The presence of the atomic force microscope (AFM) in the industrial metrology setting is rapidly increasing. Properties commonly measured in such applications are: feature spacing (pitch), feature height (or depth), feature width (critical dimension), and surface roughness. To achieve high accuracy. The scales of an AFM must be calibrated. The use of a standard is normally the most appropriate means of doing this. Presently available standards for this purpose are calibrated using stylus instruments and optical techniques. The effectiveness of this approach, however, is limited by the differences in the working ranges of the various techniques and by questions of methods divergence As the repeatability of many commercial instruments continues to improve, the importance of accurate calibration standards will increase. In order to calibrate AFM standards using an AFM, we have designed and built the calibrated AFM (C-AFM). As described elsewhere, we have designed and built the calibrated wavelength of light for all three axes. To accomplish this, a flexure translation stage, heterodyne laser interferometers. and a digital-signal-processor based closed-loop feedback system are used to control the x-y scan motion. The z?axis translation is accomplished using a piezoelectric actuator with an integrated capacitance sensor. which is calibrated using a heterodyne laser interferometer. When fully developed, this instrument will be a calibration tool for scanning probe microscope standards. Specifically, our main calibrations are expected to be of combined pitch/height or three-dimensional magnification standards. In the present work, we describe the current status of the C-AFM and the use of the instrument for measurements of pitch, height, and width. With respect to height measurements, we will place the most emphasis on some of our recent efforts using the C-AFM to study Si samples with single atomic steps.
Proceedings Title: Proceedings of American Society for Precision Engineering
Conference Dates: January 1, 1998
Conference Location: Unknown, USA
Conference Title: American Society for Precision Engineering
Pub Type: Conferences
AFM, CD, linewidth, metrology, pitch, standards, step height