Process control with chemical amplification resists using deep ultraviolet and x-ray radiation

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Abstract
Resists for optical electron beam, and x-ray lithographies that operate on the principles of chemical amplification are entering into widespread use in laboratories. They offer an attractive alternative to conventional positive Novolac photoresists and we may soon see similar use in manufacturing environments. One class of resists within this family is based on acid-hardening chemistry. We have characterized one such resist (Shipley ECX-1033) for illumination by excimer laser deep ultraviolet sources and also by x-ray radiation. A matrix of postexposure bake (PEB) conditions and development conditions was used to examine resist sensitivity and contrast. For all exposure sources we found that contrast is independent of PEB processing and that sensitivity obeys an Arrhenius dependence. Contrast increases with increasing development time while exposed resist loss is minor. A simple kinetic model was developed to explain the observed variations of apparent resist sensitivity with PEB time and temperature. The generality of this model suggests that it is widely applicable to other chemical amplification resists that require a postexposure bake. Together with aerial image calculations for different light sources, the model makes it possible to predict the dependence of linewidth on PEB conditions. In other words, we can anticipate the PEB process control required to achieve a specified critical dimension control. Electrical linewidth measurements of submicron features and their temperature dependence are compared with the predictions of the model.

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