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Fourier-transform infrared spectroscopy ͑FTIR͒ analysis is a widely used tool for the analysis of bonded hydrogen in hydrogenated silicon nitride ͑SiN x :H͒. However, the proportionality factors between the integrated absorbance and bond densities, necessary for accurate hydrogen quantification, are still under discussion. The evolution of the total hydrogen concentration in thermally stable SiN x : H during an anneal, as determined by FTIR, using previously reported proportionality factors ͓E. Bustarret et al., Phys. Rev. B 77, 925 ͑1998͒; W. A. Lanford and M. J. Rand, J. Appl. Phys. 49, 2473 ͑1978͔͒ appears to be inconsistent with the hydrogen concentration evolution as determined by elastic recoil detection ͑ERD͒ analysis. The differences indicate invalid proportionality factors for our samples. Since annealing experiments of thermally stable SiN x : H offer a set of samples that differ only in N-H and Si-H bond densities, recalibration of these factors can be achieved by fitting the anneal time-dependent FTIR data to the evolution curves of the hydrogen concentration as detected with ERD. In this way a fully experimental calibration tool for the N-H and Si-H FTIR proportionality factors is obtained for individual, thermally stable, alloy films with multiple configurations of hydrogen bonds. Calibration was applied to SiN x : H films in the range 1.09Ͻ x Ͻ 1.35, deposited at high deposition rate using the hot-wire ͑HW͒ chemical vapor deposition ͑CVD͒ technique. Each film was cut into 25 samples, which were annealed for different durations at 800°C in N 2 and investigated using FTIR and ERD analysis. ERD measurements show that for the HWCVD SiN x : H, no detectable change in N / Si ratio or mass density occurs during an anneal. The thermal stability of the samples is also confirmed by FTIR measurements, where the sensitive Si-H peak position shows negligible shift during the anneal treatment. Calibration of FTIR proportionality factors for these samples shows that both proportionality factors change with the composition of the deposited films, and that they differ from reported values.

Hot‐wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We developed processing conditions for device‐ quality silicon nitride (a‐SiNx:H) anti‐reflection coating (ARC) at high deposition rates of 3 nm/s. The HWCVD SiNx layers were deposited on multicrystalline silicon (mc‐Si) solar cells provided by IMEC and ECN Solar Energy. Reference cells were provided with optimized parallel plate PECVD SiNx and microwave PECVD SiNx respectively. The application of HWCVD SiNx on IMEC mc‐Si solar cells led to effective passivation, evidenced by a Voc of 606 mV and consistent IQE curves. For further optimization, series were made with HW SiNx (with different x) on mc‐Si solar cells from ECN Solar Energy. The best cell efficiencies were obtained for samples with a N/Si ratio of 1·2 and a high mass density of >2·9 g/cm3. The best solar cells reached an efficiency of 15·7%, which is similar to the best reference cell, made from neighboring wafers, with microwave PECVD SiNx. The IQE measurements and high Voc values for these cells with HW SiNx demonstrate good bulk passivation. PC1D simulations confirm the excellent bulk‐ and surface‐passivation for HW SiNx coatings. Interesting is the significantly higher blue response for the cells with HWCVD SiNx when compared to the PECVD SiNx reference cells. This difference in blue response is caused by lower light absorption of the HWCVD layers (compared to microwave CVD; ECN) and better surface passivation (compared to parallel plate PECVD; IMEC). The application of HW SiNx as a passivating antireflection layer on mc‐Si solar cells leads to efficiencies comparable to those with optimized PECVD SiNx coatings, although HWCVD is performed at a much higher deposition rate. Copyright © 2007 John Wiley & Sons, Ltd.

The application of hot-wire (HW) CVD deposited silicon nitride (SiN x ) as passivating anti-reflection coating on multicrystalline silicon (mc-Si) solar cells is investigated. The highest efficiency reached is 15.7% for SiN x layers with an N/Si ratio of 1.20 and a high mass density of 2.9 g/cm 3 . These cell efficiencies are comparable to the reference cells with optimized plasma enhanced (PE) CVD SiN x even though a very high deposition rate of 3 nm/s is used. Layer characterization showed that the N/Si ratio in the layers determines the structure of the deposited films. And since the volume concentration of Si-atoms in the deposited films is found to be independent of the N/Si ratio the structure of the films is determined by the quantity of incorporated nitrogen. It is found that the process pressure greatly enhances the efficiency of the ammonia decomposition, presumably caused by the higher partial pressure of atomic hydrogen. With this knowledge we increased the deposition rate to a very high 7 nm/s for device quality SiN x films, much faster than commercial deposition techniques offer [S. von Aichberger, Photon Int. 3 (2004) 40].