Three-Node Access Device for Vertical 3D Memory
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As design rules shrink, there is a challenge in fabricating memory devices with limited semiconductor space, particularly in forming DRAM arrays where existing access devices have high off-current and gate/drain induced leakage, and require body potential control due to minority carrier presence.
Innovation Solution
The formation of three-node access devices without body region contacts, integrating horizontal access devices with vertical access lines and digit lines, which operate without minority carriers, reducing the need for body potential control and minimizing gas phase doping, thereby lowering off-current and gate/drain induced leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional silicon-based access devices are used, then the memory device can be fabricated with existing processes, but the off-current is high and gate/drain induced leakage occurs
Solution Approach 1:
The patent changes the material parameter from silicon to a different semiconductor material that inherently exhibits lower off-current and reduced gate/drain induced leakage characteristics. This material substitution fundamentally alters the electrical parameters of the access device to achieve the desired reliability improvement.
Solution Approach 2:
The patent removes the body region contact structure from the access device fabrication. By taking out the body contact requirement, the device simplifies the fabrication process while simultaneously reducing the harmful leakage paths that exist in traditional silicon-based devices with body contacts.
2Ease of operation
If access devices with body region contacts are used, then body potential control can be achieved, but the device complexity increases and fabrication becomes more difficult
Solution Approach 1:
The patent extracts and removes the body contact element from the access device structure. This elimination of the body contact region simplifies the device architecture while the new material system maintains adequate electrical control without requiring separate body potential management.
Solution Approach 2:
The new access device structure integrates multiple functions into a simpler configuration. The access device simultaneously provides channel control and source/drain functionality without requiring separate body contact structures, achieving multi-functionality with reduced complexity.
3Ease of manufacture
If gas phase doping is used in fabrication, then source/drain regions can be formed, but the process complexity increases and contamination risks arise
Solution Approach 1:
The patent replaces the gas phase doping process with a solid-state or alternative deposition method for forming source/drain regions. This substitution eliminates the need for complex gas phase chemistry control and reduces contamination risks associated with gaseous precursors while maintaining effective dopant incorporation.
Solution Approach 2:
The patent changes the fabrication parameter from gas phase doping to an alternative doping or deposition method. This parameter change simplifies the fabrication process by eliminating the complexity of gas phase chemistry control, flow management, and contamination prevention associated with traditional doping techniques.
Data Source
AI summary
Systems, methods and apparatus are provided for storage node after horizontally oriented, three-node access device formation in vertical three dimensional (3D) memory. An example method includes a method for forming arrays of vertically stacked memory cells, having horizontally oriented access devices and vertically oriented access lines. The method includes depositing alternating layers of a dielectric material and a sacrificial material to form a vertical stack. A plurality of first vertical openings are formed through the vertical stack to form elongated vertical, pillar columns with sidewalls in the vertical stack. A first conductive material is conformally deposited on a gate dielectric material in the first vertical openings. Portions of the first conductive material are removed to form a plurality of separate, vertical access lines along the sidewalls of the elongated vertical, pillar columns. A second vertical opening is formed through the vertical stack to expose a first region of the sacrificial material. The first region is selectively removed to form a first horizontal opening in which to form a first source/drain material, a channel material, and a second source/drain material of the three-node access device. A third vertical opening is formed through the vertical stack to expose a second region of the sacrificial material. The second region is selectively removed after formation of the three-node access device in the first region to form a second horizontal opening in which to form a storage node electrically coupled to the first source/drain material.