Never Buy Maxim (again)

It is amazing at what they don't tell you at places where you are 
employed. If you don't need to know it, the fab will not tell you. [IBM 
wafer fabrication isn't exactly like the dog eat dog world of commercial 
semiconductors.] There are a number of latch-up prevention schemes I 
stumbled across having material companies do analysis. Probably the only 
one safe to reveal was one company that used to ion implant their wafers 
from the back to make what amounted to a low resistivity layer, like a 
faux epi wafer. This was easy to find since the sheet rho measured 
didn't match the published value. [The published value was at the 
surface of the wafer.] Since everyone uses real epi these days, there is 
no harm in revealing that one. Some companies use beta killing schemes, 
which could still be in use.