Plasma Treatment for Mixed Cu-Oxide Surface Bonding
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Solution Overview
Problem
Existing bonding methods for surfaces with copper and silicon oxide areas face challenges in achieving high-quality bonding without thermal treatments, especially when dealing with heterogeneous interfaces, and require independent treatments for each interface type to ensure good bonding and electric performance.
Innovation Solution
A plasma treatment using a gas source containing a silicon oxide nitriding agent and a copper oxide reducing agent with hydrogen is applied to both surfaces before contact, forming a nitrided silicon oxide barrier and removing copper oxide to enhance bonding and electric performance across the Cu-SiO2, Cu-Cu, and SiO2-SiO2 interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermal treatment at high temperature (1000°C) is performed to reinforce bonding energies, then bonding strength is improved, but thermal compatibility deteriorates (thermal treatment is not allowed in many applications)
Solution Approach 1:
The patent applies preliminary plasma treatment to the Cu-oxide surface before bonding to activate the surface and prepare it for bonding. This preliminary action modifies the surface chemistry to enable strong bonding without requiring subsequent high-temperature thermal treatment, thus resolving the contradiction between bonding strength and thermal compatibility
Solution Approach 2:
The patent changes the bonding approach from thermal activation to plasma activation. By using plasma treatment to modify surface parameters (surface energy, chemistry, and morphology), the method achieves strong bonding at low temperatures, eliminating the need for high-temperature processing
2Reliability
If independent treatments are performed for each interface type (Cu-SiO2, Cu-Cu, SiO2-SiO2) to ensure good bonding and electric performance, then interface quality is improved, but process complexity deteriorates
Solution Approach 1:
The patent employs a universal plasma treatment process that simultaneously addresses multiple interface types (Cu-SiO2, Cu-Cu, and SiO2-SiO2 interfaces). The plasma treatment performs multiple functions in one step: cleaning, activation, and modification of all interfaces, thereby achieving high interface quality without requiring separate independent treatments for each interface type
Solution Approach 2:
The patent merges the treatment of different interface types into a single plasma processing step. Instead of applying separate treatments for Cu-SiO2, Cu-Cu, and SiO2-SiO2 interfaces, the method combines all interface modifications into one unified plasma process, reducing process complexity while maintaining interface quality
3Stability of the object's composition
If copper oxide is present on copper surfaces to be bonded, then natural oxide layer is maintained, but electric performance deteriorates
Solution Approach 1:
The plasma treatment changes the state of copper oxide from a thick, insulating natural oxide layer to a thin, conductive sub-oxide layer. By controlling the plasma parameters (gas composition, power, time), the method transforms the oxide into a form that maintains surface stability while enabling good electric contact
Solution Approach 2:
The patent converts the harmful effect of copper oxide (which normally degrades electric performance) into a beneficial outcome. The plasma treatment transforms the oxide layer into a thin sub-oxide that actually improves bonding stability while maintaining electric conductivity, thus turning the oxide from a problem into an asset
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 method enables high-quality bonding and improved electric performance by forming a barrier against copper diffusion and removing copper oxide, while maintaining compatibility with non-thermal processing requirements, thus addressing the limitations of existing methods.
Implementation Method 1
a first surface provided with at least one copper area surrounded by a silicon oxide area is submitted, before the first and second surfaces are placed into contact, to a plasma treatment operation, characterized in that the plasma is formed from a gas source containing a silicon oxide nitriding agent
Implementation Method 2
a gas source containing a silicon oxide nitriding agent and a copper oxide reducing agent containing hydrogen
Implementation Method 3
a surface activation step prior to the placing into contact, which enables to limit the thermal bonding consolidation treatment between 200 and 400° C.
Data Source
AI summary
A method for bonding a first surface provided with at least one copper area surrounded by a silicon oxide area to a second surface includes an operation of treatment of the first surface by a plasma, before placing the first surface in contact with the second surface. The plasma is formed from a gas source containing a silicon oxide nitriding agent and a copper oxide reducing agent containing hydrogen. The gas source may include an N2 and NH3 and/or H2 gas mixture or a N2O and H2 gas mixture, or ammonia, which is then used both as a nitriding agent and as a reducing agent. The plasma obtained from this gas source then necessarily contains nitrogen and hydrogen, which enables, in a single operation, to provide a high-performance bonding between the first and second surfaces.