On the etching mechanism of ZrO2 thin films in inductively coupled BCl3/Ar plasma

The etching mechanism of ZrO₂ thin films in BCl₃/Ar plasma was investigated using a combination of experimental and modeling methods. It was found that an increase in the Ar mixing ratio causes the non-monotonic behavior of the ZrO₂ etch rate which reaches a maximum of 41.4 nm/min at about 30-35% Ar. Langmuir probe measurements and plasma modeling indicated the noticeable influence of a BCl₃/Ar mixture composition on plasma parameters and active species kinetics that results in non-linear changes of both densities and fluxes for Cl, BCl₂ and . From the model-based analysis of surface kinetics, it was shown that the non-monotonic behavior of the ZrO₂ etch rate can be associated with the concurrence of chemical and physical pathways in ion-assisted chemical reaction.     

Mechanism of selective Si3N4 etching over SiO2 in hydrogen-containing fluorocarbon plasma

This paper describes the mechanism of selective Si₃N₄ etching over SiO₂ in capacitively-coupled plasmas of hydrogen-containing fluorocarbon gas, including CHF₃, CH₂F₂ and CH₃F. The etch rate of Si₃N₄ and SiO₂ is investigated as a function of O₂ percentage in all plasma gases. Addition of O₂ in feed gases causes plasma gas phase change especially H density. The SiO₂ etch rate decreases with increase of O₂ percentage due to the decline of CF_x etchant. The Si₃N₄ etch rate is found to be strong correlated to the H density in plasma gas phase. H can react with CN by forming HCN to reduce polymer thickness on Si₃N₄ surface and promote the removal of N atoms from the substrate. Thus the Si₃N₄ etch rate increases with H intensity. As a result, a relative high selectivity of Si₃N₄ over SiO₂ can be achieved with addition of suitable amount of O₂ which corresponds to the maximum of H density.     

低阻钛酸锶钡基PTC材料的制备与电性能

BaTiO3正温度系数(PTC)陶瓷因其具有较高的室温电阻率而使其在低压领域中的应用受到限制,因此,有必要降低其室温电阻率.低阻化的一个途径是将金属与BaTiO3基PTC陶瓷复合来制备复合PTC材料.采用传统陶瓷工艺制备Ni/(Ba,Sr)TiO3复合PTC材料.为避免金属Ni被氧化,复合材料在弱还原气氛下烧成.为排除烧结气氛的影响而讨论金属Ni的影响,(Ba,Sr)TiO3 PTC陶瓷也在同一弱还原气氛下烧成.PbO-B2O3-ZnO-SiO2系玻璃料的加入改善了复合材料的两相分布,优化了复合材料的性能.     

Etch damage evaluation on (Bi4−xLax)Ti3O12 thin films during the etch process using inductively coupled plasma sources

The etching mechanism of (Bi_4−xLa_x)Ti₃O₁₂ (BLT) thin films in Ar/Cl₂ inductively coupled plasma (ICP) and plasma-induced damages at the etched surfaces were investigated as a function of gas-mixing ratios. The maximum etch rate of BLT thin films was 50.8 nm/min of 80% Ar/20% Cl₂. From various experimental data, amorphous phases on the etched surface existed on both chemically and physically etched films, but the amorphous phase was thicker after the 80% Ar/20% Cl₂ process. Moreover, crystalline “breaking” appeared during the etching in Cl₂-containing plasma. Also the remnant polarization and fatigue resistances decreased more for the 80% Ar/20% Cl₂ etch than for pure Ar plasma etch.     

Pentacene thin-film transistors with sol-gel derived amorphous Ba0.6Sr0.4TiO3 gate dielectric

An amorphous Ba_0.6Sr_0.4TiO₃ (BST) film with the thickness of 200 nm was deposited on indium-tin-oxide (ITO)-coated glass substrate through sol-gel route and post-annealing at 500 °C. The dielectric constant of the BST film was determined to be 20.6 at 100 kHz by measuring the Ag/BST/ITO parallel plate capacitor, and no dielectric tunability was observed with the bias voltage varying from −5 to 5 V. The BST film shows a dense and uniform microstructure as well as a smooth surface with the root-mean-square (RMS) roughness of about 1.4 nm. The leakage current density was found to be 3.5 × 10⁻⁸ A/cm² at an applied voltage of −5 V. The transmittance of the BST/ITO/glass structure is more than 70% in the visible region. Pentacene based transistor using the as-prepared BST film as gate insulator exhibits a low threshold voltage of −1.3 V, the saturation field-effect mobility of 0.68 cm²/Vs, and the current on/off ratio of 3.6 × 10⁵. The results indicate that the sol-gel derived BST film is a promising high-k gate dielectric for large-area transparent organic transistor arrays on glass substrate.     

High selectivity (SiN/SiO2) etching using an organic solution containing anhydrous HF

An etching process with high selectivity for SiN relative to SiO₂ at a low temperature is required for an etching process in LSI process. We achieved SiN film etching with high selectivity using an organic solvent (ethylene glycol dimethyl ether) containing anhydrous hydrogen fluoride. Selectivity as high as 15 was obtained at 80 °C. It was found that anhydrous HF effectively induces high selectivity for SiN relative to SiO₂. SiN film etching with high selectivity performed at low temperature for a single wafer process can be readily applied to future node technology devices.     

Photoelectrochemical performance of La3+-doped TiO2

La-doped TiO₂ thin films on titanium substrates were prepared by the sol-gel method with titanium tetrachloride as a precursor and La₂O₃ as a source of lanthanum. The heat-treatment temperature dependence of the photoelectrochemical performance of the La-doped TiO₂ film in 0.2 mol/L Na₂SO₄ was investigated by the Mott-Schottky equation, electrochemical impedance spectroscopy, and the open-circuit potential test. The results from the Mott-Schottky curves show that the obtained films all were n-type semiconductors, and the film at 300 ℃ had the highest conduction band position and the widest space charge layer. The electrochemical impendence spectroscopy (EIS) tests of the 300 ℃ film decreased most during the change from illuminated to dark. The potential of the La-TiO₂ thin film electrode was the lowest after the 300 ℃ heat treatment. The open-circuit potential indicated that the photoelectrical performance of the La-TiO₂ films was enhanced with the addition of the La element and the largest decline (837.8 mV) in the electrode potential was achieved with the 300 ℃ heat treatment.     

新型相变材料Al1.3Sb3Te使用CF4/Ar等离子体干法刻蚀

对使用CF4/Ar 混合气体刻蚀Al1.3Sb3Te的特性进行了研究。实验控制的参数是：气体流入刻蚀腔的速率,CF4/Ar 比例,O2的加入量,腔内压强以及加在底电极上的入射射频功率。总的气体流量是50sccm ,研究刻蚀速率与CF4/Ar的比例,O2加入量,腔内压强和入射射频功率的关系。最后刻蚀参数被优化。 使用优化的刻蚀参数CF4的浓度4%,功率300W,压强800mTorr,刻蚀速率达到70.8nm/min,刻蚀表面平整     

Effect of gas mixing ratio on etch behaviors of Ba2Ti9O20 (BTO) and Pt thin films in Cl2/Ar inductively coupled plasma

An investigation of the Ba₂Ti₉O₂₀ (BTO) and Pt thin films etch mechanism in the Cl₂/Ar inductively coupled plasma was carried out. It was found that an increase in Ar mixing ratio at fixed gas pressure and input power causes a fast decrease in the BTO etch rate (26.9-1.2 nm/min for 0-100% Ar) while the Pt etch rate increases slightly from 17.4-23.0 nm/min. Langmuir probe diagnostics and zero-dimensional plasma modeling provided the data on plasma parameters, steady-state composition and fluxes of active species on the etched surface. From the model-based analysis of etch kinetics, it was shown that the behavior of the BTO etch rate corresponds to the reaction-rate-limited etch regime, where the etch rate is limited neither by physical sputtering of the main material nor by the ion-stimulated desorption of low-volatile reaction products. The etch process of Pt appears in the transitional regime and is controlled by the neutral and ion fluxes together.     

Inductively coupled plasma etching of HgCdTe using a CH<Subscript>4</Subscript>-based mixture

We report results on a study on inductively coupled plasma (ICP) etching of HgCdTe using a CH₄-based mixture. Effects of key process parameters on etch rates were investigated and are discussed in this article in light of plasma parameter measurements, performed using a Langmuir probe. Process parameters of interest include ICP source power, substrate power, pressure, and CH₄ concentration. We show that the ICP etching technique allows us to obtain etch rates of about 200 nm/min, which is high enough to use this technique in a manufacturing process. We also observe that the ion bombardment has a strong influence on HgCdTe etch rate. Finally, we show that this etch rate is modified by the substitution of methane for hydrogen.     

Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity

We studied the effects of reductive annealing on insulating polycrystalline thin films of anatase Nb-doped TiO₂ (TNO). The insulating TNO films were intentionally fabricated by annealing conductive TNO films in oxygen ambient at 400 ℃. Reduced free carrier absorption in the insulating TNO films indicated carrier compensation due to excess oxygen. With H₂-annealing, both carrier density and Hall mobility recovered to the level of conducting TNO, demonstrating that the excess oxygen can be efficiently removed by the annealing process without introducing additional scattering centers.     

Remote plasma etching of titanium nitride using NF3/argon and chlorine mixtures for chamber clean applications

To avoid plasma induced erosion of chamber hardware, the application of remote plasma sources to activate the etch gases was introduced. We present results on the etch behaviour of titanium nitride (TiN) using mixtures of NF₃, Cl₂ and argon. The gas mixture was excited in a remote plasma source and then routed through a reaction chamber to study the etch behaviour of TiN samples which simulate the situation at the chamber walls. The dependency of the TiN etch rate on temperature, gas flow, composition and pressure was examined. While the temperature (studied in the range 25-300 °C) turned out to be the most sensitive parameter, the general etch rate was mainly dependent on the availability of atomic fluorine. Etch products and NF₃/Cl₂ dissociation have been monitored by quadrupole mass spectrometry and infrared spectroscopy. While NF₃ showed a high decomposition up to 96%, chlorine decomposition was not observed. However the addition of chlorine increased the etch rates up to 260% in the low pressure/low temperature regime. Surface effects of chlorine addition are indicated by X-Ray Photoelectron Spectrometry and REM surface analysis.     

Humidity sensitivity of Sr(Sn,Ti)O3 ceramics

The SrSn_1-x Ti _x O₃ system humidity sensors have been investigated in this study. The electrical conductivity of these sensors respond to the presence of moisture. The sensitivity of these humidity sensors depend on a number of factors including the material composition and the microstructure of the ceramic body. In this system, SrSn_0.5Ti_0.5O₃ was found to be quick in response to abrupt change in humidity, and the response does not change due to ambient temperature change. The response time to the humidity change is estimated to be within 15 sec.     

钛扩散铌酸锂平面波导的反应离子刻蚀

Reactive ion etching（RIE） of LiNbO₃（LN） in SF₆ plasma atmosphere was studied for optimizing the preparation conditions for LN ridge waveguides.The samples to be etched are Ti-diffused LN slab waveguides overlaid with a chromium film mask that has a Mach-Zehnder interferometer（MZI） array pattern.The experimental results indicate that the LN-etching rate(R_LN) and the Cr-etching rate(R_Cr) as well as the rate ratio R_LN/R_Cr increase with either increasing the radio-frequency（RF） power at a given SF₆ flow rate or increasing the SF₆ flow rate at a fixed RF power.The maximum values of R_LN = 43.2 nm/min and R_LN/R_Cr = 3.27 were achieved with 300 W RF power and 40 sccm SF₆ flow.When the SF₆ flow rate exceeds 40 sccm,an increase in the flow rate causes the etching rates and the rate ratio to decrease.The scanning electron microscope images of the LN ridge prepared after～20 min etching show that the ridge height is 680 nm and the sidewall slope angle is about 60°.     

High temperature transport kinetics in heteroepitaxial LaFeO3 thin films

Heteroepitaxial LaFeO₃(1 1 0) thin films with a thickness of 150 nm were grown on LaAlO₃(0 0 1) by reactive sputtering in an inverted cylindrical magnetron geometry. Equilibrium conductivity was measured as a function of partial pressure of oxygen at T=1000 °C, and logσ plotted vs. logP(O₂) showed a minimum in conductivity for P(O₂)=10⁻¹¹ atm and a linear response between 10⁻¹⁰ and 1 atm. This linear response makes thin films of LaFeO₃ a promising material for oxygen sensor applications. We have also measured the time response of the film conductivity upon an abrupt change in the partial pressure of ambient oxygen from 10⁻² to 10⁻³ atm, which was determined at 60 s for T=700 °C and <3.5 s at T=1000 °C.     

Recent progress of (Ba,Sr)TiO<Subscript>3</Subscript> thin films for tunable microwave devices

The (Ba_1−xSr_x)TiO₃ (BST) ferroelectric thin films exhibit outstanding dielectric properties, even at high frequencies (>1 GHz), and large, electric-field dielectric tunability. This feature makes them suitable for developing a new class of tunable microwave devices. The dielectric properties and dielectric tuning property of BST thin films are closely related to the film compositions, substrate types, and post-deposition process. The successful implementation of BST films as high-frequency dielectrics in electrically tunable microwave devices requires a detailed understanding of both their processing and material properties. This paper will review the recent progress of BST thin films as active dielectrics for tunable microwave devices. The technical aspects of BST thin films, such as processing methods, post-annealing process, film compositions, film stress, oxygen defects, and interfacial structures between film and substrate, are briefly reviewed and discussed with specific samples from the recent literature. The major issues requiring additional investigations to improve the dielectric properties of BST thin films for tunable microwave applications are also discussed.     

Growth and structure of wide-gap insulator films on SrTiO3

Wide-gap insulator films, CaZrO₃, CaHfO₃, LaGaO₃, and NdGaO₃, were grown on SrTiO₃(1 0 0) substrates with the aim of obtaining a gate insulator for epitaxial oxide devices. We show that CaZrO₃ and CaHfO₃ films were epitaxial and had a multi-domain in-plane structure due to their highly distorted perovskite structure. Most of the LaGaO₃ and NdGaO₃ films were polycrystalline, and therefore showed relatively high leak currents. CaHfO₃ had the best crystallinity among these four materials.     

Reactive-ion etching of Ge2Sb2Te5 in CF4/Ar plasma for non-volatile phase-change memories

Etching of Ge₂Sb₂Te₅ (GST) is a critical step in the fabrication of chalcogenide random access memories. In this paper, the etch characteristics of GST films were studied with a CF₄/Ar gas mixture using a reactive-ion etching system. We observed a monotonic decrease in etch rate with decreasing CF₄ concentration indicating its importance in defining the material removal rate. Argon, on the other hand, plays an important role in defining the smoothness of the etched surface and sidewall edge acuity. We have studied the importance of gas mixture and RF power on the quality of the etched film. The smoothest surfaces and most vertical sidewalls were achieved using a CF₄/Ar gas mixture ratio of 10/40, a background pressure of 80 mTorr, and power of 200 W.     

Ba(Zn_(1/3)Nb_(2/3))O_3微波介质陶瓷的研究进展

3G移动通信事业的迅速发展对应用于基站的微波介质谐振器陶瓷材料的Q值提出了更高的要求。Ba(Zn1/3Nb2/3)O3微波介质陶瓷材料因为具有很高的Q值、接近于零的τf和适宜的εr而备受关注。介绍了Ba(Zn1/3Nb2/3)O3系列微波介质陶瓷的结构和性能、改性研究、纳米化制备工艺及Ba(Zn1/3Nb2/3)O3-Ba(Co1/3Nb2/3)O3复合技术,以期对该领域其他研究者有所帮助。     

The slabs for the rutile TiO2(110) surface

Traditionally, we use a slab to mimic a surface and we constrain the slab to have the bulk-terminated 2D lattice constants. Here we propose a different model in which we impose no constraints, allowing all coordinates including the 2D slab itself to relax. We perform DFT calculations on both models. We find that the unconstrained slabs yield better agreement with experimental results and they have lower total energies. The optimized 2D lattice constants of the unconstrained slabs eventually converge to the attached bulk value. The total energy difference reveals that, with odd number trilayers, the unconstrained slab is much closer to the corresponding constrained slab. The surface energies both converge to the individual values with the number of atomic layers.