Silicon Technologies at a Glance

C.C.

Single-crystal silicon, which is the typical wafer on which ICs are fabricated, represents the high end of silicon performance. It is grown from a seed crystal and sawed into wafers. Kopin (see the April News & Views) fabricates the grid of liquid-crystal transistors and the drive circuitry on a single-crystal piece of silicon. The circuit is then transferred to a glass substrate for assembly into a complete LCD well-suited for small, high-resolution displays.

Polysilicon is made from amorphous silicon through an annealing, or thermal treatment, process. The annealing helps to organize the silicon crystal structure. High-temperature, low-temperature, and laser-annealing methods are all possible for this conversion, with performance dependent on each process.

Amorphous sil icon has the lowest electrical performance characteristics of the silicon family. Composed of a disorderly array of miniature silicon crystals, it is deposited on the substrate by chemical vapor deposition and is commonly used to fabricate solar cells and LCDs.