Atomic Layer Etching of Metal Oxide via Hydride Sublimation
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Solution Overview
Problem
Current methods for etching metal oxide layers in semiconductor device fabrication, such as using chemical etches with halogen plasma, face challenges in achieving precise control and efficiency.
Innovation Solution
A cyclical atomic layer etching process involving exposure to a reactive hydrogen-containing gas or plasma to transform metal oxide layers into metal hydride, followed by heating above sublimation temperature to sublime the hydride and cooling below sublimation temperature, is employed to selectively etch metal oxide layers without the need for chemical etchants like halogens and oxygen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical etch with halogen plasma is used to etch metal oxide layers, then etching capability is achieved, but manufacturing precision and process control are insufficient
Solution Approach 1:
The etching process is segmented into distinct sequential steps: hydrogen exposure to form metal hydride, heating to sublime the hydride, and cooling to condense any remaining vapor. This segmentation allows precise control over etch depth and rate, achieving atomic-layer precision while maintaining high productivity through the repetitive nature of each complete cycle.
Solution Approach 2:
The etching process employs periodic cycling between hydrogen exposure, heating, and cooling phases. Each cycle removes a controlled amount of metal oxide through temporary hydride formation and sublimation. The periodic repetition of these phases enables precise cumulative etching control while sustaining high processing throughput through rapid cycle execution.
2Manufacturing precision
If chemical etchants like halogens are used, then etching of metal oxide is achieved, but harmful factors and material loss occur
Solution Approach 1:
The process converts the typically harmful chemical etching action into a beneficial physical sublimation process. By using hydrogen to form temporary metal hydrides that then sublime upon heating, the method eliminates the need for harmful halogen chemicals while achieving precise etching. The harmful chemical reactions are replaced with a clean physical phase transition that leaves no toxic residues.
Solution Approach 2:
The process substitutes chemical etching mechanisms with a thermal-mechanical approach. Instead of using chemical reactions to remove material, the method uses controlled heating to induce sublimation of metal hydrides. This replacement of chemical action with thermal-physical action eliminates harmful chemical etchants while maintaining precise material removal capability.
3Productivity
If traditional etching methods are used, then material removal is achieved, but processing time is excessive
Solution Approach 1:
The process exploits the phase transition of metal hydrides from solid to gas through sublimation upon heating. This phase transition enables rapid material removal at controlled rates, significantly increasing processing speed compared to traditional chemical etching. The sharp phase change point provides a natural stop mechanism that maintains atomic-layer precision even at high processing speeds through rapid cycling.
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 process provides self-limiting etch control, reducing thickness by less than 0.1 nm per cycle, eliminates the need for chemical etchants, and allows for faster processing times due to rapid temperature changes, resulting in precise and efficient etching of metal oxide layers.
Implementation Method 1
exposing the metal oxide layer to a reactive hydrogen-containing gas or plasma to transform at least a part of the metal oxide layer into a layer of metal hydride
Implementation Method 2
heating the layer of metal hydride to at least a sublimation temperature to sublime the layer of metal hydride
Data Source
AI summary
A method for etching a metal oxide layer on a semiconductor substrate, comprising providing a plurality of cycles, is provided. Each cycle comprises exposing the metal oxide layer to a reactive hydrogen-containing gas or plasma to transform a part of the metal oxide layer into a layer of metal hydride, stopping the exposing the metal oxide layer to the reactive hydrogen-containing gas or plasma, heating the layer of metal hydride to at least a sublimation temperature to sublime the layer of metal hydride, and cooling the metal oxide layer to a temperature below the sublimation temperature.