Wet Atomic Layer Etching of Ruthenium
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Solution Overview
Problem
Conventional etch processes for ruthenium in semiconductor manufacturing face challenges such as surface roughening, metal contamination, and high costs due to the use of strong oxidizers, which are problematic for achieving uniform etching and maintaining surface quality.
Innovation Solution
A new wet atomic layer etch (ALE) process using halogenation to form insoluble ruthenium halide or oxyhalide passivation layers, which are selectively removed through ligand-assisted dissolution, providing a metal-free, cost-effective, and smoothing etching solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional strong oxidizer-based etch processes are used for ruthenium, then etching capability is achieved, but surface roughening occurs and metal contamination increases
Solution Approach 1:
The patent changes the chemical parameters of the etching process by replacing strong oxidizers with a two-solution system consisting of a halogenating agent (e.g., I2, Br2, Cl2) followed by a reducing agent (e.g., HI, HBr, HCl). This parameter change transforms the etching mechanism from oxidation-based to halogenation-reduction-based, which achieves uniform material removal without surface roughening and eliminates metal contamination.
Solution Approach 2:
The patent introduces halogen intermediates (RuX3 or RuX4 species where X = F, Cl, Br, I) as mediators in the etching process. The halogenating agent first forms these intermediate compounds on the ruthenium surface, which are then selectively removed by the reducing agent. This intermediary mechanism enables precise control over the etching reaction, achieving uniform etching while maintaining surface quality and preventing contamination.
2Manufacturing precision
If conventional etch processes are used, then material removal is achieved, but macroscopic and microscopic uniformity cannot be simultaneously maintained
Solution Approach 1:
The patent segments the etching process into two distinct sequential steps: (1) halogenation step where the halogenating agent modifies the ruthenium surface to form volatile or soluble halide compounds, and (2) reduction step where the reducing agent removes the halogenated layer. This segmentation allows each step to be independently optimized and controlled, achieving both macroscopic and microscopic etching uniformity while simplifying process control through clear separation of functions.
3Manufacturing precision
If traditional wet etching is used, then material removal occurs, but selective removal of modified layers cannot be achieved
Solution Approach 1:
The patent employs periodic action by alternating between the halogenating agent solution and the reducing agent solution in sequential cycles. Each cycle consists of: (1) applying halogenating agent to form RuX3/RuX4 species, (2) rinsing to remove excess halogenating agent, (3) applying reducing agent to remove the halogenated layer, and (4) rinsing to remove byproducts. This periodic application of different chemical agents enables selective and controlled removal of material while maintaining process simplicity through repeated cyclic treatment.
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
The process improves surface roughness and reduces contamination risks, achieving isotropic or anisotropic etching with precise control over etch amounts and surface morphology, suitable for high-volume manufacturing.
Implementation Method 1
exposing the Ru layer to a first etch solution containing a halogenating agent to form a chemically modified Ru surface layer containing a ruthenium halide or a ruthenium oxyhalide
Implementation Method 2
exposing the surface of the substrate to a second etch solution including a reactive agent and a solvent, wherein the reactive agent reacts with the passivation layer and forms soluble species that are dissolved by the solvent
Implementation Method 3
exposing the Ru layer to a first etch solution containing an oxidizer, a cation and a chlorine source reactive to the Ru layer to form a chemically modified Ru surface layer containing a ruthenium salt
Data Source
AI summary
The present disclosure provides a new wet atomic layer etch (ALE) process for etching ruthenium. More specifically, the present disclosure provides various embodiments of methods that utilize new etch chemistries for etching ruthenium in a wet ALE process. Unlike conventional etch processes for ruthenium, the wet ALE process described herein for etching ruthenium is metal-free, cost-effective and improves surface roughness during etching.