Chemical Mechanical Polishing Process Research Articles

Real-time prediction of material removal rate for advanced process control of chemical mechanical polishing

Polishing torque holds significance in monitoring the chemical mechanical polishing (CMP) process due to its close correlation with material removal. This study introduces a new model-based technique for estimating the material removal rate (MRR) using in-process data from CMP machines. The proposed method employs either the sequential least squares method or Kalman filter for real-time state estimation. Real-time estimation of MRR enables material removal control without relying on conventional endpoint detection (EDP) technologies. The accuracy of the proposed approach is validated through oxide CMP experiments, demonstrating precise estimation of the center-slowed MRR profile towards the end of the pad life.

Ultra-low damage processing of silicon wafer with an innovative and optimized nonwoven grind-polishing wheel

Silicon is essential to the production of integrated circuits and optical components. Grinding is a commonly used method of silicon surface machining, but it often leads to surface and subsurface damage. These damages need to be removed by subsequent processes, typically through polishing. The surface quality generated by grinding directly impacts the cost of polishing. To enhance the quality of the grinding surface and reduce the time and cost of polishing, a grind-polishing wheel with a different structure from the conventional diamond wheel was developed. This wheel utilized ultrafine zirconia with grit size of 200 nm as abrasives and nonwoven as substrate to support the abrasives. Furthermore, to optimize the wheel and achieve better grinding performance, various wheels with different abrasive mass fractions and elastic moduli were fabricated and grinding experiments were conducted. The surface integrity of processed silicon and the material removal rate (MRR) were used to compare the grinding performance of the various wheels. After optimization, the MRR of the grind-polishing wheel reaches its peak at 0.81 μm/min. The silicon wafer ground with the grind-polishing wheel exhibited a surface roughness Sa of 0.51 nm and a subsurface damage depth of 74 nm, which is close to the effect of chemical mechanical polishing processing. Compared to conventional diamond grinding wheel (mesh size of #5000), the optimized grind-polishing wheel is better suited for semi-fine finishing and can significantly reduce the cost and time of polishing.

Damascene versus subtractive line CMP process for resistive memory crossbars BEOL integration

In recent years, resistive memories have emerged as a pivotal advancement in the realm of electronics, offering numerous advantages in terms of energy efficiency, scalability, and non-volatility [1]. Characterized by their unique resistive switching behavior, these memories are well-suited for a variety of applications, ranging from high-density data storage to neuromorphic computing [2]. Their potential is further enhanced by their compatibility with advanced semiconductor processes, enabling seamless integration into modern electronic circuits [3]. A particularly promising avenue for resistive memory lies in its integration at the Back-End-of-Line (BEOL) stage of semiconductor manufacturing [4]. BEOL integration involves processes that occur after the fabrication of the transistors, primarily focusing on creating interconnections that electrically link these transistors. Integrating resistive memories at this stage can lead to compact, efficient, and high-performance architectures, pivotal for in-memory computing applications where data storage and processing are co-located [5]. This paper studies three ways to integrate TiOx-based resistive memory into passive crossbar array structures, using chemical mechanical polishing (CMP) processes, focusing on identifying the optimal integration techniques.

Effect of the Post‐Annealing Temperature on the Interfacial Reaction Between a High TC Superconductor and Topological Insulator

AbstractThis work reports the formation of a heterojunction composed of Tl2Ba2CaCu2O8 (Tl‐2212) and Bi2Se3 as the high critical temperature superconductor and topological insulator, respectively. The Bi2Se3 film is deposited on the Tl‐2212 by a chemical mechanical polishing process. Due to the rough surface of Tl‐2212, the treated Tl‐2212 is then subjected to post‐annealing at various temperatures. This temperature does not affect the formation of the interfacial layer at the heterojunction; however, an improved layered crystal structure of the Bi2Se3 film is observed at 500 °C. The in‐depth profile of the relative atomic concentration indicates the diffusion of Cu and Tl into the Bi2Se3 film with the Ba diffusion being closer to the interfacial layer. At 500 °C, Cu atoms are more actively diffused into the Bi2Se3 film, thus blocking Tl diffusion, and improving the layered crystal structure of the film. The density functional theory calculations reveal that the lowest formation energy of the Cu vacancy is when Bi2Se3 is in contact with Tl‐2212, which results in the diffusion of Cu atoms from Tl‐2212, thus transforming the interstitial Cu atoms into the film. These atoms have an n‐type doping effect and prefer intercalating at a vdW gap deep inside the layered Bi2Se3.

Material removal rate model for chemical–mechanical polishing of single-crystal SiC substrates using agglomerated diamond abrasive

Material removal mechanisms are essential for the selection of polishing slurries and parameter optimization of chemical–mechanical polishing (CMP) processes. This study established a material removal rate (MRR) model for CMP of single-crystal SiC substrates using a fixed agglomerated diamond (AD) abrasive pad (FADAP). The distribution of the polishing pressure between the AD abrasive and FADAP matrix was examined, and the influence of the abrasive and polishing parameters on the MRR was revealed. Furthermore, single-factor experiments were conducted to validate the rationality of the MRR model. The experiments demonstrated that when the thickness of the surface-affected layer of the single-crystal SiC substrate in the MRR model was set to 5 nm, the error between the calculated and experimental values of the model could be controlled to within 20%. This result experimentally verified the validity of the MRR model and its associated assumptions. Moreover, the MRR of the CMP process of a single-crystal SiC substrate reached 36.26 μm/h with a polishing pressure of 27.6 kPa and an AD abrasive primary particle size range of 7–10 μm. Therefore, the feasibility of efficiently processing single-crystal SiC substrates using an FADAP was theoretically confirmed.

Impact of Atomic Defects on Ceria Surfaces on Chemical Mechanical Polishing of Silica Glass Surfaces.

This study investigates the impact of atomic defects, such as oxygen vacancies and Ce3+ ions, on cerium oxide (ceria) surfaces during chemical mechanical polishing (CMP) for silica glass finishing. Using density functional theory (DFT) and reactive molecular dynamics simulations, the interaction of orthosilicic molecules and silica glass with dry and wet ceria surfaces is explored. Defects alter the surface reactivity, leading to the dissociation of orthosilicic acid on oxygen vacancies, forming a strong Si-O-Ce bond. Hydroxylated surfaces exhibit easier oxygen vacancy formation and thermodynamically favored substitution of hydroxyl groups with orthosilicic acid. A new ReaxFF library for silica/ceria interfaces with defects is validated using DFT outcomes. Reactive MD simulations demonstrate that ceria surfaces with 30% Ce3+ ions on (111) planes exhibit higher polishing efficiency, attributed to increased Si-O-Ce bond formation. The simultaneous presence of oxygen vacancies and various acidic and basic sites on ceria surfaces enhances the polishing efficiency, involving acid-base reactions with silica. Defective surfaces show superior efficiency by removing silicate chains, contrasting with nondefective surfaces removing isolated orthosilicate units. This study provides insights into optimizing CMP processes for high-precision glass industry surface finishing.

Characterization of Ceria Nanoparticles as Abrasives Applied with Defoaming Polymers for CMP (Chemical Mechanical Polishing) Applications.

Chemical mechanical polishing/planarization (CMP) is an essential manufacturing process in semiconductor technologies. This method combines chemical and mechanical forces to smooth the surfaces of wafers. The effectiveness of CMP relies on a carefully chosen slurry, demanding a sophisticated manufacturing technology. This technology must seamlessly integrate both chemical composition and mechanical elements, highlighting the intricate synergy required for successful semiconductor fabrication. Particularly in milling processes, if agglomerated particles due to slurry particle corrosion are present during polishing, uneven polishing, numerous fine scratches occur, leading to an increase in roughness and a deterioration in the quality of the finished surface. In this study, to overcome the issue of particle agglomeration and uneven polishing in commonly used ceria nanoparticle slurries during CMP processes, we investigated the ceria nanoparticle behavior based on styrene-maleic acid (SMA) dispersant polymer applied with three types of defoaming polymers. The investigations are expected to open up the possibility of utilizing ceria nanoparticles with applied defoaming polymer as an abrasive for advanced CMP applications. All samples were characterized by DLS (dynamic light scattering), SEM-EDX (scanning electron microscopy-energy dispersive X-ray spectroscopy), pH, conductivity, viscosity, a 10-day stability test at 60 °C, the AF4 test, and the polishing rate efficiency test. Our research demonstrates a significant improvement achieved through the use of SMA dispersant polymer, resulting in a polishing selection ratio exceeding 80 for oxide and nitride films. The G-336 defoaming polymer utilized here is expected to serve as a viable alternative in CMP processes by providing stable uniformity.

Three anionic surfactants for corrosion inhibition in cobalt CMP: Research on validity and mechanism

Inhibitors are introduced into the slurry to avoid excessive metal corrosion during the chemical mechanical polishing (CMP) process. The anti-corrosion effect of surfactants in CMP was not investigated systematically in past studies. In this paper, three eco-friendly anionic surfactants, potassium laurate, potassium oleate, and dodecyl benzenesulfonic acid, were studied in depth as cobalt CMP inhibitors. Electrochemical experiments demonstrated that the three inhibitors act as anodic inhibitors. Static etching tests and surface morphology analysis proved that they can effectively inhibit the corrosion rate of cobalt and improve surface morphology. XPS results demonstrated that the inhibitor reduces corrosion by inhibiting cobalt oxidation. DFT calculations demonstrated that inhibitors adsorb on the cobalt surface through the O atoms in hydrophilic groups, while the CC double bond and benzene ring can significantly enhance the adsorption. Molecular dynamics simulations showed that the inhibitors are adsorbed on the cobalt surface in parallel. Additionally, all three surfactants improved the solution's wettability on cobalt. This report provides critical insights into the corrosion inhibition specific to cobalt CMP and offers an approach to realize the multi-functionality of a single agent in slurries.

A new magnetic enhanced chemical mechanical polishing method for quartz glass slender holes

Due to the limitations of tool size, field assisted polishing methods are often employed for polishing the internal surfaces of slender holes with large aspect ratios. However, in existing polishing methods, fields are often applied in isolation, which limits the ability to obtain high surface quality. Furthermore, it is rare for polishing method studies to fully leverage the advantages of multiple fields to create a synergistic effect. Therefore, developing a polishing method that harnesses the synergistic interaction of multiple fields, and revealing the polishing mechanism, is crucial for achieving high-quality internal surfaces of quartz slender holes. To address this problem, a novel magnetic enhanced chemical mechanical polishing method was proposed in this paper and a systematic process study was carried out to analyze the synergistic effects of magnetic and chemical fields. To evaluate the effects of process parameters on material removal and forecast MRR, the material removal process was modeled and validated based on the consistency between experimental and theoretical values. Suitable process parameters are determined through experiments and analysis on magnetic field distribution and process parameters. By conducting EDS mapping and XPS analyses on the reaction product, the enhancement mechanism of magnetic field on material removal in the chemical mechanical polishing process was identified. Under the assistance of a magnetic field, the magnetic abrasive particles encircle the CeO2 particles to fully contact the workpiece surface. The contact force between the polishing tool and the workpiece surface increase. Both of the effects promote the chemical reaction and enable the reaction layer on the surface to be removed in time to obtain higher surface quality. As a result, this method achieves high-efficiency and high-quality polishing, significantly reducing the surface roughness Sa of slender holes from 0.3 μm to 77 nm, with a material removal rate of 141 μm/h.

High-Performance N-Polar GaN/AlGaN Metal–Insulator–Semiconductor High-Electron-Mobility Transistors with Low Surface Roughness Enabled by Chemical–Mechanical-Polishing-Incorporated Layer Transfer Technology

High-Performance N-Polar GaN/AlGaN Metal–Insulator–Semiconductor High-Electron-Mobility Transistors with Low Surface Roughness Enabled by Chemical–Mechanical-Polishing-Incorporated Layer Transfer Technology

Effects of pyrazine and its derivatives as inhibitors on copper film chemical-mechanical polishing properties for ruthenium-based copper interconnect

During the one-step chemical mechanical polishing (CMP) process of ruthenium (Ru)-based copper (Cu) interconnected Cu films, a high Cu removal rate (RR) while maintaining a near zero Ru RR should be required to ensure a flat surface. The most ideal and difficult part of the CMP process is how to achieve rapid removal of Cu film without affecting Ru layer. Corrosion inhibitors in the slurry fulfill a significant function in controlling RR and improving the surface quality. Therefore, in this study, pyrazine (PY) and its derivative aminopyrazine (AP) as cost-effective and harmless corrosion inhibitors for Ru-based Cu interconnected Cu film CMP were investigated under weakly alkaline conditions (pH=8.5). First, through the utilization of experimental and theoretical methods, a systematical analysis was conducted to assess the corrosion inhibition effects of AP and PY, and it was found that the corrosion inhibition effect of AP was stronger than that of PY. Then, the adsorption and inhibition mechanism of AP on Cu/Ru surface were analyzed by electrochemical testing and X-ray photoelectron spectroscopy (XPS), and the adsorption behavior of AP molecules on the Cu (111) surface was investigated at the molecular level using quantum chemical methods. Finally, tests on Cu patterned wafers showed that the combination of 0.5 wt% AP and 0.5 wt% sarcosine (Sar) proved to be successful in effectively rectifying the step height on the Cu patterned wafer. At the same time, a high RR of 7281 Å /min, a low surface root mean square deviation (Sq) of 1.35 nm in 10 μm×10 μm region and a low static etching rate (SER) of 1015 Å /min were obtained with the synergistic effect of AP and Sar. This outcome holds substantial theoretical implications for advancing the formulation of low-node Cu film slurry.

Research on Parallel Reading and Drawing Techniques for Chemical Mechanical Polishing Simulation Data Based on Multi-Thread

In advanced integrated circuit manufacturing, the quality of chemical mechanical polishing (CMP) is a key factor affecting chip performance and yield. Designers need to use CMP simulation tools to locate and analyze the defects in the layout after the CMP process. However, the advancement of process nodes and the increase in data volume presents a great challenge to the speed of graphical display of CMP simulation data. To solve this issue, we propose a solution that uses multi-threading technology to optimize both data reading and drawing. In the process of data reading, we employ OpenMP and memory mapping (Mmap) technology to achieve parallel reading of file segmentation and propose a fast-string conversion algorithm based on the properties of simulation data. In the process of data drawing, we propose an adaptive downsampling method for data graphical display that combines multi-threading and double buffering technology to enable the parallel drawing of layouts. The effectiveness of this method is verified by testing CMP simulation data of various scales. Compared to traditional methods, this approach improves reading efficiency by over 8 times and drawing efficiency by more than 10 times. Furthermore, it enhances the smoothness of interaction with the CMP simulation tool.

Triple Synergism Effect of Ammonium Nitrilotriacetate on the Chemical Mechanical Polishing Performance of Ruthenium Barrier Layers.

As the feature size of integrated circuits continues to decrease, ruthenium (Ru) has been suggested as the successor to traditional Ta/TaN bilayers for barrier layer materials due to its unique properties. This research delves into the effects of ammonium nitrilotriacetate (NTA(NH4 )3 ) on the chemical mechanical polishing (CMP) performance of Ru in H2 O2 -based slurry. The removal rate (RR) of Ru surged from 47 to 890Åmin-1 , marking an increase of about 17 times. The essence of this mechanism lies in the triple synergistic effects of NTA(NH4 )3 in promoting ruthenium (Ru) removal: 1) The interaction between from NTA(NH4 )3 and SiO2 abrasives; 2) The chelating action of [(NH4 )N(CH2 COO)3 ]2- from NTA(NH4 )3 on Ru and its oxides; 3) The ammoniation and chelation of Ru and its oxides by from NTA(NH4 )3 , which enhance the dissolution and corrosion of oxidized Ru, making its removal during the barrier layer CMP process more efficient through mechanical means. This research introduces a synergistic approach for the effective removal of Ru, shedding light on potential applications of CMP in the field of the integrated circuits.

Atomic-scale planarization surface of quartz glass induced by novel green chemical mechanical polishing using three ingredients

Traditional chemical mechanical polishing (CMP) usually employs more than three kinds of toxic or corrosive ingredients for its slurry. Quartz glass is a hard-brittle solid, and it is extremely difficult to achieve its atomic-scale planarization surface. In these respects, it is a challenge to obtain atomic surface of quartz glass using green CMP slurry with three ingredients. To solve this challenge, a novel green CMP was developed, containing three green ingredients, such as ceria, sodium alginate and aminobutyric acid. After CMP, atomic surface is acquired with surface roughness Ra of 0.093 nm and material removal rate of 12.47 μm/h. Transmission electron microscopy confirms the thickness of damaged layer is 8.57 nm. X-ray photoelectron spectroscopy shows that –OH, C–N and –COOH groups adsorbed on the surface of quartz glass after immersion in CMP slurry, which agrees well with the simulated results of molecular dynamics. Density functional theory calculations reveal that electron transfer groups of aminobutyric acid and sodium alginate were predominantly located on –NH2 and –COOH, forming the covalent bonds between them. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy indicate that new complexes were generated between aminobutyric acid and sodium alginate, increasing the viscosity of CMP slurry. Furthermore, the breakage of C–N and O–H bonds after CMP suggests that the complexes play a pivotal role in the CMP process. The developed novel green CMP with three ingredients provides new viewpoints to obtain atomic-scale planarization surface for a hard-brittle solid.

Investigation on chemical mechanical polishing of Ga-faced GaN crystal with weak alkaline slurry

A remarkable improvement in the chemical–mechanical polishing (CMP) of GaN using a weakly alkaline ZrO2–SiO2 based slurry is described in detail, and an almost complete atomic step-platform structure with a surface roughness (Ra) of 0.059 nm is obtained. ZrO2 nanoparticles were added to the CMP slurry to replace part of the SiO2 to obtain a higher removal rate. When the content of ZrO2 reaches 0.5 wt%, the material removal rate of GaN is increased by 47.5 % compared with that of SiO2 with equal content, which significantly improves the material removal rate (MRR) of GaN, and does not destroy the atomic ladder-platform structure. In addition, we also investigate the causes of the formation of atomic ladder-terrace morphology on Ga-face, and describe the removal mechanism of materials in CMP process.

Optimization and Mechanism of SiO2-Based Slurry Components for Atomically Smooth Gallium Nitride Surface Obtained Using Chemical Mechanical Polishing Techniques

Abstract With the ongoing progress of mobile communications and new energy technologies, the market interest in high-frequency and high-power semiconductor devices has risen. Gallium nitride (GaN), a wide bandgap semiconductor material, has become a popular area of research in relevant fields. A sufficiently flat material surface can significantly enhance the device's performance. Therefore, this paper explores the effect of oxidants on the quality of GaN surface during chemical mechanical polishing (CMP). Atomic force microscopy (AFM) was employed to examine the surface morphology of GaN after each CMP experiment. The aim was to evaluate the effect of specific slurry components on GaN surface quality. The results revealed that the introduction of oxidizers, particularly the potent oxidizer potassium persulfate (K2S2O8), was advantageous in reducing the surface roughness Sq and thus, enhancing the surface quality of GaN. The surface roughness (Sq) of GaN was reduced from 7.7 to 0.78 nm after the CMP process with the optimal components. AFM tests were conducted on different areas of the GaN surface within a range of 1 μm2, which revealed that clear images of the GaN atomic steps can be obtained, and the Sq can reach as low as 0.26 nm.

Experimental In-Situ Observatory on Brownian Motion Behavior of 105 nm Sized Silica Particles During Chemical Mechanical Polishing of 4H-SiC by an Evanescent Field

The experimentally observing optical systems for on-machine measurement have been developed to study on nano-polishing phenomena during the chemical mechanical polishing process, which is a wet process in semiconductor manufacturing. The developed optical system employs an evanescent field to selectively enhance exclusively the observatory of phenomena occurring on the surface being polished, offering a lateral resolving power of approximately 400 nm, in the slurry concentration of up to 5 wt% based on the numerical aperture of the objective lens. In addition, there is also the observability of 105 nm and down to 55 nm-sized silica particles without requiring additive fluorescence agents in or around the nano-particles, even when these particles are moving on surfaces such as silica glass or hard materials (silicon carbide: 4H-SiC). Consequently, the motion behavior of nano-particles disjoining with polishing pad asperity was explored and discussed, in this paper. Experimental results revealed that the polishing pad spatially constrains the movement of particles between the pad and the substrate surface, guiding them toward the surface being polished. During pad sliding, fluidically dragged nano-particles exhibit slower movement than the polishing pad sliding speed while retaining the Brownian motion. Furthermore, 105 nm-sized silica particles did not continuously approach to attach onto the SiC surface; the nano-particles approached in steps with reduced Brownian motion in all directions before attaching. This behavior can be attributed to the effects of van der Waals attraction and electrostatic repulsion forces between the particle and the substrate surfaces.

Preparation and Performance Testing of Green Non-toxic Polishing Solution for Medical Titanium Alloy

To obtain the lower toxic residue on the medical titanium alloy surface in chemical mechanical polishing process, a new green polishing solution was proposed and evaluated in this study. The humoral fluid was selected as the basic solution in which the silica abrasive particles were used for the grinding particles, and the H2O2 was added as the oxidant. A chemical mechanical polishing test was carried out for its performance investigation with titanium alloy material. Then the surface roughness and material remove ratio of test samples were analyzed and compared with that of existed polishing solution condition. At last, the toxic residue of the titanium alloy samples was obtained by scanning electron microscopy technology. The experimental results indicated that the better material removal rate and surface roughness of medical titanium alloy with humoral polishing solution are obtained comparing with existed polishing solution condition. More importantly, the content of toxic elements on the sample surface was significantly reduced due to the more aluminum and vanadium ions dissolved in polishing solution, which is more beneficial for its application in the medical prosthetics field. This study provides a new reference for the toxic residue reduction on the material surface of medical titanium alloy in chemical mechanical polishing process.

Atomic surface achieved through a novel cross-scale model from macroscale to nanoscale.

Chemical mechanical polishing (CMP) is widely used to achieve an atomic surface globally, yet its cross-scale polishing mechanisms are elusive. Moreover, traditional CMP normally employs toxic and corrosive slurries, resulting in potential pollution to the environment. To overcome these challenges, a novel cross-scale model from the millimeter to nanometer scale is proposed, which was confirmed by a newly developed green CMP process. The developed CMP slurry consisted of hydrogen peroxide, sodium carbonate, sodium hydroxycellulose, and silica. Prior to CMP, fused silica was polished by a ceria slurry. After CMP, the surface roughness (Sa) was 0.126 nm, the material-removal rate was 88.3 nm min-1, and the thickness of the damaged layer was 8.8 nm. The proposed model was built by fibers, through integrating Eulerian and Lagrangian models and reactive force field-molecular dynamics. The results predicted by the model were in good agreement with those of CMP experimentally. A model for large-sized fibers revealed that a direct contact area of 11.12% was obtained for a non-woven polishing pad during the CMP experiments. Another model constructed via combining Eulerian and Lagrangian functions showed that the stress at the intersections of the fibers varied mainly from 0.1 to 0.01 MPa and was higher than the stress at other parts. An increase in viscosity led to a decrease in the areas with low stress, demonstrating that viscosity enhanced the stress and facilitated the removal of material. At the microscale and nanoscale, the stress of the abrasive surface exposed to the workpiece changed from 2.21 to 6.43 GPa. Stress at the interface contributed to the formation of bridging bonds, further promoting the removal of material. With increasing the compressive stress, the material-removal form was transformed from a single atom to molecular chains. The proposed model and developed green CMP offer new insights to understand the cross-scale polishing mechanism, as well as for designing and manufacturing novel polishing slurries, pads, and setups.

Piezocatalysis for Chemical-Mechanical Polishing of SiC: Dual Roles of t-BaTiO3 as a Piezocatalyst and an Abrasive.

Chemical mechanical polishing (CMP) offers a promising pathway to smooth third-generation semiconductors. However, it is still a challenge to reduce the use of additional oxidants or/and energy in current CMP processes. Here, a new and green atomically smoothing method: Piezocatalytic-CMP (Piezo-CMP) is reported. Investigation shows that the Piezo-CMP based on tetragonal BaTiO3 (t-BT) can polish the rough surface of a reaction sintering SiC (RS-SiC) to the ultra-smooth surface with an average surface roughness (Ra) of 0.45nm and the rough surface of a single-crystal 4H-SiC to the atomic planarization Si and C surfaces with Ra of 0.120 and 0.157nm, respectively. In these processes, t-BT plays a dual role of piezocatalyst and abrasive. That is, it piezo-catalytically generates in-situ active oxygen species to selectively oxidize protruding sites of SiC surface, yielding soft SiO2 , and subsequently, it acts as a usual abrasive to mechanically remove these SiO2 . This mechanism is further confirmed by density functional theory (DFT) calculation and molecular simulation. In this process, piezocatalytic oxidation is driven only by the original pressure and friction force of a conventional polishing process, thus, the piezo-CMP process do not require any additional oxidant and energy, being a green and effective polishing method.