Epitaxy

 

It is a technique of depositing the epitaxial layer on the wafer, which is done after slicing and polishing. With approximately 3% of the thickness of the wafer, this layer consists of highly pure silicon and provides a buffer layer. It also hedges against other harmful impurities or undetected defects on the wafer substrate.

 

The common epitaxial layers include vapor, liquid and solid phase. It is dependent of the source of the atoms to be arranged on the substrate. Epitaxy has also recently been used in CMOS VLSI circuits. By fabricating the CMOS device on a very thin (3-7 microns) lightly doped epi layer grown over a heavily doped substrate, latch-up occurrence is minimized.