Constant-Current Stressing of SiCr-Based Thin-Film Resistors: Initial “Wearout” Investigation

We have started an investigation of the ldquowearoutrdquo characteristics of two of our thin-film resistor processes as a part of a product and process transfer. Our goals are the following: 1) to find out what happens to these resistors under accelerated stress and define ldquofailure;rdquo 2) to compare results between ldquoequivalentrdquo resistor films that are independently developed in two of our internal fabs; and 3) to generate better reliability-based design rules as a function of current density, temperature, and resistor geometry. We have characterized the changes in resistance and temperature coefficient of resistivity as a result of accelerated to highly accelerated test conditions, using thermal and constant-current stresses, and determined activation energies for some of these changes. We have found that we can produce resistance increases and resistance decreases, depending on resistor process and stress levels, with an activation energy of about 1 eV for resistance increase for one of the resistor process types at one fabrication site and an activation energy of about 3 eV for the resistance decrease for the other three process type and fabrication-site combinations.