Large Glass Substrates Research Articles

Process parameter impact on properties of sputtered large-area Mo bilayers for CIGS thin film solar cell applications

Copper indium gallium selenide (CIGS) has emerged as a promising candidate for thin film solar cells, with efficiencies approaching those of silicon-based solar cells. To achieve optimum performance in CIGS solar cells, uniform, conductive, stress-free, well-adherent, reflective, crystalline molybdenum (Mo) thin films with preferred orientation (110) are desirable as a back contact on large area glass substrates. The present study focuses on cylindrical rotating DC magnetron sputtered bilayer Mo thin films on 300mm×300mm soda lime glass (SLG) substrates. Key sputtering variables, namely power and Ar gas flow rates, were optimized to achieve best structural, electrical and optical properties. The Mo films were comprehensively characterized and found to possess high degree of thickness uniformity over large area. Best crystallinity, reflectance and sheet resistance was obtained at high sputtering powers and low argon gas flow rates, while mechanical properties like adhesion and residual stress were found to be best at low sputtering power and high argon gas flow rate, thereby indicating a need to arrive at a suitable trade-off during processing.

Thin Film Transistors as Driving Devices for Attached Devices

TFTs have been the most popular devices for the large area active matrix flat panel displays for the past 20 years. The a-Si:H TFT is suitable for driving the liquid crystal in the pixel level because of its characteristics of low power consumption, gray scale capability, low leakage current, etc. [1]. The a-Si:H TFT array can be easily fabricated on the large area glass substrate with a high throughput at a low temperature. However, the low mobility limits its applications in many areas. For example, the OLED has been widely studied as a potential replacement of the LCD for its low power consumption, contact size, and good color quality. However, for the high quality displays, TFTs are required to drive the OLED pixels [2]. It is difficult or impossible to drive each OLED pixel with a single a-Si:H TFT. The high mobility poly-Si or oxide TFTs are proper for this application. In addition, there are many studies on using the TFT as a driving or sensing device for purposes of chemical or biological sensing, detection, or imaging [2,3]. For some new applications, the high mobility is often required. In this paper, authors investigated limitations on applying a single TFT to driven a device.Figure 1 shows a simple system of a TFT attached with a resistor to the drain electrode. Since a large number of the attached devices change their conductivities upon exposure to selected chemicals, biological agents, optical intensity, or mechanical stress, the resistance is used as a reference of the change. Figure 2 shows the drain current change with the resistance (r) of the resistor attached to the TFT. The poly-Si TFT (W/L = 12m/6m) has a field effect mobility (meff ) of ~ 235 cm2/V.s, an on current (Ion ) of 1.8x10-4 A , a threshold voltage (Vt ) of 0.45V, and a subthreshold slope (S) of 0.26 V/dec. The TFT gate voltage (Vg ) was fixed at 9 V and the complete system was driven at VD’ = 10V. Both the current passing the resistor, i.e., ID , and the drain voltage (VD ) decrease monotonically with the increase of r. Since the ID ’s in Fig. 1 are below that of the TFT without the attached resistor, the performance of the system is controlled by the resistor. This kind of system can be used to detect the change of the environment, such as the light intensity or gas composition, when the resistor responds to the variation of a parameter. For the Fig. 1 system, the power applicable to the resistor is limited. For example, Figure 3 shows that the maximum power is obtained when the resistance is about 100 ohm. TFTs are usually used as switching devices. However, there are limits on the physical characteristics of the attached device. If the power required for the attached device is beyond the peak power in Fig. 3, it cannot be fully turned on although the complete system can be built. For certain applications, such as MEMS or LEDs, the peak power can be a good guideline on selecting the TFT or designing the attached device. The peak power can be increased with the improvement of the TFT characteristics, such as the meff or W/L ratio, however, with limits. The reliability of the TFT is an important issue in the Fig. 1 system. In addition to the environmental factors, e.g., humidity, light, and temperature, the lifetime has to be kept long. For example, the TFT can deteriorate, e.g., increasing the off current, the threshold voltage, or the subthreshold slope, during the driving of the attached device with a high current or for an extended period of time. Possible solutions and limitations will be discussed. Geng-Wei Chang thanks the National Science Council Graduate Students Study Abroad Program for supporting his study in Prof. Yue Kuo’s Thin Film Nano & Microelectronics Research Laboratory. [1] Y. Kuo, ECS Interface, 22(1), 55 (2013).[2] Y. Kuo, Chap. 13, Thin Film Transistors, Vol. 2, p. 464, Kluwer Academic Publishers (2004).[3] Y. Kuo, Chap. 11, Thin Film Transistors, Vol. 1, p. 485, Kluwer Academic Publishers (2004).

8.2: Invited Paper: Status and Future Promise of Excimer Laser Annealing for LTPS on Large Glass Substrates

AbstractLow‐Temperature Polycrystalline Silicon (LTPS) is the enabling backplane technology for AMOLED displays and small to medium sized high‐resolution AMLCDs. Recently, Excimer Laser Annealing (ELA) equipment has made significant progress in scaling for cost‐effective large‐scale production. In this paper, we discuss the key elements of ELA equipment and the recent and future milestones for LTPS on large substrates.

21.2: Invited Paper: MOTFT Backpanel for 880 ppi White and 440 ppi, True Full‐Color AMOLED

AbstractMOTFT‐based backpanels and corresponding manufacture related issues are discussed for a 2.5“ diagonal, 880 ppi FHD white color AMOLED. The same design can be used for a 2.5” QFHD and 5“ FHD True‐FC AMOLED Displays with 440 ppi. We demonstrate high mobility and stability MOTFT with dimensions reach the design rules of existing manufacture line. Good TFT output impedance and long‐range uniformity over large size glass substrate enables 2T1C pixel driver circuit. Such MOTFT based AMOLED backpanel can be fabricated with 5‐6 mask steps, 2 mask steps less than those used for IPS AMLCD displays with similar pixel density. Integrating an OLED array onto the MOTFT backpanel, high pixel density AMOLED display are demonstrated with performance and form factors best fit with portable and wearable electronic devices.

Large-Area Self-Assembled Monolayer of Silica Microspheres by Convective Assembly

We reported here a convective assembly process for the formation of large-area self-assembled monolayers of silica microspheres on silicon and glass substrates. Uniformly coated monolayers of silica spheres were achieved on silicon wafers with and without coated SiN2 of 3 inch of diameter and large glass substrate of 6 × 6 in2 in size. The coating of large-area uniform monolayers of silica microspheres was characterized with scanning electron microscopy and optical microscopy. The mechanism of the convective assembly has been explained by the convective flux that is generated by capillary immersion force caused from the solution evaporation and hydrodynamic drag force. The patterns of silica microspheres were transferred to the silicon substrates using a deep reactive ion etching technique. It is found that textured silicon reduced the reflectance of silicon substrate from 52.2% to 33.2% around 400 nm and from 33.9% to 19.5% around 1,100 nm. The rapid self-assembled monolayer with silica microspheres provided a glimpse at the wide range of coating and photonic device applications where convective assembly can be used.

Low temperature and self catalytic growth of ultrafine ITO nanowires by electron beam evaporation method and their optical and electrical properties

We report the self catalytic growth of Sn-doped indium oxide (ITO) nanowires (NWs) over a large area glass and silicon substrates by electron beam evaporation method at low substrate temperatures of 250–400°C. The ITO NWs growth was carried out without using an additional reactive oxygen gas and a metal catalyst particle. Ultrafine diameter (∼10–15nm) and micron long ITO NWs growth was observed in a temperature window of 300–400°C. Transmission electron microscope studies confirmed single crystalline nature of the NWs and energy dispersive spectroscopy studies on the NWs confirmed that the NWs growth proceeds via self catalytic vapor-liquid-solid (VLS) growth mechanism. ITO nanowire films grown on glass substrates at a substrate temperature of 300–400°C have shown ∼2–6% reflection and ∼70–85% transmission in the visible region. Effect of deposition parameters was systematically investigated. The large area growth of ITO nanowire films would find potential applications in the optoelectronic devices.

An Investigation of Suspension Phenomena of a Large Glass Substrate in a Vertical Transportation by the Arbitrary Lagrangian and Eulerian Method

ABSTRACTFor economizing the space of equipment and increasing the throughput of product, a vertical transportation is usually used for manufacturing a large and thin glass substrate. Due to the fragile characteristic of the large and thin glass substrate, investigation of a method for maintaining the glass substrate stably and safely on a supporting frame during manufacturing processes becomes an important subject. This subject belongs to a kind of moving boundary problem and the method of Arbitrary Lagrangian Eulerian (ALE) with a finite element scheme is suitably used to solve it. Also, related methods of the generalized minimal residual method (GMRES) and pressure convection diffusion method are adopted to calculate pneumatic pressures distributed on the glass substrate. The results show that under a low frequency of the vertical transportation the glass substrate stably lies on the supporting frame, oppositely under a high frequency of the vertical transportation the glass substrate has possibility to depart from the supporting frame. The later situation is disadvantageous to the glass substrate and should be avoided as much as possible.

An all-sputtering process and equipment for CIGS solar cells

The Swedish company Midsummer AB has developed an all-sputtering process and equipment for CIGS solar cells. The company was founded in 2004 by people from the optical disc and flat panel display industry. Most CIGS solar cells are made on large glass substrates, another option is to make the solar cells with a roll-to-roll process on a flexible stainless steel substrate. Midsummer has chosen a third approach, by adopting the founders experience from the low cost optical disc industry. Instead of increasing the productivity by increasing the substrate size, they decided to design a machine and process that produces many small substrates with fast pace. Such a machine can be very compact and the productivity is achieved by using 25 small sputter chambers. Large scale production of solar cells can them be achieved by adding many small production systems, exactly as was in the case for optical discs, that eventually lead to an annual production capacity of 35 billion CDs and DVDs. Sputterprozesse zur Herstellung von CIGS Solarzellen Die schwedische Firma Midsummer AB hat ein Verfahren und eine Produktionsanlage zur Herstellung von CIGS Solarzellen, ausschließlich auf Sputterprozessen beruhend, entwickelt. Die Firma wurde 2004 von ehemaligen Mitarbeitern aus der optische Datenträger- und Flachbildschirmindustrie gegründet. CIGS Solarzellen werden üblicherweise auf großen Glassubstraten hergestellt. Eine andere Option ist es, Solarzellen in einem rolle-zu-rolle-Prozess auf flexiblen Edelstahlsubstraten abzuscheiden. Midsummer hat basierend auf der Erfahrung der Firmengründer aus dem niedrigpreisigen Sektor optischer Datenträger einen dritten Ansatz gewählt. Anstatt die Produktivität durch Vergrößerung der Substratfläche zu erreichen hat man sich entschieden, eine Maschine und ein Verfahren zu entwickeln, in dem kleinere Substrate mit hoher Taktrate beschichtet werden. Eine derartige Maschine kann sehr kompakt gestaltet werden und erreicht ihre hohe Produktivität durch den Einsatz von 25 kleineren Sputterkammern. Die Massenproduktion von Solarzellen kann so erreicht werden, indem viele kleine Produktionseinheiten zusammengeführt werden, genauso wie es bei optischen Datenträgern der Fall ist bei denen eine Jahresproduktionskapazität von 35 Mrd. CDs und DVDs erreicht werden kann.

OLED 소자 제조를 위한 주울 가열 봉지 공정 시 도전층 구조에 따르는 열분포

Encapsulation is required since organic materials used in OLED devices are fragile to water vapor and oxygen. Laser sealing method is currently used where IR laser is scanned along the glass-frit coated lines. Laser method is, however, not suitable to encapsulating large-sized glass substrate due to the nature of sequential scanning. In this work we propose a new method of encapsulation using Joule heating. Conductive layer is patterned along the sealing lines on which the glass frit is screen printed and sintered. Electric field is then applied to the conductive layer resulting in bonding both the panel glass and the encapsulation glass by melting glass-frit. In order to obtain uniform bonding the temperature of a conductive layer having a shape of closed loop should be uniform. In this work we conducted simulation for heat distribution according to the structure of a conductive layer used as a Joule-heat source. Uniform temperature was obtained with an error of 5% by optimizing the structure of a conductive layer. Based on the results of thermal simulations we concluded that Joule-heating induced encapsulation would be a good candidate for encapsulation method especially for large area glass substrate.

Isolation and in Vitro Culture of Rare Cancer Stem Cells from Patient-Derived Xenografts of Pancreatic Ductal Adenocarcinoma

Described is the construction of a large array of releasable microstructures (micropallets) along with screening and isolation protocols for sorting rare, approximately 1 in 10,000, cancer stem cells (CSCs) from a heterogeneous cell population. A 10.1 × 7.1 cm array of micropallets (50 × 50 × 75 μm structures and 25 μm micropallet gap) was fabricated on a large glass substrate, providing an array of approximately 1.3 million releasable microstructures. Image analysis algorithms were developed to permit array screening for identification of fluorescently labeled cells in less than 15 min using an epifluorescent wide-field microscope with a computer controlled translational stage. Device operation was tested by culturing HeLa cells transfected with green fluorescent protein (GFP) admixed with wild-type HeLa cells at ratios of 1:10(4) to 1:10(6) on the array followed by screening to identify flourescent cells. Micropallets containing cells of interest were then selectively released by a focused laser pulse and collected on a numbered poly(dimethylsiloxane) (PDMS) substrate with high viability. A direct comparison of this technology with fluorescence-activated cell sorting (FACS) demonstrated that micropallet arrays offered enhanced post sorting purity (100%), yield (100%), and viability (94-100%) for rare cell isolation. As a demonstration of the technology's value, pancreatic tumor cells from Panc-1 cell lines and patient-derived xenografts were screened for the presence of CD24, CD44, and CD326: surface markers of pancreatic CSCs. Following cell isolation and culture, 63 ± 23% of the isolated Panc-1 cells and 35% of sorted human xenograft cells formed tumor spheroids retaining high expression levels of CD24, CD44, and CD326. The ability to isolate rare cells from relatively small sample sizes will facilitate our understanding of cell biology and the development of new therapeutic strategies.

Large scale antireflective glass texturing using grid contacts in anodization methods

Antireflection coatings on glass are highly desirable, since glasses are widely used as a packaging material in the solar industry due to their transparency and durability. In this report, we propose a novel anodizing method using grid line contacts for antireflective nanostructures on a large area glass substrate. The nanoholes on the glass substrate exhibit broadband and omnidirectional antireflective properties, leading to an 11.34% improvement in the short-circuit current and enhanced power conversion efficiency from 7.9% to 8.57%. Moreover, the enhanced optical properties persist for 3 months in an outdoor environment. The proposed anodizing method can be considered as an alternative technique for the fabrication of large area nanostructures.

Highly Pure Solid‐State White‐Light Emission from Solution‐Processable Soft‐Hybrids

Highly pure and solution processable white-light-emitting hybrids are presented. These soft-hybrids are designed by an organic-inorganic supramolecular co-assembly in water. White-light emission is achieved by partial energy transfer (ET) between donor and acceptor molecules anchored on the inorganic component. The unique and remarkable processability feature of these hybrids is demonstrated by painting/writing onto large glass and flexible plastic substrates.

空気静圧軸受型ガラス基板搬送装置における薄板ガラスの浮上・変形特性

A non-contact aerostatic conveyer was recently proposed to quickly feed and inspect large glass substrates for liquid crystal display. The air conveyer supports the glass substrates by compressed air film and then feeds them through while keeping them clean compared to a conventional roller conveyer. The glass substrate in the latest generation is over 3 m square, and its thickness is less than 0.7 mm. Such thin and large glass substrates are expected to easily deform due to pressure distribution in the air film. Aim of this study is to investigate the levitation and deformation characteristics of glass substrates on a non-contact aerostatic conveyer with inherent orifice restrictors and to establish a calculation method to predict the glass sheet deformation with high accuracy. The deformation behavior of glass sheet on air film was investigated numerically by using the compressible Reynolds equation and Timoshenko's thin plate theory. Numerical results were compared with experimental ones to ascertain the validity of the calculation method. It was found that the glass sheet was easily deformed with a wavy shape by the pressure distribution of the air film. Experimental and numerical results showed almost the same trend.

Experimental Investigation on Hybrid Technology of Ultrasonic Vibration Assisted Chemo-Mechanical Grinding (CMG) Silicon Wafer

For the final finishing of the substrate surface, Chemo-mechanical polishing (CMP) is often utilized. Those processes are able to offer a great sur-face roughness, but sacrifice profile accuracy. On the other hand, Chemo-mechanical grinding (CMG) is potentially emerging defect-free machining process which combines the advantages of CMP. In order to simultaneously achieve high surface quality and high profile accuracy, CMG process has been applied into machining of large size quartz glass substrates for photomask use. In this paper, based on the characteristics of higher machining efficiency and higher surface quality of ultrasonic vibration machining, a new ultrasonic vibration assisted CMG of silicon wafer hybrid technique is achieved by designing elliptical vibrator with longitudinal mode and bending mode. The experimental results show that under the elliptic ultrasonic vibration assistance, the surface roughness is decreased significantly, the surface quality is improved obviously, and moreover caused little or even doesn’t lead to the surface damage.

An Efficient and Easy Method for Measuring Warpage and Thickness of Large Liquid Crystal Display Glass Substrate Part

An Efficient and Easy Method for Measuring Warpage and Thickness of Large Liquid Crystal Display Glass Substrate Part

SOLARC® Anti-Reflective Coating Material for High Transfer Efficiency Application Process

ABSTRACTIt has been demonstrated in literature that chemical liquid deposition (CLD) processes such as dip coating, spray coating, roll coating, spin coating, curtain coating, meniscus coating etc. can be successfully used to deposit anti-reflective coatings on glass substrates. In comparison to physical vapor deposition (PVD), a CLD process generally is cost efficient because of lower capital requirements to set up coating manufacturing lines. Within the realm of CLD processes only some application techniques are suitable for high speed continuous manufacturing processes to deposit coatings on large area glass substrates. Significant differences in transfer efficiencies of these high speed application processes are readily apparent when material utilization per unit area of glass are compared. Roll coat process among all the high speed CLD processes stands out for its high material transfer efficiency due to direct contact printing on flat glass substrates. Honeywell Electronic Materials expanded its line of SOLARC® anti-reflective coating materials to include a new coating formulation SOLARC® RPV, which is customized for roll coating application. This paper highlights the advantages of using SOLARC® RPV in roll coat process and the performance attributes of SOLARC® anti-reflective coatings. Durability characteristics of these anti-reflective coatings in accelerated aging tests designed to simulate harsh field conditions will also be discussed.

P4-07-12: Identification of p53 Mutation in Whole Genome DNA from Single Circulating Tumor Cells (CTCs) and Primary Breast Cancers (BC) from Patients (pts) with Metastatic Breast Cancer (MBC).

Abstract Background: CTCs represent the source of distant metastases, and are also implied in the growth/re-growth of primary BC. Molecular/gene-level characterization of similarities and discordances between CTCs and BCs in pts with MBC may provide useful information for individualized treatment. Since somatic p53 mutations are frequently observed in primary BCs, we set out to assess the feasibility of identifying such mutations in CTCs from pts with MBCs, and compare the findings with those of the primary BCs from the same pts. Material and Method: Fiber-optic Array Scanning Technology (FAST) was used for identification and location of CTCs on large glass substrates. CTCs were identified after blood samples (10 ml) from MBC pts were stained to detect CTCs via automated digital microscopy by morphology, based on immunofuorescence staining for cytokeratin and nucleus, and the absence of CD45. Single CTCs from 10 pts with MBC were identified and removed from the glass substrates. DNA was extracted, and the whole genome of isolated CTCs was amplified by using whole genome amplification method (Sigma). P53 mutations in exon 5, exon 6, exon 7 and exon 8 were assessed. As comparison, genomic DNA from formalin-fixed and paraffin-embedded (FFPE) from primary BCs of the same pts, was amplified using the same method. Results: p53 mutations were found in 8 out of 10 CTCs, and in 4 out of 10 in primary BC samples. Of 8 mutations detected in CTCs, one silent mutation and 7 missense mutations were seen. One particular point mutation, R181L, previously assessed as functional mutation, was observed in 4 out of 8 CTCs. None of the 4 mutations (a silent mutation, one missense mutation and two different deletions) detected in tumor samples were found in CTCs. We validated that the mutations detected in CTCs were not artifacts occurring during genome amplification, by comparing p53 mutations between unamplified tumor genomic DNA vs. amplified samples. Conclusion: Whole genome amplification based on extracting DNA from single CTCs using FAST, and identification of mutations such as those in p53, is feasible. The quantitative and qualitative discordance in detecting p53 mutations between CTCs and primary BCs may be due to CTCs acquiring new -possibly epithelial-mesenchymal transition-like-characteristics with metastatic potential as they evolve from the primary tumors or metastatic sites, or, technical issues (analyzing FFPE-preserved vs. CTCs, tumor heterogeneity) may contribute to our findings. Further assessment of the functionality of high frequent functional mutations such as R181L is warranted. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-12.

Solution‐processed oxide thin‐film transistors using aluminum and nitrate precursors for low‐temperature annealing

Abstract— In this article, a solution process for oxide thin‐film transistors (TFTs) at low‐temperature annealing was investigated. Solution‐process engineering, including materials and precursors, plays an important role in oxide thin‐film deposition on large glass and flexible substrates at low temperature. Reactive material could reduce the alloy reaction temperature for a multicomponent oxide system. A volatile precursor could also reduce annealing temperature in the formation of metal‐oxide thin films. A solution process with reactive Al and a volatile nitrate precursor can demonstrates competitive oxide TFTs at 350°C.

Thin films in photovoltaics: Technologies and perspectives

Thin Film technologies based on physical vapour and plasma enhanced chemical vapour deposition (PVD and PECVD) have been developed for a number of high-tech industries over the last decades. Prominent examples are the semiconductor and display industry as well as large area architectural glass and flexible substrates deposition. Inherently linked with this development was the well known price experience curve for products in the respective industries. Analysing the price experience curves for PV crystalline silicon modules over the last 30years and those of other Thin Film based industries, it will become evident that cost efficient PV Thin Film technologies or Thin Films in conjunction with wafer based c-Si are a prerequisite to meet the anticipated cost and price goals for the upcoming decade. As PV will demonstrate to become one of the major energy provider in the future by contributing significantly to meet the goal of 100% end energy by only renewable technologies beyond 2050 we will see a huge increase of appropriate Thin Film technologies in the years to come.

Nanosphere dispersion on a large glass substrate by low dose ion implantation for localized surface plasmon resonance

Dispersing nanospheres on a large glass substrate is the key to fabricate noble metal nanostructures for localized surface plasmon resonance through dispersed nanosphere lithography. This article reports that by modifying the glass surface with low dose ion implantation and successively dip coating the surface with poly(diallyldimethyl ammonium chloride) (PDDA), polystyrene or silica nanospheres can be dispersed on a large glass substrate. Investigation shows that several kinds of ions, such as silicon, boron, argon, and arsenic, can improve the nanosphere dispersion on glass, attributed to the ion bombardment-caused silicon increment. Ion implantation imposes no surface roughness or optical loss to the glass substrate, thus this method is suitable for localized surface plasmon resonance application. Experiments show silicon ion implantation can best disperse the nanospheres. For the gold nanostructures obtained by obliquely evaporating 30 nm of gold film onto the polystyrene nanospheres, which are dispersed on a silicon ion implanted glass substrate, a localized surface plasmon resonance sensitivity of 242 nm/RIU is achieved.