Trimming Behavior and Post-Trim Characteristics of Ta2N Resistors on Silicon

Laser trimming of thin films on silicon differs in several important respects from trimming on passive substrates such as ceramic. These differences necessitate the characterization of the process and its effect on circuit performance. The trimming behavior of Ta2N thin-film resistors on silicon is studied in detail. Incremental changes in resistance are investigated for several important geometrical configurations. These results are of special value in trimming under measure and predict conditions. It is also shown that the laser trimming of these resistors results in post-trim drift. However, it is shown that proper design guidelines can minimize the effect so that high-precision monolithic circuits can be successfully produced.