Effects of various additive gases on chemical dry etching rate enhancement of low-k SiOCH layer in F2/Ar remote plasmas

N₂ and NO gas addition to F₂/Ar remote plasmas during chemical dry etching (CDE) of low-k SiOCH layer was effective in increasing the etch rate, but the addition of O₂ decreased the etch rate. And, the injection of NO gas directly into the reactor increased the SiOCH etch rate most significantly. The addition of N₂ or NO gas contributes to an effective removal of oxygen in the SiOCH layer, by forming NO₂ and HNO₃ by-products, and of carbon species in the SiOCH layer by forming CF₄ by-product, which leads to enhancement of SiF₄ formation and in turn increase in the SiOCH etch rate.     

Hydrogen plasma etching of silicon dioxide in a hollow cathode system

Chemical etching of various materials has been observed when hydrogen plasmas are used in material processing. In the case of the deposition of diamond films the preferential etching of sp² bonded carbon is considered to be of fundamental importance. A few papers have been published which have indicated that etching by hydrogen ions is different to that by hydrogen atoms. In this paper we describe the etching of silicon dioxide by hydrogen which was plasma-activated in a molybdenum-lined RF hollow cathode. The etch rate was seen to be thermally activated but decreased with increasing plasma power. The addition of a few percentage of helium increased the etch rate. The application of a − 50 V bias to the sample holder almost doubled the etch rate indicating the importance of ion bombardment for the chemical reaction. At high plasma powers and substrate temperatures in excess of 450 °C a thin molybdenum deposit was formed on the quartz samples.     

电感耦合等离子体刻蚀InP端面的掩膜特性研究

深入研究了掩膜制作工艺对电感耦合等离子体刻蚀的InP端面的影响。首先比较了光刻胶、SiO2和Si3N4三种材料的掩膜特性，发现掩膜图形的致密性、侧壁粗糙度和垂直度等对刻蚀效果具有至关重要的影响。然后通过优化SF6等离子体刻蚀Si3N4的条件，得到了边缘平整且侧壁垂直的掩膜图形。利用这一掩膜制作技术，获得了深度达7μm的光滑垂直的InP刻蚀端面，选择比达15：1。     

Dry etching of magnesium oxide thin films by using inductively coupled plasma for buffer layer of MFIS structure

Magnesium oxide thin film has been widely used as a buffer layer and substrate for growing various thin film materials because of very low Gibbs free energy, low dielectric constant and low refractive index. The investigations of the MgO etching characteristics in BCl₃/Ar plasma were carried out using the inductively coupled plasma system. It was found that the increasing BCl₃ in the mixing ratio of BCl₃/Ar plasma causes monotonic MgO etch rate. The results showed in the BCl₃-rich plasma that the etching process is dominantly supplied by the chemical pathway through the ion-assisted chemical reaction.     

Highly selective dry etching of alternating phase-shift mask (PSM) structures for extreme ultraviolet lithography (EUVL) using inductively coupled plasmas (ICP)

Extreme ultraviolet lithography (EUVL) is the most promising candidate for next generation lithography due to its feature size of 32 nm or below. We investigated the etching properties of materials in an alternating, phase-shift mask (PSM) structure for EUVL, including a Ru top capping layer, Mo-Si multilayer (ML) and Ni etch stop layer (ESL), by varying the Cl₂/O₂ and Cl₂/Ar gas flow ratios, and the dc self-bias voltage (V_dc) in inductively coupled plasma (ICP). The Ru layer could be etched effectively in Cl₂/O₂ plasmas and Mo-Si ML could be etched with an infinitely high etch selectivity over Ni ESL in Cl₂/Ar plasmas, even with increasing overetch time.     

Patterning of porous silicon nanostructures and eliminating microcracks on silicon nitride mask using metal assisted chemical etching

A method for selective formation of reproducible, high fidelity and controllable nano and micrometer size porous Si areas over n-type Si wafers is provided. A 400 nm thick Silicon Nitride layer was used as the mask layer while Platinum and Palladium nanoparticles were deposited over the unprotected areas to obtain porous areas through metal assisted chemical etching process. Nanoparticles were deposited by electroless plating solutions containing H₂PtCl₆ and PdCl₂. Good controls over pore size and depth were obtained with well defined and sharp edges of the patterned areas. The results were compared to porous structures obtained via electrochemical etching process, indicating the superiority of metal assisted etching in terms of its simplicity as well as the ability of Silicon Nitride layer acting as the mask layer.     

Formation of aligned ZnO nanotube arrays by chemical etching and coupling with CdSe for photovoltaic application

High density aligned ZnO nanotube (NT) arrays were synthesized using a facile chemical etching of electrochemically deposited ZnO nanorods (NRs). The influence of etching time and solution concentration on the ZnO NT formation was investigated. Moreover, cadmium selenide (CdSe) nanoparticles as sensitizers were assembled onto the ZnO NT and NR arrays for solar cell application. A conversion efficiency (η) of 0.44% was achieved for CdSe/ZnO NT-based solar cell under the white light illumination intensity of 85 mW/cm². An 8% enhancement in η was observed between the CdSe/ZnO NT-based and NR-based solar cell due to the enhancement of the photocurrent density. ZnO NT arrays have been proved to have a superior ability as compared with ZnO NR arrays when employed as a semiconductor film.     

Hard a-SiC:H films formed by remote hydrogen microwave plasma chemical vapor deposition using a novel single-source precursor

The a-SiC:H films were produced by remote hydrogen plasma chemical vapor deposition (RP-CVD) from bis(dimethylsilyl)ethane as a novel single-source precursor. The effect of substrate temperature (T_S) on the kinetics of RP-CVD, chemical composition, structure, surface morphology, and properties of resulting films (density, refractive index, photoluminescence, hardness, elasticity, and resistance to wear) is reported. The T_S dependence of film growth rate implies that RP-CVD is an adsorption controlled process. The increase of T_S from 30 °C to 400 °C causes the elimination of organic moieties from the film and the formation of SiC network structure. The relationships between the relative integrated intensity of SiC IR band and film properties were determined. The films deposited at T_S = 300 °C appear to be very hard materials exhibiting small surface roughness and low intensity of blue photoluminescence (PL). They seem to be suitable protective coatings for metals to increase their wear strength.     

硅基外延β-SiC薄膜在不同刻蚀气体中的等离子体刻蚀研究

用等离子体刻蚀（PE)工艺，以四氟化碳（CF4）和六氟化硫（SF6）以及它们与氧气（O2）的混合气体作为刻蚀气体分别对Si基外延生长的β-SiC单晶薄膜进行了刻蚀工艺研究。结果表明在同样刻蚀工艺条件下，以SF6＋O2作为刻蚀气体要比以CF4＋O2作为刻蚀气体具有更高的刻蚀速率；在任何气体混合比条件下经SF6＋O2刻蚀后的样品表面都不会产生富碳（C）表面的残余SiC层；而经CF4＋O2刻蚀后的样品表面是否产生富C表面残余SiC层则与气体混合比条件有关，但刻蚀后的样品表面更为细腻。文中还对不同刻蚀气体下的刻蚀产物进行了讨论比较。     

Atomic layer deposition of tungsten using sequential surface chemistry with a sacrificial stripping reaction

Tungsten (W) films were grown with atomic layer control using a novel sequence of self-limiting surface reactions. The tungsten film growth was achieved by dividing the binary reaction WF₆+Si₂H₆→W+2SiHF₃+2H₂ into two separate half-reactions. Alternating exposures to WF₆ and Si₂H₆ in an ABAB… sequence produced tungsten deposition at temperatures between 425 and 600 K. The Si₂H₆ reactant served only a sacrificial role to strip fluorine from tungsten without incorporating into the film. FTIR spectroscopic investigations demonstrated that the WF₆ and Si₂H₆ half-reactions were complete and self-limiting at T>400 K. In situ spectroscopic ellipsometry measurements determined a tungsten growth rate of 2.5 Å/AB cycle with WF₆ and Si₂H₆ reactant exposures sufficient for complete half-reactions. The surface topography of the deposited tungsten films was flat indicating smooth film growth. The tungsten films were either amorphous or composed of very small crystalline grains and contained no measurable silicon or fluorine. These results represent the first demonstration of atomic layer deposition of smooth single-element metal films using sequential surface chemistry.     

Generation of size and structure controlled Si nanoparticles using pulse plasma for energy devices

Size and structure controlled, non-agglomerated nanoparticles are essential for many applications, such as electronics and energy storage. In this study, inductively coupled and square wave modulated RF (13.56 MHz) plasma was used to control the nanoparticle size, and a heater was installed inside the substrate to change the structure of Si nanoparticles from amorphous to crystalline. We found that the size of Si nanoparticles can be controlled by the plasma on-time. The nanoparticles were not agglomerated and grown mainly by surface deposition. The Si nanoparticles generated can be used in energy devices, such as secondary batteries, supercapacitors and solar cells.     

Fabrication of the selective-growth ZnO nanorods with a hole-array pattern on a p-type GaN:Mg layer through a chemical bath deposition process

ZnO nanorod arrays were effectively selective-grown on a p-type GaN:Mg layer through chemical bath deposition (CBD) at a low temperature hydrothermal synthesis (85 °C) with a ZnO seed layer. The 5 μm-diameter hole-array patterns of the ZnO seed layer were grown on a p-type GaN:Mg layer in aqueous solution with a mercury lamp illumination. The diameter and the height of ZnO nanorods were measured as the values of 500 nm and 3 μm, respectively. The growth orientation, surface morphology, and aspect ratio of the ZnO nanorods can be controlled and formed on the hole-array patterned ZnO seed layer. The peak wavelength of the photoluminescence spectrum was measured at 384 nm.     

Post deposition annealing of aluminum oxide deposited by atomic layer deposition using tris(diethylamino)aluminum and water vapor on Si(100)

Thin stoichiometric aluminum oxide films were deposited using tris(diethylamino)aluminum precursor and water. Changes in aluminum oxide film and interfacial regions were studied after post deposition annealing under inert ambience at 600, 800 and 1000 °C using Fourier Transform InfraRed (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy, and Scanning Transmission Electron Microscopy (STEM)/Electron Energy Loss spectroscopy (EELS) techniques. STEM/EELS analyses were also done on samples annealed in situ, i.e., inside the electron microscope at temperatures as high as 800 °C. Up to an annealing temperature of 600 °C, the atomic layer deposited alumina film was thermally stable and remained amorphous with no interfacial silica growth observed. After annealing at 800 °C for 5 min, the only change observed was a small increase in the interfacial layer thickness which was found to be mainly silicon oxide without any significant silicate content. Annealing at 1000 °C induced a significant increase in the interfacial layer thickness which consisted of a mixture of silicon oxide and aluminum silicate. The composition of the interfacial layer was found to change with depth, with silicate concentration decreasing with distance from the Si substrate. Also, the FTIR spectra exhibited strong absorption features due to Al-O stretching in condensed AlO₆ octahedra which indicate crystallization of the alumina film after annealing at 1000 °C for 5 min.     

Formation and structural characterization of nanocrystalline Si/SiC multilayers grown by hot filament assisted chemical vapor deposition using CH3SiH3 gas jets

We report on the formation and the structural characterization of nanocrystalline Si/SiC (nc-Si/SiC) multilayers on Si(100) by hot filament assisted chemical vapor deposition using CH₃SiH₃ gas pulse jets. Si rich amorphous SiC (a-Si_1 − xC_x, x ~ 0.33) was initially grown at the substrate temperature (T_s) of 600 °C with heating a hot filament at ~ 2000 °C. The following crystalline SiC layers were grown at T_s = 850 °C without utilizing a hot filament. When the a-Si_1 − xC_x layer was ultrathin (< 2 nm) on Si(100), this a-Si_1 − xC_x layer was transformed to a single epitaxial SiC layer during the subsequent SiC growth process. The Si{111} faceted pits were formed at the SiC/Si(100) interface due to Si diffusion processes from the substrate. When the thickness of the initial a-Si_1 − xC_x layer was increased to ~ 5 nm, a double layer structure was formed in which this amorphous layer was changed to nc-Si and nc-SiC was grown on the top resulting in the considerable reduction of the {111} faceted pits. It was found that nc-SiC was formed by consuming the Si atoms uniformly diffused from the a-Si_1 − xC_x layer below and that Si nanocrystals were generated in the a-Si_1 − xC_x layers due to the annealing effect during further multilayer growths.     

Ultrathin silicon oxide films deposited by synchrotron irradiation of condensed layers of silanes and water

Silicon oxide and carbide ultrathin films (less than 50 Å thick) were grown at rates of up to 1 Å s⁻¹ using a previously developed technique. To form silicon oxide, a mixture of silane or tetramethylsilane and water was condensed onto a metal surface, which was then exposed to either broad-band or monochromatized synchrotron radiation. Characterization by soft X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure showed that clean, near-stoichiometric films of self-limited thickness were grown. The results also suggested that the reactions leading to film growth were predominantly excited by electrons produced by photon absorption in the substrate.     

Preparation of CuInSe2 thin films through metal organic chemical vapor deposition method by using di-μ-methylselenobis(dimethylindium) and bis(ethylisobutyrylacetato) copper(II) precursors

Highly polycrystalline copper indium diselenide (CuInSe₂) thin films on molybdenum substrate were successfully grown at 330 °C through two-stage metal organic chemical vapor deposition (MOCVD) method by using two precursors at relatively mild conditions. First, phase pure InSe thin film was prepared on molybdenum substrate by using a single-source precursor, di-μ-methylselenobis(dimethylindium). Second, on this InSe/Mo film, bis(ethylisobutyrylacetato) copper(II) designated as Cu(eiac)₂ was treated by MOCVD to produce CuInSe₂ films. The thickness and stoichiometry of the product films were found to be easily controlled in this method by adjusting the process conditions. Also, there were no appreciable amounts of carbon and oxygen impurities in the prepared copper indium diselenide films.     

Metal-organic chemical vapor deposition of ultra-thin photovoltaic devices using a pyrite based p-i-n structure

Ultra-thin photovoltaic (PV) devices were produced by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) incorporating a highly absorbing intermediate sulphurised FeS_x layer into a CdS/CdTe structure. X-ray diffraction (XRD) confirmed a transitional phase change to pyrite FeS₂ after post growth sulphur (S) annealing of the FeS_x layer between 400 °C and 500 °C. Devices using a superstrate configuration incorporating a sulphurised or non-sulphurised FeS_x layer were compared to p-n devices with only a CdS/CdTe structure. Devices with sulphurised FeS_x layers performed least efficiently, even though pyrite fractions were present. Rutherford back scattering (RBS) confirmed deterioration of the CdS/FeS_x interface due to S inter-diffusion during the annealing process.     

Metalorganic chemical vapor deposition of Er2O3 thin films: Correlation between growth process and film properties

Er₂O₃ thin films have been grown by metalorganic chemical vapor deposition (MOCVD) at 600 °C on different substrates, including glass, Si (100) and sapphire (0001) using tris(isopropylcyclopentadienyl)erbium and O₂. The effects of growth parameters such as the substrate, the O₂ plasma activation and the temperature of organometallic precursor injection, on the nucleation/growth kinetics and, consequently, on film properties have been investigated. Specifically, very smooth (111)-oriented Er₂O₃ thin films (the root mean square roughness is 0.3 nm) are achieved on Si (100), α-Al₂O₃ (0001) and amorphous glass by MOCVD. Growth under O₂ remote plasma activation results in an increase in growth rate and in (100)-oriented Er₂O₃ films with high refractive index and transparency in the visible photon energy range.     

Effect of impinging ion energy on the substrates during deposition of SiOx films by radiofrequency plasma enhanced chemical vapor deposition process

Radiofrequency (13.56 MHz) plasma enhanced chemical vapor deposition process is used for deposition of SiO_x films on bell metal substrates using Ar/hexamethyldisiloxane/O₂ glow discharge. The DC self-bias voltage developed on the substrates is observed to be varied from − 35 V to − 115 V depending on the RF power applied to the plasma. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. The deposited films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation, nano-scratch test and thermogravimetric analysis. The characterization results show strong dependency of the SiO_x films properties on the energy of the ions impinging on the substrates during deposition. Analysis of Raman spectra indicates an increase in vitreous silica content and reduction in defective Si-O-Si chemical structure in the deposited SiO_x films with increasing ion energy impinging on the substrates. The increase in inorganic (Si and O) content in the SiO_x films is further confirmed from XPS analysis. The growth of SiO_x films with more inorganic content and defect free chemical structure apparently contribute to the increase in their hardness and scratch resistance behavior. The films show higher thermal stability as the energy of the ions arriving at substrates increases with DC self-bias voltage. The possibility of using SiO_x films for surface protection of bell metal is also explored.