Phenomenological modeling of ion-enhanced surface kinetics in fluorine-based plasma etching

Gray, Dodd; Tepermeister, I.; Sawin, Herbert H.

doi:10.1116/1.586925

Cited by 238 publications

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“…The silicon etching rate increases with coil power because the ion flux density increases. Similarly, the etching rate increases with SF flow rate because of increases in the concentration of etching species and because of a reduction of etching products (SiF ) that redeposit [21]. Although not shown here, silicon etching rate could also be increased by increasing the applied electrode power during the etching cycle.…”

Section: A Silicon Etching Ratementioning

confidence: 83%

Effect of process parameters on the surface morphology and mechanical performance of silicon structures after deep reactive ion etching (DRIE)

Chen

Ayón

Zhang

et al. 2002

J. Microelectromech. Syst.

211

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Abstract-The ability to predict and control the influence of process parameters during silicon etching is vital for the success of most MEMS devices. In the case of deep reactive ion etching (DRIE) of silicon substrates, experimental results indicate that etch performance as well as surface morphology and post-etch mechanical behavior have a strong dependence on processing parameters. In order to understand the influence of these parameters, a set of experiments was designed and performed to fully characterize the sensitivity of surface morphology and mechanical behavior of silicon samples produced with different DRIE operating conditions. The designed experiment involved a matrix of 55 silicon wafers with radiused hub flexure (RHF) specimens which were etched 10 min under varying DRIE processing conditions. Data collected by interferometry, atomic force microscopy (AFM), profilometry, and scanning electron microscopy (SEM), was used to determine the response of etching performance to operating conditions. The data collected for fracture strength was analyzed and modeled by finite element computation. The data was then fitted to response surfaces to model the dependence of response variables on dry processing conditions. The results showed that the achievable anisotropy, etching uniformity, fillet radii, and surface roughness had a strong dependence on chamber pressure, applied coil and electrode power, and reactant gases flow rate. The observed post-etching mechanical behavior for specimens with high surface roughness always indicated low fracture strength. For specimens with better surface quality, there was a wider distribution in sample strength. This suggests that there are more controlling factors influencing the mechanical behavior of specimens. Nevertheless, it showed that in order to achieve high strength, fine surface quality is a necessary requisite. The mapping of the dependence of response variables on dry processing conditions produced by this systematic approach provides additional insight into the plasma phenomena involved and supplies a practical set of tools to locate and optimize robust operating conditions.[684]Index Terms-Deep reactive ion etching (DRIE), fracture strength, MEMS, plasma etching, silicon, surface morphology.

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Section: A Silicon Etching Ratementioning

confidence: 83%

Effect of process parameters on the surface morphology and mechanical performance of silicon structures after deep reactive ion etching (DRIE)

Chen

Ayón

Zhang

et al. 2002

J. Microelectromech. Syst.

211

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“…The constant K es is found to be 13. Our measurements find that the ratio (J d /J e ) is small ͑the order of 10 Ϫ2 ) for CF 4 etching of SiO 2 in the ECR tool but that it is significant ͑Ϸ2.7͒ in the RIE tool. The difference in ECR and RIE etch rates can be understood as the result of polymer deposition on the wafer.…”

Section: ͑10͒mentioning

confidence: 95%

“…For the ECR tool K es ϭ13 while for the RIE tool K es ϭ0.93. For CF 4 etching, the deposition species appears to be CF 2 .…”

Section: ͑9͒mentioning

confidence: 99%

Symmetric rate model for fluorocarbon plasma etching of SiO2

Ding

Hershkowitz

1996

Applied Physics Letters

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A symmetric rate model for plasma etching and plasma deposition in fluorocarbon plasmas is proposed. When there is no deposition, the symmetric rate model gives a plasma etch rate. When there is no etching, the model gives a plasma deposition rate. Electron cyclotron resonance and reactive ion etcher etch rates of SiO 2 in CF 4 plasma are found to be consistent with the model. © 1996 American Institute of Physics. ͓S0003-6951͑96͒02212-3͔Plasma etching is an important technology in the fabrication of very large scale integrated circuits.1 With the feature size smaller than 0.5 m, the empirical approach for the optimization of plasma etching is getting more and more difficult, and basic understanding of plasma etching is becoming crucial for process control. In the etching of SiO 2 with fluorocarbon plasmas, both etching and deposition occur simultaneously 2 and both processes need to be understood.Many rate models have been proposed for plasma etching ͑see Refs. 3-8 and references therein͒. Among these models, Zawaideh and Kim 7 proposed a model to include both linear effects of chemical and physical etching, and the nonlinear effect of ''enhanced'' chemical and physical etching. Hoffmann and Heinrich 8 simplified the model proposed by Zawaideh and Kim to describe reactive ion etching ͑RIE͒ of polysilicon with SF 6 plasma. Gottscho, Jurgensen, and Vitkavage 10 proposed an ion-neutral synergy model based on the mass transport model proposed by Mayer and Barker. 3,5 In this letter, a symmetric rate model for plasma etching and deposition is developed.In both plasma etching and deposition, energetic ions, etching species, and deposition species have been shown to be important. [9][10][11][12][13][14] showed that plasma etching and deposition rates of plasma perfluoropolymer thin films have a similar dependence on ion energy. Ding et al. 10 found in an electron cyclotron resonance ͑ECR͒ etcher that the etch rates of SiO 2 with CF 4 /O 2 /Ar plasmas only depend on ion energy flux and F-atom density. They quantified the boundary between the ion energy flux limited regime and the F-atom flux limited regime. Mutsukura et al.11 studied the deposition of hydrogenated hard-carbon films in a CH 4 rf discharge plasma. They found at high pressure that the film deposition rate was predominantly dependent on the ion energy flux. They also found at very low pressure that the film deposition rates were almost the same for different rf power at each pressure condition. Similar trends have also been found by the other groups. 12-14Based on the experimental results and the models mentioned earlier, we assume that the ion enhanced chemical etch rate and the ion enhanced chemical deposition rate are proportional to the ion energy flux multiplied by the surface coverage of the etching or deposition species. This assumption means the etch rate and deposition rate are symmetric. If the products of the reaction are volatile, then the process results in net etching. If the products of the reaction are involatile, then the process results in...

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“…On the oxide surface, we use a corresponding species SiO 2 _F 2 (S), which does not specify in any detail how the F is bonded to the surface. The sticking coefficient values for F atom adsorption on silicon surfaces is ten times higher than for oxide surfaces, and both values are taken from the beam/surface experimental work by Gray, et al [46].…”

Section: Reaction Mechanismmentioning

confidence: 99%

Chemical Reaction Mechanisms for Modeling the Fluorocarbon Plasma Etch of Silicon Oxide and Related Materials

Ho¹,

Johannes²,

Buss³

et al. 2001

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As part of a project with SEMATECH, detailed chemical reaction mechanisms have been developed that describe the gas-phase and surface chemistry occurring during the fluorocarbon plasma etching of silicon dioxide and related materials. The fluorocarbons examined are C 2 F 6 , CHF 3 and C 4 F 8 , while the materials studied are silicon dioxide, silicon, photoresist, and silicabased low-k dielectrics. These systems were examined at different levels, ranging from in-depth treatment of C 2 F 6 plasma etch of oxide, to a fairly cursory examination of C 4 F 8 etch of the low-k dielectric. Simulations using these reaction mechanisms and AURORA, a zero-dimensional model, compare favorably with etch rates measured in three different experimental reactors, plus extensive diagnostic absolute density measurements of electron and negative ions, relative density measurements of CF, CF 2 , SiF and SiF 2 radicals, ion current densities, and mass spectrometric measurements of relative ion densities. 2 AcknowledgmentsWe thank Drs.

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Phenomenological modeling of ion-enhanced surface kinetics in fluorine-based plasma etching

Cited by 238 publications

References 0 publications

Effect of process parameters on the surface morphology and mechanical performance of silicon structures after deep reactive ion etching (DRIE)

Effect of process parameters on the surface morphology and mechanical performance of silicon structures after deep reactive ion etching (DRIE)

Symmetric rate model for fluorocarbon plasma etching of SiO2

Chemical Reaction Mechanisms for Modeling the Fluorocarbon Plasma Etch of Silicon Oxide and Related Materials

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