Packaged Wafer Laser Grooving with In-Process Imaging Correction
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Solution Overview
Problem
Existing methods for processing packaged wafers with a small number of exposed key patterns struggle to accurately correct the position of the laser beam applying unit with respect to each division line, leading to potential deviations during the processing.
Innovation Solution
A packaged wafer processing method that includes an alignment step to orient division lines parallel to the X direction, a processing step to form laser processed grooves along each division line, and a correcting step where the distance between the next division line and the previously formed groove is imaged to calculate a correction index amount, allowing for precise positioning without relying on key patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the position correction is performed using the distance between the laser processed groove and the key pattern, then the position of the laser beam applying unit can be corrected, but the correction cannot be properly performed when only a small number of key patterns are exposed
Solution Approach 1:
The invention extracts the correction target from the key pattern to the division line itself. Instead of measuring the distance between the laser processed groove and the key pattern, the method measures the distance between the laser processed groove and the division line directly. This extraction allows correction to be performed using the division line as the reference, which is always visible and does not depend on the number of exposed key patterns.
Solution Approach 2:
The invention creates an optical copy (image) of the division line and laser processed groove using the imaging unit. By imaging these features and calculating the distance between them in the image data, the system can determine the actual index amount without physical contact or dependency on key patterns. This copying approach enables accurate measurement even when key patterns are not exposed.
2Productivity
If the laser beam applying unit position is not corrected, then the processing can proceed without additional measurement steps, but the position may be deviated from the target division line due to apparatus errors or heat
Solution Approach 1:
The invention implements a feedback mechanism where the actual position of the laser processed groove relative to the division line is measured by the imaging unit, and this measurement is used to calculate a correction value. This correction value is then applied to adjust the index amount for subsequent processing, creating a closed-loop system that continuously corrects position deviations caused by apparatus errors or heat expansion.
Solution Approach 2:
The invention performs the imaging and correction calculation during the processing step itself, rather than as a separate preliminary or post-processing step. By imaging the division line and laser processed groove at any arbitrary time during processing, the system proactively identifies and corrects position deviations before they accumulate, maintaining accuracy throughout the processing sequence.
3Measurement precision
If the distance measurement is performed using key patterns, then the correction can be calculated, but the method fails when key patterns are not sufficiently exposed in the peripheral portion
Solution Approach 1:
The invention extracts the measurement reference from the key pattern to the division line. The division line serves as the new reference feature for distance measurement, replacing the key pattern. This extraction is possible because the division line is always present and visible on the packaged wafer, regardless of the resin sealing status, making it a more reliable reference for measurement.
Solution Approach 2:
The imaging unit acts as an intermediary that captures images of both the division line and the laser processed groove. By using the imaging unit to obtain visual data of these features, the system can calculate distances without direct physical measurement or dependency on the visibility of key patterns. The imaging unit mediates between the physical features and the measurement calculation.
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 method ensures accurate correction of the laser beam applying unit's position with respect to each division line, even when only a few key patterns are exposed, enhancing processing accuracy and reliability.
Implementation Method 1
an imaging unit for imaging and detecting a target area of the packaged wafer to be processed
Implementation Method 2
a laser beam applying unit for applying a laser beam having an absorption wavelength to the packaged wafer held on the holding table
Implementation Method 3
processing step of processing each division line by using the laser beam applying unit and the feeding mechanism thereby forming a laser processed groove along each division line
Data Source
AI summary
A packaged wafer processing method includes a processing step of processing each division line formed on a packaged wafer by using a laser beam applying unit and a feeding mechanism, and indexing the wafer by a preset index amount “a” corresponding to the pitch of the division lines by using an indexing mechanism, thereby forming a laser processed groove along each division line. A correcting step images the next division line to be processed in an exposed peripheral portion of the wafer and the laser processed groove just formed along the present division line, at any arbitrary time during the processing step. The distance “b” between the next division line and the laser processed groove just formed is determined, and then a correction index amount “c” is calculated by using the deviation corresponding to the difference (a−b) between the preset index amount “a” and the distance “b”.