Lithography

Pall lithography filters employ a range of membrane materials to effectively eradicate contaminants in lithography process chemicals. They eliminate the possibility of deleterious particulate contamination, gel microbridge defects, microbubble void defects, and metallic contamination onto the wafer surface. High wettability membranes do not impede air displacement, resulting in less microbubble formation and shorter purge times.

Optimized filter designs reduce chemical usage during start-up and minimize bubble formation that cause defects on the wafer surface. The filter’s ability to purge air, prevents the formation of microbubbles, which is critical to reducing coating defects and increase yields. The Ultipleat filter design provides a low differential pressure across the filter and minimizes the formation of bubbles during dispense.

Pall’s innovative filter designs use large surface areas, providing low differential pressure, which improves gel removal efficiency and minimize microbubble formation. Maximized membrane surface area in the dispense filter aides in gel removal  from photoresist and prevents gels from extruding through the filter membrane onto the wafer surface.

Low operating pressure ensures the filter will not cause photochemicals to outgas as they are dispensed from high pressure to low pressure during the dispense process. This can best be achieved with a filter featuring a low pressure drop such as Pall’s asymmetric membrane. The nylon 6,6 and high density polyethylene (HDPE) membranes are fully compatible with typical lithography chemicals, are extremely clean with respect to extractables, and offer superior wettability.

Pall lithography filters keep particles minimized in complex photoresist chemistries. Selecting the proper filter can essentially remove or minimize contaminants without altering the sophisticated chemistry of the resist.

Applications

Several factors must be considered in the selection of the appropriate lithography filter. Bulk filters and point-of-use (POU) dispense filters eliminate unwanted particles. The POU filter is an integral part of any precision dispense system, therefore careful selection of this filter is necessary to reduce defects on the wafer coating. In addition to particle and gel removal, minimization of microbubble formation, reduced chemical consumption and good compatibility are all key areas for POU filter selection. The design of Pall’s point-of-use capsules also locates the vent and drain at the highest and lowest point of the capsule to ensure complete and easy venting.

Benefits:

• Decreased equipment downtime
• Higher yields
• Superior wettability for faster startups
• Variety of membranes for any lithography application
• Rapid venting design to minimal microbubble formation
• Low hold up volume for reduced chemical waste

Pall lithography filter technologies streamline manufacturing operations and decrease down time of dispensing systems while decreasing wafer surface defects. For more information, contact a Pall expert on how to optimize your photolithography process.

Filtration Products Compatibility Guide