Purpose:
in the diffusion process, POCI, is decomposed under high temperature
and generate phosphorus. Then, The phosphorus diffused on the
P-type substrate to form a PN junction. A negative concertration
gradient and proper phosphorus content are desired for homogeneous
sheet resistance and eletrode ohm contact. The concentration of the
phosphorou source, diffusion temperature and diffusion time are
are the main varibles in this proess
"Definition of diffusion:
"
Micro definition: The movement of micro particles(atoms, ions,
molecule) because of thermal motion.