Backside Diffusion Break Structure for GAA Transistor Isolation
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Solution Overview
Problem
In semiconductor IC devices, particularly those employing GAA FETs, forming diffusion breaks becomes challenging as device sizes decrease and packing densities increase, making it difficult to achieve proper electrical isolation between transistors.
Innovation Solution
The fabrication method involves forming a diffusion break isolation wall with a backside spacer, alternating series of residual nanolayer channel layers and residual inner spacers, and a gate spacer, and depositing a diffusion break dielectric within the opening formed by removing the replacement gate and active semiconductor nanolayers from the backside.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device sizes are decreased and packing densities are increased, then device integration is improved, but electrical isolation between transistors deteriorates
Solution Approach 1:
The patent transitions from traditional planar isolation to three-dimensional isolation structures. Diffusion break isolation walls are formed extending vertically from the substrate surface, and diffusion break dielectric is deposited in the spaces between these walls. This vertical dimension enables effective electrical isolation even when horizontal device spacing is minimized, resolving the contradiction between high integration density and reliable electrical isolation.
Solution Approach 2:
The diffusion break dielectric acts as an intermediary material filling the spaces between diffusion break isolation walls. This dielectric material provides the necessary electrical isolation function, preventing charge carrier flow between adjacent transistors while allowing the devices to be packed closely together, thus maintaining both high integration and reliable isolation.
2Reliability
If diffusion breaks are formed using traditional trench methods, then electrical isolation is achieved, but manufacturing complexity increases for GAA FETs
Solution Approach 1:
The diffusion break isolation walls are formed preliminarily during the GAA FET fabrication process using existing structural elements such as mandrels or sacrificial layers. By preparing these isolation walls in advance as part of the standard fabrication sequence, the patent avoids adding separate complex trench formation steps, thus maintaining manufacturing simplicity while achieving effective isolation.
Solution Approach 2:
The diffusion break isolation structure serves multiple functions: it provides electrical isolation between devices, defines device boundaries, and can be integrated with the gate alignment structure. This multi-functionality reduces the need for separate isolation fabrication steps, simplifying the overall manufacturing process while ensuring reliable electrical isolation.
Data Source
AI summary
A semiconductor integrated circuit (IC) device includes a diffusion break region that has a diffusion break dielectric adjacent to or between diffusion break isolation wall(s). The diffusion break region may separate adjacent transistors. The diffusion break isolation wall(s) may include respective retained portions of a backside spacer, a bottom isolation, respective inner spacers, and residual active semiconductor nanolayers. The diffusion break region may be fabricated by depositing a diffusion break dielectric within a diffusion break opening against the diffusion break isolation wall(s).