Wafer Processing Using Polyester Sheet for Laser Division
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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 back side of the chips, leading to quality degradation due to the melting and fixation of the adhesive layer during laser ablation.
Innovation Solution
A wafer processing method utilizing a polyester sheet without an adhesive layer for thermocompression bonding with the wafer and ring frame, followed by laser ablation to create division grooves, and applying ultrasonic waves to facilitate the separation of device chips, eliminating the need for adhesive tapes and preventing adhesive layer adherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
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 back side of device chips during laser ablation, degrading chip quality
Solution Approach 1:
The adhesive layer is completely removed from the holding structure. Instead of using adhesive tape with an adhesive layer, the patent employs a polyester sheet without any adhesive coating, thereby eliminating the source of the harmful adherence effect while maintaining the wafer holding function through alternative means
Solution Approach 2:
The polyester sheet is designed as a disposable holding medium that is used once and then discarded. This single-use approach eliminates the need for cleaning or reusing the holding surface, ensuring that no adhesive residue remains on device chips while being cost-effective
2Manufacturing precision
If laser beam is applied with sufficient energy to form deep division grooves through the wafer, then reliable wafer division is achieved, but the heat melts the adhesive layer and causes it to fix to the chip back side
Solution Approach 1:
By removing the adhesive layer entirely from the system, the harmful interaction between laser-induced heat and adhesive material is eliminated. The polyester sheet without adhesive coating can withstand the laser processing temperatures without melting and adhering to the device chips
Solution Approach 2:
The function of the adhesive layer (providing holding force) is replicated through the polyester sheet's mechanical properties and friction, without using the actual adhesive material. This functional copy achieves the same holding purpose without the harmful thermal adhesion side effect
3Ease of operation
If adhesive tape is used to accommodate the wafer in the ring frame, then the wafer can be easily positioned and held, but the adhesive layer causes quality degradation when it adheres to the device chip back side
Solution Approach 1:
The polyester sheet is used as a disposable holding medium that facilitates easy wafer positioning and handling during the process. After use, it is discarded rather than reused, ensuring that no adhesive contamination occurs on the device chips while maintaining operational ease
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 the adherence of the adhesive layer to the device chips, thereby maintaining the quality of the chips by using a polyester sheet for thermocompression bonding and ultrasonic separation, reducing the load on the chips during pickup.
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
applying a laser beam to the wafer along each division line, the laser beam having an absorption wavelength to the wafer, after performing the uniting step, thereby forming a division groove in the wafer along each division line to divide the wafer into the individual device chips
Implementation Method 3
applying an ultrasonic wave to the polyester sheet in each region of the polyester sheet corresponding to each device chip, pushing up each device chip from the polyester sheet side to pick up each device chip from 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 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 division grooves 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 region of the polyester sheet corresponding to each device chip, pushing up each device chip from the polyester sheet side to pick up each device chip from the polyester sheet.