Silane/Disilane Safety

Eugene Ngai

A wide variety of flammable silicon compounds are used in the Semiconductor Device Fabrication industry. The most common are the Silicon Hydrides (silane, disilane, trisilane). The higher molecular weight silicon hydrides such as disilane and trisilane are finding increasing use since they can be dissociated at much lower reactor temperatures than silane. Increasing the number of Si-Si bonds increases flammability and reactivity. As a result, disilane (Si-Si) is more flammable than silane, while trisilane (Si-Si-Si) is more flammable than disilane. Silane has a reported LFL of 1.37% while disilane has a reported value of 0.1% or even less depending on the report.

This ½ day PDC will present findings of a joint research project between Chemically Speaking LLC and National Kaohsiung University of Science and Technology (NKUST) to characterize the behavior of disilane under various user conditions using funding by Edwards Vacuum LLC and NKUST. Unlike silane, very little research has been done on disilane. All existing work were conducted under laboratory conditions rather than real world conditions. Comprehensive testing were carried out to determine LFL, pyrophoric limit, limiting O2 concentration, extinction velocity, and reaction overpressure, etc. These results were then used to develop test conditions in metal tubes simulating vacuum exhaust systems where air was introduced into the system at various disilane concentrations.

The final phase of the testing was in a 2-meter long clear plexiglass tube to visually observe the reaction using a high speed video camera. The results of this testing will dramatically improve the safety of disilane use.


1. Prof Jenq-Renn Chen – National Kaohsiung University of Science and Technology

2. Michael Gordon – Edwards Vacuum

3. Eugene Ngai – Chemically Speaking LLC

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