Tuning Sidewall Passivation Conformality for High Aspect Ratio Cylinder Etch
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Solution Overview
Problem
Conventional etching processes for high aspect ratio cylinders in semiconductor devices face challenges in achieving uniform etching profiles due to insufficient sidewall protection, leading to bowing and compromised structural integrity, as existing fluorocarbon-based processes struggle to form protective polymeric sidewall coatings effectively at locations undergoing lateral over-etching.
Innovation Solution
A method involving cyclic etching and deposition processes, where a protective film is deposited through plasma-assisted atomic layer deposition, with varying conformality in different iterations to prevent lateral etching, ensuring the film extends deep into the feature where it is most beneficial, such as at the bow region, using reactants with lower sticking coefficients and adsorption-based deposition techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorocarbon-based etching processes are used to etch high aspect ratio cylinders, then etching speed and productivity are improved, but sidewall protection is insufficient leading to bowing and non-uniform profiles
Solution Approach 1:
The etching process is divided into multiple cycles, each consisting of an etching step followed by a deposition step. This segmentation allows the process to achieve both high etching speed and sidewall protection by periodically replenishing the protective polymer coating during the etching sequence, rather than relying on a single continuous process
Solution Approach 2:
The patent employs periodic deposition of protective polymer coatings during cyclic etching processes. By repeatedly applying thin layers of protective material at intervals during the etching sequence, the process maintains sidewall protection throughout the high-speed etching operation, preventing bowing while sustaining productivity
2Reliability
If protective polymeric sidewall coatings are formed during etching, then sidewall protection is improved, but the coatings are insufficient at locations undergoing lateral over-etching such as the bow region
Solution Approach 1:
The patent applies protective polymer coatings before the etching process begins and replenishes them during cyclic etching steps. This preliminary and periodic application ensures that protective material is present at all locations including future bow regions before lateral over-etching occurs, preventing the formation of unprotected zones
Solution Approach 2:
The patent modifies deposition parameters including reactant flow rates, pressure, and temperature to optimize polymer coating formation. By adjusting these parameters during cyclic etching, the process enhances polymer deposition at critical regions such as the bow area where lateral over-etching tends to occur, ensuring uniform protection throughout the feature
3Ease of manufacture
If deposition conditions are kept constant throughout the etching process, then process simplicity is maintained, but the protective film conformality cannot be optimized for different feature depths
Solution Approach 1:
The patent transitions from static, constant deposition conditions to dynamic, variable conditions that change throughout the etching sequence. By adjusting deposition parameters such as reactant flow rates, pressure, and temperature at different stages of the cyclic process, the system optimizes protective film conformality for features at different depths while maintaining a manageable cyclic process structure
4Productivity
If aggressive etching conditions are used to open the feature bottom quickly, then productivity is improved, but lateral etching of sidewalls increases compromising feature integrity
Solution Approach 1:
The patent applies protective polymer coatings before aggressive etching begins and replenishes them during cyclic steps. This preliminary and periodic protective action counteracts the lateral etching that would otherwise occur during aggressive bottom-opening etching, allowing high productivity without compromising sidewall integrity
Solution Approach 2:
The patent converts the potentially harmful lateral etching effect into a beneficial process by using the etching byproducts and plasma environment to enhance polymer deposition on sidewalls. The same plasma conditions that enable aggressive etching also promote protective coating formation, turning a harmful effect into a protective mechanism
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 approach enables the formation of highly uniform, vertical sidewalls with minimized bowing, allowing for the creation of high aspect ratio features with improved structural integrity and reduced risk of capping or clogging, while optimizing etch process conditions for aggressive opening of the feature bottom.
Implementation Method 1
exposing the substrate to a first deposition reactant and allowing the first deposition reactant to adsorb onto the sidewalls of the feature
Implementation Method 2
exposing the substrate to a second plasma including a second deposition reactant, where exposing the substrate to the second plasma drives a surface reaction between the first deposition reactant and the second deposition reactant
Implementation Method 3
drives a surface reaction between the first deposition reactant and the second deposition reactant, thereby forming the protective film on the sidewalls of the feature
Implementation Method 4
generating a first plasma including an etching reactant
Data Source
AI summary
Methods, apparatus and systems for forming a recessed feature in dielectric material on a semiconductor substrate are provided. Separate etching and deposition operations are employed in a cyclic manner. Each etching operation partially etches the feature. Each deposition operation forms a protective film on the sidewalls of the feature to prevent lateral etch of the dielectric material during the etching operations. The protective film may be deposited under different conditions (e.g., pressure, duration of reactant delivery, duration of plasma exposure, RF power, and/or RF duty cycle, etc.) in different deposition operations. Such conditions may affect the degree of conformality at which the protective film forms. In various embodiments, one or more protective films may be sub-conformal. In these or other embodiments, one or more other protective films may be conformal.