Complete Elemental Analysis of Low-ka-SiC:H Thin Films by Transmission FTIR Spectroscopy

Abstract

Fourier transform infrared (FTIR) spectroscopy is a popular technique for qualitatively investigating the chemical bonding of low dielectric constant (low-k) materials utilized in nanoelectronic Cu interconnects. However, quantitative FTIR analysis of low-k materials with widely varying stoichiometry has proven challenging due to numerous optical interference effects, variations in IR absorption strength with optical constants, and a negligible IR activity for homopolar bonds. In this paper, these challenges are overcome to demonstrate full elemental composition analysis by applying multivariate partial least squares (PLS) modeling to the true IR absorbance spectra obtained using previously described methods for eliminating optical interference effects from thin film FTIR spectra. To demonstrate the validity of this approach, transmission FTIR spectra were collected from a series of low-k a-SiC:H thin films with hydrogen content ranging from 25-60%. The elemental concentrations determined from PLS analysis of the corrected low-k a-SiC:H FTIR spectra were found to be in agreement to within ±5% of results obtained from independent nuclear reaction analysis and Rutherford backscattering measurements. These results demonstrate a clear path for establishing transmission FTIR as a quantitative metrology for full compositional analysis (elemental and chemical bond) for a wide range of thin film materials.

Analysis of Low-k Dielectric Thin Films on Thick Substrates by Transmission FTIR Spectroscopy

“…It was found that, to obtain the corrected spectra with M minimized, one needed to allow both inputs to be treated as free parameters. 16,20 However, the values for refractive index and thickness that were obtained from the procedure of minimizing M did not deviate too far (<1−5%) from the ellipsometric values, so these values do serve as a good starting point for the correction procedure.…”

“…The first results from the superposition of numerous components of the IR beam that were multiply reflected at the film surface and filmsubstrate interface. 20 The frequency of these fringes varies with the film thickness and can range from 500-10,000 cm −1 depending on the thickness of the film. 21 Multiple reflections in the substrate generate the second source of interference fringes.…”

“…The magnitude of this effect is significant and it requires correction before T-FTIR spectra can be utilized for quantitative analysis. 20 ECS Journal of Solid State Science and Technology, 4 (1) N3146-N3152 (2015)…”

“…The magnitude of this effect is significant and it requires correction before T-FTIR spectra can be utilized for quantitative analysis. 20 …”

Preparation of Low-Dielectric-Constant Kaolin Clay Ceramics by Chemical Cleaning Method

“…In recent years, low-dielectric-constant materials have been commonly employed in microwave devices, ultra-large-scale integrated circuits, and other applications (Sato et al, 2013;Hong et al, 2020). Many materials have been introduced to achieve lower dielectric constants, such as Al 2 O 3 (Su et al, 2014), SiCN (Zhou and Zhang 2015), BN (Hong et al, 2016), SiC (Milosevic and King 2014), and SiO 2 (Carta et al, 2014;Joseph et al, 2015). Although the resulting materials have excellent properties, they are expensive and limited in terms of output.…”