From Silicon To Microprocessors

prostoalex writes "Jim Turley from Embedded Systems Programming magazine answers the question of where microprocessors come from. While the public generally knows about the silicon and microprocessor vendors, few can describe the process of turning the beach sand into the latest and greatest several-hundred-dollars-worth CPU."

Re:Clean Rooms

[Pulse_Instance]

I do work in a clean room, class 5 is our usual but sometimes a bit lower. I never hear the noise, it is actually nice and quited inside our Fab.

Man, I'm old!

[nordicfrost]

I read the article and find myself actually knowing in advance how silicon chips are made. You see, in the 80ies we had childrens books about computers that covered something more than how to start Word and update Winblows.

Leaves out the meat...

[HermesHuang]

While informative on what it touches on, this doesn't describe what goes into making a chip. It describes how a chip is patterned. Then follows many many diffusion, oxidation, etch, and metallization steps that go between each photoresist mask step. I suppose it makes a good read for someone who wants just a general overview. But it makes it sound like making a chip is just a glorified film development process. I do microfab work, and the lithography steps are the steps we take for granted (mostly -- they still do take effort to get right, but are in general easier then what follows).

Why just square chips?

[RobertB-DC]

From the article:
For an example, let's look at a 200mm silicon wafer, which has about 986cm2 of surface area. That's about the size of a salad plate. Let's say your chips are square (most are) and they measure 10mm on a side?that's 100mm2 per chip. If the silicon wafer was also square you could fit 986 chips on your wafer. Alas, wafers are round so you can really only get about 279 chips on a wafer.

I guess the obvious question, since using squares on a round wafer wastes a certain amount of silicon, is why squares? Why not build a hex grid? That would seem to maximize the usage of the available area.

But then, I suppose cutting them out would be significantly more difficult.

What about triangles, then? Straight lines up and down, and in one (or both) diagonal directions.

On the other hand, someone's already thought of this:
Intel's old i960MX microprocessor was octagonal. It was so big its corners had to be cut off.

So my idea has an obvious flaw. The question is... what is it?

This doesn't make sense...

[James Lewis]

"Why not just use one big piece of film to expose the entire wafer at once? The problem is focus. As any photographer knows, the bigger the picture the blurrier the image. That's why big-screen TVs don't look so great up close. Chip images need to be ultra sharp, so a blurry "mega mask" wouldn't cut it."

I thought big screen TVs were "blurry" up close because they had fewer pixels per area. Besides... in this case, you wouldn't be making the image bigger, you would just be making a LOT of tiny images at once. Can someone either explain how his explaination makes sense, or what the real reason is?

I seem to recall....

[Anonymous Coward]

While the article is a good introduction.. I think he omitted an important step in chip fab. IIRC, after you expose the photoresist and wash away the exposed sections, you need to pour a special acid which seeps into the channels of the photoresist and etches the patern into the silicon. Then you can remove the photoresist layer and move on.
As he explained it he never mentions how the pattern get burned into the silicon. Tsk tsk.

Shape of the Chip

[ackthpt]

I guess the obvious question, since using squares on a round wafer wastes a certain amount of silicon, is why squares? Why not build a hex grid? That would seem to maximize the usage of the available area.

But then, I suppose cutting them out would be significantly more difficult.

What about triangles, then? Straight lines up and down, and in one (or both) diagonal directions.

Well, NVidia discovered rotating them 45 degrees give them a diamond instead of a square. Think they're onto something?

Re:Mistakes?

[Anonymous Coward]

Regarding "mistake" #9: try fitting 310 1cm squares on a circle with area 310cm^2. You can't do it. It's a goddamn circle. I could believe 279 as cited in the article (too lazy to figure out the math).

Most of your "errors" are missing details at best. This article provides an excellent introduction to the technologies, so quit being so pedantic.

Re:Too elementary...

[Anonymous Coward]

Where do you think the very pure silane gas comes from? Magic?

recognizing people in bunny suits

[Anonymous Coward]

The article mentions that, with co-workers encased in bunny suits, you have to look at their eyes to tell people apart. When I worked in a fab, I noticed I became very attuned to people's body shapes and ways of moving. After working there for a while, I could subconsciously identify co-workers at the opposite end of a shopping mall, simply by the way they walked.

uhm...

[wisdom_brewing]

"is basically purified beach sand" - since when is deoxidation considered purification? "about 6 to 8 inches (200 to 300mm)" - make that 8 - 12 inches... slightly sad that such trivial mistakes/oversimplicications are made in an otherwise good article...

Or why even flat chips?

[burnin1965]

Your ideas are good, thinking out of the box, and check this out for thinking out of the box, spherical semiconductor circuits.

Ball Technologies [ballsemi.com]

burnin

Re:tinker-toys

[chunkwhite86]

Too bad the processors you mentioned comparitively suck :)

Perhaps that is the case if you are a l33t g4m3r. Which I suspect you are.

If you are running a nationwide medical record database with 8000 concurrent users (I am), there is NO intel machine ANYWHERE that can handle the load.

The current crop of Itanium or Xeon servers (even 8 and 16 way) cannot even come close to the performance of the GS series Alphaservers. Not even close. Not for processing power, and definitely not for memory bandwidth. What happens when you need 32 or 64 CPU's? Or more than that even? Sorry Charlie - intel servers are tinker-toys when compared to the big-iron of today.

correct

[burnin1965]

soon after the photo resist is developed it goes through an etch process which is usually a dip in a nice acid bath, or a shower in a nice acid spray, or my favorite, a plasma treatment in a vacuum chamber with RF or microwave and wonderful gases like Sulfur Hexafluoride, Hydrogen Bromide, Chlorine, Carbon Tetra-Fluoride, etc.

But this may not always be the case. It may be headed for an implant step. A nice electron beam zaps the wafer while it is laced with boron, or arsenic, etc.

burnin

Re:Leaves out the meat...

[burnin1965]

A PhD in physics would help, however, I've watched people with and Bachelors and Masters degree ranging from business to chemistry to mechanical engineering all execute the job of process development.

Of course these same people have been working in the industry for 20+ years and have more than earned a PhD with all the work they've done bringing the industry to where it is today.

I just want to make sure you don't scare anyone away making them think they have to get a PhD in physics to get into the biz.

And you are definitely on target about the diversity. I think you could take the work force from a semiconductor fab and throw them into just about any technical business and they would have the skills within the team to get the job done.

burnin

Re:Whose Power PC?

[Anonymous Coward]

Actually, I thought PowerPC was a Motorola trademark. I think Power PC (note the space) and PPC are fair game for IBM to use, however.

(posting anon as I might be totally wrong)

Re:Why just square chips?

[torpor]

What about triangles, then? Straight lines up and down, and in one (or both) diagonal directions.

Indeed, and in fact, this is one of the reasons why we need the International Space Station, because as it turns out, certain crystallization/sillication (whatever its called, apologies to the chemists...) processes, in a micro-gravity environment, are a lot easier to control in a fashion which produces high-yield, multi-dimensional composite core materials. At micro-nano-levels, gravity definitely takes its toll ... in space, presumably, things can be done a little 'smoother' without having Earth tugging at your bits and pieces ...

ISS gives us more details on how to control some of our common processes for constructing these sorts of materials, and the more we know about that, the easier it'll be to build the orbiting CPU-factories that will then lead the way to nano-assemblies and beyond ... ;)