Category Archives: FPDs and TFTs

Organic semiconductors now offer the performance, cost and route to adoption, for foldable displays; from ultra-thin, conformal, wearables to truly foldable smartphones and tablets.

BY DR. MICHAEL COWIN, SmartKem Ltd, St Asaph, Wales

Buoyed by consumer demand for fresh innovation and fierce industry competition, the display industry exists in a cycle of continuous improvement.

Today a new breed of semiconductors – a key enabling component in the evolution of active matrix displays – are competing to offer manufacturers a route to the production of high performance curved, foldable and even roll-able displays.

There are two key factors that define the impact and adoption of any new enabling technology like this; namely how will it perform and what will be the cost.

This article demonstrates that the performance of organic thin-film transistors (OTFT) for display backplane application has reached a tipping point into market adoption. OTFTs are now equal and arguably greater than competitive technology solutions while also offering ultra-flexibility and a significant cost advantage in production and ownership over the more traditional inorganic equivalents. OTFTs are now a serious contender to fill a critical gap in the market for high performance, ultra-flexible TFT backplanes to drive the next generation of conformal displays.

At first, low-temperature polysilicon (LTPS) was considered the most likely solution to replace hydro-genated amorphous silicon (a-Si:H) as the TFT channel layer for rigid flat panel display backplanes, until the advent of indium gallium zinc oxide (IGZO). While the vastly superior mobility of LTPS gave uplift in mobility over traditional a-Si TFT, it came at a price of significantly higher manufacturing costs through high CAPEX, complicated processing and much lower yields, some of which were as low as 20% in early 2014.[1]

However, the recent aggressive drive to manufacture OLED, EPD and LCD display products with new form factors so they are lightweight, conformal or flexible has placed new challenging demands on the TFT material characteristics. This has allowed new technology platforms such as OTFTs to enter into the supply chain to compete head on with LTPS and IGZO as a TFT channel material based on the same metrics of performance and cost.

Electrical performance: It’s all about power

While a semiconductor technology’s cost of ownership outlines the market entry opportunities, no TFT platform will even be considered a viable alternative to incumbent semiconductors unless it meets, and surpasses key criteria. When defining these criteria it is vital that context to the end application and how this might improve the user experience is considered. Power consumption is one such aspect becoming critical in defining the battery life of mobile and wearable displays and any new TFT channel material, such as OTFT needs to demonstrate either equal or better performance to add value to the user experience in end product form.

Screen Shot 2015-06-09 at 3.22.19 PM

The progression from a-Si semiconductors to alternative materials for rigid displays was originally driven by the charge carrier mobility bottleneck, as manufacturers tried to move to higher resolution active matrix LCD displays. The same requirement exists for AMOLED displays, and as such a parallel can be drawn to the arguments for and against the competing materials systems, but with the increasingly important necessity for physical flexibility.

Each semiconductor platform has its own advantages and disadvantages. For instance while LTPS has a very high carrier mobility it could be debated whether it’s necessary in the average pixel driver circuit for a high quality LCD or OLED display where a mobility of 5-10 cm2/V.s is more than adequate. Indeed IGZO and the latest generation of OTFTs meet this requirement with ease. In contrast TFT electrical (bias stress) stability is an issue with IGZO, usually resulting in more complexity in the TFT drive circuitry for each pixel to compensate for this short coming. From a general perspective each of the above mentioned three contenders are more than suitable as a channel semiconductor. However, these options also need to be considered in context; which of these offers the potential to add real uplift in the user experience at a price point the market will accept? Most displays today are mobile-enabled and are soon to become wearable with the advent of the smartwatch. The power consumption of these displays and its impact on battery life may well be a defining factor in the choice of TFT channel semiconductor for many manufacturers.

An important contribution to this argument was made by Sharp with the introduction to the market of IGZO. Sharp highlighted the importance of TFT leakage current which led to a clearer understanding of the mechanisms responsible for these leakage currents. The causes are found to be predominantly dependent on the smoothness of the interface between the insulator and the channel semiconductor.

So while LTPS has a rough polycrystalline surface its leakage current is higher; IGZO in contrast has smooth amorphous surfaces at this key interface and as such much lower leakage currents.

The context of lower leakage currents is that it will become a very desirable quality since less current is dissipated when the TFT is off and as such the TFT switch capacitor/s can retain an internal charge for a longer period of time. Thus the display refresh rate can be reduced which leads to a potentially dramatic reduction in power consumption – especially for displays that will have static images – ideal for wearable and mobile based displays. As such IGZO has a clear advantage over LTPS for this display based application.

However, recent advances in OTFT technology reported here for the first time show the potential for low leakage currents equivalent to IGZO; but achieved using OTFTs. By designing into solution based organic semiconductor ‘inks’ the preferred features of the single- crystal organic semiconductor combined with semiconducting polymers or ‘binders’ an amorphous semiconductor layer can be achieved. This material combination offers the high mobility of single crystals but with highly uniform processing charac- teristics required for device uniformity. Furthermore, the amorphous nature of these materials offers very smooth interfaces between the solution processed insulator and solution processed semiconductor.

The results in FIGURE 1 demonstrate that the low leakage current levels achieved by a single gate OTFT. This could be lowered further by use of a dual gate OTFT stack as with commercial IGZO TFTs.

FIGURE 1. TEM of copper hillocks

FIGURE 1. TEM of copper hillocks

Therefore OTFTs represent serious competition to IGZO as a channel material in the context for application to wearable and mobile displays for extended battery life. Coupled with the further advantages of excellent bias stress stability and low temperature processing, the case for OTFT adoption rather than IGZO becomes more attractive from a performance perspective.

Physical performance: The foldable frontier

Recently there have been a number of commercial products launched based on curved AMOLED displays such as the Galaxy Round, LG G Flex and Galaxy Note Edge with curved features (and slight flex in the case of the G Flex), all based on LTPS TFT backplanes on plastic. When the user context is taken into account it could be suggested that these products have not offered much value differentiation from glass based equivalent devices.

As such the real ‘wow’ factor in the consumer experience or user value-add has yet to be achieved.

Next generation smart and wearable technology will come with the introduction of flexible and foldable devices such as wearables, smartphones and tablets; but this demands a semicon- ductor platform with entirely new physical properties and a form factor capability which in turn raises a unique set of challenges for traditional and new TFT technologies to overcome.

The current limiting factor is the inability of LTPS and IGZO technologies to offer robust and acute bend capability in TFT form. Even with the use of exotic and expensive strain management layering techniques the maximum bend radius of these technologies have hit a roadblock at around 5 mm.

To genuinely offer a differentiated product with a compelling value-add proposition to the consumer experience, manufacturers must turn to the use of material technologies that enable truly foldable mobile devices or fully bendable, robust and light- weight smartwatches (FIGURE 2). The solution to the limitations presented by LTPS and IGZO in bend capability is the use of OTFTs. It has long been understood that the polymeric nature of OTFTs is ideally suited for bendable applications, and it has widely been reported that products such as Smart- Kem’s tru-FLEX® can withstand 10,000 bends below 1mm with minimal effect on device performance. As such OTFT technology is now considered a key enabler for a wide range of highly robust bendable and foldable display based products; and the market timing could not be better with the recent upturn in demand for smartwatch based products.

FIGURE 2: Display form factor dependency on bend radius.

FIGURE 2: Display form factor dependency on bend radius.

In the context of performance it may be suggested that while the initial market entrants in curved display products have been manufactured with LTPS, and that there is further development potential in the IGZO platform, a complete technology solution already exists – OTFT.

The OTFT technology platform offers the transistor performance for exciting new applica- tions while also holding two ‘aces’ when it comes to product-specific performance for this new generation of wearable and mobile displays; low leakage for significant battery life extension and ultra-flexibility for foldable mobile devices and bendable smart- watches.

How much will it cost?

Beyond the performance benefits of OTFTs, a commercially viable TFT channel semicon-
ductor must provide favourable characteristics for integration into a robust and cost-effective semiconductor manufacturing process. The savings in manufacturing costs compared with inorganic materials as well as the low risk approach of re-purposing existing a-Si production lines to pilot OTFT backplanes on plastic is an appealing prospect.

One of the major advantages of organic semiconductors comes from their ease of application. Solution based semiconductor inks can be applied to substrates through a range of additive processes and print production systems such as slot dye coating as well as low temperature process (FIGURE 3). Although modern organic semiconductors are stable up to 300°C the ease by which these solution-based materials can be processed at low temperatures offers manufacturers a wide range of cost effective stack materials and substrates, and easier bond/de-bond and inter-layer alignment due to less expansion and contraction. This all adds up to significantly improving production yield (over high temperature processing) and thereby reducing production costs over any area of substrate.

FIGURE 3. Commercial organic semiconductors, such as SmartKem’s tru-FLEX® material, offer a total technology solution, combining high performance mobility, low temperature processing and true flexibility.

FIGURE 3. Commercial organic semiconductors, such as SmartKem’s tru-FLEX® material, offer a total technology solution, combining high performance mobility, low temperature processing and true flexibility.

An independent study has been commissioned by SmartKem comparing the cost of key features within the TFT stack that would show the maximum variance between technology platforms; the semiconductor and gate dielectric layer. This will ensure a complete understanding of the difference in the cost of ownership and cost of production for the alternate TFT channel materials for backplane manufacture for flexible displays.

The four technology platforms chosen for the TFT array devices were: a-Si, LTPS, IGZO and SmartKem’s OTFT semiconductor tru-FLEX®. The overall cost of TFT device manufacture included manufacturing overheads to produce the two layers, depreciation of equipment (amortized over five years of production of 1.8 million substrates) and the direct materials costs.

The CAPEX for each fabrication process is determined from the type and quantity of equipment needed for producing the semiconductor and gate insulator layers with an assumed input capacity of 30,000 substrates per month. In this study, the assumed equipment and materials are shown in Table 2. The summary findings of the on-going study have shown the cost of manufacturing TFT arrays with organic semiconductors is almost half that of LTPS and a third lower than a-Si and IGZO. The most significant findings (to be published in a white paper) were that the manufacturing overheads and depreciation costs for OTFT were ten times less than LTPS and four times less than a-Si and IGZO.

Screen Shot 2015-06-09 at 3.25.26 PM

It was found that the depreciation cost of production for a ‘greenfield’ OTFT line is vastly smaller than competing technologies and could be further reduced by the re-purposing of an a-Si production line; OTFTs thus offer an easy route to adoption for the cost-down manufacture of superior performance flexible TFT backplanes.

The future is organic

The value proposition of organic semiconductors now makes sense to an industry eager for differentiated products that can be adopted and scaled with low risk. From a performance and cost perspective the immediate value-add to the consumer is longer battery life and fully foldable mobile displays. While the cost of production is reduced with OTFT, the extremely low cost of ownership offers a low risk industrialization strategy through the building of a ‘greenfield’ line or by the re-purposing of an existing a-Si line.

One of the most exciting and eagerly awaited outputs of this rapid evolution in material perfor- mance and cost is the advancement and commercialization of bendable and foldable displays. From ultra-thin, conformal, wearables to truly foldable smartphones and tablets, organic semiconductors now offers the performance, cost and route to adoption for the manufacture of a new generation of OLED, EPD and LCD displays with entirely new physical properties and form factors.

References

1. http://www.displaysearchblog.com/2014/08/waiting-for-the-apple-iwatch/

DR MICHAEL COWIN is Head of Strategic Marketing, SmartKem Ltd., St Asaph, Wales

How gases are used in the manufacture of displays is being impacted by new technologies, consumer demand, and the burgeoning China market.

BY EDDIE LEE, Linde Electronics, Hsin Chu, Taiwan

While the display market is no longer enjoying double-digit annual growth rates, it is experiencing resurgence due to increasing customer demands for larger flat-panel displays, OLED and 4K technology, ultra-slim form factor, curved and wearable displays, automotive displays, and more. This growth is particularly conspicuous in China, a late comer to the market, which is now the fastest growing region in display manufacturing.

These new technologies and markets require very large quantities of ultra-high purity bulk and electronic specialty gases and a dependable supply chain for these gases. This article will explore the impact of these technologies, consumer demand, and the burgeoning China market on the gases used in the manufacture of display.

Display market

According to IHS DisplaySearch, in 2014 the global display market saw revenue of $134 billion and is expected to grow 6% in 2015. The demand is being driven in large part due to new technologies and new uses for existing display technologies such as 4K, OLED, curved, and flexible displays.

Gases used in display

This love affair that consumers have of interacting with devices large and small not only increases the volume of displays to be manufactured, it also increases the volume of gases needed to make the displays. In the 20 years since the initial development and commercialization of the first Thin Film Transistor (TFT) LCD display panel, the gases market for the display sector has grown to around $450 million.

As shown in FIGURE 1, display manufacturing today uses a wide variety of gases, which can be categorized into two types: Electronic specialty gases (ESGs) and Electronic bulk gases (EBGs).

Displays 1 Displays 1-2

 

FIGURE 1. Market breakdown for the two types of gases used in display manufacturing. 

 

Screen Shot 2015-06-10 at 1.57.34 PM

Electronic specialty gases (ESGs)

Silane, nitrogen trifluoride, fluorine (on-site generation), sulfur hexafluoride, ammonia, and phosphine mixtures make up 52% of the gases used in the manufacture of displays and are available in both cylinder and bulk supply.

Of the major countries that manufacture displays, Taiwan and China import most of their ESGs while Korea and Japan have robust domestic production of ESGs.

Silane: SiH4 is one of the most critical molecules in flat panel manufacturing. Silane is used for deposition of amorphous Si (silicon), the most critical layer in the TFT transistor.

Nitrogen trifluoride: NF3 is the single largest Electronic Material from spend and volume stand- point for flat panel display (FPD) production. NF3 is used for cleaning the PECVD (plasma-enhanced chemical vapor deposition). This gas requires scalability to get the cost advantage necessary for the highly competitive market. Over 70% of the global capacity of NF3 comes from Korea and Japan.

Screen Shot 2015-06-09 at 2.52.37 PM

Electronic bulk gases (EBGs)

Nitrogen, hydrogen, helium, oxygen, carbon dioxide, and argon make up 48% of the gases used in the manufacture of displays.

Nitrogen: For a typical large TFT-LCD fab, nitrogen demand can be as high as 30,000 Nm3/ hour so an on-site generator, such as the Linde SPECTRA®-N 30,000, is a cost-effective solution that has the added benefit of an 8% reduction in CO2 footprint over conventional nitrogen plants.

Helium is used for cooling the glass during and after processing. Manufacturers are looking at ways to decrease the usage of helium because of cost and availability issues due it being a non-renewable gas.

New technologies and implications for gases

Currently about 20% of smartphones – the ones with lower resolution displays – use a-Si display process. Higher resolution devices and new effects such as curved displays require higher performance transistors and improvements in electron mobility. This can be achieved by switching from amorphous silicon (a-Si) transistors to low temperature polysilicon (LTPS) or metal oxide (MO), also known as transparent amorphous oxide semiconductor (TAOS).

LTPS is used in about 44% of high-end LCD smart- phone displays as it has the highest performance. Due to its higher costs and scalability limitations, LTPS is less suited for large screen displays

Small displays with very high pixel resolution are produced with LTPS. High-definition large displays can be made using MO. Metal oxide semiconductors can remain in an active state longer than traditional LCD and can cut power consumption by up to 90%, which is a huge benefit.

New process requirements

Metal Oxide TFT and LTPS: To meet the changes in technology, N2O, C2HF5, C4F8, BF3, and laser gases are replacing or at least reducing the requirement of NH3, BCl3, and SiH4.

The use of N2O is expected to double from 5,000 TPA (tons per annum) in 2013 to 10,000 TPA in 2017. Why nitrous oxide? The move from a-Si to MO requires a change in the TFT device structure where the a-Si layers (g-SiNx, a-Si, n+) are being replaced by the MO layers (g-SiOx + indium gallium zinc oxide). This requires a change from NH3 to high- volume, high-purity N2O.

LTPS process also uses N2O for its oxide layer deposition. In addition, LTPS uses XeCl (xenon monochloride) excimer lasers for annealing after the silicon deposition to change the silicon structure to polysilicon. High-performance laser gases, such as Ne, Xe, and Kr from Linde, are well-suited for this process.

Transparent Conductive Films (TCF) and ITO Replacements: TCFs are used in most high-tech displays and touchscreens, and particularly in displays that are bent or curved. Currently the electronics industry relies primarily on Indium Tin Oxide (ITO) to make electro-conductive films for display. ITO presents challenges: it is brittle and cracks so new TCFs are needed for structural flexibility.

New materials to potentially replace ITO are metal mesh, Ag nanowire (agNW), and carbon nanotube (CNT), which are all highly flexible with comparable transparency and resistance to ITO. Metal mesh is good for large displays, but is restricted on small and medium displays due to its wire width (typically 6 μm). AgNW demonstrates excellent transmittance and flexibility with small wire diameter (20 – 100 nm), but haze is an issue. CNT has excellent conductivity, transmit- tance, and flexibility, but the supply chain needs to be developed. Single walled carbon nanotubes (SWNT) technology from Linde uses liquid ammonia to produce solubilized carbon nanotubes in the form of inks, which can then be deposited as films and has the added benefit of zero carbon footprint.

F2 as replacement for NF3 and SF6: For a typical large TFT-LCD fab, chamber cleaning gas demand can exceed 300 tons per year. Traditionally NF3 has been used. The GWP100 (100-year Global Warming Potential) for NF3 is 17,200; for the replacement F2, the GWP100 is 0.

Switching to fluorine not only significantly reduces environmental footprint, but also leads to material cost savings and up to 50% reduction in cleaning time, increasing productivity (FIGURE 2). Fluorine can also be used to replace Sulfur hexafluoride (SF6), which is used in dielectric etching. The GWP100 for SF6 is 22,800, which surpasses that of NF3. Significant improvements in etch rate and etch uniformity have been measured with the shift to F2.

FIGURE 2. Switching to fluorine reduces environmental footprint, material costs cleaning time.

FIGURE 2. Switching to fluorine reduces environmental footprint, material costs cleaning time.

On-site fluorine generation, like that available from Linde, eliminates large-volume, high-pressure storage, and modular generators meet all flow and volume requirements for the largest scale fabs.

The China factor

Currently Korea is the leader in display manufacturing, with Taiwan and China on
its heels and Japan a distant fourth (FIGURE 3). This is changing, though, as China rapidly gains market share. China, which started in most traditional manufacturing industries as “factory to the world,” is a relative late comer in the display sector due to technology barriers.

FIGURE 3. Currently Korea is the leader in display manufacturing, with Taiwan and China on its heels and Japan a distant fourth. This is changing, though, as China rapidly gains market share. Source: IHS Displaysearch and Linde Internal.

FIGURE 3. Currently Korea is the leader in display manufacturing, with Taiwan and China on its heels and Japan a distant fourth. This is changing, though, as China rapidly gains market share. Source: IHS Displaysearch and Linde Internal.

Currently there are about five major domestic display manufacturers in China; they cater primarily to domestic mobile display and large screen markets. China has been aggressively investing in display fabs over the last five years and has gained market share from other regions.

It is expected that China will account for more than 50% of display capacity investment in the next four years. China capacity is expected to double with aggressive investments especially in the leading technology Low Temperature Polysilicon (LTPS) and Metal Oxide (MO).

Gas supply issues in China

Bulk gases are produced in China, mostly by large international gas companies. There are domestic producers of some ESGs (NH3, N2O, and SF6); other gases currently are mostly imported.

Silane (SiH4): Silane, primarily extracted as an interim process gas during poly silicon production, is one of the most critical molecules in FPD manufacturing. Chinese producers have a very small capacity of silane as they entered the market late. Considering the need for extensive qualification, technical support to achieve that, and the lack of scalable production base, local Chinese poly silicon producers are not able to offer a complete package and thus China still imports more than 80% of its silane and produces locally only 2% of the global capacity of silane.

The current consumption of silane in China display manufacturing is about 300 TPA, which is 7.5% of the global demand, and is expected to double in the next four years. Considering the complexity of the supply chain, import regulations, and storage requirements, companies are actively moving towards local transfilling and analytical capability.

Nitrogen trifluoride (NF3): Similar to silane, the China display manufacturing consumption of NF3 is expected to double to greater than 2000 TPA in the next four years. Considering the volume used and spend on NF3 and the rapid expansion of FPD manufacturing in China, more production will be done locally to minimize customs duties and to support domestic sourcing requirements. NF3 is relatively easy to qualify for chamber cleaning, but ISO supply to large customers is the biggest challenge since most producers do not have large-scale production and equipped facilities to make NF3 cost-effective to make. This is a major area of investment for local producers.

LTPS, Metal Oxide, and the Increase in Demand for N2O: N2O is a regional and localized product due to its low cost, making long supply chains with high logistic costs unfeasible. Currently, in the region, Korea manufactures about 63% of high-purity N2O, Taiwan about 30%, and China only about 7%. As China leap frogs its display industry into the cutting- edge metal oxide, or LTPS nodes, the demand for N2O will triple from its current requirement to 3,000 TPA in 2017 with the adoption of LTPS and MO.

Enablers of the growth of the China display industry

The key priorities for materials manufacturers to enable the growth of the China display industry are:

  • Commitment to invest in local infrastructure such as as on-site bulk gas plants
  • Localization of production facilities for high-purity gas and chemical manufacturing
  • Collaboration with global materials suppliers for development of new materials

Conclusion

To accommodate the boundless appetite that consumers have for the latest, most innovative, and highest definition displays – both large and small – display manufacturers must partner with gas suppliers to:

  • Identify the most appropriate gas and display technology match-up
  • Globally source electronic materials to provide customers with stable and cost-effective gas solutions
  • Develop local sources of electronic materials
  • Improve productivity
  • Reduce carbon footprint and increase energy efficiency through on-site gas plants

EDDIE LEE is Head of Global Market Development and OEMs Display, Linde Electronics, Hsin Chu, Taiwan

Revenues for flat panel display (FPD) manufacturing equipment are expected to grow for the third consecutive year to reach $9.1 billion, according to IHS Inc. (NYSE: IHS), a global source of critical information and insight. This level of FPD equipment spending, the highest level since 2011, is being driven by new liquid crystal display (LCD) and active-matrix organic light-emitting diode (AMOLED) panel factories targeting both large-area television and smartphone applications.

In terms of technology, spending will be split nearly evenly between amorphous silicon (a-Si) TV and low-temperature polycrystalline silicon (LTPS) smartphone plants, according to the latest IHS Quarterly FPD Supply/Demand and Capital Spending Report, LTPS investments in both 2015 and 2016 are expected to exceed all-time highs. 

“Over the past five years, spending on new LTPS LCD and AMOLED factories has been even more volatile than the overall FPD equipment market,” said Charles Annis, senior director at IHS. “LTPS-related equipment expenditures are now expected to peak in 2015 and 2016, before dropping off again in 2017, Recently announced projects are generating unprecedented levels of LTPS equipment expenditures, including new fab plans for JDI in Japan and Foxconn in Taiwan; expansions of current lines at both Samsung and LG Display in Korea; and new LTPS plants in China being built by AUO, BOE, Tianma and China Star.”

In addition to all the current LTPS fab activity, in 2015 makers continue to invest in a-Si Gen 8 factories targeted at TV applications, mainly in China. Much of this investment is the result of growing demand for large-area panels, which increased 14 percent last year – significantly outstripping capacity growth of 6 percent. This increased demand caused tight supply and firm prices last year, encouraging panel makers to extend capacity expansions. This year large-area demand and supply are forecast to grow at similar rates of 6 percent. Although factory utilization remains at relatively high levels, and there are concerns that growing set inventories will continue to push prices down in the third quarter (Q3) of this year, large-area supply and demand will be balanced for the year.

“Despite the maturing TV market, along with various concerns about the ability of all the new LTPS plants in China to ramp-up smoothly, FPD investment activity remains dynamic,” Annis said. “FPD equipment spending in 2016 is currently forecast to be flat or slightly down. BOE’s recent announcement to build a future Gen 8 factory in Fuzhou, and the world’s first Gen 10.5 fab in Hefei China, suggests that FPD makers still believe that building new factories will continue to lower costs and expand the range of applications.”

Discussion of these topics and more can be found in the IHS Quarterly FPD Supply/Demand and Capital Spending Report. The report covers the most important metrics used to evaluate supply, demand, and capital spending for all major FPD technologies and applications.

Smartwatch display unit shipments are expected to grow 250 percent year-over-year, reaching a record 34 million units in 2015, led by demand for the new Apple Watch, according to IHS Inc. (NYSE: IHS), a global source of critical information and insight. The display market is still assessing the staying power of smartwatch demand, so as not to overshoot display supply needs in the coming year, particularly for the year-end shopping season. Smartwatch display shipments are therefore forecast to decline to about 6.5 million units in the fourth quarter (Q4) of 2015, after reaching a high point of 10.5 million units in the third quarter.

Because both Apple Watch and Samsung Gear rely on active-matrix organic light-emitting diode (AMOLED) panels, that technology will comprise the majority (58 percent) of total smartwatch panels shipped. Based on the latest information from the IHS Quarterly Small/Medium Shipment and Forecast Report, Apple Watch is expected to make up 84 percent of AMOLED smartwatch panels and 49 percent of total displays for smartwatch shipped in 2015.

“Apple Watch has attracted a lot of attention from consumers, which has led to increased demand,” said Hiroshi Hayase, director of analysis and research for IHS Technology. “The display market is carefully watching consumer response to products in the smartwatch category, which should help to improve future display technologies.”

The IHS Quarterly Small/Medium Shipment and Forecast Report covers the entire range of small and medium (9 inches or smaller) displays shipped worldwide and regionally.

FUJIFILM Corporation and nano-electronics research institute, imec have demonstrated full-color organic light-emitting diodes (OLED) by using their jointly-developed photoresist technology for organic semiconductors, a technology that enables submicron patterning. This breakthrough result paves the way to producing high-resolution and large organic Electroluminescent (EL) displays and establishing cost-competitive manufacturing methods.

Organic EL displays are increasingly used for televisions, mobile devices including smartphones as well as wearable devices. Since they can be made thin and flexible, while also offering excellent response time and contrast ratio. It is said that today’s products require organic EL displays of high pixel density, i.e. around 200ppi for 4K televisions, 500ppi for full HD mobile devices and even higher density for compact displays for wearable devices. There has been active R&D for organic semiconductors to develop a high-resolution patterning method for organic EL materials to be used in these products.

In 2013, Fujifilm and imec jointly developed photoresist technology for organic semiconductors that enables submicron patterning without damaging the organic semiconductor materials, based on photolithography capable of high-resolution patterning on large substrates. There is no need for additional capital investment since an existing i-line exposure system can be used for the new technology. This is why the technology has attracted wide attention since the development announcement with anticipation of a cost-effective way of manufacturing high-resolution organic semiconductor devices.

In the latest achievement, Fujifilm and imec produced full-color OLEDs with the photoresist technology for organic semiconductors and successfully verified their performance.  Red, green and blue organic EL materials were patterned, each in the subpixel pitch of 20μm, to create full-color OLEDs. An OLED array of 40 x 40 dots at the resolution of 640ppi was realized and illuminated with UV rays to confirm that red, green and blue dots separately emitted light. The emission of red, green and blue lights was also confirmed in a test involving the application of voltage rather than illumination, confirming its correct performance.

These results open new opportunities, such as using the novel photolithography in a multiple patterning process. An example would be creating an OLED array that adds a fourth color to red, green and blue, as well as developing previously-unseen devices such as a new sensors that integrate OLED with the organic photodetector.

This research result is to be presented at the SID Display Week, one of the world’s largest international exhibitions for information displays, held in San Jose, California from May 31 to June 5, 2015.

Since the commencement of joint research in November 2012, Fujifilm and imec have broken through the boundary of conventional technology to contribute to the progress of technology associated with organic semiconductors, e.g., developing the photoresist technology for organic semiconductors that enables the realization of high-resolution submicron patterns.  The two companies will continue to undertake cutting-edge R&D involving semiconductor materials, process technology and system integration, thereby contributing to resolving challenges faced by the organic electronics industry.

Applied Materials, Inc. today announced its Applied Endura Cirrus  HTX PVD system with breakthrough technology for patterning copper interconnects at 10nm and beyond. As chip features continue to shrink, innovations in hardmask are required to preserve the pattern integrity of tightly packed, tiny interconnect structures.With the introduction of this technology, Applied enables scaling of the TiN metal hardmask – the industry’s material of choice – to meet the patterning needs of copper interconnects in advanced microchips.

“Precision engineering of metal hardmask films is key to addressing the patterning challenges for advanced interconnects,” said Dr. Sundar Ramamurthy, vice president and general manager of Applied’s Metal Deposition Products business unit. “The Cirrus HTX TiN product represents Applied’s decades of expertise in applying PVD technology for engineering TiN film properties. Incorporating our unique VHF-based technology offers customers the flexibility of tuning stress in TiN films from compressive to tensile to overcome their specific integration challenges.”

Today’s advanced microchips can pack 20 kilometers of copper wiring in a 100 square millimeter area, stacked in 10 layers with up to 10 billion vias or vertical connections between layers. The role of the metal hardmask is to preserve the integrity of these patterned lines and vias in soft ULK dielectrics. However, with scaling, the compressive stress from conventional TiN hardmask layers can cause the narrow lines patterned in ULK films to deform or collapse. The tunable Cirrus HTX TiN hardmask with high etch selectivity delivers superior CD line width control and via overlay alignment resulting in yield improvement.

This breakthrough in TiN hardmask is made possible by precision materials engineering at the wafer level to produce a high density, low-stress film. Combining exceptional film thickness uniformity with low defectivity on a proven Endura platform, the Cirrus HTX system addresses the stringent high volume manufacturing needs of patterning multiple interconnect layers.

Applied Materials, Inc. is a developer precision materials engineering solutions for the semiconductor, flat panel display and solar photovoltaic industries.

Despite the inventory adjustment caused by LCD TV brands reducing their panel orders in the first quarter (Q1) of 2015, the strong demand for leading TV brands to fulfill their panel facilitation plans — combined with a strong cross-marketing push by TV panel makers — helped LCD TV panel shipments reach a record monthly high in March 2015. According to the latest Monthly TFT LCD Shipment Databasefrom IHS Inc. (NYSE: IHS), a global source of critical information and insight, LCD TV panel shipments from global panel makers reached 23.9 million in March 2015, growing 20 percent month over month and 11 percent year over year.

Panel shipments declined seasonally in Q1 of this year, because most LCD TV modules are manufactured in China and the Chinese New Year holidays in February meant fewer working days in LCD cell fabs in Asia and LCD module lines in China. Meanwhile, as the LCD TV panel supply-demand balance shifted from tightness to oversupply, TV makers have started to reduce orders, especially for older models. However, positive year-over-year growth is still expected, especially since there was such a strong rebound for LCD TV panel shipments in March.

“Although the LCD TV panel demand has shown signs of slowing after the holidays, leading TV brands are preparing their new models for launch, so orders are not diminished,” said Yoonsung Chung, director of large area display research for IHS.  “Meanwhile, panel makers are aggressively introducing 4K resolution, wide color gamut, ultra-slim bezels and other new features, to improve panel shipment growth”

While LCD TV panel shipments reached 253 million units in 2014, panel makers are aggressively targeting 261 million units this year. “Demand will slow, beginning in the second quarter of 2015, and panel prices are already starting to fall, so TV panel shipments may face some growth challenges in the coming months,” Chung said.

IHS_Large-area_shipments_2008-2015_150427

 

LCD shipment growth also varied by size in March, representing a shift in LCD TV size trends. The 23.6-inch display, which is primarily available in emerging regions, shipped a record 2.1 million units. Other display sizes setting records last month were 40-inch displays (3.3 million), 43-inch displays (1.2 million), 49-inch displays (0.9 million), and 65-inch displays (0.4 million).

Led by Samsung Display and LG Display, 4K LCD TV panel shipments grew from 1.7 million in February to a record-setting 2.6 million units in March 2015. Red-green-blue-white (RGBW) pixel-layout technology, which can help reduce power consumption, is expected to rise rapidly in 2015 as the industry’s acceptance of this technology has gradually extended from the Chinese market to the global market.

The Monthly TFT LCD Shipment Database provides the latest panel shipment numbers, surveyed from all large-area panel makers.

Strong promotion of 4K display resolutions from TV makers, display manufacturers and distribution channels has successfully increased consumer awareness and boosted 4K LCD TV penetration in 2014, according to a new report from IHS Inc. (NYSE: IHS), a global source of critical information and insight. While 4K is best known as a feature in high-end LCD TVs, starting this year 4K displays will emerge in all major display applications, including desktop monitors, notebook PCs, OLED TVs, digital signage, smartphones and tablet PCs.

The latest Quarterly Worldwide FPD Shipment and Forecast Report from IHS reveals that the 4K display market reached $9.2 billion last year.  4K LCD TV contributed $8.8 billion to overall revenue; however, in 2015, 4K displays are coming to all major applications and will boost 4K revenue 94 percent year over year, reaching $18 billion in 2015. With the evolution of new display process technologies, to enhance the 4K display yield rate and lower costs, IHS forecasts that the 4K display market will be reach $52 billion in 2020.

“Since its market introduction in 2013, TV brands have recognized that 4K is a great way to enhance value, so they have strongly promoted 4K models,” said David Hsieh, senior director of display research for IHS. “4K content and broadcasting availability is also on the rise, which is helping more TV buyers recognize the value of this feature. Meanwhile, LCD TV panel makers have continuously improved 4K panel yield, which has reduced costs and facilitated even more consumer adoption.”

In 2015, LCD panel makers are targeting 40 million 4K LCD TV panel shipments, which represent 17 percent of all LCD TV panel shipments. In addition to TVs, consumers are starting to enjoy the benefits of ultra-high-resolution content in their smartphones and other mobile devices. Meanwhile, the “TV everywhere” concept is increasing consumer desire for higher resolution screens in their mobile devices. The professional-monitor and public-display market are also increasingly adopting 4K displays.

Source: IHS

4K LCD TVs continue to be the largest segment of the 4K display market, but smartphones and OLED TVs will experience the strongest growth this year. In order to compete with LCD TV in the high-end segment, OLED TV makers are including 4K resolutions. As display technology is improving fine-pitch pixel designs and brightness transmittance, 4K displays will become more affordable for mobile devices. In fact, panel makers like Sharp and JDI have recently announced and exhibited 4K smartphone panels. 4K tablet-PC displays, using oxide (IGZO) and low temperature poly-silicon (LTPS) processes, are also in panel makers’ plans.

On the other hand, sub-pixel rendering (SPR) technology will become an important way for panel makers to enhance 4K pixel design in their displays. For many years now, various versions of SPR have been used in the commercial production of AMOLED and LCD displays. Essentially they use two sub-pixels per white pixel, to offer a similar perceived resolution as conventional three-color red-green-blue (RGB) displays.

“The main benefits of SPR include fewer sub-pixels, higher transmission and lower power consumption,” Hsieh said. “SPR is an important element in the growth of the 4K display market.”

The IHS Quarterly Worldwide FPD Shipment and Forecast Report covers worldwide shipments and forecasts for all major flat panel display applications, including detail from over 140 flat-panel display (FPD) producers, covering more than 10 countries. The report analyzes historical shipments and forecast projections, which provide some of the most detailed information and insights available.

Applied Materials today announced the Applied Centura Tetra Z Photomask Etch system for etching next-generation optical lithographic photomasks needed by the industry to continue multiple patterning scaling to the 10nm node and beyond. The new tool extends the capabilities of Applied’s Tetra platform, delivering angstrom-level photomask accuracy for critical dimension (CD) parameters required to meet stringent patterning specifications for future logic and memory devices.

“Our Tetra Z system represents the state of the art in photomask etch technology, employing advances in precision materials engineering and plasma reaction kinetics to extend the use of 193nm lithography,” said Rao Yalamanchili, general manager of Applied’s Mask Etch product division. “Using the 193nm wavelength to produce 10nm or 7nm patterns requires a range of optimization techniques, including immersion and multiple patterning, which rely heavily on photomasks. Etch technology is key for photomask fabrication; the Tetra Z system is unique in delivering the accuracy required to etch next-generation optical photomasks for patterning advanced node designs.”

Applied developed the Tetra Z tool for advanced chrome, molybdenum silicon oxynitride (MoSi), hard mask and quartz (fused silica) etch applications used to fabricate advanced binary and phase-shift masks (PSMs). Offering continuous technical innovations and unprecedented CD performance, the system extends immersion lithography for quadruple patterning and cutting-edge resolution enhancement techniques. Vital capabilities ensuring pattern transfer fidelity include uniform, linear precision etching across all feature sizes and pattern densities with virtually zero defectivity.

Excellent CD performance combined with high etch selectivity enable the use of thinner resist films for achieving smaller photomask CD patterns on critical device layers. Controllable CD bias capability expands the system’s flexibility to meet customer specific requirements. Unique quartz etch depth control ensures precision phase angle and aids integrated circuit scaling by providing customers the capability to use alternating aperture PSMs and chromeless phase lithography. These key advances derive from a variety of system improvements in chamber design, plasma stability, ion and radical control, flow and pressure control, and real-time process monitoring and control.

Applied’s Tetra systems have been selected by a majority of mask makers worldwide to etch high-end photomasks over the past decade.

Applied Materials, Inc. is a developer of precision materials engineering solutions for the semiconductor, flat panel display and solar photovoltaic industries.

centura tetra z

Achieving precise registration accuracy is a factor of two related variables: web tension and transport velocity.

BY BIPIN SEN, Bosch Rexroth, Hoffman Estates, IL

One of the brightest developments in electronics is Organic Light Emitting Diode (OLED) TVs, which are attracting consumers with their eye-popping colors and super- thin designs. Unlike the components found in traditional flat-screen display technology, OLEDs use thin, flexible sheets of material that emit their own light and are produced using a technique similar to inkjet or sheet-feed printing.

Introduced to the consumer market only a few years ago, OLEDs are still relatively costly to manufacture in large sizes due to limitations in both shadow-mask deposition methods, and in newer laser annealing and inkjet printing techniques. To scale up large area display production economically, printed electronics manufacturers are seeing the benefits of another production method — namely, digital roll-to-roll web processing.

Like an inkjet printer deposits ink on sheets of paper, a digital roll-to-roll press patterns thin-film transistors and other devices directly onto large organic, flexible substrates. But unlike slower sheet-fed digital printing, the substrate in a roll-to-roll press is supplied from an infeed reel through the printing section onto an outfeed reel in one continuous inline web. An array of piezo- electric printheads deposit the ink — comprised of a conductive organic solution — on the substrate at precise locations. In roll-to-roll web processing, electroluminescent materials or other microcrys- talline layers are deposited on substrate at slower speeds, on the order of 10 to 100 feet (3 to 30 meters) per minute.

The speed of the roll-to-roll process reduces the cost of fabrication dramatically—but several challenges must be overcome to make it pay off.

Fast speeds create big challenges

Similar to how Sunday newspaper comics require precise color registration to keep images from blurring, printed electronics require far tighter registration. Tolerances for applications such as Thin-Film Transistors (TFTs) or OLEDs require registration smaller than 10 microns. High-speed, high-resolution cameras measure registration accuracy and provide input to the control system. To ensure that degree of accuracy, precise web tension control is required.

Achieving precise registration accuracy is a factor of two related variables: web tension and transport velocity.

Web transport control ensures proper uniform tension on the substrate web as it travels through the process. Because the substrate changes properties in response to force loading, changes in tension affect the stability of deposited materials. Substrate expansion causes cracks, broken traces, short circuiting and layer delamination. Changes in web velocity in the print zone affect registration, thickness and resolution of fine lines.

As the web travels downstream, constant tension must be maintained in each tension zone, which
is defined as an isolated area in a machine where constant tension must be maintained appropriate to the process being performed in that area. A roll- to-roll press has several tension zones. Problems occur when a change is made in one tension zone and no change is needed in other areas. When tension control is coupled between all zones, a change in one creates a cascade of changes in others, impacting the stability of the entire web.

FIGURE 1 shows how instability affects a web traveling at five meters per second with two successive tension controllers for two tension zones. A command for a step change tension reduction is sent to the green zone controllers.

FIGURE 1. Tension instability.

FIGURE 1. Tension instability.

No change is required in the upstream blue zone. But because the web is continuous, the tension disturbance is carried back to the blue zone, which causes the blue controller to compensate. In turn, this change affects the downstream green zone, sending jitter back to the blue zone. This back and forth jitter takes about 85 seconds to settle down. The web tension finally stabilizes in about 90 seconds. During that time, the machine is yielding waste product.

The challenge of tension adjustment

In an ideal world, web instability would never occur because tension adjustment would never be needed. But tension adjustment is necessary due to several mechanical factors:

  • Oscillations caused by mechanical misalignments
  • Differing inertial response (lag) of mechanical elements during web acceleration
  • Out-of-round unwind and tension rolls
  • Slipping through nip rolls
  • Over aggressive web-guide correction

Several technical process and control issues also affect tension: tension set point changes, phase offset on driven rolls, tension bleed from one zone to another, and, of course, thermal effect (contraction/expansion) as the substrate passes through various processes.

The factors requiring tension adjustment cannot all be eliminated. Variance in any one factor in a zone necessitates changes in tension control and web speed. Consequently, with coupled tension zone control, jitter is inevitable in a continuous web where the controllers cause a feedback loop.

The benefits of decoupled controllers

There is a solution: Decouple each tension zone, allowing each controller to operate independently.
This has been accomplished in digital printing applications using Bosch Rexroth controllers incor- porating a unique tension decoupling function block. As the name implies, the function block allows tension control for each zone to operate independently. As a result, tension changes can be isolated in one zone without affecting tension change in other areas.

The result can be seen in FIGURE 2. In this example, the press uses two successive controllers. But now the step change signaled by the green section controller doesn’t create a cascade effect upstream. Along with decoupling to prevent feedback, the Rexroth controller initiates a response to step reduction in tension control in one-fourth the time compared to typical controllers.

FIGURE 2. Improved tension control.

FIGURE 2. Improved tension control.

With the Rexroth solution, tension can be controlled for up to eight axes. One or multiple points can be selected to be left uncontrolled. At the selected axis, line speed is held constant. At a standstill, web tension can be maintained. In fact, Rexroth multi-axis tension control increases stand-still web tension accuracy by a factor of two to four. Achieving the desired standstill web tension is also much faster. Without decoupling, a setpoint can be achieved in 13-14 seconds; with decoupling, it takes three to four seconds.

During acceleration, tension control decoupling ensures the web is stable as soon as full production speed is reached, compared to a delay of five seconds or longer with coupled control. And when tension setpoint changes occur during runtime, the transient response with decoupling takes about one second, compared to about four seconds with coupled control.

Not unlike digital printing, the adoption of roll-to-roll web printing will accelerate as the technology demonstrates its ability to provide high accuracy at high speeds.