In-situ Copper Oxide Removal via Vacuum Baking
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Solution Overview
Problem
The existing methods for forming interconnect structures in integrated circuits, such as damascene, face inefficiencies due to the formation of copper oxide layers when copper lines are exposed to air, requiring lengthy furnace baking and additional oxide removal processes, which increase manufacturing costs and reduce throughput.
Innovation Solution
Performing the copper-oxide removal process in a vacuum environment using hydrogen as a reducing gas, either through heating or plasma processes, to eliminate the need for conventional furnace baking and minimize exposure to air, thereby maintaining the copper surface free from oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional furnace baking is performed to remove copper oxide layer, then copper oxide is reduced to copper, but the process takes two hours or longer which reduces throughput
Solution Approach 1:
The patent changes the parameters of the baking process by performing it in a vacuum environment at lower temperatures (below 400°C, preferably 200-350°C) compared to conventional atmospheric baking, which requires higher temperatures and longer times (2 hours or longer). The vacuum environment enables faster oxide removal at reduced thermal budget, thereby increasing throughput while maintaining effectiveness.
Solution Approach 2:
The patent uses vacuum environment as an inert atmosphere to perform the baking process. This vacuum environment prevents re-oxidation of copper during and after the baking process, eliminating the need for lengthy conventional atmospheric baking. The inert environment allows the copper oxide removal to be completed quickly without compromising the copper surface quality.
2Manufacturing precision
If wafer is transferred to vacuum environment for barrier layer and copper seed layer formation, then these layers can be formed properly, but copper oxide layer forms again during transfer which requires additional removal processes
Solution Approach 1:
The patent performs the copper oxide removal process as a preliminary action before transferring the wafer to the vacuum environment for barrier layer and copper seed layer formation. By removing the oxide layer in advance in the vacuum environment, the copper surface remains oxide-free during the subsequent transfer and layer formation processes, eliminating the need for additional oxide removal steps.
Solution Approach 2:
The patent merges the copper oxide removal process with the vacuum environment used for barrier layer and copper seed layer formation. Instead of performing oxide removal separately in atmospheric conditions and then transferring to vacuum, the process combines these steps by conducting oxide removal within the vacuum environment, thereby eliminating redundant processes and simplifying the overall manufacturing sequence.
3Loss of time
If Q-time is tightly controlled to reduce copper oxide thickness, then oxide thickness is reduced, but oxide formation cannot be eliminated which requires additional vacuum environment removal process
Solution Approach 1:
The patent uses vacuum environment as an inert atmosphere to prevent copper oxide formation during wafer handling. By maintaining the vacuum environment throughout the process from oxide removal through barrier layer and copper seed layer formation, the copper surface is continuously protected from oxygen exposure, eliminating oxide formation regardless of exposure time. This eliminates the need for additional oxide removal processes in the vacuum environment.
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 reduces manufacturing costs and increases throughput by eliminating redundant processes, ensuring the copper surface remains oxidation-free and improving the quality of interconnect structures.
Implementation Method 1
with hydrogen introduced into the furnace. With an elevated temperature, copper oxide layer 10 is reduced to copper, while the oxygen in copper oxide layer 10 reacts with hydrogen to form water (H2O)
Implementation Method 2
a plasma clean at room temperature (with hydrogen as a process gas) to remove the thin copper oxide layer
Data Source
AI summary
A method of forming an integrated circuit structure includes providing a substrate; forming a metal feature over the substrate; forming a dielectric layer over the metal feature; and forming an opening in the dielectric layer. At least a portion of the metal feature is exposed through the opening. An oxide layer is accordingly formed on an exposed portion of the metal feature. The method further includes, in a production tool having a vacuum environment, performing a plasma process to remove the oxide layer. Between the step of forming the opening and the oxide-removal process, no additional oxide-removal process is performed to the metal feature outside the production tool. The method further includes, in the production tool, forming a diffusion barrier layer in the opening, and forming a seed layer on the diffusion barrier layer.