Electroless Deposition of Platinum Group Metal Interconnects
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Solution Overview
Problem
The current Damascene process for forming copper interconnects in integrated circuits generates significant waste and is not suitable for platinum group metals due to high costs and environmental impact, and existing electroless deposition methods for these metals introduce impurities or use toxic reducing agents.
Innovation Solution
An oxygen-free or oxygen-poor electroless deposition method using a ruthenium (II) amine complex and a platinum group metal compound with a suitable reduction potential is employed, allowing for the formation of platinum group metal interconnects without the need for etching or polishing, and minimizing the use of reducing agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the Damascene process is used to form copper interconnects, then the interconnects can be formed with good filling quality, but significant waste is generated and the process is not suitable for platinum group metals due to high costs
Solution Approach 1:
The patent extracts and eliminates the CMP (chemical mechanical polishing) step from the Damascene process, which is the source of material waste. By removing this step, the process achieves void-free filling without requiring removal of excess metal, thereby eliminating significant material waste while maintaining good filling quality.
Solution Approach 2:
The patent changes the deposition method from electroplating (used in Damascene) to electroless deposition. This parameter change allows for conformal coating and void-free filling in high-aspect-ratio structures without requiring subsequent CMP processing, thus reducing material waste while maintaining manufacturing precision.
2Loss of substance
If electroless deposition is used to deposit platinum group metals, then material waste is reduced, but existing methods introduce impurities or use toxic reducing agents
Solution Approach 1:
The patent uses a disposable sacrificial layer (such as a self-assembled monolayer or organic coating) on the substrate surface that facilitates electroless deposition and then can be easily removed. This disposable layer enables controlled metal deposition without requiring toxic reducing agents, reducing both material waste and harmful factors.
Solution Approach 2:
The patent employs an inert or controlled atmosphere during the electroless deposition process to prevent oxidation and contamination. By conducting the deposition in an oxygen-free or controlled environment, the process avoids introducing impurities and eliminates the need for toxic reducing agents that would otherwise be required to prevent oxidation.
3Ease of manufacture
If copper is used for interconnects, then processing is easier compared to platinum group metals, but copper has high diffusivity in silicon requiring barrier layers that increase effective resistivity
Solution Approach 1:
Instead of using copper and adding barrier layers to prevent diffusion, the patent inverts the approach by directly using platinum group metals (such as ruthenium, rhodium, or iridium) that inherently have low diffusivity in silicon. This eliminates the need for barrier layers and the associated increase in effective resistivity, while the electroless deposition method maintains ease of manufacture.
4Manufacturing precision
If the Damascene process fills trenches completely with metal, then void-free filling is achieved, but excessive metal is deposited on top of the substrate requiring etching or polishing
Solution Approach 1:
The patent employs electroless deposition which naturally conforms to the trench geometry and stops when the trench is filled, without requiring external control or subsequent removal steps. The deposition process self-regulates based on the catalytic activity of the trench walls, achieving void-free filling without excessive metal deposition on the substrate surface.
Solution Approach 2:
The patent changes the deposition mechanism from electroplating (which deposits metal uniformly across all surfaces including the substrate top) to electroless deposition (which deposits metal selectively on catalytically active surfaces). This parameter change enables void-free trench filling without requiring CMP or etching to remove excess metal.
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 efficient, void-free deposition of platinum group metals with reduced waste and environmental impact, maintaining the quality of interconnects while avoiding the use of toxic agents and minimizing material loss.
Implementation Method 1
an oxygen-free or oxygen-poor electroless deposition method using a ruthenium (II) amine complex and a platinum group metal compound with a suitable reduction potential
Data Source
AI summary
An oxygen-free or oxygen-poor solution for the electroless deposition of a platinum group metal is described. The solution includes a ruthenium (II) amine complex having a first oxidation potential, and a platinum group metal compound having a reduction potential larger than the opposite of the oxidation potential of the ruthenium (II) amine complex.