Static dissolution rate of tungsten film versus chemical adjustments of a reused slurry for chemical mechanical polishing

Tungsten is widely used as deposited layer for the multi-level interconnection structures of wafers. The chemical composition of abrasive slurry plays an important role in chemical mechanical polishing (CMP) process. Removal of tungsten is driven by complex oxidation mechanisms between slurry components. The slurry for tungsten CMP generally contains oxidizer, iron catalyst, complexing agents and stabilizers in a pH adjusted solution of abrasive particles. Interaction between iron complex and H₂O₂ in the slurry is the main factor governing the chemical mode of material removal, oxidation potencies and kinetics.In this study, we investigate the effects of chemical additives in silica (SiO₂)-based slurry on the removal rate of the tungsten film. Experiments were carried out in static batch as a preliminary study to understand and optimize chemical mechanisms in CMP-Tungsten process. Experiment designs were conducted to understand the influence of the chemical additives on the main performances of W-CMP. Used slurry, concentrated and retreated with chemical adjustments, is compared to the original slurry as a reference.     

铜在氨水介质铁氰化钾CMP抛光液中抛光速率及其影响因素的研究

本文研究了腐蚀介质氨水、成膜剂铁氰化钾及磨粒γ_Al2 O3 浓度、抛光压力和抛光转速对铜化学_机械抛光速率的影响 .解释了各影响因素的影响机理 .实验表明了在一定范围内抛光速率与抛光压力及抛光转速呈线性关系 ,组分浓度对抛光速率的影响为非线性关系 ,Preston系数Kp是变量 .最大抛光速率的化学_机械抛光液的配方为 :4 %K3Fe(CN) 6 + 1 %NH3·H2 O + 2 5%γ -Al2 O3,Kp=0 .0 2 3 83 ;工艺条件为 :3 0 0r/min、80kpa .最佳抛光效果为 :Ra=50nm ,Rmax=4 0 0nm     

磨料对铜化学机械抛光过程的影响研究

利用CP-4型抛光试验机对直径为50.8 mm、表面沉积厚530 nm的铜硅片(表面粗糙度Ra为1.42 nm)进行化学机械抛光(CMP)试验,评价了CMP过程中不同磨料作用下的摩擦系数和材料去除率;利用ZYGO表面形貌分析系统测试含不同磨料抛光液抛光后的硅片表面粗糙度;采用扫描电子显微镜分析CMP后的铜硅片表面损伤形貌.结果表明,磨料的浓度和粒径直接影响CMP过程的摩擦系数:采用5%粒径25 nm硅溶胶为抛光液时的摩擦系数低于超纯水抛光时的摩擦系数;当磨料的添加量和粒度增加时摩擦系数增大.在相同试验条件下,采用10%粒径25 nm硅溶胶抛光材料的去除率为50.7 nm/min;粒径为1μm白刚玉磨料的抛光材料去除率为246.3 nm/min;单纯磨料使铜硅片表面变得粗糙,即用10%粒径25 nm硅溶胶抛光后的表面粗糙度仍大于原始表面(Ra值达3.43 nm);在单纯磨料或超纯水为抛光液抛光下铜硅片表面出现划伤.     

蓝宝石衬底的化学机械抛光技术的研究

介绍了蓝宝石衬底的化学机械抛光工艺,概述了化学机械抛光原理和设备,讨论分析了影响蓝宝石衬底化学机械抛光的因素,阐述了CMP的主要发展趋势:能定量确定最佳CMP工艺,系统地研究CMP工艺过程参数,建立完善的CMP理论模型,满足不同的工艺要求和应用领域,有效降低成本,提高产量.     

基于分子量级的化学机械抛光界面动力学模型研究

考虑抛光液/芯片的相界面氧化剂浓度和芯片氧化薄膜缺陷对材料去除机理的影响,提出化学机械抛光(CMP)中材料去除机理的量级估算方法,应用化学动力学及传质学等理论估算氧化薄膜的扩散深度量级和生成速率,采用纳米压痕仪模拟单个磨粒在芯片表面的压痕作用,应用线性回归方法分析载荷70 nN下,磨粒压入芯片的深度量级为10-11 m.结合模型估算,证实了CMP材料去除机理为单分子层去除机理.结果表明,减小氧化膜厚度可以提高材料去除率,估算结果与他人试验结果相吻合.为进一步研究CMP单分子层材料去除机理提供了理论依据.     

Modeling effects of abrasive particle size and concentration on material removal at molecular scale in chemical mechanical polishing

A novel material removal model as a function of abrasive particle size and concentration was established in chemical mechanical polishing (CMP) based on molecular scale mechanism, micro-contact mechanics and probability statistics. A close-form equation was firstly developed to calculate the number of effective particles. It found nonlinear dependences of removal rate on the particle size and concentration, being qualitatively agreement with the published experimental data. The nonlinear relation results from the couple relationship among abrasive number, slurry concentration and surface atoms’ binding energy with the particle size. Finally, the system parameters such as the operational conditions and materials properties were incorporated into the model as well.     

Strategies for Optimal Chemical Mechanical Polishing (CMP) Slurry Design

Abstract

Chemical mechanical polishing (CMP) has become the preferred route for achieving wafer‐level global planarization in microelectronics device manufacturing. However, the micro‐ to molecular‐level mechanisms that control its performance and optimization are not well understood. In CMP, complex slurry chemistries react with the first few atomic layers on the wafer surfaces forming a chemically modified film. This film is subsequently mechanically abraded by nanosized slurry particles to achieve local and global planarity for multi‐level metalization. For optimal CMP performance, high material removal rates with minimal surface defectivity are required. This can be achieved by controlling the extent of interparticle and particle–substrate interactions, which are facilitated through the manipulation of the slurry composition, solution chemistry, as well as operational parameters. Interparticle interactions must be engineered to maintain slurry stability to minimize the number and extent of surface defects during polishing while maintaining adequate removal rates. The fundamental considerations, which are necessary for the development of high performance CMP slurries, are discussed in this article through model silica CMP systems.     

Water-in-Oil Dispersion for KH2PO4 (KDP) Crystal CMP

Chemical mechanical polishing (CMP) has become an essential process in the manufacturing of advanced microelectronic devices. More recently, CMP has also been applied to the process of other advanced materials such as optical crystals and thin films. Typically, a CMP slurry is formulated as an aqueous dispersion which may contain abrasive particles, activating agent, passivating agent, surfactant, etc. Due to its sensitivity to water, hygroscopic crystals must not be processed with aqueous based slurry. In this study, a new abrasive-free system based on water-in-oil microemulsion was investigated to address this challenge. More specifically, a dispersion made of dodecanol, Triton X-100, and water was studied for its potential application in KH₂PO₄(KDP) crystal processing. In this unique polishing system, water molecules are caged into micelles so the reaction between KDP and water is controlled. As a result, the static etch rate of the substrate surface is minimized. During polishing process, the frictional action between crystal surface and pad leads to the release of reactive water molecules. The material removal is, thus, enhanced. In this paper, the techniques used to characterize such abrasive-free system were first introduced. The water-in-oil structures were characterized and confirmed by conductivity, dynamic lighting scattering and dynamic nuclear magnetic resonance (NMR) measurements. The performance of this system on the process of KDP crystals was then discussed. The static etch rate and the material removal rate in polishing process were measured under various conditions in order to elucidate the polishing mechanism. Finally, the potential application of such a novel nonaqueous polishing system in CMP beyond KDP crystals is discussed.     

The fundamental surface science of wurtzite gallium nitride

A review is presented that covers the experimental and theoretical literature relating to the preparation, electronic structure and chemical and physical properties of the surfaces of the wurtzite form of GaN. The discussion includes the adsorption of various chemical elements and of inorganic, organometallic and organic species. The focus is on work that contributes to a microscopic, atomistic understanding of GaN surfaces and interfaces, and the review concludes with an assessment of possible future directions.