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Pdf-version of the complete thesis (1,993,580 bytes) (Dutch text).
New 27/10/2003: Pdf-version of the 8-page English
summary (217,131 bytes)
Please acknowledge the source (PhD thesis, Herbert De Smet, Ghent University, Belgium, 1993) if you use anything from my manuscript..
Active matrix addressing has improved many properties of high-resolution liquid crystal displays. The strong viewing angle dependence and the noticeable cross-talk, typical for the early, passively addressed, LCDs, have disappeared and high quality full-colour flat-panel displays have come into existance. The thin-film transistors or TFTs that serve as electronic switches in the active matrix, can also be used to integrate part of the driving electronics onto the display glass. This would strongly reduce the number of interconnections and hence the assembly cost. Furthermore it would improve the system reliablility. In this work, a new technology for making p-channel germanium TFTs with a staggered bottom gate structure, compatible with the n-channel poly-CdSe active matrix technology is constructed. Several technological problems are solved to achieve this. Furthermore, many published TFT-based driver circuits are intensively studied and compared and the relevant information is summarized. Different methods to produce grey scales are compared as far as image quality, viewing angle dependence, etc. are concerned and a new method is proposed. Based on this information, a complementary TFT driver circuit is designed and network simulations are performed on the building blocks. An interesting application of a static shift register with TFTs is discussed. Stimulated by the difficulties in determining appropriate MOSFET model parameters from TFT measurements, a new, numerical, dedicated TFT model is constructed, requiring few parameters and representing the most important TFT features. This model will be used in future simulations and, at this moment, automatic parameter extraction is being built into our measurement software. A working driver circuit is realized in three steps, coinciding with three mask sets. A new 64x64 pixel active matrix mask set with ample safety margins and yet a large aperture ratio is a by-product. After devising and assembling the measurement setup, the operation of the driver circuits is demonstrated. The measured invertor delay is as low as 32 ns in our 25 um technology. In addition, a fault location system for our active matrices is designed, fabricated and used, leading to interesting conclusions.
Herbert De Smet, November 28, 1993
