Multi-Layer Gate Isolation Structure for Lower FET Capacitance
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Solution Overview
Problem
Existing methods for forming gate isolation features in semiconductor devices using high-k dielectric materials increase parasitic capacitance, leading to compromised device performance due to increased effective capacitance and RC delay.
Innovation Solution
A method involving the formation of a multi-layer dielectric feature with a low-k dielectric layer embedded in a high-k dielectric layer, or an air gap embedded in a high-k dielectric layer, to reduce effective capacitance by selectively etching and structuring the dielectric layers to create a gate isolation feature that separates high-k metal gate structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-k dielectric materials are used to form gate isolation features, then the isolation capability is improved, but parasitic capacitance increases leading to increased effective capacitance and RC delay
Solution Approach 1:
The gate isolation feature is segmented into multiple dielectric layers with different k-values. A low-k dielectric layer is embedded within a high-k dielectric layer, creating a composite structure that divides the isolation function into distinct regions with different electrical properties. This segmentation allows the high-k portion to provide isolation while the low-k portion reduces parasitic capacitance.
Solution Approach 2:
The gate isolation feature uses a composite dielectric structure combining high-k and low-k dielectric materials. The high-k dielectric layer provides strong isolation capability, while the embedded low-k dielectric layer reduces parasitic capacitance. This composite material approach allows simultaneous optimization of both isolation performance and capacitance reduction.
2Reliability
If high-k dielectric materials are used for gate isolation, then isolation effectiveness is improved, but device performance deteriorates due to increased RC delay
Solution Approach 1:
The dielectric structure is segmented into high-k and low-k regions vertically and horizontally. The high-k dielectric layer is positioned where maximum isolation is needed, while low-k dielectric layers are embedded to reduce capacitance in regions contributing most to RC delay. This spatial segmentation optimizes the balance between isolation effectiveness and signal speed.
Solution Approach 2:
The dielectric constant parameter is changed spatially within the gate isolation structure. By varying the k-value from high to low in specific regions, the structure achieves high isolation where needed while minimizing capacitance in regions affecting RC delay. This parameter optimization reduces the time constant without sacrificing isolation effectiveness.
3Ease of manufacture
If simple dielectric structures are used for gate isolation, then manufacturing complexity is reduced, but capacitance reduction capability is insufficient
Solution Approach 1:
The dielectric structure is divided into multiple layers deposited in sequence, with each layer having a specific function. The high-k layer provides isolation while embedded low-k layers reduce capacitance. This segmented approach achieves superior electrical performance while maintaining compatibility with standard multi-step deposition processes.
Solution Approach 2:
The low-k dielectric layer is nested within the high-k dielectric layer, creating a layered composite structure. This nesting arrangement allows the smaller low-k regions to be embedded in the larger high-k matrix, achieving capacitance reduction while maintaining structural integrity and using conventional deposition techniques.
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
The solution effectively reduces parasitic capacitance and improves device performance by minimizing effective capacitance, thereby reducing RC delay and enhancing overall device efficiency.
Implementation Method 1
forming a multi-layer dielectric feature with a low-k dielectric layer embedded in a high-k dielectric layer, or an air gap embedded in a high-k dielectric layer, to reduce effective capacitance
Data Source
AI summary
A semiconductor structure includes a fin protruding from a substrate, a first and a second metal gate stacks disposed over the fin, and a dielectric feature defining a sidewall of each of the first and the second metal gate stacks. Furthermore, the dielectric feature includes a two-layer structure, where sidewalls of the first layer are defined by the second layer, and where the first and the second layers have different compositions.