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Summary: How are Wafers Made?
Silicon is the second most abundant material on earth (27.8%) after carbon. It is mined from beach sand found on pristine beaches in Australia and Italy. While growing the ingot, dopants are added to control electricity in the finished semiconductor.
1. Manufacturing Method
Single crystal silicon is grown using the Czochralski (CZ) method or the Float Zone (FZ) method.
2. Crystal Pulling
Polycrystalline silicon chunks are melted in a quartz crucible at 2552°F (1400°C) with dopants (Boron, Phosphorus) to create N-type or P-type specs. A seed crystal is dipped and pulled slowly to form a monocrystalline ingot.
3. Orientation (Ori)
The ingot is machined with a flat or notch to indicate the crystal orientation, typically (100), (111), or (110).
4. Slicing
A diamond saw slices the ingot into wafers of precise thickness.
5. Edge Grinding
Edges are rounded to increase yield and prevent chipping.
6. Lapping
Lapping removes surface defects and roughness caused by sawing.
7. Etching & Cleaning
Acids (Sodium Hydroxide, Nitric Acid) remove microscopic cracks, followed by a deionized water rinse.
8. Polishing
CMP (Chemical Mechanical Polishing) uses slurry to create a mirror-flat surface for Epitaxy or device fabrication.
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What is a Silicon Wafer Made Of?
When we ask what a silicon wafer is made of, we refer to the thin substrate used to fabricate electronics. Silicon is extracted from silica sand (SiO2). For device production, the silicon must be purified to "Electronic Grade" (99.9999999% pure).
The silicon substrate provides the foundation. In many applications, an oxidation layer (SiO2) acts as an insulator. UniversityWafer, Inc. supplies both standard polished wafers and wafers with Thermal Oxide layers to prevent moisture penetration and control electrical properties.
Ingot Growth: CZ vs FZ
Most wafers are made via the Czochralski (CZ) process. This involves melting polysilicon in a quartz crucible and pulling a seed crystal. However, for applications requiring higher resistivity and lower oxygen content, Float Zone (FZ) silicon is used. FZ growth does not use a crucible, preventing oxygen impurities from entering the crystal lattice.
Metallurgical vs. Electronic Grade Silicon
Metallurgical Grade Silicon (MGS) is approximately 99% pure. It is produced by reducing silica sand with carbon in an electric arc furnace. While suitable for steelmaking, it is too impure for electronics.
Electronic Grade Silicon (EGS) is the result of further purification (such as the Siemens process). This is required for integrated circuits because even trace impurities can destroy carrier mobility and device reliability. UniversityWafer ensures all Prime Grade wafers meet these strict purity standards.
Wafer Types: MG-Si, HG-Si, and HM-Si
In the industry, you may hear various terms regarding silicon quality and doping:
- MG-Si: Metallurgical Grade. Contains heavy metals (Fe, Al) and is the precursor to solar and electronic silicon.
- HG-Si: High-Grade Silicon, often referring to highly doped substrates used for power devices.
- HM-Si: High-Mobility or specialized Hardmask layers used in advanced lithography stacks to provide etch selectivity.
Can You Make Processors From Beach Sand?
Technically, yes, but not directly. Silicon solar cells and computer chips trace their roots to silica sand. Ordinary sand contains about 80% silicon dioxide, but semiconductor manufacturing requires 99.9999999% purity. The sand must undergo reduction, purification, and crystal growth before it becomes a wafer ready for lithography.
Video: How Microchips are Made
Watch the process of turning silica sand into a functioning computer chip.