Time-of-Flight Mass Spectrometry of Positive Ions in Helicon-Wave Excited High-Density CF 4 and C 4F 8 Plasmas

Sasaki, Koichi; Ura, K.; Suzuki, Kazunari; Kadota, K.

doi:10.1143/jjap.36.1282

Cited by 19 publications

(3 citation statements)

References 9 publications

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“…6 and k ϭ K iz in Eq. 3, that is Ϫ1 ϭ wQ [19] As ␣ is not linear in Q, as shown in Fig. 4, we can see from Eq.…”

Section: Comparison Of the Model With The Data Of Chapman Et Almentioning

confidence: 88%

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Kinetics of Etching of Silicon Dioxide in a CF[sub 4] Plasma

Kim¹

2000

J. Electrochem. Soc.

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For the etching of silicon or silicon dioxide, CF 4 and NF 3 plasmas have been extensively explored, and many studies have been devoted to the understanding of the discharges in terms of plasma physics, chemistry, and surface chemistry. Among the studies, some works are reporting on modeling to grasp the main idea of the etch process.In an earlier work on modeling, 1 CF 4 plasma was approached as a "pseudo-black-box," in which expressions based on the conservation of fluorine and carbon atoms were derived which relate the concentration of the various species in the effluent gas to the etch rate. Chapman and Minkiewicz 2 proposed a simple model for flow rate effects in plasma etching, in which the etch rate is determined by the generation rate of active species and limited by lack of reactant gas at low flows and by pumping of active species at high flows. In a work by Economou and Alkire, 3 a mathematical model was formulated for a parallel plate plasma etching reactor for the case of the oxygen discharge. The model took account of the variation of electron density and energy with operating conditions, the potential distribution and ion transport in the sheath, the ion-assisted reaction kinetics on the surface, and the transport and reactions of neutral and charged species. Though the above mentioned models provided a semiquantitative understanding of several aspects of plasma etching and captured the salient features observed experimentally, quantitative comparisons were not possible owing to the lack of accurate rate reaction kinetics data.Meanwhile, several works on modeling have tried to make quantitative comparisons by using computer simulation with known kinetics data for a number of chemical reactions. 4-7 A model by Edelson and Flamm 4 simulated the CF 4 plasma etching of silicon using 40 reactions including gas-phase and surface reactions, where processes occurring at the gas-surface interface play a very important role even in the absence of silicon and gas-phase reactions of CF 2 are neglected. Disagreement in explaining the experimental results of Smolinsky and Flamm 8 was raised by Ryan and Plumb, 5,6 who developed a similar simulation model with different emphasis on the importance of gas-phase reactions. In a recent work by Meeks et al. 7 about 160 gas-phase reactions with accompanying rate coefficients are considered for modeling of chemical downstream etch systems for NF 3 /O 2 mixtures. It was noted, however, that the dominant gas-phase reaction paths can be limited to a much smaller reaction set through detailed sensitivity analysis of the fluorine atom concentration for the conditions of interest to the study.In a work on deposition kinetics of silicon carbide from plasmas of hexamethyldisiloxane (HMDSO), 9 we introduced a simple plasma chemistry model to simulate the deposition process. The plasma model is based on the postulation of direct proportionality of the electron density in the discharge to the discharge power. The postulation is supported by a recent work of Ahlrichs et al., 10 wher...

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“…6 and k ϭ K iz in Eq. 3, that is Ϫ1 ϭ wQ [19] As ␣ is not linear in Q, as shown in Fig. 4, we can see from Eq.…”

Section: Comparison Of the Model With The Data Of Chapman Et Almentioning

confidence: 88%

“…This deviation may result from the nonlinear increase in the electron concentration as a function of the discharge power measured from the same system. 19 The finding that is independent of RF power for NF 3 plasmas means, according to Eq. 3, that w and the ratio k/K iz are independent of RF power.…”

Section: Plasma Chemistry Modelmentioning

confidence: 97%

Kinetics of Etching of Silicon Dioxide in a CF[sub 4] Plasma

Kim¹

2000

J. Electrochem. Soc.

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“…17 The higher electron density for a lower gas pressure may be attributed to the fact that the excitation efficiency of a helicon wave decreases with increasing gas pressure. 18 Considering the above characteristics of the electron density, it is known from Fig.…”

Section: Excitationmentioning

confidence: 99%

Characteristics of C3 radicals in high-density C4F8 plasmas studied by laser-induced fluorescence spectroscopy

Takizawa

Sasaki

Kadota

2000

Journal of Applied Physics

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Spatial and temporal variations of C3 density in high-density octafluorocyclobutane (c-C4F8) plasmas were examined using laser-induced fluorescence spectroscopy. The C3 density varied slowly for a long time after the initiation of discharge, suggesting the importance of surface chemistry for the formation of C3. Hollow-shaped spatial distributions (the C3 density adjacent to the chamber wall was higher than that in the plasma column) were observed in the C3 density. This result indicates that C3 radicals are produced from fluorocarbon film on the chamber wall and are lost in the plasma column due to electron impact processes. The surface production of C3 was also observed in the afterglow for 1 ms after the termination of rf power. The decay time constant of the C3 density in the late (>1 ms) afterglow, where the surface production of C3 stopped, was almost independent of discharge parameters, suggesting that the loss of C3 due to gas-phase reactions is negligible.

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