MFC Gas Flow Unit Converter

What is sccm?

sccm (standard cubic centimeters per minute) is a volumetric flow rate unit commonly used in semiconductor manufacturing. It describes the volume of gas flowing per minute, corrected to standard conditions. One sccm equals one cubic centimeter of gas per minute at STP (Standard Temperature and Pressure: 0°C, 101.325 kPa). In semiconductor equipment, MFCs (Mass Flow Controllers) are often specified in sccm or slm (standard liters per minute), since volumetric flow is directly measurable and commonly used in process recipes.

STP Definition

STP (Standard Temperature and Pressure) is defined as 0°C (273.15 K) and 101.325 kPa (1 atm). At STP, one mole of an ideal gas occupies 22.414 liters. This standardization allows engineers to compare flow rates across different gases and conditions. Gas density at STP depends on molecular weight: density (g/L) = molecular weight (g/mol) ÷ 22.414 (L/mol). For example, N2 has a molecular weight of 28.013 g/mol and a density of approximately 1.25 g/L at STP.

Conversion Formulas

To convert between volumetric and mass flow, the key relationship is:

Mass flow (g/min) = Volumetric flow (L/min) × Density (g/L)

Since 1 slm = 1 L/min and 1 sccm = 0.001 L/min, we have: Mass flow (g/min) = slm × ρ, or Mass flow (g/min) = sccm × 0.001 × ρ, where ρ is the gas density at STP. To convert to kg/hr, multiply g/min by 0.06 (because 1 g/min = 0.001 kg/min = 0.06 kg/hr).

Importance in Semiconductor Processes

In semiconductor fabrication, gas flow control is critical for CVD (Chemical Vapor Deposition), etch, and other processes. MFC accuracy directly affects film thickness, stoichiometry, and device yield. Engineers often need to convert between sccm (common in equipment specs) and kg/hr or g/min (used in mass balance or cost calculations). Using the correct gas density for each species ensures accurate conversions and reliable process control.

FAQ

Why do different gases give different mass flow for the same sccm?

Because mass flow = volumetric flow × density. Heavier gases (e.g., Ar) have higher density at STP than lighter gases (e.g., H2), so the same sccm corresponds to a higher mass flow for heavier gases.

What is the relationship between sccm and slm?

1 slm = 1000 sccm. Both are volumetric flow units at STP.

Does temperature affect the conversion?

Yes. Our converter uses STP (0°C, 101.325 kPa). If your process runs at different conditions, gas density will differ. For precise applications, use the ideal gas law to adjust density for your actual T and P.