JP2001133695A - Microscope device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate flares for improving the image quality of images in a microscope device which uses laser light of deep ultraviolet range as a light source. SOLUTION: This microscope device is provided with a laser light source 10, which emits light in the deep-ultraviolet range, a microscope main body 20 which outputs an electric signal corresponding to the image of a sample 24 which is generated by irradiation of light, and an image processor 31 which forms the image of the sample 24 on the basis of the electrical signal and outputs the image signal to a monitor 32. The image processor 31 subtracts the luminance value of a background image, which has been obtained without placing the sample 24, from the luminance value of the image of the sample 24 before outputting the image signal to the monitor 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope provided with a light source for emitting light in the deep ultraviolet region.

[0002]

2. Description of the Related Art When a microstructured sample is observed with a microscope, the critical resolution of the microscope can be expressed by the following equation: δ = λ / 2NA (1)

Here, δ is the resolving power, λ is the wavelength used,
NA indicates the numerical aperture of the objective lens.

From equation (1), to increase the resolution, the wavelength λ
, The numerical aperture NA of the objective lens is increased, or the wavelength λ is shortened, and the numerical aperture N of the objective lens is reduced.
It is understood that A should be increased.

When observing a biological sample, if the biological sample receives light having a wavelength of less than the ultraviolet region, the sample itself will be damaged by a photochemical reaction or the like. Therefore, an immersion type objective lens having a large numerical aperture NA must be used. To increase the resolution.

On the other hand, when an inorganic sample (for example, a fine structure such as an IC) is observed using an immersion type objective lens, impurities may adhere to the surface of the IC or the like and become unusable. Therefore, the resolving power is increased by irradiating light below the ultraviolet region. The inorganic sample itself is rarely damaged by irradiation with light in the ultraviolet region or below.

In recent years, the scale of a fine structure such as an IC has been steadily shrinking, and the scale of a fine periodic structure (referred to as line space in a semiconductor process) has a period of less than 0.25 μm. I have.

When the period becomes 0.25 μm or less, it is theoretically difficult to obtain a high resolution with a conventional optical microscope. As a microscope having a high resolution, there is a microscope using an X-ray or an electron beam. However, the microscope is used for observing a sample surface in a vacuum, and thus is less convenient to use than an optical microscope. Therefore, there is a demand for an improvement in the resolving power of a convenient optical microscope.

On the other hand, a deep-ultraviolet ((wavelength: 200 to 300 nm)) continuous wave laser which has recently been put into practical use, for example, the fourth harmonic (wavelength: 266n) of a Nd: YAG laser
m) is continuously oscillated using _a BBO (BaB ₂ O ₄ : barium borate) crystal as a light source, and an objective lens having a high numerical aperture of about 0.9 is used to obtain 0.10 μm. Can be obtained.

[0010]

In the case of a Koehler illumination microscope, flare (reflected light from the lens surface, lens barrel, etc.) is superimposed on the image, deteriorating the image quality. is important.

In a conventional microscope apparatus, the inner surface of a metal member or a lens barrel holding an optical member is blackened with a paint or a coating to remove flare.

However, in the deep ultraviolet region, there is no paint or film which can effectively prevent flare due to low reflectance and chemical instability, so that there is a problem that deterioration of image quality cannot be prevented.

That is, few paints and coatings have been verified to have a sufficiently low reflectance in the deep ultraviolet region, and when irradiated with light in the deep ultraviolet region, the paint evaporates to cause micro-contamination. Therefore, the conventional microscope apparatus cannot be used for inspection of a fine processing process such as a semiconductor manufacturing process.

The present invention has been made in view of such circumstances, and an object thereof is to improve the image quality of an image by removing flares in a microscope apparatus using laser light in the deep ultraviolet region as a light source. .

[0015]

According to a first aspect of the present invention, there is provided a light source for emitting light in a deep ultraviolet region, and an electric signal corresponding to a sample image generated by the light irradiation. A microscope apparatus comprising: a microscope main body to output; and an image processing unit configured to image the sample based on the electric signal and output the image signal to an image display unit.
The image processing means may subtract a luminance value of a background image obtained without placing the sample from a luminance value of the sample image before outputting the image signal to the image display means.

Before outputting the image signal to the image display means,
Measure the brightness value of the background image without placing the sample,
This measured value is subtracted from the luminance value of the sample image to be observed.

According to a second aspect of the present invention, in the microscope apparatus according to the first aspect, the luminance value of the background image is an average value of all pixels.

Since the luminance value of the background image is the average value of all pixels, the calculation of the luminance value of the background image is simplified.

According to a third aspect of the present invention, in the microscope apparatus according to the first aspect, the subtraction is performed for each pixel.

Since the subtraction is performed for each pixel, the luminance value of the background image can be more accurately removed according to the distribution of the luminance value of the actual background image.

According to a fourth aspect of the present invention, in the microscope apparatus according to any one of the first to third aspects, the image processing means includes a storage means for storing a luminance value of the background image acquired in advance. It is characterized by.

Since the image processing means includes a storage means for storing the luminance value of the background image acquired in advance, it is possible to subtract each pixel from the observation target image from the background image stored in the storage means.

According to a fifth aspect of the present invention, in the microscope apparatus according to the fourth aspect, the luminance value of the background image is a value corrected based on the output of the light source.

Since the luminance value of the background image is a value corrected based on the output of the light source, for example, the luminance value of the background image can be a value proportional to the output of the light source.

According to a sixth aspect of the present invention, in the microscope apparatus of the fourth aspect, the storage means stores a map relating to a luminance value of a background image with respect to an output of the light source. .

Since the storage means stores a map relating to the luminance value of the background image with respect to the output of the light source, the luminance value of the background image can be more strictly corrected based on the output of the light source.

According to a seventh aspect of the present invention, in the microscope apparatus according to any one of the first to sixth aspects, the light source is a laser light source that emits a laser beam.

Since the light source emits a laser beam, the light source has a good light-collecting property and can be focused on a minute spot.

The invention according to claim 8 is a light source for emitting light in the deep ultraviolet region, a microscope main body for outputting an electric signal corresponding to an image of a sample generated by the irradiation of the light, and a microscope based on the electric signal. Image processing means for imaging the sample and outputting an image signal to image display means, wherein the image processing means calculates an average value of the lowest luminance values of the sample images obtained on all the horizontal scanning lines. It is characterized in that it is subtracted from the luminance value of the sample image.

The lowest luminance value of the sample image is averaged over all the horizontal scanning lines, and this average value is subtracted from the luminance value of the sample image to be observed.

[0031]

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

FIG. 1 is a block diagram of a microscope apparatus according to the first embodiment of the present invention.

A Koehler illumination type microscope system (microscope device) 1 includes a laser light source (light source) 10 for emitting a laser beam.
, A microscope main body 20, and an optical image system 30.

The laser light source 10 has a deep ultraviolet region (200 to 30).
0 nm).

The microscope body 20 includes a beam expander 22 that expands the laser light into a light beam 22 a having a size that satisfies the pupil plane of the objective lens 21, a condenser lens 23, and a laser beam that does not transmit the laser light but is reflected by the sample 24. Beam splitter 25 for transmitting reflected light 24a, and second objective lens 26
And a CCD camera 27 that detects light formed by the second objective lens 26 and converts the light into an electric signal.

Beam expander 22, condenser lens 2
3. The beam splitter 25, the objective lens 21, and the second objective lens 26 are held by metal hardware inside a cylinder 28 surrounding the optical path. No paint or coating is applied to the inner surface of the tube 28 or metal parts to prevent flare.

The optical image system 30 includes an image processing device (image processing means) 31, a monitor (image display means) 32, and the like, and aims to image the sample 24 based on an electric signal from the photodetector 27.

The microscope main body 20 is mounted on a vibration isolation table 40 in order to guarantee high image quality.

The laser light source 10 and the microscope main body 20 are connected to an optical fiber (or optical fiber bundle) 15 made of quartz or the like.
Are optically connected by

The operation of the Koehler illumination type microscope system having the above configuration will be described.

The laser light emitted from the laser light source 10 passes through the optical fiber 15 and the beam expander 22, is reflected by the beam splitter 25, and is uniformly illuminated (Koehler illumination) on the sample 24 by the objective lens 21. .

The reflected light 24a reflected by the sample 24 goes back to the objective lens 21, the beam splitter 25, and the second objective lens 26.

The reflected light 24a is condensed by the second objective lens 26, converted into an electric signal by the photodetector 27, and displayed as an image by the optical image system 30.

By the way, in the ultraviolet region having a wavelength shorter than 400 nm, the image cannot be directly visually observed, so that the flare is electrically removed.

That is, before imaging the sample 24 to be observed, the luminance value of the background image is measured without placing the sample 24. The luminance values of the background image are averaged over all pixels (the obtained value is referred to as an average luminance value). The average luminance value is subtracted from the luminance value of the image of the sample 24 to be observed.

Therefore, flare as an offset component superimposed on the image of the sample 24 to be observed is removed.

Here, since the average luminance value of the background image depends on the output of the light source, it is necessary to perform correction by multiplying the output of the laser light source 10 by a correction coefficient. For example, the correction coefficient is determined assuming that the average luminance value of the background image is proportional to the output of the laser light source 10.

To perform the correction more strictly, not only the average luminance value of the background image with respect to one output of the laser light source 10 but also the average luminance value with respect to a plurality of laser light source outputs is determined to prepare a calibration curve. To determine the correction coefficient.

Hereinafter, a specific description will be given with reference to FIG.

FIG. 2 is a diagram showing an image signal of the image processing apparatus.

Assuming that the luminance value of each pixel of the background image when the sample 24 is not placed is Ixy, the average luminance value If averaged over all the pixels is calculated from Equation 1.

[0052]

(Equation 1) Here, ΣIxy (x = 1, 2,..., M) (y = 1, 2,... N) indicates the total luminance, and (m × n) indicates the total number of pixels.

When the sample 24 to be observed is imaged, the luminance value Iu'v 'of each pixel after the flare has been removed is calculated from equation (2).

[0054]

(Equation 2) Here, Iuv (u = 1, 2,..., M) (v = 1, 2,..., N)
(U indicates the number of horizontal pixels, and v indicates the number of vertical pixels.)
Is the luminance value of each pixel of the image to be observed, I is the output of the light source used to image the image to be observed, I
o indicates the output of the light source used for imaging without the sample, respectively.

As shown in FIG. 3, a map (calibration curve) relating to the average luminance value of the background image for a plurality of laser light source outputs is created.

FIG. 3 is a diagram showing an example of the map.

In FIG. 3, the vertical axis represents the average luminance value, and the horizontal axis represents the output of the laser light source.

In FIG. 3, each dot is an average luminance value calculated by the formula 1 with respect to the output of one laser light source.

This map is stored and stored in a memory (storage means) 31a in the image processing apparatus 31.

According to this embodiment, since the flare as the superposed offset component is removed, the deterioration of the image quality of the microscope apparatus using light in the deep ultraviolet region as a light source is prevented, and the image quality is improved. Can be.

Further, since the average luminance value is used, the calculation is simplified and the expensive image processing apparatus 3 having a high processing speed is used.
Does not require one.

Further, when the map is stored and stored,
The average luminance value can be more strictly corrected based on the output of the laser light source, and higher image quality can be achieved.

Since the inner surface of the cylinder 28 and the metal are not coated with a paint or a film for preventing flare, there is no possibility of micro-contamination due to evaporation of the paint.

As a second embodiment, the memory 31a
The background image may be stored in the memory and subtracted from the luminance value of the image to be observed for each pixel.

That is, an image is displayed on the monitor 32 while calculating Iuv-Ixy for each pixel. The luminance value Iu'v 'of each pixel after the removal of the flare is calculated using Expression 3.

[0066]

(Equation 3)

According to this embodiment, the flare as the superimposed offset component is precisely removed based on the actual flare distribution, so that higher image quality can be achieved as compared with the microscope apparatus of the first embodiment.

In this embodiment, the image processing apparatus 31 capable of high-speed processing by, for example, pipeline processing, etc.
Is required.

FIG. 4 is a view for explaining flare removal in the microscope apparatus according to the third embodiment of the present invention.
(A) is a diagram showing a luminance profile in one line,
FIG. 4B is a diagram illustrating an image signal of the image processing apparatus.

This embodiment focuses on the point that a minimum luminance value always exists in a luminance profile obtained when imaging a sample to be observed (see FIG. 4A). The value 301 (Iy) is applied to all the horizontal scanning lines 302.
And the average value is subtracted from the luminance value of the sample image of the observation target.

The luminance value Iu'v 'of each pixel after the removal of the flare is calculated by using equation (4).

[0072]

(Equation 4)

According to this embodiment, the same effects as in the first embodiment can be obtained.

In each of the above embodiments, the laser light source 10
However, as a light source, a mercury lamp that emits light in the deep ultraviolet region may be used.

Further, the case where the present invention is applied to a Koehler illumination microscope has been described, but the invention can also be applied to a confocal laser scanning microscope. In particular, the effect is remarkable when applied to a laser scanning fluorescence microscope using weak light.

[0076]

As described above, according to the microscope apparatus of the first aspect of the present invention, it is possible to remove flare as a superposed offset component, and to use light in the deep ultraviolet region as a light source. Of the image is prevented from deteriorating, and the image quality can be improved.

According to the microscope apparatus of the second aspect of the present invention, an expensive image processing means having a high processing speed is not required, and the microscope system can be constructed at a low cost.

According to the microscope apparatus of the third aspect of the present invention, it is possible to achieve higher image quality.

According to the microscope apparatus of the fourth aspect, it is possible to subtract from the observation target image for each pixel from the background image stored in the storage means.

According to the microscope apparatus of the fifth aspect, the luminance value of the background image can be corrected.

According to the microscope apparatus of the present invention, it is possible to more strictly correct the luminance value of the background image based on the output of the light source.

According to the microscope apparatus of the present invention, it is possible to provide an optimal light source for observation.

According to the microscope apparatus of the present invention, it is possible to remove flare as a superposed offset component, to prevent deterioration of the image quality of the microscope apparatus using light in the deep ultraviolet region as a light source, Image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a microscope apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an image signal of the image processing apparatus.

FIG. 3 is a diagram illustrating an example of a map;

FIG. 4 is a view for explaining flare removal in a microscope apparatus according to a third embodiment of the present invention, and FIG.
FIG. 4 shows a luminance profile in one line, and FIG.
FIG. 2B is a diagram illustrating an image signal of the image processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Koehler illumination type microscope system (microscope apparatus) 10 Laser light source (light source) 20 Microscope main body 24 Sample 31 Image processing apparatus (Image processing means) 31a Memory (Storage means) 32 Monitor (Image display means)

Claims (8)

[Claims] 1. A light source that emits light in a deep ultraviolet region, a microscope main body that outputs an electric signal corresponding to a sample image generated by the irradiation of the light, and an image of the sample based on the electric signal. And an image processing unit that outputs the image signal to an image display unit.The image processing unit outputs the sample from the brightness value of the sample image before outputting the image signal to the image display unit. A microscope apparatus for subtracting a luminance value of a background image obtained without being placed. 2. The microscope apparatus according to claim 1, wherein the luminance value of the background image is an average value of all pixels. 3. The microscope apparatus according to claim 1, wherein the subtraction is performed for each pixel. 4. The microscope apparatus according to claim 1, wherein the image processing unit includes a storage unit that stores a luminance value of the background image acquired in advance. 5. The microscope apparatus according to claim 4, wherein the luminance value of the background image is a value corrected based on an output of the light source. 6. The microscope apparatus according to claim 4, wherein the storage unit stores a map relating to a luminance value of a background image with respect to an output of the light source. 7. The microscope device according to claim 1, wherein the light source is a laser light source that emits a laser beam. 8. A light source that emits light in a deep ultraviolet region, a microscope main body that outputs an electric signal according to an image of the sample generated by the irradiation of the light, and imaging of the sample based on the electric signal. An image processing means for outputting an image signal to an image display means, wherein the image processing means subtracts an average value of the lowest luminance values of the sample images obtained by all the horizontal scanning lines from the luminance values of the sample images. A microscope device characterized by calculating