|Here are the specification for Si wafers from one of the worlds top companies, Wacker Siltronic, as they appear in the Internet in Nov. 2000.|
|Notice: Concentrations here are in
cm3. The conversion to parts per .. is simple:
The atomic density of Si is 4.96 · 1022 cm3 or about 5 · 1022 cm3.
1 ppm thus corresponds to 5 · 1016 cm3.
|The lowest concentration given in the table (look for it) is 5 · 1010 cm3; it corresponds to 1 ppt or 1012.|
|Surface concentrations [S]
(given in cm2) are converted to volume concentrations
[S] = [V] /a with a = lattice constant (= 0,5431 nm) or, more precise for single crystals, distance between the crystallographic planes. With a » 0,5 nm = 5· 108 cm, we have
[V] = 5 · 1016 cm3 = 1 ppm corresponds to S = 108 cm2.
|Many specifications relate to the
"flatness" of the wafers and the perfection of the surface; the
abbreviations used are
LLS (sometimes also abbreviated LPDs): Localized Light Scattering Defect; this relates to a detection method of sub-µm size surface imperfections (resulting from bulk microdefects)
SFQR: Site flatness quality requirements (??): Definitely a measure of flatness in a region comparable to the size of a single chip
(The rest: Who knows?
|Here is a link with precise
defininitioons of geometricla parameters:
3.2.1 Single Crystals and Wafers
© H. Föll (Semiconductor - Script)