Substrate Cleaning for Electroless Deposition Cap Layers
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Solution Overview
Problem
Current post-CMP cleaning solutions for substrates before electroless deposition of cap layers on metal interconnects, such as copper, often leave behind copper oxide films that can cause defects and poor adhesion, leading to issues like spotty plating and pinholes in the cap layer.
Innovation Solution
A method involving a two-step or one-step acidic cleaning process using electroless-deposition compatible corrosion inhibitors and an inert environment, with cleaning solutions containing hydroxycarboxylic acids or their salts, surfactants, reducing agents, and pH adjustors, ensuring the substrate is not dried or dewetted during the process to maintain a clean surface for electroless deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If post-CMP cleaning solutions are used to clean the substrate surface, then copper oxide films are removed, but copper etching increases and adhesion deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the cleaning solution by using electroless deposition-compatible corrosion inhibitors instead of traditional cleaning chemicals. This allows the solution to remove copper oxide films while maintaining copper surface integrity and adhesion properties, resolving the contradiction between oxide removal and adhesion preservation
Solution Approach 2:
The patent introduces an intermediary substance - electroless deposition-compatible corrosion inhibitors - that mediates between the cleaning function and adhesion requirement. These inhibitors act as a bridge, enabling oxide removal while preventing copper etching and maintaining surface properties necessary for good adhesion
2Object-affected harmful factors
If corrosion inhibitors are added to minimize copper etching, then copper surface is protected, but plating quality deteriorates with spotty plating and pinholes
Solution Approach 1:
The patent changes the chemical composition parameters by selecting specific electroless deposition-compatible corrosion inhibitors that do not interfere with the electroless plating process. This allows copper surface protection while ensuring uniform cap layer deposition without spotty plating or pinholes
Solution Approach 2:
The patent converts the potential harm of corrosion inhibitors (causing spotty plating) into a benefit by carefully selecting inhibitors that protect copper during cleaning while being compatible with subsequent electroless deposition, thus turning a problematic additive into a beneficial component
3Productivity
If substrate is dried or dewetted between cleaning and deposition, then processing time is reduced, but surface contamination increases and deposition quality deteriorates
Solution Approach 1:
The patent maintains continuous wetting of the substrate surface from cleaning through electroless deposition without drying or dewetting steps. This continuous liquid phase ensures the surface remains clean and free from contamination while allowing seamless transition between cleaning and deposition processes
Solution Approach 2:
The patent merges the cleaning and electroless deposition processes into a continuous operation where the substrate remains wet throughout. By combining these steps without intermediate drying, the process eliminates contamination risks while maintaining high productivity
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 removes contaminants and defects, ensuring a clean substrate surface for high-quality cap layer deposition, improving adhesion and reducing defects like pinholes and spotty plating.
Implementation Method 1
exposing the surface of the substrate to a cleaning solution sufficient to clean the surface of the substrate
Implementation Method 2
cleaning solutions containing hydroxycarboxylic acids or their salts, surfactants, reducing agents
Implementation Method 3
exposing the surface of the substrate to an electroless deposition solution sufficient to deposit the cap layer
Implementation Method 4
electroless deposition of cap layers on metal and dielectric damascene metallization structures
Implementation Method 5
cleaning solutions containing hydroxycarboxylic acids or their salts, surfactants, reducing agents, and pH adjustors
Data Source
AI summary
This invention pertains to fabrication of devices. One embodiment is a method of substrate cleaning and electroless deposition of a cap layer for an integrated circuit. The method is performed on a substrate having a surface comprising a metal and dielectric damascene metallization layer. The method comprises exposing the surface of the substrate to a cleaning solution sufficient to clean the surface of the substrate and exposing the surface of the substrate to an electroless deposition solution sufficient to deposit the cap layer. Other embodiments of the present invention include solutions to clean the substrate and solutions to accomplish electroless deposition.