Category Archives: Process Materials

Technology trends in backplane technology are driving higher gas demand in display manufacturing. Specific gas requirements of process blocks are discussed, and various supply modes are reviewed.

BY EDDIE LEE, Linde Electronics, Hsinchu, Taiwan

Since its initial communalization in the 1990s, active matrix thin-film-transistor (TFT) displays have become an essential and indispensable part of modern living. They are much more than just televisions and smartphones; they are the primary communication and information portals for our day-to- day life: watches (wearables), appliances, advertising, signage, automobiles and more.

There are many similarities in the display TFT manufacturing and semiconductor device manufacturing such as the process steps (deposition, etch, cleaning, and doping), the type of gases used in these steps, and the fact that both display and semiconductor manufacturing both heavily use gases.

However, there are technology drivers and manufacturing challenges that differentiate the two. For semiconductor device manufacturing, there are technology limitations in making the device increasingly smaller. For display manufacturing, the challenge is primarily maintaining the uniformity of glass as consumers drive the demand for larger and thinner displays.

While semiconductor wafer size has maxed because of the challenges of making smaller features uniformly across the surface of the wafer, the size of the display mother glass has grown from 0.1m x 0.1m with 1.1mm thickness to 3m x 3m with 0.5mm thickness over the past 20 years due to consumer demands for larger, lighter, and more cost-effective devices.

As the display mother glass area gets bigger and bigger,so does the equipment used in the display manufacturing process and the volume of gases required. In addition, the consumer’s desire for a better viewing experience such as more vivid color, higher resolution, and lower power consumption has also driven display manufacturers to develop and commercialize active matrix organic light emitting displays (AMOLED).

Technology

Layers of display device

In general, there are two types of displays in the market today: active matrix liquid crystal display (AMLCD) and AMOLED. In its simplicity, the fundamental components required to make up the display are the same for AMLCD and AMOLED. There are four layers of a display device (FIGURE 1): a light source, switches that are the thin-film-transistor and where the gases are mainly used, a shutter to control the color selection, and the RGB (red, green, blue) color filter.

About backplane/TFT

The thin-film-transistors used for display are 2D transitional transistors, which are similar to bulk CMOS before FinFET. For the active matrix display, there is one transistor for each pixel to drive the individual RGB within the pixel. As the resolution of the display grows, the transistor size also reduces, but not to the sub-micron scale of semiconductor devices. For the 325 PPI density, the transistor size is approximately 0.0001 mm2 and for the 4K TV with 80 PPI density, the transistor size is approximately 0.001 mm2.

Technology trends TFT-LCD (thin-film-transistor liquid-crystal display) is the baseline technology. MO / White OLED (organic light emitting diode) is used for larger screens. LTPS / AMOLED is used for small / medium screens. The challenges for OLED are the effect of < 1 micron particles on yield, much higher cost compared to a-Si due to increased mask steps, and moisture impact to yield for the OLED step.

Mobility limitation (FIGURE 2) is one of the key reasons for the shift to MO and LTPS to enable better viewing experience from higher resolution, etc.

The challenge to MO is the oxidation after IGZO metalization / moisture prevention after OLED step, which decreases yield. A large volume of N2O (nitrous oxide) is required for manufacturing, which means a shift in the traditional supply mode might need to be considered.

Although AMLCD displays are still dominant in the market today, AMOLED displays are growing quickly. Currently about 25% of smartphones are made with AMOLED displays and this is expected to grow to ~40% by 2021. OLED televisions are also growing rapidly, enjoying double digit growth rate year over year. Based on IHS data, the revenue for display panels with AMOLED technol- ogies is expected to have a CAGR of 18.9% in the next five years while the AMLCD display revenue will have a -2.8% CAGR for the same period with the total display panel revenue CAGR of 2.5%. With the rapid growth of AMOLED display panels, the panel makers have accel- erated their investment in the equipment to produce AMOLED panels.

Types of backplanes

There are three types of thin-film-transistor devices for display: amorphous silicon (a-Si), low temperature polysilicon (LTPS), and metal oxide (MO), also known as transparent amorphous oxide semiconductor (TAOS). AMLCD panels typically use a-Si for lower-resolution displays and TVs while high-resolution displays use LTPS transistors, but this use is mainly limited to small and medium displays due to its higher costs and scalability limitations. AMOLED panels use LTPS and MO transistors where MO devices are typically used for TV and large displays (FIGURE 3).

How gases are used

This shift in technology also requires a change in the gases used in production of AMOLED panels as compared with the AMLCD panels. As shown in FIGURE 4, display manufacturing today uses a wide variety of gases.

These gases can be categorized into two types: Electronic Specialty gases (ESGs) and Electronic Bulk gases (EBGs) (FIGURE 5). Electronic Specialty gases such as silane, nitrogen trifluoride, fluorine (on-site generation), sulfur hexafluoride, ammonia, and phosphine mixtures make up 52% of the gases used in the manufacture of the displays while the Electronic Bulk gases–nitrogen, hydrogen, helium, oxygen, carbon dioxide, and argon – make up the remaining 48% of the gases used in the display manufacturing.

Key usage drivers

The key ga susage driver in the manufacturing of displays is PECVD (plasma-enhanced chemical vapor deposition), which accounts for 75% of the ESG spending, while dry etch is driving helium usage. LTPS and MO transistor production is driving nitrous oxide usage. The ESG usage for MO transistor production differs from what is shown in FIGURE 4: nitrous oxide makes up 63% of gas spend, nitrogen trifluoride 26%, silane 7%, and sulfur hexafluoride and ammonia together around 4%. Laser gases are used not only for lithography, but also for excimer laser annealing application in LTPS.

Silane: SiH4 is one of the most critical molecules in display manufacturing. It is used in conjunction with ammonia (NH3) to create the silicon nitride layer for a-Si transistor, with nitrogen (N2) to form the pre excimer laser anneal a-Si for the LTPS transistor, or with nitrous oxide (N2O) to form the silicon oxide layer of MO transistor.

Nitrogen trifluoride: NF3 is the single largest electronic material from spend and volume standpoint for a-Si and LTPS display production while being surpassed by N2O for MO production. NF3 is used for cleaning the PECVD chambers. This gas requires scalability to get the cost advantage necessary for the highly competitive market.

Nitrous oxide: Used in both LTPS and MO display production, N2O has surpassed NF3 to become the largest electronic material from spend and volume standpoint for MO production. N2O is a regional and localized product due to its low cost, making long supply chains with high logistic costs unfeasible. Averaging approximately 2 kg per 5.5 m2 of mother glass area, it requires around 240 tons per month for a typical 120K per month capacity generation 8.5 MO display production. The largest N2O compressed gas trailer can only deliver six tons of N2O each time and thus it becomes both costly and risky
for MO production.

Nitrogen: For a typical large display fab, N2 demand can be as high as 50,000 Nm3/hour, so an on-site generator, such as the Linde SPECTRA-N® 50,000, is a cost-effective solution that has the added benefit of an 8% reduction in CO2 (carbon dioxide) footprint over conventional nitrogen plants.

Helium: H2 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.

Gas distribution at the fab

N2 On-site generators: Nitrogen is the largest consumed gas at the fab, and is required to be available before the first tools are brought to the fab. Like major semiconductor fabs, large display fabs require very large amounts of nitrogen, which can only be economically supplied by on-site plants.

Cryogenic liquid truck trailers: Oxygen, argon, and carbon dioxide are produced at off-site plants and trucked short distances as cryogenic liquids in specialty vacuum-insulated tankers.
Compressed gas truck trailers: Other large volume gases like hydrogen and helium are supplied over longer distances in truck or ISO-sized tanks as compressed gases.

Individual packages: Specialty gases are supplied in individual packages. For higher volume materials like silane and nitrogen trifluoride, these can be supplied in large ISO packages holding up to 10 tons. Materials with smaller requirements are packaged in standard gas cylinders.

Blended gases: Laser gases and dopants are supplied as blends of several different gases. Both the accuracy and precision of the blended products are important to maintain the display device fabrication operating within acceptable parameters.

In-fab distribution: Gas supply does not end with the delivery or production of the material of the fab. Rather, the materials are further regulated with additional filtration, purification, and on-line analysis before delivery to individual production tools.

Conclusion

The consumer demand for displays that offer increas- ingly vivid color, higher resolution, and lower power consumption will challenge display makers to step up the technologies they employ and to develop newer displays such as flexible and transparent displays. The transistors to support these new displays will either be LTPS and / or MO, which means the gases currently being used in these processes will continue to grow. Considering the current a-Si display production, the gas consumption per area of the glass will increase by 25% for LTPS and ~ 50% for MO productions.

To facilitate these increasing demands, display manufacturers must partner with gas suppliers to identify which can meet their technology needs, 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. This is particularly true for the burgeoning China display manufacturing market, which will benefit from investing in on-site bulk gas plants and collaboration with global materials suppliers with local production facilities for high-purity gas and chemical manufacturing.

Technavio projects the global semiconductor glass wafer market to post a CAGR of more than 6% during the forecast period. The emergence of advanced and compact consumer electronic devices is a key driver, which is expected to impact market growth.

Consumer electronic devices have witnessed a massive transformation over the last five years. Feature phones have been replaced by smartphones, PCs by laptops, and now laptops are being replaced by tablets. Cathode ray tube (CRT) TVs are being replaced by light-emitting diode (LED) TVs and organic LED (OLED) TVs. Due to increase in unit shipments of tablets and smartphones over the last five years, the demand for ICs (including MEMS devices and CMOS image sensors) used in these devices is on the rise. As semiconductor glass wafers are integral to ICs, rising demand for ICs will generate strong demand for semiconductor glass wafers over the forecast period.

In this report, Technavio highlights the growing proliferation of IoT and connected devices as one of the key emerging trends to drive the global semiconductor glass wafer market:

Growing proliferation of IoT and connected devices

IoT is a network of interrelated computing devices comprising mechanical and digital machines or objects that possess the ability to transfer data over a network without human-to-computer interaction. More than 30 billion IoT devices, generating about 50 trillion GBs of data, are expected to be connected through IoT by 2022. IoT enables devices to collect data using sensors and actuators and transmits data to a centralized location on a real-time basis, which empowers the user to take an informed decision. Thus, the adoption of IoT is increasing in several market segments, such as consumer electronics, automotive, and medical.

According to a senior analyst at Technavio for semiconductor equipment research, “Sensors and MEMS are an integral part of IoT devices and are manufactured from semiconductor glass wafers. It is projected that a total of one trillion sensors will be produced in 2020 to support the demand for IoT devices. This will require a significant production of semiconductor glass wafers, which can be met by several fabs. Growing applications of IoT will drive the construction of fabs.”

Pure quartz glass is highly transparent and resistant to thermal, physical, and chemical impacts. These are optimum prerequisites for use in optics, data technology or medical engineering. For efficient, high-quality machining, however, adequate processes are lacking. Scientists of Karlsruhe Institute of Technology (KIT) have developed a forming technology to structure quartz glass like a polymer. This innovation is reported in the journal Advanced Materials.

“It has always been a big challenge to combine highly pure quartz glass and its excellent properties with a simple structuring technology,” says Dr. Bastian E. Rapp, Head of the NeptunLab interdisciplinary research group of KIT’s Institute of Microstructure Technology (IMT). Rapp and his team develop new processes for industrial glass processing. “Instead of heating glass up to 800 °C for forming or structuring parts of glass blocks by laser processing or etching, we start with the smallest glass particles,” says the mechanical engineer. The scientists mix glass particles of 40 nanometers in size with a liquid polymer, form the mix like a sponge cake, and harden it to a solid by heating or light exposure. The resulting solid consists of glass particles in a matrix at a ratio of 60 to 40 vol%. The polymers act like a bonding agent that retains the glass particles at the right locations and, hence, maintains the shape.

This “Glassomer” can be milled, turned, laser-machined or processed in CNC machines just like a conventional polymer. “The entire range of polymer forming technologies is now opened for glass,” Rapp emphasizes. For fabricating high-performance lenses that are used in smartphones among others, the scientists produce a Glassomer rod, from which the lenses are cut. For highly pure quartz glass, the polymers in the composite have to be removed. For doing so, the lenses are heated in a furnace at 500 to 600 °C and the polymer is burned fully to CO2. To close the resulting gaps in the material, the lenses are sintered at 1300 °C. During this process, the remaining glass particles are densified to pore-free glass.

This forming technology enables production of highly pure glass materials for any applications, for which only polymers have been suited so far. This opens up new opportunities for the glass processing industry as well as for the optical industry, microelectronics, biotechnology, and medical engineering. “Our process is suited for mass production. Production and use of quartz glass are much cheaper, more sustainable, and more energy-efficient than those of a special polymer,” Rapp explains.

This is the third innovation for the processing of quartz glass that has been developed by NeptunLab on the basis of a liquid glass-polymer mixture. In 2016, the scientists already succeeded in using this mixture for molding. In 2017, they applied the mixture for 3D printing and demonstrate its suitability for additive manufacture. Within the framework of the “NanomatFutur” competition for early-stage researchers, the team was funded with EUR 2.8 million by the Federal Ministry of Education and Research from 2014 to 2018. A spinoff now plans to commercialize Glassomer.

A Columbia University-led international team of researchers has developed a technique to manipulate the electrical conductivity of graphene with compression, bringing the material one step closer to being a viable semiconductor for use in today’s electronic devices.

By compressing layers of boron nitride and graphene, researchers were able to enhance the material's band gap, bringing it one step closer to being a viable semiconductor for use in today's electronic devices. Credit: Philip Krantz

By compressing layers of boron nitride and graphene, researchers were able to enhance the material’s band gap, bringing it one step closer to being a viable semiconductor for use in today’s electronic devices. Credit: Philip Krantz

“Graphene is the best electrical conductor that we know of on Earth,” said Matthew Yankowitz, a postdoctoral research scientist in Columbia’s physics department and first author on the study. “The problem is that it’s too good at conducting electricity, and we don’t know how to stop it effectively. Our work establishes for the first time a route to realizing a technologically relevant band gap in graphene without compromising its quality. Additionally, if applied to other interesting combinations of 2D materials, the technique we used may lead to new emergent phenomena, such as magnetism, superconductivity, and more.”

The study, funded by the National Science Foundation and the David and Lucille Packard Foundation, appears in the May 17 issue of Nature.

The unusual electronic properties of graphene, a two-dimensional (2D) material comprised of hexagonally-bonded carbon atoms, have excited the physics community since its discovery more than a decade ago. Graphene is the strongest, thinnest material known to exist. It also happens to be a superior conductor of electricity – the unique atomic arrangement of the carbon atoms in graphene allows its electrons to easily travel at extremely high velocity without the significant chance of scattering, saving precious energy typically lost in other conductors.

But turning off the transmission of electrons through the material without altering or sacrificing the favorable qualities of graphene has proven unsuccessful to-date.

“One of the grand goals in graphene research is to figure out a way to keep all the good things about graphene but also create a band gap – an electrical on-off switch,” said Cory Dean, assistant professor of physics at Columbia University and the study’s principal investigator. He explained that past efforts to modify graphene to create such a band gap have degraded the intrinsically good properties of graphene, rendering it much less useful. One superstructure does show promise, however. When graphene is sandwiched between layers of boron nitride (BN), an atomically-thin electrical insulator, and the two materials are rotationally aligned, the BN has been shown to modify the electronic structure of the graphene, creating a band gap that allows the material to behave as a semiconductor – that is, both as an electrical conductor and an insulator. The band gap created by this layering alone, however, is not large enough to be useful in the operation of electrical transistor devices at room temperature.

In an effort to enhance this band gap, Yankowitz, Dean, and their colleagues at the National High Magnetic Field Laboratory, the University of Seoul in Korea, and the National University of Singapore, compressed the layers of the BN-graphene structure and found that applying pressure substantially increased the size of the band gap, more effectively blocking the flow of electricity through the graphene.

“As we squeeze and apply pressure, the band gap grows,” Yankowitz said. “It’s still not a big enough gap – a strong enough switch – to be used in transistor devices at room temperature, but we have gained a fundamentally better understanding of why this band gap exists in the first place, how it can be tuned, and how we may target it in the future. Transistors are ubiquitous in our modern electronic devices, so if we can find a way to use graphene as a transistor it would have widespread applications.”

Yankowitz added that scientists have been conducting experiments at high pressures in conventional three-dimensional materials for years, but no one had yet figured out a way to do them with 2D materials. Now, researchers will be able to test how applying various degrees of pressure changes the properties of a vast range of combinations of stacked 2D materials.

“Any emergent property that results from the combination of 2D materials should grow stronger as the materials are compressed,” Yankowitz said. “We can take any of these arbitrary structures now and squeeze them and the strength of the resulting effect is tunable. We’ve added a new experimental tool to the toolbox we use to manipulate 2D materials and that tool opens boundless possibilities for creating devices with designer properties.”

Vladimir Mostepanenko, Chief Research Associate of KFU Cosmology Lab and Pulkovo Astronomical Observatory, explains, “Despite graphene layers’ extremely small width, it has proven to be a firm material which conducts electricity even under zero temperatures when density of charge carriers also equals zero. But something absolutely unexpected was that this residual conductivity can be expressed through fundamental physical constants – electron charge and Planck constant. Graphene has been used successfully in dozens of electronic devices and has been found in interstellar matter.”

Graphene’s unusual qualities led to speculation that the causality principle may not be observed for it. The authors, Vladimir Mostepanenko and Galina Klimchitskaya, proved that the principle is preserved for graphene. Through the direct analytic calculation it was shown that the real and imaginary parts of graphene conductivity, found recently on the basis of first principles of thermal quantum field theory using the polarization tensor in (2+1)-dimensional space-time, satisfy the Kramers-Kronig relations precisely.

The results are important for further inquiries into reflective and absorptive qualities of graphene.

Researchers at Queen Mary University of London, University of Cambridge and Max Planck Institute for Solid State Research have discovered how a pinch of salt can be used to drastically improve the performance of batteries.

They found that adding salt to the inside of a supermolecular sponge and then baking it at a high temperature transformed the sponge into a carbon-based structure.

Surprisingly, the salt reacted with the sponge in special ways and turned it from a homogeneous mass to an intricate structure with fibres, struts, pillars and webs. This kind of 3D hierarchically organised carbon structure has proven very difficult to grow in a laboratory but is crucial in providing unimpeded ion transport to active sites in a battery.

In the study, published in JACS (Journal of the American Chemical Society), the researchers demonstrate that the use of these materials in Lithium-ion batteries not only enables the batteries to be charged-up rapidly, but also at one of the highest capacities.

Due to their intricate architecture the researchers have termed these structures ‘nano-diatoms’, and believe they could also be used in energy storage and conversion, for example as electrocatalysts for hydrogen production.

Lead author and project leader Dr Stoyan Smoukov, from Queen Mary’s School of Engineering and Materials Science, said: “This metamorphosis only happens when we heat the compounds to 800 degrees centigrade and was as unexpected as hatching fire-born dragons instead of getting baked eggs in the Game of Thrones. It is very satisfying that after the initial surprise, we have also discovered how to control the transformations with chemical composition.”

Carbon, including graphene and carbon nanotubes, is a family of the most versatile materials in nature, used in catalysis and electronics because of its conductivity and chemical and thermal stability.

3D carbon-based nanostructures with multiple levels of hierarchy not only can retain useful physical properties like good electronic conductivity but also can have unique properties. These 3D carbon-based materials can exhibit improved wettability (to facilitate ion infiltration), high strength per unit weight, and directional pathways for fluid transport.

It is, however, very challenging to make carbon-based multilevel hierarchical structures, particularly via simple chemical routes, yet these structures would be useful if such materials are to be made in large quantities for industry.

The supermolecular sponge used in the study is also known as a metal organic framework (MOF) material. These MOFs are attractive, molecularly designed porous materials with many promising applications such as gas storage and separation. The retention of high surface area after carbonisation – or baking at a high temperature – makes them interesting as electrode materials for batteries. However, so far carbonising MOFs has preserved the structure of the initial particles like that of a dense carbon foam. By adding salts to these MOF sponges and carbonising them, the researchers discovered a series of carbon-based materials with multiple levels of hierarchy.

Dr R. Vasant Kumar, a collaborator on the study from University of Cambridge, commented: “This work pushes the use of the MOFs to a new level. The strategy for structuring carbon materials could be important not only in energy storage but also in energy conversion, and sensing.”

Lead author, Tiesheng Wang, from University of Cambridge, said: “Potentially, we could design nano-diatoms with desired structures and active sites incorporated in the carbon as there are thousands of MOFs and salts for us to select.”

University of Waterloo chemists have found a much faster and more efficient way to store and process information by expanding the limitations of how the flow of electricity can be used and managed.

In a recently released study, the chemists discovered that light can induce magnetization in certain semiconductors – the standard class of materials at the heart of all computing devices today.

“These results could allow for a fundamentally new way to process, transfer, and store information by electronic devices, that is much faster and more efficient than conventional electronics.”

For decades, computer chips have been shrinking thanks to a steady stream of technological improvements in processing density. Experts have, however, been warning that we’ll soon reach the end of the trend known as Moore’s Law, in which the number of transistors per square inch on integrated circuits double every year.

“Simply put, there’s a physical limit to the performance of conventional semiconductors as well as how dense you can build a chip,” said Pavle Radovanovic, a professor of chemistry and a member of the Waterloo Institute for Nanotechnology. “In order to continue improving chip performance, you would either need to change the material transistors are made of – from silicon, say to carbon nanotubes or graphene – or change how our current materials store and process information.”

Radovanovic’s finding is made possible by magnetism and a field called spintronics, which proposes to store binary information within an electron’s spin direction, in addition to its charge and plasmonics, which studies collective oscillations of elements in a material.

“We’ve basically magnetized individual semiconducting nanocrystals (tiny particles nearly 10,000 times smaller than the width of a human hair) with light at room temperature,” said Radovanovic. “It’s the first time someone’s been able to use collective motion of electrons, known as plasmon, to induce a stable magnetization within such a non-magnetic semiconductor material.”

In manipulating plasmon in doped indium oxide nanocrystals Radovanovic’s findings proves that the magnetic and semiconducting properties can indeed be coupled, all without needing ultra-low temperatures (cryogens) to operate a device.

He anticipates the findings could initially lead to highly sensitive magneto-optical sensors for thermal imaging and chemical sensing. In the future, he hopes to extend this approach to quantum sensing, data storage, and quantum information processing.

Air Liquide Advanced Materials, Inc. (ALAM) has been chosen by the New Jersey chapter of the Association for Corporate Growth as an honoree for the 2018 Corporate Growth Awards.

The ACG NJ Corporate Growth Awards were established in 2015 and honor companies that exemplify sustained innovation, excellence and corporate growth. ALAM has been a strong presence in the New Jersey business community since 2013 when it acquired Voltaix, a Branchburg, NJ-based electronics materials company founded in 1986. As the leading manufacturer of speciality chemicals in the semiconductor industry, ALAM is committed to continued long-term growth and engagement with the communities in which it operates.

ALAM is one of five New Jersey companies to receive the distinction at the ACG NJ Corporate Growth Conference and Awards on May 8, 2018 at The Palace at Somerset Park, NJ for a half-day event including a CEO panel discussion and awards ceremony.

Paul Burlingame, Air Liquide Advanced Materials, Inc. President & CEO said, “We are proud to receive the 2018 ACG NJ Corporate Growth Award in recognition of the innovation, operational agility, and customer focus exhibited by Air Liquide Advanced Materials employees every day. As a result of these efforts Air Liquide Advanced Materials remains committed to continued growth fueled by new products, collaborations and markets.”

In the wake of its recent discovery of a flat form of gallium, an international team led by scientists from Rice University has created another two-dimensional material that the researchers said could be a game changer for solar fuel generation. Rice materials scientist Pulickel Ajayan and colleagues extracted 3-atom-thick hematene from common iron ore. The research was introduced in a paper today in Nature Nanotechnology.

Hematene may be an efficient photocatalyst, especially for splitting water into hydrogen and oxygen, and could also serve as an ultrathin magnetic material for spintronic-based devices, the researchers said.

“2D magnetism is becoming a very exciting field with recent advances in synthesizing such materials, but the synthesis techniques are complex and the materials’ stability is limited,” Ajayan said. “Here, we have a simple, scalable method, and the hematene structure should be environmentally stable.”

Ajayan’s lab worked with researchers at the University of Houston and in India, Brazil, Germany and elsewhere to exfoliate the material from naturally occurring hematite using a combination of sonication, centrifugation and vacuum-assisted filtration.

Hematite was already known to have photocatalytic properties, but they are not good enough to be useful, the researchers said.

“For a material to be an efficient photocatalyst, it should absorb the visible part of sunlight, generate electrical charges and transport them to the surface of the material to carry out the desired reaction,” said Oomman Varghese, a co-author and associate professor of physics at the University of Houston.

“Hematite absorbs sunlight from ultraviolet to the yellow-orange region, but the charges produced are very short-lived. As a result, they become extinct before they reach the surface,” he said.

Hematene photocatalysis is more efficient because photons generate negative and positive charges within a few atoms of the surface, the researchers said. By pairing the new material with titanium dioxide nanotube arrays, which provide an easy pathway for electrons to leave the hematene, the scientists found they could allow more visible light to be absorbed.

The researchers also discovered that hematene’s magnetic properties differ from those of hematite. While native hematite is antiferromagnetic, tests showed that hematene is ferromagnetic, like a common magnet. In ferromagnets, atoms’ magnetic moments point in the same direction. In antiferromagnets, the moments in adjacent atoms alternate.

Unlike carbon and its 2D form, graphene, hematite is a non-van der Waals material, meaning it’s held together by 3D bonding networks rather than non-chemical and comparatively weaker atomic van der Waals interactions.

“Most 2D materials to date have been derived from bulk counterparts that are layered in nature and generally known as van der Waals solids,” said co-author Professor Anantharaman Malie Madom Ramaswamy Iyer of the Cochin University of Science and Technology, India. “2D materials from bulk precursors having (non-van der Waals) 3D bonding networks are rare, and in this context hematene assumes great significance.”

According to co-author Chandra Sekhar Tiwary, a former postdoctoral researcher at Rice and now an assistant professor at the Indian Institute of Technology, Gandhinagar, the collaborators are exploring other non-van der Waals materials for their 2D potential.

 The 2018 Critical Materials Council (CMC) Conference—held April 26-27 at the Hilton Chandler in Arizona— was a great gathering with presentations from Everspin, Intel, GlobalFoundries, and NXP discussing current fab challenges, and the relationships to near-term materials solutions. Held immediately following private CMC face-to-face meeting, this public event enabled targeted discussions on problems, opportunities, and issues in the present and future materials market.

Session 1 presentations from Keller&Heckman, KPMG, Semico, VLSI Research, and the United States’ Environmental Protection Agency reminded attendees of the many environmental, financial, and political factors impacting global fab supply-chains. Jeff Morris, the US EPA’s Director of the Office of Pollution Prevention and Toxics, reviewed the status of enforcement of the Toxic Substances Control Act (TSCA) with a focus on N-Methylpyrrolidone (NMP), per- and poly-fluorinated Substances (PFAS, PFOS, PFOA), and Photo-Acid Generators (PAG) used in semiconductor manufacturing.

Session 2 covering materials issues in fabs today explored the evolving specifications needed in silicon wafers, ion-implantation, noble gases, and metal depositions including atomic-layer (ALD) chemical-vapor (CVD) physical-vapor (PVD) and electro-chemical (ECD). The Figure shows 200mm-diameter silicon wafer global supply and manufacturing demand from 2015 to 2020, as modeled by TECHCET President and CEO Lita Shon-Roy in her presentation on materials markets. TECHCET expects that this year will see a balancing and then an excess of supply in this wafer size used for manufacturing Opto-electronics, Sensors, and Discretes (OSD) along with Radio Frequency (RF) communications chips.

The presentations on cobalt processing from Air Liquide, Applied Materials, Fraunhofer, and Fujimi—mostly in Session 3—provided fantastic perspectives on solutions to inherent integration challenges with this metal. Cobalt has been used as a barrier or a liner for on-chip copper interconnect lines for many years, but the material is now being integrated as the entire interconnect material for the smallest metal lines in the most aggressively scaled IC structures. Nicolas Blasco of Air Liquide discussed the complex path to discovering novel ALD precursors, while Michelle Garza of Fujimi discussed ways to manage the complexity of developing new Chemical-Mechanical Planarization (CMP) slurries for application-specific cobalt integration.

Senior Analyst with TECHCET Ed Korczynski presented an update on the latest lithography materials to enable patterning the smallest possible commercial IC devices, including recently disclosed Self-Aligned Multi-Patterning (SAMP) technology options to improve IC yields. Cost models for different multi-patterning process flows were recently presented at the 2018 SPIE Advanced Lithography conference showing how Extreme Ultra-Violet (EUV) lithography can be cost-effective despite double the tool costs. Key to cost-effective use of EUV will be control of stochastic yield losses which are colloquially termed “Black Swans”.

The Wednesday night reception and the Thursday night break-out roundtable discussions gave everyone time to make new connections and have discrete discussions on metrology, specifications, and technology integration. Block your calendar in 2019 for the 4th annual CMC Conference, tentatively scheduled for April 25-26 in the US. www.cmcfabs.org www.techcet.com

ABOUT CMC: The Critical Materials Council (CMC) of Semiconductor Fabricators (CMCFabs.org) is a membership-based organization that works to anticipate and solve critical materials issues in a pre-competitive environment. The CMC is a unit of TECHCET.

ABOUT TECHCET: TECHCET CA LLC is an advisory service firm focused on process materials supply chains, electronic materials technology, and materials market analysis for the semiconductor, display, solar/PV, and LED industries. Since 2000, the company has been responsible for producing the SEMATECH Critical Material Reports, covering silicon wafers, semiconductor gases, wet chemicals, CMP consumables, Photoresists, and ALD/CVD Precursors. For additional information about these reports or about CMC Fabs membership or associate-membership for suppliers please contact Diane Scott at [email protected]  +1-480-332-8336, or go to www.techcet.com or www.cmcfabs.org.