Electron-assisted PR etching in oxygen inductively coupled plasma via a low-energy electron beam

In this study, electron-assisted photoresist (PR) etching is conducted using oxygen inductively coupled plasma at a pressure of 3 mTorr. During the PR etching, a low-energy electron beam is generated and is controlled by varying the acceleration voltage (0-40 V) on the grid to assist with the PR etching. When a low acceleration voltage (< 20 V) is applied, no electron beam is generated, and PR etching is assisted by the accelerated ions. However, the acceleration voltage is increased (about 20-25 V), an electron beam is generated, and PR etching is assisted by the electron beam. At high acceleration voltages (> 25 V), the etch rate increases, and the ion bombardment energy decreases with increasing electron beam energy. The electron energy probability function is measured to verify the relation between the etch rate and acceleration voltage with respect to the sheath thickness on the grid. Furthermore, low contribution of the O radical to the etch rate increment is observed via optical emission spectroscopy measurements.