The downward scaling of semiconductor circuits has put an increasing demand for contamination control in the lithography process. With the utilization of chemically amplified photoresists for enhanced photosensitivity, there have been widespread occurrences of various defects in the coated films. 193nm photoresist systems, typically consisting of a solvent system, a polymer system, photo acid generators (PAG), acid quenchers, additives, and surfactants, are particularly sensitive to particulate and bubble-induced defects. Microbridging defects in photoresist and cone defects in the anti-reflective coatings are particularly troublesome because they may form by contaminants smaller than the nominal size of the filter membrane pore and may only be evident in the subsequent process steps.
Microbridging defects manifest themselves as resist remaining in unwanted places after exposure and development. Examples of these defects are shown in Figure 1. Microbridging was recognized as one of the critical patterning defects that were frequently observed in 193nm lithographic process in different formulations from different manufacturers. The problem becomes remarkable particularly in dense line/space L/S feature and should seriously damage the production yield. While the cause of micro-bridging defects has not been definitely identified, a hypothesis has been proposed which states that some compositional inhomogeneity potentially existing in the 193nm polymer was suspected for the root cause of micro-bridging defects. These “less-soluble” species exist in the polymer at a trace amount, which is supposed to agglomerate and eventually grow up into the size that would bridge the lines. The photoresist filtration is known to influence this defect density.
With the continuous demands for defect reduction and high productivity, Entegris has developed a new and unique photochemical Point-Of-Use (POU) filter, Impact® Duo to address these demands particularly in advance lithography processes.