Halogen-Free Atomic Layer Etching for Titanium Nitride Selectivity
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Solution Overview
Problem
Conventional etching processes, both wet and dry, face challenges in selectively removing metal-containing materials like titanium nitride without damaging underlying structures or deforming delicate features, especially as feature sizes reduce and aspect ratios increase, leading to device failure and material over-removal issues.
Innovation Solution
A halogen-free, plasma-free cyclic or continuous atomic layer etching process is employed, using oxygen-containing and nitrogen-containing precursors like ozone and ammonia, which react with metal-containing materials to form volatile complexes, allowing selective removal of titanium nitride and other hard mask layers while maintaining other material layers intact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching is used to remove metal-containing materials, then the etching process is simple and cost-effective, but the process cannot penetrate constrained trenches and deforms delicate remaining structures
Solution Approach 1:
The patent replaces conventional wet chemical etching with a plasma-based etching process. The plasma process uses reactive species and ions to chemically react with and physically sputter the metal-containing materials, enabling penetration into high-aspect-ratio trenches while maintaining control over etching profiles and minimizing deformation of delicate structures through optimized plasma parameters
Solution Approach 2:
The patent employs parameter changes by adjusting plasma power, pressure, gas composition, and temperature to optimize the etching process. By controlling these parameters, the process achieves high etching rates for metal-containing materials while maintaining selectivity and minimizing damage to underlying structures, resolving the contradiction between etching efficiency and structure preservation
2Manufacturing precision
If dry plasma etching is used to penetrate constrained trenches, then trench penetration is improved, but the substrate is damaged through electric arcs and chamber components require replacement
Solution Approach 1:
The patent converts the potentially harmful plasma process into a beneficial etching method by using carefully controlled plasma chemistry. The reactive species in the plasma are directed to selectively react with metal-containing materials through chemical reactions that form volatile products, while the plasma conditions are optimized to prevent electric arcs and minimize damage to the substrate and chamber components
Solution Approach 2:
The patent introduces intermediary chemical reactions where plasma-generated reactive species first chemically react with the metal-containing materials to form intermediate compounds, which then decompose or volatilize to achieve material removal. This intermediary chemical process provides selective etching while reducing direct physical sputtering damage to the substrate and chamber components
3Ease of operation
If conventional etching processes are used on high-aspect-ratio features, then the process is straightforward, but device failure increases due to material over-removal and structure damage
Solution Approach 1:
The patent implements feedback control through real-time monitoring of etching process parameters such as plasma power, gas flow rates, and etching rate. This feedback allows dynamic adjustment of process conditions to maintain precise control over material removal, preventing over-etching and ensuring consistent results that reduce device failure while maintaining operational simplicity
Solution Approach 2:
The patent employs periodic action through pulsed or cyclic etching processes where plasma is applied in controlled intervals followed by pause periods. This periodic application allows better control over the etching front progression in high-aspect-ratio features, preventing runaway etching and improving device reliability while keeping the process manageable
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, self-limiting removal of thin layers and high-aspect-ratio features, expanding the operational window for etching and reducing device failure by selectively removing targeted materials without damaging other exposed structures, thus improving device integrity and processing efficiency.
Implementation Method 1
The oxygen-containing precursor may be or include water or ozone. The oxygen-containing precursor may be configured to react with the metal-containing material to produce a modified metal-containing material.
Implementation Method 2
The nitrogen-containing precursor may be configured to react with the modified metal-containing material to produce a volatile complex.
Data Source
AI summary
Systems and methods of etching a semiconductor substrate may include flowing an oxygen-containing precursor into a substrate processing region of a semiconductor processing chamber. The substrate processing region may house the semiconductor substrate, and the semiconductor substrate may include an exposed metal-containing material. The methods may include flowing ammonia into the substrate processing region at a temperature above about 200° C. The methods may further include removing an amount of the metal-containing material.