Dear Bob
Thanks a lot!
That`s very helpful. You always give a lot of pointers in this forum.
But the calculation of systematic yield is by what kind of method? The
same for random yield calculation?
I knew that Yield = Ysystematic * Yrandom
So how do we get each of the term?
Anyone has any idea, kindly share with me.
Thank you!
best regards
Jason
On 8 12 , 4:27, Bob Pownall <repown...@[EMAIL PROTECTED]
> wrote:
> jasoncl...@[EMAIL PROTECTED]
wrote:
>
> <Summary: Some questions about systematic vs. random yield loss>
>
> I think the distinction between systematic yield loss and random yield
> loss comes largely after determining the _cause_ of the yield loss.
>
> For example, particle defects, while (essentially) randomly distributed
> across a wafer, would be considered a systematic yield loss mechanism,
> because particle defects affect pretty much every wafer in a batch and
> every batch in a fab.
>
> Another example of a systematic yield loss mechanism would be processing
> through equipment which is only marginally capable of doing what it's
> being asked to do. When you send the material into the equipment, you
> know that only (say) 70% of if will be good when it comes out. You just
> don't know _which_ 70%.
>
> In contrast, yield loss due to a misprocessing / execution error or
> equipment failure would be random yield loss. You can't really predict
> when somebody's going to make a mistake or when a piece of equipment is
> going to fail. (Well, if you're careful and smart enough, you can
> probably predict when equipment is going to fail, but then why would you
> keep using it?)
>
> You might also be able to categorize yield as systematic vs. random
> based on the geographic dispersion of the yield loss. If the outer 1cm
> of the upper left quadrant of a wafer is always bad, that's probably a
> systematic problem, even if you don't know what's causing it. If yield
> loss is uniform across the wafer (any particular die has a 1%
> probability of being bad), then the mechanism is probably random.
>
> Just my thoughts...
>
> HTH
>
> Bob Pownall
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