- What is a rotary magnetron?
- What is a large area substrate?
- What is the difference between rotary magnetrons and planar magnetrons?
- How do I select a rotary magnetron for my application?
- How do I calculate my dynamic deposition rate?
- Why should I use a rotary magnetron over a planar magnetron?
- How many magnetrons would I need for my application?
- How long should my target be?
- How do I connect to my SCI rotary cathode?
A rotary magnetron is a tool for depositing thin layers of metal, metal oxide, and metal nitride films onto
large area substrates in a vacuum environment.
Large area substrates are usually wide flat rigid panels (such as glass or plastic) or wide flexible webs (typically
plastic or metal) that are coated as they pass by the stationary magnetrons. Some examples of products
made from these substrates include Low-e window glass, solar panels, solar control window tint, and flat panel displays.
Planar magnetrons are sputtering deposition tools that use permanent magnets, high voltage power, and process gasses
in a vacuum chamber to deposit coatings onto substrates from flat target materials. Rotary magnetrons use all of the
same basic concepts as planar magnetrons but instead of using flat plate or tile targets they use target tubes that typically
hold much more target material and are much more efficiently cooled. This allows them to sustain much higher deposition
rates than planar magnetrons.
Most target materials that are commonly sputtered can be made into target tubes often at lower material costs and operating costs.
To help you select a rotary magnetron we have created a customer application questionnaire that asks for information such as:
- Substrate velocity
- Coating Thickness
- System Geometry
- New installation, planar magnetron upgrade, or replacement rotary magnetron
To determine your dynamic deposition rate multiply the thickness of the coating you want to make in nanometers by the
velocity of your substrate in meters per minute. As an example a SiO2 coating that is 20nm thick with a substrate speed
of 1.5 meters per minute uses the following equation:
20(nm) * 1.5(m/min) = 30(nm*m/min)
Rotary magnetrons offer the following advantages over planar magnetrons:
- Higher deposition rates
- Lower capital investment
- Lower operating costs
- Higher target material utilizations
- Reduced arcing and particle contamination
- Longer campaign times
- Shorter target change times
- Better process stability over the lifetime of the target material
- Lower impedance operation since the magnetic field designs are much narrower and stronger than the
wide weaker planar magnetron magnetic fields
- Planar magnetrons utilize wide magnetic fields to increase target material utilization while rotary magnetrons
rely on the rotating target tube to achieve higher material utilizations
If you want we will calculate the deposition rates and number of magnetrons required for your application or continue reading.
Each target material and coating process has limitations as to how fast the material can be deposited from each magnetron
and thus each different process has a limited dynamic deposition rate (DDR). These limits for most materials have been
experimentally obtained and are correlated with the power density that was applied to the target at the time of the deposition.
Using this information we create a unit for calculation the normalized dynamic deposition rate (nDDR) that has the units
of (nm*m/min)/(kw/m). This unit can be used along with the maximum power density that target vendors recommend using
with their targets to figure out approximately what the dynamic deposition rate of each magnetron will be for a particular process.
Desired (or maximum) Power Density = Power applied from power supply in kW divided by the target tube length in meters -> (kW/m)
nDDR(nm*m/min)/(kW/m) * Desired Power Density(kW/m) = DDR
DDR / Substrate Velocity = Coating Thickness per magnetron
Number of Cathodes Required = Target Coating Thickness / Coating Thickness per magnetron
Here is a list of typical nDDR values.
The length of the target tube is determined by the substrate length and the coating uniformity requirements. SCI refers to the
overall length of the backing tube as the basis for calculation as it will define the system geometry. The actual length of the
material to be sputtered will be shorter than the backing tube length. The standard calculation that we use is the following:
Backing Tube Length = Substrate Length + 4 * Target To Substrate (TTS) distance
This equation is typically used for TTS distances between 75 to 150mm. If the application has uniformity requirements higher
than +/-2% it is suggested to add additional length to the target in order to reduce the initial uniformity tuning required.
For an illustration of how to apply this calculation, click here
You will need to provide four types of connection to your SCI endblock:
Cooling water: Provided to the cathode using ¾” or 1” flexible hose, connecting to a hose barb or other customer
specified water fitting. Nominal inlet pressure should be 40 psi, with a maximum of 100 psi. Water flow rates should
be 1 liter per minute per kW of applied power, or greater. Water quality should be 100-300 micro Siemens, with 75 micron
filtration. Inlet temperature should be less than 30 degrees C and maintained above the ambient dew point to prevent condensation.
Power Supply Connection: Various connection styles are provided, using M8 or M10 screws. SCI can provide custom
length, low impedance cable assemblies which are optimized to your cathode power rating and mounting pattern.
Drive Motors: SCI provides AC inverter duty motors with its end blocks. The inputs to this motor are 230V, three phase,
10-90Hz, 480V is available. Speed control is provided by the use of a customer supplied variable frequency drive (VFD.)
The VFD can be selected to accept your local input voltage and number of phases and convert to the motor inputs.
SCI can also supply these drives upon request.
Drive Encoders: SCI provides encoders with every rotary cathode. These encoders are used to ensure cathode rotation a
nd if desired, measure rotation speed.
To connect to the encoder:
To confirm rotation only: The encoder can be connected to a signal conditioner (such as the Red Lion IFMR0036) that will
convert the encoder pulses to a digital signal which can be used to interlock rotation. SCI can provide these signal
conditioners upon request.
To measure rotation speed: The encoder is a simple 100 pulses per revolution quadrature encoder. The pulses from
channel A (and/or B) can be used for speed measurements. The SC/SM cathodes are set to 294 pulses per target
revolution while the MC/MM is 235 PPR.
SCI TRM-Bar and QRM-Bar magnetics give you the flexibility you need. Provided with encapsulated magnets,
magnet assemblies are adaptable to fit your process requirements.