Reliability Characterization of RuO sub 2 Thin Film Resistors

In the present work, we have studied RuO sub 2 film resistors deposited onto alumina substrates with a resistance (550 KiloOhms) fixed by laser trimming (two lasers cut or kerfs were made in the resistor to precisely adjust the resistance). Reliability tests were performed by exposing the resistors to high humidity (>90% RH) at room temperature under bias for each individual resistor. The change in current of each resistor together with the temperature and OH inside the cell, we monitored during the test. The alumina substrate, resistors with or without kerf, glazing and protective coatings have been tested and analyzed by using AFM and SEM. The effect of different variables on the stability of the resistance was analyzed: a) glaze, b) kerf, c) coatings and d) combination of coatings and glaze. The results of the tests from a 3 day exposure to 90% RH showed that: 1) the presence of the glazing ont he resistors increases its stability in high humidity; 2) The kerf depth has some relevance to the stability in humid air, but may not be the most important factor; 3) 3) coating A can provide good protection but stability is greatly improved by the presence of the glaze; 4) Coating B alone can provide good protection from the humid environment. The effect of various factors in the stability was studied.