Proceedings of the 3rd Seminar on Quantitative Microscopy
When using the SPM as a metrological instrument, it is essential to compensate for the hysteresis between the piezos movement and the applied control voltage. We dizabled the build-in on-line correction of our SPM and scanned samples quasi-static with 0.1 Hz in various scan ranges from 5 V to 440 V peak-to-peak.One sample consisted of lines spaced by 3.0 um, the other was a two-dimensional grid with 200 nm pitch. The typical error in length measurement even after on-line correction remains at 1-2%.In order to improve the model for the rate-independent hysteresis is set up. Instead of regarding each scan line individually as a closed hysteresis loops, we treat the scan lines in the experimentally obtained images as a sequence of connected hysteresis loops. Each loop consists of the trace and retrace scan line. The five parameters of the model are then fitted to our observed data in order to compensate for the image distortions. A standard deviation of 0.2% is reached. Furthermore, the properties of the model reveal what happens when a sudden change in scan range or scan offset is applied: the connected hysteresis loops reveal a rate-independent convergence which can be mistaken as the commonly known creep. This, however, is a time-dependent relaxation phenomenon which is not significant in our experiments. Thus our model predicts the quasi-static piezo movement within the required 0.2% error limit even for arbitrary scan movements. The model can also be applied to the critical piezo movement in the z direction. The model will be used online to determine the optimal shape of the control voltage so that the piezo moves linearly during the whole scan process.
Bibliographic Reference: Article: Proceedings of the 3rd Seminar on Quantitative Microscopy, 1998, 1-129
Record Number: 199910371 / Last updated on: 1999-03-12
Original language: en
Available languages: en