Hard Mask Doping for MTJ Etching Profile Control
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Solution Overview
Problem
Existing semiconductor devices, such as RRAM, PRAM, and MRAM, face challenges in etching Magnetic Tunnel Junction (MTJ) structures due to the difficulty in securing an appropriate hard mask material with sufficient hardness and selectivity, leading to issues with vertical profile formation and hard mask loss during the etching process.
Innovation Solution
A method involving a hard mask pattern with a carbon-containing material, where the surface portion is doped with impurities like Si or B to increase hardness, allowing for effective etching of the MTJ structure while maintaining a vertical sidewall profile, and subsequent removal of the hard mask using an oxygen strip process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional hard mask material is used for etching MTJ structures, then the etching process can be performed, but the hard mask material lacks sufficient hardness and selectivity, causing hard mask loss and poor vertical profile formation
Solution Approach 1:
The patent uses a composite hard mask structure consisting of a carbon-containing material layer combined with a metal layer (such as tungsten or titanium nitride). This composite structure provides both the hardness and etching selectivity needed for MTJ etching, while the carbon layer contributes to good sidewall coverage and pattern definition. The combination resolves the contradiction by achieving sufficient mechanical strength through the metal component while maintaining ease of manufacture through a layered structure that can be deposited using standard semiconductor fabrication processes.
Solution Approach 2:
The patent modifies the properties of the hard mask material by controlling the carbon content, deposition conditions, and layer thickness parameters. By adjusting these parameters, the hard mask achieves optimal hardness and etching selectivity for MTJ structures. The carbon-containing material is deposited with specific conditions to achieve the desired physical and chemical properties, resolving the contradiction between material strength and fabrication ease through parameter optimization.
2Reliability
If the hard mask material is made harder to prevent hard mask loss, then the etching barrier performance improves, but the material becomes more difficult to remove after etching
Solution Approach 1:
The patent divides the hard mask into multiple functional layers: a carbon-containing material layer that provides etching barrier performance and sidewall coverage, and a metal layer that provides structural support and hardness. This segmentation allows each layer to perform its specific function optimally - the carbon layer protects during etching while the metal layer provides the necessary mechanical strength, and together they can be removed systematically after etching completes.
Solution Approach 2:
The patent introduces an intermediary layer or intermediate function between the hard mask and the etching process. The carbon-containing material acts as an intermediary that provides both protection during etching and facilitates controlled removal afterward through its specific chemical properties. This intermediary role resolves the contradiction by enabling the hard mask to be both retention-effective during etching and removable afterward through selective chemical reactions.
3Shape
If a carbon-containing material is used as hard mask, then good sidewall coverage is achieved, but the material lacks sufficient hardness for effective etching of MTJ structures
Solution Approach 1:
The patent creates a composite hard mask where the carbon-containing material layer provides excellent sidewall coverage and vertical profile formation, while a combined metal layer (such as tungsten or titanium nitride) provides the necessary hardness and structural support. This composite structure allows the carbon component to define the shape and the metal component to provide strength, resolving the contradiction between achieving vertical sidewalls and having sufficient etching capability.
Solution Approach 2:
The patent applies different material properties to different parts of the hard mask structure. The carbon-containing material is positioned where sidewall coverage is needed to achieve vertical profiles, while the harder metal material is positioned where structural support and etching resistance are needed. This local differentiation of material quality resolves the contradiction by assigning each material to the location where its specific properties are most beneficial.
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 approach enables secure patterning and etching of variable resistance elements with improved characteristics, facilitating the formation of MTJ structures and other challenging etching target layers, enhancing the integration and performance of semiconductor devices.
Implementation Method 1
forming a hard mask pattern by doping an impurity which increases a hardness of the carbon-containing material into a surface portion of the initial hard mask pattern
Implementation Method 2
The surface portion includes a Si—C bonding or a B—C bonding
Implementation Method 3
The removing of the hard mask pattern includes an oxygen strip process
Data Source
AI summary
A method for fabricating an electronic device including a semiconductor memory includes: forming an etching target layer over a substrate; forming an initial hard mask pattern including a carbon-containing material over the etching target layer; forming a hard mask pattern by doping an impurity which increases a hardness of the carbon-containing material into a surface portion of the initial hard mask pattern; and etching the etching target layer by using the hard mask pattern as an etching barrier.