| kristianpaul | what is your comb-drive ref? | 01:17 |
|---|---|---|
| kristianpaul | s/ref/specs | 01:18 |
| azonenberg | My tentative plan calls for it to be made from <110> Si wafer, 15-30 microns high, 20 micron wide fingers | 01:20 |
| azonenberg | But that depends on the aspect ratios i'm able to hit experimentally | 01:21 |
| azonenberg | If i'm lucky i could potentially get like a 10:1 aspect ratio which would permit 200um high fingers | 01:21 |
| azonenberg | other papers have done that | 01:21 |
| azonenberg | it depends really on how well my hardmask sticks to the wafer and how well it survives exposure to KOH | 01:21 |
| azonenberg | Right now sol-gel Ta2O5 appears to fill both of those very well | 01:21 |
| azonenberg | its almot impossible to remove, the "scotch tape test" doesnt damage the film whatsoever | 01:22 |
| azonenberg | And its etch rate in KOH according to several publications is usper low | 01:22 |
| azonenberg | usper* | 01:22 |
| azonenberg | super* | 01:22 |
| azonenberg | like angstroms per year | 01:22 |
| azonenberg | effectively zero | 01:22 |
| azonenberg | And now that i've almost solved the problem of patterning it, i should get very good results | 01:22 |
| azonenberg | 44% KOH is extremely anisotropic - the etch rate of <110> is around 600 times that of <111> planes | 01:25 |
| azonenberg | So 100:1 aspect ratios are potentially feasible | 01:26 |
| azonenberg | that's on par with deep RIE | 01:26 |
| azonenberg | But i havent seen any literature using KOH for more than around 10:1 or 15:1 | 01:26 |
| azonenberg | It really seems that KOH is a near-ideal etchant because it's fast, gives relatively smooth surfaces if you use it right, and is extremely selective | 01:31 |
| azonenberg | the only downside is metal ions which are a problem for CMOS but not MEMS | 01:31 |
| azonenberg | And while it's pretty fast it still will take a bit over 2.5 hours to do the 500um etch i need lol | 01:32 |
| Action: azonenberg wonders if he should have gotten thinner wafers to start with | 01:33 | |
| XgF | I guess slow etchants are one of the reasons why foundries like big wafers? | 01:33 |
| azonenberg | You think that's slow? Lol | 01:34 |
| azonenberg | XeF2 will take overnight to go this fart | 01:34 |
| azonenberg | far* | 01:34 |
| azonenberg | But it doesnt have metal ions and is therefore CMOS compatible | 01:34 |
| azonenberg | But yes | 01:34 |
| azonenberg | It costs about the same amount to process a big wafer or a small one | 01:34 |
| azonenberg | but they make more money with big ones | 01:34 |
| XgF | On a commercial scale, I bet thats a bottleneck :p | 01:34 |
| azonenberg | Lol yeah | 01:35 |
| azonenberg | http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4717275 | 01:59 |
| azonenberg | very interesting paper describing fabrication of MEMS micromirrors | 01:59 |
| azonenberg | the mirror is on a <110> plane | 01:59 |
| azonenberg | <111>* | 01:59 |
| azonenberg | and is produced by a KOH etch of a <110> wafer | 01:59 |
| bart416 | azonenberg, electron gun assembly from crt extracted | 12:11 |
| Laurenceb | nice | 12:14 |
| bart416 | Still need to cut the glass all the way down | 12:17 |
| bart416 | But considering how to best do that | 12:17 |
| --- Tue Aug 9 2011 | 00:00 | |
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