Characterization and Hazards of the Silicon-Based Polymers Produced in the Manufacture of Ultrapure Polysilicon

Abstract

The process of making ultrapure polysilicon by the Siemens process results in an unwanted secondary reaction forming oligomers and polymers containing a silicon backbone. These byproducts accumulate in the exhaust piping and downstream equipment used in the polysilicon manufacturing process. They become extremely dangerous when exposed to moisture, including moisture contained in ambient air, becoming intensely flammable and shock-sensitive. This flammability is retained even in an inert atmosphere. Tragically, these byproducts were involved in the deadly explosion at the Yokkaichi Plant of Mitsubishi Materials Corporation in Japan. The work presented here characterizes these byproducts in their various states and provides insights into best practices for treating piping and equipment fouled by these materials. An example of the calculation of the energy released by ignition of these materials in an industrial piece of equipment is included.

Structural Estimation and Hazard Evaluation of Potentially Explosive Residual Silanes Generated in Semiconductor Manufacturing Processes

“…Chen et al have conducted extensive studies of the infrared spectroscopy and shock sensitivity of hydrolyzed products of HCDS; the Si–Si bond in HCDS is proposed to be preserved during hydrolysis and can be cleaved by shock, leading to intramolecular oxidation of the neighboring silanol (Si–OH) groups to form a networked Si–O–Si structure and molecular hydrogen . Although these studies based on model compounds such as HCDS for silanes and an Si 8 H 10 O 14 molecule for hydrolyzed products are very informative, the characterization and development of the appropriate method to manage the RS generated at actual manufacturing processes are still needed …”