MIM Capacitor Dielectric Stack to Block Metal Inter-Diffusion
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Solution Overview
Problem
The increasing complexity and miniaturization of semiconductor integrated circuits (ICs) pose challenges in processing and manufacturing, particularly in the formation of metal-insulator-metal (MIM) capacitors, where inter-diffusion of metals leads to time-dependent dielectric breakdown (TDDB) failures and affects the capacitance and voltage characteristics.
Innovation Solution
The use of a dielectric stack comprising high-k dielectric layers sandwiched between oxygen-rich first and second dielectric layers, formed through plasma enhanced atomic layer deposition (PEALD), acts as a barrier to prevent metal inter-diffusion and enhances capacitance, reducing TDDB failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal-insulator-metal capacitor structures are used to increase functional density, then capacitance and frequency characteristics are improved, but metal inter-diffusion occurs leading to time-dependent dielectric breakdown failures
Solution Approach 1:
The patent introduces an intermediary layer (such as a diffusion barrier layer or protective dielectric layer) between the metal electrodes and the insulator material. This intermediary layer prevents direct contact and inter-diffusion between metal atoms and insulator atoms, thereby eliminating the harmful effect of metal inter-diffusion that causes time-dependent dielectric breakdown, while still allowing the capacitor to function with high capacitance and frequency characteristics.
Solution Approach 2:
The patent employs composite material structures where multiple materials with complementary properties are combined. For example, using a stack of different dielectric materials with varying barrier properties, or combining metal layers with protective coating materials, creates a composite structure that provides both the desired electrical performance and protection against metal inter-diffusion, thus resolving the contradiction between reliability and harmful inter-diffusion effects.
2Ease of manufacture
If MIM capacitors are formed in metal interconnect layers to reduce process integration complications, then manufacturing complexity is reduced, but metal inter-diffusion still occurs affecting capacitance and voltage characteristics
Solution Approach 1:
By inserting an intermediary barrier layer within the MIM capacitor structure during the interconnect layer formation process, the patent prevents metal inter-diffusion that would otherwise degrade capacitance and voltage characteristics. This allows the capacitor to be formed within the interconnect layers (maintaining ease of manufacture) while the barrier layer ensures precise control over electrical characteristics by preventing material contamination and diffusion.
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 configuration improves the total capacitance and reduces initial voltage while minimizing metal inter-diffusion, thereby enhancing the reliability and performance of MIM capacitors.
Implementation Method 1
formed through plasma enhanced atomic layer deposition (PEALD)
Implementation Method 2
the first and second dielectric layers function as barrier layers to prevent inter-diffusion of metals between the conductive layers and the high-k dielectric layer
Data Source
AI summary
Embodiments of present disclosure provide a MIM capacitor device structure including a first conductive layer disposed over a substrate and a dielectric stack disposed on the first conductive layer. The dielectric stack includes a first dielectric layer disposed on the first conductive layer, and the first dielectric layer has a first oxygen concentration. The dielectric stack further includes a high-k dielectric layer disposed on the first dielectric layer, and the high-k dielectric layer has a second oxygen concentration different from the first oxygen concentration. The dielectric stack further includes a second dielectric layer disposed on the high-k dielectric layer, and the second dielectric layer has a third oxygen concentration different from the second oxygen concentration. The structure further includes a second conductive layer disposed on the dielectric stack.