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Did you know silicon wafers are the ultimate in semiconductor manufacturing? They’re not only extremely conductive, but incredibly affordable as well. This is why practically every single modern day electronic device utilizes them. Your silicon wafer can go through many different microfabrication processes depending on their use case. Although you may use silicon wafers in your everyday life, there are still a lot of facts some may be unsure of or misunderstand when it comes to the various properties of Si wafers. You shouldn’t go into research or experimentation without getting accurate and precise facts first. If you’re unsure of anything contact experts such as University Wafer to make sure your wafer handling is safe and secure.
In the 1950s the Egyptian-American engineer Mohamed Atalla coated a silicon wafer with a layer of SiO2. This allowed electricity to permeate to the conductive silicon layer and is known today as surface passivation. This further allowed for silicon integrated circuits to be mass-produced and is still used to this day. In 1954 Atalla announced the first silicon transistor available commercially.
Silicon is a crystalline that’s incredibly brittle but also quite solid. It’s also the 2nd most common element on Earth, just preceding Oxygen. SiO2 is the most common compound in the crust of the Earth. Silicon is also the 7th most found element in the entire universe. Don’t confuse it for silicone which is synthetic and not conductive. More than 10million square inches of silicon materials were shipped in 2015 alone!
Although shiny and gray in its purest state, silicon may look like a metal but it actually has a metalloid classification. This means it has typical properties of both nonmetals and metals, but not predominantly one or the other (the framework varies between metalloids). This makes it conductive only under certain conditions which makes Si and other metalloids well suited for industry manufacturing.
For silicon to be used for electronics it needs to have (at least) a purity of 99.9999999%. The first material used to make silicon wafers for semiconductors and solar cells is top-quality and pure sand. Sand has a high abundance of silicon and only the purest form of it, typically shipped from Australia, is used in silicon wafer production.
In 1916 Jan Czochralski demonstrated a metal crystallization method of varying rates. Because silicon wafers have to be incredibly pure and defect-free the only process to accurately achieve this is the Czochralski method. When melted at 1,425 °C boron or phosphorus can be added to the silicon to dope it. This will create a semiconductor of either an n-type or p-type. The process can create ingots of 1 and 2 metres long with diameters up to 400mm.
Silicon wafers will vary in thickness and size. This mechanical strength of the equipment used to make the wafer will always determine it’s thickness. If the silicon wafer is not thick enough it can crack during handling, so the semiconductor must also be made to support its thickness.
Most silicon wafer suppliers can quickly calculate the cost of the wafers you need. However due to their fragility and complex manufacturing process, they will often only allow you to buy wafers in bulk. Websites like University Wafer are one of the few that allows speedy ordering of silicon wafers in any amount, not just bulk orders.
Sometimes Si wafers may have unwanted particles on them, or can be damaged upon arrival or with improper handling. Polishing with a weak acid can clean wafers without damaging the silicon or substrates. When being used for solar cells, wafers have to be etched. This process can either be done in a chemical bath (wet) or a vacuum (dry) and it creates a textured surface on the wafer to increase conductivity and efficiency. It’s often done with a combination of different chemicals in a highly controlled environment.
III-V and II-VI materials can also be used for electronic wafers despite silicon ranking supreme for the process. GaAs, also known as gallium arsenide is another semiconductor that also utilizes the Czochralski process for production. Although also conductive Gallium wafers are more commonly used in microwave integrated circuits.
Without proper storage conditions Silicon Wafers can degrade or even become contaminated. The recommended storage method for wafers is to have them vacuum sealed. If this isn’t doable, Si Wafers have to be placed in an N2 cabinet with a 2 to 6 Standard Cubic Feet per Hour flow rate.