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Journal of Physics D: Applied Physics Volume 47 Number 42,2014. Kazunori Takahashi1, Taisei Motomura2,4, Akira Ando1, Yuji Kasashima2, Kazuya Kikunaga2, Fumihiko Uesugi2 , Shiro Hara3,4
1 Department of Electrical Engineering, Tohoku University, Sendai 980-8579, Japan and
2 Measurement Solution Research Center, National Institute of Advanced Industrial Science and Technology, Tosu, Saga 841-0052, Japan and
3 Nanoelectronics Research Institute, National Institutes of Advanced Science and Technology, AIST Tsukuba Central2, Tsukuba 305-8568, Japan and
4 Minimal Fab Development Association, AIST Tsukuba Central2, Tsukuba 305-8568, Japan .
Abstract
A high density argon plasma produced in a compact helicon source is transported by a convergent magnetic field to the central region of a substrate located downstream of the source. The magnetic field converging near the source exit is applied by a solenoid and further converged by installing a permanent magnet (PM) behind the substrate, which is located downstream of the source exit. Then a higher plasma density above 5 × 1012 cm−3 can be obtained in 0.2 Pa argon near the substrate, compared with the case without the PM. As no noticeable changes in the radially integrated density near the substrate and the power transfer efficiency are detected when testing the source with and without the PM, it can be deduced that the convergent field provided by the PM plays a role in constricting the plasma rather than in improving the plasma production. Furthermore it is applied to physical ion etching of silicon and aluminum substrates; then high etching rates of 6.5 µm min−1 and 8 µm min−1 are obtained, respectively.
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Significant statements
As having a high density plasma consisting of electrons and ions near the material gives some advantages in engineering, e.g., a high speed plasma etching due to the presence of the large amount of radical species produced by electron impact and a sputtering due to the presence of ions, the plasma transport from the source to the material surface is crucial technology. Although this can be done by the magnetic field lines which the charged particles are tied to; solenoid coils are used in traditional laboratory plasma devices. However it requires much electricity and increases their cost and device size. Here, a more efficient plasma transport the helicon plasma source is demonstrated by using a ‘small permanent magnet’, where the convergent and very dense plasma can be found near the material surface as shown in the photograph. As one of the application of this plasma transport, the physical ion etching is tested for silicon and aluminum substrates; the high speed etching is obtained.
