IMS 7f HIGHLIGHTS

Lateral resolution of direct ion microscopy images, in contrast to microprobe imaging only used on all other instruments, is independent of the primary beam diameter. This makes extremely short acquisition times possible with large primary ion beam. 
An example of direct secondary ion image showing the distribution of Silicon in an Aluminum matrix. This image can be visualized on a fluorescent screen, or digitally integrated with a Resistive Anode Encoder (RAE). Field of view: diam. 250 mm.

The CAMECA IMS 7f optical system allows a mass resolution up to 25 000 (at 10% definition, equivalent at least to 50 000 FWHM as quoted for TOF-SIMS).
This ensures clear, unambiguous analyses, by removing most mass interferences. The quality of the analyser design ensures the highest abundance sensitivity and sharp peak shape with minimum background and tail. The double focusing analyser and its adjustable energy slit allow also to use energy filtering of the secondary ions to reduce contribution from different species at the same nominal mass (ex: reduce a molecular or organic interference on an elemental peak).  This crucial capability for elemental analysis is not available from Reflectron TOF analysers contributing to peak tails and background noise. 

In this example, the High Mass Resolution of the magnetic sector analyzer makes it possible to perform a depth profile of Phosphorus in Silicon by discriminating between the Silicon 30 hydrides ions 30SiH and the Phosphorus ions 31P, both at mass 31. This allows an extremely low P detection limit, even in amorphous silicon. A quadrupole analyser with its low mas resolution will give a Phosphorous detection limit several orders of magnitude poorer.  
Also note the speed of analysis, guaranteeing the highest sample throughput available.
With a (DC) magnetic sector analyser, the faster the profile, the better the sensitivity or detection limits: each data point signal is integrated over a larger depth (volume). In contrary with a (pulsed) Time Of Flight analyser, the faster the profile the poorer the sensitivity: most of the material is sputtered away by the sputter gun and lost for the analysis ion gun. This explains the poor results obtained on deep profiles with TOF analysers.  
 
Matrix
Element
Detection limit (1013at/cm3)
Detection limit (ppb)
Si
H
B
C
N
O
F
Al
P
Cr
Fe
Ni
Cu
As
Ag
Pb
 7000
3
3000
50
6000
500
10
5
2
50
30
80
5
50
10		 1400
0.6
600
10
1200
100
2
1
0.4
10
6
16
1
10
2
GaAs
Si
Zn
  50
200		 20
80
InP
Zn
Si
Fe
S
  270
780
440
610		 60
180
100
140
IMS 7f Elemental detection limits in DEPTH PROFILING mode.

The combination of high transmission, optical gating, high mass resolution and ultra high vacuum ensure the obtention of benchmark detection limits together with a high sample throughput (no need to leave the sample degas in load-lock as usual with quad-SIMS).
Element
 Detection limit (at/cm2)
 Det. limit (ppm)
Li
B
Na
Mg
Al
K
Ca
Ti
V
Cr
Fe
Cu
Pb
...		 1E7
1E9
1E8
5E9
5E8
1E8
5E8
1E9
1E8
5E8
8E8
1E10
3E9		 0.01ppm
1
0.1
0.5
0.5
0.1
0.5
1
0.1
0.5
0.8
10
3
SURFACE analysis of inorganic trace elements on silicon.

The method, ASTM F1617 approved, is based on a Low Energy Sputter (3keV impact), high mass resolution, O2+ primaries  &  Oxygen flooding. High transmission at high mass resolution, energy bandwidth control and fast magnet switching ensure fast and reproducible data. In addition this fast depth profiling method ensures the correct contamination dosage by integrating the signal over a few tens nm depth, not achieved by VPD-ICPMS or TOF-SIMS. The detection limit is at the ppm level for most elements.
Data taken from Charles Evans & Associates application note. 



Boron delta structure. SEMATECH round-robin, SIMS XII, Brussels, sept. 99.
 500 eV impact energy,  O2+ at 44° incidence angle and oxygen flooding.

The IMS 7f upgraded with "accel/ decel" on the duoplasmatron source, allows state-of-art ultra-shallow profiling.

No visible rugosity is detected, and depth resolution is maintained at benchmark level:

  • decay length (1/e) 5th layer: 0.7 nm/ 16th layer: 0.7 nm
  • FWHM 5th layer: 1.8 nm/ 16th layer 1.8 nm

The position of the first layer (4.14 nm) is correct, and does not show the error and artifact obtained with normal incidence/ no flooding condition (too small value). In addition, the use of 45° angle together with gas flooding offers higher sputter rate compared to normal incidence condition, leading to a much higher sample throughput.



Measurement of Rare Earth Elements at trace level in geological samples.

The IMS 7f allows reproducible quantitative measurement of REE despite the low concentration level (sub-ppm for most), numerous mass interferences (removed by energy offset + filtering) and insulating nature of the samples (use of O- primary ions, metallic coating and/or charge compensation).