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 then cooling and expanding the sheet to release 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 held and processed, but the adhesive layer melts and adheres to the device chips, degrading their quality
Solution Approach 1:
The adhesive layer is extracted and removed from the support structure. Instead of using an adhesive tape with an adhesive layer, the patent uses a non-adhesive polyester sheet that holds the wafer through mechanical means only, preventing the adhesive layer from melting and adhering to the device chips during laser processing
Solution Approach 2:
A polyester sheet serves as an intermediary support structure between the wafer and the processing equipment. This mediator provides holding strength during laser processing without the harmful property of having an adhesive layer that could melt and contaminate the device chips
2Manufacturing precision
If a polyester sheet is used instead of adhesive tape, then the adhesive layer adherence problem is eliminated, but the bonding strength between the sheet and wafer must be maintained through thermocompression
Solution Approach 1:
The bonding parameters of the polyester sheet are changed by applying heat and pressure during thermocompression. This process modifies the physical state of the polyester sheet to achieve adequate bonding strength with the wafer, compensating for the absence of an adhesive layer while maintaining chip quality
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 by using a non-adhesive polyester sheet for bonding and 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
the 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. 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
the adhesive layer of the adhesive tape attached to the back side or the front side of the wafer is melted by the heat due to the application of the laser beam to the wafer at the position below or around each division groove formed in the wafer, and a part of the adhesive layer melted is fixed to the back side or the front side of 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 cooling 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.