What is site loss % in multi-site semiconductor testing?

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What is site loss % in multi-site semiconductor testing?

yieldHUB has developed a concept and statistic called site loss %. This is designed to capture the loss of units because of  inconsistent performance of sites when testing die in multisite testing.

Site loss % is the yield percentage decrease because all sites were not yielding the same as the best yielding site. Note that this is not the difference between the yield of any given sites. We take into account the actual number of units tested per site.

1. Example of four sites and assume 100 units tested on each site:

Site: Site 1, Site 2, Site 3, Site 4

Yield: 90%, 95%, 95%, 98%

Number Tested: 100, 100, 100, 100 = 400 tested altogether

If Site 1 yielded at 98% (site 4 yield) then 8 more units would have been good.

If Site 2 and Site 3 each yielded at 98% then 6 more units would have been good.

So 14 more units would have been found good assuming yield should be consistent.

The potential yield then is 98%.

The actual yield is 94.5% so the Site Loss % is 3.5%.

 

2. Example of four sites where there were different units tested per site:

Site: Site 1, Site 2, Site 3, Site 4

Yield: 90%, 95%, 90%, 90%

Number Tested: 100, 200, 150, 140 = 590 tested altogether

Failed: 10, 10, 15, 14 = 59 failed altogether => yield of 91.7%

Failed if all are 95% yield: 5, 10, 8, 7 = 30 that would have failed => potential yield of 94.9%

The site loss % in this case is 3.2%

So 3.2% of units were potentially lost because all sites were not yielding the same as the site with the maximum yield

2018-11-26T10:41:34+00:00 November 23rd, 2018|News, Product News|

About the Author:

John O'Donnell
John is a thirty year veteran of the semiconductor industry with a background in test development and product engineering and travels widely to customers all over the world. John has presented at numerous conferences and has several patents in test technology.