Fast, high density 4 K-bit static RAM’s (SRAM’s) have been fabricated utilizing electron beam direct slice writing and dry etch processes to demonstrate 1.25 μ VLSI MOS device technology. Access times of 15 ns were obtained for these scaled memories with channel lengths of 1.0 μ on a chip size of only 6 K mil2 vs the standard production 4 K SRAM with 35–45 ns access times, a 2.5 μ channel length and a chip size of 20 K mil2. All levels were patterned using a vector-scanned electron-beam exposure system with a capability of 1 μ resolution, ±0.2 μ level-to-level registration, and automatic chip-by-chip alignment. High speed, high resolution positive and negative electron beam resists were used for all patterning steps. All implanted, 250 Å gate oxide, scaled MOS processes with dry etching techniques for Si, SiO2, and Si3N4 were used to realize these static memories functional over full temperature.
The Digital Micromirror Device™ (DMD™) developed at Texas Instruments is a spatial light modulator composed of 500,000 to 1.3 million movable micromachined aluminum mirrors. The DMD™ serves as the engine for the current generation of computer-driven slide and video projectors, and for next generation devices in digital television and movie projectors. The unique architecture and applications of the device present several packaging and test challenges. This paper provides a description of package humidity modeling and verification testing, as well as an overview of the automated optical testing and test equipment that have been developed to support manufacturing of the DMD™.
Process control in photolithography will be a key requirement for the successful manufacturing of 0.25 micron semiconductor products. A program to study photolithography process control techniques was recently undertaken at Texas Instruments. The target for this program was 0.35 micron technology, and the lithography used a combination of conventional wet developed resists and surface-imaging dry developed resists along with both i-line and deep UV steppers. Advanced process control techniques were applied in order to achieve lithography control without lot send-ahead wafers or test wafers. A notable conclusion was the need for the development of real-time sensor technology, particularly for the stepper exposure process.
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