Depositing Controlled, Matched Resistors for Circuit Edit of Analog Circuitry

During a silicon debug, it was found that the gain of a radio receiver circuit dropped dramatically at certain frequencies due to an imbalance in one of the signal paths. A metal fix was proposed, but consensus could not be reached on how to validate it because of the difficulty of the FIB edit required and the inherent uncertainty of the approach. In this article, the authors explain how they came up with an alternative approach that proved to be faster, more reliable, and easier to validate than the cut-and-join fix initially proposed. They describe each step of the analog circuit editing process, explaining how they deposit, characterize, and connect matched resistors using focused ion beam techniques.