Many integrated circuit manufacturing processes operate in high or ultra high vacuum (UHV) environments. It is important that vacuum levels are maintained within specified limits to insure optimum process efficiency. While specification of an appropriate size vacuum pump for the system can insure that overall vacuum levels are maintained, outgassing from sealing materials can interfere in the process by changing the composition and morphology of the deposited layer. For instance, outgassing contaminants absorbed by the exposed substrate during the initial steps of the deposition process can induce undesired interactions at the interface level and consequently affect the grown film as well as the overall process. Therefore, it is important to understand the outgassing characteristics of elastomeric seal materials in order to select the appropriate material for a given application.

A methodology has been developed using a residual gas analyzer to measure the outgassing properties of elastomers. Results indicate that outgassing typically takes place in two stages. With some minor exceptions, the first stage involves the evolution of atmospheric gasses and absorbed moisture (i.e. nitrogen, water, oxygen, and carbon dioxide). The second stage and possibly of greater interest involves the evolution of gasses related to the thermal stability and decomposition of the material in question.

This paper compares the outgassing characteristics of three different types of elastomeric seals (perfluoroelastomers, fluorelastomers and silicones) typically used in semiconductor wafer processing. Data on outgassing rate as a function of time and temperature, and classification of gas species evolved for products in each material class are presented. While perfluoroelastomers offer the lowest outgassing rate at elevated temperatures, there can be some performance variation within this material class. The relationship between outgassing performance and elastomer formulation will also be discussed.