• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.3
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• pp.21-28
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• 2015

As film products are increasingly used in a wide range of areas, from producing traditional flexible packaging to high-tech electronic products, a higher level of quality is demanded. Most film products are made in the form of rolled finished goods, therefore, various quality issues related to their shape characteristics must be addressed. The thickness of the film products is one of the most common and important critical-to-quality attributes (CTQs). Particularly, the degree of thickness uniformity is more important than other thickness parameters, because it will be potential causes of many secondary thickness-related quality problems, such as wrinkles or faulty windings. To control the degree of thickness uniformity, the fixed bending region is oneof the most important CTQs to manage. Fixed bending regions are special points in the transverse direction of a rolled product with consistent minute variations of the thickness gap. This paper describes the measurement and analysis of thickness uniformity data, which were performed in a real manufacturing field of biaxial oriented polypropylene (BOPP) film. In previous researches, quality function deployment (QFD) or fault tree analysis were used to find the most critical process attributes out to controlthe CTQ of thickness uniformity. Whereas, this paper uses traditional control charts to find the most critical process attributes out in this problem. In addition, the selection of one of the major critical process attributes (CTPs) that is expected to affect the CTQ of thickness uniformity is also described. The selected critical-to-process attributes are the controlled temperatures along the transverse direction. A dramatic improvement in thickness uniformity was observed when the selected CTPs were controlled.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.56-66
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• 2011

Multi-source evaporation is one of the methods to improve the thickness uniformity of thin films deposited by evaporation. In this study, a simulator for the relative thickness profile of a thin film deposited by a multi-source evaporation system was developed. Using this simulator, the relative thickness profiles of the evaporated thin films were simulated under various conditions, such as the number and arrangements of sources and source-to-substrate distance. The optimum conditions, in which the thickness uniformity is minimized, and the corresponding efficiency, were obtained. The substrate was a 5th generation substrate (dimensions of 1300 mm ${\times}$ 1100 mm). The number of sources and source-to-substrate distance were varied from 1 to 6 and 0 to the length of the major axis of the substrate (1300 mm), respectively. When the source plane, the area on which sources can be located, is limited to the substrate dimension, the minimum thickness uniformity, obtained when the number of sources is 6, was 3.3%; the corresponding efficiency was 16.6%. When the dimension of the source plane is enlarged two times, the thickness uniformity is remarkably improved while the efficiency is decreased. The minimum thickness uniformity, obtained when the number of sources is 6, was 0.5%; the corresponding efficiency was decreased to 9.1%. The expansion of the source plane brings about not only the improvement of the thickness uniformity, but also a decrement of the efficiency and an enlargement of equipment.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.24-27
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• 2023

Until now, many research activities have been conducted to commercialize high-temperature superconducting (HTS) wires for electric applications. Most of all researchers have focused on enhancing the piece length, critical current density, mechanical strength, and throughput of HTS wires. Recently, HTS magnet for generating high magnetic field shows degraded performance due to the deformation of HTS wire by high electro-magnetic force. The deformation can be derived from widthwise thickness non-uniformity of HTS wire mainly caused by wet processes such as electro-polishing of metal substrate and electro-plating of copper. Gradient sputtering process is designed to improve the thickness uniformity of HTS wire along the width direction. Copper stabilizing layer is deposited on HTS wire covered with specially designed mask. In order to evaluate the thickness uniformity of HTS wire after gradient sputtering process, the thickness distribution across the width is measured by using the optical microscope. The results show that the gradient deposition process is an effective method for improving the thickness uniformity of HTS wire.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.19-25
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• 2023

With an attempt to investigate the correlation between the internal pressure distribution of slit nozzle and the thickness uniformity of slot-coated thin films, we have performed computational fluid dynamics (CFD) simulations of slit nozzles and slot coating of high-viscosity (4,800 cPs) polydimethylsiloxane (PDMS) using a gantry slot-die coater. We have calculated the coefficient of variation (CV) to quantify the pressure and velocity distributions inside the slit nozzle and the thickness non-uniformity of slot-coated PDMS films. The pressure distribution inside the cavity and the velocity distribution at the outlet are analyzed by varying the shim thickness and flow rate. We have shown that the cavity pressure uniformity and film thickness uniformity are enhanced by reducing the shim thickness. It is addressed that the CV value of the cavity pressure that can ensure the thickness non-uniformity of less than 5% is equal to and less than 1%, which is achievable with the shim thickness of 150 ㎛. It is also found that as the flow rate increases, the average cavity pressure is increased with the CV value of the pressure unchanged and the maximum coating speed is increased. As the shim thickness is reduced, however, the maximum coating speed and flow rate decrease. The highly uniform PDMS films shows the tensile strain as high as 180%, which can be used as a stretchable substrate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1444-1447
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• 2004

For the OLED evaporation process, thin film thickness uniformity is of great practical importance. In order to achieve the better thickness uniformity, geometric simulation of film thickness distribution profile is required. In this paper, a geometric modeling algorithm is introduced for process simulation of full-color OLED evaporating system. The physical fact of the evaporation process is modeled mathematically. Based on the developed method, the uniformity of the organic layer thickness can be successfully controlled.

• Journal of the Semiconductor & Display Technology
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• v.7 no.1
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• pp.35-40
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• 2008

In OLED vacuum evaporation process, the essential requirements include good uniformity of the film thickness over a glass substrate. And, it is commercially significant to improve the consuming efficiency of material of the evaporant which is deposited on the substrate because of high price of organic materials. In this paper, to achieve the better thickness uniformity and the better organic material consuming rate, a process optimization algorithm was developed by understanding vacuum evaporation process parameters that affect the material consuming efficiency and the uniformity of film thickness. Based on the method developed in this study, the vacuum evaporation process of OLED was successfully controlled. The developed method allowed the manufacture of high quality OLED displays with cheaper fabrication cost.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.33-38
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• 2004

To investigate the reliability of the MTJs on the roughness of insulating tunnel barrier, we prepared two MTJs with the different uniformity of barrier thickness. Namely, the one has uniform insulating barrier thickness; the other has non-uniform insulating barrier thickness as compared to different thing. As to depositing amorphous layer CoZrNb under the pinning layer IrMn, we achieved MTJ with uniform barrier thickness. Toinvestigate the reliability of the MTJs dependent on the bottom electrode, time-dependent dielectric breakdown (TDDB) measurements were carried out under constant voltage stress. The Weibull fit of out data shows clearly that $t_{BD}$ scales with the thickness uniformity of MTJs tunnel barrier. Assuming a linear dependence of log($t_{BD}$) on stress voltages, we obtained the lifetime of $10^4$years at a operating voltage of 0.4 V at MTJs comprising CoNbZr layers. This study shows that the reliabilityof new MTJs structure was improved due to the ultra smooth barrier, because the surface roughness of the bottom electrode influenced the uniformity of tunnel barrier.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.165-169
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• 2008

It is very important to decompose uniformly the metal film in semiconductor devices process. The thickness uniformity of the ITO film by standard magnetron sputtering system are about $\pm4%\sim\pm5%$ and the center of the wafer is more thick than the edge of the wafer. We designed and made the discharge electrode structure and controlled the direction of sputtering materials in magnetron sputtering system. The thickness uniformity are increased to $\pm0.8\sim1.3%$ in 4" wafer using the new sputtering gun in magnetron sputtering system. In wafer to wafer thickness uniformity, $\pm$5.3% are increased to $\pm$1.5% using the new sputtering gun. The thickness uniformity of the Al film are about $\pm$1.0% using the new sputtering gun in magnetron sputtering system.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.175-180
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• 2002

Use spctrophotometer to estimate thin film uniformity of lens, Compare, and analyze thin film uniformity availability selecting two peaks of Reflectance(R%) measuring on spectrum. Wavelength dependence's Reflectance in position of center, middle and edge of lens etc... obtain thin film's thickness (t) from Wavelength region (${\lambda}_1,{\lambda}_2$) of two peaks of Reflectance. $$t=\frac{1}{2(n^2-\sin^2{\theta})^{1/2}}{\times}\frac{{\lambda}_1{\lambda}_2}{{\lambda}_2-{\lambda}_1}$$ If Reflectance pattern is uniformity value in position of center middle of lens, edge etc... thin film has uniformity. Applied thin film uniformity estimation method to 1st layer $MgF_2$(n=1.38) coating lens. It was about thin film's thickness difference 360nm. Can analyze coating lens' thin film uniformity easily from Reflectance relationship measurement about Wavelength dependence.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.375-375
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• 2010

CdTe as an absorber material is widely used in thin film solar cells with the heterostructure due to its almost ideal band gap energy of 1.45 eV, high photovoltaic conversion efficiency, low cost and stable performance. The deposition methods and preparation conditions for the fabrication of CdTe are very important for the achievement of high solar cell conversion efficiency. There are some rearranged reports about the deposition methods available for the preparation of CdTe thin films such as close spaced sublimation (CSS), physical vapor deposition (PVD), vacuum evaporation, vapor transport deposition (VTD), closed space vapor transport, electrodeposition, screen printing, spray pyrolysis, metalorganic chemical vapor deposition (MOCVD), and RF sputtering. The RF sputtering method for the preparation of CdTe thin films has important advantages in that the thin films can be prepared at low growth temperatures with large-area deposition suitable for mass-production. The authors reported that the optical and electrical properties of CdTe thin film were closely connected by the thickness-uniformity of the film in the previous study [1], which means that the better optical absorbance and the higher carrier concentration could be obtained in the better condition of thickness-uniformity for CdTe thin film. The thickness-uniformity could be controlled and improved by the some process parameters such as vacuum level and RF power in the sputtering process of CdTe thin films. However, there is a limitation to improve the thickness-uniformity only in the preparation process [1]. So it is necessary to introduce the external or additional method for improving the thickness-uniformity of CdTe thin film because the cell size of thin film solar cell will be enlarged. Therefore, the authors firstly applied the chemical mechanical polishing (CMP) process to improving the thickness-uniformity of CdTe thin films with a G&P POLI-450 CMP polisher [2]. CMP process is the most important process in semiconductor manufacturing processes in order to planarize the surface of the wafer even over 300 mm and to form the copper interconnects with damascene process. Some important CMP characteristics for CdTe were obtained including removal rate (RR), WIWNU%, RMS roughness, and peak-to-valley roughness [2]. With these important results, the CMP process for CdTe thin films was performed to improve the thickness-uniformity of the sputtering-deposited CdTe thin film which had the worst two thickness-uniformities of them. Some optical properties including optical transmittance and absorbance of the CdTe thin films were measured by using a UV-Visible spectrophotometer (Varian Techtron, Cary500scan) in the range of 400 - 800 nm. After CMP process, the thickness-uniformities became better than that of the best condition in the previous sputtering process of CdTe thin films. Consequently, the optical properties were directly affected by the thickness-uniformity of CdTe thin film. The absorbance of CdTe thin films was improved although the thickness of CdTe thin film was not changed.