Amorphized Metal Nitride Bottom Electrode Adhesion in MTJ Devices
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Solution Overview
Problem
The protection film in MTJ elements tends to peel off from the bottom conductive layer due to low adhesion, often caused by surface damage during formation and volume expansion during heat treatment, necessitating the selection of an optimal protection film material.
Innovation Solution
The use of an amorphized metal nitride for the bottom electrode and a nitrogen-containing insulating film for the protection film improves adhesion between the two layers, preventing peeling and foreign material intrusion, thereby maintaining the integrity of the MTJ element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional materials (Ta, Ti, Cu for bottom electrode; nitride film or alumina for protection film) are used, then the manufacturing process is simple, but the adhesion between bottom electrode and protection film is low causing peeling
Solution Approach 1:
The patent uses a composite structure where the bottom electrode is formed by amorphized metal nitride (such as TaN, WN) and the protection film is a nitrogen-containing insulating film. This composite material approach creates strong chemical bonding through nitrogen diffusion at the interface, resolving the adhesion problem between conventional materials while maintaining manufacturing feasibility.
Solution Approach 2:
The patent changes the material parameters by using amorphized metal nitride instead of conventional metals (Ta, Ti, Cu) and nitrogen-containing insulating film instead of conventional protection films. This parameter change in material composition and structure enables strong adhesion while preventing peeling during device operation and heat treatment.
2Ease of manufacture
If the bottom electrode surface is damaged during formation, then the electrode can be formed, but the protection film formed over it is likely to peel off
Solution Approach 1:
The patent applies preliminary action by forming the amorphized metal nitride bottom electrode with a naturally smooth and chemically active surface that predisposes it for strong bonding. The amorphized structure creates a surface that is inherently more adhesive, preventing subsequent peeling issues before they can occur during device operation.
Solution Approach 2:
By changing the bottom electrode material to amorphized metal nitride, the surface properties are fundamentally altered. The amorphized structure provides a smooth, chemically active surface that enhances adhesion to the nitrogen-containing protection film, eliminating the peeling problem caused by surface damage in conventional materials.
3Reliability
If heat treatment is applied to the bottom electrode, then the electrode properties are improved, but the electrode expands in volume causing protection film peeling
Solution Approach 1:
The patent changes the thermal expansion parameters by using amorphized metal nitride, which has different thermal expansion characteristics compared to conventional metals. This parameter change reduces the volume expansion during heat treatment, preventing the protection film from peeling while still allowing the electrode to achieve desired properties through heat treatment.
Solution Approach 2:
The composite material system of amorphized metal nitride bottom electrode and nitrogen-containing protection film creates a thermally stable interface. The nitrogen diffusion bonding and matched thermal expansion characteristics of this composite structure prevent peeling during heat treatment, allowing reliable improvement of electrode properties.
4Reliability
If the protection film peels off, then foreign materials can intrude through the interface, but selecting optimal protection film material increases complexity
Solution Approach 1:
The patent employs a composite material system where amorphized metal nitride bottom electrode and nitrogen-containing insulating protection film create a strongly bonded interface. This composite structure prevents foreign material intrusion through nitrogen diffusion bonding, protecting MTJ element characteristics without requiring complex material optimization procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the adhesion between the bottom electrode and the protection film, preventing peeling and foreign material intrusion, which helps in suppressing the deterioration of MTJ element characteristics.
Implementation Method 1
the adhesion can be improved between the bottom electrode and the protection film
Implementation Method 2
the bottom electrode is formed by amorphized metal nitride and the protection film is formed by an insulating film containing nitrogen
Data Source
AI summary
To provide a semiconductor device that has an improved adhesion between a bottom conductive layer and a protection film protecting an MTJ element.This semiconductor device includes a bottom electrode formed over a semiconductor substrate, an MTJ element part formed over a part of the bottom electrode by lamination of a bottom magnetic film, an insulating film, a top magnetic film, and a top electrode in this order, and a protection film formed over the bottom electrode so as to cover the MTJ element part, wherein the bottom electrode is formed by amorphized metal nitride and the protection film is formed by an insulating film containing nitrogen.