MRAM MTJ Structure With Selective Etch Isolation

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Solution Overview

Problem

Conventional etch back operations in semiconductor manufacturing for MRAM devices result in insufficient isolation distance between the (N+1)th metal line and the MTJ, leading to electrical shorts and compromised data storage performance due to the thinning of the top electrode and ILD, necessitating a trade-off between isolation and contact interface.

Innovation Solution

A selective etch method is adopted to preserve the thickness of the top electrode and ILD, creating a recess region surrounded by the (N+M)th metal layer and an isolation region defined by a dielectric layer, ensuring a sufficient ratio of recess to isolation distance to maintain proper isolation without electrical shorts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If conventional etch back operation is used to create isolation, then isolation distance is increased, but top electrode and ILD thickness are reduced leading to electrical shorts

Engineering Contradiction:

Improveisolation distanceVSAvoidtop electrode thickness

Core Design Contradiction:

Length of stationary objectVSManufacturing precision

Solution Approach 1:

The patent divides the etch back operation into two distinct stages: a first etch back operation that performs partial etching to create initial isolation, and a second etch back operation that performs selective etching to complete isolation while preserving the top electrode and ILD thickness. This segmentation allows the process to achieve sufficient isolation distance without compromising the thickness of critical layers, thereby preventing electrical shorts between the (N+1)th metal line and the MTJ.

Inventive Principle:

Principle #1Segmentation

2Length of stationary object

If conventional etch back operation is used, then isolation distance is increased, but contact interface is compromised

Engineering Contradiction:

Improveisolation distanceVSAvoidcontact interface

Core Design Contradiction:

Length of stationary objectVSReliability

Solution Approach 1:

The patent segments the etch back process into two operations where the first operation creates initial isolation and the second operation selectively removes material to complete isolation. This ensures that sufficient isolation distance is achieved while the contact interface between the (N+1)th metal line and the top electrode is preserved, maintaining reliable electrical connection and preventing shorts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The selective etch back operation applies different etching conditions to different regions: it completely etches the ILD in the isolation region to achieve proper isolation distance, while preserving the top electrode and ILD thickness in the contact region. This local differentiation ensures both sufficient isolation and maintained contact interface quality, preventing electrical shorts while maintaining reliability.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20240023460A1Semiconductor structure and method of manufacturing the same

Publication Date: 2024.01.18 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides a semiconductor structure, including an Nth metal layer, a bottom electrode over the Nth metal layer, a magnetic tunneling junction (MTJ) over the bottom electrode, a top electrode over the MTJ, and an (N+M)th metal layer over the Nth metal layer. N and M are positive integers. The (N+M)th metal layer surrounds a portion of a sidewall of the top electrode. A manufacturing method of forming the semiconductor structure is also provided.