Wraparound Backside Contact Structure for Lower Source/Drain Resistance
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Solution Overview
Problem
Existing backside contacts in semiconductor devices exhibit high resistance due to limited surface area between the backside contact and the source/drain region, which is exacerbated by the inability to use high temperature annealing processes after top back end of line formation.
Innovation Solution
The implementation of a contact that wraps around the source/drain region, including a dielectric bar, to increase the surface area and reduce resistance, utilizing materials like aluminum, nickel, chromium, gold, germanium, copper, silver, titanium, tungsten, platinum, or tantalum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional backside contact structure is used, then the device structure is simple, but the contact resistance is high due to limited surface area
Solution Approach 1:
The contact structure transitions from a conventional planar configuration to a three-dimensional wraparound configuration that contacts the source/drain epi on multiple surfaces (top, sidewall, and bottom portions). This dimensional change increases the effective contact surface area from a single plane to a multi-surface geometry, thereby reducing contact resistance while maintaining structural integrity.
Solution Approach 2:
The contact is configured to wrap around and surround the source/drain epi region, with the contact material effectively nesting around the epi structure. This nested configuration maximizes the contact surface area by utilizing the top, sidewall, and bottom portions of the source/drain epi, creating a multi-faceted contact interface that reduces resistance.
2Reliability
If high temperature annealing is applied to reduce contact resistance, then contact resistance decreases, but top back end of line formation is compromised
Solution Approach 1:
The contact structure is designed to provide sufficient surface area for low contact resistance before the top back end of line formation is completed. By establishing the wraparound contact geometry earlier in the fabrication process, the need for subsequent high temperature annealing is eliminated, thereby preserving the integrity of the top back end of line formation while achieving the desired electrical characteristics.
Solution Approach 2:
The invention changes the geometric parameters of the contact structure (from planar to wraparound configuration) to achieve the desired electrical performance without requiring thermal parameter changes (high temperature annealing). This parameter change in structure allows low contact resistance to be achieved through increased surface area rather than thermal processing.
3Reliability
If the contact surface area is increased to reduce resistance, then contact resistance decreases, but the device layout becomes more complex
Solution Approach 1:
The contact geometry evolves from a two-dimensional planar shape to a three-dimensional wraparound structure that engages the source/drain epi on multiple surfaces. This dimensional transition increases the effective contact area without requiring proportionally larger footprint, as the contact utilizes vertical and lateral dimensions simultaneously to maximize surface area for resistance reduction.
Data Source
AI summary
One or more systems, devices, and/or methods of fabrication provided herein relate to reduced resistance between contacts and source/drain epis. According to one embodiment, a semiconductor device can comprise a source/drain region comprising a top portion, a sidewall portion and a bottom portion, a dielectric bar located adjacent to the source/drain region, and a contact in direct contact with the top portion, the sidewall portion and the bottom portion of the source/drain region and with the dielectric bar.