Vertical Plate-like Bottom Electrode for DRAM Capacitor Stability
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Solution Overview
Problem
As semiconductor memory devices scale down to 20 nm or below, securing sufficient capacitance in DRAM capacitors becomes challenging due to difficulties in maintaining structural stability and achieving sufficient effective capacitance with existing techniques, particularly with the reduction of dielectric layer thickness and electrode height.
Innovation Solution
The semiconductor memory device employs a capacitor design with a vertical plate-like bottom electrode structure supported by mold insulators, which allows for increased height and width, and a dielectric layer with a high-k material to enhance capacitance while maintaining structural stability, and a method of fabricating this structure involves forming mold patterns and conductive layers to create a stable and efficient capacitor configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the thickness of dielectric layer and electrode is reduced to achieve smaller cell area, then the cell area is reduced, but the capacitance becomes insufficient
Solution Approach 1:
The patent transitions from planar 2D electrode structures to vertical 3D structures. The bottom electrode extends vertically along the sidewall of the mold insulator, creating a plate-like structure that increases the effective electrode area without increasing the footprint cell area. This dimensional change allows capacitance to be maintained or improved while cell area is reduced.
Solution Approach 2:
The bottom electrode is formed by nesting it within the sidewall structure of the mold insulator. The electrode material is deposited conformally on the mold insulator sidewall, creating a nested configuration where the electrode is embedded within the insulator structure, maximizing space utilization and capacitance within the available vertical space.
2Quantity of substance
If the height of bottom electrode is increased to secure sufficient capacitance, then the capacitance is improved, but the structural stability deteriorates
Solution Approach 1:
The patent extracts the structural support function from the bottom electrode itself and assigns it to a separate mold insulator component. The mold insulator provides mechanical support and structural stability, while the bottom electrode can be optimized for capacitance without being constrained by structural stability requirements. This separation of functions allows the electrode to achieve sufficient height for capacitance while the mold insulator maintains structural integrity.
3Area of moving object
If the cylindrical structure is used to maximize bottom electrode surface area, then the electrode surface area is increased, but the manufacturing complexity and defect rate increase at 20 nm scale
Solution Approach 1:
Instead of forming a cylindrical electrode structure that requires complex self-aligned deposition and etching processes, the patent inverts the approach by forming a plate-like electrode on the sidewall of a mold insulator. This inverted structure can be fabricated using simpler conformal deposition and planarization processes, reducing manufacturing complexity and defect rates at advanced technology nodes while still achieving sufficient electrode surface area.
Data Source
AI summary
Provided are a semiconductor memory device including a capacitor and a method of fabricating the same. The capacitor may include a plurality of contacts that are electrically connected to the switching device, exposed on the top surface of a substrate, and are arranged in a first direction and a second direction different from the first direction, and the first direction and the second direction are parallel to the substrate; mold insulators that are formed on the substrate between the contacts adjacent to one another in the first direction from among the plurality of contacts, are formed to have a predetermined thickness and have a predetermined width in the second direction, and extend in a direction vertical to the substrate; bottom electrodes that have a vertical plate-like structure, are provided on and supported by sidewalls of the mold insulators, and are electrically and respectively connected to the plurality of contacts.