For the scaling down of the semiconductor design rule, 193-nm lithography technology is entering the 65-nm-node
generation. In 65-nm and finer processes, the practical application of 193-nm immersion lithography is progressing due
to its high numerical aperture (NA), which is achieved by using de-ionized water (DIW) as the medium between the lens
and wafer in the exposure system. Immersion lithography, however, generates two main concerns: the penetration of
moisture into resist film and the leaching of resist components into DIW as a result of immersing the resist film in DIW.
To prevent these effects, the use of a topcoat process has been adopted, but there have been reports that defects caused
by remaining droplets on the topcoat or particles can be transferred to the resist pattern and degrade resolution. Research
to date has clarified the generation mechanism of defects due to water droplets, and the importance of preventing
droplets from remaining is now understood. However, there are few research reports on the generation of particles, and
to reduce defects caused by the immersion process. It is essential that the generation mechanism of particle-related
defects on the resist pattern be clarified and that a suitable approach to reducing particles is needed. It is also known that
particles on the resist pattern that acts as a mask in the dry etching process can be associated with defects in etching,
which makes particle control in the process steps between lithography and dry etching all the more important.
In this paper, we clarify the defect-generation mechanism on resist pattern due to particles put on
topcoat and investigate the effects of such particles on the dry etching process.
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.
While the current standard for NA (Numerical Aperture) for the semiconductor resist process is 193 nm High NA, use of the 193 nm immersion exposure process is growing and almost ready for application in mass production. With the growing trend toward the use of finer line processes in the manufacture of semiconductor devices, the need for cleanliness of the ambient atmosphere surrounding the silicon wafer has also been increasing. In addition to ammonia, that has hitherto been the main target for elimination, the concentration of other chemicals, such as amines and N-methyl-2-pyrrolidone (NMP), need to be kept sufficiently low for the new processes. Therefore, the role of chemical filters has become an essential one. We conducted a study on the dependency of chemical filters on the molecular diffusivity of target gas species, and, based on this data, developed a filter that eliminates amines. The filter has a honeycomb structure with a wide gas-contacting area, and consists of an ion-exchange resin that has received special treatment. The filter has a greatly improved gas capture efficiency (>99.8% for ammonia, >98% for triethylamine and NMP) and a very large adsorption capacity, which enables a 50% reduction of the filter volume compared with currently available chemical filters.