Volatile Reducing Agents for ALD Metal Film Purity
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Solution Overview
Problem
The challenge in forming pure metal films using atomic layer deposition (ALD) is the presence of halogen impurities, which are common due to the use of halogen-containing metal precursors, and achieving uniform reduction in high aspect ratio structures is difficult with existing reducing agents like hydrogen plasma.
Innovation Solution
The use of specific reducing agents such as group IV element containing heterocyclic compounds, radical initiators, alkyl alanes, diborene species, and Sn(II) compounds to expose metal halide films, allowing for the abstraction of halogen impurities and formation of pure metal films with improved uniformity and volatility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen plasma is used as a reducing agent for ALD of metals, then the metal film can be formed, but plasma uniformity is poor in high aspect ratio structures
Solution Approach 1:
The patent replaces plasma-based reduction with volatile reducing agents that deliver reducing species through vapor-phase diffusion and surface reaction. This substitution eliminates plasma uniformity issues in high aspect ratio structures while maintaining effective metal halide reduction and metal film formation.
Solution Approach 2:
The patent changes the physical and chemical parameters of the reducing agent from plasma state to volatile molecular compounds. This parameter change enables conformal delivery of reducing species throughout high aspect ratio structures via vapor-phase transport, achieving uniform reduction without plasma-related non-uniformity.
2Productivity
If halogen-containing metal precursors are used in ALD, then metal films can be deposited, but halogen impurities remain in the film
Solution Approach 1:
The patent extracts halogen impurities from the metal film by introducing volatile reducing agents that react with and remove halogen atoms. The reducing agents selectively abstract halogen from the metal halide film, converting it to volatile by-products that can be pumped away, leaving pure metal film.
Solution Approach 2:
The patent uses volatile reducing agents as intermediaries to transfer reducing species to the metal halide film surface. These intermediaries (such as organometallic compounds or molecular hydrogen sources) deliver reducing equivalents that convert metal halides to pure metals while forming volatile halogen-containing by-products.
3Reliability
If conventional reducing agents are used, then metal films can be reduced, but reaction by products have limited volatility
Solution Approach 1:
The patent changes the volatility parameter of reaction by-products by selecting reducing agents and metal precursor combinations that produce highly volatile by-products. This enables complete removal of reaction products through standard vacuum pumping, preventing contamination and allowing low-temperature processing.
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
These reducing agents effectively reduce halogen impurities, resulting in metal films that are substantially free of oxygen and halogens, enhancing the purity and conformality of the films deposited in high aspect ratio features, thereby improving the performance of next-generation semiconductor devices.
Implementation Method 1
exposing a metal halide film having the formula MXn to a reducing agent to reduce the metal halide film and abstract halogen from the metal halide film
Data Source
AI summary
Methods of forming a metal film having a metal halide with a reducing agent are disclosed. The reducing agent, the reducing agent includes a group IV element containing heterocyclic compound, a radical initiator, an alkly alane, a diborene species and/or a Sn(II) compound.