Transition Metal Etching via Coordination Complex Formation
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Solution Overview
Problem
Current semiconductor deposition processes face challenges in delicately etching transition metal films, particularly cobalt, with a need for self-limiting, in situ, and selective dry etching methods that provide precise control and conformality, especially for high aspect structures and equipment cleaning.
Innovation Solution
A method involving substrate surface activation through heat, plasma, oxidizing environments, or halide transfer agents, followed by exposure to Lewis bases or π acids to form volatile metal coordination complexes, allowing for controlled etching of transition metals like cobalt, copper, and nickel, with the option to purge these complexes for precise removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional deposition processes (CVD/ALD) are used to deposit transition metal films, then film deposition is achieved, but unwanted deposition onto chamber walls and showerhead occurs, requiring additional cleaning steps
Solution Approach 1:
The patent converts the harmful unwanted deposition of transition metals on chamber walls into a beneficial feature by developing a selective etch process that targets and removes these deposits. The etch process uses specific reagents (Lewis bases or pi acids) that react preferentially with transition metal surfaces, transforming the cleaning challenge into a controlled removal process that actually improves overall process efficiency by enabling easy removal of problematic deposits.
2Ease of operation
If wet etch methods are used for cobalt removal, then some etching capability is achieved, but precise control and conformality are insufficient
Solution Approach 1:
The patent replaces wet chemical etching methods with a vapor-phase etch process. This substitution transitions from liquid-phase chemistry to gas-phase reactions, enabling better control over etch kinetics and conformality. The vapor phase process allows for more uniform distribution of reactants and better control over reaction rates, achieving the precision and conformality that wet etching cannot provide.
Solution Approach 2:
The patent changes the physical state parameter of the etchant from liquid (wet etch) to gas (vapor phase). This parameter change enables precise control over etch rate and conformality by adjusting vapor pressure, temperature, and flow rate. The gas-phase process allows for atomic-layer precision and self-limiting etch behavior, achieving manufacturing precision unattainable with conventional wet methods.
3Productivity
If non-selective etch methods are used, then general metal removal is achieved, but selective etching of specific metals cannot be performed
Solution Approach 1:
The patent applies local quality by designing etch reagents with specific chemical affinity for particular transition metals. Different Lewis bases or pi acids are selected based on their selective binding characteristics to specific metal surfaces. This allows the etch process to target only the desired metal layer while leaving other materials intact, achieving high selectivity through chemically specific interactions rather than general chemical reactivity.
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, self-limiting etching of transition metals with high control, effectively removing metal layers while maintaining the integrity of underlying structures and allowing for selective etching of specific metals, thereby addressing the challenges of conformal deposition and equipment cleaning.
Implementation Method 1
activation of the substrate surface comprises exposing the substrate surface to heat
Implementation Method 2
activation of the substrate surface comprises exposing the substrate surface to a plasma
Implementation Method 3
exposing the activated substrate surface to a reagent comprising a Lewis base or pi acid to provide a vapor phase coordination complex comprising one or more atoms of the transition metal coordinated to one or more ligands from the reagent
Implementation Method 4
provide a vapor phase coordination complex
Data Source
AI summary
Provided are methods for etching films comprising transition metals. Certain methods involve activating a substrate surface comprising at least one transition metal, wherein activation of the substrate surface comprises exposing the substrate surface to heat, a plasma, an oxidizing environment, or a halide transfer agent to provide an activated substrate surface; and exposing the activated substrate surface to a reagent comprising a Lewis base or pi acid to provide a vapor phase coordination complex comprising one or more atoms of the transition metal coordinated to one or more ligands from the reagent. Certain other methods provide selective etching from a multi-layer substrate comprising two or more of a layer of Co, a layer of Cu and a layer of Ni.