Self-Aligned Source-Channel Junctions in 3D Memory Devices
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in forming self-aligned source-channel junctions efficiently, which affects the performance and density of memory cells.
Innovation Solution
A semiconductor structure is developed with an alternating stack of insulating and electrically conductive layers, featuring a memory opening filled with a memory film, a vertical semiconductor channel, and a source cap structure surrounded by the memory film, along with a source layer contacting the source cap, formed through a method involving spacer layers, sacrificial material layers, and etch processes to create precise geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to form source-channel junctions, then the manufacturing process is simpler, but the memory device density and performance are lower
Solution Approach 1:
The source cap structure is formed in advance at the bottom portion of the memory opening before the vertical semiconductor channel is created. This preliminary formation of the source cap defines the future source-channel junction location, enabling self-alignment when the channel is subsequently formed around it, thus achieving high density without requiring complex alignment processes.
Solution Approach 2:
The source cap structure acts as an intermediary element that mediates between the source layer and the vertical semiconductor channel. It is laterally surrounded by the memory film and positioned to contact both the source layer and the channel, serving as a structural bridge that enables precise junction formation while simplifying the overall manufacturing process.
2Manufacturing precision
If self-aligned source-channel junctions are formed using the disclosed method, then manufacturing precision is improved, but the number of process steps increases
Solution Approach 1:
The source cap structure serves itself as the alignment reference for forming the vertical semiconductor channel. The channel is formed to laterally surround the cap structure, which automatically ensures precise alignment between the source and channel without requiring external alignment marks or complex photolithography steps, thus achieving high precision while maintaining manufacturing efficiency.
Solution Approach 2:
The source cap structure is nested within the memory opening and is laterally surrounded by the memory film, while the vertical semiconductor channel is formed around the cap. This nested arrangement creates a hierarchical structure where each component serves as a template for the next, ensuring precise spatial relationships without additional alignment steps.
3Reliability
If the source cap structure is laterally surrounded by the memory film, then junction reliability is improved, but the device structure becomes more complex
Solution Approach 1:
The memory film is selectively positioned to laterally surround the source cap structure at the specific location where the source-channel junction forms. This localized placement of the memory film provides enhanced reliability at the critical junction interface while maintaining simpler structures in other regions of the device, thus improving reliability without uniformly increasing overall device complexity.
Data Source
AI summary
A semiconductor structure includes an alternating stack of insulating layers and electrically conductive layers, a memory opening vertically extending through the alternating stack, a memory opening fill structure located in the memory opening and including a memory film, a vertical semiconductor channel, and a semiconductor source cap structure which is at least partially laterally surrounded by the memory film and which contacts the vertical semiconductor channel, and a source layer contacting at least a first end surface segment of the semiconductor source cap structure.