SRC: Nanostructures Require Monitoring at Molecular, Atomic Levels
Alexander E. Braun, Senior Editor -- Semiconductor International, 3/13/2008 7:27:00 AM
The development of nanotechnology to its full capabilities requires the ability to cope with things like quantum effects, and attaining this will require unprecedented advances in metrology, said Dan Herr, director of nanomanufacturing sciences for the Semiconductor Research Corp. (SRC, Triangle Park, N.C.). Over the past two years, this industry organization has exerted a concerted effort to determine what and where the metrology gaps are and how they can be closed to meet nanotech’s needs.
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| Dan Herr, Semiconductor Research Corp’s Director of Nanomanufacturing Science Research. (Source: SRC) |
The SRC is also addressing considerations that lie further out into the future. “With some of the emerging devices, it may become necessary to look at coupled nanoscale phenomena, such as spin and charge or orbital reorientation, and find ways of doing these measurements simultaneously,” Herr said. “Also, because we’re probing at increasingly smaller scales, it’s rapidly becoming crucial to have as complete an understanding about the interaction between probe and sample: With each measurement, is the probe changing the sample or the sample changing the probe?”
These are not the only areas of inquiry for the SRC. For instance, self-assembly is emerging on the research horizon. With the International Technology Roadmap for Semiconductors (ITRS) looking at functional diversification as a new vector, there will be whole new families of materials to integrate on CMOS platforms, and some of these may be organic. The problem is that we currently lack good tools for monitoring those new materials.
Herr added that an entirely new discipline is needed to enable structure correlation at the atomic and molecular level with macroscopic properties, and help determine how to fabricate or synthesize those materials. “We must develop tools to help monitor those systems,” he said, “and not just be able to measure these structures and materials locally, but across large areas as well. Finally, there is the whole area of environment, safety and health, which requires that we understand the possible impact of these nanomaterials and nanoparticles on our health.”
Herr is not unduly alarmed by the plethora of “red bricks” on the ITRS. “This may look scary,” he said, “because red means that there are no potential solutions for these needs. The flip-side is that, for the first time in probably three or four decades, there is research coming out of academia and other sources with the potential of significantly affecting how we will measure and manufacture things in the future. I never underestimate creativity. I have faith that these measurement options will be found.”
Soon it will become necessary to simultaneously bring to bear several measurement approaches on a sample. This will result in a fire hydrant’s worth of data spewing out. “Obviously, we’re going to need tools that will help us deconvolve the singles from these multiple tools,” Herr said. “Also, we’re going to increasingly have to rely on modeling and its interaction with the measurement tool to provide us with a clearer picture of what is actually happening at atomic and molecular levels. Being able to fabricate precise and repeatable atomic-scale architectures is a materials challenge. I am encouraged that the measurement tools that we’re starting to look at are moving towards operation at the atomic scale, away from bulk. This will help clarify where the real needs for these systems lie.”
Although Herr is convinced that there is considerable life still left in scaling, it will become necessary to build things differently. “Presently, we depend on things like ion implantation to deposit dopants in a channel, and expect an even dispersion there,” he said. “Within the next decade, there may be <100 dopants in the channel. In that scenario, not only the number but the position of those dopants becomes very important. Others are saying let’s go to fully depleted systems, which have no dopants in the channel. It can be argued that the same problem will still exist at the source channel and the channel drain interface, where the concentration of dopants is low enough so that the environment that the carrier sees is bumpy — no longer uniform.”
SRC researchers are convinced that we will require tools that allow us to non-destructively look at these structures in situ through some form of 3-D imaging of atomic and molecular scale embedded structures. “This would give us a handle on whether we are on the right path toward developing processes that will enable us to continue scaling for several more generations,” Herr said, while agreeing that without the metrologies required to generate the necessary data, dimensional control at atomic and molecular levels will be a difficult reality to attain.
