Cobalt Recess Etching Chemistry for Smooth Via and Trench Wiring
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Solution Overview
Problem
Current recess etching methods for semiconductor substrates are inefficient, requiring multiple steps and taking a long time, and often result in a non-smooth surface, which is critical for reliable metal wiring resistant to electromigration.
Innovation Solution
A recess etchant comprising organic acid, nitrogen-containing heterocyclic compounds, and organic solvents is used to perform recess etching on cobalt-containing metal layers in a single step, suppressing partial corrosion and achieving a smoother etched surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If repeated oxidation and etching treatments are performed on cobalt metal layer, then the amount of recess etching can be controlled, but the processing time becomes long and steps become complicated
Solution Approach 1:
The patent combines oxidation and etching functions into a single etching solution that contains both oxidizing agents (potassium permanganate, ammonium persulfate) and complexing agents (tartaric acid, citric acid). This allows the cobalt metal to be oxidized and etched simultaneously in one treatment step, eliminating the need for separate oxidation and etching steps while maintaining precise control over the recess etching amount.
2Manufacturing precision
If repeated oxidation and etching treatments are performed on cobalt metal layer, then the amount of recess etching can be controlled, but the number of steps becomes complicated
Solution Approach 1:
The patent merges multiple process steps (oxidation treatment and etching treatment) into a single etching process by formulating an etching solution that contains both oxidizing agents and complexing agents. This reduces the number of process steps from two or more separate treatments to one integrated treatment, simplifying the manufacturing process while maintaining precise control over recess etching.
Solution Approach 2:
The etching solution is designed to perform multiple functions simultaneously: it oxidizes the cobalt metal surface, complexes with the oxidized cobalt ions, and controls the etching rate. This multi-functional etching solution eliminates the need for separate oxidation and etching processes, reducing process complexity while achieving precise control.
3Reliability
If conventional etching methods are used on metal wiring, then the wiring can be formed, but the etched surface is not smooth which reduces reliability against electromigration
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by incorporating specific concentrations of oxidizing agents (0.01-10 wt% potassium permanganate, 0.01-5 wt% ammonium persulfate) and complexing agents (0.1-10 wt% tartaric acid, 0.1-10 wt% citric acid). These parameter adjustments control the etching rate and surface morphology, producing a smooth etched surface that reduces electromigration while maintaining reliable wiring formation.
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 allows for efficient, single-step recess etching of cobalt-containing metal layers, reducing processing time and improving surface smoothness, thereby enhancing the reliability of metal wiring.
Implementation Method 1
said recess etching solution comprising (A) organic acid; either or both of (B) nitrogen-containing heterocyclic compound and (C) organic solvent; and (D) water
Implementation Method 2
the smoothness of the etched surface when recess etching is performed on a metal embedded in a via or a trench as the conductive layer, is important
Data Source
AI summary
A recess etching solution for recess etching a metal wiring in a semiconductor substrate manufacturing process; and a recess etching method employing the same. The recess etching solution is for applying recess etching to a surface of a cobalt-containing metal layer embedded in a via or a trench formed in a semiconductor substrate, and contains (A) an organic acid, one of or both of (B) a nitrogen-containing heterocyclic compound and (C) an organic solvent, and (D) water. The recess etching method includes applying recess etching to a surface of a cobalt-containing metal layer by bringing the recess etching solution into contact with the surface of the cobalt-containing metal layer embedded in a via or a trench formed in a semiconductor substrate.