Influence of substrate material on plasma in deposition/sputtering reactor: experiment and computer simulation

Abstract

The aim of this work was to investigate the influence of the substrate material on the plasma enhanced chemical vapour deposition and the plasma sputtering of thin films in low pressure (3–20 Pa) parallel-plate radio frequency (rf) discharges. It was observed that the deposition or sputtering rates differed above different materials, e.g. above a substrate and substrate electrode. Moreover, the substrates placed on the bottom rf electrode seemed to be mirrored in the thickness of a thin film deposited or sputtered on the upper grounded electrode. The influence of the substrate material on the plasma parameters was studied via particle in cell/Monte Carlo computer simulation. According to our finding the mirroring of the substrate was caused by different secondary electron emission yields of the substrate material and material of the substrate electrode. This difference in the secondary electron yield affected plasma density above the substrate leading to higher or lower deposition or sputtering rates on the grounded electrode. Therefore, the role of secondary electrons in the discharge was studied. Spatial distributions of impact positions on the grounded electrode for electrons and ions emitted from the rf electrode and created in the ionization avalanche of the secondary electrons were calculated in order to simulate the mirroring of the substrates.

Monitoring of PVD, PECVD and etching plasmas using Fourier components of RF voltage

“…The RF power delivered to the discharge was 50 W during both the deposition and the etching. Details of reactor geometry can be found, e.g., in [26].…”

Effects of fast atoms and energy-dependent secondary electron emission yields in PIC/MCC simulations of capacitively coupled plasmas

“…In most studies that consider secondary electron emission (i) a constant value for the secondary electron yield, γ, is used, that is independent of the discharge conditions (e.g., the energy of impacting ions), (ii) only the ion-induced secondary electron emission is taken into account, neglecting the contributions of other plasma species, (iii) the effect of the surface conditions is not accounted for. In contrast to the α-mode, beyond the mode transition to γ-mode, secondary electron emission plays an essential role in the ionization dynamics [10,[18][19][20][21][22][23][24]. It is known that besides positive ions the fast neutrals, metastable atoms and VUV photons can as well contribute to secondary electron emission and that the importance of these species depends to a great extent on the discharge conditions (incident particle energies) and electrode surface properties (see [25]).…”

A computationally assisted spectroscopic technique to measure secondary electron emission coefficients in radio frequency plasmas

“…While the plasma alters its own boundary surfaces, depending on the shape of the flux-energy distribution functions of different particle species (electrons, ions, neutral radicals), the surface also affects the plasma via particle reflection, absorption, and generation. One of the most important plasma-surface interactions that can strongly affect the electron power absorption dynamics, the plasma density, sheath width, and other plasma parameters is the emission of secondary electrons ("γ-process") induced by the bombardment of the electrode surfaces by different species from the plasma (ions, neutrals, electrons, or photons) [4][5][6][7][8][9][10][11][12][13][14]. For instance, as the γ-coefficient increases due to a change of the electrode material or its conditions in electropositive plasmas operated at pressures above ∼50 Pa and at driving voltage amplitudes above ∼100 V, an electron heating mode transition can be induced from the α-mode, where ionization by electrons accelerated by the expanding sheaths dominates, to the γ-mode, where ionization due to secondary electrons is most important.…”