A friend asked: In 12-inch/8-inch fabs, the use of ethanol alcohol as the main cleaning agent is strictly prohibited. Why?
Application of IPA in wafer fabs:
IPA (isopropyl alcohol) is mainly used for wafer cleaning, etching, equipment installation, preventive maintenance (PM), etc. It appears in almost every area of a wafer fab.
Comparison of the properties of isopropyl alcohol and ethanol:
| Item | IPA (Isopropyl Alcohol) | Ethanol |
|---|---|---|
| Chemical Formula | C₃H₈O | C₂H₆O |
| Polarity | Moderate polarity | Stronger polarity |
| Boiling Point | 82.6°C | 78.4°C |
| Solubility | Completely miscible with water, alcohols, ketones | Also miscible with water and alcohols |
| Odor | Pungent | Relatively mild |
| Evaporation Rate | Slightly slower than ethanol | Slightly faster than IPA |
| Hygroscopicity | Strong | Stronger |
| Drying Ability (residual water) | Displaces water more easily | More residual water, poorer drying |
Why use IPA instead of ethanol?
- SEMI G5-grade IPA typically has a purity level exceeding 99.9999% (six nines). Ethanol cannot be completely dehydrated from its azeotrope and is generally available only as “analytical/reagent grade,” making it inherently difficult to meet ultra-clean standards required for wafer-level processes.
- IPA has a moderate evaporation rate, allowing it to evaporate evenly across surfaces, reducing the risk of “dry spots” or water marks. It also forms an azeotrope with DI water, making it suitable for Marangoni drying.
- IPA has slightly lower polarity than ethanol, making it more compatible with organic solvents (like NMP, ACE), and photoresist residues.
Is ethanol really unusable?
Not absolutely, but it is typically used in the following cases:
- Cleaning of low-end or laboratory glassware
- Preliminary wiping before lab-grade packaging
- PCB industry
- Temporary cleaning tasks that do not require electronic-grade purity
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