基于离轴积分腔吸收光谱技术的低浓度水蒸气测量

Measurement of Low-Concentration Water Vapor Based on Off-Axis Integrated Cavity Absorption Spectroscopy

水蒸气的浓度是半导体密封元器件生产过程的重要指标之一,水蒸气的浓度超标将对半导体的产品质量造成严重影响,开发高灵敏度、高精度的实时水蒸气检测技术至关重要。搭建了一套基于离轴积分腔吸收光谱技术的低浓度水蒸气测量实验装置,反射镜的反射率为0.99920,有效光程为250 m,探测时间为0.025s。通过激光光束离轴入射到激光谐振腔提高了谐振腔的模式密度,从而提高了积分腔输出吸收光谱的信噪比。利用该装置对水蒸气在7036.5cm-1附近的吸收进行测量,探测灵敏度为7.07×10-6 cm-1,测量误差小于5%。分别向腔内注入不同浓度的水蒸气,对系统的在线连续测量性能进行了测试,结果表明该系统可达到工艺应用的要求。

The concentration of water vapor is one of the important indices during semiconductor sealing element manufacturing process,and excessive water vapor has seriously influence on the quality of semiconductor.Therefore,a real-time water vapor measurement technique with high sensitivity and high precision is crucial.In the work,a low-concentration water vapor measurement system based on off-axis integrated cavity absorption spectroscopy is developed,the reflectivity of the mirror is 0.99920,effective optical path length is 250 m,and measurement time is 0.025 s.The mode density of the resonant cavity can be improved when the light is off-axis transmitted into the laser resonant cavity,thus the signal-to-noise ratio is significantly increased.The system is utilized to investigate the absorption line of water vapor near 7036.5 cm^-1,it is found that the sensitivity of the system is 7.07×10^-6 cm^-1,and measurement error is less than 5%.By injecting different concentrations of water vapor into the cavity,the on-line continuous measurement performance of the system is tested,the result reveals that the system can meet the process requirement.