Wafer Inspection Z-axis Control via Motorized Chuck and Camera
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Solution Overview
Problem
Current semiconductor inspection methods face challenges in precisely adjusting the probe platen's height and position relative to the wafer, due to the heavy weight and complexity of the motorized chuck stage, which can lead to improper contact and potential damage during testing.
Innovation Solution
A wafer inspection method that uses a control rod to adjust the motorized chuck stage along the Z-axis, with a displacement range and corresponding control signals to precisely control the position and movement of the wafer relative to the probe, ensuring accurate contact and minimizing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the probe platen is used to adjust the probe position relative to the wafer, then the probe can be positioned for testing, but the heavy weight makes precise fine adjustment difficult
Solution Approach 1:
The system divides the adjustment function into two independent parts: the motorized chuck stage handles coarse positioning of the wafer, while a separate camera system handles fine positioning and verification. This segmentation allows each component to be optimized for its specific function without being burdened by the other's requirements.
Solution Approach 2:
The patent replaces direct mechanical adjustment of the heavy probe platen with an optical system (camera) for fine positioning. The camera captures images to determine probe-wafer alignment, substituting mechanical fine-adjustment mechanisms with optical detection and control.
2Productivity
If the probe comes into direct contact with the pad for testing, then electrical testing can be performed, but improper contact may cause damage to the probe or wafer
Solution Approach 1:
The system performs preliminary positioning using the camera to capture images and determine the exact location of the pad before the probe makes contact. The motorized chuck stage is adjusted in advance to bring the probe into proper alignment with the pad, ensuring safe contact conditions are established before testing begins.
Solution Approach 2:
The camera system provides continuous visual feedback on the probe-wafer relative position. By capturing images and analyzing the probe trace and pad location, the system can determine whether proper contact is achieved and adjust accordingly, preventing improper contact that could cause damage.
Data Source
AI summary
A wafer inspection method was provided. A motorized chuck stage is controlled by a control rod to be displaced between an upper position and a lower position of an adjustment range along a Z-axis direction, to change a relative position of a wafer on the motorized chuck stage relative to a probe. The control rod is movable between an upper limit position and a lower limit position in a displacement range. The wafer inspection method includes: determining a position of the control rod in the displacement range based on a measurement signal; determining a moving direction and a moving distance of the control rod based on a change of the measurement signal; generating a control signal based on the moving distance of the control rod; and controlling, based on the control signal, the motorized chuck stage and a camera stage to be displaced the same distance.