222 nm Photo-induced radical reactions in silazanes. A combined laser photolysis, EPR, GC-MS and QC Study

Abstract

The initiation mechanism of the VUV-induced conversion of polyorganosilazanes into methyl-Si-O-Si networks was studied by means of model disilazane compounds. A combined experimental approach was chosen to determine the primary radicals and their properties (lifetimes, spectra) as well as the major final products. It was verified that both Si-N and Si-CH(3) cleavage occur in the condensed phase, the former with higher yield. The lifetime of the primary Si- and N-centred radicals in de-oxygenated n-hexane solution is less than </=10 mus. N-centred radicals transform into amines by H abstraction, the availability of weakly bonded H as in the case of tetramethyldisilazane accelerates the reaction considerably. In rigid matrix (frozen solutions) CH(3), silyl radicals and methylene radicals CH(2)R are trapped. In the presence of oxygen, peroxyl radicals are formed and serve as precursors of the subsequent oxidative conversion. Product analysis by GC-MS reveals linear R-(Si-O)(n)- chains rather than branched compounds as the initial products of the oxidative conversion of tetramethyldisilazane. It was shown that reactive silylene intermediates do not play a role in the conversion process. Quantum chemical calculations assist in the interpretation.

An innovative GC-MS, NMR and ESR combined, gas-phase investigation during chemical vapor deposition of silicon oxynitrides films from tris(dimethylsilyl)amine

“…43 In the case of the (Me2HSi)2N° radical, a more complex hyperfine structure (comprised of 18 lines) would be expected. 35 Thus, the measured g value is assumed to be related to a silicon-centered radical, in agreement with data reported for radicals such as SiHMe2° or SiMe3° trapped by α-phenyl-N-tert-butyl nitrone (PBN) 44,45 characterized by a g-factor of 2.0059±0.0001. Nevertheless, the Si-centered radicals resulting from the cleavage of the Si-C or Si-H bond, Equation ( 2) and ( 3) respectively, are unlikely to be trapped, as they are hindered molecules.…”

“…Further increase of the temperature up to 700°C does not significantly influence the TDMSA conversion, which increases only slightly from 81 to 83 %. The curve reaches a plateau, indicating a possible recombination of the by-products, similarly to what was described by Knolle et al 35 with the reformation of the tetramethyldisilazane (TMDSz) during its laser photolysis. Globally, the results indicate that TDMSA does not fully decompose in the probed temperature range, since it is always observed at the exit of the reactor.…”

Flexible Transparent Barrier Applications of Oxide Thin Films Prepared by Photochemical Conversion at Low Temperature and Ambient Pressure

“…Photoconversion of methylated silazanes was subjected to detailed mechanistic studies (low-temperature ESR studies, laser flash photolysis, FTIR measurements and mass spectrometric detection of gaseous products) coupled with DFT calculations. They support the above mentioned reaction scheme (Figure 7), but exhibit lower WVTR and OTR values compared to the pure inorganic thin films (Prager et al, 2009;Knolle et al, 2010).…”

“…Transient spectra observed after laser flash photolysis of an N 2 -saturated solution of tetramethylcyclotetrasilazane (molecular structure displayed on left side)(Knolle et al, 2010).…”

Studying Effect of UV Curing on Physical Properties and Wet Etch Resistance of Perhydro-polysilazane-based Inorganic Spin-on-glass (PSZ-SOG) Film

“…Prager et al also mention that VUV photon triggers the Si-N bond dissocation and accelerates the conversion rate of PSZ [4]. Moreover, the similar phenomena of VUV-induced of organsiliazanes into methyl-Si-O-Si networks also was demonstrated by Knolle et al [14]. For the SOG film, a subsequent effective thermal curing is compulsory to ensure the desired thermal oxide like film achievement, and to remove solvents from the SOG films in case film's cracking or popping [5][6] happen due to moisture or impurity outgassing.…”