Laser Scribing Semiconductor Workpiece Using Divided Beams
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Solution Overview
Problem
Existing methods for dicing semiconductor wafers, particularly those made of hard and brittle materials like SiC and GaN, face limitations in processing rate and quality due to the need for increased laser power or multiple laser passes, leading to defects and reduced production yield.
Innovation Solution
A laser scribing method using a pulsed beam laser source that generates primary and secondary pulses delayed by tens to hundreds of picoseconds, inducing thermal stress and fractures in the substrate through localized heating and rapid cooling, allowing for efficient separation with minimal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional laser dicing is used on hard and brittle substrates with functionalized layers, then the substrate can be separated, but the processing rate decreases and defects increase due to the need for increased laser power or multiple passes
Solution Approach 1:
The patent applies preliminary action by first forming a modified area in the substrate using a first laser beam before cutting with a second laser beam. This pre-modification creates a stress concentration zone that facilitates subsequent clean separation. The method performs required action in advance by creating the modified area that enables easier and cleaner cutting, thereby improving both processing efficiency and reducing defects in hard and brittle substrates with functionalized layers
Solution Approach 2:
The patent segments the laser cutting process into two distinct stages: first forming a modified area with a first laser beam, then cutting with a second laser beam. This segmentation allows each laser to be optimized for its specific function - the first for creating stress concentration and the second for clean separation - thereby improving overall processing rate while maintaining high precision and reducing defects
2Strength
If laser power is increased to process hard and brittle materials, then separation can be achieved, but defects and chipping increase on the surface layers
Solution Approach 1:
The patent applies local quality by concentrating laser energy at specific locations to create a modified area with altered physical properties. The first laser beam locally modifies the substrate structure along the intended separation line, creating a zone with different mechanical properties that facilitates clean separation without requiring high power across the entire cutting path, thereby maintaining surface quality while achieving effective separation
Solution Approach 2:
The modified area created by the first laser beam acts as an intermediary that mediates between the laser energy and the substrate. This intermediate modified zone absorbs and concentrates the energy from the second laser beam, enabling clean separation while protecting the surface layers from direct high-power laser exposure that would cause chipping and defects
3Manufacturing precision
If multiple laser passes are used to process functionalized substrates, then separation can be achieved, but processing time increases and production yield decreases
Solution Approach 1:
The patent performs preliminary action by creating the modified area in advance with the first laser beam, which prepares the substrate for subsequent cutting. This pre-processing step enables the second laser to achieve clean separation in a single pass without requiring multiple repeated passes, thereby improving production yield while maintaining high separation quality
Solution Approach 2:
The patent implements continuous useful action by using two laser beams in sequence without interruption - the first laser creates the modified area and immediately the second laser performs the cutting. This continuous process eliminates the need for multiple passes and intermediate steps, maintaining high separation quality while significantly improving processing speed and production yield
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 enables rapid and effective separation of semiconductor devices with reduced defects and increased production yield by creating damage structures that facilitate fracture along intended separation planes.
Implementation Method 1
a pulsed beam laser radiation source delivering said pulses through converging means onto and into the workpiece
Implementation Method 2
inducing thermal stress and fractures in the substrate through localized heating and rapid cooling
Implementation Method 3
localized heating and rapid cooling, allowing for efficient separation with minimal defects
Data Source
AI summary
This invention provides an effective and rapid method of laser processing for separating semiconductor devices formed on hard and solid substrates (6) with a one pass process. The method is based on generating fractures along the scribing trajectory which extend deep into the bulk of a workpiece (6), wherein thermal stress is induced by delivering at least two processing (ultra short pulse) pulsed-beams (7), containing at least primary and secondary pulses. Primary pulses are used to generate a heat accumulated zone, which allows for more efficient absorption of the secondary pulses, which generate a sufficient heat gradient to produce mechanical failures, necessary for mechanically separating the workpiece (6) into separate pieces.