Calculate the mean free path of a particle in the gas phase of a deposition system
and estimate the number of collisions it experiences in traveling from the source to the substrate in each of the cases below.
Assume that in each case the molecular collisional diameter is 0.4 nm, the source-to-substrate distance is 5 cm, and that the number of collisions is approximately equal to the source-to-substrate distance divided by the mean free path.
a. An evaporation system in which the pressure is 10-3 torr and the temperature is 25°C.
b. A sputter deposition system in which the pressure is 3 mtorr and the temperature is 25°C.
c. An LPCVD system in which the pressure is 1 torr and the temperature is 600°C.
d. An APCVD system in which the pressure is 1 atm and the temperature is 600°C.