Variable Flow Valve Pulse Shaping for Uniform ALD Dosing
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Solution Overview
Problem
Current Atomic Layer Deposition (ALD) processes suffer from non-uniformity issues due to short pulse durations and varying gas flow rates across the substrate surface, leading to localized non-uniform precursor dosing.
Innovation Solution
A variable flow valve is used to generate a predetermined flow pulse profile, controlling the gas flow to both inner and outer regions of the substrate support, ensuring consistent dosing and smoother transitions between gas pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional valve is used to generate gas pulses in ALD processes, then the valve can be opened and closed to deliver reactant pulses, but the pulse shape becomes distorted with rising and falling transitions due to pressure drops, and different parts of the substrate surface receive different doses
Solution Approach 1:
The patent applies a variable flow valve that dynamically adjusts its flow characteristics during the pulse duration. The valve transitions from a static on/off state to a dynamic system that modulates flow rate in real-time, enabling compensation for pressure drops and achieving a flat-top pulse shape that delivers uniform precursor dosing across the substrate surface.
Solution Approach 2:
The invention changes the flow rate parameter during the pulse by using a variable flow valve. Instead of maintaining constant flow rate as in conventional systems, the valve adjusts its opening degree throughout the pulse duration to compensate for pressure variations, transforming the pulse shape from distorted to uniform.
2Duration of action of moving object
If the valve transitions quickly from closed to open to minimize transition time, then the rising and falling transitions are reduced, but the pulse duration remains short causing non-uniform dosing across the substrate
Solution Approach 1:
The variable flow valve enables the system to maintain longer pulse durations while preserving uniformity. By dynamically adjusting the valve opening during the pulse, the system can extend the flat-top portion of the pulse without suffering from the pressure drop issues that plack conventional fixed-flow systems, thus allowing longer exposure time for uniform dosing.
Solution Approach 2:
The invention maintains continuous useful action during the pulse by ensuring steady flow delivery to all parts of the substrate throughout the entire pulse duration. The variable flow valve compensates for pressure drops in real-time, keeping the flow rate constant and ensuring that the useful dosing action continues uniformly across the entire substrate surface for the full pulse duration.
3Speed
If gas flow rate increases from center to edge of substrate, then gas delivery speed improves, but non-uniform precursor dosing occurs across the wafer surface
Solution Approach 1:
The variable flow valve enables local quality control by allowing different flow conditions to be maintained at different locations on the substrate. The valve modulates the overall flow to compensate for the natural acceleration from center to edge, ensuring that each region receives the appropriate amount of precursor for uniform dosing across the entire wafer surface.
Solution Approach 2:
The system implements feedback control where the valve positioning is adjusted based on the expected flow distribution pattern. By anticipating the acceleration of gas from center to edge, the variable flow valve pre-compensates by reducing overall flow rate during the pulse, creating a feedback loop that achieves uniform dosing despite the inherent flow acceleration.
Data Source
AI summary
Methods for controlling pulse shape in ALD processes improves local non-uniformity issues of films deposited on substrate surface. The methods include using a variable flow valve creating predetermined pulse shape when a reactant is provided on a substrate surface.