Atomic Layer Copper Etching for Uniform High-Aspect-Ratio Features
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor fabrication processes face challenges in forming small copper features using the dual-damascene process, particularly with etching copper, where wider features etch faster than narrower ones and sidewalls become too rough, and existing etching technologies like ion beam etch and reactive ion etch have limitations in achieving high aspect ratios and tight pitches.
Innovation Solution
A method for atomic layer etching copper or copper alloys in a plasma processing chamber, comprising cycles with a copper modification phase using nitrogen gas and an activation phase with hydrogen gas, forming volatile copper complexes to achieve precise and uniform etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional plasma etching or ion beam etching is used for copper, then etching speed may be improved, but etch uniformity across different feature widths deteriorates (wider features etch faster than narrower ones)
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas chemistries and parameters. Each step targets specific aspects of the etching process (e.g., breakthrough, main etch, overetch) to achieve uniform removal across features of varying widths while maintaining overall etching speed.
Solution Approach 2:
The patent employs dynamic adjustment of process parameters including gas flow rates, pressure, power, and temperature throughout the etching sequence. These parameter changes enable optimization for each specific etching phase, ensuring uniform etch rates across different feature dimensions while maintaining productivity.
2Manufacturing precision
If conventional etching methods are used for high aspect ratio structures, then etching capability is limited, but sidewall roughness increases
Solution Approach 1:
The patent introduces intermediary protective layers and modified plasma chemistries that act as mediators during etching of high aspect ratio structures. These intermediaries protect sidewalls from excessive damage while allowing controlled etching progression, enabling higher aspect ratios with smoother sidewalls.
Solution Approach 2:
The etching process uses periodic cycling between different gas phases and parameter sets, allowing brief recovery periods that prevent cumulative sidewall damage while maintaining etching progression. This periodic action enables achievement of higher aspect ratios without excessive roughness accumulation.
3Reliability
If dual-damascene process is used for copper interconnects, then copper deposition is improved, but device scaling becomes difficult
Solution Approach 1:
The patent replaces portions of the mechanical dual-damascene process with plasma-based direct patterning and modified etching approaches. This substitution enables direct formation of copper structures without requiring the full dual-damascene sequence, facilitating better scaling to smaller dimensions while maintaining structural reliability.
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 precise and uniform etching of copper, allowing for high aspect ratio structures and tight pitches without surface damage, improving upon existing technologies by providing a halogen-free, conformal, and selective etching process with higher aspect ratio capabilities.
Implementation Method 1
transforming the modification gas into a modification plasma, and exposing the copper or copper alloy to the modification plasma
Implementation Method 2
transforming the activation gas into an activation plasma, and exposing the modified copper or copper alloy to the activation plasma, wherein at least a volatile copper or copper alloy complex is formed
Data Source
AI summary
A method for atomic layer etching copper or copper alloy over a substrate in a plasma processing chamber comprising a plurality of cycles is provided. Each cycle of the plurality of cycles comprises a copper modification phase and an activation phase. The copper modification phase comprises flowing a modification gas into the plasma processing chamber, transforming the modification gas into a modification plasma, and exposing the copper or copper alloy to the modification plasma, wherein at least a part of the copper or copper alloy is modified. The activation phase comprises flowing an activation gas into the plasma processing chamber, wherein the activation gas, comprises a hydrogen containing gas, transforming the activation gas into an activation plasma, and exposing the modified copper or copper alloy to the activation plasma, wherein at least a volatile copper or copper alloy complex is formed.