The purpose of epitaxy is to perfect the crystal structure over the bare substrate below and improve the wafer surface's electrical characteristics, making it suitable for highly complex microprocessors and memory devices.
[6] Methods for growing the epitaxial layer on monocrystalline silicon or other wafers include: various types of chemical vapor deposition (CVD) classified as Atmospheric pressure CVD (APCVD) or metal organic chemical vapor deposition (MOCVD), as well as molecular beam epitaxy (MBE).
[8] In the dry stress lift-off process applicable when the epi-layer and substrate are suitably different materials, a controlled crack is driven by a temperature change at the epi/wafer interface purely by the thermal stresses due to the mismatch in thermal expansion between the epi layer and substrate, without the necessity for any external mechanical force or tool to aid crack propagation.
It was reported that this process yields single atomic plane cleavage, reducing the need for post-lift-off polishing and allowing multiple substrate reuses up to 10 times.
[17] In 2016, a new approach was described for producing hybrid photovoltaic wafers combining the high efficiency of III-V multi-junction solar cells with the economies and wealth of experience associated with silicon.