Dual Imaging-unit Atomic Force Microscope and its Application in Nanometer Order Length Metrolegy

摘要

Two AFM units were combined in the DIU-AFM, one as a reference unit, and the other a test one. Their probes with Z piezo elements and tips were horizontally set in parallel at the same height to reduce Abbe's errors. A reference sample and a test sample were attached to one single XY scanner on the same surface, and were imaged by the AFM units at the same time. These two images have the same lateral size, and thus the length of the test sample image could be accurately measured by counting the periodic features in the reference one. The most remarkable advantages of the DIU-AFM include: the scanning errors caused by the non-linearity or hysteresis of the piezoscanner can be successfully avoided; moreover, it's practically able to measure conductive and/or non-conductive samples. Some comparative experiments made by using periodic features of porous alumina film as reference scales were demonstrated for simultaneous length calibration. Experiments show a satisfactory matching and a wide scan range of up to 5 μm. With different reference scales, the DIU-AFM is capable of realizing nanometer and/or sub-micron length metrology accuracy for test samples with any conductivity.