Grinding Of Semiconductor Silicon Wafers

The basic technique of wafer lapping is the grinding process. Through the rotation of the grinding plate of the grinding machine and the abrasive dispersed on the grinding plate, the planetary-moving wafer is continuously ground to achieve the purpose of removing the knife marks, the slice damage layer and the thickness control generated during the slicing process.

For the wafers processed by the precision grinding machine, the thickness tolerance of the wafer on the same disc is less than 1 μm, the tolerance of different discs is less than 5 μm; the non-parallelism is less than 2 μm.

The material of the grinding plate of the grinding machine should be selected for processing different wafers. The ductile iron plate cast and processed by a special process is generally used. The hardness is uniform everywhere.

For compound semiconductor materials, grinding plates made of special glass are used for the grinding of wafers.

Abrasives are prepared from abrasives and grinding fluids. The hardness, shape, particle size and uniformity of the abrasive, as well as the ease of use of the abrasive fluid, the dispersion and suspension of the abrasive particles, and the cleanability will all affect the processing quality of the wafer surface.

For wafers with higher hardness, flaky alumina (high-purity alumina) can be used as the abrasive. The particle size of the abrasive is selected according to the physical properties of the processed wafer and the depth of the surface damage layer that may be caused. In semiconductor wafer processing, 8-10 μm, 10-12 μm or 12-14 μm flake alumina (high-purity alumina) is usually used as the abrasive to ensure faster grinding speed without leaving too deep damage layer.

During the grinding process of the wafer, the basic process parameters are: the pressure on the wafer surface from the grinding plate, the rotating speed of the grinding plate, the concentration and flow of the abrasive, the hardness and particle size of the abrasive, etc.