A global or zero-dimensional model for C4F8 plasmas is formulated by coupling gas phase and wall surface reaction kinetics. A set of surface reactions implements experimental findings and quantifies the effect of the fluorocarbon film formed on the reactor walls on the densities of species in the gas phase. The model allows the calculation of the pressure change after the ignition of the discharge and the effective sticking (surface loss) coefficients of the neutral species on the wall surface. The model is validated by comparison with experimental measurements, i.e. pressure rise and densities of F atoms, CF2 and CF radicals, in an inductively coupled plasma reactor. It is predicted that C4F8 is vastly dissociated and CF4 becomes the dominant species even at low power conditions. A net production of CF3 radical and a net consumption of CF2 radical at the reactor walls are predicted. A study on the contribution of each reaction to the production and consumption of the species shows that at least one surface reaction is among the major sinks or sources of CF4, CFx radicals and F.

Fabrication of periodic nanodot or nanocolumn arrays on surfaces is performed by top-down lithographic procedures or bottom-up self-assembly methods, which both make use of plasma etching to transfer the periodic pattern. Could plasma etching alone act as an assembly--organization method to create the pattern and then transfer it to the substrate? We present data that support this idea and propose a mechanism of periodicity formation where etching and simultaneous deposition take place.

Gas phase and reactor wall-surface kinetics are coupled in a global model for SF6 plasmas. A complete set of gas phase and surface reactions is formulated. The rate coefficients of the electron impact reactions are based on pertinent cross section data from the literature, which are integrated over a Druyvesteyn electron energy distribution function. The rate coefficients of the surface reactions are adjustable parameters and are calculated by fitting the model to experimental data from an inductively coupled plasma reactor, i.e. F atom density and pressure change after the ignition of the discharge. The model predicts that SF6, F, F2 and SF4 are the dominant neutral species while and F− are the dominant ions. The fit sheds light on the interaction between the gas phase and the reactor walls. A loss mechanism for SFx radicals by deposition of a fluoro-sulfur film on the reactor walls is needed to predict the experimental data. It is found that there is a net production of SF5, F2 and SF6, and a net consumption of F, SF3 and SF4 on the reactor walls. Surface reactions as well as reactions between neutral species in the gas phase are found to be important sources and sinks of the neutral species.

No abstract

With ever increasing demands on device patterning to achieve smaller critical dimensions, the need for precise, controllable atomic layer etching (ALE) is steadily increasing. In this work, a cyclical fluorocarbon/argon plasma is successfully used for patterning silicon oxide by ALE in a conventional inductively coupled plasma tool. The impact of plasma parameters and substrate electrode temperature on the etch performance is established. We achieve the self‐limiting behavior of the etch process by modulating the substrate temperature. We find that at an electrode temperature of −10°C, etching stops after complete removal of the modified surface layer as the residual fluorine from the reactor chamber is minimized. Lastly, we demonstrate the ability to achieve independent etching, which establishes the potential of the developed cyclic ALE process for small scale device patterning.

No abstract

No abstract

Porous organosilicate glass thin films, with k-value 2.0, were exposed to 147 nm vacuum ultra-violet (VUV) photons emitted in a Xenon capacitive coupled plasma discharge. Strong methyl bond depletion was observed, concomitant with a significant increase of the bulk dielectric constant. This indicates that, besides reactive radical diffusion, photons emitted during plasma processing do impede dielectric properties and therefore need to be tackled appropriately during patterning and integration. The detrimental effect of VUV irradiation can be partly suppressed by stuffing the low-k porous matrix with proper sacrificial polymers showing high VUV absorption together with good thermal and VUV stability. In addition, the choice of an appropriate hard-mask, showing high VUV absorption, can minimize VUV damage. Particular processing conditions allow to minimize the fluence of photons to the substrate and lead to negligible VUV damage. For patterned structures, in order to reduce VUV damage in the bulk and on feature sidewalls, the combination of both pore stuffing/material densification and absorbing hard-mask is recommended, and/or the use of low VUV-emitting plasma discharge.