CNT-FET Type Conversion via Photolithography
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Solution Overview
Problem
Current methods for converting p-type carbon nanotube field effect transistors (CNT-FETs) to n-type CNT-FETs are not reliable, stable, or compatible with existing semiconductor mass production processes, particularly due to limitations in selective and concurrent type conversion on the same plane, and high costs associated with methods like atomic layer deposition.
Innovation Solution
A complementary carbon nanotube field effect transistor using a cross-linked polyvinyl alcohol polymer with a photosensitizer, integrated into a semiconductor standard process such as photolithography, allows for the selective conversion of p-type to n-type CNT-FETs by forming a conversion induction layer between source and drain electrodes, followed by annealing, enabling the creation of both n-type and p-type devices on the same plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal contact or chemical doping is used for type conversion, then n-type conversion is achieved, but stability in air deteriorates and process cost increases
Solution Approach 1:
A polymer layer is introduced as an intermediary between the metal contact and the carbon nanotube channel. This polymer layer mediates the interaction, providing stable n-type conversion while protecting the interface from direct exposure to air, thereby improving stability without requiring expensive protective atmospheres or complex deposition processes
Solution Approach 2:
The patent uses a simple polymer material that can be applied through low-cost solution processing methods rather than expensive atomic layer deposition. The polymer serves as a temporary but effective conversion layer that provides stable n-type characteristics without requiring costly equipment or materials
2Reliability
If atomic layer deposition is used for type conversion, then conversion is achieved, but process time and cost increase
Solution Approach 1:
The patent replaces the complex atomic layer deposition process (a sophisticated vapor-phase deposition technique) with a simple solution-based polymer coating method. This substitution dramatically reduces process time and equipment requirements while maintaining conversion reliability through the chemical properties of the polymer
Solution Approach 2:
The patent changes the conversion approach from a high-temperature, vacuum-based atomic layer deposition process to a low-temperature, solution-based polymer coating process. This parameter change simplifies the manufacturing process, reduces time requirements, and lowers equipment costs while achieving reliable type conversion
3Reliability
If conventional methods are used for type conversion, then conversion is achieved, but selective conversion at desired positions is not possible
Solution Approach 1:
The patent applies the polymer conversion layer selectively to specific regions where n-type devices are desired, while leaving other regions unchanged for p-type devices. This local application enables selective type conversion at desired positions on the same substrate, allowing for complementary circuit fabrication with both n-type and p-type devices in precise spatial arrangements
Solution Approach 2:
The patent segments the substrate into regions with different device types by selectively applying the polymer conversion layer to specific areas. This segmentation allows concurrent manufacturing of both n-type and p-type CNT-FETs on the same plane, with each region having the appropriate device type for its intended function in the complementary circuit
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 provides a stable, cost-effective, and scalable method for type conversion, maintaining device characteristics and enabling the production of complementary CNT-FETs suitable for large-scale digital integrated circuits, with improved compatibility with existing semiconductor processes.
Implementation Method 1
A complementary carbon nanotube field effect transistor using a cross-linked polyvinyl alcohol polymer with a photosensitizer, integrated into a semiconductor standard process such as photolithography, allows for the selective conversion of p-type to n-type CNT-FETs by forming a conversion induction layer between source and drain electrodes
Implementation Method 2
followed by annealing, enabling the creation of both n-type and p-type devices on the same plane
Data Source
AI summary
Provided are a complementary carbon nanotube field effect transistor (CNT-FET) and a manufacturing method thereof. In particular, provided is carbon nanotube-based type conversion technology (p-type→n-type) using a photosensitive polyvinyl alcohol polymer which can be selectively cross-linked at a desired position based on a semiconductor standard process, i.e., photolithography. The CNT-FET includes: a substrate; a first channel layer formed on the substrate and made of a carbon nanotube; a first source electrode formed at one side of the first channel layer and made of a conductive material; a first drain electrode formed at the other side of the first channel layer and made of a conductive material; a conversion induction layer formed on the first channel layer between the first source electrode and the first drain electrode and configured to convert the first channel layer from a p-type to an n-type; a protective layer configured to protect the conversion induction layer; and a first gate electrode formed on the protective layer.