Characterization in Silicon Processing

Reflection High-Energy

Electron Diffraction

(RHEED)*

18

In reflection high-energy electron diffraction (RHEED), a beam of high-energy

electrons

(typically

5-50 keV), is accelerated toward the surface of a conducting or

semiconducting crystal, which is held at ground potential. The primary beam

strikes

the sample at a grazing angle (-1—5°) and is subsequently scattered. Some

of the electrons scatter

elastically.

Since their wavelengths are shorter than inter-

atomic separations, these electrons can diffract off ordered rows of atoms on the surface,

concentrating scattered electrons into particular directions,

that

depend on row sepa-

rations.