Optical testing techniques for new semiconductor processes and new materials

Industrial semiconductor manufacturing—and therefore industrial semiconductor metrology—is being faced with a new generation of processes and materials coming out of development laboratories worldwide. These need careful monitoring, particularly in the early stages of manufacture. Many metrology challenges are well met by optical techniques, and the article discusses three such techniques that have transferred to industrial production process control. Laser ellipsometry brings high precision to ultrathin 25 A gate oxide measurements and can analyse many types of (transparent) new materials. Impulsive stimulated thermal scattering is a new opto-acoustic technique and therefore is covered more fully here—it complements laser ellipsometry by analysing single and bilayer metal (opaque) films after these have been exposed to a variety of semiconductor processes. Photoluminescence is invaluable for analysing compound semiconductors, where it measures directly the quality of epitaxial layers and so helps to understand and reduce defect mechanisms and improve yields. The article concludes by discussing industrial requirements for integrating the measurement system into a deposition system for in situ process control. Copyright © 2001 John Wiley & Sons, Ltd.