Traceable calibration of a critical dimension atomic force microscope

Abstract

The National Institute of Standards and Technology (NIST) has a multifaceted program in atomic force microscope (AFM) dimensional metrology. One component of this program, and the focus of this paper, is the use of critical dimension atomic force microscopy (CD-AFM). CD-AFM is a commercially available AFM technology that uses flared tips and two-dimensional surface sensing to scan the sidewalls of near-vertical or even reentrant features. Features of this sort are commonly encountered in semiconductor manufacturing and other nanotechnology industries. NIST has experience in the calibration and characterization of CD-AFM instruments and in the development of uncertainty budgets for typical measurements in semiconductor manufacturing metrology. A third generation CD-AFM was recently installed at NIST. The current performance of this instrument for pitch and height measurements generally supports our relative expanded uncertainty (k = 2) goals in the range of 2.0×10−3 and lower. Additionally, a new generation of the NIST single crystal critical dimension reference material (SCCDRM) project is pushing toward feature widths below 10 nm, with the prospect of CD-AFM tip width calibration having expanded uncertainty (k = 2) below 1 nm.