What is the pressure leak point and oil content of a general semiconductor gas source
In semiconductor manufacturing, the quality of gas source directly affects process stability and yield. The following is a detailed analysis of key parameters and control standards:
1. Pressure dew point standard
Semiconductor factories have strict requirements on the pressure and dew point of compressed air, usually controlled at-40℃ to-70℃(Some high-end process requirements-80℃ to-110℃）。This standard is much higher than ordinary industrial scenarios for the following reasons:
- Prevent condensate pollution: Low-temperature dew point can prevent water vapor in compressed air from condensing in pipelines or equipment, preventing corrosion to precision equipment such as lithography machines and etching machines.
- Process stability requirements: Semiconductor technology is extremely sensitive to temperature and humidity. For example, the photoresist coating process requires air humidity to be ≤30%RH. Excessive dew point will cause the photoresist to absorb moisture and expand, affecting pattern accuracy.
Detection and conversion：
- pressure shaping: The gas dew point will change with the pressure, and the real value needs to be converted by a formula. For example, when the sampling pressure is 0.1MPa, the dew point is measured to-70℃. If the actual pressure is 0.8MPa, the real dew point may rise to-55℃.
- instrument selection: Commonly used capacitive dew point meters (such as SHAW type) have a flow range of 5-10L/min and require regular calibration to ensure accuracy.
2. Oil content standard
Semiconductor factories have extremely high requirements on the oil content of compressed air, which usually needs to meetTotal oil content ≤0.01mg/m³(ISO 8573-1 Class 1), some processes and even requirementsClass 0 oil-free compressed air(Close to zero oil content). The reasons are as follows:
- risk of product contamination: Oil may deposit on the surface of the wafer, causing photoresist to fall off or doping contamination, which seriously affects chip yield.
- equipment maintenance cost: Oil vapor can contaminate vacuum pumps, ion implanters and other equipment, increasing maintenance frequency and downtime.
detection and control：
- on-line monitoring: Use high-precision oil detector (such as OIL CHECK 500) to provide real-time warning of excessive oil content.
- Three-level purification：
- primary filter: Cyclone separators remove large oil droplets (efficiency>98%).
- secondary condensation: The freeze dryer cools to-40℃ and condenses oil vapor (efficiency>90%).
- tertiary adsorption: Activated carbon filter adsorbs residual oil molecules (outlet oil content <0.003mg/m³).
3. Actual cases and industry differences
| process links | Pressure dew point requirements | Oil content requirements | typical problems |
|---|---|---|---|
| lithography room | ≤-70℃ | ≤0.001mg/m³ | Excessive humidity causes deformation of photoresist |
| etching process | ≤-60℃ | ≤0.01mg/m³ | Oil contaminates the mask, reducing etching accuracy |
| ion implantation | ≤-50℃ | ≤0.01mg/m³ | Oil vapor initiates ion beam scattering, affecting doping uniformity |
| packaging and testing | ≤-40℃ | ≤0.1mg/m³ | Condensed water causes oxidation of pins |
industry comparison：
- logic chip: The highest requirements for dew point and oil content (dew point ≤-80℃, oil content ≤0.001mg/m³).
- memory chip: Requirements are slightly lower than logic chips (dew point ≤-70℃, oil content ≤0.01mg/m³).
- power semiconductor: Due to the high maturity of the process, some factories have relaxed the temperature to dew point ≤-50℃ and oil content ≤0.1mg/m³.
4. Cost control and optimization
- equipment investment: The initial investment of the tertiary purification system is about 3 million-5 million yuan (calculated based on a 10,000 ㎡ plant), and the annual operation and maintenance cost is about 500,000 – 800,000 yuan.
- energy-saving measures：
- Using variable frequency air compressor, energy consumption is reduced by 15%-20%.
- Use a waste heat recovery device to use compressed heat for heating the factory.
- Monitoring optimization：
- Deploy IoT sensors to achieve real-time remote monitoring of dew point and oil content.
- Use AI algorithms to predict equipment failures and reduce unplanned downtime.
conclusion: Semiconductor factories need to select corresponding air source standards based on process nodes (such as 28nm, 14nm, and 7nm), and ensure stable air quality through regular audits (recommended every quarter) and redundant equipment (such as backup dryers).