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    Radio-frequency plasma generator RFPG-250

    Purpose: creation and continuous maintenance of high-density gas discharge plasma in working spaces of vacuum technological machines. RFPG-250 allows obtaining of ion flux with at least ±2% uniformity on a 200 mm diameter, ion flux density up to 25 mA/cm2)

    Installation: into a view port flange or inside the vacuum chamber on a DU60 sliding seal both in new plants and when modernizing the existing ones. There are tested and tried procedures of using plasma generators in the majority of serially produced Russian plants.

    Application: processes of ion and plasmachemical etching, depositing of thin film deposition, ion-plasma surface treatment: polishing, nitriding and carbonization. The devices work with any gases that do not cause depositing of low-resistance layers on the protective screen surface. Depositing rate: up to 40 µm/min, capacity: up to 20 kW.

    Parameter

    RFPG-250

    Operating frequency, MHz

    13.56

    Maximum HF energy input, W

    5000

    Housing diameter, mm

    245

    Operating pressure range, Pa

    0.1..10

    Ion flux density at 1 kW power, mA/cm2  

    a) without accessories

    10

    b) with a specially configured magnetic system

    25


     Radio frequency plasma generator RFPG-250 – is an electrodless device designed for low temperature, dense plasma generation in a relative large volume. It can be installed on or inside any vacuum chamber. The RFPG-250 can be used in a wide range of plasma technologies:

    • Plasmachemical processes: RIE, PECVD
    • Deposition of various materials in the any operation gases (noble or reactive).
    • Ion and plasma etching.
    • Evaporation, including evaporation with additional ionization of the evaporated material.
    • Ion surface modification (oxidation, reduction, nitriding, carbonization ...).
    • Ion cleaning and assisting
    • Annealing

    RFPG-250 is designed to be used in any type of vacuum machines. Its base element is a flat inductive coil, which is placed inside an aluminium case. All inner elements of the generator are tuned fine with a precision less than 0.1 mm. The case and sliding vacuum feedthrough provides an easy installation. The surface of the generator adjacent to plasma is protected by a quartz or alumina shield. In addition, a specially designed Faraday screen can be mounted, to prevent electromagnetic shielding of the generator by deposited conductive films. The screen can easily be removed and cleaned outside of a vacuum chamber.

    The scheme of RFPG-250 is presented in figure. 2. 

    Configuration of Plasma Generator

    Fig. 2. The main elements of RFPG-250

    RFPG-250 can operate in a broad range of pressures. Plasma density distribution in vacuum chamber strongly depends on the pressure. In the case of a low pressure (0.1..1.0 Pa) the plasma fills the total volume of a vacuum chamber if additional magnetic fields are absent. Apart in the case of high pressures (1.0..10 Pa), the plasma concentrates near the surface of RFPG-250, thus increasing the total power dissipation in a smaller volume and plasma density increases. In the high pressure operation regime RFPG-250 can be used as a source of radicals, or atoms of polyatomic gases. Due to the localization of the plasma near the surface of the source, the substrate can be treated without exposure to charged particle of the plasma. This lowers substrate heating and prevents it from ion bombardment. This operation regime can be used in the following technological processes: hydrogen chemical treatment, nitriding, etching of organic substrates in atomic oxygen.
    Photos of RFPG-250 operation in both pressure regimes are presented on figure 3.
    Figure 3. Photos of the RFPG-250 operation in high pressure regime on the left and lo pressure regime on the right.

    RFPG works  in high pressure regime  RFPG works in low pressure

    RFPG-250 was installed in a plasma chemical reactor of a special design shown on figure 4. The stainless steel vacuum chamber 250 mm in diameter and 150 mm in height was equipped with magnetic coils. The vacuum chamber was pumped to a base pressure of 1 mPa, and filled with a pure argon. A water cooled 200 mm substrate holder was placed on the bottom of the vacuum chamber coaxially with RFPG-250. The substrate holder could be biased by a DC power supply or by an RF power supply.
    The experimental plasmachemical reactor scheme

    Figure 4. The experimental plasmachemical reactor
    The substrate ion current density and the generator RF voltage amplitude as a function of the external magnetic field magnitude are presented on the figure 5. The external magnetic field is generated Helmholtz magnetic coils. The substrate ion energy distribution is presented on figure 6. So any substrate with ground potential is bombarded with energetic ions from the plasma with a high current density without any additional negative bias.

    Ion current density as a function of power

    Figure 5. The substrate ion current density and the generator RF voltage amplitude as a function of the RF power.

    Ion energy distribution (Ar) Ion energy distribution (Ar+N2)

    Figure 6. The ion energy distribution on the grounded substrate.
    RFPG-250 operation in a large volume
    RFPG-250 can be used in a broad range of pressures. The operating gas pressure and an external magnetic field can be used to control the plasma density distribution in a vacuum chamber. The plasma density distribution can be various, in some cases a flat profile near the 200 mm in diameter substrate with the less than 2% relative heterogeneity, or it can be concentrated into a thin beam and directed towards a specific location inside a vacuum chamber. The operation of RFPG-250 with the plasma concentration by an external magnetic field is presented on figure 7. A stainless steel vacuum chamber is 500 mm in diameter and 700 mm in height. The plasma column diameter is approximately equal to the RFPG-250 body diameter. The process of diamond-like thin film etching in hydrogen plasma was carried out.
    Генератор плазмы РПГ-250 в камере большого объёма Травление алмазоподобного углерода в водородной плазме
    Figure. 7. The RPG-250 operation in a large volume. Diamondlike film etching, sample holder 100 mm in diameter.

    RFPG-250 operation in large volume DLC etching in Hydrogen plasma

    Figure. 8. The RFPG-250 operation in large volume. Nitrogen plasma.

    Nitrogen plasma of RFPG-250


    2 comments

    • Comment Link Камшилин Андрей Thursday, 17 November 2016 20:26 posted by Камшилин Андрей

      Добрый день!
      Каков входной импеданс РПГ-250 и РПГ-128?
      Спасибо!

    • Comment Link Василий Григорьев Saturday, 19 November 2016 12:22 posted by Василий Григорьев

      Добрый день!
      Сильно зависит от режима работы, параметров плазмы и состава газов.
      В рабочем режиме R=1,5..4,5 Ом, L=0,4 мкГн.
      Для подключения к генератору необходимо согласующее устройство. Мы предлагаем автоматические согласующие устройства СУРА.

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