JP2009146884A - Electron gun, and electron beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set an electron gun at high brightness in a device in which a pattern formation or a sample evaluation is carried out in high throughput in an electronic optical system having a plurality of optical axes. <P>SOLUTION: In the electron gun used in the device for carrying out the pattern formation or sample evaluation, when a cathode, a first anode, a second anode, and a Wehnelt electrode are equipped, and if the Wehnelt electrode and the first anode electrode are made to have a truncated cone shape, an angle from the optical axis to the Wehnelt is made θw, and the angle from the optical axis to the first anode is made θa, then by setting 40.1°<θa<90° or 48.6°<θw<149°, the brightness exceeding the Langmuir limit is obtained as shown in Fig. 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electron beam apparatus for forming a pattern on a substrate surface or evaluating a sample at an ultra-high speed, and more specifically, using a plurality of optical axes or performing batch transfer. The present invention relates to an electron beam apparatus for enabling throughput and an electron gun used for such an apparatus.

In the semiconductor manufacturing process, the design rule is about to reach 45 nm, and the production form is shifting from small-quantity mass production represented by DRAM to high-variety small-quantity production such as SOC (Silicon on chip). Along with this, the number of manufacturing processes increases, and it is essential to improve the yield for each process, and defect inspection due to the process becomes important.
Along with the high integration of semiconductor devices and the miniaturization of patterns, high resolution and high throughput inspection apparatuses are required. In order to investigate a defect of a wafer having a 45 nm design rule, a resolution of 25 nm or less is required, and an inspection amount increases due to an increase in manufacturing process due to high integration of devices, and thus high throughput is required. In addition, as the number of devices increases, the inspection apparatus is also required to have a function of detecting a contact failure (electrical defect) of a via that connects wirings between layers.
Under such circumstances, an apparatus for forming a beam on a plurality of optical axes to increase the throughput has been studied. (M. Nakasuji etal, US 7,109,484) In such a multi-optical axis device, the actual device is still in the research and development stage, and detailed examination of the entire system is required.
In addition, LEEPL (Low Energy Electron Proximity Projection Lithography) has appeared brilliantly as a next-generation lithography apparatus, but it is now disappearing due to the problems described in the problem to be solved by the invention. However, with the development of nanoimprint technology, there is a high possibility that the items with the above problems will be solved.

As the electron gun in the above-described conventional apparatus, an apparatus using a photocathode cathode is disclosed. (S. Tanimoto, etal, MNC 2007, Kyoto, Digest of paper, p 72). The photocathode cathode has poor reliability, and there is a problem that the entire system does not function if one of the plurality of electron guns deteriorates.
Further, since the secondary electrons are deflected in the direction of the detector only by the electric field, there is a problem that the influence on the primary beam cannot be ignored.
Further, in the above document, since the optical axis interval is 250 μm and larger than the scanning width, it is necessary to control the stage in a complicated motion.
Further, the secondary electron detector has a rectangular shape of 2.4 mm × 120 mm, and there is a problem that it is difficult to handle.
Further, other optical members have a large dimension in the X direction, and there is a problem that the optical axis is largely displaced due to linear expansion.
In addition, since the photocathode electron gun disclosed in the above document has a flat cathode and a low current density, an electron gun capable of reliably obtaining luminance exceeding the Langmuir limit is required.

Further, in the above-described conventional apparatus LEEPL, since the mask surface is scanned with an electron beam, the transfer time is longer than that of the batch transfer, the light source size for determining pattern blur is increased, and the pattern accuracy is deteriorated. Further, complicated control is required for fine adjustment of the transfer magnification.
There was a problem that the mask was expensive. In addition, the mask life is short, and there is a problem that contamination during transfer occurs in a short time.
Furthermore, an object of the present invention is to provide an apparatus and method for reducing the mask cost, extending the mask life, and improving the throughput.

In order to solve the above problems, in the present invention, an electron gun used in an apparatus for pattern formation or sample evaluation includes a cathode, a first anode, a second anode, and a Wehnelt electrode. When the anode electrode has a truncated cone shape, the angle of Wehnelt from the optical axis is θw, and the angle from the optical axis to the first anode is θa,
40.1 ° <θa <90 ° or 48.6 ° <θw <149 °
As a result, an electron gun capable of reliably obtaining luminance exceeding the Langmuir limit was obtained.
Further, when the anode angle θa is larger than 41.3 degrees and smaller than 48.8 degrees by the above means, the luminance is more preferable because the luminance exceeds the Langmuir limit by 100 times or more.
Further, when the Wehnelt angle θw is in the range of 110.6 ° <θw <149 ° by the above-mentioned means, the luminance exceeds the Langmuir limit 1000 times or more when the electron gun current is a small value of 1 mA or less, which is optimal.

Furthermore, in the apparatus having the electron gun, having a plurality of optical axes arranged in two dimensions, continuously moving the sample stage, and performing pattern formation or sample evaluation, the sample stage is perpendicular to the continuous movement direction. The intervals of the plurality of optical axes projected in the direction are equal, the scanning width per optical axis is substantially equal to the interval, and (sample number of optical axes) x (scanning width) by one continuous movement of the sample stage The pattern formation of the area of the range or evaluation of the sample was performed.
In the above means, the scanning width is in the range of 512 to 4096 pixels.
Further, in the above means, the optical axes are arranged at equal intervals in a substantially perpendicular direction, and the continuous movement direction of the sample stage is a predetermined angle (tan-1 (1/1 / (m + 1)), m is the number of optical axes in the direction of continuous movement of the sample stage. By tilting, the interval between the multiple optical axes projected in the direction perpendicular to the direction of continuous movement of the sample stage is made equal. .

In order to solve the above problems, in the present invention, in an apparatus having a plurality of optical axes arranged two-dimensionally, continuously moving a sample stage, and performing pattern formation or sample evaluation, each optical axis is an electron. It has a gun, objective lens, and secondary electron detector. Each optical axis irradiates the sample with an electron beam from the electron gun through the objective lens, and passes the secondary electron from the sample through the objective lens, and then with an ExB deflector. The ExB deflector is a single ExB deflector common to at least most of the optical axes. The ExB deflector is a device that deflects in the direction of the detector, enters the secondary electron detector, and detects it.
In the above means, the ExB deflector is a Wien filter having ferromagnetic electrodes having 6 or more poles.

Furthermore, in order to solve the above problems, the present invention has a plurality of optical axes arranged two-dimensionally, and in an apparatus for pattern formation or sample evaluation, each optical axis has an electron gun and an objective lens. Each optical axis is a device that irradiates a sample with an electron beam from an electron gun with an objective lens, and the electron gun is formed by forming a photoelectron substance on a single transparent substrate, and any one of the plurality of optical axes. When the characteristics of the electron gun deteriorated, the substrate was moved in a direction perpendicular to the optical axis so that a new photoelectric material was exposed to the deteriorated electron gun.
Further, in the above means, in order to be able to release the distortion caused by the difference in linear expansion, etc., the structure in which the deviation in the X and Y directions is allowed between the cathode substrate and the Wehnelt substrate.
In the above means, the electron gun, the Wehnelt and the anode can be finely adjusted at the same time in the direction perpendicular to the optical axis, and the cathode can be moved to the set of the Wehnelt and the anode in the direction perpendicular to the optical axis. It was.

In order to solve the above problems, the present invention has a plurality of optical axes arranged two-dimensionally, and in an apparatus for pattern formation or sample evaluation, each optical axis has an electron gun and an objective lens. Each optical axis is a device for irradiating a sample with an electron beam from an electron gun by an objective lens, and the electron gun has a Wehnelt electrode having a shape for isolating adjacent cathodes. More specifically, the minimum value of the distance between the Wehnelt electrode and the first anode electrode was made smaller than the distance between adjacent optical axes.
In the above means, the Wehnelt electrode has a truncated cone shape with an angle θw with respect to the optical axis larger than 67.5 degrees, and is convex or concave on the anode side as shown in FIG.
Further, in the above means, the Wehnelt electrode is formed by combining a concave truncated cone on the anode side and a cylindrical electrode on the anode side.
In the above-mentioned means, the cathode-anode distance: Dca is set to not more than twice the distance between the optical axes.
Further, in the above means, a potential difference of 4 kV · Dac or less was set between the cathode and the anode. Here, Dac is the distance between the cathode and the anode.
Furthermore, in order to solve the above problems, in the present invention, an acceleration electric field for the primary beam is applied between the mask and the wafer in an apparatus that performs batch transfer with a low energy electron beam.
In the above means, the energy of electrons when irradiating the mask is less than 2 keV, and the energy of electrons when irradiating the wafer is set to a value (9 keV) or less sufficient to penetrate the photosensitive layer of the resist.
Further, in the above means, the potential difference between the mask and the wafer is set to 10 V or more.

In order to solve the above problems, the present invention is an apparatus that performs batch transfer with a low-energy electron beam, and has a rectangular opening on the first stage, a rectangular opening on the second stage, and an opening for forming an alignment beam. The second-stage rectangular aperture is imaged on a pattern-formed mask, and a two-stage lens provided after the second-stage rectangular aperture is used to form a beam with good parallelism. Through the beam, a pattern for one die was transferred to the wafer in one batch.
In the above-described means, a deflector is provided between the two-stage apertures so that the first-stage aperture image can selectively irradiate one of the second-stage aperture or the aperture that forms the alignment beam. .
Further, in the above means, when an excitation signal is applied to the deflector, the movement of the crossover formed downstream of the second stage opening is prevented.
In the above means, the beam having a good degree of parallelism has a crossover diameter formed downstream of the second stage opening of 10 μm or less, or a cross formed downstream of the second stage opening. The distance between the over and the final lens is 250 mm or more.

Furthermore, in order to solve the above-described problems, the present invention is an apparatus that performs batch transfer with a low-energy electron beam. From the crossover formed by the first-stage lens, a second-stage lens is provided downstream of the rectangular aperture. A diverging beam forms an almost parallel beam with a second-stage lens and illuminates a mask. The divergence of the beam emitted from the lens at the position of the crossover in the optical axis direction or the excitation condition of the second-stage lens Alternatively, the convergence angle is adjusted, and the transfer magnification is finely adjusted.
In the above means, an astigmatism generator is provided in the optical system so that the transfer magnification in the X direction and the Y direction can be finely adjusted independently.

In order to solve the above problems, the present invention is a device that performs batch transfer with a low-energy electron beam, and the mask can be rotated around an axis that is parallel to the X axis or Y axis and passes through the optical axis, The squareness between the mask and the optical axis was adjusted to correct the trapezoidal distortion.
Further, in the above means, a two-stage deflector is provided on the electron gun side of the final projection lens, and the deflection center of the two-stage deflector is used as a mask surface or a main surface of the lens.

Furthermore, in order to solve the above-described problems, the present invention is a method for performing batch transfer with a low energy electron beam, and has the following steps:
A: Form a master pattern with an electron beam lithography system.
B: forming a nano mold for nanoimprint from the master pattern,
C: Transfer multiple patterns to Si wafer using nanoimprint technology with the above nano mold.
D: Etching the Si wafer transferred with the above pattern to produce a working mask
E: Transfer to the wafer with LEEPL using the working mask created in D above.

In order to solve the above problem, the present invention is a method for performing batch transfer with a low-energy electron beam, and includes the following steps:
A: It has a working chamber and a cleaning chamber, and transfers one or more wafers.
B: Remove the mask from the working chamber, put it in the cleaning chamber, and clean it.
C: The mask is removed from the cleaning chamber, returned to the working chamber, and transferred to the wafer using the mask.
In the above-described means, a plurality of masks are provided, and transfer is performed with the second mask while the first mask is in the cleaning chamber.
In the above means, after cleaning with C, the mask is returned to the working chamber after the mask reaches a predetermined temperature.
Further, in the above means, the mask is cleaned a predetermined number of times, or discarded after the transfer.

FIG. 1 is a view showing the arrangement of a plurality of optical axes of a multi-optical axis electron beam apparatus of the present invention. Reference numerals 1-1, 1-2, 1-3, and ---- 25 denote optical axes arranged in 5 rows and 5 columns. The optical axes are arranged at equal intervals in the direction close to the X axis, and also at equal intervals in the direction close to the Y axis. In this way, there is an advantage that the maximum number of optical axes can be arranged in a predetermined circle by arranging m rows and n columns in a substantially perpendicular direction and setting m = n. As shown in the figure, X and Y axes and tan-1 (1 / (m + 1)), (m is the number of optical axes in the direction of continuous movement of the sample stage) Projecting each axis in the X axis direction by tilting in radians In this case, the intervals of the respective optical axes can be made equal, and the sample can be evaluated or the pattern can be formed in the area of (mxn) × (one-axis scanning width) by one continuous stage movement.
If the scanning width of one axis is selected to be equal to the interval between the optical axes when projected in the X-axis direction, the movement of the stage is (mxn) x (single-axis scanning after one continuous movement in the Y direction. The entire surface of the specimen can be evaluated or the pattern can be formed with a simple operation of stepping in the X direction by (width).
Since the beam is scanned digitally, it is efficient to adjust the scanning width to the number of bits of the D / A converter. A high-precision, high-speed D / A converter is 10 to 12 bits. Therefore, (1024 to 4096) × (pixel size) is appropriate for the scanning width indicated by 1-26, and in the case of a 25 nm pixel, the scanning width is 25.6 μm to 101.5 μm. Therefore, in the case of 5 rows and 5 columns, the optical axis interval is 128 to 507.5 μm. Even in the case of a 10-bit DAC, if the optical axis interval is to be 200 μm or more, the optical axes may be arranged in 8 rows and 8 columns. By arranging the optical axes in two dimensions in this way, the optical axis interval can be increased to a practical size even if the scanning width of one optical axis is small.

  FIG. 2 is a cross-sectional view of an ExB Wien filter that linearly moves primary electrons and deflects secondary electrons toward the detector. 2-1, ---, 2-8 are permalloy electrodes, and the magnetic field is also formed by these magnetic poles. Since the optical axes 1-1 to 1-25 are arranged in a narrow region, the optical axes 1-1 to 1-25 can be arranged inside a region where an electric field and a magnetic field with uniform intensity can be formed. 2-9 is an insulating spacer. 2-10 is a permalloy ring. Reference numeral 2-11 denotes a coil for exciting the magnetic pole 2-1.

  FIG. 3 is a diagram showing the arrangement of secondary electron detectors. Reference numerals 3-1, 3-2, ---, and 3-25 are holes through which the primary beam passes, and a sufficiently large hole is provided so that no lens action occurs. Reference numerals 3-1 to 3-25-1 are photosensitive regions where secondary electrons with an initial energy of 10 eV or more are incident near the hole, and secondary electrons with an initial energy of 1 eV or less are incident at a position far from the hole. Detected. It is the role of the Wien filter that deflects secondary electrons from each optical axis in the direction of the photosensitive region. Reference numerals 3-26 and 3-27 denote marks for attaching the detector to the optical system. 3-4-4 is a lead wire, and 3-5-2 is a pad for taking out a signal to the outside. As shown in the figure, the photosensitive area is formed longer than the distance between the optical axes in a direction not interfering with other optical axes, so that a sufficiently long detection area can be secured, and the size of the detector is reduced to about 2 to 10 mm square, Can be manufactured with high yield. 3-0 is the outer shape of the detector chip.

FIG. 4 shows a cross section of the electron gun (left side) and a view of the anode side from the cathode side (right side). 4-1-1 is an optical axis, 4-1-2 is a Wehnelt hole corresponding to the optical axis 4-1-1, and 4-1-3 is a Wehnelt corresponding to the optical axis 4-1-1. 4-30 is an anode, and an anode hole corresponding to each optical axis is provided as shown in the figure. The anode 4-30 and the Wehnelt 4-28 are precisely drilled at each optical axis position using a jig borer or the like. The positions are accurately aligned with each other and can be fixed via insulating spacers 4-29. The cathode has a transparent substrate 4-26 coated with an optoelectronic material such as platinum or Cs on the entire surface shown in 4-27. The cathode and Wehnelt do not need to be aligned, and an electron beam is emitted from the center of the Wehnelt hole. However, when a part of the cathode is deteriorated, if it is fixed after being shifted in the x or y direction by about the diameter of the Wehnelt hole, a new cathode surface is exposed to the Wehnelt hole, and normal electron gun characteristics can be obtained.
Since the cathode and Wehnelt are different in material and temperature, distortion may occur due to the difference in linear expansion. The fixing of the two was loosened and the contact surfaces of both were mirror polished. As a result, it is possible to shift in the X and Y directions. As a result, no distortion occurs and the cathode has no axis, so that normal electron gun characteristics are maintained.
Since the Wehnelt 4-1-3 has a concave truncated cone shape whose angle with each optical axis is larger than 68 degrees, the cathode is isolated from the influence of the adjacent optical axis. If a cylindrical Wehnelt 4-1-3 is added to the anode side of each Wehnelt, this isolation becomes more reliable.
Reference numerals 4-31 and 4-32 denote holes for attaching the Wehnelt to the anode. 4-28 is a metal plate on which all Wehnelts are processed, or a ceramic whose surface is metal-coated. Ceramics have high rigidity and small deflection, so that high accuracy can be achieved. It is even better to use ceramics with a zero expansion coefficient.

In order to prevent the electron gun from being affected by the adjacent electron gun, it is necessary to reduce the Wehnelt-anode distance: Dwa. As a result of the simulation, it was preferable to set the cathode-anode distance: Dca to be not more than three times the distance between the optical axes. Cathode-anode distance: As a result of reducing Dca, the probability of discharge between the cathode and anode increases. In order to avoid this, the voltage applied between the cathode and the anode was set to Dca · 4 kV or less.
The peripheral beam of the optical axis is less subject to influence from the surroundings than the central beam, and astigmatism is increased. In order to minimize this influence, it is preferable to provide dummy optical axes at the same pitch outside the peripheral optical axis. That is, when using m rows and n columns, it is set to (m + 2) · row (n + 2) columns.

FIG. 5 is an electro-optical diagram of the LEEPL electron beam transfer apparatus of the present invention. The electron gun includes a flat cathode 1, a concave frustoconical Wehnelt 2, and an anode 3. The electron beam emitted from the electron gun forms a crossover image in the blanking aperture 6 by the condenser lens 4. The blanking deflector 5 was provided inside the electromagnetic lens 4. The size of the crossover created downstream of this lens can be adjusted by the second condenser lens 7 to adjust the current density during transfer and the pattern edge blur. That is, if the crossover diameter is reduced, the blur is reduced, and if the crossover diameter is increased, the current density can be increased. The deviation of the focusing condition between the first and second apertures caused by this adjustment was ignored because there was only a slight increase in the penumbra of irradiation.
Reference numeral 8 denotes a rectangular first opening which is designed to have a size capable of irradiating the entire rectangular opening of the second aperture plate by the projection lens 9. The deflector 10 is provided at the crossover position created by the projection lens 9 so that the position of the crossover 15 created by the third condenser lens 14 does not move when the irradiation area is switched to either a mask or four alignment beams. I made it.

In this optical system, the crossover needs to be focused on the position of the blanking aperture 6, the deflection center of the beam switching deflector 10, and the position of 15 for controlling transfer blur and current density. The second opening 14 and the mask 21 need to be optically conjugate. When both the crossover and the aperture satisfy the focusing condition at the time of design and the lens condition is changed, it is necessary to sacrifice one of the focusing conditions. Misalignment of the focusing condition between the apertures caused only a slight increase in the penumbra and was not a problem. It was ignored and priority was given to the focusing condition of the crossover.
FIG. 8 is a diagram showing a method of accurately aligning the crossover created by the condenser lens 9 with the deflection center of the deflector 10.

The two-stage deflectors 16 and 17 are for alignment, and the deflection center is the mask position or the main surface of the final lens as in the deflection trajectory indicated by 19 or 28. Therefore, the deflection sensitivity ratio of 16 and 17 was adjusted so that the irradiation area did not move when the alignment was performed, or the aberration of the final lens was minimized. The projection lens 18 is designed so that the beam irradiating the mask becomes a parallel beam when the crossover 15 is in a predetermined position. Accordingly, if the position of the crossover 15 is moved to the electron gun side, the beam exiting the lens 18 becomes a slightly convergent beam, and the transfer image from the mask to the wafer is slightly reduced. Conversely, if the position of the crossover 15 is moved to the wafer side, the beam exiting the lens 18 becomes a slightly divergent beam, and the transfer image from the mask to the wafer is slightly enlarged. With this adjustment, the transfer magnification of the transfer image is adjusted.
The crossover 15 may be fixed, and the transfer magnification may be finely adjusted by changing the excitation of the projection lens 18 to be a divergent beam or a convergent beam.

An astigmatism correction coil 29 is provided on the condenser lens 14 to cause astigmatism in the crossover 15 in case the wafer has different magnifications in the x-axis direction and the y-axis direction. The result is shown in FIG. The crossover in the X direction is formed closer to the electron gun than the crossover in the Y direction indicated by 72 as indicated by the solid line 71, and the pattern in the X direction has a mask in the convergent beam as indicated by the solid line. The pattern in the Y direction is enlarged and transferred because there is a mask in the diverging beam, as indicated by the dotted line. As a result, the transfer magnification in the x and y directions can be adjusted independently. The astigmatism corrector may be placed anywhere between the electron gun and the mask except at the crossover position.

  A method of accurately matching the crossover created by the first projection lens 9 with the deflection center of the irradiation region changing deflector 10 will be described with reference to FIG. Reference numeral 21 denotes a mask region, and 20, 23, 81, and 82 are beam forming holes for alignment. The irradiation regions in the case of irradiating these holes are 80, 83, 86, and 87 in this order. Reference numeral 90 denotes an irradiation area when the mask area is irradiated, and a thick side indicates a penumbra. First, the hole 81 is irradiated in the irradiation area 86, and the registration mark is detected. Next, the voltage of the Y electrode of the deflector 10 is changed to irradiate the same hole 81 with 88 irradiation areas, and the registration mark is also detected. The fine adjustment of the excitation of the lens 9 is repeated until both marks are detected at the same position, and the excitation conditions are recorded. Next, the same operation is performed on the hole 23, and the excitation condition of the lens 9 at which the detection position of the registration mark is the same when the voltage applied to the electrode in the X direction is changed is examined. If this value is the same, the adjustment ends. If they are not the same, astigmatism correction is performed by an astigmatism corrector provided closer to the electron gun than the deflector 10. In this astigmatism correction, the excitation of the lens 9 is set to an intermediate value between the optimum value obtained at the hole 81 and the optimum value obtained at the hole 23, and 23 or 81 while finely adjusting the astigmatism correction value. This can be done until the same mark coordinates are obtained in the hole. Briefly, the excitation conditions for the lens and the astigmatism corrector may be determined so that the mark coordinate values are the same when one beam forming hole is irradiated in different irradiation areas.

A method for adjusting the trapezoidal distortion is shown in FIG. The mask 21 passes through the center of the mask and is rotatable around an axis parallel to the x axis or the y axis. 90 in FIG. 9 shows a case where the projection lens is tilted to the upper right in the X-axis direction, and the projection lens forms a slightly convergent beam. As a result, the distance from the mask to the wafer is different between the right and left of the X axis, and the rectangular pattern is distorted as 91, as indicated by 91. Using this distortion, correction transfer can be performed on a wafer having a distortion that increases in size on the right side of the X axis.
An acceleration potential is applied to the primary beam by the control power supply 25 on the mask 21 and the wafer 27. The energy distribution of secondary electrons peaks at 2 eV and is very small at 10 eV or more. Therefore, when the potential difference is increased to about 10 V or more, the secondary electrons are almost returned to the wafer side by this potential difference. Significantly less.

In order to minimize damage to the mask due to electron beam irradiation, the energy of the electron beam that irradiates the mask should be less than 2 keV. Further, at an irradiation voltage of 500 eV or less, it is easily affected by charging inside the lens barrel and an intruding magnetic field. After all, the energy of the electrons that irradiate the mask: Em
500 eV <Em <2 k eV
It is good to make it.
Further, in order to sufficiently expose the entire resist in the thickness direction, an energy larger than 2 keV is better. On the other hand, if the energy for irradiating the resist is larger than 9 keV, the electron beam reaches the wafer, and the proximity effect due to backscattered electrons from there increases, which is not preferable. Therefore, energy to irradiate resist: Er
2 keV <Er <9 keV
However, Er depends on the resist thickness. When the power supply 25 is operated, the deflection trajectory 19 bends as shown at 22, but the entire mask is bent by the same amount, so that no alignment error occurs. The alignment signal can be detected by four backscattered electron detectors 24 and 26 provided between the mask and the wafer.

To reduce the proximity effect during LEEPL transfer, it is effective to reduce the pattern blur. FIG. 6 is a diagram for comparing the size of blur when the diameter of the crossover 15 in FIG. 5 is fixed. Reference numerals 18, 618, and 65 collectively show a case where the projection lens is on the mask, at the same position as the mask, and below the mask, in one figure. When the lens is at position 18, the trajectory 65 passing through the crossover end and intersecting with the mask is converged by the lens 18, and the blur size at the wafer 27 becomes 61.
When the projection lens 618 is at the same Z position as the mask, the trajectory 64 passing through the crossover end and intersecting with the mask is not converged by the lens 618, and the size of blur on the wafer 27 becomes 62. When the lens is at the position 65 below the mask, the trajectory 65 passing through the crossover end and intersecting with the mask is converged by the lens 65, and the size of blur on the wafer 27 becomes 63. The current density under the above three conditions is the same value because of the parallel beam from the lens 18 to the wafer. Therefore, the blur is smaller and the proximity effect is smaller at the same current density when the mask is at the same position as the lens or at the electron gun side of the lens than when the mask is under the projection lens.
In the case of an in-lens mask, the size of the transfer blur is L from crossover 15 to l, l from mask to wafer, and 250 nm from crossover.
Δ = 250 nm xl / L.
In order to make l (e) 5 mm and Δ 5 nm or less, L should be 250 mm or more. l is preferably 5 mm or less.

FIG. 7 shows a ULSI creation method according to the present invention. 1. A pattern of necessary masks of all layers is formed by an electron beam drawing apparatus. Here, a pattern in which the proximity effect at the time of electron beam writing is corrected and a slight proximity effect generated at the time of EB transfer is also corrected.
2. Create nano molds (nano stampers) with patterns for each layer. 3. Using this mold as a master mold, a large number of replica patterns are created by nanoimprint technology.
4). Create many LEEPL masks using many patterns created with replicas. 5). Transfer to the wafer with this LEEPL mask. Here, 6. Since the LEEPL mask is contaminated with the release material from the resist, the LEEPL mask is removed from the working chamber and transferred to the cleaning chamber for cleaning when one or a predetermined number of copies are transferred. The LEEPL mask is cleaned, and when the temperature rises, another LEEPL mask of the same layer is placed in the working chamber and transferred to the next wafer while returning to a predetermined temperature. In addition, the LEEPL mask that has been cleaned a predetermined number of times or transferred is discarded without being inspected in case distortion or the like that cannot be repaired even after cleaning occurs.

Next, an electron gun used in the electron beam apparatus of the present invention will be described with respect to an electron gun that can reliably obtain a luminance exceeding the Langmuir limit even when the current density is low at a flat cathode.
FIG. 11 is an enlarged view of the vicinity of the cathode of the electron gun model when the distance between the optical axes is small. 110 is a cathode, 111 is a Wehnelt, 112 is a first anode, 113 is a second anode, and 114 is an optical axis. θw is an angle from the optical axis to the Wehnelt, and is hereinafter referred to as a Wehnelt angle. θa is an angle from the optical axis to the first anode, and is hereinafter referred to as an anode angle.
When θw <90 °, a convex Wehnelt is formed, when θw = 90 ° is a flat Wehnelt, and when θw> 90 °, a concave Wehnelt is obtained. When [theta] a> 90 [deg.], a convex anode, [theta] w = 90 [deg.] is a flat anode, and [theta] w <90 [deg.] is a concave anode.

表１は、図１１の電子銃モデル例である。このようなモデルでMEBS社シュミレーションソフト“Source”を用いて、計算を行った。シミュレーション手順は、
ウエーネルト電圧をある値に設定し、”SourceV を実行するとカソード電流あるいは電子銃電流：Ie が算出される。
“SourceA“を実行するとカソード電流密度 Jcが算出される。
“SourceB”を実行すると輝度の放出角度依存性が出力される。軸上輝度Bを読み取り、その電子銃電流依存性を算出し、グラフ表示する。
図１１のモデルでの電子銃で、ウエーネルト角：θｗを９０度に固定し、アノード角θaを変化した場合の代表的なシミュレーション結果を図１２に示した。第１アノード電圧：３００Ｖ, 第２アノード電圧：２０００Ｖ、第３アノード電圧：４５００Ｖ、カソード：０Vを固定しウエーネルト電圧を変えてビーム電流を変化させた。ビーム電流を変えて輝度を算出した。図１２で横軸は電子銃電流（μＡ），縦軸は輝度（10５ A/cm2sr）。図１２で、カソードは１００μΦの平面、カソードと第１アノード電極間距離：０．３３ mmである。
輝度データ：１２０、１２１，１２２、１２３、１２４、１２５、１２６と１２７はそれぞれアノード角θaが９０、８６．４、７６、４８．８、４５、４３．３、４１．４、４０．１度である。１２８はカソード電流密度 Jcから算出したLangmuir限界である。
アノード角θaが９０°の場合では輝度１２０（点線）は輝度１１８（実線）とほぼ等しくLangmuir限界を越えていない。そして、Langmuir限界を越えない場合は輝度のシミュレーション値がLangmuir限界に近い事から、輝度のシミュレーション値が正しいと推定出来る。図１２で明らかな様に、アノード角θaが９０より小さい場合は輝度がLangmuir限界を１０倍以上越えているのが見られる。更にアノード角θaが４１．４度より大きく４８．８度より小さい場合は輝度がLangmuir限界を１００倍以上越えているのが見られる。

Table 1 shows an example of the electron gun model of FIG. Calculations were performed using MEBS simulation software “Source” with such a model. The simulation procedure is
When the Wehnelt voltage is set to a certain value and “SourceV” is executed, the cathode current or electron gun current: Ie is calculated.
When “SourceA” is executed, the cathode current density Jc is calculated.
When “SourceB” is executed, the emission angle dependency of luminance is output. The on-axis luminance B is read, the electron gun current dependency is calculated, and displayed in a graph.
FIG. 12 shows a typical simulation result when the Wehnelt angle θw is fixed at 90 degrees and the anode angle θa is changed with the electron gun of the model of FIG. The beam current was changed by fixing the first anode voltage: 300 V, the second anode voltage: 2000 V, the third anode voltage: 4500 V, and the cathode: 0 V and changing the Wehnelt voltage. The brightness was calculated by changing the beam current. In FIG. 12, the horizontal axis represents electron gun current (μA), and the vertical axis represents luminance (105 A / cm 2 sr). In FIG. 12, the cathode has a plane of 100 μΦ, and the distance between the cathode and the first anode electrode is 0.33 mm.
Luminance data: 120, 121, 122, 123, 124, 125, 126 and 127 have anode angles θa of 90, 86.4, 76, 48.8, 45, 43.3, 41.4, 40.1 degrees, respectively. It is. 128 is the Langmuir limit calculated from the cathode current density Jc.
When the anode angle θa is 90 °, the luminance 120 (dotted line) is almost equal to the luminance 118 (solid line) and does not exceed the Langmuir limit. If the Langmuir limit is not exceeded, the luminance simulation value is close to the Langmuir limit, so it can be estimated that the luminance simulation value is correct. As apparent from FIG. 12, when the anode angle θa is smaller than 90, it can be seen that the luminance exceeds the Langmuir limit by 10 times or more. Further, when the anode angle θa is larger than 41.4 degrees and smaller than 48.8 degrees, it can be seen that the luminance exceeds the Langmuir limit by 100 times or more.

FIG. 13 shows the simulation result with the anode angle θa fixed at 41.6 ° and the Wehnelt angle θw changed from 48.6 ° to 149 °. 130 is the Langmuir limit calculated from the cathode current density Jc. 131, 132, 133, 134, 135, 136, 137, 138, and 139 have a Wehnelt angle θw of 149 °, 146, 138, 126.9, 110.6, 90, 69.4, and 48.6 °, respectively. It is. As is clear from the figure, it can be seen that the luminance exceeds the Langmuir limit by a factor of 10 or more in the range of 48.6 ° to 149 ° of the Wehnelt angle θw. Therefore, the range of 48.6 ° <θw <149 ° is preferable. Further, in the range from 110.6 ° to 149 ° of the Wehnelt angle θw, it can be seen that the luminance exceeds the Langmuir limit by 1000 times or more when the electron gun current is a small value of 1 mA or less. Therefore, it is optimal to set the Wehnelt angle θw in the range of 110.6 ° <θw <149 °.

In the present invention, since a plurality of optical axes are two-dimensionally arranged, a large number of optical axes can be arranged in a certain region, so that pattern formation or sample evaluation can be performed at high speed. Furthermore, an electron gun that can reliably obtain brightness exceeding the Langmuir limit even when the current density is low at a flat cathode can be used.
Further, the LEEPL transfer method of the present invention is more advantageous than the nanoimprint method because the transfer magnification can be adjusted. In addition, it is practical because the optical system is much simpler than the EUV method. In addition, the problems of conventional LEEPL devices and methods have been almost solved.

It is a model figure of the relationship between arrangement | positioning of the multi optical axis of this invention, and an X, Y coordinate. ExB deflector used for the multi-optical axis of the present invention. The secondary electron detector used for the multi-optical axis of this invention. The electron gun used for the multi-optical axis of the present invention. LEEPL optical system of the present invention. The figure which compares the pattern blurring in the LEEPL optical system of this invention. A method of finely adjusting the transfer magnification in the X and Y directions independently. The figure which showed the method of aligning the crossover which the condenser lens 9 makes to the deflection center of the deflector 10 correctly. Keystone correction method The transfer method by LEEPL of this invention. The electron gun model of the present invention Simulation result 1 of the electron gun of the present invention Simulation result 2 of the electron gun of the present invention

Explanation of symbols

7: second condenser lens, 5: blanking deflector, 6: blanking aperture, 18, 618, 65: final projection lens, 25: accelerating electric field application power source, 26: reflected electron detector, 22: electron orbit, 21 :mask. 29: Astigmatism generating coil, 30: Electron beam trajectory at the beam end when irradiating the mask area, 31: Electron beam trajectory at the beam end when irradiating the beam forming hole 23 for registration 32: Beam forming hole 20 for registration Electron beam trajectory 110: cathode, 111: Wehnelt, 112: first anode, 113: second anode, 114: optical axis at the beam end during irradiation

Claims (5)

An electron gun for use in an apparatus for pattern formation or sample evaluation, comprising a cathode, a first anode, a second anode, and a Wehnelt electrode, wherein the Wehnelt electrode and the first anode electrode have a truncated cone shape, and an optical axis To Wehnelt angle θw, and the angle from the optical axis to the first anode θa,
An electron gun characterized by satisfying 40.1 ° <θa <90 ° or 48.6 ° <θw <149 °.   2. The electron gun according to claim 1, wherein 41.4 ° <θa <48.8 ° or 110.6 ° <θw <149 °.   In an apparatus that has a plurality of optical axes arranged two-dimensionally and performs pattern formation or sample evaluation, each optical axis has an electron gun, an objective lens, and a secondary electron detector, and each optical axis is an electron gun. A device that irradiates the sample with an electron beam from the objective lens, and secondary electrons from the sample pass through the objective lens, then deflects in the direction of the detector with the ExB deflector, and enters the secondary electron detector for detection. Further, the electron gun is an electron beam apparatus having the characteristics described in claim 1.   In an apparatus that has a plurality of optical axes arranged two-dimensionally and performs pattern formation or sample evaluation, each optical axis has an electron gun and an objective lens, and each optical axis objectives an electron beam from the electron gun. An apparatus for irradiating a sample with a lens, wherein the electron gun has the characteristics described in claim 1, and the cathode of the electron gun is formed by forming a photoelectron substance on a single transparent substrate, When the electron gun characteristics of any of the optical axes deteriorates, the substrate is moved in a direction perpendicular to the optical axis so that a new photoelectric material is exposed to the deteriorated electron gun. .   In an apparatus that has a plurality of optical axes arranged two-dimensionally and performs pattern formation or sample evaluation, each optical axis has an electron gun and an objective lens, and each optical axis objectives an electron beam from the electron gun. An apparatus for irradiating a sample with a lens, wherein the electron gun has the features described in claim 1, and the minimum distance between the Wehnelt electrode and the first anode electrode is twice the distance between adjacent optical axes. An electron beam device characterized by being smaller.

Images