Laser Dicing via Stealth Damage and Cyclical Force
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Solution Overview
Problem
Laser dicing of semiconductor wafers often results in uncontrolled crack propagation and splash damage due to high power settings, leading to reduced product yield and issues like die un-separation and chipping.
Innovation Solution
A method involving the application of laser pulses to create stealth damage regions at specific depths in the wafer, followed by a compressive and retractive cyclical force to propagate and join cracks, and expansion of the wafer to separate individual dies, using a combination of a laser saw tool, vibration tool, and wafer expander tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high power laser settings are used for dicing, then cutting efficiency is improved, but uncontrolled crack propagation and splash damage occur
Solution Approach 1:
The laser cutting process is divided into multiple passes at different depths. The first pass creates damage at a first depth, and the second pass creates damage at a second depth, with the damage regions overlapping to form complete through-cracks. This segmentation allows controlled crack propagation without the uncontrolled splash damage associated with single-pass high-power cutting.
Solution Approach 2:
The first laser pass creates preliminary damage regions at a first depth before the second pass creates damage at a second depth. These preliminary damage regions serve as initiation points for crack propagation, allowing the second pass to complete the through-crack formation in a controlled manner rather than attempting to create all damage in one uncontrolled high-power pass.
2Object-affected harmful factors
If laser power is reduced to mitigate splash damage, then splash damage is reduced, but die un-separation and chipping occur
Solution Approach 1:
The cutting process is segmented into multiple passes with different laser power settings. Each pass operates at lower power to avoid splash damage, while the cumulative effect of multiple passes at different depths achieves complete die separation. This eliminates the need for single-pass high-power cutting that causes splash damage.
Solution Approach 2:
The laser applies periodic pulses at different depths in sequence. The first pass applies laser pulses to create damage at a first depth, then the second pass applies laser pulses to create damage at a second depth. This periodic action at controlled intervals allows complete crack propagation through the wafer without requiring continuous high-power exposure that causes splash damage.
3Device complexity
If single-depth laser damage is created, then process simplicity is maintained, but complete crack propagation through the wafer thickness is insufficient
Solution Approach 1:
The laser damage creation process is segmented into multiple depth levels. The first pass creates damage regions at a first depth, and the second pass creates damage regions at a second depth. The damage regions from both passes overlap to ensure complete crack propagation through the entire wafer thickness, achieving superior manufacturing precision compared to single-depth processing.
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 mitigates splash damage and die un-separation issues, ensuring precise separation and high product yield by controlling crack propagation and reducing the risk of meander faults.
Implementation Method 1
applying laser pulses along a direction to a side of a wafer to create first and second stealth damage regions
Implementation Method 2
applying laser pulses along a direction to a side of a wafer to create first and second stealth damage regions at respective first and second depths in the wafer
Implementation Method 3
applying a compressive and retractive cyclical force to the wafer along the third direction to propagate and join the cracks
Implementation Method 4
to propagate and join the cracks from the respective stealth damage regions together
Implementation Method 5
expanding the wafer to separate individual dies from the wafer
Data Source
AI summary
A method includes applying laser pulses along a direction to a side of a wafer to create first and second stealth damage regions at respective first and second depths in the wafer and to create cracks that extend in the wafer from the respective stealth damage regions and that are spaced apart from one another along the direction, applying a compressive and retractive cyclical force to the wafer along the third direction to propagate and join the cracks from the respective stealth damage regions together, and expanding the wafer to separate individual dies from the wafer.