Fabrication of thin-film transistors on plastic substrates by spin etching and device transfer process

Abstract

This work presents a novel method to transfer thin-film transistors from a Si wafer to another flexible plastic substrate. First, high-performance poly-Si TFTs were fabricated on 1-mum thick SiO2 of a Si wafer and then adhered to a flexible plastic substrate by the optical adhesive. Next, the spin-etching process was utilized to remove the backside Si with SiO2 as a stopping layer. We have established a qualitative model to explain the relation between the chemical flow rate/rotation speed to the etching rate and the uniformity of Si removal. The Si etching rate is higher than 200 mum/min while maintaining Si to SiO2 selectivity of 250 under optimized spin-etching parameters. Compared to that before transference, no degradation or yield loss was found due to substrate bonding and Si spin-etching steps. Additionally, extrinsic stress shows little effect to the properties of poly-Si resistors on the flexible plastic substrate.