Practice-oriented evaluation of lateral resolution for micro- and nanometre measurement techniques

In the past few years, micro topography measuring techniques, such as atomic force microscopy (AFM) and white light interferometery (WLI), have been adopted by industry for quality assurance of micro structures. Since many factors influencing the uncertainty of measurements performed with these technologies are still unknown, the reliability of the measurement instruments is mostly done by comparison of different instruments at a given task. Among other things, to have a similar resolution of the instruments is an important pre-requisite. To provide a method for the evaluation of resolution, the Siemens-Star, which is widely applied in evaluation of 2D camera resolution, has been modified and applied to micro- and nano-measurement techniques. It is shown that this (non-calibrated) structure can be applied to quite different measuring techniques in order to investigate a wide range of resolutions, approximately from 0.1 µm to 6 µm. The applicability of the concept has been shown with WLI and AFM. Based on a suggested evaluation method, experimental results have been compared with the manufacturer specifications. Additionally, the lateral resolution of WLI measurements has been investigated at different positions of the field of view. Other resolution-influencing factors, such as the number of pixels and scan direction, have also been investigated. This concept also shows that it is possible to compare calibrated optical and stylus measurement devices whose resolution can vary in a wide range using non-calibrated structures.