etching through wafer

Chris Kenney kenney at
Thu Apr 8 10:12:13 PDT 2004

Hi Andrew,

Our group has been etching small, high-aspect-ratio features
since the machine was installed.

When you say a 8 micrn hole, do you mean a circular cross
section or a trench?

For circular features we obtain aspect ratios of 15 to 1
after some tuning and some luck.

During the etch the diameter tends to widen.

Several years ago we etched small holes through a 300 micron thick
wafer. The holes were drawn as 15 micron diameter circles on the
mask. As I recall it took 4-5 hours to etch through and the
holes ended up around 22-23 microns in diameter after the etch.

Most papers use trenches when discussing process development
for a DRIE machine. Trenches are easier to measure and
one can obtain higher aspect ratios with trenches.

Unless a paper is very explicit in specifying that circular
holes were used I'd assume they used trenches.



On Thu, 8 Apr 2004, Andrew Arthur Davenport wrote:

> stsetch users,
>    I'm trying to etch a 8um hole through a 325um wafer.  I've tried the
> standard recipies (deep and fastdeep), and also 7um and 10um resist.  None
> of these seem to be able to etch through within 4 hours (by that time the
> resist is burnt).  Have tried bonding to another wafer with photoresist - it
> improves the resist lifetime but will still burn eventually.  Just wondering
> if anyone had experience with small deep features (or aspect ratios >30).
> I'm currently trying one of the recipies in the Ayon paper listed on the SNF
> website, but am uncertain of whether it will work.
> Thanks,
> Andrew Davenport

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