Nanosheet Gate Layout With Short Active Gate and Longer STI Gate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor technologies face challenges in forming non-uniform gate lengths for nanosheet devices, particularly in achieving a short gate on the active region and a longer gate on shallow trench isolation (STI) regions, which is crucial for effective nanosheet multi-threshold integration.
Innovation Solution
A method involving the formation of nanosheet stacks over a substrate with shallow trench isolation regions, where a first hardmask material is deposited, a sacrificial gate is recessed, and a second hardmask material is formed to define a uniform gate length, followed by selective trimming to create a non-uniform gate length with the gate length over the nanosheet stacks being less than that over the STI regions, allowing for self-aligned work function metal patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform gate length is formed over both nanosheet stacks and STI regions, then the manufacturing process is simplified, but the work function metal cannot be properly patterned to achieve multi-threshold integration
Solution Approach 1:
The patent applies local quality by creating different gate lengths in different regions: a shorter gate length over the nanosheet stacks and a longer gate length over the STI regions. This is achieved through selective trimming of the first hardmask material, which defines the gate length. The local variation in gate length enables the work function metal to be properly patterned with different thresholds over active and isolation regions, resolving the contradiction between manufacturing simplicity and patterning versatility.
2Speed
If the gate length over nanosheet stacks is made shorter to improve device performance, then switching speed increases, but the work function metal may pinch off improperly affecting device reliability
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through region-specific gate lengths. The shorter gate length over nanosheet stacks enhances switching speed, while the longer gate length over STI regions prevents work function metal pinch-off issues. This spatial differentiation allows each region to be optimized for its specific function without compromising overall device reliability.
Solution Approach 2:
The gate structure is segmented into two distinct regions with different lengths: the active region gate over nanosheet stacks and the isolation region gate over STI. This segmentation allows independent optimization of each region's gate length to meet different performance requirements - speed for active regions and reliability for isolation regions.
3Reliability
If a longer gate length is used over STI regions to prevent work function metal pinch-off, then device reliability improves, but the gate length uniformity is compromised
Solution Approach 1:
The patent accepts and utilizes gate length non-uniformity as a deliberate local quality feature. Rather than maintaining uniform gate length throughout, the invention intentionally creates different gate lengths in different regions - longer over STI for reliability and shorter over active regions for performance. The selective trimming process precisely controls this local variation, transforming what could be seen as a precision loss into a functional advantage.
Data Source
AI summary
A method is presented for forming a nanosheet device. The method includes forming nanosheets stacks over a substrate, the nanosheet stacks separated by shallow trench isolation (STI) regions, forming a first hardmask material over the nanosheet stacks, depositing a sacrificial gate, recessing the sacrificial gate such that recesses are defined adjacent the first hardmask material, wherein a top surface of the sacrificial gate is below a top surface of the first hardmask material, forming a second hardmask material in the recesses, defining a uniform gate length in both the first and second hardmask materials, and selectively trimming the first hardmask material such that a gate length over the nanosheet stacks is less than a gate length over the STI regions.