Dual APR Control for ALD Precursor Flow and Concentration
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Solution Overview
Problem
Conventional methods for controlling the flow rate and concentration of liquid materials in Atomic Layer Deposition (ALD) face challenges due to fluctuations in line pressure, especially with high vapor pressure materials, where traditional Mass Flow Controllers (MFCs) are ineffective and Auto Pressure Regulators (APRs) struggle to maintain accurate control.
Innovation Solution
The use of separate APRs for controlling carrier gas pressure and material vapor pressure allows for independent control of material concentration and total flow rate, enabling precise management even with high vapor pressure liquids by adjusting the primary side pressure of the APR within its operation range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single APR is used to control carrier gas pressure for flow rate control, then the total flow rate can be controlled, but the material concentration changes with the flow rate and cannot be controlled independently
Solution Approach 1:
The single APR control function is segmented into two independent APRs: APR1 controls carrier gas pressure (affecting total flow rate) and APR2 controls material vapor pressure (affecting material concentration). This segmentation allows independent control of flow rate and concentration, resolving the coupling problem where changing flow rate inadvertently changed concentration.
2Quantity of substance
If carrier gas pressure is increased to lower material concentration, then the concentration decreases, but the flow rate rises which cannot be controlled
Solution Approach 1:
By segmenting the control functions into two independent APRs, the patent allows concentration to be adjusted via APR2 (material vapor pressure) without affecting the total flow rate controlled by APR1 (carrier gas pressure). This resolves the unintended flow rate increase that occurred when carrier gas pressure was changed for concentration control.
3Measurement precision
If the primary side pressure of APR is raised to APR operation compensation range by adding carrier gas pressure, then the material concentration can be controlled accurately, but the system complexity increases
Solution Approach 1:
The patent introduces a second APR (APR2) downstream of the precursor reservoir to control material vapor pressure independently. This segmentation enables accurate concentration control by ensuring the primary side pressure of APR1 is within its operation compensation range, while APR2 fine-tunes the material vapor pressure. The increased device complexity is justified by the significant improvement in concentration control accuracy.
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 accurate and independent control of flow rate and concentration, effectively addressing the limitations of traditional methods and ensuring precise deposition in ALD processes, including those with high vapor pressure materials, while minimizing material wastage and reducing operational costs.
Implementation Method 1
liquid materials of high vapor pressure, the flow rate cannot be lowered because the line pressure cannot be lowered to or below the material vapor pressure
Data Source
AI summary
A method for controlling flow and concentration of a liquid precursor includes: supplying a carrier gas to a first auto-pressure regulator and outputting therefrom the carrier gas at a first pressure to a precursor reservoir; outputting the mixture of the vaporized precursor and the carrier gas from the precursor reservoir; and supplying the mixture to a second auto-pressure regulator and outputting therefrom the mixture at a second pressure to a reactor via an orifice.