TABLE OF CONTENTS Cost of test (COT) is becoming an increasingly critical factor in the business models of semiconductor companies as well as fabless semiconductor companies. The reason for this is advances in technology. In the early days of the semiconductor industry, the goal was to simply get a good part even if there was only one good part on the whole wafer. Later on, the cost to package the parts began to become a critical factor. However, the yield (i.e., the number of good dies per wafer) increased significantly over the years and so did the size of the wafer that is used to produce those chips. In the 1970s the typical wafer size was 3 inches (and even then there were very often only a handful of good die in the center of the wafer).
In 2000 the first wafer fabs started to use 12-inch wafers to produce chips. In the meantime the yields were going up significantly and are often today in the mid-90% range or even higher. The methods of packaging have been getting more sophisticated as well over the years, and the cost of packaging has come down. Finally, the level of integration has increased to what was unthinkable just 10 years ago. Higher levels of integration, however, mean that the production testing of those dies is getting more complex and the equipment has to perform more functions and tests than in the past. This requirement, however, leads to a higher cost of the test equipment and/or...
