• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.8
• /
• pp.134-140
• /
• 2002

Chemical mechanical polishing of aluminum and photoresist using colloidal silica-based slurry was experimented. The effects of slurry pH, silica concentration, and oxidizer ($H_2O_2$) concentration on surface roughness and removal rate were studied. The optimum slurry conditions for reduction of micro-scratch were investigated. The optimum chemical mechanical polishing with the colloidal silica-based slurry was compared with conventional chemical mechanical polishing with alumina-based slurry. Chemical mechanical polishing of the aluminum with the colloidal silica-based slurry showed improved result but chemical mechanical polishing of the photoresist did not. The improved result was comparative with that of chemical mechanical polishing with filtered alumina-based slurry which one of desirable methods to reduce the micro-scratch.

• Journal of the Korean Ceramic Society
• /
• v.47 no.2
• /
• pp.151-156
• /
• 2010

Porous mullite/alumina composites have been fabricated by a freeze casting technique using TBA-based coal fly ash/alumina slurry. After sintering, unidirectional macropore channels aligned regularly along the TBA ice growth direction were developed; simultaneously, small sized micropores fromed in the outer walls of the pore channels. The physical and mechanical properties (e.g. porosity and compressive strength) of the sintered porous composites were roughly dependant of processing conditions, due to the complexity of the factors affecting them. However, with increasing solid loading and sintering temperature, the compressive strength generally increased and the porosity decreased. After sintering $1500^{\circ}C$ for 2 h, the porous specimen (porosity: 52.1%) showed a maximum compressive strength of 70.0 MPa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.227-230
• /
• 2004

As the organic acids were added in the slurry, zeta potential of alumina was changed to negative value and IEP value was shifted from alkaline to acidic pH. In citric acid based slurry, Cu surface continuously dissolved and etching depth linearly increased. On the contrary, passivation layer was grown on Cu surface in oxalic acid based slurry. As the platen rotation speed increased, Preston coefficient decreased in both slurries. With oxalic acid based slurry, at low velocity, removal rate is high value because of high friction force compared to citric acid based slurry. As platen velocity increased, removal of Cu in citric acid based slurry became higher value than oxalic acid based slurry. Typical lubrication behaviors were observed in both slurries. As Sommerfeld number increased, COF values gradually decreased and then re-increased. It indicated that lubrication was changed to direct contact or semi-direct contact mode to hydro-lubrication mode.

• Korean Journal of Materials Research
• /
• v.16 no.12
• /
• pp.731-738
• /
• 2006

It is seriously considered using Al CMP (chemical mechanical planarization) process for the next generation 45 nm Al wiring process. Al CMP is known that it has a possibility of reducing process time and steps comparing with conventional RIE (reactive ion etching) method. Also, it is more cost effective than Cu CMP and better electrical conductivity than W via process. In this study, we investigated 4 different kinds of slurries based on abrasives for reducing scratches which contributed to make defects in Al CMP. The abrasives used in this experiment were alumina, fumed silica, alkaline colloidal silica, and acidic colloidal silica. Al CMP process was conducted as functions of abrasive contents, $H_3PO_4$ contents and pressures to find out the optimized parameters and conditions. Al removal rates were slowed over 2 wt% of slurry contents in all types of slurries. The removal rates of alumina and fumed silica slurries were increased by phosphoric acid but acidic colloidal slurry was slightly increased at 2 vol% and soon decreased. The excessive addition of phosphoric acid affected the particle size distributions and increased scratches. Polishing pressure increased not only the removal rate but also the surface scratches. Acidic colloidal silica slurry showed the highest removal rate and the lowest roughness values among the 4 different slurry types.

• Journal of the Korean Ceramic Society
• /
• v.39 no.2
• /
• pp.164-170
• /
• 2002

Measurements of sedimentation, solid loading, zeta potential, and viscosity were employed to determine a proper dispersant and its amount for a well dispersed alumina powders in aqueous alumina tape casting using acrylate as a binder. Polycarboxylic acid was the most effective one among various dispersants considered in the present study and its amount was 0.23∼0.24 g per 100 g alumina for a dispersion. Better dispersion was obtained as an increase of dispersant addition. However, the dispersion was hindered as the amount of dispersant was higher than the optimum amount because of bridging or tangling of polymer chains. Excellent aqueous alumina tapes were prepared from the slurry containing the optimum amount of the polycarboxylic acid (0.2g), alumina powders(100 g), acrylate and Benzoflex as binder and plasticizer, respectively. The viscosity of the slurry was 570 cps and the alumina loading in the tape was 57 vol%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.2
• /
• pp.156-161
• /
• 2004

We investigated the effects of oxidizer additive on the performance of Cu-CMP process using commonly used tungsten slurry. In order to compare the removal rate and non-uniformity as a function of oxidizer contents, we used alumina-based tungsten slurry and copper blanket wafers deposited by DC sputtering method. According to the CMP removal rates and particle size distribution, and the microstructures of surface layer by SEM image as a function or oxidizer contents were greatly influenced by the slurry chemical composition of oxidizers. The difference in removal rate and roughness of copper surface are believed to cause by modification in the mechanical behavior of $Al_2$O$_3$abrasive particles in CMP slurry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.7
• /
• pp.568-574
• /
• 2000

We have been optimized tungsten(W) plug CMP(chemical mechanical polishing) characteristics using two different kinds of component of slurry and two different kinds of pad which have different hardness. The comparison of oxide film roughness on around W plug after polishing has been carried out. And W plug recess for consumable sets and dishing effect at dense area according to the rate of over-polishing has been investigated. Also the analysis of residue on surface after cleaning have been performed. As a experimental result we have concluded that the consumable set of slurry A and hard pad was good for W plug CMP process. After decreasing the rate of chemical reaction of silica slurry and adding two step buffering we could reduce the expanding of W plug void however we are still recognizing to need a more development for those kinds of CMP consumables.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.12
• /
• pp.1296-1300
• /
• 2004

SnO$_2$ is one of the most suitable gas sensor materials. The microstructure and surface morphology of films must be controlled because the electrical and optical properties of SnO$_2$ films depend on these characteristics. The effects of chemical mechanical polishing(CMP) on the variation of morphology of SnO$_2$ films prepared by RF sputtering system were investigated. The commercially developed ceria-based oxide slurry, silica-based oxide slurry, and alumina-based tungsten slurry were used as CMP slurry. Non-uniformities of all slurries met stability standards of less than 5 %. Silica slurry had the highest removal rate among three different slurries, sufficient thin film topographies and suitable root mean square(RMS) values.

• Journal of the Korean Ceramic Society
• /
• v.36 no.9
• /
• pp.954-964
• /
• 1999

The effect of fabrication variables and microstructures on the compressive strength of open cell alumina zirconia and silicon nitride ceramics fabricated by polymeric sponge method was investigated. Bulk density and compressive strength of open cell ceramics were mainly affected by coating characteristics of ceramic slurry on polymeric sponge that controlled a shape thickness and defect of the struts. Sintering temperature was optimized for enhancement of strut strength and compressive strength of open cell ceramics. Relative density and compressive strength behaviors were relatively well matched with the predicted values. Open cell ceramics of lower relative density below 0.1 prepared by first relatively well matched with the predicted values. Open cell ceramics of lower relative density below 0.1 prepared by first coating of ceramic slurry had thin triangular prismatic struts that were often broken or longitudinally cracked. With an application of second coating of slurry shape of struts was transformed into thickner cylindrical one and defects in struts were healed but the relative density increased over 0.2 Open cell zirconia had both the highest bulk density and compressive strength and alumina had the lowest compressive strength while silicon nitrides showed relatively high compressive strength and the lowest density. Based upon the analysis open cell silicon nitride was expected to be one of potential structural ceramics with light weight.

• Clean Technology
• /
• v.25 no.3
• /
• pp.256-262
• /
• 2019

Hydroxylammonium nitrate (HAN)-based liquid propellants are attracting attention as environmentally friendly propellants because they are not carcinogens and the combustion gases have little toxicity. The catalyst used to decompose the HAN-based liquid propellant in a thruster must have both low temperature activity and high heat resistance. The objective of this study is to prepare an Ru/alumina/metal foam catalyst by supporting alumina slurry on the surface of NiCrAl metal foam using a washing coating method and then to support a ruthenium precursor thereon. The decomposition activity of a HAN aqueous solution of the Ru/alumina/metal foam catalyst was evaluated. The effect of the number of repetitive coatings of alumina slurry on the physical properties of the alumina/metal foam was analyzed. As the number of alumina wash coatings increased, mesopores with a diameter of about 7 nm were well-developed, thereby increasing the surface area and pore volume. It was optimal to repeat the wash coating alumina on the metal foam 12 times to maximize the surface area and pore volume of the alumina/metal foam. Mesopores were also well developed on the surface of the Ru/alumina/metal foam catalyst. It was found that the metal form itself without the active metal and alumina can promote the decomposition reaction of the HAN aqueous solution. In the case of the Ru/alumina/metal foam-550 catalyst, the decomposition onset temperature was significantly lowered compared with that of the thermal decomposition reaction, and ${\Delta}P$ could be greatly increased in the decomposition of the HAN aqueous solution. However, when the catalyst was calcined at $1,200^{\circ}C$, the catalytic activity was lowered inevitably because the surface area and pore volume of the catalyst were drastically reduced and Ru was sintered. Further research is needed to improve the heat resistance of Ru/alumina/metal foam catalysts.