Polymer-Based Cantilevers With Integrated Electrodes

Abstract

Abstract-An innovative release method of polymer cantilevers with embedded integrated metal electrodes is presented. The fabrication is based on the lithographic patterning of the electrode layout on a wafer surface, covered by two layers of SU-8 polymer: a 10-m-thick photo-structured layer for the cantilever, and a 200-m-thick layer for the chip body. The releasing method is based on dry etching of a 2-m-thick sacrificial polysilicon layer. Devices with complex electrode layout embedded in free-standing 500-m-long and 100-m-wide SU-8 cantilever were fabricated and tested. We have optimized major fabrication steps such as the optimization of the SU-8 chip geometry for reduced residual stress and for enhanced underetching, and by defining multiple metal layers [titanium (Ti), aluminum (Al), bismuth (Bi)] for improved adhesion between metallic electrodes and polymer. The process was validated for a miniature 2 2 m 2 Hall-sensor integrated at the apex of a polymer microcantilever for scanning magnetic field sensing. The cantilever has a spring constant of =1 N/m and a resonance frequency of =17 kHz. Galvanometric characterization of the Hall sensor showed an input/output resistance of 200 , a device sensitivity of 0.05 V/AT and a minimum detectable magnetic flux density of 9 T/Hz 1 2 at frequencies above 1 kHz at room temperature. Quantitative magnetic field measurements of a microcoil were performed. The generic method allows for a stable integration of electrodes into polymers MEMS and it can readily be used for other types of microsensors where conducting metal electrodes are integrated in cantilevers for advanced scanning probe sensing applications.[1573]Index Terms-Dry etch, Hall sensor, integrated electrodes, polysilicon sacrificial layer, stress-reducing geometries, SU-8 cantilever, thin film metal deposition and lift off.

Magnetic Field Sensors Based on Microelectromechanical Systems (MEMS) Technology

“…For example polymerbased devices are interesting alternatives to silicon, particularly when the polymer materials can be functionalized for enhanced specific material properties (e.g, optical, electrical, and mechanical). Mouaziz et al (2006) proposed the realization of SU-8 cantilevers with an integrated Hall-probe for advanced scanning probe sensing applications. To this purpose an innovative release method of polymer cantilevers with embedded integrated metal electrodes has been employed.…”

“…12. Schematic illustration of the process for SU-8 cantilever with integrated electrodes reported by Mouaziz et al (2006).…”

Fabrication and analysis of cylindrical resin AFM microcantilevers

“…Polymers have always been useful in various MEMS fabrication processes, usually as a mask or sacrificial layer [3], but with the recent development of polymers with excellent mechanical properties and chemical stability they are increasingly being used as a structural material [4]. Polymeric materials typically have a Young's modulus and density lower than their silicon-based counterparts [5]. This results in cantilevers with high mass [1] and surface stress [6] sensitivity.…”

“…Photosensitive polymers have allowed for the integration of electronics directly into the polymer [5,13] and the embedding of ferromagnetic and paramagnetic nanoparticles to form composites [14]. This has lead to a departure from the traditional AFM actuation and sensing method of using piezoelectric stages and optical systems [15].…”

Microscopic four-point probe based on SU-8 cantilevers

“…7 The negative photoresist SU-8 is used for the fabrication of structures with high aspect ratio and has mechanical properties that allow it to be introduced as base material for an increasing number of micromechanical devices. [8][9][10][11][12] In this article, we present the design, fabrication, and characterization of 4PPs based on SU-8 cantilevers. The results obtained on thin metal films are compared to measurements performed with a commercialized macroscale resistivity meter ͑Omnimap RS75, KLA Tencor͒.…”