Polycrystalline Silicon Film Buffer RMS Roughness Control
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Solution Overview
Problem
Existing display devices with thin film transistors face challenges in achieving improved device characteristics due to variations in crystal direction, size, and defects in the polycrystalline silicon film used for the channel and source/drain regions.
Innovation Solution
A display device structure is implemented with a substrate, a polycrystalline silicon film, and a first buffer film with a root mean square (RMS) roughness of 1.5 nm or less. The polycrystalline silicon film has a surface with a specific RMS roughness range and includes hydrogen ions, with a higher average concentration near the surface than at the center, to enhance device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polycrystalline silicon film is used for the channel and source/drain regions of thin film transistors, then the transistors can be formed with standard semiconductor processing, but the device characteristics vary due to crystal direction, crystal size, and crystal defects
Solution Approach 1:
A buffer film is formed on the substrate before depositing the polycrystalline silicon film. This buffer film serves as a preliminary structural foundation that promotes uniform crystal growth and reduces defects in the subsequent polycrystalline silicon layer, thereby improving device characteristics while maintaining processing compatibility
Solution Approach 2:
The surface roughness of the buffer film is controlled within a specific range (RMS: 0.3 nm to 1.5 nm). By optimizing this physical parameter of the buffer film, the polycrystalline silicon film achieves more uniform crystal structure with reduced variations in crystal direction, size, and defects, leading to improved transistor reliability
2Manufacturing precision
If the surface roughness of the buffer film is reduced to improve polycrystalline silicon film quality, then crystal structure uniformity improves, but the manufacturing process complexity increases
Solution Approach 1:
The buffer film surface roughness is controlled within a practical range (RMS: 0.3 nm to 1.5 nm) rather than pursuing ultra-smooth surfaces. This optimized parameter range achieves significant improvement in polycrystalline silicon film quality while remaining compatible with existing manufacturing capabilities, avoiding excessive process complexity
Solution Approach 2:
The buffer film acts as an intermediary layer between the substrate and the polycrystalline silicon film. By controlling the buffer film's surface properties, it mediates the interface quality and promotes uniform crystal growth without requiring direct manipulation of the polycrystalline silicon deposition process, thus simplifying overall manufacturing
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
The proposed solution improves the device characteristics of thin film transistors by reducing hysteresis and enhancing the crystal structure of the polycrystalline silicon film, leading to better performance and reliability in display devices.
Implementation Method 1
the one surface of the first buffer film has a first root mean square (RMS) roughness range, and the first RMS roughness range is 1.5 nm or less
Implementation Method 2
the polycrystalline silicon film may include hydrogen ions, and an average concentration of the hydrogen ions in a vicinity of the one surface of the polycrystalline silicon film may be greater than an average concentration of the hydrogen ions in a vicinity of a center of the polycrystalline silicon film
Data Source
AI summary
A display device includes: a substrate; a polycrystalline silicon film on the substrate; and a first buffer film between the substrate and the polycrystalline silicon film and having one surface contacting the polycrystalline silicon film and another surface opposite to the one surface, wherein the one surface of the first buffer film has a first root mean square (RMS) roughness range, and the first RMS roughness range is 1.5 nm or less.