Recent Results on Nonlinear TFT Output Characteristics and Implications for AMLCD Pixel Charging

摘要

The pixel chairing analysis presented here shows that the TFT performance requirements need to be for various different in-product AMLCDs, as well as future larger and/or higher resolution AMLCDs. The analysis, which incorporates the effects of TFT nonlinear contact resistance on AMLCD pixel charging, is applicable to any kind of TFT processing technology, and in particular to lower cost, lower mask count technologies. We quantify the penalty in charging performance that occurs for even the smallest noticeable current crowding in TFT characteristics. It has been shown by others that the loss in performance is sensitive to the channel length and manifests itself in tow ways: 1) in an apparent reduction in device mobility and 2) in a nonlinear decrease of output conductance at low drain-to-source bias. Our results clearly demonstrate that while the first effect can be designed around, the second effect, primarily evident in the downward hooking of differential output conductance plots, may prevent the pixel from charging to its target level in a worst case scenario and must be explicitly included in the design analysis for future generation AMLCD products with smaller and/or less complex TFTs.