Wafer sorters play a critical role in semiconductor manufacturing by managing wafer transfer, identification, and organization between process steps. For newcomers to fab automation or equipment engineering, the terminology used in wafer sorting systems can be confusing at first.

This glossary explains commonly used wafer sorter terms in clear, practical language, helping beginners quickly understand system functions, component roles, and operational concepts.

1. Slot

A slot refers to a fixed wafer position inside a cassette, FOUP, or FOSB.

Each slot holds one wafer and is assigned a unique slot number, typically counted from bottom to top.

Slots are fundamental to:

● Wafer mapping

● Recipe programming

● Tracking wafer order and orientation

Accurate slot control prevents wafer collision and misplacement during transfer.

2. Cassette

A cassette is an open wafer carrier used primarily for 150 mm and 200 mm wafers.

It allows direct exposure to the cleanroom environment and is commonly used in legacy or R&D production lines.

Key characteristics:

● Open structure

● Lower cost

● Requires stricter environmental cleanliness control

3. FOUP (Front Opening Unified Pod)

A FOUP is a sealed wafer carrier designed for 300 mm wafers.

It interfaces with load ports and EFEM systems to maintain wafer cleanliness.

FOUPs support:

● Automated door opening

● Particle isolation

● Fully automated fab environments

FOUP compatibility is a core requirement for modern wafer sorters.

4. Aligner

An aligner is a module that adjusts wafer position before handling or inspection.

It ensures correct orientation by detecting features such as the wafer notch or flat.

Alignment accuracy is critical for:

● Downstream process tools

● OCR reading

● Consistent wafer placement

5. OCR (Optical Character Recognition)

OCR systems read wafer identification marks, such as:

● Wafer ID codes

● Lot numbers

● Customer or process markings

OCR enables traceability and is often combined with MES systems for data tracking and process control.

6. Mapping

Wafer mapping is the process of detecting wafer presence, absence, or position within a cassette or FOUP.

Mapping functions include:

● Identifying empty slots

● Detecting cross-slotted or misaligned wafers

● Preventing handling errors

Reliable mapping is essential for safe and efficient sorter operation.

7. Robot Arm

The robot arm is the mechanical unit responsible for wafer transfer.

It moves wafers between load ports, aligners, inspection modules, and destination carriers.

Typical features:

● Single-arm or dual-arm designs

● Vacuum or edge-grip end effectors

● High repeatability and low particle generation

Robot performance directly impacts throughput and yield.

8. Load Port

A load port is the interface between the wafer sorter and wafer carriers.

It supports cassette, FOUP, or FOSB docking and communicates carrier status to the system.

Load ports often include:

● Presence sensors

● Door opening mechanisms (for FOUPs)

● Clamp and positioning systems

9. Recipe

A recipe defines how the wafer sorter operates during a run.

It specifies rules such as:

● Source and destination slots

● Sorting logic

● ID-based classification

Recipes allow repeatable, automated operation without manual intervention.

10. End Effector

The end effector is the part of the robot arm that physically contacts the wafer.

Design varies depending on wafer size, thickness, and handling method.

Proper end-effector selection reduces wafer stress and contamination risk.

Why Understanding These Terms Matters

A clear understanding of wafer sorter terminology helps operators, engineers, and system integrators:

● Reduce operational errors

● Improve communication across teams

● Accelerate training and system ramp-up

For beginners, mastering these terms is the first step toward confidently working with semiconductor automation equipment.

If you’re exploring wafer sorter systems or looking for guidance on automation integration, Fortrend offers reliable wafer handling and sorting solutions backed by deep industry expertise.