Atomic Layer Etching of Transition Metal Oxide Layers
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Solution Overview
Problem
Current semiconductor manufacturing technologies face challenges in etching and cleaning transition metal layers, particularly for small feature sizes, due to issues like sidewall re-deposition and isotropic wet etching, which affect the precision and efficiency of via and interconnect formation in integrated circuits.
Innovation Solution
A method involving surface chemical oxidation and complexation with organic ligands to generate volatile metal oxide species, allowing for controlled, anisotropic etching of transition metals like cobalt, iron, and ruthenium, using atomic layer etching techniques to achieve precise removal and cleaning at the sub-nanometer level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional plasma etching methods are used for transition metal layers, then etching can be performed, but sidewall re-deposition occurs and precision is reduced
Solution Approach 1:
The patent changes the etching mechanism from physical plasma sputtering to chemical oxidation followed by volatile complex formation. This parameter change in the etching chemistry eliminates sidewall re-deposition by converting the metal surface to a volatile complex that desorbs cleanly, improving etching precision for transition metal layers
Solution Approach 2:
The patent replaces the mechanical/physical plasma sputtering process with a chemical oxidation and complexation process. This substitution eliminates the physical ejection of metal atoms that causes sidewall re-deposition, achieving cleaner etching with higher precision
2Ease of manufacture
If isotropic wet etching is used for transition metal layers, then etching can be performed, but anisotropic etching capability is lost
Solution Approach 1:
The patent employs periodic alternating steps of oxidation and complexation/etching. The oxidation step creates a fresh metal oxide surface, followed by the complexation step that removes it anisotropically. This periodic action maintains etching anisotropy while ensuring complete removal of the metal layer
Solution Approach 2:
The patent segments the etching process into distinct oxidation and complexation steps. This segmentation allows each step to be optimized independently - the oxidation step creates the necessary surface chemistry, while the complexation step provides anisotropic removal, achieving both processability and shape control
3Manufacturing precision
If conventional etching methods are used for small features, then etching can be performed, but cleaning and quantitative removal become difficult
Solution Approach 1:
The patent introduces organic ligands as intermediaries that form volatile complexes with the metal oxide surface. These ligands act as mediators that enable complete and clean removal of the metal layer by forming thermally unstable complexes that decompose and desorb, achieving quantitative removal without residual contamination
Solution Approach 2:
The patent utilizes phase transitions from solid metal oxide to volatile gas-phase complexes. By heating the structure to temperatures where the metal-organic complexes become volatile, the patent achieves complete removal of the metal layer with clean phase transition, ensuring no residual contamination remains
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 enables clean, quantitative, and highly selective etching of transition metals, improving the precision and efficiency of semiconductor processing, particularly for features below 14 nanometers, and addresses the limitations of traditional plasma etching methods.
Implementation Method 1
reacting a surface layer of a transition metal species of a transition metal-containing film with a molecular oxidant species to form an oxidized surface layer of the transition metal species
Implementation Method 2
reacting the oxidized surface layer of the transition metal species with a molecular etchant and thermally decomposing the reacted oxidized surface layer and the reacted molecular etchant to remove them
Data Source
AI summary
Transition metal dry etch by atomic layer removal of oxide layers for device fabrication, and the resulting devices, are described. In an example, a method of etching a film includes reacting a surface layer of a transition metal species of a transition metal-containing film with a molecular oxidant species. The method also includes removing volatile fragments of the reacted molecular oxidant species to provide an oxidized surface layer of the transition metal species. The method also includes reacting the oxidized surface layer of the transition metal species with a molecular etchant. The method also includes removing the reacted oxidized surface layer of the transition metal species and the reacted molecular etchant by volatlilization.