• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.521-526
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• 2005

Within wafer non-uniformity(WIWNU) improves as the stiffness of pad decrease. We designed the pad groove to study of pad stiffness on WIWNU in Chemical mechanical polishing(CMP) and measured the pad stiffness according to groove width. The groove influences effective pad stiffness although original mechanical properties of pad are unchanged by grooving. Also, it affects the flow of slurry that has an effect on the lubrication regime and polishing results. An Increase of the apparent contact area of pad by groove width results in decrease of effective pad stiffness. WIWNU and profile of removal tate improved as effective pad stiffness decreased. Because grooving the pad reduce its effective stiffness and it makes slurry distribution to be uniform. Futhermore, it ensures that pad conforms to wafer-scale flatness variability. By grooving the top pad, it is possible to reduce its stiffness and hence reduce WIWNU and edge effect.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.5
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• pp.222-226
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• 2017

Recently sapphire wafer has expected as smart phone cover material, however, brittle nature of sapphire needed edge grinding processes to prevent early initiation of cracks. Electro-deposited multi-layered groove tools with $35{\mu}m$ diamond particles were studied for sapphire wafer grinding. Solid particle flow behaviors in agitated electrolyte was studied using PIV(Particle Image Velocimetry), and uniform particle distribution in Ni bond were obtained when agitating impeller was located lower part of electrolyte. Hardness values of $400{\pm}50Hv$ were maintained for retention of diamond particles in electro-deposited bond layer. Sapphire wafer edge grinding test was carried out and multi-layered $160{\mu}m$ thick diamond tool showed much greater grinding capabilities up to 2000 sapphire wafers than single-layered $50{\mu}m$ thick diamond electro-deposited tools of 420 wafers. The reason why 3 times thicker multi-layered tools than single-layered tools showed 5 times longer tool lives in grinding processes was attributed to self-dressed new diamond particles in multi-layered tools, and multi-layered diamond tools could be promising for sapphire grinding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.85-91
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• 2004

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by chemical and mechanical polishing process. The sapphire crystalline wafers were characterized by double crystal X-ray diffraction. The sample quality of sapphire crystalline wafer at surfaces has a full width at half maximum of 89 arcsec. The surfaces of sapphire wafer were mechanically affected by residual stress during the polishing process. The wave pattern of optical interference of sapphire wafer implies higher abrasion rate in the edge of the wafer than its center from the Newton's ring.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.251-255
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• 2019

We propose a two-step lithography process to minimize edge-bead issues caused by thick photoresist (PR) coating. In the conventional PR process, the edge bead can be efficiently removed by applying an edge-bead removal (EBR) process while rotating the silicon wafer at a high speed. However, applying conventional EBR to the production of desired PR mold with unique negative patterns cannot be used because a lower rpm of spin coating and a lower temperature in the soft bake process are required. To overcome this problem, a two-step lithography process was developed in this study and applied to the fabrication of a polydimethylsiloxane (PDMS) film having super-hydrophobic characteristics. Following UV exposure with a first photomask, the exposed part of the silicon wafer was selectively removed by applying a PR developer while rotating at a low rpm. Then, unique PR mold structures were prepared by employing an additional under-exposure process with a second mask, and the mold patterns were transferred to the PDMS. Results showed that the fabricated PDMS film based on the two-step lithography process reduced the height difference from 23% to 5%. In addition, the water contact angle was greatly improved by spraying of hydrophobic nanosilica on the dual-scaled PDMS surface.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2315-2328
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• 1993

The turbulence effect of particle deposition on a horizontal free-standing wafer in a vertical flow has been studied numerically by using the low-Reynolds-number k-.epsilon. turbulence model. For both the upper and lower surfaces of the wafer, predictions are made of the averaged particle deposition velocity and its radial distribution. Thus, it is now possible to obtain local information about the particle deposition on a free-standing wafer. The present result indicates that the particle deposition velocity on the lower surface of wafer is comparable to that on the upper one in the diffusion controlled deposition region in which the particle sizes are smaller than $0.1{\mu}m$. And it is found in this region that, compared to the laminar flow case, the averaged deposition velocity under the turbulent flow is about two times higher, and also that the local deposition velocity at the center of wafer is high equivalent to that the wafer edge.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.310-317
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• 2013

In this paper, the contact pressure of the wafer and polishing pad for final polishing process for 300 mm-wafer were investigated through numerical analysis using FEM tool, ANSYS. The distribution of the contact pressure is one of main parameters which affects on the flatness and surface roughness of polished wafers. Two types of polishing head, a hard type head with ceramic disk and a soft type head with air bag were considered. The effects of the deformation and initial shape of table on the contact pressure were also examined. Both heads and tables were modeled as 3D finite element model from solid model, and the material properties of polishing pads and rubber plate for the air-bag head were obtained from tensile tests. The contact pressure deviation on wafer surface was smaller with air bag head than hard type head even when the table had form errors such as convex or concave. From this 3D analysis, it could be concluded that the air-bag head has better uniformity of the contact pressure on wafer. Also, the effects of inner diameter of air bag and radial clearance between wafer and retainer were investigated as view point of contact pressure concentration on the edge of wafer.

• Journal of the Semiconductor & Display Technology
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• v.8 no.1
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• pp.1-5
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• 2009

Typically, single-wafer wet etching is done by dispensing chemical onto the front and back side of spin wafer. The wafer is fixed by a number of chuck pins, which obstruct the chemical flow and would result in the incomplete removal of the remaining film, which can become a source of contamination in the next process. In this paper, we introduce a novel design of wafer chuck, in which chuck pins are groupped into two and each group of pins fixes the substrate alternatively. Two groups of chuck pins fix the high-speed spin substrate with non contact method using a magnetic material. The actual process has been executed to observe the effectiveness of this new wafer chuck. It was found that the new wafer chuck performed better than the conventional wafer chuck for removing the remaining film from the bevel and edge side of substrate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.410-413
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• 2009

Wafer pre-alignment is to find the center and the orientation of a wafer and to move the wafer to the desired position and orientation. In this paper, an area camera based pre-aligning method is presented that captures 8 wafer images regularly during 360 degrees rotation. From the images, wafer edge positions are extracted and used to estimate the wafer's center and orientation using least square circle fitting. These information are utilized for the proper alignment of the wafer.

• Journal of KSNVE
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• v.8 no.2
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• pp.324-330
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• 1998

The forced vibration analysis of the outer-clamped spinnig annular disk with arbitrary in-plane is formulated to investigate the influence of non-uniform tension on the cutting accuracy of wafer cutting machine. The arbitrary in-plan force along the outer edge of an annular plate is expressed as a Fourier series. Galerkin method and modal superposition method are employed to obtain the forced responses under the static force and the impulse force in astationary coordinate. Through qualitative and quantitative analyses, it can be found that forced and impulse responses are sensitive to the non-uniformity of in-plane force, which can bring a bad effect to the accuracy of wafer cutting process. Also, in case of a spinning disk with non-uniform in-plane force, critical speed is required to define in a different way, compared with conventional definition in axi-symmetrical spinning disk.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.12
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• pp.72-76
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• 1996

A CMP system is newly proposed and analyzed by a home-made computer progarm. The proposed system is possibly to lower bull's eye effects such that the planarity of a wafer surface using a CMP system can be drasitcally improved. The optimum conditions for a design of the proposed system are verified using the home-made simulation program. For the proposed CMP system with a 12" diameter of platen, the optimum design conditons are the 0.09", 0.10", 0.12", and 0.14", clearance from the platern edge for wafer diameters of 5", 6", 8", and 12", respectively. These clear distance such as 0.09", 0.10", 0.12", and 0.14" are optimum lengths of the sample wafers extended ffrom the platen edge. In other words, shorter orbital lengths result in lowering of Bull's eye effects.