A schematic showing the main components of the interferometric AFM. The objective, reflector, and sample stage are all maintained at fixed separation throughout imaging while the cantilever is free to move in x-y-z.
(a) A snapshot from a dynamic finite element model of a cantilever traversing a 100 × 200 nm step (b) at high scan speed. (c) and (d) are the simulated cantilever angle in the region of the tip and the simulated signal that would be obtained by an interferometer measuring the height of the point on the plane of the cantilever directly to the side of the tip, respectively. (e) shows the simulated effect of placing the interferometer spot at different positions relative to the cantilever tip which is between points 2 and 3 on the schematic.
(a) A topographic image collected at 1 frame/s showing a 32 nm feature size static random access memory (SRAM) defect sample. Scale bar represents 250 nm. Black to white represents 12 nm. (b) A rendered topographic image showing another area of the same sample containing several processing defects. Scale bar represents 250 nm. The white arrow indicates a shortened groove. The pink arrows indicate the locations of the height profile insets. The section at the top is of a particle and the one at the bottom highlights the base roughness of the sample surface. (c) A large defect in an area of solid state memory. Scale bar represents 1 μm. (d) and (e) The surface of a CMP sample. The slightly raised areas are the silicon oxide while the lower (darker) region is the copper track. The arrow in (e) indicates a defect caused by scratching by a particle during polishing. Scale bars represent 1 μm. (d) Black to white represents 18 nm. (e) Black to white represents 35 nm. (f)-(h) are a series of images of the same test wafer as in (a) zooming in on an area of interest, each collected at 1 frame/s. Scale bars represent 500 nm.
(a) The surface of a sample of HOPG showing single atomic steps (the two central steps in the image). Scale bar represents 250 nm. Black to white represent 5.8 nm. (b) A topographic image showing a silicon calibration sample. Scale bar represents 500 nm. Black to white represents 240 nm. (c) The step height measured in 250 lines captured consecutively from the sample in (b). (d) is a histogram of the distribution of step heights with a standard deviation of 0.05 nm around a value of 100.2 nm, showing the repeatability of the interferometric method. (e) Cantilever deflection (i.e., bending angle) data collected simultaneously with the topographic data in (b). (f) A rescaled version of (b) in which the small specks of debris on the sample surface visible in the deflection image (e) can be seen.
Large area images of a silicon calibration standard taken using a resonant quartz bar scan stage. Height image, (a), with cross section, (b), taken along the white line shown. The black to white color scale represents 130 nm, scale bar represents 5 μm. A 256 × 256 pixel image collected in 1 s with a peak tip velocity of 4 cm s−1, average tip velocity of 2.5 cm s−1. (c) Height image ((36 × 36) μm2) presented in pseudo 3D. A 256 × 256 pixel image collected in 1 s with a peak tip velocity of 6.6 cm s−1, average tip velocity of 4.2 cm s−1. Scale bar represents 10 μm.
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