Failure mode of high power fixed RF resistor of RuO2 thick film on AlN substrate

Fixed RF resistor based on AlN substrate and RuO₂ resistive film investigated. AlN substrate is most commonly used material for high power RF resistor recently because of low dielectric loss, high thermal conductivity and environmental problem. RuO₂ based resistive film is also most widely used resistive film material because of low TCR and chemical stability. But low adhesion strength to AlN substrate is well-known problem of reliability concerns. Reliability tests were configured to evaluate immunity to each stress. Failure analysis for failed specimen was executed nondestructively and destructively. Result of analysis revealed that CTE mismatch, diffusion between metal electrode and resistive film and adhesion strength were major stress factors of the failures.