特气室温红外探测器的噪声分析(英文)

Noise analysis of special-gas IR detector

由MEMS技术制备的特气室温红外探测器的噪声主要包括温度噪声、机械热噪声和背景噪声。从理论上建立了器件的基本热模型,推导得到器件的等效热熔和等效热导分别为8.1μJ/K和1.0×10-3W/K,温度噪声约为1.73×10-10W/Hz1/2;通过器件的工作机理和能量均分原理,推导得到热机械噪声的等效噪声功率约为9.96×10-9W/ Hz1/2,器件的背景噪声约为3 .22×10-11W/Hz1/2,从而得出器件的归一化探测率约为9 .03×106cm.Hz1/2/W。实验表明,器件的噪声中热机械噪声为主要噪声源,大小主要由浓硼硅薄膜的机械性能和器件结构决定,可以通过增大薄膜厚度,减小薄膜面积,从而增加薄膜的特征频率的方法来减小器件受外界振动的影响,但以降低器件的灵敏度为代价。另外环境振动噪声也对器件的影响很大。为了减小外界气压和温度变化的影响,提出了一种新型的双腔结构来减小和平衡外界环境变化引入的噪声。

The noises of a special gas IR detector fabricated by MEMS mainly include the temperaturefluctuation noise, mechanical-thermal noise and the background noise. Based on thermal conduction theory, a thermal model is built up to get the effective thermal content and the effective thermal conductivity to be 1.0 × 10 ^-3 W/K and 8. 1 μJ/K,respectively ,and the temperature fluctuation noise is nearly 1.73 × 10 ^-10 W/Hz^1/2. According to the device operating principle and energy equipartition theory of thermodynamics, the mechanical thermal noise is 9. 96 × 10^- 9 W/Hz^1/2 , and the background noise is nearly 3.22×10^11 W/Hz^1/2, so that the normalized detectivityis deduced to be 9.03×10^6 cm · Hz^1/2/W. Experiment results show that the mechanical-thermal noise coming from the structure and the mechanical performance of a heavily doped Si membrane is the main noise of the device, which can be reduced by minishing the membrane area and extending the membrane thickness to increase the mechanical resonant frequency of the membrane,but should be at the price of reducing the sensitivity of the device. The vibration of environment also influences on the device a lot. To decrease the noise coming from the fluctuation of air pressure and the temperature fluctuation of the surrounding, a new double cell counteracting structure is presented.