Reducing Post-Trim Drift of Thin-Film Resistors by Optimizing YAG Laser Output Characteristics

A study to determine the effects of laser parameters on tantalum nitride resistor stability is presented. A model Of the laser heat affected zone is proposed which relates laser pulse width, power, wavelength, repetition rate, and waist size parameters to energy delivered to remaining resistor material. Samples of qualified tantalum nitride resistors are trimmed with a range of laser parameters, and the results are compared with the model. The excellent agreement between the model and experiment allows these results to be used for process control and throughput versus tolerance calculations.