air bearing table
**Air bearing table** is an **ultra-stable measurement platform that floats on a thin film of compressed air** — providing friction-free, vibration-isolated support for sensitive semiconductor metrology instruments like interferometers, profilometers, and coordinate measuring machines where even micro-Newton contact forces or nanometer-scale vibrations would corrupt measurements.
**What Is an Air Bearing Table?**
- **Definition**: A precision mechanical platform supported by a thin film (5-15 µm) of pressurized air forced through porous or orifice-type bearing surfaces, creating a virtually frictionless, self-leveling, and vibration-isolating support system.
- **Principle**: The pressurized air film eliminates all metal-to-metal contact between moving and stationary surfaces — providing near-zero friction motion and complete mechanical decoupling from floor vibrations.
- **Precision**: Air bearing surfaces are flat to within 0.1-1 µm over the entire table area — providing the ultimate reference plane for precision measurements.
**Why Air Bearing Tables Matter**
- **Zero Friction**: Conventional mechanical bearings introduce friction, stick-slip, and wear — air bearings provide true frictionless motion critical for sub-nanometer positioning accuracy.
- **Vibration Isolation**: The air film acts as a natural low-pass filter — high-frequency vibrations from the floor, pumps, and building systems are attenuated before reaching the instrument.
- **No Wear**: No physical contact means no wear, no lubrication needed, no particulate generation — essential for cleanroom compatibility.
- **Flatness Reference**: The precision-lapped surface provides a stable flatness reference for optical and dimensional measurements.
**Applications in Semiconductor Manufacturing**
- **Interferometric Measurement**: Wafer flatness, surface roughness, and optical component testing require ultra-stable platforms free from vibration artifacts.
- **Profilometry**: Stylus and optical profilometers measuring step heights and surface features need vibration-free, flat reference surfaces.
- **CMM (Coordinate Measuring Machine)**: 3D dimensional measurement of semiconductor equipment components and tooling.
- **Optical Inspection**: Mask inspection and wafer inspection platforms use air bearings for precise, vibration-free wafer positioning.
- **Lithography Stages**: Wafer and reticle stages in lithography scanners use air bearings for nanometer-precision positioning at high speed.
**Air Bearing Table Specifications**
| Parameter | Typical Value | High-Precision |
|-----------|--------------|----------------|
| Surface flatness | 1-5 µm | 0.1-0.5 µm |
| Air film thickness | 5-15 µm | 3-8 µm |
| Air pressure | 4-6 bar | 6-8 bar |
| Load capacity | 100-5,000 kg | Application-specific |
| Natural frequency | 0.5-2 Hz | Determines isolation range |
Air bearing tables are **the ultimate precision platform for semiconductor metrology** — providing the friction-free, vibration-isolated, and geometrically perfect support that enables the sub-nanometer measurements modern chip manufacturing demands.