Synthesis, characterization of CeO2@SiO2 nanoparticles and their oxide CMP behavior

SiO₂ ultrafine spheres are prepared by sol-gel method using tetraethylorthosilicate and ammonia as raw materials. CeO₂-coated SiO₂ (CeO₂@SiO₂) composite nanoparticles are also synthesized through chemical precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS) and dynamic light scattering (DLS) are used to characterize the CeO₂@SiO₂ composite particles. Silicon wafer covered by thermal oxide film is polished by CeO₂@SiO₂ composite abrasives, and the polishing behavior of novel composite abrasives is characterized by atomic force microscope (AFM). The results indicate that the phases of the as-prepared CeO₂@SiO₂ composite particles are composed of cubic fluorite CeO₂ and amorphous SiO₂. CeO₂@SiO₂ composite particles have excellent spherical morphologies and uniform particle size of 150-200 nm. The particle size of CeO₂ as shell is about 10 nm. After coating, the chemical state of SiO₂ is changed due to the formation of Si-O-Ce bond. The root-mean-square (RMS) roughness within 10 × 10 μm² area of thermal oxide film after polished by CeO₂@SiO₂ composite abrasives is 0.428 nm, and material removal rate can reach 454.6 nm/min.     

Preparation of silica/ceria nano composite abrasive and its CMP behavior on hard disk substrate

A novel silica/ceria nano composite abrasive was synthesized by homogeneous precipitation using carbamide, ammonium ceric nitrate and silica. The abrasive was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and scanning electron microscopy (SEM), respectively. Then, the chemical mechanical polishing performances of the composite abrasive on hard disk substrate with nickel-phosphorous plated were investigated. Atomic force microscopy images show that the prepared abrasive gives much lower topographical variations than before polishing. The average waviness (Wa) of the polished hard substrate surface can be reduced from 15.5 Å before polishing to 8.36 Å, and the average of roughness (Ra) can be reduced from 14 Å before polishing to 4.80 Å.     

Preparation of α-alumina/polymethacrylic acid composite abrasive and its CMP performance on glass substrate

Chemical mechanic polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of key elements during CMP process. α-Alumina particles, as a kind of widely used abrasive in CMP slurries, often cause surface defects due to its high hardness and agglomeration. In order to enhance the dispersion stability and prevent agglomeration of pure alumina abrasives in CMP, α-alumina grafted with polymethacrylic acid (α-Al₂O₃-g-PMAA) composite abrasives was prepared and characterized by means of Fourier transform infrared (FTIR), Mastersizer 2000 instrument and scanning electron microscope (SEM). The results indicated that the prepared α-Al₂O₃-g-PMAA composite abrasives have better dispersion stability than pure α-Al₂O₃ abrasives. The CMP performances of the α-Al₂O₃-g-PMAA composite abrasives on glass substrate were investigated by SPEEDFAM-16B-4M CMP equipment with different process parameters. By using the optimum process parameters, the prepared abrasives exhibit better glass substrate CMP performance than pure α-Al₂O₃ abrasives. Further, the CMP mechanism of glass substrate was deduced preliminarily.     

Polishing behaviors of single crystalline ceria abrasives on silicon dioxide and silicon nitride CMP

The effects of single crystalline ceria (CeO₂) abrasives in chemical mechanical polishing (CMP) slurries were investigated for silicon dioxide (SiO₂) and silicon nitride (Si₃N₄) CMP process. The size of ceria abrasives was controlled by varying hydrothermal reaction conditions. Polishing removal rate was measured with four slurries, with different mean primary particle size of 62, 116, 163 and 232 nm. The polishing results showed that the single crystalline ceria abrasives were not easily broken-down by mechanical force during CMP process. It was found that the removal rate of oxide and nitride film strongly depend upon abrasive size, whereas the surface uniformity deteriorates as abrasive size increases. The observed polishing results confirmed that there exists an optimum abrasive size (163 nm) for maximum removal selectivity between oxide and nitride films. The polishing behavior of the single crystalline ceria abrasives was discussed in terms of morphological properties of the abrasive particle.     

蓝宝石衬底片的抛光研究

本研究对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。抛光的适宜的温度及pH值条件为:T=30℃;13.0>pH≥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、高质量的抛光除可以应用在蓝宝石的抛光以外,还可以应用在其它一些硬质材料的抛光工艺中。     

化学机械抛光浆料研究进展

化学机械抛光(CMP)作为目前唯一可以实现全面平坦化的工艺技术,已被越来越广泛地应用到集成电路芯片、计算机硬磁盘和光学玻璃等表面的超精密抛光.介绍了CMP技术的发展背景,以及目前国内外抛光浆料的研究现状,并根据CMP浆料磨料的性质,将其分为单磨料、混合磨料和复合磨料浆料,对每一种浆料做了总体描述.详细介绍了近年来发展的复合磨料制备技术及其在CMP中的应用,并展望了CMP技术的发展前景以及新型抛光浆料的开发方向.     

Temperature effects of pad conditioning process on oxide CMP: Polishing pad, slurry characteristics, and surface reactions

Temperature effects were investigated on the improvement of silicon dioxide (oxide) chemical mechanical polishing performances including removal rate and surface morphology by controlling the pad conditioning temperature. The characteristics of silica slurry including potential of hydrogen (pH), conductivity, particle size, and zeta potential were changed by the frictional heat of the polishing process and the remaining heat after a high-temperature pad conditioning process. These changed slurry properties made the oxide surface hydro-carbonate to be removed easily. The slurry residues in pores and grooves of the polishing pad were also clearly removed by the high-temperature pad conditioning process. These clear pores and enlarged grooves made the slurry attack the oxide surface. The planarity of the oxide film was improved by the use of a little softened pad after the high-temperature pad conditioning process.     

化学机械抛光用SiO2研磨料的制备及其后处理

以水玻璃为主要原料、采用多次生长法,低zeta电位生长、高电位陈化等控制过程,生产出具有不同粒径、稳定的碱性单分散硅溶胶产品,并实现120nm大粒径硅溶胶生长可控,突破生长大粒径的难题。并采用离子交换法对产品进行处理,使其金属离子含量降到10^-6级,符合微电子工业对相关耗材的要求。     

磨料黏度对CMP抛光速率的影响及机理的研究

抛光磨料在抛光衬底和抛光垫间做磨削运动,它是CMP工艺的重要组成部分,是决定抛光速率和平坦化能力的重要影响因素。因此分析磨料的各物性参数对CMP过程的影响尤为重要。随着晶圆表面加工尺寸的进一步精密化,磨料黏度作为抛光磨料重要物性参数之一,受到越来越多的重视。根据实验结果从微观角度研究了磨料黏度对CMP抛光速率的影响及机理,并由此得出当抛光液磨料黏度为1.5 mPa.s时,抛光速率可达到458 nm/min且抛光表面粗糙度为0.353 nm的良好表面状态。     

Defect formation in epitaxial oxide dielectric layers due to substrate surface relief

Defects were characterized in epitaxial (001) CeO₂ films deposited and planarizedin situ on patterned (001) LaAlO₃ substrates by ion beam assisted deposition (IBAD). A hill and valley structure with steps running parallel to the [100] LaAlO₃ axis was produced on the surface of the substrate by photolithography and ion beam etching prior to film deposition. A conformai epitaxial CeO₂ layer of ∼ 100 nm thickness was deposited on the heated substrate by e-beam evaporation. Lattice-matching between the e-beam film and the substrate was of the type: (001) CeO₂∥(001) LaAlO₃ and [110] CeO₂∥[100] LaAlO₃. Evaporative deposition of additional film onto the conformai layer was accompanied by bombardment with a 500 eV argon/oxygen ion beam to promotein situ planarization. Extreme lattice misfit for the orientation (001) CeO₂∥(001)LaAlO₃ and [001] CeO₂∥[001] LaAlO₃ caused formation of dislocations in the e-beam CeO₂ film in the vicinity of individual ledges in the substrate surface. Coherence of the CeO₂ film was locally lost in the step regions of the hill and valley structure. The large patterned steps, which are composed of numerous adjacent ledges in the LaAlO₃ surface, caused nucleation of CeO₂ with a tilt misalignment of up to ∼5‡ about the substrate [100]. Nucleation and growth of nonepitaxial CeO₂ crystallites was observed along the step regions of the film during the IBAD portion of deposition. Defect formation in the e-beam ceria layer due to substrate surface relief indicates that “lattice engineering≓ of multilayer epitaxial structures may not be possible when nonplanar surfaces are created during device fabrication. The IBAD CeO₂ layer was more defective than the conformai layer deposited without the impinging ion beam, even in the portions of the film where epitaxy was maintained throughout both layers.     

Effect of hydrogen peroxide concentration on surface micro- roughness of silicon wafer after final polishing

The effect of hydrogen peroxide (H₂O₂) concentration in alkaline slurry on the surface micro-roughness of final polished silicon wafer was investigated. The root mean square roughness (RMS) reached minimum with H₂O₂ when the concentration is 0.05 wt%. Meanwhile, the contact angle of the polished surface was decreased to 21°. This decrease was attributed to enhanced chemical reaction in the CMP process. Electrochemical impedance was measured to explore the variation with addition of H₂O₂ in the reaction process of silicon erosion. Based on the measurements, a mechanism was suggested to explain the phenomenon in combine with the coefficient of friction force in the chemical mechanical polishing (CMP) process.     

Analysis of flow between a wafer and pad during CMP processes

In this paper, we summarize the development of a numerical model for the chemical mechanical planarization (CMP) process and experimentally investigate the effects of pad conditioning on slurry transport and mixing. A simplified two-dimensional numerical model of slurry flow beneath a stationary wafer was developed to determine the pressure and shear stress beneath a wafer. The initial results indicate that in the hydrodynamic regime a positive upward pressure is exerted on the wafer. We also examined three cases to study pad effects on slurry transport; polishing with an Embossed Politex pad, an unconditioned IC1000 pad, and a conditioned IC1000 pad. Cab-O-Sperse SC1 slurry was used in a 1:1.5 dilution with water. Mixing data show that conditioning has a negligible effect on the rate of slurry entrainment and mixing; however, conditioning has a large effect on the thickness of the slurry layer between the wafer and pad. Conditioning was found to increase the slurry thickness by a factor of two. In addition the gradients in slurry age beneath the wafer were compared among the three cases. The IC1000 pads supported a gradient in the inner third of the wafer only, while the Embossed Politex pad showed a linear gradient across the wafer implying it retains pockets of unmixed slurry in the embossed topography.     

化学机械抛光对铜互连器件的影响及失效分析

探讨了Cu化学机械抛光(CMP)工艺引起Cu互连器件失效的原因以及对可靠性的影响,对Cu CMP工艺缺陷导致器件失效的案例进行分析.由于CMP的技术特点,不可避免地会产生一些工艺缺陷和工艺误差,从而引起器件失效.必须根据标准要求,出厂或封装前对圆片进行芯片功能参数测试和严格的镜检,以便在封装前剔除存在潜在工艺缺陷的芯片,达到既定可靠性要求.     

Preparation and characterization of thin films of MgO,Al2O3 and MgAl2O4 by atomic layer deposition

MgO, Al₂O₃ and MgAl₂O₄ thin films were deposited on silicon substrates at various temperatures by the atomic layer deposition (ALD) method using bis(cyclopentadienyl)magnesium, triethylaluminum, and H₂O and were characterized systematically. High-quality polycrystalline MgO films were deposited for a substrate temperature above 500°C, and amorphous thin films were deposited around 400°C. The deposited Al₂O₃ and MgAl₂O₄ thin films were characterized as amorphous in structure. Applicability of ALD to complex oxides is discussed.     

降低CMP用SiO_2溶胶中金属离子含量及其机理探析

探析了阳、阴离子树脂对SiO2溶胶中金属离子交换去除的机理,确定阳-阴-阳三步法对SiO2溶胶进行金属离子去除,而后由有机碱调节pH值至碱性稳定区,从而制得高纯度、高稳定性微电子CMP用SiO2溶胶产品。     

A study on the chemical mechanical polishing of oxide film using a zirconia (ZrO2)-mixed abrasive slurry (MAS)

We have studied the chemical mechanical polishing (CMP) characteristics of mixed abrasive slurry (MAS) retreated by adding of zirconium oxide (ZrO₂) abrasives within 1:10 diluted silica slurry. These mixed abrasives in the MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performance such as removal rate and non-uniformity. As an experimental result, the comparable slurry characteristics when compared to the original silica slurry were obtained from the viewpoint of high removal rate and low non-uniformity for excellent CMP performance. Therefore, our proposed ZrO₂-MAS can be useful to save on the high cost of slurry consumption since we used a 1:10 diluted silica slurry.     

ULSI介质CMP用大粒径硅溶胶纳米研磨料的合成及应用研究

针对超大规模集成电路多层互连结构中介质CMP抛光速率低,急需的大粒径硅溶胶研磨料,本文采用改进的粒径生长控制工艺制备介质CMP用大粒径硅溶胶,并采用TEM、激光粒度分析仪和Zeta电位测试仪等先进手段对其粒径大小、粒径分布和稳定性进行了表征。以低分散度硅溶胶纳米研磨料配制抛光浆料进行了二氧化硅介质的CMP研究,结果表明,平均粒径103．4nm的硅溶胶浆料的去除速率达630nm／min,有效解决了二氧化硅介质CMP低速率的难题。     

Formation of nickel-manganese oxide thermistors studied by XRD,SEM and auger spectroscopy

This paper describes the formation of nickel-manganeses oxide thermistor bodies at 1000–1340° C, employing analytical techniques of XRD, SEM/EPMA and AES. The micro-structural studies revealed that the main phase of nickel manganite coexists with a solid solution of NiO in Mn₃O₄ in the final product. The optimum firing conditions to achieve the necessary electrical properties as well as the development of the desired microstructure could be selected around 1200° C, for 4 hrs in an ambient atmosphere. Above this temperature, the density begins to decrease while the resistivity increases. These anomalous electrical resistivity variations could be partly attributed to the trapped oxygen which was evolved from the decomposition of the unreacted α-Mn₂O₃. At-lower temperatures, unreacted nickel oxide residuals as well as a high porosity of the samples would yield specimens with high resistivity.     

Preparation and characterization of SiO2 films with different techniques

The SiO₂ films were prepared by rf-sputtering and sol-gel techniques. The influences of film preparing methods on the characteristics including refractive index, film thickness, composition, morphology, and shrinkage were investigated. Atomic force microscopy was used to examine the surface morphology of films deposited.