Plasma Diagnostics for Science and Technology
The VGPS universal probe system has evolved from 40 years of experience designing plasma probe diagnostics. This state-of-the-art system was designed to acquire and process in real time the probe I/V characteristics and concurrently display electron energy distribution function (EEDF) and various plasma parameters. The VGPS has been extensively tested in scientific laboratories and proven to yield reliable data in commercial plasma production environment.
The VGPS can be configured to either of two operation modes. The first configuration is optimized for sensing and processing of the probe electron current, and the second invokes pulsed ion flux measurements. Each configuration implements distinctively different probes and current sensors.
In the Electron Mode, the station acquires the probe I/V characteristics and instantly calculates and displays EEDF. Plasma density, electron temperature, and other discharge parameters are calculated as EEDF integrals and made available in real time.
In the Ion Mode, the instrument acquires the probe I/V characteristics and calculates the plasma parameters based on the ion current measurements. The ion current acquisition system is designed to mitigate effect of the probe tip contamination with non-conductive deposits.
Both probes incorporate wide band RF compensation, thus making them suitable for diagnostics in commercial multi-frequency plasma reactors.
The VGPS has a unique combination of the state-of-the-art features unavailable in any other commercial products:
· Reliable high resolution real time EEDF measurements in a laboratory environment and industrial plasma equipment with reactive gases
· Accurate probe diagnostics in discharges with wide frequency range of the high voltage RF plasma potentials
· Elimination of the probe work function variation and plasma potential drift by fast (0.5-5 ms) sweeping of the probe
· Minimization of the local and global plasma perturbations via small diameter probe holder (1 mm) and probe supports (4 mm, 6.3mm)
· Suppression of the plasma noise and compensation of the probe circuit impedance through the reference probe wide band feedback
· Continuous heating to a preset temperature (500 -1500°C) of the probe for EEDF measurements, thus insuring evaporation of the non-conductive deposits
· Cleaning off the probe contamination using an internal generator of high voltage high frequency pulses