Selective Dry Etching of Metal Oxide Films Using Halogenation and Ligand Transfer
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Solution Overview
Problem
Existing etching processes for metal oxide films, such as plasma etching and thermal etching, face challenges including non-uniform etch rates and contamination, particularly when dealing with substrates comprising multiple chemical components like indium gallium zinc oxide (IGZO), leading to incomplete etching and modification of film properties.
Innovation Solution
The use of a halogenation agent, such as HF or Cl2, in combination with a ligand transfer agent like Al(CH3)3, to form a halogenated substrate surface, allowing for uniform etching of indium oxide, gallium oxide, and zinc oxide films through dry thermal etching techniques like atomic layer etching, ensuring consistent etch rates and minimizing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching is used to etch metal oxide films, then the etching process can be performed with high speed, but the etch rates of different materials are non-uniform and contamination is introduced
Solution Approach 1:
The etching process is divided into two distinct steps: first, a halogenation step where a halogen-containing compound reacts with the metal oxide surface to form metal halides; second, a removal step where the metal halides are converted to volatile species and removed. This segmentation allows each step to be optimized independently, achieving both high speed and uniform etching across different materials.
Solution Approach 2:
Metal halides serve as an intermediary species in the etching process. The halogenation step creates these intermediate compounds on the surface, which then facilitate uniform removal in the second step. This intermediary mechanism ensures consistent etch rates across different metal oxides while maintaining high productivity.
2Productivity
If plasma etching is used to etch metal oxide films, then the etching process can be performed quickly, but the film composition is modified and contaminants are introduced
Solution Approach 1:
The etching process is conducted in a controlled atmosphere using specific halogen-containing compounds and carrier gases that minimize contamination. The halogenation step uses compounds like Cl2 or CF4 in inert carrier gases, and the removal step employs oxygen plasma or thermal processing in controlled environments, preventing unwanted contaminants from being introduced while maintaining high etching speed.
Solution Approach 2:
Metal halides act as controlled intermediary species that facilitate the etching process without introducing unwanted contaminants. The halogenation step creates these intermediates in a controlled manner, and the subsequent removal step cleanly converts them to volatile products, avoiding the contamination issues associated with direct plasma etching.
3Temperature
If thermal etching is used to etch metal oxide films, then lower reaction temperatures and greater control are achieved, but the etch rates of different materials remain non-uniform and contamination occurs
Solution Approach 1:
The thermal etching process is segmented into halogenation and removal steps, allowing low-temperature halogenation to occur first, forming uniform metal halide layers across different materials. The subsequent removal step then proceeds uniformly, maintaining both low temperature operation and consistent etch rates across diverse metal oxide compositions.
Solution Approach 2:
Metal halides serve as intermediaries that enable uniform etching at low temperatures. The halogenation step creates these intermediates uniformly across different metal oxide surfaces, and the removal step proceeds consistently for all materials, eliminating the non-uniform etching rates that plague conventional thermal etching methods.
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 achieves substantially uniform etch rates for multiple metal oxides, preventing the buildup of certain species and reducing contamination, thereby improving the precision and effectiveness of the etching process, with an etch rate selectivity of at least 25:1 between different surfaces.
Implementation Method 1
The etch process generally relies on radical reactions. During the reaction process, the plasma generates volatile etch products from the chemical reactions between the elements of the substrate surface and the plasma.
Implementation Method 2
The substrate surface is exposed to a ligand transfer agent comprising one or more of MR2X or MR3, where M is In, Ga, Al or B, R is a C1 to C6 group, and X is a halogen. The etch rates of the metals in the multiple metal oxides are substantially uniform.
Data Source
AI summary
A process to selectively etch a substrate surface comprising multiple metal oxides comprising exposing the substrate surface to a halogenation agent, and then exposing the substrate surface to a ligand transfer agent. The etch rate of the metals in the multiple metal oxides is substantially uniform.