Lithography Filtration for Semiconductor Manufacturing
Enabling Shrinking Device GeometriesLithography is the key technology driver for the semiconductor industry.
The industry's continued growth is a direct result of improved lithographic resolution. The complexity of today's fabricated semiconductor chips necessitates the use of numerous microlithographic steps to achieve multilevel circuits.
Several key industry transitions have put an increased burden on contamination control in every aspect of the microlithography process. These transitions include the implementation of DUV photoresist, adoption of top and bottom antireflective coatings, the trend towards thinner coatings and the use of immersion lithography.
Each step introduces the possibility of deleterious particulate contamination, microbubble void defects and metallic contamination onto the wafer surface. The removal of particles that are smaller than the feature size is imperative to prevent circuit failure. Eliminating any air and preventing the formation of microbubbles is critical to reducing coating defects and increasing yields.
Selecting the appropriate materials to minimize metallic contributions while optimizing dispense performance is essential for optimizing the coating process.
The International Technology Roadmap for Semiconductors, sponsored by five leading chip manufacturing associations, has cited the removal of particles 20 nm as critical for advanced semiconductor devices. The reduction of feature sizes to 22 nm or smaller has led to the offering of tighter membranes to ensure the removal of yield reducing particles.
The method of delivering lithographic chemicals to the wafer surface is best accomplished by a precision dispense system. The point-of-use filter is an integral part of the dispense system, therefore careful selection of this filter is necessary to reduce defects on the wafer surface. In addition to particle and gel removal, minimization of microbubble formation, reduced chemical consumption and good compatibility are all key areas for point-of-use (POU) filter selection.
Fortunately, several membrane materials are available for filtration of the variety of lithographic chemicals needed in the fabrication of today's and tomorrow's integrated circuits.