Extended Backside Contact Plug Layout for Alignment-Tolerant 3DSFETs
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Solution Overview
Problem
In high-density semiconductor devices like 3DSFETs, precise alignment and connection of backside contact plugs with interconnect structures are challenging, leading to increased device size and contact resistance due to the need for additional metal lines to compensate for misalignment.
Innovation Solution
The implementation of an extended backside contact plug structure that is not vertically overlapped by the source/drain region, allowing direct connection to backside metal lines without additional metal lines, and is manufactured using a method involving dummy patterns and shallow trench isolation to facilitate alignment and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional metal lines are formed to compensate for misalignment between backside contact plugs and interconnect structures, then connection reliability is improved, but device size increases and manufacturing complexity increases
Solution Approach 1:
The backside contact plug is extended in advance during the formation process to preemptively cover potential misalignment areas. This preliminary extension ensures that even if alignment deviations occur during subsequent manufacturing steps, the contact plug maintains reliable electrical connection without requiring additional compensatory metal lines.
Solution Approach 2:
The backside contact plug structure is segmented into multiple regions: a first region vertically overlapped by the source/drain region and a second region extending beyond it. This segmentation allows the contact plug to serve multiple functions - direct connection under the source/drain region and extended connection for alignment compensation, thereby eliminating the need for additional metal lines.
2Reliability
If additional metal lines are formed to compensate for misalignment, then connection reliability is improved, but device area increases
Solution Approach 1:
The extended backside contact plug merges the functions of the original contact plug and the alignment compensation structure into a single integrated element. By extending the contact plug to include both the region under the source/drain region and the extended region, the design eliminates the need for separate additional metal lines, thereby maintaining connection reliability while reducing overall device area.
3Area of stationary object
If precise alignment is achieved between backside contact plugs and interconnect structures, then device size is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The geometry of the backside contact plug is changed by extending it beyond the source/drain region to create an extended region. This parameter change in the contact plug structure transforms the alignment tolerance issue - the extended region provides a larger target area that can accommodate alignment variations, thereby reducing the actual manufacturing precision requirements while maintaining compact device size.
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
Provided is a semiconductor device which includes: a backside contact plug, formed at a back side of the semiconductor device, below a source/drain region connected to the backside contact plug, wherein the backside contact plug includes a 1st portion which is not vertically overlapped by the circuit element.