After etching silicon with KOH solution, the etched surfaces are covered with
~0.3 micron globules of some material.

I'm using a thermal SiO2 etch mask.  After KOH etch, I strip the oxide in BOE.
The BOE doesn't seem to remove the contaminate, but results in this material
being broken up into a fine powder-like scum.

Can someone tell me how to remove this material?