A multi-step etch method for fabricating slightly tapered through-silicon vias based on modified Bosch process

In this paper, a multi-step etching method based on Bosch process was investigated to fabricate a slightly tapered via. The diameter of vias was scaled from 40 to 100 µm. Isotropic etching step was added into Bosch process to control the angle of the tapered vias. The slope angle could be adjusted by changing the time settings of isotropic etching step. The influence of the platen temperature was also studied. The passivation and etching steps are extremely sensitive to temperature. Silicon grass could be formed at low temperature. The two different processes of isotropic SF₆ etching and Cl₂/HBr etching were also compared. The wrinkles and cracks were observed on the surface after treatment with isotropic SF₆ etching. The Cl₂/HBr etching method is much better for removing the scallops.