In-situ Measurement and Control for Photoresist Processing in Microlithography

The lithography process is the critical step in the fabrication of nanostructures for integrated circuit manufacturing. It accounts for one third of the costs of manufacturing integrated circuits. The rapid transition to smaller microelectronic feature sizes involves the introduction of new lithography technologies, new photoresist materials, and tighter processes specifications. This transition has become increasingly difficult and costly. The application of advanced computational and control methodologies have seen increasing utilization in recent years to improve yields, throughput, and, in some cases, to enable the actual process to print smaller devices. In this paper, we point out applications in the lithography process where systems methods (the use of in-situ measurement and control) have made an impact as well as future challenges in this research. The most important variable to control in the lithography process is the linewidth or critical dimension (CD), which perhaps is the single variable with the most direct impact on the device speed and performance. Our objective is to identify key parameters in the lithography sequence that has an impact on the final critical dimension (CD).