Development of Micro-Pores Including Nano-Pores on n-Si (100) Coated with Sparse Ag Under Dark Etching in 1.0 M NH4F Containing 5.0 M H2O2

Abstract : Specimens of n-type single crystalline silicon sparsely deposited with silver nano-particles on the Si (100) surfaces were put in 1.0 M NH4F + 5.0 M H2O2 to investigate their dark etching. Through examination by scanning electron microscopy (SEM), the morphology on the n-Si (100) surface etched for 1 h revealed a sparse distribution of nano-pores (10~40 nm in diameter) according to the locations of Ag-particles; however, it exhibited porous surface consisting of micro-pores (1.5~3.1μm in diameter with 15~20μm in depth) where nano-pores (100~150 nm in diameter) were embedded inside for the etching duration prolonged for 5 h. The Nyquist plot for this system indicated two typical semicircles, in which the one in response to high frequencies revealed greater diameter and the other in response to low frequencies indicated smaller diameter. By checking the chemical bonding of silicon and silica in the NH4F/H2O2 system shows two important points at 99.3 eV and 103.4 eV.