Bonded Wafer Laser Dicing for Uniform Crack Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing stealth dicing methods face challenges in controlling the uniform formation of cracks in wafers, leading to uneven application of external forces and compromised separation performance, particularly in wafers with multiple separation lines.
Innovation Solution
The method involves bonding wafers with varying resistivities to form a bonded wafer with regions of different resistivities in the thickness direction, and irradiating with a laser to create modified regions along a dicing line, followed by an expansion process to facilitate uniform crack formation and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wavelength is changed to achieve efficient absorption of laser in the wafer, then the cracks join together more easily, but the cracks may unintentionally join together too much in some parts before application of external force, making control for uniform formation of cracks impossible
Solution Approach 1:
The wafer is divided into multiple bonded wafer layers with different resistivities. Each layer absorbs laser energy at different rates, creating modified regions at specific depths. This segmentation allows controlled crack formation in each layer while preventing premature crack joining, solving the uniformity control problem.
Solution Approach 2:
Different wafer layers are assigned different resistivity values to create local variations in laser absorption characteristics. The first wafer has lower resistivity while the second wafer has higher resistivity, causing the laser to form modified regions at different depths in each layer. This local quality differentiation enables precise control over where cracks form and how they propagate, preventing uneven crack joining.
2Productivity
If external force is applied in the expansion process, then the wafer can be separated, but the external force does not act uniformly on the entire wafer when cracks are uneven, compromising separation performance
Solution Approach 1:
Modified regions are formed in advance within each wafer layer at predetermined depths before the expansion process. These pre-formed modified regions ensure that cracks will form uniformly across all layers when external force is applied. By preparing the wafer structure beforehand with controlled modified regions, the subsequent expansion process achieves uniform force distribution and high separation performance.
Solution Approach 2:
The bonded wafer structure combines multiple wafer layers with different resistivity properties. This composite structure ensures that laser energy is absorbed and modified regions are formed at different depths in each layer, creating a coordinated crack formation pattern across the entire wafer stack. The composite nature of the bonded wafers enables uniform crack development that responds evenly to external expansion forces.
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 enhances the control for uniform crack formation, ensuring consistent separation performance and improved cutting accuracy of wafers by applying an even expansion force across the entire wafer.
Implementation Method 1
irradiating the bonded wafer with a laser while varying focal lengths in a thickness direction of the bonded wafer, thereby forming a plurality of modified regions along a dicing line
Implementation Method 2
uses lasers of different wavelengths in stealth dicing for efficient absorption of laser in each bonded component
Implementation Method 3
An external force is then applied in an expansion process, whereby the wafer can be separated, as cracks, which originate from these multiple modified regions, join together in the thickness direction of the wafer
Data Source
AI summary
A dicing method including the steps of: bonding a first wafer having a first wafer resistivity and a second wafer having a second wafer resistivity higher than the wafer first resistivity, thereby forming a bonded wafer; irradiating the bonded wafer with a laser while varying focal lengths in a thickness direction of the bonded wafer, thereby forming a plurality of modified regions along a dicing line; and dicing the bonded wafer along the dicing line by performing an expansion process on the bonded wafer formed with the modified regions.