Interference effect on laser trimming and layer thickness optimization

摘要

Abstract: Due to imprecisions in the deposition process, linear semiconductors require post-production circuit adjustment. Lasers are used to adjust (or trim) thin film resistors to precise electrical performance specifications. The effect of coherent laser beam interference in multilayer structure on thin film resistor trimming has been well documented. As the layer structure becomes more and more complex, the difficulty in determining the interference effect on the trimming results becomes greater. To assist the circuit designer and laser trimmer user, a simplified multilayer thin-film resistor interference model and a universal software program have been developed. Several verifications have been made of customer designs using the model and software programs. While the model gives the user a clear picture of the physics of the interference effect, the software provides a precise recommendation for layer structuring that results in maximum laser absorption into the resistor.!8