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What are Silicon Wafers?

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  • Written By: Mary McMahon
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  • Last Modified Date: 08 September 2016
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Silicon wafers are a key component of integrated circuits such as those used to power computers, cellphones, and a wide variety of other devices. A silicon wafer consists of a thin slice of silicon which can be treated in various ways, depending on the type of electronics it is being used in. Silicon is a very high quality semiconductor, making it ideal for the production of such circuits, although other materials have been explored historically. Much of the world's production of silicon wafers was historically centered in the aptly-named Silicon Valley in California.

If the development of the integrated circuit revolutionized human society, the silicon wafer deserves a big part of the credit. While other semiconductors were tested and tried, silicon proved to be the most stable and useful. Fortunately, the raw materials for silicon wafers are quite accessible, even if some work is required to produce wafer-grade silicon.

Making silicon wafers is a lengthy process. A lab must grow a silicon crystal in highly controlled conditions to maintain purity, although the lab may selectively dope the crystal with certain ingredients during the growth process. Once the crystal is grown, it is cut into thin slices which must then be polished before they can used to make integrated circuits.

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A number of companies specialize in the production of silicon wafers. They sell wafers in a range of sizes for various applications, and can offer wafers which have been processed in specialized ways. The amount of doping can be critically important for certain types of projects. Levels of impurities introduced through doping may be acceptable for some applications, but not for others, which requires labs to have very tight quality control.

Components of an integrated circuit can be installed inside a silicon wafer, in addition to installed on or around it. The technology behind integrated circuits is constantly evolving, as people push to make smaller and better circuits. Developments in this technology tend to increase steadily, according to a prediction known as Moore's Law, although critics of Moore's Law have pointed out that the technology cannot improve infinitely, which means that a ceiling will be reached at some point.

The production of silicon wafers is not without controversy. The process generates a range of byproducts, some of which are hazardous. In the Silicon Valley, pollution as a result of chemicals released into the environment is a major problem in some areas, and companies which manufacture wafers are constantly looking for new ways to make the process cleaner and safer for the environment.

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anon990495
Post 9

Anyone have luck with UniversityWafer as a supplier? My professor recommended them for small quantities but I was wondering if anyone has purchased through them before?

anon305388
Post 7

The green tint you see can either be from the SiO2 coating or the masking process, depending on the stage of processing.

anon305386
Post 6

@Cardsfan27: Look up the CZ or Float-zone method. These two methods are ways to grow a silicon ingot.

Sand is SiO2 silicon dioxide or silica along with many other impurities. Metallurgical grade silicon is obtained by heating the silicon to a high temperature and exposing it to carbon. The metallurgical grade silicon reacts with HCL to form SiHCl3. Finally, the SiHCl3 is exposed to hydrogen at a high temperature to create intrinsic Si or pure Si. This highly pure Si is then used to grow ingots used to make wafers.

To create a compensated semiconductor, the semiconductor material such as silicon is doped with either donor (phosphorous) which creates n-type or acceptor (boron) which creates p-type material. P-type and n-type can be joined together to form components, such as transistors or diodes.

Intel and many other chip companies have their own fabrication plants to grow the crystals they need.

stl156
Post 5

@JimmyT - The green color actually comes from a material that they place on the face of the chips during the soldering process. Like you already know, the thin silicon wafers are actually very shiny to start with. Whenever they attach things like transistors and capacitors, they have to use solder to make the connections.

By putting the green coating over the chip, the solder can only go onto places that aren't covered. Now that I think of it, though, I am not really sure what the green material itself is. That would be interesting to know, I guess.

JimmyT
Post 4

What is it that gives the silicon wafers their green color? I have seen pictures of the pure silicone that companies use to make their chips, and it is a very bright metallic color. It is definitely not green. Do they add some sort of chemical or something that gives them that color?

kentuckycat
Post 3

@cardsfan27 - Interesting question about the manufacturing of chips. I don't know if processor companies make their own or not. It wouldn't surprise me if they did. As far as just regular chips for things like TVs or kids' toys, I know there are companies that just mass produce chips for various things.

I am not an expert on the silicon wafer manufacturing process, but I know it is a lot more complicated than just using sand. Sand is mostly silica with other things mixed in. A lot of the process is getting rid of the impurities, because the chips need to be nearly 100% silicone. Judging from what the article says, I would say that a lot of the purifying process involves bad chemicals that don't react with the silicone.

cardsfan27
Post 2

What does the article mean when it talks about growing the silicon crystals? I thought that silicon wafers were made out of sand. Isn't that right? What can they do to sand to make it into a crystal?

When it talks about adding other materials to the silicon, what are those, usually? I have never heard of them using other things along with silicon.

Are there specific silicon wafer supplier companies that make chips for places like Intel, or does each company design and produce its own silicon chips so that they are up to their quality standards?

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