中国有色金属学报

文章编号:1004-0609(2010)08-1612-06

新型核-壳结构PS/CeO2和PS/SiO2复合磨料的制备

及其抛光性能

陈  杨1,隆仁伟1,陈志刚2,陈爱莲3

(1. 江苏工业学院 材料科学与工程学院,常州 213164;

2. 苏州科技学院,苏州 215011;3. 江苏工业学院 机械与能源学院,常州 213164)

摘 要:

以聚苯乙烯(PS)微球为内核,采用液相法制备具有核壳结构的PS/CeO2和PS/SiO2复合颗粒。利用X射线衍射仪、透射电子显微镜、场发射扫描电子显微镜、傅里叶转换红外光谱仪和热重分析仪等对所制备样品的物相结构、形貌和粒径等进行表征。将所制备的复合磨料用于硅晶片表面二氧化硅介质层的化学机械抛光,采用原子力显微镜观察抛光表面的微观形貌,并测量表面粗糙度。结果表明:所制备的PS/CeO2和PS/SiO2复合颗粒呈近球形,粒径为250~300 nm,且具有核壳包覆结构,包覆层的厚度为10~20 nm;硅晶片表面二氧化硅介质层经PS/CeO2和PS/SiO2复合颗粒抛光后,表面无划痕,且非常平整,在5 μm×5 μm范围内,粗糙度均方根值(RMS)分别为0.238 nm和0.254 nm。

关键词:

PS/CeO2复合磨料PS/SiO2复合磨料核-壳结构包覆化学机械抛光

中图分类号:TB383       文献标志码:A

Preparation and polishing performance of polystyrene-ceria and polystyrene-silica composite with novel core-shell structure

CHEN Yang1, LONG Ren-wei1, CHEN Zhi-gang2, CHEN Ai-lian3

(1. School of Materials Science and Engineering, Jiangsu Polytechnic University, Changzhou 213164, China;

2. Suzhou University of Science and Technology, Suzhou 215011, China;

3. School of Mechanical and Energy Engineering, Jiangsu Polytechnic University, Changzhou 213164, China)

Abstract: The PS/CeO2 and PS/SiO2 composites with core-shell structure were prepared by chemical precipitation method using polystyrene (PS) as core and ceria (silica) nanoparticles as shell. The phases structures, morphologies and particle size of PS/CeO2 and PS/SiO2 composite particles were analyzed by X-ray diffractometry (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The thermal oxide film covered silicon wafer was chemical mechanical polished (CMP) by composite abrasives, and the polishing behavior of the novel composite abrasives was characterized by atomic force microscope (AFM). The results indicate that PS/CeO2 and PS/SiO2 composite particles with core-shell morphology are obtained successfully, the particles size is 250~300 nm and PS microspheres are uniformly coated by CeO2 or SiO2. AFM 2D-morphologies show that the polished surface becomes smooth and micro-scratch can hardly be observed. The root-mean-square roughness values within area of 5 μm×5 μm is 0.238 nm and 0.254 nm, respectively after thermal oxide film surface polished with PS/CeO2 and PS/SiO2 composite abrasives.

Key words: PS/CeO2 composite abrasives; PS/SiO2 composite abrasives; core-shell structure; coating; chemical mechanical polishing

化学机械抛光/平坦化(Chemical-mechanical polishing,CMP)是超大规模集成电路制造工艺中的关键技术之一,抛光浆料中磨料的自身特性(磨料的种类、形貌、粒径和粒径分布、力学性质以及表面性质等)对抛光表面的质量(粗糙度、平整度以及缺陷的种类和数量等)和材料去除率有着至关重要的影响[1],传统的CMP磨料包括氧化硅、氧化铝和氧化铈等超细无机颗粒。

目前,有机-无机磨料的开发已经成为CMP相关技术领域中的一个研究热点,通过对纳米粒子的结构、形貌以及物理和/或化学性质进行微观设计,制备不同种类、硬度以及物理和/或化学性质的复合磨料,希望能进一步提高抛光表面质量。ARMINI等[2-8]制备以聚甲基丙烯酸酯微球为内核,表面包覆SiO2或CeO2的复合磨料,用于氧化物和铜的化学机械抛光,获得了良好的抛光效果,并将此归因于该核壳结构复合磨料所特有的弹簧状(Spinglike)结构?COUTINHO等[9]则制备了以聚N-异丙基丙烯酰胺为核,表面包覆纳米CeO2颗粒的复合磨料,并应用于氧化物化学机械抛光。此外,LEI等[10]还在Al2O3磨料表面接枝聚丙烯酰胺,通过表面改性的方法降低其硬度,使得数字光盘玻璃基片抛光表面质量得到改善。

为了研究氧化铈和氧化硅包覆聚苯乙烯纳米复合磨料,以聚苯乙烯微球为内核,采用液相法制备具有核壳结构的包覆型CeO2/PS和CeO2/PS纳米复合磨料,使用XRD、FESEM、TEM、FTIR和TGA等手段对样品进行表征;并将所制备的复合磨料配制成抛光浆料,考察其对二氧化硅介质层的化学机械抛光性能。

1  实验

苯乙烯(St),工业级,首先用5%NaOH水溶液洗涤数次除去阻聚剂,并用无水CaCl2干燥,再经减压蒸馏处理后置于冰箱中低温保存备用。二乙烯基苯、过硫酸钾、甲基丙烯酸、六水硝酸亚铈、六亚甲基四胺、正硅酸乙酯、氨水、无水乙醇等均购自上海      国药集团化学试剂有限公司,未作任何处理直接    使用。

将90 mL蒸馏水、20 mL苯乙烯(St)、1 mL二乙烯基苯和1 mL甲基丙烯酸依次加入到500 mL三口烧瓶(带有冷凝管和机械搅拌装置)中,搅拌均匀后置于105 ℃恒温油浴中加热至沸腾,5 min后加入引发剂过硫酸钾0.25 g(溶于10 mL蒸馏水中),反应2 h后即可得到牛奶状聚苯乙烯乳胶液。

量取按上述工艺所制备的聚苯乙烯乳胶液2 mL加入到350 mL蒸馏水中,超声强化分散15 min后加入2 g六水硝酸亚铈,搅拌均匀后再加入50 mL一定浓度的六亚甲基四胺水溶液,控制整个反应溶液中六水硝酸亚铈和六亚甲基四胺的浓度比为1?5。将配制的反应液在电磁搅拌的条件下于75 ℃下反应2 h,将沉淀物离心分离、洗涤(蒸馏水洗2遍、无水乙醇洗1遍,下同),再置于80 ℃鼓风干燥箱中烘干,研磨后即可得到PS/CeO2复合颗粒。

称取聚苯乙烯乳胶液2 g加入到50 g无水乙醇水中,超声强化分散15 min后依次加入3 g蒸馏水、3 g正硅酸乙酯和1 mL氨水,搅拌均匀后将反应液置于30 ℃下反应6 h,将沉淀物离心分离、洗涤,再置于80 ℃鼓风干燥箱中烘干,研磨后即可得到白色的PS/CeO2复合颗粒。

采用Rigaku X-III射线衍射仪(X-ray diffracometer,XRD)分析样品的物相结构,扫描角度范围为20?~80?;用Philips公司Tecnai-12型透射电镜(Transmission electron microscope,TEM)测定样品的微观形貌、壳层的厚度;采用Hitachi公司S-4800Ⅱ型场发射扫描电镜(Field emission scanning electron microscope,FESEM)观察样品的粒径大小、表面形貌和团聚情况;采用UV-3101型傅里叶转换红外光谱仪(Fourier transform infrared spectroscopy,FTIR)对样品的红外吸收进行测试。样品的热分析(Thermogravimetric analysis,TGA)通过美国TA公司SDT Q600型热重分析仪测定。

分别称取一定量的PS/CeO2和PS/SiO2复合磨料配制成抛光浆料,在如表1所列的抛光工艺条件下,使用丹麦Struers公司TegraForce-1/TrgraPol-15型精密抛光机对硅热氧化片(购自常州华诚常半微电子有限公司)进行抛光实验。用美国DI公司Nanoscope Ⅲa型原子力显微镜(Mutimode SPM,纵向分辨率为0.1 nm,横向分辨率为0.01 nm)观察抛光后晶片的表面微观形貌,测量表面粗糙度。

表1  抛光工艺参数

Table 1  Parameters of polishing process

2  结果与讨论

PS微球和PS/SiO2、PS/CeO2复合颗粒样品的FTIR谱如图1所示。从图1(a)可以看出,曲线a中3 400 cm-1和1 600 cm-1附近的吸收峰对应样品表面物理吸附水中O—H键的伸缩和弯曲振动吸收峰,3 100~    3 000 cm-1处的伸缩振动吸收峰对应苯环上C—H键的伸缩振动,3 000~2 800 cm-1处对应C—H键的伸缩振动,1 740 cm-1附近对应C=O键的伸缩振动,处于1 600、1 500和1 450 cm-1附近的谱带为苯环骨架振动的特征谱带,1 150 cm-1处的伸缩振动吸收峰对应的是C—O—C键的伸缩振动,760 cm-1和700 cm-1附近的吸收峰对应单取代苯环上的C—C键的伸缩振动[11-12]。从图1的曲线b和c可以看出曲线a中所有的伸缩振动吸收峰,这些特征峰的出现说明复合颗粒样品中存在聚苯乙烯。

对比图1曲线a、b和c可以看出,在PS/SiO2复合颗粒样品的FTIR谱中还出现SiO2的特征吸收    峰[13-14](1 090 cm-1附近为Si—O—Si键的反对称伸缩振动峰,800 cm-1附近为Si—O—Si键的对称伸缩振动峰,470 cm-1附近为Si—O—Si键的弯曲振动峰);PS/CeO2复合颗粒样品则在690 cm-1附近出现了Ce—O—Ce的振动峰[15],在400 cm-1附近出现了Ce—O键的伸缩振动峰[16]。由此可以说明分别形成了PS/SiO2和PS/CeO2复合材料。

图1  PS微球、PS/CeO2和PS/CeO2复合颗粒样品的红外  光谱

Fig.1  FTIR spectra of PS microsphere, PS/SiO2 composite and PS/CeO2 composite particles

PS/CeO2和PS/SiO2复合颗粒样品的XRD谱如图2所示。从图2的曲线a可以看出,PS/CeO2样品的衍射特征峰(2θ为27.9?、32.8?、47.5?和56.3?)的位置和相对强度均与CeO2的标准卡(JCPDS card, No 34-0394) 相一致,分别对应于(111)、(200)、(220) 和 (311)晶面,此外(400)、(331)和(420)等晶面峰也很明显,可以推断出样品中存在立方萤石结构的CeO2。从图2中曲线b中可以看出,PS/SiO2样品的XRD谱中没有出现尖锐的晶体衍射峰,在2θ=23.6?处衍射峰明显宽化,即在低衍射角区出现了一个馒头峰(非晶衍射峰),这表明样品中的SiO2具有无定形结构。

图2  复合颗粒样品的XRD谱

Fig.2  XRD patterns of PS/CeO2 and PS/SiO2 composite particles

图3所示为PS/CeO2和PS/SiO2复合颗粒样品的TEM像。由图3可以看出,所制备的复合颗粒呈近球形,粒径均在250~300 nm左右,分散性较好,具有明显的核-壳结构,TEM照片中颜色较浅的部分为PS内核,而周围颜色较深的部分则分别为CeO2和SiO2包覆层,包覆层的厚度在10~20 nm。PS/CeO2和PS/SiO2复合颗粒样品的FESEM像如图4所示。从图4可以看出,PS/CeO2和PS/SiO2复合颗粒的表面略显粗糙,具有明显的草莓状包覆结构。以上分析表明,所制备的复合颗粒具有明显的核-壳结构,PS内核表面包覆了CeO2或SiO2壳层,形成复合结构。

图3  PS/ CeO2和PS/SiO2复合颗粒样品的TEM像

Fig.3  TEM images of PS/CeO2 (a) and  PS/SiO2 (b) composites  particles

PS/CeO2和PS/SiO2复合颗粒样品的热重曲线如图5所示。由图5可以看出,样品的主要质量损失区在300~400 ℃的范围内,主要是由于聚苯乙烯链段断裂,即复合颗粒中聚苯乙烯内核的分解所引起的。PS/CeO2样品的TGA曲线(曲线a)中,300 ℃以下的质量损失主要是由于样品表面物理吸附水的去除所引起的,PS/SiO2复合颗粒样品TGA曲线(曲线b)中,300 ℃以下的质量损失则是由SiO2表面因物理作用而吸附的溶剂乙醇和物理吸附水的去除所造成的。样品加热到400 ℃后,质量基本达到恒定。

图4  PS/CeO2和PS/SiO2复合颗粒样品的FESEM像

Fig.4  FESEM images of PS/CeO2 (a) and PS/SiO2 (b) composites particles

图5  PS/CeO2和PS/SiO2复合颗粒样品的TGA曲线

Fig.5  TGA curves of PS/CeO2 and PS/SiO2 composites particles

此外,还可以通过热失重分析测量加热前后样品的质量变化,进而得知复合颗粒中壳层(CeO2和SiO2)的含量。经测定,PS/CeO2复合颗粒中CeO2的含量为39.26%(质量分数),PS/SiO2复合颗粒中SiO2的含量为43.93%。

图6和7所示分别为经PS/CeO2和PS/SiO2复合磨料抛光后二氧化硅表面的AFM二维形貌和三维立体形貌,其中垂直方向单位高度均为10 nm。由图6和7可以看出,抛光后表面无划痕,而且非常平整。经PS/CeO2复合磨料抛光后,表面在5 μm×5 μm范围内,Ra值和RMS值分别为0.188 nm和0.238 nm;经PS/SiO2复合磨料抛光后表面在5 μm×5 μm范围内,粗糙度Ra值和RMS值分别为0.202 nm和0.254 nm,抛光表面均具有亚纳米量级的粗糙度。以上结果表明,所制备的复合磨料对二氧化硅介质层有良好的抛光效果,并在铜和低介电常数(Low-k)材料中,CMP有着潜在的应用前景。

图6  经PS/CeO2复合磨料抛光后二氧化硅表面的AFM像

Fig.6  AFM images of oxide wafer surface polished by PS/CeO2 composite abrasives

图7  经PS/SiO2复合磨料抛光后二氧化硅表面的AFM像

Fig.7  AFM images of oxide wafer surface polished by PS/SiO2 composite abrasives

3  结论

1) 以聚苯乙烯(PS)微球为内核,采用液相法成功制备了具有核-壳结构,粒径在250~300 nm的近球形PS/CeO2和PS/SiO2复合颗粒,其壳层的厚度为10~20 nm。

2) 经PS/CeO2和PS/SiO2复合磨料抛光后的二氧化硅介质层表面几乎无划痕,且非常平整,在5 μm×5 μm范围内,粗糙度的均方根值分别为0.238 nm和0.254 nm。

3) 这种新型核壳结构的有机-无机复合磨料能够明显改善氧化物化学机械抛光表面的质量。

REFERENCES

[1] FENG Xiang-dong, SAYLE D C, WANG Zhong-lin, PARAS M S, SANTORA B, et al. Converting ceria polyhedral nanoparticles into single-crystal nanospheres[J]. Science, 2006, 312: 1504-1508.

[2] ARMINI S, WHELAN C M, MAEX K, HERNANDEZ J L, MOINPOURC M. Composite polymer core-silica shell abrasive particles during oxide cmp: A defectivity study[J]. Journal of the Electrochemical Society, 2007, 154(8): 667-671.

[3] ARMINI S, WHELAN C M, MOINPOUR M, MAEX K. Composite polymer core-silica shell abrasives: The effect of polishing time and slurry solid content on oxide CMP[J]. Electrochemical and Solid-State Letters, 2007, 10(9): 243-247.

[4] ARMINI S, WHELAN C M, MOINPOUR M, MAEX K. Composite polymer core-silica shell abrasives: The effect of the shape of the silica particles on oxide CMP[J]. Journal of the Electrochemical Society, 2008, 155(6): 401-406.

[5] ARMINI S, WHELAN C M, MOINPOUR M, MAEX K. Copper CMP with composite polymer core-silica shell abrasives: A defectivity study[J]. Journal of the Electrochemical Society, 2009, 156(1): 18-26.

[6] ARMINI S, WHELAN C M, MAEX K. Engineering polymer core-silica size in composite abrasives for CMP applications[J]. Electrochemical and Solid-State Letters, 2008, 11(10): 280-284.

[7] ARMINI S, de MESSEMAEKER J, WHELAN C M, MOINPOUR M, MAEX K. Composite polymer core-ceria shell abrasive particles during oxide CMP: A defectivity study[J]. Journal of the Electrochemical Society, 2008, 155(9): 653-660.

[8] ARMINI S, VAKARELSKI I U, WHELAN C M, HIGASHITANI K. Nanoscale indentation of polymer and composite polymer-silica core-shell submicrometer particles by atomic force microscopy[J]. Langmuir, 2007, 23(4): 2007- 2014.

[9] COUTINHO C A, MUDHIVARTHI S R, KUMAR A, GUPTA V K. Novel ceria-polymer microcomposites for chemical mechanical polishing[J]. Applied Surface Science, 2008, 255: 3090-3096.

[10] LEI Hong, LU Hai-shen, LUO Jian-bin, LU Xin-chun. Preparation of α-alumina-g-polyacrylamide composite abrasive and chemical mechanical polishing behavior[J]. Thin Solid Films, 2008, 516(10): 3005-3008.

[11] KARTSONAKIS I A, LIATSI P, DANIILIDIS I, KORDAS G. Synthesis, characterization, and antibacterial action of hollow ceria nanospheres with/without a conductive polymer coating[J]. Journal of American Ceramic Society, 2008, 91(2): 372-378.

[12] 贾进义, 刘晶冰, 张文熊, 常 琳, 井 琪. 掺钒二氧化钛中空微球的制备和光催化性能研究[J]. 无机材料学报, 2009, 24(4): 671-674.
JIA Jin-yi, LIU Jing-bing, ZHANG Wen-xiong, CHANG Lin, JING Qi. Synthesis and photocatalytic activity of vanadium doped titania hollow microspheres[J]. Journal of Inorganic Materials, 2009, 24(4): 671-674.

[13] ZHANG Wei, DEHGHANI-SANIJ A A, BLACKBURN R S. IR study on hydrogen bonding in epoxy resin–silica nanocomposites[J]. Progress in Natural Science, 2008, 18(7): 801-805.

[14] 刘立柱, 马红杰, 朱兴松, 金镇镐, 樊渝江. 聚乳酸/纳米二氧化硅原位复合材料的制备和性能[J]. 北京化工大学学报, 2007, 35(1): 66-69.
LIU Li-zhu, MA Hong-jie, ZHU Xing-song, JIN Zhen-gao, FAN Yu-jiang. Preparation and properties of polylactide/nano-silica in situ composites[J]. Journal of Beijing University of Chemical Technology, 2007, 35(1): 66-69.

[15] KSAPABUTR B, GULARI E, WONGKASEMJIT S. Sol-gel derived porous ceria powders using cerium glycolate complex as precursor[J]. Materials Chemistry and Physics, 2006, 99(2/3): 318-324.

[16] TENG Mei-ling, LUO Lai-tao, YANG Xiao-mao. Synthesis of mesoporous Ce1-xZrxO2 (x=0.2-0.5) and catalytic properties of CuO based catalysts[J]. Microporous and Mesoporous Materials, 2009, 119(1/3): 158-164.

(编辑 李艳红)

基金项目:江苏省工业支撑计划资助项目(BE2008037);常州市工业科技攻关资助项目(CE2007068,CE2008083);常州大学青年人才基金资助项目(JQ201005)

收稿日期:2009-08-25;修订日期:2010-03-03

通信作者:陈  杨,讲师,博士;电话:0519-86330066;E-mail:cy.jpu@126.com

[1] FENG Xiang-dong, SAYLE D C, WANG Zhong-lin, PARAS M S, SANTORA B, et al. Converting ceria polyhedral nanoparticles into single-crystal nanospheres[J]. Science, 2006, 312: 1504-1508.

[2] ARMINI S, WHELAN C M, MAEX K, HERNANDEZ J L, MOINPOURC M. Composite polymer core-silica shell abrasive particles during oxide cmp: A defectivity study[J]. Journal of the Electrochemical Society, 2007, 154(8): 667-671.

[3] ARMINI S, WHELAN C M, MOINPOUR M, MAEX K. Composite polymer core-silica shell abrasives: The effect of polishing time and slurry solid content on oxide CMP[J]. Electrochemical and Solid-State Letters, 2007, 10(9): 243-247.

[4] ARMINI S, WHELAN C M, MOINPOUR M, MAEX K. Composite polymer core-silica shell abrasives: The effect of the shape of the silica particles on oxide CMP[J]. Journal of the Electrochemical Society, 2008, 155(6): 401-406.

[5] ARMINI S, WHELAN C M, MOINPOUR M, MAEX K. Copper CMP with composite polymer core-silica shell abrasives: A defectivity study[J]. Journal of the Electrochemical Society, 2009, 156(1): 18-26.

[6] ARMINI S, WHELAN C M, MAEX K. Engineering polymer core-silica size in composite abrasives for CMP applications[J]. Electrochemical and Solid-State Letters, 2008, 11(10): 280-284.

[7] ARMINI S, de MESSEMAEKER J, WHELAN C M, MOINPOUR M, MAEX K. Composite polymer core-ceria shell abrasive particles during oxide CMP: A defectivity study[J]. Journal of the Electrochemical Society, 2008, 155(9): 653-660.

[8] ARMINI S, VAKARELSKI I U, WHELAN C M, HIGASHITANI K. Nanoscale indentation of polymer and composite polymer-silica core-shell submicrometer particles by atomic force microscopy[J]. Langmuir, 2007, 23(4): 2007- 2014.

[9] COUTINHO C A, MUDHIVARTHI S R, KUMAR A, GUPTA V K. Novel ceria-polymer microcomposites for chemical mechanical polishing[J]. Applied Surface Science, 2008, 255: 3090-3096.

[10] LEI Hong, LU Hai-shen, LUO Jian-bin, LU Xin-chun. Preparation of α-alumina-g-polyacrylamide composite abrasive and chemical mechanical polishing behavior[J]. Thin Solid Films, 2008, 516(10): 3005-3008.

[11] KARTSONAKIS I A, LIATSI P, DANIILIDIS I, KORDAS G. Synthesis, characterization, and antibacterial action of hollow ceria nanospheres with/without a conductive polymer coating[J]. Journal of American Ceramic Society, 2008, 91(2): 372-378.

[12] 贾进义, 刘晶冰, 张文熊, 常 琳, 井 琪. 掺钒二氧化钛中空微球的制备和光催化性能研究[J]. 无机材料学报, 2009, 24(4): 671-674.JIA Jin-yi, LIU Jing-bing, ZHANG Wen-xiong, CHANG Lin, JING Qi. Synthesis and photocatalytic activity of vanadium doped titania hollow microspheres[J]. Journal of Inorganic Materials, 2009, 24(4): 671-674.

[13] ZHANG Wei, DEHGHANI-SANIJ A A, BLACKBURN R S. IR study on hydrogen bonding in epoxy resin–silica nanocomposites[J]. Progress in Natural Science, 2008, 18(7): 801-805.

[14] 刘立柱, 马红杰, 朱兴松, 金镇镐, 樊渝江. 聚乳酸/纳米二氧化硅原位复合材料的制备和性能[J]. 北京化工大学学报, 2007, 35(1): 66-69.LIU Li-zhu, MA Hong-jie, ZHU Xing-song, JIN Zhen-gao, FAN Yu-jiang. Preparation and properties of polylactide/nano-silica in situ composites[J]. Journal of Beijing University of Chemical Technology, 2007, 35(1): 66-69.

[15] KSAPABUTR B, GULARI E, WONGKASEMJIT S. Sol-gel derived porous ceria powders using cerium glycolate complex as precursor[J]. Materials Chemistry and Physics, 2006, 99(2/3): 318-324.

[16] TENG Mei-ling, LUO Lai-tao, YANG Xiao-mao. Synthesis of mesoporous Ce1-xZrxO2 (x=0.2-0.5) and catalytic properties of CuO based catalysts[J]. Microporous and Mesoporous Materials, 2009, 119(1/3): 158-164.