Metal Mask Ion Doping for Thin Film Transistor Manufacturing
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Solution Overview
Problem
The manufacturing process of thin film transistors in flat panel displays faces issues with photoresist masks, which can introduce unnecessary mobile ions into semiconductor layers, contaminate the transistors, and increase process complexity, leading to reduced productivity and quality.
Innovation Solution
A method that eliminates the use of photoresist masks by employing a metal layer as masks for ion injection, allowing for precise control of ion doping and simultaneous formation of source, drain, and active regions in thin film transistors, using half-tone exposure to create mask patterns of different thicknesses for NMOS and PMOS transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoresist mask is used for ion injection process, then the ion injection can be performed, but mobile ions are moved into the semiconductor layer causing contamination and quality degradation
Solution Approach 1:
The patent extracts and removes the photoresist mask from the ion injection process, replacing it with a metal layer that serves as the mask. This eliminates the source of mobile ion contamination while maintaining the masking function needed for selective ion injection into semiconductor layers.
Solution Approach 2:
The patent introduces a metal layer as an intermediary material to replace photoresist for the masking function. The metal layer acts as a mediator that provides the necessary masking capability during ion injection without introducing harmful mobile ions into the semiconductor layer.
2Ease of manufacture
If photoresist mask removal process is added, then the used mask can be removed, but the number of processes increases reducing productivity
Solution Approach 1:
The metal layer mask is designed to be automatically removed or integrated into subsequent processing steps without requiring a separate dedicated removal process. The mask serves its function and then naturally becomes part of the device structure or is removed as part of normal manufacturing flow, eliminating extra productivity-losing steps.
3Ease of manufacture
If photoresist mask removal process is added, then the mask can be removed, but thin film transistors may be contaminated during cleaning process
Solution Approach 1:
The patent extracts the problematic photoresist removal step from the manufacturing process by using a metal layer mask that does not require separate removal. This eliminates the cleaning process that causes transistor contamination while maintaining mask functionality.
Solution Approach 2:
The metal layer mask is designed as a single-use component that is removed or integrated in a controlled manner without requiring aggressive cleaning processes. The mask serves its purpose and is then discarded or incorporated, avoiding contamination risks associated with photoresist removal.
4Manufacturing precision
If multiple mask patterns are formed for different transistor types, then precise ion doping can be achieved, but process complexity increases
Solution Approach 1:
The patent applies local quality by forming metal layer mask patterns with different thicknesses at different locations corresponding to different transistor types (NMOS and PMOS). This allows selective ion doping precision for each transistor type while using a single metal layer material and formation process, reducing overall process complexity.
Solution Approach 2:
The patent changes the thickness parameter of the metal layer mask pattern to differentiate between NMOS and PMOS transistor regions. By controlling mask thickness rather than using different materials or complex multi-layer structures, the patent achieves precise ion doping for different transistor types while minimizing process complexity.
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 prevents ion contamination, simplifies the manufacturing process, improves productivity, and allows for precise control of threshold voltage, resulting in high-quality thin film transistors that enhance the stability and image quality of display devices.
Implementation Method 1
The first mask pattern and the second mask pattern may be formed by half-tone exposure
Implementation Method 2
doping first ions using a first mask pattern among the mask patterns into a first semiconductor layer among the semiconductor layers to simultaneously form a source region/a drain region and an active region
Data Source
AI summary
A manufacturing method of a thin film transistor includes: forming semiconductor layers for a plurality of thin film transistors over a substrate; forming an insulating layer covering the semiconductor layers; and forming a metal layer over the insulating layer. The method further includes: patterning the metal layer to form mask patterns; doping first ions using a first mask pattern among the mask patterns into a first semiconductor layer among the semiconductor layers to simultaneously form source region/a drain regions and an active region of the first thin film transistor; and doping second ions using a second mask pattern among the mask patterns into a second semiconductor layer among the semiconductor layers to form a source region and a drain region of the second thin film transistor.