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Process Monitoring and Control in Manufacturing of Low-K Materials Disclosure Number: IPCOM000127412D
Publication Date: 2005-Aug-29
Document File: 6 page(s) / 63K

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MANUFACTURING OF LOW-K MATERIALS                                                                  


      As the feature size approaches 100 nm, the next generation of low-k materials will be required, some of which are already in development stages. It is anticipated that most likely these materials will be porous. One of the strategies to make low-k material is the introduction of a sacrificial component called porogen in the base matrix which is then removed using supercritical CO2 to introduce porosity. For example, poly(methylselsiquioxane) (PMSSQ) has been used for spin-coating low-k films. Nonporous films were prepared by spin coating a solution containing poly(propylene glycol) (PPG) in PMSSQ. The PPG porogen is then selectively removed using supercritical CO2 with a co-solvent leaving a porous structure behind leading to a lower k value product (B. Lahlouh et al., Creating Nanoporosity By Selective Extraction Of Porogens Using Supercritical Carbon Dioxide/Cosolvent Process, Mat. Res. Soc. Symp. Proc. Vol. 766).

      The basic processing of porogen extraction to make low-k materials is straightforward and is described in the reference mentioned in the previous paragraph. The material to be processed is loaded in a chamber and the chamber is sealed. The supercritical CO2 and co-solvent mixture is fed to the chamber where the mixture performs its intended operation. After certain period of time, the chamber is depressurized and the material is removed from the chamber and analyzed using one or more analytical tools.

      U.S. patent application 2004/0168709 A1 describes an apparatus to analyze CO2 gas leaving a cleaning chamber to determine if or when the process is completed or to verify that the process is within normal process operation range. Although this approach may work to analyze gas based compounds, it has several practical limitations to analyze liquid and solid compounds. Upon depressurization, the dissolves solid or liquid compounds will precipitate out in the transfer lines before they reach the analyzer resulting in inaccurate readings. The precipitated compounds will eventually plug the transfer lines and the analyzers requiring frequent disassembly for cleaning.

      Those skilled in the art will recogize that there is a need for an improved method of determining the end-point or determining when the porogen extraction process is finished so that the chamber can be depressurized. The correct knowledge of end-point is important not only from quality control point of view but can also be used to decrease the cycle time. As mentioned before, one or more co-solvents are also added during the extraction process and it is important to make sure that the co-solvent is removed completely from the processing chamber so that when the chamber is depressurized, no co-solvent is left behind on the extr...