JP3112503B2 - Screen processing method using charged beam and charged beam microscope apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microprobe apparatus for displaying a scanned image of a sample by scanning a beam of electrons, ions or X-rays, and more particularly to a size of a primary beam and a size of an image signal generating area. TECHNICAL FIELD The present invention relates to a microprobe apparatus suitable for displaying a high-resolution image in which blurring due to an image is removed from an image.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable tendency to miniaturize the processing dimensions of semiconductor devices, and measurement technology using charged particle beams requires a high resolution. A smaller beam system has been realized by improving the lens system. The resolution has been raised. However, aberrations are inevitable in lenses, and the improvement in resolution by reducing the size of the beam system is reaching its limit due to aberrations. Further, particles, X-rays, and light serving as image signals are often generated in a region spread from the primary beam, which also contributes to the limitation of resolution.

As disclosed in Japanese Patent Application Laid-Open No. 2-189848, a scanning electron microscope scans a sample with a primary electron beam, detects electrons generated therefrom by a detector, and synchronizes the electrons with a deflection signal. The image was obtained by displaying.

[0004]

In the above prior art, no consideration is given to a reduction in resolution due to blurring due to the size of the primary beam or the size of the image signal generation area, and an image obtained from the original sample cannot be obtained. There was a problem that it was not displayed correctly.

It is an object of the present invention to provide a microprobe apparatus which removes blurs from an image due to the size of a primary beam and the size of an image signal generation region and displays a high-resolution image.

[0006]

In the present invention, the size of the primary beam and the size of the image signal generation area are assumed as factors of the blur. After being detected by the detector, A / D
A memory and an arithmetic processing unit for removing, by deconvolution, blurs due to the size of the primary beam and the size of the image signal generation region, which have been obtained in advance, from the image composed of the signal once stored after the conversion. Calculate by Fourier transform and inverse Fourier transform.

[0007]

A Fourier-transformed value of the size of the primary beam or the size of the image signal generation region, which is obtained in advance as a function of blur, is substituted as the value of the denominator represented by Formula 1.
Further, an analog signal from the sample is detected by a detector, and A / A
After the D conversion, the Fourier transformed value is substituted as a numerator,
An image without blur can be obtained by performing an inverse Fourier transform.

[0008]

(Equation 1)

Here, Ψ represents a function with respect to the position of the signal from the sample after A / D conversion, I represents a function of blur obtained from the size of the primary beam and the size of the image signal generation area, and Ψ represents ₀ indicates a blur-free image after deconvolution, and F indicates a Fourier operator.

The meaning of Equation 1 will be described below.

[0011] In the first place, the image is composed of the information of the original sample and 1
It includes blur due to the size of the next beam and the size of the image signal generation area. When this image information is represented by a function, Equation 2
The blur function is shown by adding the information of the original sample in the form of convolution (convolution integration). According to Parseval's theorem, this convolution integral can be expressed in the form of a product of Fourier transform of each term (Equation 3).
Therefore, if the blurring function and the image information function are known, the original information of the sample can be obtained by deconvolution represented by Expression 1.

[0012]

(Equation 2)

[0013]

(Equation 3)

A feature of the present invention is that it is assumed that the size of the primary beam or the size of the image signal generation area is the cause of the blur, and the blur is removed from the image by deconvolution to obtain a blur-free image. It is in.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments.

FIG. 1 is a structural block diagram showing the present invention by taking a scanning electron microscope as an example. In the lens barrel 1,
The electron beam 3 emitted from the electron gun 2 is narrowly focused by an electron lens system 4 and is two-dimensionally scanned on a sample 7 by a deflector 5. Image signals such as secondary electrons and reflected electrons generated from the sample 7 are detected by the detector 8. The detected image signal is converted into a digital signal by the A / D converter 9, image
It is stored in the memory 10 in the image processing device 16 . In addition, electricity
The sub lens system 4 and the deflector 5 are controlled by the control unit 6.
It is.

On the other hand, device parameters (spherical aberration coefficient, chromatic aberration coefficient, etc.) and image observation conditions (aperture size, acceleration voltage, etc.) are input from the control unit 11, and the size of the primary beam and the image signal The size of the generation area is obtained in advance as a blur function and stored in the memory 10.

The image signal and the blur function stored in the memory 10 are appropriately called, a Fourier transform of the image signal and a Fourier transform of the blur function are performed by the signal processing device 12, and an inverse Fourier transform is performed after the division to obtain the blur. The display 13 is searched for a removed image, that is, a deconvolution image.
To be displayed. The above is the principle and overall configuration of the present invention. FIGS. 2A and 2B are examples of deconvolution according to the embodiment. FIG. 3A shows a normal SEM (Scanning Electron Mic) displaying the image signal from the detector 8 as it is.
FIG. 4B is an image obtained by removing the size of the primary electron beam obtained by calculation in advance by deconvolution.

The resolution is clearly improved in FIG. 4B, and particles that cannot be seen in FIG. 4A are confirmed.

An embodiment in which a blur function is experimentally obtained will be described with reference to FIG.

Before or after observing the sample 7 on the sample stage 14, a standard sample 15 having a sharp knife-edge interface
Is one-dimensionally scanned with an electron beam under the same conditions as the sample observation, a signal is detected by the detector 8, and the signal is stored in the memory 10 after A / D conversion. The one-dimensional scanning signal of the standard sample is called to the signal processing device 12 , a blur function is experimentally obtained from the shape thereof , and stored in the memory 10 . According to this, it is possible to incorporate into the blurring function a blurring factor whose vibrational function type is not clear.

As described above, the scanning electron microscope has been described as an embodiment. However, the primary beam and the image signal are not limited to electrons, but electrons and ions generated from a sample by beam scanning of general electrons, ions or X-rays. Or a microprobe device (SIMS, A
Needless to say, it can be applied to ES, EPMA, etc.).

Further, the effect of the present invention can be obtained as an independent image processing device 16. That is, an image observed by a normal device is also converted into an image signal captured by an image capturing device (for example, an image signal captured and digitized by a television camera, or A / D converted after detection, and written to a floppy or the like). Supplied to the signal processing device 12, while inputting device parameters and image observation conditions from the control unit 11, obtaining a blur function, and obtaining an image from which the blur has been removed by deconvolution. it can.

[0024]

As described above, since the resolution of an image is remarkably improved by the present invention, it is possible to provide a microprobe apparatus which can easily interpret an image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 shows an example of deconvolution according to the present invention.

FIG. 3 is another configuration diagram of the sample stage of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... barrel part, 2 ... electron gun, 3 ... electron beam, 4 ... electron lens system, 5 ... deflector, 6 ... control part, 7 ... sample, 8 ... detector, 9 ... A / D converter, 10 ... memory, 11 ... control unit,
12 signal processing device, 13 display, 14 sample stage, 15 standard sample, 16 image processing device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 37/22 G01N 23/04 H01J 37/256

Claims (3)

(57) [Claims] A step of detecting an analog image signal from the surface of the sample by scanning a charged primary beam; a step of obtaining a digital image signal obtained by A / D converting the detected signal; A first operation step of obtaining a function Ψ (X) for a pixel position X of an image signal, a step of performing a Fourier transform of the function Ψ (X), and a blur based on a value obtained by previously calculating a size of a primary beam. A second operation step of obtaining a function, a step of performing a Fourier transform on the function I (X) obtained in the second operation step, and an F value obtained by the Fourier transform.
A step of performing an inverse Fourier transform of a value F {Ψ (X)} / F {I (X)} divided by {I (X)}, and displaying a scan image of the sample surface by the inverse Fourier transformed function The features and image processing method using charged beam. 2. The image processing method using a charged beam according to claim 1, wherein the calculation is performed by a blur function taking into account spherical aberration, chromatic aberration, or acceleration voltage as the second calculation step. 3. A detector for detecting an analog image signal from the sample surface by scanning a charged primary beam, and means for obtaining a digital image signal obtained by A / D converting a signal detected by the detector. First calculating means for calculating a function Ψ (X) for a pixel position X of the image signal;
Means for performing a Fourier transform on (X), second calculating means for obtaining a blur function based on a value obtained in advance by calculating the size of the primary beam, and function I obtained by the second calculating means.
Means for performing a Fourier transform on (X), and performing an inverse Fourier transform on a value F {) (X)} / F {I (X)} obtained by dividing by F {I (X)} obtained by the Fourier transform; A charged beam microscope apparatus comprising a display for displaying a scanned image of the sample surface by a Fourier-transformed function.