Phase Change Memory Fabrication Using Coplanar Electrode and Shallow Opening
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Solution Overview
Problem
Conventional phase change memory (PCM) fabrication processes are complex and costly, requiring multiple etching steps and resulting in deep openings that increase the risk of errors and affect PCM performance.
Innovation Solution
A method for fabricating PCM that reduces the number of etching processes by forming a bottom electrode structure with a flush top surface, using a mask layer with a spacer to expose the electrode, and depositing a heating layer and phase change layer in a shallower opening, which reduces power consumption and improves thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PCM fabrication processes are used with multiple etching steps to form deep openings, then the bottom contact electrode can be placed to enhance PCM efficiency, but the fabrication complexity and cost increase
Solution Approach 1:
The patent combines the bottom electrode formation and the opening formation into a single etching process. The bottom electrode structure is formed with a top surface that is substantially coplanar with the substrate surface, eliminating the need for separate etching steps to create deep openings. This merging of steps reduces fabrication complexity while maintaining the ability to place the bottom contact electrode for enhanced PCM efficiency.
Solution Approach 2:
The bottom electrode structure is prepared in advance with a coplanar top surface before the mask layer is formed. This preliminary preparation ensures that subsequent deposition steps can proceed without requiring deep openings, thereby simplifying the overall fabrication process while still enabling efficient electrode contact.
2Reliability
If deep openings are formed through multiple etching processes, then the bottom contact electrode can be positioned, but the risk of fabrication errors increases
Solution Approach 1:
By combining electrode formation and opening creation into one etching step, the patent reduces the cumulative error risk associated with multiple sequential etching processes. The single process ensures consistent positioning while minimizing opportunities for fabrication errors.
3Reliability
If deep openings are formed in the substrate, then the bottom contact electrode can be placed, but heat diffusion increases reducing thermal efficiency
Solution Approach 1:
The patent creates a shallow opening with the bottom electrode top surface coplanar with the substrate surface, rather than forming deep openings. This reduces the volume of material through which heat can diffuse, thereby improving thermal efficiency and reducing energy loss while still achieving proper electrode contact for PCM performance.
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 simplified process lowers fabrication costs, reduces power consumption, and enhances the thermal efficiency and performance of the PCM by minimizing heat diffusion and error risks.
Implementation Method 1
Phase change materials constituting the phase change layer can be changed into a crystalline state or an amorphous state due to the heating effect by an applied electric current
Implementation Method 2
When the phase change layer is in a crystalline state, PCRAM has a low electrical resistance and the value of memory is assigned to be 0. When the phase change layer is in an amorphous state, PCRAM has a high electrical resistance
Data Source
AI summary
A phase change memory and its fabrication method are provided. A bottom electrode structure is provided through a substrate. A mask layer is formed on the substrate and the bottom electrode structure. A first opening is formed in the mask layer to expose the bottom electrode structure. A spacer is formed on sidewalls and bottom surface portions of the first opening to expose a surface portion of the bottom electrode structure. The first opening including the spacer therein has a bottom width less than a top width. A heating layer is formed at least on the surface portion of the bottom electrode structure exposed by the spacer. A phase change layer is formed on the heating layer to completely fill the first opening. A top electrode is formed on the phase change layer and the mask layer.