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BORON ANALYSIS AND MAPPING WITH A WINDOWLESS ENERGY DISPERSIVE DETECTOR
A. Sandborg, M. Whitehead
To cite this version:
A. Sandborg, M. Whitehead. BORON ANALYSIS AND MAPPING WITH A WINDOWLESS EN- ERGY DISPERSIVE DETECTOR. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-185-C2-188.
�10.1051/jphyscol:1984242�. �jpa-00223955�
JOURNAL DE PHYSIQUE
Colloque C2, supplément au n°2, Tome 45, février 1984 page C2-185
BORON ANALYSIS AND MAPPING WITH A WINDOWLESS ENERGY DISPERSIVE DETECTOR A.O. Sandborg and M.E. Whitehead
EDAX INTERNATIONAL^ Inc., P.O. Box 135, Prairie View, IL 60069, U.S.A.
Résumé - On a utilisé un détecteur X par sélection d'énergie sans fenêtre pour analyser des échantillons contenant du bore.
Le bore a été détecté dans un échantillon métallurgique poly- phasé et on en a fait des images X. On a utilisé un verre aux boro-silicates pour déterminer la limite de détection du bore.
Abstract - Boron has been detected and mapped in a multiphase metallurgical sample. A windowless energy dispersive detector was used on a scanning electron microscope to analyse the boron containing samples. In order to determine the detection limit for boron, a borosilicate glass was also analyzed.
Introduction - Energy dispersive detectors used in the windowless mode have extended detection capabilities to elements below Na, atomic number l l .1 Most of the work done in the past has been restricted to a lower limit of atomic number 6, carbon.2 This lower limit was due to a number of problems:
interference of electronic noise, non-linearity of the analog electronics at low energies, and effectiveness of electron trapping. Improvements in these areas have been made in a new design windowless detector, the ECON III. These improvements allow the detection of boron, atomic number 5, by an energy dispersive detector. Presented are data on the detection of boron on practical samples.
Metallurgical Sample - A sample of iron boride was investigated. This sample consisted of grains of F exBY composition with phases of high boron concentrations in the grain boundaries. Figure 1 is a backscatter micrograph at low magnification (original magnification, 655X) in which the dark areas in the intergranular region are the high boron phase's. The spectra from this phase is shown in Figure 2a and 2b. The spectrum from a F exBY grain is shown in Figure 3. These spectra were taken at 15KV with a spot size of 100 nanometers and a beam current of about one nanoampere. The accelerating voltage was chosen to optimize for the mapping of boron, rather than for the maximum enhancement of peak to background ratio or minimization of absorption. The sample was tilted at 30°.
Since the boron peak to background was quite good, a digital x-ray map was performed on another area which is shown in Figure 4. Since four regions of interest could be accumulated simultaneously, in addition to boron, the iron 1- alpha, the silicon k-alpha x-rays and a background region were also accumulated.
The results of the boron and silicon maps are shown in Figures 5 and 6. These maps are grey scale coded with white being the highest intensity. Figure 7 illustrates the instrumental parameters used for the mapping.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984242
JOURNAL DE PHYSIQUE
Fig. 1
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Iron Boride Specimen (BSE) Bar = 1 0 Microns3 1 - A U G - 8 3 0 4 : 0 8 : 0 0
RATE: C P S T I M E l O O L S E C
0 0 - Z O K E V : l O E V l C H PRST: 1 5 O L S E C A: D A R K P H A S E B:
F S = 1 1 6 8 MEM: A F S = 2 0 0 .
CURSOR ( K E V ) = 0 1 . 2 7 0 E O A X
F i g . 2b
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Expanded S c a l e of F i g . 2a3 1 - A U G - 8 3 0 4 : 1 1: 0 9
R A T E : C P S T I M E i O O L S E C 0 0 - 2 0 K E V : 1 0 E V l C H PRST: I S O L S E C A: 0 A 2 K P H A S E B:
F S = i i 6 8 MEM: h F S = 2 0 0
B F 5 M F
E I N E
CURSOR ( K E V ) = 0 5 . 0 8 0 E D A X
F i g . 2a
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Spectrum o f Boron Rich Phase3 1 - A U G - 8 3 1 4 : 1 2 : 39
RATE: CPS T I M E l O O L S E C
C H - 2 0 K E V : 1 0 E V l C H PRST: 1 5 O L S E C A: L A R G E F E X B Y 8:
F S = 3 5 1 0 MEM: A F S = 200
CURSOR (KEV) = 0 1 . 2 7 0 E O A X
F i g . 3
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Spectrum of FEX By PhaseFig. 4
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Intergranular Area (BSE) Fig. 5-
Boron X-Ray Intensity Map Bar = 10 Microns (200 CPS Full Scale or White)Fig. 6
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Silicon X-Ray Intensity Map Fig. 7-
Parameters for Intensity MapC2-188 JOURNAL D E PHYSIQUE
Borosilicate Glass
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In order t o determine the minimum detection limit for boron i n an oxide matrix, a borosilicate glass used in the semiconductor industry a s a passivation layer was analyzed. The glass layer was deposited on a Si substrate with a thickness of about 10,000 angstroms. A low beam voltage was used for several reasons; in order not t o penetrate thru t o the Si substrate, t o reduce the x-ray absorption path and t o avoid coating the layer t o prevent charging.The accelerating voltage of the beam was 2 kev. The boron concentration of the glass layer was 3 WT%. The background in the region of the boron peak is very difficult t o determine, so a seperate measurement was used for background.
This measurement utilized a phosphosilicate glass containing no boron, but otherwise of similar composition (SiO ). Normalization was accomplished by assuming that the intensity in t h e totalgPectrurn less the boron region should be the same in both the phosphosilicate glass and the borosilicate glass. Figure 8 shows a comparison of these normalized spectra. The boron peak is clearly visible. For a 200 live second measuring time, the 3 sigma minimum detectable limit is 0.52%.
E%3 - With careful design of a windowless EDS detector, boron can be At high levels of boron concentration, mapping can be performed with success. The lower limit of detection has been established in a glassy matrix a t about 0.52%.
31-AUG-03 03: 20: 3 2
RATE: C P S TIME Z O O L S E C DO-23KEV: lOEV/CH PRST: ISOLSEC A: TIEDD:: 2/30/49B: i:SODl: 2/30/$9 FS- 2 2 3 8 MEH: A/B F S = 2 1 8 7
C U R S O R (KEV) =DO. 3 2 0 E O A X
Fig. 8
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Comparison of 3% Boron Glass t o Boron Free Glass References1. Russ, J.C., Baerwaldt, G.C., hicMillan, W.K.
X-Ray Spectrometry
5
(1976) 2122. Sandborg, A.O., Nierkle, A.B., SEM/1981/163
