Edge Fill Dielectric for Planar 3D Stack Bonding
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving planarity during the encapsulation of three-dimensional stacked structures, as the encapsulant at the edges of the workpiece tends to slump, leading to non-planar surfaces and potential delamination or contamination issues when bonding subsequent workpieces.
Innovation Solution
A method is introduced where an edge fill dielectric layer is formed prior to encapsulating the device dies, providing lift and reducing or eliminating slump, thereby ensuring better planarity and stability for subsequent bonding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If encapsulation is performed on stacked structures without edge fill, then the manufacturing process is simpler, but the encapsulant surface becomes non-planar due to slump at edges
Solution Approach 1:
An edge fill dielectric layer is formed prior to encapsulation to provide preliminary structural support at the edges of the stacked structure. This preliminary action prevents the encapsulant from slumping during the encapsulation process, ensuring surface planarity is maintained throughout subsequent bonding operations.
Solution Approach 2:
The edge fill dielectric layer acts as an intermediary structural element between the stacked devices and the encapsulant. This intermediate layer provides mechanical support to the encapsulant at the edges, preventing slump and maintaining a planar surface without requiring modification to the encapsulation materials or processes.
2Reliability
If edge regions are left without support during encapsulation, then the manufacturing process is faster, but delamination and contamination occur at edges
Solution Approach 1:
The edge fill dielectric layer is formed in advance to provide continuous support from the substrate through the stacked devices to the encapsulant at the edges. This preliminary structural preparation ensures reliable bonding and prevents delamination and contamination during subsequent workpiece bonding, eliminating the need for rework or additional support structures.
3Manufacturing precision
If encapsulant material is used without edge support, then material selection is easier, but surface non-planarity causes bonding issues
Solution Approach 1:
The edge fill dielectric layer is applied locally at the edge regions of the stacked structure where support is needed, rather than requiring modification of the entire structure. This localized approach maintains surface flatness at the edges without adding complexity to the central bonding areas or requiring changes to the encapsulant material properties.
Data Source
AI summary
A process includes depositing an edge fill dielectric over a first workpiece and a device disposed thereon. The edge fill dielectric is patterned so that only the edge portions remain. A second dielectric material is formed over the first workpiece, device, and edge fill dielectric. A planarization process levels the second dielectric material and the device. A bonding layer is formed thereon and a second workpiece bonded thereto by a dielectric-to-dielectric bond.