Wafer Laser Cutting Pulse Sequencing for Throughput and Die Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing laser cutting systems for semiconductor wafers face challenges in achieving a balance between process throughput and die quality due to limitations in laser pulse duration and spacing, leading to defects such as micro-cracks and chip-outs.
Innovation Solution
The method involves irradiating the wafer with a sequence of laser beam pulses comprising two sets: the first set includes nanosecond pulses or bursts to achieve material removal, while the second set consists of ultra-short pulses to improve the quality and mechanical strength of the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nanosecond laser pulses are used for cutting, then process throughput is improved, but die strength deteriorates due to high stress-induced micro-cracks and chip-outs
Solution Approach 1:
The laser pulse sequence is segmented into multiple phases with different pulse widths (nanosecond pulses for material removal, picosecond/femtosecond pulses for damage mitigation). This segmentation allows each pulse type to perform its specialized function, resolving the contradiction between throughput and strength by combining the advantages of both pulse durations in a single cutting process
Solution Approach 2:
The pulse width parameter is dynamically changed within the laser pulse sequence, transitioning between nanosecond, picosecond, and femtosecond ranges. This parameter change enables the system to optimize material removal efficiency with longer pulses while using shorter pulses to reduce heat-affected zone damage, thereby maintaining both high throughput and die strength
2Strength
If ultra-short pulses are used for cutting, then die strength is improved by reducing defects, but process throughput deteriorates
Solution Approach 1:
The cutting process is segmented into different functional stages: nanosecond pulses handle the bulk material removal to maintain throughput, while ultra-short picosecond/femtosecond pulses are segmented into specific bursts or intervals to mitigate damage and improve die strength without compromising overall productivity
Solution Approach 2:
The invention merges nanosecond and ultra-short pulse laser technologies into a single integrated cutting system. By combining the high material removal rate of nanosecond pulses with the low damage generation of ultra-short pulses in a unified pulse sequence, the system achieves both high throughput and high die strength simultaneously
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 fracture strength of laser-separated wafers by minimizing defects and improving the cutting process quality, while maintaining productivity through the combination of different pulse widths.
Implementation Method 1
Laser removal of the semiconductor material occurs due to a rapid temperature increase of a relatively small area in which the laser beam is focused, which causes local material to melt, explosively boil, evaporate and ablate
Implementation Method 2
Laser removal of the semiconductor material occurs due to a rapid temperature increase of a relatively small area in which the laser beam is focused
Data Source
AI summary
A method of cutting a wafer by irradiating the wafer with laser energy, comprises emitting a sequence of successive laser beam pulses having a first set of laser beam pulses and a second set of laser beam pulses, the first set of laser beam pulses comprising: laser beam pulses having respective pulse widths in the range from 0.1 to 300 nanoseconds, or a plurality of bursts of laser beam pulses having an inter-burst spacing in the range from 0.1 to 100 nanoseconds, each pulse within the bursts having a pulse width of 100 picoseconds or less, and the second set of laser beam pulses comprising laser beam pulses having pulse widths of 100 picoseconds or less.