Display Manufacturing Research Articles

Precisionin situvolume measurement of micro droplets

This research presents an in situ droplet volume measurement system which is applied to the one drop fill (ODF) process of liquid crystal display (LCD) manufacture. The system developed utilizes a stroboscopic technique to synchronize the triggering of a strobe light and a CCD camera. A steady image of the droplet flying in free space can be captured in situ by the CCD camera. The method of precise volume estimation is based on a rotationally symmetric model of the droplet's shape. Polynomial fitting is used to reconstruct the droplet profile. The image resolution can thus be enhanced by a subpixel technique. Compared to a precision electronic balance, the total weight measured by this system has an error within ± 0.3%, and the computation time for each droplet is about 0.4 s. This satisfies the actual ODF requirements.

A rework-based dispatching algorithm for module process in TFT-LCD manufacture

This paper presents development of a scheduling methodology for module processing in thin film transistor liquid crystal display (TFT-LCD) manufacturing. The problem is a parallel machine scheduling problem with rework probabilities, sequence-dependent setup times and due dates. It is assumed that rework probability for each job on a machine can be given through historical data acquisition. The dispatching algorithm named GRPD (greedy rework probability with due-dates) is proposed in this paper focusing on the rework processes. The performance of GRPD is measured by the six diagnostic indicators. A large number of test problems are randomly generated to evaluate the performance of the proposed algorithm. Computational results show that the proposed algorithm is significantly superior to existing dispatching algorithms for the test problems.

EVALUATION OF SMALL- AND MEDIUM-SIZED DISPLAY MARKET FORECASTS

The main purpose of this paper is to evaluate small- and medium-sized display market forecasts made by a market research firm. Hypotheses concerning the relationship between stages of technology development and the accuracy of market forecasts are first developed. The hypotheses are then tested and evaluated using the data issued by one market research company, Techno Systems Research (TSR). Kruskal–Wallis rank sum test and nonparametric simple regression are the statistical methods used. The results of the data analysis showed that the forecasts made by the market research company are dependable for mature technology in mature markets, whereas for a new technology their forecasts are inaccurate. Furthermore, the accuracy of forecasts quite often does not improve over time. To our knowledge, no prior published works examine the accuracy of the forecasts made by market research firms. This research shows that small- and medium-sized display manufacturers have to be cautious when using forecast data from market research firms.

Factors affecting the psychophysical image quality evaluation of mobile phone displays: the case of transmissive liquid-crystal displays

Display manufacturers require new data and computational models that consider the effect of ambient illumination in order to develop higher-quality displays. In this study, typical variations of small-sized mobile LCDs that exist in the real world were first simulated using a device characterization technique. In addition, psychophysical attributes (e.g., naturalness, clearness, sharpness, contrast, colorfulness, and preference) affecting the image quality evaluation process were analyzed. Consequently, naturalness and clearness were found to be the most statistically significant psychophysical attributes for modeling image quality. As the ambient-illumination level was increased, the image quality was exponentially impaired and the contribution of clearness increased.

Flexible dot-matrix display manufacture by offset lithography

Novel thermochromic graphic displays manufactured by printing thermochromic ink films in conjunction with conductive lithographic films (CLFs) are presented. Work in formulating lithographic printing inks is described. The properties of the deposited ink films and demonstration display structures employing these materials are discussed. These low-cost printed structures could be incorporated in the manufacture of electronic systems with integrated printed power sources affording environmental benefits when compared with conventional manufacturing techniques.

Atmospheric Pressure Plasma Ashing for Display Manufacturing

Due to the various advantages of the use of atmospheric pressure, recent studies on the ashing of organic materials are focused on the atmospheric pressure plasma rather than low pressure plasma. In this study, atmospheric pressure plasma was generated using dielectric covered electrodes and AC pulsed power supply (10 kV) driven at low frequency to remove organic materials on the surfaces of metal such as Cr. In such a configuration, the effects of process conditions and ashing gases on the ashing properties have been investigated. Nitrogen (N2) and oxygen (O2) were used for ignition and ashing, respectively. By adding small amount of O2 to N2, the photoresist ashing rate was increased due to the increment of oxygen radicals in the plasma. However, further addition of oxygen decreased the photoresist ashing rate, possibly because of the lower plasma density caused by the formation of negative ions between oxygen molecules and electrons in the plasma. Additionally, the effect of input voltage on ashing was investigated. The raised input voltage increased the ashing effect possibly due to the increased chemical reaction with organic materials resulting in the increased volatilization and detachment from the surface. In this paper, optimal process condition for gas flow rate and process gap will be discussed.

Automatic inline defect detection for a thin film transistor–liquid crystal display array process using locally linear embedding and support vector data description

Defect detection plays a critical role in thin film transistor liquid crystal display (TFT-LCD) manufacturing. This paper proposes an inline defect-detection (IDD) system, by which the defects can be automatically detected in a TFT array process. The IDD system is composed of three stages: the image preprocessing, the appearance-based classification and the decision-making stages. In the first stage, the pixels can be segmented from an input image based on the designed pixel segmentation method. The pixels are then sent into the appearance-based classification stage for defect and non-defect classification. Two novel methods are embedded in this stage: the locally linear embedding (LLE) and the support vector data description (SVDD). LLE is able to substantially reduce the dimensions of the input pixels by manifold learning and SVDD is able to effectively discriminate the normal pixels from the defective ones with a hypersphere by one-class classification. After aggregating the classification results, the third stage outputs the final detection result. Experimental results, carried out on real images provided by a LCD manufacturer, show that the IDD system can not only achieve a high defect-detection rate of over 98%, but also accomplish the task of inline defect detection within 4 s for one input image.

Introduction: Special Section on Extended Papers Selected from the 2007 International Display Manufacturing Conference (IDMC '07)

Introduction: Special Section on Extended Papers Selected from the 2007 International Display Manufacturing Conference (IDMC '07)

53.4: Novel Pulsed Drive Scheme for Improved Gray‐Level Uniformity of Large‐Area Cholesteric Displays

AbstractA new drive scheme is presented for producing uniform grays over large‐area, low‐resolution cholesteric liquid crystal displays. Gray‐level sensitivity to display non‐uniformities is minimized, which simplifies display manufacturing. While applicable to both rigid and flexible displays, the impact on flexible displays will be particularly important with roll to roll manufacturing capability coming online.

P‐5: Spacer Technique to Fabricate pSi TFTs with 50nm Nanowire Channels

AbstractIn this work, polycrystalline silicon thin‐film transistors (poly‐Si TFTs) with 50‐nm nanowire (NW) channels fabricated without advanced photolithography by using a sidewall spacer formation technique are proposed for the first time. Because the poly gate electrode is perpendicularly across poly‐Si NW channels to form a tri‐gate‐like structure, the proposed poly‐Si NW TFT owns an outstanding gate controllability. In summary, a simple and low‐cost scheme is proposed to fabricate high‐performance poly‐Si NW TFT suitable for future display manufacturing and practical applications.

31.1: Invited Paper: Inkjet Technology for Large Size Color Filter Plates

AbstractIn recent years, the inkjet printing technology has advanced close to the level of application to the flat panel display manufacturing[1][2]. Especially for the TFT‐LCD color filter application, ink jet printing method offers great advantages over the conventional photolithography method in the area of cost saving and productivity enhancement[3]. In this paper, we present the process and characteristics of the inkjet printed color filter which has been developed for 40 inch FHD LCD panel for TV application fabricated from the Gen.8 size glass.

Measuring the convergence and accuracy of trainees’ knowledge structures for TFT-LCD visual defect categorization

Despite a large automated portion of the thin film transistor-liquid crystal display (TFT-LCD) manufacturing process, inspectors’ eyes are still the main resource for ensuring the display quality of TFT-LCD panels. Since recruiting and training new inspectors is a frequent process in most TFT-LCD manufacturers, and since it takes most novice inspectors at least a year to become proficient, an effective training program is crucial for TFT-LCD manufacturers to secure their process efficiency and product quality. The purpose of this study is to establish a set of methods for measuring the convergence and accuracy of trainees’ knowledge structures on TFT-LCD visual defect categorization, so that the development of knowledge during the training can be monitored and further applied to the design of training programs. The card sorting technique was first used to elicit knowledge. The sort data were then converted to the measures of edit distances and Collective Dice Coefficients. Finally, statistical analyses were applied to measure the convergence and accuracy of trainees’ knowledge structures. Results showed that the current training program did increase the convergence and accuracy of trainees’ knowledge structures. However, there was room for improvement. The training program could be enhanced by explicitly introducing the experts’ knowledge structures to trainees. In addition, the inspection process could be improved by redesigning inspection procedures to correspond to the experts’ knowledge structures. With these methods, the development of knowledge can be examined promptly and efficiently, and the effectiveness of the training program can be assured. Relevance to industry Methods applied in this paper can contribute to the research and applications in the TFT-LCD industry for the design of the inspection-training program and the supervision of trainee's learning progress.

A mixed 0‐1 integer programming for inventory model

PurposeThis paper seeks to construct a model for inventory management for multiple periods. The model considers not only the usual parameters, but also price quantity discount, storage and batch size constraints.Design/methodology/approachMixed 0‐1 integer programming is applied to solve the multi‐period inventory problem and to determine an appropriate inventory level for each period. The total cost of materials in the system is minimized and the optimal purchase amount in each period is determined.FindingsThe proposed model is applied in colour filter inventory management in thin film transistor‐liquid crystal display (TFT‐LCD) manufacturing because colour filter replenishment has the characteristics of price quantity discount, large product size, batch‐sized purchase and forbidden shortage in the plant. Sensitivity analysis of major parameters of the model is also performed to depict the effects of these parameters on the solutions.Practical implicationsThe proposed model can be tailored and applied to other inventory management problems.Originality/valueAlthough many mathematical models are available for inventory management, this study considers some special characteristics that might be present in real practice. TFT‐LCD manufacturing is one of the most prosperous industries in Taiwan, and colour‐filter inventory management is essential for TFT‐LCD manufacturers for achieving competitive edge. The proposed model in this study can be applied to fulfil the goal.

Region Mura Detection using Efficient High Pass Filtering based on Fast Average Operation

A Mura (also called “alluck”) defect that causes local deterioration of colors or brightness on a LCD(liquid crystal display) panel is one of the critical issues in display manufacturing. In this paper, we propose mura detection method using frequency filtering. As a mean of frequency filtering to eliminate the low frequency background term, subtraction of the averaged image from the raw one is utilized. And a fast averaging algorithm has been devised for reducing computational costs. The validity and the performance of the proposed method is discussed through experimental studies on actual LCD panel mura defects.

Automatic target defect identification for TFT-LCD array process inspection using kernel FCM-based fuzzy SVDD ensemble

Inline defect inspection plays a critical role in yield improvement for thin film transistor liquid crystal display (TFT-LCD) manufacturing. In array process, some defects are critical to the quality of LCD panels (target defects), while some are not (non-target defects). This paper proposes a target defect identification system by which the target defects can be automatically identified. The proposed system is composed of five parts: projection-based pixel segmentation, normal pixel removal, feature extraction, target defect identification, and decision making. For the identifier design, a novel one-class kernel classifier called fuzzy support vector data description (F-SVDD) ensemble is proposed. F-SVDD ensemble is proposed to solve two critical problems existing in SVDD, including the overfitting due to outliers, and the multi-cluster distribution. In F-SVDD ensemble, both the best number of the F-SVDD members in the ensemble and the elements of each member can be determined by using partitioning-entropy-based kernel fuzzy c-means (KFCM) algorithm. Experimental results, carried out by real defective images provided by a LCD manufacturer, indicate that the proposed F-SVDD ensemble not only greatly improves the performance of SVDD, but also outperforms other commonly used classifiers such as support vector machine (SVM), in terms of target defect identification rate. In addition, the task of target defect identification for one defective image can be accomplished within 3s by the proposed system.

A Simple Spacer Technique to Fabricate Poly-Si TFTs With 50-nm Nanowire Channels

In this letter, polycrystalline-silicon thin-film transistors (poly-Si TFTs) with 50-nm nanowire (NW) channels, which are fabricated without advanced photolithography by using a sidewall spacer-formation technique, are proposed for the first time. Because the polygate electrode is perpendicularly across poly-Si NW channels to form a trigatelike structure, the proposed poly-Si NW TFT owns outstanding gate controllability. In summary, a simple and low-cost scheme is proposed to fabricate high-performance poly-Si NW TFT suitable for future display manufacturing and practical applications.

Evaluation Method on Destruction and Removal Efficiency of Perfluorocompounds from Semiconductor and Display Manufacturing

Recently, the semiconductor and display industries have tried to reduce the emissions of perfluorocompounds (PFCs) from the globally environmental regulation. Total amount of PFC emission can be calculated from the flow rate and the partial pressures of PFCs. For the precise measurement of PFC emission amount, the mass flow controlled helium gas was continuously injected into the equipment of which scrubber efficiency is being measured. The partial pressures of PFCs and helium were accurately measured using a mass spectrometer in each sample extracted from inlet and outlet of the scrubber system. The flow rates are calculated from the partial pressures of helium and also, PFC destruction and removal efficiency (DRE) of the scrubber is calculated from the partial pressure of PFC and the flow rate. Under this method, the relative expanded uncertainties of the flow rate and the partial pressures of PFCs are ± 2% (k = 2) in case the concentrations of NF3 and SF6 are as low as 100 μmol/mol.

Introduction: Special Section on Extended Papers Selected from the Joint 6th International Meeting on Information Display and the International Display Manufacturing Conference (IMID/IDMC '06)

Introduction: Special Section on Extended Papers Selected from the Joint 6th International Meeting on Information Display and the International Display Manufacturing Conference (IMID/IDMC '06)

65.1: Invited Paper: An Overview of Display Interconnect Technology Trends: Technologies & Markets

AbstractThis paper will address general technology and market trends for the assembly of display modules, concentrating on how the maturation of the display industry is affecting technology choices and market segmentation. The year 2007 promises to be one of great change in the world of flat panel displays, with non‐LCD technology getting its first real foothold in mobile phone main screen applications, a continuing glut of glass manufacturing capacity, and the migration of display assembly factories into Eastern Europe and Mexico. This, coupled with double‐digit percentage declines in the ASPs of almost every color display technology, means that manufacturers are continuing to squeeze out production costs wherever possible. As a result, companies are reviewing the back‐end interconnect assembly portion of display manufacturing in a way that they have not done before now. The long‐term end result is likely to be a higher level of segmentation in the display industry as it follows a path similar to the semiconductor industry before it. In the shorter term, companies will aggressively review technical requirements, assembly techniques, and material choices in their quest for lower costs.

Death Hurts, But It Isn't Fatal: The Postexit Diffusion of Knowledge Created by Innovative Companies

There is little understanding of whether a firm’s innovative knowledge dies with it or if instead significant diffusion of knowledge occurs even after a firm exits an industry. Theoretical predictions about the differing effects of firm exit on private and public knowledge and implications for interfirm knowledge transfer are forwarded. We investigated main and moderating effects of a firm’s exit from the disk drive industry on knowledge diffusion to other firms, finding evidence that the ability to use a firm as a template plays a critical role in successfully replicating its knowledge. Absent this template, knowledge “stickiness” reduces knowledge diffusion. In 1999, despite millions of dollars of investment and a portfolio of innovative technologies, flat panel display manufacturer Optical Information Systems (OIS) shut down operations, unable to achieve commercial success. Although OIS failed, its technology lived on. A letter by the firm’s former director of advanced technologies to the editors of the magazine Information Display reported that even after the firm’s exit, OIS technology continued to make waves in the flat panel industry, with many of its patents covering processes that became mainstream technology. The letter then cited specific innovations by other firms that had built on OIS breakthroughs. Although the firm had exited the industry in spite of its technological strength, it left a lasting legacy for the industry’s technology. Is the OIS story unusual, or does it highlight a regular occurrence? Since technological expertise is an important determinant of firm success (Jovanovic & MacDonald, 1994; Teece, 1986), it could be argued that firms that exit an industry are typically lacking in this important area and thus have little impact on the technological progress in the industry. This formulation would imply that firms like OIS are outliers and that diffusion of the knowledge they create is generally low, both before