Announced at Electronica 2024 this week, the new source measurement unit measures nano-scale semiconductor device signals that would otherwise be drowned out by electrical noise.At Electronica here in Munich this week, Lake Shore Cryotronics, a company that provides measurement and control solutions for scientific research, released a new source measurement unit (SMU) at Electronica 2024. The company designed the SMU-10, an extremely low-noise, high-sensitivity measurement system, to operate in the ultra-low voltage regimes of sub-nanoscale and 2D nanomaterial semiconductors.
An SMU is a test and measurement instrument that combines the signal source and measurement function on a single pin. While conventional instruments inject signals on one line and measure with another line, an SMU will perform both functions on the same line. The SMU-10 is an add-in module for Lake Shore Cryotronics’ MeasureReady M81-SSM synchronous source measure (SSM) system.
All About Circuits spoke to Chuck Cimino, senior product manager at Lake Shore, to learn more about the new SMU
Lake Shore Cryotronics' Chuck Cimino (left) with All About Circuits editor-in-chief Jeff Child (right) at Electronica 2024 in Munich, Germany.
Key Features at a Glance
“There's a lot of test equipment out there that does a good job keeping up with the Moore's law curve,” Cimino said. “But if things accelerate—let's say, because of the atomic nano-scale evolution—then we feel that Lakeshore has got a lot of technologies and background to help bring some new tools to the challenge.”
Lake Shore claims the SMU-10 features several key performance metrics that can meet those nano-scale challenges, including:
- Voltage ranges: 10 mV, 100 mV, 1 V, 10 V
- Voltage measurement sensitivity: <3 nV1
- Source noise (DC to 10 MHz): <0.2 mV RMS, <1.2 mV p-p (typical)
- Overvoltage protection: _/- 100 VDC
- Current ranges: 1 nA, 10 nA, 100 nA, 1 µA, 10 µA, 100 µA, 1 mA, 10 mA, 100 mA
- Current measurement sensitivity: <1 fA1
- DC output resistance: >10 TΩ (typical)
- Source noise (DC to 10 MHz): <5 nA RMS, <25 nA p-p (typical)
- Maximum power: 1 W, four-quadrant operation
- Magnetic field exposure: Operational up to 50 mT DC
Built to Test 2D Nanomaterials
As semiconductor geometries continue to shrink, operating voltages drop to the point where ambient and test system noise can overpower the active device signal levels. High-performance semiconductors now operate at 1.8 V and lower, reaching even below one volt. 2D nanomaterials drop these operating voltages even lower. At such low voltages and small scale, unwanted heat becomes a first-order factor in its ability to skew the measurement. Test system background ambient noise becomes another first-order factor and can reduce or break the system's testability with conventional measurement equipment.
After many generations of reduced silicon geometries, the semiconductor industry is reaching the physical limits of operable silicon transistors. 2D nanomaterials are new candidate materials for continued miniaturization. They include graphene, carbon nanotubes, goldene, and other 2D structures constructed with a single-atom thickness.
These single-atom layers have shown promise as semiconductor switches. Simple test processors have already been fabricated with carbon nanotubes. According to Lake Shore Cryotronics, the first goldene FET was demonstrated in 2011, and the first processor is expected to be operational in 2025. From there, it will be a race to start developing production products. The SMU-10 is designed to characterize and test these materials.
SMU-10 Packs DC and AC Sourcing—And a Lock-in Amplifier to Boot
The Lake Shore Cryotronics SMU-10 operates with extremely low noise parameters and high sensitivities of below 10 nV/√Hz (AC) and below 100 fA (DC) with maximum voltage/current levels of ±10 V and ±100 mA DC/peak.
Noise level from SMU-10 readings vs. competitive SMUs. Image used courtesy of Lake Shore Cryotronics
The SMU-10 is a modular add-on to the company’s MeasureReady M81-SSM synchronous source measure (SSM) system. The units target applications such as I-V characterization of ultra-small transistors used in specialized sensors, nanoelectromechanical systems (NEMS), quantum computer electronics, and specialized and integrated circuit nano-scale semiconductor-based devices. Multiple SMU-10 units can be added to measure different circuit nodes simultaneously. For example, three units can be combined to measure conditions at the gate, source, and drain of a single transistor switch.
“The new SMU-10 makes highly sensitive, selective AC detection technology used in research labs conveniently available to semiconductor design and test engineers,” Cimino said. “Using the familiar four-instruments-in-one SMU format, they can easily make extremely sensitive, low-noise measurements.”
The SMU-10 is the first SMU with both DC and AC sourcing and measurement capabilities. The host unit, the M81-SSM, utilizes phase-sensitive technology, also known as lock-in amplifier technology. The SMU-10 allows users to select the amplitude and reference frequency AC signal. The processor will lock onto those signals and ignore other offset and noise signals.
In addition to its modularity and remote amplifier architecture, the SMU-10 can do DC as well as AC as well as lock-in amplification,” Cimino underscored. “We can measure RMS, we can do phase and amplitude with a lock-in, and we can make good old DC measurements, too.”
Prepping for Nanomaterial Test and Measurement
While the demise of Moore’s law has been predicted for a few decades now, ongoing performance improvements have kept fire to Gordon Moore’s prognostication. 2D nanomaterial semiconductors are just the latest innovation that promises to keep the law in place. Even so, the challenges of these materials are abundant. Researchers must still better understand nanophysics, develop semiconductors based on these materials, and invent mass fab processes. None of that, however, would be possible without corresponding advancements in test equipment, as Lake Shore Cryotronics is presenting with the SMU-10.
“We're looking at this nano convergence, where Moore's law and traditional silicon runs out of steam, and people start to look at new nanoscale, one-atom-thick sandwiches of graphene to build transistors and integrated circuits,” Cimino said. “In order to characterize, process, develop, and refine their products, they're going to need the ability to measure and source ever lower signals. We made this lock-in, typically research-oriented technology, easy to use and convenient to give you DC, AC, and lock-in—all with a press of a button or a command. This brings those needed capabilities to this evolution.”
