Dielectric Spacer Structure for Gate-Source/Drain Capacitance Reduction
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Solution Overview
Problem
The semiconductor industry faces challenges in reducing parasitic capacitance between gate and source/drain structures, which affects switching speed and device performance, as existing low-k dielectrics are prone to etching and damage.
Innovation Solution
A method involving the formation of a sacrificial dielectric layer with a lower dielectric constant than the contact etch stop layer, which is etched back to create space between the source/drain and gate structures, using a combination of anisotropic and isotropic etching processes to optimize the dielectric layers' thickness and composition for reduced parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If existing low-k dielectrics are used to reduce parasitic capacitance, then parasitic capacitance is reduced, but the dielectric layer becomes prone to etching and damage
Solution Approach 1:
A contact etch stop layer (CESL) with higher etch selectivity is introduced between the low-k dielectric layer and the etching environment. This CESL acts as a protective intermediary that is more resistant to etching, thereby protecting the low-k dielectric layer from damage while maintaining its low parasitic capacitance properties
Solution Approach 2:
The structure combines multiple dielectric materials with different properties: a low-k dielectric layer for reducing parasitic capacitance and a CESL with higher etch selectivity for protection. This composite structure allows simultaneous optimization of electrical performance and manufacturing reliability
2Productivity
If distance between gate and source/drain structures is reduced to increase density, then functional density increases, but parasitic capacitance increases
Solution Approach 1:
The low-k dielectric material is specifically applied in the critical region between the gate structure and source/drain structures. This localized application of special material properties reduces parasitic capacitance precisely where needed, allowing closer spacing without sacrificing performance
3Object-generated harmful factors
If dielectric layer thickness is reduced to reduce parasitic capacitance, then parasitic capacitance decreases, but manufacturing precision requirements increase
Solution Approach 1:
The CESL with higher etch selectivity serves as a thickness reference and protective layer during manufacturing. Its superior etch resistance provides a stable baseline that simplifies the control of the overlying low-k dielectric layer thickness, reducing the overall manufacturing precision burden
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 effectively reduces parasitic capacitance, improving semiconductor device performance by enhancing switching speed, as demonstrated by improved ring oscillator performance and reduced dielectric constant impact.
Implementation Method 1
using a combination of anisotropic and isotropic etching processes to optimize the dielectric layers' thickness and composition
Implementation Method 2
using a combination of anisotropic and isotropic etching processes to optimize the dielectric layers' thickness and composition
Implementation Method 3
A method involving the formation of a sacrificial dielectric layer with a lower dielectric constant than the contact etch stop layer
Data Source
AI summary
Semiconductor structures and methods of forming the same are provided. An example semiconductor structure includes a fin structure arising from a substrate and extending lengthwise along a direction, an isolation feature over the substrate and around the fin structure, a gate structure wrapping over a channel region of the fin structure, a first gate spacer extending along a sidewall of the gate structure, a second gate spacer over the first gate spacer, a filler dielectric layer over the second gate spacer, an epitaxial feature disposed over a source/drain region of the fin structure, a portion of the epitaxial feature being disposed over the filler dielectric layer, an contact etch stop layer (CESL) over the epitaxial feature and the filler dielectric layer, and an interlayer dielectric (ILD) layer over the CESL. A portion of the CESL extends between the epitaxial feature and the sidewall of gate structure along the direction.