The fabrication of thin-film-transistor (TFT) devices on a transparent substrate lies at the heart of active-matrix-liquid-crystal-display (AMLCD) technology. This is both good and bad. On one hand it is a difficult task to manufacture millions of intricate semiconductor devices reliably over such large display substrates. On the positive side, AMLCD technology can aspire to become much more than a “display” technology. The idea is as follows: It is possible for one to readily fabricate additional transistors to execute various electronic functions—those that would otherwise be handled by separate large-scale-integration (LSI) and very large-scale-integration (VLSI) circuits—on the periphery of the display. Since this can be done, in principle, with no—or a minimal number of—additional processing steps, substantial cost reduction is possible and significant value can be added to the final product.
Doing so and doing it well can ultimately lead to “system-on-glass” products in which the entire electronic circuitry needed for a product is incorporated directly onto a glass substrate. This means that integrated active-matrix liquid-crystal displays (IAMLCDs) have the potential to bypass conventional Si-wafer-based products and may lead TFT technology to compete directly against Si-wafer-based monolithic integrated circuits.