Nano-scale fatigue study of LPCVD silicon nitride thin films using a mechanical-amplifier actuator

• Published in: Journal of micromechanics and microengineering 2007-05, Vol.17 (5), p.938-944
• Main Authors: Chuang, Wen-Hsien, Fettig, Rainer K, Ghodssi, Reza
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Physics; Precision engineering, watch making; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transducers
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/17/5/013

This paper describes a nano-scale tensile test to study the fatigue properties of LPCVD silicon nitride thin films using a novel electrostatic actuator design. Mechanical-amplifier devices made in silicon nitride thin films can apply controllable tensile stress (2.0-7.8 GPa) to test structures with relatively low actuation voltages (5.7-35.4 VRMS) at the resonant frequencies of the devices. The test devices are fabricated using a surface micromachining technique in combination with deep reactive ion etching and ion milling. With the recently developed experimental techniques inside a focused-ion-beam system, in situ fatigue measurements are performed on silicon nitride test structures with beam widths of 200 nm. The silicon nitride test structures are found to exhibit time-delayed failures with continuous increases in their compliance. By reducing the applied tensile stress to 3.8 GPa, the test structures can survive cyclic loadings up to 108 cycles.