Wafer Laser Processing with Feedback-Controlled Crack Stability
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Solution Overview
Problem
The formation of unstable cracks during laser processing of wafers due to simultaneous formation of multiple condensing points leads to inconsistent crack lengths and decreased processing quality, especially when forming modified regions in the thickness direction of the wafer.
Innovation Solution
A laser processing device and method that includes an irradiation unit, imaging unit, and control unit to form and monitor modified regions, allowing for real-time adjustment of processing conditions based on imaging unit feedback to ensure proper formation and separation of modified regions, thereby stabilizing crack formation and improving processing quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple condensing points are simultaneously formed in the thickness direction of the wafer to improve formation speed of modified regions, then productivity is improved, but crack length becomes unstable and manufacturing precision deteriorates
Solution Approach 1:
The patent applies preliminary action by forming outer modified regions first, then forming inner modified regions between them in a sequential manner rather than simultaneously. This staged approach allows cracks to propagate properly from each modified region without interference, ensuring stable crack lengths while maintaining efficient processing. The control unit manages this sequence to prevent the crack instability that occurs with simultaneous formation of multiple condensing points.
2Manufacturing precision
If multiple modified regions are formed in advance with sufficient separation to prevent crack connection, then crack stability is improved, but processing complexity increases and manufacturing precision cannot be sufficiently ensured
Solution Approach 1:
The patent applies dynamics by making the processing conditions adaptive and adjustable based on real-time observations. The control unit modifies processing conditions (such as laser parameters and condensing point positions) according to observed crack propagation states and modified region formation. This dynamic adjustment simplifies the overall process compared to fixed complex multi-stage procedures, while ensuring stable crack formation through condition optimization rather than relying on fixed geometric separations.
Solution Approach 2:
The patent implements feedback by using an imaging unit to observe the formation state of modified regions and crack propagation in real-time, then feeding this information back to the control unit. The control unit adjusts subsequent processing based on this feedback, allowing the system to automatically ensure stable crack formation without requiring complex pre-planned processing sequences. This closed-loop control simplifies the processing method while maintaining high precision.
3Productivity
If processing conditions are not appropriately set when forming outer and inner modified regions, then productivity is maintained, but wafer quality deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting laser processing parameters (such as power, pulse duration, and condensing point positions) based on the formation state of modified regions. The control unit modifies these parameters in real-time according to feedback from the imaging unit, ensuring that both outer and inner modified regions are formed under optimal conditions. This maintains high productivity while ensuring wafer quality through adaptive parameter optimization rather than fixed conservative settings.
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
Ensures higher accuracy in determining appropriate processing conditions, leading to improved wafer quality by accurately identifying and correcting any deviations in modified region formation and crack propagation, thus enhancing the overall processing quality.
Implementation Method 1
irradiates the wafer with a laser beam from the other surface side of the semiconductor substrate to form a plurality of rows of modified regions inside the semiconductor substrate
Implementation Method 2
an imaging unit that outputs light having a property of transmitting through the wafer, and that detects the light that has propagated through the wafer
Data Source
AI summary
A laser processing device includes a control unit, and the control unit executes a first process of controlling a laser irradiation unit according to a first processing condition set such that a modified region and a modified region are formed inside a wafer; a second process of identifying a state related to each of the modified regions, and of determining whether or not the first processing condition is proper; a third process of controlling the laser irradiation unit according to a second processing condition set such that the modified regions are formed and a modified region is formed between the modified regions in a thickness direction of the wafer inside the wafer; and a fourth process of identifying a state related to each of the modified regions, and of determining whether or not the second processing condition is proper.