Pressure-Based Liquid Flow Control for Substrate Processing
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Solution Overview
Problem
Substrate processing systems face challenges in achieving precise liquid precursor flow control due to overshooting and long settling times, with issues like bubble trapping in metering tubes leading to inaccurate or halted flow, which affects the formation of the correct gas mixture in processing chambers.
Innovation Solution
A pressure-based liquid flow control system that includes a liquid ampoule with a pressure adjusting system, a capillary injector, and a controller to maintain predetermined pressure and temperature conditions, ensuring precise flow rates through a capillary tube, with adjustments made by vacuum and push gas valves and a Peltier device for temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal or Coriolis flow controllers are used to meter liquid precursor, then flow rate control is achieved, but settling time exceeds 10 seconds and overshooting occurs
Solution Approach 1:
The patent replaces mechanical flow controllers with a pressure-based control system that uses a capillary tube and pressure sensor to control liquid flow. The controller adjusts pressure in the liquid reservoir to achieve desired flow rates, eliminating the mechanical metering tube and associated settling time issues.
Solution Approach 2:
The system changes the control parameter from flow rate directly to pressure. By controlling pressure in the liquid reservoir and using the relationship between pressure and flow rate through the capillary tube, the system achieves rapid response without overshooting or long settling times.
2Productivity
If liquid flow controllers are fully opened to fill metering tube, then flow rate is achieved, but bubble trapping occurs and flow becomes inaccurate or halted
Solution Approach 1:
The patent removes the metering tube component entirely from the system. By eliminating the metering tube, the source of bubble trapping is removed, allowing continuous accurate flow without the need to fully open valves to fill a tube.
Solution Approach 2:
The system uses pressure control and fluid dynamics principles to regulate flow through the capillary tube. By controlling pressure differential across the capillary, the system achieves reliable flow without bubble trapping issues inherent in traditional metering tube designs.
3Loss of time
If pressure in liquid ampoule is adjusted to control flow rate, then rapid stabilization is achieved, but system complexity increases
Solution Approach 1:
The pressure controller serves multiple functions: it controls flow rate, maintains pressure stability, and responds to feedback from the pressure sensor. This multi-functionality reduces the need for separate components and simplifies the overall system despite the pressure-based approach.
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 system achieves rapid stabilization of liquid flow rates within seconds, minimizing overshooting and bubble trapping, ensuring accurate and consistent delivery of the liquid precursor, thereby improving the precision of gas mixtures in substrate processing systems.
Implementation Method 1
A pressure adjusting system adjusts pressure in the liquid ampoule... controlling pressure in the liquid ampoule to the predetermined pressure to provide the desired flow rate
Implementation Method 2
The temperature control device comprises a Peltier device... maintaining a temperature of the capillary tube at the predetermined temperature
Implementation Method 3
A capillary injector includes a capillary tube in fluid communication with an output of the liquid ampoule
Implementation Method 4
A vacuum source and a third valve in fluid communication with the liquid ampoule selectively increase the pressure in the liquid ampoule
Data Source
AI summary
A liquid delivery system for a substrate processing system includes a liquid ampoule to store liquid precursor. A pressure adjusting system adjusts pressure in the liquid ampoule. A pressure sensor senses a pressure in the liquid ampoule. A capillary injector includes a capillary tube in fluid communication with an output of the liquid ampoule. A temperature control device controls a temperature of the capillary tube. A first valve has an input connected to the capillary tube. A controller is configured to determine a predetermined pressure in the liquid ampoule corresponding a desired flow rate and a predetermined temperature of the capillary tube, maintain the temperature of the capillary tube at the predetermined temperature, communicate with the pressure sensor and the pressure adjusting system, and control the pressure in the liquid ampoule to the predetermined pressure to provide the desired flow rate.