| AVS 57th International Symposium & Exhibition | |
| Vacuum Technology | Monday Sessions |
| Session VT+MS-MoA |
| Session: | Gas Analysis in Vacuum and Process Applications |
| Presenter: | R. Versluis, TNO Science and Industry, Netherlands |
| Authors: | R. Versluis, TNO Science and Industry, Netherlands M.F. Dekker, TNO Science and Industry, Netherlands |
| Correspondent: | Click to Email |
In Extreme UltraViolet lithography (EUVL), 13.5 nm light is used for imaging the reticle pattern onto the wafer. Since EUV light is absorbed by all materials (including gases) a reflective optical system is uded in EUV wafer steppers. Wafer resist outgassing during exposure is one of the most important contributors to mirror contamination. Just one or a few monolayers of Carbon on the multi-layer reflective optics of the system leads to an unacceptable reflectivity loss. Considering the fact that a large fraction of the EUV induced wafer resist outgassing constitutes of hydrocarbons, suppression and mitigation of these molecules is absolutely necessary.
Different methods exist to suppress hydrocarbons and other contamination from wafer, or 'dirty' components. In order to qualify such methods, very sensitive hydrocarbon measurements need to be done at relatively high pressures.
We built a test rig capable to detect hydrocarbons at ppb level. The hydrocarbon levels that need be measured are at the order of 1E-9 Pa, while the absolute pressure is at the order of 10 Pa. The test rig therefore needs to be extremely clean during the measurements. The test rig includes six large Turbo Molecular Pumps to keep the test rig at an absolute pressure of 10 Pa, while the component under test is continously being flushed. The electro-polished setup (about 4 meters long and one meter high) can be completely baked at 150ºC to reach the extreme clean conditions needed to measure the low concentrations of hydrocarbons. Measurements are done with a very sensitive residual gas analyser (RGA) which can be baked to 200ºC. The RGA has been optimized in such a way that the sensitivity for heavy gases is increased with respect to the sensitivity for lighter gases (patent appointed). Test gases (hydrocarbons, Ar, N2 can be injected at different locations in the test rig. This way a contamination source in the wafer stage as well as wafer resist outgassing can be simulated.
With the test rig we can also do a thermal qualification of the component under test, to determine heat loads to the test component and heat load distributions.
The presentation will focus on design and engineering aspects of the test rig, the qualification of the test rig and the qualification of the component under test.