effect of optics on the infrared eye that the HgCdTe material constituted according to the diamond compound film of right 1,2.

4,, it is characterized in that having the effect of the volatilization that prevents P, As, Hg, In, S, Te, Se component and nonstoichiometry ratio according to the diamond compound film of right 1,2.

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