Aging Characteristics of Field Effect Thin Film Active Devices

The aging characteristics of thin film field effect triodes have been studied under humidity, temperature, and electrical stress. The device characteristics are very sensitive to humidity. In dry argon at room temperature the device characteristics did not change within six months. At constant elevated temperature between 50°C and 12l°C the transconductance of thin film triodes is almost constant for at least 50 days. The gate voltage at constant drain current and voltage increases during the first few days until it reaches a constant level again. Devices under electrical stress showed a similar behavior but the increase of the gate voltage continued for about 20 days. A tentative model is proposed for some of the failure modes.