Multi-charged particle beam irradiation apparatus and multi-charged particle beam irradiation method

Abstract

This suppresses the influence of secondary electrons emitted from the stopping aperture substrate on the beam. [Solution] The multi-charged particle beam irradiation device comprises a blanking aperture array substrate that blanks and deflects each beam of the multi-beam; an illumination lens that focuses the multi-beam passing through the blanking aperture array substrate to form a crossover; a stopping aperture substrate positioned at the crossover location and shielding the deflected beam so that it is in a beam-off state; a stage on which a substrate to be irradiated by the beam that has passed through the stopping aperture substrate is placed; an electrostatic deflector positioned between the blanking aperture array substrate and the stopping aperture substrate, close to the stopping aperture substrate; and a voltage control circuit that applies a predetermined voltage to the electrostatic deflector to form an electric field perpendicular to the trajectory center axis of the multi-beam.

Description

[Technical Field]

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

[0002] With the increasing integration of LSIs, the circuit line widths required for semiconductor devices are becoming smaller year by year. To form the desired circuit patterns on semiconductor devices, a method is employed in which a high-precision original pattern formed on silica is reduced and transferred onto a wafer using a reduction projection exposure system. The high-precision original pattern is drawn using an electron beam lithography system, and so-called electron beam lithography technology is employed.

[0003] For example, there are lithography systems that use multiple beams. Compared to lithography with a single electron beam, using multiple beams allows for the irradiation of many beams at once, significantly improving throughput. In a multi-beam lithography system, for example, an electron beam emitted from an electron gun is passed through a molded aperture array substrate with multiple apertures to form multiple beams, and each beam is individually blanked and controlled by a blanking aperture array substrate. The beams that are blanked and deflected by the blanking aperture array substrate are shielded by a stopping aperture substrate, and the beams that are not deflected pass through the aperture of the stopping aperture substrate and are irradiated to the desired position on the sample.

[0004] When a blanking-bent beam is shielded by a stopping aperture substrate, a large number of secondary electrons are emitted from the stopping aperture substrate. This leads to the formation of secondary electron clouds near the beam and within the spreading beam region. The resulting electric field causes the beam to be deflected, leading to a shift and instability in the beam's irradiation position on the sample. To reduce the impact of secondary electrons on the beam, materials with low secondary electron emission were used for the stopping aperture substrate.

[0005] However, there were limitations to reducing the amount of secondary electrons emitted from the stopping aperture substrate. Furthermore, the secondary electron emission rate fluctuated over time due to the degradation of the stopping aperture substrate material. Additionally, increasing the beam current to improve throughput resulted in a proportional increase in secondary electron emission, and the influence of the secondary electron field on the beam became greater. [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 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above-mentioned conventional problems, and aims to provide a multi-charged particle beam irradiation apparatus and a multi-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 multi-charged particle beam irradiation apparatus according to one aspect of the present invention comprises: a charged particle source that generates and emits a multi-beam; a blanking aperture array substrate having a plurality of blankers that blank and deflect each beam of the multi-beam; an illumination lens that focuses the multi-beam passing through the blanking aperture array substrate to form a crossover; a stopping aperture substrate positioned at the crossover location and shielding the beam deflected by the plurality of blankers to a beam-off state; a stage on which a substrate to be irradiated by the beam that has passed through the stopping aperture substrate is placed; an electrostatic deflector positioned between the blanking aperture array substrate and the stopping aperture substrate, close to the stopping aperture substrate; and a voltage control circuit that applies a predetermined voltage to the electrostatic deflector to form an electric field in a direction perpendicular to the trajectory central axis of the multi-beam.

[0009] A multi-charged particle beam irradiation method according to one aspect of the present invention comprises the steps of: generating a multi-beam using a charged particle source; blanking and deflecting each beam of the multi-beam using a blanking aperture array substrate including a plurality of blankers; focusing the multi-beam passing through the blanking aperture array substrate to form a crossover; shielding the beam deflected by the plurality of blankers to a beam-off state with a stopping aperture substrate placed at the crossover position; irradiating the beam that has passed through the stopping aperture substrate to a predetermined position on a substrate placed on a stage; and applying a predetermined voltage to an electrostatic deflector placed close to the stopping aperture substrate between the blanking aperture array substrate and the stopping aperture substrate to form an electric field in a direction perpendicular to the trajectory central axis of the multi-beam. [Effects of the Invention]

[0010] According to the present invention, the influence of secondary electrons emitted from the stopping aperture substrate on the beam can be suppressed, and the accuracy of the beam irradiation position can be improved.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic configuration diagram of a drawing device according to an embodiment of the present invention. [Figure 2] It is a plan view of a shaping aperture array substrate. [Figure 3] It is a schematic diagram of secondary electrons reaching the electrodes of an electrostatic deflector. [Figure 4] FIGS. 4A, 4B, 4C, 4D and 4E are diagrams showing configuration examples of an electrostatic deflector. [Figure 5] It is a diagram for explaining parameters of an electrostatic deflector. [Figure 6] It is a diagram showing a magnetic deflector that generates a magnetic field orthogonal to the deflection electric field. [Figure 7] It is a plan view showing an arrangement example of saddle coils. [Figure 8] It is a plan view showing an arrangement example of toroidal coils. [Figure 9] It is a schematic configuration diagram of a drawing device according to another embodiment.

Modes for Carrying Out the Invention

[0012] Hereinafter, in the embodiments, as an example of a charged particle beam, a configuration using an electron beam will be described. 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. Further, in the embodiments, a multi-beam drawing device using a multi-electron beam will be described as an example of a multi-charged particle beam irradiation device. However, the multi-charged particle beam irradiation device is not limited to a multi-beam drawing device, and the present embodiment can also be applied to a multi-beam inspection device.

[0013] Figure 1 is a schematic diagram of a multibeam lithography apparatus according to an embodiment of the present invention. As shown in Figure 1, the multibeam lithography apparatus comprises a lithography unit W and a control unit C. The lithography unit W comprises an electron-optical lens barrel 102 and a lithography chamber 103. Inside the electron-optical lens barrel 102 are arranged an electron source 201, an illumination lens 202, a molded aperture array substrate 203, a blanking aperture array substrate 204, an electrostatic deflector 20, a stopping aperture substrate 206, a positioning deflector 208, and an objective lens 210, which constitute the electron optical system of the multibeam lithography apparatus. The electrostatic deflector 20 is positioned between the blanking aperture array substrate 204 and the stopping aperture substrate 206, and is positioned close to the stopping aperture substrate 206.

[0014] An XY stage 105, which is movable in the XY direction (perpendicular to the trajectory axis of the multibeam), is arranged in the drawing chamber 103. The XY stage 105 may also be movable in the Z direction (same direction as the trajectory axis). The substrate 10 to be drawn is placed on the XY stage 105. The substrate 10 includes exposure masks used when manufacturing semiconductor devices, and semiconductor substrates (silicon wafers) on which semiconductor devices are manufactured. The substrate 10 also includes mask blanks with resist coated on them, on which nothing has been drawn yet.

[0015] Additionally, a mirror 30 for measuring the stage's position is placed on the XY stage 105.

[0016] The control unit C includes a control computer 110, a control circuit 120, a voltage control circuit 122, and a stage position detector 124. The stage position detector 124 emits a laser beam, receives the reflected light from the mirror 30, and detects the position of the XY stage 105 using the principle of laser interferometry.

[0017] Figure 1 shows the configuration necessary to explain the embodiment, and other configurations are omitted from the illustration.

[0018] Figure 2 is a conceptual diagram showing the configuration of the molded aperture array substrate 203. In Figure 2, the molded aperture array substrate 203 has apertures (first apertures) 203a formed in a matrix with a vertical (y-direction) p-columns × horizontal (x-direction) q-rows (p,q≧2) at a predetermined arrangement pitch. For example, 512 columns × 512 rows of apertures 203a are formed. Each aperture 203a is formed as a rectangle of the same dimensions and shape. The apertures 203a may also be circular. A multi-beam MB is formed when a portion of the electron beam 200 passes through each of these multiple apertures 203a.

[0019] The blanking aperture array substrate 204 is located below the molded aperture array substrate 203, and through holes (second apertures) are formed in accordance with the positions of each aperture 203a of the molded aperture array substrate 203. A blanker consisting of a pair of electrodes is placed in each through hole. One electrode of the blanker is fixed at ground potential (0V), and the other electrode is switched between ground potential and another potential. The electron beam passing through each through hole is independently deflected by the voltage applied to the blanker. In this way, multiple blankers perform blanking deflection of the corresponding beams from the multi-beam MB that has passed through the multiple apertures 203a of the molded aperture array substrate 203.

[0020] The electron beam 200 emitted from the electron source 201 (emission unit) is refracted by the illumination lens 202 and illuminates the entire molded aperture array substrate 203. The electron beam 200 illuminates the region containing multiple (all) apertures 203a. A portion of the electron beam 200 passes through multiple apertures 203a of the molded aperture array substrate 203, forming a multi-beam MB containing multiple individual beams. The multi-beam MB passes through the corresponding blankers of the blanking aperture array substrate 204. Each blanker blanks the individual beam passing through so that the beam remains ON for a set drawing time (irradiation time).

[0021] The multi-beam MB that has passed through the blanking aperture array substrate 204 forms a crossover due to the focusing action of the illumination lens 202. The stopping aperture substrate 206 is positioned such that the height of the opening 206a (third opening) formed in the center is approximately the same as the height of the crossover.

[0022] Here, the beam deflected by the blanker of the blanking aperture array substrate 204 is moved away from the opening 206a of the stopping aperture substrate 206 and is shielded by the stopping aperture substrate 206. On the other hand, the beam that is not deflected by the blanker of the blanking aperture array substrate 204 passes through the opening 206a of the stopping aperture substrate 206. In this way, the stopping aperture substrate 206 shields the beam that has been deflected by each blanker to the point of being in the OFF state.

[0023] Generally, apertures are classified into shaping apertures (including "shaping aperture arrays"), limiting apertures (sometimes called "lens apertures" or simply "apertures"), and stopping apertures. A shaping aperture shapes the beam into a desired form. It is placed where the beam has been widened by a lens system, and when the beam is shone through it, it allows only a portion of the beam corresponding to the desired shape to pass through, while cutting off the rest. A lens aperture adjusts the beam current and focusing state. It is placed before, after, or approximately at the same position as the lens, and allows the center of the widened beam to pass through while cutting off unwanted beam from the periphery. In contrast, a stopping aperture usually allows the entire beam to pass through, cutting off only the blanked-deflected beam. In optical systems for multi-beam lithography, it is placed near the crossover height where the beam widening is small.

[0024] In the embodiment shown in Figure 1, the stopping aperture substrate 206 is positioned such that the height of the aperture 206a is approximately the same as the height of the crossover. Since the lateral spread of the beam is reduced at the crossover, this position is suitable for cutting the deflected beam so that it is in the OFF state. If the height of the crossover is shifted vertically from the height of the aperture 206a, the multi-beam MB will be greatly spread at the height of the aperture 206a. Furthermore, since the electrodes of each blanker in the blanking aperture array substrate 204 are short and have a minute structure, and there are limits to the applied voltage, it is difficult to increase the amount of deflection. As a result, problems with the drawing function and drawing performance may occur, such as some beams not being sufficiently cut during beam cutting (some individual beams) or some beams continuing to be cut (some individual beams).

[0025] Each beam of one shot is formed by the beam that has passed through the stopping aperture substrate 206, which is formed from the time the beam is turned ON until the beam is turned OFF. Each beam of the multi-beam MB that has passed through the stopping aperture substrate 206 is focused onto the substrate 10 by the objective lens 210 to become an aperture image of the aperture 203a of the formed aperture array substrate 203 with a desired reduction magnification. Then, the positioning deflector 208 deflects each beam (the entire multi-beam) that has passed through the stopping aperture substrate 206 in the same direction and irradiates the substrate 10 with each beam at its respective irradiation position.

[0026] For example, when the XY stage 105 is moving continuously, the positioning deflector 208 controls the beam irradiation position so that it follows the movement of the XY stage 105. Ideally, the multi-beam MB irradiated at one time will be arranged at a pitch obtained by multiplying the array pitch of the multiple apertures 203a of the molded aperture array substrate 203 by the desired reduction ratio described above. The drawing device performs the drawing operation using a raster scan method in which shot beams are irradiated continuously in sequence, and when drawing the desired pattern, unnecessary beams are controlled to be turned off by blanking control.

[0027] In such a lithography apparatus, when the blanking-bent beam is shielded 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. However, since the hole diameter of the aperture 206a of the stopping aperture substrate 206 is small (several tens to several hundred μm), secondary electrons generated in the sample 10 do not pass through the aperture 206a and reach the upstream side of the stopping aperture substrate 206, thereby virtually not affecting the beam irradiation position.

[0028] Therefore, in this embodiment, an electrostatic deflector 20 containing multiple electrodes is placed above the stopping aperture substrate 206 (on the upstream side in the beam propagation direction, upstream side of the beam optical path) and below the blanking aperture array substrate 204, and a voltage control circuit 122 applies a voltage to each electrode of the electrostatic deflector 20 so that an electric field is formed in a direction perpendicular to the trajectory central axis of the multi-beam. The voltage applied by the voltage control circuit 122, that is, the voltage applied to each electrode of the electrostatic deflector 20, is constant (unchangeable) during the drawing operation. The voltage applied to each electrode of the electrostatic deflector 20 is constant regardless of changes in the beam ON / OFF state.

[0029] For example, as shown in Figures 3 and 4E, if the electrostatic deflector 20 has two parallel plate electrodes 20a and 20b, the voltage control circuit 122 applies a positive voltage to one electrode 20a and a negative voltage to the other electrode 20b. The stopping aperture substrate 206 is set to ground potential (0V).

[0030] As a result, an electric field is formed in the direction from electrode 20b to electrode 20a, causing secondary electrons emitted from the stopping aperture substrate 206 to be deflected toward electrode 20a, where they either hit the wall of electrode 20a or are pushed outward slightly upstream of electrode 20a. Since the secondary electron density near the multi-beam trajectory is reduced, the influence of secondary electrons on the beam is suppressed, and the accuracy of the beam irradiation position can be improved. In addition, because the secondary electrons are deflected toward electrode 20a by electric field control, there is less variation in the effect and less fluctuation over time.

[0031] If the electrostatic deflector 20 and the stopping aperture substrate 206 are far apart, secondary electrons will pass near the multi-beam trajectory over a long distance before being deflected by the electric field of the electrostatic deflector 20, and the impact on the multi-beam will not be sufficiently reduced. Therefore, the electrostatic deflector 20 needs to be positioned close to the stopping aperture substrate 206. That is, no other components should be placed between the electrostatic deflector 20 and the stopping aperture substrate 206, except for members to support them and members for electrical insulation. Typically, the downstream ends of the electrodes 20a and 20b of the electrostatic deflector 20 are positioned within 20 mm of the stopping aperture substrate 206. Furthermore, positioning them within 10 mm will yield an even greater effect.

[0032] Furthermore, if a focusing magnetic field, such as that of an objective lens, is present at the height of the electrostatic deflector 20, the secondary electrons may be affected by the focusing magnetic field and travel in a direction perpendicular to both the orbital center axis direction and the deflection electric field direction, that is, perpendicular to the plane of the paper in Figure 3. In this case, the secondary electrons do not hit the electrode 20a, but are pushed out of the space between the electrodes, thus reducing the secondary electron density near the multi-beam orbit and improving the accuracy of the beam irradiation position.

[0033] The voltage applied by the voltage control circuit 122 is determined based on the electrode length and spacing of the electrostatic deflector 20, the distance between the stopping aperture substrate 206 and the electrostatic deflector 20, and other factors.

[0034] The material of the stopping aperture substrate 206 is not particularly limited, but for example, a non-magnetic material such as Ta can be used. The shape of the stopping aperture substrate 206 and the aperture 206a is, for example, circular.

[0035] The number of electrodes in the electrostatic deflector 20 is not limited. For example, it may be an octave type (also called an "octave electrostatic deflector") with eight electrodes 20c to 20j as shown in Figure 4A, or a dodecave type (also called a "dotted electrostatic deflector") with twelve electrodes 20k to 20v as shown in Figure 4B. In the case of the octave type, a positive voltage is applied to electrodes 20c to 20f, and a negative voltage is applied to electrodes 20g to 20j. In the case of the dodecave type, a positive voltage is applied to electrodes 20k, 20m, 20n, and 20p, a negative voltage is applied to electrodes 20q, 20s, 20t, and 20v, and ground potential (0V) is applied to electrodes 20l, 20o, 20r, and 20u. These electrostatic deflectors create an electric field in a direction perpendicular to the trajectory center axis of the multibeam.

[0036] The electrostatic deflector 20 may be a quadrupole type (also called a "quadupole electrostatic deflector") having four electrodes as shown in Figure 4D. In the case of the quadrupole type, positive and negative deflection voltages are applied to the two opposing electrodes 20z, and 0V is applied to the remaining two opposing electrodes 20y. By applying voltages in this way, an electric field is formed in a direction perpendicular to the trajectory center axis of the multibeam.

[0037] The voltage application methods for the 8-pole, 12-pole, and 4-pole electrostatic deflectors described above are examples for deflection in one direction (let's call it the X direction). For deflection in a direction 90 degrees to the X direction (the Y direction), the voltage should be applied to the electrode positioned 90 degrees later, in the same manner as described above. For deflection in other directions (directions other than the X and Y directions), the voltage for X-direction deflection and the voltage for Y-direction deflection should be added together and applied to each electrode.

[0038] As shown in Figure 4C, the electrostatic deflector 20 may be configured with four electrodes that divide a cylindrical surface centered on the orbital axis, consisting of two opposing electrodes 20w with a central angle of approximately 120 degrees and the remaining two opposing electrodes 20x (with a central angle of approximately 60 degrees) (also called a "120-degree electrode deflector"). Positive and negative deflection voltages are applied to the opposing electrodes 20w with a central angle of approximately 120 degrees, and 0V is applied to the remaining two opposing electrodes 20x. By applying voltages in this way, an electric field is formed in a direction perpendicular to the orbital axis of the multibeam.

[0039] The deflection field formed by the electrostatic deflector 20 also affects the multi-beam microcontroller (MB) used for drawing. Since the electrostatic deflector 20 is positioned upstream of the stopping aperture substrate 206 where the multi-beam MB is somewhat spread out, if the non-uniformity of the deflection field is high (i.e., if the uniformity of the deflection field is low), the deflection field changes for each individual beam, increasing array distortion (displacement from the normal irradiation position) on the sample surface and degrading beam accuracy.

[0040] Reducing array distortion is a new challenge that has arisen in multibeam optical systems. Multibeam optical systems form a very large array beam, for example, with dimensions of about 100 μm in both length and width on the sample surface. Unlike conventional variable-shape beam optical systems that form small beams of about 1 μm or less, array distortion tends to increase easily, and suppressing the increase in array distortion is extremely important. By reducing the non-uniformity of the deflection field formed by the electrostatic deflector 20 and suppressing the increase in array distortion, beam accuracy can be further improved. In other words, in the design of the electrostatic deflector 20, it is important not only to form an electric field that attracts secondary electrons, but also to achieve the formation of a deflection field with low non-uniformity (i.e., high uniformity).

[0041] The increase in array distortion can be related to the electric field inhomogeneity of the electrostatic deflector 20 and the parameters (basic specifications) of the optical system and the electrostatic deflector 20. As shown in Figure 5, the parameters are the electrostatic deflector electrode length L, the electrostatic deflector electrode spacing G, and the representative value of the secondary electron energy V. SThe following are introduced: (unit eV), primary beam energy V (unit eV), shaping aperture array radius S, and crossover focusing half-angle θ (unit rad). Furthermore, the imaging magnification is M and the distortion increment is D. The electric field inhomogeneity is η. The upper limit of the distortion increment is D. MAX Let's assume that.

[0042] The electrostatic deflector electrode length L is the length of the electrodes constituting the electrostatic deflector 20 along the axis of the orbital center. The electrostatic deflector electrode spacing G is the distance between opposing electrodes of the electrostatic deflector 20, or the diameter of the inner surface of the electrodes constituting the electrostatic deflector 20 centered on the axis of the orbital center.

[0043] Generally, the energy of secondary electrons has a distribution, so V is a representative value of the energy of secondary electrons generated in the stopping aperture substrate 206 and moving upstream. S Assuming that the material of the stopping aperture substrate 206 is metal, most of the secondary electron energies are distributed below 20 eV, with a peak distribution around 2 eV. Therefore, normally, V S This can be assumed to be 2eV. The primary beam energy V is the acceleration energy of the primary beam (i.e., the multi-beam MB).

[0044] The molded aperture array radius S is the distance from the orbital center axis to the aperture 203a formed in the molded aperture array substrate that is furthest from the orbital center axis (i.e., the outermost aperture). If the apertures 203a are arranged in a rectangular region centered on the orbital center axis, S will be half the length of the diagonal of the arrangement region.

[0045] The crossover focusing half-angle θ is the half-angle of focusing the multi-beam MB to the crossover. The imaging magnification M is the magnification when the multiple apertures 203a of the molded aperture array substrate 203 are projected onto the sample surface.

[0046] The strain increment D is the strain on the sample surface caused by electric field inhomogeneity, which is added to the optical system strain (i.e., the original strain of the optical system) and increases the overall strain. Upper limit of strain increment D MAX This is the upper limit of D, and it is set considering the performance required of the device. MAXIt is necessary to set it to the same level as or lower than the optical system distortion, and usually it is set to 1 / 3 of the optical system distortion. For example, when the optical system distortion is 6 nm (6 × 10 -9 m), D MAX is set to 2 nm.

[0047] The electric field non-uniformity η is the maximum value within the region A through which the multi-beam passes in the plane perpendicular to the orbit central axis near the center in the orbit central axis direction of the electrostatic deflector 20 (that is, near the center of the upper and lower ends), of the absolute value of the difference (|E1 - E0|) between the deflection electric field E1 and the electric field E0 at the center of the same region A, divided by the absolute value of E0 (|E0|). That is, based on the electric field E0 at the center of the region A through which the multi-beam passes, the difference (non-uniform component of the electric field) from the electric field E1 within the region A is calculated, the absolute value of the difference is divided by the absolute value of the central electric field (reference electric field), and the maximum value of that value within the region A is defined as the electric field non-uniformity η. The region A is as schematically shown in FIG. 5. Also, since the electric fields E1 and E0 are vector quantities, calculations such as difference and absolute value follow the algorithm as vectors. The multi-beam MB spreads the most near the upper end (near the entrance) of the electrostatic deflector 20 and shrinks as it progresses. Therefore, as described above, if the electric field non-uniformity η is the value calculated near the center in the orbit central axis direction of the electrostatic deflector 20, it can represent the non-uniformity over the entire length of the electrostatic deflector 20. The region A can be obtained by electron beam orbit calculation, and the electric fields E1, E0, etc. can be obtained by electric field calculation.

[0048] When the electric field non-uniformity η is given, the sample surface strain increment D can be calculated by the following formula. D = η(G / L)×(V S / V)×(S / θ)×M ···(1)

[0049] As shown in Figure 5, assume that the multi-beam MB is blanked and collides with the stopping aperture substrate 206, generating secondary electrons. These secondary electrons travel upstream and are deflected by the electric field of the electrostatic deflector 20, reaching the vicinity of the upper end of the electrostatic deflector electrode 20a. Since the surface of the deflection electrode 20a is very far from the orbital center axis compared to the position where the secondary electrons collide with the stopping aperture substrate 206, the deflection angle of the secondary electrons at this time can be approximated by G / L, which is the distance G / 2 from the orbital center axis to the deflection electrode surface divided by the length L / 2 of the deflection electrode. Therefore, (G / L) in equation (1) corresponds to the deflection angle of the secondary electrons.

[0050] Secondary electrons (energy V) S The deflection angle of a primary beam (energy V) passing through a deflected electric field from the opposite direction is equal to the deflection angle of the secondary electrons (V). S It is (V) times. This is because the angle at which electrons are bent by the deflection field (deflection angle) is inversely proportional to the electron energy. Therefore, (V) in equation (1) S / V) corresponds to a coefficient that converts the deflection angle of the secondary electrons to the deflection angle of the primary beam (i.e., the multi-beam MB).

[0051] S corresponds to the radius of the outermost beam on the stopping aperture substrate 206, and θ corresponds to the angle of incidence of the outermost beam to the crossover. Therefore, (S / θ) in equation (1) is a coefficient that converts the deflection angle (i.e., the amount of angular change) of the trajectory near the stopping aperture substrate 206 into a virtual displacement of each aperture 203a of the molded aperture array substrate 203. This virtual displacement is multiplied by M by the lens system and projected onto the sample surface, becoming the displacement of the projection position. M in equation (1) is a coefficient that converts the virtual displacement of each aperture 203a of the molded aperture array substrate 203 into a displacement of the projection position.

[0052] The amount of displacement of the projection position on the sample surface described above will be constant across the entire array if the deflection field is ideally uniform, and the array image will shift in translation while maintaining its shape. However, if there is non-uniformity in the deflection field, the deflection field changes for each individual beam, and the distortion of the array shape on the sample surface increases. In equation (1), the increase in array distortion D is calculated by multiplying by the non-uniformity η of the deflection field.

[0053] In equation (1), D is the upper limit D of the sample surface strain increase. MAX By substituting this and solving for η, we obtain the following equation for calculating the upper limit of the electric field inhomogeneity η. η ≤ D MAX / {(G / L)×(V S / V) × (S / θ) × M} ... (2)

[0054] For example, electrostatic deflector electrode length L = 50 mm, electrostatic deflector electrode spacing G = 20 mm, typical value of secondary electron energy V S In an optical system with a primary beam energy of 2eV, primary beam energy V=50keV, shaped aperture array radius S=10mm, crossover focusing half-angle θ=20mrad, and imaging magnification M=1 / 200, the upper limit of distortion increment D MAX When the value is 2nm, it is calculated that the electric field inhomogeneity η must be 5% (0.05) or less.

[0055] It is desirable to use a deflector that satisfies the electric field inhomogeneity condition of equation (2) as the electrostatic deflector 20. If equation (2) is satisfied, it is possible to reduce the secondary electron density near the multi-beam trajectory while suppressing the increase in array distortion, thereby further improving the beam irradiation position accuracy.

[0056] Generally, the deflection field generated by a deflector can be calculated based on the electrode shape, etc., and the non-uniformity of the field can be determined from the calculation results. The non-uniformity of the field can be reduced by optimizing the electrode shape, etc. The electrode shape, etc., includes the number of electrodes, the spacing between electrodes (or diameter), the electrode length, the shape of each electrode, and the method of applying voltage to each electrode.

[0057] The 8-pole electrostatic deflector (Figure 4A), 12-pole electrostatic deflector (Figure 4B), and 120-degree electrode deflector (Figure 4C) have the advantage of extremely high uniformity of the deflection field, and are advantageous compared to the 4-pole electrostatic deflector (Figure 4D) and parallel plate type electrostatic deflector (Figure 4E) in terms of suppressing distortion caused by electric field non-uniformity.

[0058] In a quadrupole electrostatic deflector (Figure 4D), the uniformity of the beam's path can be improved by making the spacing between opposing electrodes (the spacing between electrodes 20y, 20y and 20z, 20z) sufficiently wide. For example, to reduce electrode non-uniformity to 5% or less, the electrode spacing of the quadrupole electrostatic deflector should be 4.2 times or more the diameter of region A through which the multi-beam MB passes.

[0059] In a parallel-plate type electrostatic deflector (Figure 4E), the uniformity of the region through which the beam passes can be improved by making the electrode spacing sufficiently larger than the beam spread passing through it, and by making the electrode width (the dimension of the beam-facing surface in the direction perpendicular to the beam propagation direction) greater than or equal to the electrode spacing. For example, to reduce the electric field non-uniformity to 5% or less, the electrode spacing should be 2.5 times or more the diameter of region A through which the multi-beam MB passes, and the electrode width should be greater than or equal to the electrode spacing.

[0060] In the above embodiment, an example was described in which the stopping aperture substrate 206 is set to ground potential, but the voltage control circuit 122 may apply a negative voltage to the stopping aperture substrate 206. The negative voltage on the stopping aperture substrate 206 accelerates the secondary electrons in the upstream direction and reduces the spatial density, thereby reducing the impact on the multi-beam MB. With the impact on the multi-beam MB reduced, the secondary electrons are moved away from the vicinity of the multi-beam MB's trajectory by the electric field of the electrostatic deflector 20, so the beam irradiation position accuracy can be further improved.

[0061] The voltage control circuit 122 may apply a positive voltage to the stopping aperture substrate 206. The positive voltage on the stopping aperture substrate 206 pulls back secondary electrons, reducing the number of secondary electrons traveling upstream, thus reducing the impact on the multi-beam MB. The secondary electrons that have traveled upstream are moved away from the vicinity of the multi-beam MB's trajectory by the electric field of the electrostatic deflector 20, while the impact on the multi-beam MB is reduced, thus further improving the beam irradiation position accuracy.

[0062] The voltage control circuit 122 may set the stopping aperture substrate 206 to ground potential and apply a voltage to each electrode of the electrostatic deflector 20 that is the sum of a voltage for forming an electric field perpendicular to the trajectory center axis and a positive common voltage. For example, if the electrostatic deflector 20 is a quad-pole type as shown in Figure 4D, a voltage equal to the sum of positive and negative deflection voltages and a positive common voltage is applied to the two opposing electrodes 20z, and a voltage equal to the sum of 0V and a positive common voltage is applied to the remaining two opposing electrodes 20y. The positive common voltage accelerates secondary electrons in the upstream direction and reduces the spatial density, thus reducing the impact on the multi-beam MB. With the impact on the multi-beam MB reduced, the secondary electrons are moved away from the vicinity of the multi-beam MB trajectory by the component of the electrostatic deflector 20's electric field perpendicular to the trajectory center axis (deflection electric field component), thus further improving the beam irradiation position accuracy.

[0063] The voltage control circuit 122 may set the stopping aperture substrate 206 to ground potential and apply a voltage to each electrode of the electrostatic deflector 20 that is the sum of a voltage for forming an electric field perpendicular to the trajectory center axis and a negative common voltage. The negative common voltage pulls back secondary electrons, reducing the number of secondary electrons moving upstream, thus reducing the impact on the multi-beam MB. The secondary electrons that have moved upstream are moved away from the vicinity of the multi-beam MB trajectory by the component of the electrostatic deflector 20's electric field perpendicular to the trajectory center axis (deflection electric field component), while the impact on the multi-beam MB is reduced, thus further improving the accuracy of the beam irradiation position.

[0064] As shown in Figure 6, it is preferable to provide a magnetic field deflector 40 that generates a magnetic field perpendicular to the electric field formed by the electrostatic deflector 20 on a plane perpendicular to the trajectory central axis of the multi-beam MB, and a current control circuit 123 that controls the current flowing through the magnetic field deflector 40. For the multi-beam MB that has passed through the blanking aperture array substrate 204, the force due to the electric field and the force due to the magnetic field cancel each other out, and the multi-beam MB travels straight downward without being deflected. In contrast, for secondary electrons emitted from the stopping aperture substrate 206, the force due to the electric field and the force due to the magnetic field act in the same direction, and the secondary electrons are deflected toward the electrode to which the positive voltage of the electrostatic deflector 20 is applied.

[0065] In a configuration without the magnetic field deflector 40, the multi-beam MB is deflected by the electrostatic deflector 20 and incident obliquely on the objective lens 210 downstream of the blanking aperture array substrate 204, slightly offset from the center. This can lead to increased aberrations and distortions on the sample surface during image formation by the objective lens 210. However, with the introduction of the magnetic field deflector 40, the deflection effect of the multi-beam MB is canceled out, causing it to travel straight downwards. This suppresses the aberrations and distortions on the sample surface that occur when deflected, thereby improving image rendering accuracy. As mentioned above, the aberrations and distortions suppressed by the introduction of the magnetic field deflector 40 are those caused by oblique incidence and center misalignment on the objective lens 210, and are different from the distortions caused by the electric field non-uniformity of the electrostatic deflector 20.

[0066] The magnetic field deflector 40 only needs to generate a magnetic field that returns some or all of the deflection of the multi-beam MB generated by the electric field of the electrostatic deflector 20, thereby reducing oblique incidence and center misalignment to the objective lens 210. Therefore, the magnetic field generated by the magnetic field deflector 40 does not need to be perfectly perpendicular to the electric field generated by the electrostatic deflector 20 at all positions; it is sufficient that the direction in which the multi-beam MB is deflected is opposite. Furthermore, the magnetic field deflector 40 may be positioned offset from the electrostatic deflector 20 in the direction of the orbital center axis, or it may be arranged in multiple stages.

[0067] The magnetic field deflector 40 includes multiple coils and generates a magnetic field that deflects the beam by passing current through the coils. For example, a saddle coil 40a as shown in Figure 7 or a toroidal coil 40b as shown in Figure 8 can be used. The magnetic field deflector 40 may be an octave type with 8 coils or a dodecave type with 12 coils.

[0068] In magnetic field deflectors, as with electrostatic deflectors, uniformity of the deflection magnetic field around the orbital central axis is required to suppress the increase in strain. To obtain sufficient uniformity, the distribution of the generated deflection magnetic field should be calculated based on the shape of the coil and surrounding magnetic material, and the shape should be optimized to ensure magnetic field uniformity. Magnetic field deflectors are usually placed outside of a vacuum and therefore have a larger diameter compared to electrostatic deflectors, so the uniformity of the magnetic field around the orbital central axis is relatively high. In particular, with the saddle coil 40a shown in Figure 7, when the angle in the circumferential direction from the central axis looking at the coil is about 120 degrees, the uniformity of the deflection magnetic field is high and advantageous. Furthermore, with octode types having 8 coils or dodecode types having 12 coils, it is easy to achieve high uniformity of the deflection magnetic field whether using saddle coils or toroidal coils.

[0069] Furthermore, a configuration in which either the electrostatic deflector or the magnetic deflector (or both) is a deflector with four or more poles, allowing control of the deflection direction (direction around the trajectory's central axis), is preferable. Mechanical manufacturing precision alone makes it difficult to precisely reverse the deflection directions of the electric field of the electrostatic deflector and the magnetic field of the magnetic deflector. However, by making one of the deflectors four or more poles and allowing control of the direction of the electric or magnetic field, the deflection directions can be reversed with high precision.

[0070] In the embodiment shown in Figure 1 described above, the objective lens is configured as a single stage, and the stopping aperture substrate 206 is positioned at the crossover location formed between the blanking aperture array substrate 204 and the objective lens 210. However, as shown in Figure 9, a reduction lens 220 and two stages of objective lenses 210 and 211 may be provided, and the stopping aperture substrate 206 may be positioned at the crossover location formed downstream of the upstream objective lens 210.

[0071] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Moreover, components from different embodiments may be appropriately combined. [Explanation of Symbols]

[0072] 10 circuit boards 20 Electrostatic deflector 40 Magnetic field deflector 102 Electro-optical lens barrel 103 Drawing room 105 XY Stages 110 Control Computer 120 Control circuits 122 Voltage control circuit 123 Current control circuit 124 Stage position detector 200 electron beam 201 Electron source 202 Illumination Lens 203 Molded aperture array substrate 204 Blanking Aperture Array Substrate 206 Stopping Aperture Substrate 208 Positioning deflector 210, 211 Objective lenses 220 Reduction Lens

Claims

1. A charged particle source that generates and emits multiple beams, A blanking aperture array substrate having a plurality of blankers that blank and deflect each beam of the multi-beam, An illumination lens that focuses the multibeam passing through the blanking aperture array substrate and forms a crossover, A stopping aperture substrate is positioned at the crossover location and shields the beam that has been deflected by the plurality of blankers to be in a beam-off state, A stage on which a substrate is placed that will be irradiated by the beam that has passed through the stopping aperture substrate, Between the blanking aperture array substrate and the stopping aperture substrate, an electrostatic deflector is positioned in close proximity to the stopping aperture substrate, A voltage control circuit applies a predetermined voltage to the electrostatic deflector to form an electric field perpendicular to the trajectory center axis of the multibeam, A multi-charged particle beam irradiation device equipped with the following features.

2. The multi-charged particle beam irradiation apparatus according to claim 1, wherein no other components are placed between the stopping aperture substrate and the electrostatic deflector.

3. The multi-charged particle beam irradiation apparatus according to claim 1, wherein a constant voltage is applied to the electrostatic deflector.

4. The electrostatic deflector has four or more electrodes, according to claim 1, for the multi-charged particle beam irradiation apparatus.

5. The electric field E in the region through which the multibeam passes in a plane perpendicular to the orbital center axis at the center of the orbital center axis direction of the electrostatic deflector. １ And the electric field E at the central axis ０ The absolute value of the difference between the electric field E ０ The upper limit of the electric field non-uniformity η, defined by the maximum value obtained by dividing by the absolute value of η, is the upper limit of the strain increase on the substrate surface D ＭＡＸ In that case, the ≦ D ＭＡＸ / {(G / L)×(V) Ｓ / V)×(S / θ)×M} L: electrode length of the electrostatic deflector, G: electrode spacing of the electrostatic deflector, V Ｓ : Typical value of secondary electron energy, V: Primary beam energy, S: Radius of shaped aperture array, θ: Crossover focusing half-angle, M: Image magnification A multi-charged particle beam irradiation apparatus according to claim 1, satisfying the requirements.

6. The upper limit D of the aforementioned strain increase ＭＡＸ The multi-charged particle beam irradiation apparatus according to claim 5, wherein the optical system distortion is set to 1 / 3.

7. The multi-charged particle beam irradiation apparatus according to claim 1, further comprising a magnetic field deflector that generates a magnetic field whose deflection direction is opposite to the direction in which the electric field deflects the multi-beam.

8. The multi-charged particle beam irradiation apparatus according to claim 7, which enables control of the deflection direction by the magnetic field.

9. The multi-charged particle beam irradiation apparatus according to claim 1, wherein the voltage control circuit applies a positive or negative voltage to the stopping aperture substrate.

10. The multi-charged particle beam irradiation apparatus according to claim 1, wherein the electrostatic deflector has a plurality of electrodes, and a voltage obtained by adding a common positive or negative voltage to each of the plurality of electrodes is applied.

11. A process for generating a multibeam using a charged particle source, A process of blanking and deflecting each beam of the multi-beam using a blanking aperture array substrate containing multiple blankers, A step of focusing the multibeam passing through the blanking aperture array substrate to form a crossover, The process involves shielding the beam, which has been deflected by the plurality of blankers to be in a beam-off state, with a stopping aperture substrate positioned at the crossover location. The process involves irradiating a predetermined position on a substrate placed on a stage with a beam that has passed through the stopping aperture substrate, The steps include: applying a predetermined voltage to an electrostatic deflector positioned close to the stopping aperture substrate between the blanking aperture array substrate and the stopping aperture substrate to form an electric field perpendicular to the trajectory center axis of the multibeam; A multi-charged particle beam irradiation method comprising the above.

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