3D Memory Source Contact Structure Using Tubular Semiconductor Tips
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in efficiently forming top source contacts to doped semiconductor source tips, which affect the performance and integration of memory structures.
Innovation Solution
A method involving the formation of a semiconductor source structure with a pillar semiconductor source portion and a tubular semiconductor source portion having an inner cavity, along with a metallic source layer, is employed to create a top source contact in a three-dimensional memory device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional top source contact formation method is used, then the manufacturing process is simpler, but the contact reliability and electrical performance are insufficient
Solution Approach 1:
The semiconductor source structure is divided into two distinct portions: a pillar semiconductor source portion and a tubular semiconductor source portion. This segmentation allows each portion to serve specific functions - the pillar portion provides mechanical support and initial contact, while the tubular portion enables enhanced electrical connection through its cavity structure that receives the metallic source layer, thereby improving contact reliability without requiring entirely new manufacturing approaches
Solution Approach 2:
The metallic source layer is nested within the cavity of the tubular semiconductor source portion. This nesting configuration ensures intimate contact between the metallic layer and the semiconductor material, maximizing electrical connection reliability. The tubular structure effectively houses the metallic contact material, creating a robust integrated contact structure
2Reliability
If a complex multi-portion source structure is formed, then the electrical connection is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The pillar semiconductor source portion is formed first as a preliminary structure before the tubular portion is added. This sequential formation approach allows the pillar to establish the basic contact footprint and electrical pathway, upon which the tubular structure is subsequently built. The preliminary pillar structure guides the subsequent manufacturing steps and simplifies the overall process by providing a foundation for the more complex tubular portion
Solution Approach 2:
Different portions of the semiconductor source structure are formed with different geometries and properties tailored to their specific functions. The pillar portion has a solid cylindrical geometry optimized for mechanical stability and initial contact, while the tubular portion has a hollow cylindrical geometry optimized for receiving and integrating the metallic source layer. This local differentiation of structure and function enables improved electrical connection without requiring the entire structure to be complex
3Reliability
If the semiconductor source structure has a larger width, then the contact area is increased, but the integration density is reduced
Solution Approach 1:
The tubular semiconductor source portion introduces a vertical dimension through its cavity structure. Instead of simply increasing the horizontal footprint to expand contact area, the invention utilizes the vertical space within the tubular cavity to house the metallic source layer. This three-dimensional configuration increases the effective contact area and connection reliability without proportionally increasing the planar footprint, thereby maintaining higher integration density
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 enhances the integration and performance of three-dimensional memory devices by providing a reliable and efficient connection to the semiconductor source tips, improving the overall functionality and manufacturing process.
Implementation Method 1
oxidizing surface portions of the semiconductor material layer and the semiconductor substrate around a bottom portion of the memory opening, whereby a semiconductor oxide spacer structure including a first cylindrical portion having a first thickness at a level of the semiconductor substrate and a second cylindrical portion having a second thickness at a level of the semiconductor material layer is formed
Data Source
AI summary
An alternating stack of insulating layers and spacer material layers is formed over a substrate. The spacer material layers are formed as, or are subsequently replaced with, electrically conductive layers. A memory opening is formed through the alternating stack. A memory material layer, a semiconductor source structure, a vertical semiconductor channel, a dielectric core, and a drain region are formed in the memory opening. Dopants in the semiconductor source structure are activated after formation of the drain region. Subsequently, the substrate and a bottom portion of the memory film are removed and a metallic source layer is formed on the semiconductor source structure.