🚀 go-pugleaf

ntaib@silver.ucs.indiana.edu (Iskandar Taib) writes:
: Perhaps they test a few processors on a wafer? And if the processors
: fail then the whole wafer is thrown out? Makes sense to me.. perhaps
: what causes problems are registration of masks or bad doping, which 
: would affect entire wafers, not just one chip on the wafer.

Some makers of very small semiconductors will just throw away the ring of
die around the edge, package the rest up, and take the hit during package
test.  Note that this is for a very mature fab process, very small parts,
very cheap packaging.

Lots of fab houses have what is called a "parametric test" which verifies
test structures included on the wafer.  If these fail, then the wafer
would be chucked.  If it passes, then the entire wafer would be tested.
This is because many defects are random: particles, metal problems, etc.

Scott Linn
scott@hpcvccl.cv.hp.com