Poly-Si peripheral circuits and contact properties of laser processed poly-Si thin film transistors

Monolithic fabrication of a-Si:H and poly-Si TFTs with a dual dielectric gate insulator and the effect of source-drain contact resistance on poly-Si transistor performance are discussed. A dual dielectric gate insulator provides the correct threshold voltages for both a-Si and poly-Si TFTs, thereby simplifying the fabrication processes. The source-drain contact properties of poly-Si TFTs are characterized from measurements of the source-drain series resistance. A comparison is made of the contact resistance between a-Si and poly-Si. The results indicate that the contact effect is negligible for long channel devices with either a-Si or poly-Si contacts. However, poly-Si contacts result in superior device performance over that for a-Si contacts for short channel devices.