High voltage active matrix backplane for driving array of MEMS devices based on offset-gate poly-Si high voltage TFT

Abstract

Active matrix TFT backplanes are widely used for driving flat panel displays. Depending on the needs and characteristics of different display media, a variety of active matrix materials, circuits, and configurations have been demonstrated: poly-Si, multi TFT/pixel backplanes for driving OLEDs ; the industry standard a-Si, single TFT/pixel backplanes on glass for driving LCDs; and low cost, inkjet printed organic TFT backplanes for driving electrophoretic media. However, the majority of AM TFT backplanes, despite the wide range of channel materials, all have limited voltage driving capability (typically less than 50V) and limited frame rate (less than 60 frames/s). Here we will present a novel active matrix backplane that is capable of driving arrays of high voltage devices (up to 100V) at extremely fast frame rates (up to 1000 frames/s). This backplane is capable of driving novel display media that have high voltage requirements (eg, MEMS) or high speed requirements (e.g., frame-sequential color/grayscale or rastered projection). We achieve this with a standard Excimer Laser Annealed, poly-Si TFT process but novel pixel design using one offset-gate TFT for high voltage driving and one standard TFT for fast frame rate operation. A QQVGA format (160×120), 500um pixel pitch active matrix backplane has been successfully designed, fabricated, and tested. In this talk, we will describe the device characteristic, circuit and mask design as well as the test result of this high voltage, high frame rate backplane.