CN108227048B - A kind of low-launch-rate infrared anti-reflection film on Silicon Wafer - Google Patents

Abstract

The invention discloses a low-emissivity infrared antireflection film on a silicon wafer. A front film system and a back film system are respectively deposited on both sides of a double-sided polished silicon wafer substrate. The film system structure of the front film system is: Substrate/1.0814M/0.4048H/1.3307L/0.235M/0.608L/Air; the film structure of the back film system is: substrate/1.3626M/0.5101H/1.6767L/0.24M/0.7661L/Air; where H represents a Ge film layer with λ ₀ /4 optical thickness, M represents a ZnS film layer with λ ₀ /4 optical thickness, L represents a YF ₃ film layer with λ ₀ /4 optical thickness, λ ₀ is the central wavelength, H The number before , M and L is the thickness ratio coefficient of the film layer. The present invention proposes an infrared anti-reflection coating with low emissivity on a silicon substrate. The pass rate is ≥97.6%, and it has a low emissivity in the working band.

Description

A Low Emissivity Infrared Anti-reflection Coating on Silicon Wafer

technical field

The invention belongs to the technical field of optical thin films, and in particular relates to an infrared anti-reflection film based on a silicon wafer, which has an anti-reflection effect on the mid-infrared band range and has a relatively low emissivity.

Background technique

With the development of infrared technology, infrared plays a pivotal role in the fields of atmospheric detection, aerospace and many civil applications. In an infrared optical system, the transmittance of infrared light energy determines the performance of the system. The reflection on the surface of the optical component not only affects the light energy of the optical component, but also the reflected light will form stray light in the instrument, affecting the performance of the optical instrument. In order to solve these problems, one or more layers of film are coated on the surface of the infrared optical element to reduce the reflected light on the surface of the infrared element. Such a film is called an infrared anti-reflection coating or (anti-reflection coating).

In the application of infrared optical systems, in addition to the high transmittance requirements for infrared energy, low emissivity is required in infrared detection of weak radiation such as radiation temperature measurement and infrared spectrometer, especially for some low-signal signals. In the infrared detection with a stable signal-to-noise ratio, the low emissivity of the infrared anti-reflection coating is very necessary.

Contents of the invention

The technical problem solved by the present invention is to provide a silicon wafer-based infrared anti-reflection coating that has an anti-reflection effect on the mid-infrared band range and has a low emissivity, which has a significant effect on the 3.5-15 μm mid-infrared band range. Anti-reflection effect, especially in the range of 4.5-8.5μm mid-infrared band, it has a stable and efficient anti-reflection effect, the highest transmittance ≥ 98%, the average transmittance ≥ 97.6%, and has a low emissivity (The average emissivity increase after coating is ≤0.02), which plays a very good role in improving the performance of infrared detection of weak radiation such as radiation temperature measurement.

In order to solve the above technical problems, the present invention adopts the following technical scheme, a low-emissivity infrared anti-reflection coating on a silicon wafer, which is characterized in that: a front film system and a back film system are respectively deposited on both sides of a double-sided polished silicon wafer substrate ,

The film structure of the front film system is:

Base/1.0814M/0.4048H/1.3307L/0.235M/0.608L/Air;

The film structure of the back film system is:

Base/1.3626M/0.5101H/1.6767L/0.24M/0.7661L/Air;

Wherein H represents a Ge film layer of λ ₀ /4 optical thickness, M represents a ZnS film layer of λ ₀ /4 optical thickness, L represents a YF ₃ film layer of λ ₀ /4 optical thickness, λ ₀ is the central wavelength, The number before H, M and L is the thickness ratio coefficient of the film layer.

The advantage of the present invention is that it proposes an infrared anti-reflection coating with low emissivity on a silicon substrate, and the anti-reflection region has a wide spectral range (with obvious anti-reflection effects in the range of 3.5-15 μm), and in the range of 4.5-8.5 μm The average transmittance in the range is ≥97.6%, and it has a low emissivity in the working band.

Description of drawings

Fig. 1 is a kind of low-emissivity infrared anti-reflection film front film system and the cross-sectional structure schematic diagram of back film system of silicon substrate;

Figure 2 is the transmittance curve of the bare substrate (silicon wafer);

Fig. 3 is the spectral transmittance curve of a kind of low emissivity infrared anti-reflection coating of silicon substrate;

Figure 4 shows the emissivity curves of the bare substrate (silicon wafer) at temperatures of 473K, 523K, and 573K;

FIG. 5 is the emissivity curves of a low-emissivity infrared anti-reflection coating on a silicon substrate at temperatures of 473K, 523K, and 573K, respectively.

In the figure: 1-front film system, 2-silicon wafer substrate, 3-back film system.

Detailed ways

The technical solution of the present invention is described in detail in conjunction with the accompanying drawings. The anti-reflection coating of the present invention has a wide range of spectral anti-reflection (with obvious anti-reflection effects in the range of 3.5-15 μm), and at the same time has more Efficient and relatively stable transmittance, the highest transmittance ≥ 98%, the average transmittance ≥ 97.6%.

At the beginning of the design, the selection of suitable optical thin film materials within the required spectral range was considered first, and finally Ge was used as a high refractive index material, ZnS as a medium refractive index material, and YF ₃ as a low refractive index material. The ZnS material is evaporated by resistance heating with an evaporation rate of 2.3Å/S; the Ge and _YF3 materials are evaporated by electron beams with an evaporation rate of 2.0Å/S and 1.5Å/S, respectively.

The anti-reflection film system of the present invention is a multi-layer non-regular film structure. During the deposition process of the film system, quartz crystal is used to monitor and control the deposition error of the film thickness, so as to obtain a result closer to the design. The present invention deposits the front film system 1 and the back film system 3 respectively on both sides of the silicon wafer substrate 2 polished on both sides, selects the central wavelength λ ₀ as 2000nm, and the film system structure is optimized by film system design software to obtain the front film system 1. The film structure is:

Base/1.0814M/0.4048H/1.3307L/0.235M/0.608L/Air;

The film structure of the back film system 3 is:

Base/1.3626M/0.5101H/1.6767L/0.24M/0.7661L/Air

Among them, H represents a Ge film layer with λ ₀ /4 optical thickness, M represents a ZnS film layer with λ ₀ /4 optical thickness, L represents a YF ₃ film layer with λ ₀ /4 optical thickness, and λ ₀ is the central wavelength , the number before H, M and L is the thickness ratio coefficient of the film layer.

By comparing Figure 2 and Figure 3, it can be seen that there is an obvious anti-reflection effect in the entire 3.5-15μm spectral range, and at the same time, it has high-efficiency and relatively stable transmittance in the range of 4.5-8.5μm, and the highest transmittance is ≥98 %, the average transmittance ≥ 97.6%, has a good performance in infrared anti-reflection. It can be seen from Figure 4 and Figure 5 that the emissivity of the sample will increase with the increase of temperature, but by comparing Figure 4 and Figure 5, it can be seen that the sample after coating (with a low emissivity of the silicon substrate Infrared anti-reflection coating) compared with the sample (bare substrate) before coating, the emissivity increase is not large (≤0.02), so it can be said that this anti-reflection coating has a lower emissivity.

The basic principles, main features and advantages of the present invention have been shown and described above. On the premise of not departing from the spirit and scope of the present invention, the present invention also has various changes and improvements, and these changes and improvements all fall into the claimed invention. range.

Claims (1)

1. A kind of low-emissivity infrared anti-reflection film on the silicon wafer is characterized in that: the two sides of the silicon wafer substrate of double-sided polishing respectively deposit front film system and back film system, The film structure of the front film system is: Base/1.0814M/0.4048H/1.3307L/0.235M/0.608L/Air; The film structure of the back film system is: Base/1.3626M/0.5101H/1.6767L/0.24M/0.7661L/Air; Wherein H represents a Ge film layer of λ ₀ /4 optical thickness, M represents a ZnS film layer of λ ₀ /4 optical thickness, L represents a YF ₃ film layer of λ ₀ /4 optical thickness, λ ₀ is the central wavelength, The number before H, M and L is the thickness ratio coefficient of the film layer; The infrared anti-reflection coating based on silicon wafer has anti-reflection effect on the mid-infrared band range and has a low emissivity, and it has obvious anti-reflection effect on the mid-infrared band range of 3.5-15 μm, especially in the range of 4.5-8.5 μm The infrared band range has a stable and efficient anti-reflection effect, the highest transmittance ≥ 98%, the average transmittance ≥ 97.6%, and has a lower emissivity in the working band, and the average emissivity increases after coating ≤0.02, it plays a very good role in improving the infrared detection performance of weak radiation in radiation temperature measurement.