T-Shaped Gate Isolation Structure for Lower Parasitic Capacitance
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Solution Overview
Problem
As semiconductor devices scale down, the reduced spacing between gate structure segments leads to higher parasitic capacitance, which negatively impacts device performance by increasing RC delays and reducing speed.
Innovation Solution
A T-shaped gate isolation structure is formed by creating a trench between gate segments, filling it with a first dielectric layer, etching back to release the upper portion, and then enlarging it with a second etching process, followed by a second dielectric layer to reduce parasitic capacitance and increase device speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If separation distances between two adjacent active regions are reduced to meet design requirements of smaller technology nodes, then functional density increases, but parasitic capacitance between gate structure segments increases
Solution Approach 1:
The gate isolation structure extends vertically into the trench, adding a depth dimension to the isolation. This vertical extension increases the separation distance between gate segments in the vertical dimension, thereby reducing parasitic capacitance while allowing horizontal spacing to remain small for high density.
Solution Approach 2:
The gate isolation structure acts as an intermediary dielectric element inserted between the two gate segments. This intermediate structure provides electrical isolation and reduces the capacitive coupling between adjacent gate segments, addressing the parasitic capacitance issue while maintaining the compact horizontal layout.
2Productivity
If spacing for forming gate isolation structure is reduced to increase functional density, then more devices fit per chip area, but parasitic capacitance increases leading to lower device speed
Solution Approach 1:
By extending the gate isolation structure vertically into the trench, the invention increases the effective separation distance in the vertical dimension. This allows horizontal spacing to be minimized for high production efficiency while the vertical depth provides sufficient isolation to reduce parasitic capacitance and maintain high device speed.
Solution Approach 2:
The invention changes the geometric parameters of the gate isolation structure by creating a deep trench with specific depth and width ratios. This parameter optimization allows the structure to provide adequate electrical isolation (reducing parasitic capacitance) while occupying minimal horizontal space, thus maintaining both high production efficiency and high device speed.
Data Source
AI summary
Semiconductor structures and methods are provided. An exemplary method according to the present disclosure includes forming a first and a second fin-shaped active region over a substrate, the first and second fin-shaped active regions extending lengthwise along a first direction, forming a gate structure over channel regions of the first and second fin-shaped active regions, the gate structure extending lengthwise along a second direction substantially perpendicular to the first direction, forming a trench to separate the gate structure into two segments, the trench extending lengthwise along the first direction and being disposed between the first and second fin-shaped active regions, performing an etching process to enlarge an upper portion of the trench, and forming a gate isolation structure in the trench, and, in a cross-sectional view cut through both the first and second fin-shaped active regions and the gate structure, the gate isolation structure is a T-shape structure.