Dual-Dielectric Gate Isolation for Lower Parasitic Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As integrated circuit technologies progress towards smaller technology nodes, parasitic capacitance of dielectric components between active device regions can lead to lower device speed due to increased RC delays, and existing methods for reducing parasitic capacitance are not entirely satisfactory in all aspects, particularly in maintaining etching resistance and structural integrity.
Innovation Solution
The formation of gate isolation features using dielectric materials with different k values, where a first dielectric material with a lower k value is configured to have a greater volume than a second dielectric material with a higher k value, arranged in specific configurations to reduce parasitic capacitance while maintaining etching resistance and structural integrity, and self-alignment capabilities for subsequent fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric components are used between active device regions, then electrical insulation is provided, but parasitic capacitance increases leading to lower device speed
Solution Approach 1:
The gate isolation feature uses a multi-layer dielectric structure where different layers have different dielectric constants (k-values). The first dielectric layer has a lower k-value to reduce parasitic capacitance, while the second dielectric layer has a higher k-value to provide adequate insulation. This local differentiation of dielectric properties allows simultaneous optimization of speed and electrical insulation.
Solution Approach 2:
The gate isolation feature is formed as a composite structure combining multiple dielectric materials with different k-values. This composite approach allows the structure to exhibit both low parasitic capacitance (from the lower-k material) and high insulation performance (from the higher-k material), resolving the contradiction between speed and electrical insulation.
2Speed
If dielectric volume is reduced to lower parasitic capacitance, then device speed improves, but etching resistance and structural integrity deteriorate
Solution Approach 1:
Different dielectric layers are assigned different k-values based on their functional requirements. The first dielectric layer with lower k-value is positioned where parasitic capacitance reduction is most critical, while the second dielectric layer with higher k-value provides the necessary etching resistance and structural support. This spatial differentiation allows optimization of both speed and etching resistance.
Solution Approach 2:
The gate isolation feature is segmented into multiple dielectric layers, each contributing different properties. The first layer segments the capacitance-reduction function, while the second layer segments the protection function. This segmentation allows the overall structure to achieve low parasitic capacitance while maintaining adequate etching resistance through the combined effect of different layers.
3Productivity
If geometry size is reduced to increase functional density, then production efficiency improves, but parasitic capacitance increases due to reduced separation distances
Solution Approach 1:
The invention changes the dielectric parameter (k-value) of the isolation material to reduce parasitic capacitance. By using a multi-layer structure with different k-values, the patent enables further scaling of geometry size while maintaining device speed performance, thus supporting continued increases in functional density and production efficiency.
Data Source
AI summary
A semiconductor structure includes fins protruding from a substrate and separated by a dielectric layer, each semiconductor fin including a plurality of semiconductor layers, source/drain (S/D) features disposed in the semiconductor fins, a first metal gate stack and a second metal gate stack disposed over the semiconductor fins and adjacent to the S/D features, where the first and the second metal gate stacks each include a top portion and a bottom portion disposed below the top portion, and where the bottom portion is interleaved with the semiconductor layers, and an isolation feature disposed on the dielectric layer and in contact with a sidewall surface of each of the first and the second metal gate stacks, where the isolation feature protrudes from the top portion of the first and the second metal gate stack, and where the isolation feature includes two compositionally different dielectric layers.