Tensile testing of insulating thin films;: humidity effect on tensile strength of SiO2 films

Humidity effect on the strength of a plasma-enhanced chemical vapor deposition (CVD) SiO2 film is evaluated with new tensile testing method using an electrostatic force grip. This method can test insulating films without troublesome specimen preparation and careful handling. To measure the humidity effect, two thin film tensile testers are used. One can perform test in air, and the other in a vacuum. With these apparatus, the tensile strength and the fracture toughness of the SiO2 films are measured both in a vacuum and in air. The mean strength is 1.2-1.9 GPa in a vacuum and 0.6-1.0 GPa in air, and the mean toughness is 1.3-2.0 MPa root m in a vacuum and 0.6-0.9 MPa root m in air. These values are strongly affected by the testing environment, and these effects must be mainly due to water in air. (C) 2000 Elsevier Science S.A. All rights reserved.