Wafer Processing 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, degrading their quality due to the melting and fixation of the adhesive layer during the 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 applying ultrasonic waves to separate the device chips from the sheet, eliminating the issue of adhesive layer adherence.
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 positioned and processed, but the adhesive layer melts and adheres to the device chips, degrading their quality
Solution Approach 1:
The invention extracts and removes the adhesive layer from the tape structure, using only the base layer to hold the wafer during laser processing. This eliminates the source of contamination while maintaining the necessary holding function.
Solution Approach 2:
The base layer acts as an intermediary between the laser processing system and the device chips, providing mechanical support and positioning without the harmful adhesive properties that would transfer to the chips.
2Strength
If adhesive tape is used to hold the wafer during laser processing, then the wafer can be securely positioned, but additional ultraviolet light treatment is required to reduce adhesion for chip pickup
Solution Approach 1:
By removing the adhesive layer entirely and using only the base layer, the invention eliminates the need for ultraviolet light treatment to reduce adhesion, simplifying the overall process.
Solution Approach 2:
The base layer is discarded after serving its purpose of holding the wafer during processing, and the device chips are recovered without additional treatment steps.
3Strength
If the adhesive layer is melted during laser processing, then the wafer is securely fixed, but the melted adhesive remains on the device chips, degrading their quality
Solution Approach 1:
The adhesive layer is extracted from the system, leaving only the base layer to provide mechanical support. This prevents any material from melting and contaminating the device chips while maintaining sufficient bonding strength during processing.
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 facilitating easy separation, reducing the load on the chips during pickup.
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
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 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 4
a pickup step of applying an ultrasonic wave to the polyester sheet in each of the plurality of separate regions corresponding to each device chip, pushing up each device chip through the polyester sheet
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 applying an ultrasonic wave to the polyester sheet in each of the plurality of separate regions corresponding to each device chip, pushing up each device chip through the polyester sheet, then picking up each device chip from the polyester sheet.