Chemical Mechanical Polishing Characteristics Research Articles

Chemomechanical magnetorheological finishing: Process mechanism, research trends, challenges and opportunities in surface finishing

Chemomechanical magnetorheological finishing (CMMRF) has emerged as a nanofinishing method that combines the characteristics of chemical mechanical polishing (CMP) and magneto-rheological finishing (MRF). The CMMRF process was designed to take into account both the chemical and mechanical effects that occur during the finishing process. In the field of material processing science, this article delves into the fundamentals of the CMMRF method. The potential research patterns linked to CMMRF are assessed and their benefits are determined. Furthermore, the challenges of improving CMMRF process capabilities, as well as the wide futuristic opportunities of the research sector, are emphasised, along with meeting all industrial needs. The findings of this analysis paper will also aid researchers in the field of advanced finishing in identifying process realisation for better results.

Effect of Using High-Pressure Gas Atmosphere with UV Photocatalysis on the CMP Characteristics of a 4H-SiC Substrate

The objective of this study was to realize high-efficiency and high-quality chemical mechanical polishing (CMP) of a silicon carbide (SiC) substrate. Consequently, the effect of a gas atmosphere on the CMP characteristics of a SiC substrate was investigated. The experimental results show that increasing the partial pressure of oxygen (O2) in the atmosphere to 300 kPa led to an over 2-fold increase in the material removal rates (MRRs) of the Si and carbon (C) faces compared to an open-air atmosphere. White light interference microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to analyze the face morphology and surface elements after processing. Si face atoms were more difficult to oxidize than C face atoms, resulting in a low MRR of the Si face after CMP. The MRR of the Si face was improved by using an ultraviolet (UV) photocatalysis reaction in the high-pressure O2 atmosphere. Excitation of O2 molecules in the slurry into HO 2 • with a stronger oxidation capability promoted the chemical reaction at the solid-liquid interface. The processing mechanism was elucidated.

Effects of Atmosphere and Ultraviolet Light Irradiation on Chemical Mechanical Polishing Characteristics of SiC Wafers

To establish a high-efficiency and high-quality polishing process by controlling the workpiece environment, a prototype chemical mechanical polishing (CMP) machine that can perform double-side CMP simultaneously in a sealed pressure chamber was developed. Using this new machine, polishing experiments on single crystalline silicon carbide (SiC) wafers were carried out. The results showed that applying a highly pressurized O2 gas and ultraviolet light irradiation were effective in SiC CMP.

Effects of Atmosphere and Ultraviolet Light Irradiation on Chemical Mechanical Polishing Characteristics of SiC Wafers

To establish a high-efficiency and high-quality polishing process by controlling the workpiece environment, a prototype chemical mechanical polishing (CMP) machine that can perform double-side CMP simultaneously in a sealed pressure chamber was developed. Using this new machine, polishing experiments on single crystalline silicon carbide (SiC) wafers were carried out. The results showed that applying a highly pressurized O2 gas and ultraviolet light irradiation were effective in SiC CMP.

Chemical mechanical polishing characteristics of ITO thin film prepared by RF magnetron sputtering

Indium-tin-oxide (ITO) thin films have attracted intensive interest because of their unique properties of good conductivity, high optical transmittance over the visible region and easy patterning ability. ITO thin films have found many applications in anti-static coatings, thermal heaters, solar cells, flat panel displays (FPDs), liquid crystal displays (LCDs), electroluminescent devices, sensors and organic light-emitting diodes (OLEDs). ITO thin films are generally fabricated by using various methods, such as spraying, chemical vapor deposition (CVD), evaporation, electron gun deposition, direct current electroplating, high frequency sputtering, and reactive sputtering. In this research, ITO films were grown on glass substrates by using a radio-frequency (RF) magnetron sputtering method. In order to achieve a high transmittance and a low resistivity, we examined the various film deposition conditions, such as substrate temperature, working pressure, annealing temperature, and deposition time. Next, in order to improve the surface quality of the ITO thin films, we performed a chemical mechanical polishing (CMP) with different process parameters and compared the electrical and the optical properties of the polished ITO thin films. The best CMP conditions with a high removal rate, low nonuniformity, low resistivity and high transmittance were as follows: platen speed, head speed, polishing time, and slurry flow rate of 30 rpm, 30 rpm, 60 sec, and 60 ml/min, respectively.

Research on CMP Characteristics Attribute to Groove Size

Groove pads are used quite widely in chemical mechanical polishing (CMP), and groove size plays an important role in CMP characteristics. This study focuses on the investigation of the groove size effect using X-Y groove pads which are different with pitch and width. The first experiment shows the size effect on the polishing characteristics including material removal rate (MRR), within wafer non-uniformity (WIWNU) on 4 inch oxide blanket wafers for 60 seconds. The second experiment verifies the reason why MRR and WIWNU are different, by the calculation of slurry duration time (SDT) resulting from the change of friction force. All experimental results indicated that a significant difference of slurry flow attributed to groove width and pitch has an impressive influence on friction force, finally the MRR and WIWNU are affected by the groove size.

Characteristics of chemical mechanical polishing using graphite impregnated pad

This paper introduces a new design for polishing pads that eliminates the need for built-in pores. Instead, a polyurethane matrix is impregnated with nanographite particles to form a graphite impregnated pad. The surface characteristics as well as the friction force, slurry flow rate, and material removal rate when polishing a dielectric oxide film were experimentally measured and compared with those for conventional porous polishing pads. The results reveal that the proposed pad has an approximately 40% lower dressing rate and consequently greater tool life. Further, use of the impregnated pad reduces slurry consumption as the removal rate at slurry flow rates of <100 ml/min is significantly higher than that for porous pads. The increased removal rate can be attributed to adsorption of slurry onto the large surface area of the nanographite particles. The results suggest interesting possibilities for significant reduction in the cost associated with CMP processing.

Platinum chemical mechanical polishing (CMP) characteristics for high density ferroelectric memory applications

The key component of ferroelectric random access memory (FeRAM) is a capacitor including a ferroelectric thin film and electrode materials. Platinum is one of the suitable metals which meet requirements such as low resistivity, high thermal stability, and good oxygen resistance. Generally, the ferroelectric and the electrode materials were patterned by a plasma etching process. The application possibility of chemical mechanical polishing (CMP) processes to the patterning of ferroelectric thin film instead of plasma etching was investigated in our previous study for improvement of an angled sidewall which prevents the densification of FeRAM. In this study, the characteristics of platinum CMP for FeRAM applications were also investigated by an approach as bottom electrode materials of ferroelectric material in CMP patterning. The removal rate was increased from 24.81 nm/min by the only alumina slurry (0.0 wt% of H 2O 2 oxidizer) to 113.59 nm/min at 10.0 wt% of H 2O 2 oxidizer. Electrochemical study of platinum and alumina slurry with various concentrations of H 2O 2 was performed in order to investigate the change of the removal rate. The decreased particle size in the alumina slurry with an addition of 10.0 wt% H 2O 2 oxidizer made the improved surface roughness of the platinum thin films. Micro-scratches were observed in all polished samples.

A Study on the Electrochemical and the Chemical Mechanical Polishing Behaviors of W and Ti Film

In this paper, the chemical mechanical polishing (CMP) performances of tungsten (W) and titanium (Ti) films according to the oxidizer content were studied through an electrochemical corrosion analysis. In order to investigate the electrochemical polishing behavior of the W and the Ti films, we used an alumina (Al2O3)-based tungsten slurry with a H2O2 oxidizer for CMP test. As an experimental result, for the case of 5 vol% added oxidizer, the removal rates were improved, and a good polishing selectivity of 1.4 : 1 was obtained, which means that the oxidizer with the highest removal rate has a high dissolution rate due to the predominant electrochemical corrosion effects. Therefore, we conclude that the CMP characteristics of W and Ti strongly depend on the amounts of H2O2 oxidizer added.

Chemical mechanical polishing characteristics in (Bi,La)Ti 3O 12 damascene process for high-density ferroelectric memories

Ferroelectric thin films such as Pb(Zr,Ti)O 3, SrBi 2Ta 2O 9, and Bi 3.25La 0.75Ti 3O 12 (BLT) thin films have been widely investigated for non-volatile ferroelectric memories. BLT thin films show advantages such as highly fatigue resistance, low processing temperature, and large remanent polarization. The patterning of these ferroelectric thin films with a vertical sidewall and without plasma damage is strongly required. Chemical mechanical polishing (CMP) process was investigated for the vertical sidewall patterning of BLT thin films. Removal rate and within-wafer non-uniformity (WIWNU%) were examined by change of process parameters. Potential of hydrogen (pH) in slurry was varied for an improvement of the removal rate and WIWNU%. Surface roughness of BLT thin films after CMP process for the improvement of densification was inquired into by atomic force microscopy. The excellent performance such as 188.4 nm/min of removal rate, 2.61% of WIWNU%, 0.95 nm of root mean square roughness, and 6.94 nm of peak-to-valley roughness was obtained. This result will lead the CMP process to pattern the BLT thin films for the vertical sidewall without plasma damage.

CMP characteristics and optical property of ITO thin film by using silica slurry with a variety of process parameters

Surface roughness by peaks, bumps, large particles, and pin-holes on the surface of indium tin oxide (ITO) thin film, which is widely used for a transparent electrode of optoelectronic devices, caused the destruction of color quality and the reduction of device life time. Chemical mechanical polishing (CMP) process was selected to smooth the surface roughness in this study. Some process parameters including polishing time, slurry flow rate, table speed, and slurry temperature were varied to optimize the ITO-CMP process. The removal rate and the non-uniformity were 60.45 nm/min and 5.17% at the condition of appropriate process parameters as follows: head speed, slurry temperature, down force, slurry flow rate, polishing time, and table speed were 60 rpm, 30 °C, 300 gf/cm 2, 40 ml/min, 60 s, and 60 rpm, respectively. However, the sufficient non-uniformity below 5.0% was not obtained in all process parameter conditions due to the unequal polishing by the silica slurry. Optical transmittance of ITO thin film was improved from 83.3% to 85.0% after CMP process.

Electrochemical corrosion effects and chemical mechanical polishing characteristics of tungsten film using mixed oxidizers

In this paper, the effects of mixed oxidizers on tungsten-chemical mechanical polishing (W-CMP) process were studied using three different kinds of oxidizers such as Fe(NO 3) 3, KIO 3 and H 2O 2. Moreover, the interaction between the tungsten film and the oxidizer was discussed by potentiodynamic polarization test, in order to compare the CMP performances and electrochemical behavior of the tungsten film as a function of mixed oxidizers. The potentiodynamic polarization results indicated that the corrosion current densities of the 5 wt% H 2O 2 and 5 wt% H 2O 2 + 5 wt% Fe(NO 3) 3 were higher than the other mixed oxidizers. Such an electrochemical corrosion effect implies that slurries with the highest removal rate have a high dissolution rate at lower pH. Therefore, we conclude that W-CMP performances are strongly dependent on the kind of oxidizers and the amounts of oxidizer additive.

CMP시 SiO2슬러리의 마찰 특성과 연마결과에 관한 연구

The effects of mechanical parameters on the characteristics of chemical mechanical polishing(CMP) can be directly evaluated by friction force. The piezoelectric quartz sensor for friction force measurement was installed, and friction force could be detected during CMP process. Furthermore. friction energy can be calculated by multiplying relative velocity by integration of the friction force throughout the polishing time. Si02 slurry for interlayer dielectric(ILD) CMP was used in this experiment to consider the relation of frictional characteristics and polishing results. From. this experiment, it is proven that the friction energy is an essential factor of removal rate. Also, the friction force is related to removal amount per unit length(dH/ds) and friction energy has corelation to the removal rate(dH/dt) and process temperature. Moreover, within wafer non-unifornity(WIWNU) is related to coefficient of friction because of the mechanical moment equilibrium. Therefore, the prediction of polishing result would be possible by measuring friction force.

H2O2산화제가 W/Ti 박막의 전기화학적 분극특성 및 CMP 성능에 미치는 영향

CMP(chemical mechanical polishing) process has been attracted as an essential technology of multi-level interconnection. Also CMP process got into key process for global planarization in the chip manufacturing process. In this study, potentiodynamic polarization was carried out to investigate the influences of <TEX>$H_2O_2$</TEX> concentration and metal oxide formation through the passivation on tungsten and titanium. Fortunately, the electrochemical behaviors of tungsten and titanium are similar, an one may expect. As an experimental result, electrochemical corrosion of the <TEX>$5\;vol\%\;H_2O_2$</TEX> concentration of tungsten and titanium films was higher than the other concentrations. According to the analysis, the oxidation state and microstructure of surface layer were strongly influenced by different oxidizer concentration. Moreover, the oxidation kinetics and resulting chemical state of oxide layer played critical roles in determining the overall CMP performance. Therefore, we conclude that the CMP characteristics tungsten and titanium metal layer including surface roughness were strongly dependent on the amounts of hydrogen peroxide oxidizer.

산화막 CMP 공정에서 슬러리 온도 변화에 따른 연마 특성

To investigate the effects of slurry temperature on the chemical mechanical polishing(CMP) performance of oxide film with silica and ceria slurries, we have studied slurry properties as a function of different slurry temperature. Also, the effects of each input parameter of slurry on the oxide CMP characteristics were investigated. The pH showed a slight tendency of decrease, the conductivity in slurries showed an increased tendency, the mean particle size in slurry decreased, and the zeta potential of slurry decreased with temperature. The removal rates significantly increased and maintained at the specific levels over 4<TEX>$0^{\circ}C$</TEX>. The better surface morphology of oxide films could be obtained at 40 <TEX>$^{\circ}C$</TEX> of silica slurry and at 90 <TEX>$^{\circ}C$</TEX> of ceria slurry. It is found that the CMP performance of oxide film could be significantly improved or controlled by change of slurry temperature.

The effect of pad conditioning on planarization characteristics of chemical mechanical polishing (CMP) with ceria slurry

AbstractA ceria-based in-situ conditioning process was successfully developed. A new single layered metal bonded conditioner was developed to solve problems encountered in implementing ceria based in-situ conditioning process. The planarity was significantly improved compared with that of conventional Ni-plated in-situ conditioning.

Colloidal Silica based High Selectivity Shallow Trench Isolation (STI) Chemical Mechanical Polishing (CMP) Slurry

AbstractAmong various properties of chemical mechanical polishing (CMP) slurry, selectivity plays a key role in global planarization of high density and small pattern size shallow trench isolation (STI) process. Lack of adequate selectivity can lead to defects such as dishing and erosion. To improve the selectivity of STI CMP process, CMP characteristics of silica and silicon nitride wafer were investigated using colloidal silica slurry as a function of slurry pH. Sodium dodecyl sulfate (SDS), an anionic surfactant, was added to increase the selectivity of the slurry. As a result, selectivity increased from 3 to 25. It was concluded that selective passivation layer formed on silicon nitride wafer surface at acidic slurry pH range was responsible for the observed selectivity increase. Adsorption characteristics of SDS on silica and silicon nitride were measured as a function of slurry pH and concentration of SDS. As indicated by zeta potential behavior under acidic pH conditions, SDS adsorption on silicon nitride was significantly higher han silica due to the electrostatic forces. Significantly higher SDS coating on silicone nitride seems to have resulted in lubrication layer leading to increased polishing selectivity.

Chemical mechanical polishing performances by filtering and retreatment of used silica abrasives slurry

In order to reduce the high cost of ownership and cost of consumables, we have collected the silica abrasive powders by filtering method after subsequent chemical mechanical polishing (CMP) process for the recycling of abrasives. From this, we have studied the possibility of recycling reused silica abrasive through the analysis of particle size distribution and field emission scanning electron microscope measurements of abrasive powders. We annealed the collected abrasive powders to promote the mechanical strength of reduced abrasion force. Finally, we compared the CMP characteristics between self-developed KOH-based silica abrasive slurry and original slurry. Our experimental results show removal rate and planarity comparable to commercial products. Consequently, we can expect the saving of high cost slurry.

Oxide-chemical mechanical polishing characteristics using silica slurry retreated by mixing of original and used slurry

Chemical mechanical polishing (CMP) technology has been widely used for global planarization of multi-level interconnection for ULSI applications. However, the cost of ownership and cost of consumables are relatively high because of expensive slurry. In this work, we have studied the possibility of recycling silica slurry in order to reduce the costs of CMP slurry. Also, we have investigated the CMP characteristics of silica slurry retreated by mixing of original slurry and used slurry. The removal rate and within-wafer non-uniformity were measured as a function of different slurry composition. As an experimental result, the retreated slurry with annealed silica abrasive of 2 weight percent (wt%) contents was showed to exhibit high removal rate and low non-uniformity. Therefore, we propose a two-step CMP process as follows: in the first-step CMP, we can polish the thick and rough film surface using retreated slurry, and then, in the second-step CMP, we can polish the thin film and fine pattern using original slurry. Consequently, we can expect to save high costs of slurry.

Improvements of oxide-chemical mechanical polishing performances and aging effect of alumina and silica mixed abrasive slurries

In this paper, in order to investigate the effects of agglomeration on the chemical mechanical polishing (CMP) performance of oxide layer using mixed abrasive slurry (MAS), we have studied an aging effect as a function of different slurry composition. Also, the effects of each slurry composition on the oxide CMP characteristics were investigated to obtain the higher removal rate and lower within-wafer non-uniformity (WIWNU). We prepared the various kinds of MAS. In order to save the cost of slurry, the original slurry was diluted by de-ionized water. Alumina (Al 2O 3) abrasives were added before and after annealing in the diluted silica slurry in order to promote the mechanical force of diluted slurry. As an experimental result, the CMP characteristics of 1:10 diluted silica slurry containing 1500 °C-annealed alumina abrasives of 0.5 wt% showed excellent removal rate and WIWNU. We think that it is due to the increase of mechanical strength of alumina abrasive particles after annealing. At the same time, we can anticipate the saving of high-cost CMP slurry for ULSI fabrication industry.