Nanosheet FET Angular Indent Spacer for Gate CD Scaling
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Solution Overview
Problem
Current semiconductor device fabrication methods face challenges in achieving uniformity and scalability in nanosheet field effect transistors (FETs) due to limitations in gate critical dimension (CD) scaling and contact resistance, particularly in maintaining effective length (Leff) and extension variation control.
Innovation Solution
The method involves forming nanosheet stacks with alternating sacrificial and active semiconductor layers, creating angular indents in the sacrificial layers, filling these with a low-κ material, and forming gate metal layers in the spaces left by the sacrificial layers' removal, using self-limiting etching techniques to ensure uniformity and allow for gate CD scaling without sacrificing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional planar FET fabrication methods are used, then manufacturing simplicity is maintained, but device density and channel control are insufficient
Solution Approach 1:
The channel region is segmented into multiple stacked nanosheets instead of a single planar channel, increasing effective channel width and device density while maintaining fabrication compatibility through sequential layer formation
Solution Approach 2:
The device architecture transitions from two-dimensional planar structure to three-dimensional stacked nanosheet structure, enabling increased device density and improved gate control without proportionally increasing footprint area
2Length of moving object
If gate CD scaling is pursued to reduce device footprint, then device density increases, but uniformity and contact resistance control deteriorate
Solution Approach 1:
Angular indents are formed in the sacrificial layers before gate deposition, pre-defining the gate footprint and enabling uniform gate CD scaling across the wafer while maintaining precise control over gate length and contact alignment
Solution Approach 2:
The sacrificial layers incorporate angular indents with specific geometries that create localized regions for optimized gate contact and uniform spacing, ensuring consistent electrical properties across different device regions
3Reliability
If effective length Leff and extension variation control are improved, then device performance increases, but fabrication complexity and process difficulty increase
Solution Approach 1:
The sacrificial layers with angular indents self-align during deposition processes, automatically defining gate positions and effective lengths without requiring additional alignment steps or complex process control
Solution Approach 2:
The angular indent geometry parameters (angles, depths, spacing) are optimized to naturally produce the desired effective length and extension characteristics, converting complex dimensional control into geometric parameter control
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 enhances top-to-bottom and across-wafer uniformity, enables effective gate CD scaling, and allows for further device pitch scaling without compromising channel electrostatics or contact resistance, improving the manufacturing of nanosheet FETs.
Implementation Method 1
filling these with a low-κ material layer
Data Source
AI summary
A method of manufacturing a nanosheet field effect transistor (FET) device is provided. The method includes forming a plurality of nanosheet stacks on a substrate, the nanosheet stacks including alternating layers of sacrificial layers and active semiconductor layers. The method includes removing portions of the sacrificial layers to form angular indents in each side thereof, then filling the indents with a low-κ material layer. The method further includes forming source drain regions between the nanosheet stacks, removing remaining portions of the sacrificial layers, and then forming gate metal layers in spaces formed by the removal of the sacrificial layers.