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Chemical vapor deposition of amorphous silicon films from disilane

Thesis/Dissertation ·
OSTI ID:6386176
Amorphous silicon films for fabrication of solar cells have been deposited by thermal chemical vapor deposition (CVD) from disilane (Si/sub 2/H/sub 6/) using a tubular flow reactor. A mathematical description for the CVD reactor was developed and solved by a numerical procedure. The proposed chemical reaction network for the model is based on silylene (SiH/sub 2/) insertion in the gas phase and film growth from SiH/sub 2/ and silicon polymers (Si/sub n/N/sub 2n/, n approx. 10). Estimates of the rate constants have been obtained for trisilane decomposition, silicon polymer formation, and polymer dehydrogenation. The silane unimolecular decomposition rate constants were corrected for pressure effects. The model behavior is compared to the experimental results over the range of conditions: reactor temperature (360 to 485/sup 0/C), pressures (2 to 48 torr), and gas holding time (1 to 70 s). Within the above range of conditions, film growth rate varies from 0.01 to 30 A/s. Results indicate that silicon polymers are the main film precursors for gas holding times greater than 3 s. Film growth by silylene only becomes important at short holding times, large inert gas dilution, and positions near the beginning of the reactor hot zone.
Research Organization:
Delaware Univ., Newark (USA)
OSTI ID:
6386176
Country of Publication:
United States
Language:
English