Toward Controllable Wet Etching of Monocrystalline Silicon: Roles of Mechanically Driven Defects

Wet chemical etching is essential not only for processing silicon (Si) wafers but also for forming diverse structures, significantly promoting the development of the semiconductor industry. However, tight control of etched topography at the nanoscale and even atom-scale in a controllable and reproducible fashion can be hardly achieved in either laboratory research or industrial production, seriously hindering further enhancement of high-performance Si-based electronic devices. Herein, the roles of mechanically driven defects in wet etching were systematically investigated toward promoting controllable wet etching of monocrystalline Si. The role of antietching of mechanically driven amorphous Si (a-Si) and the role of promoting etching of distorted Si (including dislocations and stacking faults) were revealed in anisotropic or isotropic etchants. It was also found that the nucleation of nanocrystals in the a-Si area with increasing contact pressure can lead to deactivation of the antietching mask, and the required contact pressure for deactivation in KOH and tetramethyl ammonium hydroxide solutions was much higher than that in HF/HNO₃ mixtures. The selective etching mechanisms for every defect including a-Si, distorted Si, and nanocrystals were further addressed down to the atom-scale based on the proposed dissolution model. This study provides insights into deeply understanding the role of defects in wet etching and pushes forward the idea of controllable wet chemical etching in the Si-based semiconductor industry.