As the semiconductor/integrated circuit industry retools for the processing of larger diameter (300 mm) wafers with smaller circuit features (0.13µm or less), the need for accurate full-field, in-situ and real-time inspection and reliability analysis tools becomes imperative.
In this presentation we discuss the development of a vibration insensitive interferometric method designed especially to meet these new inspection and stress management challenges. Coherent Gradient Sensing (CGS) interferometry is discussed in relation to wafer planarity issues that arise throughout the entire wafer processing cycle. In particular, we discuss CGS as a means of measuring the non-uniform curvature tensor evolution of entire wafer surfaces in real-time during the cycle, as an in-situ process diagnostic. Issues presented include a) the use of CGS during film deposition as a means of continuously monitoring film uniformity and coverage within a deposition reactor, b) its use in conjunction with elaborate stress analysis tools for the measurement of stresses on thin films and lines during wafer processing or thermal cycling and, c) its ability of mapping highly non-uniform, non-linear deformations and curvature bifurcations that become important as wafer sizes scale up.
Throughout the presentation emphasis is given to the suitability of the method as an in-situ process diagnostic. Other applications of the technique, which include deformation measurements in the die and packaging levels and the study of large deformation and gravity effects and wafer support design in large, thin, wafers are also briefly discussed.
Key Words: Curvature, Full-Field, Real-Time, In-Situ