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Archive for category: Hollow Cathode Plasma Source


Hollow Cathode Plasma Sources – a wider operating pressure range than you might think

We 20190422_143455want to correct some recent disinformation in a journal article, the review paper J. Vac. Sci. Technol. A 37 (2019) 030902, on plasma ALD, appears to have mistakenly reported a very narrow operating range for our hollow cathode plasma sources of only 0.3 to 2 Torr. It is unclear what this range was based on as none of the references cited actually provide a pressure range. Apparently it is a simple misconception of the authors, presumably due to their inexperience with hollow cathode plasma sources. However, all our designs have had larger pressure ranges than those given in the review, and in fact there have been some exciting recent advances in our designs that have extended operation down to tens of milliTorr and perhaps even lower.

For clarification, the operating pressure range of our earliest hollow cathode design is provided in Japanese Journal of Applied Physics 51 (2012) 01AF02. The optimum pressure for that cathode – used for CVD work – was 1 Torr, however measurements presented there clearly show an operating range of at least 0.23 to 6.6 Torr for that very early design, though in fact it was probably much broader.

When designing for ALD systems, lower optimum pressure ranges have been required, so from about 2014, our designs have been optimised for operation between 0.3 and 1 Torr, though the full operating range of our barrel design plasma sources – such as our series 50 source, commonly used as an ICP replacement – have  a lower  limit of approximately 100 mTorr and an upper limit of > 5 Torrs. The picture below shows one of these sources at 120 mTorr with nitrogen at 100 watts of RF power.

Our newer designs, based on our large area hollow cathode plasma sources, go to even lower pressures, which we’ve now run to the base pressure of our test systems, to as low as 35 mTorr. A measurement system upgrade will be required to see just how low these sources can go, an example at ~50 mTorr is shown top left.

Check out the Meaglow website at or contact us at or +1 807 252 4391, for more information on our plasma products.


120 mTorr nitrogen 100 watts 0.0005 sec exposure


New Hollow Cathode Plasma Source Designs Provide Better Quality Films

0.125 sec exposure 278 watt 4130 mTorr

The University of Connecticut group of Dr. Necmi Biyikli, with others, have recently published a paper (J. Vac. Sci. and Technol. A 37 (2019) 020927) where they were able to achieve good quality, highly stoichiometric AlN using hollow cathode plasma assisted atomic layer deposition (HCPA-ALD) with film densities near bulk values. Because of the high radical flux from the source, significantly lower RF power was required to achieve this improvement in material quality compared to past experience, and shorter plasma on cycles could be used at these lower powers (20 seconds at 100 watts compared to 40 seconds at 300 watts).

Similar improvements in silicon nitride deposition were recently achieved by a team at the University of Texas, Dallas, where excellent quality, highly stoichiometric, high density PA-ALD grown material was achieved using one of our hollow cathode plasma sources (see, for instance, IEEE Electron Device Letters 39 (2018) 1195 ).


Meaglow’s hollow cathode plasma sources are widely used by the ALD Research Community as replacements for inductively coupled plasma (ICP) sources because there is less oxygen contamination when depositing non-oxide materials. However, these recent papers, by the University of Connecticut and the University of Texas, Dallas, illustrate advantages that may be far more important for the industry moving forward. Those being an extremely high radical flux, to the point where the ion signal (ion densities are similar to ICP sources) is swamped by the signal of radicals during optical emission spectroscopy measurements, and relatively low plasma damage (see our company white paper on hollow cathode sources). These result in quicker deposition times with potentially more stoichiometric, better quality material.

The image to right shows the University of Connecticut plasma source with ellipsometer ports and sample entry door. The 4″ diameter source was custom made for use with an Okyay Tech ALD system.



Ammonium Nitrate Sensor/ALD Paper From Oklahoma State University

IMG-3804Congratulations to Prof. Dave McIlroy’s group, at the Physics Department of Oklahoma State University, for their recent publication in ACS Sensors Vol. 3 (2018) pg. 2367. The paper, authored by Lyndon Bastatas, provides some of the first results from the Okyay Tech ALD system recently acquired by that group. The ALD system includes a 4″ diameter Meaglow hollow cathode plasma source that was used to pretreat silica nanowire mat samples prior to the thermal deposition of ZnO in the Okyay Tech system. The ALD steps were part of a process to make a collection of 1D structures for ammonium nitrate sensors.

The picture shows Aaron Austin, one of the Oklahoma team next to the Okyay Tech ALD system with Mealgow plasma source shown at the top. Apparently more papers are on the way, with another 2019 publication already available. Meaglow is pleased to be an enabler of this next generation of research, check our products at



Meaglow Plasma Source Provides Breakthrough for Advanced Semiconductor Production Technique

Meaglow Ltd. (Privately Held) announces a breakthrough in semiconductor production. As computer chips become smaller and smaller, advanced production techniques, such as Atomic Layer Deposition (ALD) have become more important for depositing thin layers of material. Unfortunately the ALD of some materials has been prone to contamination from the plasma sources used. Meaglow Ltd has developed a hollow cathode plasma source which has reduced oxygen contamination by orders of magnitude, allowing the reproducible deposition of semiconductor materials with improved quality.

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Meaglow Hollow Cathode Plasma Source to Upgrade Atomic Layer Deposition at Bilkent University

Meaglow Ltd. (Privately Held) announces the installation of a hollow cathode plasma source for the group of Professor Necmi Biyikli, of the Institute of Materials Science and Nanotechnology, at Bilkent University in Turkey. The plasma source is being used to upgrade their Atomic Layer Deposition (ALD) system by replacing an inductively coupled plasma source. This enhancement will reduce the oxygen contamination in ALD systems and increase the quality of Nitride thin films grown.

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Meaglow Hollow Cathode Plasma Source Goes to GSU


Meaglow Ltd. (Privately Held) announces the sale of a prototype hollow cathode plasma source to Georgia State University (GSU) in the United States. The plasma source will be used for the conversion of a low pressure MOCVD system to a plasma deposition unit. Meaglow has demonstrated great success in the deposition of high indium content InGaN with its hollow cathode plasma source and recently demonstrated a yellow LED in collaboration with Lakehead University in Thunder Bay, Canada.

Meaglow is now focused on commercializing its hollow cathode plasma technology, and is looking for partners interested in developing the plasma source for MBE and other applications. Interested parties should email


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