Focused beam scatterometry apparatus and method

Abstract

The capacity to measure nanoscale features rapidly and accurately is of central importance for the monitoring of manufacturing processes in the production of computer integrated circuits. It is known that far-field scattered light requires a priori sample information in order to reconstruct nanoscale information such as is required in semiconductor metrology. Parameters of interest include, for example, trench depth, duty cycle, wall angle and oxide layer thickness. We describe a scatterometry apparatus and method that uses unconventional polarization states in the pupil of a high NA objective lens, and refer to this as focused beam scatterometry, in which the illumination consists of a focused field with a suitably tailored, spatially-varying polarization distribution. We describe how four or more parameters can be measured and distinguished with an accuracy consistent with the needs laid out in the semiconductor roadmap.