Semiconductor Device Multilayer Source Electrode Contact Design
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Solution Overview
Problem
The existing active matrix substrate faces challenges in reducing parasitic capacitances between source bus lines and gate bus lines, and in forming contact portions for connecting oxide semiconductor TFTs or crystalline silicon TFTs to predetermined lines, especially in in-cell touch-screen type display devices.
Innovation Solution
A semiconductor device with both oxide semiconductor TFTs and crystalline silicon TFTs on the same substrate, featuring a multilayer source electrode structure and specific contact hole designs to reduce parasitic capacitances and improve contact characteristics, using a conductive film for the source bus lines that is different from the TFT electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If source bus lines and gate bus lines are formed close to each other on the substrate, then wiring density is improved, but parasitic capacitance between the bus lines increases
Solution Approach 1:
An insulating film is introduced as an intermediary substance between the source bus line and gate bus line. This insulating film acts as a mediator that reduces the parasitic capacitance between the two conductive lines while allowing them to remain in close proximity for high wiring density. The insulating film effectively decouples the electrical interaction between adjacent bus lines.
Solution Approach 2:
The insulating film is selectively positioned only in regions where source bus lines and gate bus lines intersect or run adjacent to each other. This localized application of insulation maintains high wiring density in non-critical areas while reducing parasitic capacitance only where necessary, optimizing the trade-off between density and electrical performance.
2Reliability
If a protective dielectric film is formed to cover source and drain electrodes of both oxide semiconductor TFTs and crystalline silicon TFTs, then device protection is improved, but contact formation complexity increases
Solution Approach 1:
Contact holes are formed through the protective dielectric film before the TFT fabrication process begins. By performing this action in advance, the patent simplifies subsequent processing steps and avoids the need for complex post-fabrication contact formation through the protective layer.
Solution Approach 2:
The protective dielectric film serves multiple functions: it provides mechanical protection to the TFT structures, acts as an insulating layer, and serves as a medium for forming contact holes to external circuits. This multi-functionality reduces the need for additional separate protective structures.
3Adaptability or versatility
If separate wiring layers are formed for TFT electrodes and touch sensor driving lines, then functional independence is improved, but manufacturing process complexity increases
Solution Approach 1:
The source/drain electrodes of the TFTs and the driving lines for touch sensors are formed using the same conductive film in the same wiring layer. This merging of functions allows both TFT electrodes and touch sensor driving lines to coexist in a single layer, simplifying the manufacturing process while maintaining functional independence through appropriate routing and connection design.
Data Source
AI summary
A semiconductor device includes: a first thin film transistor (101) including a crystalline silicon semiconductor layer (13); and a second thin film transistor (102) including an oxide semiconductor layer (23). First source/drain electrodes (31), (33) of the first thin film transistor (101) are provided on the crystalline silicon semiconductor layer via a first interlevel dielectric layer (L1); a second source electrode (25S) of the second thin film transistor (102) is electrically connected to a line (35) which is made of the same conductive film as the first source/drain electrodes; the line (35) is provided on the second source electrode (25S) via a second interlevel dielectric layer (L2), and is in contact with the second source electrode (25S) within a second contact hole including an opening made in the second interlevel dielectric layer (L2); the second source electrode has a multilayer structure including a main layer (25m) and an upper layer (25u) disposed on the main layer such that, under the opening in the second interlevel dielectric layer, the upper layer (25u) has a first aperture and the main layer (25m) has a second aperture (p2) or recess, the second aperture (p2) or recess being larger than the first aperture (p1) as viewed from the normal direction of the substrate.