Influence of adhesion of silica and ceria abrasive nanoparticles on Chemical-Mechanical Planarization of silica surfaces

We report on a direct measurement of adhesion between abrasive nanoparticles of irregular shape, which are used in semiconductor industry in the process of Chemical-Mechanical Planarization (CMP), and silica surface. The adhesion of ceria and silica nanoparticles to silica surface is measured in multiple chemistries of different CMP slurries using a specially developed atomic force microscopy (AFM) method. Using this method, we study the influence of adhesion on the main parameters of CMP, removal rate and defectivity, scratches. While being plausible to expect correlation between these parameters and adhesion, it has not been systematically studied as of yet. We observed direct correlation between adhesion and removal rate. Comparing the measured defectivity and adhesion, we observe the presence of some correlation between these parameters. We conclude that both adhesion and shape of abrasive particles influence defectivity, micro-scratches. Direct measurements of the adhesion between abrasive nano-particles and surface can be used in the screening of new slurries as well as various modeling related to wearing of the surfaces.     

Describing Hydrodynamic Particle Removal from Surfaces Using the Particle Reynolds Number

The fundamental processes related to the removal of fine particles from surfaces in a hydrodynamic flow field are not adequately understood. A critical particle Reynolds number approach is proposed to assess these mechanisms for fine particles when surface roughness is small compared to particle diameter. At and above the critical particle Reynolds number, particle removal occurs, while below the critical value, particles remain attached to a surface. The system under consideration consists of glass particles adhering to a glass surface in laminar channel flow. Our results indicate rolling is the removal mechanism, which is in agreement with the literature. Theoretical results of the critical particle Reynolds number model for rolling removal are in general agreement with experimental data when particle size distribution, particle and surface roughness, and system Hamaker constant are taken into account.     

Stationary perturbation theory

Summary After a short recapitulation of the basic concepts of stationary perturbation theory, this is applied to a many-electron Hamiltonian, with or without an external field, given in a Fock space formulation in terms of a finite basis, the exact eigenfunctions of which are the full-CI wave functions. The Lie algebra _c ⁿ of the variational group corresponding to this problem is presented. It has an important subalgebra _c ⁽¹⁾ of one-particle transformations. Hartree-Fock and coupled Hartree-Fock (also uncoupled Hartree-Fock) as well as MC-SCF and coupled MC-SCF are outlined in this framework. Many-body perturbation theory and Møller-Plesset perturbation theory are derived from the same kind of stationarity condition and a new non-perturbative iteration construction of the full-CI wave function is proposed, the first Newton-Raphson iteration cycle of which is CEPA-0. For the treatment of electron correlation for properties two variants of Møller-Plesset theory referred to as coupled (CMP) and uncoupled (UCMP) are defined, neither of which is fully satisfactory. While CMP satisfies a Brillouin condition, which implies that first order correlation corrections to first- and second-order properties vanish, it does not satisfy a Hellmann-Feynman theorem, i.e. a first order property isnot the expectation value of the operator associated with the property. Conversely UCMP satisfies a Hellmann-Feynman theorem but no Brillouin theorem. The incompatibility of the two theorems is related to an unbalanced treatment of one-particle- and higher excitations in MP theory. CMP, which is based on coupled Hartree-Fock as uncorrelated reference, appears to have slight advantages over UCMP, but neither variant looks very promising for the evaluation of 2nd order correlation corrections to 2nd-order properties. Then four variants of the perturbation theory of properties with a nonperturbative treatment of electron correlation on CEPA-0 level (but extendable to a higher level) are discussed. While those variants which are the direct counterpart of UCMP and CMP must be discarded, the perturbative CEPA-0 derived from a perturbative treatment on full-CI level appears to satisfy all important criteria, in particular it satisfies a Brillouin-Brueckner condition and a Hellmann-Feynman theorem. A simplified version, the coupled Brillouin-Brueckner CEPA-0 appears to have essentially the same qualities. It is important to replace the Brillouin condition of MP theory by the Brillouin-Brueckner condition in non-perturbative approaches, especially if one is interested in properties.     

Preparation of alumina/silica core-shell abrasives and their CMP behavior

Abrasive is one of key influencing factors on the surface quality during the chemical mechanic polishing (CMP). α-Alumina particles, as a kind of widely used abrasive in CMP slurries, often cause to surface defects because of its high hardness. In the present paper, a series of novel alumina/silica core-shell abrasives in slurries were described. The CMP performances of the alumina/silica core-shell abrasives on hard disk substrate were investigated by using a SPEEDFAM-16B-4M CMP equipment. Experimental results indicate that the CMP performances are strong dependent on the coated SiO₂ content of the alumina/silica composite abrasives. Slurries containing the alumina/silica composite abrasives exhibited lower surface roughness and waviness as well as lower topographical variations and less scratch than that containing pure alumina abrasive under the same testing conditions.     

化学机械抛光作用与单晶基片超光滑表面的获取

单晶基片的表面光洁度指标是影响后续薄膜生长质量的重要因素.本文通过对比实验的方法,就采用CMP(chemical mechanical polish)工艺获取超光滑单晶基片做了深入的观察研究,并通过AFM(atomicforce microscope)的最终检测结果给出具有说服力的结论.     

Characterization of post-copper CMP surfaces with scanning probe microscopy: Part 1: Surface leakage measurement with conductive atomic force microscopy

We demonstrate in this paper for the first time the use of conductive atomic force microscopy (AFM) to measure surface leakage between copper structures with varying line width and spacing in the micro and sub micrometer ranges. Conducting atomic force microscopy allows subsequent measurement of the topography as well as the electrical properties of surfaces. The feasibility and interest of these measurements will be shown by studying the impact of chemical mechanical polishing (CMP) of an electrical interface bearing different micrometric copper structures. As expected the polishing time has a crucial impact on the current determined between closely spaced copper structures. This paper will also deal with issues observed during the measurement.     

Calorimetric evidence for conformational transitions of RNase A in the presence of cytidine 2′,3′-cyclic phosphate

Thermal denaturation of ribonuclease A (RNase A) complex with cytidine 3′-monophosphate (3′CMP) was studied by differential scanning calorimetry (DSC). The kinetic and binding studies of RNase A with cytidine 2′,3′-cyclic phosphate (cCMP) as a substrate, and 3′CMP as a ligand were also investigated by difference spectrophotometry. The obtained kinetic saturation curve reveals the occurrence of an anomalous non-hyperbolic shape at high substrate concentrations, and a biphasic binding isotherm. These phenomena indicate that a conformational change is occurring with RNase A during the hydrolysis of cCMP. A combination of kinetic and thermodynamic studies tends to elucidate the reasons for the formation of a non-hyperbolic behavior in a kinetic saturation curve. The thermal profile of the enzyme-3′CMP complexes shows a splitting of two distinct peaks with different structural stabilities of melting points (T_m) of 325 and 337 K. The bifurcate appearance of DSC profile of RNase A-3′CMP complexes manifests a physical view of a light kinetic structural transition. It is worthy to note, the direct binding (not via enzymatic reaction) of enzyme with 3′CMP indicates single DSC profile and monophasic binding isotherm.     

化学机械抛光中纳米颗粒的作用分析

化学机械抛光（chemical mechanical polishing, CMP）是用于获取原子级平面度的有效手 段.目前，CMP的抛光液通常使用纳米级颗粒来加速切除和优化抛光质量.这类流体的流变性 能必须考虑微极性效应的影响.对考虑微极性效应的运动方程的求解，有助于了解CMP的作用 机理.数值模拟表明，微极性将提高抛光液的等效黏度从而在一定程度上提高其承载能力， 加速材料去除.这在低节距或低转速下尤为明显，体现出其具有尺寸依赖性.通过改变抛光液 中粒子的微极性，用实验研究了微极性效应对CMP中材料去除速率的影响，证明了分析的合 理性. 关键词： 化学机械抛光 微极流体 抛光液 流变特性 材料去除速率