Wafer Laser Dicing with Multi-Depth Modified Layers
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Solution Overview
Problem
The existing methods for dividing wafers into chips using laser processing often result in irregular cracks and unintended rupture directions, leading to low-quality chips due to inclined and irregular rupture planes.
Innovation Solution
A chip manufacturing method that applies a laser beam to form modified regions with focused points along projected dicing lines, positioning additional focused points in superposed relation to existing modified regions to develop cracks in thicknesswise directions, ensuring controlled rupture and flat rupture planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a laser beam is applied to form modified layers in a workpiece, then the workpiece can be divided along projected dicing lines, but cracks may develop irregularly and not necessarily along the projected dicing lines, causing improper division and reduced chip quality
Solution Approach 1:
The laser beam is divided into multiple beams (e.g., three or more) that are focused at different positions within the workpiece thickness. Each laser beam forms a separate modified layer at a different depth, creating multiple initiation points for crack development. This segmentation ensures that cracks develop along the projected dicing lines by providing controlled starting points at various depths, resolving the issue of irregular crack propagation.
Solution Approach 2:
The invention transitions from forming modified layers at a single depth plane to forming modified layers at multiple depth planes within the workpiece thickness. By focusing laser beams at different positions along the thickness dimension, the method creates a three-dimensional distribution of modified regions, ensuring cracks develop properly along the dicing lines throughout the entire workpiece thickness.
2Ease of manufacture
If modified layers are formed in a workpiece to enable division along projected dicing lines, then division can be achieved, but the planes of division may be inclined to the thicknesswise directions and have irregular recesses and protrusions, causing malformation and dimensional errors in chips
Solution Approach 1:
The laser processing is segmented into multiple focal positions along the thickness direction, creating modified layers at different depths. This segmentation ensures that when external forces are applied, cracks initiate from multiple depths simultaneously, forcing the division plane to remain parallel to the workpiece surfaces and eliminating inclined planes and irregularities that would cause dimensional errors.
Solution Approach 2:
The invention adds the thickness dimension as a critical parameter for modified layer formation. Instead of forming modified layers only at the surface or single depth, laser beams are focused at multiple positions along the thickness axis, creating a distributed pattern of modified regions. This dimensional approach ensures that division planes extend flatwise through the entire thickness, preventing malformation and dimensional errors in the resulting chips.
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 prevents malformation and dimensional errors in chips by ensuring rupture planes align with the thicknesswise directions, enhancing the quality of the produced chips.
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
Implementation Method 2
forming a plurality of modified regions in the workpiece
Implementation Method 3
cracks are developed from the modified regions. 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
Implementation Method 4
when external forces are then exerted on the workpiece, the modified regions and the cracks function as division initiating points that cause the workpiece 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.