JPH04341741A - Image processing method and microprobe adopting it - Google Patents

Abstract

PURPOSE:To remove any blur in an image due to the size of a primary beam and the size of an image signal generation range from the image so as to provide a microprobe which can display a high-resolution image. CONSTITUTION:Secondary electrons generated from a sample by scanning of an electron beam 3 are converted into digital-signals so as to be subsequently stored into a memory 10 as image signals. Meanwhile, the size of a primary beam and the size of the image signal generation range are computed in advance as their blur functions on the basis of a device parameter and an image observing condition. A blur is de-convoluted from the image signal by means of a signal processing device 12, so that an image wherefrom the blur is removed may be obtained to be displayed on a display 13. This invension can considerably improve the resolution of an image so as to provide a microprobe by which the image can be analyzed without difficulty.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a microprobe device that displays a scanned image of a sample by scanning beams such as electrons, ions, or The present invention relates to a microprobe device suitable for displaying a high-resolution image from which blur caused by image blurring is removed.

0002

[Prior Art] In recent years, there has been a remarkable trend towards miniaturization of the processing dimensions of semiconductor devices, and measurement technology using charged particle beams requires high resolution, and lens systems have been improved to realize smaller beam systems. It increases the resolution. However, lenses inevitably have aberrations, and improvements in resolution by making the beam system smaller are reaching their limits due to aberrations. Furthermore, particles, X-rays, and light that serve as image signals are often generated in a region that extends from the primary beam, which also contributes to determining the limits of resolution.

[0003] As shown in Japanese Patent Application Laid-Open No. 2-189848, a scanning electron microscope scans a sample with a primary electron beam, detects the electrons generated from the beam with a detector, and synchronizes them with a deflection signal. Images were obtained by displaying.

0004

[Problems to be Solved by the Invention] The above-mentioned prior art does not take into account the reduction in resolution due to blurring due to the size of the primary beam or the size of the image signal generation area, and the image obtained from the original sample is There was a problem that it was not displayed accurately.

An object of the present invention is to provide a microprobe device that displays a high-resolution image by removing blur caused by the size of the primary beam or the size of the image signal generation area from the image.

[0006]

[Means for Solving the Problems] The present invention assumes that the size of the primary beam and the size of the image signal generation area are factors that cause blur. After being detected by the detector, the A/D
Memory and arithmetic processing equipment are used to remove blurring caused by the size of the primary beam and the size of the image signal generation area, determined in advance, from an image composed of signals that have been converted and stored once, by deconvolution. Prepare,
Calculations are performed using Fourier transform and inverse Fourier transform.

[0007]

[Operation] The value obtained by Fourier transforming the size of the primary beam and the size of the image signal generation area, which have been determined in advance as a function of blur, is substituted as the value of the denominator shown in Equation 1. Furthermore, the analog signal from the sample is detected by a detector, and the
After D-transforming, substitute the Fourier-transformed value as the numerator,
An unblurred image can be obtained by inverse Fourier transformation.

[0008]

[Math 1]

However, here, Ψ represents a function with respect to the position of the signal from the sample after A/D conversion, and I represents the blur function determined from the size of the primary beam and the size of the image signal generation area. indicates the unblurred image after deconvolution, and F indicates the Fourier operator.

The meaning of Equation 1 will be explained below.

[0011] In the first place, an image is based on the information possessed by the original sample.
This includes blur due to the size of the secondary beam and the size of the image signal generation area. Expressing this image information as a function, formula 2
The blur function is shown by adding the information of the original sample in the form of a convolution (convolution integral). According to Parseval's theorem, this convolution integral can be expressed as a product of Fourier transforms of each term (Equation 3). Therefore, if the blur function and the image information function are known, the original sample information can be obtained by deconvolution shown in Equation 1.

0012

[Math 2]

[0013]

[Math 3]

The feature of the present invention is to assume that the size of the primary beam or the size of the image signal generation area is the cause of blur, and to remove this from the image using deconvolution to obtain a blur-free image. There is a particular thing.

[0015]

EXAMPLES The present invention will be explained in detail below using examples.

FIG. 1 is a block diagram illustrating the present invention using a scanning electron microscope as an example. An electron beam 3 irradiated from an electron gun 2 is narrowly focused by an electron lens system 4 and scanned two-dimensionally over a sample 7 by a deflector 5. Image signals such as secondary electrons and reflected electrons generated from the sample are detected by a detector 8. The image signal is converted into a digital signal by an A/D converter 9 and then stored in a memory 10.

On the other hand, device parameters (spherical aberration coefficient, chromatic aberration coefficient, etc.) and image observation conditions (aperture size, accelerating voltage, etc.) are input from the operation unit 11, and the signal processing device 12 inputs the size of the primary beam and the image signal. The size of the occurrence area is determined in advance as a function of blur and stored in the memory 10.

The image signal and blur function stored in the memory 10 are appropriately called, and the signal processing device 12 performs Fourier transform of the image signal, Fourier transform of the blur function, and after division, inverse Fourier transform is performed to remove the blur. Display 13 for the removed image, that is, the deconvoluted image.
to be displayed. The above is the principle and overall configuration of the present invention. FIGS. 2(a) and 2(b) are examples of deconvolution according to the embodiment. Figure (a) shows a normal SEM (Scanning E) displaying the image signal from the detector 8 as it is.
Electron Microscope) image in the same figure (
b) is an image obtained by removing the size of the primary electron beam calculated in advance by deconvolution.

The resolution is clearly improved in Figure (b), and particles that are not visible in Figure (a) can be confirmed.

An example in which a blur function is experimentally determined 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 knife-edge-like sharp interface is
is one-dimensionally scanned with an electron beam under the same conditions as for sample observation, a signal is detected by a detector 8, and stored in a memory 10 after A/D conversion. The one-dimensional scanning signal of the standard sample is called into the signal processing device 10, and the blur function is experimentally determined from its shape and stored in the memory 8. According to this, it is possible to incorporate into the blur function even blur factors whose vibrational function type is not clear.

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

Furthermore, the effects of the present invention can also be obtained as an independent image processing device 16. In other words, even for images observed with a normal device, image signals captured by an image capturing device (for example, image signals captured from a television camera and digitized, detected, A/D converted, and written to a floppy disk, etc.) (image signals, etc.) are supplied to the signal processing device 12, and on the other hand, device parameters and image observation conditions are inputted from the operation unit 11, a blur function is obtained, and an image with the blur removed by deconvolution is obtained. can.

[0024]

As described above, since the present invention significantly improves the resolution of images, it is possible to provide a microprobe device with easy image interpretation.

[Brief explanation of the drawing]

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

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

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

[Explanation of symbols]

Claims (3)

[Claims] Claim 1: In a microprobe device that displays a scanned image of a sample surface by beam scanning of electrons, ions, or X-rays, the size of the primary beam and particles and
1. A microprobe device comprising means for determining the size of a line or light generation area experimentally or by calculation. 2. The microprobe device according to claim 1, further comprising means for removing from the image blur caused by the size of the primary beam and the size of the image signal generation area, and means for displaying the image from which the blur has been removed. A microprobe device characterized by: 3. Substitute the Fourier-transformed value of the size of the primary beam and the size of the image signal generation area obtained in advance as the denominator value shown in Equation 1, and further convert the analog signal from the sample to the detector. A method to obtain a blur-free image by performing A/D conversion, substituting the Fourier-transformed value as the numerator, and performing inverse Fourier transform.