Large-diameter plasma sourcs for plasma processing

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The productions of large-diameter, high density plasma are of crucial importance to establish a wide-area plasma processing. The object of this joint reseach is to develop new plasma sources for producing a large-diameter uniform plasma. The reseach has been proceeded by combining the plasma control techniques developed at Tohoku University for RF and ECR discharges with the diagnostic techniques developed at KAIST and KBSI,Korea, for detecting F-radicals by using a optical probe system. It is also quite important to clarify the relation between the distributions of plasma density and radical density.In order to carry out the experiment at Tohoku University, we produced a 60-cm-diameter MMT (Modifoed Magnetron Type) RF devices, where the conditions for producing a large-diameter plasma are inverstigated. It was found that the length of the RF electrode and the strenth of the magnetic field on the RF electrode are quite essential for the uniform plasma production. Is was also found that … More the production of high density plasma is possible when the RF impedance of a sub-electrode placed at the end of the machine was set at a parallel resonance with the RF frequency. We can produce a plasma of 10^<11>/cm^3 at the RF power of 500 W.Similar experiment was also carried out in a large chamber of 130 cm in diameter by using MMT RF discharge. We confirmed that a quite uniform plasma is prroduced over 120 cm in diameter with a uniformity of 5%.The profiles of F radicals in CF_4 plasmas were also measured in ECR and MMF RF discharge plasmas at Tohoku University in collaboration with the Korean staffs. The optical probe system was build up at the Tohoky University for the measurements. We found that the F radial profiles have a strong dependency on the gas pressuer. In order to confirm the relation between the actual etching profile of poli-silicon and the radical profile, the etching has been preformed under different conditions, and we found that a similar profile of etching with the radical density. Less