Real-time profile shape reconstruction using dynamic scatterometry

International audienceIn-line process control in microelectronic manufacturing requires real-time and non-invasive monitoring techniques. Among the different metrology techniques, the scatterometry, based on the ellipsometric signatures (i.e stokes coefficients vs. wavelengths) of light scattered by a patterned structures, seems to be well adapted to address this kind of problem. For instance, the shape evolution of a grating in real time during etch processing can be monitored. Traditionally, the direct problem of defining the shape and computing the signature is dealt with modal methods. However, the inverse problem can not be solved as easily. Different classes of algorithms have been introduced (evolutionary, simplex), but the method of library searching is more commonly used in industry. The main limit of this method is the acquisition time of data for different wavelengths. Then, a lack of data can leads to the method failure and several database patterns can be matched to the experimental data. In this article, a technique for real time reconstruction of grating shape variation using dynamic scatterometry is presented. The different tools to realize this reconstruction, such as Modal Method by Fourier Expansion, regularization technique and mostly the specific soft and hardware architecture are also developed. Results of a dynamic experiments will illustrated these presentations