JP2004153294A - Electron beam exposure device, electron beam exposure method and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam exposure device with no restriction for patterns. <P>SOLUTION: The electron beam exposure device, comprising an electron beam source and an electro-optical system for focusing the electron beam from the electron beam source onto a surface to be exposed, further comprises an electron density distribution adjusting means for adjusting the electron density distribution of the electron beams on a pupil surface in the electro-optical system so that the electron density at the peripheral part is higher than the electron density at the center part. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to an electron beam exposure apparatus and an exposure method therefor, and more particularly to an electron beam exposure apparatus and an exposure method for performing pattern writing using a plurality of electron beams for direct wafer writing or mask and reticle exposure.

  Examples of the electron beam exposure apparatus include a point beam type in which a beam is used in the form of a spot, a variable rectangular beam type in which a variable-size rectangular cross section is used, and a stencil mask type in which a stencil is used to obtain a desired cross-sectional shape. is there.

Point beam type electron beam exposure apparatuses are used only for research and development because of low throughput. The variable rectangular beam type electron beam exposure apparatus has a throughput of one to two orders of magnitude higher than that of the point type. However, when exposing a pattern in which a fine pattern of about 0.1 μm is packed with a high degree of integration, the throughput is still higher. There are many problems in this regard. On the other hand, a stencil mask type electron beam exposure apparatus uses a stencil mask in which a plurality of repeating pattern transmission holes are formed in a portion corresponding to a variable rectangular aperture. Therefore, the stencil mask type electron beam exposure apparatus has a great advantage in repeatedly exposing a pattern, and the throughput is improved as compared with the variable rectangular beam type.
US Patent No.4158140 U.S. Pat. No. 5,334,282

  FIG. 2 shows an outline of an electron beam exposure apparatus provided with a stencil mask. The electron beam from the electron gun 501 is applied to a first aperture 502 that defines an electron beam irradiation area of the stencil mask. An electron beam for illumination defined by the first aperture irradiates the stencil mask on the second aperture 504 through the projection electron lens 503, and the electron beam from the repetitive pattern transmission hole formed in the stencil mask is reduced. The system 505 performs reduction projection on the wafer 506. Further, the image of the pattern transmission hole is repeatedly moved on the wafer by the deflector 507 and is sequentially exposed.

  The stencil mask type can expose a repetitive pattern at a time, and can increase the exposure speed. However, although the stencil mask type has a plurality of pattern transmission holes as shown in FIG. 3, there is a problem that the pattern must be formed as a stencil mask in advance in accordance with the exposure pattern.

  In addition, because of the space charge effect and the aberration of the reduction electron optical system, the exposure area that can be exposed at one time is limited, so for a semiconductor circuit that requires a large number of transfer patterns that do not fit on one stencil mask, It is necessary to prepare a plurality of stencil masks, use them one by one, and use them, and the time required for mask replacement is required, resulting in a problem that the throughput is significantly reduced.

  If the stencil mask has patterns of different sizes, or if there is one pattern obtained by combining patterns of different sizes, blurring of the exposure pattern due to the space charge effect may occur depending on the size of the pattern. different. Even if the blur is corrected by refocusing, the amount of refocus varies depending on the size of the pattern, and there is a problem that the above-described pattern cannot be used as a stencil mask pattern.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and a main object of the present invention is to provide an electron beam exposure apparatus having no pattern limitation.

  (1) An electron beam exposure apparatus according to a first aspect of the present invention is an electron beam exposure apparatus having an electron beam source and an electron optical system that focuses an electron beam from the electron beam source on a surface to be exposed. An electron density distribution adjusting means is provided for causing the electron density distribution of the electron beam on the pupil plane of the electron optical system to be higher in the peripheral part than in the central part.

  (2) A second embodiment of the electron beam exposure apparatus according to the present invention includes an electron beam source, an electron optical system that projects a pattern on a surface to be exposed using an electron beam emitted from the electron beam source, Pupil plane position of the electron optical system, or at a position conjugate with the pupil plane position of the electron optical system, means for adjusting the electron density distribution of the passing electron beam on the pupil plane, I do.

  (3) A third embodiment of the electron beam exposure apparatus according to the present invention includes an electron beam source, an electron optical system for projecting a pattern on a surface to be exposed by using an electron beam emitted from the electron beam source, Means for shielding electrons passing near the optical axis of the electron optical system on a pupil plane of the electron optical system or a plane conjugate with the pupil plane of the electron optical system.

  (4) A fourth embodiment of the electron beam exposure apparatus according to the present invention includes an electron beam source, and an electron optical system that projects a pattern onto a surface to be exposed using an electron beam emitted from the electron beam. A holo beam forming means is provided at a pupil plane position of the electron optical system or at a position conjugate with the pupil plane position of the electron optical system.

  (5) According to a fifth aspect of the electron beam exposure apparatus of the present invention, a plurality of intermediate images are formed by an electron beam emitted from the electron beam source using an electron beam source and a plurality of elementary electron optical systems. A first electron optical system; and a second electron optical system that projects an intermediate image formed by the first electron optical system onto a surface to be exposed. Characterized by having a plurality of apertures for adjusting the electron density distribution of the electron beam passing therethrough.

  (6) In a first aspect of the electron beam exposure method according to the present invention, in the electron beam exposure method having a step of converging an electron beam on a surface to be exposed by an electron optical system, the electron beam on a pupil plane of the electron optical system is provided. The electron density distribution of the beam is characterized in that the electron density at the center is smaller than the electron density at the periphery.

  According to the present invention, the influence of the space charge effect can be reduced by forming the hollow beam-shaped electron beam, and in a stencil mask type electron beam exposure apparatus, the limitation on the pattern that can be used for the stencil mask can be reduced. Can be higher.

[Explanation of principle]
FIG. 4 is a diagram illustrating the principle of the present invention. PL is a reduction electron optical system, and AX is an optical axis of the reduction electron optical system PL. O1, O2, and O3 are point light sources that emit electrons, and I1, I2, and I3 are point light source images corresponding to each point light source.

  In FIG. 4A, electrons emitted from point light sources O1, O2, and O3 located on the object side of the reduction electron optical system PL and perpendicular to the optical axis AX pass through the reduction electron optical system PL. Thus, point light source images I1, I2 and I3 corresponding to the respective point light sources are formed on the image side. At this time, the point light source images I1, I2, and I3 are not formed in the same plane perpendicular to the optical axis AX due to aberration (field curvature) of the reduction electron optical system.

  Therefore, as shown in FIG. 4B, in the present invention, the point light sources O1, O2, O3 are formed so that the point light source images I1, I2, I3 are formed in the same plane perpendicular to the optical axis AX. The position in the optical axis direction is previously different depending on the aberration (field curvature) of the reduction electron optical system. Further, since the reduction electron optical system has different aberrations (astigmatism, coma, distortion) depending on the position of the light source on the object side, a more desired light source image is formed in the same plane if the light source is distorted in advance according to the aberration. .

  Therefore, in the present invention, a plurality of intermediate images of the light source are formed on the object side of the reduction electron optical system, and the aberration generated when each intermediate image is reduced and projected on the surface to be exposed by the reduction electron optical system is corrected in advance. By providing the correction electron optical system, it is possible to simultaneously form many light source images having a desired shape in a wide exposure area.

  As a matter of course, the plurality of intermediate images described above are not limited to being formed from one light source, and a plurality of intermediate images may be formed from a plurality of light sources.

  Hereinafter, the present invention will be described in detail with reference to examples.

[Exposure system component description]
FIG. 1 is a view showing Embodiment 1 of an electron beam exposure apparatus according to the present invention.

  In FIG. 1, reference numeral 1 denotes an electron gun including a cathode 11, a grid 12, and an anode 13. Electrons emitted from the cathode 11 form a crossover image between the grid 12 and the anode 13.

  This electron gun 1 can change the size of the crossover image by having the function of changing the grid voltage.

Further, by providing an electron optical system (not shown) for enlarging or reducing or shaping the crossover image, an enlarged, reduced or shaped crossover image can be obtained, whereby the size and shape of the crossover image are obtained. Can be changed. (Hereinafter, these crossover images are referred to as light sources.)
Electrons emitted from the light source are converted into substantially parallel electron beams by the condenser lens 2 whose front focal position is at the light source position. The substantially parallel electron beam is preferably supplied to a plurality of element electron optical systems (31, 32) (the number of the element electron optical systems is desirably as large as possible. (Illustrated and to be described) are incident on the correction electron optical systems 3 arranged in a plurality in a direction orthogonal to the optical axis. The details of the plurality of element electron optical systems (31, 32) constituting the correction electron optical system 3 will be described later.

  The correction electron optical system 3 forms a plurality of intermediate images (MI1, MI2) of the light source, and each intermediate image forms a light source image (I1, I2) on the wafer 5 by the reduction electron optical system 4. At this time, each element of the correction electron optical system 3 is set so that the interval between the light source images on the wafer 5 is an integral multiple of the size of the light source image. Further, the correction electron optical system 3 makes the position of each intermediate image in the optical axis direction different according to the field curvature of the reduction electron optical system 4, and each intermediate image is reduced and projected on the wafer 5 by the reduction electron optical system 4. The aberration that occurs when the correction is performed is corrected in advance.

  Further, the reduction electron optical system 4 is a symmetric magnetic tablet including a first projection lens 41 and a second projection lens 42. Assuming that the focal length of the first projection lens 41 is f1 and the focal length of the second projection lens 42 is f2, the distance between these two lenses is f1 + f2. The intermediate image of AX on the optical axis is at the focal position of the first projection lens 41, and the image is focused on the second projection lens. This image is reduced to -f2 / f1. In addition, since the two lens magnetic fields are determined so as to act in opposite directions, theoretically, there are five spherical aberrations, isotropic astigmatism, isotropic coma aberration, field curvature aberration, and axial chromatic aberration. Except for aberrations, other Seidel aberrations and chromatic aberrations related to rotation and magnification are canceled out.

  Reference numeral 6 denotes a deflector for deflecting electron beams from the plurality of intermediate images to move the images of the plurality of intermediate images on the wafer 5 in the X and Y directions. The deflector 6 is composed of a MOL (moving object lenses) type electromagnetic deflector 61 for deflecting by a convergence magnetic field and a deflection magnetic field satisfying the MOL condition, and an electrostatic deflector 62 for deflecting by an electric field. The electromagnetic deflector 61 and the electrostatic deflector 62 are selectively used according to the moving distance of the light source image. Reference numeral 7 denotes a dynamic focus coil which corrects a shift of a focus position due to deflection aberration generated when the deflector is operated, and reference numeral 8 denotes a dynamic stig coil which similarly corrects astigmatism generated by deflection.

  Reference numerals 91 and 92 denote a plurality of electrostatic deflectors for translating (X, Y directions) or deflecting (tilting with respect to the Z axis) electron beams from a plurality of intermediate images formed by the correction electron optical system. It is a deflector.

  Reference numeral 10 denotes a Faraday cup having two single knife edges extending in the X and Y directions.

  Reference numeral 11 denotes an XYZ stage movable in the XYZ directions on which the wafer 5 is placed and moved, and is controlled by the stage drive control device 23.

  The Faraday cup 10 fixed to the wafer stage cooperates with the laser interference optical system 20 for detecting the position of the XYZ stage to transfer the charge amount of the light source image formed by the electron beam from the elementary electron optical system via the knife edge. , The size of the light source image, its position (X, Y, Z), and the current emitted from the elementary electron optical system can be detected.

  Next, the component electron optical system that constitutes the correction electron optical system 3 will be described with reference to FIG.

  In FIG. 5A, reference numeral 301 denotes a blanking electrode having a pair of electrodes and having a deflection function, and reference numeral 302 denotes an aperture stop having an aperture (AP) for defining the shape of a transmitted electron beam. The wiring (W) for turning on / off the electrode with the blanking electrode 301 is formed. Reference numeral 303 denotes a unipotential lens having a converging function in which three aperture electrodes are provided, upper and lower electrodes are set to the same accelerating potential V0, and an intermediate electrode is kept at another potential V1. Reference numeral 304 denotes a blanking aperture located on the focal plane of the unipotential lens 302.

  The electron beam made substantially parallel by the condenser lens 2 forms an intermediate image (MI) of the light source on the blanking opening 304 by the unipotential lens 302 through the blanking electrode 301 and the opening (AP). At this time, if an electric field is not applied between the electrodes of the blanking opening 304, the light passes through the blanking opening 304 like an electron beam bundle 305. On the other hand, when an electric field is applied between the electrodes of the blanking opening 304, the electric field is blocked by the blanking opening 304 like an electron beam bundle 306. Further, since the electron beam 305 and the electron beam 306 have different angular distributions on the blanking aperture 304 (the object plane of the reduction electron optical system), as shown in FIG. 5B, the pupil position ( On the P plane in FIG. 1), the electron beam bundle 305 and the electron beam bundle 306 are incident on mutually different regions. Therefore, instead of providing the blanking opening 304, a blanking opening 304 'for transmitting only the electron beam bundle 305 may be provided at the pupil position (on the P plane in FIG. 1) of the reduced electron optical system. Thereby, it can be used in common with the blanking apertures of the other element electron optical systems constituting the correction electron optical system 3.

  In this embodiment, a unipotential lens having a converging function is used, but a bipotential lens having a diverging function may be used to form an intermediate image of a virtual image.

  Returning to FIG. In the correction electron optical system 3, the position in the optical axis direction of the intermediate image formed by each of the above-mentioned elementary electron optical systems is made different according to the field curvature of the reduction electron optical system 4. As one of the concrete means, each element electron optical system is made the same, and each element electron optical system is installed with its position in the optical axis direction changed. As another method, each element electron optical system is set on the same plane, and the electron optical characteristics (focal length, main surface position) of each element electron optical system, particularly the unipotential lens, are changed, and the light of each intermediate image is changed. It changes the axial position. The latter employed in this embodiment will be described in detail with reference to FIG.

In FIG. 6, a blanking electrode is formed for each opening on an aperture 302 having two openings (AP1 and AP2) having the same shape to form a blanking array. Each blanking electrode is individually wired and can turn on / off an electric field independently. (See Fig. 7)
The unipotential lenses 303-1 and 303-2 form a lens array by laminating three insulators 307, 308 and 309 provided with electrodes. The upper and lower electrodes (303U, 303D) are wired so as to set a common potential (see FIG. 8), and the intermediate electrode (303M) is wired so that the potential can be set individually (see FIG. 9). The blanking array and the lens array have an integral structure with an insulator 310 interposed.

  The electrode shapes of the unipotential lenses 303-1 and 303-2 are the same, but the focal lengths are different because the potentials of the intermediate electrodes are different. Therefore, the positions of the intermediate images (MI1, MI2) in the optical axis direction are different from those of the electron beams 311 and 312.

  Further, in order to correct astigmatism generated when each intermediate image is reduced and projected on the surface to be exposed by the reduction electron optical system 4, each element electron optical system generates reverse astigmatism. In order to generate reverse astigmatism, the shape of the aperture electrode forming the unipotential lens is distorted. As shown in FIG. 10, if the shape of the aperture electrode is circular as in the unipotential lens 303-1, both the electrons distributed in the M direction and the electrons distributed in the S direction form an intermediate image at approximately the same position 313. However, when the shape of the aperture electrode is elliptical as in the unipotential lens 303-3, electrons distributed in the M direction (minor diameter direction) form an intermediate image at the position 314 and are distributed in the S direction (long diameter direction). The resulting electrons form an intermediate image at location 315.

  Therefore, by changing the shape of the aperture electrode of the unipotential lens of each elementary electron optical system according to the astigmatism of the reduction electron optical system 4, each intermediate image is reduced and projected on the surface to be exposed by the reduction electron optical system 4. Can be corrected.

  Further, in order to correct coma aberration generated when each intermediate image is reduced and projected on the surface to be exposed by the reduction electron optical system 4, each element electron optical system generates an opposite coma aberration. In order to generate the reverse coma, as one method, each elementary electron optical system decenters the center of the aperture on the aperture stop 302 with respect to the optical axis of the unipotential lens 303. As another method, electron beams from a plurality of intermediate images formed in each element electron optical system are individually deflected by deflectors (91, 92).

  Further, in order to correct the distortion generated when the plurality of intermediate images are reduced and projected on the surface to be exposed by the reduction electron optical system 4, the distortion characteristics of the reduction electron optical system 4 are known in advance, and the reduction The position of each element electron optical system in the direction orthogonal to the optical axis of the electron optical system 4 is set.

[Description of operation]
As shown in FIG. 11A, the light source images (I1, I2) formed on the wafer 5 by the respective element electron optical systems (31, 32) correspond to the scanning fields of the respective element electron optical systems at the respective reference positions ( A and B) are used as a starting point to obtain a constant same movement amount by the polarizer 6, expose the wafer, and sequentially deflect it to the next exposure position (as indicated by an arrow in the figure) to expose the wafer. In the figure, each square indicates an area to be exposed by one light source image, a hatched area indicates an area to be exposed, and an unhatched area indicates an unexposed area.

When the pattern data of the exposure pattern as shown in FIG. 11A is input, the CPU 12 divides the pattern into scan fields for each elementary electronic optical system and, as shown in FIG. The position data (dx, dy) of the exposure position based on the position (A, B) and the exposure data (whether the hatched cells are hatched, 1 for each scanning field) at that exposure position. No cell is set to 0) as a set of exposure control data. Then, an exposure control data file in which the exposure control data is arranged in the order of exposure is created. (Because the scanning field of each elemental electron optical system obtains the same fixed amount of movement by the deflector 6 starting from each reference position (A, B), the exposure data of a plurality of scanning fields for one position data Can be combined.)
Further, of the exposure control data, the exposure control data that is not exposed in all the scan fields, that is, the exposure control data in which all the exposure data is 0 is deleted (exposure data surrounded by DEL in FIG. 11B), and FIG. Recreate the exposure control data file as shown in C). Then, the exposure control data file is stored in the memory 19 via the interface 13.

  If the input pattern has a large number of repetitive patterns having a specific cycle (pitch) (for example, a DRAM circuit pattern having many patterns having a cycle corresponding to the cell pitch), the starting position interval of each scan field is set to the specific pattern. The starting position of each scanning field (the interval between light source positions formed on the wafer via each elementary electron optical system) is set so as to be an integral multiple of the period (pitch). Thereby, the exposure control data in which all the exposure data is 0 increases, and the data can be further compressed. As a specific method, a method of adjusting the magnification of the reduction electron optical system 4 (the respective focal lengths of the first projection lens 41 and the second projection lens 42 are changed by the magnification adjustment circuit 22) and a method of adjusting each element electron optics There is a method of adjusting the position of the intermediate image formed by the system by the deflectors 91 and 92.

  Further, when a pattern is already formed on the wafer 5 and a pattern input to the apparatus is overprinted on the pattern, the wafer expands and contracts by a process which passed before the overprinting of the wafer, and the wafer is already formed. Patterns may also be stretched. Therefore, in the present apparatus, the position of at least two wafer alignment marks on the wafer 5 is detected by an alignment device (wafer mark position detection device) not shown, and the expansion / contraction ratio of the already formed pattern is detected. Based on the detected expansion / contraction ratio, the magnification of the reduction electron optical system 4 is adjusted by the magnification adjustment circuit 22 to expand or contract the interval between the light source images, and the gain of the polarizer 6 is adjusted by the deflection control circuit 21 to adjust the light source image. To expand or contract the amount of movement. Therefore, good overprinting can be achieved even for a pattern that has undergone expansion and contraction.

  Returning to FIG. 1, the operation of this embodiment will be described again. When the CPU 12 issues a calibration command for the exposure system, the sequence controller 14 determines, via the focus control circuit 15, the position in the optical axis direction of the intermediate image formed by each of the component electron optical systems of the correction electron optical system 3. The potential of the intermediate electrode of each elementary electron optical system is set so as to be set at a predetermined position.

  Then, the system controller 14 controls the blanking control circuit 16 so that only the electron beam from the elementary electron optical system 31 irradiates the XYZ stage 11 side, and operates blanking electrodes other than the elementary electron optical system 31. (Blanking on). At the same time, the XYZ stage 11 is driven by the drive controller 17 to move the Faraday cup 10 near the light source image formed by the electron beam from the elementary electron optical system 31, and the position of the XYZ stage 11 at that time is determined by the laser interferometer 20. To detect. Then, while detecting the position of the XYZ stage 11 and moving the XYZ stage, a light source image formed by the electron beam from the elementary electron optical system 31 is detected by the Faraday cup 10, and the position, size, The emitted current is detected. The position (X1, Y1, Z1) at which the light source image has a predetermined size and the current I1 applied at that time are detected.

  Next, the blanking control circuit 16 is controlled so that only the electron beam from the elementary electron optical system 32 irradiates the XYZ stage 11 side, and blanking electrodes other than the elementary electron optical system 32 are operated. At the same time, the XYZ stage 11 is driven by the drive controller 17 to move the Faraday cup 10 near the light source image formed by the electron beam from the elementary electron optical system 31, and the position of the XYZ stage 11 at that time is determined by the laser interferometer 20. To detect. Then, while detecting the position of the XYZ stage 11 and moving the XYZ stage, the light source image formed by the electron beam from the elementary electron optical system 32 is detected by the Faraday cup 10, and the position, size, The current applied at that time is detected. The position (X2, Y2, Z2) where the light source image has a predetermined size and the irradiation current I2 at that time are detected.

  Then, based on the detection result, the sequence controller sets the positions in the X and Y directions of the respective light source images formed by the electron beams from the elementary electron optical systems 31 and 32 in a predetermined relative positional relationship. Each intermediate image is translated in the X and Y directions by deflectors 91 and 92 via the optical axis alignment control circuit 18. Further, in order to position the position of each light source image formed by the electron beams from the element electron optical systems 31 and 32 in the Z direction within a predetermined range, each of the element electron optical systems is controlled via the focus control circuit 15. Reset the potential of the intermediate electrode. Further, the detected current for irradiating the wafer of each of the element electron optical systems is stored in the memory 19.

Next, when exposure of the pattern is started according to a command from the CPU 12, the sequence controller 14 determines the sensitivity of the resist applied to the wafer 5 previously input to the memory 19 and the respective values stored in the memory 19 as described above. The exposure time at the exposure position of the light source image formed by each element electron optical system (the residence time of the light source image at the exposure position) is calculated based on the irradiation current onto the wafer for each element electron optical system. It is calculated for each system and transmitted to the blanking control circuit 16. Further, the sequence controller 14 transmits the exposure control file stored in the memory 19 to the blanking control circuit 16 as described above. The blanking control circuit 16 sets a blanking OFF time (exposure time) for each element electron optical system, and sets exposure data and element electron optics for each element electron optical system in the transmitted exposure control file. Based on the blanking OFF time (exposure time) for each system, a blanking signal as shown in FIG. 12 is transmitted to each element electron optical system in synchronization with the deflection control circuit 21, and the exposure for each element electron optical system is performed. Timing and exposure amount are controlled. (Exposure time at each exposure position is longer in field 2 than in field 1)
On the other hand, the sequence controller 14 transmits the exposure control file stored in the memory 19 to the deflection control circuit 21 as described above. In the deflection control circuit 2, each of the deflection control signal, the focus control signal, and the astigmatism correction signal is converted via the D / A into the deflector 6 and the dynamic focus based on the position data in the transmitted exposure control file. The data is transmitted to the coil 7 and the dynamic stig coil 8 in synchronization with the blanking control circuit 16, and the positions of a plurality of light source images on the wafer are controlled.

  If the deviation of the focus position due to the deflection aberration generated when the deflector is operated cannot be corrected by the dynamic focus coil alone, focus is performed to position the light source image in the Z direction within a predetermined range. The position of the intermediate image in the optical axis direction may be changed by adjusting the potential of the intermediate electrode of each elementary electron optical system via the control circuit 15.

[Other Embodiment 1 of Element Electron Optical System]
Another embodiment 1 of the elementary electron optical system will be described with reference to FIG. 5, the same components as those of FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted.

  The major differences from the elementary electron optical system of FIG. 5 are the aperture shape on the aperture stop and the blanking electrode. The opening (AP) blocks an electron beam incident near the optical axis of the unipotential lens 303 to form a hollow beam (hollow cylindrical beam). The blanking electrode 321 is a blanking electrode suitable for this opening shape, and includes a pair of cylindrical electrodes.

  The electron beam made substantially parallel by the condenser lens 2 forms an intermediate image of the light source on the blanking aperture 304 by the unipotential lens 302 via the blanking electrode 321 and the aperture stop 322. At this time, if no electric field is applied between the electrodes of the blanking opening 304, the light passes through the blanking opening 304 like an electron beam bundle 323. On the other hand, when an electric field is applied between the electrodes of the blanking opening 304, the electron beam is deflected and blocked by the blanking opening 304 like an electron beam bundle 324. Further, since the electron beam flux 323 and the electron light flux 324 have different angular distributions on the blanking aperture 304 (the object plane of the reduced electron optical system), as shown in FIG. In P) of FIG. 1, the electron beam bundle 323 and the electron beam bundle 324 are incident on mutually different regions. Therefore, instead of providing the blanking aperture 304, a blanking aperture 304 'for transmitting only the electron beam bundle 323 may be provided at the pupil position of the reduction electron optical system. Thereby, it can be used in common with the blanking apertures of the other element electron optical systems constituting the correction electron optical system 3.

  Further, since the space beam effect of a hollow electron beam (hollow cylindrical beam) is smaller than that of a solid electron beam (for example, a Gaussian beam), the electron beam is focused on the wafer and a light source image with a small blur is formed on the wafer. Can be formed. That is, when the electron beam from each element electron optical system passes through the pupil plane P of the reduction electron optical system 4, the electron density distribution of the electron beam on the pupil plane is determined by comparing the electron density at the periphery with the electron density at the center. The above effect can be obtained by increasing the size. The electron density distribution on the pupil plane P is determined by the aperture on the aperture stop 320 (the center is shielded from light) at an almost conjugate position with the pupil plane P of the reduction electron optical system 4 as in this embodiment. Opening).

[Other Embodiment 2 of Element Electron Optical System]
Next, another embodiment 2 of the elementary electron optical system will be described with reference to FIG. In the figure, the same components as those in FIG. 5 or FIG.

  The major differences from the elementary electron optical system in FIG. 5 are the aperture shape on the aperture stop (the same shape as the aperture stop in FIG. 13A) and the absence of a blanking electrode.

  The electron beam made substantially parallel by the condenser lens 2 forms an intermediate image of the light source on the blanking aperture 304 by the unipotential lens 302 via the aperture stop 322. At this time, if the intermediate electrode of the unipotential lens 302 is set at a predetermined potential, the electron beam is converged and passes through the blanking opening 304 like an electron beam bundle 330. On the other hand, when the potential of the intermediate electrode of the unipotential lens 302 is set to be the same as the potential of the other electrodes, the electron beam is not converged, but is blocked by the blanking aperture 304 like the electron beam bundle 331. Blanking can be controlled by changing the potential of the intermediate electrode of the unipotential lens 302.

  Further, since the electron beam bundle 331 and the electron beam bundle 332 have different angular distributions on the blanking aperture 304 (the object plane of the reduction electron optical system), the pupil position of the reduction electron optical system as shown in FIG. In (P in FIG. 1), the electron beam 330 and the electron beam 331 are incident on mutually different regions. Therefore, instead of providing the blanking opening 304, a blanking opening 304 'for transmitting only the electron beam bundle 330 may be provided at the pupil position of the reduction electron optical system. Thereby, it can be used in common with the blanking apertures of the other element electron optical systems constituting the correction electron optical system 3.

[Exposure system component description]
FIG. 15 is a view showing Embodiment 2 of the electron beam exposure apparatus according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  In FIG. 15, electrons emitted from the light source of the electron gun 1 are converted into substantially parallel electron beams by the condenser lens 2 whose front focal position is at the light source position. A substantially parallel electron beam is formed by an element electron optical system array 130 (corresponding to the correction electron optical system 3 of the first embodiment) formed by arranging a plurality of element electron optical systems described in FIG. 13 in a direction perpendicular to the optical axis. To form a plurality of intermediate images. The element electron optical system array 130 has a plurality of subarrays in which a plurality of element electron optical systems having the same electron optical characteristics are arranged, and the electron optical characteristics of the element electron optical systems belonging to at least two subarrays differ. Details of the element electron optical system array 130 will be described later.

  Reference numeral 140 denotes a deflector for deflecting (tilting with respect to the Z axis) the electron beam incident on the sub-array, and is provided for each sub-array. The function of the deflector 140 is to correct the difference in the incident angle of the electron beam incident on the sub-array at a different position due to the aberration of the condenser lens 2 for each sub-array.

  Reference numeral 150 denotes a deflector that translates (X and Y directions) and deflects (tilts with respect to the Z axis) electron beams of a plurality of intermediate images formed by the subarray. This is equivalent to 91 and 92 of the first embodiment, and the difference is that a plurality of electron beams from the sub-array are collectively translated and deflected.

  The plurality of intermediate images formed by the element electron optical system array 130 are reduced and projected on the wafer 5 by the reduction electron optical system 100 and the reduction electron optical system 4.

  In the present embodiment, two-stage reduction is adopted to reduce the reduction ratio without increasing the size of the exposure apparatus. The reduction electron optical system 100 includes a first projection lens 101 and a second projection lens 102 similarly to the reduction electron optical system 4. That is, the reduction electron optical system 4 and the reduction electron optical system 100 constitute one reduction electron optical system.

  Reference numeral 110 denotes a refocusing coil. When the number of electron beams from the elementary electron optical system array increases, the beam size incident on the reduced electron optical system substantially increases, and blurring occurs in the light source image due to the space charge effect. In order to correct this, the focus position is controlled based on the number of light source images (the number of blanking electrodes which are turned off) to be irradiated on the wafer obtained from the sequence controller 14.

  Numeral 120 denotes a common blanking aperture of the elementary electron optical system that constitutes the elementary electron optical system array and is located on the pupil plane of the reduction electron optical system 100, and corresponds to 304 'in FIG.

  Next, the elementary electron optical system array 130 will be described with reference to FIG. This figure is a view of the elementary electron optical system array 130 viewed from the electron gun 1 side.

  The element electron optical system array 130 is an arrangement of the element electron optical systems described with reference to FIG. 13, and includes a blanking array in which a plurality of openings, corresponding blanking electrodes, and their wirings are formed on one substrate. A lens array in which electrodes constituting a unipotential lens are laminated on one substrate with an insulator interposed, and a blanking array and a lens array are positioned so that each opening faces the corresponding unipotential lens. Let be combined.

  130A to 130G are subarrays composed of a plurality of element electron optical systems. For example, in the sub-array 130A, 16 element electron optical systems 130A-1 to 130A-16 are formed. In one sub-array, the amount of aberration to be corrected is substantially the same or within an allowable range. Therefore, the same potential is applied to the unipotential lenses of the elementary electron optical systems 130A-1 to 130A-16 with the same aperture electrode shape. ing. Therefore, wiring for applying individual potentials to the electrodes is not required. However, blanking electrodes require individual wirings as in the first embodiment.

  Of course, the sub-array may be further divided into a plurality of sub-sub-arrays, and the electron-optical characteristics (focal length, astigmatism, coma, etc.) of the elementary electron optical system may be the same for each sub-sub-array. Of course, at that time, wiring of an intermediate electrode is required for each sub-sub-array.

[Description of operation]
The points different from the first embodiment will be described.

  First, when the calibration calibration of the exposure system is performed, in the first embodiment, for all the light source images, the positions (X, Y, Z) where the light source images have a predetermined size and the irradiation current I at that time are determined. In this embodiment, at least one light source image representing the sub-array is detected. Based on the detection result, the sequence controller causes the optical axis alignment control circuit 18 to position the light source images of the element electron optical systems representing the sub-arrays in the XY directions in a predetermined relative positional relationship. Then, the intermediate images in the sub-array are translated by the same amount in the direction orthogonal to the optical axis of the reduction electron optical system by the deflector 150. In addition, the potential of the intermediate electrode of each sub-array is set via the focus control circuit 15 so that the position in the Z direction of each light source image of the element electron optical system representing the sub-array is located within a predetermined range. fix. Further, the detected irradiation current of the element electron optical system representing the subarray is stored in the memory 19 as the irradiation current of each element electron optical system in the same subarray.

  As shown in FIG. 17, the light source image formed on the wafer 5 by each of the element electron optical systems in the sub-array has the same moving amount with respect to the scanning field of each element electron optical system starting from each reference position (black circle). Obtained by the deflector 6, the scanning field of each element electron optics exposes the wafer adjacently. Then, the wafer is exposed by all the sub-arrays as shown in FIG. Then, the deflector 6 performs a Ly step in the Y direction by the polarizer 7 and obtains the same moving amount by the deflector 6 starting from each reference position (black circle) in the scanning field of each element electron optical system, and exposes the wafer. By repeating the above four times, exposure fields in which the exposure fields of each subarray are adjacent to each other are formed as shown in FIG.

[Exposure system component description]
FIG. 20 is a view showing Embodiment 3 of the electron beam exposure apparatus according to the present invention. In the figure, the same components as those in FIGS. 1 and 15 are denoted by the same reference numerals, and description thereof will be omitted.

  This embodiment is different from the second embodiment in that at least one electrode for decelerating or accelerating the electron beam is added, and a means for changing the shape of the light source is provided.

  The unipotential lens, which is an electrostatic lens that constitutes the element electron optical system array 130, can achieve a smaller electron lens as the electrons have lower energy.

  However, it is necessary to increase the anode voltage in order to extract more electron beams from the electron gun 1, and as a result, the energy of the electrons from the electron gun may increase. Therefore, in this embodiment, a deceleration electrode such as DCE in the figure is provided between the electron gun 1 and the elementary electron optical system array 130. The deceleration electrode is an electrode having a lower potential with respect to the anode, and adjusts the energy of electrons incident on the elementary electron optical array 130. As for the shape, there are a type having an opening corresponding to each of the elementary electron optical systems as shown in FIG. 1A and a type having an opening corresponding to each of the subarrays as shown in FIG.

  The reduction electron optical system (4, 100) increases (accelerates) the energy of the electron beam from the unipotential lens because the space charge effect deteriorates the convergence of the electron beam on the wafer when the energy of the electron beam is low. )There is a need. Therefore, in this embodiment, an accelerating electrode such as ACE in the figure is provided between the elementary electron optical system array 130 and the reduced electron optical system (4, 100). The accelerating electrode is an electrode having a higher potential with respect to the elementary electron optical system array, and adjusts the energy of electrons incident on the reduction electron optical system (4, 100). Like the deceleration electrode, the shape of the electrode has an opening corresponding to each of the elementary electron optical systems as shown in FIG. 1A and the type having an opening corresponding to each of the sub-arrays as shown in FIG. is there.

  Also in the first and second embodiments and the present embodiment, a desired exposure pattern is formed by transferring a light source image onto a wafer and scanning. The size of the light source image is set to 1/5 to 1/10 of the minimum line width of the exposure pattern. Therefore, by changing the size of the light source according to the minimum line width of the exposure pattern, the number of light source image moving steps for exposure can be minimized. Therefore, in the present embodiment, an electron optical system for shaping the shape of the light source, such as 160 in the figure, is provided. In the electron optical system 160, a light source image S1 of the light source S0 of the electron gun is formed by the first electron lens 161 and an image S2 of the light source image S1 is formed by the second electron lens 162. With such a configuration, by changing each of the focal lengths of the first electronic lens 161 and the second electronic lens 162, it is possible to fix the position of the light source image S2 and change only its size. The focal length of the first electronic lens 161 and the second electronic lens 162 is controlled by a light source shape shaping circuit 163.

  Further, by providing an opening having a desired shape at the position S2 of the light source image, not only the size but also the shape of the light source can be changed.

[Exposure system component description]
FIG. 21 is a diagram showing Embodiment 4 of the electron beam exposure apparatus according to the present invention. In the figure, the same components as those in FIGS. 1, 15, and 20 are denoted by the same reference numerals, and description thereof will be omitted.

  The electron beam exposure apparatus of the present embodiment is a stencil mask type exposure apparatus. That is, an electron beam from the electron gun 1 is shaped by a first shaping aperture 200 having an opening that defines an illumination area, and a first shaping electron lens 210 (made up of electron lenses 211 and 212) and a shaping deflector 220 are used. To illuminate the stencil mask 230 having the pattern transmission holes. Then, the drawing pattern element of the stencil mask 230 is reduced and projected on the wafer 5 by the reduction electron optical system (4, 100).

  This embodiment is different from the conventional stencil mask type exposure apparatus in that, when the electron beam from the stencil mask 230 passes through the pupil plane near the pupil of the reduction electron optical system 100, the electron beam on the pupil plane An aperture is provided to make the electron density distribution in the peripheral portion larger than the electron density in the central portion. That is, a hollow beam forming stop 240 that shields the center of the stop as shown in FIG. Then, as shown in FIG. 22, the electron beam from the stencil mask has an electron density distribution of a holo beam. For reference, the electron density distribution of a conventional Gaussian beam is also shown.

  As described in [Embodiment 1 of the elementary electron optical system], since the space beam effect of the holo beam is smaller than that of the conventional Gaussian beam, the electron beam is focused on the wafer and the light source image with a small blur is formed on the wafer. Can be formed. An electron beam passing through the stencil mask is considered as a light source located on the stencil mask. Then, even when an image of a light source having a pattern shape of a stencil mask is formed on a wafer, a light source image faithful to the light source shape can be formed because the space charge effect is small. That is, an exposure pattern faithful to the pattern of the stencil mask can be formed on the wafer.

  In this embodiment, the hollow beam forming stop 240 is provided near the pupil plane of the reduction electron optical system 100, but a position conjugate with the pupil of the reduction electron optical system 100, for example, the pupil position of the first shaping lens 210, the position of the light source S2 The above-described effect can be achieved even if a diaphragm having the same shape as the hollow beam forming diaphragm 240 is provided.

  Further, the shape and potential of each electrode of the electron gun may be adjusted so that the light source itself has a hollow beam shape.

  Of course, in the present embodiment, the same configuration can be obtained even if the first shaping aperture 200 is formed into a rectangular opening, the stencil mask is replaced with a second shaping aperture having a rectangular opening, and the exposure apparatus is changed to a variable rectangular beam type exposure apparatus. Can achieve the same effect.

  Next, an embodiment of a device production method using the above-described electron beam exposure apparatus and exposure method will be described.

  FIG. 20 shows a flow of manufacturing micro devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, micro machines, etc.). In step 1 (circuit design), the circuit of the semiconductor device is designed. In step 2 (exposure control data creation), exposure control data of the exposure apparatus is created based on the designed circuit pattern. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the exposure apparatus and the wafer to which the prepared exposure control data has been input. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

  FIG. 21 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern is printed on the wafer by exposure using the above-described exposure apparatus. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. Step 19 (resist stripping) removes unnecessary resist after etching. By repeating these steps, multiple circuit patterns are formed on the wafer.

  By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which was conventionally difficult to manufacture, at low cost.

FIG. 1 is a diagram showing Embodiment 1 of an electron beam exposure apparatus according to the present invention. FIG. 1 is a diagram showing an outline of an electron beam exposure apparatus provided with a stencil mask. FIG. 3 is a diagram illustrating the concept of stencil mask type exposure. FIG. 2 illustrates the principle of the present invention. FIG. 3 is a diagram illustrating an element electron optical system. FIG. 3 is a diagram illustrating a correction electron optical system. The wiring diagram of a blanking electrode. The figure explaining an upper and lower opening electrode. The figure explaining an intermediate electrode. FIG. 4 is a diagram illustrating a unipotential lens having astigmatism. FIG. 4 is a view for explaining an exposure pattern and exposure control data. FIG. 3 is a diagram illustrating a blanking signal transmitted to each elementary electronic optical system. FIG. 9 is a view for explaining another embodiment 1 of the element electron optical system. FIG. 9 is a view for explaining another example 2 of the elementary electron optical system. FIG. 3 is a diagram showing Embodiment 2 of the electron beam exposure apparatus according to the present invention. The figure explaining an element electron optical system array. FIG. 3 is a diagram illustrating a scan field of a subarray. FIG. 3 is a diagram illustrating a scanning field of an element electron optical system array. FIG. 4 is a diagram illustrating an exposure field. FIG. 6 is a diagram showing a third embodiment of the electron beam exposure apparatus according to the present invention. FIG. 9 is a diagram showing Embodiment 4 of the electron beam exposure apparatus according to the present invention. FIG. 3 is a diagram illustrating an electron density distribution on a pupil plane. The figure explaining the manufacturing flow of a micro device. FIG. 3 is a diagram illustrating a wafer process.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Electron gun 2 Condenser lens 3 Correction electron optical system 31, 32 Element electron optical system 4 Reduction electron optical system 5 Wafer 6 Deflector 7 Dynamic focus coil 8 Dynamic stig coil 91, 92 Deflector 10 Faraday cup 11 XYZ stage 12 CPU
Reference Signs List 13 interface 14 sequence controller 15 focus control circuit 16 blanking control circuit 17 drive control device 18 optical axis alignment control circuit 19 memory 21 laser interference system 130 element electron optical system array 160 electron optical system for shaping light source shape DCE deceleration electrode ACE Acceleration electrode 240 Hollow beam forming diaphragm

Claims (14)

An electron beam exposure apparatus having an electron beam source and an electron optical system for focusing an electron beam from the electron beam source on a surface to be exposed,
An electron beam exposure apparatus, comprising: an electron density distribution adjusting means for causing an electron density distribution of the electron beam on a pupil plane of the electron optical system to be higher in a peripheral portion than in a central portion.   2. An electron beam exposure apparatus according to claim 1, wherein said electron optical system reduces and projects the pattern on said surface to be exposed.   2. The electron beam according to claim 1, further comprising: means for illuminating a substrate having a transmission hole with the electron beam, wherein the electron optical system reduces and projects the pattern using the electron beam transmitted through the substrate. Exposure equipment.   4. The electron density distribution adjusting means according to claim 1, wherein the aperture is provided at a pupil plane position of the electron optical system or at a position conjugate with the pupil plane position of the electron optical system. Electron beam exposure equipment.   5. A device manufacturing method comprising: exposing a wafer using the electron beam exposure apparatus according to claim 1; and developing the wafer. An electron beam source;
An electron optical system that projects a pattern on a surface to be exposed using an electron beam emitted from the electron beam source,
Means for adjusting the electron density distribution of the passing electron beam on the pupil plane at the pupil plane position of the electron optical system or at a position conjugate with the pupil plane position of the electron optical system. Electron beam exposure apparatus. An electron beam source;
An electron optical system that projects a pattern on a surface to be exposed using an electron beam emitted from the electron beam source,
Means for shielding electrons passing near the optical axis of the electron optical system on a pupil plane of the electron optical system or a plane conjugate with the pupil plane of the electron optical system. Exposure equipment. An electron beam source;
An electron optical system that projects a pattern onto a surface to be exposed using an electron beam emitted from the electron beam,
An electron beam exposure apparatus, wherein a hollow beam forming means is provided at a pupil plane position of the electron optical system or at a position conjugate with the pupil plane position of the electron optical system. An electron beam source;
A first electron optical system that forms a plurality of intermediate images with an electron beam emitted from the electron beam source using a plurality of element electron optical systems;
A second electron optical system that projects an intermediate image formed by the first electron optical system onto a surface to be exposed,
The electron beam exposure apparatus according to claim 1, wherein the first electron optical system includes a plurality of stops for adjusting an electron density distribution of an electron beam passing through the elementary electron optical system.   10. A device manufacturing method, comprising: exposing a wafer using the electron beam exposure apparatus according to claim 6; and developing the wafer.   An electron beam exposure method comprising the step of converging an electron beam on a surface to be exposed by an electron optical system, wherein an electron density distribution of the electron beam on a pupil plane of the electron optical system is changed to an electron density of a peripheral portion. An electron beam exposure method, wherein the electron beam exposure method has a smaller distribution.   11. The electron beam exposure method according to claim 10, wherein the electron density at the central portion is smaller than the electron density at the peripheral portion by using an aperture.   11. The exposure method according to claim 10, wherein an electron beam source that forms a distribution in which the electron density at the central portion is smaller than the electron density at the peripheral portion is used. 14. A device manufacturing method, comprising: exposing a wafer using the electron beam exposure method according to claim 11; and developing the wafer.

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