Reentrant Bonding Pads for Semiconductor Die Alignment
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in achieving simultaneous metal-to-metal and dielectric-to-dielectric bonding between semiconductor dies, where the recess depth of bonding pads must be precisely controlled to ensure proper alignment and contact, as excessive recess can lead to voids and degrade bonding strength.
Innovation Solution
The use of reentrant shaped bonding pads with a smaller distal area at the bonding interface and a larger proximal area away from the interface, featuring a pad base portion and a pillar portion, allows for effective accommodation of height variations and ensures proper alignment during the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bonding pads are recessed to enable simultaneous metal-to-metal and dielectric-to-dielectric bonding, then bonding strength is improved, but excessive recess depth causes voids and degrades bonding quality
Solution Approach 1:
The bonding pad structure transitions from a conventional flat two-dimensional surface to a three-dimensional reentrant shape with vertical sidewalls and a distal surface. This dimensional change allows the pad to achieve proper bonding contact through its geometric profile rather than relying solely on precise recess depth control, effectively adding a vertical dimension to the bonding interface.
Solution Approach 2:
The invention changes the geometric parameters of the bonding pad by forming a reentrant shape with specific dimensions: a proximal surface area, a distal surface area that is smaller, and vertical sidewalls. This parameter transformation from a flat pad to a reentrant-shaped pad enables the pad to accommodate height variations and achieve reliable bonding without requiring extremely precise recess depth control.
2Ease of manufacture
If bonding pads are made with uniform cross-sectional area, then manufacturing is simpler, but height variations in bonding interfaces cannot be accommodated
Solution Approach 1:
The bonding pad incorporates a vertical dimension with a reentrant shape that includes a proximal surface, vertical sidewalls, and a distal surface. This three-dimensional structure allows the pad to accommodate height variations in the bonding interface by providing a geometric profile that can adapt to different surface levels, rather than relying on a uniform two-dimensional cross-section.
Solution Approach 2:
The bonding pad features an asymmetric reentrant shape where the distal surface area is deliberately made smaller than the proximal surface area. This asymmetric geometry provides adaptability to height variations while maintaining manufacturing feasibility through standard semiconductor fabrication processes such as etching and deposition.
3Adaptability or versatility
If driver circuit is integrated on the same substrate as memory array, then device functionality is improved, but valuable substrate space is consumed
Solution Approach 1:
The reentrant-shaped bonding pads are specifically implemented at the bonding interface regions where they provide enhanced bonding capability and compact footprint. This localized structural optimization allows the driver circuit to be integrated on the same substrate without requiring excessive substrate space, as the bonding pads themselves occupy less area while maintaining effective bonding functionality.
Data Source
AI summary
A first semiconductor die includes first semiconductor devices located over a first substrate, first interconnect-level dielectric material layers embedding first metal interconnect structures and located on the first semiconductor devices, and a first pad-level dielectric layer located on the first interconnect-level dielectric material layers and embedding first bonding pads. Each of the first bonding pads includes a first proximal horizontal surface and at least one first distal horizontal surface that is more distal from the first substrate than the first proximal horizontal surface is from the first substrate and has a lesser total area than a total area of the first proximal horizontal surface. A second semiconductor die including second bonding pads that are embedded in a second pad-level dielectric layer can be bonded to a respective distal surface of the first bonding pads.