Selective Titanium Nitride Etching via Nitrogen Plasma
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Solution Overview
Problem
Current etching processes in the semiconductor industry face challenges in selectively removing titanium nitride and photoresist etch residues without damaging underlying copper, tungsten, and low-k dielectric materials, which are crucial for achieving precise critical dimensions in microelectronic devices.
Innovation Solution
A semi-aqueous composition comprising an oxidizing agent, etchant, corrosion inhibitor, source of silica, and organic solvent, with a pH range of 0 to 4 and less than 2 wt% hydrogen peroxide, is used to selectively etch titanium nitride and titanium oxynitride relative to copper, tungsten, and low-k dielectric materials, ensuring high selectivity and controlled etch rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional etching processes (CHF3, CF4, C4F8 plasma or chemical etchants) are used to remove sacrificial titanium nitride layers, then the sacrificial layer can be removed, but the functional titanium nitride layers (such as barrier or adhesion layers) are also damaged or removed
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a nitrogen-containing etching gas (such as N2, NH3, or N2O) instead of conventional fluorocarbon-based gases. This parameter change enables selective etching of the sacrificial titanium nitride layer while preserving the functional titanium nitride layers, as the nitrogen-based chemistry selectively reacts with the sacrificial layer without attacking the functional layers.
Solution Approach 2:
The patent introduces an intermediary substance - a nitrogen-containing etchant - that acts as a selective mediator between the sacrificial layer and the etching process. This intermediary enables differential removal: it reacts with and removes the sacrificial titanium nitride layer while being inert or non-reactive toward the functional titanium nitride layers, thus achieving selective etching without direct mechanical or chemical damage to the functional layers.
2Loss of substance
If over-etching is performed to ensure complete removal of the sacrificial layer, then the sacrificial layer is fully removed, but the functional layers are damaged or removed
Solution Approach 1:
The patent changes the etching chemistry parameters by using nitrogen-based gases (N2, NH3, N2O) which have different reactivity characteristics compared to fluorocarbon-based gases. This parameter change provides inherent selectivity that allows complete removal of the sacrificial layer through controlled etching without requiring excessive etching time or power that would damage functional layers. The nitrogen-based chemistry naturally stops at the functional layer interface.
Solution Approach 2:
The patent employs feedback control in the etching process by monitoring etching progress and adjusting process parameters (such as gas flow rate, power, or time) to achieve complete sacrificial layer removal while preventing damage to functional layers. The selective chemistry provides inherent feedback - when the sacrificial layer is fully removed, the etchant naturally stops attacking, preventing over-etching of functional layers.
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 solution achieves high selectivity and efficient removal of titanium nitride with TiN to tungsten and copper selectivity ratios greater than 40:1 and 20:1 respectively, while maintaining low etch rates for tungsten and copper, thereby protecting the underlying materials and enabling precise microelectronic device manufacturing.
Implementation Method 1
nitrogen-containing etching gases, such as N2, NH3, or N2O, and combinations thereof have been found to selectively etch titanium nitride
Implementation Method 2
nitrogen-containing etching gases, such as N2, NH3, or N2O, and combinations thereof have been found to selectively etch titanium nitride
Data Source
AI summary
Semi-aqueous compositions useful for the selective removal of titanium nitride and/or photoresist etch residue materials relative to metal conducting, e.g., tungsten and copper, and insulating materials from a microelectronic device having same thereon. The semi-aqueous compositions contain at least one oxidant, at least one etchant, and at least one organic solvent, may contain various corrosion inhibitors to ensure selectivity.