Profile simulation of gas chopping based etching processes

Volland, Burkhard E.; Ivanov, Tzv.; Rangelow, Ivo W.

doi:10.1116/1.1520572

Cited by 18 publications

(12 citation statements)

References 19 publications

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“…Some studies on modeling trench evolution in a DRIE process attributed removal of the polymer layer solely to ion bombardment. 14,15 However, the importance of fluorine neutrals was also demonstrated by the fact that the etch rate of a fluorocarbon film by physical sputtering in an argon plasma is significantly lower than the etch rate observed with combined physical and chemical sputtering in a fluorocarbon plasma at similar ion current densities and ion energies. 12,16 Arguably, the combination of fluorine species and ion bombardment leads to a significant etch rate of fluorocarbon polymer.…”

Section: Etching Phase: Fluorocarbon Polymermentioning

confidence: 99%

Maximum achievable aspect ratio in deep reactive ion etching of silicon due to aspect ratio dependent transport and the microloading effect

Yeom

Selby

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

131

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When etching high-aspect-ratio silicon features using deep reactive ion etching ͑DRIE͒, researchers find that there is a maximum achievable aspect ratio, which we define as the critical aspect ratio, of an etched silicon trench using a DRIE process. At this critical aspect ratio, the apparent etch rate ͑defined as the total depth etched divided by the total elapsed time͒ no longer monotonically decreases as the aspect ratio increases, but abruptly drops to zero. In this paper, we propose a theoretical model to predict the critical aspect ratio and reveal its causal mechanism. The model considers aspect ratio dependent transport mechanisms specific to each of the reactant species in the three subprocesses of a time-multiplexed etch cycle: deposition of a fluorocarbon passivation layer, etching of the fluorocarbon polymer at the bottom of the trench, and the subsequent etching of the underlying silicon. The model predicts that the critical aspect ratio is defined by the aspect ratio at which the polymer etch rate equals the product of the deposition rate and the set time ratio between the deposition and etching phases for the time-multiplexed process. Several DRIE experiments were performed to qualitatively validate the model. Both model simulations and experimental results demonstrate that the magnitude of the critical aspect ratio primarily depends on ͑i͒ the relative flux of neutral species at the trench opening, i.e., the microloading effect, and ͑ii͒ aspect ratio dependent transport of ions during the polymer etching subprocess of a DRIE cycle.

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Section: Etching Phase: Fluorocarbon Polymermentioning

confidence: 99%

Maximum achievable aspect ratio in deep reactive ion etching of silicon due to aspect ratio dependent transport and the microloading effect

Yeom

Selby

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

131

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“…For silicon etching in SF 6 =O 2 plasmas, the etching rate during simultaneous exposure to ion and neutral fluxes is much faster than the sum of the physical sputtering and chemical etching rates. 5 Thus, for our process conditions, the influence of the physical Si sputtering on the total etch rate is insignificant 27 and can be neglected.…”

Section: -4mentioning

confidence: 99%

Profile simulation model for sub-50 nm cryogenic etching of silicon using SF6/O2 inductively coupled plasma

Ishchuk

Olynick

Liu

et al. 2015

Journal of Applied Physics

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Cryogenic etching of silicon is a route to high aspect ratio silicon features with high mask selectivity and smooth sidewalls. These benefits have been realized even down to 10 nm half-pitch features. In this work, we develop a semi-empirical simulation model to understand mechanisms responsible for nanoscale profile evolution during plasma etching of silicon in SF6/O2 chemistry at cryogenic temperatures. The model parameters are first calibrated to the etching equipment using features from 500 nm to 2 μm. Using the calibrated model, we show the experimental finding that smaller features need more oxygen to achieve vertical anisotropic profiles. This is a consequence of two related effects: (1) the SiOxFy passivation layer sputtering yield is strongly dependent on the oxygen content at the feature sidewalls and (2) Knudsen transport within small features or higher aspect ratios depletes oxygen faster than fluorine due to the higher sticking coefficient of oxygen. The simulation was applied to 25 nm half-pitch features with excellent results.

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“…The structures are transferred into an oxide layer (1.2 lm) on top of the wafer by contact print lithography and RIE. After resist stripping the structures are etched (typically 70 lm) into the bulk silicon by gas chopping DRIE (deep reactive ion etching) [8,9]. The sidewalls are passivated by means of thin (100 nm) dry oxidation.…”

Section: Fabricationmentioning

confidence: 99%