| B0101 | hi | 01:57 |
|---|---|---|
| azonenberg | Hopefully going to get some more litho work done this weekend | 05:53 |
| azonenberg | The hope is to refine the liftoff process for the hardmask a little more | 05:54 |
| azonenberg | In the meantime i'm starting a wiki page on the process | 06:14 |
| Harold_parker | nice man | 06:15 |
| Harold_parker | how'd you get on with those probes last night? | 06:15 |
| azonenberg | I didnt do any more work since testing them on the pic a little | 06:15 |
| azonenberg | it was enough to verify i could hit bond pads and other big stuff | 06:15 |
| azonenberg | i dont need to do anythimg smaller until i get my process shrunk :p | 06:16 |
| Harold_parker | ahh nice :) | 06:20 |
| Harold_parker | excellent | 06:20 |
| Harold_parker | yeh for sure man | 06:20 |
| azonenberg | http://www.youtube.com/watch?v=Jx77NLsQfg8&feature=related | 06:55 |
| azonenberg | Is it bad that i recognized this SEM as a recent model Zeiss before even seeing the logo? | 06:55 |
| azonenberg | But it seems strange to see someone using one of these things who isnt dressed in a bunny suit :p | 06:55 |
| CIA-67 | homecmos r92 | wiki/Si2DLithoProcess.wiki | Created wiki page through web user interface. | 07:23 |
| azonenberg | Early draft, any thoughts? http://code.google.com/p/homecmos/wiki/Si2DLithoProcess | 07:25 |
| bart416 | Pictures! | 07:29 |
| azonenberg | So I want to start exploring alternate hardmasks | 19:21 |
| azonenberg | Ta2O5 is still worth looking into for when vacuum isnt available but i think i can get better results with evaporated Ni | 19:21 |
| azonenberg | also patterned by liftoff | 19:21 |
| azonenberg | Unfortunately i dont have a working evaporator yet | 19:22 |
| berndj | what are you hoping to achieve with this hardmask stuff? | 19:45 |
| berndj | and, does it relate to that PR "peeling" problem you were having? | 19:46 |
| azonenberg | berndj: Yes | 19:47 |
| azonenberg | A hardmask of some sort is necessary because photoresist is attacked by KOH and will disintegrate in seconds | 19:47 |
| azonenberg | So you need a material that you can pattern using photoresist (by either lift-off or etching) and then use that material as a mask for the KOH etch | 19:48 |
| azonenberg | Normally people use silicon nitride, iirc it's patterned by an HF wet etch | 19:48 |
| azonenberg | But my resist is not very good against HF | 19:48 |
| azonenberg | So I tried using lift-off, which works but i am having issues with so far | 19:49 |
| berndj | KOH is to get the oxide off? or to actualy "dig into" the silicon? | 19:49 |
| azonenberg | KOh is for etching the silicon | 19:49 |
| azonenberg | To significant depth (for MEMS applications) | 19:49 |
| azonenberg | as in several microns to a few hundred microns | 19:49 |
| berndj | was about to ask if this was for MEMS | 19:49 |
| azonenberg | Yes, thats the main application | 19:49 |
| berndj | didn't think you'd absolutely need that for making just circuits | 19:49 |
| azonenberg | No, you typically dont | 19:50 |
| berndj | for accelerometer type devices: how do you get "under" the probe mass? | 19:50 |
| azonenberg | There are a couple of methods depending on the process | 19:50 |
| azonenberg | I was going to use bulk micromachining and actually have it free hanging | 19:51 |
| azonenberg | etch from the back up until the center of the die is only a few microns thick | 19:51 |
| azonenberg | then do another etch from the top down with my target pattern | 19:51 |
| azonenberg | Another is based on surface micromachining and involves depositing a sacrificial spacer followed by polysilicon | 19:51 |
| azonenberg | you make the moving parts out of poly-si then dissolve the spacer | 19:51 |
| azonenberg | presumably at some point in between you'd put support structures through the spacer layer to hold your device up | 19:52 |
| berndj | isn't MEMS an order of magnitude harder to DIY than just "normal" devices (just circuits)? | 19:53 |
| azonenberg | Not for something simple like a comb drive | 19:53 |
| azonenberg | because CMOS is so sensitive to trace metal contamination | 19:53 |
| berndj | i'm only assuming so because it's a decade or two or three further along in history | 19:53 |
| azonenberg | mems dont really care | 19:53 |
| azonenberg | And making really complex mems usually needs RIE | 19:53 |
| azonenberg | But for simpler stuff, not necessary | 19:54 |
| berndj | does NaOH also work to etch Si? | 19:54 |
| azonenberg | Yes | 19:54 |
| berndj | works too well? | 19:55 |
| azonenberg | But KOH is apparently more repeatable | 19:55 |
| azonenberg | In mixed signal CMOS+MEMS devices they usually use TMAH which is purely organic and has no metal ions | 19:55 |
| berndj | TMAH? geez, another james bond movie death-chemical! | 19:59 |
| azonenberg | berndj: Lol | 20:01 |
| azonenberg | What do you mean? | 20:01 |
| azonenberg | It can be toxic but i'm not aware of it having been used in film :p | 20:01 |
| berndj | just looking at its wikipedia article, that makes it sound like another one of those death-on-contact chemicals like HF | 20:01 |
| azonenberg | It can definitely be nasty, i'm not planning to use it without more research | 20:02 |
| azonenberg | Which is one of the reasons i am sticking with mems for the time being | 20:02 |
| azonenberg | since i definitely dont need it | 20:02 |
| azonenberg | i want to explore alternative photoresist developers, preliminary research suggests straight household ammonia might work | 20:03 |
| berndj | if you can tell me a household-chemicals means of making PR (for pcb type resolution) i'll give you a wet sloppy kiss | 20:04 |
| azonenberg | I'm not aware of any, chemistry isnt my main strong point lol | 20:05 |
| azonenberg | i'm into this mostly for the engineering of devices | 20:05 |
| azonenberg | the process development is a necessary step to make that happen | 20:05 |
| berndj | maybe i'll just dick around sometime with indoor varnish + UV, see if anything looks workable | 20:06 |
| berndj | my outdoor timber suggests there's some UV action, but i don't want to sit with multi-year exposures! | 20:06 |
| azonenberg | lol :p | 20:07 |
| --- Sun Jun 26 2011 | 00:00 | |
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