Laser Workpiece Division with Irregular Surface Height Control
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Solution Overview
Problem
Existing methods for dividing workpieces with laser beams, such as semiconductor wafers, face challenges in forming a uniform modified layer due to thickness variations and irregularly shaped portions with extreme height differences, leading to inefficiencies and inaccuracies in the division process.
Innovation Solution
A method that detects the location of irregularly shaped portions and adjusts the focused spot of the machining laser beam based on surface height measurements, excluding the irregularly shaped portion to form a modified layer at a prescribed depth, allowing for precise division along the desired line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser machining apparatus detects surface displacements and controls the focused spot to follow detected surface displacements, then uniform modified layer formation is improved, but processing time increases significantly when encountering irregularly shaped portions with extreme height differences
Solution Approach 1:
The patent segments the workpiece surface into two categories: regular areas and irregularly shaped portions. The detection and focused spot control is selectively applied only to regular areas, while irregular portions are identified and excluded from active control, thereby maintaining precision where needed while improving overall processing speed.
Solution Approach 2:
The patent performs preliminary detection to identify irregularly shaped portions before the machining process begins. By pre-mapping the surface topology and flagging problematic areas, the system can avoid time-consuming real-time adjustments during actual machining, thus resolving the speed-precision contradiction.
2Productivity
If the focused spot of the laser beam follows surface displacements at high speed, then processing efficiency is improved, but the modified layer position becomes widely displaced in the vicinity of irregularly shaped portions
Solution Approach 1:
The patent extracts or removes irregularly shaped portions from the controlled detection region. By identifying these problematic areas and excluding them from the active focused spot control loop, the system prevents position displacement errors while maintaining high-speed processing in regular areas.
Solution Approach 2:
The patent applies different control strategies to different regions of the workpiece. Regular areas receive full active control with focused spot following, while irregularly shaped portions are handled with a different approach (exclusion from control), ensuring local optimization of both speed and precision.
3Ease of manufacture
If a laser beam is applied to a workpiece with thickness variations, then the workpiece can be divided, but a uniform modified layer cannot be formed at a prescribed depth
Solution Approach 1:
The patent employs a feedback mechanism where surface displacements are continuously detected and used to adjust the focused spot position in real-time. This closed-loop control compensates for thickness variations and ensures the modified layer is formed at a uniform prescribed depth across the workpiece.
Solution Approach 2:
The patent dynamically changes the focused spot position parameter based on detected surface topology. By adjusting the focal point location in response to surface variations, the system maintains consistent modified layer depth despite workpiece thickness variations.
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 the formation of modified layers at appropriate depths in workpieces with irregularly shaped portions, resulting in high-quality chip production by minimizing the impact of extreme height differences and improving the division process efficiency.
Implementation Method 1
measures changes in the light intensity of a laser beam reflected from the surface of the workpiece to determine surface displacements of the workpiece
Implementation Method 2
applying and focusing a machining laser beam having a wavelength which permeates the workpiece within the workpiece to form a modified layer
Data Source
AI summary
A workpiece including an irregularly shaped portion on a dividing line is divided along the dividing line by detecting the location of the irregularly shaped portion, applying a detecting laser beam to an area of the workpiece except for the detected location, along the dividing line to detect the height of a surface of the workpiece except for the location, applying and focusing a machining laser beam having a wavelength which permeates the workpiece within the workpiece while moving a focused spot of the machining laser beam based on the detected height of the surface of the workpiece to form a modified layer in an area of the workpiece except for at least the location of the irregularly shaped portion along the dividing line, and applying an external force to the modified layer to divide the workpiece along the dividing line.