COMPARATIVE-STUDY OF LARGE GRAINS AND HIGH-PERFORMANCE TFTS IN LOW-TEMPERATURE CRYSTALLIZED LPCVD AND APCVD AMORPHOUS-SILICON FILMS

The crystallization of undoped amorphous silicon films deposited by lo w-pressure and atmospheric-pressure chemical vapour deposition (LPCVD and APCVD) at temperatures ranging between 510 and 650 degrees C and s ubsequently annealed at temperatures between 510 and 700 degrees C, fo r different durations, have been studied by transmission electron micr oscopy (TEM). It is found that the grain size in these films is influe nced by the deposition and annealing temperatures and also by the depo sition rate and film thickness. Maximum grain size of approximately 64 00 Angstrom A has been obtained in LPCVD silicon films 2000 Angstrom A thick deposited at 540 degrees C and annealed at 550 degrees C for 14 4 h, whereas APCVD silicon films deposited at 590 degrees C and anneal ed at 610 degrees C for 72 h produced a grain size of-approximately 41 00 Angstrom A. At higher and lower deposition temperatures the grain s ize was found to be smaller.