Source/Drain Placeholder Layout for Uniform Nanosheet Epitaxy
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Solution Overview
Problem
The shrinking spacings between elements in semiconductor devices, particularly in FinFETs and GAA FETs, lead to non-uniform source/drain formations due to incomplete deposition of deep trench material, affecting device performance and alignment margins.
Innovation Solution
The implementation of source/drain placeholder elements in source/drain trenches ensures uniform epitaxy growth by aligning the bottom surfaces of all trenches, allowing for uniform source/drain formation through epitaxial growth from placeholder materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deep trench material is deposited in source/drain regions, then source/drain formation is achieved, but non-uniform deposition occurs leading to poor manufacturing precision
Solution Approach 1:
Placeholder elements are formed in advance in the source/drain regions before the actual source/drain material deposition. These placeholders establish uniform reference levels and facilitate consistent epitaxial growth across all source/drain regions, thereby improving manufacturing precision and uniformity.
Solution Approach 2:
The placeholder elements act as intermediary structures that mediate between the substrate and the source/drain material. They provide a uniform foundation that ensures consistent material deposition and growth, resolving the non-uniformity issue while maintaining device performance reliability.
2Productivity
If device pitch is reduced to increase packing density, then more devices fit on chip, but alignment margins are reduced causing manufacturing difficulties
Solution Approach 1:
The placeholder elements are self-aligned to the gate structure through the epitaxial growth process. The placeholders automatically position themselves relative to the gates without requiring additional alignment steps, enabling pitch reduction while maintaining manufacturing precision through self-alignment mechanisms.
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 method facilitates the formation of uniform source/drains, improving device performance and alignment margins, and addressing issues related to non-uniformity and alignment in semiconductor devices.
Implementation Method 1
forming a first source/drain on the placeholder element and a second source/drain on the deep trench placeholder element. The placeholder element formed in the first source/drain trench and the deep trench placeholder element formed in the deep trench allows for forming the first source/drain on the placeholder element and the second source/drain on the deep trench placeholder element having uniform profiles
Data Source
AI summary
A semiconductor device includes a nanosheet stack on a substrate. A first source/drain is on a first side of the nanosheet stack and a second source/drain is on an opposing side of the nanosheet stack. A backside contact includes a first contact end on a first end of the first source/drain and an opposing second contact end in electrical communication with a backside power distribution network. A frontside contact includes a first contact end on a first end of the second source/drain and an opposing second contact end in electrical communication with a backend of line (BEOL) interconnect. A placeholder extends from an opposing second end of the second source/drain.