Semiconductor Spacer Structure with Gap for Reduced Capacitance
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Solution Overview
Problem
Modern transistors face challenges in achieving improved performance due to high power consumption and reduced response time, primarily attributed to high capacitance between the gate and epitaxial layers, which is exacerbated by the large dielectric constant of existing spacer structures.
Innovation Solution
A method is introduced to form a semiconductor structure by creating a gap under a second spacer between the gate and epitaxial layers, using a third spacer with a reduced dielectric constant, achieved by forming a first and second protective layer with specific thickness ratios to allow for the gap's formation, thereby reducing the overall dielectric constant of the spacer structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spacer structure with high dielectric constant is used between gate and epitaxial layers, then structural stability and insulation are improved, but capacitance between gate and epitaxial layers increases, leading to higher power consumption and reduced transistor performance
Solution Approach 1:
The spacer structure is divided into multiple segments: a first spacer portion adjacent to the gate structure, a second spacer portion adjacent to the epitaxial layer, and a gap portion between them. This segmentation allows the structure to maintain mechanical support while reducing the dielectric material volume between gate and epitaxial layer, thereby reducing capacitance and power consumption.
Solution Approach 2:
The gap portion in the spacer structure is filled with a material having lower dielectric constant than the spacer material, creating a porous or low-k structure. This reduces the overall dielectric constant of the spacer assembly, directly lowering the capacitance between gate and epitaxial layers while maintaining structural integrity through the first and second spacer portions.
2Reliability
If the dielectric constant of the spacer structure is increased to improve insulation, then electrical insulation is improved, but capacitance between gate and epitaxial layers increases, reducing transistor response time
Solution Approach 1:
By segmenting the spacer into first and second spacer portions separated by a gap, the structure maintains electrical insulation through the spacer materials while reducing the effective dielectric volume. The gap portion with lower dielectric constant material reduces capacitance, enabling faster charge/discharge cycles and improved transistor response time.
Solution Approach 2:
The dielectric constant parameter of the spacer structure is changed by introducing a gap portion filled with low-k material. This parameter change reduces capacitance while maintaining insulation through the high-k spacer portions, thereby improving transistor response time without sacrificing electrical insulation.
3Strength
If a solid spacer structure is used between gate and epitaxial layers, then structural support is improved, but capacitance increases due to high dielectric constant, reducing overall device performance
Solution Approach 1:
The solid spacer is segmented into first and second spacer portions that provide structural support at critical locations (adjacent to gate and epitaxial layer respectively), while the gap portion between them reduces capacitance. This segmented approach maintains necessary structural support while eliminating harmful capacitive effects.
Solution Approach 2:
The gap portion is filled with porous or low-k material that provides minimal structural support while significantly reducing dielectric constant. This allows the overall structure to maintain strength through the dense spacer portions while the porous/low-k gap region reduces capacitance, eliminating the harmful capacitive effect.
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
This approach reduces capacitance between the gate and epitaxial layers, leading to lower power consumption and enhanced transistor performance by decreasing the dielectric constant of the spacer structure.
Implementation Method 1
An epitaxial layer is formed in the substrate on both sides of the first spacer, and the epitaxial layer has a surface higher than a surface of the substrate
Data Source
AI summary
A semiconductor structure and forming method are provided. The method includes providing a substrate, forming a gate structure over the substrate, forming a first spacer on a sidewall of the gate structure; forming an epitaxial layer on both sides of the gate structure and the first spacer, a surface of the epitaxial layer is higher than a surface of the substrate; forming a dielectric layer on the epitaxial layer and on surface of the first spacer, the dielectric layer is formed on both sides of the gate structure; after forming the dielectric layer, removing the first spacer to form a first opening between the epitaxial layer and the gate structure and between the dielectric layer and the gate structure, and in the first opening forming a second spacer that has a gap between the epitaxial layer and the gate structure.