Photolithography Mask Thickness Control for Array Substrate Etching
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Solution Overview
Problem
The challenge in manufacturing thin film transistor array substrates lies in controlling the thickness of photolithography masks during the 4-mask process, leading to residual ohmic contact layers or photolithography masks, which affects the display performance and stability of the array substrate.
Innovation Solution
A method involving the formation of a photolithography mask with a thickness between 1.7 μm and 1.8 μm, followed by exposure to achieve uniformity in the half-exposed area, and subsequent ashing to remove the mask, ensuring precise etching and avoiding residual layers, thereby stabilizing the array substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the photolithography mask thickness is reduced to enable complete etching of the metal layer and ohmic contact layer, then the etching completeness is improved, but the mask becomes too thin and leaves residues after etching
Solution Approach 1:
The patent applies preliminary action by performing an ashing process before the main etching step. This preliminary ashing removes the photolithography mask in the half-exposed area before etching the metal layer and ohmic contact layer, ensuring that the mask does not interfere with complete etching while preventing mask residues from forming during the etching process
Solution Approach 2:
The patent segments the photolithography mask into two functional zones: a fully exposed area where the mask is completely removed through ashing, and a half-exposed area where the mask remains to guide the etching process. This segmentation allows different regions of the mask to serve different purposes, resolving the contradiction between needing the mask thin enough for complete etching and thick enough to prevent residues
2Reliability
If the photolithography mask thickness is increased to prevent mask residues, then the mask stability is improved, but the etching completeness deteriorates due to the mask being too thick
Solution Approach 1:
The ashing process is performed as a preliminary step before etching to selectively remove the mask in the half-exposed area. This allows the mask to maintain its original thickness for stability during the ashing process, while the removed mask portions do not interfere with subsequent complete etching of the metal layer and ohmic contact layer
Solution Approach 2:
The patent applies local quality by creating different mask thicknesses in different areas: the half-exposed area has the mask completely removed through ashing, while the fully exposed area retains the original mask thickness. This local differentiation allows the mask to be stable where needed and absent where it would interfere with etching completeness
3Ease of manufacture
If the photolithography mask thickness is not precisely controlled, then the manufacturing process is simpler, but the critical dimension deviation increases
Solution Approach 1:
The patent changes the key parameter from mask thickness control to exposure uniformity control. Instead of precisely controlling the mask thickness to be within a narrow range, the invention controls the exposure uniformity in the half-exposed area to be between 20% and 40%, which is easier to achieve and maintains, thereby reducing critical dimension deviation without complicating the manufacturing process
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 ensures accurate patterning of the metal, ohmic contact, and active layers, reducing critical dimension deviations and preventing residual mask formation, thus enhancing the stability and display performance of the array substrate.
Implementation Method 1
exposing the photolithography mask through a mask plate to make a uniformity of the photolithography mask in a half-exposed area of the mask plate reach a preset uniformity
Implementation Method 2
ashing the photolithography mask to remove the photolithography mask in the half-exposed area
Data Source
AI summary
Disclosed are a method for manufacturing an array substrate, an array substrate and a display device. The method includes the following operations: sequentially forming a gate, a gate insulation layer, an active layer, an ohmic contact layer and a metal layer on a base substrate; forming a photolithography mask on the metal layer, a thickness of the photolithography mask being between 1.7 μm and 1.8 μm; exposing the photolithography mask through a mask plate to make a uniformity of the photolithography mask in a half-exposed area of the mask plate reach a preset uniformity; and manufacturing the array substrate based on the exposed photolithography mask.