Backside Power Rail Source Drain Contact Structure
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Solution Overview
Problem
As semiconductor devices shrink, forming backside power rails and source/drain contacts becomes challenging due to increased complexity and risk of damaging source/drain features, and existing structures provide insufficient silicide contact areas, leading to issues with contact resistance and parasitic capacitance.
Innovation Solution
A method for forming a semiconductor device with a backside power rail structure, where a frontside source/drain contact is formed with an epitaxial layer and a metal silicide layer, spaced apart from the channel members, and a backside source/drain contact is directly below the frontside contact, allowing for improved contact resistance and reduced risk of damage during formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If backside source/drain contacts are formed using existing processes, then packing density is improved, but source/drain features are damaged
Solution Approach 1:
The contact formation process is segmented into frontside contact formation (with epitaxial and silicide layers) and backside contact formation, allowing each to be optimized independently. The backside contact is formed as a separate structure that connects to the frontside contact, avoiding direct exposure of the source/drain features to damaging processes.
Solution Approach 2:
The power rail structure is moved from the frontside to the backside of the substrate, utilizing the third dimension (depth/substrate thickness) to resolve the packing density issue. This allows contacts to be arranged on both sides of the device, effectively doubling the available contact area without increasing the planar footprint.
2Reliability
If contact area is increased to reduce contact resistance, then electrical performance is improved, but device complexity increases
Solution Approach 1:
Multiple contact functions are merged into the backside power rail structure, which simultaneously serves as a contact, a power distribution rail, and a structural support element. The epitaxial layer and silicide layer are merged into a single integrated contact structure that provides both mechanical support and low-resistance electrical connection.
Solution Approach 2:
The backside power rail structure performs multiple functions: it provides low-resistance electrical contact to the source/drain regions, serves as a power distribution network, and acts as a mechanical support structure. This multi-functionality reduces the need for separate dedicated contact structures.
3Productivity
If geometry size is reduced to increase functional density, then production efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The epitaxial layer and silicide layer are formed on the frontside before the device is flipped for backside processing. This preliminary action protects the source/drain features and establishes a robust contact structure that can withstand subsequent backside processing steps, enabling scaling without compromising manufacturing feasibility.
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 enhances contact resistance and interface area with the metal silicide layer, reducing the risk of damage during backside contact formation and improving packing density and performance in advanced technology nodes.
Implementation Method 1
a silicide layer disposed between the epitaxial layer and the frontside source/drain contact
Data Source
AI summary
A semiconductor structure and a method of forming the same are provided. In an embodiment, a semiconductor structure includes a first plurality of channel members, a second plurality of channel members, a first gate structure over and wrapping around each of the first plurality of channel members, a second gate structure over and wrapping around each of the second plurality of channel members, and a frontside source contact disposed between the first plurality of channel members and the second plurality of channel members as well as between the first gate structure and the second gate structure.