Silicon Nitride Spacer Formation for Multiple Patterning
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Solution Overview
Problem
Conventional methods for forming sidewalls in trenches during large-scale integrated circuit manufacturing require over-etching, leading to damage and inefficiency due to the increase in sidewall thickness near the bottom, causing etching of underlying layers and damage to the layer structure.
Innovation Solution
A method involving plasma-enhanced atomic layer deposition (PEALD) using halogenated silane as a precursor and nitrogen as a reactant to form a silicon nitride film, followed by selective dry-etching to create vertical spacers with a flat top, and subsequent etching of the core material to pattern the underlying layer, utilizing fluorocarbon and Ar/O2 etchants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conformal film formation and asymmetrical etching are used to form sidewalls, then sidewalls can be formed to block etching, but over-etching is required which causes damage to underlying layers and increases process complexity
Solution Approach 1:
The patent changes the material parameter from conventional conformal films to silicon nitride film, and changes the etching parameter by using fluorocarbon-based etchants that selectively remove horizontal portions while preserving vertical portions. This parameter change eliminates the need for over-etching and prevents damage to underlying layers.
Solution Approach 2:
Instead of forming sidewalls that require over-etching to remove footing, the patent inverts the approach by using a material and etching chemistry that naturally preserve vertical sidewalls while removing horizontal portions. The silicon nitride film with fluorocarbon etching creates the opposite effect: vertical portions are maintained while horizontal portions are selectively removed, eliminating the need for damaging over-etching.
2Manufacturing precision
If over-etching is performed to remove sidewall footing, then horizontal portions can be removed, but etching of underlying layers occurs causing damage
Solution Approach 1:
The patent introduces fluorocarbon-based etchants as an intermediary that provides selective etching. This intermediary chemistry mediates between the silicon nitride film and the underlying layer, allowing removal of horizontal portions while protecting the underlying layer from damage. The fluorocarbon etchant selectively reacts with the silicon nitride film in horizontal orientations while leaving the underlying layer intact.
3Reliability
If conventional sidewall formation is used, then blocking function is achieved, but process time increases due to over-etching requirements
Solution Approach 1:
The patent extracts the harmful over-etching step from the conventional sidewall formation process. By using silicon nitride film with fluorocarbon-based etchants, the process directly forms vertical sidewalls without requiring additional over-etching time. The blocking function is achieved in the primary etching step itself, eliminating wasted process time.
4Area of stationary object
If conformal film deposition is used, then complete coverage is achieved, but sidewall thickness increases near the bottom forming a slope
Solution Approach 1:
The patent applies local quality by making the etching response different for different orientations of the same material. The fluorocarbon-based etching chemistry creates different etching rates for horizontal versus vertical portions of the silicon nitride film. Horizontal portions are selectively removed while vertical portions are preserved, creating uniform vertical sidewalls rather than sloped profiles.
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 allows for precise control of sidewall formation without over-etching, reducing damage to underlying layers and improving the uniformity and efficiency of the patterning process, enabling effective spacer-defined multiple patterning and quadruple patterning techniques.
Implementation Method 1
depositing a pattern transfer film by plasma-enhanced atomic layer deposition (PEALD) on the entire patterned surface of the template using halogenated silane as a precursor and nitrogen as a reactant
Implementation Method 2
dry-etching the template whose entire upper surface is covered with the pattern transfer film using a fluorocarbon as an etchant
Implementation Method 3
PEALD uses is a capacitively coupled plasma (CCP) and is conducted by applying 300 W or less of RF power in the reaction space
Data Source
AI summary
A method of forming spacers for spacer-defined multiple pattering (SDMP), includes: depositing a pattern transfer film by PEALD on the entire patterned surface of a template using halogenated silane as a precursor and nitrogen as a reactant at a temperature of 200° C. or less, which pattern transfer film is a silicon nitride film; dry-etching the template using a fluorocarbon as an etchant, and thereby selectively removing a portion of the pattern transfer film formed on a top of a core material and a horizontal portion of the pattern transfer film while leaving the core material and a vertical portion of the pattern transfer film as a vertical spacer, wherein a top of the vertical spacer is substantially flat; and dry-etching the core material, whereby the template has a surface patterned by the vertical spacer on a underlying layer.