Plasma Oxide Reduction via Color Sensing for Electroplating
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Solution Overview
Problem
The oxidation of metal seed layers on semiconductor wafers during the fabrication of integrated circuits leads to non-conductive oxide layers, reducing electroplating efficiency and causing defects, especially in lower technology nodes where seed layers are thin and prone to seed aging, resulting in voids and pits on pattern wafers.
Innovation Solution
A method involving plasma treatment to reduce metal oxides on the seed layer surfaces, using a plasma generator and color sensor to measure and estimate the extent of oxide reduction based on color signals, particularly the b* component, ensuring real-time monitoring and adjustment during the electroplating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the seed layer is deposited and then exposed to ambient air for queue time, then the wafer can be prepared for subsequent processing, but the seed layer oxidizes forming non-conductive oxide layers that reduce electroplating efficiency
Solution Approach 1:
The patent applies inert atmosphere by introducing nitrogen gas to displace ambient air during the queue time period. The nitrogen atmosphere prevents oxidation of the seed layer by excluding oxygen, thereby maintaining the conductive properties of the seed layer while allowing necessary processing time to elapse between deposition and electroplating operations.
Solution Approach 2:
The patent applies preliminary action by performing a plasma treatment step before the electroplating operation to reduce any oxide layers that may have formed on the seed layer during queue time. This preliminary plasma reduction ensures the seed layer is restored to a conductive state, preventing electroplating defects that would otherwise result from oxidized surfaces.
2Length of moving object
If the seed layer is made thinner for lower technology nodes, then the device scaling is improved, but the seed layer becomes more prone to oxidation and seed aging
Solution Approach 1:
The patent applies inert atmosphere by maintaining nitrogen gas flow over the wafer surface throughout the process sequence. This creates an oxygen-excluded environment that prevents oxidation of thin seed layers, allowing the seed layers to be made thinner for advanced technology nodes without suffering from increased oxidation susceptibility.
Solution Approach 2:
The patent applies preliminary action by implementing plasma treatment immediately before electroplating to reduce any oxide layers that form on thin seed layers. This ensures that even ultra-thin seed layers maintain their conductive properties and can support successful electroplating operations despite their reduced thickness and increased surface-to-volume oxidation rate.
3Reliability
If plasma treatment is applied to reduce oxide layers, then the conductive surface is maintained, but the process complexity increases
Solution Approach 1:
The patent applies merging by integrating the plasma generation capability directly into the electroplating tool. The plasma source is combined with the electroplating chamber, allowing oxide reduction and metal deposition to occur in the same device without requiring separate transfer steps. This integration adds plasma treatment functionality while minimizing the increase in overall system complexity.
Solution Approach 2:
The patent applies continuity of useful action by maintaining nitrogen gas flow continuously throughout the entire process sequence from seed layer deposition through queue time to electroplating. This continuous inert atmosphere protection eliminates the need for intermediate oxidation prevention steps, reducing process complexity while maintaining surface conductivity.
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 effectively reduces oxide layers, enhancing electroplating efficiency by maintaining a conductive surface, minimizing defects, and improving overall wafer yields by providing real-time feedback for optimal plasma pretreatment.
Implementation Method 1
contacting the surface of the semiconductor substrate with a plasma to treat the surface by reducing metal oxides thereon
Implementation Method 2
reducing metal oxides on the surface of the metal seed layer
Implementation Method 3
measuring a post-plasma-contact color signal from said surface, the color signal having one or more color components
Data Source
AI summary
Disclosed are methods of preparing a semiconductor substrate having a metal seed layer for a subsequent electroplating operation. In some embodiments, the methods may include contacting the surface of the semiconductor substrate with a plasma to treat the surface by reducing metal oxides thereon and thereafter measuring a post-plasma-contact color signal from said surface, the color signal having one or more color components. The methods may then further include estimating the extent of the oxide reduction due to the plasma treatment based on the post-plasma contact color signal. In some embodiments, estimating the extent of the oxide reduction due to the plasma treatment is done based on the b* component of the post-plasma contact color signal. Also disclosed are plasma treatment apparatuses which may implement the foregoing methods.