In cryogenic electrical characterization, even small variations in contact resistance can influence measurement accuracy and repeatability. Over years of supporting researchers who use our cryogenic probe stations to study everything from superconducting devices to compound semiconductor structures, we’ve seen a consistent theme: the probe tip material often determines whether a contact is stable and reliable.
Soft metals, hard metals, and oxide-forming contacts each respond differently to applied pressure, surface oxidation, and thermal cycling. As a result, they demand different properties from the probe tip you choose.
Probe tip choices: what’s included and what else is available
Every Lake Shore probe station ships with a probe starter kit that includes:
- (2) standard DC/RF beryllium copper (BeCu) tip probes (ZN50R-25-BECU)
- (2) standard DC/RF tungsten tip probes (ZN50R-25-W)
- (2) continuously variable temperature DC/RF tungsten tip probes (ZN50R-CVT-25-W)
BeCu tips are best for soft metallizations. They offer low contact resistance with minimal pad deformation, helping preserve pad integrity during repeated measurements and are well-suited for probing typical gold contact landing pads with minimal pad damage.
The BeCu probes included with our stations are our standard DC/RF probes and have a 25-µm tip radius, but the same probes can also be ordered with a 3-, 10-, 100-, or 200-µm tip radius.
Plus, we also offer a flexible CVT version for probing fragile or thin, soft metal materials over the course of long or variable temperature experiments. The flexible design helps maintain electrical contact between probe and contact pad over temperature sweeps — increasing the longevity of the contact pad and probe as well as improving characterization throughput. You spend less time adjusting probe positions and more time conducting research.
Tungsten tips are the best choice for making electrical contact on hard oxides. Their hardness allows them to pierce through and maintain a sharp apex longer than softer probe materials. Because breaking through the oxide layers requires sufficient tip pressure, the tungsten versions of our standard probes generally provide more reliable contact for oxidized materials than tungsten CVT probes (which apply lower tip force). That said, the tungsten CVT probe tips, while still hard enough to break through thin oxides, are preferred when you want to probe many times, re-land on the same pad, and repeat temperature sweeps. Their contact resistance is more repeatable over the course of longer experiments.
All the tungsten probes included with our stations have a 25-µm tip radius, but the standard probes can also be ordered with a 3- or 10-µm tip radius, and the CVT tungsten probes can also be ordered with a 10-µm tip radius.
And for applications involving soft contact material, such as gold, silver, and indium, we offer CVT probes with gold-coated tungsten tips. Tips with this material offer the lowest contact resistance and the widest operating range of all our CVT-style probes. They are well-suited for long-duration experiments over variable temperatures where you want reliable electrical contact while minimizing damage to the delicate metal material.
Questions about choosing a probe for your specific application? Contact us to choose the right probe type for your cryogenic probe station. We’ll help you identify the best solution for accurate, repeatable measurements at cryogenic temperatures.
Also, watch our videos demonstrating standard DC probe landing and variable temperature DC probe landing in a cryogenic probe station.