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Effect of Non-Spherical Colloidal Silica Particles on Removal Rate in Oxide CMP
이호준,김문성,정해도 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
Oxide CMP generally has used colloidal silica slurry and fumed silica slurry. To compensate the lower removal rate (RR) of colloidal silica slurry compared to the one of fumed silica slurry, the multi-step feeding method was used to produce a non-spherical silica particle, for which the existing spherical colloidal silica particle was combined with two to three particles. To improve the performances, the prepared non-spherical colloidal silica particles were assessed by both single and mixed abrasive slurry. The slurry has two different sizes, 30 nm and 70 nm, of spherical colloidal silica particles and 70nm of non-spherical colloidal silica particles. Through the experiments, it was found out that non-spherical colloidal silica slurry had the higher RR than spherical colloidal silica slurry, and its RR was similar to the one of fumed silica slurry. For mixed abrasive slurry, the combinations of spherical and spherical or spherical and non-spherical showed higher RR, which were 152.8% higher than single abrasive slurry and 19.3% higher than fumed silica slurry, and better surface roughness than the fumed silica slurry. Therefore, non-spherical colloidal silica particles are found to be efficient to gain a higher RR and a better surface roughness than the ones of fumed silica particles.
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Analysis of Removal Mechanism on Oxide CMP using Mixed Abrasive Slurry
이호준,정해도 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.3
Mixed abrasive slurry (MAS) is one of the non-traditional slurries with more than two different sizes, shapes or materials of abrasiveswhich are to improve a chemical mechanical polishing (CMP) performance such as a removal rate. This paper focuses on the MASmixed with two different sized abrasives and controlled by mixing ratio. Hybrid effect of the MAS was investigated from the removalmechanism of the mixed abrasives on oxide film. Experiments have been implemented with a 4-inch wafer with silicon dioxide filmand KOH-based colloidal silica slurries. The slurry has two different sizes, 30 nm and 70 nm, with concentration of 1~30 wt%. Theeffects of abrasive concentration and mixing ratio were investigated in the oxide CMP in order to achieve high removal rate. Duringthe oxide CMP with the MAS, the contact condition of abrasives was changed by mixing ratio. Through the experiment, it could beseen that two-body and three-body abrasions occur in mixed abrasive slurry according to the particle concentration. Finally, we couldsee that the proper ratio to achieve high removal rate was 2:1 (D30:D70) since most of the abrasives were active in material removaland carried out two-body abrasion.
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Effect of Mixing Ratio of Non-Spherical Particles in Colloidal Silica Slurry on Oxide CMP
이호준,이다솔,김문성,정해도 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.10
Colloidal silica and fumed silica are common slurry materials for oxide chemical mechanical polishing (CMP). Non-spherical colloidal silica particles are manufactured via a multi-step feeding method to compensate for the material removal rate of colloidal silica slurry, which is lower than that of fumed silica slurry. Additionally, mixed abrasive slurry has been used by combining nonspherical and spherical colloidal silica particles. Experiments were conducted on a 4-inch wafer with silicon dioxide film (SiO2, 1- μm thick) and KOH-based colloidal silica slurry. The slurry had spherical colloidal silica particles with the size of 30 nm and 70 nm and non-spherical colloidal silica particles with the size of 70 nm. Effects of different colloidal particles in the oxide CMP were observed under the same pH condition in order to achieve high material removal rate. The mixing ratios were 2:1, 1:1, and 1:2 respectively. The analysis of the particle combinations showed that the mixing of particles with different sizes caused agglomeration and increased the material removal rate. The relatively smaller spherical particles improved the surface roughness and overall performance, especially when mixed with non-spherical particles. Such mixtures of particles with different sizes and shapes mixed at an appropriate ratio can outperform the fumed silica slurry.
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이호준 대한신경손상학회 2022 Korean Journal of Neurotrauma Vol.18 No.1
Iatrogenic vertebral artery injury (VAI) caused by surgical interventions involving the cervical spine is an uncommon but catastrophic complication associated with high morbidity or mortality due to ischemic stroke, intra- or extra-dural hemorrhage, and the formation of pseudoaneurysm or arteriovenous fistulae. In cervical spine surgeries, VAI may occur during the peri- or postoperative period. This may be induced by an anterior or posterior surgical approach. Despite advanced imaging techniques and increased anatomical knowledge, VAI during cervical spinal surgery remains a challenge. Techniques for managing VAI include hemostatic tamponade, ligation, microvascular repair or anastomosis, and endovascular management. We need to consider the risk of iatrogenic VAI as a complication in patients undergoing cervical spine surgeries and a better understanding of its mechanism and proper management.
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