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Home > Nanotechnology Columns > NanotechnologyKTN > Using Atomic Layer Deposition (ALD) in nano-electronic devices, sensors and systems

Fiona Brewer
NanoKTN

Abstract:
All electronics companies face the constant challenge to develop and commercialise new products that are competitive in the marketplace. To achieve this they are increasingly looking to the nanotechnology industry for new processes to manufacture electronic devices with features below 100 nanometre. One such process is Atomic Layer Deposition (ALD), that is capable of easily building structures measuring 100 nanometre and smaller on the most advanced applications in electronics, catalysis and sensor technology. However, in order to fully capitalise on these new processes the challenge is to establish a fluid supply chain that makes it viable for nanotechnology to be effectively introduced.

May 13th, 2009

Using Atomic Layer Deposition (ALD) in nano-electronic devices, sensors and systems

Using Atomic Layer Deposition (ALD)
in nano-electronic devices, sensors and systems

Dr Alec Reader, Director, Nanotechnology Knowledge Transfer Network (NanoKTN)

All electronics companies face the constant challenge to develop and commercialise new products that are competitive in the marketplace. To achieve this they are increasingly looking to the nanotechnology industry for new processes to manufacture electronic devices with features below 100 nanometre. One such process is Atomic Layer Deposition (ALD), that is capable of easily building structures measuring 100 nanometre and smaller on the most advanced applications in electronics, catalysis and sensor technology. However, in order to fully capitalise on these new processes the challenge is to establish a fluid supply chain that makes it viable for nanotechnology to be effectively introduced.

The role of the supply chain in ALD was the theme of a Nano Micro Systems focus group activity hosted by the NanoKTN and in partnership with the Joint Equipment and Materials Initiative (JEMI), on March 31st 2009. The one-day conference considered new developments in the manufacture of advanced nano-electronic devices such as leading-edge MOS structures, as well as assessed the existing gaps in the supply chain that if not bridged will prohibit companies from realising the significant commercial gains.

The event saw presentations from key players in the industry, including Metryx, Oxford Instruments Plasma Technology, Beneq, Loughborough Surface Analysis, Centre for Process Innovation (CPI) and SAFC Hitech and featured a table top exhibition which offered a unique opportunity for exhibitors to showcase their products and services. The presentations looked at the developments of nano-electronics and nano-materials in recent years and the technologies and applications that are bringing about positive changes in these areas.

Highlights from the day included a presentation by Julia Baker, Principal Research Scientist at Kodak who looked at the development of atmospheric pressure ALD technology used in dielectrics and semiconductor layers and Mike Petty from Loughborough Surface Analysis gave an introduction to surface analytical and depth profiling techniques.

Professor Paul Chalker from the University of Liverpool looked at the use of ALD in the manufacture of VLSI semiconductor logic and memory devices, Paul Williams at SAFC Hitech demonstrated how chemical precursors can be designed to satisfy deposition requirements and Mark Berry at Metryx looked at the mass metrology technique used to develop thin films deposited through ALD processes.

Other keynote presentations looked at the recent introduction of OLEDs (organic light emitting displays), examples of emerging industrial applications in nano-electronics, displays and solar energy and the ALD processes and services being developed by CPI.

Chris Hodson, ALD Product Manager at Oxford Instruments Plasma Technology, addressed the current trends of downscaling in the semiconductor industry and the resulting boost in the use and development of nano-electronic devices and systems. These industry changes have led to ALD becoming the method of choice for depositing high quality films with ultimate growth control and excellent step coverage, on very demanding high-aspect ratio features.
ALD was first demonstrated in 1974 by Dr Suntola in Finland and the commercial use of these methods began with the need to deposit dielectric films on MOS structures. Later, ALD was developed for large area OLED substrates, needed in the manufacture of electroluminescent flat-panel displays. With nano-electronics becoming further developed during the late 1990s and early 2000s, the need for successful ALD processes became even greater, as the demand for producing thin conformal films of a specific thickness became imperative.

Within nano-electronics, ALD is a thin film deposition technique that deposits a material onto a nanostructure. The process is repeated until a thin film layer is created. The film adopts the same crystal structure as the material it is deposited on and the electrical properties of the newly created films, improve the material's electronic performance. Using processes like ALD allows manufacturers to control the electrical properties of the host material, allowing for improved performance.

ALD is currently being used in nano-electronics to deposit high-k gate oxides, high-k memory capacitor dielectrics, ferroelectrics and metals and nitrides for electrodes and interconnects. The need to control extremely thin films is essential in high-k gate oxides.

Methods of ALD are used to create high-k gate oxides such as HfO2 and nanolaminates like HfO2 - AI2O3. High aspect ratio diffusion barriers such as AI2O3, for Cu interconnects such as TiN and passivation layers for OLEDs and polymers, also require ALD processes for their manufacture. Fuel cells and the highly conformal coatings used in the production of micro-fluidic and Nano Electronic Mechanical Systems (NEMS) also require the flexible and precise thickness control processes offered by ALD, to produce wear resistant, anti-stiction and chemical resistant coatings.

Why use Plasma ALD?
With the introduction of a low-temperature plasma step in the ALD reaction cycle, it is possible to deliver additional reactivity to the surface in the form of plasma-produced species. This allows ALD to be used in an even wider range of applications by improving the film quality, particularly at lower temperatures and it also increases the number of materials that can be deposited.

Producing efficient devices is a continual challenge to the electronics market and ALD has been recognised as a vital innovation in doing this, as it is a self-limiting service that offers the benefit of giving precise thickness control. As mainstream semiconductor and other nano-electronic applications start to require a reduced dielectric layer thickness, ALD is becoming more frequently used and ever more critical.

Using remote plasma ALD means damages can be kept to a minimum, as well as the end result being higher quality films as a result of improved removal of impurities that lead to lower resistivity and higher density.

Plasma ALD processes also offer the widest choice of precursor chemistry available and higher quality films with more process control.

Conclusion
Chris Hodson concluded that the development of ALD processes is crucial to the nano-electronics industry if we are to see an advance in the manufacture of future nano-electronics and integrated circuits.

It is clear that application areas of ALD are rapidly expanding, as a result of the increase in the number of materials that can be deposited, the widened choice of precursors, improved film quality and lower deposition temperatures that open up even greater possibilities.

There are disadvantages to using ALD, with the main limitation being the slow speed of the process, with only a small fraction of a monolayer being deposited in any one cycle. In the past this has been a problem but the films required by future electronic devices are notably thinner than they have been in the past, so the speed of the ALD is not such a critical issue.

Chris Hodson and other speakers at the event acknowledged the presence of gaps in the supply chain, that have to date been prohibitive in enabling this nanotechnology deposition technique to be adopted in electronics devices to its full commercial potential. For many of the delegates it was the first opportunity for all the various stakeholders in the supply chain to come together, along with academics, to identify and work towards bridging these gaps.

It is crucial with all new technologies to ensure that all parts of the supply chain interact and keep each other informed of developments and capabilities and it is focus groups events, like this organised by Nano Micro Systems, that encourage such knowledge exchange and promotion of new developing technologies in advanced nano-electronics devices, sensors and systems.

Working together, the NanoKTN and JEMI are confident that the Nano Micro Systems focus group will meet its objective of stimulating the formation of the complete supply chain, for successful implementation of nanotechnology in these key electronic sectors. Presentations from the event are available to download from the NanoKTN website at www.nanoktn.com

The next Nano Micro Systems focus group activity takes place on June 3rd at City Hall, Cardiff and will explore the nanotechnology commercial successes and failures surrounding nano-electronic devices, sensors and systems. The event will see keynote presentations from key players in the industry including QinetiQ, NANOPLAS, Optocap and Microarray.

All sectors of the supply chain are encouraged to register for this next workshop and further information can be found by visiting the NanoKTN website: www.nanoktn.com. Membership to the NanoKTN and its focus groups are free of charge. For more information about how to join, please visit www.nanoktn.com.

Delegates to the NanoKTN workshop are encouraged to increase their networking opportunities by attending the rest of the S2K conference and table top exhibition which will be celebrating its 10th Anniversary. The conference highlights an outstanding line up of speakers including Intel, National Semiconductor and X-Fab with Future Horizons‘ Malcolm Penn as the event chairman. For more information visit: www.semiconductor2k.com

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