Dong-Pyo Kim

Volume and heterogeneous chemistry of active species in chlorine plasma

Abstract Chlorine plasma parameters and the mechanisms of both volume and heterogeneous reactions were investigated using a combination of experimental methods and plasma modeling. It was found that increasing gas pressure within the range 20–200 Pa leads to sufficient deformation of the electron energy distribution function and to corresponding changes in kinetic and transport coefficients. Direct electron impact dissociation and ionization were found to be the main mechanisms for radical and ion generation, while contributions from dissociative attachment and dissociative ionization were negligible. Heterogeneous recombination of chlorine atoms is the dominant decay channel, which is described by a first-order kinetic mechanism.

On mechanisms of argon addition influence on etching rate in chlorine plasma

Abstract Parameters of Cl 2 /Ar plasma were investigated aimed to understand the mechanism of Ar addition influence on etching rate acceleration. Analysis was carried out on the base of combination of experimental methods and plasma modelling. It was found that the addition of Ar to chlorine under a constant total pressure condition cause changes in plasma electro-physical properties (EEDF, mean electron energy) due to the ‘transparency’ effect. Direct electron impact dissociation of Cl 2 molecules was found as the main source of chlorine atoms while the contributions of dissociative attachment and stepwise dissociation involving Ar metastable atoms are negligible. It was supposed that the main reason of etching rate increasing in Cl 2 /Ar mixture plasma is connected with simultaneous action of Ar on volume chemistry and the heterogeneous stage of etching process.

Investigation of SrBi2Ta2O9 thin films etching mechanisms in Cl2 /Ar plasma

An investigation of the SrBi2Ta2O9 (SBT) etching mechanism in a Cl2/Ar plasma was carried out. Experiments showed that an increase of the Ar mixing ratio under constant pressure and input power conditions leads to increasing an etch rate of SBT, which reaches a maximum value when the Ar is 80% of the gas. The modeling of volume kinetics using the measured electron temperature and electron density indicated monotonic changes of both densities and fluxes of active species such as chlorine atoms and positive ions. Nevertheless, an analysis of surface kinetics in the framework of an ion-assisted etching mechanism confirms the possibility of nonmonotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.An investigation of the SrBi2Ta2O9 (SBT) etching mechanism in a Cl2/Ar plasma was carried out. Experiments showed that an increase of the Ar mixing ratio under constant pressure and input power conditions leads to increasing an etch rate of SBT, which reaches a maximum value when the Ar is 80% of the gas. The modeling of volume kinetics using the measured electron temperature and electron density indicated monotonic changes of both densities and fluxes of active species such as chlorine atoms and positive ions. Nevertheless, an analysis of surface kinetics in the framework of an ion-assisted etching mechanism confirms the possibility of nonmonotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.

Etching mechanism of Bi4−xLaxTi3O12 films in Ar/Cl2 inductively coupled plasma

The etching behavior of Bi4−xLaxTi3O12 (BLT) films in inductively coupled Ar/Cl2 plasma was investigated in terms of etch parameters. The etching rate as a function of Ar/Cl2 mixing ratio showed a maximum of 50.3 nm/min for the mixture of Ar(80%)/Cl2(20%). The increase of r.f. power and d.c.-bias voltage caused an increase in BLT etch rate under any fixed gas composition. To understand etch mechanism, the plasma diagnostics were performed using Langmuir probe (LP) and optical emission spectroscopy (OES). The LP measurement indicated that the increase of Ar mixing ratio in Ar/Cl2 plasma leads to monotonic changes of both electron density and total density of positive ions. The same tendencies were found for chlorine atoms and molecules using OES. The chemical states of BLT were studied using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that the La-chlorides remained on the etched surface. The analysis of surface reactions and plasma diagnostics in the frameworks of an ion-assisted etching mechanism confirms the possibility of non-monotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.

Electrical properties of Bi4−xEuxTi3O12 (BET) thin films after etching in inductively coupled CF4/Ar plasma

Abstract The etch properties of Bi4−xEuxTi3O12 (BET) thin films were evaluated with inductively coupled CF4/Ar plasma. We obtained the maximum etch rate of 78 nm/min at the gas mixing ratio of CF4 (10%)/Ar (90%). This result may suggest that sputtering by Ar ions is more effective than chemical etching by fluorine atoms for Bi4−xEuxTi3O12 (BET) etching. In X-ray photoelectron spectroscopy analysis, non-volatile etch byproducts (EuF2: 1380 °C, EuF3: 1276 °C) were observed. After the etching, the electrical properties of BET capacitors were characterized in terms of hysteresis curves, leakage current and switching polarization. After etching in CF4/Ar plasma, the remanent polarization decreased and the leakage current increased. The etched capacitors in the Ar/CF4 plasma retained 58% of their original polarization at 105 cycles. After the annealing at 600 °C in an O2 atmosphere for 10 min, the ferroelectric properties were significantly recovered. The degradation of electrical properties after the etching was considered due to the physical effect of ion bombardment and chemical residue contamination.

Etching characteristics of Bi 4-x La x Ti 3 O 12 (BLT) in inductively coupled CF 4 /Ar plasma

The etching properties of BLT in inductively coupled plasma (ICP) was studied in terms of etch rate and selectivity as functions of CF4/Ar gas mixing ratio, rf power, dc bias voltage. We obtained a maximum etch rate of 803 A/min at 20% CF4 addition into Ar plasma. The maximum etch rate may be explained by the simultaneous occurrence of physical sputtering and chemical reaction. The ion bombardment plays the role of destruction of metal (Bi, La, Ti)-O bonds to supply chemical interaction of metals with fluorine atoms, resulting in being desorbed only by ion bombardment. The variation of ion current density and of volume density for F and Ar atoms are measured by optical emission spectroscopy (OES).

The Etching Properties of Al2O3 Thin Films in BCl3/Cl2/Ar Plasma

In this study, the etch mechanism of ALD deposited Al2O3 thin film was investigated in BCl3/Cl2/Ar plasma. The experiments were performed by comparing etch rates and selectivity of Al2O3 over hard mask materials (such as SiO2, and Si3N4) as function of the input plasma parameters such as gas mixing ratio, DC-bias voltage and RF power under fixed process pressure. The maximum etch rate was obtained at 115.75 nm/min under 5 mTorr, RF power 600 W, Cl2 10% was added to BCl3/Ar plasma, and the highest etch selectivity was 1.17 over Si3N4 under the 10 mTorr process pressure, −50 V DC-bias voltage. We used the X-ray photoelectron spectroscopy (XPS) to investigate the chemical reactions on the etched surface.

The etching characteristics of YMnO3 thin films in high density Ar/CF4 plasma

Abstract Etching characteristics (etch rate, selectivity and etching profile) of YMnO 3 thin films were investigated using CF 4 /Ar inductively coupled plasma. The maximum etch rate of 18 nm/min for YMnO 3 thin films was obtained at CF 4 (20%)/Ar(80%) gas mixing ratio. Optical emission spectroscopy analysis was performed to analyze the behavior of active species as a function of gas mixing ratio and showed decreasing volume density of fluorine atoms during Ar addition. The chemical states of YMnO 3 films exposed to the plasma were investigated using X-ray photoelectron spectroscopy and secondary ion mass spectrometry (SIMS). Metal-fluorides such as YF, YF 2 , YF 3 and MnF 3 were detected using SIMS analysis. Ion assisted chemical etching was proposed as the main etching mechanism. At the process conditions, which correspond to maximum etch rate, the etch slope was approximately 65° and the surface was clean.

The surface reaction on SrBi 2 Ta 2 O 9 thin films etched in C1 2 /CF 4 /Ar inductively coupled plasma

SrBi2Ta2O9 thin films were etched in high-density Cl2/CF4/Ar in inductively coupled plasmas. The chemical reactions on the etched surface were studied using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The etching of SBT thin films in Cl2/CF4/Ar was eroded by chemically-assisted reactive ion etching. The maximum etch rate was 1060 A/min in 20% Cl2 in Cl2/CF4/Ar. The addition of a small amount of Cl2 to CF4/Ar plasma decreases the concentration of fluorine radicals and increases that of Cl radicals. We obtained an etch profile of over 80° and a clean surface.

Etching Properties of HfO2 Thin Films in Cl2/BCl3/Ar Plasma

In this study, we changed two input parameters (pressure vs. gas mixing ratio, RF power and DC bias voltage) and then monitored the effect on HfO 2 etch rate and selectivity with Si 3 N 4 and SiO 2 . When the pressure was fixed at 5 mTorr, etch rate of HfO 2 decreased with increasing Cl 2 content from 0 to 30% in BCl 3 /Ar plasma. At the conditions of 10 and 15 mTorr, the HfO 2 etch rate reached the maximum at 10% Cl 2 addition. As RF power and DC bias voltage increased in all ranges of pressure conditions, etch rates for HfO 2 showed increasing trends. The relative volume densities of radicals were monitored with optical emission spectroscopy (OES). The analysis of x-ray photoelectron spectroscopy (XPS) was carried out to investigate the chemical reactions between the surfaces of HfO 2 and etch species. Based on experimental data, the ion-assisted chemical etching was proposed as the main etch mechanism for the HfO 2 thin films in Cl 2 /BCl 3 /Ar plasma.