Eddy Current Probe Lift-Off Stabilization via Pneumatic Suspension
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Solution Overview
Problem
Conventional measuring devices for metal film thickness suffer from unstable lift-off distances, affecting accuracy due to mechanical movement inaccuracies and workpiece thickness variations, especially during the CMP process for advanced ICs with low k media layers.
Innovation Solution
A device with a rotating unit, linear driving mechanism, and an eddy current probe with self-adaptive lift-off stabilization, utilizing a cantilever beam and air-floatation system to maintain a consistent distance without contacting the film, allowing for precise and rapid global thickness measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional measuring device is used, then the eddy current probe can measure the metal film thickness, but the lift-off distance is unstable due to mechanical movement inaccuracies and workpiece thickness variations
Solution Approach 1:
The patent uses a pneumatic suspension system with air bearings to support the measuring head, replacing mechanical contact with air cushion support. This eliminates mechanical friction and movement inaccuracies, stabilizing the lift-off distance to within micrometer range while enabling precise thickness measurement through non-contact measurement
2Measurement precision
If the lift-off distance is stabilized using mechanical means, then measurement accuracy improves, but the device complexity increases due to additional stabilization mechanisms
Solution Approach 1:
The patent employs air bearings and pneumatic suspension mechanisms to stabilize the lift-off distance, using gas pressure control instead of complex mechanical stabilization systems. This approach simplifies the overall structure by eliminating the need for intricate mechanical feedback and adjustment mechanisms while achieving micrometer-level stability
Solution Approach 2:
The patent replaces traditional mechanical contact and stabilization systems with pneumatic fields and electromagnetic sensing. The measuring head is suspended by air cushions rather than mechanical supports, and lift-off distance is controlled through pneumatic pressure rather than mechanical actuators, reducing mechanical complexity
3Measurement precision
If the eddy current probe contacts the metal film for measurement, then the lift-off distance is fixed, but the copper film may be damaged during the measuring process
Solution Approach 1:
The patent uses air bearings to create a non-contact measurement environment where the measuring head hovers above the workpiece on an air cushion. This eliminates physical contact between the eddy current probe and the copper film, preventing any mechanical damage while maintaining stable lift-off distance for accurate measurement
Solution Approach 2:
The patent replaces mechanical contact measurement with non-contact eddy current measurement supported by pneumatic fields. The air bearing system substitutes mechanical support with gas pressure support, allowing the probe to measure thickness without touching or damaging the delicate copper film
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
The solution stabilizes the lift-off distance, enabling precise and rapid measurement of metal film thickness across the workpiece, independent of mechanical inaccuracies and workpiece thickness, without damaging the film, thus improving measurement accuracy and reliability.
Implementation Method 1
An eddy current method is a non-contact measuring method, which does not damage the copper film during the measuring process and has high accuracy
Data Source
AI summary
A device for globally measuring a thickness of a metal film (901), comprises: a base (10); a rotating unit (20) comprising a fixed member (21) fixed on the base (10) and a rotating member (22) having a rotating joint (23); a working table (50) fixed on the rotating member (22) and having a vacuum passage which is formed therein and connected with the rotating joint (23); a linear driving unit (30) including a guide rail (31) fixed on the base (10) and a sliding block (32) slidable along the guide rail (31); a cantilever beam (40) disposed horizontally and defining a first end fixed with the sliding block (32) and a second end; a measuring head (80) connected to the second end of the cantilever beam (40), facing a surface of the working table (50) and having an eddy current probe (82) disposed therein.