Introduction
The special gas system is a precise environment for controlling gases, providing important support for semiconductor manufacturing and scientific research through rigorous logic and precise control. In this system, data units act as “language codes,” connecting various components to ensure accurate information transmission. Today, we will reveal the key data units in the special gas system to help you.
Pressure units: The key factor in controlling gas flow
Pressure is a key parameter in the special gas system, responsible for controlling the flow of gas in the pipeline, ensuring it reaches the target equipment at an appropriate flow rate, and meeting the process requirements for pressure stability and accuracy. Understanding and using various pressure units is fundamental to the effective management of special gas systems. Next, we will provide a detailed explanation of several commonly used pressure units:
– MPa (Megapascal): The pressure standard in the International System of Units, 1 MPa is equivalent to a force of 1,000,000 Newtons per square meter. In the special gas system, MPa is commonly used to describe the pressure values at key points such as the main gas supply pipeline, inside the storage tank, and the outlet of the pressure reducing valve. Due to its moderate value and ease of integration with international standards, MPa has become the preferred pressure unit in many modern industrial facilities, especially in the fields of semiconductor manufacturing and petrochemicals.
– PSI (Pounds per Square Inch): An imperial unit representing pounds of force per square inch, commonly found in American equipment. It plays an important role in certain imported equipment within special gas systems.
– Bar: Derived from the Greek word ‘baros,’ meaning ‘weight’. It is defined as 1 bar equals 100,000 pascals (Pa). It is commonly used in Europe, where 1 bar is approximately 0.1 MPa or 14.50377 psi. In the special gas system, bar serves as an intermediate unit between MPa and psi. It facilitates connection with the International System of Units and interfaces with some equipment that still uses traditional units. This relatively small value is easy to calculate and estimate quickly, making bar highly practical in actual operations.
– atm (standard atmospheric pressure): Used to compare atmospheric pressure; 1 atm ≈ 0.101325 MPa or 14.696 psi. In special gas systems, atm is often used as a reference unit to express absolute or relative pressure. This is particularly true in scenarios such as gas purity analysis and gas leak detection, where the concept of “pressure difference relative to atmospheric pressure” is applied, making atm an indispensable reference.
– kPa (kilopascal): It is a smaller unit of pressure; 1 MPa = 1,000 kPa. In specialty gas systems, kPa is often used to indicate local pressure regulation, gas micro-leak detection, and other situations that require higher precision measurements, or to present small fluctuations in pressure changes in reports and charts. Since the conversion between kPa and MPa is simple and intuitive, it provides a flexible option for expressing pressure data, helping to achieve clear and detailed descriptions across different pressure ranges.
Flow Units: A Standard for Measuring Gas Supply
Accurate measurement of gas flow is critical to the speed and total amount of gas supply in special gas systems, affecting process efficiency, material utilization, and the quality of the final product. Different flow units are suitable for various application scenarios and accuracy requirements within special gas systems. The following flow units are commonly used in these systems:
– SLM: Standard liters per minute, at 20°C and 1 atmosphere.
– SCCM: Standard cubic centimeters per minute, also at specific standard conditions.
– Nm³/h: Standard cubic meter flow, for bulk gases, at 0°C and 1 atmosphere.
– L/min: Directly indicates volume flow, which needs to be understood in conjunction with actual operating conditions.
Concentration units: Ensure gas quality and safety. 
Purity control of gas systems is critical, especially in areas such as semiconductor manufacturing and scientific research experiments where strict gas quality requirements exist. Ensuring gas purity can guarantee process performance, product quality, operator safety, and prevent environmental pollution. The following are several concentration units used for purity control:
– ppm: Parts per million, represents the concentration of a certain component in a gas mixture. In special gas systems, ppm is often used to describe the content of a certain impurity component in a gas mixture. For example, the purity of high-purity nitrogen is marked as “5 ppm O₂”, which means that there are 5 parts of oxygen in every million parts of nitrogen. PPM is suitable for situations with extremely high gas purity requirements, such as oxidation and diffusion processes in semiconductor device manufacturing. Any tiny impurity content may affect device performance.
– ppb: Parts per billion, is used for trace gas detection and control. In occasions with extremely stringent gas purity requirements, such as ultra-large-scale integrated circuit manufacturing and advanced material synthesis, ppb-level purity control is crucial. For example, the purity of ultra-high purity argon may be required to reach “1 ppb H₂O”, which means that only 1 part of water is allowed in every billion parts of argon. Purity control at the ppb level requires special gas systems to have extremely high purification capabilities and precise detection methods.
– %VOL: Volume Percentage directly indicates the volume percentage of a gas in a mixture. Compared with ppm and ppb, %VOL is more suitable for describing gas mixtures with higher concentrations.
In specialty gas systems, %VOL is often used to indicate the proportions of the components of process gases, such as the mixed gas used in chemical vapor deposition (CVD), which may include hydrogen (H₂), silane (SiH₄), ammonia (NH₃), etc., each expressed in volume percentages. In addition, %VOL is often used to describe the proportion of diluent gases (such as nitrogen) in mixed gases.
Temperature units: Thermometers for controlling the process environment
Temperature directly affects the stable operation of the special gas system and the properties of the gas. The main units are as follows:
– ℃ (Degrees Celsius): Celsius, which is an internationally accepted temperature unit.
– °F (Degrees Fahrenheit): Fahrenheit, mainly used in the United States and areas historically influenced by it.
Other essential units: Time, Mass, and Length
– Time units: s (seconds), min (minutes), h (hours), used to record system operation time, gas consumption rate, etc.
– Mass units: g (grams), kg (kilograms), used to describe the mass or weight of the gas.
– Length units: mm (millimeters), cm (centimeters), m (meters), used for dimensional parameters such as pipeline size and distance.
Conclusion
Mastering these basic units is like having a toolbox that supports the management of the specialty gas system. The data units in the specialty gas system are the foundation of its operation. By understanding and applying these units, engineers can accurately control gas parameters to ensure the system’s efficiency, stability, and safety.
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