CORRELATING CHEMICAL AND WATER PURITY TO THE SURFACE METAL ON SILICON WAFER DURING WET CLEANING PROCESS

Trace metals in hydrogen peroxide and high-purity water, used in wet cleaning of wafers, is correlated to the metallic contamination of the wafer surface since metal contamination adversely impacts IC device yield. Hydrogen peroxide with different level of trace metals, ranging from 100 ppt level to 10 ppb level, is used in the experiment to determine the level of selected metal deposition on the silicon surface. Significant amounts of these trace metallic impurities can be removed by subsequent treatment of the silicon wafer by an acidified solution of water. Contamination of a wafer surface by sodium is also correlated to the level of sodium present in deionized water used in the final rinsing of the wafer. The threshold and mechanism for metal deposition for various metals on wafer surfaces are different. This information is useful in determining purity requirements for process chemicals and improving the wet cleaning process for the next generation of semiconductor devices.     

Synthesis and Magnetic Characterization of Metal-filled Double-sided Porous Silicon Samples

A magnetic semiconductor/metal nanocomposite with a nanostructured silicon wafer as base material and incorporated metallic nanostructures (Ni, Co, NiCo) is fabricated in two electrochemical steps. First, the silicon template is anodized in an HF-electrolyte to obtain a porous structure with oriented pores grown perpendicular to the surface. This etching procedure is carried out either in forming a sample with a single porous layer on one side or in producing a double-sided specimen with a porous layer on each side. Second, this matrix is used for deposition of transition metals as Ni, Co or an alloy of these. The achieved hybrid material with incorporated Ni- and Co-nanostructures within one sample is investigated magnetically. The obtained results are compared with the ones gained from samples containing a single metal.     

Fabrication of patterned nanostructures with various metal species on Si wafer surfaces by maskless and electroless process

Maskless and electroless fabrication was demonstrated to form patterned nanostructures of various metal species, based upon the process previously developed by the authors. In this process, the metallic nanostructures were formed on the surface of clean, hydrogen terminated p-(1 0 0) Si wafer with pre-patterned nanoscopic defects, which were confirmed to possess higher activity for the reductive deposition reaction of the metal ion species. The deposition was achieved spontaneously and selectively at the defect sites on the wafer surface by immersing into dilute aqueous fluoride solution containing trace amount of metal ion species. By optimizing the formation condition of the patterned defects and composition of the solution, fabrication of patterned nanostructures of various metallic species such as Au, Ag, and Co, was achieved. Formation of the patterned nanostructures to 10 μm² in extent, as well as control of the feature size of the deposits by adjusting the formation condition of the patterned defects were also attempted.     

Multiple internal reflection Fourier transform-infrared spectroscopy study on Si surface for measurement of PSL particles

Measurement of particles is crucial in wafer and photomask cleaning. In order to develop a simple method to quantify the number of particles on a semiconductor wafer, multiple internal reflection Fourier transform-infrared spectroscopy (MIR FT-IR) was used. The results using this measurement technique revealed that the number of polystyrene latex (PSL) particles deposited on a Si surface linearly increase with the concentration of PSL particles in deionized water. Furthermore, the ozonated deionized water (DIO₃) process was superior to the sulfuric peroxide mixture (SPM) process in suppressing the deposition of PSL particles. Using this measurement technique in combination with scanning electron microscopy (SEM) measurements, the number of PSL spheres in a unit area could be estimated from the peak absorbance intensity of C–H₂.     

Evaluation of citric acid added cleaning solution for removal of metallic contaminants on Si wafer surface

We have investigated cleaning solutions based on citric acid (CA) to remove metallic contaminants from the silicon wafer surface. Silicon wafers were intentionally contaminated with Fe, Ca, Zn, Na, Al and Cu standard solution by spin coating method and cleaned in various CA-added cleaning solutions. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). And the surface micro-roughness was also measured by atomic force microscopy (AFM) to evaluate the effect of cleaning solutions. It was found that acidic CA/H₂O solution has the ability to remove metallic contaminants from silicon surfaces. Fe, Ca, Zn and Na on silicon surface were decreased from the order of 10¹² atoms/cm² to the order of 10⁹ atoms/cm² even at low CA concentration, low temperature of CA solution and with short immersion time. CA was also effective in alkali cleaning solution. Fe, Ca, Zn, Na and Cu were reduced down to the order of 10⁹ atoms/cm² in CA added with NH₄OH/H₂O₂/H₂O solution without degradation of surface micro-roughness.     

Silicon surface wet cleaning and chemical oxide growth by a novel treatment in aqueous chlorine solutions

A few new reactants for the wet cleaning of silicon surfaces, for example, ozone dissolved in ultrapure water (UPW), have been proposed to replace the original RCA process using H₂O₂ solutions. In the present work we describe, for the first time, the mechanism of silicon surface oxidation by dilute solutions of elemental chlorine. Upon reaction with this highly oxidizing agent, the open circuit potential (OCP) shifted immediately to positive values, the effect being identical for both n- and p-type Si substrates. The surface transformation was firstly investigated by electrochemical impedance spectroscopy which showed successive semicircles representing RC equivalent circuits, showing a gradual growth of an insulating layer. X-ray photoelectron spectroscopy (XPS) recordings demonstrated unequivocally the formation of a pure and uniform chemical oxide layer, the possible contamination by Cl element being negligible.Moreover, the strong oxidizing and complexing properties of chlorinated aqueous solutions afford this reactant a high efficiency in surface cleaning from metal impurities. The effectiveness of this treatment was proven by AFM observation of the surface which was beforehand intentionally contaminated by Cu nuclei. The original flat surface was easily restored after a short cleaning using this new chemical reactant.This novel technique of surface treatment is promising with respect to the economy and environmental requirements, and also for the possible subsequent growth of multi-layer high-k dielectric structures.     

Particle Removal Efficiency and Damage Analysis on Silicon Wafers after Megasonic Cleaning in Solvents

The increasing complexity of semiconductor devices imposes challenging requirements on particle contamination and surface damage. To meet these requirements novel surface-cleaning processes are evaluated, which combine physical energy with organic solvents. In this work, the performance of megasonic cleaning with deionized water (DIW) and N-methylpyrrolidone (NMP) was evaluated in terms of particle removal efficiency (PRE) and damage analysis. The goal was to define an optimum process window where the PRE was maximum and the damage was minimum. Particle removal and damage analysis were performed on unpatterned silicon wafers and with patterned polysilicon lines, respectively, under identical sonic power and process parameters. A comparison between these two solvents reveals that at low sonic power the particle-cleaning performances in DIW and NMP are similar. At high sonic power, in both solvents a detailed analysis of the PRE and damage indicates a non-homogeneous trend over the surface of the wafer. More particularly, in DIW higher PRE and damage are noticed towards the edge of the wafer. In NMP, the opposite trend was observed. However, an equivalent performance was obtained at a lower sonic power in case of NMP compared to DIW. Further understanding of megasonic cleaning in solvents, and an optimization of the process parameters are the key to improve the performance of megasonic cleaning in organic solvents like NMP.     

一种太阳能硅片清洗剂的制备方法

研制一种用于工业生产中太阳能硅片的水基专用清洗剂,适用于硅片的表面清洗处理。该清洗剂以非离子表面活性剂和阴离子表面活性剂为主剂,溶液呈碱性,不含有机溶剂,无刺激性气味、成本低、具有良好的去污、清洗性能。清洗方法操作方便、无毒、对人体无危害、对环境无污染。     

The Increasing Importance of the Use of Ozone in the Microelectronics Industry

Recently the microelectronics industry is investigating the application of ozonated solutions in the cleaning of semiconductor devices as an alternative for the frequently used H₂SO₄-mixtures. The use of ozone would result in more environmentally friendly and cost-saving cleaning concepts. To optimize this new wet chemical cleaning processes, fundamental understanding of the behavior of ozone in ultrapure water is required. The decomposition and the solubility of ozone in ultrapure water were investigated as a function of pH, temperature and various additives. Some applications will also be discussed, namely the oxidation of silicon and the mechanistic aspects of the removal of organic contamination.     

微电子工艺中硅衬底的清洗技术

通过研究硅片表面颗粒的吸附原理,提出了优先吸附模型,并提出改进SC-1的配方,不仅能去除颗粒,而且能有效去除有机物。介绍一些操作方法更加简单、去除更加彻底以及更加环保的清洗新技术。通过分析微电子技术的发展要求,指出今后硅片清洗工艺的发展趋势。     

Selective metallization of silicon micromechanical devices

A new wet process for selective copper deposition on silicon surfaces is employed to achieve conformal metallization of silicon micromechanical devices. The method is based on galvanic displacement of the metal from a fluoride-containing bath. The plating bath also comprises a complexing agent, a surfactant and an anti-stress additive. Surface passivation of the displaced Cu film is effected by dodecanethiol self assembled monolayer coating. This surface passivation is found effective in reducing adhesion of micro-electromechanical systems.     

Fabrication of Ceramic Microstructures via Microcasting of Nanoparticulate Slurry

Fabrication of microstructures has been the subject of considerable attention in recent years. Techniques such as surface silicon micromachining and bulk silicon etch have emerged as practical methods for thin microstructures and processes such as LIGA (an acronym for the German words for lithography, electrodeposition, and molding) are being used to produce high aspect ratio structures from a limited set of electroformable metals and polymers. As microsystem technologies and application prospects continue to grow, it is of interest and much practical value to expand the material choices for LIGA-scale microstructures to ceramics and a broader class of metals. To this end, this paper investigates a new technique for the fabrication of high aspect ratio ceramic or metal microparts. This technique is based on capillary-driven microcasting and curing of an epoxy-based metallic or ceramic nanoparticulate slurry into a sacrificial plastic mold produced by microinjection molding. The cured preform is subsequently heated to remove the organic phase and to sinter the particulate ceramic or metallic phase. The fabrication process is discussed in the paper along with illustration of example microparts produced using the process. A theoretical model of the fluid flow during the microcasting process is developed and validated with experimental data from the fabrication of rectangular rib sections.     

1GW超超临界机组运行炉醮催化柠檬酸化学清洗

介绍浙江华能玉环电厂水冷壁下集箱上节流孔圈内四氧化三铁沉积导致水冷壁管超温情况,提出先进行化学清洗,然后给水处理方式由氧化性全挥发处理[AVT（0）]改用加氧（OT）的处理意见,并在4号机组实施。对4号机组先进行节流孔圈使用专用复合酸浸泡酸洗,然后使用催化柠檬酸对高压加热器和锅炉本体进行化学清洗,采用水冲洗、催化柠檬酸酸洗、漂洗及双氧水钝化的程序进行,化学清洗腐蚀指示片的平均腐蚀速率为1．41g／（m^2·h）,指示片和水冷壁监视管钝化膜形成良好,无点蚀和过洗现象。     

1GW超超临界机组运行炉的催化柠檬酸化学清洗

介绍浙江华能玉环电厂水冷壁下集箱上节流孔圈内四氧化三铁沉积导致水冷壁管超温情况,提出先进行化学清洗,然后给水处理方式由氧化性全挥发处理[AVT(O)]改用加氧(OT)的处理意见,并在4号机组实施.对4号机组先进行节流孔圈使用专用复合酸浸泡酸洗,然后使用催化柠檬酸对高压加热器和锅炉本体进行化学清洗,采用水冲洗、催化柠檬酸...     

Plasma-activated direct bonding of diamond-on-insulator wafers to thermal oxide grown silicon wafers

Diamond-on-insulator (DOI) wafers featuring ultrananocrystalline diamond are studied via atomic force microscopy, profilometer and wafer bow measurements. Plasma-activated direct bonding of DOI wafers to thermal oxide grown silicon wafers is investigated under vacuum. DOI wafer with chemical mechanical polishing (CMP) on the diamond surface makes a poor bonding to silicon wafers with thermal oxide. Our results show that plasma enhanced chemical vapor deposition of silicon dioxide on top of the DOI wafer, CMP of the oxide layer and annealing are essential to achieve very high quality direct bonding to thermal oxide grown on silicon wafers. Plasma activation results in the formation of high quality bonds without exceeding 550 °C in the direct wafer bonding process.     

Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays

Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.     

用于电脑磁头生产的电子级NMP质量监控方法

电子级NMP溶剂在电脑磁头生产中用作脱蜡剂、脱脂剂和污渍清洁剂。介绍了适用于电脑磁头生产的电子级NMP溶剂的质量控制项目(纯度、色度、水分、阴离子含量、硅油、微粒、pH值、重金属、有机痕量杂质、腐蚀试验等)和测试方法。     

Treatment of Wastewater Coming from Painting Processes: Application of Conventional and Advanced Oxidation Technologies

The process of car body painting is one of the manufacturing processes that may involve the use of organic solvents for surface treatments. As a result of this process, wastewaters containing raw materials and auxiliary products used during the cleaning step are produced. The main objective of this study is to find an appropriate purification technique to eliminate or reduce the contamination present in this kind of wastewater. Different treatments were investigated: ozonation, ozonation combined with hydrogen peroxide, photo-Fenton treatment, and coagulation- flocculation.     

Extraction and Analysis of Recovered Silver and Silicon from Laboratory Grade Waste Solar Cells

Silicon - In the present work, a new process is reported to recover metallic contacts and wafer from the crystalline silicon solar cell through chemical etching. 2 M KOH was used as an...