Ruthenium Storage Node Deposition via Surface Flushing
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Solution Overview
Problem
In semiconductor devices, particularly in sub-60 nm DRAM capacitors, achieving the required equivalent oxide thickness and uniform deposition of metal storage nodes like ruthenium is challenging due to high aspect ratios and hydrophilic surfaces, leading to island formation, poor step coverage, and prolonged incubation cycles in current ALD and CVD methods.
Innovation Solution
A method involving a metal source flushing process to alter the surface characteristics of the hydrophilic storage node oxide layer, improving adherence of metal-based materials, followed by sequential formation of a dielectric layer and plate electrode using advanced deposition techniques like ALD, PEALD, and cyclic CVD to enhance step coverage and reduce incubation cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ALD method is used to deposit Ru layer on storage node oxide layer, then uniform deposition is attempted, but source material adheres more to areas where Ru is already deposited causing island formation and non-uniform deposition
Solution Approach 1:
The patent applies a preliminary flushing process using metal source material before the main Ru deposition. This preliminary action modifies the surface characteristics of the storage node oxide layer, creating a more uniform nucleation layer that prevents preferential adhesion to already-deposited Ru areas, thereby avoiding island formation and achieving uniform deposition.
Solution Approach 2:
The patent introduces an intermediary layer formed by the flushing process between the storage node oxide layer and the Ru layer. This intermediary layer acts as a mediator that promotes uniform nucleation and prevents direct preferential adhesion of Ru source material to existing Ru deposits, resolving the island formation issue.
2Manufacturing precision
If ALD method is used for storage node formation, then deposition control is improved, but incubation cycle is prolonged with bare deposition on storage node oxide layer during initial cycles
Solution Approach 1:
The patent performs a preliminary flushing action using metal source material before the main deposition process. This preliminary action prepares the surface in advance, creating favorable conditions for immediate Ru deposition and eliminating the prolonged incubation cycle where no deposition occurs during initial cycles.
Solution Approach 2:
The flushing process uses the Ru source material itself to prepare the surface, making the source material serve a dual purpose: both as the deposition precursor and as the agent that prepares the surface for deposition, thereby reducing the incubation period.
3Quantity of substance
If high aspect ratio storage node contact holes are used in sub-60 nm devices, then capacitance density is improved, but step coverage requirement increases to above 90%
Solution Approach 1:
The patent applies a preliminary flushing process to modify the surface characteristics of the high aspect ratio contact holes before Ru deposition. This preliminary action ensures uniform nucleation throughout the deep contact holes, achieving the required >90% step coverage even in sub-60 nm devices with high aspect ratios.
Solution Approach 2:
The patent changes the surface parameters of the storage node oxide layer through the flushing process, modifying surface energy and wetting characteristics to enable uniform Ru deposition throughout high aspect ratio contact holes, achieving the required step coverage for increased capacitance density.
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 enables uniform deposition of storage nodes with improved step coverage and reduced incubation cycles, increasing device throughput and yield while minimizing defects, thereby stabilizing capacitor manufacturing processes and enhancing device performance.
Implementation Method 1
flushing a metal source onto the insulation layer to change a characteristic of a surface of the insulation layer to improve adherence of a metal-based material to the surface of the insulation
Implementation Method 2
an atomic layer deposition (ALD) method is employed to deposit a Ru layer as the storage node
Implementation Method 3
a chemical vapor deposition (CVD) method
Implementation Method 4
sequentially forming a dielectric layer and a plate electrode over the metal-based storage node
Data Source
AI summary
A method for fabricating a capacitor in a semiconductor device is provided. The method includes forming an insulation layer over a substrate; flushing a metal source onto the insulation layer to change a characteristic of a surface of the insulation layer to improve adherence of a metal-based material to the surface of the insulation layer; forming a storage node comprising the metal-based material over the flushed insulation layer; and sequentially forming a dielectric layer and a plate electrode over the metal-based storage node.