MIM Capacitor Buffer Layer for TDDB Reliability
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Solution Overview
Problem
In eDRAM devices, MIM capacitors with high-k insulators face reliability issues due to thin insulator thicknesses, which fail to pass time-dependent dielectric breakdown tests, leading to limited TDDB lifetime and reduced reliability as technology scales down.
Innovation Solution
A method for forming MIM capacitors involves treating the bottom electrode in an oxygen-containing environment to convert its top layer into a buffer layer, followed by forming an insulating layer and a top electrode, enhancing the interface and reducing surface roughness, thereby improving capacitor reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-k insulators with thickness below 100 Å are used to increase capacitance, then capacitance is improved, but TDDB lifetime and reliability deteriorate
Solution Approach 1:
A buffer layer comprising metal oxynitride is introduced between the bottom electrode (metal nitride) and the high-k insulating layer. This intermediary buffer layer improves the interface quality and reduces defects, enabling the thin high-k insulator to achieve both high capacitance and acceptable TDDB lifetime without direct contact between the electrode and insulator that would cause reliability failures.
2Quantity of substance
If insulator thickness is scaled down to increase capacitance density, then capacitance density is improved, but interface quality and reliability worsen
Solution Approach 1:
The buffer layer acts as an intermediary that improves interface quality between the bottom electrode and the thin high-k insulator. By introducing this intermediate layer, the interface defects are reduced and the quality is enhanced, allowing thin insulators to be manufactured with better interface characteristics and improved reliability.
3Ease of manufacture
If conventional MIM capacitor structure is used, then fabrication is simple, but reliability and TDDB lifetime are insufficient
Solution Approach 1:
The capacitor structure is enhanced by introducing a composite material approach: the bottom electrode is formed as metal nitride, the buffer layer as metal oxynitride, and the insulating layer as high-k dielectric material. This composite structure combines the benefits of different materials to achieve both ease of manufacture (using standard deposition processes) and improved reliability through better interface characteristics.
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
The approach significantly increases the TDDB lifetime and capacitance of MIM capacitors, with nearly two orders greater stress test results and improved breakdown voltages, demonstrating enhanced reliability and performance compared to conventional methods.
Implementation Method 1
treating the bottom electrode in an oxygen-containing environment to convert a top layer of the bottom electrode into a buffer layer
Implementation Method 2
annealing the bottom electrode in an oxygen-containing environment to convert a top portion of the bottom electrode into a buffer layer
Implementation Method 3
the oxygen-containing environment comprises a gas or a plasma selected from the group consisting essentially of O2, O3 (ozone), and combinations thereof
Data Source
AI summary
A capacitor and methods for forming the same are provided. The method includes forming a bottom electrode; treating the bottom electrode in an oxygen-containing environment to convert a top layer of the bottom electrode into a buffer layer; forming an insulating layer on the buffer layer; and forming a top electrode over the insulating layer.