NanoClean – Model 1070

CLEAN LARGE OBJECTS AND GRIDS

In addition to traditional electron microscopy applications, many other objects can benefit from plasma processing. Larger objects, such as pieces of semiconductor wafers or scanning electron microscopy (SEM), atomic force microscopy (ATM), or secondary ion mass spectrometry (SIMS) holders can also be cleaned.
For biological transmission electron microscopy (TEM) applications, grids can be subjected to the plasma to promote hydrophilic wetting.

Electron microscopy demands clean specimens and holders

Clean, well prepared specimens are imperative for imaging and microanalysis in electron microscopy. TEM requires that specimens be prepared without altering their microstructure or composition.
Modern electron microscopes with high brightness electron sources such as LaB6 filaments and field emission guns (FEG) use a small electron probe with high beam current for microanalysis, yielding high-resolution images as well as enhanced analytical data. As probe size decreases and beam current density increases, specimens tend to become easily contaminated. As a result, the quality of the specimen and the cleanliness of both the specimen and the specimen holder are more important than ever.
Contamination typically comes from several sources: inadvertent touching of specimens or specimen holders, electron microscope column contamination, and adhesives or solvents used in the preparation process. Even when great care is taken to clean the specimen, standard cleaning methods are often not completely successful.

Model 1070 NanoClean for electron microscopy applications

The Fischione Model 1070 NanoClean cleans specimens and holders immediately before they are inserted into an electron microscope. Plasma cleaning both removes existing carbonaceous debris from the specimen and prevents contamination during imaging and analysis.
A low-energy, inductively coupled, high frequency, downstream plasma effectively cleans the specimen surface without changing its elemental composition or structural characteristics. Highly contaminated specimens can be cleaned in two minutes or less.
The NanoClean readily accepts one or two side-entry specimen holders for all commercial TEMs and scanning transmission electron microscopes (STEMs), and can accept bulk specimens for cleaning before conducting SEM or surface science analysis.

Cleaning specimens and holders

The NanoClean removes contamination from a wide variety of materials prepared by a variety
of techniques. The specimen holder is inserted through a port into the plasma chamber. The port contains a vacuum-sealing surface compatible with the specimen holder’s O-ring.
The chamber is configured to accept one or two specimen holder ports. Ports are available for side entry specimen holders for electron microscopes manufactured by :

• FEI Company/Philips Electron Optics
• Hitachi High Technologies America Inc.
• JEOL Ltd.
• Carl Zeiss Microscopy

Ports are easily interchangeable without tools in as little as 10 seconds.
For cleaning specimens containing significant amounts of carbon or specimens mounted onto carbon support grids, shielded specimen holder ports are available that optimize the cleaning rate of the plasma.

Imaging with confidence

Plasma cleaning is an essential final step in the preparation of specimens for electron microscopy. Use the NanoClean to be confident that carbonaceous contamination will not interfere with imaging or analysis, even during fine probe microanalysis for extended periods.

Plasma cleaning for SEM (EDX)

The benefits of plasma cleaning are not only for TEM but also for bulk specimens, which can be readily introduced through the chamber’s top port. Specimens for SEM and surface analysis can be cleaned as well as specimen holders, aperture strips, tweezers, specimen clamping rings, and anything else that can be placed into the plasma chamber.

Plasma chamber

The plasma is created in a cylindrical chamber made of quartz and stainless steel. Sophisticated gas dynamics ensure that the plasma is evenly distributed within the chamber to clean the specimen with negligible heating. A high-frequency antenna, located outside the chamber, inductively couples the oscillating electromagnetic power to the process gas contained in the chamber. None of the instrument’s components are located within the chamber.
Receptacles on the front surface of the chamber can accept two ports for standard electron microscopy specimen holders. A view port provides the ability to observe the inside of the chamber. A lid on top of the chamber allows larger objects to be placed into the plasma.

Vacuum system

An oil-free vacuum system is essential to prevent contamination. The vacuum system for the NanoClean consists of a turbomolecular drag pump and a multistage diaphragm pump, an ideal combination for establishing suitable vacuum characteristics to activate and sustain the plasma. The vacuum level is measured by a Pirani gauge.
The chamber includes a load lock for rapid specimen exchange which allows plasma cleaning to begin almost immediately after a specimen is inserted. An electronically actuated gate valve isolates the plasma chamber from the vacuum system. Pump down time for the chamber is less than 50 seconds. Also, the chamber can be vented within 5 seconds after the conclusion of plasma processing. These features make the NanoClean ideal for high-throughput applications.
The NanoClean can also be used to evacuate individual specimen holder vacuum storage containers and cyrotransfer TEM specimen holder dewars.
A port plug inserted into the specimen holder port seals the chamber under vacuum when the instrument is not in use.

Power supply

The high frequency (13.56 MHz) oscillating power supply is used to initiate and sustain a low-energy, inductively coupled plasma (ICP). An ICP is ideal for microscopy applications since it delivers ions with energy low enough that the specimen’s properties are not altered.
An automatic matching network ensures that the high frequency power is effectively coupled to
the plasma and the delivered power is suited for the application. The matching network regulates plasma power for a variety of conditions, objects to be processed, or gases employed. It also guarantees plasma compatibility with specimen holders produced for diverse electron microscopes.
Effective shielding prevents high frequency interference and fully complies with FCC guidelines.

Process gas

The NanoClean contains three mass flow controllers and is designed to accept multiple gases. Typically, the time-proven gas mixture of 25% oxygen and 75% argon is connected to one of the gas inlets. The NanoClean is fitted with two additional gas inlets which accept gas supplies that can be blended using the NanoClean’s internal mass flow technology.

Specifications