In Situ Ellipsometry to Monitor Swelling and Dissolution of Thin Polymer Films

Thin polymer films are used as resists in the fabrication of integrated circuits. In an attempt to improve resist processing methodology, an in situ rotating‐analyzer ellipsometer has been designed for monitoring swelling and dissolution of thin polymer films. Equipment details, procedures, precision and accuracy, and data interpretation are discussed. The instrument discussed here has a precision of 0.5 nm and an accuracy of 2.9 nm when measuring the thickness of a 150 nm film in air. For polymer/solvent systems, the precision and accuracy depend on the particular optical parameters of the system. The usefulness of ellipsometry for distinguishing between swelling and dissolution, measuring swelling and dissolution rates, differentiating diffusion mechanisms, and determining equilibrium swelling compositions is demonstrated.