Reentrant Shaped Bonding Pads for Semiconductor Stacking
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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
1Adaptability or versatility
If bonding pads are recessed to accommodate height variations, then adaptability is improved, but manufacturing precision deteriorates due to difficulty in controlling recess depth
Solution Approach 1:
The bonding pad structure transitions from a two-dimensional planar shape to a three-dimensional reentrant shape with vertical walls and a recessed bottom surface. This dimensional change allows the pad to accommodate height variations in the bonding interface while the vertical walls provide mechanical support and precise dimensional control during manufacturing.
Solution Approach 2:
The reentrant shape with vertical walls is formed during the bonding pad fabrication process before the actual bonding operation. This preliminary structuring prepares the bonding pad to automatically accommodate height variations and misalignments during bonding, eliminating the need for precise recess depth control during the bonding process itself.
2Adaptability or versatility
If bonding pads are recessed deeply, then adaptability to height variations is improved, but bonding strength deteriorates due to void formation
Solution Approach 1:
The reentrant shape with vertical walls creates a three-dimensional structure that accommodates height variations without requiring deep recesses. The vertical walls provide mechanical support that prevents void formation, allowing the pad to maintain bonding strength while adapting to interface variations.
Solution Approach 2:
The bonding pad structure is differentiated into distinct regions: vertical walls providing mechanical support and structural integrity, and a recessed bottom surface providing adaptability. This local differentiation allows each region to perform its specific function optimally without compromising overall bonding strength.
3Adaptability or versatility
If driver circuit occupies substrate space, then device functionality is improved, but area available for memory array deteriorates
Solution Approach 1:
The reentrant shaped bonding pads enable more efficient three-dimensional packaging and stacking of semiconductor devices. This vertical integration approach allows driver circuits and memory arrays to be arranged in multiple layers, effectively utilizing substrate space and increasing overall device functionality without reducing the area available for memory arrays.
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.