Polycrystalline silicon thin-film transistor technology for flexible large-area electronics.

摘要

This dissertation addresses two critical issues for the ultra-low temperature (T ≤ 100°C) fabrication of poly-Si TFTs directly on polymer substrates. The first issue is the formation of the gate dielectric, since thermal oxidation and conventional low-pressure chemical vapor deposition (LPCVD) are not possible at 100°C. The work here introduces the use of high-density plasma (HDP) sources, specifically helicon and electron cyclotron resonance (ECR) PECVD, for TFT gate oxide formation at ultra low temperature.; The second area of emphasis in this dissertation focuses on the poly-Si channel-film formation. Short-pulse excimer laser crystallization (ELC) is necessary to form poly-Si when a polymer substrate is used. (Plastics are incompatible with long, high-temperature crystallization processes.) Results from this new process show an improvement in TFT performance and uniformity. The process is self-aligned and simple, so it can be easily incorporated into existing ELC-based poly-Si TFT process flows.; Two additional areas of work are presented in the latter part of the dissertation. A prototype for an active-matrix organic light-emitting diode (AMOLED) display is presented. A layout and fabrication process was designed for a monochrome 128 x 64 pixel, 80 dpi display on a 4” x 4” square glass substrate. Each pixel contains two transistors to drive an OLED. AMOLED displays are of great interest because they promise lower power, higher brightness, and wider viewing angle than the pervasive active-matrix liquid crystal display (AMLCD). In addition, the inherently low deposition temperature of organic materials allows for easy processing on flexible plastic substrates.; Lastly, a method is demonstrated for resist-free, direct patterning of thin films using an excimer laser. This technique addresses current problems plaguing the flat panel display manufacturing industry. High costs are associated with large area lithography that uses conventional photoresist coating, exposure and development. We present preliminary results for a direct patterning method that dramatically simplifies the lithography process. Specifically, the Si active layer is patterned by selectively exposing a laser beam onto a sacrificial layer of Si_xGe_1−x that sits atop the Si film. The sacrificial film mixes with the underlying Si film and is then removed by a highly selective wet etch. (Abstract shortened by UMI.)