JPH02189848A - Charged particle beam device and method of acquiring image signal therewith - Google Patents

Abstract

PURPOSE:To increase the image resolution without using any precision DA converter by performing scanning in a plurality of runs over a certain scope while this scanning scope is shifted, subjecting a plurality of obtained signals to compilation, and turning into one sort of image signal. CONSTITUTION:A certain scope on a specimen 4 is scanned by an electron beam EB. Secondary electrons generated by this scanning are sensed by a sensor 10 and entered into a frame memory 13 through an AD converter 12. Then a shift signal is impressed to a deflector 8, and the scanning scope on the specimen 4 is slightly shifted. The electron beam generated by this scanning is sensed by the said sensor 10 and stored in another frame memory 14. Thus the scanning is continued with the scope shifted little by little, and the signal sensed associate with each scanning run is stored in the frame memories 15, 16. The data in these memories 14-16 are read and re-arranged by a P/S converter 17.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for acquiring a video signal in a charged particle beam apparatus such as a scanning electron microscope that scans a sample with a charged particle beam irradiated onto the sample, and Relating to a particle beam device.

(Prior art) In an electron beam length measuring device, an electron beam is digitally scanned over a sample, secondary charges r or reflected electrons obtained from the sample are detected, and the detected signals are captured in a frame memory. Based on the data loaded into the memory, a 7Ipj length of the pattern on the sample is performed. In order to improve this length measurement accuracy, it is necessary to particularly increase the image resolution in the X direction, and if data of about 2048 pixels in the X direction is obtained, highly accurate length measurement can be performed.

(Problem to be solved by the invention) However, in order to increase the image resolution in the A highly accurate DA converter must be used to supply the data to the means. However, this high-precision DA converter is expensive and cannot perform high-speed scanning such as television scanning. Therefore, the image resolution in the X direction is usually set to 512 pixels, and a relatively inexpensive high-speed DA converter is used, which inevitably reduces the number of pixels in the X direction. There is no hope for long precision.

The present invention has been made in view of these points, and the present invention has been made in view of the above points.
The first is an image signal acquisition method in a charged particle beam device and a charged particle beam device that can increase image resolution even when scanning an electron beam at a television scanning speed without using a high viscosity DA converter. The aim is to realize this.

(Means for Solving the Problems) An image signal acquisition method in a charged particle beam device based on the present invention scans a predetermined range of a sample multiple times while slightly shifting the charged particle beam scanning range on the sample, and Accordingly, a signal obtained from the sample is detected, the detected signal is stored in a plurality of frame memories corresponding to each scan, and the data stored in the plurality of frame memories is rearranged to generate a video signal of a predetermined range of the sample. It is characterized by the fact that it forms a

The charged particle beam device based on the present invention includes a focusing lens for narrowly focusing a charged particle beam on a sample, a deflector for scanning the charged particle beam on the sample, and a device for irradiating the sample with the charged particle beam. A detector that detects the signal obtained from the sample, a plurality of frame memories to which the detection signal from the detector is supplied, and a plurality of predetermined areas of the sample by slightly shifting the scanning range of the charged particle beam on the sample. times scan row 1)
A control device that controls the deflector so that the detection signal is stored in a different frame memory for each scan, and a control device that sequentially reads data stored in a plurality of frame memories and stores the detected signal in a different frame memory for each scan. The invention is characterized in that it has a means for supplying it to a display device.

(Operation) In the invention of Claims] and 2, a predetermined range of the sample is scanned multiple times while slightly shifting the scanning range of the charged particle beam on the sample, and a signal obtained from the sample is detected with each scan, Detection signals are stored in a plurality of frame memories corresponding to each scan, data stored in the plurality of frame memories is rearranged to form a video signal of a predetermined range of the sample, and the digital scanning signal is converted into an analog signal. It is possible to increase image resolution by using a high-speed DA converter capable of television scanning instead of using a high-precision DA converter as a DA converter for converting images into images.

(Example) Hereinafter, the first embodiment of the present invention will be explained with reference to the drawings. Y-Explain in detail. FIG. 1 shows an embodiment of an electron beam length measuring device based on the present invention, in which an accelerated electron beam EB generated from an electron gun is narrowly focused onto a sample 4 by a focusing lens 2 and an objective lens 3. be done.

The irradiation range 1) JJ of the electron beam EB on the sample 4 is changed according to the deflection signal sent to the deflector 5. A scanning signal is supplied from a computer 6 to the deflector 5 via a DA converter 7. The deflector 8 is a deflector for shifting the scanning range of the electron beam on the sample 4, and is supplied with a shift signal from the computer 6 via the DA converter 9.

Secondary electrons generated by irradiating the sample 4 with the electron beam are detected by the detector 10, and the detected signal is
Amplifier] 1 and then converted into a digital signal by an AD converter 12. The digital signal from the AD converter 12 is sent to the computer 6 via the computer 6.
X5] 2-pixel first to fourth frame memories 13.
]-4, 1, 5, or 16. As mentioned above, the Conbinitaro has a DA converter 7,
The converter 17 supplies an electron beam scanning signal and an electron beam shift signal to the parallel/serial converter core. The data stored in .6 is read in order and imported into it. Further, the computer 6 supplies the captured data signal to the display device 18 to display an image, and also measures the length of the pattern based on the data.

” The operation of the dual configuration is as follows. A signal in the X direction 5 is transmitted from the computer 6 to the deflector 5 via a DA converter 7.
A scanning signal of 12 pixels and 512 pixels in the Y direction is supplied, and as a result, a predetermined area of the sample 4 is digitally scanned by the electron beam EB.

FIG. 2 shows the scanning state of the electron beam on the sample 4'' in the X direction, and the portion marked with ``■'' is the irradiation position of the electron beam at this time. Secondary electrons generated from the sample r1 by this scanning are detected by the detector 10. The detection signal of the detector 10 is amplified by an amplifier 1], and then converted into a digital signal by an AD converter 12, and then sent to a computer.

It is supplied to the first frame memory] 3 via the taro and stored therein. Next, the computer 6 applies a shift signal to the deflector 8 via the DA converter 9. As a result, the scanning area on the sample 4 is slightly shifted. At this time, the portion indicated by ``■'' in FIG. 2 is the portion irradiated with the electron beam during scanning, and the secondary electrons generated from the sample 4 during this scanning are detected by the detector 9. The detection signal at this time is sent to the amplifier 11. The signal is supplied to the second frame memory 14 via the AD converter 12 and stored therein.

In this way, the third and fourth electron beam scans of the predetermined range are performed while slightly shifting the scan range, and the signals detected during each scan are the same as those of the third and fourth electron beams. is stored in the frame memory 15, 1.6. After completing these four scans of the predetermined range, the computer 6
The serial converter 17 is commanded to sequentially read the data stored in the four frame memories, and the data is supplied to the display device]8. That is, the computer 6
As shown in the figure, the first scan results in the following data: pig ■ from the first scan, data ■ from the second scan 1.1, data ■ from the third scan, and pig ■ from the fourth scan. ~
The data stored in the fourth frame memory is repeatedly read out one by one from each pixel on the left side. As a result, a high-resolution secondary electron image of 2048 pixels (51.2×4) in the X direction is displayed on the display device 1-8. Furthermore, the computer 6 measures the length of the pattern of the sample 4 based on the pig captured in this way, but since the data in the X direction has a high image resolution, it is difficult to measure the length with extremely high precision. can.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, if a secondary electron is detected,
Reflected electrons may also be detected. In addition, although high image resolution is obtained only in the X direction, if a predetermined range is scanned while shifting the irradiation position of the electron beam in the X direction, the image resolution in the X direction can also be increased. Highly accurate length measurement is possible. Furthermore, the data may be edited by four scans, or the number of scans should be two or more. The present invention can also be applied to Furthermore, the configuration is such that the data is read out in sequence from the four frame memories and sent to the display device, but the data read out in order from the four frame memories is rearranged and stored in a 2048-pixel frame memory. The image may be displayed or the length may be measured based on the data stored in this frame memory.

In addition, a shift deflector was provided separately from the scanning deflector, and a shift signal was supplied to this deflector so that the scanning range was slightly narrowed. If a shift signal is superimposed on the scanning signal, there is no need to provide a shift deflector.

(Effects of the Invention) As explained above, in the present invention, a predetermined range is scanned multiple times while shifting the scan range, and a plurality of signals obtained from the scans are edited to create one type of image. Since it is a signal, a high-speed DA converter capable of television scanning can be used as a DA converter used for digital scanning, which eliminates the need to use an expensive high-precision DA converter. Image resolution can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an electron beam length measuring device which is an embodiment of the present invention, and FIG. 2 is a diagram for explaining the scanning state of an electron beam on a sample. 1... Electron gun 2... Focusing lens 3... Objective lens 4... Sample 5... Deflector 6... Computer 7...
・DA converter 8... Deflector 9... DA converter
]0...Detector]1...Amplifier 1
2...AD converter 13.14, 1.5, 1.6...Frame memory 17...Parallel/serial converter 18...Display device

Claims (2)

[Claims] (1) Scan a predetermined range of the sample multiple times while slightly shifting the scanning range of the charged particle beam on the sample, detect the signal obtained from the sample with each scan, and convert the detected signal corresponding to each scan. A method for acquiring a video signal in a charged particle beam apparatus in which a video signal of a predetermined range of the sample is formed by storing data in a plurality of frame memories and rearranging the data stored in the plurality of frame memories. (2) A focusing lens for narrowly focusing the charged particle beam on the sample, a deflector for scanning the charged particle beam on the sample, and a signal obtained by irradiating the sample with the charged particle beam. A detector for detection, multiple frame memories to which detection signals from the detector are supplied, and a scanning range of the charged particle beam on the sample is slightly shifted so that a predetermined area of the sample is scanned multiple times. A control device that controls the deflector and stores detection signals in different frame memories for each scan, reads data stored in multiple frame memories in order, and supplies the data to a display device. A charged particle beam device having means for.