FinFET ESD Structure With Thickened Impurity Region for Leakage Control
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Solution Overview
Problem
FinFET type ESD protection devices face challenges in effectively managing the spacing between gate structures and ensuring efficient electrostatic discharge due to the large distances between them, leading to potential junction leakage issues.
Innovation Solution
The design incorporates an active fin with gate structures extending at an angle, an epitaxial layer filling the recess between the gate structures, and a contact plug contacting the epitaxial layer, where the impurity region under the epitaxial layer is thicker at the central portion to reduce junction leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate structures are spaced apart to form finFET type ESD devices, then electrostatic discharge capability is improved, but junction leakage increases due to large distances between gate structures
Solution Approach 1:
The patent applies local quality by creating a thicker impurity region specifically at the central portion between gate structures rather than uniformly throughout. This localized thickening of the impurity region targets the specific area where junction leakage occurs most severely, allowing the device to maintain large gate spacing for ESD capability while locally addressing the leakage problem through enhanced impurity concentration in the critical central region.
2Ease of manufacture
If epitaxial layer is grown to fill recess between gate structures, then device structure is formed, but manufacturing complexity increases
Solution Approach 1:
The patent segments the impurity region into distinct thickness zones - a thicker central portion and thinner edge portions. This segmentation is achieved through selective epitaxial growth where the epitaxial layer is grown to a greater thickness at the central region compared to the edges. The segmented structure allows different regions to serve different functions: the thicker central impurity region reduces junction leakage while the overall structure maintains manufacturability through controlled epitaxial growth processes.
3Reliability
If contact plug is positioned to overlap thicker central impurity region, then electrostatic discharge pathway efficiency is improved, but precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-forming the thicker central impurity region before creating the contact plug. The epitaxial layer is selectively grown to create the thickness variation in the impurity region, establishing a clearly defined thicker central zone. This preliminary creation of the thick impurity region serves as a built-in alignment guide, making it easier to subsequently position the contact plug accurately over the central region, thereby reducing the actual precision requirements during contact plug formation.
Data Source
AI summary
An ESD protection device includes a substrate having an active fin extending in a first direction, a plurality of gate structures extending in a second direction at a given angle with respect to the first direction and partially covering the active fin, an epitaxial layer in a recess on a portion of the active fin between the gate structures, an impurity region under the epitaxial layer, and a contact plug contacting the epitaxial layer. A central portion of the impurity region is thicker than an edge portion of the impurity region, in the first direction. The contact plug lies over the central portion of the impurity region.