Effect of the native oxide on the surface passivation of Si by Al2O3

Michael N Getz,Marco Povoli,Eduard Monakhov

doi:10.1063/5.0051215

Abstract

The effect of the native silicon oxide layer on the passivation properties of Al2O3 on p-type Si surfaces has been investigated. This was done by comparing effective carrier lifetime, surface saturation current density, fixed charge, and density of interface states of samples, where the native oxide was not removed prior to Al2O3 passivation, with samples subjected to a 3 min HF-dip. The sample with the native oxide exhibits excellent surface passivation post-annealing, with a surface saturation current density of 13 fA/cm2 and significantly longer effective lifetime compared to the sample, where the native oxide was removed. Capacitance–voltage measurements of a sample with the native oxide revealed a remarkably low density of interface states (1010 eV−1 cm−2), almost three times lower than a sample where the native oxide was removed prior to Al2O3 deposition. The results indicate that a thin layer of native oxide improves the Al2O3 surface passivation of silicon.

Highlights

As microelectronic devices are continuously scaled down in size, the surface becomes an increasingly larger part of the device
For applications relying on the collection of excited charge carriers, minimizing surface recombination losses associated with the dangling bonds at the surface has become critical for device performance, in the silicon-based photovoltaics, where cost reductions in recent years have been achieved by continuously reducing wafer thickness down to the current gold standard of 160 μm,1 development made possible due to excellent passivation of the dangling bonds associated with the silicon surface
The samples used for the CV measurements deposited on single-side polished (SSP) wafers were characterized by spectroscopic ellipsometry (SE) before and after back side contacting and scitation.org/journal/jap before and after the deposition

Summary

Introduction

As microelectronic devices are continuously scaled down in size, the surface becomes an increasingly larger part of the device. For applications relying on the collection of excited charge carriers, minimizing surface recombination losses associated with the dangling bonds at the surface has become critical for device performance, in the silicon-based photovoltaics, where cost reductions in recent years have been achieved by continuously reducing wafer thickness down to the current gold standard of 160 μm, development made possible due to excellent passivation of the dangling bonds associated with the silicon surface. Two strategies have been employed to reduce surface recombination: reducing the number of electronically active defect states at the surface and/or reducing the presence of one type of charge carrier from the surface by creating an internal electric field.. Creating an internal electrical field is achieved by coating the surface with a material containing fixed charges, Qfix, that repels charges of the same polarity and reduces the possibility for electron–hole recombination.

Results

Discussion

Conclusion