Gwan-Ha Kim

Temperature dependence on dry etching of Al2O3 thin films in BCl3/Cl2/Ar plasma

During the etching process, the wafer surface temperature is an important parameter which influences the reaction probabilities of incident species, the vapor pressure of etch products, and the redeposition of reaction products on feature surfaces. In this study, the authors investigated that the effect of substrate temperature on the etch rate of Al2O3 thin film and selectivity of Al2O3 thin film over hard mask material (such as SiO2) thin film in inductively coupled plasma as functions of Cl2 addition in BCl3/Ar plasma, rf power, and dc-bias voltage based on the substrate temperature in range of 10–80 °C. The elements existed on the surface were analyzed by energy dispersive x-ray and x-ray photoelectron spectroscopy.

Etching Characteristics of (Na0.5K0.5)NbO3 Thin Films in an Inductively Coupled Cl2/Ar Plasma

The investigation of etch characteristics for (Na 0.5 K 0.5 )NbO 3 (NKN) thin films in Cl 2 /Ar inductively coupled plasma was carried out. It was found that the NKN etch rate is a monotonic function of both input power and negative dc bias as it generally expected from the corresponding variations of plasma parameters. At the same time, NKN etch rate shows a non-monotonic behavior as a function of Cl 2 /Ar mixing ratio with a maximum of 750 Å/min at Cl 2 (80%)/Ar (20%). The analysis of these data togeter with the XPS results for both as-deposited and etched NKN films allowed one to assume ion assisted etch mechanism and defined a concurence of chemical and physical etch pathways as a most probable reason for etch rate maximum.

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.

Etch Properties of Hf-Based High- k Dielectrics Using Inductively Coupled Plasma

In this work, we investigated etching characteristics of HfO 2 thin film and Si using inductive coupled plasma (ICP) system. The maximum etch rate of HfO 2 is 85.5 nm/min at a BCl 3 /(Ar+BCl 3 ) of 20% and decreased with further addition of BCl 3 gas. From the QMS measurements, the most dominant positive ion energy distributions (IEDs) showed a maximum at 20% of BCl 3 . These tendency was very similar to the etch characteristics. This result agreed with the universal energy dependency of ion enhanced chemical etching yields. From the mass spectra, the Hf chloride and bromine oxide must be included in the etching by-products as volatile species.

Dry etching of (Ba,Sr)TiO3 thin films using an inductively coupled plasma

In this study (Pb,Sr)TiO3 (PST) thin films were etched with inductively coupled Cl2∕(Cl2+Ar) plasmas. The etch characteristics of PST thin films as a function of Cl2∕(Cl2+Ar) gas mixtures were analyzed by using a quadrupole mass spectrometer. Systematic studies were carried out as a function of the etching parameters, including the radio frequency power and the working pressure. The maximum PST film etch rate is 56.2nm∕min, because a small addition of Cl2 to the Cl2∕Ar mixture increased the chemical effect. It was proposed that sputter etching is the dominant etching mechanism while the contribution of a chemical reaction is relatively low due to low volatility of the etching products.

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.

Improving the Etch Selectivity of ZrO2 Thin Films over Si by Using High Density Plasma

In this study, we carried out an investigation of the etching characteristics (etch rate, selectivity to Si) of ZrO 2 thin films in the HBr/CF 4 high density plasma (HDP) system. The maximum etch rate of 70.8 nm/min for ZrO2 thin films was obtained at HBr(75%)/ CF 4 (25%) gas mixing ratio. At the same time, the etch rate was measured as a function of the etching parameter such as HDP chamber pressure. The X-ray photoelectron spectroscopy (XPS) analysis showed an efficient destruction of the oxide bonds by the ion bombardment as well as an accumulation of low volatile reaction products on the etched surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the CF 4 -containing plasmas.

Ferroelectric properties of Bi3.25La0.75Ti3O12 films using HfO2 as buffer layers for nonvolatile-memory field-effect transistors

The ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin film and HfO2 layer were fabricated using both metal-organic decomposition and atomic-layer deposition methods. The HfO2 thin film was deposited as a buffer layer between Si substrate and BLT thin films. The electrical and structural properties of the metal-ferroelectric-insulator-semiconductor (MFIS) structure were investigated by varying the HfO2 layer thickness. Transmission electron microscopy showed no interdiffusion and reaction occurring when the HfO2 film is used as a buffer layer. The width of the memory window in the capacitance-voltage curves for the MFIS structure was decreased with increasing thickness of the HfO2 buffer layer. The experimental results showed that the BLT-based MFIS structure is suitable for nonvolatile-memory field-effect transistors with a large memory window.

Effect of Cl2/Ar gas mixing ratio on (Pb,Sr)TiO3 thin film etching behavior in inductively coupled plasma

The development of anisotropic etching process for (Pb,Sr)TiO3 (PST) thin films is an important task to provide a small feature size and an accurate pattern transfer. Etching characteristics of PST thin films were investigated using inductively coupled plasma etching system as functions of Cl2∕Ar gas mixing ratio. The PST etch rate increased with the increase of chlorine radical and ion energy intensity. It was found that the increasing of Ar content in gas mixture lead to sufficient increasing of etch rate. The maximum etch rate of PST film is 56.2nm∕min at Cl2∕(Cl2+Ar) of 0.2. It was proposed that the sputter etching is a dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products.

Etch characteristics of (Pb,Sr)TiO3 thin films using CF4/Ar inductively coupled plasma

The investigations of the (Pb,Sr)TiO3 (PST) etching characteristics in CF4/Ar plasma were carried out using the inductively coupled plasma system. Experiments showed that an increase of the Ar mixing ratio under constant pressure and input power conditions leads to increasing etch rate of PST, which reaches a maximum of 740 A/min when the Ar is 80% of the gas mixture. To understand the etching mechanism, the surface state of the etched PST samples was investigated using x-ray photoelectron spectroscopy. It was found that Pb and Ti atoms were removed mainly by the ion-assisted etching mechanism. At the same time, Sr forms extremely low volatile fluorides and therefore can be removed only by physical (sputter) etching.The investigations of the (Pb,Sr)TiO3 (PST) etching characteristics in CF4/Ar plasma were carried out using the inductively coupled plasma system. Experiments showed that an increase of the Ar mixing ratio under constant pressure and input power conditions leads to increasing etch rate of PST, which reaches a maximum of 740 A/min when the Ar is 80% of the gas mixture. To understand the etching mechanism, the surface state of the etched PST samples was investigated using x-ray photoelectron spectroscopy. It was found that Pb and Ti atoms were removed mainly by the ion-assisted etching mechanism. At the same time, Sr forms extremely low volatile fluorides and therefore can be removed only by physical (sputter) etching.