化学机械抛光中抛光垫的研究

抛光垫是化学机械抛光(CMP)系统的重要组成部分。它具有贮存抛光液，并把它均匀运送到工件的整个加工区域等作用。抛光垫的性能主要由抛光垫的材料种类、材料性能、表面结构与状态以及修整参数等决定。本文介绍CMP过程常用的抛光垫材料种类、材料性能、表面结构，总结了抛光垫的性能对CMP过程影响规律，认为：抛光垫的剪切模量或增大抛光垫的可压缩性，CMP过程材料去除率增大；采用表面合理开槽的抛光垫，可提高材料去除率，降低晶片表面的不均匀性；抛光垫粗糙的表面有利于提高材料去除率。对抛光垫进行适当的修整可以增加抛光垫表面粗糙度、使材料去除率趋于一致。与离线修整相比较，在线修整时修整效果比较好。     

基于响应面法的单晶硅CMP抛光工艺参数优化

为提高单晶硅化学机械抛光(chemical mechanical polishing,CMP)的表面质量和抛光速度,通过响应面法优化CMP抛光压力、抛光盘转速和抛光液流量3个工艺参数,结果表明抛光压力、抛光盘转速、抛光液流量对材料去除率和抛光后表面粗糙度的影响依次减小。通过数学模型和试验验证获得最优的工艺参数为:抛光压力,48.3 kPa;抛光盘转速,70 r/min;抛光液流量,65 mL/min。在此工艺下,单晶硅CMP的材料去除率为1 058.2 nm/min,表面粗糙度为0.771 nm,其抛光速度和表面质量得到显著提高。      

钇铝石榴石晶体化学机械抛光液成分优化研究

钇铝石榴石(YAG)晶体由于其优异的物理化学和光学性能,广泛用作激光器的激光增益介质。然而,目前的加工方法很难满足YAG晶体的高效高质量加工。基于传统硅溶胶抛光液的抛光机理,配制一种化学机械抛光液,并通过正交试验优化化学机械抛光液的成分配比。使用优化后的抛光液抛光YAG晶体,其化学机械抛光材料去除率提升至34 nm/min,抛光后YAG晶体表面粗糙度为0.5 nm。相比于传统硅溶胶抛光液,新型抛光液的抛光效率提升240%,抛光工件的表面粗糙度降低17%。同时,通过对比抛光液性能提出化学机械抛光界面的相互作用模式对材料去除率的影响原因。      

抛光垫特性对硬质合金刀片CMP加工效果的影响

目的研究不同种类的抛光垫对硬质合金刀片表面化学机械抛光(Chemical Mechanical Polishing/Planarization,CMP)加工过程的影响,为实现硬质合金刀片高效精密CMP加工提供有效参考。方法利用Nanopoli-100智能抛光机,通过自制的Al2O3抛光液,分别采用9种不同种类的抛光垫对牌号为YG8的硬质合金刀片进行CMP实验,将0~40、40~80、80~120 min三个加工阶段获得的材料去除率和表面粗糙度进行对比,同时观察最佳的表面形貌,分析抛光垫特性对CMP加工效果的影响。结果在抛光转速60 r/min,抛光压力177.8 k Pa的实验条件下,9种不同类型的抛光垫中仅有5种适合用于YG8硬质合金CMP加工。而且抛光垫的表面粗糙度在YG8刀片CMP加工过程中的影响最为显著,抛光垫表面粗糙度越高,CMP加工的材料去除率越高。此外,抛光垫的使用时间对CMP过程也有影响,抛光垫使用时间越长,CMP的材料去除率越小。结论 YG8硬质合金刀片经5种不同类型抛光垫CMP加工后,其表面的烧伤、裂纹等缺陷均得到了极大改善。当使用细帆布加工40 min时,材料去除率最高,为47.105 nm/min;当使用细帆布加工80min时,表面粗糙度最低,为0.039μm。     

Tribological approaches to material removal rate during chemical mechanical polishing

In this study, the effect of the friction and wear of a polishing pad on the material removal rate of a silicon oxide wafer was investigated during chemical mechanical polishing (CMP) with ceria slurry. Further, the effect of surface properties of the polishing pad, such as surface roughness and hardness, on the variation in the material removal rate was examined. From a tribological viewpoint, the in-situ friction force was monitored during the CMP process, and wear of the polishing pad was controlled by different types of conditioners. After CMP, the pad surface roughness was measured by optical profiling and scanning electron microscopy. Experimental results showed that the material removal rate was almost linearly proportional to the friction force between the pad and the wafer surface, irrespective of the properties of the pad. Experiments on the dependency of the pad wear rate on the material removal rate showed that the material removal rate increased with a decrease in the pad wear rate. Experiments and pad characterization confirmed that such a correlation was attributed to the pad surface roughness and the friction force.     

硬质合金刀具材料化学机械抛光机理研究

目的研究硬质合金刀具材料化学机械抛光(CMP)机理,为改善硬质合金刀具表面质量提供理论支持。方法分析硬质合金刀具材料在酸性抛光液中的化学反应,研究硬质合金刀具材料CMP的化学反应机理。基于接触力学理论计算抛光垫与工件的实际接触面积和单个磨粒的实际切削面积,在运动学分析的基础上,建立硬质合金刀具材料CMP的材料去除率模型,通过实验验证材料去除率模型的有效性。结果在酸性抛光液中,硬质合金被氧化成Co_3O_4。当工件、抛光垫、磨粒类型、工件安装位置确定时,材料去除率与抛光载荷、磨粒浓度和抛光盘转速有关。常用硬质合金抛光条件下,抛光YG8刀具的修正系数Kcm为8.53,抛光后刀具的最低表面粗糙度能达到48nm,材料去除率为62.381nm/min,材料去除率的理论值和实验值的最大相对误差为13.25%,消除了表面缺陷,获得了较好的镜面效果。结论建立的材料去除率模型具有一定的有效性,对硬质合金刀具材料进行化学机械抛光能消除刀具的表面缺陷,改善表面质量。     

蓝宝石衬底CMP中氧化硅磨粒粒度分布对抛光液体系性能影响研究

目的 化学机械抛光(CMP)包含化学腐蚀和机械磨削两方面,抛光液pH、磨粒粒径和浓度等因素均会不同程度地影响其化学腐蚀和机械磨削能力,从而影响抛光效果。方法 采用30~150 nm连续粒径磨粒抛光液、120 nm均一粒径磨粒抛光液、50 nm和120 nm配制而成的混合粒径磨粒抛光液,分别对蓝宝石衬底晶圆进行循环CMP实验,研究CMP过程中抛光液体系的变化。结果 连续粒径磨粒抛光液中磨粒大规模团聚,满足高材料去除率的抛光时间仅有4 h,抛光后的晶圆表面粗糙度为0.665 nm;均一粒径磨粒抛光液中磨粒稳定,无团聚现象,抛光9 h内材料去除率较连续粒径磨粒抛光液高94.7%,能至少维持高材料去除率18 h,抛光后的晶圆表面粗糙度为0.204 nm;混合粒径磨粒抛光液初始状态下磨粒稳定性较高,抛光9 h内材料去除率较连续粒径磨粒抛光液高114.8%,之后磨粒出现小规模团聚现象,后9 h材料去除率仅为均一粒径磨粒抛光液的59.6%,18 h内材料去除率仅为均一粒径磨粒抛光液的87.7%,但抛光后的晶圆表面粗糙度为0.151 nm。结论 一定时间内追求较高的材料去除率和较好的晶圆表面粗糙度选用混合粒径磨粒抛光液,但需要长时间CMP使用均一粒径磨粒抛光液更适合,因此,在工业生产中需要根据生产要求配合使用混合粒径磨粒抛光液和均一粒径磨粒抛光液。     

紫外光催化辅助SiC抛光过程中化学反应速率的影响

目的为了探究紫外光催化辅助抛光过程中,化学反应速率对SiC化学机械抛光的影响规律。方法通过无光照、光照抛光盘和光照抛光液3种光照方式,研究紫外光催化辅助作用对单晶SiC抛光过程中材料去除率的影响。测量不同条件下光催化反应过程中的氧化还原电位(ORP)值,来表征光催化反应速率,并进行了单晶SiC的紫外光催化辅助抛光实验,考察光催化反应速率对抛光效果的影响规律。结果实验表明,引入紫外光催化辅助作用后,材料去除率提高14%～20%,随着材料去除率的增加,光催化辅助作用对材料去除率的影响程度变小。光照射抛光液方式的材料去除率明显高于光照射抛光盘。不同条件下的抛光结果显示,化学反应速率越快,溶液的ORP值越高,材料去除率越大,表面粗糙度越低。在光照抛光液、H_2O_2体积分数4.5%、TiO_2质量浓度4 g/L、光照强度1500 mW/cm~2、pH=11的条件下,用W0.2的金刚石磨料对SiC抛光120 min后,能够获得表面粗糙度Ra=0.269 nm的光滑表面。结论在单晶SiC的紫外光催化辅助抛光过程中,光催化反应速率越快,溶液ORP值越高,抛光效率越高,表面质量越好。在H_2O_2浓度、TiO_2浓度、光照强度、pH等4个因素中,对抛光效果影响最大的是H_2O_2浓度,光照强度主要影响光催化反应达到稳定的时间。     

化学机械抛光中的接触状态研究概述

化学机械抛光是获取高表面平整度的有效关键技术,获得了广泛的研究和应用,其表面材料的去除作用依赖于所处的真实接触状态。归纳了抛光垫/晶圆相互作用的形式,即相互滑过而没有直接接触、混合润滑和直接接触。分析了接触状态及其转变过程中的影响因素,包括抛光垫的变形、釉化和磨损,抛光液中磨粒的影响及表面活性剂对钝化层厚度的改变等。重点总结了化学机械抛光中接触状态问题的研究进展,包括光学显微镜测量计算接触面积比、薄膜传感器测量接触面积比、利用双发射激光诱导荧光技术测量抛光液厚度、抛光垫表面形貌演变对材料去除速率的建模等方法的特点及存在的问题。最后提出了纳米间隙测量技术测量化学机械抛光中接触率动态变化,从而得到真实接触状态和接触状态转变规律的新思路。     

应用弹性砂轮对铝合金镜面磨削工艺研究

目的解决铝合金手机外壳传统抛光工艺中存在的抛光效率低等问题。方法采用聚氨酯弹性砂轮对6061铝合金进行了磨削加工,使用正交试验研究了磨料粒度、进给速度、切削深度、砂轮线速度对加工表面粗糙度及材料去除率的影响。试验中使用折线走刀方式进行加工,可减轻磨料分布不均带来的影响。使用白光干涉仪测量了加工后表面的粗糙度,通过计算单位时间内工件的质量变化得出了去除率,并通过对结果的综合优化得出了最优工艺参数。结果在选取的16组磨削工艺参数中,可获得的最低表面粗糙度为44.87 nm,最大去除率为0.329 g/min。对表面粗糙度影响最大的因素为磨料粒度,影响最小的因素为进给速度;对材料去除率影响最大的因素为切削深度,影响最小的为进给速度。经过综合优化,最佳工艺参数组合为:砂轮600#,转速2000 r/min,切削深度0.04 mm,进给速度20 mm/min。结论弹性聚氨酯砂轮应用于铝合金磨削可提高加工表面质量,可简化工艺流程,节省备料和安装调整时间,从而提高效率。     

A wafer-scale material removal rate profile model for copper chemical mechanical planarization

Chemical mechanical polishing (CMP) models based on the Preston equation, which states that the material removal rate (MRR) is proportional to the product of the pressure and relative velocity, have focused on representing the average MRR as a function of the pressure and relative velocity. In this study, we tried to establish a semi-empirical CMP model, which can provide the MRR profile. The model is based on a modified form of the Preston equation and involves the use of a spatial parameter (Ω). The relative velocity distribution, normal contact stress distribution, and chemical reaction rate distribution are considered for obtaining the MRR profile in the copper CMP process. The results of the modeling and experimental analysis performed in this study facilitate process optimization and provide information that can contribute to the development of a wafer-scale CMP simulator.     

硒化锌晶体精细雾化抛光液及去除机理研究

目的配制适合硒化锌雾化施液化学机械抛光的最优抛光液。方法选取氧化铝磨粒、pH调节剂四甲基氢氧化铵、氧化剂过氧化氢、表面活性剂聚乙烯吡咯烷酮为主要活性成分,以材料去除速率和表面粗糙度为评价指标,通过正交试验对硒化锌晶体进行精细雾化抛光,分析材料去除机理,并与传统抛光对比。结果氧化铝质量分数为9%、pH值为11、过氧化氢含量为3.5%、聚乙烯吡咯烷酮含量为0.75%时,材料去除率较高,为923.67 nm/min,同时表面粗糙度较小,为2.13 nm。在相同工况条件下,传统抛光材料的去除率和表面粗糙度分别为965.53 nm/min和2.27 nm。结论抛光液各组分对试验结果影响最大的为氧化铝磨粒,然后依次为氧化剂、pH值、表面活性剂。精细雾化抛光效果与传统抛光相近,但抛光液用量仅为后者的1/8。     

基于叶序仿生抛光垫的化学机械抛光的运动分析

为了改善化学机械抛光的接触状态和被加工工件的表面形态,基于生物学的叶序理论设计了仿生结构的抛光垫。从单颗磨粒切削理论出发,建立了抛光运动方程和材料去除率分布模型。利用所建立的运动方程和材料去除率分布模型进行了晶片表面材料去除率分布的计算分析,得到抛光机的运动参数及抛光垫的叶序参数对材料去除率的影响规律。结果表明:当抛光盘的转速较大、工件转速适中、摆臂摆动频率较小、摆臂中心角较小及叶序参数取值较小时可以获得更好的材料去除分布。     

Mechanical effect of colloidal silica in copper chemical mechanical planarization

The mechanical effect of colloidal silica concentration in copper chemical mechanical planarization (CMP) is considered in this paper by using friction force monitoring system. The copper peak was detected in the result of the energy-dispersive X-ray (EDX) spectra of the polishing residues. The addition of colloidal silica into copper CMP slurry increased both the material removal rate and the friction force. During CMP, as the concentration of the colloidal silica was increased, the temperature generated by the friction force also increased. To understand effect of abrasive concentration on the material removal and friction force, we considered the material removal and the friction energy for a single abrasive. The surface of the polished copper film was measured by X-ray photoelectron spectroscopy (XPS). All the material removal rates as a function of friction energy after polishing with various concentrations of colloidal silica had a non-linear characteristic.     

单晶蓝宝石衬底晶片的化学机械抛光工艺研究

目的设计单晶蓝宝石衬底化学机械抛光的合理方案,探究主要抛光工艺参数对抛光衬底的表面质量和材料去除率的影响,并得到一组材料去除率高且表面质量满足要求的抛光工艺参数。方法借助原子力显微镜和精密天平分别对衬底表面形貌和材料去除率进行分析,采用单因素实验法探究了抛光粒子、抛光时间、抛光压力和抛光盘转速对蓝宝石衬底化学机械抛光的表面质量和材料去除率的影响,并设计合理的交互正交优化实验寻求一组较优的抛光工艺参数。结果在蓝宝石衬底化学机械精抛过程中,在抛光时间为0.5 h、抛光压力为45.09 k Pa、抛光盘转速为50 r/min、SiO_2抛光液粒子质量分数为15%、抛光液流量为60 m L/min的条件下,蓝宝石衬底材料的去除率达41.89 nm/min,表面粗糙度降低至0.342 nm,衬底表面台阶结构清晰,满足后续外延工序的要求。结论采用化学机械抛光技术和优化的工艺参数,可同时获得较高的材料去除率和高质量的蓝宝石衬底表面。     

铜化学机械抛光材料去除机理研究

本文根据铜CMP过程中表面材料的磨损行为,建立了铜CMP时的材料去除率构成成分模型,并通过材料去除率实验,得出了各机械、化学及其交互作用所引起的材料去除率及其作用率:当np=nw=200r/min时,有最佳材料去除率,此时单纯的机械作用率为9.2%;单纯的化学作用率为仅为2.1%,抛光垫的机械与化学交互作用率为5.08%;磨粒的机械与化学交互作用率为83.6%。通过对实验结果进行分析,可得如下结论:硅片化学机械抛光中,一定的参数下有一个最优的抛光速度;在最优的速度下,机械与化学之间交互作用达到平衡,这时可获得最高的材料去除率;硅片化学机械抛光过程是一个多变的动态过程,仅仅通过增加机械作用或化学作用不能获得理想的材料去除效果。本文的研究结果可为进一步研究硅片CMP时的材料去除机理提供理论参考依据。     

Chemo-mechanical magneto-rheological finishing (CMMRF) of silicon for microelectronics applications

A new finishing process, namely, chemo-mechanical magneto-rheological finishing (CMMRF) was developed for polishing silicon blanks that combines the beneficial features of chemical mechanical polishing (CMP) and magneto-rheological finishing (MRF) without the detrimental effects of either process involved. Chemical reactions associated with CMP are used to enhance the finish quality while the magneto-rheological polishing fluid is used to control the magnitude of the forces acting on the workpiece that controls the material removal rates (MRR) and minimizes the surface integrity problems. An apparatus for CMMRF was designed and built for nanometric finishing of silicon substrates. This process is able to finish silicon blanks with nanometric finish, minimal surface defects, and higher removal rates.     

Combined ultrasonic vibration and chemical mechanical polishing of copper substrates

This paper introduces an ultrasonic, vibration-assisted, chemical mechanical polishing (UV-CMP) method and an ultrasonic, vibration-assisted, traditional diamond disk (UV-TDD) dressing method. A copper substrate is polished by traditional CMP and UV-CMP. UV-CMP combines the functions of traditional CMP and ultrasonic machining (USM) with small-amplitude, high-frequency tool vibration to improve the fabrication process and machining efficiency. The removal rate of the copper substrate, torque force, and polished surface morphology of CMP and UV-CMP are compared. The polishing pad is also dressed by traditional diamond disk (TDD) and UV-TDD. The pad cut rate, torque force, and pad surface profiles of TDD and UV-TDD are also investigated in experiments. Experimental results reveal that UV-TDD can produce twice the pad cut rate and reduce torque force compared to TDD. Consequently, a dressing time reduction by half is expected, and hence, the diamond life is extended. It is found that the removal rate of the copper substrate polished by UV-CMP is increased by approximately 50-90% relative to that of traditional CMP because in UV-CMP, a passive layer on the copper surface, formed by the chemical action of the slurry, will be removed not only by the mechanical action of CMP but also by ultrasonic action. In addition, the surface roughness improves and the torque force reduces dramatically. This result suggests that the combination processes of CMP/USM and TDD/USM are feasible methods for improving polishing and dressing efficiency.     

304不锈钢绿色化学机械抛光

目的 采用对环境友好的抛光工艺来改善304不锈钢表面抛光质量。方法 基于化学机械抛光（CMP）工艺,采用主要成分为氧化铝（Al₂O₃）磨料、L-苹果酸、过氧化氢（H₂O₂）、乳化剂OP-10、甘氨酸的绿色环保抛光液,设计并试验了pH值,H₂O₂、乳化剂OP-10、甘氨酸质量分数的4因素4水平CMP正交试验。采用极差法分析了4个因素对表面粗糙度和材料去除率的影响。采用电化学工作站,通过动电位极化曲线法,分析304不锈钢在不同抛光液环境下的静态腐蚀特性。通过X射线光电子能谱（XPS）,分析304不锈钢在不同抛光液环境下的表面元素和化学组分变化。结果 开发了一种不含任何强酸、强碱等危化物品的新型环保化学机械抛光液。通过绿色CMP加工,在70μm×50μm范围内将304不锈钢平均表面粗糙度从CMP前的7.972 nm降至0.543 nm。与之前报道的304不锈钢抛光相比,绿色CMP抛光后的表面粗糙度最低。通过正交试验,得到了绿色CMP加工的最优抛光液参数：pH=3...     

Mechanical effect of process condition and abrasive concentration on material removal rate profile in copper chemical mechanical planarization

Recently, many researchers have studied the material removal mechanism of copper chemical mechanical planarization (CMP). On the basis of their previous works, we studied the mechanical effect of copper (Cu) CMP on the material removal rate profile. Copper CMP was performed using citric acid (C₆H₈O₇), hydrogen peroxide (H₂O₂), colloidal silica, and benzotriazole (BTA, C₆H₄N₃H) as a complexing agent, an oxidizer, an abrasive, and a corrosion inhibitor, respectively. In this paper, the abrasives and process condition are main mechanical factors of CMP. The colloidal silica, used as an abrasive in copper CMP slurry containing 0.01 M citric acid and 3 vol% hydrogen peroxide, controlled the wafer edge profile by abrading the wafer edge. The polishing pressure did not contribute to the material removal rate (MRR) profile, but did to the MRR. As the rotational velocity of the polishing head and table increased, the deviation of MRR profile became smaller. The results of this paper showed that the abrasive concentration was the key factor which controlled the wafer edge profile, and also the rotational velocity was the key factor which controlled wafer center profile of MRR.