ESC
Electrostatic chucks hold the wafer flat with electrostatic force — no clamp ring — and move process heat into a temperature-controlled base.
Electrostatic chuck
Clamp the wafer.
Hold the temperature.
An electrostatic chuck (ESC) holds the wafer inside the process chamber with electrostatic force instead of mechanical clamps. A voltage applied to an electrode embedded in a ceramic puck attracts the wafer flat against the surface.
Helium flowing through grooves on the chuck surface carries heat from the wafer into a temperature-controlled base, so the wafer stays at a uniform temperature while plasma or a heater adds energy.
- No clamp ring — the full wafer surface stays usable and fewer particles are generated
- Uniform clamping force across the whole wafer, including the edge
- Backside gas cooling for tight wafer temperature uniformity
- Works in vacuum and plasma environments
Anatomy of an ESC
The chuck surface does the clamping and gas distribution; the assembly beneath it supplies power, cooling and motion.
Chuck surface
- Seal band
Raised outer rim that keeps backside helium from leaking at the wafer edge.
- Gas distribution grooves
Concentric and radial channels that spread helium evenly under the wafer for uniform heat transfer.
- Embossed mesas
Small raised contact points that limit contact area, reduce particles and set the backside gas gap.
- Lift pin holes
Three pins rise through these holes to lift the wafer for robot transfer.
- Gas feed hole
Center port that supplies backside helium to the groove network.
Assembly
- Ceramic puck — Dielectric layer with the embedded clamping electrode and, on heated chucks, heater zones.
- Base plate — Metal or ceramic base with internal channels for coolant from a chiller or heat exchanger.
- Bellows and stem — Keep the chamber sealed while the pedestal moves and route utilities out of the vacuum.
- Feedthroughs — High-voltage, heater and thermocouple connections to the power supply and controller.
Two ways to clamp
Coulomb and Johnsen-Rahbek chucks differ in dielectric, clamping force and dechuck behavior. The right choice depends on process temperature and tool.
| Item | Coulomb | Johnsen-Rahbek (J-R) |
|---|---|---|
| Clamping principle | Coulomb force across a highly insulating dielectric | Johnsen-Rahbek force from a small, controlled leakage current at the contact interface |
| Dielectric | High-resistivity ceramic (typically alumina) | Semi-conductive ceramic (typically doped alumina or aluminum nitride) |
| Clamping force at a given voltage | Lower | Higher |
| Dechucking | Fast, little residual charge | Slower — residual charge must be managed |
| Temperature sensitivity | Low | Resistivity, and therefore force, changes with temperature |
| Typical use | Etch, ion implant, low-temperature processes | High-temperature CVD and PVD, processes that need strong clamping |
Where ESCs work
Plasma etch
The cooled base removes plasma heat so the wafer stays at setpoint through the etch step.
CVD & ALD
Heated chucks hold the wafer at deposition temperature for uniform film growth.
PVD
Clamps the wafer flat and controls its temperature during sputter deposition.
Ion implant
Holds the wafer securely and removes beam heat without mechanical clamps.
Typical configuration
Configurations vary by tool and process. Tell us your equipment and we’ll send matching ESC specifications.
| Wafer size | 200 mm or 300 mm |
|---|---|
| Chuck type | Coulomb or Johnsen-Rahbek |
| Electrode | Monopolar or bipolar |
| Backside gas | Helium through surface grooves and mesas |
| Heater | Optional embedded heater zones |
| Cooling | Base plate with coolant channels connected to a chiller or heat exchanger |
| Wafer lift | Three lift pins |
| Temperature sensing | Optional thermocouple or RTD |
Keep the chuck at setpoint
An ESC is only as stable as the fluid loop behind it. CJ Tech chillers, heat exchangers and coolants control the base temperature.
Service & custom units
Need an ESC for your tool?
Tell us the tool, wafer size and process. We’ll reply with compatible ESC specifications.