Atomic Layer Deposition Pulse-Hold Purging for Precursor Efficiency
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Solution Overview
Problem
Existing atomic layer deposition (ALD) methods are inefficient due to slow reaction kinetics of certain reactants, leading to extended pulsing periods, inefficient utilization of precursors, and potential parasitic deposition, which affects the lifetime of the ALD apparatus.
Innovation Solution
The method involves pulsing a first reactant gas into a reactor assembly, holding it with a continuous low-flow inactive gas, and purging with a higher-flow inactive gas, while maintaining a constant pressure using a pressure control system with two-state valves and an active non-zero flow restrictor to enhance reactant utilization and prevent parasitic deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extended reactant pulse times are used to ensure sufficient substrate exposure, then reaction completeness is improved, but precursor utilization efficiency deteriorates
Solution Approach 1:
The reactant pulse is segmented into two distinct phases: an initial pulse phase followed by a hold phase. During the pulse phase, reactant gas is supplied at a first flow rate to ensure sufficient substrate exposure. During the hold phase, the reactant gas flow is maintained at a lower second flow rate to complete the reaction without excessive precursor accumulation. This segmentation allows the process to achieve both complete reaction and improved precursor utilization efficiency.
Solution Approach 2:
The reactant gas flow rate is dynamically adjusted during the deposition process. The system transitions from a higher flow rate during the pulse phase to a lower flow rate during the hold phase. This dynamic adjustment allows the process to adapt to the changing reaction requirements: initial rapid saturation of the substrate surface followed by slower, more efficient precursor consumption to complete the reaction.
2Productivity
If high reactant pulse intensity is used to saturate the substrate, then deposition speed is improved, but parasitic deposition increases
Solution Approach 1:
The reactant supply is segmented into a pulse phase with higher flow rate for rapid deposition, followed by a hold phase with lower flow rate. This segmentation allows the system to achieve high deposition speed during the pulse phase while preventing parasitic deposition during the hold phase when the reactant flow is reduced but substrate coverage is already sufficient.
Solution Approach 2:
The patent converts the potential harm of excessive reactant supply (which causes parasitic deposition) into a benefit by using the hold phase to deliberately reduce reactant flow after initial saturation is achieved. This controlled reduction prevents parasitic deposition while maintaining sufficient substrate coverage, effectively turning what would be a harmful condition into a beneficial control mechanism.
3Manufacturing precision
If reactive species are supplied at high concentration to ensure surface saturation, then layer uniformity is improved, but reactant waste increases
Solution Approach 1:
The reactant supply is divided into a pulse phase with higher concentration for ensuring surface saturation and achieving uniform layer formation, followed by a hold phase with reduced concentration. This segmentation allows the system to achieve the necessary layer uniformity during the pulse phase while minimizing reactant waste during the hold phase when the surface is already saturated.
Solution Approach 2:
The reactant concentration parameter is changed dynamically between the pulse and hold phases. During the pulse phase, higher concentration is supplied to ensure rapid and uniform surface coverage. During the hold phase, the concentration is reduced to prevent excessive reactant accumulation and waste, while maintaining sufficient coverage to complete the 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 improves the efficiency of ALD processes by optimizing reactant utilization, reducing parasitic deposition, and extending the lifetime of the ALD apparatus components.
Implementation Method 1
The inactive gas flows can form diffusion barriers to prevent back diffusion of the reactant gases
Implementation Method 2
maintaining a constant pressure in the feed line can comprise: creating a pressure control signal from a pressure sensor disposed upstream of the reaction space, and varying the conductance of the flow restrictor by communicating the pressure control signal to the flow restrictor
Implementation Method 3
an active non-zero flow restrictor disposed on the exhaust line between the reaction space and the vacuum source... varying the conductance of the flow restrictor
Implementation Method 4
The layer growth is based on self-limiting surface reactions that take place on the surface of the substrate to form a solid-state layer of atoms or molecules
Data Source
AI summary
Atomic layer deposition methods, methods for depositing a layer on a substrate, and associated atomic layer deposition apparatus are disclosed. The methods disclosed include pulsing a reactant gas into a reactor assembly, holding the reactant gas within the reactor assembly for a time period, and purging the reactant gas from the reactor assembly.