Yield Development

In the backbone part, there is a hypothetical yield over time curve, and some far-reaching conclusions are drawn form it.

What do real yield curves look like? Well, few people know, because that is one of the bigger company secrets.

However, in 2003, Leachman and Berglund, working for Sematech did a study and release some real (anonymous) data. Here is the interesting curve:

The yield may go up somewhat faster than on the hypothetical curve, but several things are quit clear:

Companies start production with yields as low as (10 - 20) %: In other words: Most of the chips produced go in the garbage bin!

There is a lot frustration potential: For no recognizable reason your yield suddenly collapses substantially! (If the reason would have been recognizable, it would not have happened for more than a day or two and then not shown up on the monthly data given above!)

It's rather difficult to have yields in excess of 80 % - and it is getting worse.

With frame

5.4.1 Development and Production of a New Chip Generation