Directly Comparing the Effects of Amino and Carboxyl Groups on Chemical Mechanical Polishing of Steel from the Perspective of Corrosive Wear

Cobalt (Co)-doped colloidal silica abrasives were synthesised by seed-induced growth method. Time-of-flight secondary ion mass spectroscopy was used to characterise the composition of the obtained abrasives. The morphology of the abrasives was measured by using scanning electron microscopy. The chemical mechanical polishing (CMP) performances of the Co-doped colloidal silica abrasives on sapphire substrates were investigated. Experiment results indicate that the Co-doped colloidal silica abrasives exhibit lower surface roughness and higher material removal rate (MRR) than that of pure colloidal silica abrasive under the same testing conditions. Furthermore, the inductively coupled plasma-atomic emission spectrometry and X-ray photoelectron spectroscopy were also used to investigate the acting mechanism of the Co-doped colloidal silica in sapphire CMP. Analysis results show that cobalt aluminate appears after polishing, implying the tribochemistry reaction occurs during CMP. The chemical reaction between element cobalt and sapphire surface during CMP can promote the chemical effect in CMP and lead to the increasing of MRR.

The effect of amino acid addition in CeO2-based slurry on SiO2/Si3N4 CMP: Removal rate selectivity, morphology, and mechanism research

As the semiconductor device is shrinking and gets complicated, the chemical mechanical polishing (CMP) process has become important. Various types of abrasive particles are used as CMP slurry, and among them, ceria slurry is in the spotlight due to its high material removal rate (MRR) and selectivity on oxide CMP process. It is known that the ceria abrasives form Ce-O-Si chemical bonds with oxide film, which makes it possible to achieve a high CMP performance.To further advance the performance of ceria slurry, we conducted a series of researches on ceria. A study was conducted on scanning mobility particle sizer (SMPS) measurement to accurately evaluate particle size distribution along with the basic polishing mechanism of monodisperse ceria nanoparticles. In addition, an optimization study was conducted considering the CMP performance according to the abrasive concentration of ceria slurry and the influence of ceria nanoparticles remaining on the wafer surface before the post-CMP cleaning process. Furthermore, research on synthesis method and surface modification of ceria was also conducted to improve the polishing performance. Ce3+ ions on the surface of ceria form Ce-O-Si chemical bond with the silicon dioxide film. Therefore, an important key point is to increase the concentration of Ce3+ ions to improve polishing performance. To achieve high Ce3+ ion concentration, ceria nanoparticles were synthesized through a hydrothermal method, and this performance was improved through lanthanide doping. On the other hand, methods to enhance Ce3+ ion concentration by inducing a reduction reaction on the surface of ceria nanoparticles were also proposed. First, the polishing performance was improved by adding trace metals (FeCl2, CrCl2) to induce a reduction reaction of ceria nanoparticles. Next, the reduction reaction of ceria was induced by applying an eco-friendly method which did not add chemical agents. Ultraviolet (UV) irradiation and hydrogen-gas reduction methods showed sufficient reduction reaction to improve the polishing performance of ceria slurry, and maintained physical properties without causing CMP defects such as poor surface roughness and micro-scratches.As with previous polishing studies, post-CMP cleaning is also important to decease defects. While ceria nanoparticles exhibit great polishing performance for silicon dioxide due to their ability to form chemical bonds, however, they also have the disadvantage of being difficult to remove during the post-CMP cleaning process. To efficiently remove ceria nanoparticles from the wafer surface during the post-CMP cleaning process, various methods have been studied. First, the buff cleaning process was studied in which a deionized water-based cleaning solution is injected instead of slurry after the CMP process. Since the buff cleaning process must simultaneously minimize damage of wafer surface and maximize cleaning performance, optimization research on the properties of the physical factors and cleaning solution is important. For an environmentally friendly cleaning method, we proposed controlling the viscosity of deionized water or using gas-dissolved water. It has been proven that physical factors of cleaning solutions (viscosity, micro bubbles, etc.) can be effective in removing ceria nanoparticles. Especially, hydrogen gas in gas-dissolved water induced a reduction reaction, breaking Ce-O-Si bonds and improving the cleaning performance. Limited to the bulk ceria CMP process, we also studied the improvement of cleaning performance of remained ceria nanoparticles using the tangential flow filtration (TFF) method before CMP process. We focused that small contaminant particles are difficult to remove during the cleaning process, and through the TFF method, small abrasive particles in the slurry are filtered in advance while maintaining the polishing performance.

Chemical mechanical polishing (CMP) has become a critical planarization technique in the manufacture of advanced integrated circuit devices. It can effectively remove the topography of thin film on wafer, and achieves the good planarization either in local or global region, and also the polished object will have the excellent surface quality. Recently, new materials and architectures have been introduced in the manufacturing process of IC production, so some consumables still require further study and development, mainly due to the stricter requirements. In this dissertation, the improvement in CMP performance by various pad conditioner designs and fixed nanodiamond pad was investigated experimentally. The main consumables under research, which included the polishing pad and the pad conditioner, in CMP performance were evaluated, and the polishing planarization was also analyzed and improved. The fixed nanodiamond pad was the developed consumable, and through a series of experiments in silicon CMP to obtain the proper pad design and verify the pad’s validity. In the comparison of the performance of the experimental fixed nanodiamond pad, several commercial slurries were adopted. In citing the findings from the experimental results, the value and practicality of this study was discussed. The surface roughness and thickness of the polishing pad influenced the material removal rate directly, and the uniformity of both the surface roughness and thickness of the polishing pad were significant factors of the with-in wafer non-uniformity in CMP process. The compressibility and the friction force could be used to evaluate the polishing pad. Using a corrective conditioning profile, the non-uniformity of material removal rate was significantly improved, and also the service time of the polishing pad was lengthened. The design of pad conditioner was critical as it determined the efficiency of the grooving action. The pad conditioner chose the polycrystalline diamond as its substrate, which could increase the wear resistance. The diamond cutting tips on pad conditioner had the same size, shape, and protrusion height, which was beneficial for the dressing behavior and stability. The effect of various fixed abrasive pad designs on polishing characteristics during silicon wafer polishing was investigated. Due to the different manufacturing method for these fixed nanodiamond pads, the abilities of controlling the nanodiamond particles were different. Consequently, the surface roughness of the polished silicon wafer was remarkably improved by the fixed nanodiamond pad, and result also revealed that the pad hardness was a key factor in keeping the abrasives effective in the pad-wafer interface. In comparison with the performance of slurry process in silicon CMP, although the fixed nanodiamond pad process had a relatively low polishing efficiency that depended simply on the mechanical abrasion. For the same reason, a relatively thick damaged layer was formed in the polished silicon subsurface, as the fixed nanodiamond pad was used. However, it was comparable with the slurry process in terms of surface topography of polished silicon wafer, due to its extremely small and nearly spherical particles.

Composite polystyrene-core ceria-shell abrasives are synthesized by direct chemical deposition reaction of Ce(NO3)3 and C6H12N4 on the surface of negative-charged polystyrene(PS) microsphere.The CeO2 shell thickness of composite abrasives can be tuned by changing the concentration of Ce(NO3)3 in the reaction solution.The as-synthesized samples are characterized by techniques of transmission electron microscope(TEM),field emission scanning electron microscope(FESEM),Raman spectroscope(RS),thermogravimetric analysis(TGA)and dynamic light scattering(DLS) measurements.Effects of the CeO2 shell thickness of PS/CeO2 composite abrasives on oxide chemical mechanical polishing(CMP) performance are also investigated by using atomic force microscope(AFM).The results indicate that the core-shell structured PS/CeO2 composite abrasives are in regular spherical shape with a diameter of 200～250 nm,and the shell thickness is about 10～30 nm.The CMP test results confirm that there is an obvious effect of the shell thickness of composite abrasives on oxide CMP behavior.The CMP performance is better and then worse with the increase of shell thickness from 10 to 30 nm.When the CeO2 shell thickness is 20 nm,Ra and root-mean-square roughness within 5 μm×5 μm area of thermal oxide film surface after polishing is 0.196 and 0.254 nm respectively.Moreover,the material removal rate can reach to 568.2 nm/min.

Cerium-incorporated SBA-15-type abrasives were synthesised by a two-step synthesis method in order to improve the performance of chemical mechanical polishing (CMP). An analysis using transmission electron microscope (TEM) and nitrogen adsorption showed that this new type of abrasives exhibited highly ordered mesostructures with nanoscale pore diameter, large pore volume and uniform porous size distribution. The performances of CMP on hard disk substrates using the new abrasives were then investigated. The polishing results showed that cerium-incorporated SBA-15-type composite abrasives with larger pore diameter were more likely to get higher material removal rate (MRR), while the surfaces of hard disk polished by this type of abrasives were associated with lower topographical variations and lower surface roughness as compared with those polished by sing pure SBA-15 abrasives.

The chemical mechanical polishing (CMP) process has become a widely accepted global planarization technology. The abrasive material is one of the key elements in CMP. In the presented paper, an Ag-doped colloidal SiO2 abrasive is synthesized by a seed-induced growth method. It is characterized by time-of-flight secondary ion mass spectroscopy and scanning electron microscopy to analyze the composition and morphology. The CMP performance of the Ag-doped colloidal silica abrasives on sapphire substrates is investigated. Experiment results show the material removal rate (MRR) of Ag-doped colloidal silica abrasives is obviously higher than that of pure colloidal silica abrasives under the same testing conditions. The surfaces that are polished by composite colloidal abrasives exhibit lower surface roughness (Ra) than those polished by pure colloidal silica abrasives. Furthermore, the acting mechanism of Ag-doped colloidal SiO2 composite abrasives in sapphire CMP is analyzed by X-ray photoelectron spectroscopy, and analytical results show that element Ag forms Ag2O which acts as a catalyst to promote the chemical effect in CMP and leads to the increasing of MRR.

Preparation of MgO doped colloidal SiO2 abrasive and their chemical mechanical polishing performance on c-, r- and a-plane sapphire substrate

The Copper (Cu) wiring and barrier layer Ru (Ruthenium) CMP is of vital importance to the performance of microchips. For fabricating Ru-Cu interconnect structures, a serious challenge is the galvanic corrosion of Cu that occurs during Ru chemical mechanical polishing (CMP). Previous work has presented a calculation approach to evaluate the galvanic corrosion of Cu in slurry with KIO 4 as the oxidizer. Potassium molybdate (K 2 MoO 4 ) combined with benzotriazole (BTA) acts as the inhibitor and the synergetic effect during CMP has been investigated. The work in this paper makes further improvement in the CMP performance using K 2 MoO 4 and BTA as corrosion inhibitors for Cu and Ru. Results show that the pH value, the oxidant and inhibitor concentration could significantly affect the CMP performance. The material removal rate (MRR) selectivity between Cu and Ru has been optimized by adjusting the slurry composition. Results show that in BTA contained slurry with KIO 4 as oxidant, the addition of K 2 MoO 4 helps to obtain good MRR selectivity between Cu and Ru. BTA-K 2 MoO 4 acts as good corrosion inhibitor for Cu and has complexation effect for Ru during CMP.

Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of the key elements in CMP process. In order to enhance material removal rate (MRR) and improve surface quality of sapphire substrate, a series of novel Ni-doped colloidal silica abrasives were prepared by seed-induced growth method. The CMP performances of composite abrasives on sapphire substrate were investigated using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the Ni-doped colloidal silica composite abrasives achieve lower surface roughness and higher material removal rate than that of pure colloidal SiO2 abrasive under the same experimental conditions. Furthermore, the acting mechanism of the Ni-doped colloidal silica abrasive on sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between Ni-doped colloidal silica abrasive and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removal rate.

To further clarify the effect of the polishing slurry dispersant on the chemical mechanical polishing (CMP) performance of 304 stainless steel, a series of tests were carried out. The correlation between the material removal rate (MRR), surface roughness of 304 stainless steel, dispersant composition, and their content was investigated under two kinds of polishing slurry (hydrogen peroxide oxidant and ferric chloride oxidant) conditions. The experimental results indicated that the MRR and surface roughness of 304 stainless steel arrived at the maximum when the content of sodium hexametaphosphate dispersant was 1.2% (wt) under the hydrogen peroxide–oxalic acid polishing slurry condition. The values of MRR and surface roughness were 146 nm/min and 10 nm, respectively. The MRR and surface roughness of 304 stainless also reached the maximum value as the content of the propanetriol dispersant was 1.2% (wt) under the ferric chloride–oxalic acid polishing slurry condition. However, the values of MRR and surface roughness were 457 nm/min and 22 nm, respectively. Therefore, sodium hexametaphosphate was recommended as the dispersant of hydrogen peroxide–oxalic acid polishing, and propanetriol was recommended as the dispersant of ferric chloride–oxalic acid polishing slurry condition, according to the above analysis. This study lays a theoretical foundation for the improvement of 304 stainless steel CMP performance.

A polishing pad plays an essential role in determining the chemical mechanical planarization (CMP) performance such as removal rate, planarization, and defectivity. Further, it is important for the polishing pad to maintain good CMP performance throughout its lifespan. In order to achieve high performance and durability, a hole-type pad was suggested as an alternative to the conventionally used pore-type pad. In this study, the effect of the hole density on the CMP performance was examined for a hole-type pad. Surface characterization of the hole-type pad showed that the hole density corresponded to the contact ratio between the pad and the wafer, and therefore, the contact characteristics could be controlled by a hole fabrication process. The experimental results showed that the number of holes play a key role in determining CMP performances. The removal rate decreased with an increase in the hole density. The level of dishing showed an increase with the hole density. The number of CMP scratches decreased at higher hole densities. Higher contact ratio and the presence of large particle trap sites explain the lower trend of the micro-scratch observed. An important advantage of the hole-type pad is that it retains the surface structure as CMP continues, which implies contact behavior is maintained.

Effect of EDTA-modified alumina composite abrasive on the CMP performance of sapphire substrate

Problem statement: Abrasive is one of key influencing factors on the polished surface quality in Chemical Mechanical Polishing (CMP). Solid abrasives in CMP slurries are easy to cause polishing scratches. It is well known that reducing the hardness of abrasives would improve the polished surface quality. Therefore, the change in structure or shape of the abrasives means a change in polished surface quality. The aim of this research paper is to find the differences of CMP performances on hard disk between solid silica abrasives and porous silica abrasives. Approach: A kind of spherical porous silica abrasive was prepared and its CMP performances on hard disk had been investigated. The influences of polishing parameters including polishing time, down force and rotation speed on Material Removal Rate (MRR) and average roughness (Ra) were studied in hard disk substrate CMP with these prepared spherical porous SBA-15 abrasives and solid silica abrasives. Results: After polished in slurry containing solid SiO2, the surface became smooth and Ra decreased from 8.234-1.159 nm. However some small scratches still existed there. When polished with slurry containing spherical porous SBA-15 under the same polishing conditions, the surface became smoother, the scratches could hardly be observed and Ra decreased from 8.409-0.539 nm. Conclusion: Compared with solid silica abrasive, the prepared spherical porous silica abrasive has better hard disk substrates CMP performance under the same polishing conditions.

Roles and mechanism analysis of chitosan as a green additive in low-tech node copper film chemical mechanical polishing