The optimization of electrolytes and the material removal mechanisms for Cu electrochemical mechanical planarization(ECMP)at different pH values including 5-methyl-1H-benzotriazole(TTA),hydroxyethylidenediphosphoric a...The optimization of electrolytes and the material removal mechanisms for Cu electrochemical mechanical planarization(ECMP)at different pH values including 5-methyl-1H-benzotriazole(TTA),hydroxyethylidenediphosphoric acid(HEDP),and tribasic ammonium citrate(TAC)were investigated by electrochemical techniques,X-ray photoelectron spectrometer(XPS)analysis,nano-scratch tests,AFM measurements,and polishing of Cu-coated blanket wafers.The experimental results show that the planarization efficiency and the surface quality after ECMP obtained in alkali-based solutions are superior to that in acidic-based solutions,especially at pH=8.The optimal electrolyte compositions(mass fraction)are 6% HEDP,0.3% TTA and 3% TAC at pH=8.The main factor affecting the thickness of the oxide layer formed during ECMP process is the applied potential.The soft layer formation is a major mechanism for electrochemical enhanced mechanical abrasion.The surface topography evolution before and after electrochemical polishing(ECP)illustrates the mechanism of mechanical abrasion accelerating electrochemical dissolution,that is,the residual stress caused by the mechanical wear enhances the electrochemical dissolution rate.This understanding is beneficial for optimization of ECMP processes.展开更多
Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical ...Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data.展开更多
Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velo...Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velocimetry(PTV)technique was employed to characterize the particle removal displacement and velocity in the interface between a transparent copper film and a porous polyvinyl alcohol(PVA)brush during the cleaning process.Several different cleaning conditions including rotation speeds,loading pressure and cleaning agent were examined and the particle removal rate was compared.Elastic and friction removal,hydrodynamic removal and mixed-type removal are the three types of particle removal.Particles with an arc trace and uniform velocity curves were removed by friction and elastic force which were related to the brush load.Particles with a random trace and fluctuant velocity curves were removed by hydrodynamic force which was determined by the brush rotation speed.The increase of particle removal rate(PRR)with brush rotation speed is a logistic function.It is easier to improve PRR by increasing the brush load or by adding surfactant than by increasing the brush rotation speed.展开更多
A finite element analysis(FEA)model is developed for the chemical-mechanical polishing(CMP)process on the basis of a 12-in five-zone polishing head.The proposed FEA model shows that the contact stress non-uniformity i...A finite element analysis(FEA)model is developed for the chemical-mechanical polishing(CMP)process on the basis of a 12-in five-zone polishing head.The proposed FEA model shows that the contact stress non-uniformity is less dependent on the material property of the membrane and the geometry of the retaining ring.The larger the elastic modulus of the pad,the larger contact stress non-uniformity of the wafer.The applied loads on retaining ring and zone of the polishing head significantly affect the contact stress distribution.The stress adjustment ability of a zone depends on its position.In particular,the inner-side zone has a high stress adjustment ability,whereas the outer-side zone has a low stress adjustment ability.The predicted results by the model are shown to be consistent with the experimental data.Analysis results have revealed some insights regarding the performance of the multi-zone CMP.展开更多
The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties o...The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties of abrasives play a vital role in obtaining the ultra-precision and damage-free surface of wafers for improvement of their performances.In this work,a series of fine structured rod-shaped silica(RmSiO2)-based abrasives with controllable sizes and diverse ordered mesoporous structures were synthesized via a soft template approach,and successfully applied in the sustainable polishing slurry for improving the surface quality of cadmium zinc telluride(CZT)wafers.Compared with commercial silica gel,solid and mesoporous silica spheres,the RmSiO2 abrasives present superior elastic deformation capacity and surface precision machinability on account of their mesoporous structures and rod shapes.Especially,ultra-precision surface roughness and relatively effective material removal speed were achieved by the CMP process using the RmSiO2 abrasives with a length/diameter(L/d)ratio of 1.In addition,a potential CMP mechanism of the developed polishing slurry to CZT wafer was elucidated by analyzing X-ray photoelectron spectra and other characterizations.The proposed interfacial chemical and mechanical effects will provide a new strategy for improving abrasives’machinability and precision manufacture of hard-to-machine materials.展开更多
"Solar storm" has been commonly accepted by academic community and the public as a very popular scientific term. It is avivid description of violent ejections of a huge amount of magnetized plasma from the S..."Solar storm" has been commonly accepted by academic community and the public as a very popular scientific term. It is avivid description of violent ejections of a huge amount of magnetized plasma from the Sun as strong flare/CMEs, which sweepover into interplanetary space, develop, and affect our space environment. The solar storm could bring us disastrous spaceweather, destroy crucial technology, and cause a large-scale blackout. It is one of the natural disasters faced by modern humanbeings. Here we first briefly summarize the observational features of solar storms and introduce some key issues, and then wefocus on major advances in observational studies. We mainly introduce the efforts made by the Chinese scientists and comment on the challenges and opportunities that they are facing. In this era when scientific breakthroughs in solar storm studiescrucially depend on space-borne devices and large-aperture ground-based telescopes, the Chinese solar research communityneeds to develop its own major observational facilities and improve space weather forecasting abilities.展开更多
基金Project(50975058)supported by the National Science Foundation of China
文摘The optimization of electrolytes and the material removal mechanisms for Cu electrochemical mechanical planarization(ECMP)at different pH values including 5-methyl-1H-benzotriazole(TTA),hydroxyethylidenediphosphoric acid(HEDP),and tribasic ammonium citrate(TAC)were investigated by electrochemical techniques,X-ray photoelectron spectrometer(XPS)analysis,nano-scratch tests,AFM measurements,and polishing of Cu-coated blanket wafers.The experimental results show that the planarization efficiency and the surface quality after ECMP obtained in alkali-based solutions are superior to that in acidic-based solutions,especially at pH=8.The optimal electrolyte compositions(mass fraction)are 6% HEDP,0.3% TTA and 3% TAC at pH=8.The main factor affecting the thickness of the oxide layer formed during ECMP process is the applied potential.The soft layer formation is a major mechanism for electrochemical enhanced mechanical abrasion.The surface topography evolution before and after electrochemical polishing(ECP)illustrates the mechanism of mechanical abrasion accelerating electrochemical dissolution,that is,the residual stress caused by the mechanical wear enhances the electrochemical dissolution rate.This understanding is beneficial for optimization of ECMP processes.
基金Project(50975058) supported by the National Natural Science Foundation of China
文摘Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data.
基金supported by the National Natural Science Foundation of China(Grant No.51205006)the Tribology Science Fund of State Key Laboratory of Tribology and the Program for Excellent Talents by the Beijing Ministry of Organization
文摘Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velocimetry(PTV)technique was employed to characterize the particle removal displacement and velocity in the interface between a transparent copper film and a porous polyvinyl alcohol(PVA)brush during the cleaning process.Several different cleaning conditions including rotation speeds,loading pressure and cleaning agent were examined and the particle removal rate was compared.Elastic and friction removal,hydrodynamic removal and mixed-type removal are the three types of particle removal.Particles with an arc trace and uniform velocity curves were removed by friction and elastic force which were related to the brush load.Particles with a random trace and fluctuant velocity curves were removed by hydrodynamic force which was determined by the brush rotation speed.The increase of particle removal rate(PRR)with brush rotation speed is a logistic function.It is easier to improve PRR by increasing the brush load or by adding surfactant than by increasing the brush rotation speed.
基金supported by the Science Fund for Creative Research Groups (Grant No. 51021064)the National Natural Science Foundation of China (Grant No. 51205226)the China Postdoctoral Science Foundation (Grant No. 2012M510420)
文摘A finite element analysis(FEA)model is developed for the chemical-mechanical polishing(CMP)process on the basis of a 12-in five-zone polishing head.The proposed FEA model shows that the contact stress non-uniformity is less dependent on the material property of the membrane and the geometry of the retaining ring.The larger the elastic modulus of the pad,the larger contact stress non-uniformity of the wafer.The applied loads on retaining ring and zone of the polishing head significantly affect the contact stress distribution.The stress adjustment ability of a zone depends on its position.In particular,the inner-side zone has a high stress adjustment ability,whereas the outer-side zone has a low stress adjustment ability.The predicted results by the model are shown to be consistent with the experimental data.Analysis results have revealed some insights regarding the performance of the multi-zone CMP.
基金the National Key R&D Program of China(2018YFA0703400)the Xinghai Science Funds for Distinguished Young Scholars+1 种基金Thousand Youth Talents at Dalian University of Technology,the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning,Liaoning BaiQianWan Talents ProgramDalian National Laboratory for Clean Energy(DNL),DNL Cooperation Fund,Chinese Academy of Sciences(DNL180402)。
文摘The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties of abrasives play a vital role in obtaining the ultra-precision and damage-free surface of wafers for improvement of their performances.In this work,a series of fine structured rod-shaped silica(RmSiO2)-based abrasives with controllable sizes and diverse ordered mesoporous structures were synthesized via a soft template approach,and successfully applied in the sustainable polishing slurry for improving the surface quality of cadmium zinc telluride(CZT)wafers.Compared with commercial silica gel,solid and mesoporous silica spheres,the RmSiO2 abrasives present superior elastic deformation capacity and surface precision machinability on account of their mesoporous structures and rod shapes.Especially,ultra-precision surface roughness and relatively effective material removal speed were achieved by the CMP process using the RmSiO2 abrasives with a length/diameter(L/d)ratio of 1.In addition,a potential CMP mechanism of the developed polishing slurry to CZT wafer was elucidated by analyzing X-ray photoelectron spectra and other characterizations.The proposed interfacial chemical and mechanical effects will provide a new strategy for improving abrasives’machinability and precision manufacture of hard-to-machine materials.
基金supported by the National Basic Research Program of China (Grant Nos. 2011CB811402 and 2011CB811403)National Natural Science Foundation of China (Grant Nos. 11221063, 40890161 and 11173062)
文摘"Solar storm" has been commonly accepted by academic community and the public as a very popular scientific term. It is avivid description of violent ejections of a huge amount of magnetized plasma from the Sun as strong flare/CMEs, which sweepover into interplanetary space, develop, and affect our space environment. The solar storm could bring us disastrous spaceweather, destroy crucial technology, and cause a large-scale blackout. It is one of the natural disasters faced by modern humanbeings. Here we first briefly summarize the observational features of solar storms and introduce some key issues, and then wefocus on major advances in observational studies. We mainly introduce the efforts made by the Chinese scientists and comment on the challenges and opportunities that they are facing. In this era when scientific breakthroughs in solar storm studiescrucially depend on space-borne devices and large-aperture ground-based telescopes, the Chinese solar research communityneeds to develop its own major observational facilities and improve space weather forecasting abilities.
