TFTs on Flexible Substrates

Abstract

The flat panel display industry has been built around TFTs on rigid glass substrates, but there are well-identified applications requiring flexible substrates. This chapter summarises the properties of common plastic substrate materials, and discusses the issues of implementing TFT fabrication schedules on them. It looks in detail at the strategies which have been developed in order to fabricate a-Si:H, poly-Si and organic TFTs on flexible substrates. These have included direct fabrication on the plastic substrates at reduced temperatures, as well as carrier plate and transfer plate processing. For carrier plate processing, the plastic substrates are temporarily bonded to glass carrier plates during processing, and, at its completion, the plastic substrate, plus its TFT layers, are detached from the glass. For the transfer process, the TFT layers themselves are detached from the glass, and bonded to a separate plastic substrate. A third approach has been to use an alternative flexible substrate, which is easier to handle, such as thin foils of stainless steel. In addition to these technological considerations, the mechanics of bending and strain in flexible substrates is summarised.