Anchor Pad Structures for Uniform Wafer Planarization and Bonding
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Solution Overview
Problem
The challenge in semiconductor image sensor devices is achieving uniform planarization and bonding of stacked dies to prevent structural weaknesses and device failures due to concave or convex surfaces formed during the planarization process, leading to voids at the interface that can cause device failure.
Innovation Solution
The introduction of anchor structures, including thin anchor layers and anchor pads on dielectric layers, which provide uniform planarization by matching the planarization selectivity of interconnection materials, and are formed using materials that promote wafer bonding, such as silicon-based compounds, to ensure coplanar surfaces and reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional planarization processes are used on stacked dies, then the planarization process can be completed, but concave or convex surfaces are formed leading to voids at the bonding interface
Solution Approach 1:
The patent applies preliminary action by forming a planarization layer before the bonding process. This layer is specifically designed to provide a substantially planar upper surface that enables uniform bonding across the entire bonding interface, preventing void formation while maintaining manufacturing feasibility
Solution Approach 2:
The planarization layer acts as an intermediary between the stacked dies and the bonding process. It mediates the planarization requirement by providing a uniform surface without requiring the underlying die surfaces to be perfectly planar, thus eliminating voids at the bonding interface
2Manufacturing precision
If anchor structures are introduced to improve planarization uniformity, then planarization quality improves, but device complexity increases
Solution Approach 1:
The planarization layer serves multiple functions simultaneously: it provides mechanical support, enables uniform planarization, facilitates bonding, and prevents void formation. This multi-functionality reduces the need for separate dedicated structures, thereby managing device complexity while achieving high planarization uniformity
Data Source
AI summary
The present disclosure is directed to anchor structures and methods for forming anchor structures such that planarization and wafer bonding can be uniform. Anchor structures can include anchor layers formed on a dielectric layer surface and anchor pads formed in the anchor layer and on the dielectric layer surface. The anchor layer material can be selected such that the planarization selectivity of the anchor layer, anchor pads, and the interconnection material can be substantially the same as one another. Anchor pads can provide uniform density of structures that have the same or similar material.