多项选择题
Why must a high vacuum be provided during vacuum evaporation?
A、The mean free path of vapor atoms / molecules must be larger than the distance between the crucible and the wafer.
B、The mean free path of vapor atoms / molecules must be smaller than the distance between the crucible and the wafer.
C、Oxidization of the deposited film must be avoided.
D、The deposited film must be of high purity.
Why must a high vacuum be provided during vacuum evaporation?
A、The mean free path of vapor atoms / molecules must be larger than the distance between the crucible and the wafer.
B、The mean free path of vapor atoms / molecules must be smaller than the distance between the crucible and the wafer.
C、Oxidization of the deposited film must be avoided.
D、The deposited film must be of high purity.