Sokwon,

  The aspect ratio of glass wet etching highly depends on the adhesion
between glass surface and the mask layer. I was using Cr/Au/PR as a
etching mask in Pyrex 7740 wet etching and the aspect ratio was around
3~4 when using 49%HF. Anodic bonded Si wafer provides much better
results (please refer to the paper : Deep wet etching of borosilicate
glass using an anodically bonded silicon substrate as mask) but still
larger than 1.5.

  If you are looking for aspect ratio smaller than 1, dry etching
looks more feasible to your application


On 1/11/06, sokwon Paik  wrote:
> Hi
>
>  I need to etch out Pyrex glass for 1-5 micro meter.
>
>  If the aspect ratio is good then I'll do 5 micro meter and if the aspect
ratio is bad then I'll etch only 1 micro meter or 100nm is OK.......
>
>  Could anybody tell me your dry etching ratio and wet etching ratio for Pyrex
glass?
>
>  I'll cover the wafer with S1818 which is not intended to etch out. I wonder
whether RIE or wet etching do not attack the S1818 layer also.....
>