Local Silicidation of Via Bottoms in Semiconductor Metallization
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Solution Overview
Problem
In advanced integrated circuits, the interface between copper interconnects and dielectric cap layers is a major diffusion path for electromigration-induced material transport, leading to premature device failure, and existing solutions like conductive cap layers and surface modifications can increase leakage currents and dielectric breakdown.
Innovation Solution
A copper/silicon compound, or copper silicide, is locally formed at the interface between metal lines and vias to enhance electromigration behavior without requiring sophisticated metal cap layers, using techniques like plasma-based treatments and silicon diffusion to improve surface characteristics and reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive cap layers or surface modifications are applied to improve electromigration behavior, then electromigration performance is improved, but leakage currents and dielectric breakdown increase
Solution Approach 1:
The patent applies local silicidation specifically at the via bottom interface region rather than uniformly across the entire copper surface. This localized treatment modifies only the critical area where electromigration is most severe, forming copper silicide at the via bottom while leaving other regions unchanged, thereby improving electromigration performance without the harmful effects associated with broader surface modifications
2Reliability
If barrier layers are added to prevent copper diffusion, then diffusion suppression is improved, but device complexity and process complexity increase
Solution Approach 1:
The patent combines the barrier layer formation and copper surface modification into a single integrated process step. The silicon-containing barrier layer is deposited concurrently with the copper fill process, eliminating the need for separate barrier deposition and surface modification steps, thereby reducing process complexity while maintaining effective copper diffusion suppression
3Productivity
If via dimensions are reduced to increase circuit density, then productivity is improved, but electromigration-induced material transport increases
Solution Approach 1:
The patent changes the chemical and physical parameters of the via bottom surface by forming copper silicide through local silicidation. This parameter change in the material composition and surface properties at the via bottom increases electromigration resistance, allowing smaller via dimensions to be used without compromising reliability
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 approach improves electromigration performance at critical interfaces without increasing overall resistance or process complexity, enhancing the reliability of copper-based interconnects by forming copper silicide in a controlled manner, thus reducing premature failure.
Implementation Method 1
a silicon species is locally introduced into a portion of the metal line, i.e., a copper-containing surface area, in order to locally provide a copper/silicon compound or a copper silicide
Implementation Method 2
using techniques like plasma-based treatments and silicon diffusion to improve surface characteristics
Data Source
AI summary
Electromigration behavior in complex metallization systems of semiconductor devices may be enhanced at critical areas between a metal line and a via by locally forming a copper/silicon compound. In some illustrative embodiments, the formation of the copper/silicon compound may be combined with other treatments for cleaning the exposed surface areas and/or modifying the molecular structure thereof.