Quasi-vertical multi-tooth thin film transistors based on low-temperature technology (T ⩽ 600 °C)

A new concept of vertical thin film transistor (TFT), called thin film transistor comb (TFTC), is proposed based on polycrystalline silicon (polysilicon) deposited at low temperature (T ⩽ 600 °C). This structure, compatible with glass substrates, is designed to have up to 4 teeth and enables to get a high channel width W with a short channel length L. The channels of TFTC are made of a non-intentionally doped (NID) polysilicon layer between two in situ heavily-doped polysilicon layers; all these three layers are deposited by low pressure chemical vapor deposition (LPCVD) method. Electrical characteristics of TFTC show relatively high on-currents (ION) correlated with the geometric parameters. However, high off-currents (IOFF) are also observed due to the large overlapping area between drain and source regions.

► We design and fabricate quasi-vertical multi-tooth thin film transistors. ► Devices are based on polysilicon deposited in low-temperature technology. ► On-current is in good agreement with the geometric parameters. ► High off-current is observed due to the large overlapping area between source and drain. ► Off-current can be reduced by mask design modification.