Buried Power Rail in Semiconductor Device

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Solution Overview

Problem

In semiconductor devices, the conventional placement of power rails above the active layer occupies space that could be used for routing tracks, leading to reduced space for interconnections and increased IR drops due to the use of Vias for power distribution.

Innovation Solution

A buried power rail is integrated at the same level as the active layer, below the metal routing layers, eliminating the need for Vias and allowing for increased routing tracks and reduced IR drops by direct electrical connection to contacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the power rail is arranged in a metal layer above the interconnection layer, then the power distribution is achieved, but the space for routing tracks is reduced

Engineering Contradiction:

Improvepower distributionVSAvoidspace for routing tracks

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The power rail is moved from the vertical dimension (metal layer M1) to the horizontal dimension (interconnection layer M0), allowing it to coexist with routing tracks in different spatial planes rather than competing for the same layer space

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The power rail is integrated into the interconnection layer structure, effectively copying the layer organization of signal interconnections and treating power distribution as another interconnection function within the same plane

Inventive Principle:

Principle #26Copying

2Reliability

If a Via is used to connect the power rail to the active layer, then electrical connection is achieved, but IR drop increases

Engineering Contradiction:

Improveelectrical connectionVSAvoidIR drop

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The Via connection element is extracted and eliminated from the power distribution path by integrating the power rail directly into the interconnection layer, removing the source of additional resistance and IR drop

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The power rail and interconnection layer are merged into a single integrated structure, combining power distribution and signal routing functions into one continuous conductive plane without discontinuities

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If the power rail occupies the same level as routing tracks, then power distribution is simplified, but the number of available routing tracks decreases

Engineering Contradiction:

Improvepower distribution structureVSAvoidrouting capacity

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The power rail is repositioned to the interconnection layer M0, creating a dimensional separation where power distribution and signal routing operate in the same layer but with distinct functional zones, increasing overall routing capacity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9570395B1Semiconductor device having buried power rail

Publication Date: 2017.02.14 SAMSUNG ELECTRONICS CO LTD

AI summary

A semiconductor device includes: a substrate; a power rail on the substrate; an active layer on the substrate and at same layer as the power rail; and a contact electrically connecting the power rail to the active layer. The active layer includes source/drain terminals.