[공학]diffusion

소개

During a constant-source diffusion, the impurity concentration is held constant at the surface of the wafer.
N0 is the impurity concentration at the wafer surface (x = 0).
Q is the total number of impurity atoms per unit area in the silicon
A Gaussian distribution results from a limited-source diffusion. As the Dt product increases, the diffusion front moves more deeply into the wafer, and the surface concentration decreases

목차

Diffusion Process
Mathematical model for diffusion
Diffusion coefficient
Successive diffusion
Solid-solubility limits
Junction formation and characterization
Sheet resistance
Generation-Depth and Impurity Profile Measurement
Diffusion systems
Gettering

본문내용

Diffusion follows the theory of Slide 10 as long as the impurity concentration remains below the value of the intrinsic-carrier concentration ni at the diffusion temperature. ( Ci < ni )
Above this concentration, the diffusion coefficient becomes concentration dependent, and each of the common impurities exhibits a different behavior ( Ci > ni )
A fixed current is injected into the wafer through the two outer probes, and the resulting voltage is measured between the two inner probes.
An energy of 1~20KeV ion beam( cesium, oxygen) is used to remove atoms from the surface, one or two atomic layer at a time. These ions are collected and analyzed by a mass spectrometer, which identifies the atomic species. The analysis is performed continuously during the sputtering process, and a profile of atomic distribution versus depth.

참고자료

· 없음