We measured the pitch of a 144-nm pitch, two-dimensional grid in two different laboratories. Optical Diffraction gave very high accuracy for mean pitch and Atomic Force Microscopy measured individual pitch values, gaining additional information about local pitch variation. The measurements were made traceable to the international meter. Optical diffraction gave mean value 143.928 ± 0.015 nm (95% confidence limit, per GUM). AFM gave mean value 143.895 ± 0.079 nm. Individual pitch values had standard deviation 0.55 nm and expanded uncertainty ± 1.1 nm. Mean values measured by the two methods agreed within 0.033 nm. Because this was less than the uncertainty due to random variation in the AFM results, it suggests that the AFM measuring and analysis procedures have successfully corrected all systematic errors of practical significance in microscopy. We also discuss what precision may be expected from the AFM method when it is applied to measure smaller pitches.
We describe a computerized method to analyze the microstructure of optical disks. On digital versatile disks (DVDs), the smallest features are pits or bumps about 400 nm long, 320 nm wide, 120 nm high, with a track pitch of 740 nm. We measured the following parameters: track pitch, bump height, bump width and length (at various threshold levels), and four sidewall slope angles, in each case reporting the mean, standard deviation, and other statistics. In a single 10×10 μm image of a DVD stamper containing about 100 bumps, we tabulated about 1000 values. In a plot of bump width versus bump length, we found that the width at half height increased from 328 nm for the shortest bumps (440 nm long) to about 385 nm for bumps longer than 800 nm; this matches the increase seen for corresponding optical signals produced when a finished disk is played. Where a sidewall angle deviated from the norm, we were able to review the image data to identify the specific nature of the defect. This automated method yields statistically robust results, not only for mean values of structural parameters, but also for the standard deviations so that process windows can be determined. Thus, feature geometry will no longer be a hidden variable in the path between controlling production equipment and observing the good or bad electrical performance of a finished disk.
We directly measure track wobble amplitude in recordable optical disc media using AFM images and automated analysis procedures. Wobble amplitude of 30 nm is easily measured, but calibration is important in order to avoid errors.
We describe statistical analysis of AFM measurements of bump size, shape and position on DVD stampers. We present statistical concepts that lead to useful measurements of process position (such as bump length) and process noise (bump length variation). These physical measurements are compared with key electrical measurements such as asymmetry and jitter.
We have developed a new technique for measuring pit geometry, track pitch, jitter and wobble on compact discs (CD) and digital versatile discs (DVD). This method uses direct physical inspection with a Atomic Force Microscope (AFM). The images are analyzed by our automated method and yield statistically robust results, so that process windows can be determined. In both types of media we report a variety of statistical parameters including mean and standard deviation and create trend charts and other graphs. In addition to the media previously mentioned we demonstrate imaging the data marks of a written CD-RW using surface potential.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.