An analysis of two technological options to achieve a high deposition rate, low stress PECVD silicon nitride to be used in Capacitive Micromachined Ultrasonic Transducers (CMUTs) fabrication is presented. A tradeoff between deposition rate, residual stress and electrical properties is showed. A double layer of silicon nitride with a deposition rate of ~100 nm/min and low compressive residual stress is obtained, which is suitable for the fabrication of the thick nitride layer used as mechanical support. A mixed frequency nitride with compliant insulating performance is analyzed. A complete characterization is reported in terms of interface density influence on residual stress, refractive index, deposition rate, and thickness variation. A complete device was fabricated using the optimized nitrides and its performance was tested, demonstrating full functionality in ultrasound imaging applications.
PECVD Low Stress Silicon Nitride Analysis and Optimization for the Fabrication of CMUT Devices
Bagolini, Alvise;Picciotto, Antonino;Boscardin, Maurizio;Bellutti, Pierluigi;
2015
Abstract
An analysis of two technological options to achieve a high deposition rate, low stress PECVD silicon nitride to be used in Capacitive Micromachined Ultrasonic Transducers (CMUTs) fabrication is presented. A tradeoff between deposition rate, residual stress and electrical properties is showed. A double layer of silicon nitride with a deposition rate of ~100 nm/min and low compressive residual stress is obtained, which is suitable for the fabrication of the thick nitride layer used as mechanical support. A mixed frequency nitride with compliant insulating performance is analyzed. A complete characterization is reported in terms of interface density influence on residual stress, refractive index, deposition rate, and thickness variation. A complete device was fabricated using the optimized nitrides and its performance was tested, demonstrating full functionality in ultrasound imaging applications.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
