Measurement of trench depth by infrared interferometry

Measurement and control of high-aspect-ratio structures such as dynamic ran dom-access memory trenches is an important step in the manufacture of moder n memory devices. We present a novel technique based on infrared interferom etry that has been implemented in manufacturing and is capable of measuring sub-0.25-mu m-wide and 10-mu m-deep trenches nondestructively and with an accuracy of better than 0.1 mu m. (C) 1999 Optical Society of America.