Silicon Nanostructure Cyclic Etching for Sub-20 Nm Recess Formation
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Solution Overview
Problem
Current technologies face challenges in fabricating nanostructures with lateral sizes below 20 nm, as they struggle with spatial resolution and achieve poor line edge roughness and line width roughness in semiconductor device manufacturing.
Innovation Solution
A method involving a cyclic process for processing silicon nanostructures, which includes oxidizing the surface, applying an anisotropic etching process to remove the oxide layer from the main surface while preserving it on inclined surfaces, and then using these oxide layers as masking layers for selective etching of the silicon nanostructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional lithography methods (UVL, EUV) are used for fabricating nanostructures below 20 nm, then spatial resolution is improved, but line edge roughness and line width roughness worsen
Solution Approach 1:
The patent segments the patterning process into multiple distinct steps: forming mandrels, depositing first spacers, selectively removing mandrels, depositing second spacers, and selective removal. This multi-stage self-aligned multi-patterning (SAMP) approach divides the complex task of creating sub-20nm features into manageable sequential operations, each optimized for specific precision requirements while minimizing roughness propagation
Solution Approach 2:
The patent applies preliminary actions by pre-forming mandrels and first spacers before final pattern definition. The mandrels serve as preliminary structures that guide subsequent spacer formation, and the first spacers are prepared in advance with controlled thickness and material properties to enable precise final patterning while reducing edge roughness
2Manufacturing precision
If self-aligned patterning is used to achieve required resolution, then manufacturing precision is improved, but process complexity and number of processing steps increase
Solution Approach 1:
The patent employs universal materials and processes that serve multiple functions: the same spacer material (e.g., silicon nitride or silicon oxide) is used for both first and second spacers, the same deposition techniques (CVD, PECVD, ALD) are applied throughout, and selective removal is achieved through material property differences rather than additional process types. This multi-functionality reduces overall process complexity while maintaining high resolution
Solution Approach 2:
The patent utilizes parameter changes in material properties (etch selectivity, deposition temperature, film thickness) to achieve differentiation between process steps without adding procedural complexity. By varying these parameters, the same basic process tools can perform multiple functions, reducing the number of distinct processing steps needed
3Manufacturing precision
If multiple separate processes are used for oxidizing and etching, then process selectivity is improved, but productivity and throughput decrease
Solution Approach 1:
The patent merges oxidizing and etching processes into integrated sequence operations where oxidation is performed immediately followed by selective etching in closely coupled process steps. The cyclic application of oxidation-etching-oxidation-etching sequences allows in-situ process control and eliminates intermediate handling steps, improving throughput while maintaining selectivity through the inherent material property differences
Solution Approach 2:
The patent ensures continuity of useful action by implementing continuous cyclic processes where oxidation and etching alternate without interruption or intermediate non-productive steps. The process flows continuously through oxidation → selective etching → oxidation → selective etching sequences, maximizing equipment utilization and throughput while maintaining precise selectivity control through the continuous cyclic nature of the operations
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 method integrates multiple processes into a single cyclic process, enhancing process control, reducing costs, and improving throughput while enabling the formation of recesses in silicon nanostructures with precise control over the etching process.
Implementation Method 1
oxidizing the main surface and the inclined surfaces forming a silicon oxide layer on the main surface and the inclined surfaces
Implementation Method 2
applying a first etching process configured to anisotropically etch the silicon oxide layer from the main surface while preserving the silicon oxide layer on the inclined surfaces
Implementation Method 3
applying a second etching process configured to selectively etch the exposed silicon of the silicon nanostructure using the silicon oxide layers of the inclined surfaces as masking layers
Data Source
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Figure 3A~3D
AI summary
A method for processing a silicon nanostructure having a main surface delimited by, in relation to the main surface, inclined surfaces is presented. The method comprises subjecting the silicon nanostructure for a first cyclic process. Each cycle of the first cyclic process comprises: oxidizing the main surface and the inclined surfaces forming a silicon oxide layer on the main surface and the inclined surfaces; applying a first etching process configured to anisotropically etch the silicon oxide layer from the main surface while preserving the silicon oxide layer on the inclined surfaces, thereby exposing the silicon of the silicon nanostructure; and applying a second etching process configured to selectively etch the exposed silicon of the silicon nanostructure using the silicon oxide layers of the inclined surfaces as masking layers. Whereby selective etching of the main surface relative to the inclined surfaces is achieved such that a recess in the silicon nanostructure is formed, the recess having its opening at the main surface of the silicon nanostructure.