Thermal Atomic Layer Etching for Plasma-Free Halide Removal
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Solution Overview
Problem
Current atomic layer etching processes often require plasma reactants, which can be damaging to substrates and lack control in isotropic etching of non-line of sight features, and existing thermal etching methods may not provide sufficient selectivity and efficiency in removing specific materials like metal nitrides and oxides.
Innovation Solution
A thermal atomic layer etching process using sequential pulses of vapor-phase halide reactants, where a first halide reactant forms adsorbed species on the substrate, and a second reactant converts these species into volatile adducts that can be removed, allowing for controlled etching without plasma, specifically targeting materials like TiN, TaN, SiN, and Al2O3 with reactants such as NbF5 and CCl4.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma reactants are used in atomic layer etching, then etching efficiency is improved, but substrate damage increases and control in isotropic etching of non-line of sight features deteriorates
Solution Approach 1:
The patent replaces plasma-based chemical reactions with thermal chemical reactions using vapor-phase reactants. Specifically, it uses a first vapor-phase reactant (e.g., NF3, CF4) to form volatile compounds with the film material, followed by a second vapor-phase reactant (e.g., H2, N2) to remove the formed compounds. This substitution eliminates plasma-related substrate damage while maintaining controlled etching through sequential thermal reactions.
Solution Approach 2:
The patent changes the reaction conditions from plasma state to thermal vapor-phase reactions. By controlling temperature, pressure, and reactant flow rates, the process achieves selective etching without the harsh conditions of plasma. The sequential introduction of reactants at controlled temperatures enables precise control over etching depth and selectivity, improving both efficiency and substrate integrity.
2Object-affected harmful factors
If conventional thermal etching methods are used, then substrate damage is reduced, but selectivity and efficiency in removing specific materials like metal nitrides and oxides deteriorate
Solution Approach 1:
The patent divides the etching process into two distinct sequential steps: (1) a first vapor-phase reactant selectively reacts with and removes the desired film material (e.g., metal nitrides, oxides), and (2) a second vapor-phase reactant removes any remaining species. This segmentation allows each reactant to be optimized for specific selectivity requirements, enabling precise removal of target materials while preserving the substrate and other structures.
Solution Approach 2:
The patent introduces intermediate reaction species formed during the thermal reaction between vapor-phase reactants and the film material. These intermediates act as mediators that enable selective removal of specific materials like metal nitrides and oxides. The first reactant forms volatile intermediate compounds with the target film, which are then removed by the second reactant, achieving high selectivity without direct plasma damage.
3Manufacturing precision
If sequential pulses of vapor-phase reactants are used, then control in etching is improved, but process complexity increases
Solution Approach 1:
The patent employs periodic sequential pulsing of different vapor-phase reactants into the reaction chamber. The first reactant pulse performs selective etching, followed by a purge, then a second reactant pulse completes the removal process. This periodic action provides precise control over etching depth and rate through simple temporal sequencing, avoiding the need for complex real-time feedback systems while maintaining high manufacturing precision.
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 and efficient removal of sub-monolayers with high conformality and selectivity, reducing damage to substrates and allowing for isotropic etching of complex features, as demonstrated by the etching of various films like TiN, TiO2, TaN, and Al2O3 with significant changes in thickness and sheet resistance observed after multiple cycles.
Implementation Method 1
exposing the substrate to a first vapor-phase halide reactant, such as a non-metal halide reactant, to form adsorbed species on the substrate
Implementation Method 2
the second vapor-phase reactant converts the adsorbed species into volatile adducts that comprise one or more atoms from the surface to be etched
Data Source
AI summary
Thermal atomic layer etching processes are disclosed. In some embodiments, the methods comprise at least one etch cycle in which the substrate is alternately and sequentially exposed to a first vapor phase halide reactant and a second vapor halide reactant. In some embodiments, the first reactant may comprise an organic halide compound. During the thermal ALE cycle, the substrate is not contacted with a plasma reactant.