Metal Feature Sidewall Oxidation for Critical Dimension Control
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in achieving precise control of critical dimensions and reducing device contact resistance for small metal features, particularly in next-generation metallization using interconnect metals like Ru, W, Mo, and Nb, where conventional damascene and subtractive metal etch strategies face challenges in processing very small features with high aspect ratios.
Innovation Solution
A two-step process involving directing an oxidizing gas cluster ion beam (GCIB) at an angle of 5° to 85° to selectively oxidize metal-containing features, followed by reactive ion etching (RIE) to remove the oxidized layer, providing controlled critical dimensions and improved precision in metal feature processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional damascene or subtractive metal etch strategies are used to form small metal features, then the fabrication process can be implemented, but the critical dimension control deteriorates and contact resistance increases for very small features
Solution Approach 1:
The patent applies preliminary action by performing GCIB oxidation of the metal feature sidewalls before the final etch step. This pre-treatment modifies the sidewall surface chemistry and morphology, creating a more etch-resistant surface that prevents over-etching and improves critical dimension control in subsequent processing steps.
Solution Approach 2:
The patent changes the physical and chemical parameters of the metal feature sidewalls by applying GCIB oxidation. This process alters the surface composition and structure of the sidewalls, transforming them from a state prone to over-etching to a state with improved etch resistance and uniformity, thereby resolving the contradiction between manufacturability and precision.
2Productivity
If metal features are scaled to smaller dimensions to increase circuit density, then more transistors can be placed in an individual device, but sidewall uniformity deteriorates and over-etching increases
Solution Approach 1:
The GCIB oxidation process changes the surface parameters of the metal feature sidewalls, creating a uniform oxidized layer that protects against non-uniform etching. This parameter transformation enables continued scaling to smaller dimensions while maintaining sidewall uniformity and preventing over-etching, thus resolving the contradiction between productivity and manufacturing precision.
3Loss of substance
If GCIB is applied at normal incidence to etch metal features, then material removal can be achieved, but sidewall damage and loss of metal material occur
Solution Approach 1:
The patent applies preliminary GCIB oxidation to modify the sidewall surface before etching. This pre-treatment creates a protective oxidized layer that reduces material loss and sidewall damage during subsequent etching operations, allowing for better preservation of metal material and improved sidewall integrity.
Solution Approach 2:
The oxidized sidewall layer acts as an intermediary protective layer between the metal feature and the etch process. This intermediate layer reduces the direct interaction between the etch chemistry and the metal, minimizing material loss and sidewall damage while still allowing controlled material removal where needed.
4Manufacturing precision
If oxidizing GCIB is directed at metal-containing features to selectively oxidize, then critical dimensions can be controlled, but additional processing steps are required
Solution Approach 1:
The patent merges the oxidation and etch resistance enhancement functions into a single GCIB oxidation step. By combining these functions, the process achieves improved critical dimension control without adding excessive complexity, as the same GCIB treatment that oxidizes the sidewalls also provides the protective effect needed for precise etching control.
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 control of critical dimensions and reduces sidewall thickness, enhancing the quality of small metal features by limiting over-etching and improving sidewall uniformity, thus addressing the challenges of miniaturization in semiconductor fabrication.
Implementation Method 1
directing an oxidizing gas cluster ion beam (GCIB) at the major surface plane of a substrate to selectively oxidize the metal-containing material feature to form an oxidized metal layer
Implementation Method 2
etching the substrate with a reactive ion etching (RIE) process to remove the oxidized metal layer
Data Source
AI summary
A method of processing metal-containing features in a semiconductor substrate where the metal-containing feature comprises a sidewall normal to the major surface plane of the semiconductor substrate, and a top surface having a hard mask cap layer on the top surface is treated by directing an oxidizing gas cluster ion beam (GCIB) at the major surface plane with a first irradiation angle α between the gas cluster ion beam and the major surface plane of from 5° to 85° to selectively oxidize at least a portion of the metal-containing material feature to form an oxidized metal layer. The semiconductor substrate is then treated by dry plasma etching with a reactive ion etching (RIE) process to remove the oxidized metal layer to provide size adapted metal-containing features.