High rate (∼3 nm/s) deposition of dense silicon nitride films at low substrate temperatures (<150 °C) using the expanding thermal plasma and substrate biasing

• Published in: Thin solid films Vol. 484; no. 1; pp. 46 - 53
• Main Authors: van Assche, F.J.H., Kessels, W.M.M., Vangheluwe, R., Mischke, W.S., Evers, M., van de Sanden, M.C.M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 22-07-2005; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Low substrate temperature; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Plasma processing and deposition; Silicon nitride; Substrate biasing; Vapor phase epitaxy; growth from vapor phase; Low substrate temperature; Substrate biasing; Plasma processing and deposition; Silicon nitride; RBS; Inorganic compounds; Spectroscopic ellipsometry; Refractive index; Plasma assisted processing; Experimental study; Density; Thin films; Growth from vapor; Thermal expansion; Amorphous hydrogenated material; Preparation; Silicon nitrides; Effective medium model
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2005.01.095

The deposition of amorphous silicon nitride (a-SiN
x
:H) films at high deposition rates (∼3 nm/s) and at low substrate temperatures (<150 °C) has been studied using the expanding thermal plasma technique operated on an Ar–NH
3–SiH
4 reactant mixture. To increase the atomic density of the films by ion bombardment, low frequency (lf, 400 kHz) and radio-frequency (rf, 13.6 MHz) substrate biasing has been employed during deposition such that the ions are accelerated towards the substrate up to energies of ∼250 eV. From spectroscopic ellipsometry and Rutherford backscattering measurements, it is demonstrated that the film density increases with increasing substrate bias even under these high deposition rate conditions. An increase in film atomic density from 7.6×10
22 cm
−3 to 8.8×10
22 cm
−3 has been observed for rf biasing when going from almost zero substrate bias to a bias voltage of −250 V. It is shown that this increased film density reduces the oxygen content in the a-SiN
x
:H caused by post-deposition oxygen and/or moisture permeation by more than 50%.