Hello,

   I am trying to anisotropically etch a 200 um well in a silicon wafer
coated with 1 um of oxide. I'm using KOH mixed at 30% concentration and
have tried temperatures at 60 C and 70 C. Both trials the etch worked fine
all the way up to about 90-100 um, and then it just stopped. Even if I
leave the wafer in for extra hours, the etch still remains at 90-100 um.
Nothing else has been done to the wafer before this except a BOE etch to
pattern the oxide. Any ideas would be greatly appreciated.

---Chris