Flexible ICs and TFTs: A Roll-to-Roll Excimer Laser Crystallization System for Silicon Films on Polymeric Sheets

Thin-film transistor (TFT) technology has enabled important applications, such as flat-panel displays (FPDs), that cannot be addressed by conventional silicon-wafer-based electronics. There are several benefits to fabricating TFTs on flexible substrates,including lower cost, increased versatility, and improved durability. In addition, flexible substrates allow for a shift from batch to continuous roll-to-roll processing.One challenge is the inability of plastic substrates to withstand high-temperature processing. Excimer-laser-based processes have been used to replace some of the high-temperature steps in TFT fabrication - for example, excimer laser crystallization(ELC).Previously, conventional ELC techniques have been used to crystallize silicon films on flexible substrates; but films crystallized in this manner cannot be used to produce high-performance TFTs. Sequential lateral solidification (SLS) can produce thelow-defect-density microstructures necessary for high-performance TFTs. Anvik Corporation is actively involved in the development of SLS equipment for the manufacturing of TFT-LCD displays. Anvik has also pioneered the development of high-resolution,roll-to-roll lithography systems for fabricating flexible circuits.Herein we propose to develop a roll-to-roll SLS processing system with the capability to conduct SLS on silicon films deposited on flexible substrates. Low-defect-density crystalline silicon films on flexible substrates represents a heretofore unavailablematerial, and would enable numerous flexible circuits applications.The anticipated benefits include the creation of equipment enabling a new processing method: continuous roll-to-roll SLS crystallization of silicon thin films on flexible substrates; aswell as the creation of a new materials category: low-defect-density crystalline silicon thin films on flexible substrates. Such materials would be expected to enable significant performance improvements in flexible circuits applications, such as flexibleintegrated TFT-based displays (e.g., AMLCDs and AMOLEDs), smart cards, and embedded processors for information appliances.