Copper-Capped Aluminum Pad Interconnects for Clean Hybrid Bonding
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Solution Overview
Problem
The integration of aluminum pads in advanced packaging processes leads to contamination of dry etching tools and results in unreliable copper-to-aluminum interconnects, making it difficult to incorporate aluminum pads into existing hybrid bonding processes.
Innovation Solution
The formation of additional copper layers over aluminum pads, including a cap and via, to facilitate copper-to-copper interconnects by recessing the aluminum pad and forming copper layers through etching and plating processes, ensuring compatibility with existing process flows and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If aluminum pads are used in advanced packaging processes, then cost and design flexibility are improved, but contamination of dry etching tools occurs and processing compatibility deteriorates
Solution Approach 1:
The aluminum pad structure is segmented into multiple functional layers: the original aluminum pad layer, an intermediate copper layer, and an upper aluminum layer. This segmentation allows each layer to serve its specific function while preventing contamination - the copper layer acts as a barrier that isolates the dry etching process from the aluminum material, enabling subsequent copper-based processes without tool contamination.
Solution Approach 2:
A copper layer is introduced as an intermediary between the aluminum pad and the subsequent processing steps. This intermediate copper layer serves as a mediator that is compatible with dry etching tools and copper-based processes, allowing the aluminum pad to remain in the structure while preventing it from contaminating the etching equipment during subsequent fabrication steps.
2Ease of manufacture
If direct copper-to-aluminum bonding is performed, then processing simplicity is improved, but interconnect reliability deteriorates
Solution Approach 1:
The bonding interface is segmented into distinct copper-to-copper bonding regions and aluminum-to-aluminum bonding regions, separated by dielectric material. This segmentation allows each bonding interface to be optimized for its material pair, ensuring reliable copper-to-copper bonds while maintaining the aluminum pad structure, thereby improving overall interconnect reliability without significantly complicating the manufacturing process.
3Reliability
If additional copper layers are formed over aluminum pads, then interconnect reliability is improved, but device complexity increases
Solution Approach 1:
The copper layer serves multiple functions simultaneously: it acts as a barrier to prevent aluminum contamination during dry etching, provides a reliable bonding surface for subsequent copper-to-copper hybrid bonding, and serves as an electrical interconnect layer. This multi-functionality improves reliability while minimizing the increase in device complexity, as the same layer structure accomplishes multiple objectives.
Solution Approach 2:
The copper layer is formed in advance, before the dry etching processes that would otherwise be contaminated by aluminum. This preliminary action of depositing the copper barrier layer ensures that subsequent etching steps can be performed without contamination, and the structure is already prepared for reliable copper-to-copper bonding, thereby improving reliability while keeping the process sequence manageable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the integration of aluminum pads into existing processes without contaminating etching tools and enhances the reliability and performance of interconnects by forming stable copper-to-copper bonds.
Implementation Method 1
a first layer over the pad, wherein the first layer comprises copper
Implementation Method 2
processing that involves aluminum can lead to contamination of the dry etching tool used for subsequent copper based processes
Data Source
Figure 1A~1B
Figure 2A
Figure 2B~2C
AI summary
Embodiments disclosed herein include an apparatus that comprises a pad, and the pad comprises aluminum. In an embodiment, a liner is on a sidewall of the pad, and the liner extends past a surface of the pad. In an embodiment, a first layer is over the pad, and the first layer comprises copper. In an embodiment, a second layer is over the first layer, and the second layer is a dielectric material. In an embodiment, a via that passes through the second layer and contacts the first layer.