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 melting and adhering to the back side of the chips, leading to quality degradation.
Innovation Solution
A wafer processing method utilizing a polyester sheet without an adhesive layer for thermocompression bonding with the wafer and ring frame, allowing laser ablation to divide the wafer without adhesive issues, and enabling clean pickup of device chips.
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 back side of device chips, degrading chip quality
Solution Approach 1:
The patent removes the adhesive layer from the holding structure. Instead of using adhesive tape that melts during laser processing, the invention uses a polyester sheet without adhesive that is thermocompression-bonded to the wafer and ring frame. This extraction of the harmful adhesive component eliminates the problem of adhesive residue on chip surfaces while maintaining the necessary holding function during processing.
Solution Approach 2:
The patent changes the bonding mechanism from adhesive-based to thermocompression bonding. By using heat and pressure to bond the polyester sheet directly to the wafer and ring frame without adhesive, the process parameters are changed to avoid the melting and transfer of adhesive material during laser processing, thereby preventing contamination of device chip surfaces.
2Reliability
If laser beam is applied with sufficient energy to form deep division grooves, then reliable wafer division is achieved, but the adhesive layer melts and transfers to device chips
Solution Approach 1:
The patent converts the harmful effect of high-temperature laser processing into a beneficial bonding mechanism. The heat generated during laser processing, which previously caused adhesive melting and contamination, is instead utilized to thermocompression-bond the polyester sheet to the wafer and ring frame. This transforms the harmful thermal effect into a useful bonding function that secures the wafer without leaving adhesive residue.
3Ease of operation
If adhesive tape is used to accommodate wafer in ring frame, then wafer positioning is achieved, but additional processing steps are required to remove adhesive effects
Solution Approach 1:
The patent extracts the adhesive layer from the holding structure, using only the polyester sheet substrate. This eliminates the need for additional ultraviolet treatment steps that would be required to deactivate adhesive tape after laser processing. The non-adhesive polyester sheet provides sufficient holding and positioning functionality without requiring post-processing to remove adhesive effects.
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
Prevents adhesive layer adherence to device chips, thereby maintaining chip quality by using a polyester sheet for thermocompression bonding and laser ablation, eliminating the need for adhesive tapes.
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
the laser beam is applied from the laser processing unit to the wafer. When the laser beam is applied to the wafer, laser ablation occurs to form a division groove in the wafer along each division line
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 picking up each device chip from the polyester sheet.