Directly Bonded Aluminum Structures Through Oxide Layers
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Solution Overview
Problem
Existing methods for forming bonded structures, particularly those involving aluminum features, face challenges due to the formation of aluminum oxide layers that hinder the interdiffusion of conductive features, leading to inadequate electrical and mechanical connections.
Innovation Solution
A method involving the formation of recessed conductive features with controlled oxide layers, followed by controlled heating to facilitate hillock growth that penetrates and merges the oxide layers, enabling direct metal-to-metal bonding without the need for high-temperature annealing or vacuum processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum features are directly bonded without oxide layer removal, then the bonding process is simpler and requires lower temperature, but the oxide layers hinder interdiffusion and prevent adequate electrical and mechanical connections
Solution Approach 1:
The patent converts the harmful oxide layer into a beneficial element by controlling its formation and thickness. The oxide layer is allowed to form on the aluminum features but is maintained at a controlled thickness (e.g., 2-10 nm) that enables it to serve as a bonding interface. During the bonding process, the oxide layers from opposing aluminum features react with each other to form aluminum oxide bonds, while hillock formation creates metallurgical connections through the oxide layers, achieving both mechanical and electrical connectivity without requiring oxide removal or high-temperature annealing.
2Reliability
If conventional high-temperature annealing is used to remove oxide layers, then adequate metal-to-metal bonding is achieved, but the thermal budget increases and damages sensitive device features
Solution Approach 1:
The patent changes the bonding parameters by using lower temperatures (e.g., 200-400°C) combined with controlled oxide layer thickness and hillock formation mechanisms. Instead of relying on high-temperature thermal energy to remove oxides or enable diffusion, the process uses the presence of controlled oxide layers and mechanical hillock formation to achieve bonding at temperatures that preserve sensitive device features while still creating reliable electrical and mechanical connections.
3Reliability
If vacuum processing is employed to prevent oxide formation, then direct metal-to-metal bonding is achieved, but the process complexity and cost increase
Solution Approach 1:
The patent enables the bonding process to proceed in ambient conditions by allowing controlled oxide formation that actually facilitates bonding. The aluminum features are exposed to air or ambient atmosphere, and the oxide layers that naturally form are maintained at controlled thicknesses through process parameters rather than requiring vacuum environments. This self-service approach eliminates the need for complex vacuum processing equipment and steps while achieving reliable bonding through the oxide-mediated mechanism combined with hillock formation.
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 effective electrical and mechanical bonding of aluminum features by promoting hillock formation to pierce through oxide layers, resulting in robust connections at reduced thermal budgets and costs.
Implementation Method 1
controlled heating to facilitate hillock growth that penetrates and merges the oxide layers
Implementation Method 2
promoting hillock formation to pierce through oxide layers, resulting in robust connections
Data Source
AI summary
An element, bonded structure that includes the element, and methods forming the same are disclosed. A bonded structure can include a first element having a first nonconductive field region and a first conductive feature, and a second element having a second nonconductive field region and a second conductive feature. The second element is directly hybrid bonded to the first element such that the first and second nonconductive field regions are directly bonded to one another along a bond interface and the first and second conductive features are directly bonded to one another. The first conductive feature can include a perforated oxide layer. 1 at. % to 20 at. % of the first aluminum feature can be aluminum oxide.