Programmable vapor-phase metal-assisted chemical etching for versatile high-aspect ratio silicon nanomanufacturing

Abstract

Defying the isotropic nature of traditional chemical etch, metal-assisted chemical etching (MacEtch) has allowed spatially defined anisotropic etching by using patterned metal catalyst films to locally enhance the etch rate of various semiconductors. Significant progress has been made on achieving unprecedented aspect ratio nanostructures using this facile approach, mostly in solution. However, the path to manufacturing scalability remains challenging because of the difficulties in controlling etch morphology (e.g., porosity and aggregation) and etch rate uniformity over a large area. Here, we report the first programmable vapor-phase MacEtch (VP-MacEtch) approach, with independent control of the etchant flow rates, injection and pulse time, and chamber pressure. In addition, another degree of freedom, light irradiation is integrated to allow photo-enhanced VP-MacEtch. Various silicon nanostructures are demonstrated with each of these parameters systematically varied synchronously or asynchronously, positioning MacEtch as a manufacturing technique for versatile arrays of three-dimensional silicon nanostructures. This work represents a critical step or a major milestone in the development of silicon MacEtch technology and also establishes the foundation for VP-MacEtch of compound semiconductors and related heterojunctions, for lasting impact on damage-free 3D electronic, photonic, quantum, and biomedical devices.