Generation and control of electron beam via DC grid biased voltage in inductive coupled plasma

An electron beam generation using the grid system was investigated in an inductively coupled plasma (ICP). The electron beam was controlled and measured with varying pressure, ICP source power, and DC grid biased voltage. At low pressure (3 mTorr), an electron beam was generated even when a small voltage (10 V) was applied to the grid, but at high pressure (80 mTorr), an electron beam was generated when a higher voltage (30 V) was applied. At low pressure, the electron could be accelerated without collision between electrons and neutral species. However, when the applied DC voltage becomes too high, an electron beam is not generated, and the electron temperature decreases sharply. Because electrons gain high energy by the strong DC electric field, electrons lose their energy by ionizing neutral gases in the grid system. In addition, when the sheath length is shorter than the grid hole length, electrons that include both low and high energy electrons flow down through the grid freely. Therefore, generating an electron beam at the high electron density regime is difficult, such as increasing ICP source power because sheath length decreased.