The authors have demonstrated a method to form 20nm contact features of uniform size over a large area by integrating a self-assembling diblock copolymer with optical lithography. The diblock copolymer contacts are formed in topographical placers which are patterned with using optical lithography. A diblock copolymer pattern can only be formed in a placer and not in the narrower trenches that connect to the placer. This concept can be applied to form local interconnects using a single mask dual damascene process, where vias are self-aligned to the line. Some design rule restrictions must be applied to certain structures to enable patterning with diblock copolymer. They also observed that diblock copolymer contact formation was strongly influenced by the shape of the placer and the size of the cylindrical contact hole could be varied by the molecular weight of the block copolymer.

In this study, we have developed a thermal freezing process to prevent intermixing between 1 st patterned positive resist and 2 nd positive resist. Based on solvent solubility switch characteristic of polymer after higher temperature bake, a prototype of polymer consisting of methyladmantane mathacrylate, norbornanecarbo lactone mathacrylate and hydroxyl admantane mathacrylate was selected for resist-on-resist double exposure experiment to prevent the intermixing between layers. Photo sensitivity shifting of this prototype resist after post develop bake further facilitates the design by preventing 1st layer resist distortion from 2nd exposure. Lastly, through composition and formulation optimization, 35nm L/S patterns were successfully demonstrated by using a 1.2NA stepper.

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Depth of Focus (DOF) and exposure latitude requirements have long been ambiguous. Techniques range from scaling values from previous generations to summing individual components from the scanner. Even more ambiguous is what critical dimension (CD) variation can be allowed to originate from dose and focus variation. In this paper we discuss a comprehensive approach to measuring focus variation that a process must be capable of handling. We also describe a detailed methodology to determine how much CD variation can come from dose and focus variation. This includes examples of the statistics used to combine individual components of CD, dose and focus variation.

A tool has been developed that can be used to characterize or validate a BEOL interconnect technology. It connects various process assumptions directly to electrical parameters including resistance. The resistance of narrow copper lines is becoming a challenging parameter, not only in terms of controlling its value but also understanding the underlying mechanisms. The resistance was measured for 45nm-node interconnects and compared to the theory of electron scattering. This work will demonstrate how valuable it is to directly link the electrical models to the physical on-wafer dimensions and in turn to the process assumptions. For example, one can generate a tolerance pareto for physical and or electrical parameters that immediately identifies those process sectors that have the largest contribution to the overall tolerance. It also can be used to easily generate resistance versus capacitance plots which provide a good BEOL performance gauge. Several examples for 45nm BEOL will be given to demonstrate the value of these tools.