Essential Guide to Semiconductors, The

Testing Phase I

After several passes through the deposition-expose-etch-repeat process, our chip is finished! It takes, on average, 20 to 30 individual steps to finish a chip of medium complexity. By this time, the chip has been in production for several weeks and has passed through dozens of people's hands and almost as many robotic handlers. In short, an enormous amount of expensive time and effort has been expended to produce this wafer full of chips. Now it's time to see how many of them actually work.

When a new fab is built, it's a sad reality that practically all of the chips it produces for the first few weeks will probably be bad. Hundreds of wafers will be processed, representing thousands of chips, and not one of them will work. Over ...