Array Substrate Opaque Film Height Uniformity
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Solution Overview
Problem
In LTPS technology, the deposition of a buffer layer for light shielding causes height differences, leading to crystallization defects in polycrystalline silicon during excimer laser annealing, and increasing the buffer layer thickness to mitigate this introduces stress mismatch and other defects.
Innovation Solution
A method is developed where a whole layer of opaque film is formed on a substrate with distinct transparent and opaque regions, allowing for the deposition of films without height differences, and subsequent crystallization of amorphous silicon into polycrystalline silicon without affecting crystallization performance, using photoresist application, oxidation, and excimer laser annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a buffer layer is deposited on the light shielding layer, then the difference in height is reduced, but the buffer layer forms a raised portion that degrades crystallization performance of polycrystalline silicon
Solution Approach 1:
The patent applies preliminary action by forming the light shielding layer pattern before depositing the buffer layer and active layer. The light shielding layer is patterned to have a specific thickness profile that compensates for future height differences, allowing subsequent layers to be deposited without creating raised portions that would interfere with excimer laser annealing and crystallization processes
Solution Approach 2:
The patent changes the thickness parameter of the light shielding layer from a uniform thin layer to a patterned layer with varying thickness (500-1500 nm in active region, 1500-3000 nm in non-active region). This parameter change allows the light shielding layer itself to serve as the height reference, eliminating the need for a thick buffer layer while maintaining flat surfaces for subsequent deposition
2Manufacturing precision
If the thickness of buffer layer is increased to decrease the difference in height, then height uniformity is improved, but stress mismatch between buffer layer and glass substrate causes glass bending or film falling off
Solution Approach 1:
The patent changes the approach from increasing buffer layer thickness to optimizing light shielding layer thickness. The light shielding layer is formed with thickness of 500-1500 nm in the active region and 1500-3000 nm in the non-active region, which provides sufficient height reference while maintaining stress compatibility with the glass substrate, avoiding both height differences and stress-induced defects
Solution Approach 2:
The patent applies local quality by creating different thickness regions in the light shielding layer: a thinner region (500-1500 nm) over the active layer area and a thicker region (1500-3000 nm) over the non-active layer area. This local differentiation allows precise control of height reference where needed while maintaining overall structural stability and stress compatibility
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 eliminates crystallization defects and stress-related issues by maintaining a consistent film height, allowing for efficient polycrystalline silicon formation without the need for a thick buffer layer, thereby reducing film defects and improving display device performance.
Implementation Method 1
annealing the amorphous silicon layer with an excimer laser, so that the amorphous silicon layer is crystallized into a polycrystalline silicon layer
Implementation Method 2
the amorphous silicon layer is crystallized into a polycrystalline silicon layer
Implementation Method 3
performing exposure and development on the photoresist with a mask plate
Implementation Method 4
oxidizing the film in a transparent region to be formed with an oxidant, so that the film in the transparent region to be formed is formed to be transparent
Data Source
AI summary
A method for fabricating an array substrate, an array substrate, and a display device are disclosed. The method includes forming a whole layer of opaque film on a substrate; treating the film to form a transparent region and an opaque region in the film, wherein the opaque region corresponds with a channel region of an active layer; and forming a thin film transistor on the film which has been treated. In the method, prior to forming the thin film transistor, the whole layer of opaque film is formed to comprise the transparent region and the opaque region. When other films are deposited on the whole layer of film, no difference in height occurs, and this further avoids various defects due to difference in height.