JP2002208369A - Surface state observastion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface state observation device which enables observation at high resolution without causing a device to be any larger even in case of distortion aberration remaining at a secondary optical system. SOLUTION: With the surface state observation device provided with a primary optical system irradiating a primary electron beam on a sample, a secondary optical system focusing secondary electron beam obtained by irradiating the primary electron beam on the sample, and an image pick-up element picking up an optical image of the secondary beam through the secondary optical system, distortion aberration generated at the secondary optical system is corrected by arrangement of picture elements C1 to C1024 the image pick-up element has in accordance with distortion aberration of the secondary optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating an object with a charged particle beam such as an electron beam or an ion beam or an electromagnetic wave such as light or X-ray as a primary beam and irradiating the object with the primary beam. The present invention relates to a surface state observation device that detects a beam (secondary electron, reflected electron, backscattered light, reflected light) to observe or inspect the surface state of an object.

[0002]

2. Description of the Related Art A semiconductor element has a fine pattern formed on the surface of a semiconductor substrate by using a planar technique.
Due to the demand for miniaturization of semiconductor devices, their patterns are miniaturized and highly integrated. A charged particle beam microscope using charged particles such as an electron beam (electron beam) is used for observing the surface state of the semiconductor element and performing defect inspection. Conventionally known as a charged particle microscope, a microscope frequently used is a scanning electron microscope (S
EM: Scanning Electron Microscope. A scanning electron microscope irradiates a point on the surface of an object with an electron beam,
By detecting secondary electrons, reflected electrons, and backscattered electrons generated from the point irradiated with the electron beam, and performing such an operation while scanning the object relatively to the irradiated electron beam, an image of the object surface is obtained. Form. The scanning electron microscope has a problem that the observation requires a relatively long time because it is necessary to relatively scan the electron beam and the object over the entire area to be observed.

In recent years, a mapping electron microscope has been proposed as an apparatus for solving this problem. This mapping electron microscope irradiates a charged particle beam such as an electron beam or an ion beam or an electromagnetic wave such as light or X-ray in a plane onto an observation surface of an object, and as a result, secondary electrons generated from the surface of the object and reflections are generated. A device for observing the surface of an object by accelerating and converging electrons and backscattered electrons, enlarging and projecting the image by an electron optical system to form an image on an imaging surface, and converting the electron intensity distribution into a light intensity distribution. It is. A mapping electron microscope for irradiating an object with an electron beam is disclosed in, for example, JP-A-10-197462 and JP-A-11-64256.

[0004] In particular, a mapping electron microscope disclosed in Japanese Patent Application Laid-Open No. H10-197462 mounts an object to be observed on a stage, and moves a stage to move a two-dimensional image formed on an imaging surface by a TDI. (Time-Delay-Integration;
Time delay integral type) Array CCD (Charge Coupled Devic)
e). Here, the configuration of the TDI array CCD will be briefly described as follows. The TDI array CCD has a plurality of rows (e.g., 256) and a plurality of columns (e.g., 1024), pixels are arranged at intersections of the respective rows and columns, and accumulated in the pixels arranged in the respective rows. In this configuration, charges are transferred to adjacent rows for each column. In other words, the TDI array CCD can be considered as a line sensor for the number of rows having the length of the number of columns. Therefore, T
By synchronizing the charge transfer timing of the DI array CCD with the stage movement timing, the same signal is sequentially added each time charge is transferred, so that the detection sensitivity can be improved.

[0005] In a mapping electron microscope, a commonly used CCD is used, and a stage on which an object is placed is moved by a certain distance to take an image with the CCD, and then the stage is further moved by a certain distance to take an image with the CCD. , That is, the stage can be observed by step-and-repeat driving. However, observing while scanning the stage on which an object is placed can be easily realized in consideration of mechanical accuracy and the like, rather than observing by driving the stage step-and-repeat. . Further, since the TDI array CCD has high sensitivity, high-speed scanning is possible. For this reason, the mapping electron microscope disclosed in the above publication detects the two-dimensional image formed on the imaging surface while moving the stage with the TDI array CCD at high speed and high sensitivity.

[0006]

By the way, in order to precisely inspect the surface condition of an object, it is necessary to focus secondary electrons, reflected electrons, and backscattered electrons from the object surface to form an image on an imaging surface. It is necessary to minimize aberrations of the secondary optical system, especially distortion. FIG. 8 is a diagram illustrating an example of distortion.
Now, as shown in FIG. 8A, when the lattice shape is arranged on the object plane (for example, the surface of the object to be observed), and when the secondary optical system has distortion, the image plane The image formed on (for example, the imaging surface) is deformed into a barrel shape, for example, as shown in FIG. Such a deformed image is transferred to a CCD
In the case where the image is picked up, the surface of the object is observed in a state where an error corresponding to the deformation occurs.

Further, when the image shown in FIG. 8B is picked up by the TDI array CCD, the detection accuracy is further deteriorated due to the configuration of the TDI array CCD. Hereinafter, the cause will be described. FIG. 9 is a diagram for explaining deterioration of detection accuracy when an image having distortion is detected by the TDI array CCD. Now, for ease of understanding, it is assumed that there is a point light source on the observation surface on the object. When observing with a TDI array CCD, since the observation is performed while moving the stage as described above, the locus tr1 of the point light source on the object surface (observation surface) becomes linear as shown in FIG. 9A. If no distortion occurs in the secondary optical system, a linear trajectory is also formed on the image plane.

However, when distortion occurs in the secondary optical system, the image formed on the image plane is deformed as shown in FIG. 8B, so that the point light source moves on the object plane. Then, the trajectory on the image plane does not become a straight line, and FIG.
A locus tr2 of the curve is obtained as shown in FIG. When the locus tr2 of such a curve is detected by the TDI array CCD,
In rows r1 and r3 located at the ends of the TDI array CCD, the pixels are observed at the j-th (j is a natural number) column of pixels, and TD
In row r2 located at the center of the I-array CCD,
It is detected at the pixel of the i-th (i is a natural number satisfying i <j) column. As described above, since the TDI array CCD sequentially transfers the accumulated charges to the adjacent rows, the image of the point light source on the object plane is located at the distance Δ between the i-th column and the j-th column on the image plane.
Observed blurred by the width of X. As described above, when an optical image having distortion is detected by the TDI array CCD, the image deteriorates. The same applies to the resolution in the image scanning direction. In the scanning direction, the scanning speed of the point light source image on the image plane is not constant. In order to solve the problems described above, it is necessary to set the distortion of the secondary optical system to be equal to or less than the resolution of the TDI array CCD.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a surface capable of observing at a high resolution without increasing the size of the apparatus even when distortion remains in the secondary optical system. It is an object to provide a state observation device.

[0010]

In the following, in the examples shown in this section, for ease of understanding, specific items of the present invention will be described with reference numerals shown in the drawings of the embodiments. ,
The configuration of the present invention or the specific matters of the present invention are not limited to those restricted by these reference numerals. In order to solve the above problems, a surface state observation apparatus according to a first aspect of the present invention includes a primary optical system (11) for irradiating a primary beam (B1) onto an object (4), and the primary beam (B1). And a secondary optical system (20) for focusing a secondary beam (B2) obtained by irradiating the object (4) with the object (4), and a secondary beam (B2) passing through the secondary optical system (20) is detected. Detecting means (30,
34, 35), wherein the surface state observation device is adapted to respond to distortion occurring on the detection surface of the detection means (30, 34, 35) due to the optical characteristics of the secondary optical system (20). And a correction means for performing the correction. According to the present invention, even if the secondary beam obtained by irradiating the primary beam to the object causes distortion on the detection surface due to the optical characteristics of the secondary optical system, the distortion is corrected by the correction unit. Therefore, even if the distortion of the secondary optical system cannot be completely corrected, the distortion can be observed with high resolution even if the distortion remains. Here, the primary beam and the secondary beam include charged particle beams such as electron beams and ion beams, or electromagnetic waves such as light and X-rays. Further, in the surface state observation device according to a second aspect of the present invention, in the surface state observation device according to the first aspect, the correction unit corrects a pixel on a detection surface of the detection unit (30, 34, 35) by the distortion. It is characterized by being arranged according to aberration. The surface state observation device according to a third aspect of the present invention is the surface state observation device according to the second aspect, wherein the stage (40) movable with the object (4) mounted thereon; 40) A position information detecting device (42) for detecting position information, and the stage (40) detected by the position information detecting device (42).
Control means (37) for causing the detection means (30, 34, 35) to detect the secondary beam (B2) while synchronizing with the movement of the stage (40) based on the positional information of the stage (40). Features. The surface state observation device according to a fourth aspect of the present invention is the surface state observation device according to the third aspect, wherein the position information detection device (42).
Is a movable mirror (4) arranged on the stage (40).
1) and an interferometer (42) arranged to face the mirror surface of the movable mirror (41). The surface state observation device according to a fifth aspect of the present invention is the surface state observation device according to the third aspect or the fourth aspect, wherein the detecting means (30, 34, 35) includes a time-delay integration type imaging device. It is characterized by comprising an element (35).
Further, the surface state observation device according to the sixth aspect of the present invention includes:
In the surface state observation device according to the first aspect, the pixels provided in the detection means (30, 34, 35) are two-dimensionally arranged at equal intervals on the detection surface, and the correction means is provided in the detection means (30 , 34, and 35), and a processing device (37) for correcting a pixel signal output from each pixel according to the distortion.
Further, the surface state observation device according to the seventh aspect of the present invention includes:
In the surface state observation apparatus according to a sixth aspect, a storage unit (44) for storing a distortion amount of the secondary optical system (20) previously obtained from a design value of the secondary optical system (20) or an actually measured value. Wherein the processing device (37) corrects the pixel signal based on the distortion amount stored in the storage means (44). The surface state observation device according to an eighth aspect of the present invention is the surface state observation device according to the sixth or seventh aspect, wherein the stage (4) movable with the object (4) mounted thereon is provided.
0) and the secondary beam (B) is applied to the detection means (30, 34, 35) while synchronizing with the movement of the stage (40).
And a control means (37) for detecting (2). The surface state observation device according to a ninth aspect of the present invention is the surface state observation device according to the first to eighth aspects, wherein the primary beam (B1) is a charged particle beam, and the secondary beam (B1) is a charged particle beam. B2) is characterized by being at least one of secondary electrons, reflected electrons, and backscattered electrons generated by irradiating the charged particle beam to the object (4). A surface state observation device according to a tenth aspect of the present invention is the surface state observation device according to the ninth aspect, wherein the detecting means (30, 34, 35)
Comprises a conversion means (32) for converting the secondary beam (B2) focused by the secondary optical system (20) into photons, and detecting the photons converted by the conversion means (32) to obtain the photons. It is characterized by detecting the secondary beam (B2). The semiconductor element of the present invention is subjected to surface observation using the surface state observation device, and the microdevice manufacturing method of the present invention includes a step of observing the surface of the microdevice using the surface state observation device. Features.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface state observing apparatus according to an embodiment of the present invention will be described below in detail with reference to the drawings. [First Embodiment] FIG. 1 is a view showing the arrangement of a surface state observation apparatus according to a first embodiment of the present invention. In the following description, the XYZ rectangular coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to the XYZ rectangular coordinate system. In the XYZ orthogonal coordinate system shown in FIG. 1, an XY plane is set in the object plane of the sample, and the normal direction of the object plane of the sample is set in the Z-axis direction. XY in FIG.
In the Z coordinate system, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set vertically downward.

The surface state observation apparatus according to the present embodiment mainly comprises a primary column 1 for accelerating an electron beam and guiding it to a sample.
A secondary column 2 for focusing a secondary electron beam generated when the sample is irradiated with an electron beam on a detection surface of the electron beam detector 30, and a chamber containing a sample (object) 4 to be observed And 3. The optical axis of the primary column 1 is set oblique to the Z axis, and the optical axis of the secondary column 2 is set substantially parallel to the Z axis. Therefore, the primary electron beam B1 as a primary beam is incident from the primary column 1 to the secondary column 2 from an oblique direction. A vacuum exhaust system (not shown) is connected to the primary column 1, the secondary column 2, and the chamber 3, and the primary column 1, the secondary column 2, and the chamber 3 are exhausted by a vacuum pump such as a turbo pump provided in the vacuum exhaust system. Will be maintained.

A thermionic emission electron gun 10 is provided inside the primary column 1, and a primary optical system 11 is arranged on the optical axis of a primary electron beam B1 emitted from the thermionic emission electron gun 10. You. Here, as a chip of the thermionic emission electron gun 10, for example, lanthanum hexaborite (LaB ₆ ) which can take out a large current with a rectangular cathode is preferably used. The primary optical system 11 has a field stop FS
1, irradiation lenses 12, 13, 14 and aligners 15, 1
6, a scan aligner 17, an aperture 18, and the like. Here, the irradiation lenses 12, 13, and 14 are electronic lenses, for example, circular lenses, quadrupole lenses,
A pole lens or the like is used. The convergence characteristics of the irradiation lenses 12, 13, and 14 of the primary optical system 11 with respect to the primary electron beam B1 are changed by changing the applied voltage. The irradiation lenses 12, 13, and 14 may be rotationally symmetric lenses called unipotential lenses or Einzel lenses.

A secondary optical system 20 is arranged in the secondary column 2. The secondary optical system 20 is for converging a secondary electron beam B2 as a secondary beam generated when the sample 4 is irradiated with the primary electron beam B1 to form an image on a detection surface of the electron beam detector 30. , The cathode lens 21, the first aligner 22, the aperture stop AS, the e-cross bee 23, and the stigmator 2 in the order from the sample 4 side to the −Z direction.
4, an imaging lens front group 25, a second aligner 26, a stig meter 27, a field stop FS2, an imaging lens rear group 28, and a third aligner 29 are arranged.

The field stop FS2 of the secondary optical system 20
Is set in a positional relationship conjugate with the object plane of the sample 4 with respect to the cathode lens 21 and the imaging lens front group 25. The front lens group 25 and rear lens group 28 of the secondary optical system 20 are electronic lenses, for example, a circular lens, a quadrupole lens, an octupole lens, or the like. still,
The cathode lens 21, the imaging lens front group 25, and the imaging lens rear group 28 may be rotational axis symmetric lenses called unipotential lenses or Einzel lenses. Also, the cathode lens 2 provided in the secondary optical system 20
1. The convergence characteristics of the front lens group 25 and the rear lens group 28 with respect to the secondary electron beam B2, that is, the focal position of the secondary electron beam B2 is changed by changing the applied voltage. The deflection characteristics and the convergence characteristics of the e-cross B 23 with respect to the primary electron beam B1 and the secondary electron beam B2 are changed by changing the applied voltage or current.

Further, an electron beam detector 30 is arranged in the -Z direction of the third aligner 29 provided in the secondary optical system 20. On the detection surface of the electron beam detector 30, a secondary electron beam B2 emitted when the sample 4 is irradiated with the electron beam B1 is imaged by the secondary optical system 20. here,
The electron beam detector 30 includes an MCP for amplifying electrons.
(Micro Channel Plate) 31, a fluorescent plate 32 as conversion means for converting electrons into photons, and a vacuum window for emitting light converted by the fluorescent plate to the outside of the secondary column 2 maintained in a vacuum state. 33.
The light emitted from the electron beam detector 30, that is, the optical image of the sample 4 is transmitted through the relay lens 34, and the TDI (Time-D
elay-Integration; time delay integration type) Array CCD (Ch
(Arge Coupled Device).

Here, the configuration of the image sensor 35 will be described. FIG. 2 shows a TDI array CC as an image sensor 35.
FIG. 3 is a functional block diagram showing a configuration of D. TDI array C
CD has 1024 pixels C1 in the horizontal direction (X-axis direction).
To C1024 to form a linear CCD pixel row, and 256 rows of C pixels in the vertical direction (Y-axis direction).
It is configured by arranging CD pixel rows R1 to R256. CC
The accumulated charges on the pixels arranged in each of the D pixel rows R1 to R256 are transferred in the vertical direction at a time by one CCD pixel row by one vertical clock signal supplied from the outside.

Of the images formed on the image pickup surface (detection surface) of the image pickup device 35, the image picked up by the CCD pixel line R1 at a certain point in time moves vertically by one CCD pixel line, and is synchronized with it. When a vertical clock signal is applied, the pixel signals accumulated in each pixel of the CCD pixel row R1 are transferred to the CCD pixel row R2. In the CCD pixel row R2, the same image as the image picked up by the CCD pixel row R1 is taken before the vertical clock signal is applied, so that the charge of the image stored in the CCD pixel row R2 is doubled. Subsequently, when the image is further moved in the vertical direction by one CCD pixel row and a synchronous clock signal is applied, the stored image is transferred to the CCD pixel row R3, where triple image charges are stored. Subsequently, the CCD pixel row R follows the movement of the image.
When the transfer of charges and the imaging are repeated up to 256, the result of storing 256 times the charge initially stored in the CCD pixel row R1 is serially output as a pixel signal from the horizontal output register HR.

Next, the arrangement of each pixel of the image sensor 35 will be described. FIG. 3 is a diagram showing an arrangement of pixels included in the image sensor 35 on an imaging surface. In FIG.
The portions denoted by reference symbols R1 to R256 are CCDs shown in FIG.
The pixel rows R1 to R256 are shown. As shown in FIG. 3, the pixels included in the imaging element 35 are arranged according to the distortion generated in the secondary optical system 20. In the example shown in FIG. 3, the pixels C1 to C1024 arranged in the CCD pixel rows R1 to R256 are not linearly arranged in the peripheral portion of the imaging surface, and the pixels arranged in the same row are not linearly arranged. They are not arranged in a pattern.

By arranging the pixels of the image sensor 35 in accordance with the distortion of the secondary optical system 20 as shown in FIG. 3, the linear locus tr1 shown in FIG. 9A was observed. In this case, the locus tr of the curve shown in FIG.
2 are imaged, but since the pixels are arranged according to the distortion of the secondary optical system 20, the pixel signal output from the image sensor 35 is a signal reflecting the linear locus tr1, that is, A pixel signal obtained when there is no distortion in the next optical system 20 is obtained. The electron beam detector 30, the relay lens 34, and the image sensor 35 described above constitute a detecting means according to the present invention. The pixels of the image sensor 35 arranged so as to correct the distortion of the secondary optical system 20 form a correction unit.

Returning to FIG. 1, a control unit 36 is connected to the image pickup device 35. The control unit 36 serially reads out pixel signals output from the image sensor 35 and sequentially outputs the pixel signals to the main control system 37. The main control system 37 performs image processing such as template matching on the pixel signal output from the control unit 36 to determine whether or not the sample 4 has a defect. Further, the main control system 37 outputs a control signal to the primary optical system control unit 38 and the secondary optical system control unit 39 to control the optical characteristics of the primary optical system 11 and the secondary optical system 20 and to control the e-cross bee 23
Is performed. The image signal output from the control unit 36 to the main control system 37 is converted to a CRT (Cathod) signal.
If the image is displayed on a display device such as a Ray Tube, the image of the sample 4 is displayed on the display device.

Next, the configuration inside the chamber 3 will be described. An XY stage 40 configured to be movable in an XY plane while the sample 4 is placed inside the chamber 3.
Is arranged. An L-shaped movable mirror 41 is attached to one end of the XY stage 40, and a laser interferometer 4 as a position information detecting device is provided at a position facing the mirror surface of the movable mirror 41.
2 are arranged. Although shown in a simplified manner in FIG. 1, the movable mirror 41 includes a plane mirror having a reflection surface perpendicular to the X axis and a plane mirror having a reflection surface perpendicular to the Y axis. In addition, the laser interferometer 42 moves the movable mirror 4 along the X axis.
1 is composed of two X-axis laser interferometers for irradiating a laser beam and a Y-axis laser interferometer for irradiating the movable mirror 41 with a laser beam along the Y-axis. With the laser interferometer and one laser interferometer for the Y axis,
The X and Y coordinates of the XY stage 40 are measured. Also, due to the difference between the measured values of the two laser interferometers for the X axis,
The rotation angle of the XY stage 40 in the XY plane is measured.

The measurement result of the laser interferometer 42 is transmitted to the main control system 3
7, the main control system 37 outputs a control signal to the driving device 43 based on the measurement result, and controls the position of the XY stage 40 in the XY plane. Incidentally, the main control system 37 forms a control means according to the present invention. Although not shown, a Z stage that can change the position of the sample 4 in the Z-axis direction and a tilt stage that controls the inclination of the object surface of the sample 4 with respect to the XY plane are provided in addition to the XY stage 40. Is preferred. Reference numeral 44 denotes a storage device serving as storage means for storing a distortion amount of the secondary optical system 20 obtained in advance from a design value of the secondary optical system 20 or an actually measured value.

The configuration of the surface state observation apparatus according to one embodiment of the present invention has been described above. Next, the trajectory of the primary electron beam B1 and the secondary electron beam B2 of the surface state observation apparatus according to one embodiment of the present invention will be described. This will be described in detail. FIG. 4 is a diagram showing the trajectory of the primary electron beam B1 of the surface state observation device according to one embodiment of the present invention. In FIG. 4, some of the members included in the primary optical system 11 are omitted for easy understanding. The primary electron beam B1 emitted from the thermionic electron gun 10 is focused and diverged under the influence of the electric field formed by the irradiation lenses 12, 13, and 14, as shown in FIG. Here, when the long axis direction of the rectangular chip of the thermoelectron emission type electron gun 10 is set in the x-axis direction and the short axis direction is set in the y-axis direction, the chip is emitted in the x-axis section of the rectangular cathode. electron trajectories becomes trajectory shown by a reference numeral P _x in FIG. 4, the trajectory of electrons emitted in the x-axis direction cross-section of the rectangular cathode is the trajectory shown by a reference numeral P _y in FIG.

After being affected by the electric field by the irradiation lenses 12, 13, and 14, the primary electron beam B1 is incident on the e-cross bee 23 from an oblique direction. Primary electron beam B1
Enters the e-cross bee 23, its optical path is Z
It is deflected in a direction substantially parallel to the axis. The primary electron beam B1 deflected by the e-cross beam 23 reaches the aperture stop AS, and at this position, the thermionic electron gun 10
To form an image of the crossover. After passing through the first aligner 22, the primary electron beam B1 that has passed through the aperture stop AS is subjected to a lens action by the cathode lens 21, and
The sample 4 is illuminated with Koehler.

When the sample 4 is irradiated with the primary electron beam B1, secondary electrons, reflected electrons, and backscattered electrons having a distribution according to the surface shape, material distribution, potential change, and the like of the sample 4 are emitted from the sample 4. The generated secondary electron beam B2 is generated. Among them, the secondary electron beam B2 mainly due to the secondary electrons is the observation electron beam. The initial energy of the secondary electron beam B2 is low, about 0.5 to 2 eV. Next, the trajectory of the secondary electron beam B2 generated from the sample 4 will be described.
FIG. 5 is a diagram showing the trajectory of the secondary electron beam B2 of the surface state observation device according to one embodiment of the present invention. In FIG. 5, some of the members included in the secondary optical system 20 are not shown for easy understanding.

The secondary electron beam B2 emitted from the sample 4
Is a cathode lens 21 provided in the secondary optical system 20;
Aligner 22, aperture stop AS, e-cross bee 23
Pass in order. When the secondary electron beam B2 is
After passing through the bee 23, the light is converged by the front lens group 25, and an image of the sample 4 is formed at the position of the field stop FS2. The secondary electron beam B2 that has passed through the field stop FS2 is converged again by the rear lens group 28, and an enlarged image of the object surface of the sample 4 is formed on the detection surface of the electron beam detector 30. At this time, if the distortion remains in the secondary optical system 20, the image formed on the detection surface reflects the distortion. When the secondary electron beam B2 is incident on the electron beam detector 30, the number of electrons is first amplified by the MCP 31, and then is incident on the fluorescent screen 32 and converted into photons. The optical image converted by the fluorescent plate 32 forms an image on an imaging surface of an imaging device 35 via a relay lens 34. At this time, since the size of the image of the sample 4 on the fluorescent screen 32 is larger than the imaging surface of the imaging device 35, the relay lens 3
Reference numeral 4 is set to reduce the optical image converted by the fluorescent screen 32 at a predetermined magnification.

Next, the e-cross bee 23 provided in the surface state observation apparatus according to one embodiment of the present invention will be described in detail. FIG. 6 is a diagram for explaining the configuration and operation principle of the e-cross bee 23 provided in the surface state observation device according to one embodiment of the present invention. FIG. 6A is a perspective view showing the configuration of the e-cross bee 23. FIG.
As shown in FIG. 3A, the primary electron beam B1 emitted from the thermionic electron gun 10 is converged by the lens action of the primary optical system 11, enters the e-cross bee 23, and then e-beams. -The trajectory (optical path) of the cross bee 23 is bent by the deflecting action. This is because, as shown in FIG. 6B, in the electric field E and the magnetic field B which are orthogonal to each other, the electrons (primary electron beam B1) of the electric charge q move in the + Z direction with the velocity v.
, The force F _E (= q
E) and the resultant force of the magnetic field force F _B (= qvB). Thereby, the trajectory of the primary electron beam B1 is bent in the XZ plane.

On the other hand, the secondary electron beam B 2 generated from the sample 4 irradiated with the primary electron beam B 1 is subjected to a lens action by the cathode lens 21,
Passes through the aperture stop AS arranged at the focal position of
After entering the cross bee 23, e-cross bee 2
Continue straight on 3 This is for the following reason. As shown in FIG. 6C, an electric field E and a magnetic field B orthogonal to each other
Inside, the electron of the charge q (secondary electron beam B2) is -Z
When advancing at a speed v in a direction, receives a force F _E by the electric field acting in the -X direction, the resultant force of the force F _B by the magnetic field acting in the + X direction. At this time, the absolute value of the force F _B by the force F _E and the magnetic field due to the electric field is set to equal (E = vB) so as to, i.e. Vienna condition is satisfied. Therefore, the force F _E due to the electric field and the force F _B due to the magnetic field cancel each other, and the apparent force received by the secondary electron beam B2 becomes zero,
The secondary electron beam B2 travels straight in the e-cross bee 23. As described above, the e-cross bee 23 has a function as a so-called electromagnetic prism for selecting the optical path of the passing electron beam.

The configuration of the surface state observation apparatus according to one embodiment of the present invention has been described above. Next, the operation of the surface state observation apparatus according to one embodiment of the present invention at the time of observation will be described. First, when the sample 4 to be observed is placed on a loader (not shown), the sample 4 is transported into the chamber 3 by the loader. When the sample 4 is carried into the chamber 3, the sample 4 is placed on the XY stage 40, and the main control system 37 drives the XY stage 40 via the driving device 43 to move the sample 4 to the measurement range. Here, a case where the surface state of the sample 4 shown in FIG. 7 is observed will be considered. FIG. 7 is a diagram for explaining the operation when observing the surface state. Here, a case where the observable observation target area 4a of the sample 4 is observed will be considered.

At the time of observation, the main control system 37 first outputs a control signal to the secondary optical system control unit 39 based on the measurement result of a Z sensor (not shown) to increase the magnification of the second optical system 20. Adjusted, secondary electron beam B emitted from sample 4
The focal position of No. 2 is set on the detection surface of the electron beam detector 30. The main control system 37 is provided with the thermionic electron gun 10.
To start emitting electrons to the primary optical system 11, the e-cross bee 23, the aperture stop AS, and the first aligner 2.
2 and the primary electron beam B via the cathode lens 21
7 is irradiated on the sample 4 and the XY stage 40 is moved at a constant speed via the driving device 43 in a direction parallel to the Y-axis direction in FIG.
By irradiating the sample 4 with the primary electron beam B1, the secondary electron beam B2 generated from the object surface of the sample 4 is condensed by the secondary optical system 20, and the image is formed on the detection surface of the electron beam detector 30. Image. The light emitted from the electron beam detector 30, that is, the optical image of the sample 4 passes through the relay lens 34 and forms an image on an imaging surface of an imaging device 35 in which pixels are arranged according to the distortion of the secondary optical system 20. I do. The optical image formed on the imaging surface of the image sensor 35 is photoelectrically converted into a pixel signal by the image sensor 35.

In FIG. 7, it is assumed that an area denoted by reference numeral 50 is an area to be imaged by the image pickup device 35, and a linear area denoted by reference numeral R1 in the area 50 is indicated by C in FIGS.
It is assumed that the CCD pixel row R1 captures an image, and the CCD pixel row R256 captures an image of a linear region denoted by reference symbol R256. Assuming that the observation is started from the state shown in FIG. 7, the optical image from the coordinates (X1, Y1) to (X1024, Y1) of the observation target area 4a is converted into a TDI array CCD forming the image sensor 35.
The photoelectric conversion is performed in the CCD pixel row R1 of FIG. By moving the sample 4 in the −Y axis direction,
When the area 50 imaged by the image sensor 35 moves in the direction indicated by the symbol d, and the area 50 moves by one CCD pixel row, the main control system 37 sends the image sensor 35 based on the measurement result of the laser interferometer 42. , One vertical clock signal is sent out.

When the vertical clock signal is transmitted, the electric charges stored in the CCD pixel row R1 of the image pickup device 35 are transferred to the CCD pixel row R2, and the CCD before the vertical clock signal is transmitted. The optical image captured by the pixel row R1 moves to the position of the CCD pixel row R2. Accordingly, the CCD pixel row R2 captures an optical image similar to the optical image captured by the CCD pixel row R1 before the vertical clock signal is transmitted until the next vertical clock signal is transmitted. become. In addition, the CCD pixel row R1 captures an optical image from the coordinates (X1, Y2) to (X1024, Y21) of the observation target area 4a.

Here, a high sensitivity TD is used as the image pickup device 35.
In order to perform high-speed observation using an I-array CCD, an optical image that is the same as the optical image captured by the CCD pixel array that transfers the electric charges must be captured by the CCD array to which the electric charges have been transferred. Is assumed. If an image sensor having a conventional configuration in which pixels are arranged at equal intervals is used when distortion occurs in the secondary optical system 20, this assumption cannot be satisfied, and the image resolution deteriorates. However, in the present embodiment, the image pickup device 35 according to the distortion of the secondary optical system 20
Are arranged, even if the optical image formed on the imaging surface of the imaging device 35 reflects the distortion of the secondary optical system 20, the distortion is corrected. Can be satisfied.

In the same manner, when the linear portion with R1 in the region 50 to be imaged by the CCD pixel row R1 reaches the position from (X1, Y256) to (X1024, Y256), the imaging ends. Then, the sample images from (X1, Y1) to (X1024, Y1) are first output to the main control system 37 via the control unit 36. From the next transmitted vertical clock signal,
The sample images from (X1, Y2) to (X1024, Y2) are output to the main control system 37, and the images are sequentially acquired by the main control system 37 for observation.

As described above, according to the surface state observation apparatus according to the embodiment of the present invention, the primary electron beam B1
The secondary electron beam B2 obtained by irradiating the sample 4 with the sample 4 causes distortion on the detection surface due to the optical characteristics of the secondary optical system 20, even if the pixel of the imaging element 35 is distorted on the imaging surface. , The distortion on the imaging surface is corrected, so that even if the distortion of the secondary optical system 20 cannot be completely corrected, the pixel signal output from the imaging element 35 is not corrected. Is corrected, and as a result, there is an effect that observation can be performed with high resolution. Further, the surface state of the sample 4 is observed while moving the XY stage 40 with the sample 4 to be observed placed on the XY stage 40. Moreover, since the image detected by the image sensor 35 has been corrected for distortion, the sample 4 can be observed with high resolution in a short time. In addition, control is easier when mechanical accuracy and the like are taken into consideration than when observation is performed by driving the XY stage in a step-and-repeat manner, and there is an effect that detection can be performed with high resolution.

Further, according to the present embodiment, the image pickup device 35
Since a TDI array CCD having high detection sensitivity is used, in particular, when detection is performed while moving the XY stage 40, it is possible to prevent insufficient detection signal intensity, and as a result, resolution is not reduced in a short time. There is an effect that observation can be performed. When high-resolution detection is performed using a TDI array CCD as the image sensor 35, the transfer direction of the charges accumulated in the image sensor 35 and the moving direction of the optical image on the imaging surface coincide with each other as described above. Need to be done. When distortion occurs in the secondary optical system 20, the direction of charge transfer in the image sensor 35 and the direction of movement of the optical image on the image sensing surface are different. By arranging the pixels in accordance with the distortion of the secondary optical system 20, the transfer direction of the electric charge in the image sensor and the moving direction of the optical image on the image pickup surface coincide with each other, so that deterioration of the resolution can be prevented. This has the effect.

The surface state observation apparatus according to one embodiment of the present invention has been described above. Next, another embodiment of the present invention will be described. In the above-described embodiment, the distortion of the secondary optical system 20 is corrected by arranging the pixels of the image sensor 35 in the imaging plane according to the distortion of the secondary optical system 20. In another embodiment of the present invention described below, an image is captured using an imaging device in which pixels are arranged at equal intervals in an imaging surface, and a pixel signal output from the imaging device is distorted by the secondary optical system 20. It is corrected according to. Hereinafter, another embodiment of the present invention will be described.

In the above-described embodiment, a TDI array CCD is used as the image pickup device 35. However, in another embodiment of the present invention, a CCD in which pixels are arranged at equal intervals in the image pickup plane, for example, an inter Line CC
D is used. In the above-described embodiment, the main control system 37 performs image processing such as template matching on the pixel signal input via the control unit 36 to determine whether the sample 4 has a defect. A main control system 37 according to another embodiment of the present invention functions as a processing device according to the present invention. In the main control system 37, a pixel signal input via a control unit 36 before image processing such as template matching is performed on the pixel signal. Secondary optical system 20
A correction process is performed in accordance with the amount of distortion.

Here, the distortion amount of the secondary optical system 20 is stored in the storage device 44 shown in FIG. Storage device 4
The distortion amount stored in 4 is obtained from a design value of the secondary optical system 20 or by actually measuring the distortion amount of the secondary optical system 20. The actual measurement value of the distortion amount of the secondary optical system 20 is, for example, the pixel of the lattice pattern obtained by mounting a test sample on which a precise lattice pattern is formed in advance on the XY stage 40 and observing the pattern. It can be obtained by calculating the amount of deviation between the signal and the design value of the lattice pattern formed on the test sample. The amount of distortion stored in the storage device 44 may be, for example, the amount of deviation described above may be stored according to the position of the imaging surface, or the obtained amount of deviation may be approximated by a function and stored as an approximated function. good. The timing of obtaining the amount of distortion may be arbitrary, but it is preferable to obtain it periodically (for example, every day), and it is preferable to obtain it for each observation object in order to observe while maintaining high accuracy.

The primary electron beam B1 emitted from the thermionic electron gun 10 is applied to the sample 4 via the primary optical system 11, the e-cross bee 23, the aperture stop AS, the first aligner 22, and the cathode lens 21. Irradiation, the secondary electron beam B2 generated from the sample 4 forms an image on the detection surface of the electron beam detector 30 via the secondary optical system 20, and further the image formed on the detection surface of the electron beam detector 30 The process is the same as that of the above-described embodiment until the optical image is converted into an optical image by the fluorescent plate 32 and the optical image is formed on the imaging surface of the imaging device 35 via the relay lens 34.

The optical image formed on the image pickup surface of the image pickup device 35 is affected by distortion remaining in the secondary optical system 20, and in the present embodiment, the pixels of the image pickup device 35 are located within the image pickup surface. Since they are arranged at intervals, the image sensor 3
The pixel signal output from 5 is affected by the distortion of the secondary optical system 20. Therefore, for example, sample 4
Is observed as a curved pattern.

When a pixel signal affected by the distortion of the secondary optical system 20 is output from the image sensor 35 and input to the main control system 37 via the control unit 36, the main control system 37 stores the image data in the storage device 44. Is performed based on the amount of distortion stored in the. As described above, in the present embodiment, the secondary optical system 20 stored in the storage device 44 is used.
Since the pixel signal output from the image sensor 35 is corrected based on the distortion of the secondary optical system 20, even if the distortion of the secondary optical system 20 changes with time, the distortion of the secondary optical system 20 , The pixel signal can be appropriately corrected.

When the sample 4 is stationary without moving the XY stage 40, the pixel signal output from the image sensor 35 does not change with time, so that the time required for the correction processing may be longer. When observing the surface state of the sample 4 while moving the XY stage 40, it is necessary to perform the correction process for each screen (one frame). The main control system 3 based on the distortion amount stored in the storage device 44
7 performs the correction processing of the pixel signal, the secondary optical system 20
It is preferable because the pixel signal can be appropriately corrected in accordance with the temporal change of the distortion. However, if the main control system 35 cannot correct the pixel signal in time, a dedicated correction of the pixel signal by a certain correction amount is performed. Hardware may be provided in the main control system 37 to speed up the correction process. In addition, since the processing capability of the hardware has been remarkably improved in recent years, the main control system 37 is controlled based on the amount of distortion stored in the storage device 44 with the improvement in the processing capability of the hardware constituting the main control system 35. Correction processing of the pixel signal can be performed without any problem.

According to the other embodiment of the present invention described above, the pixel signal reflecting the distortion of the secondary optical system 20 is corrected in accordance with the distortion of the secondary optical system 20. Can be observed with high resolution. In addition, since a general imaging element in which pixels are arranged at equal intervals on the imaging surface is used, high-resolution observation can be performed while suppressing an increase in the cost of the apparatus. In addition, the amount of distortion is determined in advance from the design value of the secondary optical system 20 or from the actually measured value of the secondary optical system 20, and the main control system 37 outputs a pixel signal output from each pixel based on the amount of distortion. Is corrected, the secondary optical system 2 is changed over time or according to the characteristics of the device.
0, the secondary optical system 2
The pixel signal can be corrected according to the distortion amount of 0.

As described above, the surface state observing apparatus according to one embodiment of the present invention has been described. However, the present invention is not limited to the above embodiment and can be freely changed within the scope of the present invention. For example, in the above-described embodiment and other embodiments, at least a secondary electron, a reflected electron, and a backscattered electron obtained by irradiating the sample 4 with the primary electron beam B1 and using the primary electron beam B1 as a primary beam. Although the case where the secondary electron beam B2 including one is photoelectrically converted by the fluorescent plate 32 and the converted optical image is captured by the image sensor 35 has been described as an example, an ion beam may be used instead of the electron beam, for example. Alternatively, an optical image obtained by irradiating the sample 4 with light in the visible region may be directly captured by the image sensor 35.
In this case, although the secondary optical system 20 is configured to include an optical lens, the number of optical lenses constituting the secondary optical system 20 is increased in order to completely correct the distortion of the secondary optical system 20. Since it is not necessary to perform the operation, observation can be performed with high resolution without increasing the size of the apparatus. When light is used as the primary beam, the secondary beam is reflected light obtained by irradiating the object surface with light.

In the above embodiment, the case where the primary electron beam B1 is deflected by using the e-cross bee 23 to irradiate the sample 4 and the secondary electron beam B2 generated from the sample 4 is made to travel straight. did. However, the present invention is not limited to this, and an electromagnetic prism that directs the primary electron beam B1 and deflects the secondary electron beam B2 may be used. Furthermore, the present embodiment is provided with a so-called surface-to-surface projection optical system that illuminates the object surface of the sample with an electron beam from the radiation source and forms an image on the image surface. The present invention can be easily applied not only to a single device but also to a semiconductor exposure apparatus or the like.

As described above, according to the present embodiment, the distortion on the imaging surface is corrected by arranging the pixels on the imaging surface of the imaging element 35 in accordance with the distortion. Even if the distortion of 20 cannot be completely corrected, the detection result of the image sensor 35 is a corrected distortion, and as a result, observation with high resolution is possible. When the secondary optical system 20 includes an optical lens, it is not necessary to increase the number of optical lenses constituting the secondary optical system 20 in order to completely correct the distortion. It is possible to observe at high resolution without increasing the size of the object.

Further, according to the present embodiment, the object surface is observed by the image sensor 35 while moving the XY stage 40 while the object to be observed is placed on the XY stage 40. Moreover, since the image detected by the image sensor 35 has been corrected for distortion, the object can be observed with high resolution in a short time. In addition, control is easier when mechanical precision and the like are taken into consideration than when observation is performed by driving the XY stage 40 step-and-repeat, and detection can be performed with high resolution. When a time-delay-integration type image sensor having high detection sensitivity is used as the image sensor 35, insufficiency of the detection signal can be prevented particularly when the detection is performed while the XY stage 40 is moved. Observation can be performed in time without lowering the resolution. When high-resolution detection is performed using a time-delay integration type image sensor, it is necessary to make the transfer direction of the accumulated charge in the image sensor 35 coincide with the moving direction of the image on the imaging surface. When the secondary optical system 20 has distortion, the transfer direction of the accumulated charges in the image sensor and the moving direction of the image on the detection surface are different. By arranging in accordance with the distortion, the transfer direction of the accumulated charges in the image sensor 35 and the moving direction of the image on the image pickup surface coincide with each other, so that deterioration of the resolution can be prevented.

Further, according to the present embodiment, the image pickup device 35
In the case where the pixels included in are arranged two-dimensionally at equal intervals on the imaging surface, if a distortion occurs in the secondary optical system 20, the detection signal of the imaging element 35 reflects the distortion. However, since the detection signal reflecting the distortion is corrected according to the distortion of the secondary optical system 20, the object can be observed with high resolution. Further, according to the present invention, it is not necessary to manufacture an imaging device 35 in which pixels are arranged according to distortion, and a general imaging device 35 in which pixels are two-dimensionally arranged at equal intervals can be used. It is possible to observe at high resolution while suppressing an increase in cost.

According to the present embodiment, the secondary optical system 2
Since the amount of distortion is obtained in advance from a design value of 0 or an actually measured value of the secondary optical system 20, the main control system 37 corrects a pixel signal output from each pixel based on the amount of distortion. Even if the distortion of the secondary optical system 20 changes due to a change over time or according to the characteristics of the device, the pixel signal can be corrected according to the amount of distortion of the secondary optical system 20. . Further, even in the case where the general imaging elements 35 arranged two-dimensionally at equal intervals in the imaging plane are used, the effect of the distortion in the secondary optical system 20 is corrected and the simple control is performed. And it can observe at high speed.

Next, a method of manufacturing a micro device according to an embodiment of the present invention will be described. FIG. 10 is a diagram showing a flowchart of a manufacturing example of a micro device (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, etc.). As shown in FIG. 10, first, in step S10 (design step), a function / performance design of a micro device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, step S11
In a (mask manufacturing step), a mask (reticle) on which the designed circuit pattern is formed is manufactured. On the other hand, in step S12 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.

Next, in step S13 (wafer processing step), using the mask and the wafer prepared in steps S10 to S12, an actual circuit or the like is formed on the wafer by lithography or the like, as described later. . Next, in step S14 (device assembling step), device assembly is performed using the wafer processed in step S13. Step S14 includes, as necessary, processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation).
Finally, in step S15 (inspection step), inspections such as an operation confirmation test and a durability test of the micro device manufactured in step S14 are performed. This step S
At 15, the surface state of the microdevice is observed by the above-described surface state observation apparatus according to one embodiment of the present invention. After these steps, the microdevice is completed and shipped. Note that the flowchart shown in FIG. 10 illustrates a case where the surface state of the microdevice is observed by the surface state observation apparatus according to the embodiment of the present invention after step S14. Before assembling, the surface state of the processed wafer may be appropriately observed through step S13.

[0054]

As described above, according to the present invention, the secondary beam obtained by irradiating the primary beam to the object causes distortion on the detection surface due to the optical characteristics of the secondary optical system. However, since the distortion is corrected by the correction means, even if the distortion of the secondary optical system cannot be completely corrected, the distortion can be observed at a high resolution even if the distortion remains.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a surface state observation device according to a first embodiment of the present invention.

FIG. 2 is a functional block diagram showing a configuration of a TDI array CCD as an image sensor 35.

FIG. 3 is a diagram showing an arrangement of pixels included in an imaging element on an imaging surface.

FIG. 4 is a diagram showing a trajectory of a primary electron beam B1 of the surface state observation device according to one embodiment of the present invention.

FIG. 5 is a diagram showing a trajectory of a secondary electron beam B2 of the surface state observation device according to one embodiment of the present invention.

FIG. 6 is a diagram for explaining a configuration and an operation principle of an e-cross bee 23 included in the surface state observation device according to the embodiment of the present invention.

FIG. 7 is a diagram for explaining an operation when observing a surface state.

FIG. 8 is a diagram illustrating an example of distortion.

FIG. 9 shows an image in which distortion has occurred by using a TDI array CC.
FIG. 7 is a diagram for explaining deterioration of detection accuracy when detection is performed by D.

FIG. 10 is a flowchart showing an example of a micro device manufacturing process.

[Explanation of symbols]

 4 Sample (Object) 11 Primary Optical System 20 Secondary Optical System 30 Electron Beam Detector (Detecting Means) 32 Fluorescent Plate (Converting Means) 34 Relay Lens (Detecting Means) 35 Image Sensor (Detecting Means) 37 Main Control System (Control Means) , Processing apparatus) 40 XY stage (stage) 41 moving mirror 42 laser interferometer (positional information detecting device, interferometer) 44 storage device (storage means) B1 primary electron beam (primary beam) B2 secondary electron beam (secondary beam) )

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 37/29 H01J 37/29 H01L 21/66 H01L 21/66 J (72) Inventor Erika Kanematsu Chiyoda, Tokyo 3-2-3, Kumarunouchi Nikon Corporation F-term (reference) 2F067 AA33 AA53 AA54 BB04 CC17 EE04 HH04 HH06 HH08 JJ05 KK04 KK08 LL02 LL16 PP12 RR35 SS13 4M106 BA02 CA38 DB04 DB05 DB12 DB14 DJ07 DJ05 JJ07 NN01 NP01 NP05 NP06 NP08 UU03 UU04 UU05

Claims (12)

[Claims] 1. A primary optical system for irradiating a primary beam onto an object surface, a secondary optical system for focusing a secondary beam obtained by irradiating the primary beam onto the object surface, and a secondary optical system A surface state observing apparatus comprising: a detection unit that detects a secondary beam that passes through the surface state detection unit, wherein the correction unit performs a correction according to a distortion generated on a detection surface of the detection unit due to an optical characteristic of the secondary optical system. A surface state observation device comprising a correction unit. 2. The surface state observation apparatus according to claim 1, wherein the correction unit arranges pixels on a detection surface of the detection unit in accordance with the distortion. 3. A stage movable with the object mounted thereon, a position information detecting device for detecting position information of the stage, and a position information of the stage detected by the position information detecting device. 3. The surface state observation apparatus according to claim 2, further comprising control means for causing the detection means to detect the secondary beam while synchronizing with movement of the stage. 4. The position information detecting device according to claim 3, wherein the position information detecting device has a movable mirror disposed on the stage, and an interferometer disposed opposite to a mirror surface of the movable mirror. Surface condition observation device. 5. The surface state observation device according to claim 3, wherein the detection unit includes a time delay integration type image pickup device. 6. The pixels provided in the detection means are arranged two-dimensionally at equal intervals on the detection surface, and the correction means changes a pixel signal output from each pixel of the detection means according to the distortion. 2. The surface state observation device according to claim 1, further comprising a processing device for performing correction. 7. A storage unit for storing a distortion amount of the secondary optical system obtained in advance from a design value or an actual measurement value of the secondary optical system, wherein the processing device is stored in the storage unit. 7. The surface state observation device according to claim 6, wherein the pixel signal is corrected based on the amount of distortion. 8. A stage comprising: a stage movable with the object mounted thereon; and a control unit for causing the detection unit to detect the secondary beam in synchronization with the movement of the stage. The surface state observation device according to claim 6 or 7. 9. The primary beam is a charged particle beam, and the secondary beam is at least one of secondary electrons, reflected electrons, and backscattered electrons generated by irradiating the object with the charged particle beam. The surface state observation device according to any one of claims 1 to 8, wherein: 10. The detecting means includes a converting means for converting a secondary beam focused by the secondary optical system into a photon, and detecting the photon converted by the converting means to convert the secondary beam. The surface state observation device according to claim 9, wherein the surface state is detected. 11. A semiconductor element whose surface has been observed using the surface state observation apparatus according to claim 1. Description: 12. A method for manufacturing a micro device, comprising a step of observing a surface of a micro device using the surface state observing apparatus according to any one of claims 1 to 10.