Tungsten Probes for Low-Voltage Nanoprobing – Custom Fabrication
Nanoprobing under low accelerating voltages in the SEM presents unique challenges that lab engineers regularly face during fault analysis of advanced semiconductor devices. Standard tungsten probes, while mechanically robust and conductive, can introduce unexpected imaging distortions when operated below ~200 eV. This is primarily due to the paramagnetic nature of tungsten, which interacts with the SEM’s electron beam and amplifies the effects of even weak magnetic fields—leading to beam deflection, image drift, or degraded resolution.
To maintain stability and precision in such sensitive conditions, specially prepared probe needles are required. These must be mechanically sharp, clean and minimize the magnetic interaction to reduce the impact on beam alignment during probing. Off-the-shelf needles often fail to meet these criteria, especially for high-precision contact on sub-10 nm structures.
This Application Note outlines a practical, lab-proven method for fabricating tungsten probe tips optimized for low-voltage SEM nanoprobing. The process enables consistent production of sharp, contamination-free tips with tailored geometry—allowing for stable, high-resolution imaging and accurate electrical contact in challenging low-kV environments.
Production
Before etching, the tungsten wires must be properly prepared. This includes cutting them to the desired length. We offer pre-cut tungsten wires in various lengths at a fair price, saving customers time and effort. After cutting, the needles must be bent to the required angle. For this, we provide a bending station along with the etching system. It allows users to precisely set both the angle and working distance of the needle, ensuring consistent preparation. The entire process takes only a few seconds and delivers repeatable results every time.
Component handling
The prepared tungsten wire can be quickly and easily clipped into the etching station using tweezers. This step is straightforward and takes only a few seconds. Just make sure that the bent part of the wire roughly points downward during insertion.
The etching station allows up to three probes to be processed simultaneously, enabling the preparation of a complete set of nanoprobes in a very short time. Once the wires are loaded, the tower can be lowered into the etching solution, and the etching process can be started.
Active aligment
The etching station comes with dedicated software that includes both the ability to create custom recipes and a set of standard presets. Among them is a recipe specifically optimized by us for probe geometries tailored to ultra-low acceleration voltage applications. Recipes can be loaded with a single click, and the etching process runs fully automated from start to finish.
If special needle shapes are required, we also offer a custom recipe service after a brief feasibility check—feel free to contact us for more information.
Supply and removal
At the end of the etching process, a specially developed process parameter analysis evaluates the quality of the fabricated probes. Using a simple traffic light color scheme, it indicates whether the needle geometry meets high-quality standards. This allows poorly fabricated probes to be identified and discarded before installation, saving valuable time.
Afterward, the probes are briefly cleaned in a dedicated cleaning solution and are then ready for immediate use in the nanoprober.
Result
Fig.1: 100 eV SEM image of the low-eV tungsten probes during nanoprobing.
The example image clearly demonstrates that our probes enable high-quality imaging with minimal distortion even at just 100 eV. Since the probes are freshly fabricated and immediately cleaned in a dedicated solution, the tungsten surface remains oxide-free and free of contaminants. This ensures excellent contact resistance right from the start—no cross cleaning in the SEM is required, allowing measurements to begin immediately.
With our all-in-one etching solution, you can prepare high-quality tungsten probes in just a few steps. Pre-cut wires and the included bending station ensure consistent geometry every time. Up to three probes can be etched simultaneously using our intuitive software with optimized standard recipes—perfect for low-voltage SEM imaging down to 100 eV.
An integrated process analysis instantly indicates the quality of each fabricated probe, and a final cleaning step ensures contamination-free tips. Since the probes are freshly made, the tungsten remains oxide-free—allowing immediate use without additional Cross Cleaning.