GAA Gate Spacer Structure for Precise Gate Definition
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Solution Overview
Problem
The semiconductor industry faces challenges in forming non-planar transistor devices with precise control over gate structures and minimizing epitaxial growth issues, which affect the integration density and reliability of electronic components.
Innovation Solution
A method for forming a gate-all-around (GAA) field-effect-transistor (FET) device involves creating a dummy gate structure over semiconductor layers, removing it to form a gate trench, and then wrapping an active gate structure around the channel layers, with a gate spacer formed after source/drain structures, allowing for greater material selection and reducing the risk of epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gate spacers are formed before source/drain structures, then the gate structure is defined early in the process, but epitaxial growth issues occur and material selection is limited
Solution Approach 1:
The gate spacer is formed in advance during the dummy gate structure formation phase, but its full functionality is realized later after source/drain structures are created. This preliminary positioning allows the spacer to define the gate structure boundaries early while avoiding epitaxial growth issues by using materials and processes that prevent unwanted growth during intermediate steps.
Solution Approach 2:
The gate spacer acts as an intermediary structure that temporarily defines the gate region during fabrication. It serves as a placeholder and boundary marker that guides subsequent processing steps, including source/drain formation and active gate structure creation, without directly participating in epitaxial growth processes.
2Adaptability or versatility
If gate spacers are formed after source/drain structures, then material selection freedom increases and epitaxial growth risk is reduced, but the gate structure definition occurs later in the process
Solution Approach 1:
The gate spacer formation is performed as a preliminary step during dummy gate creation, establishing the gate region boundaries early in the fabrication sequence. This timing allows subsequent source/drain and active gate formation steps to proceed without delay, maintaining process efficiency while enabling versatile material choices for the spacer itself.
Solution Approach 2:
The gate spacer utilizes materials and formation parameters that differ from conventional approaches, allowing greater flexibility in material selection. By changing the parameters of spacer formation (timing, material composition, deposition methods), the process achieves both early structural definition and enhanced adaptability for subsequent processing steps.
3Productivity
If minimum feature size is reduced continuously, then integration density improves, but manufacturing precision and reliability become more challenging to maintain
Solution Approach 1:
The gate structure formation is segmented into distinct phases: dummy gate creation with gate spacer definition, source/drain structure formation, and active gate structure creation. This segmentation allows each step to be optimized independently for precision, with the gate spacer providing a stable reference framework that maintains manufacturing precision even as overall feature sizes are reduced to increase integration density.
Solution Approach 2:
The gate spacer serves as an intermediary reference structure that maintains dimensional stability and defines critical boundaries during the fabrication of smaller features. As minimum feature sizes are reduced, the spacer provides a stable framework that helps maintain manufacturing precision by serving as a physical reference for alignment and dimensional control in subsequent processing steps.
Data Source
AI summary
A semiconductor device includes a plurality of semiconductor layers vertically separated from one another. The semiconductor device includes a gate structure that comprises a lower portion and an upper portion. The lower portion wraps around each of the plurality of semiconductor layers. The semiconductor device includes a gate spacer that extends along a sidewall of the upper portion of the gate structure and comprises a first layer and a second layer. The first layer is in contact with a first portion of the sidewall and the second layer is in contact with a second portion of the sidewall.