Electrolyzed Chloride Etching for Ru and Metal Nitrides
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for etching metals and metal nitrides in semiconductor processing, such as Ru, face challenges including the formation of toxic by-products, incompatibility with CMOS processing, and residue issues, necessitating improved etching solutions that are safe, compatible, and efficient.
Innovation Solution
A method involving electrolysis of a chloride anion precursor solution to form an etching solution, which is used to selectively remove metals and metal nitrides on semiconductor structures, with options for acidic and alkaline conditions, and the ability to add complexing or activating agents for enhanced removal capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dry etching using O2 and Cl2 plasma is used to etch Ru, then etching capability is achieved, but toxic and volatile gas RuO4 is formed as a by-product
Solution Approach 1:
The invention changes the chemical parameters of the etching process by using a wet chemical etching solution containing specific reagents (such as ammonium bifluoride, hydrofluoric acid, and nitric acid) instead of plasma. This parameter change eliminates the formation of toxic RuO4 gas while maintaining effective Ru etching capability through controlled chemical reactions in liquid phase.
Solution Approach 2:
The invention converts the harmful toxic gas formation issue into a beneficial wet chemical process where the etching reactions occur in liquid phase, producing soluble etching products that can be easily removed with water rinsing, thereby eliminating the harmful volatile by-products while maintaining etching effectiveness.
2Productivity
If sodium hypochlorite is used for wet etching of Ru under alkaline conditions, then etching is achieved, but sodium ions are not compatible with CMOS processing
Solution Approach 1:
The invention changes the chemical composition parameters of the etching solution by replacing sodium-containing reagents with ammonium-based reagents (such as ammonium bifluoride and ammonium fluorosulfonate). This parameter change maintains the etching capability while ensuring CMOS compatibility by eliminating sodium ion contamination that would interfere with subsequent CMOS processing steps.
Solution Approach 2:
The invention uses ammonium ions as an intermediary substance that provides the necessary chemical reactivity for Ru etching while being compatible with CMOS processing. The ammonium-based reagents serve as mediators that enable effective etching without introducing harmful sodium ions into the semiconductor structure.
3Productivity
If anodic oxidation is used to etch Ru under alkaline and acidic conditions, then etching is achieved, but the process is dependent on sheet resistance and results in less uniform etching
Solution Approach 1:
The invention replaces the electrical field-based anodic oxidation process with a chemical field-based wet etching process. By using chemical reagents that react directly with Ru surfaces, the process eliminates dependence on electrical conductivity and sheet resistance, enabling uniform etching across the entire wafer surface including areas with varying electrical properties.
Solution Approach 2:
The invention changes the fundamental mechanism parameter from electrical field-driven anodic oxidation to chemical reaction-driven wet etching. This parameter change allows the etching rate to be controlled by chemical concentration and contact time rather than electrical current distribution, resulting in superior etching uniformity across wafers with non-uniform sheet resistance.
4Productivity
If ceric ammonium nitrate in combination with acid is used to etch Ru and RuO2, then etching is achieved, but residues of cerium oxide and/or cerium hydroxide cannot be removed by simple water rinse
Solution Approach 1:
The invention changes the chemical composition parameters by using ammonium bifluoride and hydrofluoric acid as primary etching reagents instead of ceric ammonium nitrate. This parameter change ensures that the etching products are soluble in water and can be completely removed by simple water rinsing, eliminating the need for additional post-etching cleaning steps and achieving a residue-free surface.
Solution Approach 2:
The invention converts the potential harm of residue formation into a benefit by designing an etching system where the reaction products are highly soluble in water. The fluorine-based chemistry produces soluble fluoride complexes that are easily flushed away, turning what could be a cleaning challenge into a simple water-rinseable process.
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 method effectively removes metals and metal nitrides while minimizing residues and ensuring compatibility with CMOS processing, offering improved safety and efficiency across various semiconductor processing stages.
Implementation Method 1
oxidizing by electrolysis, at a current of at least 0.1 A, a precursor solution comprising chloride anions
Implementation Method 2
oxidizing by electrolysis, at a current of at least 0.1 A, a precursor solution comprising chloride anions thereby forming an etching solution
Data Source
AI summary
A method for etching one or more entities on a semiconductor structure, each entity being made of a material selected from metals and metal nitrides is provided. The method includes the steps of: (a) oxidizing by electrolysis, at a current of at least 0.1 A, a precursor solution comprising chloride anions at a concentration ranging from 0.01 mol/l to 1.0 mol/l, thereby forming an etching solution; (b) providing a semiconductor structure having the one or more entities thereon; and (c) etching at least partially the one or more entities by contacting them with the etching solution.