Dummy Fin Gate Isolation for Precise Semiconductor Etching
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Solution Overview
Problem
As semiconductor devices scale down, achieving desired density and performance is challenging due to issues with etching processes, leading to residual dielectric features and parasitic capacitance, which affect device performance and efficiency.
Innovation Solution
A method for forming dummy fins between adjacent active regions, where the height of the dummy fins is selectively controlled to isolate or connect metal gate stacks, allowing for precise etching and reducing parasitic capacitance, involving the formation of dielectric features, recessing, and metal gate stack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching process is extended to remove residual dielectric features, then manufacturing precision improves, but adjacent features suffer damages
Solution Approach 1:
A dummy fin structure is introduced as an intermediary sacrificial element between adjacent active regions. This dummy fin is selectively removed through etching processes, serving as a buffer that protects adjacent features from damage while enabling precise etching control. The dummy fin absorbs the harmful effects of extended etching that would otherwise damage neighboring structures.
Solution Approach 2:
The dummy fin structure is formed in advance before the critical etching processes. By pre-positioning this sacrificial element, the patent enables subsequent etching steps to be performed with greater precision and extended duration without risking damage to adjacent features, as the dummy fin is already in place to protect them.
2Productivity
If device density is increased by reducing separation distances, then productivity improves, but parasitic capacitance increases leading to lower device speed
Solution Approach 1:
The patent modifies the dielectric properties of the material filling the trench between active regions. By changing the dielectric constant parameter of the trench filler, parasitic capacitance is reduced even when separation distances are minimized for high density. This parameter change enables both high productivity and high speed performance.
3Manufacturing precision
If over-etching is performed to reduce residual sacrificial features, then manufacturing precision improves, but adjacent features suffer damages
Solution Approach 1:
The dummy fin acts as a mediator that enables aggressive etching to remove residual sacrificial features. By placing the dummy fin between the etch source and adjacent features, it absorbs the excessive etching action, allowing over-etching to be performed without damaging neighboring structures while still achieving complete removal of unwanted residues.
Data Source
AI summary
A semiconductor structure and a method of forming the same are provided. In an embodiment, an exemplary method includes providing a workpiece having a first active region and a second active region protruding from a substrate, lined by cladding layers, and spaced by a first trench. The method also includes forming a dielectric layer over the workpiece to substantially fill the first trench, forming a mask film directly on a portion of the dielectric layer in the first trench after the forming of the dielectric layer, selectively recessing the dielectric layer after the forming of the mask film to form a dummy fin in and protruding from the first trench, performing an etching process to selectively remove the cladding layers to form second trenches, and forming a gate structure over the workpiece to fill the second trenches.