Rate constants of reactions involving SiH₄as an association product from quantum Rice–Ramsperger–Kassel calculations

Abstract

Quantum Rice Ramsperger Kassel (QRRK) calculations are carried out to calculate the pressure-dependent rate constants of reactions involving SiH 4 as an association product. It is shown that good estimates of pressure-dependent rate constants can be obtained from QRRK in spite of the very poor treatment of the activated complex in this simple theory. However, possible errors arising from energy truncation must be avoided and reliable kinetic data must be fitted in order to select the final value of the adduct's mean vibrational frequency. The results obtained in this work are satisfactorily compared with the experimental data available and with previous RRKM calculations. Parameterized forms of the pressure-dependent rate constants are derived for several bath gases, which can be used over the whole pressure and temperature range of interest for chemical vapour deposition (CVD) and related processes.

Multifluid Eulerian modelling of a silicon Fluidized Bed Chemical Vapor Deposition process: Analysis of various kinetic models

“…The most recent kinetics proposed for (R 1 ) are those of Ho et al [38] and Dollet et al [37]. They were theoretically determined for a wide range of temperatures and have been relatively successfully compared with experiments around 600-650 • C. However, the authors used different methods (RRKM and QRRK models) to determine them and they obtain significantly different results: at 600 • C, these kinetics differ by a factor of 1.6.…”

“…Simultaneously, silane decomposition can lead to another radical species, SiH 3 , but in insignificant amount, even at very high temperature [37]. The higher the temperature and the longer the residence time of the gas phase in hot zones, the more advanced the silane pyrolysis and the more numerous are the reactions (R −n , R n ) to be considered: the model of Coltrin et al counts 27 reactions [36].…”

Pressure-dependent rate coefficients of chemical reactions involving Si2H4 isomerization from QRRK calculations

“…QRRK theory is simpler; its main assumptions are that: (i) the vibrational energy E of the reacting system is quantized, (ii) the s vibrational degrees of freedom of adduct are considered as harmonic oscillators represented by a single mean frequency hni and the energy E is divided into E/hhni vibrational quanta. Despite its simplicity, QRRK theory can provide fast but reliable estimations of pressure dependent rate coefficients [7]. Compared to RRKM theory, less input data are required which are: (i) the preexponential factors and activation energies of the reactions in their high-pressure limit (A 1 and E 1 ), (ii) the number of vibrational degrees of freedom for the adduct, (iii) the mean vibrational frequency of adduct (usually the geometric mean of adduct's individual frequencies), (iv) the collision efficiency, evaluated from the average energy transferred per collision with the third-body gas (hDE coll i) by using Troe's relation [26], and (v) the Lennard-Jones transport properties s and e/k, for the adduct and for the thirdbody gas.…”

“…Our QRRK calculations also use a Gamma function formulation as in reference [27], in order to suppress errors arising from energy truncation [7].…”

“…[1][2][3][4][5][6]. Despite this effort, however, there is still a need for a more accurate and complete reaction scheme describing the homogeneous chemistry of small silicon hydrides (containing less than four Si atoms) over the temperature and pressure ranges of interest for CVD [7]. For instance, the pressure dependence of reactions involving Si 2 H 4 isomers remains today poorly known.…”