The immersion fluid in the lens - wafer gap of advanced lithography scanners has the propensity to be a transport media
for imaging defects. A great deal of effort has been devoted to understanding and eliminating the root causes of
patterned defects in immersion lithography. Characterization of patterned and unpatterned defects on the wafer top
surface has helped to drive improvements in lithography equipment, processes and materials design that subsequently
enabled immersion defect density levels to be commensurate with dry lithography. This has enabled the insertion of
immersion lithography into mainstream manufacturing. However, the "ever improving" yield impetus drives the need to
search for and eliminate defect sources beyond the conventional top surface. This paper describes progress in extending
these efforts to and beyond the wafer's edge.
Minimizing defectivity, improving critical dimension control and improving productivity continue to be key drivers for 300mm IC manufacturing. New and unique hardware and process solutions are required to meet both technology and production demands. IBM is evaluating a new and unique resist developer hardware process. The key elements of the new process are 1) the impact or contact of the developer is uniform on the resist surface. 2) defects due to slow dissolution and redeposition are reduced, 3) developer consumption is reduced up to 60% and 4) the process time is up to 40% shorter than common develop processes. This paper presents results of our evaluation of the new developer hardware and process, and demonstrates that this is a robust process exhibiting good CD control with low defectivity and high throughput.
Demands for continued defect reduction in 300mm IC manufacturing are driving process engineers to examine all aspects of the chemical apply process for improvement. Historically, the defect contribution from photoresist apply nozzles has been minimized through a carefully controlled process of "dummy dispenses" to keep the photoresist in the tip "fresh" and remove any solidified material, a preventive maintenance regime involving periodic cleaning or replacing of the nozzles, and reliance on a pool of solvent within the nozzle storage block to keep the photoresist from solidifying at the nozzle tip. The industry standard has worked well for the most part but has limitations in terms of cost effectiveness and absolute defect elimination. In this study, we investigate the direct washing of the chemical apply nozzle to reduce defects seen on the coated wafer. Data is presented on how the direct washing of the chemical dispense nozzle can be used to reduce coating related defects, reduce material costs from the reduction of "dummy dispense", and can reduce equipment downtime related to nozzle cleaning or replacement.
Characterization of linewidth variation by a three-step methodology is presented. Via electrical linewidth measurement, sources of linewidth variation with distinct spatial signatures are first isolated by spatial analysis. Causes with similar spatial signatures are then separated by contributor-specific measurements. Unanticipated components are lastly identified by examination of the residuals from spatial analysis. Significant sources include photomask error, flare, aberrations, development nonuniformity, and scan direction asymmetry. These components are then synthesized to quantify the contributions from the three modules of the patterning process: photomask, exposure system, and postexposure processing. Although these modules are independent of one another, their effects on linewidth variation may be correlated. Moreover, the contributions of the modules are found to vary with exposure tool, development track, and lithography strategy. The most effective means to reducing the overall linewidth variation depends on the relative importance between these components. Optical proximity correction is efficacious only for a well-controlled process where proximity effect is the predominant cause of linewidth variation.
Characterization of line width variation by a three-step methodology is presented. Causes of line width variation with distinct spatial signatures are first isolated by spatial analysis. Sources with similar spatial signatures are then separated by contributor-specific measurements. Unanticipated components are lastly identified by examination of the residual from spatial analysis. Significant sources include photomask error, flare, aberrations, development non-uniformity, and scan direction asymmetry. These components are synthesized to quantify the contributions from the three modules of the patterning process: photomask, exposure system, and post-exposure processing. Although these modules are independent of one another their effects on line width variation may be correlated. Moreover, the relative contributions of the modules are found to vary with exposure tool, development track, and lithography strategy, affirming the usefulness of the methodology in process tracking and optimization.
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