Capacitor Metal Bilayer for High-k Dielectric Reliability
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Solution Overview
Problem
MIM capacitors in semiconductor devices face challenges in achieving high capacitance density, high frequency stability, reduced leakage, and minimized charge trapping, with existing materials like ruthenium leading to capacitance loss and reliability issues when reduced in thickness.
Innovation Solution
A novel capacitor structure featuring a bilayer working electrode with a noble metal and a metal nitride cap layer, where the noble metal is in a zero valent state and the metal nitride is sufficiently thin to avoid increasing the equivalent oxide thickness, while being in direct contact with a high-k dielectric layer, enhancing capacitance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the dielectric layer is reduced to increase capacitance density, then capacitance is improved, but reliability deteriorates due to insufficient thickness
Solution Approach 1:
The patent uses a composite top electrode structure consisting of a noble metal layer (Ru, Pt, Pd, or Ir) combined with a metal nitride cap layer (TiN, TaN, ZrN, HfN, or NbN). This composite structure enables the dielectric layer to be sufficiently thin for high capacitance density while maintaining reliability through the protective cap layer that prevents electrode material diffusion and degradation into the dielectric.
2Ease of manufacture
If ruthenium metal is used as electrode material to improve work function and patterning, then ease of manufacture is improved, but capacitance deteriorates due to capacitance loss and increased EOT
Solution Approach 1:
The metal nitride cap layer serves as an intermediary between the noble metal electrode and the dielectric layer. This cap layer prevents direct contact and interaction between the noble metal and dielectric, eliminating the capacitance loss and EOT increase that occur when noble metals are in direct contact with the dielectric, while still allowing the noble metal to provide its beneficial patterning and work function properties.
3Length of stationary object
If noble metal thickness is reduced to decrease EOT, then EOT is improved, but capacitance stability deteriorates at high frequency
Solution Approach 1:
The composite structure of noble metal plus metal nitride cap layer maintains capacitance stability at high frequency even when the noble metal thickness is reduced. The cap layer provides a stable interface that prevents degradation and maintains consistent electrical properties, allowing thin noble metal layers to be used without sacrificing high-frequency performance.
4Quantity of substance
If dielectric layer thickness is reduced to increase capacitance, then capacitance is improved, but leakage increases due to insufficient thickness
Solution Approach 1:
The metal nitride cap layer acts as an intermediary protective barrier between the electrode and dielectric layer. This cap layer prevents direct interaction that would cause leakage paths, allowing the dielectric layer to be made thinner for higher capacitance while maintaining low leakage current through the protected interface.
Data Source
AI summary
A method for using a metal bilayer is disclosed. First, a bottom electrode is provided. Second, a dielectric layer which is disposed on and is in direct contact with the lower electrode is provided. Then, a metal bilayer which serves as a top electrode in a capacitor is provided. The metal bilayer is disposed on and is in direct contact with the dielectric layer. The metal bilayer consists of a noble metal in direct contact with the dielectric layer and a metal nitride in direct contact with the noble metal.