NanoMill TEM Specimen Preparation System – Model 1040

PLASMA CLEANING

Following the NanoMillingSM process, Fischione highly recommends that you plasma clean the specimen and specimen holder.

During fine-probe microanalysis, organic contamination may build up on the specimen. A 10 seconds to 2 minutes cleaning time in the Fischione Model 1020 Plasma Cleaner or Model 1070 NanoClean removes the contamination without altering the specimen’s structure or composition. Longer cleaning times can remove contamination spots caused by previous TEM viewing of specimens that were not plasma cleaned.

Create thin specimens for TEM

Fischione’s Model 1040 NanoMill® TEM specimen preparation system is an excellent tool for preparing the ultra-thin, high-quality specimens needed for transmission electron microscopy (TEM) imaging and analysis.
The variable energy ion source generates ion energies as low as 50 eV. In addition, the beam size is as small as 1 μm, enabling removal of amorphization, implantation, or redeposition from targeted areas.
An ideal application for the NanoMill systemis post-focused ion beam (FIB) processing. Although the FIB is highly effective in preparing TEM specimens, its liquid metal (Ga) ion source often results in amorphization and Ga implantation. These damaged layers can be as much as 10 to 30 nm thick. The NanoMill system is ideally suited to removing these layers.

Targeted, ultra-low-energy milling

The NanoMill system’s ion source features a filament-based ionization chamber and electrostatic lenses. This source was specifically developed to produce ultra-low ion energies and a small beam diameter. The source uses an inert gas, argon, and has an operating voltage range of 50 eV to 2 kV at variable working distances. The source yields sufficient current density to remove specimen damage within a reasonable time. The NanoMilling process can be accomplished in as little as 20 minutes.
Because the ion beam can be focused into a 1 μm diameter spot, redeposition of sputtered material onto the area of interest is avoided. Beam current and spot size are adjusted by using different sized TEM-type apertures.
The feedback control algorithm for the ion source automatically produces stable and repeatable ion beam conditions over a wide variety of milling parameters.
The beam can be either targeted at a specific point or scanned over the specimen’s surface. This is particularly important when targeting a specific area for selective milling or directing the ion beam to a FIB lamella positioned on a support grid.
Ion source parameters are easy to program; simply enter the emission current and accelerating voltage. In addition, it is easy to establish the specimen position. Once you enter the operating parameters, the computer controls the instrument functions.
In the imaging mode, select the scan speed, magnification, focus, brightness, and contrast. With a 3 mm field of view, the entire surface of a grid or specimen can be imaged, making it extremely easy to mill the area of interest. This is useful when targeting a FIB lamella.

SED specimen targeting

During operation, it is essential to know the position of the ion beam in relation to the specimen. This is of particular importance for post-FIB processing in which the FIB lamella, mounted onto a support grid, can be as small as 10 μm².
Targeting directs the beam to a specific area of interest. An Everhart-Thornley secondary electron detector (SED) is used to image the ion- induced secondary electrons generated from the targeted area. The SED output is processed by the NanoMill system’s imaging electronics to provide a real-time view of the specimen, implicitly aligned with the ion beam. You can select the scan speed – either faster imaging or enhanced image quality. Frame averaging is employed to reduce noise.
The SED image is displayed on the Main tab. In point mode, place the cursor on the specimen
to focus the ion beam to that point. If you need to thin a larger area, select the area and the ion beam will scan within it. The position and the dimensions of the scan box are displayed (in microns).

Computer control

The NanoMill system operates with minimal user intervention. Milling conditions, such as ion source parameters, milling angle, specimen position, temperature threshold, and processing time, are programmed via a single window. The system software allows you to :

• Store and reuse milling sequences (recipes), which leads to highly reproducible results
• Control access to the various instrument controls and maintenance functionality through the assignment of user privileges
• Use shortcut keys to speed programming and operation
• Review system operation through the Data and Error Logs

Typical processing sequence

For effective specimen preparation, a series of operational sequences can be established. Typical methodology starts with rapid milling at higher ion energies. As the specimen thins, the ion energy is reduced, resulting in a lower milling rate that eliminates artifacts. User-determined ion beam targeting at each step of the operation ensures that the proper area of the specimen is processed.

Automatic gas control

Gas is regulated automatically using precision mass flow control technology. An integral particulate filter ensures that high-purity gas is delivered to the ion source. This reduces specimen contamination and allows the NanoMill system to operate for longer cumulative periods before maintenance is required. The ion source uses low flow resulting in minimal gas consumption.

Contamination-free, fully integrated dry vacuum system

The fully integrated vacuum system includes a turbomolecular drag pump backed by a multistage diaphragm pump. This oil-free system assures a clean environment for specimen processing.
The operating system vacuum is 1 x 10-4 mbar and the base vacuum is 3 x 10-7 mbar. The chamber vacuum level is measured with a combination cold cathode and Pirani gauge. Vacuum status is displayed on the Main tab and the vacuum level is displayed on the Maintenance tab.

Specimen mounting

To prevent specimen shadowing, a unique specimen holder provides unobstructed ion trajectories to the specimen, even at 0°. This is particularly important when the ion beam is targeted at the leading edge of a FIB-prepared specimen.
The specimen is mechanically affixed to the specimen holder, thus eliminating the possibility of contamination from an adhesive. A separate loading station (included) provides a platform for the specimen that eases holder positioning.

Automatic load lock for quick specimen transfer

The NanoMill system features a load lock for rapid specimen exchange. The specimen holder is connected to the end of a conventional transfer rod. After the load lock door is closed and the load lock is evacuated, an automatic gate valve opens and the specimen holder is manually inserted into the specimen stage using the transfer rod.
You can observe the specimen holder through
a viewing window during transfer to and from the specimen stage. A chamber light facilitates the transfer process. Once closed, the gate valve prevents light from entering the chamber and affecting the SED signal. After the load lock is vented, the specimen can be rapidly transferred to the TEM, thus reducing specimen contamination from ambient conditions.