Multi-Layered Protective Layer for Phase Change Memory
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Solution Overview
Problem
Conventional methods for manufacturing phase change memory devices often result in cracks or voids at the interface between the chalcogenide material and the protective layer, leading to device failure, whether due to high-temperature processing causing outgassing or low-temperature processing resulting in poor film conformity.
Innovation Solution
A method involving the formation of a phase change memory device with a multi-layered protective layer comprising nitride and oxide layers, and the use of sealing layers formed at controlled temperatures to prevent outgassing and ensure better film conformity, including a first sealing layer at a low temperature to prevent cracks and a second sealing layer at a higher temperature for improved conformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed by a high temperature process, then the protective layer provides good protection, but temperatures exceeding about 300° C. cause the underlying chalcogenide material to outgass, leading to cracks or voids at the interface
Solution Approach 1:
The protective layer is divided into multiple sub-layers with different functions: a first protective layer formed at low temperature to prevent outgassing damage, and a second protective layer formed at higher temperature to provide enhanced protection and conformity. This segmentation allows each layer to operate within its optimal temperature range without causing harm to the underlying chalcogenide material.
Solution Approach 2:
The formation temperature parameter is changed and optimized for different protective layers. The first protective layer is formed at a controlled low temperature (below 300° C.) to prevent outgassing, while the second protective layer is formed at a higher temperature to improve conformity and protection. This parameter change resolves the contradiction between protection quality and outgassing prevention.
2Object-affected harmful factors
If a protective layer is formed by a low temperature process, then outgassing is prevented, but the resultant protective layer exhibits poor film conformity, leading to cracks or voids at the interface
Solution Approach 1:
The protective layer structure is segmented into two distinct layers: a first protective layer formed at low temperature to prevent outgassing, and a second protective layer formed at higher temperature to achieve good film conformity. Each layer performs its specific function optimally without the drawbacks of the alternative approach.
Solution Approach 2:
The protective layer is constructed as a composite structure with multiple materials and formation conditions. The first protective layer (formed at low temperature) and second protective layer (formed at higher temperature) work together as a composite system, combining the advantages of both low-temperature outgassing prevention and high-temperature conformity achievement.
3Ease of manufacture
If a single protective layer is formed, then the process is simple, but it cannot simultaneously prevent outgassing and achieve good film conformity
Solution Approach 1:
The protective layer formation process is segmented into two sequential steps: first forming a protective layer at low temperature to prevent outgassing, then forming a second protective layer at higher temperature to achieve good conformity. This segmentation enables both outgassing prevention and conformity achievement, resolving the contradiction between process simplicity and dual functionality.
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 effectively prevents the formation of cracks and voids, enhancing the reliability and performance of phase change memory devices by maintaining the stability of the chalcogenide material and improving the conformity of the protective layer.
Implementation Method 1
The chalcogenide semiconductors, also called phase change materials, have a crystalline state and an amorphous state. In the crystalline state, the phase change materials have low resistivity; while in the amorphous state, they have high resistivity.
Implementation Method 2
The heater comprises a conductive material that, due to its resistive properties, heats up when a sufficiently high voltage differential is applied.
Implementation Method 3
The set pulse heats the phase change material to a temperature higher than a crystallization temperature, but below a melting temperature, for a time longer than the required crystalline time, for the crystallization to take place.
Implementation Method 4
The reset pulse, which turns the phase change material into an amorphous state, heats the phase change material to a temperature higher than the melting temperature. The temperature is then quickly dropped below the crystallization temperature for a time period short enough to reduce or prevent the crystallization.
Data Source
AI summary
A phase change memory device and a method of manufacture are provided. The phase change memory device includes a phase change layer electrically coupled to a top electrode and a bottom electrode, the phase change layer comprising a phase change material. A mask layer is formed overlying the phase change layer. A first sealing layer is formed overlying the mask layer, and a second sealing layer is formed overlying the first sealing layer.