Differential Pressure Flow Meters: Providing Precise Gas Flow Control for Semiconductor Manufacturing
Operating Principles and Core Technologies
Laminar differential pressure flow meters are based on the Hagen-Poiseuille law. By converting turbulent flow into laminar flow and utilizing the linear relationship between pressure difference and flow rate, they achieve precise measurement. Their core components include precision laminar flow elements and differential pressure sensors, which calculate flow rates by determining the pressure difference between two points in real time. Compared to traditional flow meters, their optimally designed laminar flow elements eliminate turbulence interference, significantly improving measurement accuracy.
Analysis of Core Advantages
- High Accuracy and Stability
Measurement accuracy reaches ±0.5% RD and remains stable even at low flow rates (e.g., in the mL/min range), meeting the stringent requirements of semiconductor processes for gas concentration.
The laminar flow design ensures long-term stability, reduces the frequency of calibration, and is suitable for continuous production scenarios.
- Rapid Response Capability
Millisecond-level response speed (dependent on pressure wave propagation) accommodates millisecond-level gas switching requirements in processes such as atomic layer deposition (ALD). For example, in plasma etching, real-time regulation of the Cl₂/SF₆ ratio keeps etching rate fluctuations within 0.3 nm/min.
- Adaptability to Extreme Environments
With an operating temperature range of -80°C to 110°C and a pressure rating of up to 2.5 MPa, it is suitable for the high-temperature, low-temperature, and high-pressure conditions of semiconductor equipment.
Constructed from corrosion-resistant materials such as 316L stainless steel and fluorocarbon rubber, it can withstand long-term exposure to highly toxic gases like Cl₂ and HF.
- Contamination Resistance and Versatility
The laminar flow element design effectively blocks particulate contamination, maintaining high performance even in the complex internal environment of lithography systems.
It supports mixed gas measurement and switching from a database of over 70 gases, meeting the flexible requirements of both laboratory and industrial applications.
Key Application Cases in Semiconductor Manufacturing
- Lithography Process: Precise Control of Nitrogen and Hydrofluoric Acid
During the lithography exposure process, laminar differential pressure flow meters monitor nitrogen and hydrofluoric acid flow rates in real time to ensure stable gas concentrations. For example, a leading chip manufacturer used this technology to improve exposure uniformity to 99.8% and increase wafer yield by 15%.
- Etching Process: Dynamic Ratio Control of Oxygen and Argon
Etching rates are directly influenced by gas flow rates. A foundry utilized this flowmeter to adjust the O₂/Ar ratio, reducing etching rate fluctuations from ±5% to ±0.5% and minimizing edge damage to wafers.
- Chemical Vapor Deposition (CVD): Nanometer-Level Control of Film Thickness
In silicon nitride film deposition, by precisely controlling the SiH₄/NH₃ flow ratio, film thickness uniformity was achieved within ±1%, significantly reducing device leakage current.
- Specialty Gas Delivery and Leak Detection
In hydrogen delivery, flow meters enable leak detection-level control with a leak rate below 10¹¹ Pa·m³/s, eliminating the risk of deflagration and ensuring fab safety.
Breakthroughs in Domestic Production and Technological Trends
- Examples of Domestic Substitution
A domestic equipment manufacturer independently developed a laminar flow differential pressure MFC covering the full range from 0.5 sccm to 5000 slpm. Its precision matches that of major international manufacturers, and the delivery cycle has been shortened from 8 months to 6 weeks.
In silicon carbide substrate manufacturing, domestic MFCs have limited epitaxial wafer thickness fluctuations to within 0.5 μm, enabling reverse exports to Europe and the United States.
- Future Development Directions
Intelligent Integration: Features such as touchscreen operation and RS485 communication enhance integration efficiency in industrial settings.
Range Expansion: Development of miniaturized products with a resolution of 0.1 mL/min to meet more precise process requirements.
With their atomic-level precision and industrial-grade reliability, laminar differential pressure flowmeters have become the “invisible guardians” of semiconductor manufacturing. From lithography to etching, and from specialty gas delivery to breakthroughs in domestic production, their technological evolution has not only driven a leap in chip yield but has also become a key competitive advantage in the global semiconductor industry.