Laser Singulation of Thick Microchip Substrates Using Recessed Scribe Lines
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Solution Overview
Problem
Laser-based separation methods for microchips are limited by the penetration depth of the laser beam, which cannot effectively generate microcracks across the entire thickness of substrates thicker than standard wafers, leading to incomplete separation and potential damage during mechanical post-processing.
Innovation Solution
The method involves creating recesses in the substrate to reduce its thickness locally, allowing the laser beam to penetrate deeper and generate microcracks across the entire substrate thickness, enabling complete separation of microchips without mechanical damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser-based separation methods are used for thick substrates, then contamination is reduced and damage to sensitive components is prevented, but the laser beam cannot penetrate the substrate to sufficient depth to generate complete microcracks
Solution Approach 1:
The substrate is divided into multiple segments or layers, with recesses created at specific depths to segment the laser path. This allows the laser to effectively process thick substrates by breaking the continuous thick path into manageable segments separated by recesses, enabling complete microcrack generation throughout the entire substrate thickness.
Solution Approach 2:
The solution introduces a vertical dimension element by creating recesses that extend into the substrate depth. This dimensional modification creates stepped surfaces that allow the laser beam to access deeper regions of the substrate, effectively transforming the laser's penetration capability from a single-depth limitation to a multi-level processing approach.
2Manufacturing precision
If mechanical post-processing is used to complete separation, then separation can be achieved, but mechanical damage may occur to the microchips
Solution Approach 1:
The recesses are created in advance before the laser separation process. This preliminary structuring of the substrate prepares the material in advance to receive the laser beam at the correct depth, ensuring that complete microcracks can be generated without requiring subsequent mechanical intervention that could damage the microchips.
Solution Approach 2:
The invention replaces the need for mechanical post-processing with a purely laser-based process. By creating recesses that enable the laser to reach the required depth, the complete separation is achieved through laser-generated microcracks alone, eliminating the harmful mechanical forces that would otherwise be needed to complete the separation.
3Length of stationary object
If the laser penetration depth is increased to process thicker substrates, then complete separation can be achieved, but the laser parameters must be significantly adjusted
Solution Approach 1:
Instead of uniformly increasing laser penetration depth across the entire substrate, the recesses create local variations in substrate thickness. This allows the laser to maintain its original parameters while the local geometry (recesses) provides the necessary depth access, avoiding the complexity of adjusting laser parameters for the entire thick substrate.
Solution Approach 2:
The invention changes the geometric parameter of the substrate (creating recesses) rather than changing the laser parameters. This approach maintains the laser's original operating conditions while achieving the desired effect of increased effective penetration depth through structural modification of the workpiece.
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 allows for the effective separation of microchips from substrates exceeding standard thickness, ensuring clean fracture edges and minimizing mechanical post-processing risks, thereby improving the efficiency and reliability of the laser-based singulation process.
Implementation Method 1
the laser beam penetrates the substrate (e.g. wafer) and generates microcracks in the substrate in the focal point
Implementation Method 2
In laser-based separation methods, damages only occur in the crystal grid in the sawing lanes due to focusing of the laser. There is no ablation of the material to be separated.
Implementation Method 3
generating at least one recess in the substrate, wherein the recess extends at least partially in a lateral direction along one of the singulating scribe lines
Data Source
AI summary
The subject-matter of this disclosure is a method for singulating microchips. The method includes providing a single-layer or multi-layer substrate. The method further includes laser-based creating microcracks in the substrate using a laser beam that penetrates the substrate, wherein the laser beam is guided laterally around the microchips so as to generate singulating scribe lines in the substrate along which the microchips are to be singulated. The laser beam is guided laterally across the substrate in multiple passes, wherein the focal point of the laser beam is set to different penetration depths in different passes each so that the microcracks generated in the focal point are generated in the substrate in a step-wise manner. According to the disclosure, at least one recess is generated in the substrate, wherein the recess extends at least partially in a lateral direction along one of the singulating scribe lines.