Piezoelectric Diaphragm Liquid Flow Control for Semiconductor Vaporization
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Solution Overview
Problem
Conventional liquid flow control systems in semiconductor fabrication face challenges with accurate low-rate liquid flow control due to viscosity and surface tension, leading to variability in liquid delivery and unsteady vapor generation, exacerbated by significant dead volume and droplet formation at the end of delivery tubes.
Innovation Solution
A novel apparatus using a flexible diaphragm and piezoelectric transducer to control liquid flow through an orifice, reducing dead volume and surface tension effects, with a pneumatic piston for shutoff and a gas jet to prevent droplet formation, achieving precise and steady liquid delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional liquid flow control systems are used, then liquid delivery can be achieved, but accurate low-rate liquid flow control is difficult due to viscosity and surface tension effects
Solution Approach 1:
The patent replaces conventional mechanical flow control valves with a piezoelectric transducer that uses electrical signals to control diaphragm position, thereby eliminating mechanical friction and improving control precision at low flow rates. The piezoelectric actuator provides fine-adjustable control of the orifice opening based on applied voltage.
Solution Approach 2:
The patent employs a flexible diaphragm that can be precisely positioned by the piezoelectric transducer to control the orifice opening. The diaphragm's flexibility allows for smooth, frictionless adjustment of the flow path, enabling accurate control of low liquid flow rates without the stick-slip effects common in mechanical systems.
2Productivity
If liquid flows through delivery tubes, then vapor generation occurs, but dead volume causes delays and unsteady vapor generation
Solution Approach 1:
The patent extracts and eliminates the dead volume problem by designing a flow control apparatus where the liquid path is minimized and directly connected to the vaporization zone. The diaphragm and orifice configuration allows liquid to be delivered directly to the heating element without traversing long delivery tubes, thereby removing the source of delays.
Solution Approach 2:
The piezoelectric transducer can be controlled to deliver liquid precisely when needed, eliminating delays associated with filling dead volume. The system can pre-position the diaphragm to control flow start timing, ensuring liquid reaches the vaporization zone exactly when required without unnecessary delays.
3Reliability
If liquid flows through delivery tubes, then vapor generation occurs, but droplet formation at the end of delivery tubes causes variability
Solution Approach 1:
The patent removes the delivery tube endpoint where droplet formation occurs by delivering liquid directly through the orifice into the vaporization zone. The flexible diaphragm controls the orifice opening such that liquid is atomized or vaporized immediately upon exit, preventing droplet accumulation and subsequent variability in vapor generation.
Solution Approach 2:
The patent introduces a gas jet as an intermediary that interacts with the liquid emerging from the orifice. The gas stream breaks up liquid into finer droplets or promotes immediate vaporization, preventing the formation of large variable droplets that would cause instability in vapor generation.
4Measurement precision
If flexible diaphragm is used to control flow, then precise liquid flow control is achieved, but device complexity increases
Solution Approach 1:
The flexible diaphragm serves multiple functions simultaneously: it acts as the flow control element, the structural support for the piezoelectric transducer, and the seal between the liquid and gas sides of the apparatus. This multi-functionality reduces the number of separate components needed, thereby limiting the increase in device complexity despite the precision control capability.
Solution Approach 2:
The patent combines the flow control mechanism and the actuation mechanism into a single integrated unit. The piezoelectric transducer is mounted directly on the diaphragm, merging the electrical actuation function with the mechanical flow control function. This integration reduces the number of separate components and simplifies the overall apparatus structure.
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
The solution significantly reduces dead volume, ensures precise control of liquid flow, and stabilizes vapor generation, minimizing variability and droplet formation, thereby improving the reliability and efficiency of liquid-source vaporization in semiconductor fabrication.
Implementation Method 1
flexing said diaphragm to vary a size of the gap
Implementation Method 2
The diaphragm is sufficiently flexible to vary the gap thereby controlling the rate of liquid flowing through the orifice
Data Source
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AI summary
A method for controlling liquid flow through an apparatus comprising an orifice (245) and an adjacent flexible diaphragm (220) separated from each other by a gap (225) through which a liquid flows, the orifice (245) comprising a liquid outlet (255) within a gas flow passageway (290), the method comprising: flexing the diaphragm (220) to vary a size of the gap (225) to control the rate of liquid flowing through the orifice (245) or to provide a positive liquid shutoff of liquid from flowing through the orifice (245); characterised by providing a gas to flow at a velocity higher than approximately 20 meters/second through the gas flow passageway outlet (300) and flowing the gas through the gas outlet (300) in substantially the same direction as the liquid flowing through the liquid outlet (255) to reduce the size of liquid droplets formed at the outlet (255), wherein the outlet (255) is located downstream of the orifice (245) and in fluid communication therewith.