Apr 7, 2016 - A Newsletter from Oxford Instruments Plasma Technology. Follow us on. ..... Technology 2016 training cours
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PROCESSNEWS
A Newsletter from Oxford Instruments Plasma Technology
Follow us on...
IN THIS ISSUE: Providing leading edge tools and processes to key markets worldwide
2 Two dimensional materials and heterostructures
Optoelectronics Nanotechnology Discrete Devices Sensors
4 Collaboration proves a ‘win-win’ for TU/e and Oxford Instruments
3 Low temperature plasma assisted ALD of conductive films
6 PlasmaPro® systems bought for Chinese LED Manufacture 7 Training: buy one get one half price 8 The Application of Bosch™ Deep Silicon Etch to the Manufacture of X-Ray Lenses 10 Micromachining silicon structures on thin membranes using plasma etching 12 Power device development enabled through University of Glasgow collaboration 13 Energy savings win us a ‘Go Green’ award 13 Record numbers attend 4th BTNT seminar in Chennai, India 14 New etching process for Magnetic RAM developed by Cornell and Oxford Instruments 16 Watch our informative webinars
www.oxford-instruments.com/plasma PROCESSNEWS 1
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Two dimensional materials and heterostructures
Low temperature plasmaassisted ALD of conductive films
Dr Ravi Sundaram, Oxford Instruments Plasma Technology
Harm Knoops, Thomas Sharp, Annika Peter, Owain Thomas, and Robert Gunn, Oxford Instruments
Vapour deposition techniques have gained a lot of interest for growth of two dimensional (2D) materials1-4. The ability to grow large area graphene has spurred research into vapour deposition of a wide variety of atomically thin layered materials.
Many applications have a limited thermal budget for processing, especially when organic materials are involved or diffusion of elements has to be minimized (e.g. dopants in electronic devices).
In the recent past there has been a growing interest in studying atomic planes of these Van der Waals solids and build 2D
The Oxford Instruments Nanofab® is ideal for this field of research as it combines several essential features for high performance 2D material deposition:
• High temperature (1200 ºC) table • Capable of handling up to 200 mm wafers • Shower head technology • Automatic load lock for wafer handling • Plasma enhancement via in chamber (parallel plate ) plasma
Since ALD relies on thermally activated reactions, ALD at low temperatures can be a challenge. A paper presented at the BALD 2015 conference in Tartu, Estonia discussed low temperature plasma-assisted ALD of conductive films where the ALD of TiN and ZnO in the Oxford Instruments FlexAL® remote plasma ALD system serve as case examples.
or remote plasma via ICP
Using a multistep ALD process as shown in Fig. 1, allows deposition of Pt at room
One of the key requirements for developing robust 2D
temperature by O2 plasma and H2 plasma in the cycle [Mackus et al., Chem. Mater.
materials deposition processes is the ability to efficiently
25, 1769 (2013)]. Similarly, this work showed that interleaving H² plasma in an ALD
technologies and processes for large area deposition of these
deliver liquid and solid state precursors in addition to
process for ZnO using ZnEt2 (DEZ) and O2 plasma, allows relatively low resistivity
materials need to be developed.
traditional gases. We offer flexible options for liquid/solid
values, i.e., 5.7 mΩcm for a ~45 nm film at temperatures of 100°C.
heterostructures by stacking layers with complementary characteristics to achieve novel functionality . For successful 5
scaling up of prototypical applications demonstrated to date,
Chemical Vapour Deposition (CVD) has been one of the most successful techniques for the large area fabrication of nanostructured materials such as graphene, carbon nanotubes
•
precursor delivery. Example:
MoCl5, Mo(CO)6, W(CO)6,
For deposition of metals and metal nitrides that are difficult to reduce from their
DTBSe, DETe etc)
oxide, exposure to oxygen should be avoided. To increase reactivity for ALD of those
• Multiple precursor pod options for depositing a combination
materials plasmas with higher ion energies can be used. Low-resistivity titanium nitride was obtained from the metal-organic precursor Ti(NMe2)4 (TDMAT) and mixed
of 2D materials
and other 1D/2D nanomaterials.
N2/H2 plasma at 200°C. Through precise control of the plasma conditions we were
We have demonstrated growth of monolayer graphene and related graphene-like allotropes using this system. Recently, we Nanofab with precursor delivery system.
have developed a thermal CVD route to synthesize hexagonal Boron Nitride (hBN) and we are currently investigating other 2D materials.
Current library of 2D materials investigated to date5.
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able to achieve a resistivity of 250 µΩ∙cm at 26nm thickness and even 180 µΩ∙cm for Examples of graphene and hBN growth.
a 74 nm film as shown in Fig. 2. TiN from TDMAT therefore offers a viable alternative for devices where chlorine-containing precursors risk device degradation. Control
References
of plasma properties and multistep ALD processes are expected to provide the best
[1]. Li, X et al. Large-area synthesis of high-quality and uniform graphene films on copper foils. Science 324, 1312-1314 (2009) [2] Bae, S. et al. Roll-to-roll production of 30-inch graphene films for transparent electrodes. Nat Nanotech. 5, 574 (2010) [3] Ismach, A. et al. Toward the Controlled Synthesis of Hexagonal Boron Nitride Films. ACS Nano, ,6, 6378 (2012) [4] Zhan, Y et al. Large-Area Vapor-Phase Growth and Characterization of MoS2 Atomic Layers on a SiO2 Substrate. Small, 8, 966 (2012). [5] Geim, A.K and Grigorieva, I.V., Van der Waals heterostructures, Nature, 499,419 (2013)
route to deposition of conductive films by ALD.
For further information on our toolset please email:
[email protected]
Figure 1. A schematic representation of the various steps in a multistep process. For low temperature ZnO ALD, B is an O2 plasma and C is an H2 plasma.
Figure 2. The film resistivity as a function of thickness for TiN deposited from TDMAT. Relatively low resistivity values are obtained for thicknesses above 20 nm.
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Collaboration proves a ‘win-win’ for TU/e and Oxford Instruments Sonja Knols, Eindhoven University of Technology
To be able to keep innovating its products, Oxford Instruments invests in close cooperation with academic research groups. One example is the Plasma and Materials Processing group of Eindhoven University and Technology.
low temperatures. “For CVD processes, typically temperatures
He immediately gives an example. “Some time ago, PhD
of over a 1000 degrees Celsius are needed. That is often fatal for
student Harald Profijt developed a method to manipulate the
applications in semiconductors because the high temperature
energy of the deposited atoms by applying an RF voltage on
increases the diffusion of the atoms, which makes it harder to
the substrate. Normally, in plasma assisted ALD, you need
place them at the right spot. We want to have a process that
the incoming ions to have as low an energy as possible. But
yields materials of high quality at lower temperatures. This is
sometimes, the process would improve if you were to increase
especially important for the two-dimensional heterogeneous
that energy a little, thereby increasing the mobility of the
“Our cleanroom facilities are vitally important for our research”
layers I am working on, since at lower temperatures less
atoms at the surface. So now we can offer that option to other
diffusion of atoms between the layers will occur.”
clients too.” Furthermore, Oxford profits from the extensive
says associate professor Ageeth Bol.
Two-way street
Ageeth Bol holds a PhD in physical chemistry and returned to academic research in 2011, after a decade of working in industry. “The presence of the cleanroom facilities here in Eindhoven certainly was a selling point for me in deciding where I wanted to go,” she says. Bol works on the development of new production processes for graphene-like, two-dimensional materials. “To be able to make these very thin layers of materials, you need to have nanometre control over the layer thickness. The Plasma and Materials Processing group I work in has in-depth knowledge of a specific method to produce these layers.” This so-called plasma-assisted atomic layer deposition (ALD) is a technique that makes use of gaseous phases of materials, which are alternately flushed onto a surface. Carefully picked precursor molecules react with specific molecular groups at the surface in a self-limiting way. “That is one of the advantages of ALD over chemical vapour deposition (CVD),” Bol explains. “With ALD, as soon as all the reactive sites are used, the reaction stops. This results in very thin and even layers.”
Replacing scotch tape The group Bol is working in, is interested in optimising these type of ALD processes for a variety of applications, such as thinfilm solar cells and new types of semiconductor devices. “My
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infrastructure in the cleanroom facility, he says. “At Oxford, we have a relatively small ALD lab. The university campus hosts a
Supplier Oxford Instruments is heavily involved in this type of
dedicated cleanroom with all kinds of diagnostic tooling. The
adjustments, she explains. “They help us in customising the
research done there on ALD-processes gives us insight into
machine for our specific needs. In fact, one of their employees
what is happening inside the reactors during the deposition.”
personal focus lies in the usage for two-dimensional layers,
works here in Eindhoven, to make sure the lines are as short
such as graphene. This is important for a new generation
as possible. This employee is technical sales specialist Harm
of nanoelectronics. Even known materials start to behave
Knoops. “For us, this cooperation is a win-win situation,”
differently when you force them into a 2D architecture.”
he says. “Whenever the researchers in Eindhoven publish an
At present, the most sophisticated production method for
article on new results achieved with our machines that helps
these types of structures is the ‘scotch tape method’: you
me to show other potential clients the possibilities of our
stick something to the surface, and rip off a single layer of
equipment.” The cooperation is a genuine two-way street, he
molecules. “Of course, this is not the most reproducible way
emphasises. “When their research requires new options we try
to do it, and more importantly: it is certainly not scalable for
to co-develop them. But also the other way around, when we
industrial purposes.”
have developed some new features they can test them for us.
Bol’s research strongly leans on the cleanroom facilities, in
And their publications act as independent quality markers for
which Oxford Instruments play an important role. “Here in
our products.” For the ALD machines, Oxford Instruments’ main
Eindhoven, we have the equipment to both fabricate and
market lies in research institutes and universities. “Nothing sells
analyse devices. Ranging from lithography and deposition tools
better in that sort of environment than refereed publications in
to a scanning electron microscope and X-ray photoelectron
high impact scientific journals.”
These insights also help Bol in her quest for new production processes. After receiving the prestigious Vici grant in 2014, she was recently awarded an ERC Consolidator Grant as well. With those funds, she will spend the next few years stretching the current limits of the technique: “When we can actually fabricate truly two-dimensional layers, I want to take it to the next level: stack two-dimensional layers made out of different materials. That way we can combine different properties in one device. We will have to do that at low temperatures to prevent the different layers from mixing, since that will deteriorate the quality of the materials. And if we can achieve that, it will open up a whole new field of possibilities for even smaller electronic circuits with totally new properties.” Our thanks to TU Eindhoven for allowing us to publish this article
spectroscopy to characterise the layers we have deposited.” The research group uses advanced commercial tools and ones they have partly constructed themselves. “I am going to work with ALD machines from Oxford Instruments, which have been configured to meet our needs. We want to be able to play around with different parameters of the ALD process,” Bol explains. The researchers are particularly interested in relatively
Image by Mikhail Ponomarev
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PlasmaPro® systems bought for Chinese LED manufacture
Training: buy one get one half price
Ground breaking research into graphene and other 2D materials
Training Offer!
Are you looking for advanced maintenance training or simply training for new users to be safe and competent in the use of your Oxford Instruments tools?
We have developed a range of courses giving our customers the choice to suit you and your users different levels. Book your place on any Oxford Instruments Plasma Technology 2016 training course by 31st May 2016 and your colleagues can book a place on the same course for half
High tech Chinese manufacturer, Enraytek Optoelectronics Co recently purchased several leading edge Oxford Instruments PlasmaPro 800 PECVD systems for the manufacture of their High Brightness LEDs. Enraytek’s key products are High Brightness LEDs for TV
Says Mr.Xu Chunchao. Vice President
backlighting and LED lighting, with manufacturing capability
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‘2D Materials Processing Technology’
7th April 2016, National Graphene Institute, University of Manchester
Book one get one 1/2 price Offer ends 31/05/2016
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is taking place at The University of Manchester’s new National Graphene Institute using multiple plasma etch and deposition systems. The workshop includes a wide range of talks presented by the University of Manchester National Graphene Institute, outside guest speakers and Oxford Instruments process and technology experts. It is open to all those people working in industry and academia, with an interest in recent progress plus future trends in research and development, and the application of 2D materials. Talks will include: for 2D materials • ALD Chris Hodson, Oxford Instruments Process Developments • Etch Bob Gunn, Oxford Instruments
Suspended 2D Materials • Truly Jose Luis Sambricio Garcia, Manchester Uni
Materials: Technology Requirements for Potential • 2D Applications in Electronics Prof.Dr.-Ing. Max Lemme, Universität Siegen
Process Technology for 2D Materials • ICP-CVD Michael Stokeley, Oxford Instruments
and Processes for Deposition of 2D • Technology Materials and Heterostructures Dr Ravi Sundaram, Oxford Instruments
Dimensional Contact to a Two Dimensional • One Material Gregory Auton, University of Manchester Developments in Low Temperature • Recent Measurement Tools for Graphene Dr John Burgoyne, Oxford Instruments
• Technical posters • Tour of the National Graphene Institute
demanded by the LED industry.
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The Application of Bosch™ Deep Silicon Etch to the Manufacture of X-Ray Lenses Katarzyna Korwin-Mikkea, Mark E McNiea, Lucia Alianellib, a Oxford Instruments Plasma Technology bSTFC Diamond Light Source, Oxfordshire, UK
The trend in X-Ray optical devices, such as refractive lenses, zone plates, curved mirrors, multilayers and multilayer Laue lenses[1], is towards shrinking dimensions and/or deeper optics.
respectively. The focus of this work was to develop the process
Due to excellent properties, such as thermal resistance, low
passivation is regularly refreshed to maintain sidewall integrity
x-ray absorption, diamond is highly desirable material for
through rapid switching with controlled ion energies. Etching
use in many optical instruments[2], however, due to cost of
microstructures on the samples with a high silicon exposed area
manufacturing, extreme hardness and resistance to chemical
reduces the etch rate due to loading effects and may cause the
attack, diamond is a difficult material to realize structures
undercut of the mask as the result of the sidewall plasma attack
suitable for x-ray lenses and this is why silicon is the leading
on isolated features (Fig.1) even when over passivated. One of
material for x-ray lens production. Nanofocusing silicon x-ray
the solutions to reducing the negative impact of the ions on the
etch depths in excess of 70µm with smooth sidewalls (scallops
latest generation deep silicon etch system can trade high rate
lenses require not only high quality material but also high
etched lenses is to tune the process to operate at low pressures
25µm/min) to
the sidewalls to minimize aberrations and parasitic scattering
number of ion impacts on the sidewalls by protecting the lenses
for etching silicon x-ray lenses with good profile control and smooth sidewalls in the Bosch process DSiE. To achieve high aspect ratio lenses with vertical profiles and smooth sidewalls, a short cycle time is used in conjunction with lower powers for less aggressive process conditions. The
with sacrificial features that can be removed after the process. Figure 1. The negative impact of the ions on etched X-Ray lens structure.
without compensating features – Fig.2). The results gave close to vertical lens profiles (89.90°) without compensating features etched to 50µm depth with no mask undercut and controlled scallops to below 50nm (Fig.3). This process was adapted and extended to the lenses with compensation features to achieve
Figure 2. Device mask patterns. Lens with compensation features
Figure5. PlasmaPro 100 Estrelas
The X-Ray silicon lens etch processes were carried out in a PlasmaPro 100 Estrelas deep silicon etch tool (Fig.5). This
In the Oxford Instruments Applications Laboratory, etch processes for each approach were developed (i.e. with and
Lens without compensation features
Figure 4. SEM of a lens with compensation features etched to 75µm depth
Figure 3. SEM of a lens without compensation features etched to 50µm depth.
[1] L Alianelli, K J S Sawhney, R Barrett, I Pape, A Malik M C Wilson, Optics Express (2011) vol. 19, no.12, 11120-11127 [2] A M Malik, O J L Fox, L Alianelli, A M Korsunsky, R Stevens, I M Loader, M C Wilson, I Pape, K J S Shawhney, P W May, Journal of Micromechanics and Microengineering 23 (2013), 125018 (7pp) Adapted from work presented at the International Micro Nano Engineering (MNE) Conference, Sept. 2014 An article ‘Aberration-free short focal length x-ray lenses’ was published in Optics Letters Lucia Alianelli, 1* Manuel Sánchez del Rio, 2 Oliver J. L. Fox 1,3 and Katarzyna Korwin-Mikke 4 *Corresponding author:
[email protected]
nanoscale etching. The lens processes are being transferred to a third party commercial supplier for production of the lenses going forwards. (Article published in Optics Letters (Impact Factor: 3.29). 12/2015; 40(23):5586. DOI: 10.1364/OL.40.005586) Available from: https://www.researchgate.net/publication/284519056_Aberration-free_ short_focal_length_x-ray_lenses 1 Diamond Light Source Ltd., Chilton, Didcot OX11 0DE, UK 2 European Synchrotron Radiation Facility, BP 220 38043 Grenoble Cedex, France 3 School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK 4 Oxford Instruments Plasma Technology, Yatton, BS49 4AP, UK
Inventory Sale Now On! Up to 75% off list price from our new online catalogue We’re selling some quality items of surplus stock, previously purchased for our leading edge process tools. Take a look at the variety of spares available from pumps and chillers to
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• Unused stock • Up to 75% off list price • Efficient worldwide delivery
We have a variety of stock at discount prices, so have a browse and see what you find! 8 PROCESSNEWS
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Micromachining silicon structures on thin membranes using plasma etching Zhong Ren, Mark E McNie, Colin C Welch, Mike Cooke Oxford Instruments
Micromachining detailed silicon structures on thin membranes is regarded as one of the primary MEMS fabrication techniques, but also one of the more difficult processes.
This tool can operate successfully over more than an order of
There is a very sharp transition in chemical loading effect, as
removing polymer which enables a full cycle of deposition,
the silicon clears from the membrane layer whilst the lateral
break through and etch to be as low as 1 s.
heat dissipation from etching structures on a membrane
Results given here used cycle times up to 2.5s. Whilst an
decreases significantly as the membrane is approached. The
electrostatic chuck (ESC) clamps over the whole wafer surface
exothermic etch reaction can even cause the resist pattern
in contact and to conductive layers on the membrane, where
and etch passivation to degrade when the associated heat is
membranes are proud of the clamping plane the gap is large
focused in a small area.
and so heat removal efficiency via Helium back side cooling is
There is a need for very high etch rates to remove bulk material
dramatically reduced. Thus in order to be able to etch structures
to expose the membrane, but also a need for very precise
on membranes without overheating and maintaining profile
profile control in fabricating micro- or nano-scale features. The
control, a low power process capability is also required.
bulk etch can use an anisotropic wet etch that is selective to the
Three devices have been realized using this combination of
crystallographic planes, such as KOH or TMAH. The wet
high rate and precision processing: a micro-resonator high-Q
chemistry is only suitable for low aspect ratio (AR) features and
cavity with a vertical profile (90º) and uniform scallop size
results in a characteristic slope at a 54.74º for silicon
(Fig 1&2); a fine periodic deep grating with 50:1 high AR
wafers that limits geometric freedom and packing density[1].
(Fig 3&4); and a large length-width ratio cantilever on a
A Bosch (or gas-chopping) deep silicon etching (DSiE) process
photoresist (PR) membrane where avoiding mask overheating
with alternating deposition and etch steps can realize a vertical
and not damaging the polymer film underneath the cantilever
profile at high aspect-ratio (AR) with etch rates of up to 30µm/
was key (Fig 5&6). Moreover, high quality and smooth sidewalls
min, and can etch arbitrary shapes as defined by the mask
were also achieved on these etched structures.
magnitude of inductively coupled plasma (ICP) source power, from 5 kW, opening the possibility of both high rate and precision, low rate processes in the same chamber. The minimum time of a single process step is 100-300 ms for
Figure 2. Micro-resonator structure: (a) side view with vertical profile and a 60 µm etch depth; (b) sidewall roughness (scallop size) of 78nm
Figure 5. Challenges on Si membrane etch: (a) grass and striations in corners; (b) optimised etch gives striation-free and smooth sidewall; (c) PR mask burnt out during Bosch etch; (d) optimised etch avoids overheating on PR mask.
Figure 3. Schematic section of gratings in a SOI wafer: the back cavity defined by a high rate Bosch etch and fine period optical gratings realised in the device layer using a precision Bosch etch.
pattern[2, 3] with high packing density. This paper presented at MNE 2015 reports a technique which addresses these problems, and gives example results on three typical structures, using a DSiE tool (PlasmaPro 100 Estrelas)
Figure 6. Si cantilever: (a) Illustration of cantilever fabrication in Si membrane by means wet-etching and Bosch process; (b) 5 mm length × 200 µm width × 50 µm thickness cantilever; (c) and (d) Enlarged view of the cantilever after polymer removal.
in the Bosch process (SF6-C4F8 chemistry). Most DSiE process tools are optimised for high rate anisotropic etch but may be limited in their ability to perform precision, lower rate processes. Such fast switching etch processes often need a significant minimum power to maintain the plasma during the transition between etching and deposition steps.
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Figure 1. Schematic section of a micro-resonator on a Si3N4 membrane: back cavity by KOH etching and the top pattern defined in a silicon membrane using the Bosch process
Figure 4. High aspect-ratio (50:1) fine period (200nm) gratings etched by a Bosch process: (a) Etch depth 5µm; (b) minimal bow at top of trenches
[1] H. Seidel, L. Csepregi, A. Heuberger, H. Baumgartel, J. Electrochem. Soc. 137 (11) (1990) 3614–3626 [2] F. Laermer, A. Schilp, German Patent DE-4241045, 1994 [3] Z.Ren, M.E.McNie, Microelec. Eng. 141 (2015) 261-266 The authors would like to thank Dr. S Vollmeke (CiS Forschungsinstitut fur Mikrosensoik GmbH, Erfurt) for providing cantilever samples for etching at Oxford Instruments and permission to use the SEM images.
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Power device development enabled through University of Glasgow collaboration
500 attendees 2 days 24 talks 30 posters
Oxford Instruments and the University of Glasgow (GU) have entered into a collaboration as part of a project to develop next generation GaN-on-Si power devices. The project will use an Oxford Instruments four chamber cluster
potential in realising smaller, cheaper, better performing and
system combined in a unique configuration. Under vacuum the
more efficient power devices, with the ensuing commercial
cluster will allow device manufacturing and characterisation
rewards.”
measurements to be performed on device interfaces and surfaces without exposure to atmosphere. System installation is currently underway in the James Watt Nanofabrication Centre at Glasgow University and development work is due to commence in March 2015.
“Using Oxford instruments state-of-the-art equipment, the ultimate aims of this project are to produce smaller GaN-on-Si based power devices that offer better performance and levels of efficiency than those currently available.” says Dr David Haynes, Sales & Marketing Director at Oxford Instruments
The cluster system combines a FlexAL® Atomic Layer Deposition
Plasma Technology, “This will result in commercial benefits
tool used for depositing very thin films of metals, oxides and
for various applications, from electronic component power
nitrides using both thermal and inductively coupled plasma
supplies in laptops to aerospace and automotive applications,
(ICP) ALD processes, a PlasmaPro System100 ICP for etching
in particular electric vehicles. Additionally, Glasgow University
of compound semiconductor materials and a PlasmaPro
will run a second project on the cluster focussing on scalable
System100 ICP for High-Density PECVD deposition system
solar thermoelectrics and photovoltaics.”
providing for low damage, low temperature thin films; plus the Omicron Nanoscience NanoSAM LAB, for surface sensitive chemical analysis and high resolution imaging of small (micro
Bringing the Nanoworld Together
Oxford Instruments will continue to support GU throughout the collaboration period, assisting with process development, and sponsoring a PhD student as part of the project, who will
Energy savings win us a ‘Go Green’ award Joining Go Green has inspired and challenged us to make further sustainable improvements to our business.
wide band gap semiconductors and latest advances in sensor
but implementing this in a large organisation takes
fabrication. There followed talks from Nanoanalysis, Asylum
considerable planning and effort. We did just that, and
Research, Nanoscience, and Andor all part of the Oxford
our initiatives have just resulted in our company winning
Instruments group.
Bristol’s ‘Go Green’ Energy & Efficiency Best Newcomer award. We’re also working hard to implement more ‘Green’ initiatives.
This EPSRC funded project bridges the gap between
www.oxinst.com/GoGreen16
manufacture.
fundamental research and commercial manufacture. Funding
Instruments provides an opportunity to be in the vanguard as the power semiconductor market looks to move towards GaNon-Si.”, Comments Prof Iain Thayne, of Glasgow University, “Successful development of GaN-on-Si enables the use of low cost, large diameter substrates and easier routes to high volume manufacture of power devices. This offers significant
12 PROCESSNEWS
Walther-Meissner-Institute, Technical University of Munich. On Day 2, Thin Film Processing sessions covered fabrication of
unique capability for analysis of each stage of prototype device
“This flagship project for both Glasgow University and Oxford
Nanosciences’, with keynote Professor Dr Rudolf Gross from
way of being more sustainable and saving costs,
See how we did it:
Scanning Electron Microscopy (SEM). Installed, this provides a
Plenary sessions on Day 1 were themed ‘Convergence of the
Reducing energy consumption may seem an obvious
work on the newly installed cluster tool.
and nano) structures by Scanning Auger Microscopy (SAM) and
Record numbers attend 4th ‘BTNT’ seminar in Chennai, India
These educational seminars are aimed to enhance our customers’ knowledge and keep them informed of the latest technological advances our systems have to offer.
IISc Bangalore is the venue for 2016: watch out for further details on our website
was granted to GU as part of a consortium of UK Universities (Bristol,
Cambridge,
Glasgow,
Liverpool,
Manchester,
Nottingham and Sheffield) and industrial partners. This five year project will connect the very capable but currently fragmented, world-class UK GaN academic materials and device community, align them with key players in the UK academic power electronics sector, and directly link with the significant UK power semiconductor industry.
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New etching process for Magnetic RAM developed by Cornell and Oxford Instruments Vince Genova, Cornell University Colin Welch, Oxford Instruments
The Cornell Nanoscale Science and Technology Facility (CNF), a leading university research facility located at Cornell University, Ithaca, NY, and Oxford Instruments Plasma Technology (OIPT), UK have collaborated...
suffers from low etch rates, low selectivity, undesirable sidewall
...to develop a novel etching process targeted specifically
CNF/OIPT process is a result of a Design of Experiment (DOE)
redeposition especially for nanoscale features, and damage to the device structure itself. Recently, several research groups have shown that chemical etching of Co, Fe, and Ni based alloys can be achieved using plasmas formed from methanol (CH3OH) and argon. The new
at magnetic random-access memory MRAM based device
in which the level of CH3OH in Ar varied, along with variations
fabrication. These results, obtained at CNF, add a significant
in the ICP power, bias power, and pressure. Methanol, as the
contribution to OIPT’s large portfolio of etching processes.
principal plasma reactant, forms volatile carbonyl compounds
MRAM is a high performance, low power, low degradation,
(e.g. Ni(CO)4, Fe (CO)5, and Co2(CO)8) at room temperature.
non-volatile data storage technology that some suggest gives it the potential to become a “universal memory”, able to replace SRAM, DRAM, EEPROM and flash. Etching of magnetic based materials for the development and scaling of MRAM and spintronic devices is therefore of keen interest to several leading research groups using the CNF.
This chemistry-based process avoids the disadvantages of purely physical milling. The antiferromagnet IrMn also etches in a methanol plasma. In addition, the selectivity over common mask materials such as Al2O3, Ta, Ti, TaN, and TiN is high, while leaving no residue on the etched devices. We demonstrated successful etching of a 41nm thick magnetic tunnel junction
coupled plasma (ICP) based reactive ion etch platform is configured for state of the art nanoscale etching vital to the research work of CNF. The system includes many extras that make for a highly flexible and powerful etch research tool. These include a wide range temperature (-150°C to +400°C) electrode, which greatly enhances the spectrum of materials that can be etched with volatile chemistries, low frequency electrode biasing and a vapour delivery system for methanol
stack stopping on the tantalum under layer (see figure). High
(CH3OH).
Vincent J. Genova, a Research Staff Member at CNF, explains
selectivity (>10:1) over both the Ta mask and under layer is
the technology and the new process, “An element of
This advanced methanol-based etch capability for magnetic
achieved through the formation of tantalum carbide in the
MRAM consists of a magnetic tunnel junction (MTJ) and
materials is an enabling process that is now available to
methanol process.
the researchers at CNF and to the newly formed National
a CMOS transistor.
One of the most challenging steps in
MRAM fabrication is the etching of the MTJ stack. The stack typically contains a non-magnetic seed layer to promote proper crystalline growth (e.g. Ta), an
Nanotechnology Coordinated Infrastructure Network (NNCI). This research work at CNF adds a significant contribution to Oxford Instruments Plasma Technology’s extensive portfolio of etching processes, enabled through the use of our state of the art PlasmaPro 100 Cobra ICP etch system. We are delighted that our technology is assisting such a prestigious research centre achieve its fundamental research goals. For further technical information, please contact Vincent Genova at
[email protected] or Colin Welch at
[email protected]
CNF was pleased to announce the full facilitation of the new PlasmaPro 100 Cobra ICP etch system from Oxford Instruments Plasma Technology (OIPT) in 2015. This inductively
antiferromagnet such as PtMn or IrMn, a stack of alloy pinned layers (CoFeB), a tunnelling barrier such as MgO, metals such as Ru and/or Pt, and a suitable hard mask such as TiN or Ta. The problem is that magnetic materials have
difficulty
reacting
with
most
chemically active plasma species to form volatile etch products, so users often have to resort to purely physical ion milling processes. However, ion milling
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Scanning electron micrograph of the 41nm thick MTJ
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