| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS+SS+TF-WeM |
| Session: | Atomic Layer Etching (ALE) and Low-Damage Processes I |
| Presenter: | Shahid Rauf, Applied Materials, Inc. |
| Authors: | S. Rauf, Applied Materials, Inc. A. Agarwal, Applied Materials, Inc. L. Dorf, Applied Materials, Inc. K.S. Collins, Applied Materials, Inc. D.R. Boris, US Naval Research Laboratory S.G. Walton, US Naval Research Laboratory |
| Correspondent: | Click to Email |
Plasmas generated using energetic electron beams have unique properties that make them attractive for emerging plasma processing applications. In the work done at the Naval Research Laboratory, [1] it has been demonstrated that electron temperature (Te) in the electron-beam plasmas generated in molecular gases is typically < 0.6 eV while electron densities are comparable to those obtained in radio-frequency (RF) inductively and capacitively coupled plasmas. In addition, the ions and radicals are primarily produced by highly energetic electrons (few keV) instead of electrons in the tail of a low energy distribution. The plasma chemistry in electron-beam generated plasmas is therefore significantly different than RF plasmas with a much higher ion to neutral radical density ratio in electron beam plasmas. As feature dimensions shrink below 20 nm in microelectronics devices with atomic level precision required during manufacturing, the unique properties of electron-beam generated plasmas (low Te, low ion energy and unique chemistry) are becoming attractive for plasma processing in the semiconductor industry.
This paper focuses on a multi-dimensional computational model for electron-beam generated plasmas. A fluid model for the bulk plasma is coupled with a Monte Carlo kinetic model for beam electrons. The fluid plasma model uses the drift-diffusion approximation for electrons and negative ions. The momentum equation is solved for positive ions. The model includes the effect of magnetic field on charged species transport. The Monte Carlo model for beam electrons considers electron motion in the ambipolar electric field and externally imposed static magnetic field. Additionally, important collision processes including elastic collisions, ionization, excitation, dissociation and dissociative attachment are considered during the Monte Carlo simulation.
The computational model is validated in Ar, Ar/N2 and O2 plasmas using probe measurements over a range of gas pressures and electron beam properties. One factor that has important implications on quantitative accuracy of the model is the influence of magnetic field on electron transport properties. The paper will discuss the classical transport model as well as variations based on semi-empirical approximations. The validated model is applied to the design of electron beam based plasma processing systems.
This work was partially supported by the Naval Research Laboratory Base Program.
[1] S.G. Walton et al., ECS Journal of Solid State Science and Technology, 4 (6) N5033-N5040 (2015)