Thermal Atomic Layer Etching Using Metal-Ligand Complexes
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Solution Overview
Problem
Current atomic layer etching (ALE) methods lack effective, self-limiting thermal reactions for a wide range of materials, often requiring energetic processes that can damage substrates and lack control over etching rates and temperatures.
Innovation Solution
The development of sequential, self-limiting thermal ALE reactions using metal-ligand complexes and halogen-containing gases, with optional treatment by radicals, ions, photons, or molecular adsorbates to enhance etching rates and precision, allowing for anisotropic etching and reduced operational temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma ALE processes are used to achieve atomic layer control, then etching precision is improved, but substrate damage increases
Solution Approach 1:
The patent replaces plasma-based physical processes with thermal chemical processes. Instead of using energetic ion or noble gas atom bombardment (physical/mechanical action), the invention employs sequential thermal reactions between metal precursors and halogen-containing gases to achieve self-limiting etching. This substitution eliminates the need for high-energy plasma while maintaining atomic layer control through chemistry-driven self-limiting reactions.
Solution Approach 2:
The patent fundamentally changes the operational parameters from plasma conditions (high energy, ion bombardment) to thermal conditions (controlled temperature, chemical reactions). By operating at lower temperatures with thermal chemistry, the process achieves etching precision without the damaging effects of plasma. The self-limiting nature is achieved through thermodynamic control of sequential surface reactions rather than physical sputtering.
2Object-affected harmful factors
If thermal ALE reactions are developed to reduce substrate damage, then substrate damage decreases, but reaction spontaneity becomes problematic due to thermodynamic constraints
Solution Approach 1:
The patent divides the etching process into two separate sequential steps: (1) fluorination of the metal oxide surface by HF to form a metal fluoride layer, and (2) ligand exchange reaction with metal precursors (Sn(acac)2 or TMA) to form volatile etch products. Each step is self-limiting and thermodynamically favorable, with negative ΔG values. This segmentation allows the overall endothermic process to proceed through two spontaneous exothermic sub-reactions.
Solution Approach 2:
The patent introduces a fluoride intermediate layer as a mediator. HF first fluorinates the metal oxide surface to create a metal fluoride intermediate, which then reacts with the metal precursor in a ligand exchange reaction. This intermediate species enables the etching process to proceed through thermodynamically favorable steps, overcoming the thermodynamic barrier of direct thermal etching of metal oxides.
3Adaptability or versatility
If conventional ALE methods are used for various materials, then material compatibility is limited, but process versatility improves
Solution Approach 1:
The patent establishes a universal thermal ALE process using HF and metal precursors (Sn(acac)2 or TMA) that can etch multiple different metal oxide materials including Al2O3, HfO2, and other oxides. The same chemical mechanism (fluorination followed by ligand exchange) applies across different materials, providing a multi-functional etching approach that improves both material compatibility and process efficiency without requiring material-specific process optimization.
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 precise, efficient, and controlled etching with enhanced rates and lower temperature operations, suitable for various materials and substrates, improving the fabrication of nanodevices and reducing surface roughness.
Implementation Method 1
During the thermal ALE reactions, HF fluorinates the metal oxide and forms a metal fluoride layer on the surface
Implementation Method 2
The metal precursors, either Sn(acac)2 or TMA, then accept fluorine from the metal fluoride and transfer their ligands to the metal fluoride in a ligand-exchange reaction. This transmetalation or redistribution process can form volatile species such as AlF(acac)2 or AlF(CH3)2
Implementation Method 3
ALD can deposit a wide range of materials from metal oxides to metals, and is typically accomplished using thermal chemistry. ALD has developed rapidly over the last 10-15 years to meet industrial needs such as the miniaturization of semiconductor devices
Data Source
AI summary
The invention includes a method of promoting atomic layer etching (ALE) of a surface. In certain embodiments, the method comprises sequential reactions with a metal precursor and a halogen-containing gas. In other embodiments, the etching rate is increased by removing residual species bound to and/or adsorbed onto the surface.