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It is well known that within-wafer nonuniformity (WIWNU) due to the variation in material removal rate (MRR) in chemical mechanical
polishing (CMP) significantly affects the yield of good dies. The process control for a batch CMP operation is further complicated
by wafer-to-wafer nonuniformity (WTWNU) caused by MRR decay when a number of wafers are polished with the same unconditioned
pad. Accordingly, the present work focuses on modeling the WIWNU and WTWNU in CMP processes. Various material removal models
suggest that the MRR is strongly influenced by the interface pressure. It is also well known that the viscoelastic properties
of the pad play an important role in CMP. In the present work, an analytical expression for pressure distribution (and its
associated MRR) at the wafer-pad interface for a viscoelastic pad is developed. It is observed that under constant load, which
is typical during main polishing in CMP, the spatial distribution of the interface pressure profile may change with time from
edge-slow to edge-fast, depending on the combination of wafer curvature, down pressure, and pad properties. For constant displacement
operations, the pressure profile retains its edge-slow or edge-fast characteristics over time. The analytical model predictions
of MRR based on viscoelastic pad properties also correlate very well to existing experimental observations of MRR decay when
an unconditioned pad is used to polish a number of wafers. Based on these observations, it may be conjectured that the viscoelastic
material properties of the pad play a primary role in causing the observed MRR decay. The analytical results obtained in the
present work can also provide an estimation of evolution of thickness removal distribution over the entire wafer. This may
be used for determining the optimum thickness of the overburden material and its polishing time, and for effective control
of CMP processes. 相似文献
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Effect of abrasive particle concentration on material removal rate (MRR), MRR per particle and the surface quality in the preliminary chemical mechanical polishing (CMP) of rough glass substrate was investigated. Experimental results showed that the MRR increases linearly with the increase of abrasive concentration and reaches to the maximum when the abrasive concentration is 20 wt.%, and then tends to be stable. When the abrasive concentration increases from 2 to 5 wt.%, the MRR per particle increases greatly and reaches a peak. Then the MRR per particle decreases almost linearly with the increase of the abrasive concentration. The root mean squares (RMS) roughness almost decreases with increasing particle concentration. In addition, in situ coefficient of friction (COF) was also conducted during the polishing process and the zeta potentials of abrasive particles in slurry with different solid concentration were also characterized. Results show that COF value is not related to zeta potential but be sensitive to glass surface conditions in terms of rough peaks in preliminary polishing of glass substrate. 相似文献
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Chemical mechanical polishing of polycarbonate and poly methyl methacrylate substrates 总被引:1,自引:0,他引:1
In recent years, polymeric materials such as polycarbonate (PC) and poly methyl methacrylate (PMMA) are replacing silicon as major substrates in microfluidic system fabrication due to the outstanding features like low cost and good chemical resistance. In this study, chemical mechanical polishing (CMP) of PC and PMMA substrates was investigated. First, four types of slurry were tested. Then, the slurry producing relatively high material removal rate (MRR) and low surface roughness was chosen, and experiments were designed and carried out to investigate the effects of key process parameters. The experimental results show impacts of key CMP process parameters on MRR and surface finish of PC and PMMA substrates. An increase in head load or table speed would cause an increase in surface roughness heights and MRR. The surface quality of the polymers after CMP appeared to be acceptable for most of microelectromechanical system applications as the process conditions were restrained within the process window. 相似文献
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In this paper, the impact on non-planarization index by the down force and rotational speed during a SiO2 or Cu CMP process was investigated. Since the magnitudes of down force and rotational speed have limits, we choose the dynamic programming approach because of its ability to achieve constrained optimization by the down force and rotational speed. The duration and the amount of input were computed based on the chemical mechanical polishing model by Luo and Dornfeld [J. Luo, D.A. Dornfeld, IEEE Trans. Semiconduct. Manufact. 14(2) (2001) 112-132.] when the other parameters were fixed. Experiments done for blanket wafers based on dynamic programming operation and conventional constant removal rate operation was compared with each other. The non-planarization index could be improved consistently by dynamic programming operation versus constant removal rate operation. The improvement ranges from 2% to 39% improvement over the base recipe of constant removal rate in all experiments as shown in Table 3 and Table 6. The thickness removal error is consistently smaller by constant removal rate operation versus dynamic programming operation in all experiments as shown in Table 3 and Table 6. To get the best performance of both planarization and thickness removal, it is recommended that planarization step and overpolish step in SiO2 and Cu CMP should use different mode of operation, i.e., dynamic programming operation during planarization step for minimizing non-planarization index and constant removal rate operation during overpolish step for minimizing thickness removal error. The incremental time calculation for eliminating thickness removal error during overpolish step can be done using the thickness error and removal rate derived from Luos’ removal rate model based on constant wafer pressure and platen speed at the end of planarization step.Our contribution is a new approach for CMP. Standard CMP uses constant removal rate operation in both planarization step and overpolish step. Our new approach uses dynamic programming operation during planarization step and constant removal rate operation during overpolish step. 相似文献
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Jongwon Seok Andrew T. Kim Cyriaque P. Sukam Anurag Jindal John A. Tichy Ronald J. Gutmann Timothy S. Cole 《Microelectronic Engineering》2003,70(2-4):478-488
This paper describes a mechanical model for a representative dual axis rotational chemical mechanical planarization (CMP) tool. The model is three-dimensional, multiscale and includes sub-models for bulk pad deformation, asperity deformation, lubrication based slurry flow, carrier film deformation, wafer compliance and material removal by abrasive particles in the slurry. With the model, material removal rate (MRR) can be determined as a function of stress applied to the wafer, relative sliding speed, and material and geometric parameters of the pad and slurry. Experimental material removal rate profiles obtained from Cu polishing experiments performed on a wafer without rotation are analyzed as an inverse problem. We use MRR data to predict local CMP conditions such as fluid film thickness, fluid pressure and contact pressure. The results are consistent with available experimental and analytical information. This inverse technique offers promise as an improved method of CMP model verification. 相似文献
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A. K. Sikder Frank Giglio John Wood Ashok Kumar Mark Anthony 《Journal of Electronic Materials》2001,30(12):1520-1526
Chemical mechanical planarization (CMP) has been proved to achieve excellent global and local planarity, and, as feature sizes
shrink, the use of CMP will be critical for planarizing multilevel structures. Understanding the tribological properties of
a dielectric layer in the CMP process is critical for successful evaluation and implementation of the materials. In this paper,
we present the tribological properties of silicon dioxide during the CMP process. A CMP tester was used to study the fundamental
aspects of the CMP process. the accessories of the CMP tester were first optimized for the reproducibility of the results.
The coefficient of friction (COF) was measured during the process and was found to decrease with both down pressure and platen
rotation. An acoustic sensor attached to this tester is used to detect endpoint, delamination, and uniformity. The effects
of machine parameters on the polishing performance and the correlation of physical phenomena with the process have been discussed. 相似文献
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Metal oxidation under stress plays a significant role in many industrial applications, particularly in chemical mechanical
polishing (CMP). Here we report effects of mechanical stimulation on tantalum (Ta) oxidation during CMP. A tantalum surface
was polished at various anodic potentials and under different mechanical forces. A potentiostat was used to measure the anodic
reaction current during electrochemical mechanical polishing (ECMP). The material removal rate (MRR) measured using atomic
force microscopy (AFM) was compared with that calculated using Faraday’s law. Relationship was linked (or established) between
the anodic potential and a mechanical force. The MRR was a second-order polynomial function of potential at constant mechanical
force, followed by a logarithmic function. It was found that more suboxides were present at extreme potentials (low and high),
while substantial pentoxide was generated under intermediate potentials. A model is proposed to explain the oxidation process
of Ta during ECMP. The oxidation of Ta was a function of the anodic potential and mechanical force. The ex situ method used in this study fulfilled the in situ observation on Ta oxidation in polishing. Additionally, this technique can be used to investigate oxidation of other metals. 相似文献
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The effect of the ammonium molybdate concentration on the material removal rate(MRR) and surface quality in the preliminary chemical mechanical polishing(CMP) of a rough glass substrate was investigated using a silica-based slurry.Experimental results reveal that the ammonium molybdate concentration has a strong influence on the CMP behaviors of glass substrates.When the ammonium molybdate was added to the baseline slurry,polishing rates increased,and then decreased with a transition at 2 wt.%,and the ro... 相似文献
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Many researchers studying copper chemical mechanical planarization (CMP) have been focused on mechanisms of copper removal using various chemicals. On the basis of these previous works, we studied the effect of slurry components on uniformity. Chemical mechanical planarization of copper was performed using citric acid (C6H8O7), hydrogen peroxide (H2O2), colloidal silica, and benzotriazole (BTA, C6H4N3H) as a complexing agent, an oxidizer, an abrasive, and a corrosion inhibitor, respectively. As citric acid was added to copper CMP slurry (pH 4) containing 3 vol% hydrogen peroxide and 3 wt% colloidal silica, the material removal (MRR) at the wafer center was higher than its edge. Hydrogen peroxide could not induce a remarkable change in the profile of MRR. Colloidal silica, used as an abrasive in copper CMP slurry containing 0.01 M of citric acid and 3 vol% of hydrogen peroxide, controlled the profile of MRR by abrading the wafer edge. BTA as a corrosion inhibitor decreased the MRR and seems to control the material removal around the wafer center. All the results of in this study showed that the MRR profile of copper CMP could be controlled by the contents of slurry components. 相似文献
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The abrasion mechanism in solid-solid contact mode of the chemical mechanical polishing (CMP) process is investigated in detail. Based on assumptions of plastic contact over wafer-abrasive and pad-abrasive interfaces, the normal distribution of abrasive size and an assumed periodic roughness of pad surface, a novel model is developed for material removal in CMP. The basic model is MRR=ρwNVol removed, where ρw is the density of wafer N the number of active abrasives, and Volremoved the volume of material removed by a single abrasive. The model proposed integrates process parameters including pressure and velocity and other important input parameters including the wafer hardness, pad hardness, pad roughness, abrasive size, and abrasive geometry into the same formulation to predict the material removal rate (MRR). An interface between the chemical effect and mechanical effect has been constructed through a fitting parameter Hw a “dynamical” hardness value of the wafer surface, in the model. It reflects the influences of chemicals on the mechanical material removal. The fluid effect in the current model is attributed to the number of active abrasives. It is found that the nonlinear down pressure dependence of material removal rate is related to a probability density function of the abrasive size and the elastic deformation of the pad. Compared with experimental results, the model accurately predicts MRR. With further verification of the model, a better understanding of the fundamental mechanism involved in material removal in the CMP process, particularly different roles played by the consumables and their interactions, can be obtained 相似文献
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Polymeric materials such as polycarbonate (PC) and poly-methyl methacryate (PMMA) are replacing silicon as the major substrate in microfluidic system fabrication due to their outstanding features such as low cost and good chemical resistance. In this study, chemical mechanical polishing (CMP) of PC and PMMA substrates was investigated. Four types of slurry were tested on CMP of the polymers under the same process conditions. The slurry suitable for polishing PC and PMMA was then chosen, and further CMP experiments were carried out under different process conditions. Experimental results showed that increasing table speed or head load increased the material removal rates of the polymers. The polymeric surface quality after CMP was acceptable to most MEMS applications. Analysis of variance was also carried out, and it was found that the interaction of head load and table speed had a significant (95% confidence) effect on surface finish of polished PMMA. On the other hand, table speed had a highly significant (99% confidence) effect on surface finish of polished PC. 相似文献
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Chemical mechanical polishing (CMP) has been widely accepted for the metallization of copper interconnection in ultra-large scale integrated circuits (ULSIs) manufacturing. It is important to understand the effect of the process variables such as turntable speed, head speed, down force and back pressure on copper CMP. They are very important parameters that must be carefully formulated to achieve desired the removal rates and non-uniformity. Using a design of experiment (DOE) approach, this study was performed investigating the interaction effect between the various parameters as well as the main effect of the each parameter during copper CMP. A better understanding of the interaction behavior between the various parameters and the effect on removal rate, non-uniformity and ETC (edge to center) is achieved by using the statistical analysis techniques. In the experimental tests, the optimized parameters combination for copper CMP which were derived from the statistical analysis could be found for higher removal rate and lower non-uniformity through the above DOE results. 相似文献
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The kinematics of conventional, rotary chemical mechanical planarization (CMP) was analyzed, and its effect on polishing results
was assessed. The authors define a novel parameter, ζ, as a “kinematic number,” which includes the effects of wafer size,
distance between rotation centers, and rotation ratio between wafer and pad. The analysis result suggests that velocity distribution,
direction of friction force, uniformity of velocity distribution, distribution of sliding distance, and uniformity of sliding-distance
distribution could be consistently expressed in terms of the kinematic number ζ. These results become more important as the
wafer size increases and the requirement of within-wafer nonuniformity is more stringent. 相似文献
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Electro-chemical mechanical planarization (ECMP) process dissolves copper ions electrochemically by applying an anodic potential on the copper surface in an aqueous electrolyte, and then removes a copper (Cu) complex layer by the mechanical abrasion of a polishing pad or abrasives in the electrolyte. The ECMP process is a low pressure polishing method for metals such as copper, aluminium (Al) and tungsten (W) on dielectric materials such as silicon dioxide, low-k (LK) and ultra low-k (ULK) dielectrics, comparing to the amount of defects by the traditional Cu chemical mechanical planarization (CMP). The polishing pad used in the ECMP process is a conventional closed cell type pad (IC 1400 K-groove pad) with holes. It supplies the aqueous electrolyte to the copper surface and removes the copper complex layer. The material removal rate (MRR) and MRR profile were simulated and tested according to the changes of the wafer overhang distance (WOD) from the platen and the electric contact area (ECA). In order to derive the design rule of the system, the experimental results are compared with the simulation results. After the ECMP process, it was verified that the within wafer non-uniformity (WIWNU) was lower than 2% using the relatively uniform ECA pad (C-type) under the smallest WOD condition. The experimental results well matched the simulated results. 相似文献
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A model for calculating friction torque during the chemical mechanical polishing(CMP) process is presented,and the friction force and torque detection experiments during the CMP process are carried out to verify the model.The results show that the model can well describe the feature of friction torque during CMP processing. The research results provide a theoretical foundation for the CMP endpoint detection method based on the change of the torque of the polishing head rotational spindle. 相似文献