Dummy Fin Separation Structure for Source/Drain Isolation
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Solution Overview
Problem
Conventional dummy fins in semiconductor devices pose challenges when standard cell dimensions shrink, leading to uneven heights and structures due to etch loading, which can result in merging of source/drain features and device failures.
Innovation Solution
The process involves forming different dummy fins of varying widths and structures, including a first dummy fin and a second dummy fin that is narrower, to ensure even heights and effectively separate neighboring source/drain features, thereby reducing standard cell sizes or improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dummy fins are used to isolate source/drain features, then isolation function is achieved, but uneven heights and structures occur due to etch loading, leading to merging of source/drain features and device failures
Solution Approach 1:
The patent divides the dummy fin structure into multiple segments with different widths. Specifically, it uses a first dummy fin with a first width and a second dummy fin with a second width that is different from the first width. This segmentation allows different etch loading characteristics for different segments, preventing uniform etching that would lead to merging of source/drain features.
Solution Approach 2:
The patent applies local quality by creating dummy fins with non-uniform widths at different locations. The first dummy fin has a first width while the second dummy fin has a second width, allowing each location to have tailored etch resistance properties. This local variation in geometry prevents uniform etching across all dummy fins, maintaining height uniformity and preventing source/drain feature merging.
2Productivity
If standard cell dimensions are reduced to achieve smaller geometry sizes, then production efficiency increases and costs decrease, but dummy fins take up more relative space and pose greater challenges
Solution Approach 1:
The patent changes the geometric parameters of dummy fins by varying their widths. The first dummy fin has a first width while the second dummy fin has a second width, creating a parameter variation that optimizes the isolation function. This allows effective source/drain feature separation even as standard cell dimensions are reduced, managing the complexity that arises from scaling.
3Ease of manufacture
If uniform width dummy fins are used, then manufacturing process is simpler, but etch loading causes uneven heights and structures
Solution Approach 1:
The patent segments the dummy fin population into different width categories (first dummy fin with first width, second dummy fin with second width). This segmentation creates variation in etch loading across different dummy fins, preventing the uniform etching that would otherwise cause height non-uniformity and source/drain feature merging.
Solution Approach 2:
The patent introduces asymmetry in dummy fin widths rather than using uniform widths throughout. The first dummy fin has a different width than the second dummy fin, creating an asymmetric structure that deliberately varies etch loading to prevent uniform etching and maintain height uniformity across all dummy fins.
Data Source
AI summary
A method according to the present disclosure includes receiving a structure. The structure includes a substrate, a first fin-shaped structure, a second fin-shaped structure, and a third fin-shaped structure disposed over the substrate, and a first isolation feature between the first fin-shaped structure and the second fin-shaped structure and a second isolation feature between the second fin-shaped structure and the third fin-shaped structure. The method further includes depositing a first dielectric layer over the first isolation feature and the second isolation feature, depositing a second dielectric layer over the first dielectric layer and the first isolation feature, but not over the second isolation feature, performing a first selective etching process to the first dielectric layer and the second dielectric layer, and performing a second selective etching process to the first dielectric layer over the second isolation feature. The second dielectric layer and the first dielectric layer have different etch resistance.