Silicon microchips are produced in a process that’s a combination of the familiar and the weird. Some facets are as familiar as creating a photograph in a dark room, whereas many others are like space exploration or subatomic physics. In the end, it all comes together and the method gets stranger and more fascinating the more you understand about it.
Chips might appear small and flat, but they’re really three-dimensional sandwiches 10 or 20 layers thick. It requires over two dozen steps to build up this silicon sandwich, and tons of stuff could go wrong along the way. It’s not until near the end that you discover if the process turned out good or not
The first step in semiconductor manufacturing starts with the creation of a wafer – a thin, round slice of a semiconductor material, usually silicon.
Within this procedure, purified polycrystalline silicon, generated in sand, is heated to a molten liquid. Silicon crystals have been melted at a vat and compacted to 99.9999 percent purity and expanded to ingots, long sausage-like cylinders which are thick and glistening. A little bit of strong silicon (seed) is set on the molten liquid, and since the seed is slowly pulled out of the meltdown the liquid cools to form a single crystal ingot. The surface tension between the seed and also nitric oxide induces a small quantity of the liquid to grow with all the seed and trendy.Wafers are around as thick as a company business card. Wafers arrive in a couple of standard sizes, generally 6 inches, 8 inches, or 300 millimeters (only under 12 inches) in diameter.
1 edge of the round wafer is often cut off. That is partially to assist the automatic equipment manage the wafer, howeer the engineer operating the gear might tell which way is “up”.
All these wafers will be quite so smooth after they are completed you could not discover any imperfections on the surface in spite of a microscope. The practice is known as chemical-mechanical polishing (CMP). As its name suggests, it involves grinding off any imperfections and lightly bathing the wafers in chemicals that are particular.
The wafers will need to be flat and smooth because the characteristics which are going to be projected onto them at the processor “darkroom” are very small and intimate together. Any variations from the surface of the silicon wafer is likely to produce the chip look from focus resulting in faults and shorts.
