Laser Wafer Orientation Flat Formation via Crack Detection
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Solution Overview
Problem
Existing laser processing methods for forming orientation flats on wafers fail to meet the required accuracy for division initiating points due to angular deviations in the formation of modified layers, which can result in cracks and inaccuracies in crystal orientation detection.
Innovation Solution
A laser processing apparatus that includes a chuck table, a laser beam applying unit, and a camera, controlled by a unit capable of detecting the provisional orientation flat and forming modified layers to determine the crystal orientation with high accuracy, ensuring that the modified layers are parallel to the crystal orientation without cracks, thereby forming a true orientation flat that meets the required accuracy standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If modified layers are formed along directions parallel to projected dicing lines formed along an orientation flat, then the processing efficiency is improved, but the angular deviation from crystal orientation increases beyond the required 0.005° accuracy
Solution Approach 1:
The invention performs preliminary action by forming an inspection modified layer before the final orientation flat to detect crystal orientation. The inspection modified layer is formed along the provisional orientation flat direction, and crack detection is performed to determine the actual crystal orientation, which then guides the formation of the final high-precision orientation flat.
Solution Approach 2:
The invention implements feedback by using crack detection results from the inspection modified layer to determine crystal orientation. The crack detection provides feedback information about the angular deviation, which is then used to adjust the orientation flat formation process to achieve the required 0.005° accuracy.
2Device complexity
If the orientation flat is formed based on provisional orientation flat with 0.5° or smaller deviation, then the device complexity is reduced, but the manufacturing precision of division initiating points deteriorates
Solution Approach 1:
The invention uses an inspection modified layer as an intermediary to transfer information about crystal orientation. This intermediary layer allows the system to detect the actual crystal orientation without requiring complex direct detection equipment, while still achieving high precision in the final orientation flat formation.
Solution Approach 2:
The invention replaces complex mechanical orientation detection systems with a laser-based inspection modified layer formation and crack detection method. This substitution simplifies the device while achieving the required 0.005° angular deviation accuracy for division initiating points.
3Loss of time
If modified layers are formed without accurate crystal orientation detection, then the processing time is reduced, but cracks extend from modified layers causing reliability deterioration
Solution Approach 1:
The invention performs preliminary crack detection after forming the inspection modified layer to identify the correct crystal orientation before forming the final orientation flat. This preliminary action prevents cracks from extending into the final structure, ensuring reliability while maintaining efficient processing.
Solution Approach 2:
The crack detection provides feedback on whether the inspection modified layer is properly aligned with the crystal orientation. This feedback mechanism ensures that only correctly oriented modified layers proceed to the final orientation flat formation, preventing crack propagation and ensuring wafer division reliability.
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 apparatus accurately determines the crystal orientation and forms an orientation flat that meets the stringent accuracy requirements for division initiating points, ensuring high reliability and precision in wafer division, which is essential for applications like automobile lights.
Implementation Method 1
a laser beam applying unit configured to apply a laser beam having a wavelength that can be transmitted through the wafer to the wafer held on the chuck table
Implementation Method 2
a camera for capturing an image of the wafer held on the chuck table
Data Source
AI summary
A laser processing apparatus has a control unit including an inspection modified layer former detecting a provisional orientation flat of a bare wafer and applying a laser beam of a predetermined output power level to the bare wafer depending on the direction of the provisional orientation flat thereby to form a modified layer for detecting the crystal orientation closely to an outer edge of the bare wafer, and a crack detector detecting a crack extending from the modified layer toward a Y-axis and an exposed surface of the bare wafer, providing the modified layer extends along an X-axis in an image captured of the modified layer. If the crack detector detects no crack, the control unit determines the modified layer with no crack extending therefrom as extending parallel to the crystal orientation of the bare wafer.