To facilitate the use of AFMs for manufacturing we have initiated a project to develop and calibrate artifacts which can in turn be used to calibrate a commercial AFM so that subsequent AFM measurement are accurate and traceable back to the wavelength of light. We plan to calibrate our artifacts using a specially designed AFM system which we call the Calibrated AFM (C-AFM). The C-AFM has been constructed as much as possible out of commercially available components. We use a flexure stage driven by piezoelectric transducers for scanning; a heterodyne interferometer to measure the X-Y position of the sample; a capacitance sensor to measure the Z position of the sample; and a commercially available AFM control system. The control system has two feedback loops which read from the X and Y interferometers, respectively, and adjust the piezoelectric voltages to keep the X-Y scan position accurate. The critical electromechanical and metrology issues involved in the construction and operation of such a system are discussed in detail.
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