Bonded Wafer Protection Structure for Void-Free Interconnect Plugs
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Solution Overview
Problem
The challenge in the semiconductor industry is to effectively form interconnect structures between stacked semiconductor wafers while minimizing voids and ensuring reliable bonding, which is crucial for achieving high-density, low-power, and cost-effective semiconductor devices.
Innovation Solution
The solution involves forming a protection layer and an etch stop layer during the bonding process of stacked wafers, which helps in protecting the bonded interface, reducing voids in conductive plugs, and improving the adhesion of conductive barrier layers, thereby enhancing the electrical connectivity between wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding techniques are used to bond stacked wafers, then the bonding process can be completed, but voids form in the conductive plugs at the bonded interface, reducing electrical connectivity
Solution Approach 1:
A protection layer is deposited on the first wafer before bonding, and an etch stop layer is formed on the second wafer prior to bonding. These layers are prepared in advance to prevent void formation during the subsequent bonding and conductive plug formation processes
Solution Approach 2:
The protection layer and etch stop layer act as intermediary layers between the bonded wafers. These intermediary layers control the etching process and prevent direct contact that would cause voids in the conductive plugs
2Reliability
If the bonded interface is exposed during etching to form conductive plugs, then conductive connectivity can be established, but the bonded interface becomes damaged, reducing bonding quality
Solution Approach 1:
The etch stop layer serves as an intermediary that allows the etching process to proceed to the desired depth while stopping before damaging the bonded interface. This mediator layer enables conductive plug formation without compromising bonding quality
Solution Approach 2:
The etch stop layer is formed in advance on the second wafer to define the etching depth. This preliminary action ensures that subsequent etching processes will not expose or damage the bonded interface while still allowing conductive plug formation
3Reliability
If multiple layers are added to protect the bonded interface, then bonding quality improves, but the device structure becomes more complex
Solution Approach 1:
The protection layer and etch stop layer serve multiple functions: they protect the bonded interface during processing, control etching depth, enable conductive plug formation, and maintain structural integrity. This multi-functionality reduces the need for additional separate layers
Data Source
AI summary
A method includes bonding a first wafer to a second wafer. The first wafer includes a plurality of dielectric layers, a metal pipe penetrating through the plurality of dielectric layers, and a dielectric region encircled by the metal pipe. The dielectric region has a plurality of steps formed of sidewalls and top surfaces of portions of the plurality of dielectric layers that are encircled by the metal pipe. The method further includes etching the first wafer to remove the dielectric region and to leave an opening encircled by the metal pipe, extending the opening into the second wafer to reveal a metal pad in the second wafer, and filling the opening with a conductive material to form a conductive plug in the opening.