Substrate Bonding via Electrochemical Deposition and CMP
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Solution Overview
Problem
Current copper-copper bonding techniques in substrate-level packaging face issues such as high temperatures and pressures leading to alignment inaccuracies and damage to substrates due to coefficient of thermal expansion mismatch, long processing times, and stringent vacuum requirements, which increase costs and reduce throughput.
Innovation Solution
The methods involve electrochemical deposition and chemical mechanical polishing to form a bonding interface on substrates, allowing for alignment and bonding at lower temperatures (230°-250°C) and pressures, using materials like tin-silver eutectic solder, and physical vapor deposition to deposit materials for bonding, enabling efficient and cost-effective substrate bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperatures and pressures are used for Cu-Cu bonding, then bonding strength is improved, but alignment accuracy deteriorates due to CTE mismatch
Solution Approach 1:
The patent changes the bonding parameters from high temperature/pressure to low temperature/pressure regime. Specifically, it uses temperatures of 230-250°C and pressures of 0.1-10 MPa, which are significantly lower than conventional Cu-Cu bonding conditions. This parameter change allows achieving sufficient bonding strength while minimizing thermal expansion effects that cause alignment inaccuracies.
Solution Approach 2:
The patent introduces an intermediary material layer (such as tin-silver eutectic solder or other compatible materials) between the copper surfaces to facilitate bonding at lower temperatures. This intermediary enables bonding without requiring the high temperatures that cause CTE mismatch problems, thus maintaining alignment accuracy while achieving adequate bonding strength.
2Strength
If high temperatures and pressures are used for bonding, then bonding strength is improved, but substrate damage increases
Solution Approach 1:
The patent fundamentally changes the bonding parameters from high temperature/pressure to low temperature/pressure conditions. By using temperatures of 230-250°C and pressures of 0.1-10 MPa, it achieves sufficient bonding strength while avoiding the substrate damage and circuit damage that occur with conventional high-temperature bonding processes.
3Reliability
If long processing times and stringent vacuum requirements are used, then oxidation on Cu surface is reduced, but throughput decreases and cost increases
Solution Approach 1:
The patent uses an intermediary material layer (such as tin-silver eutectic solder or other compatible materials) that can be deposited via ECD or PVD. This intermediary layer provides oxidation resistance without requiring long vacuum processing times, as the deposition processes can be completed quickly and the resulting layers are inherently resistant to oxidation.
Solution Approach 2:
The patent replaces the mechanical vacuum system requirements with chemical/depositional approaches. By using ECD or PVD to deposit oxidation-resistant materials, the process eliminates the need for prolonged vacuum conditions, thereby increasing throughput and reducing processing costs while maintaining oxidation resistance.
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
These methods provide a cost-efficient and accurate bonding process with reduced thermal stress and damage, achieving fine pitch interconnects without gaps, while maintaining low processing costs and improving throughput.
Implementation Method 1
performing electrochemical deposition (ECD) to deposit at least one material on each of a first substrate and a second substrate
Implementation Method 2
performing chemical mechanical polishing (CMP) on the first substrate and the second substrate to form a bonding interface on each of the first substrate and the second substrate
Implementation Method 3
performing physical vapor deposition (PVD) to deposit a first material on each of a first substrate and a second substrate
Data Source
AI summary
Methods for bonding substrates used, for example, in substrate-level packaging, are provided herein. In some embodiments, a method for bonding substrates includes: performing electrochemical deposition (ECD) to deposit at least one material on each of a first substrate and a second substrate, performing chemical mechanical polishing (CMP) on the first substrate and the second substrate to form a bonding interface on each of the first substrate and the second substrate, positioning the first substrate on the second substrate so that the bonding interface on the first substrate aligns with the bonding interface on the second substrate, and bonding the first substrate to the second substrate using the bonding interface on the first substrate and the bonding interface on the second substrate.