Abstract
Thickness characterization of thin films is of primary importance in a variety of nanotechnology applications, either in the semiconductor industry, quality control in nanofabrication processes or engineering of nanoelectromechanical systems (NEMS) because small thickness variability can strongly compromise the device performance. Here, we present an alternative optical method in bright field mode called Spatially Multiplexed Micro-Spectrophotometry that allows rapid and non-destructive characterization of thin films over areas of mm2 and with 1 μm of lateral resolution. We demonstrate an accuracy of 0.1% in the thickness characterization through measurements performed on four microcantilevers that expand an area of 1.8 mm2 in one minute of analysis time. The measured thickness variation in the range of few tens of nm translates into a mechanical variability that produces an error of up to 2% in the response of the studied devices when they are used to measure surface stress variations.
Highlights
We demonstrate the capability of the Spatially Multiplexed Micro-Spectrophotometry (SMMS) technique in bright field mode for thin film characterization
We demonstrated the fast thickness characterization of thin suspended films by using a novel optical technique, called Spatially Multiplexed Micro-Spectrophotometry (SMMS) in bright field mode
The great advantage compared to standard micro-spectrophotometry is that the spectral analysis of a large sample area is performed in a parallel way, ensuring at least two orders of magnitude shorter analysis time than state-of-the-art micro-spectrophotometers
Summary
The knowledge of the thickness of a thin film is of primary importance in a large variety of application fields ranging from fabrication of integrated circuits in the semiconductor industry [1], engineering of optical coatings [2], optimization of thin-film batteries [3], photovoltaic cells [4] and the quality control of nanofabrication processes [5] Optical techniques, such as imaging ellipsometry [6,7,8], white light interferometry [9,10,11,12,13,14,15,16] and micro-spectrophotometry [17,18,19,20,21,22] are widely used experimental methods for thin film thickness characterization. The present technique makes it possible to observe small thickness inhomogeneities and structural defects over large devices in the mm range, representing a useful tool in nanotechnology for the assessment of the mechanical variability of a device due to the nanofabrication process
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