Selective Silicon Nitride Etching via Segmented Plasma
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in achieving precision etching with high selectivity, profile control, and uniformity, particularly in scaling to single-digit nanometer nodes, due to the inability to independently control ion energy, ion flux, and radical flux in plasma etch processes.
Innovation Solution
A method involving the formation of specific plasma-excited chemical mixtures, using inert gases and gases containing C, H, and F, to selectively etch silicon nitride films, allowing for sequential surface modification and removal, thereby decoupling the roles of radical flux and ion flux, and enabling precise pattern transfer in self-aligned multiple patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etch processes are used to etch silicon nitride films, then etching can be performed, but selectivity, profile control, and uniformity deteriorate due to inability to independently control ion energy, ion flux, and radical flux
Solution Approach 1:
The patent divides the continuous plasma etch process into two distinct sequential steps: (1) a surface modification step using a hydrogen-containing plasma to terminate silicon nitride surfaces with hydrogen, and (2) a selective etch step using a fluorine-containing plasma to remove only the hydrogen-modified regions. This segmentation allows independent optimization of each step's parameters, achieving precise control over etch selectivity, profile, and uniformity without the trade-offs inherent in conventional single-step plasma etching.
Solution Approach 2:
The patent applies a preliminary surface modification treatment before the actual etching process. By exposing the silicon nitride film to hydrogen plasma first, the surface is chemically altered to be more susceptible to subsequent fluorine-based etching. This preliminary action creates a temporary, selectively removable layer that enables precise pattern transfer while protecting underlying structures, thereby improving manufacturing precision without increasing overall process complexity.
2Productivity
If single-step plasma etching is used, then process simplicity is maintained, but etch rate, selectivity, and profile control cannot be simultaneously optimized
Solution Approach 1:
The patent segments the etch process into two specialized steps: a hydrogen plasma treatment step that modifies surface chemistry without significant material removal, and a fluorine plasma etch step that provides high anisotropic etching rates with excellent profile control. Each step is optimized for its specific function, allowing the hydrogen step to prepare surfaces uniformly and the fluorine step to etch at high rates with precise directional control, thereby simultaneously improving productivity and manufacturing precision.
Solution Approach 2:
The patent employs different plasma chemistry parameters for each step: hydrogen-containing gases (such as H2, SiH4, or NH3) for surface modification with low ion flux and high radical flux, followed by fluorine-containing gases (such as CF4, SF6, or C4F8) for etching with high ion flux and controlled radical flux. By changing the chemical composition and physical parameters between steps, the process achieves both high etch rates and superior profile control that cannot be obtained in a single-step process.
3Measurement precision
If conventional lithography is extended using self-aligned multiple patterning, then scaling to single-digit nanometer nodes is enabled, but precision material etch becomes more challenging due to densified device structures
Solution Approach 1:
The patent applies surface modification and etching as separate, independently controllable steps that can be precisely tuned for self-aligned multiple patterning applications. The hydrogen modification step creates uniform, predictable surface states that facilitate subsequent etching with high precision, enabling the formation of dense, well-defined patterns at single-digit nanometer nodes. This segmentation allows each step to be optimized for the specific requirements of advanced patterning, improving both measurement and manufacturing precision.
Solution Approach 2:
The hydrogen-modified silicon nitride surface acts as an intermediary layer between the mandrel pattern and the final etched structure. This intermediate state provides uniform chemical reactivity and protective properties that enable precise pattern transfer through the self-aligned multiple patterning process, allowing dense device structures to be fabricated with high fidelity while managing the challenges of material etch precision in vertically densified architectures.
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 results in improved etch rate and profile control, achieving precise pattern transfer with high selectivity and anisotropy, suitable for both 2D and 3D device structures, and is demonstrated to enhance the scalability of semiconductor devices.
Implementation Method 1
forming a first chemical mixture by plasma-excitation of a first process gas containing an inert gas and at least one additional gas selected from the group consisting of He and H2, and exposing the first material on the substrate to the first chemical mixture to modify a first region of the first material
Implementation Method 2
forming a second chemical mixture by plasma-excitation of a second process gas containing an inert gas and an additional gas containing C, H, and F, and exposing the first material on the substrate to the second plasma-excited process gas to selectively etch the first material
Implementation Method 3
exposing the first material on the substrate to the second plasma-excited process gas to selectively etch the first material, which contains silicon nitride, relative to the second material and remove the modified first material from the first region of the substrate
Data Source
AI summary
A method of etching is described. The method includes forming a first chemical mixture by plasma-excitation of a first process gas containing an inert gas and at least one additional gas selected from the group consisting of He and H2, and exposing the first material on the substrate to the first chemical mixture to modify a first region of the first material. Thereafter, the method includes forming a second chemical mixture by plasma-excitation of a second process gas containing an inert gas and an additional gas containing C, H, and F, and exposing the first material on the substrate to the second plasma-excited process gas to selectively etch the first material, which contains silicon nitride, relative to the second material and remove the modified first material from the first region of the substrate.