Transparent Handler Wafer Bonding and Debonding
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Solution Overview
Problem
Existing wafer debonding techniques, such as the 3M light-to-heat-conversion method, face challenges in inspecting underlying circuitry due to opaque layers and incomplete adhesion removal, which hinders efficient processing and integration in 3D chip technologies.
Innovation Solution
A method involving a transparent handler with a distinct release layer that absorbs ultraviolet light, allowing for optical inspection and complete adhesion removal using a UV laser, enabling transparent inspection and cleaner debonding without thermal softening of the adhesive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a LTHC layer is used for debonding, then the adhesive bonding strength is greatly diminished, but the underlying circuitry becomes difficult to inspect due to the dark and opaque nature of the LTHC layer
Solution Approach 1:
The patent divides the functional layer into two separate layers: a transparent adhesive layer for bonding and a separate LTHC layer for debonding. This segmentation allows the adhesive layer to remain transparent for inspection purposes while the LTHC layer provides the necessary light-to-heat conversion for debonding when activated by laser irradiation.
Solution Approach 2:
The patent introduces a transparent adhesive layer as an intermediary between the device wafer and the handler wafer. This intermediary layer maintains bonding functionality while allowing optical transparency for inspection, and works in conjunction with the LTHC layer to enable controlled debonding without compromising inspection capabilities.
2Reliability
If a YAG laser operating at 1064 nm is used for LTHC debonding, then heat is generated in the LTHC layer to loosen the adhesive, but complete ablation of the interface is not achieved resulting in residual adhesion
Solution Approach 1:
The patent changes the laser operating parameters by using a frequency-doubled YAG laser operating at 532 nm (green light) instead of the conventional 1064 nm infrared wavelength. This parameter change in light frequency increases the energy absorption by the LTHC layer, enabling complete ablation of the adhesive interface while maintaining controlled debonding.
3Use of energy by moving object
If the LTHC layer is made dark and opaque to absorb infrared light effectively, then light-to-heat conversion is improved, but optical inspection of the underlying circuitry is hindered
Solution Approach 1:
The patent segments the functional layers into a transparent adhesive layer and a separate LTHC layer with dark, light-absorbing properties. This segmentation allows the adhesive layer to provide optical transparency for inspection while the LTHC layer maintains its light-absorbing capability for effective light-to-heat conversion during debonding.
Solution Approach 2:
The patent applies different optical properties to different layers: the adhesive layer is made transparent to allow inspection, while the LTHC layer is made dark and opaque to maximize light absorption. Each layer has optimized local quality suited to its specific function in the bonding and debonding process.
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
Enables transparent inspection and efficient removal of the semiconductor wafer from the handler, facilitating defect detection and repair before debonding, resulting in cleaner and more reliable integration for 3D chip technologies.
Implementation Method 1
The release layer is ablated by irradiating the release layer through the transparent handler with a laser
Implementation Method 2
The release layer is ablated by irradiating the release layer through the transparent handler with a laser
Implementation Method 3
irradiating the release layer through the transparent handler with a laser
Data Source
AI summary
A method for processing a semiconductor wafer includes applying a release layer to a transparent handler. An adhesive layer, that is distinct from the release layer, is applied between a semiconductor wafer and the transparent handler having the release layer applied thereon. The semiconductor wafer is bonded to the transparent handler using the adhesive layer. The semiconductor wafer is processed while it is bonded to the transparent handler. The release layer is ablated by irradiating the release layer through the transparent handler with a laser. The semiconductor wafer is removed from the transparent handler.