JP2006258539A - Surface analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the point that rapid sweeping can not performed heretofore because an eneagy shift is produced in a spectrum to be observed. <P>SOLUTION: This surface analyzer is equipped with a primary beam source, an electrostatic type energy analyzer for spectrally diffracting the secondary beam emitted from a sample by the primary beam emitted from the primary beam source, a sweep signal forming means for forming a sweep signal and a sweep voltage producing means for applying sweep voltage to the electrostatic type energy analyzer on the basis of the sweep signal and constituted so as to add a correction signal to the sweep signal so as to negate the energy shift component of sweep voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sample surface analyzer such as an Auger microprobe or a photoelectron spectrometer that irradiates a sample with a primary beam such as an electron beam or an X-ray to analyze the sample surface.

  There is an Auger microprobe as an apparatus for analyzing the composition and chemical state of a sample. Such Auger microprobes irradiate finely focused electrons on the sample surface, and focus the Auger electrons generated from the sample ultrathin layer by the input lens to the electrostatic hemispherical analyzer for energy spectroscopy. . Then, the dispersed Auger electrons are detected by a detector, an energy spectrum of the detected Auger electrons is obtained, and the spectrum is analyzed to analyze the composition, chemical state, and the like of a minute region (nano-order level) of the sample. In other words, by calculating the amount of the predetermined element from the position of the peak appearing in the energy spectrum, the amount of the predetermined element on the sample surface can be determined, and measurement is performed by sequentially shifting the irradiation position of the electron beam, and the amount of element at each position An Auger image can be obtained by displaying the mapping corresponding to the above.

  There is a photoelectron spectrometer as an apparatus for analyzing the composition and chemical state of a sample. Such a photoelectron spectrometer irradiates a sample with X-rays from an X-ray source, and the photoelectrons generated from the sample by irradiation are focused by an input lens and led to an electrostatic hemispherical analyzer where energy spectroscopy is performed. Then, the dispersed photoelectrons are detected by a detector, the energy spectrum of the detected photoelectrons is obtained, and the spectrum is analyzed to analyze the composition and chemical state of the sample.

In order to obtain a spectrum, a sweep voltage, which is a voltage that increases linearly with time, is applied to the electrostatic hemispherical analyzer. FIG. 2 is a circuit diagram of a sweep voltage amplifier that applies a sweep voltage. A voltage V _i is applied to the input terminal. The operational amplifier to one input resistor R _i is connected, to reduce the high pressure sweep signal V _o of the noise is the output voltage of the sweep voltage amplifier, the capacitor 21C _f are connected in parallel with the feedback resistor 20R _f ing. Here, when the sweep signal V _i (t) = αt (α is an increase rate), which is an input voltage of the sweep power supply that linearly increases with time, the high-voltage sweep signal V _o is expressed by the following equation. However, T _f = R _f · C _f (constant).
V _o (t) = − α · (R _f / R _i ) · (t−T _f · (1−exp (−t / T _f ))) (1)
Expression (1) is shown in FIG. In a range where exp (−t / T _f ) << 1 (excluding the initial stage), the following equation is obtained.
V _o (t) = − α · (R _f / R _i ) · t + α · (R _f / R _i ) · T _f (2)
α · (R _f / R _i ) · T _f is an energy shift amount.

  An energy shift occurs in the spectrum observed when the sweep is performed as described above, and a fast sweep cannot be performed because the energy shift occurs.

  As a conventional technique, there is a photoelectron spectrometer that adjusts an output voltage value by a voltage correction circuit according to a bias voltage applied to a sample (for example, Patent Document 1).

JP-A-6-109672

  The problem to be solved by the present invention is that a fast sweep could not be performed because of an energy shift in the observed spectrum.

  The invention of claim 1 generates a primary beam source, an electrostatic energy analyzer for splitting a secondary beam generated from a sample by a primary beam irradiated from the primary beam source, and a sweep signal. In a surface analysis apparatus comprising a sweep signal generating means and a sweep voltage generating means for applying a sweep voltage to the electrostatic energy analyzer based on the sweep signal, so as to cancel the energy shift component of the sweep voltage, The surface analysis apparatus is characterized in that a correction signal is added to the sweep signal.

  According to a second aspect of the present invention, the sweep signal generating means includes a first signal generator that generates the sweep signal that increases substantially linearly with respect to time, and the correction signal that is a direct current corresponding to a sweep speed. The surface analyzer according to claim 1, further comprising: a second signal generator that generates, and a signal adder that adds both outputs of the first signal generator and the second signal generator. .

  According to a third aspect of the present invention, in the surface analysis apparatus according to the second aspect, the second signal generator includes a DA converter.

  According to a fourth aspect of the present invention, the second signal generator includes an inverting amplifier for inverting the output of the first signal generator, and a differential for generating a DC signal corresponding to a sweep speed based on the signal from the inverting amplification. The surface analysis apparatus according to claim 2, wherein the surface analysis apparatus is constituted by a vessel.

  According to a fifth aspect of the present invention, the energy analyzer includes a decelerating electrode for decelerating the secondary beam and a spectroscopic electrode for dispersing the decelerated secondary beam. 4. The surface analysis apparatus according to claim 4, further comprising: a spectroscopic power source that applies a voltage that generates an electric field for spectroscopy to the spectroscopic electrode, and applies the sweep voltage to the deceleration electrode and the spectroscopic power source. This is a surface analysis apparatus characterized by the above.

  The invention according to claim 6 is the surface analysis apparatus according to any one of claims 1 to 5, wherein the primary beam is an electron beam and the secondary beam is Auger electrons.

  The invention according to claim 7 is the surface analysis apparatus according to any one of claims 1 to 5, wherein the primary beam is an X-ray and the secondary beam is a photoelectron.

  When the correction signal is added to the sweep signal according to the present invention and the sweep is performed, the decelerated sweep voltage signal does not include an energy shift component, and as a result, a spectrum without an energy shift is obtained and a fast sweep is possible.

  Hereinafter, the present invention will be described in detail according to the best mode for carrying out the invention. FIG. 1 is a schematic view of a photoelectron spectrometer according to the present invention. An X-ray source (not shown) is installed obliquely above the sample 1, and an input lens system 2 for focusing photoelectrons generated from the sample 1 near the entrance slit 10 of the blocking electrode 3 is provided above the sample 1. It has been. Reference numerals 10 and 11 denote amplifiers of the respective input lenses. The blocking electrode 3 generates a decelerating electric field by the voltage from the sweep voltage amplifier 8 and decelerates photoelectrons to spectral energy. The sweep signal generator 9 supplies the sweep signal to the sweep voltage amplifier 8 and the lens amplifiers 11 and 12.

  The spherical electrode 4 of the hemispherical energy analyzer 5 is applied with the analyzer path energy from the analyzer power supply 6 superimposed on the output voltage RV from the sweep voltage amplifier 8. The hemispherical energy analyzer 5 creates an electric field corresponding to spectral energy, and splits photoelectrons guided through the entrance slit 10 with respect to energy. Reference numeral 6 denotes an analyzer power source for giving a potential difference (+ A, −A) between the electrodes of the hemispherical energy analyzer 5. A plurality of detectors 7 are arranged in the vicinity of the exit of the hemispherical energy analyzer 5 along the energy spectral direction of the hemispherical energy analyzer 5 (only one detector is shown in the figure for convenience).

  For example, when the photoelectrons having the energy Ei are separated by the hemispherical energy analyzer 5, as the detector 7 located in the center moves the photoelectrons having the energy Ei from the center detector 7 to the left and right, the energy Ei− Detect photoelectrons with energy close to 1 and Ei + 1. Signals based on the photoelectrons detected by the detectors 7 are sent to control devices (not shown) via amplifiers (not shown). The energy spectrum of the photoelectron detected according to the command from the control device is displayed by a display device (not shown).

That is, in the apparatus having such a configuration, the sample 1 is irradiated with X-rays from an X-ray source (not shown), and photoelectrons generated from the sample 1 by the irradiation are focused by the input lens system 2 to be electrostatic hemispheres. Guided to a type energy analyzer 5 where energy spectroscopy is performed.
In the case of this example, in order to separate the photoelectrons entering the entrance slit 10 of the blocking electrode 3 with a constant analyzer path energy, the potential difference (+ A, −A) between the electrodes of the spherical electrode 4 is kept constant. The voltage applied to each electrode of the spherical electrode 4 is swept. For this purpose, the sweep voltage from the sweep voltage amplifier 8 is superimposed on the analyzer voltage.
Then, the photoelectrons subjected to energy spectroscopy are detected by the detector 7, and an energy spectrum based on a signal based on the detected photoelectrons is displayed on a display device (not shown).
Of course, it is also possible to sweep only the spherical electrode 4 with a constant reduction ratio without changing the blocking voltage.

FIG. 2 is a circuit diagram of the sweep voltage amplifier 8 for applying the sweep voltage. A voltage V _i is applied to the input terminal. The operational amplifier to one input resistor R _i is connected, to reduce the high pressure sweep signal V _o of the noise is the output voltage of the sweep voltage amplifier, the capacitor 21C _f are connected in parallel with the feedback resistor 20R _f ing.

Here, when the sweep signal V _i (t) = αt (α is an increase rate) that is the input voltage of the sweep voltage amplifier that linearly increases with time, the high-voltage sweep signal V _o is expressed by the following equation. However, _Tf = _Rf * _Cf.
V _o (t) = − α · (R _f / R _i ) · (t−T _f · (1−exp (−t / T _f ))) (1)
Expression (1) is shown in FIG. In a range where exp (−t / T _f ) << 1 (excluding the initial stage), the following equation is obtained.
V _o (t) = − α · (R _f / R _i ) · t + α · (R _f / R _i ) · T _f (2)
α · (R _f / R _i ) · T _f is an energy shift amount.
α is a variable, and the values of R _f , R _i , and T _f are known constant values. Therefore, the energy shift amount α · (R _f / R _i ) · T _f is also a value corresponding to α. Therefore, a correction voltage is added to the input voltage so that the energy shift amount α · (R _f / R _i ) · T _f is zero.

Here, α · T _f is set as the correction voltage. The input voltage V _ic (t) to which the correction voltage is added is expressed by the following equation.
V _ic (t) = α · t + α · T _f (3)
_Assuming that the output voltage based on the α · T _f component is V _oco (t), V _oco (t) is expressed by the following equation.
V _oco (t) = − α · T _f · (R _f / R _i ) · (1-exp (−t / T _f ))
Of the input voltage V _ic (t), the output voltage V _o (t) due to the α · t component is the same as the equation (1) and is given by the following equation.
V _o (t) = − α · (R _f / R _i ) · (t−T _f · (1−exp (−t / T _f )))
Therefore, the output voltage V _oc (t) when the correction voltage is applied is expressed by the following equation.
V _oc (t) = V _oco (t) + V _o (t) = − α · (R _f / R _i ) · t (5)
FIG. 4 shows these waveforms.

As can be seen from the waveform of V _oc (t) shown in Expression (5) and FIG. 4, V _oc (t) is a signal without α · (R _f / R _i ) · T _f corresponding to the energy shift amount. Therefore, if such a signal is used as a decelerated sweep voltage signal, a spectrum without an energy shift can be obtained, and a fast sweep with a larger α can be achieved.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, an electron beam source may be used instead of the primary X-ray source, Auger electrons may be used instead of the secondary line photoelectrons, and an Auger microprobe may be used.

FIG. 5 is a detailed view of the sweep voltage amplifier 8 and the sweep signal generator 9 in FIG. The configuration and operation of FIG. 5 will be described. From the signal generator 31 which is a sweep signal generating means, a voltage that rises linearly from an increase rate α arbitrarily determined with respect to time t is generated. A DC voltage generator 32 which is a correction signal generating means generates a DC voltage of α · _Tf . The switch 33 connected to the DC voltage generator 32 is turned on in synchronization with the scanning signal start (corresponding to t = 0). Since α · t + α · T _f is input to the sweep voltage amplifier 8 from the adder 34 to which the signal generator 31 and the switch 33 are connected, the output is −α · (R _f / R _i ) · t from the equation (5). It becomes. As described above, when the added signal (α · t + α · Tf) is input to the sweep voltage amplifier 8, a spectrum without an energy shift is obtained as described in the above principle.

FIG. 6 is a detailed view of the sweep voltage amplifier 8 and the sweep signal generator 9 in FIG. In FIG. 6, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The second embodiment is the same as the first embodiment except that the DC voltage generator 32 is replaced with a DA converter 36. The input code of the DA converter 36 is set corresponding to various α (sweep speed), and an output of α · T _f which is a correction signal is obtained.

FIG. 7 is a detailed view of the sweep voltage amplifier 8 and the sweep signal generator 9 in FIG. In FIG. 7, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The third embodiment is the same as the first embodiment except that the DC voltage generator 32 is replaced with an inverting amplifier 37 and a differentiator 38. The output of the inverting amplifier 37 is -α · t (the amplification degree is set to 1) with respect to the input α · t. When this output is input to a differentiator 38 shown in FIG. 8 (the values of C _f and R _f are set to the same values as the sweep voltage amplifier 8), the output is α · R _f · C _f = α · T _f It becomes.

1 is an overview of an apparatus according to the present invention. It is a circuit diagram of a sweep voltage amplifier. It is a figure which shows the input / output waveform of the sweep voltage amplifier in a prior art. It is a figure which shows the input / output waveform of the sweep voltage amplifier in this invention. It is a circuit diagram in Example 1 of the present invention. It is a circuit diagram in Example 2 of the present invention. It is a circuit diagram in Example 3 of the present invention. It is a circuit diagram of the differentiator in Example 3 of this invention.

Explanation of symbols

1 Sample 2 Input Lens System 3 Stopping Electrode 4 Spherical Electrode 5 Hemispherical Energy Analyzer 6 Analyzer Power Supply 7 Detector 8 Sweep Voltage Amplifier 9 Sweep Signal Generator 10 Incident Slit 11 Lens Amplifier 12 Lens Amplifier 20 Feedback Resistor 21 Capacitor 22 Sweep Signal 23 High-voltage sweep signal 24 Operational amplifier 31 Signal generator 32 DC voltage generator 33 Switch 34 Adder 36 DA converter 37 Inverting amplifier 38 Differentiator

Claims (7)

A primary beam source;
An electrostatic energy analyzer for dispersing a secondary beam generated from the sample by the primary beam irradiated from the primary beam source;
A sweep signal generating means for generating a sweep signal;
Sweep voltage generating means for applying a sweep voltage to the electrostatic energy analyzer based on the sweep signal;
In a surface analysis apparatus equipped with
A surface analysis apparatus, wherein a correction signal is added to the sweep signal so as to cancel an energy shift component of the sweep voltage. The sweep signal generating means is
A first signal generator for generating the sweep signal increasing substantially linearly with respect to time;
A second signal generator for generating the correction signal which is a direct current corresponding to the sweep speed;
A signal adder for adding both outputs of the first signal generator and the second signal generator;
The surface analysis apparatus according to claim 1, comprising:   The surface analysis apparatus according to claim 2, wherein the second signal generator includes a DA converter.   The second signal generator includes an inverting amplifier that inverts the output of the first signal generator, and a differentiator that generates a DC signal corresponding to a sweep speed based on a signal from the inverting amplification. The surface analysis apparatus according to claim 2. 5. The energy analyzer according to claim 1, wherein the energy analyzer includes a decelerating electrode for decelerating the secondary beam and a spectroscopic electrode for dispersing the decelerated secondary beam. A surface analyzer,
A spectroscopic power source for applying a voltage for generating an electric field for spectroscopy to the spectroscopic electrode;
A surface analysis apparatus, wherein the sweep voltage is applied to the deceleration electrode and the spectroscopic power source.   The surface analysis apparatus according to claim 1, wherein the primary beam is an electron beam, and the secondary beam is an Auger electron. 6. The surface analysis apparatus according to claim 1, wherein the primary beam is an X-ray and the secondary beam is a photoelectron.

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