NIST-Traceable Pitch Standard Enables CD-SEM Calibration

摘要

When a semiconductor manufacturer needs to use an imaging system, whether it be optically based or an atomic force microscope (AFM), it must first ensure -that the platform's results will be accurate. This requires that the imaging system's magnification. be calibrated. For a CD-SEM, for example, the best way to do this commonly is through the use of a pitch reference, which is a precisely fabricated sample that has a repeating pattern of a known pitch. As circuit features and dimensions continue getting smaller, calibrating magnification at a higher level becomes even more essential. This, in turn, requires increasingly smaller-pitch-value standards. To this effect, VLSI Standards Inc. (San Jose) has developed a NIST-traceable sample with a 100 nm pitch ― called the NanoLattice ― specifically designed to cope with the needs of magnification calibration. Another application for the sample is in the verification of the imaging system's linearity. Across a CD-SEM's field of view (FOV), magnification may be different on the screen's left side than on the right side, possibly resulting in distortions. In this case, having a periodic pattern of a known, constant pitch across the FOV enables the user to detect those distortions and perform the necessary scan linearity calibration.