Transistors, the backbone of modern electronics, continue to face failure challenges despite advancements in technology. These failures can be traced to a variety of factors, including environmental stress, material degradation or manufacturing defects. Addressing these issues is critical in sectors like telecommunications, automotive and aerospace, where transistor reliability directly impacts overall system performance.
Understanding Transistor Failure Modes
Two prominent failure modes for transistors are Short Circuit and Open Circuit.
Short Circuit: In this failure mode, the transistor acts as a short circuit. The resistance across the junction becomes negligible, causing the transistor to remain in a conducting state, regardless of the input signal. This behavior disrupts the intended switching or amplifying operations of the transistor and can result in catastrophic damage to the surrounding circuitry.
Open Circuit: In this mode, the transistor behaves like an open circuit, with the junction resistance becoming exceedingly high or infinite. This causes the transistor to fail to conduct current, rendering it ineffective in its designated role within the circuit.
Both disrupt the intended operations of circuits, with short circuits leading to unregulated current flow and open circuits preventing any current flow. As transistors are used in more advanced and compact applications, these failure modes are becoming increasingly problematic, necessitating more innovative solutions such as improved self-healing mechanisms or the use of gate-all-around (GAA) technologies for enhanced control of channel behavior.
Common Causes of Transistor Failures
Manufacturing Defects
Manufacturing remains one of the most significant contributors to early transistor failures. As devices scale down to nanometer dimensions (e.g., sub-7nm technologies), maintaining precise manufacturing tolerances is challenging. FinFET technology is giving way to Gate-All-Around (GAA) FETs in 3nm and smaller nodes, where enhanced transistor control is necessary to mitigate the effects of parasitic capacitances and improve device performance. Additionally, defects such as improper packaging, inadequate thermal management and contamination during fabrication can severely compromise the device's longevity. Issues such as wire bonding problems, mechanical stress and poor soldering quality can all introduce vulnerabilities that lead to early-stage failures.
Hot Electron Effects:
This issue is particularly acute in transistors operating at high frequencies or in AlGaN/GaN HEMTs used for high-power applications. The accelerated charge carriers can penetrate insulating layers, leading to irreversible damage. Recently, wide bandgap semiconductors such as gallium nitride (GaN) have been introduced to improve thermal and electrical performance, especially in power and high-frequency circuits. GaN-based HEMTs show higher resistance to electron-induced degradation, but they introduce new challenges like current collapse due to charge trapping. Additionally, this effect is even more pronounced in short-channel MOSFETs (common in modern high-performance circuits), especially in sub-100nm geometries. The high electric fields in these smaller devices accelerate carriers, increasing the risk of oxide damage and long-term degradation.
Parasitic Structures
Unwanted parasitic effects, such as latch-up in BJTs or self-heating in GaN-based HEMTs, degrade the performance of high-power devices. The trend toward nanosheet transistors has been proposed as a solution, offering better electrostatic control and reducing parasitic capacitances. This advancement helps in high-frequency applications, mitigating the parasitic structures that otherwise lead to performance bottlenecks.
PCB Faults
The role of PCB design is often underestimated, but thermal and mechanical stress on the PCB can affect transistor performance. Especially in high-speed applications, electromagnetic interference (EMI) caused by faulty PCB layouts can degrade switching times and lead to erratic behavior of transistors. Modern rigid-flex PCB designs help reduce stress points and improve the overall longevity of transistors, particularly in compact, high-frequency circuits.
Increased Contact Resistance Electromigration
This a persistent problem in finer process nodes (sub-5nm) where high current densities cause metal atoms in interconnects to migrate, increasing contact resistance and leading to hot spots. Emerging solutions include the use of cobalt and ruthenium-based interconnects in advanced nodes, which show higher resistance to electromigration compared to traditional copper-based designs.
Voltage Spikes
To counteract voltage-induced failures, especially in GaN-based power transistors, engineers are implementing Transient Voltage Suppression (TVS) diodes more frequently. This reduces the likelihood of junction breakdown or dielectric failure during high-voltage switching. GaN transistors, particularly in HEMT configurations, are also benefiting from enhanced designs to cope with current collapse under voltage spikes.
Diagnosing and Overcoming Transistor Failures
Soak Testing for Early-Stage Faults
Soak testing remains a reliable method for exposing potential transistor failures before they are integrated into more complex systems. Automotive-grade power transistors, for instance, are subjected to extensive soak testing to identify temperature-induced degradation under harsh conditions.
Self-Testing in Real-World Applications
Built-in self-testing (BIST) continues to grow in importance, especially in mission-critical applications like aerospace and autonomous vehicles, where real-time fault detection is essential. Advanced machine learning models are also being explored to predict failure modes based on real-time data collected from BIST systems, enabling more proactive failure prevention.
Multimeter Diode Test Method
The diode test is still an effective, quick, and manual way to diagnose whether a transistor is functioning as expected. However, for more advanced transistors, such as wide-bandgap GaN devices, additional tools like thermal imaging and advanced parametric testing are increasingly necessary to detect early signs of degradation.
Replacement of Faulty Transistors
With the advent of field-programmable gate arrays (FPGAs) and system-on-chip (SoC) solutions, replacing faulty transistors is becoming more complex. Engineers must ensure that replacement components are not only compatible in terms of electrical characteristics but also capable of handling the same thermal and environmental stresses.
Implementing Voltage Protection Measures
In advanced power management circuits, GaN-based transistors are being paired with clamping diodes and TVS devices to safeguard against high-voltage transients. These protective components help extend transistor life by diverting excess voltage, reducing the risk of thermal runaway or junction breakdown.
The ongoing development of transistor technology—particularly in wide-bandgap semiconductors and nanoscale architectures like GAA—holds promise for mitigating the persistent issues surrounding transistor failures. By integrating advanced testing methods, predictive diagnostics and better material choices, engineers are poised to extend the operational life and reliability of these critical components in modern circuits.
McKinsey Electronics supports engineers in selecting the right components and mitigating transistor failures. With its expansive line card of advanced semiconductors and deep expertise in circuit design, we, at McKinsey Electronics ensure that our clients receive the most reliable, cutting-edge components for high-performance applications. Contact us today.