Dual-Layer MTJ Top Contact for Short-Resistant Low-Height MRAM

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current MRAM fabrication methods require tall top electrodes to prevent electrical shorts, which increases the MRAM cell height, limiting its integration into advanced semiconductor nodes.

Innovation Solution

A dual layer top contact structure is introduced, comprising a wider conductive lower contact with outwardly or inwardly sloped sidewalls and a narrower conductive upper contact, which physically and electrically connects to the lower contact, thereby reducing the overall MRAM cell height.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single layer top contact is used to connect to the top electrode, then the structure is simple, but the MRAM cell height increases due to the need for tall top electrodes to prevent electrical shorts

Engineering Contradiction:

Improvecontact structure complexityVSAvoidMRAM cell height

Core Design Contradiction:

Device complexityVSLength of stationary object

Solution Approach 1:

The top contact is divided into two separate conductive layers (first conductive layer and second conductive layer) instead of using a single layer. The first conductive layer has a first contact opening and the second conductive layer has a second contact opening, allowing each layer to be independently optimized in height and width to prevent electrical shorts while reducing overall cell height

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution transitions from a single-layer contact structure to a multi-layer contact structure, adding the vertical dimension of layering to solve the problem. By distributing the contact function across multiple layers at different heights, the design achieves both short height prevention and reduced overall cell height

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If tall top electrodes are used to prevent electrical shorts, then reliability improves, but the MRAM cell height increases

Engineering Contradiction:

Improveelectrical short preventionVSAvoidMRAM cell height

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The contact structure is segmented into two conductive layers, each with its own contact opening. The first conductive layer provides initial contact and the second conductive layer provides additional contact path, together ensuring reliable electrical connection while allowing each layer to be shorter than a single tall electrode would need to be

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dual layer structure provides redundant contact paths before electrical shorts can occur. By having two separate conductive layers with contact openings, the design creates a buffer zone that prevents shorts even if one layer is compromised, thereby improving reliability without requiring excessive height

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS12219881B2Dual layer top contact for magnetic tunnel junction stack

Publication Date: 2025.02.04 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A semiconductor device includes a dual layer top contact upon a MTJ stack. The dual layer top contact includes lower contact and upper contact. The lower contact may be wider and/or shallower relative to the upper contact. This wide and/or shallow geometry of the lower contact may decrease the propensity for over etching, during the formation of the upper contact, opening downward into the MTJ stack and may therefore prevent undesired shorting of the MTJ stack. Further, the lower contact may further protect the MTJ stack even when the upper contact is misaligned to the MTJ stack.