Automated, high precision measurement of critical dimensions using the atomic force microscope

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 stati...