p‐ and n‐Type Silicon Electrochemical Properties in Dilute Hydrofluoric Acid Solutions

Abstract

electrodes with surface films which are porous and rough on their solution side. Li deposition in LiPF6 solutions was found to be more uniform than in LiClO4 solutions. This correlates very well with previous studies (Fourier transform infrared, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy) which revealed that different surface chemistries are developed on the electrodes in these systems.9 In LiC1O4 solutions the surface films comprise a mixture of ROCO2Li, Li2CO3, Li halides, and LiOH-Li20, while in LiPF6 solutions LiF is the major surface species. This may lead to the conclusion that the more homogeneous the composition of the surface films, the more uniform is Li deposition.

Light Enhanced Hydrofluoric Acid Passivation: A Sensitive Technique for Detecting Bulk Silicon Defects

“…It was found that when silicon wafers are immersed in 15%-30% HF, the lowest surface recombination is attained. This occurs because the HF concentration is high enough to passivate most of the silicon dangling bonds with hydrogen, and provides a field effect passivation mechanism by retaining a high surface charge caused by a difference in the silicon Fermi level and reduction potential of the HF solution 23 . The choice of 15% HF was for safety reasons.…”

“…Another important addition to the HF solution was the inclusion of HCl. By adding a small amount of HCl in the 15% HF solution, the hydrogen concentration in the HF solution is increased, which in turn increases the amount of hydrogen available for the surface passivation of silicon wafers, allowing the bulk silicon lifetime to be obtained post illumination 23 .…”

“…Illumination of silicon wafers immersed in HF can significantly improve the surface passivation by creating additional bonds with chemical species in the solution through electron and hole transfer across the silicon/HF interface 23,24 . There are a number of chemical bonds that can form at the silicon/HF interface, such as Si-H, Si-OH and Si-F [23][24][25][26][27] .…”

“…There are a number of chemical bonds that can form at the silicon/HF interface, such as Si-H, Si-OH and Si-F [23][24][25][26][27] . Passivation of silicon immersed in HF has been shown to primarily come from the creation of Si-H bonds, which is considered to be one of the most stable bonds when silicon is immersed in HF 26,27 .…”

Temporary Surface Passivation for Characterisation of Bulk Defects in Silicon: A Review

“…In general, it is possible to measure band-bending at the silicon-electrolyte interface using electrochemical based techniques. [25,26] By this method a potential difference is applied across a silicon wafer and counter electrode immersed in an electrolytic solution (e.g., HF). By varying the potential, information regarding space charge capacitance can be inferred, and the resulting band bending can be determined.…”