Single Crystal Silicon Node on Silicide for Memory Diode Drivers
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Solution Overview
Problem
Current technologies face challenges in providing reliable and cost-effective access devices for programmable resistance memory cells that can deliver sufficient current while avoiding cross-talk and being compatible with high-performance logic circuitry, particularly due to issues with parasitic device activation and the difficulty in forming single crystal silicon nodes on top of silicides.
Innovation Solution
The development of a memory device with a diode driver comprising a silicide element on a silicon substrate, featuring a single crystal silicon node on top of the silicide, which acts as a conductive element, and a manufacturing method that forms protruding single crystal silicon elements with a silicide conductor acting as a buried word line, separating the single crystal silicon features from the underlying substrate to prevent carrier migration and parasitic device activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single crystal silicon node is formed on top of a silicide element, then the current drive capability and electrical integrity are improved, but the manufacturing complexity increases due to the difficulty of forming single crystal silicon on silicide
Solution Approach 1:
The device is segmented into distinct functional regions: a silicide access device region and a single crystal silicon node region. The silicide element serves as the access device while the single crystal silicon node provides the memory function, allowing each material to be optimized for its specific purpose without requiring integration at the material level
Solution Approach 2:
An intermediary structure is introduced between the silicide element and the single crystal silicon node. This intermediary layer or interface structure enables the connection between the two dissimilar materials, facilitating current flow while maintaining the integrity of both the silicide access device and the single crystal silicon node
2Ease of manufacture
If doped polysilicon is used for both diode regions, then the manufacturing process is simplified, but the off current becomes unacceptably high
Solution Approach 1:
Different regions of the diode structure are assigned different material qualities: one region uses doped polysilicon for ease of manufacture while the other region uses doped single-crystal silicon for low off current. This local differentiation allows each region to optimize for its specific functional requirement
Solution Approach 2:
The diode structure employs a composite material approach, combining doped polysilicon and doped single-crystal silicon in a single device. This composite structure leverages the manufacturing advantages of polysilicon while incorporating the electrical performance benefits of single-crystal silicon
3Ease of manufacture
If buried diffusion lines are used for interconnection, then the manufacturing process is simplified, but parasitic devices are activated causing breakdown or current leakage
Solution Approach 1:
The harmful function of parasitic device activation is extracted and eliminated by replacing the buried diffusion line interconnection method with an alternative approach. The silicide-based access device provides the necessary interconnection function without creating parasitic devices that cause breakdown or leakage
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 provides reliable current delivery for programmable resistance memory cells, reduces cross-talk, and is compatible with high-performance logic circuitry, while enabling the formation of single crystal silicon nodes on top of silicides, enhancing the structural and electrical integrity of the memory device.
Implementation Method 1
A self-aligned process for forming silicide involves depositing a silicide precursor over a substrate that includes exposed regions of silicon, and annealing the silicide precursor to form a silicide in the exposed regions
Implementation Method 2
Phase change based memory materials, such as chalcogenide based materials and similar materials, can be caused to change phase between an amorphous state and a crystalline state by application of electrical current
Implementation Method 3
The change from crystalline to amorphous, referred to as reset herein, is generally a higher current operation, which includes a short high current density pulse to melt or breakdown the crystalline structure
Data Source
AI summary
A memory device includes a diode driver and a data storage element, such as an element comprising phase change memory material, and in which the diode driver comprises a silicide element on a silicon substrate with a single crystal silicon node on the silicide element. The silicide element separates the single crystal silicon node from the underlying silicon substrate, preventing the flow of carriers from the single crystal silicon node into the substrate, and is capable of acting as a conductive element for interconnecting devices on the device. The single crystal silicon node acts as one terminal of a diode, and a second semiconductor node is formed on top of it, acting as the other terminal of the diode.