Ion Beam Etching
Ion Milling | FIB | HIM
Argon Ion Milling
Argon ion beam etching systems, also known as ion milling systems, generate Ar ions in a Kaufman source and accelerate them through a grid towards the substrate. Behind the source, the ion beam is then typically neutralized by an additional electron source. The ion beam hits the substrate relatively well directed and offers a very uniform etching profile over a diameter of a few centimeters. Ion beam etching is a purely physical etching process without chemical selectivity. Depending on the combination of the layer to be etched and the mask material, ratios of up to 1:5 can be achieved in the etching rate.
- Roth & Rau Ionmill (AG Fleischer)
- Ionmill (AG Kleiner/Kölle)
FIB - Focused Ion Beam
An FIB works principally similar to a scanning electron microscope, with the difference of typically gallium ions being focused into a beam instead of electrons. The gallium ions are obtained from a liquid metal ion source whose lifetime is limited by the consumption of the Ga supply. Since Ga ions have a multiple of the mass of an electron and are typically also accelerated to 30kV, the energy input into the substrate is significantly higher, so that the surface atoms of the substrate are removed. With the gallium beam it is possible to create structures with a resolution of up to 30 nm.
FEI Strata DB235
The Strata DB235 is a dual beam system, i. e. in addition to the Ga-column it has an additional electron column for imaging. The columns are mounted at an angle of 52° to each other so that the electron beam can be used to analyze the vertical intersection of a cross section very well.
In addition, our FIB has a gas injection system with platinum precursor. Thus, cutting edges of e. g. cross sections and lamellas can be protected or 3D structures such as tips, columns or etching masks can be created directly (see ion beam induced deposition).
Our FIB is also equipped with two Kleindiek micromanipulators to manipulate nanoparticles or to remove TEM lamellae.
Unfortunately, our system is out of order, but we will happily give advice on alternative systems from our colleagues at other institutes.
HIM - Helium Ion Microscope
The helium ion microscope not only provides excellent imaging resolution but can also be used for high-resolution structuring. The helium ions are produced at a tip of only three individual atoms, the trimer. Each of these atoms generates an ion beam in the helium atmosphere at the tip. The most intensive beam is selected and directed into the microscope's optics and focused on the sample. The atomically small source of the beam enables an optical system with a depth of field of > 1.5 µm. This makes it surprisingly easy to create structures of a few nanometers with almost vertical side walls even in relatively thick layers.
Zeiss ORION Nanofab
Our Orion Nanofab with neon option allows the source to be operated with neon instead of helium. For this purpose the emitter is run in an neon atmosphere. In operation with neon ions, the gap between the Ga-FIB and the helium ions is closed in both the achievable resolution and the etch rate.
The Orion Nanofab also has two Kleindiek manipulators that can be used, for example, to position nanoparticles or contact individual electrodes.
In addition, the gas injection system with three precursors can also be used to selectively deposit platinum, tungsten or silicon oxide containing layers (see ion-beam-induced deposition).
