Comparing the molecular contamination contribution of clean packaging films

Steve Lin and Sarah Graves, In the past few years, antistatic polyethylene (PE) films, also known as pink poly, have been used as an all-purpose packaging material for a wide range of cleanroom-compatible packaging applications. Intended to protect such products as components used in semiconductor process equipment, these films should not contribute to the degradation or recontamination of the package contents. During the film manufacturing process, however, a number of chemical additives are incorporated to meet various functional requirements; for example, an amine or amide may be added as an antistatic agent, calcium carbonate or calcium silicate as an antiblock, and an antioxidant or high-temperature stabilizer for chemical stability. The concern in the semiconductor industry is that outgassing of these additives can contaminate, and potentially corrode, tool components that come in direct contact with packaging films. Indeed, it has been confirmed that black residue found between antistatic PE and aluminum foil was closely related to the incorporation of chemical additives in the packaging film. Furthermore, outgassing measurements have shown that test coupons packaged in generic polymer films exhibited excessive levels of hydrocarbons. Figure 1: Black residues from packaging materials collected on cleanroom wipes prior to component installation. Figure 1 shows examples of black residue collected from the surfaces of a component packaged in a polymeric film. Because of such contamination, it is common practice to wipe critical components prior to their installation in process tools. This labor-intensive practice results in a significant productivity loss, and tool decontamination has become a critical quality issue, which can only worsen if no effective resolution is implemented soon. At Applied Materials, various issues relating to clean packaging practices were clearly identified more than a year ago, and a number of strategic projects focusing on packaging material selection for contamination-free manufacturing have been completed. It was