Researchers at Adelaide University have developed a way to peer inside working electronic chips without ever opening their packaging, effectively creating a form of “X-ray vision” for semiconductors. By using terahertz waves for semiconductor monitoring, the team can remotely observe the electrical activity of transistors in real time, providing a glimpse into the internal operations of a device while it remains fully functional.
This non-invasive approach allows scientists to detect tiny movements of electrical charge inside packaged semiconductors without disturbing their operation. Unlike traditional testing methods that often require physical access to the chip’s internal components, this system can penetrate the non-metallic materials typically used in chip packaging, such as plastic and ceramics.
The research, led by Professor Withawat Withayachumnankul, represents a significant shift in how engineers can diagnose and test electronics. While traditional X-ray inspections can produce detailed images of a chip’s physical structure, they cannot observe its electrical behavior. This new system fills that gap, allowing for the observation of transistors as they switch on and off during actual use.
The Mechanics of Terahertz Probing
The system operates by utilizing the unique properties of the terahertz spectrum, which spans from 0.1 to 10 THz and sits between the microwave and infrared bands. One of the primary advantages of these waves is their ability to penetrate non-metallic materials with high spatial and depth resolutions, making them ideal for non-destructive evaluation via the Terahertz Engineering Laboratory at the University of Adelaide.
The process begins with a vector network analyzer (VNA), a laboratory tool used to generate microwave signals with a known frequency and phase. This signal is then converted into a terahertz wave using a VNA frequency extender. To ensure precision, the radiation passes through an objective lens that concentrates the beam onto a tiny area—as small as one square millimeter—which is sufficient to encompass several bipolar junction transistors.
When these transistors switch states, they slightly alter the properties of the terahertz signal. The reflected wave then travels back to a receiver in the VNA extender, where This proves converted back to a microwave frequency and compared with the original signal. By measuring minute differences in amplitude and phase, the researchers can infer changes in the movement of charge. Specifically, as the PN junctions in the monitored transistors become more conductive, the reflected terahertz signal grows stronger.
A critical component of this setup is the homodyne quadrature receiver. Because the interaction between the terahertz wavelength and the tiny chip features produces only a very small change in the signal, noise from the VNA’s oscillator could easily obscure the data. The homodyne receiver compares the probe signal with the original, effectively cancelling out shared noise and leaving only the changes induced by the chip’s electrical activity.
A Safer, Non-Invasive Alternative to Testing
For years, the semiconductor industry has relied on electronic probing and X-ray inspection. However, electronic probing is invasive, and X-rays involve ionizing radiation. Terahertz waves provide a safer alternative because they are non-ionizing, meaning they do not have enough energy to remove electrons from atoms or molecules.
Because the plastic and ceramic used in most semiconductor packaging are thin enough to allow terahertz waves to pass through without excessive absorption, the researchers can measure semiconductor activity in situ. This means the chip does not need to be removed from its housing or have its packaging stripped away, which is essential for maintaining the integrity of the device under test.
This capability is particularly promising for safety-critical applications, such as high-power electronics. In these environments, taking a device offline for testing can cause significant operational disruptions. A remote, non-invasive monitoring system would allow engineers to verify the health and performance of these components while they remain in active service.
Current Limitations and Future Applications
Despite the breakthrough, the technology is still in its early stages. One of the primary hurdles is the architecture of modern integrated circuits. Many contemporary chips consist of multiple layers of interconnects and active circuitry. If these over-layers are opaque to terahertz radiation, the system may struggle to diagnose devices buried deep within a multi-layered chip.
Currently, the system’s sensitivity is best suited for discrete devices. The team has successfully monitored the switching states of rectifier diodes, bipolar junction transistors, and field-effect transistors (FETs). They have as well begun testing integrated circuits containing up to six FETs, but increasing sensitivity will be necessary to examine more densely integrated, complex chips.
Looking ahead, the implications of this research extend beyond simple diagnostics. Professor Withayachumnankul, collaborating with partners in Germany, is exploring the possibility of using this technique to read encrypted data within chips. This potential for non-invasive data extraction could have significant implications for hardware security and forensics.
The research was formally published in the IEEE Journal of Microwaves on March 17, 2026, and continues to be developed through the University of Adelaide’s ongoing initiatives in terahertz engineering.
As the team works to refine the sensitivity of the system and overcome the challenges of multi-layered chip opacity, this technology could redefine the standard for semiconductor quality control and security auditing.
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