Tracing method based on heterodyne interferometer for scanning electron microscopes

Abstract

In this study, a tracing method for a scanning electron microscope was developed based on a heterodyne interferometer, which can directly trace the measured values to the laser wavelength and then to the internationally defined meter length reference. In this method, a sample scanning motion is introduced, and the measuring mirror of the interferometer is fixed on the sample stage. The movement and displacement of the sample stage is recorded by the laser interferometer displacement measurement system, which synchronously collects the secondary electrons or backscattered electron signals excited on the sample surface. The feature size of the sample is measured, and the value can be traced directly to the international unit of length using the frequency-stabilized laser reference, which proves that the proposed method is an absolute measurement method. This study analyzed the specific technology implementation methods and experimental results, including positioning control of the displacement system and its measurement and control during the measurement process. Measurement uncertainty budgets are also discussed. Experimental measurements were carried out and their accuracy was verified. Results showed that this method could effectively obtain the performance parameters of the feature size intuitively and significantly improve the measurement accuracy.