Composite diamond protective film, preparation method thereof and chip base material

The invention relates to the field of photoelectricity, and discloses a composite diamond protective film and a preparation method thereof and a chip base material, and the preparation method comprises the following steps: placing the base material in an absolute ethyl alcohol suspension of diamond nano powder for ultrasonic treatment; placing the treated base material on a sample table of a microwave plasma chemical vapor deposition system, and carrying out plasma cleaning; growing a diamond transition layer on the surface of the base material; growing a nanocrystalline diamond layer with high density; growing a high-orientation (100) micron crystal diamond layer; performing plasma cleaning on the surface of the base material; and stopping introducing the argon, reducing the hydrogen flow, the air pressure and the microwave power at the cooling rate of less than 1 DEG C per second, breaking the vacuum, and taking out the base material with the composite diamond protective film. The composite diamond protecti