Chamfered Replacement Gate Structures for FinFET Scaling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As FinFETs shrink in size, achieving a desired threshold voltage through work-function metal chamfering becomes challenging due to increased gate resistance and issues with metal fill and contact formation, leading to potential shorting at smaller technology nodes like 22 nm.
Innovation Solution
The structure and method involve forming a recessed gate dielectric material in a trench with workfunction metals, allowing for a planar surface of gate metal and additional workfunction materials, which reduces gate resistance and prevents shorting by ensuring adequate space for metal fill and self-aligned contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If work-function metal chamfering is performed to achieve desired threshold voltage, then threshold voltage control is improved, but gate resistance increases and metal fill becomes challenging
Solution Approach 1:
The gate structure is segmented into multiple functional layers: a first work-function metal layer (TiN) for threshold voltage control, a second work-function metal layer (Ta) for additional work-function adjustment, and a low-resistance metal layer (W) for reducing gate resistance. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between threshold voltage control and gate resistance management.
Solution Approach 2:
The gate conductor uses a composite structure combining multiple metal materials (TiN, Ta, and W) with different properties. TiN and Ta provide work-function characteristics for threshold voltage control, while W provides low resistance. This composite material approach simultaneously achieves both threshold voltage precision and low gate resistance.
2Productivity
If gate dimensions are reduced to continue scaling, then device density is improved, but gate resistance increases and contact formation becomes problematic
Solution Approach 1:
The gate conductor is divided into distinct functional segments: work-function metal layers (TiN, Ta) for electrical characteristic control and a separate low-resistance metal layer (W) for resistance reduction. This segmentation enables continued scaling while maintaining reliable electrical performance through specialized functional zones.
Solution Approach 2:
Different regions of the gate structure have locally optimized properties: the work-function metal layers provide specific electrical characteristics at the gate interface, while the low-resistance metal layer provides superior conductivity in the gate electrode region. This local quality optimization allows scaling without compromising overall gate performance.
3Measurement precision
If chamfering process is used for work-function metal, then threshold voltage is controlled, but critical dimension control becomes challenging
Solution Approach 1:
The work-function metal layers are deposited and patterned first to establish the threshold voltage characteristics, then the low-resistance metal layer is deposited afterward to fill the remaining space. This preliminary action sequence allows precise control of work-function metal critical dimensions before the low-resistance metal fill, avoiding CD control issues during the chamfering process.
Solution Approach 2:
The low-resistance metal layer acts as an intermediary that fills the space above the work-function metal layers after they are already in place. This intermediary approach allows the work-function metals to be precisely controlled first, then the low-resistance metal to be added without interfering with the already-established critical dimensions.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to chamfered replacement gate structures and methods of manufacture. The structure includes: a recessed gate dielectric material in a trench structure; a plurality of recessed workfunction materials within the trench structure on the recessed gate dielectric material; a plurality of additional workfunction materials within the trench structure and located above the recessed gate dielectric material and the plurality of recessed workfunction materials; a gate metal within the trench structure and over the plurality of additional workfunction materials, the gate metal and the plurality of additional workfunction materials having a planar surface below a top surface of the trench structure; and a capping material over the gate metal and the plurality of additional workfunction materials.