US3757116A - Ment in a material device for direct measurement of the curve of concentration of an ele - Google Patents

Ment in a material device for direct measurement of the curve of concentration of an ele Download PDF

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Publication number
US3757116A
US3757116A US00227979A US3757116DA US3757116A US 3757116 A US3757116 A US 3757116A US 00227979 A US00227979 A US 00227979A US 3757116D A US3757116D A US 3757116DA US 3757116 A US3757116 A US 3757116A
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Prior art keywords
current
ions
curve
recorder
receives
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US00227979A
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English (en)
Inventor
B Blanchard
N Hilleret
J Monnier
J Quoirin
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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En Atomique Comm
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
    • G01N23/2251—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident electron beams, e.g. scanning electron microscopy [SEM]
    • G01N23/2254—Measuring cathodoluminescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/081—Investigating materials by wave or particle radiation secondary emission incident ion beam, e.g. proton
    • G01N2223/0816—Investigating materials by wave or particle radiation secondary emission incident ion beam, e.g. proton incident ion beam and measuring secondary ion beam [SIMS]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/601—Specific applications or type of materials density profile

Definitions

  • the invention is directed to a method for plotting the curve of concentration of an element in a material and also to an apparatus which carries out said method and is primarily applicable to the curve obtained by diffusion or implantation of an impurity in a semiconductor (doping of Si or Ce).
  • a further aim of the invention is to obtain a record of the curve of impurities directly by electronic means in a single measurement, thus dispensing with the need for tedious analysis which is necessary in devices of the prior art in order to find the concentration curve as a function of the depth.
  • the invention proposes a method for direct measurement of the curve of concentration of an element in a material, wherein said material is subjected to bombardment by a beam of primary ions and said material in turn emits a beam of secondary ions, wherein said method consists in recording simultaneously the total current corresponding to all the ions
  • the aim of this invention is to provide a method and contained in said secondary beam and the ratio of the current which corresponds solely to the ions of said element contained in said beam, to said total current.
  • the invention also proposes a device which serves to carry out said method and comprises a source of primary ions, an ionic optical system for accelerating and focusing, an electromagnet which separates the secondary ions ejected from said material according to their mass and retains only the ions of said element, an ion collector for delivering a current lc which is proportional to the quantity of ions received, said device being essentially characterized in that it comprises A metallic grid interposed between said optical system and said electromagnet and followed by an amplifier for delivering a current I, which is proportional to the total quantity of secondary ions.
  • a ratio circuit which makes it possible to obtain the quantity Ic/I and receives at both inputs respectively said current Ic which is derived from the ion collector and a fraction of said current I
  • a recorder XY which receives at the input X the remaining fraction of the current I, by means of an integrating circuit and receives at the input Y the current delivered from said ratio circuit, the curve of impurities of said material being thus directly displayed by said recorder.
  • the ratio circuit comprises two logarithmic amplifiers, the outputs of which are connected to a subtracting device, which makes it possible to provide a wider range of recording.
  • FIG. 1 shows very diagrammatically a device of the prior art
  • FIG. 2 shows the device according to the invention associated with the device of the. prior art.
  • FIG. 1 The elements of FIG. 1 have already been described in the foregoing. However, it is necessary to add the diaphragm 16 which is placed after the optical system 10. This diaphragm allows only the central portion of the secondary-ion beam to pass through the electromagnet 12 in order to increase the resolution of the measurement.
  • the probe of FIG. 1 gives the current Ic corresponding to the ionic abundance of the doping element in the secondary beam as a function of time.
  • FIG. 2 the elements which are common to FIG. 1 are designated by the same reference numerals. It is noted that provision is made on the path of the secondary beam for a metallic grid 18 which is placed between the diaphragm l6 and the electromagnet 12. This grid is made up of copper wires having a thickness of 25 a and spaced at intervals of I [1.- This grid collects a small fraction (namely a maximum of one-quarter) of the ions contained in the secondary beam. Said grid is followed by an amplifier 20 for delivering a current I which is proportional to the total quantity of secondary ions.
  • the ratio of the current Ic, relative to the ions of impurities, to said current I as measured before the electromagnet, is proportional to the concentration of impurities.
  • a further advantage of the invention appears from a study of relations (5) and (6), namely the possiblity of obtaining directly by means of an analog circuit the concentration curve of impurities, that is to say C as a function of x. Inasmuch as the concentrations are expressed to the power of 10, it is usually more convenient to calculate log.C.
  • the result thereby achieved as shown in FIG. 2 is that the current I, at the output of the amplifier drives on the one hand an integrator 22 preceded by a potentiometer 24 and, on the other hand, in the case of the figure shown, a first logarithmic amplifier 26.
  • the current llc delivered by the ion collector 14 drives a second logarithmic amplifier 28.
  • a recorder X-Y designated by the reference 32 and advantageously consisting in this case of a plotting table receives at its input X the current which is delivered by the integrator 22 and is representative of the depth x of pulverization of the material and, at its input Y, the quantity log Ic/I which is delivered by the subtraction device 30 is representative of the concentration C of impurities in said material.
  • FIG. 2 also shows another mode of operation by means of a changeover switch 34.
  • a fraction of the current 1 at the output of the amplifier 20 as well as the current 10 delivered by the ion collector l4 drive directly a quotientmeter 36 which restores the ratio lc/I
  • This quotientmeter is connected at the output to a variable potentiometer 38 which transmits said ratio of the currents I0 and I to the channel Y of the recorder 32 by means of a changeover switch 30 whilst the channel X continues to receive the current delivered by the integrator 22.
  • the switches 34 and 40 are actuated simultaneously according to the type of recording which is chosen, a broad dynamic range being made possible in the case of logarithmic recording.
  • Initial adjustment of the device can be carried out from material having a known impurity curve.
  • the potentiometer 24 serves to calibrate the quantity as abscissae, namely in this case the depth of pulverization. Similary, the variable gain of the subtracting device 36 or the potentiometer 38 makes it possible to calibrate the quantity as ordinates, namely in this case the concentration expressed respectively by log [CH and Ic/I It is clearly demonstrated by the foregoing that the de vice as described has numerous advantages over existing devices and among these can be mentioned the following I independence of the parameters C and x with respect to variations in the rate of pulverization,
  • a device for direct measurement of the curve of concentration of an element in a material including a source of primary ions, an ionic optical system for accelerating and focusing the ejected secondary ions, an electromagnet which separates the secondary ions ejected from said material according to their mass and which retains only the ions of said element, an ion collector for delivering a current lc which is proportional to the quantity of ions received comprising a metallic grid interposed between said optical sys tem and said electromagnet and followed by an amplii'ier for delivering a current I, which is proportional to the total quantity of secondary ions,
  • a ratio circuit to obtain the quantity lc/l and receives at its two inputs respectively said current lc which is derived from the ion collector and a fraction of said current I a recorder XY which receives at the input X the remaining fraction of the current I, by an integrating circuit and, of the input Y, the current derived from said ratio circuit, the curve of impurities of said material being thus displayed directly by said recorder.
  • said ratio circuit comprises a first logarithmic amplifier which receives said fraction of the current I at its input, a second logarithmic amplifier which receives said current Ic at its input, a variable-gain subtraction device whose inputs are connected respectively to the output of said logarithmic amplifiers so that the quantity log /1 is obtained.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Electron Tubes For Measurement (AREA)
US00227979A 1971-02-22 1972-02-22 Ment in a material device for direct measurement of the curve of concentration of an ele Expired - Lifetime US3757116A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7105932A FR2127065A5 (OSRAM) 1971-02-22 1971-02-22

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US3757116A true US3757116A (en) 1973-09-04

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FR2127065A5 (OSRAM) 1972-10-13

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