Wafer Processing Using Polyolefin Sheet Bonding
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Solution Overview
Problem
The existing wafer processing methods degrade the quality of device chips due to adherence of the adhesive layer from the adhesive tape during the division process, as the adhesive layer is melted and fixed to the back side of each chip during laser ablation.
Innovation Solution
A wafer processing method using a polyolefin sheet without an adhesive layer for thermocompression bonding with the wafer and ring frame, allowing laser ablation to create division grooves and air blowing to pick up device chips, eliminating the issue of 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 positioned and processed, but the adhesive layer melts and adheres to the back side of device chips, degrading their quality
Solution Approach 1:
The invention extracts and removes the adhesive layer from the holding structure. Instead of using adhesive tape that melts and adheres to chips, the patent uses a dual-layer sheet where the first layer (contacting the wafer) has no adhesive properties, preventing harmful adherence while the second layer provides release functionality.
Solution Approach 2:
The invention introduces a dual-layer sheet as an intermediary holding structure between the wafer and the processing equipment. This mediator consists of a first layer without adhesive properties for wafer contact and a second layer with release properties, eliminating the harmful adhesive effect while maintaining secure positioning during laser processing.
2Manufacturing precision
If laser beam is applied with sufficient energy to reliably form division grooves through the wafer, then complete division is achieved, but the heat melts the adhesive layer of the adhesive tape
Solution Approach 1:
The invention removes the adhesive layer from the system by using a first layer without adhesive properties that contacts the wafer during laser processing. This eliminates the problematic component that would otherwise melt and adhere to chips when exposed to laser-generated heat, while still enabling complete division groove formation.
Solution Approach 2:
The dual-layer sheet exhibits different local properties: the first layer has no adhesive properties for heat resistance during laser processing, while the second layer has release properties for easy chip separation. This localized functional differentiation allows the system to withstand high temperatures during division while enabling easy chip release afterward.
3Ease of manufacture
If adhesive tape is used to unit the wafer and ring frame, then the frame unit can be formed for processing, but the adhesive layer cannot be completely removed from device chips after processing
Solution Approach 1:
The invention extracts the adhesive layer from the wafer-contact surface by using a first layer without adhesive properties. This allows the frame unit to be easily formed through thermocompression bonding while ensuring that no adhesive residue remains on the device chips after processing, maintaining their quality.
Solution Approach 2:
The invention uses a composite dual-layer sheet structure where the first layer is made of heat-resistant material without adhesive properties for wafer contact, and the second layer has release properties. This composite structure enables both easy frame unit formation through thermocompression bonding and complete absence of adhesive residue on finished chips.
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 polyolefin sheet for bonding and picking up individual device chips without the need for an adhesive tape.
Implementation Method 1
a laser processing unit for applying a laser beam to the wafer held on the chuck table, the laser beam having an absorption wavelength 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 polyolefin sheet as applying a pressure to the polyolefin sheet after performing the polyolefin sheet providing step, thereby uniting the wafer and the ring frame through the polyolefin sheet by thermocompression bonding
Data Source
AI summary
A wafer processing method includes a polyolefin sheet providing step of positioning a wafer in an inside opening of a ring frame and providing a polyolefin sheet on a back side of the wafer and on a back side of the ring frame, a uniting step of heating the polyolefin sheet as applying a pressure to the polyolefin sheet to thereby unite the wafer and the ring frame through the polyolefin 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 polyolefin sheet to push up each device chip, thereby picking up each device chip from the polyolefin sheet after performing the dividing step.