Paper PS-MoA4
Real Time and 3D Characterization Techniques to Control Plasma Etch Processeses at the Nanometer Scale

Monday, October 20, 2008, 3:00 pm, Room 304

As the industry approaches the ability to create microcircuit structures on the order of 20 nm, this technology faces fresh challenges. To make progress, we need to go back to the basic science of how plasmas interact with surfaces. Several trends are at work: First, circuit patterns need to be accurate to within 1 nm and below, within a single wafer and across several wafers. Second, plasma etching is becoming an integral part of pattern generation (using lateral erosion of the lithographic photoresist to improve resolution, for example). Third, aspect ratios of the final structures (that is, the ratio of length to width) are increasing dramatically. Finally, the number of potential new material candidates and their possible combinations in future structures is exploding. In this context, understanding the fundamentals of the etch mechanisms and their correlations to key process parameters is crucial. Each etch step must be characterized not only by etch rate and uniformity, but also by more fundamental properties such as the composition, thickness, and line-edge roughness of the sidewall layers of the structure, the chemical nature of etch by-products deposited on the chamber walls (which affects process stability and reproducibility), the thickness of the etch-front mixing layer (correlated to etch rate and selectivities between layers), and the impact of aspect ratio–dependent etching phenomena. In this talk, we will describe in details the latest development in scatterometry that can be used to monitor in real time resist trimming processes or more complex processes. We will also discuss the latest results obtained using the 3D AFM technique to characterize the transfer of photoresist line edge roughness in complex stacks. Finally we will also discus the importance of monitoring passivation layers formed on the feature sidewalls as well as the coatings formed on chamber walls during plasma processes since both impact directly the critical dimension of patterned structures.