TFT Manufacturing via Merged Ohmic and Electrode Patterning
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Solution Overview
Problem
The manufacturing process for active matrix flat display devices is complex and costly due to the large number of masks required, leading to low process yield and high production expenses.
Innovation Solution
A method that simplifies the manufacturing process by reducing the number of masks used, specifically by forming the ohmic contact layer and source/drain electrodes with the same pattern, and utilizing a half-tone exposure process to pattern these elements, thereby simplifying the formation of TFTs and reducing the overall mask processes from at least 7 to 3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conventional manufacturing process is used with multiple masks, then the TFT structure can be formed with proper separation, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent combines the formation of the ohmic contact layer and source/drain electrodes into a single patterning step using one mask. The ohmic contact layer is doped in regions that will become the source and drain electrodes, allowing both structures to be formed simultaneously rather than requiring separate masking and deposition steps for each component.
Solution Approach 2:
The single mask used in the improved process serves multiple functions: it defines the pattern for the ohmic contact layer, determines the source and drain electrode positions, and establishes the pixel defining layer boundaries. This multi-functional mask replaces what would traditionally require multiple specialized masks, reducing overall process complexity.
2Manufacturing precision
If more mask processes are used to form separate patterns, then each component can be precisely controlled, but the production cost and time increase
Solution Approach 1:
The patent merges the patterning of the ohmic contact layer, source/drain electrodes, and pixel defining layer into a single exposure and development step. By doping the ohmic contact layer in the same pattern as the source/drain electrodes, the process achieves precise component control without requiring sequential mask applications, thereby improving production efficiency.
3Productivity
If the number of manufacturing steps is reduced, then the production cost decreases and yield improves, but the structural precision may be compromised
Solution Approach 1:
The patent performs preliminary doping of the ohmic contact layer in the exact pattern where source and drain electrodes will be formed. This preliminary action ensures that when the metallic layer is deposited and patterned in a single step, the underlying doped regions already define the precise locations, maintaining pattern accuracy even though fewer masking steps are used.
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 simplifies the manufacturing process, reduces costs, and improves yield by minimizing the number of masks and processes involved, making the production more efficient and cost-effective.
Implementation Method 1
an ohmic contact layer interposed between the active layer and the source and drain electrodes
Implementation Method 2
utilizing a half-tone exposure process to pattern these elements
Data Source
AI summary
Provided is a flat display device, and more particularly, an active matrix (AM) flat display device having a thin film transistor (TFT). The flat display device includes a substrate, a plurality of TFTs (thin film transistors) provided on the substrate, each TFT comprising an active layer, a source electrode and a drain electrode that contact the active layer, and an ohmic contact layer interposed between the active layer and the source and drain electrodes, and a light emitting device electrically connected to the TFT, wherein the ohmic contact layer and a layer including the source and drain electrodes are formed to have the same pattern.