JPH0328016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a high-precision positioning method for an electronic probe device that positions an electronic probe with high precision at a specified point on a surface scan image obtained in a surface scan mode. and devices.

[Conventional technology]

For example, when measuring the internal potential distribution of an LSI (integrated circuit) or VLSI using a scanning microscope, first,
An electron beam is irradiated onto the sample in surface scanning mode, a surface scanning image is displayed on a CRT screen, an arbitrary point is selected on the surface scanning image, and the electron beam is irradiated thereon in point irradiation mode. . In such a case,
Conventionally, the method used was to display a surface scan image in surface scan mode, then switch to point irradiation mode, and then manually move the bright spot on the afterimage of the surface scan image to position it at a desired point. ing.

By the way, when trying to automatically perform the above positioning using a digital signal processing device using a computer, etc., in the surface scanning mode, a digital scanning signal (address) that changes in steps as shown in FIG. A signal) is generated, which is D/A (digital/analog) converted and supplied to a scanning coil to obtain a surface scanning image by digital scanning. Therefore, by specifying a digital scanning signal corresponding to a desired point on a surface scanning image, the electron beam can be positioned in point irradiation mode to measure, for example, the internal potential distribution of an LSI. .

[Problem that the invention seeks to solve]

However, in the point irradiation mode, in which the electron beam is moved to a point by specifying an address on a computer, and in the area scanning mode, the beam scanning method, that is, the beam movement path and movement speed, are different, so the response of the scanning coil is Positioning errors occur due to characteristics and hysteresis, and compared to the area scanning image shown by the solid line as shown in Figure 5, the image obtained by slowly moving the electron beam in point irradiation mode using the digital scanning signal of the same address is , do not match as shown in the image by dotted lines. In this way, there is a one-to-one correspondence between the address and the amount of current flowing through the scanning coil, but it is possible to read out the address of a certain point P _A on the surface scanning image (for example, v _s shown in Figure 4) and use it in point irradiation mode. Even if the same address is specified, there is no guarantee that the electron beam will move exactly to that point, and it will shift to point P _B. Conventionally, there has been no effective means of measuring this error, and therefore there has been no hope of high precision positioning.

The present invention solves the above-mentioned problems, and is a high-precision positioning system for an electronic probe device that can accurately position an electron beam at any point specified on a surface scanning image using a point irradiation mode. It is an object of the present invention to provide a method and apparatus.

[Means for solving problems]

Therefore, the high-precision positioning method for an electronic probe device of the present invention is a high-precision positioning method for an electronic probe device that positions an electronic probe at a specified point on a surface scan image obtained in a surface scan mode. In addition to obtaining a surface scanning image using the point irradiation mode, a partial image corresponding to the surface scanning image is obtained using the point irradiation mode. The present invention is characterized in that the electronic probe is positioned in a point irradiation mode at the specified point on the surface scanning image by correcting the deviation of the irradiation point position at the specified point. The device is a high-precision positioning device for an electronic probe device, which includes a digital scanning signal generating device, a digital scanning device having a digital/analog converter, and a signal detecting device, and includes an image calculation device, a frame memory, and an image display device. and an arithmetic processing unit that controls the electronic probe device and the image processing device. At the same time, the address is memorized, and the area near the arbitrary point is sequentially irradiated in the point irradiation mode, the address corresponding to the arbitrary point on the partial image is memorized, the difference between the two addresses is calculated, and the area is scanned on the area scanned image. The electronic probe is characterized in that the electronic probe is positioned in a point irradiation mode to the designated point on the surface scanning image by correcting the difference between the two addresses to the address of the designated point. .

[Effect]

In the high-accuracy positioning method and apparatus for an electronic probe device of the present invention, a difference in scanning signals at the same point between a surface scanning image and a partial image is obtained, and this difference is used to perform point irradiation at a specified point on the surface scanning image. Since the scanning signal in the mode is corrected, the electronic probe can be positioned with high precision.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of a high-precision positioning system for an electronic probe device according to the present invention, FIG. 2 is a diagram for explaining image processing using two display screens, and FIG. 3 is a diagram of the present invention. FIG. 3 is a diagram for explaining the flow of processing by the high-precision positioning system for the electronic probe device according to the invention. In the figure, 1 is an electronic probe device, 2 is a digital scanning signal generator, 3 is a D/A converter, 4 is a scanning coil, 5 is a signal detector, 6 is a host computer, 7 is an image processing device, and 8 is a frame 9 indicates a memory and a display device.

As shown in FIG. 1, the overall configuration of the high-precision positioning system for an electronic probe device according to the present invention is as follows:
Digital scanning signal generator 2, scanning coils 4, 2
An electronic probe device body such as an SEM that has a signal detector 5 that detects signals such as secondary electrons and characteristic X-rays;
It consists of a host computer 6 that generates a point irradiation signal and captures detection signals such as secondary electrons, an image calculation device 7, a frame memory 8, and a display device 9.

In FIG. 1, the host computer 6 starts the digital scanning signal generator 2 in the area scanning mode, and digitally controls the amount of current flowing to the scanning coil 4 through the D/A converter 3 in the spot irradiation mode. Yes, digital scanning signal generator 2
is activated by the host computer 6 and scans the scanning coil 4 through the D/A converter 3 in area scanning mode.
This is to digitally control the amount of current (corresponding to the address on the screen in the surface scanning image) flowing through the area. The signal detector 5 detects quantum signals such as secondary electrons and characteristic X-rays generated by irradiating a sample with a beam, and sends the signals to a host computer 6 and an image processing device 7. It will be done. In the area scanning mode, the image processing device 7 stores the detection signal from the signal detector 5 in the area a of the frame memory 8 using the digital scanning signal generated by the digital scanning signal generator 2 as an address, and in the point irradiation mode, it stores the detection signal in the area a of the frame memory 8. The signal detector 5 uses the digital scanning signal generated at 6 as an address.
The detection signal from the frame memory 8 is stored in area b of the frame memory 8. The display device 9 has two display screens and can simultaneously display an image in area a and an image in area b of the frame memory 8,
When a specific point on the image is instructed to be input using a cursor on each screen, its coordinate values are sent to the host computer 6. For example, the image shown in FIG. 2a as the image of area a of the frame memory 8 and the image shown in FIG. 2b as the image of area b of the frame memory 8 are displayed on the screen of the display device 9,
If there is an instruction to input specific points P _A and P _B , those specific points
The coordinate values of P _A and P _B are sent to the host computer 6. From this coordinate value, the host computer 6
The correction value, that is, the difference between the coordinate values of P _A and P _B is determined. FIG. 3 shows the flow of processing in this case.

The overall operation of the high-precision positioning system for an electronic probe device according to the present invention, including the above processing, is as follows: 1) Measurement of positioning error, 2) Correction of point irradiation program, 3) Confirmation of correction effect. It is divided into three stages.

1 Measurement of Positioning Error Image scanning is performed using the digital scanning signal generator 2, and the resulting image (image A) is stored in area a of the frame memory 8.

Using a point irradiation mode program by the host computer, the entire area or a part of area a is two-dimensionally scanned, and the image at this time (image B) is stored in area b of the frame memory 8.

Images A and B are displayed on the display device 9 as shown in FIG.
are displayed simultaneously on the screen, and the addresses of the corresponding locations P _A and P _B on the screen are read out using a cursor or the like. The difference between these addresses is the difference between the beam landing points, that is, the positioning error.

2. Correction of the point irradiation program The point irradiation mode program is corrected in consideration of the deviation in the irradiation point position (address) between the surface scanning mode and the point irradiation mode in 1).

3. Confirming the correction effect Execute steps 1) and () to) again to confirm the effect of the correction.

Through experiments, we confirmed that the beam could be irradiated anywhere on the SEM screen, which consists of 512 x 512 addresses, within an error range of ±1 address, regardless of acceleration voltage, magnification, and image rotation. This is the magnification
At 10,000 times magnification, it was ±0.016 μm. This value is
It is sufficient for the positioning of current and future VLSIs.

Note that the present invention can be modified in various ways and is not limited to the above embodiments. For example, the frame memory and display screen may each be equipped with the equivalent of one image, and the coordinate values of a specific point may be stored in the area scanning mode and the point illumination mode, and the difference between them may be determined. The two images shown in Figure 2 a and b are superimposed on the display screen and the points are
P _A and P _B may also be specified. It goes without saying that the present invention is not limited to scanning electron microscopes, but can be widely applied to X-ray microanalyzers, Auger microprobes, EB testers, and other magnetic field deflection type electron probe devices using magnetic coils. Nor.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a two-dimensional image is obtained using a point irradiation program as it is, and is compared with a surface scanning image using an image processing device, which is a method that has not been conventionally effective. We were able to measure the positioning error. In addition, using a point irradiation program that corrects the measured error, for example, magnification
At 10,000x magnification, ± anywhere on the surface scanning screen
Positioning is now possible with an accuracy of 0.016μm. This is sufficient for positioning current and future VLSI electron beam testing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of a high-precision positioning system for an electronic probe device according to the present invention, FIG. 2 is a diagram for explaining image processing using two display screens, and FIG. 3 is a diagram of the present invention. A diagram for explaining the flow of processing by the high-precision positioning system of the electronic probe device according to the invention, FIG. 4 is a diagram for explaining the digital scanning signal, and FIG. 5 is a diagram for explaining the deviation between the area scanning image and the point illumination image. FIG. DESCRIPTION OF SYMBOLS 1...Electronic probe device, 2...Digital scanning signal generator, 3...D/A converter, 4...Scanning coil, 5
...Signal detector, 6...Host computer, 7...Image calculation device, 8...Frame memory, 19...Display device.

Claims (1)

[Claims] 1. A high-precision positioning method for an electronic probe device that positions an electronic probe at a designated point on a surface scan image obtained in a surface scan mode, the method comprising: obtaining a surface scan image in a surface scan mode; , Obtain a partial image corresponding to the plane scanned image in the point irradiation mode, find the deviation of the irradiation point position at the corresponding point between the plane scan image and the partial image, and place the irradiation point at the specified point on the plane scan image. 1. A high-precision positioning method for an electronic probe device, characterized in that the electronic probe is positioned in a point irradiation mode at a specified point on a surface scanning image by correcting positional deviations. 2. A high-precision positioning device for an electronic probe device comprising a digital scanning signal generating means, a digital scanning means having a digital/analog converter, and a signal detecting means, and comprising an image calculation means, a frame memory, and an image display means. It is equipped with an arithmetic processing device that controls an image processing device, an electronic probe device, and an image processing device, stores and displays a surface scanned image in a frame memory in a surface scanning mode, and stores an address of an arbitrary point on the surface scanned image. At the same time, the area near the arbitrary point is sequentially irradiated in the point irradiation mode, the address corresponding to the arbitrary point on the partial image is memorized, the difference between the two addresses is found, and the area specified on the surface scanning image is The height of the electronic probe device is characterized in that the electron probe is configured to correct the difference between the two addresses to the address of the point specified, and position the electronic probe to the specified point on the surface scanning image in a point irradiation mode. Precision positioning device. 3 Consists of at least two frame memories,
The electronic probe device according to claim 2, wherein the electronic probe device is configured to store a surface scanning image in the surface scanning mode and a partial image in the point irradiation mode in each frame memory and display them on the screen. High precision positioning device.