Microwave Plasma Source

Microwave technology is finding new applications in plasma laboratories and industries due to the advantages of microwave plasmas such as dense plasma–ions, high active species, electrode less (no contamination) and wide working pressure range. Microwave-assisted plasmas find applications in diamond thin film deposition, surface activation, sterilization, synthesis of nanomaterials, gas abatement etc. To meet the ever demanding requirements from the applications, SAIREM has developed its own range of plasma sources and reactors.

SAIREM can offer advice on choosing the plasma equipment and the microwave frequency adapted to your needs; special configurations are also available upon request.

Surface Wave Plasma Source

Whats is Surface Wave Plasma?

The plasma is created in a dielectric tube placed inside the source
The microwave electric field propagates longitudinally at the dielectric/plasma interface (plasma behaves as an electrical conductor), the wave is progressively absorbed when increasing the distance from the application of the electric field
Radially the wave is strongly attenuated on skin depth

This principle allows to create and maintain plasma columns with lengths which depend on the operating pressure, microwave power and gas nature. Sairem has designed following microwave plasma sources based on this principle for users to choose. Please see following information.

Downstream plasma source @ 2.45 GHz

This surface wave type of plasma source generates plasma in a dielectric material tube (diameter 20-60 mm) placed in a standard WR340 waveguide. This plasma source enables the ignition and sustaining of long plasma columns depending on the pressure, the microwave power and the nature of the ‘plasma’ gas.

Pressure Range:
A few 10^-2 mbar up to atmospheric pressure
Gas Type:
Ar, N2, O2, air, …
Maximum Power:
6kW
Applications:
Creation of radicals / reactive species, surface activation, PECVD, gas abatement, gasification, sterilization (UV), nanopowder synthesis

Surfaguide plasma source @ 2.45 GHz

Surfaguide plasma source generates plasma in a dielectric tube via a surface wave. The main feature of the Surfaguide is the reduced height of the standard waveguide to locally intensify the microwave electric field and consequently, help with the ignition and sustaining the plasma. This source is principally suited for operation in the range of a few mbar up to atmospheric pressure.

Pressure Range:
A few 10^-2 mbar up to atmospheric pressure
Gas Type:
Ar, N2, O2, air, …
Maximum Power:
6kW
Applications:
Creation of radicals / reactive species, surface activation, PECVD, gas abatement, gasification, sterilization (UV), nanopowder synthesis

S-Wave plasma source @ 2.45 GHz

The S-wave is a plasma reactor used for microwave propagation and designed to launch a surface electromagnetic wave. The S-wave is an effective plasma source for the production of reactive / excited species using a 6 mm or 8 mm diameter dielectric tubes. When used for measurements and analysis, to avoid spurious spectral lines due to the mains 50/60 Hz, we recommend using Sairem low ripple solid state microwave generator GMS 200 W.

Pressure Range:
A few 10^-2 mbar up to a few bars
Gas Type:
Argon or argon based gas mixture at atmospheric pressure. All gases at reduced pressure.
Maximum Power:
300W
Applications:
Creation of radicals / reactive species, surface activation, elementary analysis

Coaxial Plasma Source (ECR)

Sairem's coaxial plasma sources adapts state-of-the-art ECR design, featuring:

High plasma density
Multi-source configuration in source plane for large plasma processing area
Combined with Sairem solid-state microwave generator, these sources can maintain plasmas at power levels from 1 W to a few W. For small mismatches due to operating condition limitations, it is always possible to vary the frequency of the solid state generator to match the impedance.

Depending on pressure range and process parameters, Sairem have 2 coaxial sources for users to choose.

Aura-Wave ECR Plasma Source
Hi-Wave ECR Plasma Source

Aura-Wave ECR Plasma Source

	Pressure range	10^-4 mbar ~ 10^-2 mbar
	Input gas	Ar, N₂, O₂, CH₄, He, air ...
	Plasma density	> 10¹¹ cm^-3 at 10 cm from sources in multisource configuration
	Application	Creation of radicals, surface activation, PECVD, etching, surface treatment, sterilization via reactive species / UV / ionic bombardment

Microwave Components

Sairem can offer advice on choosing the standard component better adapted to your needs; special configurations are also available upon request. These components include

Wave Guide & Flange
A waveguide is a hollow metal structure that allows the transmission of the electromagnetic waves. Sairem offers standard waveguides at 2.45 GHz, i.e. WR284, WR340 and WR430 and at 915 MHz, i.e. WR975, with or without flanges.
Impedence Turner
An impedance tuner is a section of waveguide usually placed between the microwave generator and the applicator used to help optimizing the transfer of energy from the source to the load. Sairem makes impedance tuners that can be operated manually or automated.
Sliding Short-Circuit
A sliding short circuit is a waveguide-based component used in tuning applications for the adjustment of the resonance frequency of a monomode cavity; the sliding short circuit can be also used in connection with a hybrid T for the tuning of microwave applicators at high power. Sairem sliding short circuit features an innovative quarter wavelength non-contact movable short.
Directional Couplers
The directional coupler is a waveguide device that should be placed between the microwave generator and the applicator/cavity to measure the incident and/or reflected power. The essential feature of the directional coupler is that it can only couple power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the coupled port. The N-type connectors of Sairem’s dual directional coupler must be connected to a 2-probe milliwattmeter for the simultaneous measurement of incident and reflected power.
Microwave Window
The role of the microwave quartz or PTFE window is to transfer the microwave energy between two media without inducing any reflected power. The window allows the separation of different environments at pressure close to atmospheric; in addition, the PTFE window can be used as a ‘light barrier’, i.e. hides the light emitted by plasma that could trigger off the arc detector installed in some microwave generators.

Microwave Leakage Meter

2.54GHz Microwave Leakage Meter
915Hz Microwave Leakage Meter

2.54GHz Microwave Leakage Meter

	REF	IFP
	Frequency	2450 MHz
	Graduation	0 to 5 mW/cm²
	Precision	5% at full scale, 10% on linearity
	Size	Detector 26mm x 72mm x 142mm
	Total weight	350g

915Hz Microwave Leakage Meter

	REF	DFM L24DC
	Frequency	915 MHz (integral band filter from 902 ~ 928 MHz)
	Detection distance	Adjustable for a microwave leakage of 2.3 mW/cm² at distance up to 20m; delivery preset 2.3 mW/cm² at 5m. CE Directive 2004-40 states max. microwave leakage level of 23 W/m², i.e. 2.3 mW/cm²
	Mains	24 VDC, consumption 2 mA in stand-by mode, 50 mA in detection mode
	Connectors	M12A, female 5 pins, for M12 standard cables, 5m standardd length (10m optional) 2 terminals for 24 VDC, 3 terminals to contact alarm
	Contacts	1 inverter, power cut-off 1 A at 24 VDC
	Dimensions	160 mm x 119 mm x 62 mm, weight 350g
	Wall fixing	Base to fix on the wall with 2 screws (not provided); upper block mounts on the base through bayonet-type system.

Tags: Microwave plasma, Sairem