# Ion beam sources

> Original page (HTML): https://vaclab.ru/devices/ion_beam_sources
> Markdown version: https://vaclab.ru/devices/ion_beam_sources.md
> Manufacturer: LLC "Laboratory of Vacuum Technologies Plus" (LVT), vaclab.ru

The ion sources II made by LLC "Laboratory of Vacuum Technologies Plus" (LVT) operate as anode-layer accelerators. A discharge sustained in crossed electric and magnetic fields burns in the gap between an elongated anode and the magnet poles serving as the cathode. Ions are produced in a thin anode layer and accelerated by the field, forming a beam with a divergence of no more than 2°. The source contains neither grids nor a hot filament cathode: reactive gases do not harm it, and its lifetime is not limited by consumable electrodes.

The beam needs no neutralizer cathode: its charge is compensated by electrons of the secondary plasma generated around the beam itself. This simplifies the vacuum system: the source requires only a dedicated power supply ([BP 351](/bp-351-ion-source-power-supply-1kw), [BP 356.01](/bp-356-01-ion-source-power-supply-gas-flow-control-system)), a gas line and cooling water.

The beam current is regulated by the working gas flow. Within the operating range the ion current is directly proportional to the flow up to a certain limit, specific to each gas. Beyond it the discharge turns into a high-current mode: the voltage drops, the discharge current exceeds the permissible value severalfold, beam formation breaks down and the cathode electrodes erode. Operation in this mode is not allowed. The mean ion energy is roughly half the supply voltage, so the voltage is chosen for the task: lower energies for cleaning and assistance, higher ones for sputtering.

In elongated models the beam is linear: ions are distributed uniformly along the slit, the beam length of standard models ranges from 100 to 825 mm, and a linear current density of up to 25 mA/cm is maintained over the entire length. Such a beam is placed along a rotating drum: parts fixed on its surface pass uniformly through the ion layer as the drum rotates. The source is mounted by its end face or by the rear wall onto a chamber wall, either outside or inside the drum. In the [NIKA-151](/nika-151-mfc-vacuum-processing-complex) system the source is outside the drum, in the [NIKA-158](/nika-158-magnetron-sputtering-system) it is inside, and the [NIKA-146](/nika-146-compact-multifunctional-system) carries two sources at once: one inside and one outside.

For substrate cleaning and deposition assistance, argon, oxygen and nitrogen are normally used. Argon is applied for sputtering materials and cleaning metallic and semiconductor substrates. Oxygen is used to clean oxide substrates such as glass, ceramics and sitall: it removes organic contamination effectively without contaminating the substrate with metal sputtered from the fixtures. Oxygen is also used to assist oxide deposition. Nitrogen suits substrates made of organic materials and assists nitride deposition.

Typical operations with the linear beam include substrate cleaning prior to deposition, ion etching, ion polishing, surface modification and assistance during magnetron and thermal evaporation. The chamber pressure starts at 0.001 Pa. The upper limit for each model is given in its specifications, while the lower limit is set only by the pumping capability: the lower the pressure, the cleaner the treatment.

The separate modification [II-52](/ion-source-ii-52) forms the most compact beam in the range: a cylindrical one with an outer diameter of 24 mm, yet as long as the beams of the other sources and with the same small divergence. The source concentrates power on a small area and is therefore the best choice for sputtering targets up to 50 mm in diameter made of any material: metals including ferromagnetic ones, dielectrics, precious or simply expensive materials, powders. The target is consumed economically, as only its central zone takes part in the process.

For sputtering the source is positioned so that the beam strikes the target at an angle of about 30°. This applies to all sources in the range, including the elongated ones. At this angle the sputtering rate reaches its maximum, the sputtered material travels along the normal to the target surface, where the substrate is placed, and does not coat the source itself, which is normally moved as far from the target as the chamber allows. Ions reflected from the target leave along the law of reflection away from the substrate and do not damage the growing film structure; this matters, for example, for transparent conductive coatings such as ITO.

Key specifications of the ion sources:

- supply voltage 500–5000 V, mean ion energy 250–2500 eV;

- linear ion-current density up to 25 mA/cm;

- maximum beam current from 120 to 2000 mA depending on the model;

- linear beam length from 100 to 825 mm;

- beam divergence no more than 2°;

- working gases: argon, oxygen, nitrogen and others that do not deposit high-resistivity films on the source parts;

- no neutralizer cathode, no grids, no hot filament;

- lifetime over 10 years of intensive operation.

Detailed specifications of each model (beam length and current, voltage range, dimensions) are given on its product page.