Amorphous Silicon Thin-Film Transistors for Digital Circuits

Abstract

AbstractFor any integrated circuit technology used in digital design, digital circuits can be modeled as an inverter. Once the operation and characteristics of the inverter circuit are thoroughly understood, the results can serve as a foundation to be extended to the design of logic gates and other more complex circuits. This chapter fits with this context. It is concerned with amorphous silicon technology as an alternative means for the implementation of digital circuits using a transistor-level approach. In an attempt to probe such circuits performance, some design considerations are discussed in terms of stability and reliability. Being the basic building blocks for the construction of logic circuits, logic gates are technology process dependent, and as such, some trends of their manufacturability are to be suggested. For this purpose, the chapter adopts a standard integrated circuit design flow to set up the representative model of the a-Si transistor. The lack of p-type complementary transistor makes the realization of stable and reliable a-Si-based thin-film circuits with comparable CMOS-like performance a challenging task. The criteria assessment of such circuits is associated to several parameters such as threshold sensitivity, high and low levels, propagation delay time and noise margin. The chapter aims to develop and investigate the feasibility of building a-Si-based digital circuits. On the other hand, the operation and characteristics of some amorphous silicon-based logic gates circuits are thoroughly investigated via the implementation of the a-Si:H TFTs operation model established in Chaps. 4 and 6 using LTspice. The model validation allowed the gates performance investigation and the exploration of the trade-offs available in their design.Keywordsa-Si:H TFTa-Si technologyDigital circuitsLogic design