MMIC capacitor dielectric reliability

Field strength and leakage are intrinsic dielectric properties which alone are not sufficient to ensure high reliability. To analyze lifetime, one also needs to consider “charge to breakdown” failure caused by defects and their effect on the dielectric thinning. The linear field model was used to explain the aging effects of electric field and temperature on capacitors. This model shows the field effect is considerably more important than the temperature effect over typical ranges. It is this insensitivity to temperature aging which causes the reliability of capacitors to be overlooked during MMIC temperature accelerated life testing. Using the ramped voltage method, we have determined the predicted median lifetime (for operation at 10 volts and 160 nm thickness) of our dielectric film to be 50 million hours with a lognormal standard deviation (sigma) of 0.1. Analysis of data from capacitors fabricated with a test mask set has shown that the failure mechanism may be modeled as random defects where the defect density is independent of either capacitor area or periphery