Multiscale overlay measurements

In the microelectronics industry, the lithography step is monitored using image-based overlay (IBO) or diffraction-based overlay (DBO) measurement techniques. These techniques are relatively simple to implement, fast and their specifications meet the needs of mature technologies (CMOS20nm and earlier). To exploit these techniques, dedicated metrology structures need to be integrated into specific areas. These structures have a specific design that differs from the product being manufactured. This raises the question of the representativeness of the overlay measurement resulting from these metrology techniques compared with the overlay in the product. New methods such as scanning electron techniques (SEM) are currently being developed, the major advantage of which is their ability to measure at any point in the product and in a repeatable manner. However, this technique deteriorates certain materials. Further studies must therefore be carried out to find the best conditions for using this technique in order to establish the link between misalignment in the product and comparison with measurements using conventional techniques (IBO and DBO). Other techniques, such as X-ray techniques or other methodologies will be investigated (defect analysis method, machine learning, etc.). This work will enable us to address more effectively the new technological nodes currently being developed at LETI.