Wafer Cutting Index Correction via Measurement Grooves
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Solution Overview
Problem
In wafer processing, especially for WL-CSP where the front side is sealed with resin, the limited number of exposed target patterns makes it difficult to correct the index amount of cutting blades accurately and in a timely manner, leading to reduced processing accuracy due to potential deviations in cutting blade alignment.
Innovation Solution
A wafer processing method using a cutting apparatus with first and second cutting blades, imaging means for detecting target areas, and indexing means to form cut grooves and measurement grooves, allowing for correction of the index amount without relying on target patterns, ensuring accurate and timely adjustments of the cutting blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the front side of the wafer is sealed with resin for WL-CSP packaging, then packaging protection is improved, but the number of exposed target patterns is reduced, making index amount correction difficult
Solution Approach 1:
The patent introduces measurement grooves as intermediary features that serve as reference markers for index amount correction. These grooves are formed by the cutting blade itself and can be detected by imaging means, replacing the need for target patterns that are obscured by resin sealing. The measurement grooves act as a mediator between the cutting blade and the detection system, enabling accurate measurement without requiring exposed target patterns.
Solution Approach 2:
The patent replaces the optical detection method (relying on target patterns visible to imaging means) with a mechanical marking method. The cutting blade mechanically creates measurement grooves that serve as reference features, substituting the need for pre-formed target patterns. This mechanical approach to creating reference features works independently of the resin sealing status.
2Ease of operation
If target patterns are used for identifying groove position, then alignment is simplified, but accuracy is reduced when target patterns are defective or insufficiently exposed
Solution Approach 1:
The cutting blade performs dual functions: it cuts the wafer and simultaneously creates measurement grooves that serve as reference features for its own position verification. The measurement grooves are generated by the cutting action itself, making the system self-sufficient and eliminating dependence on externally provided target patterns that may be defective or obscured.
Solution Approach 2:
The measurement grooves are formed in advance during the cutting process before final position verification is needed. By creating these reference features during the cutting operation itself, the system prepares the necessary measurement markers beforehand, enabling accurate index amount correction in subsequent operations without relying on pre-existing target patterns.
3Productivity
If cutting blade index amount is not corrected, then processing speed is maintained, but cutting accuracy deteriorates due to gradual deviation from division lines
Solution Approach 1:
The patent implements a feedback mechanism where the position of measurement grooves is detected by imaging means, and the detected position information is used to calculate and correct the index amount of the cutting blade. This closed-loop feedback system continuously monitors cutting blade position accuracy and makes real-time corrections, preventing gradual deviation accumulation while maintaining processing speed.
Data Source
AI summary
A wafer processing method includes a first correction step of measuring a distance “a” between a first cut groove previously formed by a first cutting unit and a division line for the next cut groove, and correcting an actual index amount by using a deviation “b” of the first cutting unit equivalent to the difference between the distance “a” and a proper index amount of the first cutting unit, and a second correction step of forming a measurement groove by using a second cutting unit along the division line for the next cut groove, measuring a distance “c” between the first cut groove and the measurement groove, and correcting an actual index amount of the second cutting unit by using a deviation “d” equivalent to the difference between the distance “c” and a proper index amount of the second cutting unit during the cutting step.