FinFET Gate Spacer Structure for Tight Pitch Scaling
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Solution Overview
Problem
Conventional methods for forming finFET devices face challenges in scaling down due to difficulties in forming a dummy gate between fin structures, leading to damage from heavy etching and limitations in fin structure size and pitch.
Innovation Solution
A sacrificial material is deposited between fin structures, and a dummy gate is formed as a planar structure, allowing for lateral etching and replacement with a dielectric material, which enables the removal of the sacrificial material and subsequent formation of a real gate, thereby improving fin height and pitch scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form dummy gates between fin structures, then finFET devices can be manufactured, but heavy etching causes damage to fin structures and limits pitch scaling
Solution Approach 1:
A sacrificial material is deposited between the fin structures to serve as an intermediary that enables dummy gate formation without requiring heavy etching. The sacrificial material is later removed through selective etching, allowing the fin structures to remain intact while achieving the desired pitch scaling.
Solution Approach 2:
The sacrificial material is deposited in advance before forming the dummy gate structure. This preliminary action allows the dummy gate to be formed with reduced etching intensity, preventing damage to the fin structures while maintaining manufacturing feasibility.
2Productivity
If fin pitch is reduced to increase device density, then IC functional density increases, but conventional dummy gate formation becomes difficult and causes fin structure damage
Solution Approach 1:
The sacrificial material acts as a mediator that enables the formation of dummy gates at reduced pitch dimensions. By providing a temporary structural support during fabrication, it allows pitch scaling while protecting fin structures from damage.
Solution Approach 2:
The fabrication process is segmented into distinct stages: first depositing the sacrificial material, then forming the dummy gate, and finally removing the sacrificial material. This segmentation allows each step to be optimized independently, enabling pitch reduction while maintaining fin structure integrity.
3Ease of manufacture
If heavy etching is used to remove polysilicon residue between fin structures, then dummy gate formation is completed, but fin structures are damaged
Solution Approach 1:
The sacrificial material serves as an intermediary that simplifies dummy gate formation while protecting fin structures. It allows for milder etching conditions to be used, completing the dummy gate formation process without damaging the fin structures.
Solution Approach 2:
The process converts the potential harm of etching into a benefit by using the sacrificial material as a protective layer. The etching that would normally damage fin structures is instead used to selectively remove the sacrificial material, leaving the fin structures intact.
Data Source
AI summary
According to one example, a semiconductor structure includes a fin-shaped structure, a gate structure disposed over a region of the fin-shaped structure and having a sidewall including a lower portion and an upper portion above the lower portion, a first dielectric sidewall structure disposed along the lower portion of the sidewall, a second dielectric sidewall structure disposed along the upper portion of the sidewall and disposed on the first dielectric sidewall structure, and a source/drain feature disposed over a source/drain region of the fin-shaped structure and adjacent to the gate structure. The source/drain feature is separated from the gate structure by the first dielectric sidewall structure and the second dielectric sidewall structure. The first dielectric sidewall structure includes a different material than the second dielectric sidewall structure.