Metal-Assisted Etching of n-Type and p-Type Silicon Using Patterned Platinum Films: Spatial Distribution of Mesoporous Layer and Open Circuit Potential of Silicon

Abstract

Platinum (Pt) is one of the interesting catalysts in metal-assisted etching (metal-assisted chemical etching) of silicon (Si). The Pt-assisted etching induces not only the dissolution of Si under the Pt catalysts but also the formation of mesoporous layer on the Si surface away from them. In this work, we etched n-Si and p-Si by using patterned Pt films with a diameter of 5 μm and an interval of 50 μm. For both cases, the Si surface under the Pt catalysts was selectively etched and macropores with a diameter of 5 μm were formed. The macropores formed on n-Si were deeper than those formed on p-Si. The mesoporous layer was observed only around the macropores on n-Si, while it was observed over the entire surface of p-Si. We also measured the open circuit potential of Si in the etching solution. The positive shift of potential of n-Si by the Pt deposition was smaller than that of p-Si except for the initial stage of etching, which can be explained by the polarization characteristics. We discussed the etching behavior of n-Si and p-Si on the basis of the results of structure observation and electrochemical measurements.

Platinum-Particle-Assisted Etching of Low-, Moderately-, and Highly-Doped p-Type Silicon: Change of Composite Porous Structure

“…[1][2][3][4]7,8,10,[22][23][24][25][26][27][28][29][30][31][32] For example, when using platinum (Pt) catalysts, not only straight pores formed by the preferential dissolution of Si beneath the Pt catalysts but also mesopores covering on the entire surface of Si can be obtained. [33][34][35][36][37][38][39][40] However, the formation mechanism of the composite porous structure is not fully understood. We previously demonstrated that a characteristic composite structure (mesoporous layer thickness exceeds straight pore depth) is formed on highly-doped p-Si and the thick mesoporous layer can be attributed to the tunneling effect at the Si/electrolyte interface.…”