Buried-Channel Array Transistor Work-Function Layering
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Solution Overview
Problem
Buried-channel array transistors (BCATs) suffer from low driving current and threshold voltage sensitivity, affecting the performance and stability of semiconductor devices due to the short channel effect as semiconductor devices miniaturize.
Innovation Solution
A semiconductor structure with specific word line structures and layers, including a substrate with active and isolation regions, and trenches with distinct work-function layers (bottom, middle, and top) to enhance driving current and reduce threshold voltage sensitivity, comprising a method of manufacturing that forms these layers and trenches to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buried-channel array transistor (BCAT) device is used to deal with short channel effect, then the short channel effect is improved, but the driving current decreases and threshold voltage sensitivity increases
Solution Approach 1:
The patent applies local quality by creating different work-function layers at different locations within the word line structure. Specifically, a first work-function layer with a first work-function value and a second work-function layer with a second work-function value (different from the first) are formed in different regions of the word line, allowing localized optimization of electrical properties to simultaneously address short channel effects and maintain driving current
Solution Approach 2:
The patent changes the work-function parameter by using multiple work-function layers with different work-function values. The first work-function layer has a first work-function value and the second work-function layer has a second work-function value, creating a gradient or stepped work-function profile that optimizes both short channel effect control and driving current characteristics
2Reliability
If a buried-channel array transistor (BCAT) device is used to deal with short channel effect, then the short channel effect is improved, but threshold voltage sensitivity increases
Solution Approach 1:
The patent applies local quality by creating different work-function layers at different locations within the word line structure. Specifically, a first work-function layer with a first work-function value and a second work-function layer with a second work-function value (different from the first) are formed in different regions of the word line, allowing localized optimization of electrical properties to simultaneously address short channel effects and maintain driving current
Solution Approach 2:
The patent changes the work-function parameter by using multiple work-function layers with different work-function values. The first work-function layer has a first work-function value and the second work-function layer has a second work-function value, creating a gradient or stepped work-function profile that optimizes both short channel effect control and driving current characteristics
Data Source
AI summary
A method of manufacturing a semiconductor structure includes providing a substrate having an active region surrounded by an isolation layer; forming a first trench and a second trench in the active region, and a third trench and a fourth trench in the isolation layer; forming a bottom work-function layer in the third trench and the fourth trench, respectively; forming a middle work-function layer on the bottom work-function layer and in the first and the second trenches; forming a top work-function layer on the middle work-function layer; and forming a capping layer on the top work-function layer that fills a remaining region of the first, the second, the third and the fourth trenches.