DRAM Contact Fabrication via Segmented Conductive Layers
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Solution Overview
Problem
The challenge in fabricating Dynamic Random Access Memory (DRAM) devices is the formation of voids during the scaling down of contact sizes, which reduces the reliability of the devices due to defects in the trench filling process, leading to increased contact resistance and reduced element density.
Innovation Solution
A method involving the formation of isolation regions, word lines, and conductive material layers, followed by a series of etching and deposition processes to create contacts with a lining layer and protection layer, ensuring the contact area is maintained and voids are minimized, thereby improving the contact area and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the contact size is scaled down to increase element density, then the element density is improved, but voids are formed during trench filling which reduces device reliability
Solution Approach 1:
The contact structure is divided into multiple segments: a lower conductive material layer filling the trench, and an upper conductive material layer formed after etching back the first dielectric layer. This segmentation allows each layer to be optimized independently, with the lower layer providing structural support and the upper layer ensuring reliable electrical connection, thereby preventing void formation while maintaining high element density
Solution Approach 2:
The lower conductive material layer is formed in advance before the upper conductive material layer. This preliminary action ensures that the trench is properly filled and prepared, providing a stable foundation for subsequent processing steps and preventing void formation in the final contact structure
2Quantity of substance
If the contact size is scaled down, then the element density is improved, but contact resistance increases due to void formation
Solution Approach 1:
The contact is segmented into lower and upper conductive material layers, with the lower layer providing a void-free foundation and the upper layer ensuring low-resistance electrical connection. This segmentation allows optimization of each layer's properties to minimize overall contact resistance while maintaining high element density
Solution Approach 2:
The lower conductive material layer acts as an intermediary between the substrate and the upper conductive material layer, providing a stable, void-free interface that ensures reliable electrical connection and minimizes contact resistance in scaled-down contacts
3Ease of manufacture
If a simple filling process is used, then the manufacturing process is simpler, but voids are formed reducing contact reliability
Solution Approach 1:
The filling process is segmented into two stages: first forming the lower conductive material layer, then etching back the first dielectric layer and forming the upper conductive material layer. This segmentation transforms a complex single-step process into two simpler, more controllable steps, each with lower void formation risk
Solution Approach 2:
The lower conductive material layer is formed as a preliminary step before the upper layer. This preliminary action prepares the trench structure in advance, ensuring proper filling and providing a stable base for subsequent processing, thereby improving overall contact reliability
4Ease of manufacture
If the contact height is reduced, then the manufacturing process is simpler, but contact resistance increases
Solution Approach 1:
The contact structure is segmented vertically into lower and upper conductive material layers. This segmentation allows the total contact height to be distributed across multiple layers, with each layer contributing to the overall electrical connection, thereby maintaining low contact resistance without requiring excessive height in a single layer
Data Source
AI summary
A method for fabricating a memory device includes: forming a first dielectric layer disposed on a substrate, and a first opening in the first dielectric layer; filling a lower portion of the first opening with a first conductive material layer; conformally forming a lining layer over sidewalls of an upper portion of the first opening and a top surface of the first conductive material layer; filling the upper portion of the first opening with a second conductive material layer; etching back the second conductive material layer and the lining layer to form a recess; conformally forming a protection layer on sidewalls and a bottom portion of the recess and a top surface of the first dielectric layer; forming a second opening that penetrates through the protection layer, the second conductive material layer, the lining layer and the first conductive material layer; forming a pair of contacts in the first opening.