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Atomic number 14 is the most common semiconductor. It's energy gap Eg= 1.12 eV- indirect bandgap; crystal structure- diamond, lattice constant 0.543 nm, atomic concentration 5 x 1022 atoms/cm-3, index of refraction 3.42, density 2.33 g/cm3, dielectric constant 11.7, intrinsic carrier concentration 1.02 x 1010 cm-3, mobility of electrons and holes at 300°K: 1450 and 500 cm2/V-s, thermal conductivity 1.31 W/cm°C, thermal expansion coefficient 2.6 x 10-6°C-1, melting point 1414°C; excellent mechanical properties (MEMS applications); single crystal Si can be processed into wafers up to 300mm in diameter.
P type= Always Boron (B) Doped
N type= Dopant typically as follows:
Res: .001-.005 Arsenic (As)
Res: .005-.025 Antimony (Sb)
Res: >.1 Phosphorous (P)
Why are Wafer Flats used?
Any plant can make wafers with any flat cut out of them that they want. A silicon wafer flat's purpose is to help the end user see the dopant type and orientation of the wafer. This function helps avoid mistakes when using the wafer in equipment
Orientation of wafer before entering semiconductore equipment.
Indicate type and orientation of silicon crystal
Primary Flat = When a wafer has more than one flat then the longest flat will specify the silicon wafer's crystal orientation relative to the wafer surface. This primary flat is also called a major flat. Some wafers are made with just one flat for many reasons.
Secondary Flat defines the silicon wafer's crystal orientation and wafers doping whether it be undoped (nominally n-type), boron doped or arsenic doped and antimony doped. The secondary flat location varies. Below is an example of the flat position.
P type <111> No secondary Flat
P type <100> 90°±5° Clockwise from Primary Flat
N type <111> 45°±5° Clockwise from Primary Flat
N type <100> 180°±5° Clockwise from Primary Flat
Wafer Notches can be found on silicon wafer diameter greater than 150mm and are standard on 300mm.
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