Chialun,
        A slight correction. Conical or tapered holes can be made in glass
and silicon with mechanical drilling.
        As for smoothness mechanically drilled holes can be quite smooth,
depending on what one considers to be "smooth".
        John Klemic

>Dear MEMS community,
>    Here's a summary of responses to my original question of glass drilling
>technology.  I have found nine possible methods for machining glass wafer.
>I also list contact info or service links forwared to me.  Hope this helps
>to people who are interested in this issue.  Thank you all for your inputs.
>
>Glass machining methods,    potential for large production,    smoothness,
>conical or tapered profile
>1. Mechanical drilling             no
>rough                no
>2. Ultrasonic drilling                yes
>rough                yes
>3. Laser drilling                       yes
>smooth             yes
>    (eximer and CO2)
>4. Micro-sandblasting            yes
>(?)                      yes
>    (Crystal Mark, Mems, Inc)
>5. Ultrasonic drilling w/EDM  ?
>no                      no
>    (Prof. Masuzawa team in Tokyo University)
>6. FIB                                       ?
>smooth              yes
>7. FIB enhanced etching        yes
>unknown           unknown
>   (Norsam Technologies)
>8. Selective etching with photosensitive glass (Foturan)
>                                                  yes
>unknown           unknown
>9. chemical-assisted laser etching
>    (Revise Inc., DARPA project)
>                                                  unknown
>unknown           unknown
>