JP2002157968A - Evaluation apparatus and device manufacturing method using the evaluation apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To achieve high-precision evaluation of a sample by making the intensities of plural beams uniform. An electron gun for emitting a primary electron beam (1), a condenser lens (2) for converging the emitted primary electron beam to form a crossover, and between a condenser lens and a crossover imaging point (4). , A first multi-aperture plate (3) having a plurality of apertures (20) for separating a primary electron beam into a plurality of beams, and an imaging optical system (4) for reducing and imaging the plurality of beams on a wafer (8). 5, 7), a deflector (1) for deflecting the plurality of beams so that each irradiation spot of the plurality of beams imaged on the wafer is scanned.
9), a multi-detector (12, 60) for detecting the intensity of each of a plurality of secondary electron beams emitted from each irradiation spot, and evaluation of the wafer (8) based on an image of the detected secondary electron beam. And a control unit (16) for performing the following. The first multi-aperture plate is stepped so that the aperture having a greater distance from the optical axis is closer to the crossover imaging point so that the intensities of the plurality of beams are equal to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaluation apparatus for evaluating a sample by irradiating a sample such as a semiconductor wafer with primary charged particles and detecting secondary charged particles generated from an irradiation spot of the sample. And a device manufacturing method for performing an evaluation such as a defect inspection of a device using the apparatus.

[0002]

2. Description of the Related Art As a method for detecting a defect in a sample such as a semiconductor wafer or a mask, a probe such as a plurality of finely focused electron beams is used to simultaneously scan the sample and detect secondary electrons generated from the sample with a detector. Accordingly, a technology for detecting defects with high resolution and high throughput is known. With this technology,
A plurality of electron beams are formed by passing a primary electron beam emitted from one electron gun through a multi-aperture plate having a plurality of openings. Then, these electron beams are imaged on a sample via a primary optical system to form a plurality of irradiation spots, and each irradiation spot is scanned on an inspection surface of the sample using a deflector. Next, secondary electrons generated from each irradiation spot are imaged on a multi-detector via a secondary optical system to obtain an image signal.

In such an electron beam apparatus, when inspecting a defect of a sample with a plurality of beams with high accuracy, the influence of aberration of a primary optical system or a secondary optical system is avoided, and the uniformity of the plurality of beams is reduced. It is important to ensure the quality. Therefore,
By tilting the multi-aperture plate or changing the position of each aperture in the optical axis direction, the optical path length from each aperture of the separated multiple primary electron multi-beams to the surface of the sample is made equal, thereby causing field curvature. Corrections have been proposed. Also, since the intensity of the primary electron beam emitted from the electron gun has a peak at the center of the beam and decreases toward the periphery, the diameter is increased toward the periphery of the multi-aperture plate to compensate for this, and as a result, the multi-beam There are also proposals in which the strength of each is almost constant.

[0004]

However, in the above-mentioned prior art in which the optical path length from each aperture of a plurality of primary electron multi-beams to the surface of a sample is equal, the intensity of the electron gun varies from direction to direction, When the system has a decrease in the peripheral transmittance or the like, there is a problem that the intensity of the multi-beam cannot be made almost constant. Further, in another method using a multi-aperture plate having a larger diameter as the peripheral opening becomes larger, the beam diameter becomes larger as the primary electron beam passes through the peripheral opening, and the resolution may be reduced. There is also a problem that the influence of other aberrations is not taken into account.

[0005] The present invention has been made in view of the above facts,
High resolution and high aberration correction are possible in an evaluation device that evaluates a sample by scanning the sample with multiple probes such as primary charged particle beams and detecting secondary charged particles generated from the sample with a detector. It is another object of the present invention to provide an evaluation device that enables highly accurate evaluation by making the intensities of a plurality of beams uniform.

It is another object of the present invention to provide a device manufacturing method in which a device being manufactured is inspected by using the evaluation apparatus, thereby improving the inspection accuracy and shortening the device manufacturing time.

[0007]

In order to solve the above problems, a first aspect of the present invention is an evaluation apparatus for evaluating a sample on which a pattern is formed, wherein the charged particle source emits a primary charged particle beam. And a condenser lens that converges the emitted primary charged particle beam to form a crossover, and is disposed between the condenser lens and the imaging point of the crossover, and a plurality of the primary charged particle beams that pass through the condenser lens Beam forming means having a plurality of apertures for forming a beam, an imaging optical system for imaging a plurality of beams passing through the plurality of apertures on a sample, and each irradiation spot of the plurality of beams imaged on the sample. Deflecting means for deflecting the plurality of beams so as to be scanned on the sample, and a plurality of secondary charged particles emitted from each irradiation spot of the plurality of beams scanned on the sample surface Detecting means for detecting the intensity of each, based on the intensity distribution of the secondary charged particle beam on the sample detected by the detecting means, to evaluate the sample, including evaluation means, including, beam forming means, The position of each of the plurality of apertures in the optical axis direction is determined so that the intensities of the plurality of beams when formed on the sample are substantially equal to each other.

According to the present invention, there is provided a charged particle source,
A single primary charged particle beam having a certain intensity distribution is converged by a condenser lens to form a crossover image. On the way, the primary charged particle beam passes through a plurality of openings of the beam forming means and separates into a plurality of beams. These beams are imaged on the sample surface by the imaging optical system.
The intensity of the primary electron beam just before passing through these apertures
Generally, there is a variation between the apertures according to the intensity distribution. However, the beam forming means uses a plurality of apertures so that the intensities of the plurality of beams when imaged on the sample are substantially equal to each other. Are respectively determined in the optical axis direction. In other words, the position in the optical axis direction is determined such that the smaller the intensity of the passing charged particle beam is, the larger the solid angle for the crossover becomes. As a result, the variation in the intensity of the beam emitted from the charged particle source between the apertures is smoothed. When the position (z) in the direction of the optical axis is determined from the measured intensity of the primary charged particle beam actually formed on the sample, not only the variation in the intensity of the charged particle source between apertures but also the secondary optical system Can be simultaneously corrected by adjusting the position of the opening.

Thus, a plurality of irradiation spots of the primary charged particle beam having substantially the same intensity are formed on the sample, and the secondary charged particles are emitted from each irradiation spot. During this time, the deflecting means deflects an area slightly wider than the interval between adjacent beams. By this deflection, the irradiation spot on the sample can scan the beam arrangement direction without a break.

Next, the detecting means detects the intensities of the plurality of secondary charged particle beams emitted from the respective irradiation spots of the plurality of beams scanned on the sample surface. The evaluation unit executes the evaluation of the sample based on the intensity distribution of the secondary charged particle beam on the sample detected by the detection unit. Since this intensity distribution is based on the image of the secondary charged particle beam by the primary charged particle beam having almost uniform intensity between the openings, it is used for defect inspection, line width measurement, etc. due to insufficient brightness of the peripheral image. Errors are reduced, and highly accurate evaluation becomes possible.

Further, in the present invention, by adjusting the position of the aperture in the direction of the optical axis (accordingly, the distance from the crossover imaging point), the intensities of the plurality of beams are made uniform, so that the diameter of the aperture can be reduced. High resolution can be maintained without having to be as large as the periphery. Further, since there is a degree of freedom in the arrangement of the apertures, there is a possibility that aberrations such as image surface distortion can be corrected by this arrangement.

A second aspect of the present invention includes the same components as the first aspect, but the beam forming means provides substantially uniform emission characteristics of secondary charged particles at each irradiation spot of a plurality of beams. The method is characterized in that the intensity of the plurality of secondary charged particle beams detected by the detecting means when the calibration sample is used is adjusted to be substantially equal to each other.

In the second aspect, the distance between the plurality of openings is determined such that the intensities of the plurality of secondary charged particle beams actually detected by the detecting means are substantially equal to each other. When a secondary optical system for forming an image of a line on the detection means is provided, not only the influence of the variation of the intensity of the charged particle source between apertures and the decrease in the peripheral transmittance of the primary optical system, but also the peripheral transmission of the secondary optical system The effect of the rate reduction can be corrected at the same time.

The primary charged particles emitted from the charged particle source generally have an intensity distribution that has a peak at the center and decreases with the radial distance. In addition, the brightness of the aberration of the imaging optical system or the like generally decreases toward the periphery. In such a case, the beam forming means is provided as an aperture plate in which a plurality of apertures are formed, and the aperture plate is stepped so that an aperture having a greater distance from the optical axis is closer to a crossover imaging point. Have been.

[0015] The evaluation means includes: detecting a defect in the pattern of the sample;
Line width measurement of the pattern of the sample, potential measurement of the pattern,
Measurement of alignment accuracy between layers when the sample is formed from a plurality of layers, and operation analysis of the sample based on potential measurement of the pattern while irradiating a short pulse width primary charged particle beam It is preferable that at least one of them is executable.

A device manufacturing method including a step of evaluating a wafer being processed or a finished product can be performed using the above-described evaluation apparatus.

Other aspects and effects of the present invention will become more apparent from the following description.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment; Evaluation Apparatus Using Electron Beam) FIG. 1 shows a schematic configuration of an evaluation apparatus 30 according to a first embodiment of the present invention. The evaluation device 30 includes the electron beam device 18 and a control unit 26 for controlling the device and analyzing a detection signal.

The electron beam device 18 comprises an electron gun 1 for emitting a primary electron beam, a condenser lens 2 for converging the emitted primary electron beam to form a crossover, a condenser lens 2 and a crossover image point 4. And a first multi-aperture plate 3 having a plurality of apertures 20 for forming a plurality of beams from the primary electron beam passing through the condenser lens 2, and reducing the plurality of beams on the wafer 8. , A reducing lens 5 and an objective lens 7, and a deflector 19 for deflecting the beams so that each irradiation spot of the plurality of reduced-formed beams is scanned over a predetermined range on the wafer 8.

The above-described primary optical system for irradiating the wafer with the primary electron beam is configured to be axially symmetric with respect to the optical axis 50, and the primary electrons are incident on the inspection surface of the semiconductor wafer 8 substantially perpendicularly. The wafer 8 is mounted on a stage 22 that can move one-dimensionally or two-dimensionally within a predetermined range in a horizontal plane by an actuator (not shown).

When the electron beam device 18 is used as an EB tester to be described later, a primary blank is generated between the first multi-aperture plate 3 and the crossover image point 4 so as to generate a temporal blank in the primary electron beam. A blanking deflector 17 for deflecting the electron beam is provided.

The E × B separator 6 is arranged between the reduction lens 5 and the objective lens 7 and generates a field E × B in which the electric field E and the magnetic field B are orthogonal. The secondary electron beam emitted from the irradiation spot on the wafer by irradiating the primary electron beam onto the wafer 8 is moved from its main surface to the optical axis by the field E × B generated by the E × B separator 6. It is deflected in a direction (obliquely upward in the figure) at a predetermined angle (for example, 35 °) with respect to 50.

The secondary optical system for guiding the secondary electron beam to the detecting means is disposed so that its optical axis 52 coincides with the center path of the secondary electron beam deflected by the E × B separator 6. Magnifying lenses 9 and 10 for magnifying and projecting the electron beam, a deflector 56 for deflecting the secondary electron beam according to the deflection of the primary electron beam,
Is provided.

The detecting means has a second opening 21 having a plurality of openings 21.
Multi-aperture plate 11 and multi-detector elements 6 for detecting the intensities of a plurality of secondary electron beams passing through these apertures 21, respectively.
And a detector 12 made of zero. The plurality of openings 21 formed in the second multi-aperture plate 11 and the plurality of openings 20 formed in the first multi-aperture plate 3 correspond one-to-one (FIG. 2 shows the first multi-aperture plate). An opening 21 of the second multi-aperture plate 11 is indicated by a broken line on the opening 20 of the multi-aperture plate 3 for reference). As the multi-detection element 60, for example, a PN junction diode that directly detects the intensity of an electron beam, or a CCD (charge imaging device) that detects the emission intensity via a fluorescent plate that emits light by electrons can be used.

Each multi-detection element 60 of the detector 12 is connected via an amplifier 13 to an image processing section 14 for converting a detection signal into image data. A scanning signal for deflecting the primary electron beam is supplied to the image processor 14 by the deflector 1.
9, the image processing unit 14 can form an image representing the scanned surface of the wafer 8 from the detection signals obtained during the beam scanning.

The image processing unit 14 is connected to the control unit 26 so that data communication is possible. As shown in FIG. 1, the control unit 26 can be configured by a general-purpose personal computer or the like as an example. The computer includes a control unit main body for executing various control and arithmetic processing in accordance with a predetermined program, a CRT 25 for displaying the processing results and the secondary electronic image 27 and the like, and a keyboard and a mouse for inputting instructions by an operator. And an input unit 28, of course.
The control unit 26 may be configured by hardware dedicated to the defect inspection device or a workstation.

The main body of the control unit 26 includes a CPU (not shown),
It is composed of various control boards such as a RAM, a ROM, a hard disk, and a video board. On the hard disk, a secondary electron image storage area 24 for storing secondary electron image data of the wafer 8 received from the image processing unit 14 and reference image data of a wafer having no defect are stored in advance. The reference image storage unit 23 is assigned. Further, a wafer evaluation program 29 is stored on the hard disk in addition to a control program for controlling the entire pattern inspection apparatus. This evaluation program 29
Has a function of automatically detecting a defect on the wafer 8 based on image data according to a predetermined algorithm, as will be described in detail later.

FIG. 2 shows a top view and a side sectional view of the first multi-aperture plate 3 which is a feature of the present invention.
The number and arrangement of the openings 20 can be arbitrarily and suitably changed without departing from the gist of the present invention.

As shown in the figure, the first multi-aperture plate 3
Is provided as a metal plate in which a plurality of openings 20 are formed. The metal plate has a cross-over connection with an opening having a larger distance r from the optical axis 50 in a radial direction (a direction perpendicular to the optical axis). It is stepped so that the distance h from the image point 4 becomes small. For example, the central opening 20 located on the optical axis 50
a distance h ₀ between the crossover imaging point 4, and the optical axis 50 near than spaced radial distance r from the k th opening 2
The distance h _k between Ob and the crossover imaging point 4 is h _k <h
There is a relationship of ₀ . In other words, the solid angle at which the crossover is seen from the opening is larger in the peripheral aperture, so that for a primary electron beam having the same intensity, a primary electron beam with a higher intensity is emitted in the peripheral aperture. In fact, electron gun 1
Since the intensity of the primary electron beam emitted from the device generally decreases toward the periphery, the intensities of the plurality of primary electron beams that have passed through the plurality of openings 20 are corrected so that variations among the openings are reduced. In an embodiment of the present invention, all of the openings, the distance _{h (h 0, .. h k} , .. h n), therefore the position z in the optical axis direction _{(z 0, .. z k,} .. z n) Is adjusted so that the intensities of the plurality of primary electron beams become substantially equal.

The full aperture 20 in the first multi-aperture plate 3
As a method of determining the distance h to the crossover imaging point of
The following methods are mentioned.

With the first multi-aperture plate 3 removed, the primary electron beam is irradiated at a plurality of positions corresponding to the irradiation spots of a plurality of beams which are expected to be irradiated when the first multi-aperture plate 3 is present. The strength is measured separately. In this measurement, for example, 2
A Faraday cage 54 having a hole of about 0 μmΦ is arranged, a primary electron beam is emitted from the electron gun 1 under the same emission conditions, and the intensity (luminance) of the primary electron beam imaged at the plurality of locations is measured. . The ratio of these intensities is determined, and each distance h (h ₀ ,...) Between each aperture and the crossover imaging point 4 is determined.
h _k,. . h _n ) is determined so that each ratio h is the square root of the measured intensity ratio. Since the electron beam intensity is inversely proportional to the square of the distance, the electron dose passing through each aperture as viewed from the crossover imaging point 4 is substantially the same. When each distance h is determined, the position z (z ₀ ,... Z _k ,... Z _n ) of each aperture in the optical axis direction is uniquely determined according to the radial distance r. One multi-aperture plate 3 can be easily manufactured.

As described above, in the first embodiment, the variation in the intensity of the plurality of primary electron beams is measured by the Faraday cage 54 or the like on the inspection surface of the wafer 8, and the variation is calibrated based on the measured values. This means that not only the radial dependence of the beam intensity of the gun 1 but also the characteristics of the primary optical system, such as a decrease in peripheral transmittance, are actually corrected.

Incidentally, a flat substitute multi-aperture plate (not shown) provided with a plurality of openings having exactly the same number, diameter and arrangement as the openings 20 of the first multi-aperture plate 3 is prepared, and the first multi-aperture plate is prepared. The intensity of the primary electron beam may be measured as described above after being arranged at the same position as the aperture plate 3 and actually split into a plurality of beams.

In the electron beam apparatus of the present embodiment, the primary electron beam passing through the opening of the first multi-aperture plate 3 is focused on the surface of the wafer 8 and the secondary electron beam emitted from the wafer 8 is detected. In forming an image on the imager 12, it is preferable to take particular care to minimize the effects of the three aberrations of the primary optical system, such as distortion, field curvature, and field astigmatism. For example,
The adjacent apertures 20 of the first multi-aperture plate 3 are used so that the field curvature of the reduction lens 5 and the objective lens 7 does not occur.
Are preferably arranged at equal intervals. Further, regarding the relationship between the intervals between the plurality of primary electron beams and the secondary optical system, crosstalk between the beams can be eliminated by separating the intervals between the primary electron beams by a distance larger than the aberration of the secondary optical system. be able to.

Next, the operation of the electron beam device according to the first embodiment will be described.

The single primary electron beam emitted from the electron gun 1 and having a peak at the center and having an intensity distribution that decreases with the radial distance is converged by the condenser lens 2 to form a crossover image. On the way, the primary electron beam passes through the first multi-aperture plate 3 to form a plurality of beams. These multiple beams are converted to a point 1 by a reduction lens 5.
The image is focused on 5, and further reduced and focused on the surface of the wafer 8 via the objective lens 7. The intensity of the primary electron beam immediately before passing through these openings is lower in the peripheral openings. However, as described above, since the first multi-aperture plate 3 is provided with steps so that the intensities of the plurality of primary electron beams imaged on the wafer are substantially the same, the beam intensity varies. Smoothed.

Thus, a plurality of irradiation spots are formed on the wafer 8 by the primary electron beams having substantially the same intensity, and secondary electrons are emitted from each irradiation spot.
During this time, the electrostatic deflector 19 deflects an area slightly larger than the interval between adjacent beams. By this deflection, the irradiation spot on the wafer can scan the beam arrangement direction without a break. Note that the wafer 8 may be synchronously moved sequentially or continuously at a predetermined width so that the stage 22 can scan the entire inspection surface of the wafer.

The multi-beam of secondary electrons generated from each irradiation spot on the wafer is attracted by the electric field of the objective lens 7 to be narrowly focused, reaches the E × B separator 6, where the light is generated by the field E × B. The light is deflected in a direction at a predetermined angle with respect to the axis 50 and travels along the optical axis 52 of the secondary optical system. The secondary electron image is located at point 1 closer to the objective lens 7 than point 15.
Focus on 6. This is because each primary electron beam has energy of, for example, 500 eV on the wafer surface, whereas a secondary electron beam generally has energy of only several eV. The multi-beams of these secondary electrons are magnified by magnifying lenses 9 and 10 and detected by each of the multi-detecting elements 60 via the second multi-aperture plate 11. At this time, the deflection of the secondary electron beam caused by deflecting the primary electron beam by the deflector 19 is canceled by the correction deflection of the deflector 56. That is, regardless of the scanning of the plurality of primary electron beams that have passed through the opening 20, each of the multi-beams of secondary electrons always passes through the corresponding opening 21 of the second multi-aperture plate 11, and It is detected by a certain detection element 60.

The image processing section 14 controls the deflection of the primary electron beam and the stage 22
In synchronization with the movement control of the semiconductor wafer 8 to form intensity distribution image data of the secondary electron beam over the entire inspection surface of the semiconductor wafer 8. The obtained image data is transferred to the control unit 26 and stored in the memory 24.

The controller 26 performs various evaluations of the wafer 8 based on the image data stored on the memory 24.
Since this image data is based on the secondary electron beam image of the primary electron beam whose radial intensity distribution is almost uniform, errors such as defect inspection and line width measurement due to insufficient brightness of the peripheral image are reduced. It is possible to perform evaluation with high accuracy. In addition, in the present embodiment, as described above, by adjusting the arrangement and the interval of the openings 20 formed in the first multi-aperture plate 3, the field curvature aberration of the reduction lens 5 and the objective lens 7, and In addition, since crosstalk between a plurality of beams can be prevented at the same time, more accurate evaluation can be performed.

Examples of various evaluations by the control unit 26 are shown below.

In the pattern defect inspection method of the wafer 8 by the pattern matching, the control unit 26 controls the secondary electron beam reference image of the defect-free wafer stored in the memory 23 in advance and the actually detected secondary electron beam. The line image is compared and collated, and the similarity between the two is calculated. For example, when the similarity falls below the threshold, it is determined that there is a defect, and when the similarity exceeds the threshold, it is determined that there is no defect. At this time, C
The detection image 27 may be displayed on the RT 25. Thereby, the operator can finally confirm and evaluate whether or not the wafer 8 actually has a defect. Further, each partial area of the image may be compared and collated to automatically detect an area where a defect exists. At this time, it is preferable to display an enlarged image of the defective portion on the CRT 25.

In the case of a wafer having many identical dies, a defective portion can be detected by comparing the detected images of the detected dies without using the reference image as described above. For example, FIG. 3A shows an image 31 of a die detected first and an image 32 of another die detected second. If the image of another die detected third is determined to be the same or similar to the image 31 of the first die, the portion 33 of the second die image 32 is determined to have a defect, and the defective portion is detected. it can. At this time, the detected image may be displayed on the CRT 25 and the portion determined to be defective may be displayed as a mark.

FIG. 3B shows an example of measuring the line width of a pattern formed on a wafer. The actual secondary electron intensity signal when the actual pattern 34 on the wafer is scanned in the direction of 35 is 36, and the signal where the signal continuously exceeds a threshold level 37 predetermined by calibration Can be measured as the line width of the pattern. If the line width measured in this way is not within the predetermined range, it can be determined that the pattern has a defect.

The line width measurement method shown in FIG. 3B can be applied to measurement of alignment accuracy between layers when the wafer 8 is formed of a plurality of layers. For example, a second alignment pattern formed by the second-layer lithography is formed in advance near the first alignment pattern formed by the first-layer lithography. These two
The pattern spacing of the book is measured by applying the method of FIG. 3B, and the measured value is compared with a design value to determine the alignment accuracy between the two layers. Of course, the present invention can be applied to the case of three or more layers. In this case, the interval between the first and second alignment patterns is determined by the electron beam device 18.
By setting the interval substantially equal to the interval between the adjacent primary electron beams, the alignment accuracy can be measured with a minimum scanning amount.

FIG. 3C shows an example of measuring the potential contrast of a pattern formed on a wafer. In the electron beam apparatus 18 shown in FIG. 1, an axially symmetric electrode 39 is provided between the objective lens 7 and the wafer 8, and a potential of, for example, -10 V is applied to a wafer potential of 0 V. At this time, the −2V equipotential surface has a shape as indicated by 40. Here, it is assumed that the patterns 41 and 42 formed on the wafer have a potential of -4V and 0V, respectively. In this case, the secondary electrons emitted from the pattern 41 have an upward velocity corresponding to the kinetic energy of 2 eV on the -2V equipotential surface 40. It escapes from 39 and is detected by the detector 12. On the other hand, the secondary electrons emitted from the pattern 42 cannot cross the potential barrier of -2 V, and
As shown in (1), it is not detected because it is driven back to the wafer surface. Therefore, the detected image of the pattern 41 is bright, and the detected image of the pattern 42 is dark. Thus, wafer 8
The potential contrast of the region to be inspected is obtained. If the brightness and the potential of the detected image are calibrated in advance, the potential of the pattern can be measured from the detected image. Then, a defective portion of the pattern can be evaluated from the potential distribution.

In FIG. 1, a blanking deflector 17 is provided, and the primary electron beam is supplied to the knife-edge beam stopper 7 near the crossover image point 4 by the deflector 17.
By deflecting the beam to 0 at a predetermined cycle and repeatedly passing the beam for a short period of time and blocking it at other times, a beam bundle having a short pulse width can be produced. If the potential measurement on the wafer as described above is performed using such a short pulse width beam, the device operation can be analyzed with high time resolution. That is, the present electron beam apparatus is so-called EB
Can be used as tester. (Second Embodiment) The second embodiment is different from the first embodiment only in the method of determining the step (distance h) of the first multi-aperture plate 3. The other components and the basic operation are the same as those of the first embodiment, and therefore, are described with the same reference numerals, and detailed description is omitted.

In the second embodiment, a wafer having uniform secondary electron emission characteristics, that is, a ratio of the intensity of a primary electron beam and the intensity of a secondary electron beam emitted by the wafer is set on the stage 22 over the entire inspection surface. A wafer having characteristics that are substantially constant over the entire area is arranged. With the first multi-aperture plate 3 removed, or the above-described proxy multi-aperture plate (not shown)
Are prepared and arranged at the same position as the first multi-aperture plate 3, primary electrons are emitted from the electron gun 1, and the intensity of a plurality of secondary electron beams is measured by the multi-detection element 60 of the detector 12. . As in the first embodiment, the ratio of these intensities is determined, and the distance h between each aperture 20 and the crossover imaging point 4 is determined.
_{(H 0, .. h k,} .. h n) ratio is such that the square root times the measured secondary electron beam intensity ratio, determines each distance h. Thus, the first multi-aperture plate 3 that makes the intensity of the secondary electron multi-beam almost constant can be easily formed.

In the second embodiment, not only the radial dependence of the beam intensities of the electron gun 1 and the primary optical system but also the influence of a decrease in the peripheral transmittance of the secondary optical system are simultaneously calibrated. Accuracy can be evaluated. (Third Embodiment; Method of Manufacturing Semiconductor Device) In this embodiment, the electron beam apparatus described in the above embodiment is applied to evaluation of a wafer in a semiconductor device manufacturing process.

An example of the device manufacturing process will be described with reference to the flowchart of FIG.

This example of the manufacturing process includes the following main steps. Wafer manufacturing process for manufacturing wafer 8 (or preparation process for preparing wafer) (Step 100) Mask manufacturing process for manufacturing a mask used for exposure (or mask preparation process for preparing mask) (Step 1)
01) Wafer processing step for performing necessary processing on the wafer (Step 102) Chip assembling step for cutting out chips formed on the wafer one by one and making it operable (Step 1)
03) Chip inspection step of inspecting the assembled chip (step 104) Each step is further composed of several sub-steps.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps. A thin film forming step (using CVD, sputtering, etc.) for forming a dielectric thin film, a wiring portion, or a metal thin film for forming an electrode portion, which serves as an insulating layer; an oxidizing process for oxidizing the formed thin film layer or the wafer substrate; Lithography process to form resist pattern using mask (reticle) to selectively process wafer substrate etc. Etching process to process thin film layer and substrate according to resist pattern (eg using dry etching technology) Ion / impurity implantation Diffusion process Resist stripping process Inspection process for inspecting the processed wafer The wafer processing process is repeated as many times as necessary to manufacture semiconductor devices that operate as designed.

FIG. 5 is a flowchart showing the lithography step which is the core of the wafer processing step. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the previous step (step 2)
00) Exposure step of exposing the resist (Step 201) Development step of developing the exposed resist to obtain a resist pattern (Step 202) Annealing step for stabilizing the developed pattern (Step 203) Known processes are applied to the device manufacturing process, the wafer processing process, and the lithography process.

In the above-described wafer inspection process, when the evaluation device according to each of the above embodiments of the present invention is used, even a semiconductor device having a fine pattern can be evaluated with high throughput and high accuracy. Yield can be improved and defective products can be prevented from being shipped.

The above is each of the above embodiments, but the present invention is not limited only to the above examples.

For example, in the multi-aperture plate 3 of the above example, the center opening 20a has a larger distance h from the crossover imaging point 4 than the peripheral opening 20b. This is because the radial intensity distribution has a peak in the center, and is used to calibrate a typical beam variation that decreases in the periphery. The present invention is equally applicable to a plurality of primary electron beams (or secondary electron beams) exhibiting any other radial distribution intensity. For example, in the case of a primary electron beam having a peak at the periphery and decreasing at the center, it can be dealt with by making the distance h of the opening 20 of the first multi-aperture plate 3 small at the center and large at the periphery.

In the above example, the beam intensity distribution for determining the distance h was measured by the inspection surface of the wafer in the first embodiment, and by the multi-detection element 60 in the second embodiment. However, the present invention is not limited to these. For example, when the reduction in the peripheral transmittance of the primary and secondary optical systems is so small that it does not matter, the intensity distribution of the beam is measured at the first multi-aperture plate 3, and the distance h is obtained from the measurement result. Is also good.

Further, in the first and second embodiments, a preferred example in which the optical axis 50 of the primary optical system is substantially perpendicular to the wafer, and the secondary electron beam is deflected to the detector in a direction oblique to the optical axis. showed that. However, the electron beam apparatus according to the present invention irradiates a primary electron beam to a wafer surface in an oblique direction, thereby detecting secondary electrons emitted from the wafer in an oblique direction, without using an E × B separator. Can also be used.

Although a semiconductor wafer has been described as an example of a sample to be inspected, the sample to be inspected according to the present invention is not limited to this, and any sample on which a pattern capable of detecting a defect by an electron beam or the like is formed, for example, A mask or the like can be evaluated.

Further, charged particles other than electrons may be used as long as the pattern of the wafer can be inspected.

[0061]

As described above in detail, according to the evaluation apparatus of the present invention, at least one of the plurality of primary charged particle beams detected on the sample and the plurality of secondary charged particle beams detected by the detecting means. By adjusting the positions of the plurality of apertures formed in the beam forming means in the direction of the optical axis, that is, by adjusting the distance from the crossover image point, almost uniformity can be obtained, so that high resolution and high aberration correction can be achieved. While enabling
An excellent effect is obtained in that errors in defect inspection, line width measurement, and the like due to uneven brightness of an image are reduced, and highly accurate evaluation is possible.

Further, according to the device manufacturing method of the present invention,
Since the wafer being processed or the finished product is evaluated using the above-described evaluation device, highly accurate evaluation is possible, and the yield of device manufacturing is improved, and the shipment of defective products can be prevented beforehand. . An excellent effect is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an evaluation device according to the present invention.

FIG. 2 is a top view and a side sectional view of a first aperture plate according to the present invention.

3A and 3B are diagrams illustrating a wafer inspection method according to the present invention, wherein FIG. 3A shows pattern defect detection, FIG. 3B shows line width measurement, and FIG. 3C shows potential contrast measurement, respectively.

FIG. 4 is a flowchart showing a semiconductor device manufacturing process.

FIG. 5 is a flowchart showing a lithography process in the semiconductor device manufacturing process of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron gun 2 Condenser lens 3 Multi-aperture plate 4 Crossover imaging point 5 Reduction lens 6 ExB separator 7 Objective lens 8 Semiconductor wafer 9, 10 Magnification lens (secondary optical system) 11 Second multi-aperture plate 12 Detector 14 Image processing unit 17 Blanking deflector 18 Electron beam device 19 Deflector 20 Plural openings of first multi-aperture plate 21 Plural openings of second multi-aperture plate 23 Memory for reference image 24 Secondary electrons Image memory 25 CRT 26 Control unit 27 Secondary electron beam image 29 Evaluation program 30 Evaluation device 31 Detected image on first die 32 Detected image on second die 33 Defect portion of die 34 Pattern 35 Scanning range 36 Secondary electron intensity signal 37 Threshold level 38 Line width 39 Axisymmetric electrode 40 2V equipotential surface 41 Low point Initial pattern 42 High potential pattern 43 Secondary electron trajectory from low potential pattern 44 Secondary electron trajectory from high potential pattern 50 Optical axis of primary optical system 52 Optical axis of secondary optical system 56 Correction deflection for secondary electron beam Instrument 60 Multi-detector element 70 Knife-edge beam stopper

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/027 H01L 21/66 J 21/66 21/30 502V (72) Inventor Mamoru Nakasuji Ota-ku, Tokyo 11-1 Haneda Asahimachi Ebara Meister Co., Ltd. (72) Inventor Shinji Noji 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Works Co., Ltd. (72) Inventor Tohru Satake Tokyo Asahi-cho, Ota-ku, Tokyo 11-1 F-term in EBARA CORPORATION F-term (Reference) 4M106 AA01 BA02 CA39 DB05 DB20 DB21 DE01 DE03 DE04 DE06 DE16 DJ11 DJ14 DJ18 DJ21 DJ23 5B047 AA12 BA02 BB01 BC05 CA19 DA06 DC06 5C030 AA01 AA02 AB02 5C033 BB02 BB03 TT02 UU03 UU04

Claims (5)

[Claims] An evaluation apparatus for evaluating a sample on which a pattern is formed, comprising: a charged particle source that emits a primary charged particle beam; and a condenser lens that focuses the emitted primary charged particle beam to form a crossover. A beam forming means disposed between the condenser lens and the imaging point of the crossover, the beam forming means having a plurality of apertures for forming a plurality of beams from the primary charged particle beam passing through the condenser lens; An imaging optical system for imaging a plurality of beams, each of which has passed through the sample, on the sample such that each irradiation spot of the plurality of beams imaged on the sample is scanned on the sample. Deflecting means for deflecting, and detecting means for detecting intensities of a plurality of secondary charged particle beams emitted from respective irradiation spots of the plurality of beams scanned on the sample surface, respectively. And evaluating means for performing the evaluation of the sample based on the intensity distribution of the secondary charged particle beam on the sample detected by the detecting means. The evaluation device, wherein the positions of the plurality of apertures in the optical axis direction are determined so that the intensities of the plurality of beams when being imaged are substantially equal to each other. 2. An evaluation apparatus for evaluating a sample on which a pattern is formed, comprising: a charged particle source for emitting a primary charged particle beam; and a condenser lens for converging the emitted primary charged particle beam to form a crossover. A beam forming means disposed between the condenser lens and the imaging point of the crossover, the beam forming means having a plurality of apertures for forming a plurality of beams from the primary charged particle beam passing through the condenser lens; An imaging optical system for imaging a plurality of beams, each of which has passed through the sample, on the sample such that each irradiation spot of the plurality of beams imaged on the sample is scanned on the sample. Deflecting means for deflecting, and detecting means for detecting intensities of a plurality of secondary charged particle beams emitted from respective irradiation spots of the plurality of beams scanned on the sample surface, respectively. And evaluating means for evaluating the sample based on the intensity distribution of the secondary charged particle beam on the sample detected by the detecting means. The beam forming means comprises: When a calibration sample having substantially uniform secondary charged particle emission characteristics at each irradiation spot is used, the intensity of the plurality of secondary charged particle beams detected by the detection means is adjusted to be substantially equal to each other. The evaluation device. 3. The beam forming means is provided as an aperture plate in which the plurality of apertures are formed, and the aperture plate is closer to the image point of the crossover as the aperture is larger from the optical axis. The evaluation device according to claim 1, wherein the evaluation device is stepped on the evaluation device. 4. The method according to claim 1, wherein the evaluating unit detects a defect of the pattern of the sample, measures a line width of the pattern of the sample, measures a potential of the pattern, and adjusts each layer when the sample is formed of a plurality of layers. 4. The method according to claim 1, wherein at least one of measurement of accuracy and operation analysis of the sample based on potential measurement of the pattern while irradiating the primary charged particle beam with a short pulse width is executable. Item 4. The evaluation device according to any one of items 3. 5. A device manufacturing method, comprising a step of evaluating a wafer being processed or a finished product by using the evaluation apparatus according to claim 1.