Probe Contact Detection Using Dithered Motion in IC Testing
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Solution Overview
Problem
Precise positioning of nanoscale probe tips onto integrated circuit elements is challenging due to increasing feature density and structural complexity, making it difficult to predict contact with the surface using open loop positioning systems.
Innovation Solution
The method involves dithering a probe in a plane parallel to the surface using a periodic motion, directing a beam of charged particles to generate detector data, and detecting contact using a lock-in amplifier tuned to the dither frequency, allowing for improved probe tip localization and contact detection without detailed knowledge of the surface position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If open loop positioning is used for probe placement, then positioning speed and system simplicity are maintained, but positioning precision deteriorates due to nanoscale tolerance limitations
Solution Approach 1:
The probe is made to vibrate at a specific frequency (e.g., 100 kHz element frequency) during scanning. When the probe tip contacts the sample surface, the vibration is damped or stopped, providing a detectable signal change that indicates contact. This allows precise contact detection without requiring complex closed-loop positioning systems.
Solution Approach 2:
A periodic dithering signal is applied to the probe to induce oscillatory motion. The probe is dithered back and forth at a known frequency, and contact with the surface is detected by monitoring changes in this periodic motion. The system scans through multiple frequencies to identify resonance, then uses that resonance frequency for contact detection.
2Difficulty of detecting and measuring
If imaging-based contact detection is used, then contact detection capability is improved, but probe visibility deteriorates due to nanoscale feature similarity
Solution Approach 1:
Instead of relying on visual imaging to detect contact, the system uses mechanical vibration of the probe. The vibration provides a dynamic signal that changes upon contact, making the probe's contact state detectable through its motion characteristics rather than through visual observation, thus overcoming the probe visibility problem.
Solution Approach 2:
The system continuously monitors the probe's vibration response and uses this feedback to detect contact. By measuring changes in the probe's oscillatory motion (such as amplitude or frequency shifts) and comparing them to expected values, the system can determine when contact occurs without needing to visually distinguish the probe from surrounding features.
3Productivity
If probe scanning speed is increased to improve productivity, then throughput is improved, but contact detection accuracy deteriorates due to reduced measurement time
Solution Approach 1:
The periodic vibration provides a continuous, high-frequency signal that can be sampled at various rates. Even during fast scanning, the probe maintains its oscillatory motion, allowing contact detection through frequency analysis of the vibration signal rather than requiring slow, continuous positional measurement, thus maintaining accuracy during high-speed operation.
Solution Approach 2:
The vibration-based detection method is inherently more sensitive to contact events than position-based methods. The mechanical oscillation amplifies the contact signal, allowing accurate detection even with reduced measurement time during fast scanning operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise detection of contact between the probe tip and the surface, enhancing the performance of integrated circuit testing systems by isolating the influence of contact on the probe motion and reducing vibration and background noise.
Implementation Method 1
directing a beam of charged particles toward a region of the probe. The method can include generating detector data describing the periodic motion of the probe based at least in part on an interaction between the beam of charged particles and the region of the probe
Implementation Method 2
Detecting the contact can correspond to an attenuation of an output of the lock-in amplifier at the dither frequency
Implementation Method 3
dithering a probe in a plane substantially parallel with a surface using a periodic motion having a dither frequency
Data Source
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AI summary
Systems, methods, and techniques for detecting a contact between a probe tip and a sample surface. A method can include dithering a probe in a plane substantially parallel with a surface using a periodic motion having a dither frequency. The method can include directing a beam of charged particles toward a region of the probe. The method can include generating detector data describing the periodic motion of the probe based at least in part on an interaction between the beam of charged particles and the region of the probe. The method can include displacing the probe toward the surface. The method can also include detecting a contact between the probe and the surface using the detector data.