- 1 - In-Situ Metrology for Deep Ultraviolet Lithography Nickhil Jakatdar and Costas Spanos Electrical Engineering and Computer Sciences University of California at Berkeley, Berkeley, CA 94720 Office: (510) 642-7156 Fax: (510) 642-2739 Abstract We are developing DUV metrology for measuring the thickness and the degree of bleaching simultaneously. This is done in-situ and in quasi real-time, and is used in unison with Experimental Designs to build semi-empirical models that characterize the process parameters. 1.0 Introduction In an effort to keep up with Moore’s Law, semiconductor industries are switching to the deep ultravio- let (DUV) lithography technology. However, the advances in technology should be accompanied by the high yield and efficiency required to stay competitive. The chemically amplified nature of DUV resists, the lack of resist bleaching after exposure and the measurement related parasitic exposure, make in-situ DUV metrology a very challenging problem. The goal of this paper is to investigate various approaches towards the development of in-situ metrol- ogy for DUV lithography that will ultimately be used for lithography process control and diagnosis. We begin by discussing the structure and mechanism of chemically amplified resists as an aid in understanding the practical difficulties encountered in developing in-situ metrology.This paper investigates the possible parameters to monitor and describes the control experiment to investigate the effect of the parasitic expo- sure due to actinic reflectance measurements. The latter part describes the experimental setup and the designed experiment that is used to build the equipment models. 2.0 Deep ultraviolet photoresist structure and mechanism In our experiments, we use the IBM APEX-E DUV resist. The main ingredients are the Photo-Acid Generator (PAG), a modified resin and a casting solvent. The structure of the resin, which plays an impor- tant role, is a 3:1 modification of parahydroxystyrene (pHOST) serving as the backbone and tertbutoxyox- ycarbonstyrene (tBOC) as the side chains of the polymer [1]. POST-EXPOSURE BAKE EXPOSURE DEVELOPMENT Fig. 1 Bleaching takes place during the PEB step