aligner

Aligners orient wafers by detecting the notch or flat and rotating to a standard position for consistent processing. **Purpose**: Tools require wafers in known orientation for pattern placement, alignment marks, and consistent processing. **Detection methods**: Optical sensors detect notch (300mm) or flat (200mm and earlier) as wafer spins. **Edge grip**: Gripper or chuck holds wafer by edge while rotating. No contact with active surface. **Rotation**: Precision rotation stage positions wafer to specified angle. Sub-degree accuracy. **Integration**: Usually built into EFEM. Wafer aligned before entering process chamber. **Wafer mapping**: May also perform wafer mapping - detect which slots have wafers, detect double-slotted or cross-slotted wafers. **OCR**: Some aligners read wafer ID (OCR or RFID) simultaneously with alignment. **Throughput consideration**: Alignment adds cycle time. Optimized for speed while maintaining accuracy. **Notch location**: Standard specifies notch at specific position (e.g., 3 oclock or 6 oclock) to match tool requirements. **Pre-aligning**: Some tools have pre-aligners and fine aligners for multi-stage alignment.