Dry pump PM services vacuum pumps that provide rough and backing vacuum for process chambers, requiring regular maintenance to ensure reliable operation. Dry pump types: screw pumps, scroll pumps, roots blowers, claw pumps—all oil-free designs avoiding wafer contamination. PM tasks: (1) Tip clearance check—critical for roots/screw pumps, measured with feeler gauges; (2) Bearing inspection/replacement—listen for noise, measure vibration, replace per schedule; (3) Seal replacement—shaft seals, O-rings preventing air leaks; (4) Purge gas verification—N2 purge to prevent corrosive gas buildup; (5) Exhaust line cleaning—remove byproduct deposits (especially from CVD, etch processes); (6) Temperature monitoring—check cooling water flow, heat exchanger efficiency. Rebuild triggers: increased ultimate pressure, higher motor current, excessive noise/vibration. Rebuild: complete disassembly, clean all components, replace wear items, reassemble to specification. Pump performance verification: ultimate pressure test, pumping speed measurement, leak-up rate. Spare pumps: hot-swap capability to minimize tool downtime. Preventive actions: gas-specific abatement to reduce pump loading, heated exhaust to prevent condensation. Typical PM intervals: weekly checks, quarterly service, annual rebuild depending on process severity.