Dual-Laser Wafer Cutting for Byproduct Removal and Surface Flatness
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Solution Overview
Problem
Conventional laser cutting methods for wafers in 3D IC fabrication result in deteriorated surface flatness due to thermal effects and byproduct accumulation, affecting subsequent bonding processes.
Innovation Solution
A dual-laser system is employed, where a first laser with a longer pulse width cuts the substrate and a second laser with a shorter pulse width clears byproducts, ensuring a time lag or spatial separation to enhance cutting efficiency and surface flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single laser is used to cut the substrate, then cutting efficiency is achieved, but surface flatness deteriorates due to thermal effects and byproduct accumulation
Solution Approach 1:
The single laser cutting process is segmented into two distinct functions: a first laser performs the primary cutting operation, while a second laser performs byproduct removal. This segmentation allows each laser to be optimized for its specific function, with the first laser focused on cutting efficiency and the second laser focused on surface quality, thereby resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The second laser acts as an intermediary that removes the harmful byproducts (dross and vaporized material) generated by the first laser. This intermediary action prevents the accumulation of byproducts that would otherwise deteriorate surface flatness, allowing the first laser to maintain high cutting efficiency without compromising surface quality
2Speed
If laser radiation is applied to cut the substrate, then cutting speed is improved, but thermal effects adversely affect surface morphology
Solution Approach 1:
The harmful thermal effects and byproduct generation from the first laser are converted into a beneficial process by introducing the second laser. The second laser specifically targets and removes the dross and vaporized material created by the first laser's thermal cutting action, thereby converting the harmful thermal byproducts into a controlled removal process that improves surface morphology while maintaining cutting speed
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
The dual-laser approach achieves high cutting efficiency while significantly improving post-cutting substrate surface flatness by effectively removing byproducts, thereby enhancing the quality of subsequent bonding processes.
Implementation Method 1
the laser radiation can instantaneously raise the temperature at the irradiated location of a surface of the wafer 10 over a vapor point of a material at the wafer surface, thereby vaporizing the material
Implementation Method 2
vaporizing the material
Implementation Method 3
the second laser radiation is used to clear byproducts produced from the cutting of the substrate by the first laser radiation
Data Source
AI summary
A laser cutting apparatus and a method for dicing a wafer. The laser cutting apparatus is used to cut a substrate retained on a support table and includes a laser. The substrate is disposed between the laser and the support table. The laser is adapted to emit first and second laser radiations so that the first laser radiation and the second radiation act on the substrate at different locations, a difference T between the time at which the second laser radiation acts on the substrate at the location and the time at which the first laser radiation acts on the substrate at the location is longer than or equal to 0. The first laser radiation is used to cut the substrate, and the second laser radiation is used to clear byproducts produced from the cutting of the substrate by the first laser radiation.