Encapsulated Chip Transfer for Active-Layer-Safe Substrate Removal
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Solution Overview
Problem
The existing die-to-wafer transfer method for electronic chips with III-V material active layers, particularly in image sensors, faces issues of damage to the active layers and residue from the initial substrate during grinding, which affects the performance of image sensors due to spectral absorption.
Innovation Solution
A method involving the formation of successive dielectric encapsulating layers and a directional etch to protect the active layers during substrate removal, using a first encapsulating layer for initial protection, a second encapsulating layer to preserve the flanks, and a selective chemical etch to efficiently remove the initial substrate residue while minimizing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the initial substrate is removed by grinding, then the active layer can be accessed and transferred, but the active layer flanks are damaged and substrate residue remains
Solution Approach 1:
A protective layer is formed on the active layer before the substrate removal process. This preliminary protective action prevents damage to the active layer flanks during grinding while allowing complete substrate removal. The protective layer is applied in advance to shield the vulnerable active layer surfaces that would otherwise be exposed to mechanical damage.
Solution Approach 2:
The protective layer acts as an intermediary between the grinding tool and the active layer. It absorbs the mechanical stress and contact during substrate removal, preventing direct interaction between the grinding tool and the active layer flanks. This intermediary layer can be removed afterward without damaging the underlying active layer.
2Object-generated harmful factors
If the initial substrate is completely removed by grinding, then no residue remains, but the active layer is damaged during the process
Solution Approach 1:
The protective layer is deposited on the active layer before substrate removal to prevent surface damage. This preliminary protection ensures that when grinding occurs, the active layer flanks are shielded from mechanical contact, maintaining their surface quality while still allowing the substrate to be completely removed.
Solution Approach 2:
A thin film protective layer is applied to the active layer surfaces. This thin film is sufficient to prevent damage during grinding but thin enough to be completely removed afterward without leaving residue. The flexible nature of this thin film allows it to conform to the active layer geometry while providing protection.
3Reliability
If protective layers are added before substrate removal, then the active layer is protected, but the process complexity increases
Solution Approach 1:
The protective layer formation and removal steps are extracted as separate, standardized processes that can be integrated into existing manufacturing workflows. By isolating these protective actions, the overall process complexity is managed through modular addition rather than fundamental process redesign, making the enhanced protection approach more implementable.
Solution Approach 2:
The protective layer is used temporarily and then completely removed after serving its protective function. This temporary protective layer approach adds minimal permanent complexity to the final structure, as the protective material is discarded after use. The process complexity is justified by the temporary nature and complete removal of the protective elements.
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 effectively protects the active layers from grinding damage and reduces initial substrate residue, ensuring the integrity and performance of image sensors by using dielectric encapsulating layers and selective etching techniques.
Implementation Method 1
performing a directional etch of a part of the second encapsulating layer extending over the remaining part of the initial substrate of each of the electronic chips to: superficially expose the remaining part of the initial substrate of each of the electronic chips, preserve the second encapsulating layer extending over the flanks of the electronic chips
Implementation Method 2
performing a selective chemical etch of the remaining part of the initial substrate of each of the electronic chips, step f) being carried out with a chemical etchant that permits selective etching of the remaining part of the initial substrate with respect to the second encapsulating layer and with respect to the dielectric layer
Implementation Method 3
removing a part of the initial substrate from each of the electronic chips by grinding
Data Source
AI summary
A method for protecting active layers of electronic chips including the following successive steps: using a stack comprising, successively: a carrier substrate, a hybrid bonding interface, electronic chips, each comprising successively an active layer, a dielectric layer, and an initial substrate, forming a first encapsulating layer about the electronic chips, removing a part of the initial substrate by grinding and preserving a remaining part, forming a second encapsulating layer about the electronic chips, performing a directional etch of a part of the second encapsulating layer to: superficially expose the remaining part of the initial substrate, and preserve the second encapsulating layer extending over the flanks of the electronic chips, and performing a selective chemical etch of the remaining part of the initial substrate.