Ion beam#Uses

The ion milling is a commonly used physical method that is applied to structure most electrical components, as well as for the production of ultra-thin samples. It is a dry etching. Other designations are ion etching, ion beam etching, ion milling or English. When bundled defined ion beam and the detectors suitable method for imaging or material analysis is used, see Focused Ion Beam.

Operation

Accelerating ions, usually argon, under a high vacuum in the direction of the substrate to be processed results in the impingement of a pulse transmission of the high energy ions takes place on the substrate, and its surface is sprayed and ablated. This process is also referred to as sputtering.

Application

The ion milling allows to produce thin samples with a thickness below 100 nm. Samples of this thickness are a necessary condition for transmission electron microscopy. It occurs in crystalline samples to amorphization of the near-surface layers (a few nanometers). However, the original crystal structure remains in the interior of the sample obtained, and the amorphous layer does not disturb the observation. Due to the limited geometry of the sample, the heat generated by the ion milling not only can be effectively removed, and the samples heated to several hundred degrees Celsius ( highly dependent on the thermal conductivity of the sample and thus the material used ). Temperature-sensitive samples are therefore separately cooled with liquid nitrogen during the ion thinning.

Also sample thicknesses less than 5 nm can be achieved by Ionendünnungsverfahren as it is necessary for high-resolution transmission electron microscopy. Here disturb the amorphous surface layers, so they must also be removed. The samples are again nachgedünnt after the actual ion milling at a very flat angle with very low ion energy. The actual thinning occurs under greater angle and with more energy, since a higher removal rate is achieved.

The ion milling is used as an etching process for patterning of microchips. To engage, for example, structures in a layer of less than 200 nm, can not be rough mechanical process, such as laser machining, etc., to use, it is necessary to rely on delicate procedure. So you can coat the layer of photoresist, transferred into these structures by photolithographic patterning method and then pay off the exposed areas with ion irradiation.