Nano-Sheet Gate Metal Composition Gradient for Threshold Voltage Control
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Solution Overview
Problem
Semiconductor devices with nano-sheets face challenges in achieving consistent threshold voltages and reducing gate resistivity as they are downscaled, requiring innovative solutions to manage the composition and structure of metal layers in the gate architecture.
Innovation Solution
The semiconductor device incorporates a nano-sheet structure with a gate that includes a single metal layer with varying compositions of metal atoms at its surface and interior, along with a gate insulating layer and source/drain regions, allowing for adjustable work function and resistivity through precise control of metal atom composition ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the semiconductor device is down-scaled, then the device size is reduced, but the threshold voltage control becomes difficult and gate resistivity increases
Solution Approach 1:
The gate electrode employs a gradient composition structure where the metal atom composition varies spatially - the surface layer has a different metal composition than the interior layer. This local quality variation allows the surface to provide low resistivity for current flow while the interior provides appropriate work function for threshold voltage control, resolving the contradiction between device scaling and electrical performance.
Solution Approach 2:
The invention changes the physical-chemical parameters of the gate electrode by creating a composition gradient of metal atoms. By controlling the ratio and distribution of different metal elements in the surface versus interior layers, the device achieves simultaneous optimization of resistivity and work function, enabling reliable threshold voltage control in down-scaled devices.
2Reliability
If the gate resistivity is reduced, then the device performance is improved, but the work function control becomes difficult
Solution Approach 1:
The gate electrode is designed with spatially varying metal composition - the surface layer is optimized for low resistivity while the interior layer is optimized for appropriate work function. This local quality differentiation allows independent optimization of electrical conductivity and threshold voltage characteristics without compromise.
Solution Approach 2:
The gate electrode is segmented into functionally distinct regions: a surface layer and an interior layer, each with different metal compositions tailored to specific functions. The surface layer provides low resistivity for signal transmission while the interior layer provides stable work function for threshold voltage control, resolving the contradiction between performance and manufacturing precision.
3Ease of manufacture
If a single metal layer is used in the gate, then the manufacturing process is simplified, but the ability to control both resistivity and work function is limited
Solution Approach 1:
Instead of using multiple separate metal layers, the invention achieves property control by varying the composition parameters within a single continuous metal layer. The gradient composition allows different regions of the same layer to have different effective properties, maintaining manufacturing simplicity while achieving versatile electrical characteristic control.
Solution Approach 2:
The gate electrode functions as a composite material system where multiple metal elements are combined in a gradient distribution within a single layer. This composite structure provides the benefits of multiple materials (low resistivity and appropriate work function) while avoiding the complexity of multiple discrete layers, thus maintaining ease of manufacture.
Data Source
AI summary
A semiconductor device includes an active region in a substrate, at least one nano-sheet on the substrate and spaced apart from a top surface of the active region, a gate above or below the nano-sheet, a gate insulating layer between the at least one nano-sheet and the gate, and source/drain regions on the active region at both sides of the at least one nano-sheet. The at least one nano-sheet includes a channel region; a gate disposed above or below the nano-sheet and including a single metal layer having different compositions of metal atoms of a surface and an inside thereof; a gate insulating layer between the nano-sheet and the gate; and source/drain regions disposed in the active region of both sides of the at least one nano-sheet.