TShin film transistors fabricated at low thermal budgets in various types of polycrystalline silicon films on glass substrates

摘要

Polycrystalline silicon thin film transisors (TFTs) were fabricated in as-de-osited plysilicon films as sell as in various kinds of crystallized films. These included films deposited by LPCVD in the amorphous phases using silane or disilane and films deposited, using silane, in a composite structure containing a mixed phase layer. The devices were fabricated, at low precessing temperatures, in these different types of films on high strain point Corning Code 1734 and 1735 glass substrates. The distribution of grain sizes for all types of films was shown to be wider for larger average grain size. TFTs that were fabricated in crystallized films exhibited field effect electron mobility values of 20 to 40 cm~2/V centre dot sec, subthreshold swings of abut 0.5-1.5 V/dec and threshold voltage values of 2-3 V. TFTs in as-deposited polysilicon films had a smaller mobility of about 5 cm~2/V centre dot sec, similar sugbthreshold swing and slightly higher threshold voltage.