Richard L. Martens

First Data from a Commercial Local Electrode Atom Probe (LEAP)

The first dedicated local electrode atom probes (LEAP [a trademark of Imago Scientific Instruments Corporation]) have been built and tested as commercial prototypes. Several key performance parameters have been markedly improved relative to conventional three-dimensional atom probe (3DAP) designs. The Imago LEAP can operate at a sustained data collection rate of 1 million atoms/minute. This is some 600 times faster than the next fastest atom probe and large images can be collected in less than 1 h that otherwise would take many days. The field of view of the Imago LEAP is about 40 times larger than conventional 3DAPs. This makes it possible to analyze regions that are about 100 nm diameter by 100 nm deep containing on the order of 50 to 100 million atoms with this instrument. Several example applications that illustrate the advantages of the LEAP for materials analysis are presented.

Atomic-scale analysis of CoFe/Cu and CoFe/NiFe interfaces

Internal interfaces in metallic multilayers grown on planar silicon substrates have been chemically analyzed with atomic resolution using three-dimensional atom probe microscopy. The structure studied was a NiFe/CoFe/Cu/CoFe multilayer grown with (111) texture. Atom probe measurements across the NiFe/CoFe interfaces yield widths of 1.1±0.2 nm for NiFe grown on CoFe and 1.7±0.2 nm for CoFe grown on NiFe. The widths of interfaces between CoFe and Cu layers vary as well, with values of 0.82±0.10 nm for CoFe grown on Cu, but only 0.47±0.15 nm for Cu grown on CoFe. In addition, the Fe concentration is enriched at the interface where Cu is grown on CoFe, and depleted where CoFe is grown on Cu. These results indicate that the Fe segregates to the surface during the deposition of CoFe so that the composition at the top of this layer is Fe rich.

Intermixing and phase separation at the atomic scale in Co-rich (Co,Fe) and Cu multilayered nanostructures

Despite the fact that Co-rich (Co,Fe) alloys and Cu are immiscible materials in bulk form, evidence of thermally induced mixing at the atomic scale has been observed in thin-film multilayers of (Co,Fe) and Cu. However, long term anneals at lower temperatures produced a breakup of the multilayers into a two-phase mixture of (Co,Fe) and Cu particles. The observations were made with the use of the three-dimensional atom probe technique, with supporting evidence from differential scanning calorimetry and x-ray diffraction. Besides their scientific importance, these results are of interest where these (Co,Fe) and Cu thin films are used to produce the giant magnetoresistive effect.

Local Electrode Atom Probes: Prospects for 3D atomic-scale metrology applications in the semiconductor and data storage industries

Recent developments in atom probe technology provide promise of a revolutionary new metrology tool that will offer information about the location and species of the atoms within the sample under investigation. Historically, atom probes have been applied mostly to needle-shaped metal specimens by a small number of experts in the world, and have been confined mostly to the research environment. This is all changing. With the developments in Scanning Atom Probes and Local Electrode Atom Probes, three-dimensional atomic-scale compositional images of almost any material may be obtained from planar specimens (wafers) by non-experts. Furthermore, the data collection rates for three-dimensional images are expected to be orders of magnitude faster than current instruments. Typical images will require hours or minutes to acquire rather than days. These developments suggest that these new atom probes can be applied to problems in the semiconductor and data storage industries on time scales that make them attractive ...