2-24.Wafer Orientation

Wafers are grown from crystal having a regular crystal structure, with silicon having a diamond cubic structure with a lattice spacing of 5.430710 Å (0.5430710 nm).When cut into wafers, the surface is aligned in one of several relative directions known as crystal orientations. Orientation is defined by the Miller index with [100] or [111] faces being the most common for silicon.Orientation is important since many of a single crystal’s structural and electronic properties are highly anisotropic. Ion implantation depths depend on the wafer’s crystal orientation, since each direction offers distinct paths for transport.Wafer cleavage typically occurs only in a few well-defined directions. Scoring the wafer along cleavage planes allows it to be easily diced into individual chips (“dies”) so that the billions of individual circuit elements on an average wafer can be separated into many individual circuits.

In silicon carbide,the growth plane of the crystalline silicon carbide.  Orientations are described using Miller Indices such as (0001) etc.  Different growth planes and orientations have different arrangements of the atoms or lattice as viewed from a particular angle.


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