Charged particle beam irradiation device and charged particle beam irradiation method

Abstract

To reduce the influence on a beam of secondary electrons emitted from a stopping aperture substrate.SOLUTION: A charged particle beam irradiation device comprises: a stopping aperture substrate that blocks a beam deflected by a blanker; a front stage electrode that is arranged on the upstream side of the stopping aperture substrate in the direction of travel of the beam; and a potential control circuit that applies a predetermined potential so as to increase the potential of the front stage electrode compared to the potential of the stopping aperture substrate, thereby forming an electric field in a direction directed from the stopping aperture substrate to the front stage electrode. The inner diameter d of the front stage electrode is determined on the basis of the distance L1 from an upper end of the front stage electrode to the stopping aperture substrate, the distance r1 from the center of the beam to a position where the beam subjected to blanking deflection impinges on the stopping aperture substrate, and the spread radius r2 of secondary electrons at the upper end of the front stage electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charged particle beam irradiation apparatus and a charged particle beam irradiation method. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer every year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision master pattern formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure system. The high-precision master pattern is drawn using an electron beam drawing system, and so-called electron beam lithography technology is used.

[0003] For example, there is a lithography system that uses multiple beams. Compared to lithography using a single electron beam, using multiple beams allows for the irradiation of many beams at once, thereby significantly improving throughput. In a multi-beam lithography system, for example, an electron beam emitted from an electron gun is passed through a shaping aperture array substrate with multiple openings to form multiple beams, and each beam is individually blanked and controlled by a blanking aperture array substrate. The beam that is blanked and deflected by the blanking aperture array substrate is blocked by a stopping aperture substrate, while the undeflected beam passes through the openings in the stopping aperture substrate and is irradiated onto the desired position on the sample.

[0004] When the blanking deflected beam is blocked by a stopping aperture substrate, secondary electrons (including reflected electrons) are emitted from the stopping aperture substrate. The electric field of the electron cloud of the secondary electrons deflects the beam, causing the beam irradiation position on the sample to shift, so materials that emit a small amount of secondary electrons have been used for the stopping aperture substrate.

[0005] However, there was a limit to how much secondary electrons could be reduced from the stopping aperture substrate. Furthermore, the secondary electron emission rate fluctuated over time due to the degradation of the stopping aperture substrate material. Furthermore, increasing the beam current to improve throughput increased the amount of secondary electrons emitted in proportion to the beam current, significantly increasing the effect of the secondary electron field on the beam. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-149885 [Patent Document 2] Japanese Patent Application Publication No. 62-66546 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned conventional problems, and has an object to provide a charged particle beam irradiation device and a charged particle beam irradiation method that can suppress the influence of secondary electrons emitted from a stopping aperture substrate on the beam and improve the beam irradiation position accuracy. [Means for solving the problem]

[0008] A charged particle beam irradiation apparatus according to one aspect of the present invention includes a charged particle source that generates and emits a beam, a blanker that blanks and deflects the beam, a stopping aperture substrate that shields the beam deflected by the blanker so as to be in a beam-off state, a deflector that deflects the beam that has passed through the stopping aperture substrate and irradiates the beam at a predetermined position on a substrate, a front-stage electrode that is located upstream of the stopping aperture substrate in the direction of travel of the beam, and a stop aperture substrate that is arranged so that the potential of the front-stage electrode is higher than the potential of the stopping aperture substrate. and a potential control circuit that applies a predetermined potential to at least one of the stopping aperture substrate and the pre-stage electrode to form an electric field in a direction from the stopping aperture substrate to the pre-stage electrode, as shown in FIG. 1, and the inner diameter d of the pre-stage electrode is calculated based on the distance L1 from the upper end of the pre-stage electrode to the stopping aperture substrate, the distance r1 from the center of the beam to the position where the blanking-deflected beam hits the stopping aperture substrate, and the spread radius r2 of secondary electrons at the upper end of the pre-stage electrode.

[0009] a step of blanking deflecting the beam using a blanker; a step of shielding the beam deflected by the blanker so as to be in a beam-off state with a stopping aperture substrate; a step of deflecting the beam that has passed through the stopping aperture substrate with a deflector and irradiating the beam at a predetermined position on a substrate; and a step of applying a predetermined potential to at least one of the stopping aperture substrate and the front-stage electrode so that the potential of a front-stage electrode located upstream of the stopping aperture substrate in the beam propagation direction is higher than the potential of the stopping aperture substrate, thereby forming an electric field in a direction from the stopping aperture substrate to the front-stage electrode, wherein the inner diameter d of the front-stage electrode satisfies d>2×(r1+r2), where r1 is the distance from the center of the opening of the stopping aperture substrate to the farthest position, and r2 is the secondary electron Larmor radius calculated based on the magnetic field and energy. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress the influence of secondary electrons emitted from the stopping aperture substrate on the beam, and improve the accuracy of the beam irradiation position. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a drawing device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of a shaped aperture array substrate. [Figure 3] FIG. 2 is a schematic diagram of secondary electrons emitted from a stopping aperture substrate. [Figure 4] FIG. 4 is a diagram illustrating the inner diameter of the front-stage electrode. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the following embodiments, a configuration using an electron beam will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and a beam using charged particles such as an ion beam may also be used. Furthermore, in the embodiments, a multi-beam lithography system using multiple electron beams will be described as an example of a charged particle beam irradiation system. However, the multi-charged particle beam irradiation system is not limited to a multi-beam lithography system, and the present embodiments can also be applied to a multi-beam inspection system.

[0013] Fig. 1 is a schematic diagram of a multi-beam lithography apparatus according to an embodiment of the present invention. As shown in Fig. 1, the multi-beam lithography apparatus includes a lithography unit W and a control unit C. The lithography unit W includes an electron optical column 102 and a lithography chamber 103. Inside the electron optical column 102, there are arranged an electron source 201, an illumination lens 202, a shaping aperture array substrate 203, a blanking aperture array substrate 204, a front-stage electrode 20, a stopping aperture substrate 206, a deflector 208, and an objective lens 210, which constitute the electron optical system of the multi-beam lithography apparatus.

[0014] An XY stage 105 movable in the X and Y directions is disposed within the patterning chamber 103. The XY stage 105 may also be movable in the Z direction. A substrate 10 to be patterned is disposed on the XY stage 105. The substrate 10 includes an exposure mask used in manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which the semiconductor device is manufactured, and the like. The substrate 10 also includes a mask blank coated with resist and on which nothing is yet patterned.

[0015] In addition, a mirror 30 for measuring the position of the stage is placed on the XY stage 105.

[0016] The control unit C has a control computer 110, a control circuit 120, a potential control circuit 122, and a stage position detector 124. The stage position detector 124 irradiates a laser, receives the light reflected from the mirror 30, and detects the position of the XY stage 105 based on the principle of laser interference.

[0017] FIG. 1 shows the configuration necessary for explaining the embodiment, and other configurations are omitted from the illustration.

[0018] 2 is a conceptual diagram showing the configuration of shaping aperture array substrate 203. In FIG. 2, shaping aperture array substrate 203 has p columns (y direction) x q rows (x direction) (p, q≧2) of apertures (first openings) 203a formed in a matrix at a predetermined arrangement pitch. For example, 512 columns x 512 rows of apertures 203a are formed. Each aperture 203a is formed as a rectangle with the same dimensions. The apertures 203a may also be circular. Multibeams MB are formed when portions of electron beam 200 pass through these multiple apertures 203a.

[0019] The blanking aperture array substrate 204 is provided below the shaping aperture array substrate 203, and has passage holes (second openings) formed in alignment with the positions of the apertures 203a of the shaping aperture array substrate 203. A blanker consisting of a pair of two electrodes is disposed in each passage hole. One electrode of the blanker is fixed at ground potential, and the other electrode is switched between ground potential and another potential. The electron beams passing through each passage hole are deflected independently by the voltage applied to the blanker. In this way, the multiple blankers perform blanking deflection on the corresponding beams among the multi-beams MB that have passed through the multiple apertures 203a of the shaping aperture array substrate 203.

[0020] An electron beam 200 emitted from an electron source 201 (emitter) is refracted by an illumination lens 202 and illuminates the entire shaping aperture array substrate 203. The electron beam 200 illuminates an area including multiple (all) apertures 203a. A portion of the electron beam 200 passes through the multiple apertures 203a in the shaping aperture array substrate 203, thereby forming a multibeam MB including multiple individual beams. The multibeam MB passes through corresponding blankers in a blanking aperture array substrate 204. The blankers perform blanking control on each individual beam passing through them so that the beam is in an ON state for a set writing time (irradiation time).

[0021] The multi-beams MB that have passed through the blanking aperture array substrate 204 are refracted by the illumination lens 202 and travel toward the opening 206a (third opening) formed in the center of the stopping aperture substrate 206. The multi-beams MB then form a crossover at the height position of the opening 206a.

[0022] Here, the beams deflected by the blankers of the blanking aperture array substrate 204 are displaced from the openings 206a of the stopping aperture substrate 206 and are blocked by the stopping aperture substrate 206. On the other hand, the beams not deflected by the blankers of the blanking aperture array substrate 204 pass through the openings 206a of the stopping aperture substrate 206. In this way, the stopping aperture substrate 206 blocks the beams deflected by the blankers to be in the beam OFF state.

[0023] Each beam of one shot is formed by the beams that pass through stopping aperture substrate 206 from when the beam is turned on until when it is turned off. Each beam of multi-beam MB that has passed through stopping aperture substrate 206 is turned by objective lens 210 into an aperture image of opening 203a of shaping aperture array substrate 203 at a desired reduction magnification, and is focused on substrate 10. Then, deflector 208 deflects each beam that has passed through stopping aperture substrate 206 (the entire multi-beam) in the same direction, and each beam is irradiated onto its respective irradiation position on substrate 10.

[0024] For example, when the XY stage 105 is moving continuously, the deflector 208 controls the beam irradiation position so that it follows the movement of the XY stage 105. Ideally, the multiple beams MB irradiated at one time are arranged at a pitch obtained by multiplying the arrangement pitch of the multiple apertures 203a in the shaping aperture array substrate 203 by the desired reduction ratio described above. The drawing device performs drawing operations using a raster scan method in which shot beams are irradiated continuously in order, and when drawing a desired pattern, unnecessary beams are turned off by blanking control.

[0025] In such a drawing apparatus, when the blanking deflected beam is blocked by the stopping aperture substrate 206, secondary electrons are emitted from the stopping aperture substrate 206, and these secondary electrons affect the beam irradiation position.

[0026] Therefore, in this embodiment, a front-stage electrode 20 set to ground potential is placed above the stopping aperture substrate 206 (upstream in the direction of multi-beam propagation), and a potential control circuit 122 applies a negative potential to the stopping aperture substrate 206.

[0027] This creates an electric field in the direction from the stopping aperture substrate 206 toward the front-stage electrode 20, causing secondary electrons emitted from the stopping aperture substrate 206 to accelerate toward the upstream side of the optical path and exit upward, as shown in Figure 3. This reduces the secondary electron density, thereby suppressing the effect of the secondary electrons on the beam and improving the accuracy of the beam irradiation position. Furthermore, because the secondary electrons are accelerated by electric field control and exit upward, there is little variation in the effect and little change over time.

[0028] The level of potential that the potential control circuit 122 applies is determined based on the beam current of the multi-beam, the material of the stopping aperture substrate 206, the distance between the stopping aperture substrate 206 and the front-stage electrode 20, and the like.

[0029] There are no particular limitations on the material of the stopping aperture substrate 206, but for example, Ta can be used. The shape of the stopping aperture substrate 206 and the opening 206a is, for example, circular.

[0030] The shape of the front-stage electrode 20 is not particularly limited, but for example, a cylindrical electrode can be used. The material of the front-stage electrode 20 is not particularly limited, but for example, Ti can be used.

[0031] It is necessary that the secondary electrons emitted from the stopping aperture substrate 206 pass above the cylindrical pre-stage electrode 20 without colliding with the inner circumferential surface of the pre-stage electrode 20. For this reason, the inner diameter d (bore diameter) of the pre-stage electrode 20 is set to a value expressed by the following formula.

[0032] In the following formula, r1 is the distance from the center of the opening 206a of the stopping aperture substrate 206 to the position where the blanking-deflected beam hits the stopping aperture substrate 206. r2 is the spreading radius of the secondary electrons at the top end of the pre-stage electrode 20.

[0033] Inner diameter d>2×(r1+r2)

[0034] When the pre-stage electrode 20 is placed in a magnetic field, the secondary electrons move in a spiral due to the magnetic field, and the spreading radius r2 of the secondary electrons is the secondary electron Larmor radius calculated based on the minimum magnetic field and energy within the distance L1 from the upper end of the pre-stage electrode 20 to the stopping aperture substrate 206.

[0035] When the pre-electrode 20 is located outside the magnetic field, the trajectory of the secondary electrons is assumed to be a straight line, and the trajectory is estimated from the emission angle and energy of the secondary electrons. The electrode radius at which the proportion of secondary electrons that collide with the pre-electrode 20 is equal to or less than a predetermined value is determined as the secondary electron spread radius r2. For example, the electrode radius at which the proportion of secondary electrons of 20 eV or less is equal to or less than 50% can be determined as the secondary electron spread radius r2.

[0036] The magnetic field (axial magnetic flux density) generated when a magnetic lens is installed attenuates as the distance from the lens magnetic pole increases. The axial magnetic flux density is usually at its maximum on the optical axis near the middle of a pair of magnetic poles (two magnetic poles) of the magnetic lens. Empirically, areas where the axial magnetic flux density is greater than, for example, 1 / 10 of the maximum value, or areas where the magnetic flux density is at a minimum, can be considered "inside the magnetic field," while other areas can be considered "outside the magnetic field."

[0037] The center of the opening 206a of the stopping aperture substrate 206 and the cylindrical axis of the cylindrical pre-electrode 20 are preferably positioned on the central axis of the trajectory of the multi-beams.

[0038] In the above embodiment, a configuration was described in which the front-stage electrode 20 is set to ground potential and a negative potential is applied to the stopping aperture substrate 206. However, it is sufficient that the potential of the front-stage electrode 20 is made higher than the potential of the upper surface of the stopping aperture substrate 206, and an electric field is formed in a direction from the stopping aperture substrate 206 to the front-stage electrode 20. For example, the stopping aperture substrate 206 may be set to ground potential, and the potential control circuit 122 may apply a positive potential to the front-stage electrode 20.

[0039] Alternatively, the potential control circuit 122 may apply a positive potential to the front-stage electrode 20 and a negative potential to the stopping aperture substrate 206 .

[0040] In the above embodiment, an apparatus using multiple beams has been described, but the present invention can also be applied to an apparatus using a single beam.

[0041] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0042] 10 Substrate 20 Front electrode 102 Electron Optical Tube 103 Drawing room 105 XY stage 110 Control computer 120 control circuit 200 electron beam 201 Electron source 202 Lighting lens 203 Shaped Aperture Array Substrate 204 Blanking aperture array substrate 206 Stopping aperture substrate 208 Deflector 210 objective lens

Claims

1. a charged particle source that generates and emits a beam; a blanker for blanking and deflecting the beam; a stopping aperture substrate that blocks the beam deflected by the blanker to be in a beam-off state; a deflector that deflects the beam that has passed through the stopping aperture substrate and irradiates the beam at a predetermined position on the substrate; a front-stage electrode disposed upstream of the stopping aperture substrate in the beam propagation direction; a potential control circuit that applies a predetermined potential to at least one of the stopping aperture substrate and the front-stage electrode so that the potential of the front-stage electrode is higher than the potential of the stopping aperture substrate, thereby forming an electric field in a direction from the stopping aperture substrate to the front-stage electrode; Equipped with A charged particle beam irradiation device, wherein the inner diameter d of the front-stage electrode is calculated based on the distance L1 from the upper end of the front-stage electrode to the stopping aperture substrate, the distance r1 from the center of the beam to the position where the blanking-deflected beam hits the stopping aperture substrate, and the spread radius r2 of secondary electrons at the upper end of the front-stage electrode.

2. When the front-stage electrode is provided in a magnetic field, the radius r2 is the secondary electron Larmor radius calculated based on the minimum magnetic field and energy within a distance L1 from the upper end of the front-stage electrode to the stopping aperture, and the inner diameter d of the front-stage electrode is d>2×(r1+r2) The charged particle beam irradiation device according to claim 1 , wherein the above formula (1) is satisfied.

3. the potential control circuit applies a negative potential to the stopping aperture substrate; 2. The charged particle beam irradiation system according to claim 1, wherein the front-stage electrode is set to a ground potential.

4. the potential control circuit applies a positive potential to the front-stage electrode; 2. The charged particle beam irradiation device according to claim 1, wherein the stopping aperture substrate is set to a ground potential.

5. generating a beam using a charged particle source; blanking deflecting the beam using a blanker; a step of blocking the beam deflected by the blanker to be in a beam-off state with a stopping aperture substrate; a step of deflecting the beam that has passed through the stopping aperture substrate with a deflector and irradiating the beam at a predetermined position on the substrate; applying a predetermined potential to at least one of the stopping aperture substrate and the front-stage electrode so that the potential of the front-stage electrode disposed upstream of the stopping aperture substrate in the beam traveling direction is higher than the potential of the stopping aperture substrate, thereby forming an electric field in a direction from the stopping aperture substrate to the front-stage electrode; Equipped with The inner diameter d of the front-stage electrode is expressed as follows, where r1 is the distance from the center of the opening of the stopping aperture substrate to the farthest position, and r2 is the Larmor radius of secondary electrons calculated based on the magnetic field and energy: d>2×(r1+r2) A charged particle beam irradiation method that satisfies the above.

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