Tantalum Alignment Markers for Precise Multilevel E-Beam Lithography
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Solution Overview
Problem
In semiconductor manufacturing, maintaining accurate alignment between multiple layers of integrated circuits is challenging due to misalignment issues at the nano-scale, particularly with existing alignment markers like tungsten, which have limitations in line edge roughness and resistance to etching processes.
Innovation Solution
The use of tantalum alignment markers embedded in substrates, detected using backscatter electron detectors, with line edge roughness of less than 2.5 nm, and formed through dry etching with fluorinated plasma, providing improved selectivity to etch masks and resistance to wet etching solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tungsten alignment markers are used, then alignment markers can be formed in substrate, but line edge roughness is high and resistance to wet etching is poor
Solution Approach 1:
The patent changes the material parameter from tungsten to tantalum, which fundamentally alters both the line edge roughness and wet etching resistance properties. Tantalum provides superior line edge roughness control and enhanced resistance to wet etching solutions compared to tungsten, resolving the technical contradiction between manufacturing precision and reliability.
Solution Approach 2:
The alignment marker is formed as a composite structure with tantalum as the core material, potentially combined with other materials to optimize both line edge roughness and etching resistance. This composite approach allows simultaneous achievement of high manufacturing precision and reliability in wet etching environments.
2Measurement precision
If alignment markers are used for multi-level ebeam lithography, then alignment between layers can be maintained, but detection precision is limited
Solution Approach 1:
The patent utilizes backscatter electron detection which relies on atomic number contrast (effectively a 'material color' in electron microscopy) to detect alignment markers. Tantalum's high atomic number provides strong contrast against the substrate, enabling precise detection of alignment marker edges and centroids without increasing system complexity.
Solution Approach 2:
The patent replaces potential mechanical or optical detection methods with electron beam-based backscatter detection. This substitution enables high-precision alignment marker detection by utilizing electronic interactions (backscatter electron yield) that are highly sensitive to atomic number differences, achieving superior measurement precision.
3Productivity
If wet etching is used for substrate processing, then substrate can be etched, but alignment markers may be etched away
Solution Approach 1:
The patent changes the alignment marker material parameter to tantalum, which has fundamentally different chemical properties compared to tungsten. Tantalum exhibits superior resistance to wet etching solutions, allowing the substrate to be efficiently etched while the alignment markers remain stable and intact throughout the wet etching process.
Solution Approach 2:
The tantalum alignment marker acts as an intermediary element with selective chemical stability. It serves as a stable reference structure that mediates between the substrate processing requirements (needing etching) and the alignment marker requirements (needing stability), allowing substrate etching to proceed while markers remain protected.
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 enhances positional accuracy of transistors and other features, maintains alignment precision, and exhibits higher etch rates and selectivity compared to tungsten markers, ensuring stable adhesion and resistance to acidic and basic solutions during semiconductor fabrication.
Implementation Method 1
determining, utilizing a backscatter electron detector of an electron beam lithography tool, a location of an edge of the alignment marker based on an atomic number contrast between the alignment marker and the substrate
Implementation Method 2
Patterning the deposited alignment marker material may include dry etching the deposited alignment marker material utilizing a fluorinated plasma and a mask
Implementation Method 3
E-beam lithography utilizes a focused beam of electrons to draw custom shapes and patterns on a surface of a material that is covered with an electron-sensitive resist
Data Source
AI summary
One or more embodiments of the present disclosure are directed toward improved methods of fabricating a semiconductor device utilizing multi-level electron beam lithography (e-beam lithography), an alignment marker for multi-level e-beam lithography, and a semiconductor device including the alignment marker. A method of fabricating a semiconductor device may include: forming an alignment marker in a substrate, the alignment marker including tantalum; determining, utilizing a backscatter electron detector of an electron beam lithography tool, a location of an edge of the alignment marker based on an atomic number contrast between the alignment marker and the substrate; and forming, utilizing the electron beam lithography tool, at least one transistor in the substrate based on the location of the edge of the alignment marker.