Plato Probe

Plato Probe

A Philosophical Approach To Plasma Measurement

The Plato Probe is a planar Langmuir Probe designed to work in deposition plasmas when an insulating film is deposited on the probe surface. This deposition tolerant Langmuir Probe can remain inside a plasma reactor while aggressive insulating gasses are in use.

The Plato Probe measures plasma parameters such as plasma density, ion current density and electron temperature in plasmas with high deposition rates, like plasma enhanced chemical vapour deposition (PEVCD).

For many years it has been difficult to measure the parameters of plasma in high deposition environments. Impedans have developed a groundbreaking technology which measures the parameters of plasma, even when a thick insulating layer is deposited on the probe surface.


Deposition Tolerant | High Speed Acqusition | Spatial Scanning | Customisable Form Factor for Process Integration


Fundamental Research | Process Development | Equipment Design | Model Validation


The Plato Probe is a planar Langmuir Probe for deposition plasma when an insulating film is deposited on the probe surface. The Plato Probe is the first Langmuir probe on the market that can operate in plasmas with high deposition rates. A unique feature of the Plato Probe is its ability to measure accurately key plasma parameters through a deposited layer several microns thick. The deposition of insulating layers does not affect the accuracy of the probe measurement.

The Plato Probe is a unique instrument enabling scientists to measure the plasma density and electron temperature of plasma including deposition plasma. The Plato Probe provides plasma parameter measurement in DC, RF, microwave, continuous and pulsed plasma. The Plato Probe has the most advanced patented technology on the market using ultra-fast biasing to penetrate the deposited film to obtain accurate measurements of the real plasma parameters in a wide range of plasma applications.

The Plato Probe is used to establish plasma process repeatability, even in reactive gas plasma. It is the perfect instrument to understand plasma changes and the impact on surface treatment. The Plato Probe is an essential plasma process diagnostic to understand the correlation between plasma inputs and the plasma state in environments with a high rate of deposition, such as plasma enhanced chemical vapour deposition (PEVCD). The Plato Probe reduces process and tool development time, as well as the time to market for new plasma products. Pulsed plasmas are used to tailor the electron or ion energy and the Plato Probe is an integral part of such a process development.

Plasma Parameters Measured

  • Plasma Density
  • Ion Current Density
  • Electron Temperature

Measurement Functionality

Time Averaged Measurements
This provides an average over time of the plasma parameters measured by the Plato Probe in the bulk of the plasma.

Time Resolved Measurements
This allows the user to synchronise the plasma parameters measured by the Plato Probe with an internal synchronisation signal. The user can then obtain detailed information on the plasma parameters as a function of time or phase through the synchronisation pulse period. Typically the pulse period would be on a timescale of milliseconds to microseconds.

Time Trend Measurements
This allows the user to obtain information on the variation of the plasma parameters as time progresses through a particular process. This feature does not require external synchronisation and the timescales involved can be in range of seconds to hours.

Further Product Information

Plato Probe Automated Electronics and Software Electronics Unit

Electronics UnitThe user-friendly electronics and software takes accurate and reliable measurements with a speed not seen on any other commercial Langmuir Probe. Using an intelligent pre-scan feature, the optimal plasma parameter measurements are performed easily and repeatedly.

Plato Probe Replaceable Tips

Probe tips are easily replaced with the “Easy-Fit” probe tip holder design. Probe tip material is tungsten as standard, with molybdenum, platinum and invar available. Custom probe lengths, diameters, materials, and shapes can be supplied on request and easily updated in the software analysis.

Time-Resolved Measurements

A high-speed mode is available to support high resolution time-resolved measurements with a time-step resolution of 10µs for pulsed and low frequency applications. Trigger frequencies 10Hz to 50kHz are supported, and a built-in programmable delay allows gating of the probe measurements.

Time Averaged Measurements

In applications where high speed resolution is not required averaging the measurement over a number of data points can be used to significantly reduce the noise.

External Trigger

The Plato Probe System is equipped with a TTL trigger of 10Hz to 50kHz.

RF Compensation

The Plato Probe includes RF chokes to provide RF compensation at the plasma driving frequency.

Measuring Parameters

Plasma Density 4x10⁸ to 3x10¹³cm⁻³
Ion Current Density 26µA/cm² to 300mA/cm²
Electron Temperature 0.1 to 15eV

Plato Probe Specifications

Plasma Power Source DC, RF, Microwave, Continuous, Pulsed Plasma
RF Plasma Broadband Probe 13.56MHz to 100MHz
Probe Length 300mm to 1400mm (Custom Available)
Probe Diameter 9.5mm
Probe Tip Diameter 7mm
Probe Customisation On Request
Maximum Operating Temperature 230°C

Electronics Control Unit

Probe Voltage Scan Range Floating Potential ±30V
Current Range 300µs to 20mA
Communication USB 2.0
Signal Bandwidth 40 kHz
Data Acquisition Resolution 4.5mV, 4.5nA
Time Resolved Step Resolution 1µs to 1ms
External Trigger 10Hz to 50KHz

Application Software

Operating System Windows 2000 / XP / Vista / Windows 7 / Windows 8 / Windows 10

Operating Parameters

Pressure (Pascal) <0.1Pa to 1,000Pa
Pressure (Torr) <1mTorr to 10Torr
Density 10⁶cm⁻³ to 10¹⁴cm⁻³
Gas Reactivity Inert to Highly Reactive
Power Frequency DC (0kHz) • pDC (10Hz to 50kHz) • RF (13.56MHz to 100MHz)
UHF (100MHz to 1GHz) Microwave (1GHz to 3 GHz)

The Plato Probe used in Dusty Plasma applications
Coming soon
The Plato Probe used in Plasma Etching applications
Coming soon
The Plato Probe used in HiPIMS Plasma applications

Characterization of HiPIMS plasma via process compatible measurement probe


This study looks at the characterization of a HiPIMS plasma using a process compatible plasma measurement probe which can be used in situations which require measurements at a fast time resolution, where in some cases the application may be depositing insulating layers.

PP01: Characterization of HiPIMS plasma via process compatible measurement probe

The Plato Probe used in PECVD applications
Coming soon
The Plato Probe used in Space Plasma applications
Coming soon
The Plato Probe used in Plasma Sputtering applications
Coming soon

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Time Averaged Measurement

Measurements include setup with base level setting. Scan at 50w, 75w and 100w.

Time Resolved Measurement

Scan at 50w, 75w and 100w.

A word from our clients

"The Semion system together with Impedans’ friendly and immediate customer service – an effective team for plasma analysis"