Photoluminescence imaging under applied bias for characterization of Si surface passivation layers

Abstract

In this work, we present a novel characterization technique for the analysis of Si surface passivation layers, using a photoluminescence imaging setup. In this technique the effective lifetime of passivated Si wafers is measured while applying an external bias over a rear side dielectric film. We demonstrate that this method can be used to analyze the passivation of silicon surfaces in inversion, depletion and accumulation conditions. In this paper the method is illustrated by characterization of a-SiN x :H passivation layers deposited by plasma enhanced chemical vapor deposition. The characterization results are interpreted both in the framework of the extended Shockley-Read Hall theory and by PC1D simulations. For the a-SiN x :H layers, the effective surface recombination velocity parameter is found to be 5-7 times larger for electrons than for holes and the fixed insulator charge density is found to be 6.1 − 6.5 • 10 ଵଵ cm -2 under illumination, in agreement with results from capacitance-voltage measurements.

Modulating the field-effect passivation at the SiO2/c-Si interface: Analysis and verification of the photoluminescence imaging under applied bias method

“…The excess carrier concentration Δ was then calculated from the PL intensity averaged over the electrode area as described in Ref. 7. The steady state effective lifetime can then be calculated as…”

“…Another alternative, which was used in Ref. 7, is to use a known passivation layer with a low SRV on the front of the wafer, so that is dominated by recombination on the rear side. We estimate the uncertainty in the determination of to be 10%.…”

“…Recently we proposed a new technique for analyzing the surface recombination for passivated silicon substrates 7 . The technique is based on measurements of the effective carrier lifetime in a photoluminescence (PL) imaging setup 8 while a voltage is applied over the rear side passivation layer.…”

On the c-Si/SiO2 interface recombination parameters from photo-conductance decay measurements

“…On the other hand, Kho et al 21 reported lifetime data, from which SRV can be extracted, for a range of carrier injections and positive dielectric charge densities, yet their proposed model parameters did not fit the experimental data. Most recently, Haug et al 27,28 proposed an original method to characterise SRV using photoluminescence (PL) imaging and a direct metal contact to the dielectric to control field effect passivation. In this method, the SRV was measured using a fixed photon flux, thus corresponding to different injections levels.…”

“…Although these studies provided a remarkable insight into the Si/SiO 2 interface, in particular, for the development of MOSFET technology, the D it and r p;n extracted from them have not produced an accurate characterisation of the macro-scale SRV, especially when carrier injection and dielectric charge are considered together in a broad domain. Haug 27,28 and Chen 48 have recently obtained accurate models by lumping together the D it Âr n;p product into the S p;n ðEÞ parameter, and extracting empirical values for the latter such that theory fits experimental data. Here, a similar approach is taken where S n;p values are used to find a good empirical fit of experimental SRV.…”