Seal deterioration can cause unnecessary contamination, wafer loss and concern. Kalrez® 9100, the latest product from DuPont Performance Elastomers, is proven to help fabricators improve their planned maintenance (PM) schedule, cost of ownership and more.

In a number of evaluations at fablines, customers have reported that Kalrez® 9100 perfluoroelastomer parts exhibited less erosion, lower particle generation and longer seal life compared to competitive perfluoroelastomer (FFKM) parts. Kalrez® 9100 parts demonstrated significantly improved wafer production where oxygen and fluorinated plasmas were used during the cleaning cycle.

Here are just a few examples of the success Kalrez® 9100 has found in semiconductor processes.

• The PM cycle time was extended from 60 to 180 days at a U.S. fabline operating an HDPCVD/STI process. Kalrez® 9100 had no evidence of erosion, leakage, mechanical damage or compression set after 180 days of service.
• At a European fabline in a PECVD process, wafer output increased from 30,000 to >55,000 pairs of wafers in a VAT MONOVAT® application. Kalrez® 9100 showed no evidence of erosion, mechanical damage, compression set or deformation of the seal lip.
• In an oxide etch and dual damascene copper process pendulum valve seal, wafer output increased from 6,000 to 18,000 wafers at a U.S. fabline. No evidence of erosion, cracking or compression set after processing 18,000 wafers.

Figure 1. Relative Particle Generation (Log Scale); 6 Hours at 200 Watts, 0.5 Torr, Direct      Exposure, Downstream Plasma Reactor

Conventional perfluoroelastomer sealing materials normally contain carbon black and/or mineral fillers. Newer products are either unfilled or formulated with polymeric fillers like Kalrez® 9100. Plasma resistance can be significantly different depending upon the type of filler used. If the filler has high resistance to plasma, such as BaSO₄ , TiO₂ , SiO₂ , aluminum oxide, aluminum silicate, etc., it can "shield" the polymer to reduce weight loss or erosion, but have the high potential for particle generation by leaving discrete particles behind once the polymer has become etched. Unfilled or polymeric filled products can be etched to form volatiles, thereby significantly reducing the potential for particle generation. Figure 1 shows the relative particle generation of Kalrez® 9100 versus a nano-silica and a metallic-oxide filled FFKM product in different plasmas.

In addition to contamination from particles, metallic contamination, i.e., titanium, copper, magnesium, calcium, iron, etc., is another concern in plasma processes. Metallic contamination can produce negative effects at different levels of CMOS manufacturing. For instance, it can modify intrinsic properties of the film such as the dielectric constant or negatively affect interface properties which are critical for integration.

Figure 2. Bulk Elemental Content Using XRF Analysis

Plasma can break materials down to atomic or ionic species that can contaminate the deposited layer composition. Conventional mineral filled products contain metallic fillers as primary components, whereas newer polymeric or unfilled products essentially contain no other elements other than carbon, fluorine and oxygen. Thus, sealing materials containing metallic fillers have the potential to generate metallic ions. Figure 2 provides a breakdown of the bulk metallic content of Kalrez® 9100 versus a nano-silica and a metallic oxide filled FFKM product using XRF Analysis.

Since purity is critical to high wafer yield, reducing contamination from particles caused by seal deterioration are major goals of semiconductor fabricators. Perfluoroelastomers (FFKMs) are widely used in critical seal locations in deposition processes due to their extraordinary chemical resistance and thermal stability. Despite these qualities, FFKM performance can vary widely depending upon their chemical composition. Specially formulated perfluoroelastomer compounds, such as Kalrez® 9100 perfluoroelastomer parts, are designed to reduce contamination while maintaining sealing functionality in aggressive plasma environments.

For more information on this subject, please refer to: www.dupontelastomers.com/semiarticle2/

MONOVAT® is a registered trademark of VAT Vaccum Valves A.G.