Wafer Laser Division via Polyolefin Sheet Bonding
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Solution Overview
Problem
The existing wafer processing methods degrade the quality of device chips due to adherence of the adhesive layer from the adhesive tape used in the dicing process, which affects the integrity and performance of the chips.
Innovation Solution
A wafer processing method utilizing a polyolefin sheet without an adhesive layer for thermocompression bonding with the wafer and ring frame, allowing the laser beam to form modified layers for division without adhering to the chips, and using air to pick up the chips, reducing the load and preventing adhesive residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive tape is used to hold the wafer during laser processing, then the wafer can be securely fixed and processed, but the adhesive layer melts and adheres to the device chips, degrading their quality
Solution Approach 1:
The patent extracts and removes the adhesive layer from the tape structure, using only the non-adhesive base layer (polyolefin sheet) to hold the wafer. This eliminates the source of the harmful adhesive residue that degrades chip quality, while the base layer still provides sufficient mechanical support for wafer handling during laser processing.
Solution Approach 2:
The patent introduces a polyolefin sheet as an intermediary material between the wafer and the processing equipment. This mediator provides the necessary mechanical support and holding function during processing, while its non-adhesive nature prevents contamination of the device chips, thus resolving the contradiction between secure holding and chip quality.
2Ease of operation
If adhesive tape is used to accommodate the wafer, then the wafer can be held in place during processing, but the adhesive layer melts and remains on the device chips, affecting their integrity
Solution Approach 1:
The patent removes the adhesive layer from the tape structure, retaining only the non-adhesive base layer (polyolefin sheet). This extraction eliminates the source of contamination that compromises chip integrity, while the base layer continues to provide adequate mechanical support for wafer handling and processing operations.
Solution Approach 2:
The patent uses a disposable polyolefin sheet that serves its purpose during processing and is then discarded. This single-use approach eliminates the need for cleaning adhesive residues from chips, simplifying the process while ensuring chip integrity is maintained throughout handling and processing.
3Manufacturing precision
If laser beam is applied to divide the wafer, then precise division can be achieved, but leaked laser light reaches the adhesive layer and melts it, causing adherence to chips
Solution Approach 1:
The patent extracts the adhesive layer from the system, using only the non-adhesive polyolefin sheet to hold the wafer during laser processing. This removal eliminates the target for leaked laser light to melt, thereby preventing adhesive residue formation on the device chips while maintaining precise laser division capability.
Solution Approach 2:
The patent converts the potential harmful effect of leaked laser light by removing the vulnerable adhesive layer. The leaked light, which would normally cause harmful melting and adherence, now has no adhesive material to act upon, thus the harmful effect is neutralized while the beneficial laser division function remains intact.
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 prevents adhesive layer adherence to the device chips, maintaining their quality and integrity by using a polyolefin sheet for bonding and chip separation, ensuring efficient and clean separation of individual device chips.
Implementation Method 1
a laser processing unit for focusing a laser beam inside the wafer held on the chuck table, the laser beam having a transmission wavelength to the wafer
Implementation Method 2
the laser beam is applied from the laser processing unit to the wafer along each division line. When the laser beam is focused inside the wafer, a modified layer serving as a division start point is formed in the wafer along each division line
Implementation Method 3
a uniting step of heating the polyolefin sheet as applying a pressure to the polyolefin sheet after performing the polyolefin sheet providing step, thereby uniting the wafer and the ring frame through the polyolefin sheet by thermocompression bonding
Implementation Method 4
a pickup step of blowing out air from the polyolefin sheet side to push up each device chip and picking up each device chip from the polyolefin sheet after performing the dividing step
Data Source
AI summary
A wafer processing method includes a polyolefin sheet providing step of positioning a wafer in an inside opening of a ring frame and providing a polyolefin sheet on a back side or a front side of the wafer and on a back side of the ring frame, a uniting step of heating the polyolefin sheet as applying a pressure to the polyolefin sheet to thereby unite the wafer and the ring frame through the polyolefin sheet by thermocompression bonding, a dividing step of applying a laser beam to the wafer to form modified layers in the wafer, thereby dividing the wafer into individual device chips, and a pickup step of blowing out air to push up each device chip and picking up each device chip from the polyolefin sheet.