Study on the Dust Concentration Evaluation for Submicron Semiconductor Particles in Confined Space Based on Laser Transmission

Abstract

Metal dust is generally recognized as a major reason for explosion-related accidents in semiconductor industry. Based on laser transmission, this study proposes a method of rapid dust concentration measurement for three common types of raw materials (Si, GaAs, and SnSe2) under a low-concentration condition in semiconductor manufacturing. First, according to the Lambert-Beer law, the quantitative relations between the extinction coefficient of the experimental system and some characteristic parameters including particle diameter and optical path were derived. Next, the experimental system consisting of five modules (namely, light source module, photoelectric receiving module, differential amplification module, signal processing module, and data acquisition module) was constructed. The wave optical model for metal dust concentration measurement was also established. Further, the effects of particle material, diameter and concentration on the electromagnetic field intensity distribution and laser transmissivity within a wavelength range of 405–830 nm were discussed. The results showed that the imaginary part of the refractive index of the dust material imposed a significant effect on laser transmissivity. From the perspective of a complex refractive index of the material, the optical detection wavebands for these three dust particles ranged from 532 nm to 650 nm. The increase in dust particle size reduced the total number of particles along the unit optical path, leading to the overall increase of transmissivity. Moreover, the transmissivity dropped in a quasi-linear manner with the increase of dust concentration. A comparative analysis of the theoretical and experimental results revealed that the established model could well predict the dust concentrations and distributions of semiconductor raw materials, showing favorable guidance for their rapid detection in semiconducting industry.