Thin-Film Semiconductor Substrate with Variable Conductive Layer Thickness
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Solution Overview
Problem
In thin-film semiconductor substrates, it is challenging to simultaneously achieve low resistance wiring and a flat upper layer for thin-film transistors (TFTs) in active matrix display devices, as thick wiring for low resistance often complicates the formation of a flat organic electroluminescence (EL) layer.
Innovation Solution
The solution involves a thin-film semiconductor substrate design where the second gate electrode is thinner than the data line, with the data line connected to either the source or drain electrode, and a continuous protection layer from the second gate electrode to these electrodes, allowing for thick data lines while maintaining the thinness of the gate electrodes and source/drain electrodes, thereby ensuring low resistance and flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick wiring is used to reduce resistance, then wiring resistance decreases, but the flatness of the upper layer becomes difficult to ensure
Solution Approach 1:
The patent segments the wiring structure into two distinct parts: thick data lines for low resistance and thin gate electrodes for flatness. This is achieved by forming the gate electrode and data line from the same continuous conductive layer but with different local thicknesses, where the gate electrode portion is thinner than the data line portion. This segmentation allows each component to have optimal thickness for its specific function.
Solution Approach 2:
The patent applies local quality by making different portions of the conductive layer have different thicknesses based on their functional requirements. The gate electrode portion is made thinner to maintain flatness for subsequent layer formation, while the data line portion is made thicker to reduce resistance. This localized variation in thickness optimizes both electrical performance and manufacturing precision.
2Manufacturing precision
If thin gate electrodes are used to maintain flatness, then upper layer flatness is ensured, but wiring resistance increases
Solution Approach 1:
The conductive layer is segmented into functional zones with different thickness requirements. The gate electrode zone uses thinner conductive material to ensure flatness, while the data line zone uses thicker conductive material to ensure low resistance. This segmentation resolves the contradiction by allowing each zone to have optimal thickness for its specific purpose.
Solution Approach 2:
A single continuous conductive layer serves multiple functions: it forms both the gate electrode and the data line. By making this universal layer have variable thickness (thinner at gate electrode, thicker at data line), the patent achieves both flatness and low resistance without requiring separate conductive layers for each function.
Data Source
AI summary
A thin-film semiconductor substrate includes a top-gate first TFT, a top-gate second TFT, and a data line (source line), in which the first TFT has a first semiconductor layer, a first gate insulating film, a first gate electrode, a first source electrode, a first drain electrode, and a first protection layer, the second TFT has a second semiconductor layer, a second gate insulating film, a second gate electrode, a second source electrode, a second drain electrode, and a second protection layer, the data line is connected to the first source electrode, the first drain electrode is an extension of the second gate electrode, and the second gate electrode is thinner than the data line.