Mechanical and Material Characterization of Bilayer Microcantilever-based IR detectors
- PDF / 352,249 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 38 Downloads / 228 Views
Mechanical and Material Characterization of Bilayer Microcantilever-based IR detectors I-Kuan Lin1,2, Ping Du3, Yanhang Zhang3 and Xin Zhang3 Global Science & Technology, Greenbelt, MD 20770, USA 2 NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 3 Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA
1
ABSTRACT Infrared radiation (IR) detection and imaging are of great importance to a variety of military and civilian applications. Microcantilever-based IR detectors have recently gained a lot of interest because of their potential to achieve extremely low noise equivalent temperature difference (NETD) while maintaining low cost to make them affordable to more applications. However, the curvature induced by residual strain mismatch within the microcantilever severely decreases the device performance. To meet performance and reliability requirement, it is important to fully understand the deformation of IR detectors. Therefore, the purpose of this study is threefold: (1) to develop an engineering approach to flatten IR detectors, (2) to model and predict the elastic deformation of IR detectors using finite element analysis (FEA), and (3) to study the inelastic deformation during isothermal holding. INTRODUCTION Bilayer microcantilever-based infrared radiation (IR) detectors have received extensive attention for wide use in military and civilian applications. These detectors can achieve a theoretical noise-equivalent temperature difference (NETD) of below 5 mK [1]. This type of IR detector is based on the bending of bilayer structures upon absorption of IR. The subsequent deformation can be readily determined by using piezoresistive, optical, or capacitive methods. However, the bilayer structures curve significantly after release from a sacrificial layer, largely due to the mismatch of residual stress/strain in the two materials [2]. Therefore, curvature modification is one of the important topics in the post-process assessment of IR detectors. It is also important to understand the deformation of IR detectors over a significant period of operation time, in order to meet performance and reliability requirements. The inelastic strain behavior (creep) in metal layers [3] results in inelastic deformation in IR detectors. Neglecting the inelastic deformation can lead to misinterpretations of the measurement data from IR detectors and can compromise performance. In previous study, the temperature and time dependent deformations of SiNx/Al bilayer microcantilever beams are characterized by using thermal cycling and isothermal holding testes [4]. In this study, we applied the same characterization methods on IR detectors to understand the thermomechanical behavior in device level. First, the thermal cycling technique was employed to flatten as-released IR detectors and characterize the linear thermoelastic behavior. Second, the characterized Power-law creep was used to develop a numerical model for predicting and simulating the inelastic behavior in longterm operation. The experimental met
Data Loading...
