Poly-Si Thin Film Transistors Fabricated with Rapid Thermal Processing

ABSTRACTIn this work, we studied the rapid crystallization and the rapid tbermal oxidation of amorphous silicon films deposited at 465°C by low-pressure chemical vapor deposition (LPCVD) from disilane. The crystallization is well-controlled and the thermal bugdet is reduced compared to conventional processes. Results concerning the electrical and structural characteristics of poly-Si thin film transistors (TF7) are given. Furthermore, we obtained after plasma hydrogenation better mobilities in the case of rapid thermal processing (RTP) (μp-61 cm2/V.s, VT−8.3 V, subtbreshold slope−-0.8 V/decade, ION/IOFF− 1. 106 for p-type and μn-80 cm2/V.s, VT−3. 7 V, subthreshold slope−1.4 VWdecade, ION/IOFF−5.104 for n-type) compared to conventional processing performed at 600°C. The mobilities are improved by a factor of 2 to 3 despite the smaller grain size in the silicon films. We also showed a correlation between the optical absorption coefficient k (at 405nm) and the mobility wbicb appears not only dependent upon, the grain size but also upon the grain quality (grain boundaries and defects inside the grain).This study shows that the structural and electrical properties of thin-films and oxides fabricated by RTP are at least as good as those obtained by conventional techniques.