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Semion RFEA System

The Semion Retarding Field Energy Analyser (RFEA) system measures the ion flux and ion energy distribution function (IEDF) hitting a surface in real-time using an imitation substrate (holder plate) with integrated sensors. The Semion Multi Sensor system can have up to 13 sensing elements distributed around the imitation substrate, which is primarily used to investigate the uniformity of ion energy and ion flux at the substrate in industrial plasma applications. A range of replaceable sensing elements with different signal sensitivities are available to probe a wide range of plasma ion current densities. This is the industry standard for substrate level measurement of the ion energy distribution, used in over 100 publications for fundamental research and plasma process development.

Key Features
Measure the Ion Flux and Ion Energy Distribution with energy range up to 2000eV (process dependant).
Suitable for grounded, floating and RF biased conditions.
Up to 13 sensors integrated into a single holder allowing uniformity measurements.
Holders with different shapes and designs available upon request.
Fully automated software analysis of the IEDF and automatic DC bias potential measurement.
Replaceable sensor elements with different sensitivities ranging from 0.001 A m-2 to 700 Am-2.
Sensor elements and holder available in anodised aluminium, bare aluminium or stainless-steel options.
Key Benefits
Portable system allowing analysis in multiple chambers using a single system.
Provides in-situ measurements of Ion Energy Distribution (IED) under plasma processing conditions.
Automatically generates contour maps of energy and flux uniformity over the wafer area.
High Pressure Button Probes extend the pressure ranging to 1.5 Torr (limited to 150 eV energy range).
Provides insight for fundamental research and for plasma model validation.
Generate process data for customer escalations or product marketing.
Correlate process performance with the key plasma process drivers (Ion Energy and Ion Flux).

Electronics Box

The Semion Retarding Field Energy Analyser (RFEA), Electronics box is calibrated accurately for voltages ranging from -2000V to +2000V and currents ranging from 100 pA to 60 mA.

Model Number Product Name Desciption


Semion Single Electronics Unit

Compatible with single holders only.


Semion Multi Electronics Unit

Compatible for all holders.



The vacuum Feed-through transmits electrical signals by connecting the Electronics Box from Outside the Vacuum chamber to the Semion Sensor inside the vacuum chamber.

Model Number Product Name Description


Single Single Feedthrough

Compatible with single holders only.


Semion Multi Feedthrough

Compatible for all holders.


Semion Single Time Resolved Feedthrough

Compatible with fully grounded single holders only.


Semion Multi Time Resolved Feedthrough

Compatible for all holders when fully grounded.


Button Probes

The Button Probes of the sensor are designed to be replaceable in the field. Lifetime is typically 10 to 100 hours of plasma exposure, depending on chamber conditions. For use in deposition systems the sensing element will survive 10 microns of deposition before needing to be replaced.

High Pressure Buttons, which extend the maximum pressure range to 1.5 Torr, are available upon request

Anodised Aluminium as standard. Bare Aluminium and Stainless-Steel available upon request.

Model Number Product Name Description


Low Density

0.001 to 3 Am-2


Standard Density

0.01 to 50 Am-2


High Density

0.1 to 700 Am-2



The main purpose of the sensor holder is to hold the replaceable Button Probe sensors. It can withstand temperature up to 150°C without the need for cooling.

Anodised Aluminium as standard. Bare Aluminium and Stainless-Steel available upon request.

Model Number Product Name Description


50 mm Single Holder

Single Holders also available up to 300mm


70 mm Single Holder

1 sensing element mounting holes available


150 mm Multi Holder

7 sensing elements


200 mm Multi Holder

9 sensing elements


300 mm Multi Holder

13 sensing elements


450 mm Multi Holder

13 sensing elements

RFEA Probe Specifications
Number of sensors (Button Probes)
1 to 13 ( depending on holder)
Probe configuration
Button Probe diameter (sensing element)
Holder diameter
50 - 450 mm diameter options (custom avilable)
Holder thickness
Max. operating temperature
Button Probe material
Aluminium, anodised aluminium, stainless steel
Holder material
Aluminium, anodised aluminium, stainless steel
RFEA Probe cable length
650 mm (custom available)
Flange Type
CF40 as standard, KF40 and custom options available
Semion System Specifications
Ion Energy Range
0 to 2000 eV (standard/ low density Button Probe)
0 to 150 eV (high pressure Button Probe)
Ion Flux
0.001 to 3 Am-2 (low density Button Probe)
0.01 to 50 Am-2 (standard Button Probe)
0.1 to 700 Am-2 (high density Button Probe)
Pressure Range
Pressure Range
≤ 300 mTorr (standard Button Probe)
≤ 1.5 Torr (high pressure Button Probe)
IEDF Resolution
±1 eV nominal
Ion Density Range
1012 to 1020 m-3 (Button Probe dependent)
Max. RF Bias Voltage (applied to probe)
1 kV**(peak to peak)
Max. DC Bias Voltage
-1940 V
Bias Frequency Range
100 kHz to 80 MHz
Sync Frequency Range (Time Resolved)*
4 Hz to 100 kHz
Time Resolved Method*
Boxcar intergration
Time Resolved*
100 µs
* For Pulsed Plasmas with Semion mounted on Grounded electrode (Requires Time Resolved Feedthrough)

** @ 13.56 MHz. Reduced to 0.3 kV @ 60 MHz

Software Screenshots

Ion Energy Contour Map.
IV curve and IEDF on an RF Biased electrode.
IV curve and IEDF on a Grounded electrode.
Talk to Us Today

Do you want to learn more about our sensors or applications? Contact us and a member of the team will get back to you