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Integrated Circuit Fabrication
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First, a design of the circuitry layout must be created. This design is broken down into layers that will be built using different processes. More information on IC Design |
This image is of a typical CMOS Op-Amp
The following is a break down of the circuit:
Red - Polysilicon
Blue - Metal (layer 1)
Green - N-doped Si
Brown - P-doped Si
X's - cross layer connections Ref: 3 |
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Ingots of Silicon, "grown" from pure silicon, are sliced and polished into wafers about .75mm thick. Typically, ingots of 8, 10, and 12inch diameter are used and thus results in the terms 8in, 10in, and 12in wafers.
More information on Wafer Production
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Now comes the different processing steps to add the circuitry on top of the silicon wafer. To simplify the processes, I tried to break the steps down into what seems like the main processes: Masking, Etching, and Doping. |
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Masking: The wafer is treated with an Insulating Silicon then covered with a special photosensitive film. A UV light is shone through the mask above a section of the wafer. (Since we can build multiple ICs on one wafer, the wafer is "stepped" to each position and exposed with the Mask until the entire wafer has been exposed with each individual IC circuitry layout.) The photosensitive film is "processed" and the sections of the film that were exposed to UV light are washed away which leaves exposed sections of the Insulating Silicon. |
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Etching: The wafer is then treated with chemicals to Etch away the sections of the Insulating Silicon that are exposed which now leaves sections of the Wafer silicon surface exposed. The photosensitive film is rinsed away.
Doping: The wafer is then run through a process that alters the electrical properties of the sections of the exposed Wafer Silicon. Ref:2,7
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These steps are repeated to build the circuitry layer by layer.
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This is definately a simplified version of the many chemical processes going on here which can be explained even further through the NEC Electronics website:
Video of IC Fabrication Processess. |
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The finished wafer is then cut into its individual ICs in a process called Dicing. Each IC is then mounted, bonded, and packaged. This picture is of an IC package that has been cut away to show the IC inside. The tiny gold wires are what Bond the IC to the connecting pins of the package: |
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Now the IC is ready to be mounted on a circuit board and put to use!
You can find ICs in many products like phones, cars, home appliances, computers, cameras, hearing aids, anything you want to digitally control... |
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What about the Future of Fabrication?
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