Monday, August 10, 2009

IMEC Update 8/10/09

As my time here is winding down, I'm scrambling to get in as much work as I possibly can. From today, I have a little more than 2 weeks left here in Belgium. All good things must come to an end, there are no exceptions.

So what have I been up to at IMEC? Almost all the work that I do is inside the clean room. All day I go in and out, changing into the clean room suits probably more than 5 times a day. Every instrument involved in lithographic fabrication is inside one of the many sections of the clean room here, including thermal evaporators, sputter systems, ion-milling systems, electron beam evaporators, profilometers and ellipsometers, solvent/acid wet benches, plasma etchers, dicing tools, optical microscopes, spin-coaters, mask aligners (3 in a single room capable of handling 8" wafers. They have more than 3 mask aligners here. These 3 are just the ones that I have access to.) and numerous other instruments used for functions that I'm not aware of.

As I've mentioned months earlier, the most annoying part about research here at IMEC is still the fact that technicians operate most the instruments. Yes, I'm thankful that it's less work for me since I don't have to run the instrument, however, sometimes I'll wait a day or 2 for my sample to be processed. Although I have enough work to do to keep me busy in the mean time, sometimes the samples that I need processed are the ones that I desperately need the most. The worst offending instrument is the e-beam (electron beam instrument used for lithography).

There are multiple different forms of lithography. Two such types include photolithography and electron beam lithography. The advantage of e-beam lithography over photolithography is the resolution that you're able to achieve. Electron beam lithography is used to pattern nanoscale structures while photolithography is conventionally used to pattern microscale structures. In an earlier post I tried to describe the basics of lithography. First you start with a bare silicon wafer, spin coat a resist material onto the wafer, and then pattern something into the resist using, in these cases, photolithography or e-beam lithography. In photolithography, UV light is exposed to certain areas of the wafer using a mask to block the UV light from penetrating other areas of the wafer. If a positive resist is spin-coated onto the wafer, then once it's placed in a developing solution, those areas exposed to UV light will be etched away. With a negative resist, the opposite occurs such that areas NOT exposed to UV become etched.

Here at IMEC, I'm using electron beam lithography. Instead of using UV light to pattern my samples, an electron beam scans across the areas defined in my mask. . This is probably the most important step in the process because it creates your pattern. Without any patterns you don't have any structures. After being exposed to the e-beam, the patterns are developed similarly to photolithography, however a different solution is used as the developer.

The e-beam is the bottleneck that's holding back my research. It's a very delicate and expensive instrument, so a technician operates it. There are numerous research teams here at IMEC and a lot of people require the use of the instrument. As a result, each group is technically only allowed to use the instrument once every seven days. For my structures, I require two steps of e-beam lithography, so that already sets me back 2 weeks to process one batch of samples. For the past couple weeks, the technician has been on vacation and will continue to be on vacation until after I leave Belgium. Two people in the group I work in are trained on the instrument, however their use of it is limited. They've also been taking vacations on and off, so it's tough to catch them, let alone ask them to do extra work for you. Everyone here is very friendly though, so they're always willing to do the work for you. You just may have to wait a couple extra days when they're not on vacation or busy with their own projects.

Currently, I'm still in the fabrication stage of my structures. I'm in and out of the clean room fabricating them and then occasionally taking images with a scanning electron microscope. In the next couple days I'll be changing my routine as I begin to take optical measurements of my samples. I think I said that in my last post, but I'm hoping that if I keep saying it then it'll actually happen.

I'll end with a couple more random observations:

-With reference to the cost of something, in the number system Europeans use a comma to separate the equivalent of dollars and cents. I'm actually not quite sure what they call the equivalent of the American cent. If I go to the store and buy something for 5,50, the cashier says that it cost five euro fifty.

-The cost to use the facilities at the laundromat are significantly more expensive than Hopkins. One load of laundry (in a washing machine half the size of what you see at the campus facilities) costs a whopping 3.80 euros. I forgot what I paid to use the dryer. The cost is per every 8 minutes and I don't remember how long I used it. I just keep refeeding the hungry meter until my clothes are dry.

-When I was in Paris, I checked out a McDonalds to see what the menu looked like. A medium fries cost 2.20 euros (~$3.12)!!! I haven't been to a McDonald's in the states in probably 2 years now, but I recall it being on the dollar menu. You can also buy beer at McDonalds.

-Speaking of beer, you can usually buy it in vending machines as well (at least here in Belgium). It's the cheap kind though, so it's the equivalent of Natty Boh or Keystone Light in the states.

-Still speaking of beer, it's not illegal to walk around with an open alcoholic beverage in public.

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