Nanoscale roughness and bias in step height measurements by atomic force microscopy

作者：Seah M P^*

来源：Measurement Science and Technology, 2013, 24(3): 035004.

DOI：10.1088/0957-0233/24/3/035004

• AFM
• atomic force microscopy
• depth profiling
• roughness
• SPM
• step heights

The roughness of a surface exhibiting a Gaussian distribution of heights is analysed, computationally, for scans using two- and three-dimensional probes with flat and spherical tips with various tip widths and radii. These simulate aspects of roughness and surface measurement as observed at the nanoscale with atomic force microscopes. In the Gaussian population of heights, the data points are uncorrelated and at a lateral displacement interval of delta. These initial data points may then be linked by a straight line or by a plane to make a continuum surface. Scanning this surface with a hemispherical probe shows that whilst there is significant distortion (dilation) in the measured profile, the measured root mean square roughness is only slowly reduced as a function of the increasing tip radius. However, the mean measured height of the surface increases significantly with the tip radius in a manner that biases step height measurements for films that are rougher than their respective substrates and vice versa. The calculations show universal curves for this bias as a function of the tip size. The step height bias is important and this is contrasted with results for surfaces exhibiting defined surface waveforms. The bias needs to be included in step height measurements as a correction or as an added uncertainty.

• 出版日期2013-3