Reducing Gas Ambient for Substrate Oxidation Prevention
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Solution Overview
Problem
During semiconductor fabrication, substrates undergo unintended oxidation when loaded into process chambers, especially at elevated temperatures, leading to increased resistivity in conductive materials like metal nitrides, which is exacerbated by the scale-down of integrated circuits.
Innovation Solution
Establishing a reducing gas ambient in the process chamber before loading substrates and maintaining it during processing suppresses oxidation, using a reducing gas that constitutes a minority component of the gas mixture, typically 0.1 to 4 vol.%, which is safe and non-explosive, allowing for efficient control of oxidation and maintenance of low resistivity in deposited films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If substrates are loaded into process chambers at elevated temperatures to improve processing efficiency, then productivity increases, but oxidation of substrate surfaces occurs leading to increased resistivity
Solution Approach 1:
A reducing gas ambient is established in the process chamber before substrates are loaded, preventing oxidation from occurring in the first place during the loading and heating process. This preliminary protective action allows substrates to be processed at elevated temperatures without surface degradation.
2Manufacturing precision
If reducing gas concentration is increased to suppress oxidation more effectively, then resistivity control improves, but safety risks increase due to explosive hazards
Solution Approach 1:
The patent optimizes the reducing gas concentration to a specific range (0.1-4 vol.%) that provides sufficient oxidation protection while remaining below explosive thresholds. This parameter optimization achieves both effective resistivity control and safety.
Solution Approach 2:
A carrier gas (such as nitrogen or argon) is used as an intermediary to deliver the reducing gas to the substrate. The carrier gas dilutes the reducing gas concentration to safe levels while still maintaining an effective reducing ambient that prevents oxidation.
3Object-affected harmful factors
If conventional inert gas ambients are used during substrate loading, then oxidation is prevented, but oxygen incorporation in deposited films increases leading to higher resistivity
Solution Approach 1:
Instead of using inert gas that prevents oxidation but introduces oxygen incorporation issues, the patent uses a reducing gas ambient that actively suppresses oxidation through chemical reduction. This inverted approach uses a reactive rather than inert atmosphere to achieve both oxidation prevention and low oxygen incorporation in films.
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
The reducing gas ambient effectively reduces oxygen incorporation in metal-containing films, maintaining low resistivity levels, particularly in thin films, and allows for clustered processing without contamination, achieving resistivity of 70 μΩ·cm or less in TiN films at thicknesses of 10 nm or less.
Implementation Method 1
A reducing ambient is provided in the second process chamber during subsequently loading the substrate into the second process chamber
Data Source
AI summary
In some embodiments, a reducing gas ambient containing a reducing agent is established in a batch process chamber before substrates are subjected to a deposition. The reducing atmosphere is established before and/or during loading of the substrates into the process chamber, and can include flowing reducing gas into the process chamber while the chamber is open. The reducing gas can be a mixture of a reducing agent and an inert gas, with the reducing agent being a minority component of the reducing gas. Using the reducing gas ambient, oxidation of substrate surfaces is reduced.