JP2000292384A - Sample analytical method and electron beam analytical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute drift correction correctly, even if a sample surface shape is changed by ion sputtering onto a sample at the time of analysis of the sample. SOLUTION: A drift correction signal forming means 16 forms binary image data by executing binarization processing of image data sent from a central control device 17, and obtains a coordinate of the central position of a pit based on the binary image data. Also, the drift correction signal forming means 16 forms binary image data by executing binarization processing of image data memorized in an image data memory means 20 before analysis, and obtains a coordinate of the central position of a pit based on the binary image data. The drift correction signal forming means 16 obtains the difference between the coordinates and sends it to a deflection control means 14 as drift correction data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for analyzing a sample in an Auger electron spectrometer or the like, and an electron beam analyzer such as an Auger electron spectrometer.

[0002]

2. Description of the Related Art An Auger electron spectrometer irradiates a specific position on a sample with an electron beam, detects Auger electrons emitted from an extremely thin layer on the sample surface by the irradiation of the electron beam, and detects the Auger electrons. This is a device for examining elements present in an extremely thin layer of a sample.

[0003] This Auger electron spectroscopy system is, for example, I
It is used for analysis of dust attached to the surface of an IC during a C (integrated circuit) manufacturing process. Further, recent Auger electron spectrometers have a drift correction function in order to prevent movement of an electron beam irradiation position due to drift of a sample or the like. In other words, recent Auger electron spectrometers compare the image collected before analysis with the image collected during analysis to determine the amount of shift in the electron beam irradiation position, and provide a deflection signal for correcting the amount of shift in electron beam deflection. Feedback to the means. In an Auger electron spectrometer having such a drift correction function,
During the sample analysis, the electron beam irradiation position is kept at a specific position on the sample.

[0004]

However, when the sample is ion-sputtered for analysis in the depth direction of the sample at the time of analyzing the sample in which such drift correction is performed, the surface shape of the sample due to the ion sputtering is reduced. May appear in the secondary electron image collected during the analysis, and drift correction may not be performed correctly. If the drift correction is not performed correctly, the electron beam irradiation position moves from a specific position on the sample during the sample analysis.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sample analysis method in which drift correction is correctly performed even when the sample is ion-sputtered during sample analysis and the sample surface shape is changed. A method and an electron beam analyzer are provided.

[0006]

Means for Solving the Problems A sample analysis method of the present invention that achieves this object irradiates a specific position on a sample with an electron beam and detects a signal emitted from the sample by the irradiation of the electron beam. In a sample analysis method for performing sample analysis, scan data for scanning a predetermined area including pits artificially formed on a sample with an electron beam is stored in a scan data storage unit, and the sample data is stored in a sample data storage section before sample analysis. A scanning signal corresponding to the scanning data stored in the scanning data storage means is supplied to the electron beam deflection means to perform electron beam scanning, and a signal emitted from the sample by the electron beam scanning is stored as image data;
Interrupting the irradiation of the electron beam to the specific position during sample analysis,
During the suspension of the sample analysis, a scanning signal corresponding to the scanning data stored in the scanning data storage unit is supplied to the electron beam deflecting unit to perform electron beam scanning, and a signal emitted from the sample by the electron beam scanning is output. Converting the image data into image data, creating a drift correction signal based on the image data and the image data stored in the image data storage unit, and supplying the drift correction signal to the deflection unit to perform drift correction. And

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an Auger electron spectrometer, which is one of the electron beam analyzers of the present invention.

First, the configuration of FIG. 1 will be described.

In FIG. 1, reference numeral 1 denotes a sample, and the sample 1 is placed on a sample stage 2. An electron optical device 3 is disposed directly above the sample 1.
Has an electron gun 4, a focusing lens 5, and a deflecting means 6.

Reference numeral 7 denotes an ion optical device. The ion optical device 7 is disposed near the electron optical device 3. The ion optical device 7 includes an ion gun 8 and a focusing lens 9.
And deflection means 10.

Reference numeral 11 denotes an electron spectroscope for detecting Auger electrons generated from the sample 1. Reference numeral 12 denotes a secondary electron detection device that detects secondary electrons generated from the sample 1.

The sample 1, the sample stage 2, the electron spectroscope 11, and the secondary electron detector 12 are arranged in a sample chamber 13. The electron optical device 3 and the ion optical device 7 are connected to the sample chamber. Mounted on the wall. The inside of the sample chamber 13 is evacuated to an ultra-high vacuum by an exhaust device (not shown).

Reference numeral 14 denotes a deflection control means for controlling the deflection means 6. The deflection control means 14 is connected to the scanning data generation means 15, the drift correction signal creation means 16, and the central control unit 17, respectively. . The scanning data generator 15 is connected to the central controller 17 and a pit generator 18 that controls the ion optical device 7. Further, the drift correction signal creating means 16 is connected to the central control device 17, and the scan data storage means 19 is also connected to the central control device 17.

The electron spectroscope 11 and the secondary electron detector 1
The output of 2 is configured to be sent to the central control unit 17, and the image data storage unit 20 stores the image data representing the secondary electron image sent from the central control unit 17. This image data storage means 20 is connected to the drift correction signal creation means 16.

Reference numeral 21 denotes a depth direction analysis control device. The depth direction analysis control device 20 controls the ion optical device 7 and the electron spectrometer 11 based on a signal from the central control device 17.
Control.

The central control unit 17 includes an instruction unit 22, an analysis position information storage unit 23, a pit generation position information storage unit 24, an image matching unit 25, a sample stage control unit 26, a display unit 27, and the pit generation unit. 1
8 is connected. The image matching device 25 is connected to the pit generation device 18, and the sample stage control device 26 is connected to the sample stage 2.

The configuration of the apparatus shown in FIG. 1 has been described above. Next, the operation of the apparatus shown in FIG. 1 will be described.

First, the operator gives an instruction to acquire a secondary electron image by the instruction means 22 in order to obtain a secondary electron image of the sample 1. When an instruction to acquire a secondary electron image is issued, the central control unit 17 sends a scan data generation signal to the scan data generation unit 15, and the scan data generation unit 15 receiving the scan data generation signal sends the scan data generation signal to the scan data generation unit 15. Is sent to the deflection control means 14. The deflection control means 14 sends a scanning signal corresponding to the sent scanning data to the deflection means 6. The deflecting means 6 receiving the scanning signal deflects the electron beam emitted from the electron gun 4 and focused by the focusing lens 5 two-dimensionally. As a result, certain areas S ₁ of the sample 1 is scanned by the electron beam. At this time, sample 1
Is orthogonal to the optical axis of the electron optical device 3.

When the sample is irradiated with an electron beam, secondary electrons are generated from the sample, and the secondary electrons are detected by the secondary electron detector 1.
2 detected. The secondary electron detector detects the detected secondary
The image data corresponding to the next electron is sent to the central control unit 17. The central control device 17 stores the image data in the image matching device 25. In addition, the central controller 1
Reference numeral 7 denotes the image data and the scan data generating means 15
Based on the scan data to the generated, to display a secondary electron image of the predetermined region S ₁ on the screen of the display device 27. FIG. 2 shows an area S ₁ displayed on the screen of the display device 27.
3 shows the secondary electron image of FIG.

When the secondary electron image of the sample is displayed on the display device 27, the operator specifies the analysis position and the pit generation position using the secondary electron image. To explain the position designation, the operator operates the indicating means 22 to move the cursor K displayed superimposed on the secondary electron image to the position to be analyzed, and designates the analysis position. Further, the operator operates the instruction means 22 to move the cursor K to a position where a pit is to be generated, and designates a pit generation position. The pit generation position is a position where a hole is formed by ion beam irradiation. As shown in FIG. 3, the analysis position A and the pit generation positions P ₁ , P ₂ , P ₃
Are respectively specified, the analysis position data A (x, y) of the analysis position A is generated by the central control unit 17 and stored in the analysis position information storage means 23, while the pit generation positions P ₁ , P ₂ and P ₃ pit generation position data P ₁ (x ₁ ,
y ₁ ), P ₂ (x ₂ , y ₂ ) and P ₃ (x ₃ , y ₃ ) are generated by the central control unit 17 and stored in the pit generation position information storage means 24.

When the analysis position and the pit generation position are determined in this way, the central control unit 17 outputs the tilt signal for making the sample surface of the sample 1 orthogonal to the optical axis of the ion optical device 7. It is sent to the sample stage controller 26.
The sample stage controller 26 that has received the tilt signal
Tilts the sample stage 2 so that the sample surface is orthogonal to the optical axis of the ion optical device 7.

When the sample stage 2 is tilted as described above,
The central control unit 17 includes the scanning data generation unit 15.
A scan data generation signal. The scanning data generating means 15 receiving the scanning data generating signal outputs the same scanning data as the scanning data sent to the deflection control means 14, that is, the scanning data for scanning the fixed area S1 of the sample ₁ with an ion beam. Is sent to the pit generator 18.
The pit generation device 18 sends a scanning signal corresponding to the sent scanning data to the deflecting means 10. The deflecting means 10 receiving the scanning signal deflects the ion beam emitted from the ion gun 8 and focused by the focusing lens 9 two-dimensionally.

When the sample is irradiated with the ion beam, secondary electrons are generated from the sample, and the secondary electrons are detected by the secondary electron detector 12. The secondary electron detection device sends image data corresponding to the detected secondary electrons to the central control device 17. The central control device 17 stores the image data in the image matching device 25.

The image matching device 25 performs a matching process between the image data obtained by the ion irradiation and the image data obtained by the electron beam irradiation described above, and obtains a shift of the observation visual field by the matching process. . This shift is caused by, for example, tilting the sample, and the image matching device 25 sends the obtained shift to the pit generation device 18 as ion beam irradiation position correction data (Δx, Δy). This data will be described later.
It is used when irradiating the sample with the ion beam, and is used to accurately irradiate the pit generation positions P ₁ , P ₂ , and P ₃ with the ion beam.

In this manner, the ion beam irradiation position compensation is performed.
When the positive data is sent to the pit generation device 18,
The control device 17 controls the pit generation position information storage means 24
Pit generation position data P stored in₁(X₁,
y₁), P_Two(X_Two, Y_Two), P_Three(X_Three, Y_ThreeRead out)
To the pit generator 18. Pit generator 18
Is pit generation position data and ion beam irradiation position correction
The data is added and the ion beam irradiation signal P₁(X₁+ Δ
x, y₁+ Δy), P_Two(X_Two+ Δx, y_Two+ Δy), P _Three
(X_Three+ Δx, y_Three+ Δy) and create them before
It is sent to the deflecting means 10. As a result, the ion beam
Recording pit generation position P₁, P_Two, P_ThreeIrradiated for a predetermined time
Pit p₁, P_Two, P_ThreeIs formed
You. FIG. 4A shows a pit p formed on the sample 1.₁,
p_Two, P_ThreeFIG. 4B is a view of the sample viewed from above, and FIG.
Is the pit p₁FIG. As shown in FIG.
In addition, the hole diameter of the pit becomes smaller as the hole becomes deeper.
ing.

When the pits p ₁ , p ₂ , and p ₃ are formed on the sample 1, the central control unit 17 sends a tilt signal for making the sample surface of the sample 1 orthogonal to the optical axis of the electron optical device 3. Is sent to the sample stage controller 26. Upon receiving the tilt signal, the sample stage control device 26 controls the sample stage 2 so that the sample surface is orthogonal to the optical axis of the electron optical device 3.
Tilt.

In this way, when the sample is returned to the original horizontal state, the central control unit 17 stores the pit generation position data P ₁ (x ₁ , y ₁ ), P ₂ (x ₂ , y ₂ ), P ₃ (x ₃ ,
Read y ₃ ). Then, the central control unit 17, based on the pit generated position data, the scan data D for scanning a predetermined area Sp ₁ comprising the pit p ₁ with an electron beam
(Sp ₁ ), scanning data D (Sp ₂ ) for scanning the fixed area Sp ₂ including the pit p ₂ with an electron beam, and scanning for scanning the fixed area Sp ₃ including the pit p ₃ with an electron beam. Data D (Sp ₃ ) is created, and the scan data D (Sp ₁ ), D (Sp ₂ ), and D (Sp ₃ ) are stored in the scan data storage unit 19.

The central control unit 17 sends the scanning data D (Sp ₁ ), D (Sp ₂ ) and D (Sp ₃ ) to the deflection control means 14 in order. The deflection control means 14 sends a scanning signal corresponding to the sent scanning data to the deflection means 6. The deflecting means 6 receiving the scanning signal deflects the electron beam emitted from the electron gun 4 and focused by the focusing lens 5 two-dimensionally. As a result, the fixed regions Sp ₁ , Sp ₂ and Sp _{3 of} the sample 1 are sequentially scanned by the electron beam.

When the sample is irradiated with an electron beam, secondary electrons are generated from the sample. The secondary electron detector 12 converts the detected secondary electrons into image data and outputs the scan data D.
Image data D ₂ (Sp ₁ ) corresponding to (Sp ₁ ) and image data D ₂ (S ₁ ) corresponding to the scan data D (Sp ₂ ).
p ₂ ), and sends image data D ₂ (Sp ₃ ) corresponding to the scanning data D (Sp ₃ ) to the central control unit 17. The central controller 17 stores these image data in the image data storage means 20.

After the above processing is performed, the analysis of the analysis point A is started. The operation of the apparatus during the analysis will be described below.

First, the central control unit 17 analyzes the analysis position data A stored in the analysis position information storage means 23.
(X, y) is read out and sent to the deflection control means 14.
The deflection control means 14 having received the analysis position data A (x, y) sends a deflection signal corresponding to the analysis position data to the deflection means 10. The deflecting unit 10 that has received the deflection signal deflects the electron beam so that the electron beam irradiates the analysis point A on the sample, so that the analysis point A of the sample 1 is irradiated with the electron beam. Secondary electrons, Auger electrons, and the like are emitted from the sample by the irradiation of the electron beam, and the Auger electrons are detected by the electron spectroscope 11.

The central control unit 17 sends the analysis position data to the deflection control means 14 as described above, and sends a signal representing the element to be analyzed to the depth direction analysis control unit 21.
Send to Since the depth direction analysis control device 21 sends this signal to the electron spectrometer 11, the electron spectrometer 11 collects the spectrum of the specified target element from the detected Auger electrons, and reports the collected result to the central control unit. Send to device 17.

Further, the central control unit 17 sends a signal indicating the cycle t of the ion sputtering to the depth direction analysis control unit 21. The depth direction analysis control device 21 controls the ion optical device 7 based on this signal so that the sample is ion-sputtered at the cycle t. In this ion sputtering, the ion beam is irradiated over a wide area on the sample, and the analysis position A and the pits p ₁ , p ₂ , p ₃
Is also irradiated with the ion beam. The sample surface is shaved by this ion sputtering, and Auger analysis in the depth direction of the sample is performed.

The information on the element to be analyzed and the cycle of the ion sputtering can be provided by the instruction means 22 by the operation of the operator.
Is input to the central controller 17 in advance, and when ion sputtering is performed, the electron spectrometer 1
1 has interrupted spectrum collection.

The apparatus shown in FIG. 1 has a drift correction function. The drift correction will be described below.

The central control unit 17 controls the analysis position A
When the analysis T has started and, for example, a time T longer than the period t has elapsed, the supply of the analysis position data A (x, y) to the deflection control means 14 is stopped. That is, the Auger analysis at the analysis position A is interrupted.

Then, the central controller 17 scans the scan data D (Sp) stored in the scan data storage means 19.
₁ ), D (Sp ₂ ) and D (Sp ₃ ) are read out and sent to the deflection control means 14 in order. Deflection control means 14
Sends a scanning signal corresponding to the transmitted scanning data to the deflecting means 6, which deflects the electron beam two-dimensionally.

When the sample is irradiated with an electron beam, secondary electrons are generated from the sample. The pits p ₁ formed on the sample,
The amount of secondary electrons generated from p ₂ and p ₃ is smaller than in other portions, and the pits are dark portions in the secondary electron image. The secondary electron detection device 12 converts the detected secondary electrons into image data, and outputs image data D ₂ ′ (Sp ₁ ) corresponding to the scan data D (Sp ₁ ) and scan data D (Sp ₂ ).
The image data D ₂ ′ (Sp ₂ ) corresponding to the image data D ₂ ′ (Sp ₂ ) and the image data D ₂ ′ (Sp ₃ ) corresponding to the scan data D (Sp ₃ ) are sent to the central control unit 17. The central controller 17 sends these image data to the drift correction signal generator 16. Hereinafter, the operation of the drift correction signal creating means 16 will be described in detail.

The drift correction signal creating means 16 outputs the image data D ₂ ′ (S
p ₁ ), D ₂ ′ (Sp ₂ ) and D ₂ ′ (Sp ₃ ) are each 2
A binarization process is performed to generate binarized image data. That is,
The drift correction signal creating means 16 compares the signal intensity of the image data at each pixel with a predetermined value Q, and
Value. FIG. 5 shows an image of binarized image data obtained by binarizing image data D ₂ ′ (Sp ₁ ). In FIG. 5, a circular portion M ₁ corresponds to the pit p _1, although shaded portion corresponds to the portion other than the pit p _1, wherein the predetermined value Q can determine pit portion as this It is set as follows.

When the image data is binarized in this way, the drift correction signal generating means 16 calculates the coordinates p ₁ ′ of the center position of each of the pits p ₁ , p ₂ , p ₃ based on the binarized image data. _{(x 1, y 1),} p 2 '(x 2, y 2), p 3'
(X ₃ , y ₃ ) are obtained.

The drift correction signal generating means 16
Before the analysis, the image data D ₂ (Sp ₁ ), D ₂ (Sp ₂ ), and D ₂ (Sp ₃ ) stored in the image data storage means 20 are read, and they are binarized in the same manner as described above. Create binary image data. FIG. 6 shows image data D ₂ (S
p ₁ ) shows an image based on the binarized image data obtained by the binarization processing. 6, circular portion M ₁ is corresponds to the pit p _1, hatched portions correspond to portions other than the pit p _1. When the image data is binarized in this way, the drift correction signal creating means 16 calculates the pits p ₁ , p ₂ ,... Based on the binarized image data.
coordinates p ₁ of the center position of the _{p 3 (x 1, y 1} ), p 2 (x 2,
y ₂ ) and p ₃ (x ₃ , y ₃ ) are obtained.

[0043] Now, as shown in FIG. 6, the before analysis start pit p ₁ was in the middle of the image, as shown in FIG. 5, the pit p ₁ is the image center when the time T has elapsed from the start of the analysis Is out of range. This is because a drift or the like of the sample occurred during the sample analysis. The reason why the diameter of the pit in FIG. 5 is slightly smaller than the diameter of the pit in FIG. 6 is due to the ion sputtering described above.

The drift correction signal creating means 16 further calculates the coordinates p ₁ (x ₁ , y ₁ ), p ₂ (x ₂ , y ₂ ),
p ₃ (x ₃ , y ₃ ) and coordinates p ₁ ′ (x ₁ , y ₁ ), p ₂ ′
The difference between (x ₂ , y ₂ ) and p ₃ ′ (x ₃ , y ₃ ) is obtained, and the drift amount dp ₁ (x ₁ , y ₁ ), dp ₂ (x ₂ , y ₂ ), dp
₃ (x ₃ , y ₃ ) is obtained. Then, the drift correction signal generating means 16 calculates an average value ((dp ₁ + dp ₂ + dp ₃ ) / 3) of these three drift amounts, and outputs the drift correction data corresponding to the average value to the deflection control means 1.
Send to 4.

When the drift correction data is sent to the deflection control means 14 in this way, the central control unit 17
Converts the analysis position data A (x, y) into deflection control means 1
Send to 4. Then, the deflection control means 14 adds the analysis position data A (x, y) and the drift correction data, and sends a deflection signal corresponding to the added data to the deflection means 6. As a result, when the analysis is restarted, the electron beam is applied to the analysis position A specified first.

Thereafter, sample analysis, ion sputtering and drift correction are performed in the same manner.

The operation of the apparatus shown in FIG. 1 has been described above. When the sample is ion-sputtered, the surface shape (pit diameter) of the sample changes.
It does not change unless drift occurs. In the apparatus shown in FIG. 1, the drift correction is performed by detecting the movement of the center position of the pit. Therefore, even if the sample is ion-sputtered during the sample analysis and the sample surface shape changes, the drift correction is correctly performed.

In the apparatus shown in FIG. 1, pits to be opened around the position to be analyzed are generated by the ion optical apparatus attached to the Auger electron spectrometer, but other ion optical apparatuses are mounted. The position to be analyzed may be found using a device such as the above, a pit may be generated in advance, and then the sample may be attached to the Auger electron spectrometer.

In the above example, pits are generated in the ion-sputtered area. However, the pits may be located anywhere outside the analysis target, and need not be in the sputtered area.

Further, the present invention can be applied to an apparatus capable of analyzing a small area, such as an X-ray microanalyzer.

[Brief description of the drawings]

FIG. 1 is a diagram showing an Auger electron spectroscopy apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a secondary electron image displayed on a display device 27.

FIG. 3 is a diagram shown for explaining designation of an analysis position and designation of a pit generation position.

FIG. 4 is a diagram shown for explaining pits formed on a sample.

FIG. 5 is a diagram showing a binarized image of a sample.

FIG. 6 is a diagram showing a binarized image of a sample.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... sample, 2 ... sample stage, 3 ... electron optical device, 4 ...
Electron gun, 5, 9, focusing lens, 6, 10, deflecting means, 1,
DESCRIPTION OF SYMBOLS 1 ... Electron spectroscope, 12 ... Secondary electron detection device, 13 ... Sample chamber, 14 ... Deflection control means, 15 ... Scan data generation means,
16 Drift correction signal creation means 17 Central control device 18 Pit generation device 19 Scan data storage device 20 Image data storage device 21 Depth direction analysis control device 22 Instruction means 23 Analysis position information storage means, 24 pit generation position information storage means, 25 image matching device, 26 sample stage control device

Claims (3)

[Claims] 1. A sample analysis method for irradiating a specific position on a sample with an electron beam, detecting a signal emitted from the sample by the irradiation of the electron beam, and analyzing the sample, wherein the sample is artificially placed on the sample. Scan data for scanning a predetermined area including the formed pits with an electron beam is stored in a scan data storage unit, and before a sample analysis, a scan signal corresponding to the scan data stored in the scan data storage unit is stored. Is supplied to the electron beam deflecting means to perform electron beam scanning, a signal emitted from the sample by the electron beam scanning is stored as image data, and irradiation of the specific position with the electron beam during sample analysis is interrupted, During the suspension of the sample analysis, a scanning signal corresponding to the scanning data stored in the scanning data storage unit is supplied to the electron beam deflecting unit to perform electron beam scanning, and a signal emitted from the sample by the electron beam scanning is output. image Converting the data into data, creating a drift correction signal based on the image data and the image data stored in the image data storage unit, and supplying the drift correction signal to the deflection unit to perform drift correction. Sample analysis method. 2. An electron beam analyzer for irradiating a specific position on a sample with an electron beam, detecting a signal emitted from the sample by the irradiation of the electron beam, and analyzing the sample, wherein the electron beam is deflected. Deflecting means, scan data storage means for storing scan data for scanning a predetermined area including pits artificially formed on the sample with an electron beam, and irradiating the specific position on the sample with the electron beam. Means for interrupting sample analysis,
Control means for supplying a scan signal corresponding to the scan data stored in the scan data storage means to the deflecting means before sample analysis and during sample analysis suspension, and the predetermined area is scanned by an electron beam before sample analysis. Image data storage means for storing a signal emitted from the sample as image data, image data obtained by the electron beam scanning during the suspension of sample analysis, and image data stored in the image data storage means. An electron beam analyzer comprising: a drift correction signal generating unit that generates a drift correction signal based on the drift correction signal and supplies the drift correction signal to the deflection unit. 3. The electron beam analyzer according to claim 2, further comprising pit generation means for generating pits on the sample.