Automated Cross-Cleaning of Probes

This application example demonstrates how closed-loop position control of the probes ensures consistently safe and user-friendly cross-cleaning processes.

In advanced semiconductor failure analysis and device characterization, nano-probes are used to make electrical contact with individual structures deep within integrated circuits. Over time, these probe tips become contaminated with oxides, carbon residues, or other materials from previous contacts. This contamination can lead to poor electrical contact and unstable measurement results. To restore probe performance, one technique used is known as electrical cross cleaning.

Electrical cross cleaning involves bringing two nano-probes into direct contact and applying a precise, constant current between them. The current flow generates localized heating at the contact point, which can help remove built-up contaminants from the probe surfaces and re-establish reliable electrical behavior.

However, this method is not without risks. One major concern is overheating, which can lead to melting or deformation of the probe tips if the current is too high or the contact is maintained for too long. Additionally, prolonged heating can cause the tips to become blunt, reducing their sharpness and, consequently, their ability to make precise and low-resistance contact with nanoscale features. The effectiveness of electrical cross cleaning is also highly dependent on the operator, as the process lacks standardization. Variables such as contact force, alignment, duration, and current level must be carefully controlled, making the success of the procedure inconsistent and sometimes unpredictable.

Another important risk involves the mechanical fragility of the nano-probes. Due to their extremely fine and delicate structure, they can easily bend or deform during contact, especially if the motion induces vibrations or mechanical oscillations in the probes. Even minor uncontrolled movements can compromise the tip geometry and reduce probing accuracy.

Despite these challenges, electrical cross cleaning remains a commonly used method due to its speed and convenience. To minimize risks, it is crucial to carefully control the applied electrical parameters and follow standardized procedures wherever possible.

Electrical cross cleaning requires precise, stable probe control to avoid damage. Our system uses closed-loop piezo-driven axes, allowing probes to make contact gently and safely.

Thanks to integrated position sensors on all axes, we eliminate creep and hysteresis, which are typical in piezo systems and could otherwise lead to uncontrolled probe bending.

This combination of SmarAct’s proven motion technology and intuitive software makes the cross cleaning process safer, more reliable, and easier to perform—as demonstrated in the following example video.

To support users during complex procedures, our software provides Guided Workflows—application-specific, standardized processes that simplify and secure operation. One of these workflows is dedicated to Cross Cleaning of nano-probes.

At the beginning of the process, the user selects the two probes to be used. Their positions are then automatically detected in the SEM, and the system aligns them at two predefined cross points. The user only needs to lower the upper probe until mechanical contact is established.

Once the contact points are set, the system—using its built-in position sensors—automatically alternates between them. Heating is performed at the rear position, while contact resistance is measured at the front. With each cycle, the current is gradually increased.

This automation ensures a controlled and repeatable process, which:

1. Prevents overheating, as the current starts low and only increases if needed.
2. Avoids excessive heating duration, since current flow stops automatically upon reaching preset limits.
3. Eliminates mechanical damage, through consistent, vibration-free probe movements.
4. Ensures reproducible results, as all process parameters are precisely managed by the software.

The video demonstrates how this intelligent workflow makes cross cleaning simpler, faster, and safer for every user.