Originally posted by: Phynaz
Well firstly, you're talking about binning and not yields...
Parametric yield is the major factor in binning.
You can bin down, you can't bin up.
From my days at TI we rarely cared to distinguish the break-downs of "yield" unless we had major outlier activity going on and we needed to track down the source of the poor yield.
Binning 100% functioning chips that operated at unsellable speeds (400 MHz Niagara anyone? No, OK let's just call that poor yield then) made TI just as much money as binning chips at 0 MHz (particle causing metal opens or malformed xtors).
The accountants only cared about sellable product at the product's specs. Only the fab people who relied on hitting certain scrap parameter milestones (for personal bonuses of course) cared about making pareto's of excuses as to why product was not sellable. (I know because I was one of these fab guys for a period of time)
Having an excursion of particles causing bad yield was important to know when you wanted to go about solving a particle excursion. Having xtor parametrics going crazy because an implanter is having issues with beam current stability is important to know if you are trying to dial in bin speeds.
But only a fab guy should care about these nitty-grittys, the accountants, customers, and shareholders should really just focus on the highlights: how many sellable chips are making it to the hands of paying customers?
Everything else is just an excuse for failing to execute as well as your competitors. Go with best of breed, not with best at excuse making.