load lock

Load locks are vacuum-compatible chambers that transition wafers between atmospheric and vacuum environments. **Purpose**: Allow wafers to enter vacuum process chambers without breaking vacuum. Cycle between atmosphere and vacuum. **Operation cycle**: Vent to atmosphere, open atmosphere door, load wafer, close atmosphere door, pump down to vacuum, open vacuum door, transfer wafer. Reverse for unload. **Pump down time**: Critical for throughput. Large chambers take longer. Optimized for fast cycling. **Vacuum level**: Pump to base pressure compatible with process chamber requirements (typically 10^-3 to 10^-6 Torr). **Slit valves**: Doors between load lock and adjacent chambers (atmosphere or vacuum). Sealed when closed. **Heating/cooling**: Load locks may include wafer heating or cooling stages. Condition wafer for process. **Batch load locks**: Some load multiple wafers at once to improve throughput. **Outgassing**: Must pump away gases released from wafer and carrier. May require extended pump time for some wafers. **Materials**: Vacuum-compatible materials (aluminum, stainless), sealed construction, vacuum pumping system.