Controlling the amount of Si-OH bonds for the formation of high-quality low-temperature gate oxides for poly-Si TFTs

Lowering process temperatures for polysilicon Thin-Film-Transistors (TFTs) has given rise to new worries about the quality of TFT gate oxides. Specifi cally, the presence of large amounts of Si-OH bonds in gate oxides has beco me a matter of concern. We discuss methods for suppressing the formation of Si-OH bonds during Chemical Vapor Deposition (CVD) of Low-Temperature Proc essed (LTP) gate oxides. In various kinds of CVD techniques, the use of Rem ote-Plasma Enhanced CVD (RPCVD) is shown to be efficacious for the suppress ion. The control of the reaction between the silicon source gas and the oxy gen source gas is also shown to be effective. We also show that decreased a mounts of Si-OH bonds in LTP-CVD gate oxides result in desirable decreases in both leakage current and fixed oxide charge densities, and that the amou nt of Si-OH bonds can be used as an index of gate oxide quality.