Physicochemical Characteristics and Occupational Exposure of Silica Particles as Byproducts in a Semiconductor Sub Fab.

Kwang-Min Choi,Soo-Jin Lee

doi:10.3390/ijerph19031791

Abstract

This study aimed to elucidate the physicochemical characteristics and occupational exposure of silica powder and airborne particles as byproducts generated from the first scrubbers of chemical vapor deposition and diffusion processes during maintenance in a semiconductor facility sub fab to reduce unknown risk factors. The chemical composition, size, morphology, and crystal structure of powder and airborne particles as byproducts were investigated using a scanning electron microscopy and transmission electron microscopy equipped with an energy dispersive X-ray spectroscopy, and an X-ray diffraction. The number and mass concentration measurements of airborne particles were performed by using an optical particle sizer of a direct-reading aerosol monitor. All powder and airborne particle samples were mainly composed of oxygen (O) and silicon (Si), which means silica. The byproduct particles were spherical and/or nearly spherical and the particle size ranged from 10 to 90 nm, based on primary particles. Most of the particles were usually agglomerated within a particle size range from approximately 100 nm to 35 µm. In addition, most of the powder samples exhibited diffraction patterns with a broad and relatively low intensity at 2θ degrees 21.6–26.7°, which is similar to that of pure amorphous silica. The above results show the byproduct particles are amorphous silica, which are considered a less toxic foam compared to crystalline silica. The number and mass concentrations of PM10 (particles less than 10 µm in diameter) ranged from 4.250–78.466 particles/cm3 and 0.939–735.531 µg/m3, respectively. In addition, 0.3–1.0 and 2.5–10 µm particles occupied the highest portion of the number and mass concentrations, respectively. Meanwhile, several peak exposure patterns were observed at a specific step, which is the process of removing powder particles on the inner chamber and cleaning the chamber by using a vacuum cleaner and a clean wiper, during the maintenance task.

Highlights

The semiconductor industry is one of the fastest growing and most rapidly changing manufacturing sectors in the world
Chemical vapor deposition (CVD); detail step—silicon nitride (Si3 N4 ), and diffusion; detail step—poly Si and SiO2 film deposition were selected as target processes, because silica powder byproducts are capable of being generated from the processes
For the scrubber of chemical vapor deposition (CVD) silicon nitride (Si3 N4 ), all powder and airborne particle samples were mainly composed of oxygen (O) and silicon (Si), which means silica particles, and fluorine (F) elements were intermittently detected according to the sample

Summary

Introduction

The semiconductor industry is one of the fastest growing and most rapidly changing manufacturing sectors in the world. The demand for novel, diverse and complicated chemical substances is increasing, according to the shrinkage of the design rules [1,2,3]. An extremely well-controlled and clean environment is needed, and must be maintained at the correct temperature, humidity and pressurization of the clean room, and provide forced air circulation. Workers, including the operator, and the process and facilities engineers, in the clean room must be covered from head to toe in dust-free garments, to protect against the spread of contaminant particles [4]. Almost all items of production equipment in the semiconductor industry are closed in operation, and the excess chemicals used in the manufacturing process are removed by exhaust ventilation systems.

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