Self-Aligned Backside Source-Drain Contact With Increased Contact Area
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Solution Overview
Problem
In semiconductor manufacturing, the formation of backside contacts for nanosheet FETs poses challenges due to the need for precise alignment and the limitations of traditional lithography processes, which can lead to inaccuracies and increased complexity in forming reliable contacts with minimal distortion.
Innovation Solution
A self-aligned sacrificial backside contact method is developed, where a sacrificial backside contact placeholder is formed under the source drain epitaxy, allowing for pre-defined contact location and enabling contact formation from either above or below the structure, reducing the reliance on backside lithography alignment and allowing for greater spacing between contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional top-side contact approach is used for nanosheet FETs, then the contact can be formed directly above the source drain region, but the device footprint increases and lithography alignment becomes more difficult
Solution Approach 1:
The patent forms the backside contact from the opposite side of the substrate rather than from the top-side. The contact is created through a backside opening that penetrates through the substrate to reach the source drain region, thereby inverting the conventional contact formation approach. This inversion reduces the device footprint and improves lithography alignment accuracy by allowing greater spacing between contact features.
2Reliability
If the bottom source drain contact width is increased to improve electrical connection, then contact reliability improves, but the contact may interfere with surrounding structures
Solution Approach 1:
The patent extends the bottom source drain contact laterally beyond the source drain region boundaries in the horizontal plane. By utilizing the lateral dimension and allowing the contact to surround the source drain region, the contact area is increased for improved reliability without vertical interference with gate or channel structures.
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 the flexibility and accuracy of source drain contact formation, reduces the need for multiple contacts above the nanosheet device, and improves backside lithography alignment accuracy, resulting in a more reliable and efficient contact formation process.
Implementation Method 1
bonding a carrier wafer to the nanosheet FET structure
Data Source
AI summary
A first source drain region adjacent to a first transistor, a second source drain region adjacent to a second transistor, an upper source drain contact above the first source drain region, a bottom source drain contact below the second source drain region, the bottom and the upper source drain contacts are on opposite sides, a horizontal surface of the bottom source drain contact is adjacent to a horizontal surface of dielectric side spacers surrounding the second source drain region. An embodiment where a bottom source drain contact surrounds vertical sides of a source drain region. A method including forming a forming a first and a second nanosheet stacks, forming a top source drain contact to a first source drain region adjacent to the first nanosheet stack, forming a bottom source drain contact to a lower horizontal surface of a second source drain region adjacent to the second nanosheet stack.