• Walmsley, Byron A.
• Martyniuk, Mariusz
• Antoszewski, Jarek
• Dell, John M.
• Musca, Charles A.
• Jung, Yeon-Gil
• Lawn, Brian R.
• Faraone, Lorenzo

Abstract

Thin-film MEMS are essential to realization of intelligent integrated microsystems. Of critical importance in such microsystems is the determination and control of mechanical properties in the thin films used for construction of the MEMS, which can be the decisive factor in the realization and subsequent performance, reliability, and long-term stability of the system. In future microsystems the need to fabricate MEMS on temperature sensitive, non-standard substrates will be of particular importance. In this work, mechanical properties of low-temperature (50-300°C) plasma-enhanced chemical vapour deposited silicon nitride thin films have been investigated using depth sensing indentation. Young's modulus, E, and hardness, H, values obtained for the examined film/substrate bilayers were found to vary asymptotically from the thin film properties for shallow indents to the substrate properties for deep indents. A simple empirical formulation is shown to relate E and H obtained for the film/substrate bilayers to corresponding material properties of the constituent materials via a power-law relation. The temperature of the deposition process was found to strongly influence the thin film mechanical properties. Values of E ∼ 150-160GPa and H ∼ 14-15GPa were observed for depositions above 225°C. Decreasing the deposition temperature initially caused a moderate and linear decrease in E and H parameters, which was followed by an abrupt decrease in E and H once the deposition temperature was lowered below 100°C, such that E ∼ 50GPa and H ∼ 3.5GPa at a deposition temperature of 50°C.

Topics

• Deposition
• impedance spectroscopy
• thin film
• nitride
• hardness
• nanoindentation
• Silicon