A true Prime wafer with a perfect or near perfect Epitaxial layer is a wafer that is suited for manufacture of advanced semiconductor devices. EPI-Prime wafers can be available for a reasonable price.
EPI-Prime wafers usually come in two flavors: The first kind is the EPI substrate wafer. This is a highly doped N or P-type wafer usually <1 Ohm/cm without the Epi layer. The second is the true EPI wafer. This wafer also has a highly doped N or P-type substrate with a layer of N or P-type Epitaxial silicon (various doping) on the front surface of the wafer. Both of these wafer types may have what is called an oxide backseal on them usually 3,000-5,000 Å. This oxide is placed on the backside of the wafer before the Epitaxial Deposition to prevent Boron, Phosphorous, or other dopants from outgassing from the backside and contaminating the front side Epi layer during the high temperature Epitaxial Silicon deposition process. So if you see this Oxide on the backside of the wafer you know it is typically an Epi wafer. EPI-Prime substrates and EPI Wafers can be of great use to Semiconductor tool companies looking for a cheaper alternative to the high priced Prime wafers discussed earlier. Uses we have found they work well for are: Photo-lithography, CMP characterization, and in most cases the Prime EPI substrates work well as particle monitors. They work well with most deposited thin films. See inventory purchase list for availability.