TFT Mask Halftone Layer Uniform Channel Width
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Solution Overview
Problem
In the manufacturing of display substrates, the formation of channel portions in thin-film transistors (TFTs) using existing masks results in non-uniform widths and recessed channel edges due to light diffraction patterns, leading to defects and non-uniform driving characteristics.
Innovation Solution
A mask with a light-blocking layer and a halftone layer is designed, featuring a source electrode pattern and a drain electrode pattern with a dummy halftone portion that prevents excessive exposure and etching, ensuring a uniform channel portion width and length by controlling light transmission and blocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a slit bar is used for exposure process, then the channel portion can be formed, but the width of the channel portion becomes non-uniform due to light diffraction pattern
Solution Approach 1:
The patent applies a halftone layer that partially transmits light to convert the harmful diffraction effect into a beneficial exposure pattern. The halftone layer's partial light transmission creates a gradual exposure gradient that compensates for diffraction, transforming the light diffraction problem into a solution that achieves uniform channel width
Solution Approach 2:
The halftone layer serves as an intermediary between the light source and the photoresist. It mediates the light exposure by partially blocking and partially transmitting light, creating a controlled exposure pattern that eliminates the direct harmful effect of light diffraction from the slit bar
2Manufacturing precision
If a halftone layer is used for exposure process, then the channel portion becomes more uniform, but the channel portion becomes more recessed than the source electrode edge
Solution Approach 1:
The light-blocking layer is formed in advance with electrode pattern portions that extend beyond the intended channel boundaries. This preliminary extension compensates for the recessed effect that will occur during exposure, ensuring that after etching, the channel portion reaches the correct length and aligns properly with the source electrode edge
Solution Approach 2:
The light-blocking layer performs a preliminary counter-action by blocking light in specific areas to prevent over-exposure at the channel edges. This pre-blocking compensates for the recessed effect, ensuring the final channel length is sufficient and properly aligned
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 solution achieves uniform channel widths and sufficient lengths in TFTs, reducing defects and improving driving characteristics by minimizing the impact of light diffraction and exposure variations during the photolithography process.
Implementation Method 1
a halftone layer formed on the transparent substrate... a halftone portion corresponding to a spaced-apart portion between the source electrode pattern portion and the drain electrode pattern portion
Implementation Method 2
a light-blocking layer formed on the transparent substrate... including a source electrode pattern portion and a drain electrode pattern portion
Data Source
AI summary
A mask includes a transparent substrate, a light-blocking layer and a halftone layer. The light-blocking layer includes a source electrode pattern portion including a first electrode portion, a second electrode portion and a third electrode portion, and a drain electrode pattern portion disposed between the second electrode portion and the third electrode portion. The halftone layer includes a halftone portion corresponding to a spaced-apart portion between the source electrode pattern portion and the drain electrode pattern portion, and a dummy halftone portion more protrusive than ends of the second electrode portion and the third electrode portion. Thus, a photoresist pattern corresponding to a channel portion of a thin film transistor (TFT) may be formed with a uniform thickness, to thereby prevent an excessive etching of the channel portion.