FinFET Edge Fins Reduce Fin Width Variation

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Solution Overview

Problem

FinFETs face challenges in minimizing fin width variation across the active area due to localized loading effects during manufacturing, leading to variations in threshold voltage and on-state current, which complicates electrical modeling and can cause mismatches with planar transistors.

Innovation Solution

Incorporating edge fins that are not connected to the drain or source regions, allowing them to be considered as dummy fins for electrical modeling, thereby reducing fin width variation and simplifying the electrical behavior of FinFETs, with options to connect these edge fins to a constant potential or an interconnect structure to mitigate noise and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional FinFET structures are used with all fins connected to drain/source regions, then electrical connectivity is improved, but fin width variation and threshold voltage mismatch increase due to localized loading effects

Engineering Contradiction:

Improveelectrical connectivityVSAvoidfin width variation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The fin structure is segmented into two distinct groups: connected fins (404) that are electrically connected to drain/source regions, and edge fins (403) that are isolated or connected to constant potential. This segmentation allows different portions of the fin structure to serve different functions - the connected fins provide electrical connectivity while the edge fins act as dummy structures to compensate for localized loading effects and reduce fin width variation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the fin structure are given different electrical characteristics. The connected fins (404) maintain electrical connectivity for current flow, while the edge fins (403) are configured with different electrical properties (isolated or constant potential) to specifically address edge effects and reduce variation in fin width and threshold voltage across the active area.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If edge fins are added to reduce fin width variation, then manufacturing precision is improved, but device complexity increases

Engineering Contradiction:

Improvefin width variationVSAvoidfin structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The edge fins (403) serve multiple functions: they act as dummy structures to compensate for localized loading effects during manufacturing, reduce fin width variation across the active area, and can be configured to mitigate noise and reduce power consumption. By making the edge fins multi-functional, the patent reduces overall device complexity while achieving multiple benefits simultaneously.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The edge fins (403) automatically serve as dummy structures that compensate for manufacturing variations without requiring additional active control or complex circuitry. Their presence alone provides the necessary compensation for localized loading effects, and they can self-adjust by being connected to constant potential or left isolated, depending on the specific implementation.

Inventive Principle:

Principle #25Self-service

3Object-affected harmful factors

If edge fins are isolated or connected to constant potential, then noise and power consumption are reduced, but electrical connectivity is worsened

Engineering Contradiction:

Improvenoise and power consumptionVSAvoidelectrical connectivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The fin structure is segmented into connected fins (404) that maintain electrical connectivity for current flow and edge fins (403) that are isolated or connected to constant potential to reduce noise and power consumption. This segmentation allows the device to achieve both good electrical connectivity through the connected fins and reduced harmful effects through the isolated edge fins.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the fin structure have different electrical characteristics tailored to their specific functions. The connected fins (404) have high electrical connectivity for current flow, while the edge fins (403) have different electrical properties (isolated or constant potential) specifically to reduce noise and power consumption, demonstrating local optimization of electrical properties.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9196540B2FinFET structure with novel edge fins

Publication Date: 2015.11.24 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device including field-effect transistors (finFETs) formed on a silicon substrate. The device includes a number of active areas each having a number of equally-spaced fins separated into regular fins and at least one edge fin, a gate structure over the regular fins, and a drain region as well as a source region electrically connected to the regular fins and disconnected to the at least one edge fin. The edge fins may be floating, connected to a potential source, or serve as a part of a decoupling capacitor.