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Gans Ganesan, Gary Lewis, Thomas Anderson, Howard Berg, Motorola Inc.
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A reliable IC package requires excellent adhesion in all of its internal interfaces. A common inhibitor of good interfacial adhesion is surface contamination accumulated prior to encapsulation. These contaminants, which are usually organic in nature, interfere with the adhesion of the various package features with the molding compound. In IC packaging, the three major sources of organic contamination are the dicing tape, epoxy outgas, and atmospheric contamination. This paper discusses a low-cost, fast, and quantitative method for characterizing surface cleanliness by combining uv/ozone cleaning with contact angle measurements. It is a known fact that uv/ozone removes organics at a uniform rate. The method presented in this paper for assessing organic contamination on surfaces combines uv/ozone cleaning to remove organics and DI water contact angle measurements to detect organics. Using this method, the level of organics from IC assembly materials and processes was quantified. Very importantly, the deleterious effect of thin organic layers deposited on the chip surface with respect to interfacial integrity was demonstrated. A critical level of cleanliness was also shown in this paper to achieve a Level 1 delamination-free silicon-mold compound interface.
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