Evaluation of Characteristics of a Tantalum-Nitride Thin Film Resistor on an AIN submount

Abstract

An AIN submount with a thin film resistor and high heat conductivity has been developed for precisely mounting a laser diode (LD) in an optical-disk storage system or a LD module for optical communication. The thin film resistor consisted of a tantalum-nitride (Ta ₂N) thin film deposited by RF magnetron reactive sputtering at a deposition rate of 50 nm/min, a substrate temperature of 350°C, and a nitrogen pressure ratio of 6.0%. We measured the electrical properties of the Ta ₂N thin film resistor on the AIN submount. The resistance was approximately 57.8 Ω and the temperature coefficient of resistance was -30.9 ppm/°C. Moreover, we found that the rate of change of resistance was less than 1.76% on average after reliability tests under conditions such as damp heat (85°C, 85%, 1000 hours), high temperature (150°C, 1000 hours), high temperature in operation (85°C, 40 mA, 1000 hours), and temperature cycling (-30-90°C, 1000 cycles). We thus concluded that the Ta ₂N thin film resistor has high reliability, and such reliable characteristics make the AIN submount suitable for optical devices.