Inductively Coupling Plasma Reactor With Plasma Electron Energy Controllable in the Range From ${\sim}{6}$ to ${\sim}{\rm 100}~{\rm eV}$

This paper discusses a theoretical and experimental investigation of parameters of plasma [hydrogen (H2) and argon (Ar)] developed in an inductively coupling plasma reactor. The reactor was shaped as a planar chamber inserted between two gaps formed between two separated identical halves of a quasi-closed solenoid cut along its diameter and powered with a 13.56-MHz RF to generate a closed loop of alternating magnetic field crossing the reactor chamber twice. It has been shown that the solution of the Hamilton-Jacobi equation describing motion of a charged particle with the certain momentum in a radial cylindrical wave generated in a gap of the quasi-closed solenoid can be presented as the particle motion along a closed Fig. 8-type trajectory. Simple estimation based on this solution has shown that energy of plasma electrons captured and accelerated in the gap at reasonable power applied to the solenoid should run up to ~ 70 eV. Experiments have shown that in the reactor filled with H2 at 6 mtorr and powered, for example, with 2 kW of 13.56-MHz RF, the electrons accelerated in electromagnetic fields were arranged in three distinct populations: 1) electrons of ~ 130-eV energy detected as stable electron flows; 2) certain portion of electrons mentioned in 1) diffused on neutrals and forming in velocity space a layer with thickness ~ 6 eV at average energy ~ 100 eV; and 3) a small population of cold electrons of ~ 20-eV energy in plasma potential vicinity. It has been shown also that the certain disposition of one of the quasi-closed solenoid halves with respect to the other one leads to the electron energy variation at approximate conservation of their density for all of the electron populations in the range from ~ 6 to ~ 100 eV. The same effect can be obtained by shift of phase of the RF source powering one of the solenoid halves with respect to the other one.