Unambiguous determination of Fourier-transform infrared spectroscopy proportionality factors: The case of silicon nitride

Abstract

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.

Bonding rearrangement in amorphous silicon nitrides deposited by hot-wire chemical vapor deposition upon thermal annealing

“…They suggested that the enhanced oscillation strength of Si-H bonds after annealing can be attributed to a change in the Si-H bond absorption. Although such large changes in oscillator strength are possible [18], the observations in Fig. 1(c), i.e.…”

Hot Wire Chemical Vapor Deposition: Recent Progress, Present State of the Art and Competitive Opportunities

“…The low H concentration of 9 at.-%, specifically the low density of Si-H bonds [43], is an advantage for the use as sidewall and liner material in ultra large scale integration p-type metal-oxide-semiconductor transistors. This is the case because H, coming from the SiN x at the sidewalls, can create defects at the gate/gate-insulator interface [44].…”

Opto-Structural Properties of Silicon Nitride Thin Films Deposited by ECR-PECVD

“…Despite the enormous use of FTIR in the analysis of chemical bonds in the hydrogenated thin film a-Si:H, a-SiN:H and a-C:H. Several values of conversion factors for the various bonds (oscillators) have been reported in the literature [30] [31]. Verlann et al [32] have first recalibrated these conversion factors in the case of SiN x films by ERDA technique according to its stoichiometry. Figure 5 shows the dependence of the Si-N, Si-H and N-H absorption bands on the gas flow ratio R. The (700 -1100 cm −1 ) characteristic absorption band of Si-N largely depends on the ratio R. Its maximum position (830 cm −1 ) shows that SiN films are less contaminated by others elements during deposition and characterization.…”