Selective Oxide Etching with In-Situ Metal Hardmask Deposition
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Solution Overview
Problem
Current selective etching processes for silicon oxide (SiO2) are not selective enough, leading to excessive etching of spacer materials and increased electric leakage and device failure rates, particularly in features smaller than 10 nm with high aspect ratios, due to limited etch resistance and pattern loading issues with traditional carbon-based polymer masks.
Innovation Solution
A method involving the use of a fluorocarbon gas and a metalloid or metal halide gas to form a plasma, which selectively etches silicon oxide regions while depositing a metalloid or metal containing hardmask over lower oxygen containing regions, providing high etch selectivity and preventing corner loss and pinch-off issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional carbon-based polymer masks are used for selective etching, then the etching process can proceed, but the etch resistance is insufficient leading to excessive etching of spacer materials and corner loss
Solution Approach 1:
The patent changes the chemical composition parameters of the mask material from carbon-based polymer to metalloid or metal-containing hardmask (such as silicon nitride, silicon oxy-nitride, or silicon oxy-carbon-nitride). This parameter change provides significantly higher etch resistance and selectivity, preventing excessive etching of spacer materials while maintaining the ability to selectively etch silicon oxide regions.
Solution Approach 2:
The patent employs composite material strategies by combining metalloid or metal-containing compounds with specific chemical compositions to create a hardmask that exhibits both high etch resistance and selective etching capability. The composite nature of these materials allows them to resist etching of spacer materials while permitting selective removal of silicon oxide, thereby resolving the contradiction between etch selectivity and spacer material integrity.
2Reliability
If thicker carbon-based polymer masks are deposited to increase etch resistance, then etch selectivity improves, but pattern loading increases and deposition uniformity decreases
Solution Approach 1:
The patent changes the material parameters from carbon-based polymer to metalloid or metal-containing hardmask, which inherently provides higher etch resistance at much thinner thicknesses (5-15 nm). This eliminates the need for thick deposits that cause pattern loading, thereby maintaining deposition uniformity while achieving the required etch resistance.
Solution Approach 2:
The patent uses a thin, consumable hardmask layer that is deposited uniformly and then selectively removed after serving its protective function. The thin nature of this hardmask (5-15 nm) prevents pattern loading issues associated with thicker masks, while still providing sufficient etch resistance during the selective etching process.
3Device complexity
If conventional selective etch processes are used, then the process is simpler, but etch selectivity is insufficient leading to device failure
Solution Approach 1:
The patent changes the chemical parameters of the etch gas composition to include fluorocarbon gases combined with metalloid or metal halide gases. This parameter change enables highly selective etching of silicon oxide regions while protecting spacer materials, thereby reducing device failure rates without significantly complicating the overall process flow.
Solution Approach 2:
The patent introduces a metalloid or metal-containing hardmask as an intermediary protective layer during the etching process. This intermediary layer selectively protects spacer materials from etching while allowing controlled etching of silicon oxide regions, thereby preventing device failure without requiring complex multi-step processes.
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 achieves highly selective etching of silicon oxide with respect to lower oxygen containing regions, maintaining the integrity of spacer materials and reducing device failure rates by using a thin, high etch resistance metalloid or metal containing hardmask, thereby preventing electric leakage and ensuring accurate feature placement.
Implementation Method 1
An etch gas is provided comprising a fluorocarbon gas and at least one of a metalloid halide gas or metal halide gas. The etch gas is formed into a plasma.
Data Source
AI summary
A method for selectively etching at least one feature in a silicon oxide region with respect to a lower oxygen containing region is provided. An etch gas is provided comprising a fluorocarbon gas and at least one of a metalloid halide gas or metal halide gas. The etch gas is formed into a plasma. At least one feature is selectively etched in the silicon oxide region with respect to the lower oxygen containing region, while simultaneously forming a metalloid or metal containing hardmask over the lower oxygen containing region.