Laser Trim Pattern Optimization for CuAlMo Thin-Film Resistors

The influence of varying laser trim patterns on the electrical performance of a novel CuAlMo thin-film resistor material is investigated. The benefits and limitations of various trim geometries are considered before two patterns, the "L" cut and serpentine cut, are selected to laser-trim resistor samples to target values of 1-10 Omega, using previously optimized laser conditions. The effect of increasing trim gain and varying trim pattern on the stability and standard deviation of the films is then systematically investigated. A two-stage trimming process is used to reduce resistance drift to <0.1% following storage for 168 h at 125 degrees C in air, which also allows much tighter resistance tolerances of < +/-0.1% to be achieved.