Laser Dicing Focus Control for Flat Wafer Rupture Planes
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Solution Overview
Problem
Existing chip manufacturing methods using laser processing to form modified layers in wafers often result in irregular crack development, leading to improper wafer division along projected dicing lines, which can cause malformation and dimensional errors in the produced chips.
Innovation Solution
A chip manufacturing method that applies a laser beam focused into two points to form modified regions in a workpiece, positioning a second focused spot in superposed relation to an already formed region, causing cracks to develop along the thicknesswise directions of the workpiece, facilitating clean rupture along the dicing lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is applied to form modified regions along projected dicing lines, then cracks are developed to enable wafer division, but the cracks may develop irregularly and cause unintended rupture directions
Solution Approach 1:
The laser beam is focused at two distinct positions (first focused point and second focused point) within the workpiece thickness, creating separate modified regions at different depths. This segmentation of the modification process ensures that cracks develop in controlled directions from each modified region, preventing irregular crack propagation and unintended rupture directions.
Solution Approach 2:
The invention extends the modification process from a single-plane modification to three-dimensional modification by focusing the laser beam at two different positions along the thickness direction (Z-axis). This dimensional extension ensures that modified regions are created throughout the workpiece thickness, guiding cracks to develop along the thicknesswise direction and ensuring rupture planes align with the dicing line.
2Ease of manufacture
If modified regions are formed in the workpiece to enable division along projected dicing lines, then division is facilitated, but rupture planes become inclined to thicknesswise directions with irregular recesses and protrusions
Solution Approach 1:
The laser modification is segmented into two distinct focused positions along the thickness direction, creating multiple modified regions that work together to control crack development. This segmentation ensures that cracks propagate through the entire thickness of the workpiece in a controlled manner, resulting in flat rupture planes without irregular recesses or protrusions while maintaining ease of division.
Solution Approach 2:
The invention changes the parameter of laser focus position from a single point to two distinct positions along the thickness direction. By adjusting the focus positions and the spacing between modified regions, the crack development path is controlled to ensure rupture planes are flat and perpendicular to the thicknesswise direction, eliminating irregularities while facilitating division.
3Productivity
If external forces are applied to divide the workpiece along projected dicing lines, then chips are produced, but chips may be malformed or suffer dimensional errors due to irregular rupture planes
Solution Approach 1:
The laser modification process performs a preliminary action by creating modified regions throughout the workpiece thickness before external forces are applied. These pre-formed modified regions act as controlled initiation points for crack development, ensuring that when external forces are applied, cracks propagate in the correct direction and produce flat rupture planes, thereby preventing chip malformation and dimensional errors.
Solution Approach 2:
By changing the laser processing parameters to create modified regions at two different focus positions, the physical state of the workpiece is altered in advance. This parameter change ensures that the material structure is prepared to respond predictably to subsequent external forces, resulting in controlled crack development and accurate chip dimensions without malformation.
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 approach ensures that the planes of division extend flatwise, reducing malformation and dimensional errors in the produced chips, thereby maintaining chip quality.
Implementation Method 1
applying a laser beam that is transmittable through the workpiece and focused into a first focused point and a second focused point, to the workpiece along the projected dicing line while positioning the first focused point and the second focused point within the workpiece, thereby forming a plurality of modified regions in the workpiece
Implementation Method 2
The modified regions of the wafer and regions of the wafer where the cracks have been developed are more brittle than the other remaining regions of the wafer. Therefore, when external forces are then exerted on the wafer, the modified regions and the cracks function as division initiating points that cause the wafer to be divided along the projected dicing lines.
Data Source
AI summary
A chip manufacturing method for dividing a workpiece along a projected dicing line established thereon into a plurality of chips includes a modified layer forming step of applying a laser beam that is transmittable through the workpiece and focused into a first focused point and a second focused point, to the workpiece along the projected dicing line while positioning the first focused point and the second focused point within the workpiece, thereby forming a plurality of modified regions in the workpiece. The modified layer forming step includes applying the laser beam to the workpiece while forming one of the modified regions around a region where the first focused spot is positioned, and positioning the second focused spot in superposed relation to another modified region that has already been formed in the workpiece.