Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Patent
1982-01-26
1984-10-09
Smith, Alfred E.
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
250307, G01N 23223, G01N 23225
Patent
active
044763867
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and apparatus for material analysis of the kind in which a beam of energy is caused to fall on a spot on the surface of the sample of material to be analysed and signals, such as X-ray signals or backscattered electron signals are generated each representing an effect of the beam at the spot and from which signals information as to the makeup of the material can be derived.
Methods of the above kind are adapted for use where a scanning electron microscope provides the beam of energy and it is principally in this context that the invention is particularly described thereinafter. However, the invention is not confined to use of scanning electron microscopes.
The invention broadly contemplates, in one aspect, a method of analysis in which a beam of energy is caused to fall on a spot on the surface of a sample to be analysed and X-rays then generated at the spot are detected by one or more detectors to produce first signals representative of the energies of detected X-rays; a first count of the nunber of said first signals each representative either of an energy within a relatively broad range of such energies or of a combination of discrete energy intervals across said first relatively broad range said combination including coincident, anti-coincident or contiguous intervals being made and a second count of the number of said first signals each representative of one particular energy or of an energy in an associated relatively narrow range of energies about said particular energy being made, wherein information relating to the relative proportion of a particular chemical element, characterized by production of X-rays of or about of said particular energy is obtained in the form of a normalized ratio of said second count to said first count, said normalized ratio being represented by the value of said second count assumed when the said first count reaches a predetermined value. The first said count may as a particular case consist of the sum of all or some subset of the second said counts.
In another aspect, the invention broadly contemplates apparatus for material analysis including:
energy generating and directing means for causing a beam of energy to fall on a spot on the surface of a sample of the material to be analysed;
detector means for detecting X-rays generated at said spot and for producing first signals representative of the energies of detected X-rays;
first accumulating means coupled to accumulate a first count of the number of said first signals each representative either of an energy within a first relatively broad range of such energies or of a combination of discrete energy intervals across said first relatively broad range, said combination including coincident, anti-coincident or contiguous intervals;
second accumulating means for accumulating a second count of the number of said first signals each representative of one particular energy or of an energy in an associated relatively narrow range of energies about said particular energy;
presettable means coupled to said first accumulating means and responsive, on said first count reaching a predetermined value, to control said second accumulating means to hold the value of said second count then assumed, whereby said assumed value represents a normalized ratio of said second count to said first count which normalized ratio is dependent on the proportion of a particular chemical element in said sample.
In addition to the normalized value already notionally divided, an actual division can be carried out if desired and the results obtained therefrom may be further manipulated.
The invention is further described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a diagram illustrating the use of a scanning electron microscope to obtain image information from a sample;
FIG. 2 is a circuit diagram of apparatus useful in analysing X-ray signal information;
FIG. 3 is a circuit diagram of apparatus useful in processing backscattered electron information;
FIG. 4 is a circuit diagram of a
REFERENCES:
patent: 3204095 (1965-08-01), Watanabe
patent: 3351755 (1967-11-01), Hasler
patent: 3909612 (1975-09-01), Gibbard
patent: 4288692 (1971-09-01), Schamber et al.
Reid Alan F.
Zuiderwyk Martin A. M.
Berman Jack I.
Commonwealth Scientific and Industrial Research Organization
Smith Alfred E.
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