JP2000188075A - Inspection method and inspection device for circuit pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently set inspection conditions and enhance reliability by irradiating large and small electron beams from large and small current mirror bodies having an electron gun, a lens system, and a deflecting system to a sample on a stage within a vacuum chamber, detecting and converting secondary charged particles produced, inspecting defects, and individually inspecting again defects with the large and small current mirror bodies. SOLUTION: Coarse alignment is conducted with an optical microscope, conditions of electron optics system are set, fine alignment of an image with electron beams are conducted, trial inspection is conducted, and image processing conditions are set. The whole surface of a wafer is inspected at high speed with an inspecting electron optics system 101, and defective places are displayed on a control screen. A defective coordinate part is moved to a visual field of a reviewing electron optics system 200 with low accelerating voltage and small chromatic aberration, and the truth or not of the defect is discriminated. In both inspections, threshold values of an image processing parameter are lowered, and inspection is repeated. Since image quality on a review screen is good, judgment of good or not of image processing parameter selection is correct, and the number of trial and errors is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique for inspecting a pattern on a wafer in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art As an inspection method for detecting a defect of a circuit pattern formed on a wafer in a semiconductor device manufacturing process,
2. Description of the Related Art An apparatus has been put to practical use that acquires images of the same kind of patterns of two or more LSIs on one wafer by light, compares them, and inspects them.

[0003] In particular, an apparatus for comparing and inspecting patterns using an electron beam is disclosed in Japanese Patent Application Laid-Open No. 59-192943, Journal
Of Vacuum Science and Technology (J.Vac. Sci. Tech.) B, Vol. 9, No. 6, pp. 3005-
3009 (1991), J. Vac. Sci. Tech. B, Vol. 10, No. 6,
Pp. 2511-2515 (1992), SPI (SPI)
E) Vol.2439 and JP-A-5-258703. In order to obtain a practical throughput with such an apparatus, it is necessary to acquire images at a very high speed. Then, in order to secure the SN of the image acquired at high speed, it is 100 times or more (10n) that of a normal scanning electron microscope.
A or more), the SN of the image is secured while maintaining a practical inspection speed. At this time, the beam diameter is considerably wider than that of a normal scanning electron microscope, and is about 0.05 μm to 0.2 μm. This is a value limited by the brightness of the electron gun and the Coulomb effect due to the large beam current.

An image signal obtained by such an electron optical system is sent to an appropriate image processing system, and a comparison inspection is performed between adjacent image of the same pattern portion. If there is a different brightness portion when comparing the images, the portion is regarded as a defect and the coordinates are stored. With such a configuration, it is possible to detect a defect having a size of about 0.05 to 0.1 μm.

[0005]

When an inspection is started by using the above-mentioned conventional apparatus, it is necessary to set various necessary parameters in advance. First, the setting parameters of the electron optical system include the irradiation energy of the electron beam, the gain of the secondary electron signal detection system for forming an image, the pixel size, the beam current, and the like. On the other hand, when the image processing apparatus compares two adjacent images of the same pattern, there is a threshold for determining whether or not the image is defective. When this threshold value is set low, the defect detection sensitivity is improved, but the possibility that non-defect portions are regarded as defects is increased. On the other hand, when the threshold value is increased, the detection sensitivity decreases.

The optimum values of the above parameters vary depending on the process to be inspected, the pattern size, and the type of defect to be detected. Therefore, it is necessary to perform a trial inspection before the inspection, display an image of the detected defect coordinates, and set the above parameters to an optimum value while confirming whether a defect to be detected is detected.

[0007] Further, after the completion of the main inspection, it is necessary to obtain an image of a defect coordinate portion and to confirm what kind of defect has been detected by an operator. That is, in order to detect the presence of a defect, an image is acquired at high speed, and not only the defect is detected by image processing, but also a specific narrow visual field is imaged and visually observed in the same manner as a normal scanning electron microscope. The function of observing and confirming with is also essential. This is called a review below.

At the time of review, it is not necessary to form an image at a particularly high speed. On the other hand, since it is necessary to recognize not only the presence or absence of a defect but also the shape and type of the defect to some extent, it is necessary to be able to acquire a high-resolution image.

However, in the conventional apparatus, the electron optical system is designed optimally for acquiring an image by high-speed scanning with a large current, and sufficient resolution cannot be obtained simply by changing the conditions of the electron optical system. Was. Therefore, the accuracy for determining whether the detected defect is a true defect or an erroneous detection caused by improper parameter setting is low. For this reason, the inspection is often performed without setting the setting parameter to an optimum value.

An object of the present invention is to provide a method and an apparatus for inspecting defects, foreign matter, residues and the like by an electron beam by comparing image information between the same design patterns such as circuit patterns on a wafer in the process of manufacturing a semiconductor device. Another object of the present invention is to provide a method and an apparatus that can efficiently set inspection conditions, shorten inspection time, and improve inspection reliability.

[0011]

In the present invention, two columns, an electron optical system for high-current high-speed image formation for inspection and an electron optical system for small current and high resolution for review, are provided on the same sample chamber. The above-mentioned problem was solved by operating each independently.

That is, the method and apparatus of the present invention provide a large current mirror capable of irradiating a sample with a large current electron beam on one vacuum vessel, and an electron having a small current and a smaller diameter than the large current mirror. There is a small current mirror that can irradiate a beam, and all the mirrors have an electron gun that generates an electron beam, a lens system for narrowing down the electron beam, and a mechanism for scanning the sample to be inspected with the electron beam. It is equipped with a deflector and simultaneously scans the sample with the electron beam while continuously moving the stage on which the sample is placed in the vacuum vessel, detects generated secondary charged particles, and outputs the detection signal to the image of the sample. And converting the position of the defect coordinates detected by the inspection to a position immediately below the small current mirror, and checking the defect. Large current above Change the test conditions by the body again which comprises carrying out the inspection.

In the above structure, the electron beam of the small current mirror has a lower acceleration voltage than the electron beam of the large current mirror.

In the above arrangement, a negative potential for decelerating to a desired energy is applied to the sample and the stage immediately before the electron beam irradiation to observe the image of the sample with the small current mirror. The method is characterized in that a negative potential smaller than that for the inspection with the large current mirror is applied.

In the above arrangement, the small current mirror is provided with an X-ray detector, and the material at the irradiation position is analyzed from the energy of the X-ray emitted by electron beam irradiation.

In the above structure, the small current mirror includes an energy filter, and detects a potential at an electron beam irradiation position by filtering energy of secondary electrons emitted by electron beam irradiation. And

[0017]

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
FIG. 2 shows the operation of the above apparatus and the flow of scanning.

The inspection apparatus is roughly divided into an inspection electronic optical system 10.
1, a review electron optical system 200, a sample chamber 102, a control unit 104, and an image processing unit 105. The inspection electron optical system 101 includes an electron gun 1, an electron beam extraction electrode 2, an insulator 3, a condenser lens 4, a blanking deflector 17, a scanning deflector 8, a diaphragm 5, and an objective lens 7. The secondary electron detector 9 is located below the objective lens 7, and the output signal of the secondary electron detector 9 is amplified by the preamplifier 12, converted into digital data by the AD converter 30, and sent to the image processing unit 105. .

The review electron optical system includes an electron gun 201, an electron beam extraction electrode 202, a condenser lens 204, a scanning deflector 208, an aperture 205, and an objective lens 207. A secondary electron detector 209 is located above the objective lens 207, and an output signal of the secondary electron detector 209 is amplified by a preamplifier 212 and sent to a low-speed image display circuit 218 via an AD converter 230.

The sample chamber 102 includes a stage 24 and an optical sample height measuring device 29.

The image processing unit 105 includes image storage units 18 and 19, a calculation unit 20, and a defect determination unit 21. The captured electron beam image and optical image are displayed on the monitor 22.

An operation command and an operation condition of each part of the inspection apparatus are input and output from the control unit 104. The conditions such as acceleration voltage, electron beam deflection width, deflection speed, sample stage moving speed, detector signal capture timing, and the like when an electron beam is generated are input to the control unit 104 in advance. Also, the optical sample height measuring device 29
And a correction signal is sent to the objective lens power supply 26 and the scanning signal generator 13 so that the electron beam 6 is always irradiated to the correct position.

FIG. 2 is a diagram showing a scanning and operation flow of the semiconductor pattern appearance inspection apparatus using an electron beam. The method for inspecting the pattern appearance of a semiconductor wafer according to the present invention will be described with reference to FIG.

First, after loading a wafer, rough alignment is performed by an optical microscope. This is because the scanning range is narrow in an electron beam scanning image, and there is a possibility that the alignment mark does not fall within the scanning range of the electron beam only by mechanical positioning during loading. Therefore, alignment is performed with an accuracy of approximately several tens of μm using a low-magnification optical microscope having a wide field of view.

Next, conditions for the electron optical system are set. The irradiation energy of the electron beam, the pixel size, the beam current, etc. are set according to the type of the pattern of the wafer to be inspected. The optimum electron beam irradiation energy varies depending on the material of the pattern. Normally, it is preferable to set the energy to a higher value of several keV or more so as to obtain a high resolution in a conductive material, and to set the energy to 1.5 keV or less in a pattern including an insulator to prevent charging.

Next, a pixel size corresponding to the defect size of particular interest is set. Insignificantly reducing the pixel size increases the time required for inspection. Next, the beam current is set. Although the default value is unique to the apparatus, it is preferable to set the current to a smaller value especially for a wafer which is easily charged. In addition, if it is known in advance that the defect to be detected has a high contrast, the current can be made smaller so that the electron beam can be narrowed down, and high-resolution inspection can be performed.

Next, an image of the wafer to be inspected by the electron beam is displayed, and focus and astigmatism are corrected. This can be automated by capturing an image and using a computer or a dedicated image processing device.

After the above setting is completed, next, the image is finely aligned by the electron beam. As a result, the coordinate system of the stage and the coordinate system of the wafer accurately match, and a desired position on the wafer can be inspected by measuring the coordinates of the stage with a laser length measuring device or the like. next,
The area to be inspected is input from a control screen such as a display of a control workstation.

Next, a test inspection is performed. The trial inspection is performed to determine whether the various parameters set above are appropriate. Specify the part of the pattern you want to inspect. This is the test inspection area designation. Then, a test inspection is performed. In the trial inspection, an image is detected by an electron beam in the same operation as in the actual inspection, but all the acquired images are simply loaded into the memory without passing through the image processing circuit.

Next, image processing conditions are set. This condition is a threshold for judging whether or not there is a defect when the image processing apparatus compares two adjacent images of the same pattern. When this threshold value is set low, the defect detection sensitivity is improved, but the possibility that non-defect portions are regarded as defects is increased. On the other hand, when the threshold value is increased, the detection sensitivity decreases. Here, the brightness threshold value is a threshold value of a difference between luminance signals.

An image formed by an electron beam has a greater roughness than an optical microscope image (that is, the SN of the image). For this reason, even though the inspection objects to be compared are the same and have the same average brightness, there is a slight variation in brightness when viewed from pixel to pixel. Therefore, a light and dark threshold value is provided, and images are compared to detect only a portion where a light and dark difference is greater than the threshold value as a defect, so that the roughness of the image is not recognized as a defect.

The position deviation threshold value is provided to prevent erroneous recognition of incomplete registration of two images to be compared as a defect. It is considered that there is an image positional deviation about the threshold set here, and only when a difference larger than that occurs, is judged as a defect. The filter type is a filter to be applied to the acquired image, and exists to reduce the roughness of the detected image and enhance the edge. In this method, an optimum one is selected by trial and error according to a type of a pattern and a defect to be detected.

After setting the above parameters, image processing is performed. In the image processing in the trial inspection, a comparative inspection is performed using a series of images already acquired. This inspection detects a defect, stores its coordinates, and displays the location of the defect on a control screen. If no defect is detected at this time, the sensitivity is increased by lowering the threshold value of the image processing parameter, and the comparison inspection is performed again using the image on the memory.

Next, an image of the coordinates detected in the trial inspection is observed. This is a review. Since the image of that portion has already been stored in the memory, the image is first displayed on a display of a control workstation or a display dedicated to image display, and the type of defect detected is visually observed. Here, for a considerably large defect, the shape, type, and the like of the defect can be easily found visually. However, a fine defect close to the performance limit of the device or a defect having a small contrast cannot often be sufficiently visually determined.

Therefore, the defect coordinate portion is moved into the field of view of the high-resolution electron optical system dedicated to review, and the high-resolution image is carefully observed. This makes it possible to easily determine whether or not the defect detected in the test inspection is a true defect, whether or not the defect is a defect to be detected. From the result, it is possible to find out a condition for reliably detecting a defect to be detected by repeatedly setting the parameters of the image processing and repeating the review.

In a conventional apparatus that does not have a high-resolution review electron optical system, an image is formed by a large current electron beam. As a result, the sample is destroyed or the image cannot be observed due to charging. Further, the purpose is to confirm the presence or absence of a defect, and the resolution is insufficient for judging the details of the defect by visual observation.

In the past, trial and error had to be repeated in the review and the setting of the image processing parameters, which required a great deal of time. However, according to the present invention, since the quality of the review screen is good, the quality of the selection of the image processing parameter can be accurately determined, and the number of trial and error can be significantly reduced. As a result, the time required for manned work has been significantly reduced, and the overall operation efficiency of the apparatus has been improved.

After the review for setting the conditions is completed, the main inspection is started. This inspection is performed automatically and unattended.
When this inspection is completed, the review is conducted again. After confirming whether the defect detected by this review is a true defect, the wafer is unloaded. If necessary, move to another analysis and inspection apparatus to perform various inspection and analysis.

Next, the specifications, differences and features of the review electronic optical system and the inspection optical system, which are the points of the present invention, will be described.

FIG. 3 shows a comparison of the performance between the inspection electron optical system and the review electron optical system. The inspection electron optical system can perform very high-speed image acquisition because the inspection of the entire wafer is performed in a practical time. That is, the time for forming an image of 100 μm square with a pixel size of 0.1 μm or less is 20 msec or less. The stage is continuously moved for high-speed image acquisition, and the electron beam is scanned in the orthogonal direction. The beam current was designed to be 20 nA or more in order to realize a high-speed and image formation of SN that can withstand inspection.

More specifically, the current density obtained from the electron source was set to about 1 mA / sr, which is the limit value at which the current can be stably obtained. This is about 20 times that of a high-resolution scanning electron microscope (SEM). In addition, the aperture of the lens is high-resolution SE
M is larger than M, and the take-in angle α of the electron beam from the electron source (that is, the opening angle of the electron beam emitted to the sample among the electron beams emitted from the electron source at a wide angle) is determined. It was about 20 times.

In addition, if the peripheral portion of the image is distorted or the resolution is lower than that of the central portion, the inspection sensitivity becomes non-uniform. Therefore, it is necessary to provide a margin for the electron beam scanning area. Therefore, an objective lens whose focal length and operating distance are considerably longer than that of a normal high-resolution SEM is adopted.

Further, when the sample opening angle β of the electron beam is increased, the depth of focus becomes shallower. Since β is obtained by dividing α by the magnification M of the entire optical system, the magnification M cannot be made very small. Therefore, the high resolution S
The magnification is considerably larger than that of EM.

With the above design, it is possible to obtain a large current required for high-speed operation while ensuring the resolution required for inspection. As described above, even if the electron beam current is simply reduced, the electron optical system cannot obtain the same resolution as that of a high-resolution SEM because of the magnification of the optical system, the focal length of the objective lens, and the operating distance. it is obvious.

On the other hand, a reviewing electronic optical system does not require high speed. Also, since the coordinates of the place to be observed are accurately known, a field of view of 20 μm is sufficient. Therefore, the electron beam current may be small. In addition, the focal length and operating distance of the objective lens can be short, and the magnification of the optical system can be reduced, so that ordinary high-resolution SEM
A high-resolution image similar to the above can be obtained.

The outline of the embodiment of the present invention has been described above.
The following describes the components of the electron optical system and the functions of each unit.

First, the components of the inspection electron optical system and the operation thereof will be described in detail. As the electron source 1, a Zr / O / W type electron source which is a diffusion-supply type thermal field emission electron source was used. This electron source can emit electrons stably for a long time.
In addition, by controlling the extraction voltage, the emission angular current density can be reduced to 0.
It can be set freely within the range of 02 mA / sr to 1 mA / sr. However, when the current density is increased, the energy width of the emitted electrons also increases, so that the chromatic aberration increases.

The inspection electron optical system 101 can perform very high-speed image acquisition because the inspection of the entire surface of the wafer is performed in a practical time. That is, pixel size 0.1μ
m and the time for forming an image of 100 μm square is 20 msec or less. For this purpose, it is necessary to secure an SN that can withstand an inspection even when an image is acquired at a high speed. To achieve this, it was necessary to obtain an electron beam current of 20 nA or more. Therefore, the emission angular current density of the electron beam emitted from the electron source 1 is used in the range of 0.5 to 1 mA / sr. As a result, an image with small brightness fluctuations can be obtained, and the electron beam current can be increased, thereby enabling high-speed inspection.

The electron beam 6 is extracted from the electron source 1 by applying a voltage to the extraction electrode 2. The electron beam 6 is accelerated by applying a high negative potential to the electron source 1. In the inspection optical system 101, the acceleration voltage can be set to 10 kV or more. This is because the use of a large current electron beam suppresses the chromatic aberration caused by the increase in the energy width of the electron beam described above, and also suppresses the phenomenon (coulomb effect) that the large current electron beam spreads due to the interaction and cannot be stopped down. That's why.

The electron beam 6 travels in the direction of the stage 24 at an energy corresponding to about 10 kV, is converged by the condenser lens 4, further narrowed down by the objective lens 7, and mounted on the stage 24 (wafer). Or a chip or the like). Distance between the objective lens 7 and the substrate 10 to be inspected (operating distance) in order to make the deflection area 100 μm square or more and obtain an image without distortion even in the peripheral part.
Was set to 25 mm. As a result, the focal length of the objective lens 7 is as long as about 30 mm.

A high voltage power supply 25 can apply a negative voltage to the substrate 10 to be inspected. This high voltage power supply 2
By adjusting 5, it becomes easy to adjust the electron beam irradiation energy to the inspection target substrate 10 to an optimum value. For image formation, a method was employed in which the electron beam 6 scans only one dimension and the stage 24 is continuously moved in a direction perpendicular to the scanning direction.

Signal detection for image formation is performed as follows. That is, secondary electrons are generated by the electron beam 6 applied to the sample 10. These secondary electrons are
Cannot be directly drawn into the detector 9 because it is rapidly accelerated by the potential applied to the detector 9. Therefore, the E × B deflector 14 and the conversion electrode 1 are provided between the substrate 10 to be inspected and the detector 9.
1 is provided.

Here, the E × B deflector 14 is a deflector in which an electric field and a magnetic field are orthogonal to each other, and the deflecting action of the magnetic field and the electric field is opposite to the primary electron beam 6 incident from above. This is a deflector in which secondary electrons coming from below are deflected and added together.

After the secondary electrons are deflected by the E × B deflector 14, they are irradiated on the conversion electrode 11. Then, secondary electrons generated from the conversion electrode 11 are detected by the detector 9. The detector 9 has a PI for realizing high-current and high-speed detection.
An N-type semiconductor detector was used. The secondary electron signal detected here is amplified by the preamplifier 12 and the A / D converter 30 is used.
, And is sent to the image storage unit 18 or 19.

The movement of the stage 24 causes the substrate 10 to be inspected to move.
Is moved, and an image for comparison inspection is acquired with the electron beam 6 from the electron source 1 to execute the comparison inspection. In the automatic inspection as described in the present invention, a high inspection speed is essential. Therefore, unlike a normal SEM, a beam current of the order of pA is scanned at a low speed, and scanning is not performed a plurality of times. Therefore,
For example, 100n which is about 100 times or more that of a normal SEM
An image was formed by scanning the large current electron beam A only once. One image is 1000 × 1000 pixels and 10msec
Acquired in ~ 20 msec.

According to the above-described method, a defect is detected by comparing and judging the image of the same pattern repetition portion adjacent to the semiconductor pattern at high speed by the arithmetic unit 20 and the defect judgment unit 21.

Next, an electronic optical system for review will be described.

As the electron source 201, a Zr / O / W type electron source which is a diffusion-supply type thermal field emission electron source similar to the electron optical system for inspection is used. When the current density is increased, the energy width of the emitted electrons also increases, and chromatic aberration increases. Since the beam current may be 100 pA or less in the review electron optical system, the emission angular current density is set to 0.05 mA / sr or less. Thereby, the energy width of the electron beam 206 is reduced to about 1/3 to 1/4 as compared with the case of the inspection electron optical system, and the chromatic aberration is also reduced accordingly.

The electron beam 206 is extracted from the electron source 201 by applying a voltage to the extraction electrode 202. Electron beam 2
The acceleration of 06 is performed by applying a high negative potential to the electron source 201. In the review optical system 200, the acceleration voltage can be varied from 500 V to 10 kV. Since the review optical system 200 requires a small current, the chromatic aberration is small and the Coulomb effect can be neglected as described above. Therefore, since a sufficiently small beam diameter can be obtained with a low acceleration voltage, the acceleration voltage is set to 2 kV as a standard.

The electron beam 206 travels in the direction of the sample stage 24 with an energy corresponding to 2 kV, is converged by the condenser lens 204, further narrowed down by the objective lens 207, and mounted on the stage 24 (wafer or wafer). Chip, etc.). The objective lens 207 was very close to the substrate 10 to be inspected, and the operating distance was 5 mm. The focal length of the objective lens 207 is 8 mm. As a result, an objective lens with small aberration was realized. The resolution is mostly determined by chromatic aberration. Therefore, since the aberration coefficient is about 1/4 and the energy width of the electron beam is about 1/3 of that of the inspection optical system as compared with the inspection objective lens, the resolution is about 1/12.

The substrate to be inspected 10 is common for inspection and review, so that a negative voltage can be applied by the high voltage power supply 25. By adjusting the high-voltage power supply 25, the irradiation energy of the electron beam to the substrate 23 to be inspected can be adjusted to an optimum value. Since images having different contrasts can be obtained by changing the irradiation energy, information such as whether the defect is due to a difference in shape, due to a material, or due to electrical continuity can be obtained from various angles.

For image formation, the electron beam 206 is two-dimensionally scanned. That is, the stage 24 is fixed. Secondary electrons generated by the electron beam 206 applied to the substrate 10 to be inspected are similar to the optical system 101 for inspection.
Is accelerated by the potential applied to Objective lens 207
Is very close to the substrate 10 to be inspected,
09 is provided above the objective lens 207, and secondary electrons pass through the center of the objective lens 207. Since the potential applied to the inspection target substrate 10 is lower than that of the inspection optical system 101, the energy of the secondary electrons is weak, but it is still difficult to directly draw the secondary electrons into the detector 209. Then conversion electrode 2
Then, the secondary electrons emitted therefrom are detected by a detector 209.

As the detector 209, a detector using a phosphor and a photomultiplier used in a normal SEM was used. The secondary electron signal detected here is supplied to the preamplifier 212.
The digital signal is amplified by the A / D converter 230, converted into a digital signal by the AD converter 230, displayed on the monitor 22 for image observation, and stored as an image file in the external storage device 219 such as a disk or printed out as necessary. ing.

The first embodiment has been described above.
The numerical value of each function is an example. The point is that the review electron optics, which can achieve a beam diameter of about 1/10 compared to the inspection electron optics, are arranged side by side on the same sample chamber as the inspection electron optics. It is the essence of the present invention that the inspection and review operations can be quickly switched only by translation.

(Embodiment 2) As a second embodiment, the objective lens 207 of the review electron optical system 200 of the first embodiment is used.
An X-ray detector 240 is incorporated in the lower magnetic path so that characteristic X-rays generated by electron beam irradiation can be detected. As a result, EDX analysis becomes possible, and the material of the defect can be specified at the time of review. FIG. 4 is a diagram showing the vicinity of an objective lens when an annular X-ray detector having a hole at the center is incorporated.

The X-ray analyzer may be inserted between the objective lens and the sample by making the operating distance of the objective lens slightly longer than in the first embodiment.

(Embodiment 3) In the inspection using an electron beam,
It is possible to inspect not only shape defects but also electrical conduction and non-conduction. This is because the conductive portion is not charged, and only the non-conductive portion is charged, so that the energy and the trajectory of the secondary electrons generated change, and the brightness of the image is different. This occurs as a particularly large contrast due to the irradiation of the high-current electron beam. However, in the review electron optical system, the difference in electrification is small because the current is small, and it is difficult to appear as a contrast. Therefore, a secondary electron energy filter capable of filtering even a small difference in the energy of secondary electrons with high sensitivity is provided.

The energy filter was provided on the objective lens. A diagram of this analyzer is shown in FIG. Hemispheric mesh 2
Reference numeral 20 is provided above the objective lens 207 so as to block the secondary electron trajectory. A hole through which the primary electron beam 206 passes is formed in the center of the mesh 220. A potential in a range of about ± 20 V from the potential of the substrate 10 to be inspected is applied to the mesh 220 by the power supply 221. This makes it possible to visualize the state of charging of the substrate to be inspected. The secondary electrons have an energy distribution peaking at about 2 eV with respect to the potential φ at the place where the secondary electrons are emitted. Therefore,
The energy peak of the secondary electrons viewed from the ground potential is (−φ + 2) eV.

For example, if a retarding potential of 500 V is applied to the substrate 10 to be inspected, the peak of the secondary electron energy becomes 502 eV. If the primary beam irradiation position is originally a place to be electrically connected to the substrate, but that part is not electrically conductive due to a pattern defect, the part is negatively charged. Then, the energy of the secondary electrons emitted therefrom is higher by the charged voltage. If the charging voltage is 5 V, it is 507 eV. Therefore, if -505 V is applied to the mesh, most of the secondary electrons from the uncharged portion cannot pass through the mesh. Therefore, only the charged portion looks bright. In this way, a high-contrast image can be obtained even from a slight charge.

Here, only the case of negative charging has been described. However, in an actual semiconductor, the mechanism of charging by electron beam irradiation is complicated and may be positive. In that case, the potential applied to the mesh may be equal to or slightly higher than the retarding potential. In that case, the portion charged positively is dark, and the other portions are bright.

The resolution of this energy analyzer is about 0.1 V
You can get a degree. Therefore, at the time of review, even if the charge amount of the defective portion is small because the electron beam current is small, the contrast by the potential is emphasized, so that the defect can be easily specified.

[0072]

According to the present invention, defects of the same design pattern of a semiconductor device on a wafer in the process of manufacturing the semiconductor device can be obtained.
In a method of inspecting foreign matter, residue, and the like by using an electron beam, it has become possible to efficiently set inspection conditions. As a result, the speed of the inspection process can be increased and the reliability of the inspection result can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of an inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing scanning and operation of the method according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of specifications of an electron beam optical system of the apparatus according to the first embodiment of the present invention.

FIG. 4 is a partial cross-sectional perspective view illustrating a structure of an objective lens unit according to a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view illustrating a configuration of an inspection device according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron source, 2 ... Extraction electrode, 3 ... Insulator, 4 ... Condenser lens, 5 ... Aperture, 6 ... Electron beam, 7 ... Objective lens, 8 ... Scanning deflector, 9 ... Secondary electron detector, 10 ... Inspection substrate, 11 conversion electrode, 12 preamplifier, 13 scanning signal generator, 14 E × B deflector, 17 blanking deflector, 18 image storage unit, 19 image storage unit, 20
... Arithmetic unit, 21 ... Defect determination unit, 22 ... Monitor, 24 ... Stage, 25 ... High voltage power supply, 26 ... Objective lens power supply, 27
... Correction control circuit, 29 ... Optical sample height measuring instrument, 30 ...
AD converter, 101: inspection electron optical system, 102: sample chamber, 104: control unit, 105: image processing unit, 200: review electron optical system, 201: electron source, 202: extraction electrode, 204: condenser lens , 205 ... aperture, 2
06: electron beam, 207: objective lens, 208: scanning deflector, 209: detector, 211: conversion electrode, 212:
Preamplifier, 218: Image storage unit, 219: External storage device, 220: Mesh, 221: Power supply, 230: AD converter, 240: X-ray detector.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01L 21/66 G01R 31/28 L (72) Inventor Takanori Ninomiya 882, Ige, Hitachinaka City, Ibaraki Pref. Within Hitachi Measuring Instruments Division (72) Inventor Yuko Iwabuchi 882 Ma, Hitachinaka-shi, Ibaraki F-term within Hitachi Measuring Instruments Division (reference) 2G032 AD08 AF07 AF08 AJ04 AK04 4M106 AA01 BA02 BA20 CA39 CA41 DB05 DB11 DB21 DJ14 5C033 AA05 DD02 FF03 GG03 JJ03 MM02 NP03 9A001 BB06 BZ05 HH23 KZ16 LL05

Claims (10)

[Claims] 1. A large current mirror capable of irradiating a sample with a large current electron beam on one vacuum vessel, and a small current capable of irradiating an electron beam having a smaller diameter than the large current mirror with a small current. There is a mirror body, each of which has an electron gun for generating an electron beam, a lens system for narrowing down the electron beam, a deflector for scanning the electron beam on a sample to be inspected, and the vacuum While continuously moving the stage on which the sample is placed in the container, the electron beam is simultaneously scanned on the sample, the generated secondary charged particles are detected, the detection signal is converted into an image signal of the sample, and the image is converted. A step of inspecting the pattern for defects using a signal, and moving the position of the defect coordinates detected by the inspection to a position immediately below the small current mirror, and checking the defect. Change the condition and again on Inspection method of a circuit pattern which comprises carrying out the inspection. 2. The circuit pattern inspection method according to claim 1, wherein the electron beam of the small current mirror has a lower accelerating voltage than the electron beam of the large current mirror. 3. A negative current for decelerating to a desired energy is applied to the specimen and the stage immediately before the electron beam irradiation, and when observing an image of the specimen with a small current mirror, inspection is performed with the large current mirror. 3. The circuit pattern inspection method according to claim 1, wherein a lower negative potential is applied than when performing the test. 4. The small current mirror body is provided with an X-ray detector, and analyzes a material at an irradiation position from energy of X-rays emitted by electron beam irradiation.
The method for inspecting a circuit pattern according to any one of the above. 5. The small current mirror according to claim 1, further comprising an energy filter, wherein a potential at an electron beam irradiation position is detected by filtering energy of secondary electrons emitted by electron beam irradiation. 4. The method for inspecting a circuit pattern according to any one of claims 1 to 3. 6. A large current mirror capable of irradiating a sample with a large current electron beam on one vacuum vessel, and a small current capable of irradiating an electron beam having a smaller diameter than the large current mirror with a small current. There is a mirror body, each of which has an electron gun for generating an electron beam, a lens system for narrowing down the electron beam, a deflector for scanning the electron beam on a sample to be inspected, and the vacuum While moving the stage on which the sample is placed in the container continuously, the electron beam is simultaneously scanned on the sample and the generated secondary charged particles are detected to image the sample, and pattern defects are detected using the image. Inspection process, the position of the defect coordinates detected by the inspection is moved immediately below the small current mirror, the defect is confirmed, and the inspection conditions for the large current mirror are changed based on the result, and the inspection is performed again. Specially Inspection apparatus for circuit pattern to. 7. The circuit pattern inspection apparatus according to claim 6, wherein the electron beam of the small current mirror has an acceleration voltage lower than that of the electron beam of the large current mirror. 8. A large current mirror is used to apply a negative potential for decelerating to a desired energy immediately before irradiating an electron beam to the sample and the stage, and to observe an image of the sample with a small current mirror. The circuit pattern inspection apparatus according to claim 6, wherein a negative potential smaller than that when applying is applied. 9. The small current mirror body is provided with an X-ray detector, and the material at the irradiation position is analyzed from the energy of the X-ray emitted by electron beam irradiation.
The circuit pattern inspection device according to any one of the above. 10. The small current mirror according to claim 6, further comprising an energy filter, wherein a potential at an electron beam irradiation position is detected by filtering energy of secondary electrons emitted by electron beam irradiation. 9. The circuit pattern inspection apparatus according to any one of claims 8 to 8.