300mm晶圆化学机械抛光流体润滑行为研究

正化学机械抛光(CMP)是集成电路制造的一个关键工艺步骤。随着晶圆尺寸增加至300 mm,对CMP全局平坦化效果的要求越来越高。目前人们对CMP机理的认识多集中在晶圆表面材料的去除机理,而对全局平坦化机理的研究很少。本文在CMP装备研发和在线测量系统研制的基础上,以流体作用为切入点,对300 mm晶圆CMP过程抛光接触面的流体润滑行为和晶圆状态进行系统的试验研究,为工业CMP过程晶圆平坦化机理研究奠定基础。主要研究工作如下。     

化学机械抛光中Si/Cu/Ta/low-k界面剥离和断裂特性研究

超大规模集成电路随着布线层数增加和线宽的缩小,low-k材料的介电常数进一步降低,多孔low-k材料力学性能随之降低,使得晶圆在化学机械抛光(Chemical mechanical polishing,CMP)中面临的主要问题是Cu/Ta/low-k或者超低k材料的界面剥离。针对Si/Cu/Ta/low-k在CMP过程中的承载特性,建立单层布线和多层布线体系的界面力学模型,采用断裂力学理论和有限元法研究Si/Cu/Ta/low-k界面在CMP过程中界面的应力分布规律和界面裂纹的断裂强度。采用能量释放率来描述裂纹的扩展情况,根据界面裂纹能量释放率数值计算方法对裂纹长度、材料性质及不同的布线层数对裂纹扩展时的界面断裂/剥离特性进行仿真分析,得到界面应力分布、能量释放率、相位角与裂纹长度、材料性能、布线层数之间的关系变化曲线。结果表明:随着low-k力学性能降低和布线层数增加,裂纹能量释放率升高,界面裂纹更容易扩展。     

300mm晶圆化学机械抛光机关键技术研究与实现

在芯片微细化和互连多层化趋势下,化学机械抛光(Chemical mechanical polishing,CMP)成为集成电路制造的核心技术。针对300 mm晶圆CMP装备被极少数国外厂家垄断、国内300 mm晶圆CMP装备水平远远落后的现状,开展300 mm晶圆CMP装备关键技术研究。研制出300 mm晶圆多区压力抛光头及其压力控制系统,该抛光头具有多区压力、浮动保持环及真空吸附等功能,每个腔室均可实现施加正压、抽负压、通大气和泄漏检测;压力控制系统性能测试结果表明,该系统可实现689.5 Pa的超低压力,其精度和响应速度均能满足常规压力及超低压力CMP的要求;开发了300 mm晶圆超低压力CMP样机,创建出一套比较稳定、可靠的工艺流程,并利用该样机初步开展铜CMP试验研究。试验结果表明:抛光压力为15.169 kPa时,材料去除率达671.3 nm/min,片内非均匀性为3.93%。     

ULSI制造中铜化学机械抛光的腐蚀磨损机理分析

以超大规模集成电路(ULSI)芯片多层互连结构制造中的关键平坦化工艺——铜化学机械抛光(Cu—CMP)为研究对象，针对Cu—CMP中存在的抛光液的化学腐蚀作用和磨料的机械磨损现象，采用腐蚀磨损理论分析了Cu—CMP材料去除机理。提出铜CMP的材料去除中存在着机械增强的化学腐蚀和化学增强的机械磨损，并分析了Cu—CMP的静态腐蚀材料去除、机械增强的腐蚀去除与化学增强的机械去除机理。     

化学机械平坦化中晶圆姿态瞬态调整的数值模拟研究

化学机械平坦化(Chemical mechanical planarization,CMP)是集成电路制造的关键技术之一。晶圆夹持器是CMP系统的核心零部件。为研究万向球头位置对平坦化过程中晶圆姿态瞬态调整能力的影响,采用混合软弹流润滑模型分析抛光垫表面的流动与接触行为,并结合夹持器的瞬态运动方程分析晶圆姿态的动态变化过程。分析结果表明,夹持器姿态的调整能力随万向球头的中心高度增加而提高,摩擦力矩的增加有利于晶圆姿态稳定在平衡位置,但同时接触应力不均匀性增加。因此,合理设计夹持器结构对CMP加工质量非常重要,提出的瞬态混合润滑模型对夹持器的动态特性进行分析可以为设计提供非常有意义的理论指导。     

阴离子表面活性剂及复配对阻挡层抛光液性能的影响

为提高铜互连化学机械抛光(CMP)后表面质量，在抛光液中需引入适当的表面活性剂以改善磨料的稳定性以及CMP后铜的表面粗糙度。研究了十二烷基硫酸铵(ADSA)、脂肪醇聚氧乙烯醚硫酸铵(AESA)、直链烷基苯磺酸(LABSA)3种不同阴离子表面活性剂，以及非离子表面活性剂脂肪醇聚氧乙烯醚(AEO-9)和LABSA复配表面活性剂对钽阻挡层抛光液润湿性、分散性以及对材料去除速率的影响。通过接触角测量仪、纳米粒度仪、扫描电镜和原子力显微镜测试表面张力、接触角、大颗粒数、粒径分布以及CMP后铜的表面粗糙度，并分析复配表面活性剂的作用机制。结果表明：抛光液中加入LABSA后，因其具有直链型结构，抛光液的润湿性和分散性效果最好，抛光后铜表面的粗糙度最低；AEO-9和LABSA进行复配，相较于单一的LABSA,抛光液的润湿性、分散性、稳定性和抛光后铜表面粗糙度均有所改善，体积分数0.1%LABSA+0.1%AEO-9的复配表面活性剂性能最优，CMP后铜表面粗糙度降至0.7 nm。     

超大规模集成电路制造中硅片平坦化技术的未来发展

在集成电路(IC)制造中,化学机械抛光(CMP)技术在单晶硅衬底和多层金属互连结构的层间全局平坦化方面得到了广泛应用,成为制造主流芯片的关键技术之一。然而,传统CMP技术还存在一定的缺点或局限性,人们在不断完善CMP技术的同时,也在不断探索和研究新的平坦化技术。在分析传统CMP技术的基础上,介绍了固结磨料CMP、无磨料CMP、电化学机械平坦化、无应力抛光、接触平坦化和等离子辅助化学蚀刻等几种硅片平坦化新技术的原理和特点以及国内外平坦化技术的未来发展。     

8寸CMP设备对小尺寸镀铜InP晶圆的工艺开发

为了实现在8寸化学机械抛光设备上进行小尺寸镀铜InP晶圆的减薄抛光工作,提高设备的兼容性,缩减工艺步骤,减少过多操作导致InP晶圆出现裂纹暗伤和表面颗粒增加等问题,自制特殊模具,使小尺寸InP晶圆在8寸化学机械抛光设备上进行加工,再根据InP晶圆易碎的缺陷问题,通过调整设备的抛光头压力、转速和抛光垫的转速等相关工艺参数,使其满足后续键合工艺的相关需求。实验结果表明：在使用特殊模具下,当抛光头的压力调整为20.684 kPa、抛光头与抛光垫的转速分别为：93 r/min和87 r/min时,InP晶圆的表面粗糙度达到：Ra≤1 nm;表面铜层的去除速率达到3 857×10-10/min;后续与8寸晶圆的键合避免键合位置出现空洞等缺陷,实现2寸InP晶圆在8寸设备上的CMP工艺,大大降低了CMP工艺成本,同时避免晶圆在转移过程中出现表面颗粒度增加和划伤的情况,实现了InP晶圆与Si晶圆的异质键合及Cu互连工艺。     

硬脆材料的化学机械抛光机理研究

化学机械抛光(Chemical Mechanical Polishing,简称CMP)技术是目前唯一可提供全局平面化的超精密表面加工技术,加工后无表面和亚表面损伤。该技术广泛应用于光学元件、微机电系统、集成电路芯片等表面的处理,可达到纳米级的表面粗糙度和微米级的面形精度。目前的研究主要集中在化学机械抛光工艺上,抛光机理尚未形成统一的学说。针对硬脆材料(Si、SiC)的CMP技术进行综述,介绍了CMP技术的发展现状,并对加工过程中存在的材料去除机理做了可能性解释,最后对CMP技术的发展和研究重点做了预测和建议。     

超精密砷化镓晶片抛光机的研制

化学机械抛光(CMP)技术作为目前唯一可提供在整个晶圆片上全面平坦化的工艺技术,已被越来越广泛地应用到了半导体领域。通过了解化学机械抛光(CMP)技术原理,分析出影响晶片抛光质量的主要因素基础上开发了超精密砷化镓晶片抛光机。重点介绍了该抛光机结构组成,及其研制的关键技术和创新点。     

Effect of wafer size on material removal rate and its distribution in chemical mechanical polishing of silicon dioxide film

Chemical mechanical polishing (CMP) is a semiconductor fabrication process. In this process, wafer surfaces are smoothed and planarized using a hybrid removal mechanism, which consists of a chemical reaction and mechanical removal. In this study, the effects of wafer size on the material removal rate (MRR) and its uniformity in the CMP process were investigated using experiments and a mathematical model proposed in our previous research; this model was used to understand the MRR and its uniformity with respect to wafer size. Under constant process conditions, the MRR of a silicon dioxide (SiO₂) film increased slightly along with an increase in wafer size. The increase in MRR may be attributed to the acceleration of the chemical reaction due to a rise in process temperature. Based on the results obtained, the k and α values in the mathematical model are useful parameters for understanding the effect of wafer size on the MRR and its distribution under a uniform, relative velocity. These parameters can facilitate the prediction of CMP results and the effective design of a CMP machine.     

CMP过程芯片表面氧化膜生成速度影响因素的分析

根据理论和试验分析,将机械化学抛光(CMP)过程分成两个阶段:化学作用主导阶段和机械作用主导阶段,并从机械作用角度导出CMP过程两个阶段芯片表面材料去除率的数学模型,模型全面地考虑了抛光盘特性参数(弹性模量、硬度、表面粗糙度峰的尺寸分布)、CMP工作参数(压力和抛光速度)、抛光液中磨粒的机械作用和氧化剂种类、氧化剂浓度等化学作用的影响。然后根据这两个阶段的平衡点导出定量描述芯片表面氧化膜生成速度的数学模型。详细分析机械作用因素(磨粒的浓度、磨粒的粒度分布特性)、化学作用因素(抛光液中氧化剂种类、浓度)以及磨粒/芯片/抛光盘的材料特性参数对芯片表面氧化膜生成速度的影响规律。该CMP过程芯片表面氧化膜生成速度定量模型的导出,对进一步深入研究CMP材料去除机理和更加准确地控制CMP过程,具有一定的指导作用。     

一种基于非晶层粘性流动的机械化学抛光模型

通过分析单个微纳米磨粒滑动接触的分子动力学模拟的研究结果，提出了在典型的机械化学抛光（CMP）过程中芯片表面材料的去除应为表面非晶层物质粘性流动所致的新观点。基于这种机理，应用微观接触力学和磨粒粒度分布理论建立了一种新的表征CMP过程材料去除速率的数学模型。模型中引入了一个表征单个磨粒去除芯片表面非晶层能力的比例系数k，k综合反映了磨粒的机械作用、抛光液对芯片表面的化学作用和芯片的材料特性。通过实验验证发现该模型的理论预测值与实验测定值十分吻合。     

基于AFM的化学机械抛光磨粒模拟研究

当前的化学机械抛光(CMP)磨损模型中大多数都缺少微观试验数据的支持。为进步揭示CMP中纳米磨粒对材料表面的磨损机制,提出了采用原子力显微镜(AFM)来模拟CMP中的单个磨粒的试验方案,并验证该模拟试验方案的可行性。结果表明:采用AFM探针来模拟CMP过程中单个磨粒对芯片表面的磨损与相互作用的试验方案是完全可行的;可以通过AFM探针对芯片表面的相互作用与磨损,模拟得出单个磨粒对芯片表面的作用与磨损状况,并可以在此微观试验数据的基础上建立起新的CMP磨损模型。     

Hydrodynamic analysis of chemical mechanical polishing process

Chemical Mechanical Polishing (CMP) refers to a material removal process done by rubbing a work piece against a polishing pad under load in the presence of chemically active abrasive containing slurry. The CMP process is a combination of chemical dissolution and mechanical action. The mechanical action of CMP involves hydrodynamic lubrication. The liquid slurry is trapped between the work piece (wafer) and pad (tooling) forming a lubricating film. For the first step to understand the mechanism of the CMP process, hydrodynamic analysis is done with a semiconductor wafer. Slurry pressure distribution, resultant forces and moments acting on the wafer are calculated in typical conditions of the wafer polishing, and then nominal clearance of the slurry film, roll and pitch angles at the steady state are obtained.     

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.     

High precision chemical mechanical polishing of highly-boron-doped Si wafer used for epitaxial substrate

The surface waviness with concentric circular pattern is generated on highly-boron-doped Si wafer by chemical–mechanical polishing (CMP) with amine system polishing slurry. To investigate the generation mechanism of the waviness, the mechanical and chemical characteristics were clarified using the silicon crystal samples with various boron concentration level ranging from 2.9 × 10¹⁷ cm⁻³ to 1.3 × 10²⁰ cm⁻³. The conventional silicon substrate used as epitaxial wafer has boron concentration of about 2.5 × 10¹⁸ cm⁻³, a region at which the radical change of etching rate is induced with amine system chemical reagent. The mechanical micro-hardness of highly-boron-doped Si is 30% higher than that of lightly-doped Si. It is found that SiB bond in crystal lattice is firmed up and stabilized for mechanical stress and chemical reaction. To cancel the difference in CMP rate based on boron concentration deviation, increasing the mechanical action in CMP was proposed and performed. The precision CMP was performed using the harder polishing pad and a smooth surface without waviness was obtained.     

A kinematic analysis of disk motion in a double sided polisher for chemical mechanical planarization (CMP)

Double sided polishers are commonly used for industrial applications, such as lapping of silicon substrates and chemical mechanical planarization (CMP) of rigid disks. Whereas a kinematic analysis of a single sided polisher, extensively used for IC wafer CMP, is well known, available sources of such an analysis are limited for a double sided polisher, due to its more complicated design.The present work demonstrates a kinematic analysis for obtaining trajectory and relative velocity of a single location on a work piece during double side polishing. Relative velocity is used to calculate travel distance to be compared with the amount removed experimentally obtained. This paper presents mathematical derivation of the analysis and its effectiveness/limitations in conjunction with comparison between the analytical and experimental results.     

化学机械抛光过程中护环对硅片表面接触压强分布和宏观轮廓的影响

为了获得单晶硅片化学机械抛光过程中护环对接触压强分布的影响规律,根据有护环化学机械抛光实际出发,建立了抛光过程的接触力学模型和边界条件,利用有限元的方法对有护环抛光接触状态接触压强分布进行了计算和分析,并利用抛光实验对计算获得结果进行了验证;获得了硅片与抛光垫间的接触表面压强分布形态,以及护环几何参数对压强分布的影响规律;结果表明护环抛光接触压强的分布也存在不均匀性,而且在硅片外径邻域内接触压强最大,这些也能导致被加工硅片产生平面度误差和塌边,选择合理地护环几何参量和负载比,可以改善接触压强场分布的均匀性。     

MEMS中基底和薄膜的CMP制造技术

化学机械抛光(ChemicalMechanical Polishing,CMP)工艺已运用于微机电系统(Micro-Electro-Mechanical System,MEMS)中,并逐渐成为研制高品质微纳器件不可或缺的一道关键技术。区域压力调整、抛光终点检测等技术已经引入到CMP工艺,确保片内不均匀性(Within-wafer Nonuniformity,WIWNU)小于5%,同时有效减小"蝶形"和"腐蚀"等抛光缺陷。CMP在MEMS领域中的运用工艺过程更为复杂,抛光对象更为多元,表面质量要求更高。结合硅、介质层、石英、锗、铂和聚合物等自行开发的CMP工艺以及抛光后清洗处理,详细讨论和阐述CMP工艺如何运用于MEMS领域。实验结果表明,采用CMP工艺,结合抛光液改进和兆声清洗,不仅可以实现薄膜的全局平坦化,而且可以获得高品质的超薄基底、无损的硬质应变薄膜和用于低温直接键合的表面粗糙度小于0.5nm键合表面。CMP技术是研制高品质的可应用于MEMS器件的基底和薄膜的有效手段。