Optimized time-of-flight secondary ion mass spectroscopy depth profiling with a dual beam technique

Abstract

High resolution depth profiling has been performed in a time-of-flight secondary ion mass spectroscopy (TOF-SIMS) instrument equipped with independent ion sources for sputtering (crater formation) and for SIMS analysis. In this dual beam mode a low energy sputter gun (Cs or any gas ion) allows a free selection of optimum sputter conditions with regard to depth resolution and matrix optimization. For secondary ion generation an independent high energy ion beam, optimized with regard to focussing and secondary ion yield (Ga or gas ion source) is applied. For different sputter gases (Ar, Xe, O2, and SF6), energies (0.3–2 keV) and angles of incidence a systematic investigation of B layers in Si and GaAlAs multilayers has been carried out. Decay lengths of 0.53 nm were achieved for low energy sputtering of B layers in Si with 0.6 keV SF5+. In this dual beam mode the depth profiling performance of TOF-SIMS exceeds that of state of the art quadrupole and magnetic sector field instruments in several fields of application, important in particular in microelectronics.

Use of C60 cluster projectiles for sputter depth profiling of polycrystalline metals

“…1,2 This approach, however, has its disadvantages because it is difficult to focus the beam to a small size of micrometres or less, and the sputter yields decrease significantly for primary ions with low kinetic energies. Another approach is to use polyatomic or cluster projectiles such as CF 3 , 3 N 2 O 4 or SF 5 . 5,6 Because the polyatomic or cluster ions dissociate upon collision with the target surface, the initial ion energy is split among the constituent atoms.…”

“…Another approach is to use polyatomic or cluster projectiles such as CF 3 , 3 N 2 O 4 or SF 5 . 5,6 Because the polyatomic or cluster ions dissociate upon collision with the target surface, the initial ion energy is split among the constituent atoms. As a consequence, there is a shallow penetration of incident particles and the deposited energy remains close to the surface.…”

Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions

“…ToF-SIMS depth profiles were acquired in dual beam mode [26] using a ToF-SIMS IV (Ion-Tof GmbH, Münster, Germany). The analysis beam (Bi 3 + at 25 keV; current:~25 pA, pulse width: 20 ns; pulse width after bunching: 0.75 ns; repetition rate: 10 kHz), rastered over a 300 × 300 μm² area and the erosion beam (Cs + at 500 eV, current: 37-41 nA), rastered over a 500 × 500 μm² area were operated in noninterlaced mode with one analysis frame (1.6384 s), 10 s erosion, and 1 s pause per cycle, both with a 45°incidence angle to the sample surface.…”

SIMS analysis of oxynitrides: evidence for nitrogen diffusion induced by oxygen flooding

“…The IONTOF IV 14,15 is equipped with two analysis guns (Ga C and Ar C ) and two sputter guns (Ar C and Cs C ). For the samples under study, the electron impact Ar C analysis gun was operated under the following standard conditions: 10 keV Ar C , 1 pA and 30 ð 30 µm 2 .…”