Laser Wafer Cutting with Soft X-Ray Particle Control
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Solution Overview
Problem
When cutting wafers into chips, particles often attach to the chips, particularly in MEMS wafers with fragile films, posing a challenge for secure prevention of particle attachment during the cutting process.
Innovation Solution
A laser processing method that forms a modified region within the object using multiphoton absorption and applies a stress through an elastic sheet, irradiating the forming material with soft x-rays to prevent particles from attaching to the chips by ensuring they fall on the sheet instead of dispersing randomly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser cutting is used to divide wafers into chips, then cutting efficiency is improved, but particles attach to the chips
Solution Approach 1:
An elastic sheet is introduced as an intermediary between the laser processing system and the wafer chips. The sheet serves as a protective barrier that prevents particles generated during laser cutting from attaching to the chip surfaces, while still allowing the cutting process to proceed efficiently.
Solution Approach 2:
The invention converts the harmful effect of particle generation during laser cutting into a beneficial outcome by using the elastic sheet to collect and contain these particles. The particles that would otherwise contaminate the chips are instead captured on the sheet, which can then be removed or cleaned.
2Ease of operation
If stress is applied through an elastic sheet to separate chips, then chip separation is achieved, but particles may attach to chips during the process
Solution Approach 1:
The elastic sheet acts as a mediator that facilitates chip separation through applied stress while simultaneously serving as a protective barrier against particle attachment. The sheet's elasticity allows it to transmit stress effectively for separation while its surface properties prevent particle adhesion to the chips.
3Productivity
If protective tape is expanded to divide the wafer, then wafer division is achieved, but particles may still attach to the chips
Solution Approach 1:
The elastic sheet is positioned between the expanding protective tape and the wafer chips, serving as an intermediary barrier. This allows the tape expansion to effectively divide the wafer while preventing particles generated or present during this process from attaching to the chip surfaces.
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 effectively prevents particles from attaching to the chips, ensuring a clean cutting process and maintaining the integrity of the chips by controlling the separation and dispersion of particles during the cutting of planar objects.
Implementation Method 1
The modified region to become the cutting start point is formed by causing optical absorption such as multiphoton absorption within the object to be processed by irradiating the object with laser light while locating a converging point within the object
Implementation Method 2
a forming material of the object is irradiated with a soft x-ray when applying the stress to the object through the sheet
Data Source
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AI summary
A laser processing method which can securely prevent particles from attaching to chips obtained by cutting a planar object is provided. When applying a stress to an object to be processed 1 through an expandable tape 23, forming materials of the object 1 (the object 1 formed with molten processed regions 13, semiconductor chips 25 obtained by cutting the object 1, particles produced from cut sections of the semiconductor chips 25, and the like) are irradiated with soft x-rays. As a consequence, the particles produced from the cut sections of the semiconductor chips 25 obtained by cutting the object 1 fall on the expandable tape 23 without dispersing randomly. This can securely prevent the particles from attaching to the semiconductor chips 25 obtained by cutting the object 1.