JP2002118158A - Method and apparatus for inspecting circuit pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed, stable, and accurate inspection of circuit pattern having insulating materials in a method for inspection by detecting a defect, contamination, residue, or the like appearing on the circuit pattern of a semiconductor-device wafer, by radiating an electron beam onto the wafer and comparing the secondary electron image with a reference image. SOLUTION: A high-current electron beam 19 is radiated only at one time or several times of short time duration onto the wafer 9 to be inspected to form an electron beam image before the electric potentials of the circuit pattern materials change. Besides, in addition to the first electron beam for forming the image for the inspection, a second charged-particle beam 104 is radiated beforehand onto the wafer 9 to be inspected to conduct the inspection after the condition of the electric potentials of the circuit pattern materials are stabilized. The secondary-electron detection signal is digitized and transferred to efficiently obtain a high-quality electron-beam image with a high S/N ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a substrate having a fine circuit pattern such as a semiconductor device or a liquid crystal, and more particularly to a technique for inspecting a pattern of a semiconductor device or a photomask. The present invention relates to a pattern inspection technology and a comparative inspection technology using an electron beam.

[0002]

2. Description of the Related Art An inspection of a semiconductor wafer will be described as an example.

A semiconductor device is manufactured by repeating a process of transferring a pattern formed on a semiconductor wafer on a photomask by a lithography process and an etching process. In the manufacturing process of the semiconductor device, the quality of the lithography process and the etching process and the like, the generation of foreign matter, etc., greatly affect the yield of the semiconductor device,
2. Description of the Related Art A method of inspecting a pattern on a semiconductor wafer in a manufacturing process in order to detect abnormality or defect occurrence early or in advance has been conventionally implemented.

As a method of inspecting a defect present in a pattern on a semiconductor wafer, a defect inspection apparatus that irradiates a semiconductor wafer with white light and compares the same circuit patterns of a plurality of LSIs using an optical image has been put into practical use. The outline of the inspection method is described in "Monthly Semiconductor World", August 1995, pp96-99. In the inspection method using an optical image, as described in Japanese Patent Application Laid-Open No. 3-167456, an optically illuminated region on a substrate is imaged by a time delay integration sensor, and the image is input in advance. A method of detecting defects by comparing design characteristics
As described in Japanese Patent No. 58220, there is disclosed a method of performing a comparative inspection with a stable optical image by monitoring image deterioration at the time of image acquisition and correcting it at the time of image detection. When a semiconductor wafer in a manufacturing process is inspected by such an optical inspection method, no residue or defect of a pattern having a surface of a silicon oxide film or a photosensitive photoresist material through which light is transmitted cannot be detected. In addition, it was not possible to detect an unetched residue or a non-opening defect in a minute conduction hole, which was lower than the resolution of the optical system. Furthermore, a defect generated at the bottom of the step of the wiring pattern could not be detected.

[0005] As described above, with the miniaturization of circuit patterns, the complexity of circuit pattern shapes, and the diversification of materials, it has become difficult to detect defects by optical images, and thus electron beam images having higher resolution than optical images. There has been proposed a method of comparing and inspecting a circuit pattern by using the method. In order to obtain a practical inspection time when comparing and inspecting a circuit pattern using an electron beam image, a scanning electron microscope (Scanning Electron) is required.
It is necessary to acquire an image at a very high speed as compared with observation by Microscopy (hereinafter abbreviated as SEM). Then, it is necessary to ensure the resolution of the image acquired at high speed and the SN ratio of the image.

As an apparatus for comparing and inspecting patterns using an electron beam, J. Vac. Sci. Tech. B, Vol. 9, No. 6, pp. 3005
-3009 (1991), J. Vac. Sci. Tech. B, Vol. 10, N
o.6, pp. 2804-2808 (1992), and JP-A-5-258703
And USP 5,502,306, it is more than 100 times (10nA
An electron beam having the above electron beam current is irradiated onto a conductive substrate (such as an X-ray mask), and any of secondary electrons, reflected electrons, or transmitted electrons generated is detected, and an image formed from the signal is detected. There is disclosed a method of automatically detecting a defect by comparing and inspecting the defects.

A method for inspecting or observing a circuit board having an insulator with an electron beam is disclosed in Japanese Unexamined Patent Publication No. 59-155941.
Japanese Patent Application Publication and "Electron, Ion Beam Handbook" (Nikkan Kogyo Shimbun), pp. 622-623, discloses a method of acquiring a stable image by irradiating a low-acceleration electron beam of 2 keV or less to reduce the influence of charging. Further, Japanese Patent Laid-Open No. 2-15546
Japanese Patent Laid-Open Publication No. H10-181605 discloses a method of irradiating ions from the back of a semiconductor substrate,
Japanese Patent Application Laid-Open No. 6-338280 discloses a method of irradiating light to the surface of a semiconductor substrate to cancel the charge on the insulator.

In the case of an electron beam having a large current and a low acceleration, it is difficult to obtain a high-resolution image due to the space charge effect.
No. 03 discloses a method of decelerating a high acceleration electron beam immediately before a sample and irradiating the sample with a substantially low acceleration electron beam.

As a method of acquiring an electron beam image at high speed, a method of continuously irradiating a semiconductor wafer on a sample stage with an electron beam while continuously moving the sample stage to acquire the image is disclosed in Japanese Patent Application Laid-Open No. 59-160.
No. 948 and JP-A-5-258703.
In addition, as a secondary electron detection device used in the conventional SEM, a configuration using a scintillator (a phosphor on which Al is deposited), a light guide, and a photomultiplier tube is used.
This type of detection device has poor frequency response and is unsuitable for high-speed electron beam image formation because it detects light emitted by a phosphor. To solve this problem, Japanese Unexamined Patent Publication No. 5-258703 discloses a detecting device using a semiconductor detector as a detecting device for detecting a high-frequency secondary electron signal.

[0010]

When a circuit pattern is inspected in the process of manufacturing a semiconductor device having a fine structure by using the above-described optical inspection method of the prior art, an optical wavelength which is an optically transparent material and is used for the inspection. Residues such as silicon oxide films and photosensitive resist materials whose optical distance depends on the refractive index are sufficiently small cannot be detected. It was difficult to detect non-opening defects of holes.

On the other hand, observation and inspection using an SEM have the following two problems. One is that the conventional method of forming an electron beam image by SEM requires an extremely long time, and therefore, it takes an enormous amount of time to inspect a circuit pattern over the entire surface of a semiconductor wafer. Therefore, it has been necessary to acquire an electron beam image at a very high speed in order to obtain a practical throughput in a semiconductor device manufacturing process or the like. Further, it is necessary to secure the SN ratio of the electron beam image acquired at high speed and to maintain a predetermined accuracy.

Another problem is that the material constituting the circuit pattern to be inspected is formed of an insulating material such as a photosensitive resist or a silicon oxide film. In the case where these materials are mixedly formed, it is difficult to obtain an image with stable luminance in an inspection using an electron beam and to obtain a predetermined inspection accuracy. This is because when a material is irradiated with an electron beam, secondary electrons are generated from that part, but since the irradiated current value is not equal to the secondary electron current value, the material is charged when the inspection target is an insulator. When charging occurs, the efficiency of secondary electron generation from that part and the trajectory of secondary electrons after generation are affected, changing the brightness of the image and simultaneously reflecting the shape of the actual circuit pattern in the image. It is distorted. This charged state is sensitive to the irradiation condition of the electron beam, and if the irradiation speed or the irradiation range of the electron beam is changed, an image having a completely different contrast will be obtained even with the same circuit pattern at the same place.

As described in the above prior art, in order to detect a defect that cannot be detected by the optical inspection method, Japanese Patent Application Laid-Open
59-160948 and JP-A-5-258703 discloses a method for irradiating a conductive substrate with an electron beam to acquire an electron beam image and performing comparative inspection. A method for doing so is disclosed. However, this prior art does not describe a method for adjusting inspection conditions for a material such as an insulator. Also, another prior art, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 59-155941 discloses a method for observing a substrate having an insulator, in which a primary electron beam applied to a sample substrate is decelerated to lower the irradiation energy to a low acceleration, for example, 2 keV or less. However, this conventional technique is a method of continuously irradiating an electron beam in a certain local area and obtaining an image after the local area is stabilized in charge. Not suitable for testing large areas. Further, even if the charge in the local area is stable, it is difficult to control another area to be compared to a similar charge state, and it is difficult to inspect a wide area such as a semiconductor wafer. .

When a sample is slowly irradiated with a narrow and narrow electron beam having a small electron beam current as in a conventional SEM, and signal detection is also performed over a long period of time, a unit pixel is required to obtain an S / N ratio required for comparative inspection. The signal detected during the detection time per is integrated to obtain an image signal of the unit pixel. As already mentioned,
Since the state of charging changes with time according to the irradiation time, the image signal changes during integration, and it is difficult to obtain a stable contrast. As a method for inspecting a circuit board having such an insulating material, the present inventors have set the detection time of the secondary electron signal to be sufficiently short to obtain a stable contrast, and to reduce the contrast fluctuation due to the integration and other processes. It has been found that it is effective to suppress the influence of the change with time due to charging as well as to eliminate it. In addition, the present inventors have found that a thick electron beam of about 50 nm to 10 nm can be used as a sample at a higher speed than an electron beam image based on contour information of a shape obtained with an electron beam narrowed down to 5 nm to 10 nm as in a conventional SEM. By irradiating and acquiring an image instantly, it was found that an electron beam image having a contrast generated by the secondary electron generation efficiency of the sample material was more suitable. Thus, compared with the prior art, a thicker electron beam is scanned at a higher speed, an electron beam image of light-dark contrast generated by the material is obtained instantaneously, and the S / N ratio of the present electron beam image is sufficient for the comparative inspection of the image. It is an object of the present invention to ensure the resolution.

As described above, in order to irradiate an electron beam at a high speed, detect a signal at a high speed, and secure an S / N ratio and a resolution of an electron beam image, as described in the above-mentioned prior art, a conventional method is used.
It is necessary to irradiate the substrate to be inspected with an electron beam having an electron beam current larger than that of the SEM. As described in the above-mentioned prior art, it is difficult to obtain a high-resolution image due to a space charge effect with an electron beam having a large current and a low acceleration. Is decelerated, and the sample is irradiated with a substantially low-acceleration electron beam on the sample. In order to decelerate the primary electron beam, it is necessary to apply a negative voltage for deceleration to the sample substrate or the sample stage. When the primary electron beam decelerated by the negative voltage is applied to the sample substrate, secondary electrons having energy of about several tens of mV are generated from the substrate surface. An electric field generated by the negative voltage for deceleration acts on the secondary electrons, and the secondary electrons are accelerated to an energy of several kV, so that it is difficult to collect high-speed secondary electrons to the detector. . As a method for collecting secondary electrons in a detector, a deflector (hereinafter referred to as a deflector (hereinafter, referred to as a deflector) that deflects electrons by overlapping electric and magnetic fields for a primary electron beam and superimposing both electrons on a secondary electron beam. A method using an ExB deflector) has been proposed in the prior art. However, when the detector is located at a position deviated from the primary electron beam orbit, it is necessary to largely deflect the secondary electrons with the ExB deflector in order to collect secondary electrons at the detector, and the amount of deflection is reduced. If it is too large, there is a problem that secondary electrons collide with the deflection plate itself of the ExB deflector and cannot be led to the detector. In addition, when the deflection by the ExB deflector is increased, aberration occurs in the primary electron beam, and it is difficult to narrow down the electron beam on the surface of the sample substrate with an objective lens or the like.

As described in the above-mentioned prior art, there is a detecting means using a semiconductor detector as a detecting device for detecting a high-frequency secondary electron signal in order to form an electron beam image at high speed. The technical means includes a reverse-biased semiconductor detector having a high response speed, a preamplifier for amplifying an analog signal detected by the semiconductor detector, and a means for optically transmitting the analog signal amplified by the preamplifier. The semiconductor detector and the preamplifier are floating at a positive high potential. In this conventional method,
The analog signal detected by the semiconductor detector is transmitted as an analog signal by an optical transmission means. The optical transmission means includes a light emitting element for converting an electric signal into an optical signal, an optical fiber cable, and an optical signal. Since the configuration includes the light receiving element for converting into a signal, there is a problem that noise generated in the light emitting element and the light receiving element is added to the original analog signal, and the SN ratio of the secondary electron signal is reduced.

A first object of the present invention is to provide a circuit pattern which is difficult to detect in an optical image and which is formed of a material having an insulating property, or a circuit pattern formed of a material having an insulating property and a material having a conductive property. An object of the present invention is to provide an inspection technique that can inspect a circuit pattern using an electron beam image.

A second object of the present invention is to acquire an electron beam image as a high-quality image with high speed, stability, high resolution, large contrast, and a large SN ratio in order to perform the inspection using the electron beam image. Thus, a defect generated on a fine circuit pattern in the comparative inspection is detected without error.

A third object of the present invention is to irradiate a sample with a relatively large electron beam having a large current at a high speed and to detect the generated secondary electrons instantaneously and efficiently, so that the contrast of light and dark generated by the material of the sample is obtained. An object of the present invention is to provide a technique for obtaining a stable electron beam image of an insulating material by forming an electron beam image composed of the sample under conditions according to the material of the sample.

A fourth object of the present invention is to provide means for efficiently detecting secondary electrons generated by irradiating a sample with an electron beam and detecting high-speed high-frequency secondary electrons at a high SN ratio. Thereby, the first, second, and third objects are achieved.

A fifth object of the present invention is to solve the above first to fourth problems, to provide a technique for inspecting a circuit pattern with high accuracy, and to apply the inspection to a semiconductor device and other fine circuit patterns. Accordingly, it is an object of the present invention to provide an inspection method that reflects the inspection result in the manufacturing conditions of the semiconductor device and the like, thereby improving the reliability of the semiconductor device and the like and reducing the defective rate.

[0022]

A substrate having a fine circuit pattern, such as a semiconductor device, often includes not only a conductive film but also an insulating material. In order to achieve the above-mentioned object of irradiating a circuit pattern having an insulating material with an electron beam to rapidly detect fine defects on a fine pattern, a circuit pattern inspection method and an inspection apparatus according to the present invention will be described below. .

According to the study of the present inventors, when a local region on the surface of a substrate including an insulator is irradiated with a large amount of electron beams non-uniformly, the contrast greatly changes depending on time and place. An electron beam is uniformly irradiated on the sample to be inspected in a state of almost the same potential as compared with the potential,
When secondary electrons generated in a very short time are detected, an electron beam image with stable contrast can be obtained even with an insulating material. This means that even in the transient state where the sample is charged by irradiating the electron beam, it is possible to acquire a signal with a small variation in the secondary electron generation rate with time by instantaneously detecting the secondary electrons in a very short time. That's why. Also, the present inventors have found that 5 nm to 10
By irradiating a sample with a thicker electron beam of about 50 nm to 10 nm at a higher speed and acquiring an image instantaneously than an electron beam image based on contour information of a shape acquired with an electron beam narrowed down to nm, It has been found that a contrast electron beam image generated by the secondary electron generation efficiency is more suitable for defect detection. Since the efficiency of secondary electron generation differs depending on the material and film thickness of the surface pattern and the base on which the circuit pattern is formed, if an electron beam image with a large contrast between the pattern generated by this material and the base is obtained, the pattern Alternatively, it becomes easy to detect a defect on the base. The secondary electron generation efficiency of each material constituting the circuit pattern changes depending on the conditions for irradiating the electron beam. The secondary electron generation efficiency also changes depending on the charging state. Therefore, by optimizing the irradiation conditions or charging conditions that increase the contrast between the surface pattern and the underlying material depending on the material, an electron beam image suitable for detecting each defect corresponding to various combinations of materials can be obtained. It can be formed. One method is to form an electron beam image by detecting the secondary electrons generated by irradiating the electron beam once in a very short time. There is a method of detecting secondary electrons generated in a state where the contrast is increased in a very short time.
In addition, the method of irradiating an electron beam once or several times at a high speed, detecting secondary electrons in a very short time while the transient change of the potential due to charging is small, and obtaining an electron beam image, and a combination of materials. There is a method of irradiating the sample substrate in advance with an electron beam or other charged particle beam, detecting secondary electrons in a very short time after obtaining a stable charging state and increasing contrast, and obtaining an electron beam image I found that. In either method, the electron beam is uniformly irradiated on the inspection area in the same potential state, that is, in the same charged state as compared with the electric potential in the vicinity of the substrate inspection area. In contrast, when the electron beam image is compared and inspected, a change in contrast does not result in an erroneous detection.

In order to realize the former inspection method, a high-current electron beam is uniformly irradiated on a substrate to be inspected at a high speed, and a secondary electron signal corresponding to the position is instantaneously detected almost simultaneously with the irradiation. The method was found to be effective. In all inspection areas, electron beams are evenly irradiated for a moment during inspection,
At that moment, the substrate potential due to the charging is uniform, and by detecting the secondary electrons in that state instantaneously, it is possible to avoid the influence of the transient time fluctuation of the charging. Also, by controlling the energy of the electron beam irradiating the sample, the ratio between the number of electrons incident on the sample and the number of secondary electrons emitted from the sample can be set to be substantially equal, depending on the material. The contrast is stabilized, and damage to the sample circuit board can be avoided. That is, an image having a stable contrast can be formed even in a circuit pattern having an insulating material. Controlling the energy of the electron beam irradiating the sample can be achieved by applying a negative potential to the sample or sample stage, decelerating the primary electron beam directly above the sample, and variably controlling the applied voltage to vary the degree of deceleration. It becomes possible.

As means for automatically inspecting a defect generated on the surface of a circuit pattern such as a semiconductor wafer at a high speed, an electron beam is rapidly moved in a direction orthogonal to the moving direction while continuously moving the sample stage in one direction. The scanning is performed, secondary electrons are detected in real time during the movement of the sample stage, an image is formed, and the image is compared and inspected. In order to realize this inspection method, the irradiation condition of the electron beam differs depending on the material, but the image is formed by irradiating the electron beam once or several times at high speed. In order to secure the image quality of the electron beam image that can be used for the comparison inspection by irradiating the electron beam once or several times, the following four means are possible. The first means is to irradiate a sample with a high-density electron beam, thereby ensuring the S / N ratio of a secondary electron signal that is a source of an electron beam image required for inspection. The inspection is performed using an electron beam having a current value of 270 pA or more, preferably 13 nA or more. This current value is achieved by setting the square root of the number of irradiated electrons to be sufficiently larger than the SN ratio of the electron beam image required for the inspection. The second means is
When irradiating a sample with a high-current electron beam, the electron beam is narrowed so that the diameter of the electron beam on the sample is sufficiently small, thereby ensuring the resolution required for inspection of a fine circuit pattern. As described in the related art, when observing a semiconductor or the like having an insulating material with an electron beam, it is desirable that the energy of the electron beam applied to the sample be low. In the case of a large current and low acceleration electron beam, aberration occurs due to the space charge effect, and it is difficult to narrow the electron beam on the sample. Therefore, this problem can be solved by using the same means as the method described in the means for controlling the energy for irradiating the sample with the electron beam. In other words, the electron source generates an electron beam at high acceleration to suppress the space charge effect, and by applying a negative potential to the sample or the sample stage, the high acceleration electron beam is decelerated immediately before the sample, and By irradiating the electron beam with a substantially optimal low-acceleration energy, the diameter of the electron beam on the sample can be narrowed down, and the required resolution can be secured. The third means is to secure the S / N ratio of the electron beam image required for inspection by efficiently guiding the secondary electrons generated on the surface to the detector. When the sample is irradiated with the electron beam by the second means, secondary electrons generated from the sample are accelerated by a negative potential electric field for temporarily reducing the speed of the electron beam. The accelerated secondary electrons are deflected by the ExB deflector and guided to the detector, and the secondary electrons are irradiated onto a metal piece provided between the optical path of the temporary electron beam and the detector. By deflecting and guiding the low-speed secondary electrons generated by the metal piece to the detector, it is not necessary to largely deflect the high-speed secondary electrons in the direction of the detector, and the amount of deflection can be reduced. As a result, problems that occur when a high-speed secondary electron is largely deflected, such as loss of secondary electrons due to collision with a secondary electron deflector and reduction in resolution due to the influence on a primary electron beam, are solved. It is possible to obtain more secondary electrons than the number of electrons of the primary electron beam by using a material having a high generation efficiency of secondary electrons for the metal piece, thereby improving the SN ratio of the image. It becomes possible. The fourth means is to use a semiconductor detector as a detector in order to form an image with a high SN ratio at high speed, and to digitize and transmit an analog signal detected by the semiconductor detector. The semiconductor detector further includes means for converting the digitized signal into an optical signal, transmitting the optical signal by means of an optical fiber or the like, and converting the transmitted signal into an electric signal again. The components up to the means are floated to a positive potential. As a result, the analog signal detected by the semiconductor detector is digitized by the AD converter and transmitted optically. By using a semiconductor detector, it becomes possible to secure the responsivity necessary for detecting secondary electrons at high speed, and light-emitting elements or photoelectric conversion means by optically transmitting a digitized signal. Even slight noise in the light receiving element does not affect the determination of digital 1 or 0, so that noise can be suppressed. Also, by floating the semiconductor detector to the light conversion means at a positive potential, secondary electrons can be drawn into the semiconductor detector, and the circuits subsequent to the light conversion means can be operated at the ground potential. . Therefore, secondary electrons generated from the sample by irradiating the sample with the electron beam can be detected at high speed with little influence of noise.

By the various means described above, a stable image can be obtained even under a condition that the image contrast fluctuation due to charging is suppressed, and a high sensitivity, a high speed and a high SN ratio can be obtained even for a circuit pattern having an insulating material. Can be formed.

In the above description, an electron beam is irradiated once or several times at a high speed, which is effective for inspecting a circuit pattern having an insulating material as described above, and an electron beam image is obtained before a potential change due to charging occurs. Of the two methods, a method for obtaining an electron beam and a method for irradiating an electron beam or another charged particle beam to obtain an electron beam image after a charged state is stabilized have been described. The means of the latter inspection method will be described below.

In order to stabilize the charged state before the inspection, there are two means. First, the first means is to irradiate a substrate to be inspected with a second charged particle beam, for example, an electron beam, an ion beam, plasma, an electron shower, or the like in advance in a spare room or the like different from the chamber to be inspected, and correct the substrate before the inspection. Alternatively, it is a method of negatively charging. The second means transfers the substrate to be inspected to a chamber for inspecting, and irradiates the substrate with a second electron beam at a position for forming an inspection image. In order to irradiate the inspection area with the second electron beam before the inspection without affecting the inspection, (1) the first electron beam irradiation and the second electron beam irradiation for forming an inspection image are performed. Irradiation is shifted in time. (2) The first electron beam for forming the inspection image is raster-scanned on the substrate to be inspected, and the second electron beam is irradiated while the electron beam is turned back during the scan. (3) The first electron beam and the second electron beam for forming the inspection image are coaxially and simultaneously irradiated on the substrate to be inspected, but the second electron beam is sufficiently larger than the diameter of the first electron beam. The current density is a diameter and is sufficiently smaller than the maximum current density of the first electron beam. As a configuration, one or more second electron beam sources are arranged around an opening where the first electron beam for inspection image formation is irradiated, and they operate independently, and the first electron beam The second electron beam may be irradiated to the region to be inspected on the substrate to be inspected before the irradiation is performed.

As means for irradiating the second charged particle beam by a method other than the above, the charged particle beam may be an ion beam,
An ion source is provided around the opening where the first electron beam for image formation is irradiated, and the inspection target substrate is irradiated with the ion beam when the inspection target substrate is inspected. The timing of irradiation is the same as the case where the second charged particle beam is an electron beam,
Irradiating the first electron beam and the ion beam with a time delay,
Alternatively, there is no problem if the irradiation is performed during the return of the scanning of the first electron beam.

By the above-described means, the substrate to be inspected is irradiated with the second charged particle beam to make the charged state of the substrate surface uniform, and then the first electron beam for forming the inspection image is formed. By irradiating the electron beam, an electron beam image can be always formed in a stable charged state with respect to a circuit pattern having an insulating material. Depending on the insulating material, there is a case where the contrast with the underlying material increases when charged. In such a case, fluctuations in the electron beam image due to charging can be suppressed by merely controlling the irradiation conditions of the first electron beam for forming the inspection image, but sufficient contrast for performing the comparative inspection can be obtained. Therefore, the method of irradiating the second charged particle beam according to the present invention is effective.

In the above-described means for forming an electron beam image after stabilizing the charged state of the surface of the substrate to be inspected by the second charged particle beam, conditions and means for irradiating the first electron beam are as follows. This is similar to the means for irradiating the first electron beam once or several times to form an image before fluctuation due to charging occurs. The means for high-speed inspection and the means for making the image quality of the electron beam image high in SN ratio and high resolution at the time of high-speed inspection are the same as those described above. Further, in the means for irradiating a second charged particle beam to stabilize the charge and then form an electron beam image for inspection with the first electron beam, the first electron beam irradiating the sample and the second electron beam By controlling the irradiation energy of the charged particle beam, it is possible to use a means for adjusting the charging state together. When a charged particle beam other than the electron beam for image formation is irradiated simultaneously or almost simultaneously with the electron beam, a secondary electron signal which is not necessary for image formation may be generated and detected.
In this case, it is means for forming an image of the circuit pattern of the substrate to be inspected by secondary electrons, and a stop is arranged on the image surface of the sample surface, and the secondary electron beam generated from the area irradiated with the electron beam for inspection image formation. Unnecessary secondary electrons can be eliminated by guiding only the secondary electrons to the secondary electron detector through the aperture.

So far, various means for forming an electron beam image among the means for inspecting a substrate on which a fine circuit pattern has been formed with an electron beam have been described. A means for detecting a defect generated on a circuit pattern from an electron beam image will be described below. The first region of the sample is irradiated with the first electron beam, secondary electrons generated from the sample surface are detected at high speed and high efficiency, and an image signal of the electron beam in the first region of the substrate to be inspected is obtained. The information is stored in the first storage unit. At this time, if necessary, a second charged particle beam is irradiated before the first electron beam is irradiated. Similarly, while obtaining the electron beam image of the region having the same circuit pattern as the first region, which is the second region of the sample, and storing the electron beam image in the second storage unit, After performing a detailed position adjustment on the image by the image processing unit, compare the images of the first and second areas to obtain a difference image, and when the absolute value of the brightness of the difference image is equal to or greater than a predetermined threshold value Then, processing such as judging a pixel as a defect candidate is performed. As another means, an electron beam image of a non-defective circuit pattern different from the inspected substrate is formed and stored under predetermined conditions in the first storage unit, and the first area of the inspected substrate is stored in the first storage unit. Irradiation with one electron beam, secondary electrons generated from the sample surface are detected at high speed and high efficiency, and an image signal of the electron beam in the first area of the substrate to be inspected is obtained and stored in the first storage unit. The images of the non-defective circuit patterns are compared, and when the absolute value of the brightness of the difference image is larger than a predetermined threshold value, processing such as determination as a defect is performed. Also in this case, if necessary, the second charged particle beam is irradiated before the first electron beam is irradiated. In addition, since the first region and the second region of the substrate to be inspected are all irradiated once or several times with the first electron beam to form an image, the first region and the second region are not irradiated with the electron beam except for image formation. As means for performing this, a monitor for adjusting the focal position of the first electron beam is constantly irradiated with, for example, white light other than the electron beam, and the reflected light is monitored.
Alternatively, prior to inspection, when setting sensitivity conditions and electron beam irradiation conditions according to the substrate to be inspected, an electron beam image is acquired in a region other than the inspection target region, and the inspection target region is always the first inspection. By means of managing the electron beam irradiation, it is possible to prevent the inspection target area of the inspection target substrate from being locally charged, and to eliminate the cause of erroneous detection.

By performing the above-described inspection method, a circuit pattern on a substrate including an insulator material can be inspected with an electron beam at high speed and high sensitivity, and a defect generated on the circuit pattern can be automatically detected. A method and an inspection device can be realized.

By inspecting a substrate having a circuit pattern, for example, a semiconductor device in a manufacturing process, by using these methods and apparatuses, the semiconductor device in each process can be inspected by process processing which cannot be detected by the conventional technology. The resulting pattern defect or defect in the pattern can be detected at an early stage, and as a result, problems latent in the process or the conditions of the manufacturing apparatus can be revealed. As a result, it is possible to take measures against the causes of defects in the manufacturing process of various substrates including a semiconductor device with higher speed and higher accuracy than before, and to secure a high yield, that is, a non-defective product rate, and at the same time, to perform the inspection which has been a problem. Since the number of erroneous detections occurring at the time is reduced, highly accurate inspection can be performed.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of an inspection method and an apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 shows the configuration of a circuit pattern inspection apparatus 1 according to a first embodiment of the present invention. The circuit pattern inspection apparatus 1 includes an inspection room 2 where the room is evacuated, and an inspection room 2
A preliminary chamber (not shown in this embodiment) for transporting the sample substrate 9 is provided therein, and this preliminary chamber is configured to be able to evacuate independently of the inspection chamber 2. Further, the circuit pattern inspection apparatus 1 includes a control unit 6 and an image processing unit 5 in addition to the inspection room 2 and the spare room. The inside of the inspection room 2 is roughly composed of an electron optical system 3, a secondary electron detection unit 7, a sample room 8, and an optical microscope unit 4. The electron optical system 3 includes an electron gun 10, an electron beam extraction electrode 11, a condenser lens 12, a blanking deflector 13, a scanning deflector 15, an aperture 14, an objective lens 16, a reflection plate 17, and an ExB deflector 18. ing.
In the secondary electron detector 7, a secondary electron detector 20 is arranged above the objective lens 16 in the inspection room 2. The output signal of the secondary electron detector 20 is amplified by a preamplifier 21 installed outside the inspection room 2, and converted into digital data by an AD converter 22. The sample chamber 8 contains a sample stage 30, an X stage 31, and a Y stage 3.
2. It is composed of a rotating stage 33, a length monitor 34 for position monitoring, and a height measuring device 35 for a substrate to be inspected. Optical microscope section 4
Is installed in the vicinity of the electron optical system 3 in the room of the inspection room 2 and at a distance so as not to affect each other, and the distance between the electron optical system 3 and the optical microscope unit 4 is known. . Then, the X stage 31 or the Y stage 32 reciprocates a known distance between the electron optical system 3 and the optical microscope unit 4. The optical microscope unit 4 includes a light source 40, an optical lens 41, and a CCD camera 42. The image processing unit 5 includes a first image storage unit 46, a second image storage unit 47,
8. It is composed of a defect determination unit 49. The captured electron beam image or optical image is displayed on the monitor 50. Operation commands and operation conditions of each unit of the device are input and output from the control unit 6. The control unit 6 can arbitrarily or select conditions such as acceleration voltage, electron beam deflection width, deflection speed, signal capturing timing of the secondary electron detector, and sample stage moving speed at the time of electron beam generation according to the purpose. It has been entered so that it can be set. The control unit 6 monitors the position and height deviations from the signals of the position monitor length measuring device 34 and the substrate height measuring device 35 to be inspected by using the correction control circuit 43, and generates a correction signal from the result. Then, a correction signal is sent to the objective lens power supply 45 and the scanning deflector 44 so that the electron beam is always irradiated to the correct position.

In order to obtain an image of the substrate 9 to be inspected,
The substrate to be inspected 9 is irradiated with the narrowed electron beam 19 to generate secondary electrons 51, and these are detected in synchronization with the scanning of the electron beam 19 and the movement of the stages 31 and 32, thereby detecting the substrate to be inspected.
Obtain 9 surface images. As described in the subject of the present invention, in the automatic inspection of the present invention, a high inspection speed is essential.
Therefore, unlike an ordinary SEM, an electron beam having an electron beam current on the order of pA is scanned at a low speed, and a large number of scans and superimposition of images are not performed. Further, in order to suppress charging of the insulating material, it is necessary to perform the electron beam scanning once or several times at high speed. Therefore, in this embodiment, the normal SE
The configuration is such that an image is formed by scanning only once with a large current electron beam of about 100 times or more compared to M, for example, 100 nA. The scanning width was 100 μm, one pixel was 0.1 μm ^square, and one scan was performed in 1 μs.

The electron gun 10 uses a diffusion-supply type thermal field emission electron source. By using the electron gun 10, a stable electron beam current can be secured compared with a conventional tungsten (W) filament electron source or a cold field emission type electron source, so that an electron beam with less fluctuation in brightness can be obtained. An image is obtained. In addition, since the electron gun 10 can set a large electron beam current, a high-speed inspection as described later can be realized. The electron beam 19 is extracted from the electron gun 10 by applying a voltage between the electron gun 10 and the extraction electrode 11. The electron beam 19 is accelerated by applying a high negative voltage to the electron gun 10. This allows the electron beam
19 travels in the direction of the sample stage 30 with energy corresponding to the potential, is converged by the condenser lens 12, is further narrowed down by the objective lens 16, and is narrowed down by the XY stage 31 on the sample stage 30,
The target substrate 9 (substrate having a fine circuit pattern such as a semiconductor wafer, a chip or a liquid crystal or a mask) mounted on the substrate 32 is irradiated. A signal generator 44 for generating a scanning signal and a blanking signal is connected to the blanking deflector 13, and a lens power supply 45 is connected to the condenser lens 12 and the objective lens 16, respectively. A negative voltage can be applied to the substrate 9 to be inspected by the high-voltage power supply 36. By adjusting the voltage of the high-voltage power supply 36, the primary electron beam can be decelerated, and the irradiation energy of the electron beam to the substrate 9 to be inspected can be adjusted to an optimum value without changing the potential of the electron gun 10.

The secondary electrons 51 generated by irradiating the substrate 9 with the electron beam 19 are accelerated by the negative voltage applied to the substrate 9. An ExB deflector 18 is disposed above the substrate 9 to be inspected, whereby the accelerated secondary electrons 51 are deflected in a predetermined direction. The deflection amount can be adjusted by the voltage applied to the ExB deflector 18 and the strength of the magnetic field. Further, this electromagnetic field can be changed in conjunction with a negative voltage applied to the sample. The secondary electrons 51 deflected by the ExB deflector 18 collide with the reflector 17 under predetermined conditions.
The reflector 17 has a conical shape integrally with a shield pipe of a deflector for an electron beam (hereinafter, referred to as a primary electron beam) for irradiating a sample. When the accelerated secondary electrons 51 collide with the reflector 17, a second secondary electron 52 having an energy of several V to 50 eV is generated from the reflector 17.

The secondary electron detector 7 includes a secondary electron detector 20 inside the evacuated inspection room 2, and a preamplifier 21, an AD converter 22, a light conversion means 23 outside the inspection room 2, It comprises means 24, electric conversion means 25, high voltage power supply 26, preamplifier drive power supply 27, AD converter drive power supply 28, and reverse bias power supply 29. As already described, the secondary electron detector 20 of the secondary electron detector 7 is arranged above the objective lens 16 in the inspection room 2. The secondary electron detector 20, preamplifier 21, AD converter 22, optical conversion means 23, preamplifier drive power supply 27, and AD converter drive power supply 28 are floated to a positive potential by the high voltage power supply 26. The second secondary electrons 52 generated by colliding with the reflection plate 17 are guided to the detector 20 by the attraction electric field. The secondary electron detector 20 includes a second secondary electron 52 generated while the electron beam 19 is irradiated on the substrate 9 to be inspected and then accelerated to collide with the reflector 17. Is detected in conjunction with the scanning timing of the electron beam 19. The output signal of the secondary electron detector 20 is
Amplified by preamplifier 21 installed outside
2 becomes digital data. The AD converter 22 is configured to convert an analog signal detected by the semiconductor detector 20 into a digital signal immediately after being amplified by the preamplifier 21 and transmit the digital signal to the image processing unit 5. Since the detected analog signal is digitized immediately after detection and then transmitted, it is possible to obtain a signal with higher speed and higher SN ratio than before. The substrate 9 to be inspected is mounted on the XY stages 31 and 32, a method of stopping the XY stages 31 and 32 during the inspection and scanning the electron beam 19 two-dimensionally, and a method of performing the inspection during the inspection. Any method of scanning the electron beam 19 linearly in the X direction by moving the Y stages 31 and 32 continuously at a constant speed in the Y direction can be selected. When inspecting a specific relatively small area, it is effective to make the former stage stationary while inspecting it, and when inspecting a relatively large area, it is effective to continuously move the stage at a constant speed and inspect it It is. When the electron beam 19 needs to be blanked, the electron beam 19 is deflected by the blanking deflector 13 so that the electron beam 19 can be controlled so as not to pass through the aperture 14.

In this embodiment, a length measuring device based on laser interference is used as the position measuring length measuring device 34. The positions of the X stage 31 and the Y stage 32 can be monitored in real time and transferred to the control unit 6. Similarly, data such as the number of rotations of the motors of the X stage 31, the Y stage 32, and the rotation stage 33 are also configured to be transferred from each driver to the control unit 6, and the control unit 6 The region and position where the electron beam 19 is irradiated can be accurately grasped on the basis of the position of the electron beam 19, and the position deviation of the irradiation position of the electron beam 19 is corrected by the correction control circuit 43 in real time as necessary. It has become. Further, an area irradiated with the electron beam can be stored for each substrate to be inspected.

As the optical height measuring instrument 35, an optical measuring instrument other than the electron beam measuring method, for example, a laser interferometer or a reflected light measuring instrument for measuring a change in the position of reflected light is used. , The height of the substrate 9 to be inspected mounted on the XY stage 31, 32 is measured in real time. In the present embodiment, the elongated white light that has passed through the slit is irradiated onto the substrate 9 to be inspected through a transparent window, the position of the reflected light is detected by a position detection monitor, and the amount of change in height from the position change is calculated. The calculation method was used. This optical height measuring instrument 35
Based on the measurement data, the focal length of the objective lens 16 for narrowing down the electron beam 19 is dynamically corrected, so that the non-inspection area can always be irradiated with the electron beam 19. In addition, it is possible to configure so that the warp and the height distortion of the substrate 9 to be inspected are measured in advance before the electron beam irradiation, and the correction conditions for each inspection area of the objective lens 16 are set based on the data. It is.

The image processing section 5 comprises a first image storage section 46, a second image storage section 47, an operation section 48, a defect determination section 49, and a monitor 50. The image signal of the substrate 9 to be inspected detected by the secondary electron detector 20 is amplified by a preamplifier 21,
After being digitized by the converter 22, it is converted into an optical signal by the optical converter 23, transmitted by the optical fiber 24, and
After being converted into an electric signal again at 25, the first image storage unit 46
Alternatively, it is stored in the second storage unit 47. The arithmetic unit 48 performs alignment of the stored image signal with the image signal of the other storage unit, normalizes the signal level, performs various types of image processing for removing noise signals, and compares the two image signals. Calculate. The defect determination unit 49 compares the absolute value of the difference image signal calculated and compared by the calculation unit 48 with a predetermined threshold value, and if the difference image signal level is higher than the predetermined threshold value, the pixel is defective. The overall configuration of the circuit pattern inspection apparatus 1 for determining a candidate and displaying the position, the number of defects, and the like on the monitor 50 has been described above. Among them, the configuration and operation of the secondary electron 51 detection means are described. Will be described in more detail. When the primary electron beam 19 enters the solid, it enters the inside and excites electrons in the shell at each depth to lose energy. Also, there occurs a phenomenon in which the reflected electrons in which the primary electron beam is scattered backward travel toward the surface while also exciting the electrons in the solid. Through these multiple processes, the electrons in the shell pass from the solid surface to the surface barrier and turn into secondary electrons with a few volts to 50 eV of energy and exit into the vacuum. As the angle between the primary electron beam and the solid surface becomes smaller, the ratio of the entrance distance of the primary electron beam to the distance from the position to the solid surface becomes smaller, and secondary electrons are more likely to be emitted from the surface. Therefore, the generation of secondary electrons depends on the angle between the primary electron beam and the solid surface, and the amount of secondary electrons generated is information indicating unevenness and material of the sample surface.

FIG. 2 shows a main configuration diagram of the electron optical system 3 for detecting the secondary electrons 51 and the secondary electron detector 7. The primary electron beam 19 is irradiated on the sample substrate 9 to generate secondary electrons 51 on the surface of the sample substrate 9. The secondary electrons 51 are accelerated by the negative high voltage applied to the sample substrate 9. In this embodiment,
The negative voltage applied to the sample substrate 9 was set to 3.5 keV. The secondary electrons 51 are accelerated and converged and deflected by the objective lens 16 and the ExB deflector 18 and collide with the reflector 17. The reflector 17 is integrated with a shield pipe for preventing a voltage applied to the detector from affecting the primary electron beam.
It has a tapered conical shape. The material is CuBeO, which has a secondary electron multiplication effect as a configuration that emits secondary electrons on average about 5 times the number of irradiated electrons. Due to the collision of the accelerated secondary electrons 51, several V to 5
Second secondary electrons 52 having an energy of 0 eV are generated.
The second secondary electrons 52 are attracted to the front surface of the secondary electron detector 20 by the attraction electric field generated by the secondary electron detector 20 and the attraction electrode 53 attached to the secondary electron detector 20. In this embodiment, since the secondary electrons 51 generated on the surface of the sample substrate 9 are deflected about 5 degrees toward the secondary electron detector 20 by the ExB deflector 18, the voltage and magnetic field applied to the ExB deflector 18 When the negative high voltage applied to the sample substrate 9 was 3.5 keV, the electrode spacing was 35 V, 1.0 × 10 ⁻⁶ T (tesla), and 10 mm, respectively. This electromagnetic field can be variably set in conjunction with a negative high voltage applied to the sample substrate 9. With the above configuration and conditions, the secondary electrons 51 generated on the surface of the sample substrate 9 by the small angle deflection of about 5 degrees, the acceleration by the voltage of -3.5 keV applied to the sample substrate 9, and the convergence by the objective lens.
When passing through the ExB deflector 18, 95% or more of the secondary electrons 51 can be passed through the reflector 17, and the 95% of the secondary electrons 51 are multiplied by about five times to the second secondary electrons 52. Was able to occur.

As the secondary electron detector 20, in this embodiment, PI
An N-type semiconductor detector was used. PIN type semiconductor detector
The responsiveness is faster than that of the PN type semiconductor detector. By applying a reverse bias voltage from a reverse bias voltage power supply, a high frequency secondary electron signal with a sampling frequency of up to 100 MHz could be detected. The PIN semiconductor detector 20 and a preamplifier 21, an AD converter 22, and a light conversion unit 23, which are detection circuits,
Was floated to 6 keV, and the suction electrode 53 was set to 0 V. Incidentally, the effective size of the PIN-type semiconductor detector 20 is 4 mm ^□
It is. The second secondary electrons 52 generated by the reflection plate 17 are attracted to the PIN semiconductor detector 20 by an attraction electric field, enter the PIN semiconductor detector 20 in a high energy state, and have a constant energy at the surface layer. After the disappearance, an electron-hole pair is generated,
It becomes a current and is converted into an electric signal. Used in this example
The PIN semiconductor detector 20 has very high signal detection sensitivity,
Considering the energy loss in the surface layer, the second secondary electrons 52 that are accelerated to 6 keV by the attracting electric field and incident are about 1000
It becomes a double amplified electric signal. This electric signal is further amplified by the preamplifier 21, and the amplified signal (analog signal) is converted into a digital signal by the AD converter 22. Here, a 12-bit AD converter having a clock frequency of 100 MHz is used. The output of the AD converter 22 was transmitted in parallel by providing an optical conversion unit 23, a transmission unit 24, and an electric conversion unit 25 for each bit. According to this configuration, each transmission means only needs to have the same transmission speed as the clock frequency of the AD converter 22. Now, the signal converted to the optical digital signal by the optical conversion unit 23 is transmitted to the electric conversion unit 25 by the optical transmission unit 24, where it is converted from the optical digital signal to an electric signal again and sent to the image processing unit 5. . The transmission after converting to an optical signal is PI
This is because the components from the N-type semiconductor detector 20 to the light conversion means 23 are floated to a positive high potential by the high-voltage power supply 26. Can be converted to a signal. In this embodiment, a light emitting element for converting an electric signal into an optical signal is used as the light converting means 23, an optical fiber cable for transmitting the optical signal is used as the transmitting means 24, and the optical signal is converted to an electric signal as the electric converting means 25. A light receiving element was used. Since the optical fiber cable is formed of a highly insulating material, a signal at a high potential level can be easily converted to a signal at a ground potential level. Furthermore, since the digital signal is optically transmitted, there is no signal degradation at the time of optical transmission. As a result, it is possible to obtain an image less affected by noise as compared with the conventional technique of optically transmitting an analog signal. With these configurations, when the incident current of the second secondary electrons 52 to the PIN semiconductor detector 20 is 100 nA, a high-frequency secondary electron signal having a sampling frequency of 100 MHz can be detected with a signal SN ratio of 50 or more. Now you can.

In the above embodiment, the semiconductor detector 20
Has been applied with a reverse bias voltage by the reverse bias voltage power supply 29, but may be configured so as not to apply the reverse bias voltage. In this embodiment, a PIN semiconductor detector is used as the semiconductor detector 20, but another type of semiconductor detector, for example, a Schottky semiconductor detector or an avalanche semiconductor detector may be used. Moreover, if conditions such as responsiveness and sensitivity are satisfied, MCP (micro channel plate) can be used as a detector.

Next, the operation in the case where the circuit pattern inspection apparatus 1 inspects a semiconductor wafer on which pattern processing in the manufacturing process has been performed as the sample 9 to be inspected will be described.
First, although not shown in FIG. 1, the semiconductor wafer is loaded into the sample exchange chamber by the means for transporting the semiconductor wafer 9. Therefore, the semiconductor wafer 9 is mounted on a sample holder, held and fixed, and evacuated, and when the sample exchange chamber reaches a certain degree of vacuum, the semiconductor wafer 9 is transferred to the inspection room 2 for inspection. In the inspection room 2, the sample stage 30, the XY stages 31, 3
2. The sample holder is placed on the rotating stage 33 and held and fixed. The set semiconductor wafer 9 is arranged at predetermined first coordinates below the optical microscope unit 4 by moving the XY stages 31, 32 in the X and Y directions based on predetermined inspection conditions registered in advance, An optical microscope image of a circuit pattern formed on the semiconductor wafer 9 is observed by the monitor 50,
It is compared with an equivalent circuit pattern image at the same position stored in advance for position rotation correction, and a position correction value of the first coordinate is calculated. Next, it moves to a second coordinate where a circuit pattern equivalent to the first coordinate exists at a fixed distance from the first coordinate,
Similarly, the optical microscope image is observed and compared with the circuit pattern image stored for position rotation correction, and the position correction value of the second coordinates and the amount of rotation deviation with respect to the first coordinates are calculated. The rotation stage 33 corresponds to the calculated rotation deviation amount.
Rotates and corrects the amount of rotation. In the present embodiment, the amount of rotation deviation is corrected by the rotation of the rotation stage 33. However, without using the rotation stage 33, correction can also be made by a method of correcting the scanning deflection position of the electron beam based on the calculated amount of rotation deviation. . In this optical microscope image observation, a circuit pattern that can be observed not only with an optical microscope image but also with an electron beam image is selected. In addition, for future position correction, the first coordinate, the displacement amount of the first circuit pattern by the optical microscope image observation, the second coordinate, the displacement amount of the second circuit pattern by the optical microscope image observation are It is stored and transferred to the control unit 6.

Further, a circuit pattern formed on the semiconductor wafer 9 to be inspected is observed by using an image obtained by an optical microscope, and the position of the chip of the circuit pattern on the semiconductor wafer 9, the distance between the chips, or the memory cell The repetition pitch of the repetition pattern like is measured in advance,
The measured value is input to the control unit 6. In addition, a chip to be inspected on the semiconductor wafer 9 to be inspected and a region to be inspected in the chip are set from an image of the optical microscope, and input to the control unit 6 in the same manner as described above. The image of the optical microscope can be observed at a relatively low magnification, and when the surface of the semiconductor wafer 9 to be inspected is covered with, for example, a silicon oxide film, the image can be transmitted down to the base and observed. This is because the arrangement of the chips and the layout of the circuit patterns in the chips can be easily observed, and the inspection area can be easily set.

As described above, when the preparatory work such as the predetermined correction work and the inspection area setting by the optical microscope unit 4 is completed, the semiconductor wafer 9 is moved below the electron optical system 3 by moving the X stage 31 and the Y stage 32. Moved to When the semiconductor wafer 9 is placed below the electron optical system 3, the same operation as the correction operation and the setting of the inspection area performed by the optical microscope unit 4 is performed using an electron beam image. The acquisition of the electron beam image at this time is performed by the following method. Based on the coordinate values stored and corrected in the alignment by the optical microscope image, the electron beam 19 is scanned two-dimensionally in the XY direction by the scanning deflector 44 on the same circuit pattern as observed in the optical microscope unit 4. Irradiated. By the two-dimensional scanning of the electron beam, secondary electrons 51 generated from the observed region are detected by the configuration and operation of each unit for detecting the secondary electrons, thereby obtaining an electron beam image. Since simple inspection position confirmation, position adjustment, and position adjustment have already been performed using optical microscope images, and rotation correction has also been performed in advance, positioning and position correction have higher resolution and higher magnification than optical images, and have higher accuracy. , Rotation correction can be performed.
When the sample 9 is irradiated with the electron beam 19, the portion is charged. In order to avoid the influence of the electrification at the time of the inspection, a circuit pattern to be irradiated with the electron beam 19 in the pre-inspection preparation work such as the position rotation correction or the inspection area setting selects a circuit pattern existing outside the inspection area in advance. Alternatively, an equivalent circuit pattern in a chip other than the chip to be inspected can be automatically selected from the control unit 6. This allows the electron beam 19 to be
Does not affect the inspection image.

Next, an inspection is performed. The conditions of the electron beam 19 irradiating the semiconductor wafer 9 to be inspected during the inspection were obtained by the following method. First, generally, the SN ratio in an electron beam image has a correlation with the square root of the number S of irradiated electrons per unit pixel of the electron beam irradiated on the sample. When comparing and inspecting images, the S / N ratio of the electron beam image needs to be a value that can detect the signal amount of the normal part and the defect part, and the minimum S / N ratio needs to be 10 or more, and preferably 50 or more. is necessary. As described above, the S / N ratio of the electron beam image is correlated with the square root of the number S of irradiated electrons per unit pixel of the electron beam irradiated on the sample.
To obtain an N ratio of 10, at least 100 or more electrons are required per single pixel, and to obtain an S / N ratio of 50, at least 2500 or more electrons must be irradiated.

The main purpose of applying the circuit pattern inspection method of the present invention is to detect minute defects which cannot be detected by the optical pattern inspection method as described above. It was necessary to recognize the difference. In order to achieve this, in this embodiment, the pixel size is set to 0.1 μm. Therefore, from the minimum required number of electrons per single pixel and the pixel size, the required electron beam irradiation amount per unit area is 0.16 μC / cm ² ,
Preferably, it is 4 μC / cm ² . This electron irradiation amount is
In order to obtain the electron beam current of EM (about several pA to several hundred pA), for example, the electron beam current of 20 pA causes the area of 1 cm ²
To irradiate the electrons 0.16μC / cm ² requires a 8000 seconds, to further irradiation of electrons 4μC / cm ² requires 200,000 seconds. However, the inspection speed required for inspection of a circuit pattern, for example, inspection of a semiconductor wafer is 600 s / cm ² or less.
It is preferably at most 300 s / cm ² , and if the inspection time is longer than this, the practicality of inspection in semiconductor manufacturing becomes extremely low. Therefore, in order to satisfy these conditions and irradiate the sample with a necessary electron beam in a practical inspection time, the electron beam current must be at least 270 pA (1.6 μC / cm ² , 600 s /
cm ² ) or more, preferably 13 nA (4 μC / cm ² , 300 s / cm ² )
It is necessary to set above. Therefore, in the circuit pattern inspection method of the present embodiment, an electron beam image is formed by one scan using a high current electron beam of 13 nA or more.

Forming an electron beam image with a single scan using an electron beam having a large current (270 nA or more, preferably 13 nA or more), which is about 100 times or more that of a normal SEM, can reduce the inspection speed. It has been determined by the present invention that not only is it necessary from the point of view, but also for the reasons described below, that the base film or surface pattern is particularly necessary for inspecting a circuit pattern formed of an insulating material.

When an electron beam image of a circuit pattern having an insulating material is obtained by a normal SEM, an electron beam image different from the actual shape is obtained due to the influence of charging, and the contrast often differs completely depending on the field magnification. This is done by repeatedly scanning the weak electron beam current (several pA to several hundred pA) locally, or when changing the field magnification, to exceed the electron dose required for image formation for focus and astigmatism correction. This is because, when the electron beam is locally scanned, the electron beam irradiation amount is intensively applied to a certain location, and the charge of that portion becomes uneven. As a result, the quality of an electron beam image of a pattern formed of an insulating material is completely different depending on the field of view, and such an image cannot be applied to an inspection for comparing electron beam images. Therefore, in order to be able to inspect a circuit pattern having an insulating material in the same way as a circuit pattern made of a conductive material, a single scan is performed using a high-current electron beam that is about 100 times or more that of a normal SEM. An electron beam image was formed. That is, in the present embodiment, the amount of electron beam irradiation on the sample per unit area and per unit time is constant, and the electron dose required to form an image quality sufficient for performing the comparative inspection, and An electron beam image is obtained by scanning the electron beam once at a scanning speed suitable for the practicality of the inspection method for semiconductor wafers and the like. Then, as described above, an electron beam image of a circuit pattern having an insulating material was obtained by one scan using a large current electron beam that is about 100 times or more as compared with a normal SEM, and an electron beam image in one field of view was obtained. It has been confirmed that the amount of charge and the contrast of the image are different depending on the constituent materials and structures of the various circuit patterns constituting, and that the same image contrast can be obtained between the same patterns of the same kind of material. In this embodiment, the scanning with the large current electron beam is performed only once. However, the scanning may be performed several times as long as the above-described operation is substantially realized.

FIGS. 3 (a), 3 (b) and 3 (c) schematically show the secondary electron generation efficiency and the degree of charging when a point P of the sample is irradiated with an electron beam. The vertical axis in FIG. 3A shows the relative intensity of the primary electron beam irradiated on the sample, and the horizontal axis shows time and distance. In FIG. 3B, the vertical axis indicates the relative degree of charging of the sample, and the horizontal axis indicates time. The vertical axis in FIG. 3C indicates the relative amount of secondary electrons generated, and the horizontal axis indicates time. When the sample is irradiated with an electron beam by the inspection method of the present invention described above, the electron beam scans and passes the point P at a high speed. The point where the intensity of the electron beam is relatively large during 10 ns is the point P
Pass through. In this embodiment, the scanning speed of the electron beam is 100 MHz /
Since it is set to a pixel, this 10 ns corresponds to one pixel. Further, in this embodiment, since one pixel is set to 0.1 μm ^□ , this 10 ns corresponds to 0.1 μm. At point P on the sample,
When the sample is irradiated with an electron beam at the timing of 3 (a),
The sample is charged as shown in FIG. The degree of charge and the degree of discharge with the passage of time vary depending on the material of the sample. When the sample is an insulator, the charge remains even after the passage of the electron beam, and in some cases, the charge is not discharged until a long time elapses. As shown in FIG. 3C, secondary electrons are generated from the moment when the primary electron beam is irradiated on the sample. The amount of secondary electrons generated depends on the secondary electron generation efficiency determined for each material,
Since it depends on the degree of charging shown in (b), for example, in the first scan, the amount of secondary electrons shown in FIG.
If the degree of charging in the second scan is different from the degree of the first scan, the amount of generated secondary electrons is also different.

Next, irradiation conditions that affect the contrast of an electron beam image will be described. The contrast of an electron beam image is formed by the amount of secondary electrons generated and detected by an electron beam irradiated on a sample. For example, a difference in the amount of secondary electrons generated due to a difference in material or the like results in a difference in brightness. .
4 (a) and 4 (b) are graphs showing the effect of electron beam irradiation conditions on the contrast. FIG. 4 (a) shows the case where the irradiation conditions are appropriate, and FIG. 4 (b) shows the irradiation conditions. Indicates an inappropriate case. The vertical axis indicates the degree of charging, which has a large correlation with the brightness of the image, and the horizontal axis indicates the irradiation time of the electron beam. The solid line A indicates the case where photoresist was used for the sample, and the dotted line B indicates the case where wiring material was used for the sample.

As shown in FIG. 4A, in the time region C where the irradiation time is short, the change in brightness of each material is small, and in the time region D where the irradiation time is relatively long, the change in brightness due to the irradiation time is large. Finally, in the time region E where the irradiation time is long, the brightness variation due to the irradiation time is reduced again. From FIG. 4B, when the irradiation conditions are not appropriate,
Even in the time region C where the irradiation time is short, the fluctuation in brightness with respect to the irradiation time is large, and it is difficult to obtain a stable image. Therefore, in order to acquire a stable and fast electron beam image, it is important to acquire an image under the irradiation conditions of FIG.

The conditions for irradiating the sample with the electron beam are as follows.
The irradiation amount of the electron beam per unit area, the electron beam current value, the scanning speed of the electron beam, and the irradiation energy of the electron beam for irradiating the sample are exemplified. Therefore, it is necessary to determine the optimum values of these parameters for each circuit pattern shape and material.
For this purpose, it is necessary to freely adjust and control the irradiation energy of the electron beam irradiating the sample. Therefore, as described above, in this embodiment, the high-voltage power supply 3
Apply a negative voltage to decelerate the primary electrons by 6 and
By adjusting this voltage, the irradiation energy of the electron beam 19 can be appropriately adjusted. This allows
When changing the acceleration voltage applied to the electron gun 10, the axial change of the electron beam 19 occurs and various adjustments are required,
In this embodiment, similar effects can be obtained without performing such adjustment.

Next, a method of scanning the electron beam 19 for forming an electron beam image for performing the inspection according to the present invention will be described. In a normal SEM, an electron beam is two-dimensionally scanned while a stage is stationary, and an image of a certain area is formed. According to this method, when inspecting a wide area thoroughly, for each image acquisition area, in addition to the time for scanning the electron beam at rest, the time obtained by adding the acceleration / deceleration / position setting of the stage as the movement time. It takes. Therefore, a long time is required for the entire inspection time. Therefore, in the present invention, while moving the stage continuously in one direction at a constant speed, the electron beam is scanned in one direction at a high speed in a direction orthogonal to or intersecting with the stage movement direction, so that the image of the inspection area can be obtained. The acquired inspection method was used. Thus, the electron beam acquisition time for one scanning width of the predetermined distance is only the time for the stage to move the predetermined distance.

FIG. 5A shows that when the Y stage 32 is continuously moving at a constant speed in the Y direction by the above method, the electron beam 19 is not moved.
Shows an example of a scanning method. When the electron beam 19 is scanned by the scanning deflector 44, the electron beam is irradiated on the semiconductor wafer 9 as a sample in only one direction indicated by a solid line, and is applied to the semiconductor wafer 9 during the return of the electron beam indicated by a broken line. By blanking so that the electron beam 19 is not irradiated, the semiconductor wafer 9 can be uniformly and temporally irradiated with the electron beam. Blanking is performed by deflecting the electron beam 19 by the blanking deflector 13 so as not to pass through the aperture 14.

FIG. 5B shows a method in which the electron beam 19 reciprocates at a constant speed as an example of another scanning method. When the electron beam 19 is scanned at a constant speed from one end to the other end, the XY stages 31 and 32 are fed by one pitch, and the electron beam is scanned in the opposite direction to the original end at a constant speed. In the case of this method, the time for turning back the electron beam can be omitted.

The area or position where the electron beam is irradiated is obtained by transferring the measurement data of the position monitor length measuring device 34 installed on the XY stages 31 and 32 to the control unit 6 every moment. , It is grasped in detail. In this embodiment, a laser interferometer is employed. Similarly, the fluctuation of the height of the region or position irradiated with the electron beam 19 can be grasped in detail by transferring the measurement data of the optical height measuring device 35 to the control unit 6 every moment. Based on these data, the deviation of the irradiation position or the focal position of the electron beam is calculated, and the correction control circuit 43 automatically corrects these deviations. Therefore, a highly accurate and precise method of operating the electron beam is secured.

According to the scanning method of the electron beam 19 described above, the entire surface of the semiconductor wafer 9 as a sample or an inspection area set in advance is irradiated with the electron beam, and the secondary electrons 51 are irradiated according to the principle described above.
Is generated, and the secondary electrons 51 and 52 are detected by the method described above. A high-quality image can be obtained by the configuration and operation of each unit described above. For example, by irradiating the reflector 17 with the above-described configuration and method, it is possible to obtain a secondary electron multiplying effect of about 20 times, and to suppress the influence of aberration on the primary electron beam more than the conventional method. Can be. Further, by adjusting the electromagnetic field applied to the ExB deflector in the same configuration, the second secondary electron beam obtained by irradiating the reflection plate 17 with the reflected electrons generated from the surface of the semiconductor wafer 9 in the same manner as the secondary electrons is obtained. The detection of the electrons 52 can be easily performed. Also, ExB
By adjusting and controlling the electric and magnetic fields of the deflector 18 in conjunction with the negative high voltage applied to the sample, secondary electrons can be detected efficiently even under irradiation conditions that differ for each sample. Also,
The method of detecting secondary electrons using the semiconductor detector 20, digitizing the detected image signal immediately after detection, and then transmitting the light, reduces the effect of noise generated in various conversions and transmissions, and reduces the S / N ratio. High image signal data can be obtained. In the process of forming an electron beam image from the detected signal, the image processing unit 5 outputs a detection signal every time corresponding to a desired pixel at the electron beam irradiation position designated by the control unit 6 according to the signal level. The stored brightness gradation values are sequentially stored in the first storage unit 46 or the second storage unit 47. An electron beam image of the sample circuit pattern is two-dimensionally formed by associating the electron beam irradiation position with the amount of secondary electrons associated with the detection time. In this way, SN with high accuracy
A high-quality electron beam image with a high ratio can be acquired.
In this embodiment, the inspection method and apparatus for detecting secondary electrons generated from the sample have been described. However, backscattered electrons and reflected electrons are generated from the sample simultaneously with the secondary electrons. These secondary charged particles as well as secondary electrons can be similarly detected as electron beam image signals.

When the image signal is transferred to the image processing unit 5,
The electron beam image of the first area is stored in the first storage unit 46.
The arithmetic unit 48 performs positioning of the stored image signal with the image signal of the other storage unit, normalization of the signal level, and various types of image processing for removing noise signals. continue,
The electron beam image of the second area is stored in the second storage unit 47, and while performing the same arithmetic processing, the same circuit pattern and the same location of the electron beam image of the second area and the first electron beam image are stored. The image signals are compared and calculated. The defect determination unit 49 compares the absolute value of the difference image signal calculated and compared by the calculation unit 48 with a predetermined threshold value, and if the difference image signal level is higher than the predetermined threshold value, the pixel is defective. It is determined as a candidate, and the position, the number of defects, and the like are displayed on the monitor 50. Next, thirdly, the electron beam image of the region is stored in the first storage unit 46, and the same operation is performed while performing a comparison operation with the electron beam image of the second region previously stored in the second storage unit 47. Is determined. Thereafter, by repeating this operation, image processing is performed on all inspection areas.

By obtaining a high-precision and high-quality electron beam image by the above-described inspection method and performing comparative inspection, it is possible to detect a minute defect occurring on a fine circuit pattern in an inspection time conforming to practicality. Can be. In addition, by acquiring an image using an electron beam, light transmitted by the optical pattern inspection method cannot be inspected, and a pattern formed by a silicon oxide film or a resist film, and foreign materials and defects of these materials can be removed. Be able to inspect. Further, the inspection can be stably performed even when the material forming the circuit pattern is an insulator.

(Embodiment 2) In this embodiment, an application example in which a semiconductor wafer is inspected using the circuit pattern inspection apparatus 1 and the method of the present invention will be described. FIG. 6 shows a manufacturing process of the semiconductor device. As shown in FIG. 6, the semiconductor device repeats many pattern forming steps. The pattern forming process is roughly composed of steps of film formation, photosensitive resist coating, light exposure, development, etching, resist removal, and cleaning. If the manufacturing conditions for processing are not optimized in each of these steps, the circuit pattern of the semiconductor device formed on the substrate will not be formed properly. FIGS. 7A and 7B schematically show circuit patterns formed on a semiconductor wafer in a manufacturing process.
FIG. 7A shows a normally processed circuit pattern.
(B) shows a pattern in which a processing failure has occurred. For example, if an abnormality occurs in the film forming process of FIG. 6, particles are generated and adhere to the surface of the semiconductor wafer, resulting in an isolated defect or the like in FIG. 7B. In addition, if the conditions such as the focus of the exposure apparatus and the exposure time for the exposure during the exposure are not optimal, there may be places where the amount or intensity of the light irradiated by the resist is too large or where the resist is insufficient. Shorts, disconnections, and thinner patterns occur. If there is a defect in the mask reticle at the time of exposure, a similar pattern shape abnormality occurs at the same location for each shot which is a unit of exposure. In addition, when the etching amount is not optimized, and due to a thin film or a particle generated during the etching, a short circuit, a protrusion, an isolated defect, a defective opening, or the like occurs. At the time of cleaning, fine particles are generated due to contamination of the cleaning layer, re-adhesion of the peeled film or foreign matter, and uneven thickness of the oxide film is easily generated on the surface due to the condition of drainage during drying.

Therefore, by applying the circuit pattern inspection method and apparatus 1 of the first embodiment to a semiconductor device manufacturing process, occurrence of an abnormality can be detected with high accuracy and at an early stage. Can take
Processing conditions can be optimized so that these defects do not occur. For example, if a circuit pattern inspection process is performed after the development process and a defect or disconnection of the photoresist pattern is detected, it is estimated that the exposure condition and the focus condition of the exposure apparatus in the exposure process are not optimal, Alternatively, these conditions are immediately improved by adjusting the exposure amount. In addition, by examining whether or not these defects are common among the shots from the defect distribution, the defects of the photomask and reticle used for pattern formation are estimated, and inspection and replacement of the photomask and reticle are performed. Is implemented sooner. The same applies to other steps. By applying the circuit pattern inspection method and apparatus of the present invention and performing the inspection step,
Various defects are detected, and the cause of the abnormality in each manufacturing process is estimated based on the content of the detected defects.

As described above, by performing the circuit pattern inspection method and apparatus 1 in-line in the process of manufacturing a semiconductor device, it is possible to detect fluctuations in various manufacturing conditions and occurrence of abnormalities within the inspection real time. Failure can be prevented from occurring. Further, by applying the circuit pattern inspection method and apparatus, it is possible to predict the non-defective product acquisition rate of the entire semiconductor device from the degree and frequency of occurrence of detected defects, and to improve the productivity of the semiconductor device. become.

(Embodiment 3) In the third embodiment of the present invention,
As shown in FIG. 8, the objective lens 16 in the electron optical system 3 was installed above the secondary electron detector 20, and the other configuration of the inspection device was the same as in the first embodiment. FIG. 8 shows an enlarged partial view inside the inspection room 2 of the circuit pattern inspection apparatus. Hereinafter, the operation of the configuration of the third embodiment will be described.
In the same manner as in the first embodiment, an electron beam 19 is applied to the substrate 9 to be inspected. As in the first embodiment, a negative high voltage is applied to the sample inspection substrate 9. In this embodiment,
The negative voltage for primary electron deceleration applied to the sample substrate 9 was set to -3.5 keV. By the electron beam irradiation, secondary electrons 51 are generated from the surface of the sample substrate 9 by the action already described. Secondary electrons 51 generated on the surface of the sample substrate 9
Is accelerated to 3.5 keV due to the negative voltage applied to the substrate, the secondary electrons 51 generated on the substrate surface 9 are aligned in the same direction, and the accelerated secondary electrons 51 colliding with the reflector 17 Since the spread of 51 is as small as several millimeters,
Even if is not converged by the objective lens 16, the detection efficiency does not decrease. Therefore, even in the configuration of the present embodiment in which the objective lens 16 is arranged at a position where only the primary electron beam 19 is converged, the accelerated secondary electrons 51 collide with the reflecting plate 17 to generate the second secondary electrons 52. Since detection and signal conversion can be performed with high efficiency, a high-quality electron beam image can be obtained. According to the present embodiment, the focal length of the objective lens 16 is longer than that of the first embodiment. As a result, even if the primary electron beam 19 is largely deflected as compared with the first embodiment, the resolution and the resolution can be improved. Accuracy can be maintained. Other configurations and operations are the same as those of the first embodiment, and thus will not be described here.

(Embodiment 4) As a fourth embodiment, a reflecting plate
17 was formed by curving, and the other parts were formed in the same manner as in the first embodiment. FIG. 9 is an enlarged partial view showing the structure of the reflector. In this embodiment, since the shape of the reflector 17 integrated with the shield pipe is curved, the sample substrate 9 is irradiated with the electron beam 19, and the secondary electrons 5 generated on the surface of the sample substrate 9 are exposed.
1 is accelerated by the negative high voltage applied to the sample substrate 9, is deflected by the ExB deflector 18, and irradiates the reflection plate 17, when the second secondary electron 52 according to the position of the reflection plate 17 Is changed, and as a result, the second secondary electrons 52 generated on any part of the reflector 17 are also detected by the semiconductor detector 20.
Makes it easier to supplement. Therefore, when the secondary electrons 51 accelerated by the ExB deflector 18 are deflected, the selection range of the deflection angle is widened, and even if the generation angle of the secondary electrons 51 generated on the surface of the sample substrate 9 is widened, it is high. Since signals can be detected with high efficiency, a high-quality electron beam image can be obtained. For other configurations and operations,
Since it is the same as the first embodiment, the description is omitted here.

Fifth Embodiment As a fifth embodiment, the sample substrate is irradiated with the second charged particle beam to charge the substrate to be inspected, and the potential of the member forming the circuit pattern of the substrate to be inspected is stabilized. The configuration of the method and apparatus for performing the inspection afterwards will be described below.

FIG. 10 shows the configuration of a circuit pattern inspection apparatus 1 according to the fifth embodiment. The circuit pattern inspection apparatus 1 includes an inspection chamber 2 in which the chamber is evacuated, a first spare chamber (not shown in this embodiment) for transferring a sample into the inspection chamber 2, and a second charged particle. A second preliminary room 100 for irradiating the radiation, a control unit 6 and an image processing unit 5; the first preliminary room (not shown) and the second preliminary room 100 Are configured to be independently evacuated. The second preliminary chamber 100 includes an electron gun 101, a lens 102, and a large-angle deflection coil 103. The inside of inspection room 2 is roughly divided,
It comprises an electron optical system 3, a secondary electron detector 7, a sample chamber 8, and an optical microscope (not shown). The electron optical system 3 includes an electron gun 10, an electron beam extraction electrode 11, a condenser lens 12,
It comprises a blanking deflector 13, a scanning deflector 15, an aperture 14, an objective lens 16, a reflection plate 17, and an ExB deflector 18. In the secondary electron detector 7, a secondary electron detector 20 is arranged above the objective lens 16 in the inspection room 2. The output signal of the secondary electron detector 20 is amplified by a preamplifier 21 installed outside the inspection room 2, and converted into digital data by an AD converter 22. The sample chamber 8 has a sample stage 30, an X-Y stage 31.3
2. It is composed of a rotating stage 33, a length monitor 34 for position monitoring, and a height measuring device 35 for a substrate to be inspected. The optical microscope (not shown) is provided near the electron optical system 3 in the inspection room 2 and at a position away from the electron optical system 3 so as not to affect each other. Is known. The captured electron beam image or optical image is displayed on the monitor 50. Operation commands and operation conditions of each unit of the device are input and output from the control unit 6. The control unit 6 has an acceleration voltage, an electron beam deflection width, a deflection speed,
The conditions such as the timing of signal acquisition of the secondary electron detector and the moving speed of the sample stage are input so that they can be set arbitrarily or selectively according to the purpose. The control unit 6 monitors the position and height deviations from the signals of the position monitor length measuring device 34 and the substrate height measuring device 35 to be inspected by using the correction control circuit 43, and generates a correction signal from the result. Then, a correction signal is sent to the objective lens power supply 45 and the scanning deflector 44 so that the electron beam 19 is always irradiated to a correct position. The image processing unit 5 includes an image storage unit 46
47, a calculation unit 48, and a defect determination unit 49. The electron beam image signal detected by the secondary electron detection unit 7 is stored in the image storage unit, subjected to various operations, and then compared with other adjacent electron beam images to extract only a defective portion.

Hereinafter, the second spare room 100 will be described in detail. Electron gun 101 and lens installed in spare room 100
Reference numeral 102 denotes a position in the vicinity of the electron optical system 3 in the inspection room 2 but at a distance so as not to affect each other. The substrate to be inspected 9 is loaded into a first spare chamber (not shown), which is a sample exchange chamber, by the substrate transfer means. Therefore, the substrate to be inspected is mounted on the sample holder, held and fixed, and evacuated. When the first preliminary chamber, that is, the sample exchange chamber reaches a certain degree of vacuum, the substrate to be inspected together with the sample holder is moved to the second auxiliary chamber. Transferred to room 100. The second spare chamber 100 is evacuated in advance. In the second preliminary chamber 100, the electron beam 101 for preliminary irradiation is irradiated from the electron gun 101 onto the substrate 9 to be inspected. Electron gun
101 is suitable for a large light source and a large current. In this embodiment, an oxide cathode is used in which a low work function oxide used in a CRT monitor is heated by a heater to emit thermoelectrons. The electron lens 102 is provided to limit the irradiation area of the preliminary irradiation electron beam 104 from the electron gun 101 to a certain extent, and the diameter of the preliminary irradiation electron beam 104 is several centimeters to several millimeters on the substrate 9 to be inspected. Can be narrowed down. The large-angle deflector 103 is capable of deflecting at a very wide angle as used in CRT monitors such as televisions. Even with the above size, the pre-irradiation electron beam 104 can scan the substrate 9 to be inspected to every corner of the sample. At this time, the pre-irradiation electron beam is used so that the irradiation amount of the electron beam is uniform over time and space.
The current of 104, the number of scans, and the scan speed are kept constant. The irradiation energy of the pre-irradiation electron beam 104 in the pre-room 100 is controlled by the electron beam 19 irradiated by the inspection electron optical system 3 in the inspection room 2.
And the same irradiation energy. During the irradiation of the electron beam 104 in the second preliminary chamber 100 described here, another substrate 9 ′ to be inspected is set in the adjacent inspection room 2, and the inspection is performed by the electron beam 19 from the electron gun 10. ing. That is, inspection room 2
The second spare room 100 is configured so that the operation can proceed independently. Electron beam 1 for preliminary irradiation in second preliminary room 100
Since the irradiation of 04 can be performed in a time sufficiently shorter than the time required for the inspection, even if the pre-processing of the substrate 9 to be inspected in the second preliminary chamber 100, the time required for the entire inspection hardly increases. .

By irradiating the substrate 9 to be inspected with the preliminary electron beam 104, the substrate 9 is charged. As already described in the first embodiment, the charging state of the substrate 9 to be inspected changes depending on the time and energy for irradiating the electron beam, and as a result, the contrast of the image fluctuates. FIG. 11 (a) and FIG.
FIG. 11B shows the effect of the electron beam irradiation time on the contrast. FIG. 11A shows a case where the photoresist (solid line A) and the wiring material (dotted line B) are used for the sample shown in FIG. 4A, and FIG. 11B shows a case where the photoresist (solid line A) is used for the sample. The case where a silicon oxide film (dotted line C) is used is shown. In the region F where the irradiation time is short, the change in brightness of each material is small, and in the time region G where the irradiation time is relatively long, the change in brightness with time becomes largely unstable, and in the time region H where the irradiation time is long. Again, time-dependent brightness variations are reduced. In the combination of the two samples shown in FIG. 11A, the difference in brightness between the two materials, that is, the contrast D is larger in the time domain F than in the time domain F.
In the combination of (b), the contrast E ′ is larger in the time domain H. Since the inspection of the circuit pattern is a comparative inspection, it is advantageous to detect a defect if the contrast between the underlying material forming the pattern and the surface material is large. It can be seen that the irradiation time or charging state for obtaining an electron beam with stable brightness and high contrast differs depending on the combination of materials for forming the circuit pattern. In the first embodiment, the irradiation time zone F in FIG.
Inspection was carried out in the pre-irradiation electron beam 104 of this embodiment
, The substrate 9 to be inspected is uniformly charged, whereby the charged state in the time region H can be set in advance before the inspection. Thereafter, the inspection room 2 irradiates an electron beam 19 to acquire an electron beam image, and inspects a circuit pattern.

The preliminary irradiation electron beam 104 in the second preliminary chamber 100
When the irradiation of the sample is completed, the substrate 9 to be inspected is
0, the sample holder is placed on the XY stages 31 and 32 and the rotary stage 33, and is held and fixed. Subsequent inspection methods are the same as in the first embodiment, and a description thereof will be omitted.
By performing the inspection according to the present embodiment, for each combination of materials, an electron beam image under optimal conditions for performing the comparative inspection, that is, an electron beam image in which the brightness is stable and the contrast of the member forming the circuit pattern is large. Could be obtained. Further, according to the inspection method described in the first embodiment, the SN
Because high-quality images with a large ratio can be obtained at high speed,
As a result, a high-accuracy and high-sensitivity fine defect detection can be performed without erroneously detecting a non-defect portion even in an inspection using an insulating material or the like.

(Embodiment 6) In the sixth embodiment, the preliminary irradiation electron beam 104 is applied to the substrate 9 without providing the second preliminary chamber 100 for preliminary irradiation described in the fifth embodiment. The configuration and method of irradiation will be described. The basic configuration is the same as that of the first embodiment, but a second electron source is added to the electron optical system 3. FIG. 12 shows a main configuration diagram of the inspection room 2 of the inspection device 1. Refer to the first embodiment for details of the control unit 6, the image processing unit 5, the detection system, and the like. The electron beam emitted from the second electron gun 110 is introduced between the objective lens 16 and the condenser lens 12 of the electron optical system 3. The second electron gun 110 is usually set to the same negative potential as the potential of the image forming electron gun. Also a second electron gun
The electron beam 104 emitted from 110 is converged by the second condenser lens 111, and further in the direction of the substrate 9 to be inspected mounted on the sample stage by the deflector 112 for merging with the optical axis of the electron optical system. Be deflected. As an example of the deflector 112, the principle of an electromagnetic deflector is shown in FIG. A coil is wound in the axial direction of the cylindrical ferromagnetic material, and a current flows. Therefore, a circumferential magnetic field exists in the ferromagnetic material. A small hole is formed on the side wall of the cylindrical ferromagnetic material, and the second electron beam is arranged to enter the small hole. Since the magnetic field in the ferromagnetic material leaks into the space in the small hole, the second electron beam passing therethrough is deflected and introduced on the optical axis of the electron optical system. Thereafter, the laser beam travels on the substantially same optical axis as the electron beam for image formation and is irradiated on the substrate to be inspected. However, the second electron beam does not focus on the substrate to be inspected because the imaging condition is different from the electron beam for image formation.

As described above, a method of simultaneously irradiating the preliminary irradiation electron beam 104 and the image forming electron beam 19 traveling substantially in the same optical axis, and a method of irradiating with a staggered timing can be considered. Normally, simultaneous irradiation makes it impossible to distinguish and detect secondary electrons generated by irradiating the electron beam 19 for image formation and secondary electrons generated by the electron beam 104 for preliminary irradiation. Can not get. However, FIG. 14 (a) and FIG.
As shown in (b), when the diameter of the pre-irradiation electron beam 14 is sufficiently larger than the diameter of the image-forming electron beam 19, the secondary electrons generated by the pre-irradiation electron beam 14 hardly have a background signal. Level, and the formed electron beam image is almost formed from the image signal by the irradiation of the image forming electron beam 19. Therefore, by adjusting the condenser lens 111 of the second electron gun 110, the pre-irradiation electron beam 104 is not focused on the surface of the substrate 9 to be inspected and has a size of 10 μm or more. FIG. 14 (a) and FIG.
(B) shows a cross-sectional profile of the beam of the second electron beam 104 and the beam 19 of the image forming electron beam applied to the substrate 9 to be inspected. In FIG. 14A, the image forming electron beam 19 is located at the center of the electron beam from the second electron gun 110, but in FIG.
As shown in (2), the centers of both do not have to coincide. However,
Preferably, the image forming electron beam 19 is located within the range of the diameter of the electron beam from the second electron gun 110. this is,
If the two are largely separated, it is necessary to increase the operating range of the scanning deflector in order to cause both electron beams to scan the non-inspection area, thereby preventing an increase in inspection time.

The image forming electron beam 19 and the second electron gun
When irradiating the substrate to be inspected with the irradiation timing of the electron beam 104 from the 110 shifted, the preliminary irradiation electron beam 104 is irradiated at the time when the scanning of the image forming electron beam 19 is turned back. The image forming electron beam 19 is raster-scanned one-dimensionally or two-dimensionally as necessary.For example, the electron beam is scanned straight from left to right in the image acquisition area and then returned to the left again. Since an image signal is not acquired, secondary electrons generated by irradiating the preliminary irradiation electron beam 104 during the reversion do not affect the image.

The method of irradiating the electron beam from the second electron gun 110 as described above is also an image after charging and stabilizing the potential, which is described in the fifth embodiment, and Contrast and stable images could be obtained.

(Embodiment 7) In the seventh embodiment, the second electron source of the pre-irradiation electron beam 104 described in the sixth embodiment is placed on the periphery of the opening where the electron beam for image formation is irradiated. The configuration of the method and the device are described. FIGS. 15A and 15B show an electron optical system according to the seventh embodiment. The other parts are the same as in the fourth and sixth embodiments. As shown in FIG. 15A, the tip of the objective lens 16 has a truncated cone shape, and an electron gun 120 for the preliminary irradiation electron beam 104 is arranged in a space facing the substrate 9 to be inspected.
As the electron gun 120, one having a large light source and capable of obtaining a large current is suitable. In this case, an oxide cathode, which is used for a CRT monitor and has a low work function and is heated by a heater to emit thermoelectrons, is used. The irradiation energy of the electron beam from the second electron gun 120 to the substrate 9 to be inspected was the same as that of the image forming electron beam 19. The preliminary irradiation electron beam 104
The electron gun 120 is composed of two or four independently operating electron guns arranged two or four times symmetrically with respect to the axis on which the stage continuously moves during image formation.
FIG. 15B shows the arrangement of the electron gun 120, and is a view when the lower surface of the objective lens 16 is viewed from the side of the substrate 9 to be inspected. The plurality of electron guns 120 operate so as to irradiate the pre-irradiation electron beam 104 to a position immediately before scanning of the electron beam for image formation in accordance with the moving direction of the stage. For example, as shown in FIG. 15A, when the stage is moving from left to right, the second electron gun 120 on the left side of FIG. 15B operates.

In this embodiment, even when the preliminary electron beam irradiation 104 and the image forming electron beam irradiation 19 are performed simultaneously by the following method, the secondary electrons generated by the preliminary electron beam irradiation 104 adversely affect the electron beam image. Can be prevented. Figure
Fig. 16 shows a schematic diagram of the method. Secondary electrons 51 generated from the substrate 9 to be inspected travel upward in the objective lens 16 by the acceleration electric field described in detail in the first embodiment. At this time, the secondary electrons are focused by the influence of the magnetic field of the objective lens. The position of the focal point in the lateral direction changes depending on the location where the secondary electrons are generated. For example, secondary electrons generated from point A on the surface of the substrate to be inspected are focused on A ', and secondary electrons generated from point B are focused on B'. Therefore, the aperture 121 is provided at the focal position of the secondary electrons,
By disposing the secondary electron detector 20 thereabove, secondary electrons generated from the vicinity of the center of the optical axis, that is, the place where the image forming electron beam 19 is irradiated can be selectively detected. Since the irradiation position of the preliminary electron beam 104 is several hundred μm away from the irradiation position of the image forming electron beam 19,
The secondary electrons generated by 4 are not detected by being blocked by the aperture. In this embodiment, similarly to the fifth or sixth embodiment, the sample was charged in advance, and an image with good contrast could be obtained after the potential was stabilized.

(Embodiment 8) For example, in the process of manufacturing a semiconductor device, in addition to the circuit pattern inspection apparatus of the present invention, SE
In some cases, the substrate to be inspected has already been irradiated with an electron beam during inspection or observation by M. In such a case, a local part of the surface of the substrate to be inspected is charged before the circuit pattern inspection is performed. In the inspection method according to the embodiments described above, the locally charged region is charged. It is difficult to uniformly charge the same as in other areas, so that the locally charged portion may become an electron beam image with a unique contrast and may not be inspected. In order to avoid such a situation, the surface charge may be neutralized before the inspection, and then the circuit pattern inspection according to each of the embodiments described above may be performed.

In the present embodiment, a second preliminary chamber 130 is added to the configuration of the circuit pattern inspection apparatus 1 described in the first embodiment. Irradiation was performed. FIG. 17 shows the inspection room of this embodiment.
2 shows a partial configuration of the second and second spare chambers 130.

The second preliminary chamber 130 is provided with a gas inlet 134 and an electrode 132 for applying an electric field for ionizing the introduced gas, and is connected to a high frequency power supply 131. The substrate 9 to be inspected mounted on the sample holder in the first preliminary chamber (not shown) is evacuated and then transferred to the second preliminary chamber 130 which has been evacuated. Then a few Pa to the second spare room 130
A rare gas such as Ar or air having the following pressure is introduced, a high-frequency voltage is applied to the electrode 132, and these gases are ionized to form a plasma 133. The substrate 9 to be inspected is the plasma 133
For a certain period of time, during which the charged portion is neutralized. After performing the pre-processing, the substrate to be inspected 9 is transferred into the inspection room 2, and the inspection is performed. Since the inspection method has already been described in detail in the first embodiment, it is omitted here. By the pretreatment described in the present embodiment, the local electrification of the substrate 9 to be inspected is neutralized immediately before the inspection. The nine surfaces are all uniformly charged, and the electron beam image used for the comparative inspection has a uniform contrast, so that a highly accurate and stable inspection can be performed. During the irradiation of the plasma 133 in the preliminary chamber 130 described in the present embodiment, another substrate 9 'to be inspected is set in the adjacent inspection chamber and the inspection is performed. Since the time required for the pretreatment by plasma irradiation is sufficiently shorter than the time required for the inspection, there is almost no increase in the overall inspection time due to the pretreatment.

As described above, the configuration of the representative apparatus of the present invention and the method of inspecting a circuit pattern are described below. The method of inspecting after stabilizing the potential of the substrate to be inspected, the method of efficiently detecting the secondary electrons generated from the substrate to be inspected, and obtaining the electron beam image of high quality, the circuit pattern inspection of the present invention Although some embodiments such as a method for improving the productivity of a manufacturing process of a substrate having a semiconductor device and other circuit patterns by performing the above have been described, but without departing from the scope of the present invention,
An inspection method and an inspection apparatus that combine a plurality of features listed in the claims are also possible.

[0085]

The typical effects obtained by the present invention will be briefly described below.

By inspecting a substrate such as a semiconductor device having a circuit pattern using the circuit pattern inspection apparatus of the present invention, a silicon oxide film or a resist film which transmits light which cannot be detected by the conventional optical pattern inspection. Inspection of the formed circuit pattern was realized.
In addition, a circuit pattern having an insulating material, which has been difficult to obtain a stable image with the conventional SEM, can be inspected with an inspection time that can be practically used in a method of manufacturing a semiconductor device or the like.

By applying this inspection to the substrate manufacturing process, defects that could not be detected by the above-described conventional technology, that is, abnormalities in manufacturing equipment and conditions, etc. can be found quickly and with high accuracy. It is possible to take an abnormal countermeasure process as early as possible in the process. As a result, the defect rate of the semiconductor device and other substrates can be reduced, and the productivity can be increased. Also, by applying the above inspection, the occurrence of an abnormality can be detected quickly, so that a large number of defects can be prevented from occurring, and as a result, the occurrence of defects can be reduced. The reliability of a semiconductor device or the like can be improved, the development efficiency of a new product or the like can be improved, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a device configuration of a circuit pattern inspection device.

FIG. 2 is a diagram showing a configuration of a main part of an electron optical system and a secondary electron detection unit.

FIG. 3 is a diagram showing a correlation between electron beam irradiation, sample charging, and secondary electron generation.

FIG. 4 is a diagram illustrating the effect of electron beam irradiation conditions on contrast.

FIG. 5 is a diagram illustrating a scanning method of an electron beam.

FIG. 6 is a diagram illustrating a semiconductor device manufacturing process flow.

FIG. 7 is a view for explaining a semiconductor device circuit pattern and defect contents.

FIG. 8 is a diagram illustrating a configuration of a main part of an electron optical system according to a third embodiment.

FIG. 9 is a diagram illustrating an enlarged partial configuration of an electron optical system according to a fourth embodiment.

FIG. 10 is a diagram illustrating a device configuration of a circuit pattern inspection device according to a fifth embodiment.

FIG. 11 is a diagram illustrating the effect of electron beam irradiation time on contrast.

FIG. 12 is a diagram illustrating a configuration of a main part of an inspection apparatus according to a sixth embodiment.

FIG. 13 is a diagram illustrating the principle of a deflector according to a sixth embodiment.

FIG. 14 is a diagram illustrating the shape of an electron beam according to a sixth embodiment.

FIG. 15 is a diagram illustrating a configuration of a main part of an electron optical system according to a seventh embodiment.

FIG. 16 is a diagram showing the operation of the seventh embodiment.

FIG. 17 is a diagram illustrating a configuration of a main part of an inspection apparatus according to an eighth embodiment.

[Explanation of symbols]

 1 ... Circuit pattern inspection device 2 ... Inspection room 3 ... Electronic optical system 4 ... Optical microscope unit 5 ... Image processing unit 6 ... Control unit 7 ... ..Secondary electron detector 8 ... Sample chamber 9 ... Substrate to be inspected 10 ... Electron gun 11 ... Extraction electrode 12 ... Condenser lens 13 ... Blanking deflector 14.・ ・ Aperture 15 ・ ・ ・ Scanning deflector 16 ・ ・ ・ Objective lens 17 ・ ・ ・ Reflector 18 ・ ・ ・ ExB deflector 19 ・ ・ ・ Electron beam 20 ・ ・ ・ Secondary electron detector 21 ・ ・ ・ Preamplifier 22・ ・ ・ AD converter 23 ・ ・ ・ Optical conversion means 24 ・ ・ ・ Optical transmission means 25 ・ ・ ・ Electrical conversion means 26 ・ ・ ・ High voltage power supply 27 ・ ・ ・ Preamplifier drive power supply 28 ・ ・ ・ AD converter drive power supply 29・ ・ ・ Reverse bias power supply 30 ・ ・ ・ Sample stage 31 ・ ・ ・ X stage 32 ・ ・ ・ Y stage 33 ・ ・ ・ Rotary stage 34 ・ ・ ・ Position monitor length measuring instrument 35 ・ ・ ・ Inspection substrate height measuring instrument 36 ・ ・ ・ Retarding power supply 40 ・ ・ ・ White light source 41 ・ ・ ・ Optical lens 42 ・ ・ ・ CCD camera 43 ・ ・ ・ Correction control circuit 44 ・ ・ ・ Scan signal generation Unit 45 Power supply for objective lens 46 First storage unit 47 Second storage unit 48 Operation unit 49 Defect judgment unit 50 Monitor 51 Secondary electron 52 … Second secondary electron 53… Attraction electrode 54… Ground electrode 100… Second preliminary chamber 101… Electron source 102… Lens 103… Large angle deflector 104… .. Pre-irradiation electron beam 110 ・ ・ ・ second electron source 111 ・ ・ ・ second condenser lens 112 ・ ・ ・ deflector 120 ・ ・ ・ second electron source 121 ・ ・ ・ diaphragm 130 ・ ・ ・ second Preparatory room 131 ・ ・ ・ High frequency power supply 132 ・ ・ ・ Electrode 133 ・ ・ ・ Plasma 134 ・ ・ ・ Gas inlet.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) H01L 21/027 H01L 21/30 502V (31) Priority claim number Japanese Patent Application No. 9-33476 (32) Priority date February 18, 1997 (Feb. 18, 1997) (33) Priority Country Japan (JP) (72) Inventor Katsuya Sugiyama 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72 Inventor Atsuko Takato 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Takashi Hiroi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Production Technology Laboratory (72) Inventor Kazushi Yoshimura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Production Technology Research Laboratory, Hitachi, Ltd. 2326, Imai, Ume City, Hitachi, Ltd.Device Development Center, Hitachi, Ltd. (72) Inventor Haruo Yoda 882, Ma, Hitachinaka, Ibaraki Pref., Ltd.Measurement Equipment Division, Hitachi, Ltd. (72) Katsuhiro Kuroda, Katsuhiro Kuroda, Kokubunji, Tokyo No. 280, Hitachi Central Research Laboratory Co., Ltd. (72) Inventor Yasutoshi Usami 882 Ma, Hitachinaka-shi, Ibaraki Pref.Hitachi, Ltd.Measurement Equipment Division (72) Inventor Maki Tanaka Yoshida, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture 292-machi, Hitachi, Ltd.Production Technology Research Laboratories, Ltd. (72) Inventor Yutaka Kaneko 1-280, Higashi-Koigakubo, Kokubunji-shi, Tokyo, Japan (72) Inventor Hiroshi Toyama 1-280, Higashi-Koikekubo, Kokubunji-shi, Tokyo, Japan Address: Hitachi, Ltd. Central Research Laboratory Co., Ltd. (72) Inventor Tadao Ino 1-280 Higashi Koigakubo, Kokubunji, Tokyo Prefecture Hitachi, Ltd. Central Research Laboratory Co., Ltd. 1-280 Higashi Koigakubo, Hitachi, Ltd.Central Research Laboratory, Hitachi, Ltd. (72) Inventor Kimiaki Ando 1-280 Higashi Koikekubo, Kokubunji, Tokyo, Japan Inside Central Research Laboratories, Hitachi, Ltd. (72) Inventor Shunji Maeda Yoshida, Yokohama, Kanagawa 292 Machi-cho, Hitachi, Ltd. Production Technology Research Laboratories (72) Inventor Hitoshi Kubota 3-3-2 Fujibashi, Ome-shi, Tokyo F-term (reference) 2F067 AA54 BB01 CC16 CC17 EE03 EE04 HH06 HH13 JJ05 KK04 LL15 PP12 QQ01 QQ11 QQ13 RR12 RR35 2G014 AA01 AA02 AA03 AB51 AC11 4M106 AA01 AA09 BA02 CA39 DB05 DH33 DJ11 DJ18 5C001 AA03 AA07 BB07 CC04 5C033 UU01 UU03 UU05 UU06

Claims (25)

[Claims] 1. A step of scanning a first region of a substrate surface on which a circuit pattern is formed with a primary electron beam, and a step of detecting a signal generated secondary from the first region by the primary electron beam. Forming an electron beam image of the first area from the detected signal; storing the electron beam image of the first area; and scanning a second area of the substrate with a primary electron beam. Performing a step of detecting a signal generated secondarily from the second region by the primary electron beam, forming an electron beam image of the second region from the detected signal, A step of storing an electron beam image of the second area, a step of comparing the stored image of the first area with the stored image of the second area, and detecting a defect of the circuit pattern on the substrate from the comparison result. An inspection method including a step of determining, wherein a first region and a second region are In the step of scanning with an electron beam, an electron beam is scanned to form an electron beam image of the target region so that the average charge amount of a region sufficiently larger than the feature of the pattern to be inspected on the substrate is substantially uniform. A method for inspecting a circuit pattern, comprising: 2. The inspection method according to claim 1, wherein, in the step of forming the first and second electron beam images, the amount of electron beam irradiation per unit area on the substrate surface on which the circuit pattern is formed is controlled. Forming an electron beam image of the target area by scanning the electron beam to be substantially uniform in the inspection area;
Circuit pattern inspection method. 3. A step of scanning a first area on a substrate surface on which a circuit pattern is formed with a primary electron beam, and a step of detecting a signal generated secondarily from the first area by the primary electron beam. Forming an electron beam image of the first region from the detected signal; storing an electron beam image of the first region; and scanning a second region of the substrate with a primary electron beam. Performing a step of detecting a signal generated secondarily from the second region by the primary electron beam, forming an electron beam image of the second region from the detected signal, An inspection including a step of storing an electron beam image of the second area, a step of comparing the image of the first area and the image of the second area, and a step of determining a defect of the circuit pattern on the substrate from the comparison result A method comprising: forming a circuit pattern on a surface of a member on the substrate; Position by scanning the electron beam at high speed to form an electron beam image of the target area within which does not change, the inspection method of a circuit pattern to be tested using this image. 4. The inspection method according to claim 3, wherein said scanning step is a step of scanning a high-current electron beam several times over the surface of the substrate on which the circuit pattern is formed by high-speed scanning. . 5. The circuit pattern inspection method according to claim 4, further comprising the step of setting a current value of an electron beam applied to the surface of the substrate on which the circuit pattern is formed to 13 nA or more. 6. The inspection method according to claim 4, further comprising a step of setting a current value of an electron beam applied to a substrate surface on which the circuit pattern is formed to 270 pA or more. 7. A step of scanning a first area on a substrate surface on which a circuit pattern is formed with a primary electron beam, and a step of detecting a signal generated secondarily from the first area by the primary electron beam. Forming an electron beam image of the first region from the detected signal; storing an electron beam image of the first region; and a second region of the substrate with the primary electron beam. Scanning, detecting a signal secondary generated from the second region by the primary electron beam, forming an electron beam image of the second region from the detected signal, A step of storing an electron beam image of a second area, a step of comparing the image of the first area and the image of the second area, and a step of determining a defect of the circuit pattern on the substrate from the comparison result. An inspection method that provides a zero or negative potential to a sample. There the inspection method of a circuit pattern, characterized in that the addition and controlling the irradiation energy of the primary electron beam by applying zero or negative voltage in the vicinity of the sample stage or sample, the. 8. The inspection method according to claim 7, wherein the incident energy of the electron beam for forming an image on the substrate to be inspected is an energy at which the number of incident electrons and the number of emitted secondary electrons are substantially equal. A circuit pattern inspection method including a setting step. 9. A state in which a first region on a surface of a substrate on which a circuit pattern is formed has a substantially same potential as a primary electron beam having a predetermined thickness compared with a potential around the first region of the substrate. A first scanning step of a primary electron beam for uniformly scanning the first area so as to obtain a signal, and a step of detecting a signal generated secondarily from the first area by the primary electron beam. Forming an electron beam image of the first region from the signal; storing an electron beam image of the first region; and storing a second region of the substrate with the primary electron beam in the second region of the substrate. A second scanning step of a primary electron beam for uniformly scanning the second region so that the potential is substantially the same as the potential around the region, and a second scanning operation of the second region by the primary electron beam. Detecting a signal that occurs next; and detecting the second region from the detected signal. Forming an electron image, a step of storing the electron beam image of the second region, the first
Circuit pattern inspection, comprising: comparing a stored image of the area with the stored image of the second area; and determining a defect of the circuit pattern on the substrate from the comparison result. Method. 10. The circuit pattern inspection method according to claim 1, further comprising a step of continuously moving the sample stage. 11. An electron source for generating a primary electron beam, lens means for focusing the primary electron beam, a sample stage on which the sample is mounted, and scanning means for scanning a predetermined area on the sample with the focused primary electron beam. Detecting means for detecting secondary charged particles generated secondarily from a sample; storing means for forming and storing an image based on a signal from the detecting means; and a first memory stored in the storing means. Means for comparing the image of the area with another image of the second area on which the same circuit pattern is formed; means for determining a defect on the circuit pattern from the comparison result; Means for controlling the irradiation amount of the primary electron beam so that the average charge amount is uniform, or the electron beam irradiation amount per unit area or unit time on the sample surface is substantially uniform. Characteristic circuit pattern Inspection equipment. 12. The apparatus according to claim 1, wherein said scanning means scans one of the first and second regions a plurality of times.
2. The circuit pattern inspection apparatus according to claim 1. 13. A means for controlling the irradiation amount, wherein a current value of a primary electron beam irradiating the first or second region of the sample is adjusted.
12. The circuit pattern inspection apparatus according to claim 11, wherein the circuit pattern is at least 270 nA. 14. A method for controlling the amount of irradiation, wherein a current value of a primary electron beam irradiating the first or second region of the sample is adjusted.
The circuit pattern inspection apparatus according to claim 11, wherein the circuit pattern is 13pA or more. 15. A step of scanning a first area of a substrate surface on which a circuit pattern is formed with a primary electron beam, and a step of detecting a signal secondary generated from the first area by the primary electron beam. Forming an electron beam image of the first area from the detected signal; storing the electron beam image of the first area; and scanning a second area of the substrate with a primary electron beam. And the step of detecting a signal generated secondarily from the second region by the primary electron beam, and forming an electron beam image of the second region from the detected signal,
A step of storing an electron beam image of the second area, a step of comparing the image of the first area and the image of the second area, and a step of determining a defect of the circuit pattern on the substrate from the comparison result. A method for inspecting a circuit pattern, further comprising a step of stabilizing a potential of a surface of a member forming a circuit pattern on the substrate before scanning the substrate with an electron beam. 16. The inspection method according to claim 15, wherein
A circuit pattern inspection method, wherein an amount of the second charged particle beam applied to the inspection area of the substrate is substantially uniform. 17. The inspection method according to claim 16, wherein
A method for inspecting a circuit pattern, wherein the second charged particle beam is irradiated in a preliminary chamber. 18. The inspection method according to claim 16, wherein
A circuit pattern inspection method, wherein scanning of the first electron beam for forming the inspection image and scanning of the second charged particle beam are performed with a time lag. 19. The inspection method according to claim 15, wherein
In the method for inspecting a circuit pattern, the step of stabilizing includes irradiating the substrate with the electron beam during the return of the scanning of the electron beam. 20. The inspection method according to claim 15, wherein
As a step of stabilizing, a circuit pattern inspection method in which a member forming a circuit pattern on the substrate is allowed to exist in a plasma atmosphere for a predetermined time in a preliminary chamber where plasma is generated. 21. The inspection method according to claim 15,
A step of storing image data in advance, a step of scanning a region to be inspected on a substrate to be inspected with a primary electron beam, and a step of detecting a signal generated secondary from the region to be inspected by the primary electron beam, Forming an electron beam image of the inspection area from the detected signal; storing the electron beam image of the inspection area; reading the stored image data; A circuit pattern inspection method including a step of comparing electron beam images of an inspection area and a step of determining a defect of a circuit pattern on a substrate from a result of the comparison. 22. The inspection method according to claim 15, wherein, as a step of forming an electron beam image from the detected signal, the detected secondary charged particle signal is converted into a digital signal while floating at a high voltage. A circuit pattern inspection method that forms an image after conversion and transmission. 23. A step of setting at least a portion to be inspected of a sample to be inspected to a predetermined charged state in advance, a step of irradiating the portion to be inspected with a high-density electron beam for image formation, and A step of detecting secondary charged particles a predetermined time after the moment when the electron beam is irradiated in the portion, a step of forming an image based on the detected secondary charged particle signal, and using the formed image Inspecting the part to be inspected,
A method for inspecting a circuit pattern, comprising: 24. An electron source for generating a primary electron beam, a lens system for focusing the primary electron beam, a sample table on which a sample is mounted, and a transfer arm for transferring the sample to a sample chamber including the sample table. A deflection electrode for deflecting the focused primary electron beam on the sample, and a deflection signal generator for driving the deflection electrode;
A secondary charged particle detector for detecting secondary charged particles generated from the sample by irradiating the sample with the primary electron beam, a first power supply for applying zero or positive voltage to the detector, and -D converter for converting a signal from a dynamic detector into a digital signal, an electro-optical converter for converting a digital signal from the A / D converter into an optical signal, and a light for optically transmitting the optical signal. A fiber, an optical / electrical converter for converting an optical signal transmitted through the optical fiber into an electric signal,
An image memory for forming and storing an image to be inspected based on a signal from the electrical converter, and a comparison operation circuit for comparing the stored image of the region with another image of the same circuit pattern; An arithmetic circuit for determining a defect on a circuit pattern from a comparison result, a second power supply for applying a negative voltage to the sample stage, and controlling a voltage applied by the second power supply. And a blanking deflection electrode for preventing the sample from being irradiated with the electron beam except when the inspection image is formed. 25. An electron source for generating a primary electron beam, lens means for focusing the primary electron beam, a sample stage on which a sample is placed, and transport means for transporting the sample to a sample chamber including the sample stage. A primary electron beam scanning means for scanning the focused primary electron beam on a sample, a means for detecting secondary charged particles generated secondarily from the sample, and forming an image based on a signal from the detector Means for comparing the image of the area stored in the storage means with an image of another area in which the same circuit pattern is formed, and means for determining a defect on the circuit pattern from the comparison result And a circuit pattern inspection apparatus, wherein the average charge amount of a region that is sufficiently larger than the feature of the pattern to be inspected of the sample is uniform, or a unit area or a unit time per unit time on the sample surface. Electric As the line dose is substantially uniform, having a means for controlling the irradiation amount to the sample of the primary electron beam device for inspecting a circuit pattern.