Stressed Metallic Source/Drain Structure for Higher GAA Drive Current
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Solution Overview
Problem
The semiconductor industry faces challenges in enhancing drive current in gate all-around (GAA) logic devices, as metals are needed to replace part of the silicon epitaxy region to reduce device resistance, but current techniques are inadequate for significant improvements.
Innovation Solution
A method involving the formation of epitaxy layers with doped and metal channels, deposition of spacers and stressed metal fillers in source/drain cavities, and etching to create voids for inner spacers, which introduces tensile or compressive stress to improve channel mobility and drive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metals are used to replace part of the silicon epitaxy region, then device resistance is reduced and drive current is increased, but manufacturing complexity increases due to multiple deposition and etching steps
Solution Approach 1:
The source/drain structure is segmented into multiple functional regions: silicon epitaxy regions for channel formation, metal channels for conductivity, spacers for isolation, and voids for stress application. This segmentation allows each region to be optimized independently while achieving the overall goal of high drive current
Solution Approach 2:
The structure employs nested configurations where spacers are deposited around metal channels, voids are created within metal channels, and inner spacers are placed within voids. This nested approach maximizes the use of available space and enables multiple functions to be integrated in a compact structure
Solution Approach 3:
The patent applies stress parameters to the metal channels by creating voids and filling them with stressed metal fillers. This changes the mechanical state of the channel, inducing tensile or compressive stress that enhances carrier mobility and drive current
2Reliability
If stressed metal fillers are deposited in source/drain cavities, then channel mobility is enhanced through stress transfer, but process steps and manufacturing complexity increase
Solution Approach 1:
Voids are created in the metal channels before final filler deposition, and spacers are deposited in advance to define the geometry of these voids. This preliminary structuring enables controlled stress application in subsequent steps without requiring complete redesign of the fabrication process
Solution Approach 2:
Spacers serve as intermediary structures that define the geometry of voids and control the placement of stressed metal fillers. These spacers act as templates that mediate between the metal channel structure and the stress-inducing filler material
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 results in a 10-20% increase in drive current by transferring stress from the metallic fillers to the channels, enhancing mobility and performance in GAA transistors.
Implementation Method 1
depositing a stressed metal filler in the source/drain cavity... transferring stress from the metallic fillers to the channels
Data Source
AI summary
A system and method for fabricating a gate all-around (GAA) field effect transistor (FET) is disclosed. The method includes: forming a plurality of epitaxy layers on a substrate, wherein a formed epitaxy layer includes a plurality of doped channels, a plurality of metal channels, and a dummy gate; depositing a spacer in a source/drain cavity, wherein at least a portion of the spacer is deposited on a dummy gate of a formed epitaxy layer; partially etching the plurality of metal channels of to create a plurality of voids; depositing an inner spacer in each void of the plurality of voids; and depositing a stressed metal filler in the source/drain cavity.