Marie I. Harrington

Thin-film transistor fabrication for high brightness reconfigurable vacuum fluorescent displays

The design and fabrication of a thin-film transistor array for use in a reconfigurable, active matrix vacuum fluorescent display suitable for high ambient light operating conditions such as automotive instrument clusters is described. Thin-film transistor (TFT) arrays were fabricated in a novel 4-transistor per pixel configuration using a p-channel polycrystalline silicon transistor fabrication process. Display assembly was then completed by the Futaba Corporation. The robust transistor structure is capable of enduring the 550/spl deg/C post-processing anneal temperature associated with phosphor deposition and packaging, Initial displays yielded luminances of 2500 ftL when operated at 40 V, and suggest an ultimate brightness of 5000 ftL for 55 V operation.

Materials and Processes For Silicon TFT's On Aluminosilicate Glass: An Alternative Soi Technology

As-deposited polycrystalline silicon and argon ion laser recrystallized silicon thin film transistors (TFTs) have been fabricated on Corning Code 1729 glass substrates. This novel aluminosilicate glass has an expansion coefficient matched to that of silicon and a chemical durability comparable to that of fused silica. N-channel enhancement mode transistors were made using conventional IC device fabrication procedures (including thermal oxidation to form the gate insulator) modified to have a maximum processing temperature of 800 C. The- polycrystalline silicon TFTs exhibit leakage currents of less than 2x10 -11 A/ μm; of channel width and good stability and reproducibility. Transistors made in the recrystallized silicon show field effect electron mobilities as high as 270 cm 2 /V s, approximately 15 times the mobility of comparable devices made in as-deposited polycrystalline silicon. The recrystallized silicon devices also exhibit lower threshold voltages and lower leakage currents than do the comparable polycrystalline silicon devices. Major advantages of this TFT technology include the use of a novel, potentially low cost glass substrate and the simultaneous processing of both polycrystalline and recrystallized silicon devices on the same substrate material. This approach represents a new avenue for the incorporation of active devices into a variety of applications including integrated active matrix displays.