🚀 go-pugleaf

In article <4rlrf7c@lynx.unm.edu>, swami@chtm.eece.unm.edu (Swami srinivasan) 
writes:
> 
> I need to make a 50 microns x 1000 microns section of glass surface
> ROUGH. I have  a mask with the required dimensions. Most etchants are
> "smooth", and I suspect the common HF based etchants are, too. Are there
> any wet chemical etchants that can be used? 
> 					I also have access to RIE
> and RIBE systems, but cannot think of any obvious ways to use them to
> make a rough surface - so far, we have always wanted a smooth etch!
> We have a full-fledged cleanroom with the usual equipment, so we should
> be able to try out most  suggestions, including uncertain leads.
> 
> We are trying to make a low reflectivity strip on a mirror. This 
> will be used in an external cavity configuration. Initially we thought
> of making crossed diffraction gratings, but there will still be a zero
> order reflection.. and grating fabrication is a little involved. Hence
> we are trying to find ways to make the surface diffusive using some 
> form of etching, with the dimensions decided by a mask.
> 
> Any suggestions will be helpful. Thanks!
> 
> 							     swami


	You might try using gaseous HF instead of aqueous HF.  I recall 
reading somewhere that aqueous HF will leave a "clearer" (smoother?) etch,
while the gas was used to frost light bulbs.  This might provide a coarser
surface.

	Form the gaseous HF by mixing Sodium Fluoride and concentrated
Sulfuric Acid in a lead dish (keep this in a fume hood).


 
> =======================================================================
> swaminathan srinivasan
> center for high tech materials
> eece,university of new mexico,
> albuquerque, nm 87131, usa			swami@chtm.eece.unm.edu
> ========================================================================
> 						


Ken