Chemical Mechanical Polishing Slurry Research Articles

Study on polishing slurry of hydrogen peroxide-oxalic acid in CMP 304 stainless steel

Stainless steel will become the substrate material of the flexible display, requirements of the flexible substrate in the surface quality and performance are very strict. Chemical mechanical polishing (CMP) is one of the most appropriate technologies to achieve the surface processing of ultra-thin stainless-steel flexible display substrate with ultra-smooth and damage-free. In this paper, the design of CMP slurry of 304 stainless steel on the hydrogen peroxide-oxalic acid type was proposed. Through experiment and analysis, the basic ingredients of CMP slurry was obtained. The research results showed that the hydrogen peroxide can increase the hydrophilicity of the stainless steel surface, and the Fenton type Haber-Weiss reaction can occur on the surface of the fresh metal substrate of stainless steel. The trivalent iron ions generated by the Fenton type reaction combined with oxygen to generate iron oxide and promoted the removal of the surface material. Under acidic conditions, the oxalic acid can decrease the stability of the oxide film on the stainless steel surface, promote the diffusion of oxygen into the metal interface, improve the oxygen reduction reaction, and increase the material removal rate. The results will provide an important reference for the next researching the CMP slurry of 304 stainless steel.

Development of a novel chemical mechanical polishing slurry and its polishing mechanisms on a nickel alloy

Conventional chemical mechanical polishing (CMP) slurries of pure nickel (Ni) and its alloys usually consist of toxic and corrosive acids, which is dangerous and contaminative to the operators and environment. It is a big challenge to develop a novel environment friendly CMP slurry for Ni alloys. In this study, a novel environment friendly CMP slurry was developed, containing of silica, hydrogen peroxide (H2O2), malic acid and deionized water. The surface roughness Ra, and peak-to-valley (PV) values are 0.44, and 4.49 nm, respectively with an area of 71 × 53 μm2. To the best of our knowledge, surface roughness in this work is the lowest for pure Ni and its alloys at a scan area of 71 × 53 μm2. The CMP mechanisms are elucidated by electrochemical, X-ray photoelectron spectroscopy, and infrared measurements. Firstly, H2O2 dominated the oxidation process in CMP, forming oxides of nickel (Ni), chromium (Cr), and molybdenum (Mo) on the surface of Ni alloy. Then, the Ni oxides were dissolved by hydrogen (H) ions. The oxides of Cr and Mo were stable in malic acid. Chelating formulas are proposed between malic acid and Ni ions. Finally, the passivated film was removed by the polishing pad.

Design of composite abrasives and substrate materials for chemical mechanical polishing applications

Chemical mechanical polishing (CMP) has attracted much attention for high-performance manufacturing and setups, in which the surface roughness Ra is required to be less than 1 nm. In CMP, abrasives play a significant role in polishing quality and efficiency. Herein, we review the synthesis methods of abrasives including sSiO2@mSiO2, PS@CeO2, PS@SiO2 composites and their applications in CMP slurries. Then, the problems and solutions in CMP for soft- and hard-brittle solids and metals are presented in detail, such as cadmium zinc telluride (CdZnTe, soft brittle), silicon carbide (SiC, hard brittle) and copper (Cu, metal). After that, we summarize the molecular dynamics simulations of the CMP processes. Finally, the current problems of CMP and its development perspectives are discussed.

Polishing single-crystal silicon carbide with porous structure diamond and graphene-TiO2 slurries

In this study, a self-modified diamond (SMD) slurry for mechanical polishing is presented as well as a novel TiO2-graphene slurry used with the aid of UV light for a chemical mechanical polishing (CMP) technique that improves the rate of polishing. The surface characteristics and removal rate of silicon carbide (SiC) samples polished with the slurry were compared with the results obtained by polishing with both a conventional diamond slurry and CMP slurry. The experimental results indicated that the material removal rate (MRR) of SiC from the wafer surface with the SMD slurry was higher, and surface finish and lapping efficiency was better than that achievable with other slurries. The experimental data also showed that a TiO2-graphene slurry had a higher removal rate compared to the TiO2 slurry using the same intensity of UV light. The TiO2-graphene slurry showed a 3-fold increase in removal rate over that of a traditional CMP slurry. An experiment was also carried out where nanodiamond (50 nm and 500 nm) abrasive was added to the graphene-TiO2. As expected, the removal rate increased but the average surface roughness was poor because the nanodiamond particles caused small scratches. The graphene-TiO2 with nanodiamond abrasives has 5 times the removal rate achieved with a traditional CMP slurry. This novel method can facilitate the extensive production of well-polished single-crystal SiC wafers.

A novel chemical mechanical polishing slurry for yttrium aluminum garnet crystal

Yttrium aluminum garnet (Y3Al5O12, YAG) crystal is widely used for laser applications. However, due to its high hard and brittle nature, high surface quality and high material removal rate (MRR) are difficult to be achieved. In this study, to solve the problem, a novel CMP slurry was developed, which contains 8 wt% ZrO2 abrasives, 5 wt% Na2SiO3·5H2O, 0.3 wt% MgO and deionized water. After polishing, the surface roughness and MRR achieved 0.08 nm Ra and 34 nm/min respectively. The reaction mechanism during polishing was elucidated based on the results of grazing incidence small angle X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS). The results show that AlOOH and YOOH generated from hydration reaction react with Si–OH in Na2SiO3 aqueous solution to form soft andalusite and yttrium silicate, then MgO combines with andalusite to produce montmorillonite. All soft products are removed mechanically by ZrO2 abrasives, obtaining the ultra-smooth surface of YAG crystal.

An Efficient and High Quality Chemical Mechanical Polishing Method for Copper Surface in 3D TSV Integration

The goal of chemical mechanical polishing (CMP) is to achieve a flat and smooth surface for through silicon via (TSV) application. In order to obtain high efficiency and high quality copper CMP process, we have developed copper CMP slurry with optimal component ratio of peroxide, citric acid, benzotriazole, and silica particle. A high-resolution surface profile measuring instrument combined with other measurements is used to analyze the CMP performance of TSV. In addition, the chemical reaction mechanism in slurry for removal copper has been discussed considering surface adsorption. It is revealed that the polishing time increases with decreasing content of oxidizing agent peroxide. The polishing speed for silica particle mixed slurry is accelerated comparing with the conventional slurry. The polishing time becomes longer with increasing value of pH owing to declining sharply of free hydrogen ion in slurry solution. Further, the high quality of polishing appears on the wafer with smooth and glossy surface of copper by applying fast and slow slurry, which is contributed to reduction of the chemical polishing and enhancement of the mechanical polishing. The optimized polishing slurry prepared in this paper and the proposed two-stage polishing technique can achieve high quality copper surface polishing while greatly improving polishing efficiency.

Quantification of shear induced agglomeration in chemical mechanical polishing slurries under different chemical environments

The impact of shear on agglomeration in CMP slurries needs to be studied to reduce the defectivity resulting from large agglomerates (>0.5 μm) during Chemical Mechanical Planarization/Polishing (CMP) process. In this work the impact of the change in the pH of CMP slurries on their agglomeration behavior at different quantified shear rates are studied. The threshold value of Camp number (equal to shear rate x time) which represents total shear that is required for causing agglomeration in CMP slurries for different pH values (pH 2, 7 and 10) are measured. The value of the threshold Camp number required to cause agglomeration in a slurry was lowest for acidic pH conditions (Camp number 1E5), highest for basic pH conditions (Camp number 1.5E6) and value of threshold Camp number for neutral pH conditions (Camp number 1.5E5) was between acidic and basic conditions. It was concluded that the value of the threshold Camp number is dependent on the inter-particle forces or surface charges on silica particles in the slurry, and higher inter-particle repulsive forces increases the threshold value of Camp number. Good co-relations between Camp number and the extent of agglomeration in different CMP slurry samples are demonstrated. This method can be used for designing better slurry delivery systems for different slurry chemistries, to reduce the formation of the shear induced agglomerates during slurry handling and in turn reducing the defects during CMP process.

Effect of Cystine in Alkaline CMP Slurry on Controlling the Galvanic Corrosion at Al-Co Interface

As the feature size of integrated circuit (IC) shrinks down to 28 nm and below, aluminum (Al) is considered to be one of the suitable gate materials, and cobalt (Co) is considered to be one of the suitable barrier materials. During chemical mechanical polishing (CMP) of the Al-Co gate, galvanic corrosion occurs when Al and Co with large open-circuit potential (Eocp) difference contact each other in device structure and are exposed to conductive CMP slurry. In this paper, the adsorptive properties of the complex products formed by cystine and metal Al and Co were investigated. By means of potentiometric dynamic and static polarization measurements, impedance monitoring technology and adsorption model establishment, the complex products were adsorbed on the surface of Al and Co in physical and chemical form, which hindered the corrosion of Al and Co and achieved the goal of reducing their galvanic corrosion. The dynamic potential difference between Al and Co was reduced to 23 mV, and the static Ecorr difference was reduced to 30 mV with cystine concentration of 8 mM/L. The dynamic corrosion current (Icorr) difference was 2.936 μA/cm2, and the static Icorr difference was 0.835 μA/cm2.

Effect of Glycine and TT-LYK in Alkaline CMP Slurry on Controlling the Galvanic Corrosion at Al-Co Interface

As the feature size of integrated circuit (IC) shrinks down to 28nm and below, aluminum (Al) is considered to be one of the suitable gate materials, and cobalt (Co) is considered to be one of the suitable barrier materials. During chemical mechanical polishing (CMP) of the Al-Co gate, galvanic corrosion can occur when two kind of metals with a large open circuit potential (Eoc) difference contact with each other within the device architecture and are exposed to charge conducting CMP slurries. Al is severely corroded as an anode in the presence of Co because the standard electrode potential (E = −1.66 V) is lower than that of Co (E = −0.27 V). In this paper, using the advantages of different materials in adsorption and dissolution of different metal, the effect of glycine and TT-LYK (TT) with different concentrations on galvanic corrosion of Al and Co was studied by potentio dynamic and static polarization measurements with impedance monitoring. The potential different between Al and Co electrodes was significantly reduced for selective adsorption characteristics of the complex formed by glycine with Al and Co significantly reduced the potential difference between Al and Co electrodes. The substances formed by TT with Al and Co can be adsorbed on both surfaces well, and the current difference between Al and Co electrodes can be significantly reduced due to the difference in solubility of the reactants. When glycine and TT were used synergistically, the dynamic corrosion potential (Ecorr) difference between Al and Co electrodes was reduced to 10 mV, and the static Ecorr difference was reduced to 17 mV with glycine concentration of 1000 ppm and TT concentration of 100 ppm. The dynamic corrosion current (Icorr) difference was 0.587μA/cm2, and the static Icorr difference was 2.361μA/cm2.

Characterization of the nature of shear-induced agglomerates as hard and soft in chemical mechanical polishing slurries

The nature of agglomerates either hard or soft could determine the kind of defects created during the chemical mechanical planarization/polishing process. To understand the nature of shear-induced agglomerates, the silica slurry at different pH is subjected to high shear rate and time to form agglomerates. Subsequently, these stressed slurry samples are subjected to low shear rates 100–1000 s−1 for time 100–1000 s, corresponding to the conditions for which de-agglomeration is observed. Based on the comparison of percentage de-agglomeration in stressed versus as-received slurries, it is qualitatively shown that agglomerates formed due to shear-induced agglomeration in basic pH slurries are soft agglomerates, whereas those formed in neutral and acidic pH slurries are hard agglomerates. Also, between neutral and acidic pH slurries, shear-induced agglomerates in acidic pH slurry are relatively strongly held than the ones that are formed in neutral pH slurries. Subsequently, the nature of agglomerates was compared to defectivity and surface roughness trend of BD1 low-k wafers in silica slurries at different pH from the previous work.

Removal of BTA Adsorbed on Cu: A Feasibility Study Using the Quartz Crystal Microbalance with Dissipation (QCMD) Technique

In the formation of copper interconnects by Chemical Mechanical Polishing (CMP), benzotriazole (BTA) is used as a copper corrosion inhibitor in barrier CMP slurries and post-CMP cleaning formulations. Removal of BTA adsorbed on copper is important for the overall success of copper CMP process. In this study, adsorption/uptake of BTA and its removal from copper surface was investigated using a quartz crystal microbalance with dissipation monitoring capability (QCMD). Adsorption of BTA was carried out from a series of BTA solutions (20, 50, 100, 200 ppm) in tetramethylammonium hydroxide (TMAH) in the presence of hydrogen peroxide. Following the uptake step, removal of BTA by TMAH and acetohydroxamic acid (AHA) solutions maintained at pH 10 were studied in-situ. TMAH solutions remove some physisorbed BTA, while AHA is able to completely remove BTA.

Effect of pH Value and Glycine in Alkaline CMP Slurry on the Corrosion of Aluminum by Electrochemical Analysis

As the feature size of integrated circuit (IC) shrinks down to 28nm and below, Aluminum (Al) is considered to be one of the suitable gate materials. During chemical mechanical polishing (CMP) of the Al gate, Al is very easy to be scratched. The purpose of Al gate polishing is to achieve effective removal and improve surface quality. The pH value and additives of slurry are critical factors affecting the material removal rate and the surface quality. Taking the advantage of enhancing chemical action and solubility of product in CMP process, the potentio dynamic polarization measurements with dynamic impedance monitoring were performed to evaluate the effects of pH value and glycine on the behavior of the electrochemical corrosion. The results showed that the corrosion potential decreased as the pH value and glycine concentration increased. Meanwhile, the dissolution rate and reversing proportion to the polarization resistance increased with the increasing of pH value and glycine concentration, the removal rate of by-products (Al(OH)3) from the interfacial reaction accelerated, and the chemical adsorption of NH2−group identified by FTIR was converted into a soluble form, the removal rate was increased from 216 Å/min to 594 Å/min, and the surface roughness was greatly reduced from 18.6nm to 1.57nm. The synergetic effects of pH and glycine, combined with the analysis of the EIS for the aluminum alkaline CMP, indicated the RR and the surface quality of aluminum after CMP was obviously improved due to the chemical dissolution efficiency of interfacial by-product enhanced.

Optimization of cleaning process parameters to remove abrasive particles in post-Cu CMP cleaning * * Project supported by the Major National Science and Technology Special Projects (No. 2016ZX02301003-004-007), the Natural Science Foundation of China (No. 61704046), the Scientific Innovation Grant for Excellent Young Scientists of Hebei University of Technology (No. 2015007), and the Hebei Natural Science Foundation Project (No. F2018202174).

The cleaning of copper interconnect chemical mechanical polishing (CMP) is a key process in integrated circuits (ICs) fabrication. Colloidal silica, which is used as the abrasive material in copper CMP slurry, is considered as the main particle contamination. Abrasive particle residuals can cause device failure which need to be removed efficiently. In this paper, a type of CMP cleaner was used for particle removal using a cleaning solution consisting of FA/O II chelating agent and FA/O I surfactant. By varying the parameters of brush rotation speed, brush gap, and de-ionized water (DIW) flow rate, a series of experiments were performed to determine the best cleaning results. Atomic force microscope (AFM) measurement was used to characterise the surface morphology of the copper surface and the removal of abrasive particles. A scanning electron microscope (SEM) with EDX was used to observe and analyze the particles shape and elements. The optima parameters of CMP cleaner were obtained. Under those conditions, the abrasive silica particles were removed effectively.

Atomistic mechanisms of chemical mechanical polishing of diamond (1 0 0) in aqueous H2O2/pure H2O: Molecular dynamics simulations using reactive force field (ReaxFF)

Diamond CMP mechanisms have been widely investigated using the CMP experimental methods. However, the experiment could not observe the details of the removal process, it could not explain the mechanism of removal. The atom removal mechanism of chemical mechanical polishing (CMP) process on the diamond surface polished with a silica abrasive in aqueous H2O2/pure H2O was elucidated using ReaxFF molecular dynamics (MD) simulations. The research shows that the oxidation of diamond surface plays a dual role in the removal of C atoms. First, the diamond surface absorbs OH, O or H to form CO, COH or CH bonds. Then, the C atoms on the oxidized diamond surface are removed under the mechanical action of abrasive in aqueous H2O2. Three types of C atom removal pathway are detected in the CMP process: it can be removed in the form of CO, CO2 or C chain and C atom removal occurs on the first layer. However, no C atoms are removed in pure H2O. The friction in pure H2O is less than that in aqueous H2O2 due to the lubrication of pure H2O. In addition, comparing the different pressures applied to the abrasive, it is found that the greater the pressure applied, the more OH adsorbed on the diamond surface so that the more C atoms are removed. This work shows that the removal of C atoms is the result of the combination of chemical and mechanical effects, which helps understand the removal process of C atoms at the atomic scale in the CMP process and provide an effective method to choose the CMP slurry.

Environment friendly chemical mechanical polishing of copper

Chemical mechanical polishing slurry of copper usually contains more than four compositions, in which strong acids, alkalis or hazardous chemicals are normally employed. With these slurries, surface roughness less than 1 nm is difficult to obtain on the surface of copper after chemical mechanical polishing. It is a challenge to develop a kind of novel chemical mechanical polishing slurry for copper including three environment friendly compositions. In this study, a kind of novel chemical mechanical polishing slurry is developed consisting of silica, hydrogen peroxide and chitosan oligosaccharide, where all the three compositions are environment friendly. After chemical mechanical polishing, surface roughness Ra and peak-to-valley values are 0.444 and 5.468 nm respectively. Chemical mechanical polishing mechanism is elucidated by infrared and X-ray photoelectron spectra and electrochemical measurements. Firstly, Cu surface is oxidized by hydrogen peroxide, forming CuO and Cu(OH)2. Then, CuO and Cu(OH)2 are dissolved by H+ ions released by the ionization of chitosan oligosaccharide. Subsequently, Cu2+ ions are chelated by chitosan oligosaccharide molecules. Finally, the adsorbed layer is removed by silica nanospheres, generating ultra-smooth surface of copper. The findings propose a new route for fabrication devices of copper and other transition metals used in integrated circuits, graphene, transformers, batteries and electronics industries.

Effect of Polystyrene-Sulfonate Surfactant on Reduction of Remaining Abrasives and Surface Roughness in Tungsten-Film Chemical-Mechanical-Polishing

The W-film chemical-mechanical-polishing (CMP) has been utilized for the formation of via-hole and metal wiring as an essential semiconductor process. In the W-film CMP, key performance parameters are high polishing rate, low surface roughness of W-film, and high selectivity between SiO2 and W-film CMP. Recently, the remaining nanoscale abrasives in sub-micron W lines has been seriously issued as the design rule has scaled down below 20 nm in memory devices, as shown in Fig.1. In addition, the surface roughness after W-film CMP has been important since it influences directly the metal contact resistance. Thus, in our study, we designed a novel W-film CMP slurry using the sulfonate functional group (i.e., polystyrene sulfonate (PSS)) and 10-nm-diameter ZrO2 abrasives to reduce remaining abrasive in the sub- micron W-lines and surface roughness after W CMP. Principally, a W CMP slurry was fabricated with nanoscale ZrO2, Fe based catalyst, corrosion inhibitor, pH stabilizer, and anionic surfactant (i.e., PSS). First, we investigated the dependency of the W-film polishing rate on the PSS concentration. The W-film polishing rate decreased from 126 to 53 Å/min when the concentration increased from 0 to 1.0 wt%, and then it increased from 53 to 100 Å/min when the concentration increased from 1.0 to 2.0 wt%, as shown in Fig. 2(a). This result indicates that the W-film polishing rate minimized at a specific concentration; i.e., 0.5 wt% in which mechanism will be presented in the conference. Second, the W-film surface roughness [root-mean-square (RMS) at 2 x 2-um scanning area] after CMP increased from 1.302 to 1.662 nm when the concentration increased from 0 to 0.5 wt%, and then it decreased from 1.662 to 1.289 nm when the concentration increased from 0.5 to 2.0 wt%, as shown in Fig.2(b). This result means that the surface roughness peaked at a specific concentration; i.e., 1.0 wt%. Finally, the area ratio of ZrO2 abrasives remained at sub-micron W lines after W-film CMP decreased from 95.7 to 2.4 % when the concentration from 0 to 0.5 wt%, and then it increased from 2.4 to 97.6 % when the concentration from 0.5 to 2.0 wt%, as shown in Fig. 3. This result imply that the area ratio of ZrO2 abrasives remained at sub-micron W lines after W-film CMP minimized at a specific concentration; i.e., 0.5 wt%. In our presentation, we will review the mechanism of polystyrene-sulfonate surfactant effect on tungsten-film chemical-mechanical-polishing properties improvement such as remaining abrasive in sub-micron W lines and surface roughness. Figure 1. SEM images of the remaining nanoscale abrasives in sub-micron W lines. Figure 2. Dependency of polishing rate (a) and surface roughness (b) as a function of PSS concentration Figure 2. Dependency of the area ratio of ZrO2 abrasives remained at sub-micron W lines after W-film CMP as a function of PSS concentration Acknowledgement This research was supported by the MOTIE(Ministry of Trade, Industry & Energy (10085643) and KSRC(Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device. This investigation was financially supported by the Brain-Korea 21 PLUS Program in 2017 and Semiconductor Industry Collaborative Project between Hanyang University and SK Hynix Figure 1

Polystyrene/Ceria Core/Shell Abrasive Based Slurry for Highly Enhanced Oxide-Film Polishing Rate and Scratch-Less in Chemical-Mechanical-Planarization

The SiO2-film chemical-mechanical-polishing (CMP) is essential process for Shallow Trench Isolation (STI) and Inter Layer Dielectric (ILD) CMP. The key performance parameters are high polishing rate and scratch-less in SiO2-film CMP. In SiO2-film CMP, wet-ceria was widely used for scratch-less SiO2-film CMP. However, the wet-Ceria abrasive has crystalline sharp <100>, <100>, and <111> facet, which resulted in generating scratches on SiO2-film by stick and slip mechanism after SiO2 CMP, as shown in Fig.1. Thus the scratches induced by wet-ceria abrasives can be a major cause of poor device operation and yield drop in the memory device manufacturing. In our study, therefore, we designed a novel SiO2-film CMP slurry using the PS/ceria core/shell as an abrasive to enhance SiO2-film polishing rate and scratch-less after SiO2-film CMP. PS/ceria core/shell particles were synthesized, which are relatively soft and round by using polystyrene and ceria particles. Figure 2(a) shows the synthesis mechanism of PS/ceria core/shell, illustrating that Ce4+ ion was added in the PS of negative charge to form Ce4+ seed on the surface and grow it during 7 h with 70 ℃. The TEM image of the synthesized PS/ceria core/shell was shown in Fig. 2(b). First, we investigated the polishing rate of SiO2-film using PS/ceria core/shell abrasives. The polishing rate of SiO2-film was 564 Å/min when using PS/ceria core/shell and 350 Å/min when using wet-ceria as abrasives, as shown in Fig.3. This result means that the real contact area of PS/ceria core/shell is larger than that of 70 nm size wet-ceria. Second, we measured the surface roughness [root-mean-square (RMS) at 10 x 10-um scanning area] of SiO2-film and the surface defect such as scratch after CMP. The surface roughness of SiO2-film was 0.327 nm using wet-ceria and 0.202 nm using PS/ceria core/shell, respectively, as shown in Fig. 4(a). The number of scratch was 51-ea in 10-mm2 area and the deepest depth of scratch was 18 nm using 70 nm size wet ceria. However, the number of scratch was 10-ea in 10-mm2 area and the deepest depth of scratch was 2.3 nm using PS/ceria core/shell, as shown in Fig. 4(b). These results indicate that the hardness of PS/ceria core/shell is smaller than that of 70 nm size wet-ceria. In our presentation, we will review the mechanism for improving CMP performance such as high polishing rate, low surface roughness and scratch-less after CMP when using the PS/ceria core/shell abrasive based slurry. * This research was supported by the MOTIE(Ministry of Trade, Industry & Energy (10085643) and KSRC(Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device. This work was financially supported by the Brain Korea 21 Plus Program in 2018 and Research & Business Development Program Announcement funded by the MOTIE (N0002026). Figure 1

Preparation and Performance Study of Chemical Mechanical Polishing Slurry for New-type Aluminium Alloy

Aluminium alloys are widely used in various industries because of their lightness and easy processing, leading to higher requirements for aluminium alloys in terms of the flatness and finish of aluminium alloy surface. In this paper, chemical mechanical polishing (CMP) technology, which combines the advantages of chemical and mechanical polishing techniques, was studied to prepare one slurry suitable for new-type aluminium alloy and test its polishing performance. CeO2 powders were obtained as abrasive particles by a series of processes such as firing the mixture of NH4HCO3 and CeCl3 by precipitation method. The optimum ratio of the slurry included: 2.5% cerium oxide abrasive particles, NaOH as a pH adjuster at the optimal pH 10, and 3% sodium polyacrylate as the dispersant, so as to mix the CMP slurry with good dispersibility and stability. Then, the performance evaluation test of polishing was made by using the CMP slurry prepared under the optimal conditions on the aluminium alloy. The results showed that the polishing efficiency of the CMP slurry was higher, and the surface flatness, finish and roughness after polishing were in conformity with the requirements about aluminium alloy surface precision, with good polishing effect.

Probing Interactions at the Polymeric Filtration Media/ CMP Slurry Interface Using Dynamic Electrochemical Quartz Crystal Nanobalance (EQCN) and Atomic Force Microscopy (AFM)

As devices continue to shrink, the demands on chemical mechanical polishing (CMP) become more stringent, requiring slurries to be modulated in order to enhance surface quality. Achieving angstrom level uniformity and minimizing defects, results in the need to develop polymeric filtration media that also increases polishing efficiency. Probing the interactions that can occur at the particle/polymer/slurry interface is essential in order to understand the impact of altering the chemistry and the filtration media on the filterability, rate of diffusion, adhesion force, surface roughness, and activation energy (EA). This work focuses on investigating the interactions between common abrasive particles, such as ceria and silica (in various chemistries), as well as different polymeric filtration media through the use of an electrochemical quartz crystal nanobalance (EQCN) and atomic force microscopy (AFM). The AFM tip is effectively functionalized in solution using epoxy glue to mimic a nanoparticle, which is used to measure the adhesion force between the particle and membrane via force distance curves. These nanoparticles can be reduced, oxidized, or functionalized and can be used to measure the adhesion force at different filtration time intervals, monitoring the change in the particle-polymer interaction. Preliminary results suggest that altering the complexing agent in the slurry can heavily influence the EA of the interaction between the slurry and filter membrane. Specifically, the activation energy for a copper CMP slurry and an amine-based filter was found to be negative, indicating a barrier-less reaction, due to non-covalent interactions present at the slurry-polymer interface. Changing the complexing agent from glycine to L-alanine and β-alanine revealed the EA to be positive and negative, respectively, which also changed with the structure of the membrane. Ultimately, both the backbone of the filter and the complexing agent alter the interactions on the surface of the polymer membrane and have shown to have a direct impact on CMP performance.

Study of Agglomeration Behavior of Chemical Mechanical Polishing Slurry under Controlled Shear Environments

The presence of large oversize particles (>0.5 μm) in the slurry is known to cause polishing defects during chemical mechanical planarization/polishing (CMP) process. One of the reasons for presence of large particles in the slurry is due to usage of pumps during slurry delivery. The shear rate of pumps is known to cause agglomeration problem in CMP slurries, with increasing shear rate leading to increase in agglomeration in the slurries. However, till now all the work on shear-induced agglomeration has been qualitative or at best semi-quantitative in nature. In the present work, a novel technique to study agglomeration behavior as a function of quantified shear rates has been developed. A rheometer was used as a means to subject slurry to different shear rates for various times. The resulting change in oversize particle distribution was measured using a single particle optical sensing (SPOS) system. It was observed that the behavior of silica slurry when subjected to different shear rates falls into three regions namely de-agglomeration, transition region and agglomeration region. This technique provides a deterministic way for slurry stability and can be used as a guide for design of slurry, slurry selection and design of slurry delivery systems.