High Reliability 225-400 MHz 50 Watt Silicon Transistor

High reliability NPN transistors were designed and fabricated to operate at 50-watt output power levels in the frequency range from 225 to 400 MHz with power gains in excess of 5 dB. (1) A refractory metallization system consisting of Pt-Si, NiCr, W, Au was investigated and implemented. Devices were tested for electromigration induced failures and compared to those fabricated with an aluminum based system. (2) Geometrical design, material and processing were judiciously chosen to give the devices the required output power, gain and ruggedness under load mismatch conditions. The temperature distribution across the entire surface of the chip was measured under various adverse conditions to anticipate any reliability problems. Additionally, safe operational area testing was performed to check if secondary breakdown would occur at elevated levels of dc power dissipation. (Author)