Hard Disk Substrate Research Articles

Preparation of copper-incorporated mesoporous alumina abrasive and its CMP behavior on hard disk substrate

To improve the chemical mechanical polishing (CMP) performances, copper-incorporated mesoporous alumina abrasive was synthesized by sol–gel method. X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption analyses show that the prepared mesoporous abrasives have highly ordered mesostructures with nanoscale pore diameter and uniform porous size distribution. The CMP performances of the mesoporous abrasives on hard disk substrates were investigated. The results show that, by comparison with pure mesoporous alumina and solid alumina, the copper-incorporated mesoporous alumina abrasives have much larger material removal rate (MRR). And the surfaces of hard disk polished by the porous alumina abrasives (mesoporous alumina or copper-incorporated mesoporous alumina) have much lower topographical variations and surface roughness (Ra) than that polished by solid alumina.

Preparation of porous alumina abrasives and their chemical mechanical polishing behavior

Porous alumina abrasives with different pore sizes were prepared using hydrothermal synthesis method by different hydrothermal temperatures. The pore structure, pore size and pore volume of the products were characterized by transmission electron microscopy and nitrogen adsorption desorption isotherm measurement. The chemical mechanical polishing (CMP) performances of porous alumina abrasives in hard disk substrate CMP were investigated. The results show that, the polished surface average roughness (Ra) decreases when the pore diameter of porous alumina abrasive increases. By comparison with solid alumina abrasive, the prepared porous alumina abrasives give lower Ra, and the porous alumina abrasive with 8.61nm pore diameter has higher material removal rate under the same polishing conditions.

Preparation of Porous Alumina Abrasives with Different Morphologies and their Chemical Mechanical Polishing Behavior

The traditional solid alumina abrasive has been widely used in commercial slurries. But it is easy to cause polishing scratches due to its dense solid structure. The morphology of the abrasives can also impact on the chemical mechanical polishing (CMP) performances. To improve the CMP performances of the hard disk substrate, rods-like porous alumina and flower-like porous alumina abrasives were prepared and their chemical mechanical polishing behavior investigated. The results showed that the porous alumina abrasives with different morphologies exhibited lower topographical variations and surface roughness than solid alumina abrasives under the same testing conditions.

Effect of Abrasive and Surfactant on Chemical Mechanical Polishing of Hard Disk Substrates

Chemical mechanical polishing (CMP) has been a widely applied process for hard disk substrates with nickel–phosphorous (Ni–P) plated. In this paper, the effects of abrasive and surfactant on the polishing performance of hard disk substrates using prepared colloidal silica-based alkaline slurry were investigated. The experimental results indicate that the material removal rate (MRR) strongly depends on the abrasive concentration and nonionic surfactant have little influence on the material removal rate. Under the testing conditions, smaller SiO2, moderate SiO2 concentration and higher surfactant concentration can obtain high surface quality in the prepared slurry. These results have been explained by which the abrasive particles move through the cover layer caused by surfactant adsorption on the disk substrates surface being polished.

Cerium-incorporated SBA-15-type materials for CMP: synthesis, characterisation, and CMP application on hard disk substrate

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.

Polishing Mechanism and Technology of Hard Disk Substrates by Colloidal Silica Alkaline Slurry

Chemical mechanical polishing (CMP) has been a widely applied process for nickel-phosphorus (Ni-P) coating hard disk substrate polishing. In this study, colloidal silica-based alkaline slurry was prepared for polishing Ni-P plated substrates and its CMP mechanism was studied with alkali slurry. Effects of the various process parameters such as polishing pressure and plate speed on hard disk substrate were investigated. The results show that the polishing pressure and plate speed have a strong influence on the material removal rate and surface roughness of the hard disk substrate. The oxidization layer formed on hard disk substrate surface after polishing. The nickel ions were bounded with amidocyanogen to form stable and soluble macromolecular amidocyanogen-complex agent, improved selectivity of convex region and concave region, enhanced the chemical reaction uniformity and the mass transfer velocity, and thus high removal rate and low surface roughness could be realized.

Preparation of Silica-Based Alkaline Slurry and its Application on Chemical Mechanical Polishing of Hard Disk Substrates

Chemical mechanical polishing (CMP) is the effective technology which obtains high accuracy surface of hard disk substrate with nickel-phosphorus (Ni-P) coating. The slurry is significant factor in hard disk substrate CMP. Colloidal silica-based alkaline slurry was prepared based on negative pressure vortex method. The effects of slurry parameters such as abrasive concentration, organic alkali concentration and oxidant concentration on material removal rate and surface characteristics were investigated. The experimental result indicated that the abrasive concentration was 20wt%, the slurry pH value was 11.2, the oxidant concentration was 15ml/L, improved surface roughness and polishing efficiency of hard disk substrates, a smooth surface was obtained and micro scratches could hardly be observed.

Polish Properties of Nano-Cluster Diamonds on Glass Substrates

Hard disk substrates play a key role in the data storage process of magnetic storage hard disk drives (HDDs). However, a potential failure mode exists with the head clearance requirements caused by surface variation which is induced by substrate nano-asperities. Consequently, developing a polish process to eliminate surface asperities and residual surface defects in the glass substrate disks process is therefore a necessity to meet the challenges of future technology. Currently, the leading candidate utilizes nano cluster diamond (NCD) abrasive which is a synthetic diamond created in a controlled explosion process. A great effort is now underway to modify these NCD clusters to reduce light scratches and asperities in the perpendicular magnetic recording media polish process. Three distinct diamond types of NCD-90, NCD-80 and NCD-70 were utilized in this study. The major difference among these three distinct cluster diamond types is the diamond percentage amounts. Because of the differing diamond percentage content, one achieves a different structure which changes the polish properties. HRTEM, XPS, Raman, BET, AFM, Optical Surface Analyzer and disk defect testers were used for the diamond particles, polished substrate and disk analysis. The detail shall be discussed in this study.

CMP Behavior of α-Alumina-g-Polyvinylpyrrolidone Composite Abrasive on Hard Disk Substrate

A novel α-alumina-g-polyvinylpyrrolidone (α-Al2O3-g-PVP) composite abrasive was prepared by surface grafting polymerization. The chemical mechanical polishing (CMP) performances of the composite abrasive on hard disk substrate were investigated with a UNIPOL-1502 polishing machine. Analyses on the surface of polished substrate indicated that the α-Al2O3-g-PVP composite abrasive exhibited lower surface roughness, less scratch, and improved post-CMP cleaning performances than pure α-alumina abrasive under the same testing conditions.

Post-CMP Cleaning of Atom-Scale Planarization Surface of Computer Hard Disk Substrate

At present, the surface of computer hard disk substrate has reached atom-scale planarization after chemical mechanical polishing (CMP). Post-CMP cleaning is one of the key factors influencing the CMP performances. During cleaning, cleaning solution and cleaning methods play a key role in cleaning quality and effectiveness. In the present paper, alkylpolyoxyethylene alcohol carboxylic ester (FAC) surfactant was synthesized and its cleaning performances on atom-scale planarization surface of computer hard disk substrate were investigated. Microscope analysis indicated that the prepared detergent containing FAC surfactant exhibited improved cleaning performances compared with the commercial detergent. Further, inductively coupled plasma (ICP) atomic emission spectrometer, auger electron spectrogram (AES) and atomic force microscopy (AFM) analyses after static corrosion test showed that the prepared cleaning solution had lower corrosion to hard disk substrate.

Chemical mechanical polishing of hard disk substrate with α-alumina-g-polystyrene sulfonic acid composite abrasive

α-Alumina-g-polystyrene sulfonic acid (α-Al 2O 3-g-PSS) composite abrasive was prepared by surface activation, graft polymerization and sulfonation, successively. The composition, dispersibility and morphology of the product were characterized by Fourier transformed infrared spectroscopy, laser particle size analysis and scanning electron microscopy, respectively. The chemical mechanical polishing (CMP) performances of the composite abrasive on hard disk substrate with nickel-phosphorous plating were investigated. The microscopy images of the polished surfaces show that α-Al 2O 3-g-PSS composite abrasive results in improved CMP and post-CMP cleaning performances than pure α-alumina abrasive under the same testing conditions.

Polishing properties of porous silica abrasive on hard disk substrate CMP

Chemical mechanical polishing (CMP) is the only technology to provide global planarisation of topography with a low post-planarisation slope. Abrasive is one of the key influencing factors on the surface quality during the CMP. Traditional silica abrasive is easy to cause polishing scratches since it is compact solid particle. In this work the polishing properties of porous silica abrasive in hard disk substrate CMP were investigated. The results show that the polishing down force and rotating speed have a strong influence on the material removal rate and average surface roughness of the hard disk substrate. After polishing with the slurry containing the porous silica abrasive, a smooth hard disk substrate surface was obtained.

Preparation and Polishing Properties of Spherical Porous Silica Abrasive

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.

Preparation of silica/ceria nano composite abrasive and its CMP behavior on hard disk substrate

A novel silica/ceria nano composite abrasive was synthesized by homogeneous precipitation using carbamide, ammonium ceric nitrate and silica. The abrasive was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and scanning electron microscopy (SEM), respectively. Then, the chemical mechanical polishing performances of the composite abrasive on hard disk substrate with nickel–phosphorous plated were investigated. Atomic force microscopy images show that the prepared abrasive gives much lower topographical variations than before polishing. The average waviness (Wa) of the polished hard substrate surface can be reduced from 15.5 Å before polishing to 8.36 Å, and the average of roughness (Ra) can be reduced from 14 Å before polishing to 4.80 Å.

Particles detection and analysis of hard disk substrate after cleaning of post chemical mechanical polishing

Scrub, ultrasonic and megasonic are widely used in industry as post-CMP (chemical mechanical polishing/planarization) cleaning procedure. In this paper experiments and results are described to analyze the particle contaminations of hard disk substrate after each process of post-CMP cleaning. A scatter spot method has been exploited to detect the location and characteristics of the particles. SEM with EDX is used to observe and analyze the particles’ shape and size as well as the elements. The results indicate that brush scrub process can remove 99% contaminations after CMP but not that efficient for submicron particle. Megasonic is a refined method for cleaning nano-particles. However, contaminations like metallic particles and bacteria from the equipment may cause pollution. The abrasive particles embedded in the plating pits cannot be removed by mechanical force. Pollution in the dryer is also discussed.

Step and flash imprint lithography for manufacturing patterned media

The ever-growing demand for hard drives with greater storage density has motivated a technology shift from continuous magnetic media to patterned media hard disks, which are expected to be implemented in future generations of hard disk drives to provide data storage at densities exceeding 1012 bits/in.2. Step and flash imprint lithography (S-FIL) technology has been employed to pattern the hard disk substrates. This article discusses the infrastructure required to enable S-FIL in high-volume manufacturing, namely, fabrication of master templates, template replication, high-volume imprinting with precisely controlled residual layers, and dual-sided imprinting. Imprinting of disks is demonstrated with substrate throughput currently as high as 180 disks/h (dual sided). These processes are applied to patterning hard disk substrates with both discrete tracks and bit-patterned designs.

Precision Grinding and Slicing of Glass-Like-Carbon

High density and isotropic poreless structure of Glass-like-carbon makes it practically used for fuel cells of space-shuttles and hard disk substrate etc. Glass-like-carbon is one of the new materials which attract attention, but it is so hard and brittle that precise machining of this material is difficult. Surface grinding and slicing were performed to collect the fundamental data of precise machining. The main results obtained in this study are as follows. (1) The transition from brittle mode to ductile mode in surface grinding occurs at a grain mesh size between #5000 and #3000. (2) The maximum grain depth of cut ‘dg’ necessary for ductile mode grinding is 0.021-0.006 mm or less. (3) When it is being sliced, the kerf width of the #1000 grinding wheel becomes wider than that of the #2000 grinding wheel because of the fact that the material removal capability of the #1000 grinding wheel is bigger than that of the #2000 grinding wheel. (4) It is extremely effective to use the fine grinding wheel, since the Young's modulus of glass-like-carbon is considerably low and eventually causes compression transformation,.

Detecting dynamic signals of ideally ordered nanohole patterned disk media fabricated using nanoimprint lithography

The authors have fabricated ideally ordered alumina nanohole patterned disk media via anodic oxidation and nanoimprint lithography with a thermoplastic resist. The ordered arrays of alumina nanoholes with 100nm pitch, filled with Co by electrodeposition, were created over a macroscopically large area on a hard-disk substrate using these industrially applicable nanofabrication technologies. Stable flight of a perpendicular magnetic head above the media and perpendicular magnetic anisotropy of the Co nanopillars enable high-speed dynamic magnetic recording and playback. Dynamic periodic signals that matched the nanopillar periodicity were clearly observed after writing bit patterns, showing alternate reversal of magnetization of the nanopillars.

Preparation of alumina/silica core-shell abrasives and their CMP behavior

Abrasive is one of key influencing factors on the surface quality during the chemical mechanic polishing (CMP). α-Alumina particles, as a kind of widely used abrasive in CMP slurries, often cause to surface defects because of its high hardness. In the present paper, a series of novel alumina/silica core-shell abrasives in slurries were described. The CMP performances of the alumina/silica core-shell abrasives on hard disk substrate were investigated by using a SPEEDFAM-16B-4M CMP equipment. Experimental results indicate that the CMP performances are strong dependent on the coated SiO 2 content of the alumina/silica composite abrasives. Slurries containing the alumina/silica composite abrasives exhibited lower surface roughness and waviness as well as lower topographical variations and less scratch than that containing pure alumina abrasive under the same testing conditions.

Variations of hard disk substrate induced by nanoparticle impacts

In order to investigate the damage of the nickel-phosphorous (NiP) coating the surface on computer hard disk substrate after SiO2 nanoparticle impact, a test of nanoparticle impact on a hard disk substrate with the NiP coating is carried out and the variation of the microstructure of the impacted surface is examined by using a high resolution transmission electron microscope (HRTEM), an atomic force microscope(AFM), an auger electron spectrogram (AES), and an X-ray photoelectron spectroscopy (XPS). The experimental results indicate that lots of fine craters and scratches in the nano-scale can be seen on the impacted surface, and some nanoparticles can be embedded in the surface during the impacts. HRTEM observations from the cross-section specimen under different test conditions show the existence of nano-crystalline transformation in the subsurface layer after the impact, and the sizes of these crystalline relate closely to the exposure time. Nanoparticle impacts aggravate the oxidation of the Ni-P alloy coating, and the impact with an exposure time of three minutes promotes the concentration of element phosphorus in the subsurface below about 6 nm.