Room Temperature SiO2 ALD Film via Lewis Base Purge
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Solution Overview
Problem
Current silicon oxide deposition techniques at room temperature suffer from significant contamination issues, particularly with chlorine and nitrogen, due to the inclusion of contaminants like NH4Cl salts, which affect the quality and purity of the film.
Innovation Solution
A process involving sequential exposure of silicon tetrachloride, water, and a Lewis base agent, such as ammonia, with optimized purge times and gas flow ratios, is used to minimize contamination, employing nitrogen gas purges after each precursor exposure to reduce the incorporation of impurities in the film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If silicon oxide deposition is performed at room temperature using conventional techniques, then the deposition process is compatible with temperature-sensitive substrates, but the film quality deteriorates due to significant chlorine and nitrogen contamination from NH4Cl salts
Solution Approach 1:
The deposition process is divided into distinct sequential steps: (a) exposing the substrate to silicon tetrachloride vapor, (b) purging with nitrogen gas, (c) exposing to water vapor, and (d) purging again. This segmentation allows complete removal of reaction byproducts and excess precursors between deposition steps, preventing NH4Cl salt formation and contamination while maintaining room temperature processing
Solution Approach 2:
Nitrogen gas is used as an inert purge atmosphere to replace reactive species and byproducts in the reaction chamber between deposition steps. This inert environment prevents unwanted secondary reactions that would form contaminated salts, while allowing the deposition to proceed at room temperature without requiring high-temperature vacuum conditions
2Manufacturing precision
If sequential exposure of precursors is used to reduce contamination, then film purity improves, but the deposition cycle time increases due to multiple exposure and purge steps
Solution Approach 1:
The purge times are optimized to be sufficient for complete removal of byproducts and excess precursors but not excessively long. The nitrogen gas flow rate and purge duration are tuned to achieve the minimum necessary cleaning action, removing just enough contaminants to prevent NH4Cl formation without unnecessarily extending the cycle time
Solution Approach 2:
The process parameters including nitrogen gas flow rate, purge time duration, precursor exposure times, and pressure levels are systematically optimized to achieve the fastest possible cycle time that still maintains film purity below contamination thresholds. This allows the sequential process to approach the speed of continuous deposition while maintaining superior purity
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 results in silicon oxide films with reduced chlorine contamination levels, achieving a growth rate of 0.5 Å/cycle and maintaining a low level of impurities, suitable for applications requiring low-κ porous silicon oxide layers with superhydrophilic and insulating properties.
Implementation Method 1
the proposed mechanism that considered the hydrogen bonding between the Lewis base and either the SiOH* surface species or the H2O reactant
Implementation Method 2
invention is directed to a process of atomic layer deposition... performed at room temperature, involving at least three precursors... the one Lewis base agent being in various instances ammonia. The process comprises the steps of (a) exposing on the substrate during an exposure time the one Lewis base agent, (b) exposing on the substrate during an exposure time the silicon tetrachloride, and (c) exposing on the substrate during an exposure time the water
Data Source
AI summary
A method for atomic layer deposition for the deposition of silicon oxide on a substrate, performed at room temperature, involving at least three precursors, being silicon tetrachloride, water and one Lewis base agent, being in various instances ammonia. The process comprises the steps of exposing on the substrate during an exposure time (a) the one Lewis base agent, (b) the silicon tetrachloride, and (c) the water. The process is remarkable in that at least one step of purge with nitrogen gas is performed after each of the steps (a), (b) and (c) during a purge time. Additionally, a film of silicon oxide which is remarkable in that it comprises a low level of chlorine contaminant and a significant degree of porosity with pores, the pores being in various instances micropores, mesopores or nanopores.