Embedded Catalyst for Low-Temperature Silicon Oxide ALD
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Solution Overview
Problem
Conventional atomic layer deposition methods for silicon oxide films face challenges with low growth rates and high substrate temperatures, leading to diffusion issues and undesirable by-products, particularly in miniature semiconductor devices where precise control and low-temperature processing are required.
Innovation Solution
A catalyzed atomic layer deposition process using a silicon-and-oxygen-containing precursor with a nitrogen-containing catalytic ligand, which forms a silicon bridge bond between surface-bound oxygens, allowing for deposition at low temperatures and increased growth rates by reducing the number of precursor exposures needed to achieve a target thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional CVD process is used to deposit silicon oxide film, then deposition temperature can be reduced to below 450°C, but growth rate becomes very low and atomic layer control is lost
Solution Approach 1:
The patent introduces a catalyst (such as pyridine or other nitrogen-containing compounds) as an intermediary substance that mediates the reaction between silicon precursor and oxygen source. The catalyst enables the reaction to proceed at lower temperatures by providing an alternative reaction pathway with lower activation energy, thus maintaining growth rate while reducing substrate temperature
Solution Approach 2:
The patent changes the chemical parameters of the deposition system by introducing catalytic species that modify the reaction kinetics. By changing the chemical environment through catalyst addition, the system achieves low-temperature deposition with maintained growth rates, transforming the reaction mechanism from direct thermal decomposition to catalyst-mediated reaction
2Reliability
If conventional oxidation process is used at high temperatures (>1000°C), then silicon oxide film can be formed with good quality, but diffusion occurs at interfaces degrading electrical characteristics
Solution Approach 1:
The patent fundamentally changes the temperature parameter from conventional high-temperature oxidation (>1000°C) to low-temperature catalyzed deposition (<200°C). This parameter change eliminates thermal diffusion at interfaces while still forming high-quality silicon oxide through the catalyst-mediated reaction pathway, preserving electrical characteristics
3Temperature
If additional catalyst step is introduced to enable low-temperature deposition, then substrate temperature can be reduced below 200°C, but deposition rate further decreases
Solution Approach 1:
The patent merges the catalyst function with the deposition process by using catalysts that remain active throughout the deposition cycle. The catalyst is introduced in the first step and continues to facilitate reactions in subsequent steps, eliminating the need for separate catalyst introduction steps and maintaining continuous deposition activity
Solution Approach 2:
The patent ensures continuous catalytic action throughout the deposition process by using catalysts that remain active across multiple deposition cycles. The catalyst continuously facilitates the reaction between silicon precursor and oxygen source, maintaining steady deposition rates without interruption or additional introduction steps
4Manufacturing precision
If multiple precursor exposures are used to achieve target film thickness, then atomic layer control can be maintained, but number of process steps increases reducing overall efficiency
Solution Approach 1:
The catalyst acts as an intermediary that enhances the reactivity and efficiency of each precursor exposure step. By improving the effectiveness of each individual step through catalysis, the target film thickness can be achieved in fewer cycles while maintaining atomic layer control through the self-limiting nature of the catalyzed reaction
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 efficient deposition of silicon oxide films at low substrate temperatures, increasing growth rates and reducing by-product formation, while maintaining atomic layer control and conformality, thus addressing the limitations of existing methods.
Implementation Method 1
The SiCl4 source reacts with the hydroxyl group in this first deposition step, and —SiCl3 is adsorbed on the surface of the substrate
Implementation Method 2
Such a reaction is referred to as self-limiting. At this point, the surface of the substrate is terminated with —SiCl3 surface chemical species
Implementation Method 3
H2O reacts with the —SiCl3 surface chemical species to generate adsorption of the hydroxyl group thereto and HCl by-products
Implementation Method 4
A catalyst, e.g. pyridine, may be introduced sequentially, following exposure of the surface to the silicon source described above in order to facilitate deposition at lower substrate temperatures
Implementation Method 5
Silicon oxide CVD processes typically occur at temperatures ranging from 600° C. to 800° C. or below 450° C. depending on the application
Data Source
AI summary
Catalyzed atomic layer deposition from a reduced number of precursors is described. A deposition precursor contains silicon, oxygen and a catalytic ligand. A hydroxyl-terminated substrate is exposed to the deposition precursor to form a silicon bridge bond between two surface-bound oxygens. The surface-bound oxygens were part of two surface-bound hydroxyl groups and the adsorption of the deposition precursor liberates the hydrogens. The silicon atom is also chemically-bound to one or two additional oxygen atoms which were already chemically-bound to the silicon within a same deposition precursor molecule. At least one of the additional oxygen atoms is further chemically-bound to the catalytic ligand either directly or by way of a hydrocarbon chain. Further exposure of the substrate to moisture (H2O) results in displacement of the additional oxygen which are replaced by hydroxyl groups from the moisture. The surface is again hydroxyl-terminated and the process may be repeated. The catalytic nature of the reaction enables the deposition to occur at low substrate temperatures. The chemically-embedded nature of the catalyst increases the deposition per cycle thereby reducing the number of precursor exposures to grow a film of the same thickness.