Wet etching of sputtered tantalum thin films in NaOH and KOH based solutions

In this paper, a wet chemical etching technique to selectively etch tantalum thin film in sodium hydroxide and potassium hydroxide based solutions was developed. Tantalum thin films were deposited by a DC-magnetron sputtering technique on silica and yttria-stabilized zirconia (YSZ) substrates. After deposition, the films were etched in hot NaOH/ H₂O₂ and KOH/H₂O₂ based solutions with Au/Cr film as a hard mask. The etch rate was studied as a function of temperature and concentration of the etchants.     

InP/InGaAsHBT湿法化学选择腐蚀技术

用H3PO4:H2O2系和HCl系腐蚀液实现了InP对InGaAs、InGaAs对InP的湿法化学选择腐蚀,并将其应用于InP/InGaAsHBT制作,发射极面积为10μm×20μm的单管共发射极直流增益β为70,截止频率Ft和最大振荡频率Fmax分别为11GHz和12GHz.     

InGaAs／InAlAs异质结的H3PO4／H2O2系的湿法腐蚀

采用了H3PO4/H2O2系化学腐蚀液对GSMBE外延的InGaAs/InP和InAIAs/InP材料湿法腐蚀特性进行了研究,研究了不同浓度和配比对于腐蚀速率和形貌影响.结果表明该腐蚀液体系具有良好的均匀性,腐蚀速率随浓度呈指数关系,表面形貌基本不受浓度影响.在增加腐蚀液中双氧水含量时,腐蚀速率先增大后减小,表面形貌良好;增加磷酸浓度腐蚀速率亦有增大趋势,表面出现尖锥状小丘.并对腐蚀液配比变化对腐蚀特性影响及腐蚀机理进行了讨论分析.     

Enlargement of diatom frustules pores by hydrofluoric acid etching at room temperature

Based on the fact that SiO₂ can dissolve in HF solution, three kinds of diatom frustules were treated with 1% HF solution at room temperature. Given the proper reaction times (0–2 h for the diatoms Coscinodiscus and Navicula, and 0–3 h for the diatom Melosira), the size of the pores on the frustules gradually increased and the structures of the frustules remained. While HF treatment does not affect the composition, chemical bonds, or photoluminescence signature of the diatom frustules, the treatment reduces their surface areas. This method may be beneficial to diatom studies, diatom nanotechnology, and diatom device applications that make use of diatom pores.     

Properties of sealants based on alkaline-earth silicate glasses

In the present work, sealant compounds based on MO-BaO-SiO₂ (where MO is MgO, CaO, and SrO) were synthesized. These materials are used for manufacture of electrochemical devices with solid electrolytes. The sealant properties such as the temperature coefficient of linear expansion, softening temperature, and temperature of electrolyte wetting were studied, and X-ray diffraction analysis of the samples was carried out. Original Russian Text ? V.P. Ishchuk, M.V. Glumov, A.K. Demin, 2009, published in Neorganicheskie Materialy, 2009, Vol. 45, No. 4, pp. 492–495.     

Chemical etching of berlinite in sulphuric acid solutions

The aim of this work is to chemically etch AT wafers of berlinite AIPO₄ in sulphuric acid solutions in order to reach a thickness previously chosen (manufacturing of high frequency plate resonators). The kinetics of etching is studied: the decrease of thickness is followed by frequency measurement. The influence of temperature and acid concentration is measured and the evolution of surface texture is checked both by roughness measurements, resonance frequency and scanning electron microscopy methods.     

Titanium-containing hydrofluoric acid pretreatment for aluminum chemical vapor deposition

A new solution pretreatment has been developed to improve the surface morphology of chemical vapor deposition (CVD0 Al films on SiO₂. This method is simple: substrates are dipped into Ti-containing hydrofluoric acid and are dried before Al CVC. With this pretreatment, the surface morphology of the deposited Al films is improved. This improvement in surface morphology may be attributable to enhancement in Al nucleation due to the Ti adsorbed from the solution onto the substrate surface. Furthermore, the Al deposition temperature on SiO₂ was able to reduced from 260 to 210°C. Lowering of the deposition temperature also improved the surface morphology of Al films. Moreover, Al films deposited at the lower temperature have a stronger (111) orientation, which is expected to provide higher electromigration resistance.     

Characteristics of the etching of undoped silica in MCVD-fabricated optical fibers with buffered hydrofluoric acid

The etching reaction between the undoped silica cladding in MCVD-fabricated fibers and buffered hydrofluoric acid (BHF) has been studied by examining the outer diameter decrease of the fibers in a given etching time. The study has revealed that the etching reaction is not diffusion limited. The etch rate is determined and compared with values published for SiO₂ - films. We have also determined the activation energy of the process, which agrees well with values reported for SiO₂ - films.     

Compositional effects in the dissolution of multicomponent silicate glasses in aqueous HF solutions

The dissolution rate of multicomponent silicate glasses in a 2.9m aqueous HF solution is investigated as a function of its composition. The glasses studied are composed of SiO₂, B₂O₃, Al₂O₃, CaO, MgO, ZnO, Na₂O and K₂O, covering the compositions of most of the technologically important glasses. Unlike many physical properties, no linear relations are observed between the composition of the glass and its dissolution rate. The dissolution rate of a multicomponent silicate glass is found to be largely determined by two factors: The degree of linkage or connectivity of the silicate network and the concentration of SiO₂ in the glass. It is proposed that the dissolution of the glasses is preceded by the leaching of alkali and alkaline earth components present in the glass, followed by the subsequent dissolution of the leached layer. Probably fluorine species will diffuse into the leached layer to enhance the dissolution rate. Analysis of the activation energy data indicates that in some corrosive glasses the leaching itself becomes rate determining.     

Dynamics of an electrolyte-n-type silicon system during anodization in hydrofluoric acid solutions

The dynamics of the morphology of porous silicon during anodization in hydrofluoric acid has been investigated. The current-voltage characteristics and their variation with time as well as the time dependence of the voltage in an electrolyte-silicon system are highly informative for the construction of a general theory of pore formation in silicon. Attention is drawn to the possible existence of a bifurcation in the transition to harmonic oscillations of U(t) in the course of anodization. In this case, the laws governing the pore formation processes before and after the bifurcation will obviously differ. Pis’ma Zh. Tekh. Fiz. 23, 1–7 (March 12, 1997)     

Sorption properties of silicate materials based on Ca2SiO4 in humic acid solutions

The effect of humic acids (HA) in river water on the sorption properties of metallurgical slag (major component Ca₂SiO₄) was revealed in batch sorption experiments. Interaction of HA with sorbate cations in solution and with the sorbent surface affects the character of the sorption process found previously for dicalcium silicate. This interaction results in a decrease in the affinity of dicalcium silicate to multiple-charged cations [REE(III), U(VI), Th(IV)] in their sorption from river water by more than an order of magnitude. Possible chemical transformations responsible for a decrease in the sorption affinity of the silicate sorbent are discussed: complexation of HA with metal cations in the aqueous phase and competing reactions of the sorption of HA and calcium humate complexes on the surface of sorbent particles.     

Selective etching of n-type silicon in pn junction structure in hydrofluoric acid and its application in silicon nanowire fabrication

Boron is selectively implanted on the surface of an n-type silicon wafer to form a p-type area surrounded by an n-type area. The wafer is then put into a buffered oxide etch solution. It is found that the n-type area can be selectively etched without illumination, with an etching rate lower than 1?nm?min(-1), while the p-type area can be selectively etched under illumination with a much higher etching rate. The possible mechanism of the etching phenomenon is discussed. A simple fabrication process of silicon nanowires is proposed according to the above phenomenon. In this process only traditional micro-electromechanical system technology is used. Dimensions of the fabricated nanowire can be controlled well. A 50?nm wide and 50?nm thick silicon nanowire has been formed using this method.     

Thermal expansion of lead silicate glasses

The thermal expansion, when heated from 77 to 273 K, of two samples of lead silicate glass, containing 21 and 28.5 mol % PbO, has been measured. The temperature dependence of the thermal expansion coefficient,α, is in qualitative agreement with the expansion behaviour of sodium silicate glass. However, the addition of ∼ 21 mol % PbO to silica is required to produce an increase in the magnitude ofα comparable to the addition of only ∼ 10 mol % Na₂O. The differences in the magnitudes ofα for lead and soda glasses are considered in the right of previous proposals for their structures.     

Some results on chemical etching of AT-cut quartz wafers in ammonium bifluoride solutions

The kinetics of etching of AT-cut quartz plates are studied as a function of the etchant composition. Since etch rates are more rapid on a lapped surface, this investigation is essentially concerned with plates whose surfaces are free of a disturbed layer. Values of dissolution rates and a value of the activation energy determined for saturated ammonium bifluoride solution agrees quite well with published results. The dissolution rates are found to depend linearly on the concentration of etchant for concentrated solutions. A typical value of the activation energy of about 41.85 kJ mol^–1 is deduced from an Arrhenius plot of etch rate against concentration of ammonium bifluoride. This value is consistent with previously published values for fluoride solutions. Some progress in the design of an etch system for high-frequency quartz resonators can thus be made by using some of the information provided in this paper.     

Neutron-induced autoradiography of lithium silicate glasses

Immiscibilities between silica and lithium disilicate were investigated. Alpha particles ejected from ⁶Li atoms by thermal neutrons were used to autoradiograph surfaces representing diffusion-zone cross-sections. Etchant-enlarged alpha tracks in nitrocellulose disclosed the distribution of lithium. For autoradiography, procedural details were established, suitable operating conditions were selected, and the method was calibrated. For diffusion, adequate couples had to be prepared. Subsequent experiments indicated phase separations along an 885° C isotherm of the silica-lithium disilicate system. There was evidence of metastable compositions near 30, 25, 20, 16, 11, and 7 mol % of lithia in silica. These results have been given a very tentative interpretation: The first two compositions may correspond to metastable extensions of liquidus boundaries, projected through a eutectic point of the system. The third and sixth compositions are probably points on a liquid-liquid miscibility boundary, and the fourth and fifth compositions could be on an associated spinodal boundary.     

Luminescence of electron-irradiated nanoporous silicate glasses

It is experimentally demonstrated that the point electron-beam irradiation of a nanoporous silicate glass leads to the appearance of or significant increase in the UV-excited luminescence from the entire sample in the spectral intervals of 500–700 and 900–950 nm. The observed effect is related to (i) partial reduction of SiO₂ and H _x SiO _y phases by electrons that spread via through pores in the glass and (ii) an increase in the number of Si-H and Si-OH bonds.     

GaAs/InGaP异质界面的湿法腐蚀

对柠檬酸系、盐酸系溶液腐蚀GaAs/InGaP异质结构材料体系时出现的腐蚀不均匀现象进行了实验研究,采用原子力显微镜(AFM)、电子显微镜、台阶仪等分析了不同腐蚀条件下GaAs/InGaP异质界面的腐蚀形貌,找到了简单有效的办法,可获得很好的表面平整度,同时侧向腐蚀也较小.     

Morphology of pores produced in <Emphasis Type="Italic">n</Emphasis>-Si {100} by etching in hydrofluoric acid solutions

Variations in the contours of pores produced in n-type silicon by electrochemical etching in hydrofluoric acid solutions are interpreted in terms of the mechanism underlying the chemical interaction of the etchant with silicon and the anisotropy of the etchant–silicon system. Mathematical expressions are proposed which describe the contours and limiting radial sizes of pores forming at the very beginning of the etching process (~10–15 s).     

Pyrex玻璃金属化凹坑的湿法腐蚀

为在Pyrex玻璃基片上湿法腐蚀出易于金属化(如电镀等)的深凹坑(或凹槽),选用HF:HNO3:H3O为腐蚀液,分别以Cr/Au(30nm/300nm,溅射)加光刻胶(15μm)和Cr/Pt(30nm/300nm,溅射)加光刻胶(15μm)作为掩膜进行腐蚀实验.实验发现在Cr/Pt/光刻胶掩膜下,Pyrex玻璃的腐蚀凹坑横向钻蚀小(钻深比1.34:1),侧壁倾斜光滑,并在凹坑(深约28μm)内成功地电镀了焊盘.该实验结果对要求高深宽比沟槽的微流体器件的制造也有一定参考意义.