| Silicon nitride materials have many excellent properties, such as high-melting-point, high hardness, strong stability, low expansion coefficient, good thermal conductivity, strong thermal shock resistance and excellent optical performance. Silicon nitride block material and film can be widely used in photoelectron, micro-electronics, machining, chemical industry, solar battery, aerospace and integrated circuit industry, etc. Based on all kinds of microspheres, micro plate and micro ring echo, and with high sensitivity, no marks and other notable features, Whispering Gallery Mode (WGM) resonators have important applications in biological, chemical sensing and testing field. The traditional WGM resonators used the semiconductor process with silica material to form microstructure, then through the CO2laser reflow heat treatment to get micro cavity. This WGM sensors based on silica material has a quality factor (Q value) of108. If we can use high refractive index and low absorption thin film material to preparation micro cavity, it is expected to further improve the quality factor, and so as to improve the sensitivity. With regard to semiconductor compatibility, the silicon nitride transparent film of which refractive index up to2.0is an ideal candidate to prepare such WGM resonant micro cavity.The research aim is to investigate the influence of sputtering technology to silicon nitride thin film components, microstructure, and optical performance, and therefore to get the best performance of silicon nitride thin film preparation process. Transmittance is as high as possible near infrared band, refractive index near2.0and film thickness is above2μm.Radio Frequency (RF) magnetron sputtering is employed to prepare First determine the silicon nitride thin film’s preparation process is RF magnetron sputtering, and then to prepare the thin film samples of with different process conditions are deposited. Experimental tests of the above samples are conducted by Spectroscopic ellipsometry and spectrophotometer for optical performance evaluation with the aim to get the optimized sputtering process. Silicon nitride thin film samples are examined through the XRD, SEM, FTIR and EPMA tests, the correlation of deposition process with thin film microstructure, composition and surface topography are generated.The experimental results of the study show that meeting the optimized requirements of the silicon nitride thin film’s best coat sputtering process of silicon nitride coatings are as follows:Ar/N2flow ratio is1:1, and the pressure are between0.01mbar～0.02mbar; In the situation of the same sputtering power and sputtering time, when Ar/N2flow ratio are the same the refractive index of silicon nitride thin film samples’refractive index presents the tendency of increasing with the rising increase of pressure when Ar/N2flow ratio are the same. Transmittance increases in turn with the rising of deposition pressure raise. The film is amorphous, and no crystalline material appear material appears after heat treatment; With the increase of pressure, Si-N key characteristic peak spectral intensity decreased significantly in turn; After high temperature treatment at600℃, the surfaces of microscopic reunion in film structure becomes smooth and density, while at the same time, the gaps between the reunion things become larger and appears gaps between the clusters become larger and appear some big channels and holes. FTIR test investigation results show that the silicon nitride thin film samples which under the heat treatment by400℃,"H2O peak"(1400-1800cm-1) disappear and the major peak strength of Si-N key weakened obviously, which explain demonstrates that the film thickness decrease after heat treatment and density improved in a certain extent. After high temperature treatment in700℃, the "H2O peak" of silicon nitride thin film sample disappear, Si-N key vibration peak presents a red shift phenomenon. |
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