| B0101 | azonenberg: you there? | 06:09 |
|---|---|---|
| azonenberg | Yep | 06:09 |
| B0101 | i was thinking about making a mini clean room, in a box | 06:10 |
| azonenberg | You mean a glove box? | 06:10 |
| azonenberg | Yeah, entirely feasible | 06:10 |
| azonenberg | Building one is on my to-do list too, for certain critical operations | 06:10 |
| azonenberg | for example wafer clean followed by spin coating | 06:11 |
| B0101 | similar to a glove box, but this time, they can be detached/attached to a process machine... | 06:11 |
| azonenberg | You mean a sealed container for carrying between tools? | 06:12 |
| azonenberg | Yeah, thats doable too | 06:12 |
| B0101 | yes | 06:12 |
| B0101 | tell me when my ideas get crazy though | 06:13 |
| azonenberg | What you're descriibng is SOP for most modern fabs | 06:13 |
| azonenberg | the cleanrooms are like class 1000 and the tools are all sealed and filtered to below class 1 | 06:13 |
| azonenberg | nobody ever handles the wafers, they're moved by robot between tools in sealed boxes | 06:13 |
| azonenberg | Basically, around 10 years or so ago | 06:13 |
| azonenberg | Somebody finally realized that humans are dirty | 06:13 |
| azonenberg | and putting them in a clean environment isnt the best idea | 06:14 |
| azonenberg | So now the outer "container" cleanroom is only used for servicing etc | 06:14 |
| azonenberg | and the tools themselves do all of the interesting stuff | 06:14 |
| azonenberg | So what are your crazy ideas? | 06:16 |
| B0101 | hmm, well I ws thinking about getting to 45nm scale (really crazy idea though) | 06:16 |
| azonenberg | lol that *is* crazy :p | 06:17 |
| azonenberg | Not saying impossible, very little is | 06:17 |
| azonenberg | But it will be far from easy lol | 06:17 |
| azonenberg | For prototype-scale volumes your best bet would probably be e-beam direct write | 06:17 |
| azonenberg | forget about masks | 06:17 |
| azonenberg | build yourself a SEM and then make a direct-write module | 06:18 |
| azonenberg | I suggest you set a more reachable goal first | 06:18 |
| azonenberg | and see how feasible that is | 06:18 |
| azonenberg | say, 500nm | 06:18 |
| azonenberg | then 180 | 06:18 |
| azonenberg | I mean, certainly doing this kind of stuff on the prototype scale will be easier than mass production | 06:18 |
| azonenberg | but by how much? | 06:18 |
| azonenberg | I intend to start out by building a nice contact aligner | 06:18 |
| horizontally | build yourself a SEM.. azonenberg is one of the few people i know who could probably build it (and somehow acquire a diffusion pump from the lab manager) in his spare time | 06:19 |
| azonenberg | That will let me hit 12.5 um design rules with professionally made film masks (laserlab.com) | 06:19 |
| horizontally | what do you think of photosciences? | 06:19 |
| azonenberg | are they a mask shop? | 06:19 |
| horizontally | yeah | 06:19 |
| azonenberg | Never heard of them, photronics is the only other one i know of besides laserlab | 06:19 |
| horizontally | i was told about photosciences from our lab manager | 06:20 |
| azonenberg | Anyway so that'd be a temporary step though | 06:20 |
| azonenberg | The next step is to build my own laser direct write rig ;p | 06:20 |
| azonenberg | So i can make my own chrome-on-glass masks | 06:20 |
| azonenberg | Then the most involved tool (on the lithography front at least) would be an H-line stepper | 06:20 |
| azonenberg | probably 4x reduction of a 12.5um design rule mask | 06:21 |
| horizontally | why do you want to make stuff so small? | 06:21 |
| horizontally | what is your intended goal from there? | 06:21 |
| horizontally | sure it's nice and all | 06:21 |
| azonenberg | would put me at a 3.125um design rule | 06:21 |
| azonenberg | horizontally: a) have fun | 06:21 |
| horizontally | sure | 06:21 |
| azonenberg | b) advance the state of the art in low-budget fab | 06:22 |
| azonenberg | to the point that a 350nm fab is something you could have in every high school science classroom | 06:22 |
| horizontally | wow, sure, cool | 06:22 |
| azonenberg | Thats really the idea, there is not enough people getting into nanotech and having it available might help | 06:23 |
| azonenberg | Also, just the coolness factor of being able to, say, design a custom ASIC instead of using a CPLD for some glue logic :p | 06:23 |
| azonenberg | imagine having a little project with a PIC and a homemade MEMS accelerometer in a flip-chip BGA package | 06:23 |
| azonenberg | FCBGA is how i plan to package all of my stuff, actually | 06:24 |
| azonenberg | because it means i dont need to wirebond | 06:24 |
| azonenberg | just put the chip on a hot plate, heat to melting point of solder | 06:24 |
| B0101 | brb | 06:25 |
| azonenberg | and under a 30x stero microscope use fine tweezers to place a solder ball on each bond pad | 06:25 |
| azonenberg | then cool | 06:25 |
| azonenberg | flip over, put on PCB, and put board in oven to reflow | 06:25 |
| horizontally | i don't know much about packaging | 06:25 |
| horizontally | how did you learn about it? | 06:25 |
| azonenberg | this would basically be a chip scale BGA | 06:25 |
| horizontally | i have a pcb design book i haven't read through yet either | 06:25 |
| azonenberg | a) look at premade chips and study them from the outside | 06:25 |
| horizontally | though it's meant for orcad | 06:25 |
| azonenberg | b) reverse engineering | 06:25 |
| horizontally | oh jesus, the long road | 06:26 |
| azonenberg | decapping premade chips and studying how things fit together | 06:26 |
| azonenberg | plus various reading on wiki etc | 06:26 |
| azonenberg | but once you actually look at a DIP that you've dissolved the plastic from | 06:26 |
| azonenberg | and see how everything fits together | 06:26 |
| azonenberg | it all makes sense | 06:26 |
| horizontally | how do you dissolve the plastic but not the chip inside? | 06:26 |
| horizontally | so there's a bit of wirebonding | 06:26 |
| azonenberg | Hot nitric acid is the SOP | 06:26 |
| horizontally | and some polymer container | 06:26 |
| horizontally | nitric acid really? wow | 06:27 |
| azonenberg | it eats organic mateirals but not silicon, glass, or gold | 06:27 |
| azonenberg | the chip is usually passivated with SiO2 and has gold bond wires | 06:27 |
| azonenberg | Though if you arent careful it will eat the tin-plated copper legs | 06:27 |
| azonenberg | but the die itself survives with no problem | 06:27 |
| azonenberg | The cheap option is to just throw the whole chip into a beaker of sulfuric | 06:27 |
| azonenberg | and cook for a while | 06:27 |
| azonenberg | less selective but if you want a bare die to study its fine | 06:27 |
| azonenberg | You can do that method with nitric too | 06:28 |
| azonenberg | In either case, you will want a fume hood or to be working outside | 06:28 |
| horizontally | i got nitric and sulfuric | 06:28 |
| horizontally | i'll try nitric soon | 06:28 |
| horizontally | that sounds cool | 06:28 |
| azonenberg | Hot acid vapor is somewhat unpleasant | 06:28 |
| horizontally | yeah i've smelt it before | 06:28 |
| azonenberg | if you think the fumes are bad at room temp try at 150C | 06:28 |
| horizontally | shit | 06:28 |
| azonenberg | lol | 06:28 |
| azonenberg | http://colossus.cs.rpi.edu/pictures/2010/September/9-25-2010%20-%20chiprev/S7309665_annotated.jpg | 06:30 |
| azonenberg | This was the first chip i ever decapped | 06:30 |
| azonenberg | Didnt go too well but it demonstrates the technique | 06:30 |
| azonenberg | you can see i broke a few bond wires | 06:30 |
| azonenberg | The blue stuff was a silicone rubber i used to try and keep the acid from falling off the side and damaging the pins | 06:30 |
| horizontally | how do they get all of those bond wires on there jesus | 06:30 |
| horizontally | so tiny and seemingly error prone | 06:30 |
| azonenberg | its some kind of CPLD or FPGA, i dont know details of the part | 06:30 |
| azonenberg | Later i discovered things went better by drilling or milling into the middle of the package | 06:31 |
| azonenberg | until you're a few hundred um above the die | 06:31 |
| azonenberg | this makes a well | 06:31 |
| azonenberg | you then heat the chip on a hot plate, put one drop of acid in the well | 06:31 |
| azonenberg | let it sit, then pull out and swish in a beaker of acetone | 06:31 |
| azonenberg | repeat | 06:31 |
| azonenberg | Or, as I did originally, spray with acetone http://colossus.cs.rpi.edu/pictures/2010/October/10-7-2010%20-%20decapping/S7309756_sm.jpg | 06:31 |
| azonenberg | The problem with that technique is that it has a habit of dislodging bond wires | 06:32 |
| azonenberg | swishing seems to give better results | 06:32 |
| horizontally | you got a clean lab | 06:34 |
| azonenberg | Thats my old lab | 06:34 |
| azonenberg | I stopped doing as much wet chem when i moved out of it | 06:34 |
| azonenberg | It was a storage room in the building next door to my apartment | 06:34 |
| azonenberg | the landlord told me i could use it until he remodeled it the next year | 06:35 |
| azonenberg | Which is now happening :p | 06:35 |
| azonenberg | http://colossus.cs.rpi.edu/pictures/2010/October/10-31-2010%20-%20chiprev/S7300154.JPG is an example of how nice the results can be | 06:36 |
| azonenberg | No, i didnt eat off the pins, its a 44-QFN | 06:36 |
| azonenberg | seen closer | 06:36 |
| azonenberg | http://colossus.cs.rpi.edu/pictures/2010/October/10-31-2010%20-%20chiprev/S7300152_annotated.jpg | 06:36 |
| azonenberg | Notice the unbonded pads | 06:36 |
| azonenberg | the part comes in 44 and 64 pin versions and they use the same silicon for both | 06:36 |
| azonenberg | It's the Microchip ENC424J600 / 624J600 | 06:36 |
| azonenberg | ethernet PHY/MAC with SPI+parallel interfaces | 06:37 |
| azonenberg | the MAC is at top left, that big mess of analog circuitry | 06:37 |
| azonenberg | the PHY* | 06:37 |
| azonenberg | the DSP and MAC logic are at the right in that pile of standard cells | 06:37 |
| azonenberg | then under the CMP filler at center is the RAM | 06:37 |
| azonenberg | i havent fully reversed it though, been busy working on other stuff | 06:37 |
| azonenberg | horizontally: My current lab, as of a few months ago http://imgur.com/a/Bnwst | 06:38 |
| horizontally | i see your "gold light" | 06:38 |
| azonenberg | Yep, i use that for when i do litho | 06:39 |
| azonenberg | the lamp to the right of the glassware drying rack is yellow too | 06:39 |
| B0101 | back | 06:45 |
| --- Thu Dec 1 2011 | 00:00 | |
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