Nitrogen Plasma CESL Treatment for Copper Interconnect Void Control
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Solution Overview
Problem
The integration circuit (IC) industry faces challenges in reducing resistance-capacitance (RC) delay due to increased capacitance from decreased distances between interconnects, leading to stress-induced void formation and degradation in IC performance, particularly at the copper etch stop layer (CESL)/copper interface, which affects the reliability and speed of ICs.
Innovation Solution
A nitrogen plasma treatment is applied to the CESL to increase nitrogen concentration and bonding, enhancing its ability to block copper diffusion and reduce void formation by increasing the surface nitrogen concentration at the CESL/copper interface, thereby preventing copper vacancies from accumulating and minimizing stress-induced voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the distance between interconnects is decreased to reduce RC delay, then the capacitance increases, but this leads to stress-induced void formation and degradation in IC performance
Solution Approach 1:
The patent applies nitrogen plasma treatment specifically to the CESL/copper interface region to increase nitrogen concentration and bonding at this critical location. This localized enhancement of nitrogen bonding prevents copper diffusion and void formation at the interface without affecting the overall interconnect geometry, thereby maintaining signal speed while improving reliability.
Solution Approach 2:
The patent changes the nitrogen concentration and bonding strength parameters at the CESL/copper interface through nitrogen plasma treatment. By increasing the nitrogen concentration and bonding energy at this specific interface, the material properties are optimized to prevent copper diffusion and void formation, resolving the contradiction between reduced geometry (faster speed) and void formation (poorer reliability).
2Reliability
If nitrogen plasma treatment is applied to increase nitrogen concentration at CESL/copper interface, then copper diffusion blocking ability is enhanced, but the process complexity increases
Solution Approach 1:
The nitrogen plasma treatment is applied to the CESL before copper deposition, preparing the interface in advance to prevent copper diffusion. This preliminary action ensures that the interface is pre-conditioned with enhanced nitrogen bonding, which will block copper diffusion during subsequent processing steps, thereby improving reliability without requiring complex additional steps later in the fabrication process.
Solution Approach 2:
The patent replaces mechanical or physical barrier methods with a chemical approach using nitrogen plasma treatment. Instead of relying solely on physical barrier layers, the nitrogen plasma creates strong chemical bonds at the CESL/copper interface, providing a more effective and integrated solution for blocking copper diffusion while maintaining process simplicity.
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 nitrogen plasma treatment effectively reduces copper diffusion and void formation, improving the reliability and performance of ICs by enhancing the blocking ability of the CESL and maintaining the integrity of copper interconnects, thus optimizing the performance of scaled-down ICs.
Implementation Method 1
A nitrogen plasma treatment is applied to the CESL to increase nitrogen concentration and bonding
Data Source
AI summary
Interconnect structures exhibiting reduced accumulation of copper vacancies along interfaces between contact etch stop layers (CESLs) and interconnects, along with methods for fabrication, are disclosed herein. A method includes forming a copper interconnect in a dielectric layer and depositing a metal nitride CESL over the copper interconnect and the dielectric layer. An interface between the metal nitride CESL and the copper interconnect has a first surface nitrogen concentration, a first nitrogen concentration and/or a first number of nitrogen-nitrogen bonds. A nitrogen plasma treatment is performed to modify the interface between the metal nitride CESL and the copper interconnect. The nitrogen plasma treatment increases the first surface nitrogen concentration to a second surface nitrogen concentration, the first nitrogen concentration to a second nitrogen concentration, and/or the first number of nitrogen-nitrogen bonds to a second number of nitrogen-nitrogen bonds, each of which minimizes accumulation of copper vacancies at the interface.