Parameter characterization of anodic bonded electrical interconnect in MEMS/NEMS devices

The approach to realize the electrical interconnect and qualities of the contact have a direct impact on the performance and reliability of devices. Herein, Si-Au/Pt/Ti contact structure is fabricated using anodic bonding as a novel approach to realize the electrical interconnect. In order to evaluate the qualities of the anodic bonded contact, the contact resistance is extracted. The cross-bridge Kelvin method is optimized and a new method is presented to directly measure the contact resistance, named four-terminals bonded vertical Kelvin method (BVD). The two-dimensional resistor network model of the BVD method indicates that the relationship between the contact resistance and the measured resistance can be easily established. The BVD method can directly and precisely measure the contact resistance since kinds of interferences from parasitic resistances are minimized. Data obtained from the test indicate that the anodic bonded contact is Ohmic contact when the area of the contact is larger than 15*20μm² with the contact length not smaller than 15μm; whereas, the contact is not Ohmic contact and not stable when the area of the contact is smaller than 15*20μm². The qualities of small-size anodic bonded contact is related with the effects of interfacial states, native oxide layer, series resistances at the interface, and the other particularities such as interfacial inter-diffusion, Au/Si eutectic reaction and surface topology.

I. Introduction

The property of electrical interconnect plays a critical role in micro/nano-electro-mechanical system fields. The approach to realize the electrical interconnect and the quality of the contact have a direct impact on the performance and reliability of devices, especially when there exist complicate structures, for example, high aspect ratio structures and deep trenches. In such cases, the restrictions resulted from lithography alignment errors and conformal capability of metal deposition will make it hard to achieve ideal metal pattern. If the electrical contact quality is not ideal, the resulted parasitic capacitance and parasitic resistance will affect the performance of devices and circuits. Therefore, it is necessary to find a new approach to achieve reliable electrical interconnect in MEMS/NEMS field.