Controlling Energetic Neutral Beams Produced from Inductively Coupled Plasmas for Material Processing Applications

Plasma etching and deposition are essential processes for for microelectronics fabrication. Precise control of energy and angular distributions (EADs) of ions accelerated onto biased wafers is required to stimulate critical surface chemical reactions. However, charge buildup in the feature can perturb ion trajectories or damage the electronic device. This is particularly the case for fabrication of 2-dimensional devices that consist of nearly monolayer thickness. Energetic neutral beams have been proposed as a damage-free technique for etching and deposition [1]. The neutral beams are often produced by first accelerating ions, followed by reflection and neutralization on the walls of apertures of a biased grid. In this paper we discuss results from a computational investigation of the properties of neutral beams produced in inductively coupled plasmas using this technique. The Plasma Chemistry Monte Carlo Module (PCMCM) in the Hybrid Plasma Equipment Model (HPEM) was improved to track the motion of ions as they neutralize on and reflect from a grid, and collide with background particles before reaching the wafer. Typical conditions are pressures of tens of mTorr, gas mixtures containing Ar, Cl₂ or O₂ and biases of hundreds of volts. The effect of aperture aspect ratio, bias, pressure and gas mixture on the neutralization efficiency and neutral EADs to the wafer will be discussed.

[1] S. Samukawa, ECS J. Solid State Sci. Technol. 4, N5089 (2015).