Microsystem Tool for Microsystems Characterization Profile Measurement of High Aspect-ratio Microstructures Jean-Bernard POURCIEL *a , Eric LEBRASSEUR a , Tarik BOUROUINA a , Takahisa MASUZAWA** b , Hiroyuki FUJITA** b a LIMMS /CNRS and b Institute of Industrial Science, University of Tokyo. ABSTRACT A microsystem for the measurement of profiles of high aspect-ratio microstructures has been developed. This microsystem uses a silicon micro-probe with a sharp tip at its end and an integrated piezoresistive strain gauge force sensor. The probes are from 500 µm to 1 mm long with a cross-section of 20x20µm 2 ; they were previously mainly designed for the characterization of narrow and deep micro-holes having a radius as small as 50µm. The profile measurement method has been extended to the characterization of other microstructures. In a first part of this paper, we explain the method based on an original algorithm to measure profiles with the greatest precision and reproducibility. In a second part we give some information about the capabilities for horizontal and vertical profiles measurement, concave and convex surfaces profiles plotting. We conclude with some experimental results for several types of profiles. Keywords: Stylus Profiler, profile measurement, microstructures, metrology for microsystems. 1. INTRODUCTION Microfabrication techniques such as Micro-Electro-Discharge-Machining 1 or Micro-Ultrasonic Machining 2 allow the micromachining of micro-holes, typically some tens of micrometers in diameter and about 1mm in depth. On the other hand, LIGA and deep RIE can also lead to very high aspect ratio-structures. Manufacturing of such high aspect structures has led to a new problem of characterization. Indeed, the existing characterization tools, including stylus surface profilers and optical profilers, are not suitable for the measurement of vertical profiles, especially inside narrow and deep structures. On the other hand, instruments based on SPM methods are dedicated to planar surfaces and are limited in terms of scanning area and/or scanning speed. One solution to this rather new characterization need consists of using long and thin probes, whose dimensions are typically 1 millimeter in length with a cross-section area of about 20x20μm 2 . An actuating element as well as a sensing element is associated to the probe so that it can be moved or vibrated, with the simultaneous detection of the contact with the sidewall. Starting from this, several possible implementations are possible, depending on the nature of the actuating and sensing elements and also on the measurement methodology. A first solution was successfully tested in a previous work. It is the so-called VibroScanning Method (VS-method) 3,4,5 . In this method, the probe is vibrated by means of a piezo-actuator near the surface to be measured. The contact is detected through the electrical contact between the probe and the surface. The VS-method has shown a measurement resolution of 500nm, the main limitation being due to the stability of the electrical contact. More recently, Yamamoto et al. 6 have reported profile measurements of high aspect-ratio microstructures using a method, derived from the VS- method. In this case, the probe is in tungsten carbide and it is coated with PZT thin films for vibration sensing. The method is based on the detection of a resonance frequency shift, which is induced by the strain caused by the mechanical contact between the probe and the side. For this reason it was called the Resonant mode VibroScaning method (RVS-method). In what follows, we present the method 7 , which uses both new measurement algorithm and new probes. This method is based on the use of force measurement for the detection of the mechanical contact. This is done using a micro-probe with integrated piezoresistive sensor. Integration of a sharp tip at the end of the probe is aimed to improve the lateral resolution. The measurement setup is completely automated for fast and safe measurements. Then we describe how the system has been used to plot profiles of various type of microstructures. * pourciel@iis.u-tokyo.ac.jp; phone +81 3 5452 6036; fax +81 3 5452 6088; http://www.fujita3.iis.u-tokyo.ac.jp/~limms/; Institute of Industrial Science, University of Tokyo, 4-6-1, Komaba, Meguro-ku, 153-8505 Tokyo Japan; ** Institute of Industrial Science, University of Tokyo, 4-6-1, Komaba, Meguro-ku, 153-8505 Tokyo Japan;