Backside-Coupled Epitaxial Layers for Low-Resistance SRAM VSS

Solution Overview

Problem

Legacy SRAM implementations with deep boundary via (DVB) rings consume multiple front side metal layers and result in resistive voltage drops due to lengthy electrical paths from VSS connections to epitaxial structures, limiting SRAM performance and increasing metal resource usage.

Innovation Solution

Direct electrical coupling of epitaxial layers with backside contact metals reduces the distance to VSS, eliminating the need for front side metal layers and conductive rings, thereby providing a shorter electrical path and minimizing resistive voltage drops.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If deep boundary via (DVB) rings and multiple front side metal layers are used to provide VSS to epitaxial structures, then electrical connection is established, but resistive voltage drop increases and metal layer resources are consumed

Engineering Contradiction:

Improveelectrical connectionVSAvoidresistive voltage drop

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent transitions from planar front-side metal layer connections to a vertical backside connection architecture. By moving the VSS connection to the backside of the substrate and using vertical vias to connect to epitaxial structures, the electrical path is shortened and resistance is reduced while eliminating the need for multiple front-side metal layers.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Instead of providing VSS connections from the front side through multiple metal layers, the patent inverts the approach by providing VSS connections from the backside of the substrate. This inversion allows direct vertical connections to epitaxial structures, reducing the electrical path length and resistive voltage drop.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If deep boundary via (DVB) rings and multiple front side metal layers are used to provide VSS to epitaxial structures, then electrical connection is established, but metal layer resources are consumed

Engineering Contradiction:

Improveelectrical connectionVSAvoidmetal layer resources

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent transitions from planar front-side metal layer connections to a vertical backside connection architecture. By moving the VSS connection to the backside of the substrate and using vertical vias to connect to epitaxial structures, the electrical path is shortened and resistance is reduced while eliminating the need for multiple front-side metal layers.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent extracts the VSS connection function from the front-side metal layer stack and relocates it to the backside of the substrate. This extraction eliminates the need for multiple front-side metal layers dedicated to VSS distribution, simplifying the overall device structure.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If lengthy electrical paths are used from VSS connections to epitaxial structures, then VSS is provided to all structures, but resistive voltage drop increases

Engineering Contradiction:

ImproveVSS distributionVSAvoidelectrical path length

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent transitions from planar front-side metal layer connections to a vertical backside connection architecture. By moving the VSS connection to the backside of the substrate and using vertical vias to connect to epitaxial structures, the electrical path is shortened and resistance is reduced while eliminating the need for multiple front-side metal layers.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent establishes VSS connections at the backside of the substrate before front-side processing, allowing vertical vias to be formed that directly connect to epitaxial structures. This preliminary action creates short electrical paths that minimize resistive voltage drop before the device is completed.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP4258334A1Epitaxial layers of a transistor electrically coupled with a backside contact metal

Publication Date: 2023.10.11 INTEL CORP

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AI summary

Embodiments described herein may be related to apparatuses, processes, systems, and techniques directed to electrical couplings between epitaxial structures and voltage sources within transistors in SRAM bit cells. Embodiments include direct electrical couplings between a backside contact metal (BMO) and a backside of an epitaxial structure, as well as electrical connection structures that electrically couple the BMO to a front side of an epitaxial structure. Other embodiments may be described and/or claimed.