Skip navigation.
640K will be enough for anybody...

What is semiconductor reliability?

The semiconductor device reliability is defined as a degree or characteristics that indicates the functional stability of the device over a time. The degree of reliability is the probability in that the device executes its defined functions during an estimated period under defined conditions. In general, the failure rate at time 0 is expressed as part per million (ppm). The failure rate during the periods of initial and random failures is expressed as Failure in time (Fit), where 1 Fit=10-9/time. The wear-out failure period is expressed as Time To Failure (TTF), which refers to the life until a certain cumulative failure rate is reached.

The reliability of a semiconductor device is represented by a failure rate curve as shown in Figure 1.This is often called a "bathtub curve" for its shape.The curve is divided into three parts.The first part indicates initial failures that occur immediately or in a short period after the device is started to use. The second part, which is relatively long, shows random failures. The final part represents wear-out failures that occurs due to fatigue and degradation, which increase as the device is expiring its life. The reliability of a semiconductor device is represented by a failure rate curve as shown in Figure 1.This is often called a "bathtub curve" for its shape.The curve is divided into three parts.The first part indicates initial failures that occur immediately or in a short period after the device is started to use. The second part, which is relatively long, shows random failures. The final part represents wear-out failures that occurs due to fatigue and degradation, which increase as the device is expiring its life.

Semiconductor reliability bathtub curve

Figure 1: Ssemiconductor reliability bathtub curve

Initial failures, which often originate in the production and testing stages, decrease as time passes. Random failures depend on the device's inherent reliability...It is determined by the design and stable during the middle period. Wear-out failures increase as the time passes due to increased deterioration and fatigue.However, since a semiconductor device has a very long life compared to other devices and the ware-out period starts at very last part of its life, it is not generally a problem.