Wafer Processing Using Polyester Sheet for Laser Dicing
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Solution Overview
Problem
The existing wafer processing methods using adhesive tapes for dividing wafers into device chips result in adhesive layer adherence 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 air blowing to pick up the 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 the device chips during laser ablation, degrading chip quality
Solution Approach 1:
The patent extracts and removes the adhesive layer from the holding structure. Instead of using adhesive tape that contacts the wafer back side, the invention uses a dicing tape with an adhesive layer only on its front side, which bonds to the wafer front side. This eliminates the source of the harmful adhesive adherence to the chip back side during laser processing.
Solution Approach 2:
The patent introduces a polyester sheet as an intermediary holding structure. The polyester sheet serves as a mediator that holds the wafer during laser processing without using an adhesive layer that would melt and adhere to the chip. The polyester sheet is positioned between the laser processing system and the wafer back side, preventing direct contact between melting adhesive and the chip.
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 of the adhesive tape, causing it to fix to the chip back side
Solution Approach 1:
The patent removes the adhesive layer from the position where it would be harmful (on the back side holding structure). By using a polyester sheet without adhesive layer on the wafer-contacting surface, or using adhesive tape with adhesive only on the front side, the invention eliminates the material that would otherwise melt and adhere to the chip during high-energy laser ablation.
Solution Approach 2:
The patent converts the harmful effect of heat during laser ablation into a beneficial process. The high-energy laser beam that would otherwise melt harmful adhesive is now used to effectively cut through the wafer, while the polyester sheet or front-side-only adhesive structure ensures that the heat energy is directed toward clean division rather than harmful adhesive melting.
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 adhesive layer adherence to the device chips, thereby maintaining chip quality by using a polyester sheet for bonding and picking up the chips without the issues associated with adhesive tapes.
Implementation Method 1
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
Implementation Method 2
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
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 blowing air to each device chip through the polyester sheet to push up each device chip, thereby picking up each device chip from the polyester sheet after performing the dividing step.