Wafer Processing Using Adhesive-Free Polyester Sheet Bonding
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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 chips, leading to quality degradation due to the adhesive layer's adherence to the device chips.
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 shield tunnels for division, and then cooling the polyester sheet to facilitate easy chip pickup, 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 patent extracts and removes the adhesive layer from the holding structure. Instead of using adhesive tape, the invention uses a dual-layer polyester sheet structure where the first polyester sheet is bonded to the wafer and the second polyester sheet is bonded to the ring frame, eliminating the adhesive layer that causes chip contamination during laser processing.
Solution Approach 2:
The patent introduces polyester sheets as intermediary materials between the wafer and the ring frame. The first polyester sheet serves as an intermediary between the wafer and the second polyester sheet, while the second polyester sheet serves as an intermediary between the first polyester sheet and the ring frame. This intermediary structure allows secure holding without adhesive contamination.
2Manufacturing precision
If a polyester sheet is used for thermocompression bonding without an adhesive layer, then chip quality is maintained, but the bonding strength may be insufficient
Solution Approach 1:
The patent merges multiple polyester sheets into a composite holding structure. The first polyester sheet and the second polyester sheet are bonded together through thermocompression bonding to form a unified structure that combines the advantages of both layers: direct contact with the wafer and secure attachment to the ring frame.
Solution Approach 2:
The patent uses a composite structure consisting of two polyester sheets with different functional characteristics. The first polyester sheet is designed for direct bonding to the wafer surface, while the second polyester sheet is designed for bonding to the ring frame, creating a composite material system that optimizes both chip quality and bonding strength.
3Ease of manufacture
If the polyester sheet is heated for thermocompression bonding, then bonding is achieved, but the heating process may affect the wafer or devices
Solution Approach 1:
The patent performs thermocompression bonding of the first polyester sheet to the wafer and the second polyester sheet to the ring frame as preliminary actions before the laser processing step. This ensures that the holding structure is fully established and stable before subjecting the wafer to laser processing, preventing any movement or damage during the subsequent high-precision operations.
Solution Approach 2:
The patent carefully controls the heating parameters during thermocompression bonding, using temperatures and pressures that are sufficient to bond the polyester sheets but low enough to avoid affecting the wafer or the devices formed on it. This parameter optimization allows bonding to proceed without compromising device integrity.
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 the quality of the chips by using a non-adhesive polyester sheet for bonding and division, reducing the load on the chips during separation.
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 held on the chuck table in a state in which a focal point of the laser beam is positioned inside the wafer, the laser beam having a transmission wavelength to the wafer... a filament-like region called a shield tunnel is sequentially formed along each division line
Implementation Method 3
cooling the polyester sheet in each region of the polyester sheet 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 shield tunnels in the wafer, thereby dividing the wafer into individual device chips, and a pickup step of cooling the polyester sheet, pushing up each device chip through the polyester sheet, and picking up each device chip from the polyester sheet.