Sand. Made up of 25 percent silicon, is, after oxygen, the second most abundant chemical element that�s in the earth�s crust. Sand, especially quartz, has high percentages of silicon in the form of silicon dioxide (SiO2) and is the base ingredient for semiconductor manufacturing.
After procuring raw sand and separating the silicon, the excess material is disposed of and the silicon is purified in multiple steps to finally reach semiconductor manufacturing quality which is called electronic grade silicon. The resulting purity is so great that electronic grade silicon may only have one alien atom for every one billion silicon atoms. After the purification process, the silicon enters the melting phase. In this picture you can see how one big crystal is grown from the purified silicon melt. The resulting mono-crystal is called an ingot.
A mono-crystal ingot is produced from electronic grade silicon. One ingot weighs approximately 100 kilograms (or 220 pounds) and has a silicon purity of 99.9999 percent.
The ingot is then moved onto the slicing phase where individual silicon discs, called wafers, are sliced thin. Some ingots can stand higher than five feet. Several different diameters of ingots exist depending on the required wafer size. Today, CPUs are commonly made on 300 mm wafers.
Once cut, the wafers are polished until they have flawless, mirror-smooth surfaces. Intel doesn�t produce its own ingots and wafers, and instead purchases manufacturing-ready wafers from third-party companies. Intel�s advanced 45 nm High-K/Metal Gate process uses wafers with a diameter of 300 mm (or 12-inches). When Intel first began making chips, it printed circuits on 50 mm (2-inches) wafers. These days, Intel uses 300 mm wafers, resulting in decreased costs per chip.
The blue liquid, depicted above, is a photo resist finish similar to those used in film for photography. The wafer spins during this step to allow an evenly-distributed coating that�s smooth and also very thin.
At this stage, the photo-resistant finish is exposed to ultra violet (UV) light. The chemical reaction triggered by the UV light is similar to what happens to film material in a camera the moment you press the shutter button.
Areas of the resist on the wafer that have been exposed to UV light will become soluble. The exposure is done using masks that act like stencils. When used with UV light, masks create the various circuit patterns. The building of a CPU essentially repeats this process over and over until multiple layers are stacked on top of each other.
A lens (middle) reduces the mask�s image to a small focal point. The resulting �print� on the wafer is typically four times smaller, linearly, than the mask�s pattern.
In the picture we have a representation of what a single transistor would appear like if we could see it with the naked eye. A transistor acts as a switch, controlling the flow of electrical current in a computer chip. Intel researchers have developed transistors so small that they claim roughly 30 million of them could fit on the head of a pin.
After being exposed to UV light, the exposed blue photo resist areas are completely dissolved by a solvent. This reveals a pattern of photo resist made by the mask. The beginnings of transistors, interconnects, and other electrical contacts begin to grow from this point.
The photo resist layer protects wafer material that should not be etched away. Areas that were exposed will be etched away with chemicals.
After the etching, the photo resist is removed and the desired shape becomes visible.
More photo resist (blue) is applied and then re-exposed to UV light. Exposed photo resist is then washed off again before the next step, which is called ion doping. This is the step where ion particles are exposed to the wafer, allowing the silicon to change its chemical properties in a way that allows the CPU to control the flow of electricity.
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