Low-energy electron beam control via magnetic confinement and acceleration voltage: implications for photoresist etching

초록

We investigated the effects of a magnetic field on electron beam energy, beam flux, electron density (n), electron temperature (T), and photoresist (PR) etching in an inductively coupled plasma (ICP) system with a grid system. The acceleration voltage ( Vacc) was applied to the grid system to extract a low-energy electron beam. Cylindrical and planar Langmuir probes were employed to measure these parameters. Optical emission spectroscopy was used to monitor the O radical density. PR etching experiments were performed in O2 at 0.67 Pa and an ICP power of 300 W was used to evaluate the etching characteristics. When Vacc increased from 10 V to 50 V, the electron beam energy gradually increased. However, a different trend was observed when a magnetic field was present. When Vacc <= 20 V, the beam energy decreased with increasing magnetic field strength, whereas at higher Vacc (>= 30 V), it increased. This behavior originates from the combined effects of the plasma potential difference between the source and extraction regions and magnetic confinement, which modify the electron transport path and energy gain mechanism. The electron beam flux also increased with magnetic field, while the electron density varied only slightly and the electron temperature remained nearly constant (similar to 1.2 eV). The PR etching results indicated that the magnetic field enhances the etch rate primarily through its influence on the electron beam energy and flux, rather than through changes in bulk plasma parameters.

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