Multi-Layer Electrode Work Function Optimization
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Solution Overview
Problem
Semiconductor memory devices face challenges in reducing leakage current to increase integration density, as the reduction in capacitor thickness leads to decreased effective work function and increased leakage current.
Innovation Solution
A semiconductor memory device design featuring a capacitor with a second electrode comprising layers of A-metal nitride, an intermediate layer with A-metal and B-metal, and a nickel layer, where the B-metal has a higher work function than the A-metal nitride, is used. This configuration increases the effective work function and reduces leakage current while maintaining or increasing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the capacitor electrode is reduced to increase integration density, then the integration density is improved, but the effective work function decreases and leakage current increases
Solution Approach 1:
The second electrode is divided into multiple layers (first layer with A-metal nitride, second layer with A-metal and B-metal, third layer with B-metal) to segment the functional requirements. Each layer contributes differently to the work function and capacitance, allowing the thin electrode structure to maintain high effective work function while achieving integration density
Solution Approach 2:
The electrode uses composite material structure combining A-metal nitride, A-metal, B-metal, and nickel layers. This composite structure enables the thin electrode to simultaneously achieve high effective work function (through B-metal with higher work function) and sufficient capacitance (through nickel layer), resolving the contradiction between thin thickness and performance
2Quantity of substance
If the thickness of the capacitor electrode is reduced to increase integration density, then the integration density is improved, but the capacitance decreases
Solution Approach 1:
Different layers of the second electrode have different local qualities: the first layer (A-metal nitride) provides interface stability, the second layer (A-metal and B-metal) optimizes work function, and the third layer (B-metal with higher work function) maximizes effective work function. This local differentiation allows the thin electrode to maintain sufficient capacitance while achieving integration density
Solution Approach 2:
The composite structure with nickel layer and B-metal layer enables the thin electrode to achieve both high capacitance and high integration density. The nickel provides sufficient capacitance in reduced thickness, while the B-metal layers maintain high effective work function
Data Source
AI summary
A semiconductor memory device includes a capacitor on a substrate. The capacitor includes a first electrode, a second electrode on the first electrode, and a dielectric layer between the first electrode and the second electrode. The second electrode includes a first layer, a second layer, and a third layer. The first layer is adjacent to the dielectric layer, and the third layer is spaced apart from the first layer with the second layer interposed therebetween. A concentration of nickel in the third layer is higher than a concentration of nickel in the first layer.