Molecular Contamination Control Technologies for High Volume Production Phase in High NA 193nm Lithography

摘要

The current semiconductor lithography process is in the high volume production phase of 193nm high NA (Numerical Aperture) exposure, and further reaching the high volume production phase with 193nm immersion exposure lithography. As a result of miniaturization of the devices, it has becomes necessary to reduce the concentration of basic compounds (such as ammonia, amines, and N-methyl-2-pyrrolidone (NMP), which are used to insolubilize the chemical amplified resist in developing process, in the environment surrounding the wafer. For this purpose, chemical filters are used. In the clean room, in addition to these basic gases, there exist various organic compounds and the effects of organic compounds on the chemical filter cannot be ignored. This paper reports the results of basic research on the adsorption behavior of physical adsorption under the presence of the above-mentioned basic compounds and ion exchange reaction. Then the adsorption behavior of activated carbon chemical filter impregnated with acidic chemicals and strongly acidic cation exchange chemical filter for basic compounds was studied in the coexistence of organic components. The performance of impregnated activated carbon chemical filter deteriorates due to the coexisting organic compounds because removal of NMP is based on the physical adsorption mechanism. On the other hand, the performance to remove ammonia and NMP of strongly acidic cation exchange chemical filter is not affected by organic compounds because the filter exchanges ions with weakly basic compounds. The strongly acidic cation exchange chemical filter can provide desired performance for basic compounds under an actual clean room environment.