TWO STEPS CHEMICAL-MECHANICAL POLISHING OF RIGID DISK SUBSTRATE TO GET ATOM-SCALE PLANARIZATION SURFACE

In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness （Ra） and the average waviness （Wa） of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy （AFM） analysis shows that the final polished surfaces are ultra-smooth without micro-defects.

Preparation of Non-spherical Colloidal Silica Nanoparticle and Its Application on Chemical Mechanical Polishing of Sapphire

Non-spherical colloidal silica nanoparticle was prepared by a simple new method, and its particle size distribution and shape morphology were characterized by dynamic light scattering(DLS) and the Focus Ion Beam(FIB) system. This kind of novel colloidal silica particles can be well used in chemical mechanical polishing(CMP) of sapphire wafer surface. And the polishing test proves that non-spherical colloidal silica slurry shows much higher material removal rate(MRR) with higher coefficient of friction(COF) when compared to traditional large spherical colloidal silica slurry with particle size 80 nm by DLS. Besides, sapphire wafer polished by non-spherical abrasive also has a good surface roughness of 0.460 6 nm. Therefore, non-spherical colloidal silica has shown great potential in the CMP field because of its higher MRR and better surface roughness.

Effect of Abrasive Concentration on Chemical Mechanical Polishing of Sapphire

Effects of abrasive concentration on material removal rate CMRR） and surtace quality m the chemical mecnamcal polishing （CMP） of light-emitting diode sapphire substrates are investigated. Experimental results show that the MRR increases linearly with the abrasive concentration, while the rms roughness decreases with the increasing abrasive concentration. In addition, the in situ coefficient of friction （COF） is also conducted during the sapphire polishing process. The results present that COF increases sharply with the abrasive concentration up to 20 wt% and then shows a slight decrease from 20wt% to 40wt%. Temperature is a product of the friction force that is proportional to COF, which is an indicator for the mechanism of the sapphire CMP.

MORPHOLOGY CONTROL OF ULTRAFINE CeO_2 AND ITS POLISHING EFFICACY

Homogenous precipitation and subsequent calcination has been used tosynthesize ultrafine ceria from cerium nitrate and urea solution. The ceria calcined from theprecursor inherit the size and morphology of it. The size and morphology of the precursor areclosely related to the preparation process. The morphology, size and distribution of the precursorcould be tailored by changing the reaction condition and the ageing time. Monodispersed 200 nm sizedspherical particles is prepared by this method. The powder is used in the chemical-mechanicalpolishing of Si wafer. The average surface roughness of the polished Si wafer is 0.171 nm measuredby AFM.

Method of surface treatment on sapphire substrate

Sapphire single crystals are widely used in many areas because of the special physic properties and important application value. As an important substrate material, stringent surface quality requirements, i.e. surface finish and flatness, are required. The use of CMP technique can produce high quality surface finishes at low cost and with fast material removal rates. The sapphire substrate surface is treated by using CMP method. According to sapphire substrate and its product properties, SiO2 sol is chosen as abrasive. The particle size is 15-25 nm and the concentration is 40%. According to the experiment results, pH value is 10.5-11.5. After polishing and cleaning the sapphire surface, the surface roughness was measured by using AFM method and the lowest value of Ra 0.1 nm was obtained. From the results, it can be seen that using such method, the optimal sapphire surface can be gotten, which is advantageous for epitaxial growth and device making-up.

蓝宝石光学曲面柱形宽缎带磁流变抛光仿真分析及实验研究

目的针对目前光滑无损伤光学曲面蓝宝石加工成本高、效率低的问题,对加工过程中磁流变抛光缎带进行流体仿真,进而优化抛光轮表面结构。方法设计并提出3种表面结构柱形宽缎带磁流变抛光轮,介绍了磁流变抛光轮加工的基本原理,建立了磁流变抛光垫Bingham流体特性加工仿真模型,分析了3种抛光轮表面结构对工件表面磁通密度模、流场流速、流场压力分布的影响。同时对3种抛光轮的抛光效果进行了实验探究,探究了抛光轮表面结构对材料去除率和抛光后表面粗糙度的影响规律。结果仿真结果表明,抛光轮表面槽型结构具有能增强磁通密度模、增大流体流速和流体压力的特性。实验结果表明,螺旋槽抛光轮的抛光效果最好,在螺旋抛光轮作用下,材料去除率为0.22mg/h,抛光后蓝宝石表面粗糙度为1.08nm。最终抛光轮近壁区总压力和速度的乘积结果与抛光轮实验去除率结果具有较好的一致性。结论槽型结构可以提高抛光液在抛光轮表面的固着效果,影响工件表面流场运动状态,增强工件表面受到抛光垫的作用力。相较于光滑和横条槽抛光轮,螺旋槽抛光轮的抛光效率最高,表面粗糙度最低,可有效提高抛光效果。

工艺参数对浸没式直流介电泳辅助化学机械抛光蓝宝石晶片的影响

目的为了实现蓝宝石晶片的高效超光滑表面加工,提出浸没式直流介电泳辅助化学机械抛光方法,研究该方法对蓝宝石晶片的加工适应性。方法搭建了浸没式直流介电泳辅助化学机械抛光系统,通过单因素实验探究接入电压、工件及抛光盘转速、偏摆移动速度、抛光时间及抛光垫类型对蓝宝石晶片的加工效果,并深入分析负介电泳效应对CMP加工过程的影响。结果直流介电泳辅助CMP方法可以显著提高蓝宝石晶片的抛光效果,在2000V的接入电压下,化学机械抛光的材料去除率MRR提高了99.97%,达到了7.53nm/min,表面粗糙度Ra降低至2.51nm,工件表面划痕数量明显减少。工件及抛光盘转速、偏摆移动速度的提升都会使抛光MRR和Ra先升后降,带槽的抛光垫对介电泳效应控制磨料起促进作用。各个因素的影响对提高有效磨料数起交互作用,负介电泳效应促使磨料聚集在抛光垫表面,而工件与抛光垫的相对运动促使磨料更新循环。结论采用接入电压2000 V、工件及抛光盘转速80 r/min、偏摆速度60 r/min,在精抛垫下抛光蓝宝石晶片90 min,可以获得表面粗糙度Ra为0.953 nm的光滑表面。

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p H、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9h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。

气囊抛光蓝宝石弧面研究分析

随着国防军工和LED产业发展,对蓝宝石衬底的需求和形状复杂度的要求逐步提升。蓝宝石传统抛光方式如化学机械抛光存在效率低、曲面加工效果不佳等问题,而气囊抛光作为快速抛光方式之一,适用于各种曲面的抛光,故将气囊抛光技术应用于蓝宝石弧面抛光。首先基于机器人平台建立抛光运动模型,随后通过单因素试验和正交试验得到较优工艺参数,最后在较优工艺参数下进行整弧面抛光并探究抛光时间对蓝宝石表面质量的影响。结果表明,抛光时间为8 min时,工件弧面表面粗糙度Ra从541.5 nm下降至41.2 nm并成功保形,验证了气囊抛光蓝宝石弧面的工艺可行性。

Preparation of Ag2O modified silica abrasives and their chemical mechanical polishing performances on sapphire

The chemical mechanical polishing (CMP) process has become a widely accepted global planarization technology.The abrasive material is one of the key elements in CMP.In the presented paper,an Ag-doped colloidal SiO2 abrasive is synthesized by a seed-induced growth method.It is characterized by time-of-flight secondary ion mass spectroscopy and scanning electron microscopy to analyze the composition and morphology.The CMP performance of the Ag-doped colloidal silica abrasives on sapphire substrates is investigated.Experiment results show the material removal rate (MRR) of Ag-doped colloidal silica abrasives is obviously higher than that of pure colloidal silica abrasives under the same testing conditions.The surfaces that are polished by composite colloidal abrasives exhibit lower surface roughness (Ra) than those polished by pure colloidal silica abrasives.Furthermore,the acting mechanism of Ag-doped colloidal SiO2 composite abrasives in sapphire CMP is analyzed by X-ray photoelectron spectroscopy,and analytical results show that element Ag forms Ag2O which acts as a catalyst to promote the chemical effect in CMP and leads to the increasing of MRR.

Novel model of material removal rate on ultrasonic-assisted chemical mechanical polishing for sapphire

Ultrasonic-assisted chemical mechanical polishing(UA-CMP)can greatly improve the sapphire material removal and surface quality,but its polishing mechanism is still unclear.This paper proposed a novel model of material removal rate(MRR)to explore the mechanism of sapphire UA-CMP.It contains two modes,namely two-body wear and abrasive-impact.Furthermore,the atomic force microscopy(AFM)in-situ study,computational fluid dynamics(CFD)simulation,and polishing experiments were conducted to verify the model and reveal the polishing mechanism.In the AFM in-situ studies,the tip scratched the reaction layer on the sapphire surface.The pit with a 0.22 nm depth is the evidence of two-body wear.The CFD simulation showed that abrasives could be driven by the ultrasonic vibration to impact the sapphire surface at high frequencies.The maximum total velocity and the air volume fraction(AVF)in the central area increased from 0.26 to 0.55 m/s and 20%to 49%,respectively,with the rising amplitudes of 1–3μm.However,the maximum total velocity rose slightly from 0.33 to 0.42 m/s,and the AVF was nearly unchanged under 40–80 r/min.It indicated that the ultrasonic energy has great effects on the abrasive-impact mode.The UA-CMP experimental results exhibited that there was 63.7%improvement in MRR when the polishing velocities rose from 40 to 80 r/min.The roughness of the polished sapphire surface was R_(a)=0.07 nm.It identified that the higher speed achieved greater MRR mainly through the two-body wear mode.This study is beneficial to further understanding the UA-CMP mechanism and promoting the development of UA-CMP technology.

蓝宝石切割研磨及抛光技术研究进展

蓝宝石晶体由于其高硬度、良好的化学、光学特性,被广泛应用于许多领域。但蓝宝石晶体本身的高硬度、高脆性和高耐蚀性,使其切割、研磨及抛光难度增加。本文介绍了蓝宝石加工技术的研究进展,探讨了蓝宝石加工过程中存在的问题,分析了提高蓝宝石切割、研磨和抛光技术的工艺措施,提出了蓝宝石切割研磨和抛光技术的发展方向。

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 。

用于GaN生长的蓝宝石衬底化学抛光研究

蓝宝石是生长GaN材料最常用的衬底，本文研究了H2SO4和H3PO4的混合酸液的温度、混合酸的比例以及腐蚀时间对蓝宝石腐蚀速率的影响．发现在H2SO4：H3PO4=3：1的溶液中的腐蚀速率是由表面化学反应速率所控制．利用X射线双晶衍射对除去蓝宝石表面的机械损伤层情况进行了测量．

蓝宝石基LED外延片背减薄与抛光工艺研究

研究了蓝宝石基LED外延片背减薄过程中去除速率和表面粗糙度与研磨转速和研磨压力的关系,比较了不同的磨料颗粒度对去除速率和表面粗糙度的影响,并研究了抛光过程中表面粗糙度随时间的变化规律,为背减薄与抛光工艺的优化提供了依据。

不同磨料对蓝宝石晶片化学机械抛光的影响研究

本文制备了几种含不同磨料(SiC、Al2O3、不同粒径SiO2)的抛光液,通过纳米粒度仪分析磨料粒径分布,采用原子力显微镜观察磨料的粒径大小。研究了不同磨料对蓝宝石晶片化学机械抛光(CMP)的影响,利用原子力显微镜检测抛光前后蓝宝石晶片表面粗糙度。实验结果表明,在相同的条件下,采用SiC、Al2O3作为磨料时,材料去除速率与表面粗糙度均不理想;而采用含1%粒径为110 nm SiO2的抛光液,材料的去除速率最高为41.6 nm/min,表面粗糙度Ra=2.3 nm;采用含1%粒径为80 nm SiO2的抛光液,材料的去除速率为36.5 nm/min,表面粗糙度最低Ra=1.2 nm。

蓝宝石衬底片的精密加工

对SiO2磨料抛光蓝宝石衬底片进行了研究。结果表明,采用大粒径、高浓度的SiO2磨料抛光,可以获得良好的表面状态和较高的去除速率。抛光的适宜温度及pH值条件为:T=30℃;12.0>pH值≥9.0。并且,在抛光时应加入适量添加剂,方可获得较为理想的表面状态和较高的去除速率。实验同样证明,这种低成本、高质量的抛光除了可以应用于蓝宝石的抛光以外,还可以应用在其它一些硬质材料的抛光工艺中。

LED蓝宝石衬底抛光表面原子台阶形貌及其周期性研究

LED蓝宝石衬底的表面质量会极大影响到后续外延质量,进而影响到LED器件性能。蓝宝石研磨片经Al2O3磨粒粗抛液、SiO2磨粒精抛液下进行化学机械抛光(CMP),最终表面经原子力显微镜(AFM)所测表面粗糙度达到0.101nm,获得亚纳米级粗糙度超光滑表面,并呈现出原子台阶形貌。同时,通过使用Zygo表面形貌仪、AFM观察蓝宝石从研磨片经Al2O3粗抛液、SiO2精抛液抛光后的表面变化,阐述蓝宝石表面原子台阶形貌的形成原因,提出蓝宝石原子级超光滑表面形成的CMP去除机理。通过控制蓝宝石抛光中的工艺条件,获得a-a型、a-b型两种不同周期规律性的台阶形貌表面,并探讨不同周期规律性台阶形貌的形成机理。

SiO_2/CeO_2复合磨粒的制备及在蓝宝石晶片抛光中的应用

采用均相沉淀法制备了SiO2/CeO2复合磨料,并利用X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FT-IR)等对样品的相组成和形貌进行了表征。将所制备的SiO2/CeO2复合磨料用于蓝宝石晶片的化学机械抛光,利用原子力显微镜检测抛光后的蓝宝石晶片表面粗糙度。结果表明:所制备的SiO2/CeO2复合磨粒呈球形,粒径在40-50nm;在相同条件下,经过复合磨料抛光后的蓝宝石晶片表面粗糙度为0.32nm,材料去除速率为16.4nm/min,而SiO2抛光后的蓝宝石晶片表面粗糙度为0.92nm,材料去除速率为20.1nm/min。实验显示,复合磨料的材料去除速率略低于单一SiO2磨料,但它获得了较好的表面质量,基本满足蓝宝石作发光二极管(LED)衬底的工艺要求。

纳米SiO_2抛光液的制备及在蓝宝石抛光中的应用

制备一种纳米氧化硅抛光液,采用扫描电子显微镜、激光粒度仪、颗粒计数仪等对其物性参数进行表征;使用该抛光液对LED蓝宝石衬底进行机械化学抛光,采用轮廓仪、表面缺陷检测设备、原子力显微镜等对抛光后的蓝宝石衬底表面进行表征。结果表明,制备的纳米氧化硅抛光液对LED蓝宝石衬底具有优异的抛光性能,抛光后的表面无划伤、无腐蚀坑,且粗糙度小于0.2 nm。