JPS63142247A - Auger electron spectroscopic apparatus - Google Patents

Abstract

PURPOSE:To accurately analyze a specimen having an inclined surface, by calculating the signal corresponding to the inclination of an Auger electron spectrum and correcting an Auger electron energy value due to the inclination of the specimen on the basis of said signal. CONSTITUTION:The Auger electron generated by irradiating a specimen 4 with electron beam from an electron gun 1 is supplied to an analyzer 7 to select the energy Ep of a noticeable element and an Auger electron signal I(Ep) is detected by a detector 9. In the same way, the energy Eb of the background region in the vicinity of the energy Ep is selected to detect an Auger electron signal I(Eb). Each pixel is read from the electron signals I(Ep), I(Eb) to calculate the peak background ratio R(theta) of an angle theta of inclination. Further, the signal G corresponding to the inclination of the base line of an Auger electron spectrum is preliminarily calculated in the background region. On the basis of this signal G, theta of the peak background ratio R(theta) is brought to 0 to perform correction so as to eliminate inclination. Therefore, the specimen containing an inclined surface can be accurately analyzed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an Auger electron analyzer that analyzes a sample by detecting Auger electrons via an energy analyzer.

[Prior Art] As shown in Fig. 5, when an electron beam EB is irradiated onto a sample surface S having concavities and convexities, the spectrum peak on the surface A that is inclined toward the side facing the energy analyzer A is the loudest, followed by The peak at the west exit of the inclination angle O is the highest, and the peak at the oppositely inclined surface C is the lowest. When trying to analyze the composition of a sample, it is better not to be influenced by the shape of the sample surface, so in the past, the so-called peak background ratio R was calculated to eliminate the influence of the shape. There is.

That is, as shown in Figure 6, the spectral peak intensity of the element whose concentration distribution is to be determined at a certain analysis point is ((Ep),
If the intensity in the background part near this peak is I (Eb), then R-(I (Ep)-1(E
b) )/I (Eb) is determined, and concentration distribution data is determined based on this value.

Now, as shown in FIG. 7, let n be the normal to the sample surface S at the electron beam irradiation point, and the angle from the electron beam EB to the normal n measured by rotating toward the analyzer A is the positive inclination angle θ. ,
Let the angle θ measured by rotating in the opposite direction be expressed as a negative inclination angle θ. Also, the peak background ratio R when the tilt angle is θ is expressed as R(θ), and the sample tilt angle is 0.
When the peak background ratio at is expressed as RO, when the value of γ(θ)-R(θ)/RO is plotted against σ, the experimental results shown in Figure 8 for the Cu-LMM peak are obtained. Almost similar results were obtained for other spectral peaks. These results show that the angular dependence of R(θ) is negligible in regions where the sample inclination angle is less than 40”, but when θ exceeds about 40°, the angular dependence becomes significant. I understand.

[Problems to be Solved by the Invention] Conventionally, however, even when the inclination angle of the sample exceeds 45°, compositional analysis of the sample is performed based on the value of the peak-background ratio. It is not possible to accurately analyze the composition of the sample.

The purpose of the present invention is to solve such conventional problems and provide an Auger electron analyzer that can perform accurate quantitative analysis of a sample even for a sample including an inclined surface with a large inclination angle. There is.

[Means for solving the problem] Therefore, the present invention irradiates a sample with an electron beam, guides Auger electrons generated from the sample based on the irradiation of the electron beam to an energy analyzer, and converts the Auger electrons through the analyzer. By detecting with a detector, the Auger peak intensity I (Ep)) of the element of interest and the background intensity 1 (Eb) near the peak are measured, and based on these measurement results, the peak background ratio (I (
In an Auger electron analyzer configured to calculate Ep)-I(Eb))/I(Eb), means for setting energy selection values by the analyzer to mutually different energy values in a background region; An Auger electron spectrum at the analysis point is obtained based on the signal from the detector obtained by irradiating the same analysis point with an electron beam when the energy selection value is set to each of the different energy values by the analyzer. means for determining a signal corresponding to the slope of the baseline; and means for correcting the peak-background ratio to a value independent of the slope angle of the sample surface at the analysis point based on the signal corresponding to the slope of the baseline. It is characterized by having the means.

[Operation of the Invention] When the sample was Cu and the inclination angle θ of the sample was variously changed, Auger electron spectra were obtained, and the results shown in FIG. 9 were obtained. Furthermore, when we obtain Auger electron spectra by changing the sample to, for example, 8102 and similarly varying the inclination angle θ of the sample, we obtain the results shown in Figure 10, and from these results, It was found that the slope of the baseline of the spectrum has a certain relationship with the tilt angle of the sample as shown below. That is, as a quantity corresponding to the slope of the baseline of the spectrum, two energy values that become the background region, for example, Eα - 1500 eV, Eβ
= ratio of spectral intensities G − at 2000 e v
1 (1500) / I (2000) and plotted how this ratio G changes when the sample inclination angle θ is changed, the results shown in Figure 11 are obtained. It was found that the results were almost the same regardless of the sample. In addition, in FIG. 11, the vertical axis is θ,
The horizontal axis is the ratio G=(1500)/r(2000).

Therefore, if we know the value of the ratio G=Eα/Eβ, we can find θ, and if we can find θ, we can find the value of γ(θ) using the above relationship. can be corrected to the value RO when the sample inclination angle θ is O.

[Example] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 schematically shows an apparatus according to an embodiment of the present invention, in which 1 is an electron gun, 2 is a deflector, 3 is a focusing lens, 4 is a sample, 5 is a digital scanning signal generation circuit, and 6 is a DA. converter, 7
is a cylindrical mirror type energy analyzer, 8 is an analyzer sweep signal generator, 9 is an Auger electron detector, 10 is an AD converter, 11 is a CPU, 12 is a storage device,
13 is a console, 14 is an input device, and 15 is a pass line.

The storage device 12 stores a conversion table as shown in FIG. 3 for converting G into θ based on the relationship shown in FIG. That is, this table contains the corresponding θi (i-1,2.
, . . . , n) are stored. The storage device 12 also stores a conversion table as shown in FIG. 4 for converting θ into γ(θ). That is, in this table, a certain value θ1(i-1
, 2, . . . , n), data for reading out the corresponding value of γ(θi) (i-1, 2, . . . , n) is stored. In addition, the above 8
As is clear from the figure and Fig. 11, both of these figures show θ=
Since it is symmetrical with respect to the axis O, any of the above tables may be created for a region where θ is about 0 to 80 degrees.

In such a configuration, when the input device 13 is used to instruct the start of analysis, the CPU 11 sends a control signal to the sampling signal generator 8 in accordance with the stored program, and changes the energy selection value in the analyzer 7 of the element of interest. Let it be energy beak ITEp. Therefore, next, the CPU
11 sends a control signal to the scanning signal generation circuit 5, and the electron beam E
When the start of scanning by B is commanded, a scanning signal is generated from the scanning signal generating circuit 5, and each pixel (x, y) on the sample 4 is sequentially irradiated with the electron beam EB, thereby performing two-dimensional scanning. A detection signal I of Auger electrons having energy Ep obtained from the detector 9 along with this scanning
(Ep) is converted into a digital signal by the AD converter 10, and then sent to the storage device 12 and stored in its first image storage area tR12p. Next, based on a control signal from the CPU 11, the energy selection value of the analyzer 7 is changed to a value Eb in the background area near the Ep.
After that, the Auger electron signal I (Eb) from each pixel (x, y) on the sample 4 is detected and stored in the storage device 12.
is stored in the second image storage area 12b. Similarly, CPU
Reference numeral 11 denotes the energy selection value of the analyzer 7 as the energy value Eα (Eα is, for example, 1 sooe v > and Eb (Eb is, for example, 200
06 V), and then after each setting,
A two-dimensional scan of the electron beam is performed to scan each pixel (x.

Auger electronic signals 1 (Eα) and I (Eb) from y) are detected and stored in the 3rd and 4th image area memories 12α and 12β of the storage device 12, respectively.

Next, the CPU 11 receives the signals I (Ep), r(
Eb) is read out for the pixel (xj, yk), and as shown in block 18, using both of them, the peak background ratio R(θi) given by equation (2) is calculated for the pixel (xj, yk).
, yk). On the other hand, CPLJ11 each has a third . The signal 1 (E(2), I (Eb)) of the pixel (xj, yk) is read out from the fourth image storage area 12α, 12β, and further, as shown in block 21, using these two, Gi=l(E
α)/I(Eb) is calculated. Next, as shown in block 22 of the figure, the table shown in FIG. 3 is addressed based on the signal representing the calculated value Qi, and the pixel (xi,
Read the sample inclination angle θi of yk). Next, as shown in block 23 of FIG. 1, the table shown in FIG. 4 is addressed based on the signal representing θi, and the correction coefficient 1 is
/γ(θi) is read. Next, the CPU 11 uses block 2
4, for the pixel (xj, yk), R(Gi)/γ is calculated based on the signal representing R(θi) from block 18 and the signal representing γ(θ1) from block 23.
By calculating (Gi), the pixel (xj, yk)
Find the peak background ratio RO when the sample inclination angle θ is 0. The CPU 11 performs similar calculation control for each pixel (xj, yk) (j =
1. =-, Ik = 1
．． −.

m), and the values for each pixel (xj, yk) are stored in the image storage area 12c of the storage device 12 for each pixel (xj, yk).
, yk). Next, the CPU il calculates the concentration of the element of interest in each pixel based on the calculated peak background ratio RO of each pixel, and sends the concentration distribution data of the element of interest to the CRTl 4 based on the calculated concentration value. indicate.

In this way, when the tilt angle of the sample exceeds 40°, Auger electron analysis data that is independent of the tilt angle of the sample can be obtained.

The embodiment described above is only one embodiment of the present invention, and can be modified and implemented.

For example, in the above embodiment, the angle between the axis of the energy analyzer and the electron beam irradiating the sample was relatively large, but the angle between the axis of the energy analyzer and the electron beam irradiating the sample was O1, that is, coaxial. The present invention is similarly applicable to certain devices.

In addition, in the above embodiment, in order to obtain a mother corresponding to the slope of the baseline of the Auger electron spectrum, 15ooey and 2000 included in the background region are used.
e I tried to find the spectral intensity at V, but
If it is the spectral intensity value of the background [, this value may be determined based on the intensities at the other two energy values.

Furthermore, in the above embodiment, after determining the slope corresponding to the slope of the baseline of the spectrum, the slope angle of the sample is calculated based on the slope, and then R(θ) is calculated based on the slope angle.
The correction coefficient 1/γ(θ) for conversion to O is calculated, but the relationship between the correction coefficient and the amount proportional to the slope of the baseline is calculated in advance, The correction coefficient 1/γ(θ) may be directly determined based on the above.

Further, in the above-described embodiment, the distribution of the obtained values of θ may be displayed.

Furthermore, in the above embodiment, the sample was scanned two-dimensionally each time the energy selection value of the analyzer was set, but each time the electron beam was irradiated to each pixel, four types of energy selection values of the analyzer were set. Alternatively, a detection signal for quantitatively analyzing a sample may be obtained by switching and performing one electron beam scan.

Furthermore, in the above embodiment, a conversion table was used to correct the peak-background ratio to a value independent of the sample tilt angle based on the signal corresponding to the slope of the baseline of the Auger electron spectrum. A relational expression may be determined in advance, and the conversion may be performed by calculation without using a conversion table.

Furthermore, in the embodiments described above, the present invention was applied to two-dimensional analysis of a sample, but the present invention can be similarly applied to point analysis.

[Effect of the invention] As is clear from the above explanation, the present invention has the following effects:
The base of the Auger electron spectrum at the analysis point is based on the signal from the detector obtained by irradiating the same analysis point with an electron beam when the energy selection value is set to each of different energy values by the analyzer. A signal corresponding to the slope of the line is obtained, and based on the signal corresponding to the slope of the baseline, the peak background ratio R〈θ) is calculated as an IR value independent of the slope angle θ of the electron beam irradiation point.
Since the Q is corrected, the present invention makes it possible to obtain quantitative analysis data based only on the composition, which is not affected by the slope of the sample surface, even when analyzing a sample that includes a sloped surface with a large slope angle. An electronic analysis device is provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the main part of an embodiment of the present invention,
FIG. 2 is an overall diagram of an embodiment of the present invention, FIG. 3 is a diagram not showing a conversion table for determining Gi from Gi, and FIG.
The figure shows a conversion table for determining γ (θ1) from Gi, Figure 5 is a diagram to explain the relationship between sample unevenness and spectral signal intensity, and Figure 6 shows the peak-background ratio. Figure 7 is a diagram for explaining the sample tilt angle θ, Figure 8 is a graph showing the relationship between θ and γ (θ), and Figures 9 and 10 are graphs showing the sample tilt angle θ. Diagrams for illustrating spectra when variously changed,
FIG. 11 is a graph showing the relationship between θ and G. 1: N-type gun 2: Deflector 3: Focusing lens 4: Sample 5: Scanning signal generation circuit 6: D△ converter 7: Energy analyzer

Claims (1)

[Claims] A sample is irradiated with an electron beam, Auger electrons generated from the sample are guided to an energy analyzer based on the irradiation of the electron beam, and the Auger electrons are detected by a detector via the analyzer to obtain the Auger peak intensity I ( Ep) and the background intensity I(
Eb), and based on these measurement results, the peak background ratio {I(Ep)-I(Eb)}/I(E
(b) in an Auger electron analyzer configured to calculate energy selection values by the analyzer, means for setting energy selection values by the analyzer to mutually different energy values in a background region; Based on the signal from the detector obtained by irradiating the same analysis point with an electron beam when each value is set, a signal corresponding to the slope of the baseline of the Augier electron spectrum at the analysis point is determined. and means for correcting the peak-background ratio to a value independent of the tilt angle of the sample surface at the analysis point based on the signal corresponding to the slope of the baseline. Spectroscopic device.