Variable-Thickness Metal Layer for Single-Mask Display Contact Holes
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Solution Overview
Problem
The manufacturing process of display devices is complex and prone to over-etching, which affects the reliability of transistors and overall device performance.
Innovation Solution
A display device design featuring a first metal layer with varying thicknesses and a semiconductor layer connected to it, along with a specific insulating layer structure, allows for the formation of contact holes using a single mask, simplifying the process and reducing over-etching risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional manufacturing process with uniform metal layer thickness is used, then the process is straightforward, but over-etching occurs affecting transistor reliability
Solution Approach 1:
The metal layer is designed with different thicknesses in different regions: a first metal layer with first thickness and a second metal layer with second thickness greater than the first thickness. This local variation in thickness provides etch margin protection in the second region, preventing over-etching damage to the semiconductor layer while maintaining process simplicity.
2Ease of manufacture
If multiple masks are used to form contact holes at different levels, then precise alignment is achieved, but the manufacturing process becomes complex and time-consuming
Solution Approach 1:
The metal layer with varying thickness is formed in advance before contact hole formation. The second portion with greater thickness serves as a pre-formed etch stop, eliminating the need for additional masks to protect the semiconductor layer during contact hole etching. This preliminary structural preparation simplifies the manufacturing process while maintaining precision.
Solution Approach 2:
The metal layer serves multiple functions: it provides electrical connection and simultaneously acts as an etch stop layer due to its varying thickness. The second portion with greater thickness universally protects both the semiconductor layer and simplifies the contact hole formation process, reducing the number of manufacturing steps required.
3Productivity
If aggressive etching is used to form contact holes, then etching speed increases, but over-etching damages the semiconductor layer
Solution Approach 1:
The second portion of the metal layer with greater thickness is formed beforehand to provide an etch margin or cushion. This extra thickness absorbs the over-etching that occurs during contact hole formation, protecting the semiconductor layer from damage while allowing faster, more aggressive etching conditions to be used.
Data Source
AI summary
A display device according to an embodiment includes: a first metal layer disposed on a substrate; a first insulating layer disposed on the first metal layer; a first transistor disposed on the first insulating layer and including a semiconductor layer; and a light-emitting device electrically connected to the first transistor, wherein the first metal layer includes a first portion with a first thickness and a second portion with a second thickness, the second thickness is greater than the first thickness, and the semiconductor layer is electrically connected to the first metal layer.