SiC Contact Electrode with TiN Barrier Layer
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Solution Overview
Problem
In the manufacturing of silicon carbide semiconductor devices, the formation of nickel contact electrodes is challenging due to the ease of void formation and difficulty in controlling the thickness and etching of nickel layers, leading to issues with side-etching and surface roughness, which affects the reliability and performance of the devices.
Innovation Solution
A silicon carbide semiconductor device and method involving a barrier metal layer of titanium nitride or other nitrides on the interlayer insulating film, with thermal annealing to form nickel silicide in contact holes while scattering nickel metal aggregates outside the holes, followed by chemical solution immersion to remove these aggregates, ensuring a smooth surface and preventing nickel silicide formation on the barrier metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel is deposited to form a contact electrode with thickness of 50 to 100 nm, then the contact resistance is reduced, but voids are formed and side-etching becomes uncontrollable
Solution Approach 1:
A barrier metal layer is deposited on the interlayer insulating film before nickel deposition. This preliminary barrier layer prevents nickel from forming voids and uncontrollable side-etching, while still allowing nickel to form a low-resistance contact with the silicon carbide substrate through the contact hole.
Solution Approach 2:
The barrier metal layer acts as an intermediary between the nickel contact electrode and the interlayer insulating film. It mediates the interaction by preventing direct contact between nickel and the insulating film, thereby eliminating side-etching issues while permitting nickel-silicon carbide contact formation.
2Reliability
If thermal annealing is performed to form nickel silicide contact electrode, then low resistance contact is achieved, but nickel metal aggregates form on the interlayer insulating film surface
Solution Approach 1:
The harmful nickel metal aggregates that form on the interlayer insulating film surface during thermal annealing are selectively removed using a chemical solution. This extraction process eliminates the harmful aggregates while preserving the beneficial nickel silicide contact electrode formed within the contact hole.
Solution Approach 2:
The thermal annealing process that initially creates harmful nickel aggregates on the surface is converted into a beneficial process by subsequently using chemical solution to selectively remove only those aggregates, while the nickel silicide contact electrode remains intact and functional.
3Manufacturing precision
If wet etching is used to form contact electrode pattern, then pattern formation is achieved, but side-etching reaches several times the film thickness
Solution Approach 1:
The barrier metal layer serves as an intermediary protective layer that prevents excessive side-etching during wet etching processes. It allows the etching to proceed sufficiently to form the contact electrode pattern while stopping before etching reaches several times the film thickness, thereby controlling the etched depth.
4Device complexity
If nickel contact electrode is formed directly on interlayer insulating film, then simple process is used, but surface roughness increases and reliability decreases
Solution Approach 1:
The contact electrode structure is segmented into multiple functional layers: a barrier metal layer for protection and adhesion, and a nickel layer for low-resistance contact. This segmentation improves reliability by assigning specific functions to each layer while maintaining a relatively simple overall 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 enables a self-aligned, controllable contact electrode formation with improved surface flatness and reliability, preventing abnormal crystal grain growth and void generation, thus enhancing the semiconductor device's performance and stability.
Implementation Method 1
thermal annealing to form nickel silicide in contact holes while scattering nickel metal aggregates outside the holes
Implementation Method 2
chemical solution immersion to remove these aggregates
Implementation Method 3
the silicon included in the silicon carbide and the nickel react to form nickel silicide
Data Source
AI summary
In a silicon carbide semiconductor device in which a contact electrode is formed on a single-crystal silicon carbide semiconductor substrate, a barrier metal (titanium nitride layer) covers an interlayer insulating film in a region other than a contact hole, and a contact electrode of a predetermined electrode material is formed only in a region on the silicon carbide semiconductor substrate in the contact hole opened in the interlayer insulating film on the silicon carbide semiconductor substrate. A top of the barrier metal is covered by a metal electrode (wiring layer) and no nickel metal aggregates are present between the barrier metal and the metal electrode.