Phase Change Memory GST Layer Adherence via Alkyl Silane Coating
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Solution Overview
Problem
The existing methods for manufacturing phase change memory devices face challenges in achieving constant thickness and improved step coverage of the phase change layer, particularly with GeSbTe (GST) layers, which result in high reset currents due to difficulties in controlling the growth and densification of the GST layer, and the organic metal compounds used have poor adherence on silicon oxide layers at low temperatures.
Innovation Solution
A surface treatment method is employed using a coating layer with a chemical structure represented by (alkyl)x(OR)y(Cl)zSi, formed via dip coating or spin coating, followed by atomic layer deposition (ALD), to enhance adherence and control the thickness of the phase change layer, reducing the reset current and improving integration density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a GST layer is formed using a PVD method, then the deposition speed is improved, but the growth control and densification of the GST layer deteriorate
Solution Approach 1:
An organic metal compound layer is deposited as an intermediary layer before the GST layer. This organic layer serves as a mediator that enables better control of GST growth and improves densification when subsequently converted to GST through thermal processing, resolving the contradiction between deposition speed and growth control.
Solution Approach 2:
The method involves changing the chemical composition and physical state parameters through a two-step process: first depositing an organic metal compound layer, then converting it to GST phase through thermal processing. This parameter transformation enables precise control of GST layer properties while maintaining efficient deposition.
2Manufacturing precision
If a GST layer is formed using an ALD method, then the growth control and densification are improved, but the deposition speed deteriorates
Solution Approach 1:
The GST layer formation process is segmented into two distinct stages: (1) rapid deposition of an organic metal compound layer using PVD method, and (2) thermal conversion of the organic layer to GST phase. This segmentation allows each stage to optimize for its specific function, achieving both high deposition speed and precise growth control.
Solution Approach 2:
The method replaces the traditional direct physical vapor deposition of GST with a chemical substitution approach: depositing an organic metal compound that is then thermally converted to GST. This substitution enables better growth control and densification while maintaining deposition efficiency.
3Quantity of substance
If the thickness of the phase change layer is increased to improve storage capacity, then the integration density is improved, but the reset current increases
Solution Approach 1:
The method creates a composite structure where the GST layer is formed from an organic metal compound precursor. This composite approach enables precise thickness control at the nanometer scale, allowing sufficient storage capacity while minimizing the actual GST material volume and corresponding reset current requirements.
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
The method ensures a constant thickness and improved step coverage of the phase change layer, leading to a significant reduction in reset current by more than 50% and increased integration density of the phase change memory device.
Implementation Method 1
the coating layer may have a chemical structure for contributing to the adherence of an alkyl radical to the surface of the bottom layer
Implementation Method 2
the organic metal compound may not be easily absorbed on a silicon oxide layer at a relatively low temperature
Implementation Method 3
A phase change material is a material that may switch between a crystalline state and an amorphous state with changes in temperature
Implementation Method 4
The temperature of the phase change material for switching the phase change material in the crystalline state to the amorphous state should be greater than the melting point of the phase change material
Data Source
AI summary
A method of surface treating a phase change layer may include, before forming the phase change layer, forming a coating layer on a surface of a bottom layer on which the phase change layer is to be formed, wherein the coating layer has a chemical structure for contributing to the adherence of an alkyl radical to the surface of the bottom layer. After forming the coating layer, the phase change layer may be formed using an atomic layer deposition (ALD) method.