Carbon and Sputter Coaters – high vacuum
Q150T Plus -Series from Quorum Technologies
The Q150T Plus series are fully automated, modular coating systems for the deposition of electrically conductive carbon or metal films recommended for electron microscopic applications at low and medium-high resolutions. The Q150T Plus can be acquired solely as a carbon coater (TE), sputter coater (TS) or as a combined system for carbon and sputter coating (TES). The application of a turbomolecular pump enables the sputtering of oxidising metals, which have a lower grain-size and are suited for high-resolution electron microscopy applications.
| Fully automated coating process |
(incl. download of process log files in .csv format via USB)
|Built-in turbo pump, vacuum down to 5 x 10-5 mbar|
|Large sample chamber: 150 mm Ø|
|Fast turnover times / coating cycles|
| TE: carbon fibre or rod evaporation, optional: |
metal evaporation set-up
|TS: sputter coating of noble metals and non-oxidising metals|
|TES: a combined system both for sputtering and carbon coating|
|GB: combined system for use in a glovebox|
The Q150T Plus series is available in four configurations:
- Q150T E Plus – an automatic carbon cord coater, can be optionally fitted to evaporate metals
- Q150T S Plus – an automatic sputter coater for non-oxidising metals, can be optionally fitted with a glow discharge insert
- Q150T ES Plus – a combined system both for sputtering and carbon coating
- Q150 GB – a combined system for use in a glovebox
The different head plates can easily be exchanged within seconds. The unit recognizes the replacement and the operating menu changes accordingly. A touch screen is used to enter coating parameters, display the coating sequence and show error messages. Multiple users can store up to 1000 recipes including all parameters. By awarding access rights, selected parameters can be protected against deletion and unauthorized modification. Only the administrator has access to all settings. A USB-port allows the download of recipes and process logs.
Several optional sample stages ensure the efficient and reproducible coating of samples within a wide range of geometries.
The fully automated process does not require tedious adjustment of a needle valve to control argon gas flow. Instead, the user can control the process vacuum, gas flow is adjusted automatically. Depending on the set gas value (vacuum), the voltage is adjusted accordingly and the desired sputter current (mA) is kept at a constant. This way, samples with strongly irregular topography can also be uniformly coated at low sputtering currents.
The glass chamber can be completely removed, granting easy access to the sample stage and facilitating the cleaning process.
Operating principle: carbon coater
Thin conductive layers of carbon are generated by resistive evaporation of carbon filaments or rods. A current of up to 70 A is needed to evaporate carbon from rod or filament. The pulsed carbon rod/fibre evaporation can be controlled by using an optional film thickness monitor. By evaporating a carbon fibre, up to 20 nm of carbon film can be deposited, whereas with carbon rods, thicknesses from 3 to 15 nm can be reached. Amorphous carbon films evaporated from a carbon rod in a turbo pumped system are much finer and of higher quality than those from a rotary pumped system. High quality carbon films are used as support films or surface replicas in TEM applications or for EBSD and high-resolution SEM applications.
Operating principle: magnetron sputtering
Magnetron sputter coaters (also referred to as "Cool Sputter Coaters") are equipped with a special magnet, which is located in the sputter head (cathode) near the target.
- electrons are available for ionization of further process gas ions
- excessive heating is avoided
- optimisation of the utilisable target surface
During sputter coating, a vacuum is produced in a vacuum chamber and a process gas, preferably argon, is continuously leaked into the chamber. Argon has an optimal ion size and does not chemically react with other molecules.
Within a vacuum window from approx. 1 x 10-1 mbar to 5 x 10-3 mbar, process gas atoms are ionized in an electrical field, which creates a plasma. Positively charged argon atoms are accelerated towards the magnetron head with the target (cathode) and erode target atoms, which reach all surfaces within the vacuum chamber, including the sample to be coated.
The Q150T Plus Series comes equipped with a turbomolecular pump and a special power supply, making it possible to sputter oxidising metals. Films sputtered from such materials exhibit a smaller grain size which allows imaging at higher resolutions in the SEM. In order to sputter oxidising metals like chromium, the oxide layer needs to be removed from the target’s surface (requires a current up to 200 mA) and the atmosphere in the work chamber needs to be oxygen-free
|Q150T S / E / ES Plus|
|Instrument case||585 mm B x 470 mm D x 410 mm H (total height with coating head open: 650 mm)|
|Work chamber||Borosilicate glass 150 mm ID x 133 mm H|
|Safety shield||Polyethylene terephthalate (PET) – cylinder|
|Display||115.5 mm x 86.4 mm (active area) capacitive touch colour display|
|User interface||Intuitive full graphical interface with touch screen buttons, includes log of the last 1000 processes and USB-port.|
|Sputter target||Disc style 57 mm Ø x 0.1 mm thick chromium (Cr) target is fitted as standard. (TS/TES versions only)|
|Turbomolecular pump||Internally mounted, 70 l/s air-cooled|
|Rotary pump||50 l/min. two-stage rotary pump with oil mist filter (order separately, see AG-DS102)|
|Vacuum measurement||Pirani gauge as standard. A full range gauge (10428) is available as an option|
|Typical ultimate vacuum||∼5x10-5 mbar in a clean system after pre-pumping with dry nitrogen gas|
|Sputter vacuum range||Between 5x10-3 and 1x10-1 mbar|
|Specimen stage||50 mm Ø rotation stage. Rotation speed 8-20 RPM. For alternative stages see options and accessories|
|Sputtering||0–80 mA to a pre-determined thickness (with optional FTM) or by the built-in timer. The maximum sputtering time is 60 minutes (without breaking vacuum and with built in cooling periods)|
|Carbon evaporation||A robust, ripple free DC power supply featuring pulse evaporation or ensures reproducible carbon evaporation from rod or fibre sources. Current pulse: 1–90 A|
|Metal evaporation/aperture cleaning insert |
|or thermal evaporation of metals from filaments or boats. For cleaning SEM or TEM apertures a standard molybdenum boat (supplied) can be fitted. The metal evaporation head is set up for downwards evaporation, but upward evaporation can be achieved by fitting two terminal extensions (supplied).|
|Gases||Argon sputtering process gas, 99.999% (TS and TES versions)|
|Electrical supply||90–250 V 50/60 Hz 1400 VA including rotary pump power. 110/240 V voltage selectable.|
|Conformity||CE conformity: Power factor correction. Complies with the current legislation (CE Certification) and ensures efficient use of power, which means reduced running costs|
|Options and accessories|
|10879||Carbon rod evaporation insert for 3.05 mm Ø rods (TE and TES only). Includes manual rod shaper and 3.05 mm Ø x 300 mm (pack of ten) carbon rods.|
|10262||Glow discharge insert. Used to modify surface properties (e.g. hydrophobic to hydrophilic conversion) (TS and TES versions only). Can be retrofitted.|
|10726||Additional sputter insert for quick metal change (TE and TES versions only). NB: This is an entire sputtering assembly; individual targets can also be purchased.|
|10360||Variable angle 'Rotacota' rotary planetary specimen stage (rotational speed 8-20 RPM). 50 mm Ø specimen platform with six stub positions for 15 mm, 10 mm, 6.5 mm or 1/8" pin stubs. Stage rotation speed variable between 8–20 RPM.|
|10357||Variable tilt angle specimen stage with adjustable tilt up to 90˚. 50 mm Ø specimen platform with six stub positions for 15 mm, 10 mm, 6.5 mm or 1/8" pin stubs. Stage rotation speed variable between 8–20 RPM.|
|10458||Flat rotation specimen stage for 4"/100 mm wafers, includes gear box for increased coverage. Stage rotation speed variable between 8-20 RPM.|
|10454||Film thickness monitor (FTM) attachment. Including oscillator, feed-through, quartz crystal holder and quartz crystals.|
|10429||Extended height vacuum chamber (214 mm in height - the standard chamber is 127 mm high). For increased source to specimen distance and for coating large specimens.|
|10731||Vacuum spigot allows more convenient connection of the vacuum hose to the rear of the Q150T when bench depth is limited.|
Thermal evaporation of thin carbon layers
Thin carbon layers are evaporated onto non-conductive samples in electron microscopy for applications like EDX or WDX to prevent charging of the sample. Carbon has a low x-ray absorption, assuring better detection of x-rays than with metal coatings.
Deposition of thin metal layers
Sputter coaters are used to deposit a thin metal layer on the surface of a sample/substrate. For electron microscopy applications, electrically conductive films need to be deposited on non-conductive surfaces, to prevent electrons from the microscope's electron beam from accumulating on the sample surface, causing the latter to become charged. Such a charge would prevent imaging of these surfaces with the SEM. The desired films should be extremely thin, but electrically conductive, with a thickness of 3 - 20 nm.
Advantages of sputter coating and evaporating in high vacuum
Chromium or high-vacuum sputter coaters have become more established in the past few years. Their advantages are a virtually “clean” vacuum, due to the application of a turbomolecular pump, and a powerful magnetron head, capable of removing the oxide layer on the target material. Sputter currents as high as 150 – 200 mA enable the highly efficient removal of oxide layers on oxidising targets. Rotary pumped sputter coaters do not support sputtering of oxidising metals.
The deposition of carbon films also benefits from lower pressure in the work chamber. Under high-vacuum conditions, very thin, amorphous carbon layers can be produced. These can be used as sample support films or to create surface replicas for TEM applications.
Glow discharge is used to alter the properties of sample surfaces. TEM carbon support films are hydrophobic after fabrication. After treatment with glow discharge, they become hydrophilic, thus allowing an even spread of aqueous solutions.