JP2007088385A - Mask for electron beam exposure, and method and device for electron beam exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proximity effect correction mask required for correcting proximity effect occurring on the periphery of an adjoining pattern drawn by using a partial collective exposure mask precisely by a partial collective exposure method, to provide a proximity effect correction method employing that mask, and to provide an electron beam exposure device performing proximity effect correction. <P>SOLUTION: In the method for the electron beam exposure, exposure is repeated on the periphery of an adjoining pattern drawn by using a partial collective exposure mask by using an electron beam exposure mask having proximity effect correction openings arranged such that the size of the openings varies periodically at a predetermined ratio in the order of arrangement. Repeated exposure on the periphery of the pattern may be performed using a part of the electron beam exposure mask. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electron beam exposure mask, an electron beam exposure method, and an electron beam exposure apparatus that correct proximity effects in electron beam exposure using a partial batch exposure mask.

  In recent years, an electron beam exposure apparatus has been used to form a fine pattern in a lithography process in manufacturing a semiconductor device or the like.

  In an electron beam exposure apparatus, it is known that a phenomenon in which the line width of a pattern transferred onto a resist differs from a design value occurs due to the influence of a so-called proximity effect in which incident electrons are scattered in the resist.

  For example, when exposure and development are performed using a line & space mask pattern 1 as shown in FIG. 1A, even if the mask has the same size pattern, as shown in FIG. Pattern 2 has a small pattern shape. This is because the amount of energy received by backscattering of incident electrons differs between the internal pattern and the peripheral pattern, as shown in the accumulated energy distribution of FIG. FIG. 1C shows stored energy 3 to 4 in which the dose of the primary beam is superimposed on the stored energy 6 caused by backscattering of incident electrons. When the pattern is configured to repeat regularly in this manner, the influence of the proximity effect due to backscattering is saturated and uniformed inside the drawing area, but the peripheral portion is as shown in FIG. The distribution is such that the stored energy decreases as the distance from the center decreases.

  When developing a wafer to which stored energy is applied as shown in FIG. 1C, for example, if the threshold is 5 lines, the line width at the position where the threshold 5 and the energy 3 to 4 by the primary beam intersect is developed. Line width. Therefore, as shown in FIG. 1B, the line width differs between the inside and the periphery of the device formation pattern.

  Various methods for correcting such a proximity effect have been studied. For example, Patent Document 1 discloses a method in which a second exposure pattern for correcting a first exposure pattern is overlaid and exposed on the same field region of a sample.

Patent Document 2 discloses an exposure method in which a so-called GHOST exposure method, in which a proximity effect is corrected by overlaying and exposing an auxiliary exposure pattern around a target device formation pattern, is applied to a figure batch drawing method. Has been.
JP-A-6-53129 JP-A-5-335221

  Conventionally, in the peripheral part of the device forming pattern with low accumulated energy, the irradiation time is changed for each pattern by the variable rectangular exposure method, and the pattern is drawn so that the accumulated energy in the inside and the peripheral part becomes almost equal.

  However, since the variable rectangular exposure method is used, each pattern is exposed, and much time is required as compared with the partial batch exposure method.

  Further, when the large pattern and the small pattern are exposed adjacently, the following inconvenience occurs.

  FIG. 2A shows an example in which the large pattern 21 and the small pattern 22 are adjacently exposed. The small pattern 22 uses a partial collective exposure pattern 23 indicated by a broken-line rectangle. In this case, as shown in FIG. 2B, the pattern is not uniformly exposed, and a portion that is exposed thickly or exposed thinly occurs. That is, even if a sample is exposed using a partial collective exposure pattern that is a line pattern having the same line width, the accumulated energy increases as it goes to the inner side (upper side in FIG. 2B) due to the influence of the adjacent large pattern 21. It becomes lower as it goes to the outside (lower side in FIG. 2B). Therefore, in the partial batch exposure pattern, although the same line width is used, as shown in FIG. 2B, the large pattern 21 side of the line 24 is the thickest and the small pattern 22 side of the line 25 is the thinnest.

  On the other hand, for example, a variable rectangular exposure method can be used to correct the pattern, but a long time is required, resulting in a decrease in throughput.

  In addition, although the method described in patent document 1 is performing the overlap exposure in order to perform proximity effect correction, since it is not a partial lump exposure method, it will take much time.

  Further, in the method described in Patent Document 2, the auxiliary effect is exposed outside the device formation pattern to correct the proximity effect. Therefore, the correction cannot be performed without a region therefor. Moreover, although the auxiliary exposure amount is determined according to the device formation pattern, it is difficult to make a partially different pattern equal to the internal energy.

  The present invention has been made in view of the above problems, and an object thereof is to accurately correct the proximity effect generated in the peripheral portion of an adjacent pattern drawn using a partial batch exposure mask by the partial batch exposure method. To provide a necessary proximity effect correction mask, a proximity effect correction method using the mask, and an electron beam exposure apparatus for correcting the proximity effect.

  The above-described problem is solved by an electron beam exposure mask having openings for proximity effect correction arranged so that the size of the openings periodically changes at a predetermined rate in the arrangement order. Here, the direction of the change may be either the row direction or the column direction, or may be a direction obtained by rotating the change in the row direction or the column direction by a predetermined angle around the center of the mask.

  In addition, the above-described problem is that partial collective exposure is performed using an electron beam exposure mask having openings for proximity effect correction arranged so that the size of the openings periodically changes at a predetermined ratio in the arrangement order. This is solved by an electron beam exposure method characterized in that exposure is performed by superimposing the peripheral portions of adjacent patterns drawn using a mask for masking.

  In the electron beam exposure method according to the above aspect, the exposure performed on the periphery of the pattern may be performed by blurring the focus of the electron beam or by shifting the electron beam further in the plane direction.

  Further, in the electron beam exposure method according to the above aspect, the exposure to be superimposed on the periphery of the pattern may be performed using a part of the electron beam exposure mask.

  Furthermore, the above-described problem is an electron beam generation unit that generates an electron beam, and an electron that has an opening for proximity effect correction that is arranged so that the size of the opening periodically changes at a predetermined ratio in the arrangement order. A mask for beam exposure, a mask deflector for deflecting the electron beam on the mask for exposure, a substrate deflector for deflecting the electron beam that has passed through the mask for exposure and projecting it on the substrate, and the mask deflection This problem is solved by an electron beam exposure apparatus comprising a control unit for controlling a deflection amount in the substrate deflection unit.

  In the present invention, the openings are arranged at predetermined positions in the peripheral portions of adjacent patterns drawn using the partial batch exposure mask so that the size of the openings periodically changes at a predetermined ratio in the arrangement order. Are exposed using a proximity effect correction mask having In addition, a part of the proximity effect correction mask can be selected when overlapping exposure is performed. This makes it possible to correct a part of the periphery of the pattern drawn by the partial collective exposure mask to a desired shape.

  Also, by performing exposure for proximity effect correction in a blurred manner, the energy level can be flattened without resolving the pattern configured for proximity effect correction. This makes it possible to expose a desired pattern with high accuracy.

  Embodiments of the present invention will be described below with reference to the drawings.

   First, the configuration of the electron beam exposure apparatus used in this embodiment will be described. Next, the aperture distribution and the like of the proximity effect correction mask will be described. Next, a proximity effect correction method using a proximity effect correction mask will be described.

(Configuration of electron beam exposure system)
FIG. 3 is a block diagram of the electron beam exposure apparatus according to the present embodiment.

  The electron beam exposure apparatus is roughly divided into an electron optical system column 100 and a control unit 200 that controls each part of the electron optical system column 100. Among these, the electron optical system column 100 includes an electron beam generating unit 130, a mask deflecting unit 140, and a substrate deflecting unit 150, and the inside thereof is decompressed.

  In the electron beam generator 130, the electron beam EB generated from the electron gun 101 is converged by the first electromagnetic lens 102, then passes through the rectangular aperture 103 a of the beam shaping mask 103, and the cross section of the electron beam EB is rectangular. To be shaped.

  Thereafter, the electron beam EB is imaged on the exposure mask 110 by the second electromagnetic lens 105 of the mask deflection unit 140. The electron beam EB is deflected to a specific pattern S formed on the exposure mask 110 by the first and second electrostatic deflectors 104 and 106, and the cross-sectional shape thereof is shaped into the pattern S.

  Although the exposure mask 110 is fixed to the mask stage 123, the mask stage 123 is movable in a horizontal plane, and the deflection range (beam deflection region) of the first and second electrostatic deflectors 104 and 106 is set. In the case of using the pattern S in the portion exceeding, the pattern S is moved into the beam deflection region by moving the mask stage 123.

  The third and fourth electromagnetic lenses 108 and 111 arranged above and below the exposure mask 110 play a role of forming an image of the electron beam EB on the substrate W by adjusting their current amounts.

  The size of the electron beam EB that has passed through the exposure mask 110 is reduced by the fifth electromagnetic lens 114 after being returned to the optical axis C by the deflection action of the third and fourth electrostatic deflectors 112 and 113.

  The mask deflection unit 140 is provided with first and second correction coils 107 and 109, which correct beam deflection aberrations generated by the first to fourth electrostatic deflectors 104, 106, 112, and 113. Is done.

  Thereafter, the electron beam EB passes through the aperture 115a of the shielding plate 115 constituting the substrate deflecting unit 150, and is projected onto the substrate W by the first and second projection electromagnetic lenses 116 and 121. As a result, the pattern image of the exposure mask 110 is transferred to the substrate W at a predetermined reduction ratio, for example, a reduction ratio of 1/60.

  The substrate deflecting unit 150 is provided with a fifth electrostatic deflector 119 and an electromagnetic deflector 120, and the electron beam EB is deflected by these deflectors 119 and 120, and an exposure mask is formed at a predetermined position on the substrate W. The pattern image is projected.

  Further, the substrate deflection unit 150 is provided with third and fourth correction coils 117 and 118 for correcting the deflection aberration of the electron beam EB on the substrate W.

  The substrate W is fixed to a wafer stage 124 that can be moved in the horizontal direction by a driving unit 125 such as a motor. By moving the wafer stage 124, it is possible to expose the entire surface of the substrate W.

  On the other hand, the control unit 200 includes an electron gun control unit 202, an electron optical system control unit 203, a mask deflection control unit 204, a mask stage control unit 205, a blanking control unit 206, a substrate deflection control unit 207, and a wafer stage control unit 208. Have. Among these, the electron gun control unit 202 controls the electron gun 101 to control the acceleration voltage of the electron beam EB, beam emission conditions, and the like. Further, the electron optical system control unit 203 controls the amount of current to the electromagnetic lenses 102, 105, 108, 111, 114, 116 and 121, and the magnification and focus of the electron optical system in which these electromagnetic lenses are configured. Adjust the position. The blanking control unit 206 controls the voltage applied to the blanking electrode 127 to deflect the electron beam EB generated before the start of exposure onto the shielding plate 115, and onto the substrate W before exposure. Prevents EB from being irradiated.

  The substrate deflection control unit 207 controls the voltage applied to the fifth electrostatic deflector 119 and the amount of current to the electromagnetic deflector 120 so that the electron beam EB is deflected to a predetermined position on the substrate W. To. The wafer stage control unit 208 adjusts the driving amount of the driving unit 125 to move the substrate W in the horizontal direction so that the desired position of the substrate W is irradiated with the electron beam EB. The above-described units 202 to 208 are controlled in an integrated manner by an integrated control system 201 such as a workstation.

(Proximity effect correction mask)
FIG. 4A is a plan view of the exposure mask 110 described above. The exposure mask 110 is made of a silicon material, and a plurality of rectangular sections 7 are arranged in a matrix. As shown in FIG. 4B, each rectangular section 7 has rectangular small sections 8 each having a side of about 300 μm arranged in a matrix, and openings of plural kinds of patterns are formed in the small sections 8. Provided. This small section 8 is called CP (cell projection). The pattern opening provided in the CP is called a partial collective shape.

  When the pattern is formed using the partial collective shape, a pattern different from the desired pattern is formed around each formed pattern due to the proximity effect by the adjacent pattern. Therefore, it is necessary to make the line width of the pattern formed in the peripheral part thicker than the partial collective shape prepared in advance.

  In recent years, when a light exposure mask is used for light exposure, a phenomenon in which a desired pattern is not formed has occurred. In particular, when the line width to be exposed becomes fine, the influence of the light proximity effect increases. When the proximity effect of light in this case is obtained by calculation, the pattern shape of the mask is periodically narrowed. For this reason, it is necessary to give an intensity change that periodically increases the line width of only a part of the mask for light exposure.

  For this reason, in this embodiment, various patterns for correcting the proximity effect received from the adjacent patterns are prepared. Furthermore, a pattern for correcting to a periodic pattern necessary for use as a mask for light exposure is prepared.

  FIG. 5A is a diagram illustrating an example of a configuration of a proximity effect correction mask pattern used in the present embodiment. Here, a pattern for correcting the energy distribution so as to have periodicity is shown.

  As shown in FIG. 5A, the proximity effect correction mask of this embodiment is formed with aperture groups 51a to 51i whose sizes change periodically. The openings are arranged so that the centers of the openings are in a lattice pattern, and openings of the same size are arranged in the same row.

  FIG. 5A shows a pattern in which openings periodically change in the X direction (column direction), and FIG. 5B shows a pattern in which openings change periodically in the Y direction (row direction). Yes.

  Also, a pattern obtained by rotating the basic proximity effect correction pattern described above is prepared so that the drawn pattern can cope with the influence of the proximity effect from any direction from the surrounding pattern. . For example, FIG. 6 shows proximity effect correction patterns (62 to 68) that are rotated every 45 ° using the pattern 61 as a basic pattern. Note that this angle is not limited to 45 °, and for example, 36 patterns may be prepared every 10 °.

  As such a mask for proximity effect correction, for example, the mask magnification (the size of the pattern formed on the mask with respect to the pattern formed on the sample) is 10 times, and the fine opening has a thickness of 2 μm. The mask is a rectangle having a side length of 500 nm to 200 nm. The fine openings are formed with different densities as shown in FIGS.

  The patterns shown in FIGS. 5 and 6 are masks for forming a pattern of a function having periodicity such as a wave function. Various other patterns are prepared in order to efficiently correct the proximity effect. For example, an aperture distribution of a concave surface function, a convex surface function, and a two-dimensional Fourier function is prepared.

  In addition to the periodic function, the stored energy may have a gradient in intensity distribution in addition to the periodic change. For example, an increase / decrease pattern rotated every 45 ° may be formed in advance, but here, it seems that the intensity distribution is inclined periodically in combination with a pattern corresponding to a monotonically increasing (decreasing) function. A simple pattern is formed.

  FIG. 7 shows a pattern corresponding to a monotonically increasing function. As this pattern, four types of patterns are prepared as shown in FIGS. The pattern shown in FIG. 7A has a configuration in which aperture groups 71a to 71f having different sizes are formed and the size of the apertures decreases linearly in the X direction (column direction). 7 (b) to 7 (d) show patterns (72a to 72f) in which openings are reduced in the Y direction (row direction), patterns (73a to 73f) in which openings are increased in the X direction (column direction), and Y It is a pattern (74a-74f) in which an opening becomes large in the direction (row direction).

  By using these patterns, the exposure intensity distribution can be changed.

  When the above-described periodicity and the intensity distribution have an inclination, the pattern corresponding to the periodic function shown in FIG. 5 and the pattern changing the intensity distribution shown in FIG. 7 are combined and used for exposure. First, in order to cope with the periodicity, exposure for proximity effect correction is performed at a predetermined place in the peripheral portion of the pattern using any one of the masks shown in FIGS. Next, using a mask for changing the intensity distribution shown in FIG. Thereby, it is possible to deal with a case where there is periodicity and the intensity distribution is inclined.

  The pattern shown in FIG. 7 is a pattern that increases or decreases in the X direction and the Y direction. However, it is also possible to increase or decrease in the direction rotated every 45 ° by combining and exposing them. That is, as shown in FIG. 7A, the mask changes from the large opening 71a to the small opening 71f in the right direction of the figure, and the small opening 74f in the downward direction of the figure as shown in FIG. 7D. By using a mask that changes to the opening 74a and performing exposure with the same amount of exposure, it is possible to reduce energy in the direction of 45 ° diagonally downward to the right in the figure.

  Further, by using a combination of the masks shown in FIGS. 7A to 7D and adjusting each exposure amount, the energy can be increased or decreased in an arbitrary direction.

  When the intensity distribution has an inclination in addition to the periodic change, an opening that is periodic and has an inclination in the intensity distribution may be formed.

  Moreover, although the shape of the aperture group constituting the proximity effect correction mask has been described as a rectangle in the present embodiment, the shape is not limited to this, and may be, for example, a circle.

(Proximity effect correction method)
Next, a method for correcting the proximity effect using the proximity effect correction mask described above will be described.

  FIG. 8 is a flowchart showing an example in which proximity effect correction processing is performed using a proximity effect correction mask.

  First, in step S11, a partial collective exposure mask in which a correction process for the optical proximity effect is performed on the central portion of the mask is prepared. The central portion of the mask is a range that is not affected when the surrounding pattern is exposed by partial collective exposure. That is, the shape is deformed so that a desired shape is drawn on the sample. Note that this processing is not necessary when the purpose is not to form a mask for light exposure.

  Next, in step S12, a proximity effect correction mask for correcting the proximity effect appearing in the peripheral portion of the adjacent pattern exposed using the partial collective exposure mask is selected. The proximity effect correction mask corresponding to the proximity effect mask to be used is obtained in advance by calculating what kind of proximity effect appears by the partial batch exposure mask to be used. When forming a mask for light exposure, the influence of the optical proximity effect is also obtained in advance, and the corresponding mask is selected together with the proximity effect by the adjacent pattern. At this time, a part of the mask pattern may be selected without using the entire pattern of the proximity effect correction mask.

  Next, in step S13, an exposure process is performed using a partial batch exposure mask. In this exposure, exposure is performed with a weakened exposure intensity. Since the exposure is performed later using the proximity effect correction mask, the accumulated energy obtained by summing the exposure using the partial batch exposure mask and the exposure using the proximity effect correction mask is made uniform in the drawing region. It is to make it.

  Next, in step S14, a predetermined portion of the peripheral portion of the adjacent pattern exposed using the partial batch exposure mask is exposed using the proximity effect correction mask. In the case where the proximity effect correction mask is used for exposure, the exposure is performed so that the mask pattern is not resolved. This is for flattening the accumulated energy at the periphery of the pattern as a result of exposure using the proximity effect correction mask. As a method of blurring the pattern, for example, exposure is performed by shifting the focus of the lens. Further, exposure may be performed by shifting the position of irradiation with the electron beam.

  Note that the above-described overexposure may be performed every time the subfield exposure is completed, or may be performed every frame. For example, partial batch exposure may be performed by frame exposure, and overexposure for proximity effect correction may be performed at the time of return.

  As described above, the line width of a part of the drawing pattern can be obtained by overlapping exposure using a proximity effect correction mask at a predetermined position in the peripheral part of the adjacent pattern drawn by the partial batch exposure mask. Can be corrected.

  In addition, by using the proximity effect correction mask, the exposure intensity can be changed periodically and the exposure intensity can be changed periodically and gradually, so that the proximity effect can be corrected efficiently and flexibly. Can be done.

FIGS. 1A to 1C are views (No. 1) for explaining the proximity effect by electron beam exposure. It is FIG. (2) for demonstrating the proximity effect by electron beam exposure. It is a block diagram of the electron beam exposure apparatus used by embodiment of this invention. 4A and 4B are views (No. 1) for explaining the proximity effect correction mask used in the embodiment of the present invention. FIGS. 5A and 5B are diagrams illustrating an example of a proximity effect correction mask having periodicity. It is a figure which shows an example of the mask for proximity effect correction | amendment which has periodicity. It is an example of a proximity effect correction mask for forming a linear function pattern. It is a flowchart which shows an example of the electron beam exposure method of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Line & space mask pattern, 2 ... Pattern after exposure, 3, 4 ... Energy by primary beam, 5 ... Threshold value, 6 ... Accumulated energy, 8, 23 ... CP (cell projection), 21 ... Large pattern, 22 ... Small Pattern, 24, 25 ... Line, 51, 52, 71, 72, 73, 74 ... Opening, 61, 62, 63, 64, 65, 66, 67, 68 ... Mask for proximity effect correction, 100 ... Electron optical system column 101 ... Electron gun, 102 ... First electromagnetic lens, 103 ... Beam shaping mask, 103a ... Rectangular aperture, 104 ... First electrostatic deflector, 105 ... Second electromagnetic lens, 106 ... Second electrostatic deflector, DESCRIPTION OF SYMBOLS 107 ... 1st correction coil, 108 ... 3rd electromagnetic lens, 109 ... 2nd correction coil, 110 ... Exposure mask, 111 ... 4th electromagnetic lens, 112 ... 3rd electrostatic deflector, 1 DESCRIPTION OF SYMBOLS 3 ... 4th electrostatic deflector, 114 ... 5th electromagnetic lens, 115 ... Shielding plate, 115a ... Aperture, 116 ... 1st projection electromagnetic lens, 117 ... 3rd correction coil, 118 ... 4th correction coil, 119 ... 5th electrostatic deflector, 120 ... electromagnetic deflector, 121 ... second projection electromagnetic lens, 123 ... mask stage, 124 ... wafer stage, 125 ... drive unit, 127 ... blanking electrode.

Claims (17)

  An electron beam exposure mask comprising openings for proximity effect correction arranged so that the size of the openings periodically changes at a predetermined ratio in the arrangement order.   2. The electron beam exposure mask according to claim 1, wherein the direction of the change is either a row direction or a column direction.   3. The electron beam exposure mask according to claim 2, wherein the direction of the change is a direction rotated by a predetermined angle around the center of the mask.   4. The electron beam exposure mask according to claim 1, wherein the shape of the opening is rectangular or circular.   Drawing was performed using a partial collective exposure mask using an electron beam exposure mask having openings for proximity effect correction arranged so that the size of the openings periodically changes at a predetermined ratio in the arrangement order. An electron beam exposure method, wherein exposure is performed by superimposing on a predetermined position in a peripheral portion of an adjacent pattern.   6. The electron beam exposure method according to claim 5, wherein the exposure to be performed on the periphery of the pattern is performed using a part of the electron beam exposure mask.   Furthermore, using an electron beam exposure mask having openings arranged so that the size of the openings changes in a linear function in the order of arrangement, exposure is performed in a superimposed manner at a predetermined position on the periphery of the pattern. The electron beam exposure method according to claim 5 or 6,   The electron beam exposure method according to claim 5, wherein the direction of the change is either a row direction or a column direction.   9. The electron beam exposure method according to claim 8, wherein the direction of the change is a direction rotated by a predetermined angle around the center of the mask.   8. The electron beam exposure method according to claim 5, wherein the rate of change is performed by changing an exposure amount.   The electron beam exposure method according to claim 5, wherein the shape of the opening is rectangular or circular.   8. The electron beam exposure method according to claim 5, wherein the exposure to be performed on the periphery of the pattern is performed by blurring the focus of the electron beam. 9.   8. The electron beam exposure method according to claim 5, wherein the exposure to be performed on the periphery of the pattern is performed by further shifting the electron beam in a plane direction. 9. An electron beam generator for generating an electron beam;
An electron beam exposure mask having openings for proximity effect correction arranged so that the size of the openings periodically changes at a predetermined rate in the arrangement order;
A mask deflector for deflecting the electron beam on the exposure mask;
A substrate deflecting unit that deflects and projects the electron beam that has passed through the exposure mask onto the substrate;
An electron beam exposure apparatus comprising: a mask deflection unit; and a control unit that controls a deflection amount in the substrate deflection unit.   15. The electron beam exposure apparatus according to claim 14, wherein the direction of the change is either a row direction or a column direction.   16. The electron beam exposure apparatus according to claim 15, wherein the direction of the change is a direction rotated by a predetermined angle around the center of the mask.   The electron beam exposure apparatus according to any one of claims 14 to 16, wherein the shape of the opening is rectangular or circular.

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