Graphene Touch Sensor Fabrication Using Metal Mask Lithography
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Solution Overview
Problem
Existing methods for fabricating touch screens with narrow frames and high etching precision face challenges, such as degradation of graphene film conductivity due to contact with alkaline solutions during lithographic processes, and inefficiencies in producing ultra-lightweight and ultra-thin products.
Innovation Solution
A method involving gray-scale reticle lithography and using a metal layer as a lithographic mask to protect the graphene film from alkaline solutions, allowing for precise etching and pattern formation without degrading the graphene's electrical conductivity, and reducing the number of masks required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithography is used to fabricate patterned graphene layer, then the graphene film contacts alkaline developing solution and alkaline stripping solution causing electrical conductivity degradation, but using ITO film avoids this problem
Solution Approach 1:
A metal layer is introduced as an intermediary between the graphene film and the alkaline developing/stripping solutions. The metal layer serves as a protective barrier that prevents direct contact between the alkaline solutions and the graphene film, thereby maintaining the electrical conductivity of the graphene while enabling the lithography process to proceed.
Solution Approach 2:
The metal layer is deposited on the graphene film before the lithography process begins. This preliminary action creates a protective structure in advance that prevents the graphene from being exposed to harmful alkaline solutions during subsequent developing and stripping steps, eliminating the need for alternative materials like ITO.
2Manufacturing precision
If ITO film is used and etched through lithographic approach, then high etching precision is achieved, but the ITO film may be damaged during etching the metal layer
Solution Approach 1:
The metal layer acts as a protective intermediary that shields the graphene film during the etching process. By placing the metal layer between the etching solution and the graphene, the system achieves high etching precision for the metal leading wire while preventing damage to the underlying graphene film, eliminating the need to use ITO film.
Solution Approach 2:
The metal layer is deposited in advance to create a protective barrier that prevents the etching solution from damaging the graphene film. This preliminary protective measure counteracts the potential harmful effect of the etching process on the graphene, allowing precise metal wire fabrication without compromising graphene integrity.
3Ease of manufacture
If direct screen printing technique is used to form leading wire, then the process is simple, but the line width cannot be controlled with high etching precision for narrow frame requirements
Solution Approach 1:
The mechanical screen printing process is replaced with a lithographic approach that uses light exposure and chemical etching. This substitution enables precise control of leading wire line width through photolithography patterns, achieving the high etching precision required for narrow frame touch screens while maintaining manufacturing feasibility through established lithography techniques.
Solution Approach 2:
The fabrication process transitions from mechanical deposition parameters (screen printing) to optical and chemical parameters (lithography exposure, etching solution concentration, etching time). This parameter change enables precise control of leading wire dimensions through controllable photolithographic patterns and chemical etching, achieving narrow line widths suitable for ultra-narrow frame designs.
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 increases yield and reduces production costs while enabling the creation of high-precision metal leading wires for ultra-narrow frame touch screens, maintaining the graphene's conductivity and facilitating the production of ultra-lightweight and ultra-thin touch-sensitive display devices.
Implementation Method 1
exposing the photoresist layer by using a gray-scale reticle and developing the exposed photoresist layer to obtain a photoresist completely removed region, a photoresist partially remained region, and a photoresist completely remained region
Implementation Method 2
removing the metal layer located in the photoresist completely removed region; removing the metal layer located in the photoresist partially remained region
Implementation Method 3
striping off the remainder photoresist
Data Source
AI summary
The present disclosure provides a method of fabricating a graphene touch sensor, a graphene sensor and a touch-sensitive display device. The method comprises: forming a graphene layer on a substrate; forming a metal layer on the graphene layer; coating a photoresist layer on the metal layer; exposing the photoresist layer by using a gray-scale reticle and developing the exposed photoresist layer to obtain a photoresist completely removed region, a photoresist partially remained region, and a photoresist completely remained region; removing the metal layer located in the photoresist completely removed region; removing the graphene layer located in the photoresist completely removed region; removing the metal layer located in the photoresist partially remained region; coating a protective film on the graphene layer located in the photoresist partially remained region; striping off the remainder photoresist. The embodiment of the present disclosure avoids the alkaline developing solution and the alkaline stripping solution from contacting the graphene film to degrade the conduction of the graphene, thereby increasing yield and reducing cost.