Research On Key Technology Of Infrared Detection Based On Thermal-induced Mechanical Deflection

Infrared radiation detectors are widely used in the military, civilian, medical, security, defense, etc. It becomes a national high-tech imaging technology hot chase, especially for the use of an optical reading system. A number of studies had been done on the infrared imaging technology in recent years, especially for the technology based on an optical readout system of micro-cantilever structure.Based on an optical readout method a thermal infrared detection system was provided in this paper. Infrared detector was a sensitive detection unit, which was composed of a micro-cantilever structure and based on the principle of Bi-material thermal-induced mechanical deflection. Stress properties and infrared characteristics of the silicon nitride film were the focuses and the production process of the infrared detector was also studied. The main results were as following:1) An infrared focal plane arrays based on bi-material beams of thermal-induced mechanical deflection was design:A K9 glass was used as the substrates, element array was 120 x 120, unit size was 40μm × 40μm, which relatively had a simple structure and the reflector area and infrared radiation absorption area were increased simultaneously.2) The effects of process parameters on the stress properties, infrared absorption characteristics and etching characteristics of silicon nitride films were studied:PECVD RF power, reaction pressure and other parameters were changed in the experiment, different stress state of the films was shown. The film minimum compressive stress was 65Mpa at the thickness of 600nm; PECVD RF power, deposition time, temperature and other process parameters were changed, the film maximum relative absorption intensity was about 4.0 at the thickness of 600nm; ICP power reaction pressure, bias power and other process parameters were changed, the maximum etching rate of the film reach to the speed of 14.5nm/s, Si3N4/EPG533 selection ratio was close to 4.25.3) The manufacturing process of detector was studied:photolithography techniques, magnetron sputtering, PECVD techniques, ICP etching and other MEMS process were used to prepare the sacrificial, the reflective and the infrared absorption layer. The optimum parameters of the experiment:the gold film sputter was prepared at the power of 200W, the argon flow rate of 75mL/min, the air pressure of 3.1 Pa; the silicon nitride film is perpetrated by PECVD at the temperature of 250℃, the power of 180W, the pressure of 60Pa, the SiH4 flow rate of 40mL/min and the N2 flow rate of 60mL/min; the silicon nitride film was etched at the ICP power of 300W, the bias power of 70W, the reaction pressure of 30mTorr, the SF6 flow rate of 30 mL/min and the O2 flow rate of 13 mL/min.