Carrier Thickness Measurement for Eccentric Wafer Holes
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Solution Overview
Problem
Conventional carrier measurement devices fail to accurately measure the thickness and shape of carriers, particularly the hole surrounding portion, which is eccentric, leading to variations in semiconductor wafer quality during double-side polishing.
Innovation Solution
A carrier measuring device with a rotary table, upper and lower thickness sensors, and a slide unit that allows for non-contact measurement of the carrier's thickness and shape, including the hole surrounding portion, by aligning the carrier's eccentric hole with the rotary table's center and rotating the table to measure along the entire circumference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional contact sensors and reference rods are used to measure carrier thickness, then the measurement can be performed with simple equipment, but the measurement precision is insufficient for detecting variations in the hole surrounding portion
Solution Approach 1:
The patent replaces the mechanical contact sensor system with a laser-based optical measurement system. The laser displacement sensor non-contactly measures the position of the carrier upper surface, eliminating mechanical contact and enabling high-precision detection of the hole surrounding portion thickness variations without the limitations of contact-based reference rods.
Solution Approach 2:
The patent creates a detailed measurement value distribution map that copies the three-dimensional shape information of the carrier, particularly the hole surrounding portion. This visual representation allows for precise analysis and comparison of carrier geometries without physically handling or risking damage to the carriers.
2Measurement precision
If the carrier hole is eccentric with respect to the carrier center, then the carrier can accommodate the wafer properly, but the conventional measurement devices cannot accurately measure the hole surrounding portion
Solution Approach 1:
The patent employs a rotatable stage that can rotate the carrier to various angular positions. This dynamic positioning capability allows the laser displacement sensor to measure the hole surrounding portion at multiple angles, accommodating the eccentric hole configuration and enabling complete circumferential measurement that adapts to any hole position relative to the carrier center.
Solution Approach 2:
The patent adds the angular dimension to the measurement process by rotating the carrier on the rotatable stage. This transforms a single-point measurement approach into a multi-dimensional measurement system that captures the hole surrounding portion geometry at various angular positions, fully accommodating eccentric hole configurations.
3Manufacturing precision
If carriers with varying thickness and shape are used in one batch of double-side polishing, then the polishing process can accommodate different carrier conditions, but the quality uniformity of the polished wafers deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where measurement results from the laser displacement sensor are fed back to evaluate carrier quality. The measurement value distribution map provides quantitative feedback on carrier thickness and shape variations, enabling selection of carriers with consistent geometry for batch polishing, thereby ensuring uniform wafer quality while maintaining manufacturing efficiency.
Solution Approach 2:
The patent performs preliminary measurement and evaluation of carriers before they are used in batch polishing. By pre-assessing carrier thickness and shape using the laser measurement system and rotation stage, carriers can be selected and grouped based on their geometric consistency, ensuring that only carriers meeting quality criteria are used together in polishing batches.
4Measurement precision
If the measurement process focuses only on the central portion of the carrier, then the measurement process is simplified, but the hole surrounding portion variations are not detected
Solution Approach 1:
The patent implements continuous measurement around the entire carrier circumference by combining the laser displacement sensor with the rotatable stage. As the stage rotates, the sensor continuously measures the hole surrounding portion at multiple angular positions, ensuring complete coverage of the measurement area and detection of any thickness variations without requiring multiple separate measurement operations.
Solution Approach 2:
The patent performs preliminary positioning of the carrier on the rotatable stage with the hole surrounding portion appropriately oriented. This preliminary action, combined with the continuous rotation and measurement capability, ensures that the hole surrounding portion is measured completely in one continuous operation, detecting variations efficiently without time-consuming repeated measurements.
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
Enables accurate selection of carriers with minimal variance in thickness and shape for batch processing, improving the uniformity and quality of semiconductor wafer polishing.
Implementation Method 1
a laser displacement sensor configured to be positioned above the carrier and measure a position of an upper surface of the carrier in a non-contact manner
Data Source
AI summary
A carrier measuring device includes a rotary table, a table drive motor, an upper thickness sensor, a lower thickness sensor and a slide unit. The rotary table includes a carrier receiver configured to horizontally house a carrier formed with a hole in which a semiconductor wafer is held, the hole being eccentric with respect to the carrier. The table drive motor rotates the rotary table around a center axis thereof as a rotation axis. The upper thickness sensor and the lower thickness sensor are positioned above and below the carrier, respectively, and measure a thickness of the carrier in a non-contact manner. The slide unit slides the rotary table in a horizontal direction. The carrier receiver is formed to be capable of housing the carrier in a manner that a center of the hole coincides with a center of the rotary table.