Suppression of Inelastic Deformation in Multilayer Microcantilevers with Nanoscale Coating
- PDF / 2,859,544 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 89 Downloads / 201 Views
1222-DD02-19
Suppression of Inelastic Deformation in Multilayer Microcantilevers with Nanoscale Coating I-Kuan Lin1, Xin Zhang1 and Yanhang Zhang1, 2* 1 Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA 2 Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA ABSTRACT Multilayer microcantilevers present in micro-/nano- electromechanical system (MEMS/NEMS) applications serving passive and active structural roles. The application and commercialization of MEMS devices suffer from reliability problems. Appropriate nanocoatings, such as atomic layer deposition (ALD), have been demonstrated to be promising solutions for these reliability problems in MEMS devices. However, the micro/nano- mechanics within and/or between the microcantilevers and nanocoatings are not fully understood, especially when temperature, time, microstructural evolution and material nonlinearities play significant roles in thermomechanical response. The overall goal of this work is to suppress and understand the inelastic deformation and microstructural evolution in multilayer microcantilevers with nanocoatings. Moreover, to better understand the stress relief and Al2O3 suppression mechanism, scanning electron microscopy (SEM) was employed to explore the microstructural evolution. INTRODUCTION The physical movement of multilayer microcantilevers was widely employed in MEMS for a variety of sensor and actuator applications [1]. From the design viewpoint, the ideal multilayer microcantilevers deform linearly proportional to temperature change, and do not exhibit any inelastic deformation over the operation period. However, the metal layers in the multilayer microcantilevers are typically not stable after deposition. When subjected to thermal loading, the microstructural evolution in metal layer can be triggered, such as extinction of excess vacancies, subgrain coalescence and grooving [2, 3]. The microstructural evolution results in creep and stress relaxation phenomena in metal layer which is the one of the main sources of highly inelastic deformation of microcantilevers. Neglecting the inelastic deformation can result in misinterpretations of the measurement data from microcantilever-based sensors and can also compromise the control precision of actuators. Hence, it is of vital importance to perform accurate thermomechanical behavioral characterization on microcantilevers and to develop an appropriate model for time-dependent inelastic deformation. In this paper, we not only fully characterized the thermomechanical behavior of Au/SiNx microcantilevers, associated with microstructural evolution in the metal thin film, but also demonstrated that the time-dependent inelastic deformation due to creep, stress relaxation, can be suppressed by the use of nanocoatings realized by ALD [4]. However this suppression phenomenon can not be predicted by finite element analysis (FEA) with power law behavior in previous studies [4]. This suggests both an alternation of the stress state in the metal layer by the n
Data Loading...
