The use of critical dimension atomic force microscopes (CD-AFMs) in semiconductor manufacturing, both for process control and as a reference metrology tool, is increasing. If the tip width is calibrated consistentlybetween measurements, a CD-AFM can function as an excellent width comparator. Relative width differences can be measured with uncertainties of 1 nm or less. However, to perform traceable measurements, the absolute tip width must be accurately calibrated. Until recently, conventional methods for accomplishing this had standard uncertainties on the order of 5 nm. Recently developed CD reference materials now make it possible to calibrate absolute tip width with uncertainties at the 1 nm level. The highlights of our methodology are: (1) the use of single-crystal silicon and preferential etching to pattern well-defined and highly uniform features, (2) the use of high resolution transmission electron microscopy (HRTEM) to directly access the Si lattice spacing as a source of traceable width information, and (3) the use of CD-AFM to transfer width information form the HRTEM samples. These standards are known as single crystal critical dimension reference materials (SCCDRM) and prototype SCCDRMs have recently been delivered to SEMATECH Member Companies for evaluation.
Citation: J. Vacuum Sci. Technol. B
Pub Type: Journals
AFM, calibration, CD, linewidth, traceability