Wafer Thinning and Laser Debonding for Crack-Free Transfer
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Solution Overview
Problem
Conventional wafer thinning methods using back-grinding tapes are prone to breaking the wafer during processing, especially when attempting to thin down multilayered memory chips and power devices with higher withstand voltages, and peeling off the wafer from a support substrate can cause cracking due to the heat-resistant adhesive layer.
Innovation Solution
A method involving a composite substrate formed by joining a wafer with patterns to a support substrate using a joint member, followed by grinding to thin the wafer, applying a transfer member, breaking the joint member with a laser beam, and applying a bending moment to facilitate peeling and transferring the wafer without damaging the patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional back-grinding tapes are used to support thinned wafers, then wafer thinning can be achieved, but the wafer is prone to breaking in subsequent processing steps
Solution Approach 1:
The patent applies preliminary action by bonding the wafer to a support substrate before the thinning process. This preparatory step provides mechanical strength to the wafer during subsequent thinning and processing operations, preventing breakage while achieving the desired thin dimensions.
Solution Approach 2:
The support substrate acts as an intermediary element between the thin wafer and the processing equipment. It provides the necessary mechanical support during thinning and handling, and can be removed later without damaging the finished thin wafer structure.
2Reliability
If a wafer is bonded to a support substrate for thinning, then wafer breakage risk is reduced, but the wafer may crack when peeled off due to heat-resistant adhesive layer
Solution Approach 1:
The patent changes the physical parameters of the adhesive layer by heating it to its melting point or above. This temperature change transforms the adhesive from a solid, strong-bonding state to a molten, easily separable state, allowing the wafer to be peeled off the support substrate without cracking while maintaining integrity during processing.
Solution Approach 2:
The adhesive layer undergoes a phase transition from solid to liquid (melting) when heated. This phase change reduces the adhesive's strength and allows for easy separation of the wafer from the support substrate after the thinning process is complete, eliminating the peeling difficulty caused by heat-resistant adhesives.
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 reduces the risk of wafer breakage during thinning and subsequent processing steps, allowing for reliable peeling and transfer of the wafer while minimizing damage to the patterns and support substrate.
Implementation Method 1
breaking the joint member by applying a laser beam having a wavelength transmittable through the support substrate and absorbable by the joint member to the composite substrate
Implementation Method 2
applying a laser beam having a wavelength transmittable through the support substrate and absorbable by the joint member
Implementation Method 3
grinding a reverse side of the wafer of the composite substrate to thin down the wafer to a finished thickness
Data Source
AI summary
A method of processing a wafer includes a composite substrate forming step of joining a face side of a wafer and a surface of a support substrate to each other with a joint member interposed therebetween, a grinding step of grinding a reverse side of the wafer of the composite substrate to thin down the wafer to a finished thickness, a transfer member affixing step of affixing a transfer member to the reverse side of the wafer, a joint member breaking step of breaking the joint member by applying a laser beam having a wavelength transmittable through the support substrate and absorbable by the joint member to the composite substrate from another surface side of the support substrate, and a transferring step of peeling off the support substrate from the wafer and transferring the wafer to the transfer member.