Method of forming die seal structures having substrate trenches

摘要

A die seal structure having trenches is provided. The die seal structure is formed on a silicon substrate and used to prevent lateral stress from causing damage to internal circuits in a die when a wafer is being cutted. A die seal comprises a buffer area, a seal ring and a buffer space. The buffer area is adjacent to the internal circuit. The buffer space is adjacent to a scribe line. The seal ring having a structure of stacked metal layers and dielectric layers is located between the buffer area and the buffer space. A trench for enhancing the stress-protection ability of the die seal is formed in the buffer space. The trench is formed by wet-etching SiO2 residues on the buffer space using buffered HF, or wet-etching Si3N4 residues on the buffer space using phosphoric acid at 180° C. In addition, a portion of the substrate may be removed by wet etching using HNO3 and HF. Dry etching may also be used to remove the dielectric residues and a portion of the silicon substrate on the buffer space.