Agilent Enables In-depth Analysis of Semiconductor Failure

In an interview with EDN Asia, Roger Stancliff, Chief Technology Officer, Microwave Measurements, Agilent Technologies, talks about the scanning microwave microscopy (SMM) technology and how the solution provides in-depth analysis of semiconductor failure, as well as enables doping analysis, capacitance measurement of different layers, and other solid state analysis. Excerpts:

Please explain the backdrop that led to the company’s development of its SMM solution.
Agilent has a history of working across disciplines to make instruments that solve problems more effectively using the best of our Electronic Measurement, Chemical Analysis, and Life Sciences capabilities. A classic example of this is our new 32.5GHz real time oscilloscope, which uses Agilent proprietary ADCs. Similar ADCs are used in our TOF Mass Spectrometers to increase their time resolution and, hence, their mass accuracy. The story of SMM is really kind of similar and maybe even better demonstrates synergy across product lines in Agilent. In 2006 we purchased Molecular Imaging to begin a major company push into Nano metrology. It seemed to me and others that there could be some very interesting things possible with “network analysis at the Nano scale”. What we have now is our PNA series network analyzers working with our 5400 and 5600 AFMs in a number of ways. First, at certain discrete frequencies of the network analyzer, we can measure capacitance at the same time that we are scanning and creating an AFM image. This allows us to “co-image” and fuse the images to give our customers new ways of looking at their samples of interest. We can also park over a spot on the sample and vary the dc bias and measure capacitance. This is typically done at low frequencies with a parameter analyzer but we gain a lot of sensitivity in the capacitance measurement by doing it at microwave frequencies. Finally, we can measure at several frequencies (multiples of 2 GHz) to get a beginning sense of dielectric spectroscopy of samples. This particular capability will evolve in the direction of more complete (more frequencies) spectroscopy in the future.

What are the advantages of SMMs, and which industry or end-application segments are they suitable for?
SMM adds a third dimension to AFMs in that the evanescent microwave field created at the tip penetrates below the surface of the sample, while AFM typically looks at surface topography only. Now there are other modes of AFM where some subsurface features can be detected. But SMM can actually scan down into the sample by varying the tip bias, depleting carriers deeper into the sample as a function of bias, and then measuring capacitance with the enhanced microwave sensitivity. The “below the surface” imaging capability coupled with 5-10nm resolution is particularly useful for doping analysis, capacitance measurement of different layers, and other solid state analysis. This 3D profiling is unique to SMM.

What specific key applications could the SMMs be used for?
They can be used for doping measurement, dielectric measurements, calibrated capacitance measurements, and any other relationship that can be determined from these parameters. We have looked at alloy oxidation defects below the surface, graphene homogeneity, silicon nanowires, nanoparticle properties, oxide and doping layer characterization in semiconductors, and even some early work on measurements of living cells, where the ability to look beneath the cell membrane wall could be quite powerful.

What other technology challenges does your SMM address that other high-end measuring equipment cannot?
Beyond the ability to make nano scale microwave measurements and image in 3D we have an impedance transforming capability in the SMM that allows us to make very sensitive measurements at high impedances. Also, our network analyzers continue to evolve toward higher frequency, non-linear measurements, and improved speed and sensitivity, so those capabilities will transfer to the SMM over time.

As the semiconductor industry moves to even lower technology process nodes, what are the challenges facing the test and measurement industry and what is SMM offering to address these challenges?
The main challenges are the spatial resolution and the ability to measure smaller and smaller currents, voltages, capacitances, and making good network analyzer measurements at very high impedances. Since SMM resolution is defined by the tip size and material dielectric properties, we can potentially scale down our resolution even further by shrinking the tip. When you do this your capacitance sensitivity goes down as well so we need to continue to improve our network analyzer sensitivity. We are working on ways to do this as these improvements will help all network analyzer measurements, not just SMM.

It seems like your competitors haven’t really came out with anything yet in response to your SMM products. Why do you think this is so?
None of our AFM competitors have microwave design capability and none of our microwave instrument competitors have nano scale metrology capability. This is an Agilent hallmark of combining a broad range of disciplines and core competencies to create new measurement paradigms. Growing multiple disciplines in an organization takes a lot of time and money and Agilent has been doing this for 72 years.

What can you say about the industry response on your SMM? Which end application segments were the key adopters?
Industry response has been good but this product represents a long term evolution of capabilities. We have a research group in Europe that is collaborating broadly to enhance SMM, its calibration methodologies, and its range of applications. Initial focus has been on semiconductors and other solid state materials but we will slowly evolve this into new directions. Every publication that comes out from this group and early customers enhances the reputation of this technique and expands its breadth of applicability. Our early customers have been mostly semiconductor companies, researchers in Universities looking for something new to attract research grants, and anyone interested in dielectric properties at the nano scale.

What significant emerging applications do you expect will adopt your scanning microwave microscopy solutions?
I think there are boundless opportunities going forward in the life sciences for this technique. Understanding the basic building blocks of life is now about where electronics was 70-80 years ago. There is so much to learn and physics is at the core of this understanding. Measurement enabled rapid progress in electronics and it is already doing that in the life sciences. There are difficulties making microwave measurements in vivo or in vitro because of the “water” content but we are working on ways to better address this.

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