The Study of Different Structuring Techniques for Creation of Non-Evaporable Getters

The results of observation of different structuring techniques of thin metal layers applied in micro system technologies are presented. The Ti V getter films formed by magnetron sputtering have been explored using scanning electron and atomic-force microscopy, Brunauer-Emmett-Teller method, thermogravimetric analysis and fractal geometry. The film sorption capacity for hydrogen given by thermogravimetry was of 7.7 m3·Pa·g-1. To estimate the effective surface area, the fractal geometry tools were used and the calculated value of the specific surface area was about 155 m2/m3. The second object under investigation was a structure composed of micro- and mesoporous silicon and copper layer deposited electrochemically on the pore walls. Porous silicon when coupled with a reactive metal or alloy is expected to be an effective getter for micro system techniques. The use of porous silicon and specific conditions of depositions allows to form the structure of complex fractal type with a specific surface area of 167 m2/cm3.

Pumping characteristics of Ti-based non-evaporable getter

The application of non-evaporable getters is increasing, they have been widely used in sealed-off vacuum or controlled atmosphere devices. A new type of Ti-based sintered non-evaporable getter has been studied. The room temperature pumping speeds under three activation processes for H2 were measured as a function of sorbed gas quantities in this paper. At the same time, the optimal activation processes were discussed. The results indicate that the getter combines high porosity and large specific surface area which confirm good performances at room temperature. The threshold of activation temperature is about 500℃ and optimal pumping speed and pumping capacity can be achieved with activation temperature around 600℃ for 30 min. Besides, different configurations can be available in accordance with requirements.

Aging effect of non-evaporable getter coatings

Introduction The pumping performance of getter materials has becoming one of the hotspots in accelerator field.The recovery of pumping performance after air venting,also called aging effect,is important for applications in accelerators.Materials and methods In this work,we investigated the aging effect of Ti-V-Zr-Hf-and Ti-V-Zr-coated copper tubular chambers,and the effect of initial air exposure time on the aging properties.The samples presented hierarchically micro/nano-structures and showed a featured aging curve,giving about 9 effective pumping cycles.Conclusion The pumping performance is inversely correlated with air exposure time suggesting that the getter coated cham-bers should be properly preserved before applied as a"pump".

Intermetallic Getters Reactants for Vacuum Applications

The present work continues a series of publications devoted to the study of the sorption properties of reactive alloys based on IIA metals and the development of advanced getter materials for gas and vacuum technologies. This publication attempts to answer the current challenges in the field of gas sorption associated with the emergence of new vacuum products such as vacuum insulated glasses, electronic systems, cryogenic devices, etc. An analysis of the problems that arise here, as well as the results of sorption measurements, carried out with the participation of intermetallic phases of the composition CaLi2 and Ca0.33Li0.48Mg0.19, show that the best getter support for these new hermetically sealed products can be provided by intermetallic compounds formed in systems Li-IIA metals. Intermetallic phases of this family are easy to manufacture and demonstrate outstanding service characteristics: their specific sorption capacity is recorded high, exceeding traditional gas sorbents in this respect by at least an order of magnitude;the kinetics of gas capturing is set at the stage of alloy production, i.e., is adjustable;the temporary resistance of these phases to atmospheric gases allows to install the getter at its workplace in air, without further thermal activation. The sorption superiority of reactive intermetallics is explained by their special sorption mechanism: the gas/metal interaction is formed here as a combination of two processes, continuous growth of reaction products on a metallic surface and corrosion decay of brittle intermetallic phase under mechanical forces, which feeds the chemical reaction with a fresh surface. The advantages of sorption processes of this new type are undoubted and significant: compared with the conventional sorbents, an intermetallic getter reactant solves two important problems;it reduces production costs and increases the sorption yield.

一种高性能非蒸散型吸气剂的性能分析

非蒸散型吸气剂(NEG)是高真空和超高真空系统维持真空度的重要材料,具有高稳定性和高气体吸附性能,文章采用粉末冶金的方法制备出Zr_(59.46)V_(29.81)Al_(10.73)吸气剂,并基于小孔流导法搭建了一套吸气剂性能测试的高真空系统,分别测试了气体种类及工作温度对吸气剂性能的影响,实验结果表明:Zr_(59.46)V_(29.81)Al_(10.73)吸气剂对H_(2)、CO_(2)、N2都有很好的吸气性能,其对H_(2)的吸气性能远超N2和CO_(2),但它不吸收He等惰性气体,不同工作温度对吸气性能有很大差异,其最佳工作温度为200℃。利用X射线衍射图谱(XRD)和扫描电子显微镜(SEM)及能量色散图谱(EDS)对吸气剂进行晶相、形貌和成分分析,结果表明Zr_(59.46)V_(29.81)Al_(10.73)吸气剂表面呈现多孔状结构,其主要由α-Zr基固溶体、C15 Laves相及少量Zr_(x)Al_(y)化合物组成,多孔的结构及α-Zr基固溶体、C15 Laves相的高比例有利于吸气剂对活性气体的吸附,因此Zr_(59.46)V_(29.81)Al_(10.73)吸气剂展现出较好的性能。

超纯氩的纯化与检测

介绍了氩气纯化器的纯化工艺和超纯氩的检测方法,对超纯氩检测的结果表明,该纯化工艺满足超纯氩生产要求,该检测方法具有检测可靠性。

NEG泵抽气性能仿真模拟与测试系统设计

烧结型非蒸散吸气剂(NEG)泵HV400具有对氢及氢同位素有很高的亲和力,即使室温状态下也能发生吸附效应。为了适用于EAST托卡马克中性束注入器工作条件下稳定抽气,针对HV400的抽气性能开展了模拟仿真和实验研究。采用Molflow软件仿真分析了工作状态下不同进气量的压力分布规律与抽气性能,得到了系统平衡压力与进气量以及抽速随着平衡压力而变化的特性曲线,发现三种气体在10^(-3)~10^(-2)Pa时抽速有微小起伏,表明HV400对H_(2)、CO_(2)和N2抽气性能稳定,评估结果与实际抽速相比误差分别为1.95%、3.13%和2.09%,均在合理误差范围内。基于标准化流量计法完成了NEG泵抽速测试系统设计与平台搭建,并进行了抽速性能测试实验,实验结果与仿真模拟都验证了系统设计的可行性,且在10-3Pa量级下抽氢效果最好,为NEG泵在中性束注入器的真空系统设计提供了理论依据和技术支持。

差压法测定NEG吸氢性能

通过对定压法进行改进提出了差压法,用于测试非蒸散型吸气剂(NEG)的吸氢性能。该方法在进气室和吸气室之间安装固定流导元件,利用调节微调阀提供可控的进气流量,通过测量吸气室、进气室和参考室的压力计算NEG的吸气性能参数。利用两种NEG比较了差压法和改进的定压法所测吸气性能。结果表明:差压法测得的吸气容量比改进的定压法测得的吸气容量低0.07268 Pa·L;腔室壁面吸附能力使改进定压法的试验结果高于理论结果,而差压法的试验结果不受影响;对改进的定压法进行优化后,其计算结果与差压法的接近。差压法可以获得更准确、更有效的吸气剂性能参数,在差压法中,参考部分和试验部分同时进行测试,可缩短测试时间,减少控制进气带来的误差。

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it attains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions （from 500-750℃）.

Preparation of Ti-Mo getters by injection molding

Ti-Mo getters have been fabricated via metal injection molding (MIM) using three kinds of Ti powders with different mean particle sizes of 46 μm,35 μm and 26 μm,respectively. The surface morphology,porosity,and hydrogen sorption properties of Ti-Mo getters formed by MIM using paraffin wax as a principal binder constituent were examined. It has been proven that the powder injection molding is a viable forming technique for porous Ti-Mo getters. The particle size of Ti powders and the powder loading influence the porosity of getters,and this affects the sorption capacity of Ti-Mo getters. Ti-Mo getters produced with the Ti powders possessing a mean particle size of 35 μm using a powder loading of 40 vol.% have a high porosity,resulting in a good sorption capacity.

Different effect of NiMnCo or FeNiCo on the growth of type-Ⅱa large diamonds with Ti/Cu as nitrogen getter

In order to synthesize high-quality type-Ⅱa large diamond, the selection of catalyst is very important, in addition to the nitrogen getter. In this paper, type-IIa large diamonds are grown under high pressure and high temperature（HPHT） by using the temperature gradient method（TGM）, with adopting Ti/Cu as the nitrogen getter in Ni70Mn25Co5（abbreviated as NiMnCo） or Fe（55）Ni（29）Co（16）（abbreviated FeNiCo） catalyst. The values of nitrogen concentration（Nc） in both synthesized high-quality diamonds are less than 1 ppm, when Ti/Cu（1.6 wt%） is added in the FeNiCo or Ti/Cu（1.8 wt%） is added in the NiMnCo. The difference in solubility of nitrogen between both catalysts at HPHT is the basic reason for the different effect of Ti/Cu on eliminating nitrogen. The nitrogen-removal efficiency of Ti/Cu in the NiMnCo catalyst is less than in the FeNiCo catalyst. Additionally, a high-quality type-Ⅱa large diamond size of 5.0 mm is obtained by reducing the growth rate and keeping the nitrogen concentration of the diamond to be less than 1 ppm, when Ti/Cu（1.6 wt%） is added in the FeNiCo catalyst.

Mitigation of laser damage growth in fused silica by using a non-evaporative technique

A non-evaporative technique is used to mitigate damage sites with lateral sizes in a range from 50 μm to 400 μm and depths smaller than 100 μm.The influence of the pulse frequency of a CO 2 laser on the mitigation effect is studied.It is found that a more symmetrical and smooth mitigation crater can be obtained by increasing the laser pulse frequency form 0.1 to 20 kHz.Furthermore,the sizes of laser-affected and distorted zones decrease with the increase of the laser pulse frequency,leading to less degradation of the wave-front quality of the conditioned sample.The energy density of the CO 2 laser beam is introduced for selecting the mitigation parameters.The damage sites can be successfully mitigated by increasing the energy density in a ramped way.Finally,the laser-induced damage threshold（LIDT） of the mitigated site is tested using 355 nm laser beam with a small spot（0.23 mm 2） and a large spot（3.14 mm 2）,separately.It is shown that the non-evaporative mitigation technique is a successful method to stop damage re-initiation since the average LIDTs of mitigated sites tested with small or large laser spots are higher than that of pristine material.

Getters: From Classification to Materials Design

The demand for getters with high sorption efficiency has generated a need for resources to assist in qualification of getter materials for their practical use. This paper discusses innovative steps which should provide a dramatic improvement in the selection and application of getter technologies used in various processes. The first step was to build a natural classification of chemisorbents, from which we obtain a corresponding order of suitability related to known getter products. The classification system suggested by the authors is based on criteria which are directly connected with the sorption behavior of the material. This has lead to the challenge of developing of a computing algorithm for characterization of sorption properties of getter materials and for solving the inverse problem—the problem of designing a chemisorbent based on the requirements of a fully realized application. The employment of the new methodology is demonstrated in the example of the calculations supporting the selection of getter films for MEMS.

The Newest Getter Technologies: Materials, Processes, Equipment

The efficiency of sorption purification of gases, as measured by an improvement in product quality and/or lowering of its cost, can be significantly increased via simple solutions: the substitution of current getter technology with reactive getters;and stimulation of the material in the sorption process using mechanochemical methods instead of heating or cooling. These ideas were embodied by the authors in new sorption apparatuses and devices such as mechanochemical sorption apparatuses for production of ultra pure gases, improved gas purifiers with reactive sorbent for production of pure and high purity gases and, finally, fluidized bed columns for mass production of pure and high purity gases.

Gettering of copper impurity in silicon by aluminum precipitates and cavities

Al precipitates as well as cavities (or open-volume detects) are known for their ability to getter impuri-ties within Si. In order to compare their relative gettering strength we produced both Al precipitates and cavities atdifferent depths within one Si wafer. This was done by H+ and Al+ implantation with different energies and subse-quent annealing process, resulting in Al-Si alloy and cavities at depth of 300 nm and 800 nm, respectively. Cu wasthen implanted with an energy of 70 keV to a fluence of 1 × 1014 / cm2. The Cu implanted samples were annealed attemperature from 700℃ to 1200℃. It was found that Cu impurities were gettered primarily by the precipitated Allayer rather than by cavities at the temperature of 700～1000℃, while gettering of Cu occured in both regions at thetemperature of 1200℃. The secondary ion mass spectrometry and transmission electron microscopy analyses wereused to reveal the interaction between Cu impurities and defects at different trap sites.

Hazy Backside Gettering with a-Si: H Film

Hazy backside gettering of boron-doped <111> siljcon wafer with a-Si: H film deposited by rf glow discharge technique (rf-GD) has been investigated by SEM, optical microscope and preferential etching tech- lique. lt is evident that the deposited film can effectively getter the haze after annealing at l l00℃in wet oxy- len ambient for 120 min. The pre-crystallization annealing at 650℃ in argon ambient for 10 min enhances the gettering effectiveness. The low temperature(200～300℃) process of growing extrinsic gettering film reduces the processing contamination.

Dynamic Ni gettered by PSG from S-MIC poly-Si and its TFTs

A dynamic phosphor-silicate glass （PSG） gettering method is proposed in which the processes of the gettering of Ni by PSC and the crystallizing of α-Si into poly-Si by Ni take place simultaneously. The effects of PSC gettering process on the performances of solution-based metal induced crystallized （S-MIC） poly-Si materials and their thin film transistors （TFTs） are discussed. The crystallization rate is much reduced due to the fact that the Ni as a medium source of crystallization is extracted by the PSC during crystallization at the same time. The boundary between two neighbouring grains in S-MIC poly-Si with PSG looks blurrier than without PSG. Compared with the TFTs made from S-MIC poly-Si without PSC gettering, the TFTs made with PSC gettering has a reduced gate induced leakage current.

Oxygen gettering in Si by He ion implantation-induced cavity layer

Oxygen gettering in Si by the He induced cavity layer was investigated in this work.A cavity layer was generated in Si sample by He implantation and annealing.The morphology of the cavity layer depending on the dose of He and the annealing temperature was presented in the paper.This cavity layer may serve as an efficient oxygen gettering layer during the high temperature oxidation process and accumulate the oxygen from the annealing atmosphere as well as the implanted oxygen.The phenomenon gives the idea that the cavity layer can be employed to define the oxide formation in Si and further to facilitate the formation of the buried oxide layer(BOX) in Si aiming at the Si-on-Insulator(SOI) structure fabrication.The oxygen gettering ability of the cavity layer in Si was investigated by cross section transmission electron microscopy and auger electron spectroscopy.

Influence of rapid thermal process on intrinsic gettering in fast neutron irradiated Czochralski silicon

A rapid thermal process (RTP) was first introduced into the intrinsic gettering (IG) processes of fast neutron irradiated Czochralski (CZ) silicon. The effect of RTP conditions on bulk microdefects (BMDs) and denuded zone (DZ) was investigated. Fourier transform infrared absorption spectrometer (FTIR) was used to measure the concentration of interstitial oxygen ([Oi]). Bulk microdefects were observed by optical microscope. The results show that, according to the variation of [Oi], it is found that RTP doesn’t change the processes of oxygen precipitation in fast neutron irradiated Czochralski silicon. Perfect denuded zone, dense oxygen precipitates and defects form in the bulk of irradiated samples. With increasing temperature of RTP, the width of denuded zone decreases. Increasing RTP cooling rate, the density of Bulk microdefects increases. DZ forms in the sample that annealed in nitrogen atmosphere.

HALF银铜管道的多腔TiZrV镀膜初步研究

NEG镀膜技术可以在狭长的真空腔内实现超高真空,这对衍射极限储存环至关重要。为满足HALF光源工程对NEG镀膜真空腔的进度和质量需求,基于之前的单管NEG镀膜工作,发展了多腔镀膜技术并开展了系列技术研究,利用扫描电子显微镜,原子力显微镜,能量色散X射线能谱对NEG薄膜进行表征,利用X射线光电子能谱对NEG薄膜的激活特性进行分析。结果表明多腔系统中各真空管之间,以及与之前的单管镀膜真空管内壁薄膜的表面形貌,断面形貌,表面粗糙度和组成成分大体相同,在180℃保温2 h后,NEG薄膜表面的金属高价态被还原成了低价态并出现了Ti、Zr、V的金属态,这与之前单个镀膜真空腔的结果一致。三根此种方法镀膜真空腔串联安装,并配有SIP组成真空系统来模拟HALF储存环真空的实际工作状态。经180℃激活24 h后,腔体远端真空度为4.13×10^(-8)Pa,且真空度随时间变化缓慢变好,放置260 h后真空度可以达到3.74×10^(-8)Pa,这将为HALF真空系统工作提供有利的技术支持。