「Large-Scaled Line Plasma Source by Microwave」

[Basis of Line Plasma Source]  

 The source is a large-scaled line plasma with several meter's using 2.45 GHz microwave, the key technology of which is large-scaled linearly unoform plasma production. By employing an elongated wavelength of waveguide mode of microwave, a long line-shaped plasma can be uniformly produced, available for a variety of large area material processing. The line plasma is possible to produce in low pressures and in atmospheric environment as well. This makes the plasma application possible in a variety of fields.

 As shown in Fig.1, the wavelength of microwave in waveguide is dependent on the size of waveguide width a, for an example of TE10 mode and it becomes larger as the width a is smaller. Then it is possible to produce a long line uniform plasma if the microwave is irradiated in the condition of longer wavelength in the waveguide. The line plasma production becomes possible when the microwave is irradiated from the slot antenna. The microwave of 2.45 GHz is introduced from the source through tapered waveguide et ct to the chamber and the microwave power is irradiated there via the slot antenna to generate the line plasma. At the end of the system, the short plunger is equipped for an arrangement of microwave phase. In the picture, one example of the plasma production in Ar is illustrated. The plasma is just seen from the microwave power source side, and a beautiful line plasma is seen over 2 m length. According to measurement of plasma the uniformity becomes improved to be about 4 % scatter over 1 kW power as reported by the technical paper.


[Future Line Plasmas: ECR Line Plasma and Atmospheric Line Plasma]

 The line plasma production method introduced here has a potential to extend to new sources. The one is to produce ECR plasma, so that the ECR line plasma with large-scaled. In Fig.2, one data of preliminary test of ECR plasma production is shown, where the measured electron density is plotted as a function of the distance along the microwave slot surface and compared with the case of non-ECR. It is clearly seen that the electron density is greatly enhanced by the electron cyclotron resonance effect, almost at the position of 875 Gauss. In the preliminary test, the permanent magnet of only 40 cm in length,thus the 40 cm ECR line plasma, is examined , but one can confirm that the ECR effect is enough in not-so-large scale. It is highly expected, therefore, that the ECR line plasma makes large-scaled, available for various large area material processing.
On the other hand, atmospheric pressure plasma is now becoming imoprtant in a variety of applications. For these plasmas, the present line plasma source is highly expected, particularly for large area processes. An atmospheric line plasma of 30 cm in length is available now. It is inevitable to extend the present line plasma to several meter's.





 The line plasma system proposed here has several advantages over the other. First of all, the scaling is possible over several ten meters, enabling large-scaled plasma processing in plant. Secondly the plasma production is possible in atmospheric enviroment, making the apllication field in a variety. Our plasma production in atmospheric pressure has been already succeeded and thus it is highly expected to make large-scaled as well.