Horizontal Nanowire Formation via Selective Oxidation
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Solution Overview
Problem
Current methods for forming horizontal nanowires for gate-all-around field effect transistors (GAA-FETs) face challenges in achieving uniform critical dimension (CD) and scalability, particularly in maintaining the same width across multiple nanowires, which is crucial for CMOS scaling and device performance.
Innovation Solution
A method involving the sequential formation of horizontal nanowires using a sacrificial spin-on carbon layer and a cladding layer, with cyclic selective removal of materials, allows for uniform coverage and preservation of nanowire diameter, enabling the formation of multiple nanowires with consistent dimensions, compatible with CMOS manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective wet etching is used to remove sacrificial SiGe layers, then nanowires are formed, but the critical dimension (CD) cannot be scaled to 5 to 7 nm and uniformity across nanowires is not achieved
Solution Approach 1:
The patent applies preliminary action by performing selective oxidation of SiGe layers before etching. This pre-treatment step creates a distinct oxide layer that enables subsequent selective removal, allowing precise control of nanowire critical dimensions at 5 to 7 nm scale while maintaining uniformity across multiple nanowires.
Solution Approach 2:
The patent changes the physical and chemical parameters of the sacrificial material by oxidizing SiGe to SiGeO3. This parameter transformation creates a material with different etch selectivity, enabling precise control of nanowire dimensions and uniformity that cannot be achieved with direct etching alone.
2Manufacturing precision
If selective dry plasma etching is used with a priori selective oxidation, then nanowires are formed, but CD scaling to 5 to 7 nm and uniformity requirements are not satisfied
Solution Approach 1:
The patent transforms the sacrificial SiGe material into SiGeO3 oxide through controlled oxidation, changing its physical and chemical parameters. This enables selective removal with plasma etching while maintaining nanowire diameter consistency at 5 to 7 nm, overcoming the limitations of direct etching methods.
Solution Approach 2:
Selective oxidation is performed as a preliminary step before plasma etching. This pre-treatment creates a differentiated material state that allows subsequent selective removal, achieving uniform nanowire dimensions without requiring complex in-situ control during etching.
3Manufacturing precision
If sacrificial material is selectively removed to form horizontal nanowires, then nanowire structures are created, but non-uniformities between incoming wafers are not compensated
Solution Approach 1:
The oxidation step transforms SiGe into SiGeO3, creating a material with distinct chemical properties. This parameter change provides a robust selectivity mechanism that compensates for wafer-to-wafer variations in incoming material, ensuring uniform nanowire formation across multiple wafers without reducing throughput.
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 ensures the formation of horizontal nanowires with consistent diameters, improving device performance by maintaining the desired CD and enabling scalable GAA-FETs down to 5 to 7 nm, addressing the limitations of existing techniques.
Implementation Method 1
forming a spin-on carbon layer on the fin structure
Implementation Method 2
providing a cladding layer, selectively, on the suspended horizontal nanowire
Implementation Method 3
selective removal of the spin-on carbon layer
Data Source
Figure 1~2b
Figure 3~4a
Figure 4b~4c
AI summary
A method for forming horizontal nanowires, the method comprising providing a substrate (9) comprising a dielectric layer (2) and a fin structure (5) comprising a portion protruding from the dielectric layer, and a multilayer stack consisting of a layer of a first material stacked alternately and repeatedly with a layer of a second material. Horizontal nanowires are formed by performing a cycle comprising: - removing selectively the first material (4") up to the moment that a horizontal nanowire (12) of the second material becomes suspended over a remaining portion of the partially un-masked protruding portion, - forming a sacrificial layer (6) on the remaining portion, while leaving the suspended horizontal nanowire (12) uncovered, - providing, selectively, a cladding layer (7) on the suspended horizontal nanowire, and thereafter - removing the sacrificial layer (6). During the repetitive cylces the horizontal nanowires become suspended starting from the top. The cladding layer is removed, after the bottom horizontal nanowire becomes suspended.