Metal Gate Air-Gap Isolation for Lower Gate-to-Gate Capacitance
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Solution Overview
Problem
Aggressive scaling down of semiconductor IC dimensions increases parasitic gate-to-gate capacitance, reducing ring oscillator frequency and degrading circuit performance.
Innovation Solution
Incorporating an air gap as a separation feature between metal gate stacks over adjacent fins in semiconductor devices, which reduces parasitic capacitance by utilizing a protection layer, a filling layer, and a supporting layer to define and maintain the air gap, thereby isolating the metal gate stacks and reducing dielectric constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If IC dimensions are scaled down, then production efficiency is improved and costs are lowered, but parasitic gate-to-gate capacitance is increased
Solution Approach 1:
A dielectric layer is introduced as an intermediary substance between adjacent metal gates. This dielectric layer acts as a mediator that reduces the parasitic capacitance coupling between gates while allowing the gates to remain in close proximity for high-density integration, thus resolving the contradiction between scaling down and reducing parasitic effects
Solution Approach 2:
The dielectric constant parameter of the material between metal gates is changed by using a low-k dielectric material instead of traditional high-k materials. This parameter change directly reduces the parasitic capacitance value while maintaining the scaled-down geometry, enabling both high productivity and reduced parasitic effects
2Area of moving object
If distance between adjacent metal gates is decreased, then integration density is improved, but parasitic gate-to-gate capacitance is increased
Solution Approach 1:
The dielectric layer serves as a protective intermediary between metal gates, enabling them to be placed closer together without directly coupling their electric fields. This intermediary structure allows high integration density while mitigating the parasitic capacitance that would otherwise result from close spacing
Solution Approach 2:
A composite structure is formed by combining metal gates with a low-k dielectric material between them. This composite approach leverages the conductive properties of metal for high-density interconnects while using the low-k dielectric to reduce parasitic capacitance, achieving both high integration density and reduced harmful effects
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The air gap reduces parasitic gate-to-gate capacitance, enhancing ring oscillator frequency, reducing power consumption, and improving device performance.
Implementation Method 1
reduces parasitic capacitance by utilizing a protection layer, a filling layer, and a supporting layer to define and maintain the air gap, thereby isolating the metal gate stacks and reducing dielectric constant
Data Source
AI summary
Semiconductor device and the manufacturing method thereof are disclosed herein. An exemplary semiconductor device comprises a first semiconductor fin and a second semiconductor fin formed over a substrate, wherein lower portions of the first semiconductor fin and the second semiconductor fin are separated by an isolation structure; a first gate stack formed over the first semiconductor fin and a second gate stack formed over the second semiconductor fin; and a separation feature separating the first gate stack and the second gate stack, wherein the separation feature includes a first dielectric layer and a second dielectric layer with an air gap defined therebetween, and a bottom portion of the separation feature being inserted into the isolation structure.