Tag: Wisconsin Life

Contributor Post Created with Sketch. Recommended by Ricochet Members Created with Sketch. How to Build a Computer 11: The Binary Search Algorithm

 

We’re taking a break from the manufacturing process to cover some ideas in programming. Algorithms, what that means and why. Sounds fancy, doesn’t it? It ain’t as bad as it sounds. Let’s jump right in:

What’s An Algorithm?

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Contributor Post Created with Sketch. Recommended by Ricochet Members Created with Sketch. How to Build a Computer 8: Organic Chemistry

 

I started with a discussion of the magic of photoresist, however (say it with me!) it got long-winded and I cut it down to the organic chemistry review. Next week photoresist. This week we’re going over some basic organic chemistry. Sounds fun, right? It’s going to be even more fun than that! You wait and see. We’re going to start small though, with methane.

You smell something? No? It’s probably just me.

This is a carbon atom, often found in the presence of ranch dressing. It’s surrounded by four olives, or hydrogen atoms. The pimento is only there for flavor. Carbon though is much like Silicon in that it comes with four electrons in its outer shell. In terms of orbitals that works out to 1s2 2s2 2p2. Carbon is in something of a unique position; you can make long and interesting chains of molecules with it. You can try making chains of other molecules, say, oxygen, but the results get… explosive. Anyway, a single carbon atom makes the simplest possible carbon chain. Let’s make it a more complicated.

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Contributor Post Created with Sketch. Recommended by Ricochet Members Created with Sketch. How to Build a Computer 9: Photoresist

 

We’ve just got off a quick overview on organic chemistry. Now we’re getting back to photoresist. The point of photoresist, if you’ll recall, is to take a pattern so you can print stuff on your wafer. To do that it has to be a chemical that responds to ultraviolet light. And I mean more “responds to” than get a mild sunburn; it’s got to chemically change so you can transfer the pattern of light into a pattern of stuff.

It’s a polymer made of benzene rings. Someone’s showing off.

The word “Photoresist” covers a great deal of variation, but the nature of the job it has to do requires certain commonalities. For starters, rather than all one substance, it’s a mix of three different things. You’ve got a photoactive compound, naturally. You’ve also got a resin, for stability. And then you’ve also got a solvent, for instability. The solvent keeps your resist liquid so you can apply it evenly. The resin keeps it solid once it’s on, so that it doesn’t move around as you’re working with it. That picture up there is of a resin. A thing called meta-cresol novolac. Can’t tell you why.

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