[mems-talk] Question about perforation

[Morten Aarøe]

Hi,

If you do HF vapor etching, of a 1 micron oxide layer, you shouldn't 
need holes in the suspended structure unless it is very large. I am 
currently using it to release a structure about 200 microns wide with no 
holes in it, and have used it for 50 micron structures before, so in any 
case these values are definitely doable. Of course, this is only vapor 
etching.

I'm not sure why you need to do wet etching, except maybe for speed, but 
wet etching of 1 micron layers will probably give you trouble with 
surface tension/wetting and may be limited by diffusion in the water.

Hope it helps and good luck :-)
// Morten

Yan Xin wrote:
> Hi everyone,
>
> For the inertial sensors, we usually need to perforate the suspended
> structure to release the structure with wet etching process.
> -But how to know if the holes are big or dense enough to release the structure
> completely?
>
> For example, in the SOIMUMPs process, the oxide layer is 1 microm, the
> structure layer is about 25 micron, undercut is 1.8 micron per side by  HF
> vapor etching,
> -Does this mean that  the distance between edges of  two adjacent etched
> holes must be less the 1.8*2 micron if i need  to release the structure
> completely?