Sustainable Technologies for the Regeneration of Acidic Tin Stripping Solutions used in PCB Fabrication

Electroplated tin deposits are used as etch resists during the processing of Printed Circuit Boards (PCB). The tin coating protects the copper tracks during etching but is subsequently removed (stripped), to expose the defined copper circuitry. The commonly used stripping solutions are based on nitric acid and after use they represent a very acidic waste product with a high metal content. The disposal of these spent strippers is typically via offsite neutralisation and precipitation followed by subsequent landfill. This is clearly a non-sustainable waste of valuable resources and a practice that is increasingly undesirable as environmental legislation becomes more stringent. This paper outlines the results of a scoping study carried out into current industry practices for tin- stripping and details components of a potential integrated treatment system for these stripping solutions. Individual technologies for such an integrated system incorporate the recovery of the tin oxide by filtration, the concentration and re-use of nitric acid solutions by diffusion dialysis and the reclamation of other metals, i.e., copper by electrowinning.     

Dislocation of Cz-sapphire substrate for GaN growth by chemical etching method

The diameter of Czochralski （Cz） sapphire crystals is 50 ram. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing（CMP） method using alkali slurry with SiO2 abrasive. After obtaining the smooth surfaces, the chemical-etching experiments were processed by using fused KOH and NaOH etchants at different temperature for different times. The dislocation was observed by means of optical microscope and scanning electron microscope. The clear and stable contrast images of sample etching pits were observed. On the whole, the dislocation density is about 104-105 cm^-2. Comparing the results under the conditions of different etchants, temperatures and times during the etching proceeding, it was found that the optimal condition for dislocation displaying is etching 15 min with fused KOH at 290 ℃. At the same time, the formation of the etch pits and the reducing method of dislocation density were also discussed.     

High density large area hydrogen plasma by hollow cathode plasma array

Hydrogen plasma becomes an alternative to the conventional oxygen plasma in stripping photoresist in the next generation semiconductor processing because the conventional oxygen plasma is known to degrade ultralow dielectric constant films by depleting carbons from the films. An array of hollow cathode plasma is designed to have uniform and high density hydrogen plasma. From many combinations of cavity size and distribution, it is found that cylindrical ceramic cavity with 6 mm inner diameter, 10 mm depth and 30 mm spacing between neighboring cavities shows the widest process window. Nineteen cavities are engraved into the cathode plate of 200 mm diameter. Ceramic cavities are needed to survive against energetic ion bombardment. Dependence of the stripping rate on mixture ratio of N₂/H₂, gas flow rate, chamber pressure and RF power is investigated, and we have found that a stripping rate of more than 260 nm/min with 7% uniformity can be achieved when chamber pressure is 213 Pa, gas flow rate 10000 sccm, N₂/H₂ mixture ratio of 3:7 and RF power 2.5 KW. This high density hydrogen plasma in the order of 10¹¹/cm³can be a very effective method of photoresist stripping in the dual damascene process of copper metal and low-k dielectrics where oxygen plasma cannot be used.     

锌对SnxZn/Cu界面微空洞的影响

通过向锡钎料中添加不同含量的Zn元素,系统研究了锌对SnxZn/Cu(x=0,0.2,0.5,0.8(质量分数,％))界面处柯肯达尔空洞形成的影响.结果表明,经热老化处理后,纯Sn/Cu接头中的Cu3 Sn层和Cu3 Sn/Cu界面出现了大量柯肯达尔空洞.然而随着Zn元素含量的增加,反应界面处的Cu3Sn层逐渐变薄甚至消失,柯肯达尔空洞也随之显著减少或消失;锌在反应界面处的富集现象越来越显著.锌参与了界面反应,形成了(Cu,Zn)6Sn5相、Cu6(Sn,Zn)5相和Cu-Zn固溶合金,其中Cu-Zn固溶合金层可以显著影响铜的界面扩散.Zn元素直接参与了界面扩散,在很大程度上缓和铜和锡的不平衡扩散,从而有效抑制了柯肯达尔空洞的形成.     

Glass surface modification by lithography-free reactive ion etching in an Ar/CF4-plasma for controlled diffuse optical scattering

Micro- and nanostructuring of glass surfaces is normally realized by pattern transfer via a lithographical process including wet chemical or reactive ion (i.e. dry) etching. In this contribution we introduce a technology for roughening glass surfaces without lithography. We make use of self-masking that appears under certain process parameters during reactive ion etching in an Ar/CF₄-plasma. This way a multitude of different surface roughness morphologies can be realized. In a first step an about 10 nm thin unstructured metallic layer (preferably of Cu) is deposited onto the cleaned glass substrates. This layer is not laterally structured by lithography, but rather by nucleation or coalescence. These metal spots impose an initial etch pattern on the glass surface, which is getting increasingly coarse during further etching. Choice of the metal layer and variation of the etch parameters like etch time, total pressure, gas fluxes of Ar and CF₄, ion energy, and plasma density affect the resulting morphology. Each morphology is characterized by its root-mean-square surface roughness and the correlation length of its height profile. We mainly used borosilicate thin glass D263?T from Schott AG, Mainz, Germany as substrates. The resulting individual surface structures like cones, hemispheres, pits, and trenches possess typical dimensions of 0.1 to 0.8 μm. The diverse surface roughness morphologies show individual scattering characteristics so that nearly any proportion of diffuse to total transmitted light power is realized. Thus user-defined light diffusers are feasible. The process can be scaled up to large substrate sizes.     

Fabrication of SMD 32.768 kHz tuning fork‐type crystals: Photolithography and selective etching of an array of quartz tuning fork resonators

Negative photoresist photolithography was used to etch array of quartz tuning forks for use in Qualcomm® mobile station modem (MSM)‐3000™ central processing unit (CPU) chips of code division multiple access (CDMA), personal communication system (PCS), and global system for mobile communication (GSM) units. It was found superior to positive photoresist photolithography. Quartz tuning fork blanks with optimum shock‐resistant characteristics were designed using finite element method (FEM) and processing condition was devised for reproducible precision etching of Z‐cut quartz wafer into array of tuning forks. Tuning fork pattern was transferred via ordinary photolithographical chromium/quartz glass template using a standard single‐sided aligner and subsequent negative photoresist development. Tightly adhering and pinhole‐free 600/2000 Å chromium/gold mask is coated over the developed photoresist pattern which was subsequently stripped in acetone. This procedure was repeated on the backside of the wafer. With protective metallization area of tuning fork geometry thus formed, etching through quartz wafer was done at 80°C in a ± 1.5°C controlled bath containing concentrated solution of ammonium bifluoride to remove unwanted area of the quartz wafer. Surface finish of quartz wafer prior to etching and the quality of quartz crystals used primarily affected the quality of quartz wafer surface finish after quartz etching. At 80°C, selective etching of 100 μm quartz wafer could be effected within 90 min. Reproducible precision selective etching method has thus been established and enables mass production of miniature tuning fork resonators photolithographically.     

A study on the reactive ion etching of SiC single crystals using inductively coupled plasma of SF<Subscript>6</Subscript>-based gas mixtures

Inductively coupled plasma reactive ion etching (ICP-RIE) of SiC single crystals using SF₆-based gas mixtures was investigated. Mesas with smooth surfaces with vertical sidewalls were obtained, with an etch rate of about 360 nm/min, roughness of about 0.8 nm, and verticality of 85° at optimum conditions. Efforts to increase the etch rate by increasing bias power resulted in a trenching effect. Sloped sidewalls (about 50°) could be obtained by performing RIE (without ICP power) with a photoresist or SiO₂ etch mask. Results of various surface characterizations and I-V measurements using an Au Schottky barrier diodes indicated little contamination and/or damage on the etched SiC surfaces.     

Void formation and alloy enrichment during anodizing of aluminium alloys containing cadmium, indium and tin

The formation of voids at the alloy/anodic film interface and the enrichments of alloying elements in a thin alloy layer immediately beneath the anodic film as a consequence of anodizing have been examined for Al-0.28 at.% In alloy and Al-0.5 at.% Cu alloys containing 0.11 at.% Cd, 0.07 at.% In or 0.27 at.% Sn. Fine voids are formed for the indium- and tin-containing alloys for the selected conditions of anodizing, which is suggested to be associated with the relatively low Pilling–Bedworth ratios of the alloying element oxides incorporated into the anodic films. Thus, the formation of voids is dependent upon oxidation of the alloying element. Consequently, no voids were resolved for the cadmium-containing alloy for which limited or no oxidation of cadmium occurred. The enrichment of the binary alloy was equivalent to 3.5 at.% In, with enrichments of the ternary alloys to the ranges 11–16 at.% Cu and 2–7 at.% Cd, In or Sn respectively, for an assumed 2 nm thick enriched layer.     

Effects of pretreatment on the aluminium etch pit formation

The effect of chemical pretreatments on the electrochemical etching behavior of aluminium was investigated with the topographic studies of surface and the analysis of initial potential transients. Two-step pretreatments with H₃PO₄ and H₂SiF₆ result in a high density of pre-etch pits on aluminium surface by the incorporation of phosphate ion inside the oxide film and the removal of surface layer by aggressive fluorosilicic acid solution. It generates a high density of etch pits during electrochemical etching and results in the capacitance increase of etched Al electrode by expanding the surface area, up to 61.3 μF/cm² with the pretreatment solution of 0.5 M H₃PO₄ at 65 °C and 10 mM H₂SiF₆ at 45 °C.     

Raman microscopy of chromate interactions with corroding aluminum alloy 2024-T3

Raman microspectroscopy was used to observe actively corroding aluminum alloy 2024-T3 directly in a solution containing NaCl and dilute K₂Cr₂O₇. Raman spectra acquired in and near corrosion pits allowed identification of two products of Cr^VI interactions with the corroding alloy. If the alloy potential was fixed negative of the pitting potential, an Al^III-Cr^VI mixed oxide formed in formerly active or metastable pits. This mixed oxide is similar to a covalent compound which can be made synthetically by adding NaOH to solutions containing Al³⁺ and CrO₄²⁻. If the alloy potential was held positive of the pitting potential, the corrosion product was primarily a Cr^III-Cr^VI mixed oxide, formed by partial reduction of Cr^VI to Cr^III by exposed Al metal or by H₂. At the pitting potential, a mixture of Al^III and Cr^III mixed oxides was observed, with the Al^III species located primarily within pits. A model for the formation mechanism of the mixed oxides is proposed, and the consequences of the findings to corrosion inhibition by Cr^VI are considered. In particular, the concentration of Cr^VI in and near pits driven by mixed oxide formation may serve to direct the inhibitor from the solution to sites of corrosion.     

TREATMENT OF METALS, POLYMER FILMS, AND FABRICS WITH A ONE ATMOSPHERE UNIFORM GLOW DISCHARGE PLASMA (OAUGDP) FOR INCREASED SURFACE ENERGY AND DIRECTIONAL ETCHING

1. IntroductionUntil recently plasma processing procedures that use glow discharges fOr sterilization,deposition and etching of thin films, increasing the surface energy of materials, and otheraPplications have been conducted under vacuum at pressures below 10 Torr, where stablepla8mas are easily generatedI1l2]. This has tended to limit such plasma processing tohigh value workpieces, as the re8ult of the large caPital cost of vacuum systems and theproduction constraillts imposed by batch pro…     

Prediction of plasma etch process by using actinometry-based optical emission spectroscopy data and neural network

Optical emission spectroscopy (OES) data were used to construct neural network models of plasma etch process. According to a statistical experiment, actinomeric OES data were collected from the etching of oxide thin films in a CHF₃–CF₄ magnetically enhanced reactive ion etching system. The etch responses modeled include an etch rate, a profile angle, and an etch rate-nonuniformity. Principal component analysis was applied to reduce the dimensionality of OES data. Three data variances adopted are 98, 99, and 100%. For each data variance, backpropagation neural network models were constructed. The training factors optimized by genetic algorithm include the training tolerance, magnitude of initial weight distribution, number of hidden neurons, and two gradients of activation functions in the hidden and output layers. The presented models demonstrated much improved predictions over the previous ones. The improvements were 43, 61, and 17% for the etch rate, profile angle, and etch rate-nonuniformity models, respectively.     

含硫金刚石的合成及杂质分析

本文分别用Ni70Mn25Co5合金粉末和含添加剂硫的Ni70Mn25Co5合金粉末作触媒合成了金刚石单晶，通过对比，发现添加剂硫的引入使得金刚石内的包裹体含量增加，使晶体表面出现熔坑；利用X射线荧光光谱对晶体的杂质成分、相对含量进行了分析，发现杂质元素锰、硫的含量随着触媒中硫的添加量的增加呈增加趋势，由此推测在金刚石生长过程中生成了难熔的MnS，MnS以包裹体的形式进入金刚石中，在一定程度上破坏了金刚石的晶格排列，使得表面出现熔坑。     

Säurekorrosion und Korrosionsinhibition auf atomarem Maßstab

Atomic scale studies of corrosion and corrosion inhibition High-resolution, in-situ scanning tunneling microscopy studies of the surface structure and the microscopic mechanisms of the dissolution of Cu(100) in hydrochloric and sulfuric acid solutions at low dissolution rates are presented. On clean Cu surfaces dissolution proceeds exclusively at surface defects in form of atomic steps and is strongly dependent on the anion species. Foreign metal impurities can either inhibit Cu dissolution via pinning or enhance it by inducing the formation of etch pits. In the presence of inhibiting, organic adlayers the removal of Cu atoms at the steps is significantly slower and corrosion is determined by the formation of etch pits at higher potentials.     

ITO靶刻蚀时间对沉积ITO薄膜光电性能的影响

在磁控溅射过程中,通过观察在2～50 h的刻蚀时间下制备的ITO薄膜的表面形貌,研究了在磁控溅射过程中ITO靶表面的黑色凸起的形成过程,并探讨了刻蚀时间对沉积ITO薄膜的光电性能的影响。结果表明,随着刻蚀时间的增长,ITO靶材表面的In和Sn分布发生变化,导致ITO膜不均匀。薄膜的电学和光学性能因结节的形成而显著退化。而当刻蚀时间在40 h以下时,ITO薄膜的光电性能变化不大。然而,当蚀刻时间继续延长,薄膜的光电性能会迅速恶化。     

Adsorbed corrosion inhibitors studied by electron spectroscopy: Benzotriazole on copper and copper alloys

Surface films formed by adsorption of benzotriazole (BTA), on copper and copper alloys have been studied by X-ray photo-electron spectroscopy (XPS). It is found that on both copper and copper-nickel alloys, benzotriazole forms a Cu(I)BTA surface complex. For the copper-nickel alloys the time taken to form the Cu(I)BTA film is dependent on the alloy composition. The Cu(I)BTA films were found to oxidize rapidly to a Cu(II) species on removal from the liquid phase. Surface films formed by BTA on 70 Cu : 30 Zn alloy were found to contain both copper and zinc, the copper again being in the Cu(I) state.A study of the adsorption of BTA on cathodically reduced copper surfaces strongly supports previous suggestions that the presence of Cu₃O facilitates formation of the surface film.     

Al含量和烧结温度对Ti_(50)Ni_(50)与Ti_(47)Ni_(47)Al_6合金耐蚀性的影响

采用粉末冶金方法制备了Ti_(50)Ni_(50)与Ti_(47)Ni_(47)Al_6合金,通过极化曲线、配备能谱分析的扫描电镜测试手段研究了Al含量和烧结温度对烧结合金耐蚀性的影响。结果表明:1080℃烧结Ti_(50)Ni_(50)合金表现为钝化特征,蚀孔尺寸较小,弥散分布;Al含量为6%时,合金表现为活性溶解,蚀孔尺寸及腐蚀区域面积显著增加,耐蚀性降低;烧结温度提高至1180℃时,合金重新表现为钝化,蚀孔尺寸及腐蚀区域面积显著减小,耐蚀性最佳。     

Nonmetallic inclusions in alloys of the YuNDK24 type

Conclusions Different types of inclusions have various effects on the type of microstructure formed. Sulfides are the most active. Corundum and carbides affect the structure to a lesser extent than sulfides.Relatively large sulfide inclusions, with an expansion coefficient differing from that of the base metal, create stress fields during cooling (heating), inducing the formation of lattice defects visible as etch pits and subboundaries.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 43–44, September, 1970.     

ESCA studies of the composition profile of low temperature oxide formed on chromium steels—II. Corrosion in oxygenated water

ESCA (Electron Spectroscopy for Chemical Analysis) has been used to analyse the chemical composition of passive films formed on chromium steels with 4–30% Cr at 25 and 70°C in oxygenated water for different times. The composition-depth profile of the films has been investigated by successive stripping of the film by ion etching.The composition of the film varies with exposure time: short time yields an Fe---Cr ratio corresponding to that of the alloy; prolonged exposure produces increasing enrichment of chromium through the whole layer, with the highest concentration at the outer surface. The passive film generally seems to consist of two layers: outermost one of (Cr(OH)₃) and underneath one of iron-chromium oxide (Fe_1+xCr_2−xO₄. The low alloy steels (3·9 and 7·8%Cr) were passive for a limited time during which the Cr enrichment was high (8 times); after breakdown of the chromium-rich passive layer, it was replaced by FeOOH.When a dry-formed oxide film, which consists mainly of iron oxide, is exposed to water, its composition slowly changes until that of a water-formed film is reached.     

A356����Ͻ��п���̵���֯�ݻ�

 铝硅合金经硝酸、氢氟酸出光后，形成了基体晶界和晶粒两部分，文章用扫描电镜观察了这两部分锌晶粒的生长过程，用能谱仪测试了浸锌层的组成；对比了不同浸锌温度锌晶粒的形貌。结果表明，锌晶粒优先在晶界处的腐蚀坑边缘、近晶界处、基体晶粒的孔洞边缘及晶粒内高活性点区域生长，并由腐蚀坑、孔洞边缘向周围及由近晶界处向基体晶粒中心扩散，直至布满大部分基体；浸锌初期发现锌晶粒之间有晶须生成。随浸锌温度的升高，锌晶粒逐渐长大，并由粒状转变为片状。