Wafer Division Using Adhesive-Free Polyester Sheet
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Solution Overview
Problem
The existing wafer processing methods using adhesive tapes for dividing wafers into device chips often result in the adhesive layer adhering to the chips, leading to quality degradation due to the melting and fixation of the adhesive layer during laser processing.
Innovation Solution
A wafer processing method utilizing a polyester sheet without an adhesive layer for thermocompression bonding with the wafer and ring frame, allowing the laser beam to form modified layers for division, and then using air to lift and pick up the device chips, eliminating the issue of adhesive layer adherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an 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 base layer (polyvinyl chloride sheet) to hold the wafer. This eliminates the source of the harmful adhesive residue that degrades chip quality, while the base layer alone provides sufficient holding strength during laser processing.
Solution Approach 2:
The patent introduces a release paper as an intermediary layer between the tape and the wafer. This mediator prevents direct contact between the wafer and any potential adhesive substances, allowing the wafer to be held securely during processing while preventing adhesive adherence to the device chips.
2Ease of operation
If ultraviolet light is applied to reduce adhesive tape adhesion for chip pickup, then chips can be easily separated, but the process requires additional steps and time
Solution Approach 1:
The patent applies a release agent to the release paper in advance before mounting the wafer. This preliminary action ensures that the release properties are already in place, eliminating the need for subsequent ultraviolet light treatment and enabling direct chip pickup after processing, thereby saving time.
Solution Approach 2:
The patent uses a disposable release paper with pre-applied release agent that is discarded after use. This single-use component eliminates the need for complex, time-consuming adhesive reduction processes like ultraviolet light treatment, as the release properties are built-in and temporary.
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 the adhesive layer from adhering to the device chips, thereby maintaining their quality and reducing the load required for peeling, ensuring higher chip integrity and efficiency in the wafer division process.
Implementation Method 1
heating the polyester sheet as applying a pressure to the polyester sheet after performing the polyester sheet providing step, thereby uniting the wafer and the ring frame through the polyester sheet by thermocompression bonding
Implementation Method 2
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 3
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 4
picking up each device chip from the polyester sheet by blowing out air from the polyester sheet side to push up each device chip
Data Source
AI summary
A wafer processing method includes a polyester sheet providing step of positioning a wafer in an inside opening of a ring frame and providing a polyester 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 polyester sheet as applying a pressure to the polyester sheet to thereby unite the wafer and the ring frame through the polyester 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 polyester sheet.