No abstract

No abstract

No abstract

Hydrogenated amorphous silicon nitride films with a high nitrogen content were prepared by RF plasma-enhanced chemical vapour deposition from a mixture of and at . The influence of the main operating variables on the quality of the material was examined. Characteristics and properties of the films were investigated using optical absorption, infrared spectroscopy, x-ray photo-electron spectroscopy and capacitance - voltage measurements. From infrared transmission and reflection measurements, it was found most of the IR peaks obtained by direct transmission in the range , which have often been mentioned in the literature, are caused not by absorption but rather by a strong reflection due to the Reststrahlen effect. IR studies carried out with polarized light revealed an anisotropic beam - sample interaction probably due to short-range phonon vibration modes: a parallel `LO mode' (), a parallel and perpendicular `TO mode' (). For sufficiently high values of the N/Si ratio, a decreasing percentage of or an increasing RF power leads to a decrease in the trapped charge density which should be related simultaneously to an increase in the N/Si ratio and a decrease in the Si - H bond density in the deposited films. It is suggested that, under our experimental conditions, the charged particle bombardment due to the RF discharge does not play an important role in the charge trapping and that the trapping rate seems to be controlled only by the nature of the traps.

No abstract

A numerical model of silicon nitride deposition from an NH,-SiH, mixture in a largesized radiofrequency plasma reactor has been developed. A bidimensional treatment of transpolt phenomena, of major importance in this type of reactor, was used. Analysis of the modelling results showed that aminosilane radicals were the main deposition precursors. The steep decrease in deposition rate in the flow direction that was observed can be explained by examining the calculated concentration profiles. Concentration of ith species (mol m-3) Initial concentration of ith species (mol m -3, Diffusion coefficient of ith species in the mixture (m's-l) Electron impact dissociation constant (m3s-') Electron impact ionization constant (m3s-l) Rate constant of reaction i (mol-' m3 s-l) Molar mass on species i (kgmol-') Electronic density Pressure (Pa) Volumic flow rate of species A Ideal gas constant (8.32Jmol-' K-') Deposition rate (ms-I) Reaction term in the gas phase (m01m~s-l) Reaction term at a surface (molm2s-') Sticking coefficient of the ith species Deposition temperature (K) Axial velocity (ms-') Radial velocity (ms-') Electrical power dissipated in the discharge (W) C0!!ip,ip'on \re!p'ocity

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.

No abstract