Cu Wiring Formation via Ru Wetting Layer and Ionized PVD
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Solution Overview
Problem
Current methods for forming Cu wiring in semiconductor devices face challenges in achieving high burying efficiency and low resistance, particularly in dual damascene structures with varying trench widths, due to poor wettability of Cu with barrier films and limited step coverage of physical vapor deposition (PVD) techniques.
Innovation Solution
A method involving the formation of a barrier film, a wetting target layer, and a Cu-based seed film by PVD, followed by heating to flow the seed film into trenches and vias, and subsequent PVD deposition of a Cu-based film on a wetting target layer to fill trenches, while using high-temperature ionized PVD for improved step coverage and reduced impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PVD is used to form Cu seed film on barrier film, then the process is simple and fast, but the step coverage is low and Cu wettability for barrier film is poor
Solution Approach 1:
A wetting target layer made of Ru or Co is introduced as an intermediary between the barrier film and the Cu-based seed film. This wetting target layer has high wettability with Cu, enabling the Cu-based seed film to be properly formed by PVD without the poor wettability issues between Cu and the barrier film directly.
2Manufacturing precision
If heating is performed to flow Cu-based seed film into vias, then fine vias can be filled effectively, but wide trenches cannot be filled efficiently
Solution Approach 1:
The filling process is segmented into two distinct stages: (1) heating to flow the Cu-based seed film into vias, and (2) ionized PVD to deposit Cu-based film into trenches. This segmentation allows each process to be optimized for its specific purpose, avoiding the inefficiency of using heating for wide trench filling.
3Reliability
If ionized PVD is used to deposit Cu-based film, then impurities are reduced and resistance is lowered, but the process complexity increases
Solution Approach 1:
The physical state parameters of the PVD process are changed by performing ionized PVD at a high temperature (room temperature or higher). This parameter change enables the Cu-based film to be deposited with better crystal structure and fewer impurities, achieving lower resistance without requiring additional process steps.
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 enhances burying efficiency and reduces resistance by allowing easy filling of fine vias and trenches without voids, minimizing impurities, and optimizing crystal size for lower resistance, while avoiding inefficient reflow processes for wide trenches.
Implementation Method 1
filling the via by heating the substrate on which the Cu-based seed film is already formed and flowing the Cu-based seed film into the via
Implementation Method 2
forming, on the surface of the substrate on which the via is already filled, a Cu-based film made of the Cu or Cu alloy by PVD under a condition that allows the Cu-based film to be flown on the wetting target layer to bury the Cu-based film in the trench
Implementation Method 3
forming, on the surface of the substrate on which the via is already filled, a Cu-based film made of the Cu or Cu alloy by PVD under a condition that allows the Cu-based film to be flown on the wetting target layer
Data Source
AI summary
A method of forming, on a substrate having on a surface thereof a film having a trench of a preset pattern and a via at a bottom of the trench, a Cu wiring by burying Cu or Cu alloy in the trench and the via includes forming a barrier film (process 2); forming, on a surface of the barrier film, a wetting target layer of Ru or the like (process 3); forming, on a surface of the wetting target layer, a Cu-based seed film by PVD (process 4); filling the via by heating the substrate and flowing the Cu-based seed film into the via (process 5); and forming, on the substrate surface, a Cu-based film made of the Cu or Cu alloy by PVD under a condition where the Cu-based film is flown on the wetting target layer to bury the Cu-based film in the trench (process 6).