Self-Aligned Via Structure for Backside Power Rail Connection
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Solution Overview
Problem
As semiconductor devices scale down, they interfere with each other and forming connections to a backside power network becomes increasingly difficult due to the proximity and size constraints.
Innovation Solution
A semiconductor device structure is developed with a dielectric fill and self-aligned contact caps, where the dielectric liner is recessed and filled with a conductive material to form a via to the backside power rail, reducing the risk of frontside contact-to-gate shorts and enabling efficient connection between nanodevices and the backside power rail.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If devices are scaled down and placed closer together, then device density and integration are improved, but device interference increases and connection formation becomes more difficult
Solution Approach 1:
The connection structure is segmented into multiple functional portions: a first portion extending from the frontside contact through the gate region, and a second portion extending to the backside surface. This segmentation allows each portion to be optimized independently for its specific function, enabling formation of connections in high-density nanosheet devices where conventional single-structure connections fail.
Solution Approach 2:
The connection structure utilizes three-dimensional space by extending vertically through multiple layers (from frontside contact through gate to backside power rail) rather than relying solely on planar routing. This vertical dimension provides additional routing paths that avoid interference between closely-spaced nanosheet devices.
2Area of stationary object
If devices are placed closer together, then area utilization is improved, but the risk of frontside contact-to-gate shorts increases
Solution Approach 1:
The gate region acts as an intermediary zone that the connection structure carefully navigates. The connection portions are positioned to extend through the gate region without making direct contact with the gate electrode, using the gate region as a spatial corridor rather than a direct connection path. This intermediary approach maintains electrical isolation while enabling physical routing through the dense device structure.
Solution Approach 2:
The connection structure exhibits local quality variations: the first portion has specific dimensional constraints to avoid gate contact, while the second portion extends freely to the backside. The head section width differs from the shaft section width, with each portion optimized for its local environmental constraints and functional requirements.
3Device complexity
If conventional connection structures are used in scaled devices, then manufacturing process simplicity is maintained, but connection reliability to backside power rail deteriorates
Solution Approach 1:
The connection structure is formed preliminarily during the nanosheet device fabrication sequence, integrating the backside power rail connection formation into the existing manufacturing flow rather than requiring separate post-processing steps. The dielectric liner recess and connection structure are formed before final device assembly, ensuring proper alignment and reducing subsequent processing complexity.
Data Source
AI summary
According to the embodiment of the present invention, a semiconductor device includes a first nanodevice and a second nanodevice. The second nanodevice is adjacent to and parallel to the first nanodevice along an x-axis. A dielectric fill is located between the first nanodevice and the second nanodevice. A dielectric liner is comprised of a first dielectric liner and a second dielectric liner. The first dielectric liner is located between the first nanodevice and the dielectric fill. The second dielectric liner is located between the second nanodevice and the dielectric fill. A plurality of self-aligned contact (SAC) caps is comprised of a head section and a shaft section. The head section extends a first width parallel to the x-axis and is in direct contact with a frontside of the dielectric liner. The shaft section extends a second width parallel to the x-axis. The first width is greater than the second width.