Grrrarrgghh@#%!!!!!!
I've been rushing all week to get the latest two samples processed so that I could get them tested before Paul started growing the next set tomorrow. To make a long story short, I failed. But it wasn't my fault...Honestly. I encountered a new disaster at every step along the way. It's been utterly ridiculous. I mean, I'm a believer in Murphy's Law (that everything that can go wrong, will) but I'm talking about things that couldn't go wrong going wrong! Things going wrong that made no sense. Things going wrong that came from so far out in left field that they must have actually started from miles outside of the stadium.
It all started on Sunday. I went on Sunday to do the first step in the process thinking I'd get a jump on it and easily beat my Thursday deadline. The first step has the most parts and relies on the most machinery being available for use, so doing it on Sunday meant less competition from other grad students for the equipment. Everything went ok, the Ion Mill milled through a bit more material than it should have, but no big deal, the samples came out in great shape. I had been there processing for about five hours by that point, but I decided to press on and get the second step (which is the shortest) done too.
That's when the avalanche began.
On the second photolift, both of the samples moved during their exposures (each is done separately), and so I needed to run them again. And they moved again. To explain a little better, what we do is cover the sample with a thick liquid called Photo Resist (PR), line it up beneath a mask (a glass plate with a pattern on it), and then expose it to a strong ultraviolet light. Since the pattern blocks some of the light, only some of the sample is exposed. The exposure changes the chemical properties of the PR so that it will be removed when we dunk the sample in developer, while the PR that was not exposed stays on the sample throughout whatever the processing step is that we need to do. In the second step, we're actually aligning the pattern that actually defines the devices to the pattern that we made in the first step, so it's important that the sample doesn't move during the exposure.
The mask aligner we use to do this is a simple contact aligner, you work it by basically smashing your sample up against the mask and then an arm with a set of mirrors moves forward so that the light from the lamp is directed down into the sample from above the mask (it's all very technical). The problem with this particular aligner is that the arm doesn't so much move forward anymore, it's more like it lurches forward. Which causes the sample to get knocked out of place no matter how tightly you put it into contact. After two failures I decided to give it a rest and come back in the morning.
Monday morning I failed twice more, same problem as before...And then it got worse. One of my samples slipped off of the plate and into the aligner mechanism underneath the mask holder. Well, of course, I totally freaked. It didn't fall out the bottom and I couldn't see it, it was stuck. The aligner still worked perfectly, but I was sure that I would break it if I went prodding around inside, and these things are expensive. Really expensive. I ran off to find Paul, but he was no help. I went off to find Tony (who is in charge of the cleanroom/fabrication rooms), but he's out of the office this week. At this point, Paul emailed me to reiterate that I had until Thursday to finish testing the samples.
Luckily, by now I had calmed down a bit. I went back into the cleanroom and found where the sample was standing, yes standing upright, next to the mechanism, not really stuck in anything, just sitting on a little outcropping. I was able to knock it free and clean it up with surprisingly little fuss. I did the exposure once more, they moved again. But they didn't move much and I was losing my tenuous grip on my sanity so I decided to move on, this wasn't the most critical alignment step anyway--the devices would still work fine. Then I discovered that the cleanroom was out of the developer we use. Screw this.
I went to watch the Physics Van show in Loomis, they did a great job and had twelve volunteers there (one had been in my 212 discussion section last semester, he was a pretty good presenter too)!
After my break, I found Kevin (Tony's assistant/backup/whatever) and he said that he was under the impression that Tony had decided to no longer stock the developer we use and that there was no more left!! Plus, he hadn't bothered to tell anyone, even Kevin, until the day before! (As a side note, everyone in our group and everyone who we've talked to uses that same developer too. Tony gets back tomorrow, should be interesting.) So now I have to learn how to use a new developer, on actual samples no less, since I have no time for testing. And of course, everyone has their own recipe. Even though we all use the regular AZ Developer (that they're no longer stocking) most people I talk to have resorted to one of the others in the past when the regular one ran short, and they all swear by completely different mixtures/times. In the end I went with Kevin's recipe of diluting AZ 351 three to one instead of using the regular AZ at two to one. It worked beautifully. The mesas I was defining in the photolift came out square and clear, and the rest of step two went without a incident.
Things were finally looking up! Except that it had taken me an entire day to do the shortest step and the alignment was terrible. Yeah, except for that, things were looking up.
So to recap, the processing so far has gone from "good" to "bad" to "worse" to "a little tiny bit better". I'm going to stop here tonight, but stay tuned because in steps three and four it actually goes to" incredibly more worse" and then to "you've got to be kidding me" and finally stopping at "oh for the love of...Just...@$#%&!...I mean, come on, really!"
-Tim
It all started on Sunday. I went on Sunday to do the first step in the process thinking I'd get a jump on it and easily beat my Thursday deadline. The first step has the most parts and relies on the most machinery being available for use, so doing it on Sunday meant less competition from other grad students for the equipment. Everything went ok, the Ion Mill milled through a bit more material than it should have, but no big deal, the samples came out in great shape. I had been there processing for about five hours by that point, but I decided to press on and get the second step (which is the shortest) done too.
That's when the avalanche began.
On the second photolift, both of the samples moved during their exposures (each is done separately), and so I needed to run them again. And they moved again. To explain a little better, what we do is cover the sample with a thick liquid called Photo Resist (PR), line it up beneath a mask (a glass plate with a pattern on it), and then expose it to a strong ultraviolet light. Since the pattern blocks some of the light, only some of the sample is exposed. The exposure changes the chemical properties of the PR so that it will be removed when we dunk the sample in developer, while the PR that was not exposed stays on the sample throughout whatever the processing step is that we need to do. In the second step, we're actually aligning the pattern that actually defines the devices to the pattern that we made in the first step, so it's important that the sample doesn't move during the exposure.
The mask aligner we use to do this is a simple contact aligner, you work it by basically smashing your sample up against the mask and then an arm with a set of mirrors moves forward so that the light from the lamp is directed down into the sample from above the mask (it's all very technical). The problem with this particular aligner is that the arm doesn't so much move forward anymore, it's more like it lurches forward. Which causes the sample to get knocked out of place no matter how tightly you put it into contact. After two failures I decided to give it a rest and come back in the morning.
Monday morning I failed twice more, same problem as before...And then it got worse. One of my samples slipped off of the plate and into the aligner mechanism underneath the mask holder. Well, of course, I totally freaked. It didn't fall out the bottom and I couldn't see it, it was stuck. The aligner still worked perfectly, but I was sure that I would break it if I went prodding around inside, and these things are expensive. Really expensive. I ran off to find Paul, but he was no help. I went off to find Tony (who is in charge of the cleanroom/fabrication rooms), but he's out of the office this week. At this point, Paul emailed me to reiterate that I had until Thursday to finish testing the samples.
Luckily, by now I had calmed down a bit. I went back into the cleanroom and found where the sample was standing, yes standing upright, next to the mechanism, not really stuck in anything, just sitting on a little outcropping. I was able to knock it free and clean it up with surprisingly little fuss. I did the exposure once more, they moved again. But they didn't move much and I was losing my tenuous grip on my sanity so I decided to move on, this wasn't the most critical alignment step anyway--the devices would still work fine. Then I discovered that the cleanroom was out of the developer we use. Screw this.
I went to watch the Physics Van show in Loomis, they did a great job and had twelve volunteers there (one had been in my 212 discussion section last semester, he was a pretty good presenter too)!
After my break, I found Kevin (Tony's assistant/backup/whatever) and he said that he was under the impression that Tony had decided to no longer stock the developer we use and that there was no more left!! Plus, he hadn't bothered to tell anyone, even Kevin, until the day before! (As a side note, everyone in our group and everyone who we've talked to uses that same developer too. Tony gets back tomorrow, should be interesting.) So now I have to learn how to use a new developer, on actual samples no less, since I have no time for testing. And of course, everyone has their own recipe. Even though we all use the regular AZ Developer (that they're no longer stocking) most people I talk to have resorted to one of the others in the past when the regular one ran short, and they all swear by completely different mixtures/times. In the end I went with Kevin's recipe of diluting AZ 351 three to one instead of using the regular AZ at two to one. It worked beautifully. The mesas I was defining in the photolift came out square and clear, and the rest of step two went without a incident.
Things were finally looking up! Except that it had taken me an entire day to do the shortest step and the alignment was terrible. Yeah, except for that, things were looking up.
So to recap, the processing so far has gone from "good" to "bad" to "worse" to "a little tiny bit better". I'm going to stop here tonight, but stay tuned because in steps three and four it actually goes to" incredibly more worse" and then to "you've got to be kidding me" and finally stopping at "oh for the love of...Just...@$#%&!...I mean, come on, really!"
-Tim
posted by tjmcardl | 11:13 PM
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