Oxide Semiconductor Film Hard Mask Patterning
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Solution Overview
Problem
Miniaturization of transistors using oxide semiconductors leads to increased yield and reduced electrical variations, but challenges arise from unevenness at the end portions of the oxide semiconductor film, affecting electrical characteristics and reliability.
Innovation Solution
The use of a hard mask and a resist mask with a small line width, formed by electron beam exposure or liquid immersion exposure, to microfabricate the oxide semiconductor film, reducing line edge roughness and allowing for a shorter channel length, along with the inclusion of energy-matched oxide films to stabilize the conduction band, enhancing the transistor's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the oxide semiconductor film is miniaturized to achieve high-speed operation and low power consumption, then transistor performance is improved, but yield decreases due to increased variations in the shape of the oxide semiconductor film
Solution Approach 1:
A hard mask layer is introduced as an intermediary between the resist mask and the oxide semiconductor film. This hard mask serves as a buffer that absorbs the line edge roughness from the resist pattern, preventing it from being transferred to the oxide semiconductor film during etching, thereby maintaining film shape uniformity even in miniaturized transistors
Solution Approach 2:
The hard mask layer is formed and patterned before the oxide semiconductor film is etched. This preliminary patterning step establishes a smooth reference pattern that guides the subsequent etching process, ensuring that the oxide semiconductor film is transferred with minimal line edge roughness before the actual device fabrication begins
2Productivity
If the oxide semiconductor film is miniaturized to achieve high integration, then device density is improved, but manufacturing precision deteriorates due to unevenness at end portions of the film
Solution Approach 1:
The hard mask layer acts as a mediator that decouples the resist pattern quality from the final oxide semiconductor film quality. By forming the hard mask with a smooth pattern first, and then using it to etch the oxide semiconductor film, the film achieves high shape uniformity regardless of the small feature sizes required for high integration
Solution Approach 2:
The line edge roughness is extracted and isolated in the hard mask layer during the patterning process, preventing it from being transferred to the oxide semiconductor film. This separation allows the oxide semiconductor film to maintain its shape uniformity independent of the resist pattern quality
3Length of moving object
If a resist mask with small line width is used to shorten channel length, then transistor size is reduced, but line edge roughness increases affecting electrical characteristics
Solution Approach 1:
The hard mask layer serves as a critical intermediary that receives the small-line-width pattern from the resist mask but transforms it into a smooth pattern for the oxide semiconductor film. This intermediary layer allows short channel lengths to be achieved while maintaining low line edge roughness in the final device structure
Solution Approach 2:
The patterning process is segmented into two distinct steps: first forming the hard mask pattern, then using it to etch the oxide semiconductor film. This segmentation allows the line edge roughness to be controlled at each step independently, enabling short channel lengths without compromising the final film quality
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 enables the production of miniaturized transistors with improved electrical characteristics, high yield, and increased reliability, achieving high performance and productivity in semiconductor devices.
Implementation Method 1
a resist mask having a small line width, which is formed by exposing a resist to light using electron beam exposure, liquid immersion exposure, or the like
Implementation Method 2
a resist mask having a small line width, which is formed by exposing a resist to light using electron beam exposure, liquid immersion exposure, or the like
Data Source
AI summary
When an oxide semiconductor film is microfabricated to have an island shape, with the use of a hard mask, unevenness of an end portion of the oxide semiconductor film can be suppressed. Specifically, a hard mask is formed over the oxide semiconductor film, a resist is formed over the hard mask, light exposure is performed to form a resist mask, the hard mask is processed using the resist mask as a mask, the oxide semiconductor film is processed using the processed hard mask as a mask, the resist mask and the processed hard mask are removed, a source electrode and a drain electrode are formed in contact with the processed oxide semiconductor film, a gate insulating film is formed over the source electrode and the drain electrode, and a gate electrode is formed over the gate insulating film, the gate electrode overlapping with the oxide semiconductor film.