point-of-use (pou) filter

Point-of-use (POU) filters provide final purification of chemicals or gases immediately before they enter the process tool. **Location**: Mounted directly at or inside the process tool, as close to use point as possible. **Purpose**: Remove any particles or impurities introduced during distribution, provide final ultra-pure delivery. **Types**: **Gas POU filters**: Sintered metal, membrane, or molecular sieve media. Sub-nm particle ratings. **Chemical POU filters**: PTFE or PFA membrane filters for liquid chemicals. 0.02-0.1 micron ratings. **Contamination sources addressed**: Particles from piping, valve wear, pump operation, ambient contamination during system upsets. **Change frequency**: Based on usage volume, pressure drop, or scheduled intervals. Critical to maintain. **Validation**: Regular testing to verify filter integrity and performance. **Pressure drop**: Adds some pressure drop - factor in system design. **Cost**: Expensive specialty filters, but critical for process quality. **Integration**: Part of tool hook-up, included in tool qualification. Some tools have multiple POU filters for different supply lines.