Low-Temperature Plasma Etching for Silicon Nitride and Oxide Selectivity
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Solution Overview
Problem
Existing plasma processing methods struggle to efficiently etch both silicon nitride and silicon oxide films on substrates with high precision and selectivity, particularly when using polysilicon masks, due to the challenges in controlling the etching process and achieving uniformity.
Innovation Solution
A plasma processing method involving the use of distinct processing gases and temperature control for etching silicon nitride and silicon oxide films, where a first plasma with HF-based gases etches the nitride film at a specific temperature, followed by a second plasma with different gases etching the oxide film at a lower temperature, ensuring precise and selective etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single plasma processing method is used for both silicon nitride and silicon oxide films, then the process complexity is reduced, but the etching selectivity and uniformity deteriorate
Solution Approach 1:
The patent divides the etching process into two separate plasma processing steps: first etching the silicon nitride film with a nitrogen-containing plasma, then etching the silicon oxide film with a fluorine-containing plasma. This segmentation allows each step to be optimized for its specific target material, achieving high selectivity between the two films while maintaining manageable process complexity through systematic division of tasks.
2Productivity
If high etching rate is achieved for silicon nitride film, then the productivity is improved, but the etching uniformity and film quality worsen
Solution Approach 1:
The patent employs parameter changes by adjusting plasma conditions (gas composition, power, pressure) and substrate temperature for each etching step. For silicon nitride etching, nitrogen-containing plasma with specific temperature control achieves high etching rates. For silicon oxide etching, fluorine-containing plasma with adjusted parameters ensures uniform etching. These parameter optimizations resolve the contradiction between etching rate and uniformity.
3Productivity
If room temperature or higher is used for substrate processing, then the etching rate is improved, but the film damage and stress increase
Solution Approach 1:
The patent applies local quality control by maintaining different temperature conditions for different processing stages and regions. The substrate temperature is controlled to be 0°C or lower during plasma exposure to minimize film damage and stress, while the plasma chemistry is optimized to maintain high etching rates. This localized temperature control resolves the contradiction between etching rate and film quality.
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 enhances etching rates and improves the uniformity of the process by promoting the adsorption of HF species onto both films, resulting in improved etching performance and film selectivity.
Implementation Method 1
generating a first plasma from a first processing gas including HF gas, CxFy gas (x and y are integers of 1 or more), or CsHtFu gas (s, t, and u are integers of 1 or more), and an oxygen-containing gas to etch the silicon nitride film
Implementation Method 2
promoting the adsorption of HF species onto both films
Implementation Method 3
generating a second plasma from a second processing gas including HF gas, CvFw gas (v and w are integers of 1 or more), and an oxygen-containing gas to etch the silicon oxide film
Implementation Method 4
promoting the adsorption of HF species onto both films
Data Source
AI summary
A plasma processing method includes: (a) providing a substrate having an etching target film including a silicon oxide film and a silicon nitride film, and a mask film defining an opening over the etching target film, on a substrate support in a chamber of a plasma processing apparatus; (b) generating a first plasma from a first processing gas including HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and an oxygen-containing gas to etch the silicon nitride film; and (c) generating a second plasma from a second processing gas including HF gas, CvFw gas (v and w are integers of 1 or more), and an oxygen-containing gas to etch the silicon oxide film. In (b) and (c), a temperature of the substrate support is set to 0° C. or lower.