3DSFET Source/Drain Contact Spacer for Short-Circuit Isolation
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Solution Overview
Problem
The high density of three-dimensionally-stacked field-effect transistor (3DSFET) devices poses challenges in forming source/drain contact structures, particularly due to the close proximity and risk of short circuits between lower and upper source/drain contact structures, which complicates manufacturing and increases the footprint of the device.
Innovation Solution
A spacer structure is formed at the sidewall of the upper source/drain contact in 3DSFET devices, using materials with higher etch selectivity and dielectric constant, such as silicon nitride, to isolate and separate the contact structures, facilitating easier formation of lower source/drain contacts and reducing the risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the upper source/drain contact structure is formed close to the lower source/drain contact structure to achieve high device density, then the device footprint is reduced, but the risk of short circuits between contact structures increases and manufacturing precision becomes more difficult to achieve
Solution Approach 1:
A spacer structure made of dielectric material is introduced as an intermediary element between the upper and lower source/drain contact structures. This spacer provides physical separation and electrical insulation, preventing short circuits while allowing the contact structures to be positioned closely together for high device density. The spacer acts as a mediator that enables both close proximity and electrical isolation simultaneously.
Solution Approach 2:
Instead of separating contact structures only in the horizontal plane, the solution extends separation into the vertical dimension by forming a spacer structure that rises from the lower contact structure. This vertical dimension approach allows horizontal proximity for density while achieving vertical separation for isolation, effectively using three-dimensional space to resolve the contradiction.
2Area of moving object
If the upper source/drain contact structure is formed close to the lower source/drain contact structure to achieve high device density, then the device footprint is reduced, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The spacer structure is formed preliminarily before forming the upper source/drain contact structure. This preliminary action establishes a predefined separation distance and provides a physical template that guides the subsequent formation of the upper contact, ensuring precise positioning and spacing without requiring complex alignment procedures during later manufacturing steps.
Solution Approach 2:
The spacer structure serves as a mediator that simplifies the manufacturing process by providing a physical reference and separation barrier. This intermediary element makes it easier to form the upper contact structure with precise spacing, reducing the difficulty of manufacturing precision while maintaining high device density.
3Reliability
If a spacer structure is formed at the sidewall of the upper source/drain contact structure to improve insulation and reduce short circuit risk, then reliability is improved, but device complexity increases
Solution Approach 1:
The spacer structure segments the upper and lower contact structures by introducing a distinct dielectric material layer between them. This segmentation creates clear electrical isolation zones and physically divides the contact structure into separable components, improving insulation while adding only a simple layered element rather than complex interconnections.
Solution Approach 2:
The spacer structure applies local quality by introducing dielectric material specifically at the critical sidewall region where insulation is needed, rather than uniformly throughout the entire device. This localized approach provides enhanced insulation exactly where short circuits are most likely to occur without unnecessarily increasing overall device complexity.
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 spacer structure enhances the insulation between conductive elements, allowing for more precise and efficient formation of source/drain contacts, thereby reducing manufacturing difficulties and preventing short circuits, while maintaining a smaller footprint.
Implementation Method 1
using materials with higher etch selectivity and dielectric constant, such as silicon nitride, to isolate and separate the contact structures
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3
AI summary
Provided is a three-dimensional field-effect transistor, 3DSFET, device including: a 1st source/drain region on a substrate, and a 2nd source/drain region on the 1st source/drain region; and a 1st source/drain contact structure on the 1st source/drain region, and a 2nd source/drain contact structure on the 2nd source/drain region, wherein the 2nd source/drain region is isolated from the 1st source/drain region through an interlayer structure, and wherein a spacer is formed at an upper portion of a sidewall of the 2nd source/drain contact structure, between the 1st source/drain contact structure and the 2nd source/drain contact structure.