Metastable Inert Gas Etching for Sub-Surface Damage Reduction
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Solution Overview
Problem
Atomic layer etching in semiconductor manufacturing often results in sub-surface damage and undesirable modifications due to high-energy plasma etching, particularly evident in the loss of silicon below the gate dielectric during plasma etching, where ion energies greater than 100 eV can induce damage up to 20-40 Angstroms depth.
Innovation Solution
The use of metastable inert gas species, generated from a plasma source, is employed to perform atomic layer etching by adsorbing etchant gases onto the substrate surface, with a separating plate structure and collimator plate preventing energetic plasma ions from contacting the substrate, minimizing damage and promoting directional, anisotropic etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-energy plasma etching is used, then etching speed and efficiency are improved, but sub-surface damage and modification to underlying structures increase
Solution Approach 1:
The etching process is divided into two distinct stages: a high-energy plasma etching stage for efficient material removal, followed by a low-energy metastable species stage for damage-free completion. This segmentation allows each stage to optimize its specific function without compromising the other.
Solution Approach 2:
The patent employs periodic alternation between high-energy plasma exposure and metastable species exposure. The substrate is subjected to cycles of plasma etching followed by metastable species treatment, creating a periodic action that progressively removes material while periodically repairing sub-surface damage.
2Manufacturing precision
If ion energies greater than 100 eV are used in plasma etching, then etching precision is improved, but damage depth increases to 20-40 Angstroms
Solution Approach 1:
Metastable species act as an intermediary between the high-energy plasma and the substrate surface. They transfer the etching function to the substrate through chemical reactions rather than physical bombardment, thereby achieving precision etching without the damaging effects of high-energy ion impact.
Solution Approach 2:
The patent replaces the mechanical bombardment mechanism of high-energy ions with a chemical reaction mechanism using metastable species. Instead of relying on kinetic energy transfer that causes physical damage, the etching is achieved through selective chemical reactions that proceed without mechanical impact.
3Object-affected harmful factors
If metastable inert gas species are used instead of high-energy plasma ions, then sub-surface damage is reduced, but etching efficiency decreases
Solution Approach 1:
The etching process is divided into two distinct stages: a high-energy plasma etching stage for efficient material removal, followed by a low-energy metastable species stage for damage-free completion. This segmentation allows each stage to optimize its specific function without compromising the other.
Solution Approach 2:
The patent employs periodic alternation between high-energy plasma exposure and metastable species exposure. The substrate is subjected to cycles of plasma etching followed by metastable species treatment, creating a periodic action that progressively removes material while periodically repairing sub-surface damage.
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 significantly reduces sub-surface damage by using metastable inert gas species with lower energy (about 0.025 eV) to induce surface reactions, ensuring precise etching with minimal unintentional damage, thereby maintaining the integrity of underlying layers.
Implementation Method 1
an etchant source gas that is suitable for etching the substrate layer is introduced into the substrate processing region of the chamber to promote adsorption of the etchant gas at the substrate surface
Implementation Method 2
The use of metastable inert gas species, generated from a plasma source, is employed to perform atomic layer etching
Data Source
AI summary
A substrate processing system having a processing chamber for etching a layer on a substrate is provided. The system includes a chuck upon which the substrate is disposed during etching. The system also includes the chamber being divided into a plasma generating region and a substrate processing region by a separating plate structure. The system further includes a plasma source for generating plasma in the plasma generating region. The system further includes logic for introducing a first gas into the chamber, wherein the gas is suitable for etching the layer. The logic also allows the first gas to be present in the chamber for a period of time sufficient to cause adsorption of at least some of the first gas into the layer. The logic further replaces the first gas with an inert gas, generates metastables from the inert gas, and etches the layer with the metastables.