Mechanical Properties of Si02 and Si3N4 Coatings: A BAM/NIST Cooperative Project

Published

September 24, 1998

Author(s)

U Beck, Douglas T. Smith, G Reiners, S J. Dapkunas

Abstract

Mechanical properties, i.e., hardness and elastic modulus, of amorphous Si₀₂ and Si₃N^4^ PE-CVD coatings have been studied for two coating thicknesses (0.1 υm and 1.0 υm) and two substrate materials (fused silica, i.e., Herasil, and borosilicate glass, i.e., BK7) using low load instrumented indentation. The coating systems are being considered for possible use as reference materials for thin film mechanical property test methods. Single layers of Si₀₂ and Si₃N^4^ and a multilayer stack consisting of five double layers of Si₀₂/Si₃N^4^ (indivudal layer thickness: 0.1 υm) were investigated on both substrate materials. A special plasma pre-treatment of the substrates prior to deposition ensured that coating adhesion exceeded inner film stress for all systems considered. The applied indentation load ranged from 700 mN down to 0.1 mN and resulted in indentation depths from more than 1 υm to about 15 nm. The influence of coating thickness and the effect of the substrate on the measurement of hardness and elastic modulus of the films are discussed, with emphasis on the effects of indentation depth versus coating thickness on the observed coating properties. One coating-substrate system (1.0 um Si₃N₄ on Herasil) out of ten was found to be above a critical threshold for tensile cracking of the coating. In this system, termed overcritical, tensile cracks occurred both prior to, and a result of, indentation, indicating that Berkovich indentation may also be used to prove residual film stress.

Citation

Thin Solid Films

Volume

332

Pub Type

Journals

Keywords

coatings, hardness, indentations, modulus, silica, silicon nitride, thin films

Citation

Beck, U. , Smith, D. , Reiners, G. and Dapkunas, S. (1998), Mechanical Properties of Si₀₂ and Si₃N₄ Coatings: A BAM/NIST Cooperative Project, Thin Solid Films (Accessed April 26, 2024)