Multi-Tone Mask Thin Film Transistor Manufacturing
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Solution Overview
Problem
The existing manufacturing processes for thin film transistors, particularly those using amorphous silicon, have limitations in field-effect mobility and require complex photolithography processes with multiple light-exposure masks, increasing costs and reducing productivity.
Innovation Solution
A method for manufacturing an inverted staggered thin film transistor using an oxide semiconductor with a multi-tone mask for simplified photolithography, reducing the number of light-exposure masks and steps through wet and dry etching processes, and employing an In--Ga--Zn--O-based non-single-crystal film with a crystal grain structure for improved electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photolithography process using multiple light-exposure masks is used to manufacture thin film transistors, then manufacturing precision can be maintained, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent combines multiple light-exposure masks into a single multi-tone mask that can form different pattern depths in one exposure step. The mask includes transparent regions with different light transmittance values, allowing simultaneous creation of first and second patterns at different depths without requiring separate photolithography steps.
Solution Approach 2:
The invention introduces a depth dimension to the mask structure by creating transparent regions with varying light transmittance values. This multi-level transparent structure allows different portions of the mask to transmit different amounts of light, enabling formation of patterns at different depths within the semiconductor layer in a single exposure.
2Manufacturing precision
If multiple light-exposure masks are used for photolithography, then pattern precision is maintained, but productivity decreases due to increased process steps
Solution Approach 1:
The patent combines multiple light-exposure masks into a single multi-tone mask that can form different pattern depths in one exposure step. The mask includes transparent regions with different light transmittance values, allowing simultaneous creation of first and second patterns at different depths without requiring separate photolithography steps.
Solution Approach 2:
The multi-tone mask is designed in advance with specific transparent regions having predetermined light transmittance values. This preliminary design allows the mask to automatically differentiate between first and second patterns during a single exposure process, eliminating the need for sequential mask application and development steps.
3Ease of manufacture
If amorphous silicon is used for thin film transistor manufacturing, then ease of manufacture over large areas is improved, but field-effect mobility deteriorates
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor, which fundamentally alters the electrical properties. Oxide semiconductors inherently provide higher carrier mobility while maintaining compatibility with low-temperature processing and large-area manufacturing techniques, thus resolving the contradiction between ease of manufacture and field-effect mobility.
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 results in a semiconductor device with higher field-effect mobility, reduced manufacturing costs, and increased productivity by simplifying the photolithography process and utilizing an oxide semiconductor film that can be formed at lower temperatures, enhancing the reliability and performance of the thin film transistor.
Implementation Method 1
a photolithography process using a number of light-exposure masks (also referred to as photomasks) is employed
Implementation Method 2
The first etching step is performed by wet etching in which an etchant is used
Implementation Method 3
the second etching step is performed by dry etching in which an etching gas is used
Implementation Method 4
An oxide semiconductor film can be formed at temperatures of 300° C. or lower by a sputtering method
Data Source
AI summary
An object is to manufacture a semiconductor device including an oxide semiconductor at low cost with high productivity in such a manner that a photolithography process is simplified by reducing the number of light-exposure masks In a method for manufacturing a semiconductor device including a channel-etched inverted-staggered thin film transistor, an oxide semiconductor film and a conductive film are etched using a mask layer formed with the use of a multi-tone mask which is a light-exposure mask through which light is transmitted so as to have a plurality of intensities. In etching steps, a first etching step is performed by wet etching in which an etchant is used, and a second etching step is performed by dry etching in which an etching gas is used.