| Description |
The miniaturization of mechanical, electrical, and optical systems has created the need for a viable microillumination technology. This thesis reports the results of the development and testing of a miniature light source for use in microsystems. The light source, called a microlamp, consists of a micromachined tungsten thin-film filament, suspended above a glass substrate, which is resistively heated to incandescence. Microlamp modeling, fabrication, and testing are described and performed to determine device efficienciency, lifetime, and cost. The results of these measurements are compared to other microillumination technologies. Computer modeling was used to design the microlamps. To obtrain an accurate model, the properties of sputtered tungsten thin films were characterized and compared to bulk values. Included in the study were the temperature-dependent mechanical, electrical, and thermal properties. The simulated results were compared to measured values and were found to accurately model imcrolamp operation. Microlamps were successfully fabricated with lengths ranging from 250 to 2000 um, thicknesses from 0.25 to 2 um, and widths of 9um. Microlamp fabrication is simple, inexpensive, and compatible with standard IC processes. Control of fil stress was aided by a tabulation of the effects of sputter parameters on thin film properties. Wet and dry etching of tungsten thin films and wet etching of a sacrificial layer was performed. The fresse-dry antistiction method was performed to assure the complete release of the tungsten filaments from the substrate. A computer-controlled vacuum test chamber was built to perform measurements on the microlamps. The illuminance, power, and time to failure were directly measured and used to compute the temperature, luminous efficacy, and lifetime of the devices. Possible failure mechanisms were analyzed. |
