Residual stress behavior of thin plasma-enhanced chemical vapor deposited silicon dioxide films as a function of storage time

Abstract

Residual stress in thin silicon dioxide films has been studied as a function of storage time. Films of varying microstructure and impurity content were deposited by plasma-enhanced chemical vapor deposition. Initially, all the films exhibited compressive stress, the magnitude of which was found to increase rapidly with time for the first few hours after deposition. For all the deposited thin films, this increasing compressive stress eventually saturates and then begins to decrease with time. The time at which the transition occurs depends on film thickness and quality, whereas, for relatively thicker films deposited under identical conditions, a saturation in compressive stress after long aging time was observed. No existing model of thin oxide films successfully explains the observed time variation of stress. In this paper, the variation of film stress as a function of storage time and film properties, such as porosity and impurity content, is discussed. Three driving forces, namely, surface reactivity, silanol buildup, and water dipole interaction, each of whose contribution varies depending on film thickness and quality, have been identified as potential mechanisms behind stress change in oxide films. A unified model consisting of these driving forces can explain the time variation of stress behavior in oxide films, irrespective of film quality and thickness.

Influence of Tetramethyldisiloxane‐Oxygen Mixtures on the Physical Properties of Microwave PECVD Coatings and Subsequent Post‐Plasma Reactions

“…Due to the rearrangement of these bonds, the stress in the coatings became less tensile. This has also been reported by Haque et al in a study which described stress changes due to either a surface effect or a silanol effect for PECVD derived SiO 2 coatings. The silanol effect is defined as the rearrangement of Si‐OH type terminations to a more relaxed O‐Si‐O network.…”

“…The stress changed to a more tensile state; in this situation the stress change was dominated by dipole interactions with ingressing water as proposed by Hirsch and Haque et. al . It was observed that there was a mass increase for these coatings which may support the notion of significant uptake of water.…”

“…al. [44,46] It was observed that there was a mass increase for these coatings which may support the notion of significant uptake of water. This then led to plasticization, which was observed as a reduction in compressive stress for these samples.…”

Design, Simulation, Fabrication, and Characterization of an Electrothermal Tip-Tilt-Piston Large Angle Micromirror for High Fill Factor Segmented Optical Arrays

“…It was observed that the device reached a steady state after a month. One possible explanation to this effect could be due to the quality of the oxide layer, where the SiO 2 grown by PECVD at low temperature (200 °C) tends to react with the humidity in the environment creating a change in stress over time, as reported by [ 38 , 39 , 40 ]. This translates to a change of elevation over time in the undercarriage.…”

Long-term environmental stability of residual stress of SiNx, SiOx, and Ge thin films prepared at low temperatures

“…Generally, reversible absorption (desorption) of water vapor into a porous thin-film matrix is reported to be correlated with compressive (tensile) stress changes as the film expands (contracts) to accommodate the water molecules [3][4][5][6][7][8]. However, absorption and desorption of species with a permanent dipole moment (e.g., water) into thin-film porous structure can exhibit an opposite effect (i.e., films becoming more tensile on absorbance of the impurity) due to the alignment geometry and electrostatic interactions between the incorporated dipoles and the thin-film matrix [9][10][11][12]. In addition, atmospheric exposure has been frequently reported [13][14][15][16][17] to oxidize thin films, and in the case of thermally evaporated silicon monoxide [13][14][15] has been cor- [16,17].…”