Laser Processing Method for Wafer Warping Control
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Solution Overview
Problem
Conventional laser processing methods can cause warping of objects due to internal stresses, particularly when forming multiple modified regions for cutting, leading to deviations in autofocus control and unintentional cutting.
Innovation Solution
The method involves forming first and second modified regions within the object to generate fractures tilted with respect to the object's thickness direction, which connect to reduce internal stresses and prevent warping, allowing for precise cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a modified region is formed within the object using laser light, then cutting precision is improved, but internal stress causes warping of the object
Solution Approach 1:
The modified region is divided into multiple segments (first modified region, second modified region, third modified region) positioned at different locations along the cutting line. Each segment generates fractures that connect to form a network, distributing the stress and preventing overall warping of the object while maintaining cutting precision.
Solution Approach 2:
Different regions of the object are subjected to different laser processing conditions to create modified regions with specific local properties. The first, second, and third modified regions are formed with different characteristics (depth, density, orientation) to locally manage stress distribution and prevent warping while achieving precise cutting.
2Manufacturing precision
If multiple modified regions are formed for one cutting line, then cutting accuracy is improved, but internal stress increases causing warpage
Solution Approach 1:
The cutting process is segmented into multiple modified regions (first, second, third) along the cutting line. Each region is processed separately with controlled laser parameters, allowing the internal stress to be distributed and managed across multiple zones rather than concentrated in a single region, thus reducing overall warpage.
Solution Approach 2:
The laser processing is applied periodically at different locations along the cutting line to create multiple modified regions. By spacing these regions appropriately and controlling the processing parameters, the internal stress is distributed in a periodic pattern that prevents cumulative warping while maintaining cutting accuracy.
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 effectively reduces warping and ensures accurate cutting by meshing fractures to manage internal stresses, maintaining autofocus control and achieving high precision.
Implementation Method 1
irradiating an object to be processed with laser light while locating a converging point within the object, so as to form a modified region to become a cutting start point within the object
Data Source
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AI summary
An object to be processed is restrained from warping at the time of laser processing. A modified region M2 is formed within a wafer 11, and fractures a2, b2 extending in directions parallel to the thickness direction of the wafer 11 and tilted with respect to a plane including lines 5 are generated from the modified region M2. A modified region M3 is formed within the wafer 11, and a fracture a3 extending in a direction parallel to the thickness direction of the wafer 11 and tilted with respect to the plane including the lines 5 is generated from the modified region M3 so as to connect with the fracture b2. That is, the fractures a2, a3, b2 are generated so as to be connected together. Therefore, at the time of laser processing, the fractures cause both side parts holding the lines to cut 5 therebetween in the wafer 11 to mesh with each other, whereby internal stresses occurring in a direction parallel to the thickness direction of the wafer 11 and perpendicular to the surface including the lines 5 when the modified regions are formed can be reduced.