Depth resolution function of the laser assisted tomographic atom probe in the investigation of semiconductors

Abstract

The investigation of boron delta layers by tomographic atom probe (3DAP) is used to demonstrate that a depth profiling resolution of 0.9 nm (full width at half maximum) can be achieved. Results are compared with measurements provided by secondary ion mass spectrometry. The steepness is found to be below 1 nm/decade. In addition, silicon atomic planes are resolved in the real space demonstrating an in-depth spatial resolution of the 3DAP below 0.2 nm.

Atom probe tomography in nanoelectronics

“…This clearly suggests that (4 0 0) planes will not be resolved in APT experiments. APT analyses that we conducted indeed confirmed that (4 0 0) are not visible in reconstructions [21].…”

“…Laser pulses give rise to very rapid thermal pulses that promote the field evaporation of surface atoms. In the instrument that we have designed in collaboration with CAMECA (FlexTAP), the specimen is field evaporated by ultrafast laser pulses (<500 fs) and the wavelength can be changed from IR to green or UV, depending on application [19][20][21][22]. This innovation has made APT a very powerful approach in nanosciences, in particular for the investigation of microelectronics materials, nanowires (silicon based or metallic) and magnetic multilayers for spintronic including tunnel junctions containing highly resistive oxide barriers [23].…”

“…Indeed, the calibration in depth using atomic planes is not possible in (1 0 0)-oriented silicon. Indeed the resolution of the laser assisted APT in depth is not sufficient to distinguish (4 0 0) planes as demonstrated in reference [21]. Some authors claimed it was possible to map out these (4 0 0) planes [37].…”

The investigation of boron-doped silicon using atom probe tomography

“…As shown in figure 5, the background in this particular experiment was larger than 10 19 at/cm 3 . A more detailed discussion is available in reference [15]. …”

“…The implantation dose was chosen high (5x10 15 at/cm 2 , boron ions of 10 keV), close to that of ultra-shallow junctions in last generation nano-transistors. Experiments were conducted on (001) implanted silicon.…”