The Process Flow of the Back Metal Process

This article will analyze the specific process flow of the back metal process and the process principle of each step.

The Process Flow of the Back Metal Process:

0040-09095 Gas Box, Wcvd

As is shown in above picture, the steps are：
tape→grinding →Si etch → Detape → Pre-treatment →back metal
Adhesive Paper Quick Sticking→Downgauging→Silicon Etching→Peeling Off Adhesive Paper→pre-treatment→back metal

1,tape


Apply the blue tape shown in the image above to the front of the wafer to protect the pattern on the front side of the wafer.
2,grinding ：The back side of the silicon wafer is ground and thinned to an appropriate thickness, and the method of mechanical polishing is adopted
3,Si etch：After backside thinning, there will be many defects on the backside of the wafer and there will be silicon powder residue. At this time, the internal stress of the wafer is very large and easy to fragment, and silicon corrosion can eliminate its internal stress, and make its surface roughness greater, and the metal is easier to accumulate on it.

Nitric acid and hydrofluoric acid are commonly used for etching, and the equation is： Si+HNO3+6HF=H2SiF6+H2NO2+H2O+H2
4,Pre-treatment：The cleanliness of the back of the silicon wafer has a great influence on the binding force of the metal in the seed layer to Si, so it is necessary to ensure adequate cleaning. Generally, BOE is used to wash off the natural oxide layer on the surface of silicon.

5,back metal：Using electron beam evaporation or magnetron sputtering, the corresponding metal layer is deposited, taking Ti/Ni/Au (Ag as an example), the corresponding metal thickness I have seen is: Ti1kÅ, Ni3.5kÅ, Au(Ag)1kÅ (6kÅ), of course, the thickness can vary according to the specific scene.

0021-09760 Gas Box Dxz