Optical testing techniques for new semiconductor processes and new materials

Industrial semiconductor manufacturing-and therefore industrial semiconduct or metrology-is being faced with a new generation of processes and material s coming out of development laboratories worldwide. These need careful moni toring, particularly in the early stages of manufacture. Many metrology cha llenges are well met by optical techniques, and the article discusses three such techniques that have transferred to industrial production process con trol. Laser ellipsometry brings high precision to ultrathin 25 Angstrom gat e oxide measurements and can analyse many types of (transparent) new materi als. Impulsive stimulated thermal scattering is a new opto-acoustic techniq ue and therefore is covered more fully here-it complements laser ellipsomet ry by analysing single and bilayer metal (opaque) films after these have be en exposed to a variety of semiconductor processes. Photoluminescence is in valuable for analysing compound semiconductors, Where it measures directly the quality of epitaxial layers and so helps to understand and reduce defec t mechanisms and improve yields. The article concludes by discussing indust rial requirements for integrating the measurement system into a deposition system for in situ process control. Copyright (C) 2001 John Wiley & Sons, L td.