化学机械抛光机理研究

虽然CMP过程材料去除机理得到了广泛深入研究,取得了许多理论成果,但是每一种理论都存在着或多或少的缺陷,没有一种理论完全正确的解释了CMP的机理。在众多CMP材料去除机理里,比较得到认可的是抛光垫、颗粒和工件表面三体磨损理论和化学腐蚀理论[1~4]。但是表面质量较好的工件在CMP之后没有观察到划痕,三体磨损理论受到了极大的挑战。而化学腐蚀理论很难解释腐蚀速度和腐蚀后表面质量关系[5,6]。本文结合CMP过程的实际环境,实验得到了化学机械抛光的抛光机理。     

铜化学机械抛光中电化学理论的应用研究

概述了电位-pH图、极化曲线、交流阻抗谱和开路电压测试等电化学方法在铜化学机械抛光(Cu—CMP)中的应用，并分析了采用电化学方法进行CMP分析存在的问题，指出采用以上电化学方法进行Cu—CMP分析有利于对Cu—CMP的过程的理解，并可以为抛光液组分的选配提供依据。     

铜布线化学机械抛光技术分析

对用于甚大规模集成电路(ULSI)制造的关键平坦化工艺——铜化学机械抛光(CMP)技术进行了讨论。着重分析了铜化学机械抛光的抛光过程和相关的影响因素；根据现有的研究成果主要介绍了铜化学机械抛光的化学材料去除机理；在分析抛光液组成成分的基础上，总结了现有的以H2O2为氧化剂的抛光液和其他酸性、碱性抛光液以及抛光液中腐蚀抑制剂的研究情况；指出了铜化学机械抛光今后的研究重点。     

集成电路芯片制造中电化学机械平整化技术的研究进展

大马士革(Damascene)结构的Cu/低k介质材料互连技术为集成电路芯片制造提出了方向和挑战。电化学机械平整化(ECMP)作为化学机械平整化（CMP）的一种拓展加工手段,可对传统CMP技术进行补偿,可对含有易损多孔电介质材料的新型互连结构进行低压力平整化。比较了ECMP和CMP 的特点,
对ECMP技术的研究现状和发展趋势进行了综述。指出ECMP过程控制的深层次的技术基础是摩擦电化学理论,只有深入系统地研究ECMP过程中的外加电势、摩擦磨损、化学反应三者间的相互作用,才能揭示ECMP过程中材料的加速去除原理和超光滑无损伤表面的形成机理。     

表面活性剂在集成电路多层布线CMP工艺中的应用研究

随着集成电路(IC)特征尺寸不断缩小,集成电路多层布线加工精度面临更高的要求,而化学机械抛光(CMP)凭借化学腐蚀和机械磨削的耦合协同作用,成为实现晶圆局部和全局平坦化的唯一可靠技术。抛光液作为CMP工艺中关键要素之一,其主要成分表面活性剂的选择以及含量会严重影响晶圆的表面质量。介绍表面活性剂的特性及其类型,回顾近年来国内外表面活性剂在集成电路多层布线相关材料CMP中的应用及作用机制,归纳总结得出表面活性剂在CMP过程中可以起到缓蚀保护、增强润湿、分散磨料、去除晶圆表面残留污染等多种作用,具有广泛的应用领域。同时,对表面活性剂在CMP中的应用前景进行了展望。     

CMP材料去除机制的研究进展

CMP已成为IC制造中的关键工艺之一,其材料去除机制及理论模型的研究已经成为当前CMP研究的热点.综述基于流体润滑、磨粒磨损、化学作用、原子/分子去除等不同机制的集成电路芯片化学机械抛光(CMP)材料去除率的理论模型的研究现状和进展,分析和比较基于不同假设的理论模型,展望CMP材料去除机制研究的未来发展方向.CMP理论真正应用于实际生产指导,许多影响因素的定量研究还要细化,抛光盘的黏弹性和抛光液的流体动力学性能对CMP过程的影响还需深入研究.     

无磨料化学机械抛光的研究进展

无磨料化学机械抛光(AFP)技术克服传统化学机械抛光(CMP)易产生凹陷、腐蚀和微观划痕等表面损伤的特点,成为解决半导体晶片上Cu膜表面平坦化的重要技术;AFP已广泛用于铜大马士革层间互连及其他材料的加工.综述了AFP技术的研究现状,指出了AFP急待解决的技术和理论问题,并对其发展趋势进行展望.     

添加剂对电诱导GaN晶片化学机械抛光的影响

为研究添加剂对氮化镓(GaN)晶片化学机械抛光(CMP)材料去除率的影响,采用直流电源对n型GaN晶片进行电化学刻蚀,利用X射线光电子能谱(XPS)和原子力显微镜(AFM)研究电诱导辅助下GaN晶片CMP过程中,对苯二甲酸(PTA)和H 2O 2对其材料去除的影响。结果表明:在添加电流的条件下,随着H 2O 2体积分数增大,GaN材料去除率先升高后降低;随着PTA浓度的增加,GaN材料去除率先增加后减少;在H 2O 2体积分数为4%,PTA浓度为10 mmol/L条件下,GaN晶片的化学机械抛光材料去除率最高,为693.77 nm/h,抛光后GaN晶片表面粗糙度为0.674 nm;通过XPS分析,电诱导后GaN晶片表面的Ga 2O 3含量增加,表明电流作用促进了GaN材料表面的氧化腐蚀作用,进而提高了其CMP材料去除速率。     

雾化施液CMP工艺及材料去除机制研究

介绍通过雾化供液方式进行化学机械抛光(CMP)的工作原理以及试验装置设计,通过雾化供液抛光工艺试验考察该方法的抛光效果,分析其材料去除机制。结果表明,雾化施液CMP方法的抛光浆料利用率高,在达到去除率为257.5 nm/min,表面粗糙度小于3.8 nm的抛光效果时,雾化抛光液消耗量仅为350 mL。雾化抛光材料去除机制是表面材料分子级氧化磨损去除,即通过抛光液中氧化剂的化学作用使表面原子氧化并弱化其结合键能,通过磨粒的机械作用将能量传递给表面分子,使表面分子的能量大于其结合键能而被去除。     

聚苯乙烯-二氧化硅复合颗粒对铜层的化学机械抛光性能

随着集成电路线宽变窄,要求铜互连表面具有更低的表面粗糙度,对化学机械抛光(CMP)技术提出更高的要求。采用聚苯乙烯(PS)-二氧化硅(SiO2)复合颗粒作为铜层CMP的抛光磨粒,研究出PS-SiO2核壳结构的形成条件,分析新型抛光液体系中各颗粒含量、pH值等因素对Cu抛光效果的影响,通过X射线光电子能谱(XPS)、扫描电镜(SEM)等手段探讨其中的抛光机制和颗粒残留等问题。结果表明:较之PS、SiO2颗粒抛光液,复合颗粒抛光液抛光Cu后,获得更大的去除和更好的表面质量,且与抛光过程中摩擦因数的关系相符合。     

Material Removal Mechanism of Copper CMP from a Chemical�CMechanical Synergy Perspective

The material removal in chemical?Cmechanical planarization/polishing (CMP) of copper involves both chemical and mechanical effects. The roles of chemical corrosion, abrasive wear, and their synergistic effects on the material removal mechanism were studied by electrochemical analysis and nano-scratching method using atom force microscopy, respectively. Combining with the results of CMP experiments, dominant factors (chemistry and mechanics) in slurries within the range of pH 3.0?C10.0 were assessed. Consequently, a removal mechanism map of copper CMP depending on pH values was constructed. In the alkaline slurry, the wear?Ccorrosion effect predominated in the material removal at pH 8.0 and 9.0; while the copper removal mechanism changed to corrosion?Cwear action in the acidic slurry from pH 4.0 to 6.0, and good surface quality was also obtained. The results and the strategies provide thorough understanding of the material removal mechanism and further optimization of the CMP process.     

A micro-contact and wear model for chemical–mechanical polishing of silicon wafers

A micro-contact and wear model for chemical–mechanical polishing (CMP) of silicon wafers is presented in this paper. The model is developed on the basis of elastic–plastic micro-contact mechanics and abrasive wear theory. The synergetic effects of mechanical and chemical actions are formulated into the model. A close-form equation of material removal rate from the wafer surface is derived relating to the material, geometric, chemical and operating parameters in a CMP process. The model is evaluated by comparing the theoretical removal rates with those experimentally determined. Good agreement is obtained for both chemically active and inactive polishing processes. The model reveals some insights into the micro-contact and wear mechanisms of the CMP process. It suggests that the removal rate is sensitive to the particle concentration in the slurry, more sensitive to the applied load and operating speed and most sensitive to the surface hardness and slurry particle size. The model may be used to study the effects of different materials, geometry, slurry chemistry and operating conditions on CMP processes.     

An investigation of the corrosive wear of stainless steels in aqueous slurries

Pumping installations made of stainless steels have been widely used for transporting slurries in chemical process industry. However, knowledge of the attack of stainless steels due to corrosive wear in two-phase liquid-particle flow is still incomplete. This paper studies the behaviors and mechanisms of corrosive wear for two austenitic stainless steels, 24Cr-25Ni-4Mo and 18Cr-12Ni-2Mo, using a rotating disc apparatus made by the authors. The two components, wear by slurry abrasion and corrosion, within the corrosive wear process, are first examined individually. Then the synergistic effect between wear and corrosion is investigated. The research we have done shows that corrosive wear rate of samples is closely related to such factors as the solution, type of abrasive, flow velocity, impingement angle and temperature. In addition, a threshold of flow velocity exists which is called the breakaway velocity V_k, above which the corrosive wear rate increases rapidly. The combined effects of abrasion and corrosion result in a total wear loss larger than the added effects of each process alone. An analytical model is developed which would help to reveal the mechanisms of the corrosive wear processes.     

Mathematical modeling of tool wear rate in ultrasonic machining of titanium

Ultrasonic machining is a mechanical material removal process used to erode holes and cavities in hard or brittle workpiece by using shaped tools, high-frequency mechanical motion, and an abrasive slurry. In the present study, outcome of the Taguchi model has been used for developing a mathematical model for tool wear rate; using Buckingham’s π-theorem for stationary ultrasonic machining of titanium and its alloys. Six input parameters, namely, tool material, power rating, slurry type, slurry temperature, slurry concentration, and slurry grit size were selected to give output in form of tool wear rate. This study will provide main effects of these variables on tool wear rate and will shed light on the tool wear mechanism in ultrasonic machining of titanium and its alloys. The comparison with experimental results will also serve as further validation of model.     

Corrosion–erosion wear behaviors of 13Cr24Mn0.44N stainless steel in saline–sand slurry

The corrosion–erosion wear behaviors of austenitic stainless steels, 316L and 13Cr24Mn0.44N, were investigated in water–sand slurry and saline–sand slurry, respectively. The corrosion–erosion wear mass-loss was measured to evaluate the influence of medium and materials. The worn surface and corrosion–erosion wear mechanism were analyzed using a scanning electron microscopy and a non-contact optical profilometer. Results show that the corrosion–erosion wear mass-loss of 13Cr24Mn0.44N is lower than that of 316L in both the slurries. The relative wear resistance increases with the increasing of the impingement velocity and arrives at maximum of 1.6. The dominant wear mechanism of 13Cr24Mn0.44N is abrasive wear in the water–sand slurry, whereas it becomes abrasive wear associated with little corrosive pitting in the saline–sand slurry. As the impingement velocity increased all the synergism ratios exhibit a tendency of increase, among which the synergism ratio of 13Cr24Mn0.44N is always lower than that of 316L at any given velocity. The results indicate that 13Cr24Mn0.44N possesses a predominant anti-corrosion–erosion wear property.     

A review on the progress towards improvement in surface integrity of Inconel 718 under high pressure and flood cooling conditions

Self-conditioning performance of polishing pad is an important characteristic to influence processing efficiency and service life in chemical mechanical polishing (CMP). The slurry can react with the pad surface, which affects its self-conditioning performance in fixed abrasive polishing process. Wear ratio of wafer material removal rate (MRR) and pad wear rate is introduced to evaluate self-conditioning performance of fixed abrasive pad (FAP). To clear the effect of chemical additive on FAP self-conditioning, wear ratio, FAP surface topography, friction coefficient, and acoustic emission signal of polishing process were investigated in fixed abrasive polishing of quartz glass with ferric nitrate, ethylenediamine (EDA), and triethanolamine (TEA) slurry, respectively. Results indicate that TEA slurry can provide excellent self-conditioning of FAP in fixed abrasive polishing of quartz glass. MRR and wear ratio maintain high levels during the whole polishing process. Friction coefficient and acoustic emission signal are more stable than that of the other two chemical additives. An appropriate amount of TEA, which is beneficial to enhance MRR and extends service life of FAP, is added in the polishing slurry to improve FAP self-conditioning in fixed abrasive polishing process.     

磨粒对ADZ复合陶瓷材料磨损性能的影响

采用块 -块摩擦磨损试验机在不同磨粒的 5 %NaOH泥浆中 ,对氧化铝增强四方氧化锆多晶陶瓷材料 (ADZ)的磨损性能进行了研究。研究结果表明尖锐磨粒对ADZ复合陶瓷材料磨损的影响要比球形磨粒严重的多 ,磨料硬度是影响陶瓷材料磨损率的重要因素 ,磨损率随磨粒硬度的提高而增大。在不同形状的SiO2 磨粒的泥浆中ADZ陶瓷材料的主要磨损机理为塑性变形和微犁削。在高硬度Al2 O3磨料的泥浆中ADZ陶瓷材料磨损表面以断裂机制占主导地位。     

On the synergistic effects of abrasion and corrosion during wear

The interactive effects of abrasion and corrosion were studied as a function of abrasive load, corrosion time and the frequency of abrasive and corrosive treatments. The initial rate of corrosion is independent of abrasive load but the percentage contribution to wear of corrosion decreases with increasing abrasive load. It has also been found that increasing the frequency of exposure to abrasion and corrosion increases the wear loss for a constant total amount of abrasion and corrosion. These effects are discussed in terms of the nature of the work-hardened surface layer and the chemical activity of this layer.     

Tribo‐electrochemical study of stainless steel surfaces during chemical–mechanical polishing

Chemical–mechanical polishing combines the synergistic effect of chemical etching and mechanical abrasion to achieve surface planarisation. These effects are discussed in this paper based on a tribocorrosion study of stainless steel (SS) immersed in two different acidic polishing slurries containing iron oxide nanoparticles. The effect of slurry chemistry and contact area on depassivation–repassivation phenomena are investigated and discussed. In case of the point‐contact geometry it was found that high friction and wear caused by formation of third body particles in the contact contributed to slow repassivation time of the SS, and wear accelerated corrosion was the dominant mechanism under these conditions. An increase in the contact area caused a removal of oxides from a larger surface area, leading to much slower repassivation rates and the appearance of a tarnish layer on the SS immersed in a slurry with high acid content. Surface chemistry investigations revealed an enrichment of chromium oxide. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of cathodic protection on corrosive wear of 304 stainless steel

Corrosive wear involves interaction of electrochemical and mechanical processes. The synergism of these two processes often results in significant material loss, compared to those caused by individual processes. Reduction of either corrosion or wear may effectively decrease material loss under certain circumstances. Since cathodic protection can reduce corrosion of metallic materials, it may also diminish corrosive wear if the corrosion process is suppressed. However, under a cathodic potential (potentiostatic condition) or enforced current (galvanosatic condition), properties of a material could be affected and thus its corrosive wear behavior could be different from what is expected. The present research demonstrated that cathodic protection under potentiostatic condition was beneficial under low wearing force but it became ineffective under higher wearing forces or more negative cathodic potentials. Hydrogen embrittlement could be responsible for this change.