Low-Voltage Accelerating-Voltage SEM Magnification Standard Prototype

Abstract

The National Bureau of Standards has had a continuing effort for almost a decade to develop feature-size measurement techniques and the associated linewidth standards for the semiconductor industry. Recently, work began on a scanning electron microscope (SEM) based feature-size measurement program specifically aimed at the development and certification of SEM linewidth standards and the associated techniques for their calibration and use.Primary to the development and use of SEM linewidth measurement standards is the calibration of the magnification of the SEM. The only standard reference material presently available from NBS for calibrating the magnification of the SEM is the NBS SRM 484.1 This standard provides a known pitch between gold lines in a nickel matrix that is traceable to NBS primary standards. This standard has proven useful for many SEM applications and should continue to be useful for some time to come. However, since SRM 484 was developed prior to the recent interest in low accelerating voltage operation for integrated circuit wafer inspection and measurement, this SRM, in its present form, is unsuitable for use in many of the newly introduced SEM measurement instruments.