Agilent’s Scanning Microwave Microscope is a breakthrough with the potential to make a significant impact. The company’s Vice President and General Manager of the Component Test Division (CTD), Greg Peters, tells Microwave Journal’s Richard Mumford how the instrument evolved, highlights its key features and outlines its health, environmental, semiconductor research and general electronics applications.

Greg Peters has 24 years of experience in a variety of design, test and measurement fields as an engineer and manager at Hewlett-Packard and Agilent Technologies. He started his career at Hewlett-Packard in Colorado Springs, was named local analyser product manager in 1996, marketing manager in 1999 and operations manager of the Signal Integrity operation in Andover, MA in 2001. He transitioned to marketing manager for the CTD in Santa Rosa in 2004 and to VP/GM of the RF and microwave signal sources division in 2006. Peters’ insight into market trends stems from frequent and direct contact with Fortune 500 technology leaders who struggle to design and test their latest innovations.

MWJ – What is the background to the development of the Scanning Microwave Microscope?

Peters – Globally, health and environment are of increasing concern as the population ages in Western countries and in emerging societies such as the BRIC countries. People are increasingly concerned about toxins and other environmental contaminants By way of contrast I would say that the communications revolution is continuing at a slower growth rate, with the electronics industry being a mature cyclical industry at this point.

To address health and environmental questions and to comprehend medical issues there is a need to understand the fundamental materials sciences. This is the interaction of molecules, chemicals – even down to the physical properties of atoms, and to be able to characterise them.

What Agilent has done in its traditional Life Sciences activities has been largely chemical analysis, which includes mass spectrometry for example and we are also pushing into tools to analyse the human genome. The missing gap is what we would call materials measurement, which is the characterisation of materials at a nanoscale.

MWJ – How have you gone about trying to fill this measurement gap?

Peters – In mid 2005 Agilent acquired Molecular Imaging, located in Chandler Arizona, which developed and marketed an innovative atomic force microscope (AFM), which is now part of our Life Sciences and Chemical Analysis business unit. During the course of our technology investigations at Agilent Central Labs we concluded that we could integrate the atomic force microscope with the fundamentals of vector network analysis.

We’ve added a S11 (otherwise known as a reflection or TDR measurement) to a standard AFM. You can think of an AFM as a very precise needle which either touches or hovers above the surface of a material. This needle moves up and down over the surfaces, giving a topological profile.

Of course, we know that there is more to any material than what you can discover by just scratching the surface and what you want to be able to do is to look inside. So, what we have done is taken a standard performance network analyser (PNA) and with some additional custom hardware, a specially designed tip and a structure to hold that tip and we have created a Scanning Microwave Microscope. This has a resolution of 5 nm and it gives not only the surface level resolution, which the AFM does and the positional information but it also provides information that can be translated into a 3D image. In essence you get depth information as well.

MWJ – So, what are the advantages of such a system?

Peters – The best way to explain is to give the example of the semiconductor processes, which we are all familiar with. Semiconductor devices are simply the sum of a set of etched wells and deposited layers of different materials. An AFM can accurately trace what’s on the surface. A Scanning Microwave Microscope can add additional insight. The scanning microwave microscope can image wells, including their sides and their depth and provide quantitative as well as qualitative measurements. The qualitative comes form the visual, of course, and the quantative comes from the fact that there is dimensional information. This all comes from the TDR measurement that is combined with the atomic force microscope spatial measurements.

MWJ– What specific applications could the Scanning Microwave Microscope be used for?

Peters – One target market in the electronics sector would be semiconductor materials characterisation. There are hundreds of semiconductor fabs around the world. The majority of them are research labs. Throughout the world and particularly in Western Europe there are universities with research labs that are investigating silicon topologies and different doping profiles. The traditional way of measuring this would be to design something, simulate it and look at it with a regular microscope or regular AFM. However, the only way to get a doping profile and discover what is going on beneath the surface is by etching it back and examine it or ultimately take a series of measurements and infer the status. With the Scanning Microwave Microscope you can now see it in 3D.

The technological key is how do you get a microwave signal to the tip and back? An atomic force microscope moves, and we are talking about very precise capacitive measurement. In order to make that happen we had to do some custom mechanical engineering that enabled us to move the head at the same rate of speed which it moves during regular AFM measurements – while at the same time it has to be phase stable because anything that moves or changes the phase slightly is going to give a measurement error.

The PNA has the appropriate level of network analysis performance that is required and with the addition of this custom hardware and custom mechanical structure we have a product that can make the appropriate measurements.

MWJ – Tell me more about using the SMM in semiconductor research?

Peters – There are two areas of application in the fab sector – one would be in process and materials characterisation and the other in failure analysis. Often in failure analysis you look at a chip and etch away at the cover of the packaging to get to the die itself. Then you are faced with the dilemma of do I measure my way in and infer what happened or continue to etch away and see if you discover the problem. There is now a third approach, which is to look inside with a sort of ‘x-ray’ vision.

To get a quantative measurement you need to have a traceable calibration regimen. There need to be cal standards that we can scan and these would be precisely designed cal standards that would allow us to calibrate the instrument and remove any spurious effects. We are currently working on this with the NIST [National Institute of Standards and Technology].

The Scanning Microwave Microscope is two products that have come together – the atomic force microscope, which is one product with its features and options and the PNA, which comes with a set of accessories which makes the component parts work as one system. All that someone who is not familiar with network analysers has to do is plug it in, turn it on, load some software and hook up a cable.

And in the semiconductor field the beauty of using the PNA is that almost all of the labs have one. They just need to hook it up to their AFM and they have this new measurement system.

MWJ – Are there other significant emerging applications?

Peters – Yes, particularly relating to materials, which is everything from measuring carbon nanotubes and the types of structures built around that, through to biological samples. We are doing research with partners on measuring biological samples. We have made measurements on fixed samples – fixed tissue that has been extracted from an animal or human. We have made measurements on human nerve cells from a biopsy. Our future goal is to make measurements of live cells that are unfixed in place. These typically would be scanned in multiple ways – visually, of course, using regular microscope, as well as the AFM and the associated scanning using the Scanning Microwave Microscope.

An important emerging area focuses on the cellular ion channel. While this is not my area of expertise, the ion channel is how nutrients are moved in and out of the cell itself. These channels are a complex chemical process, which uses a potential or differential in order to move the nutrient in or out of the cell. This is of particular interest to cancer researchers who are considering how cancer cells differ to normal cells and how appropriate drugs or treatments can kill the cancer cells without impacting on the patient.

MWJ – In continuing your work are you cooperating with other research establishments?

Agilent Labs is working with the University of Linz (Austria), which is well known in the industry for such fundamental research. The Materials Science division is working with researchers around the world and beginning to develop measurements that will lead to new instruments.

As someone on the electronics side of Agilent I feel fortunate that we have the Life Sciences side to be our guide. It would be difficult for us to get into these labs otherwise but they are already there.

MWJ – Do you have patents?

Peters – There are several patents pending and of course both the AFM and PNA have numerous patents.

MWJ – Can you sum up the significance of this new product?

Peters – It is significant in that while an AFM provides 2D static images the SMM can move that to 3D kinetic images. The Scanning Microwave Microscope is unique, with the capability of making an impact in all of the sectors I have mentioned – health, environment and semiconductor – and others that we have still to discover.