Multi-charged particle beam writing system

Abstract

Provided is a multi-charged particle beam drawing device that can ensure a margin for the arrangement of a focus correction lens, suppress the retention of secondary electrons, and stabilize the beam irradiation position. The multi-charged particle beam drawing device includes a plurality of blankers that blank and deflect each beam of a multi-charged particle beam, an acceleration lens that is composed of an electrostatic lens having a plurality of electrodes and accelerates the multi-charged particle beam, a limiting aperture member that blocks the beam deflected by the blanker, two or more stages of objective lenses composed of magnetic lenses that focus the multi-charged particle beam on a substrate, and three or more correction lenses including a first correction lens, a second correction lens, and a third correction lens that correct the imaging state of the multi-charged particle beam on the substrate. The first correction lens is an electrostatic correction lens that also serves as at least one of the plurality of electrodes of the acceleration lens.

Description

[Technical field]

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

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer year by 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 apparatus. To create the high-precision master pattern, a technique known as electron beam lithography is used, in which a resist is exposed to light by an electron beam drawing apparatus to form a pattern.

[0003] Development of electron beam lithography devices using multiple beams is underway to replace the conventional single-beam lithography devices that deflect one beam and irradiate the required location on a sample. By using multiple beams, more beams can be irradiated than when lithography is performed with a single electron beam, so throughput can be significantly improved. In a multi-beam lithography device, for example, an electron beam emitted from an electron source is passed through a shaping aperture array member with multiple openings to form multiple beams, blanking control is performed for each beam on a blanking aperture array substrate, and the unblocked beams are reduced in size by an optical system and irradiated onto a sample placed on a movable stage.

[0004] In an electron beam lithography system, the beam of each shot is focused on the sample by an objective lens, and the position of the multi-beam array image in the optical axis direction (imaging height) is corrected by dynamically correcting the focus during lithography (dynamic focusing) using, for example, an electrostatic lens to correspond to the unevenness of the sample surface. Here, the optical axis means the central axis of the optical system from when the electron beam is emitted until it is irradiated on the sample. However, when dynamic focusing is performed, rotation and magnification fluctuations occur in the beam array image on the sample, degrading the lithography position accuracy. Therefore, it is necessary to minimize the rotation and magnification fluctuations of the beam array image that depend on dynamic focusing.

[0005] In order to suppress rotation and magnification fluctuation of the beam image due to dynamic focus, a multi-beam drawing device has been proposed in which three electrostatic lenses are provided and at least one electrostatic lens is disposed in the lens magnetic field of each stage of two stages of objective lenses (see, for example, Patent Document 1).

[0006] In the electron optical system of a multi-beam lithography device, in order to increase the accuracy of the beam array image dimensions and array pitch, it is necessary to form the beam array image on the sample surface at a high reduction ratio, for example, a magnification of about 1 / 200.To achieve such a high reduction ratio while ensuring a distance between the lower surface of the lens and the sample that allows the sample to move (often called the working distance), it is necessary to form the beam array image by the objective lens at least twice.

[0007] When imaging is performed twice, the number of stages of the objective lens is two. Here, "stage" means that imaging is performed once, and in many cases, one stage of the objective lens is composed of one lens, but in order to reduce aberration and distortion, one stage of the objective lens may be composed of two or more adjacent magnetic lenses (i.e., one imaging is performed with two or more adjacent magnetic lenses).

[0008] In Patent Document 1, three electrostatic lenses are arranged in the magnetic field of two stages of objective lenses, so two electrostatic lenses are arranged close to each other in the magnetic field of one of the objective lenses. The region where the lens magnetic field exists is the position where the magnetic pole exists in the beam traveling direction and a limited short section before and after it. In addition, most of the region where the lens magnetic field exists is surrounded by magnetic poles with small diameters, so it is a narrow and limited space even in the direction perpendicular to the beam traveling direction.

[0009] On the other hand, electrostatic lenses must be placed in a vacuum through which the electron beam passes, and so require complex structures such as vacuum seals and wiring drawn from the vacuum region. Furthermore, to apply a voltage to the electrostatic lens, an insulator is essential to support the lens electrode, and to prevent beam position fluctuations due to charging, the insulator must be surrounded by a conductor so that it is not visible from the electron beam trajectory. It is difficult to create two of these complex structures in a short section where the lens magnetic field exists, and in a narrow space surrounded by magnetic poles.

[0010] In an electron beam lithography device, when an electron beam is irradiated to a sample, drift (i.e., beam position fluctuation, beam position instability) occurs due to the influence of electrons reflected off the sample (reflected electrons) and electrons generated by being incident on the sample (secondary electrons), and the electrons may be irradiated to a position shifted from the target position. For this reason, an electrostatic lens is operated in a positive voltage range with respect to the sample surface, and secondary electrons, etc. are accelerated and guided upward from the sample surface (see, for example, Patent Document 2).

[0011] When two electrostatic lenses are placed in the magnetic field of the objective lens and are operated with a positive voltage relative to the sample surface, if the voltage of the upstream electrostatic lens becomes lower than that of the downstream electrostatic lens, secondary electrons from the sample surface will remain near the boundary between the two electrostatic lenses, and the beam (primary beam) will be deflected by the Coulomb force from the remaining secondary electrons, making the beam position unstable and causing drift.

[0012] The voltage applied to the electrostatic lenses changes depending on the height of the sample surface during drawing, so the magnitude relationship between the voltages applied to the two electrostatic lenses is reversed during drawing. Although no drift occurs at the beginning of drawing, drift may occur midway through drawing.

[0013] Thus, when two electrostatic lenses are placed close to each other in the magnetic field of a single-stage objective lens, there is a problem in that drift occurs due to the retention of secondary electrons.

[0014] [Patent Document 1] JP 2013-197289 A [Patent Document 2] JP 2013-191841 A Summary of the Invention

[0015] An object of the present invention is to provide a multi-charged particle beam drawing apparatus that can ensure sufficient space for the placement of a focus correction lens, suppress the retention of secondary electrons, and stabilize the beam irradiation position.

[0016] A multi-charged particle beam drawing apparatus according to one embodiment of the present invention includes a plurality of blankers that blank and deflect each beam of a multi-charged particle beam, and an acceleration lens that is composed of an electrostatic lens having a plurality of electrodes and accelerates the multi-charged particle beam, a limiting aperture member that blocks beams of the multi-charged particle beam accelerated by the acceleration lens that are deflected by the blanker to be in a beam-off state, two or more stages of objective lenses composed of magnetic lenses that focus the multi-charged particle beam that has passed through the limiting aperture member on a substrate, and three or more correction lenses including a first correction lens, a second correction lens, and a third correction lens that correct the imaging state of the multi-charged particle beam on the substrate, wherein the first correction lens is an electrostatic correction lens that also serves as at least one of the plurality of electrodes of the acceleration lens. Effect of the Invention

[0017] According to the present invention, it is possible to ensure a margin for the arrangement of a focus correction lens, suppress the retention of secondary electrons, and stabilize the beam irradiation position. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of a multi-charged particle beam drawing apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a shaped aperture array substrate. [Diagram 3] 3A to 3C are diagrams showing the configuration of an acceleration lens. [Figure 4] FIG. 11 is a schematic diagram of a multi-charged particle beam drawing apparatus according to a second embodiment of the present invention. [Diagram 5] FIG. 11 is a schematic diagram of a modified multi-charged particle beam writing apparatus. [Figure 6] FIG. 11 is a schematic diagram of a modified multi-charged particle beam writing apparatus. [Figure 7] FIG. 11 is a schematic diagram of a multi-charged particle beam drawing apparatus according to a third embodiment of the present invention. [Figure 8] FIG. 11 is a schematic diagram of a modified multi-charged particle beam writing apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] [First embodiment] 1 is a schematic diagram of a multi-charged particle beam writing apparatus according to a first embodiment of the present invention. In this embodiment, a configuration using an electron beam as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and may be another charged particle beam such as an ion beam.

[0021] This drawing apparatus includes a drawing unit W that irradiates an electron beam onto a substrate 24 as a drawing target to draw a desired pattern, and a control unit C that controls the operation of the drawing unit W.

[0022] The imaging unit W has an electron optical column 2 and an imaging chamber 20. Provided within the electron optical column 2 are an electron source 4, an illumination lens 6, a shaping aperture array substrate 8, a blanking aperture array substrate 10, an acceleration lens 50, a limiting aperture member 14, two-stage objective lenses 16 and 17, and two electrostatic correction lenses 66 and 67. The objective lenses 16 and 17 are magnetic lenses.

[0023] The illumination lens 6 is disposed between the electron source 4 and the shaping aperture array substrate 8. The illumination lens 6 may be a magnetic lens or an electrostatic lens. The acceleration lens 50 is disposed between the blanking aperture array substrate 10 and the objective lens 16. The acceleration lens 50 is an electrostatic lens composed of multiple rotationally symmetric electrodes, and the electrode potential changes between an intermediate potential on the upstream side and a ground potential on the downstream side.

[0024] The limiting aperture member 14 is disposed between the acceleration lens 50 and the objective lens 16, but may be disposed between the objective lens 16 and the objective lens 17. The objective lens 17 is disposed on the most downstream side in the beam traveling direction among a plurality of objective lenses provided in the drawing apparatus. The objective lens 16 is disposed on the upstream side in the beam traveling direction of the objective lens 17. Due to such a positional relationship, the objective lens 16 may be called the upper objective lens, and the objective lens 17 may be called the lower objective lens. The objective lens 17 may be called the final objective lens. The electrostatic correction lens 66 is disposed in the magnetic field (i.e., in the magnetic field, in the magnetic field) of the objective lens 16 constituted by a magnetic lens. The electrostatic correction lens 67 is disposed in the magnetic field of the objective lens 17 constituted by a magnetic lens.

[0025] The objective lens magnetic field refers to a region where the magnetic flux density is high, for example, the space surrounded by the magnetic poles of the objective lens. The objective lens' magnetic field (axial magnetic flux density) attenuates as it moves away from the objective lens' magnetic poles, but 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 objective lens. Empirically, the region where the axial magnetic flux density is greater than, for example, 1 / 10 of the maximum value, or the region where the magnetic flux density is at a minimum, can be considered "inside the magnetic field," and the other regions can be considered "outside the magnetic field."

[0026] In addition, in order to reduce aberration and distortion, a single objective lens may be composed of two or more adjacent magnetic lenses. In such cases, even if there is a location between the adjacent magnetic lenses that make up a single objective lens where the magnetic flux density is 1 / 10 or less or is extremely small, this is not considered to be a boundary between inside and outside the lens magnetic field of the objective lens, but is considered to be "inside the magnetic field."

[0027] The electrostatic correction lenses 66 and 67 generate a small rotationally symmetric electric field to correct the imaging state of the multi-beam. For example, the electrostatic correction lenses 66 and 67 are composed of a cylindrical electrode, and a voltage for correction is applied to the electrode. Cylindrical earth electrodes may be placed in front of and behind the electrode to which the voltage is applied.

[0028] In addition, a configuration in which a cylindrical or ring-shaped electrode is divided (for example, divided into an 8-pole deflector) and voltages that generate a focusing electric field (rotationally symmetric electric field), a deflecting electric field, a multipole electric field, etc. are added and applied to this electrode group, thereby combining the functions of a lens, a deflector, a multipole, etc., also generates an electric field that has a lens effect, and therefore such an electrode group is also included in a single electrostatic correction lens.

[0029] An XY stage 22 is disposed in the pattern writing chamber 20. A substrate 24 to be patterned is placed on the XY stage 22. The substrate 24 to be patterned is, for example, a mask blank or a semiconductor substrate (silicon wafer).

[0030] An electron beam 30 emitted from an electron source 4 illuminates a shaping aperture array substrate 8 almost perpendicularly via an illumination lens 6. FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate 8. In the shaping aperture array substrate 8, openings 80 are formed in a matrix of m columns (y direction) by n columns (x direction) (m, n≧2) at a predetermined arrangement pitch. For example, 512 columns by 512 columns of openings 80 are formed. Each opening 80 is formed as a rectangle of the same dimensions. Each opening 80 may be a circle of the same diameter.

[0031] The electron beam 30 illuminates an area including all the openings 80 of the shaping aperture array substrate 8. A portion of the electron beam 30 passes through each of the multiple openings 80, thereby forming a multi-beam 30M as shown in FIG.

[0032] Through holes are formed in the blanking aperture array substrate 10 in accordance with the positions of the openings 80 of the shaping aperture array substrate 8, and blankers consisting of a pair of two electrodes are disposed in each through hole. The multi-beams 30M passing through each through hole are deflected independently by a voltage applied to the blanker. Each beam is blanked by this deflection. In this manner, the blanking aperture array substrate 10 performs blanking deflection on each beam of the multi-beams 30M that have passed through the multiple openings 80 of the shaping aperture array substrate 8.

[0033] An electric field generated by the acceleration lens 50 acts as a focusing field on the multi-beams 30M that have passed through the blanking aperture array substrate 10. The acceleration lens 50 reduces the size and arrangement pitch of each beam while increasing the acceleration energy of the multi-beams 30M, forming a crossover CO1 slightly upstream of the objective lens 16. The limiting aperture member 14 is disposed so that the center of the opening formed in the limiting aperture member 14 approximately coincides with the crossover CO1. Here, the electron beam deflected by the blanker of the blanking aperture array substrate 10 has its trajectory displaced and is no longer positioned at the opening of the limiting aperture member 14, and is blocked by the limiting aperture member 14. On the other hand, the electron beam that has not been deflected by the blanker of the blanking aperture array substrate 10 passes through the opening of the limiting aperture member 14.

[0034] In this way, the limiting aperture member 14 blocks each electron beam deflected to a beam OFF state by the blanker of the blanking aperture array substrate 10. Then, the beam that passes through the limiting aperture member 14 from when the beam is turned ON until when the beam is turned OFF becomes the electron beam for one shot.

[0035] The upper objective lens 16 acts on the multibeam 30M that has passed through the limiting aperture member 14, forming a reduced intermediate image IS1 of the multiple openings 80 of the shaping aperture array substrate 8 and forming a crossover CO2. The lower objective lens reduces the intermediate image IS1, forming an image (beam array image) IS2 of the multiple openings 80 of the shaping aperture array substrate 8 at a desired reduction ratio on the surface of the substrate 24. The reduction ratio is the reciprocal of the magnification, and is, for example, the ratio between the size (or pitch) of the electron beam formed by each of the multiple openings 80 of the shaping aperture array substrate 8 passing through a portion of the electron beam 30, and the size (or pitch) of the image formed on the surface of the substrate 24.

[0036] By using two stages of objective lenses, a high reduction ratio (for example, a magnification of about 1 / 200) can be achieved while also ensuring a distance (working distance) between the underside of the final lens (objective lens 17) and substrate 24 that allows the substrate 24 to move.

[0037] The electrostatic correction lenses 66, 67 operate in a positive voltage range with respect to the surface of the substrate 24. Note that, for example, in cases where the ratio of the area of ​​the pattern to be written to the entire writing region is very low, the generation of reflected electrons and secondary electrons on the sample is small, and it is determined that the influence of these electrons does not need to be taken into consideration, the electrostatic correction lenses 66, 67 may operate at a negative voltage.

[0038] The electron beams (all of the multi-beams) that have passed through the limiting aperture member 14 are deflected in the same direction by a deflector (not shown) and irradiated onto the substrate 24. The deflector (not shown) may be disposed downstream of the blanking aperture array substrate 10, but disposing it downstream of the upper objective lens 16 has the advantage of reducing distortion and aberration. When the XY stage 22 moves continuously, the beam is deflected so that the irradiation position of the beam follows the movement of the XY stage 22. Also, the XY stage 22 moves and the drawing position changes each time, and the height of the surface of the substrate 24 where the multi-beams are irradiated changes. Therefore, the defocus of the multi-beams is dynamically corrected (dynamic focus) during drawing by the electrostatic correction lens 54 and electrostatic correction lenses 66 and 67 in the acceleration lens 50 described later.

[0039] The multiple beams irradiated at one time are ideally arranged at a pitch obtained by dividing the arrangement pitch of the multiple openings 80 in the shaping aperture array substrate 8 by the desired reduction ratio described above (i.e., multiplying by the magnification). This drawing device performs drawing operations using a raster scan method in which shot beams are continuously irradiated in sequence, and when drawing a desired pattern, the beams required according to the pattern are turned on by blanking control.

[0040] The control unit C has a control computer 32 and a control circuit 34. The control computer 32 performs multiple stages of data conversion processing on the drawing data to generate shot data specific to the device, and outputs it to the control circuit 34. The shot data defines the dose and irradiation position coordinates of each shot. The control circuit 34 calculates the irradiation time by dividing the dose of each shot by the current density, and applies a deflection voltage to the corresponding blanker of the blanking aperture array substrate 10 so that the beam is turned on for the calculated irradiation time when the corresponding shot is performed.

[0041] The control computer 32 holds data on a relational expression that links the excitation amounts of the electrostatic correction lens 54 in the acceleration lens 50 and the electrostatic correction lenses 66 and 67, which will be described later, and calculates the excitation amount of each correction lens using this relational expression. The control circuit 34 operates the electrostatic correction lenses 54, 66, and 67 by applying the excitation amount calculated from the relational expression. Note that the excitation amount is an excitation current in the case of a magnetic correction lens, and is an applied voltage in the case of an electrostatic correction lens.

[0042] 3A, the acceleration lens 50 has a plurality of cylindrical or ring-shaped electrodes 51, 52, and 53. The same voltage (potential) as that of the shaping aperture array substrate 8 and the blanking aperture array substrate 10 is applied to the intermediate potential electrode 51 located on the upstream side. A ground potential is applied to the earth electrode 52 located on the downstream side. For example, when accelerating a negatively charged electron beam, −45 kV is applied to the intermediate potential electrode 51, and 0 V is applied to the earth electrode 52.

[0043] A voltage optimized to reduce aberration and distortion within a range in which the potential difference between adjacent electrodes does not exceed the discharge withstand voltage is applied to the multiple electrodes 53 located between the intermediate potential electrode 51 and the earth electrode 52. Normally, the intermediate potential electrode 51 and the earth electrode 52 are longer (in the beam travel direction) than the electrode 53.

[0044] In this embodiment, a part of the electrodes of the acceleration lens 50 is made to function as an electrostatic correction lens that corrects the imaging state of the multi-beams.

[0045] 3B, for example, the earth electrode 52 is divided into two in the cylindrical axis direction, and a correction voltage is applied to the upstream earth electrode 52 to operate it as an electrostatic correction lens 54. When not used to correct the imaging state of the multi-beams, an earth potential is applied.

[0046] Alternatively, as shown in FIG. 3C, a voltage for the acceleration lens and a correction voltage may be added and applied to at least one (one) of the multiple electrodes 53 to operate as an electrostatic correction lens 54.

[0047] The beam acceleration capability of the acceleration lens 50 is determined by the potential at the entrance and exit of the acceleration lens. In the configurations shown in Figures 3B and 3C, the most upstream entrance electrode potential and the most downstream exit electrode potential are the same as those in the configuration shown in Figure 3A, so even if a correction voltage is added to the applied voltage of some of the electrodes to operate as an electrostatic correction lens 54, the beam acceleration capability does not change.

[0048] In addition, a group of electrodes that generates rotationally symmetric electric field components, such as a configuration in which a cylindrical or ring-shaped electrode is divided (for example, into an 8-pole deflector) and voltages that generate a rotationally symmetric electric field (having focusing and acceleration effects), a deflection electric field, a multipole electric field, etc. are added and applied to this group of electrodes, is also considered to be one (single) electrode that constitutes the acceleration lens.

[0049] When a correction voltage is applied to the electrode that operates as the electrostatic correction lens 54, the total lens effect (beam focusing force) of the acceleration lens and the electrostatic correction lens changes. As a result, the imaging height and magnification of the intermediate image IS1 change. Since the objective lens 17 at the rear stage reduces and images the intermediate image IS1, the change in imaging height caused by the intermediate image IS1 is reduced, and the change in imaging height of the beam array image IS2 on the surface of the substrate 24 becomes small. In other words, the imaging height correction sensitivity of the electrostatic correction lens 54 is low. The change in magnification (magnification ratio) caused by the intermediate image IS1 is directly transmitted to the change in magnification of the beam array image IS2 regardless of the imaging magnification of the objective lens 17 at the rear stage, so the magnification correction sensitivity of the electrostatic correction lens 54 is high. Since the combination of the electrostatic lens and the electrostatic correction lens does not cause image rotation, the rotation correction sensitivity of the electrostatic correction lens 54 is extremely low.

[0050] As described above, the electrostatic correction lens 54, which also serves as an electrode for the acceleration lens 50, has high magnification correction sensitivity, low image height correction sensitivity, and extremely low rotation correction sensitivity.

[0051] The electrostatic lens placed in the magnetic field of the objective lens (magnetic lens) changes the energy of the beam in the electrostatic lens, changing the focusing effect that the beam receives from the magnetic lens, thereby changing the imaging height. This change in focusing effect also causes a change in magnification. Rotation does not usually occur with an electrostatic lens alone, but when placed in the lens magnetic field, the rotation also changes due to the energy change through the magnetic lens action. Here, the magnetic field generated by the objective lens to focus the beam is extremely strong, so the focusing effect and rotation effect of the entire lens magnetic field change significantly even with a small energy change caused by a small change in the voltage applied to the electrostatic lens. Therefore, the electrostatic correction lens 67 placed in the lens magnetic field of the final stage objective lens 17 has high correction sensitivity for imaging height, magnification, and rotation.

[0052] On the other hand, the upstream electrostatic correction lens 66 has a low correction sensitivity for the imaging height. This is because the final stage objective lens 17 reduces and images the intermediate image IS1, and the change in the height direction is also reduced to form the beam array image IS2 on the surface of the substrate 24. However, the magnification change (magnification ratio) and rotation do not change. Therefore, the electrostatic correction lens 66 arranged within the lens magnetic field of the upstream objective lens 16 has a low correction sensitivity for the imaging height, but has high correction sensitivity for magnification and rotation that is comparable to that of the electrostatic correction lens 67.

[0053] In this way, the electrostatic correction lenses 54, 66, and 67 each have different correction characteristics (the ratios of the image height correction sensitivity, magnification correction sensitivity, and rotation correction sensitivity are different), so by controlling the excitation amounts (applied voltages) of these three correction lenses in conjunction with an appropriate relational expression, it is possible to correct the image formation state as follows. The imaging height is changed in response to variations in the substrate surface height, without changing the magnification or rotating the microscope. The substrate surface height is kept constant, there is no rotation, and the imaging height remains unchanged, but the magnification is changed. The substrate surface height is kept constant, the imaging height and magnification are constant, and the rotation is changed. Of the three types of image correction, the first type is used for focus correction (dynamic focus) during imaging to accommodate the unevenness of the sample surface, the second type can be used for fine adjustment of magnification, and the third type can be used for fine adjustment of rotation.

[0054] The relational equation for the linkage of the excitation amount in correcting the imaging state is different for each of the three adjustment patterns. The relational equation for the excitation amount can be adjusted with sufficient accuracy if it is a first-order or higher polynomial of the adjustment amount (imaging height, magnification, rotation). The coefficients of the polynomial are found by trajectory simulation. The coefficients may be calculated based on the dependence of the imaging height, magnification, and rotation on the excitation amount, which are actually measured.

[0055] In this manner, in this embodiment, since only one electrostatic correction lens is placed within the lens magnetic field of the objective lens of each stage, it is possible to ensure a sufficient margin for placement. Since the electrostatic correction lenses are not placed close to each other, it is possible to easily design structures required for electrostatic correction lens placement, such as vacuum seals, wiring leads from the vacuum area, and insulators supporting the lens electrodes. In addition, the assembly work is made easier, and work efficiency can be improved.

[0056] Furthermore, since there is no electrostatic correction lens located nearby in the lens magnetic field, it is possible to suppress the retention of secondary electrons caused by differences in voltage between adjacent electrostatic lenses and stabilize the beam position.

[0057] The electrostatic correction lens, which also serves as an electrode for the acceleration lens, is placed in a location where there are no magnetic poles around it and where a wide diameter space is available, so there is ample space for placement.

[0058] [Second embodiment] In the first embodiment described above, one electrostatic correction lens 66, 67 was placed in the lens magnetic field of the objective lenses 16, 17, respectively. However, it is also possible to omit one of the electrostatic correction lenses and place a magnetic field correction lens outside the lens magnetic field of the objective lenses.

[0059] For example, as shown in FIG. 4, the electrostatic correction lens in the lens magnetic field of the objective lens 16 is omitted, and a magnetic field correction lens 40 is disposed outside the lens magnetic field.

[0060] The magnetic field correction lens 40 is disposed upstream of the objective lenses 16 and 17, outside the lens magnetic field. The magnetic field (axial magnetic flux density) of the magnetic field type objective lens attenuates as it moves away from the objective lens magnetic pole. Empirically, the region where the axial magnetic flux density is, for example, 1 / 10 or less of the maximum value can be regarded as "outside the magnetic field". Note that the axial magnetic flux density is usually maximized on the optical axis near the middle of a pair of magnetic poles (two magnetic poles) of the objective lens. In this embodiment, the magnetic field correction lens 40 is disposed between the acceleration lens 50 and the objective lens 16, but the position of the magnetic field correction lens 40 may be outside the magnetic field of the objective lenses 16 and 17 and downstream of the blanking aperture array substrate 10. For example, a coil may be disposed to surround the acceleration lens 50, and the coil may be used as the magnetic field correction lens 40.

[0061] The magnetic field correction lens 40 generates a small rotationally symmetric magnetic field to correct the imaging state. For example, the magnetic field correction lens 40 is a circular coil or a solenoid coil with the beam optical axis as its central axis, and a current for correction is passed through it. The coil may be surrounded by a magnetic material such as ferrite.

[0062] The magnetic field correction lens has the effect of rotating the beam image (rotation effect), and this effect occurs regardless of whether the position of the magnetic field correction lens in the optical axis direction is inside or outside the lens's magnetic field. The rotation of the image is a simple addition of the rotation effect of the objective lens magnetic field and the rotation effect of the magnetic field correction lens magnetic field, and even if the two magnetic fields overlap, no synergistic effect (a rotation effect proportional to the product of the two magnetic fields) occurs.

[0063] When the magnetic field correction lens is placed inside the lens magnetic field, the sensitivity of the image height correction increases, and the magnification correction effect also increases accordingly. Because the focusing force of the lens magnetic field is proportional to the square of the axial magnetic flux density, if the magnetic field of the objective lens and the magnetic field of the magnetic field correction lens overlap in the optical axis direction, a synergistic effect (a focusing effect proportional to the product of the two magnetic fields) occurs, and a large change in focusing force is obtained for a small change in the magnetic field of the correction lens. On the other hand, if the magnetic field correction lens is placed outside the lens magnetic field, the change in focusing force becomes very small, and the correction sensitivity of the image height and magnification decreases.

[0064] Therefore, the magnetic field correction lens 40 arranged outside the lens magnetic field as in this embodiment has the characteristics that the correction sensitivity of the image height and magnification is low, but the correction sensitivity of the rotation is high.

[0065] Since the electrostatic correction lenses 54, 67 and the magnetic field correction lens 40 each have different correction characteristics (the ratios of image height correction sensitivity, magnification correction sensitivity, and rotation correction sensitivity are different), the excitation amounts of these three correction lenses (applied voltage for the electrostatic correction lenses, and excitation current for the magnetic field correction lenses) can be linked and controlled using an appropriate relational expression to achieve correction of the imaging state similar to that of the first embodiment described above.

[0066] Unlike electrostatic correction lenses, magnetic field correction lenses are usually placed outside of a vacuum, and therefore do not require complex structures such as vacuum seals, wiring outside the vacuum, and insulator supports in the vacuum. In this embodiment, the magnetic field correction lens 40 is placed outside the magnetic field between the acceleration lens 50 and the objective lens 16, so it is not surrounded by the objective lens magnetic poles, and a large space can be used, eliminating the problem of space for placement.

[0067] Furthermore, as in the first embodiment described above, there is no electrostatic correction lens located nearby in the lens magnetic field, so that it is possible to suppress the stagnation of secondary electrons caused by differences in voltage between adjacent electrostatic lenses and stabilize the beam position.

[0068] The position of the magnetic field correction lens 40 is not limited to being outside the lens magnetic field upstream of the objective lenses 16 and 17, but may be placed outside the lens magnetic field between the two stages of objective lenses 16 and 17 as shown in FIG.

[0069] For example, when the excitation directions (directions of the focusing magnetic field) of the two objective lenses 16, 17 are opposite to each other, a location where the magnetic flux density becomes 0 is generated between the two lenses, and the magnetic field correction lens 40 is disposed in the vicinity of that location.

[0070] Even if the excitation direction of the two objective lenses 16, 17 is the same, there is often a region between them where the magnetic flux density is sufficiently attenuated (for example, a region where the axial magnetic flux density is 1 / 10 or less of the maximum value), so a magnetic field correction lens 40 is placed in that vicinity.

[0071] In the imaging device shown in Fig. 4, the electrostatic correction lens 67 is disposed within the lens magnetic field of the objective lens 17, but as shown in Fig. 6, the electrostatic correction lens 67 may be omitted and the magnetic field correction lens 42 may be disposed within the lens magnetic field of the objective lens 17. Although not shown, in the imaging device shown in Fig. 5, the electrostatic correction lens 67 disposed within the lens magnetic field of the objective lens 17 may be omitted and the magnetic field correction lens 42 may be disposed within the lens magnetic field of the objective lens 17.

[0072] The magnetic field correction lens disposed in the magnetic field of the objective lens is an air-core circular coil or solenoid coil, and is preferably not surrounded by a magnetic material such as ferrite so as not to disturb the magnetic field of the objective lens.

[0073] As already explained, when the magnetic field correction lens is placed in the lens magnetic field, the sensitivity of the image height correction and the effect of magnification correction become large, and it also produces the effect of rotating the beam image regardless of whether it is inside or outside the lens magnetic field. As a result, the magnetic field correction lens 42 placed in the lens magnetic field of the objective lens 17 has high correction sensitivity for all of the image height, magnification, and rotation.

[0074] Since the electrostatic correction lens 54 and the magnetic field correction lenses 40, 42 each have a different correction characteristic, by controlling the excitation amounts of these three correction lenses in conjunction with an appropriate relational expression, it is possible to correct the imaging state in the same way as in the first embodiment described above.

[0075] [Third embodiment] In the above first embodiment, a configuration has been described in which one electrostatic correction lens 66, 67 is disposed within the lens magnetic field of each of the objective lenses 16, 17, but at least one of the electrostatic correction lenses 66, 67 may be replaced with a magnetic field correction lens. Since the electrostatic correction lens and the magnetic field correction lens have different structures and implementation forms, the term "replace" here means that they are disposed at approximately the same position in the optical axis direction. Specifications other than the position in the optical axis direction, for example, the diameter and length (length in the optical axis direction) of the electrodes of the electrostatic correction lens and the coil of the magnetic field correction lens are usually different.

[0076] Fig. 7 shows a configuration in which the correction lens in the lens magnetic field of objective lens 16 is a magnetic correction lens 41, and the correction lens in the lens magnetic field of objective lens 17 is an electrostatic correction lens 67. Fig. 8 shows a configuration in which the correction lens in the lens magnetic field of objective lens 16 is a magnetic correction lens 41, and the correction lens in the lens magnetic field of objective lens 17 is a magnetic correction lens 42.

[0077] Although not shown in the figure, the correction lens in the lens magnetic field of the objective lens 16 may be an electrostatic correction lens 66, and the correction lens in the lens magnetic field of the objective lens 17 may be a magnetic correction lens 42.

[0078] The magnetic field correction lens 42 arranged in the magnetic field of the objective lens 17 has high image height correction sensitivity and magnification correction sensitivity. The magnetic field correction lens 41 arranged in the magnetic field of the objective lens 16 has low image height correction sensitivity because the image height correction amount is reduced by the subsequent objective lens 17, but the magnification correction effect is high without being affected by the subsequent lens. In this way, the magnetic field correction lens arranged in the lens magnetic field of the objective lens has a correction sensitivity of focus and magnification in a ratio similar to that of the case where an electrostatic correction lens is arranged. In addition, the magnetic field correction lens has high rotation correction sensitivity regardless of whether it is inside or outside the magnetic field of the objective lens. Therefore, by controlling the excitation amount of the correction lenses having different correction characteristics, that is, the applied voltage of the electrostatic correction lens 54, the excitation current of the magnetic field correction lens 41, and the applied voltage of the electrostatic correction lens 67 in the embodiment of FIG. 7, and the applied voltage of the electrostatic correction lens 54 and the excitation current of the magnetic field correction lenses 41 and 42 in the embodiment of FIG. 8, in conjunction with each other based on a relational expression, it is possible to perform correction of the image formation state similar to that of the first embodiment.

[0079] Unlike electrostatic correction lenses, the magnetic field correction lenses (40, 41) arranged in the lens magnetic field of the objective lens are usually arranged outside the vacuum, so no complicated structure is required, and space for arrangement can be secured. Also, since there is no electrostatic correction lens arranged nearby in the lens magnetic field, it is possible to suppress the retention of secondary electrons caused by the difference in voltage between nearby electrostatic lenses, and stabilize the beam position.

[0080] In the imaging device shown so far, a configuration using three correction lenses has been described, but the number of correction lenses used to correct the imaging state is not limited to three, and four or more lenses may be used.

[0081] In addition, although the drawing device shown so far has been described as having a configuration using two stages of objective lenses, even when three or more stages of objective lenses are used, it is possible to correct the imaging state while ensuring sufficient space for the placement of focus correction lenses and suppressing the retention of secondary electrons and stabilizing the beam irradiation position.

[0082] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. [Explanation of symbols]

[0083] 2 Electron Optical Tube 4 Electron source 6 Lighting Lens 8 Molded aperture array substrate 10 Blanking aperture array board 14 Limiting aperture member 16, 17 Objective lenses 20 Drawing room 22 XY Stage 24 Substrate 40, 41, 42 Magnetic field correction lens 50 Acceleration Lens 54,66,67 Electrostatic correction lens

Claims

1. A plurality of blankers for blanking and deflecting each beam of the multi-charged particle beam; an acceleration lens configured by an electrostatic lens having a plurality of electrodes and accelerating the multi-charged particle beam; a limiting aperture member for blocking a beam deflected by the blanker to be in a beam-off state out of the multi-charged particle beam accelerated by the acceleration lens; an objective lens having two or more stages, which is made of a magnetic lens, for focusing the multi-charged particle beam that has passed through the limiting aperture member onto a substrate; three or more correcting lenses including a first correcting lens, a second correcting lens, and a third correcting lens, which correct an imaging state of the multi-charged particle beam on the substrate; Equipped with The number of electrostatic correction lenses arranged in each of the two or more stages of objective lenses is one or less; A multi-charged particle beam drawing apparatus, wherein the first correction lens is an electrostatic correction lens that also serves as at least one of the plurality of electrodes of the acceleration lens.

2. the second correction lens is an electrostatic correction lens disposed within a lens magnetic field of a first objective lens which is one of the objective lenses of the two or more stages, 2. The multi-charged particle beam drawing apparatus according to claim 1, wherein the third correction lens is an electrostatic correction lens arranged within a lens magnetic field of an objective lens other than the first objective lens among the two or more stages of objective lenses.

3. the second correction lens is a magnetic field correction lens disposed outside the lens magnetic field of the two or more stages of objective lenses, 2. The multi-charged particle beam writing apparatus according to claim 1, wherein the third correction lens is disposed within a lens magnetic field of any one of the two or more stages of objective lenses.

4. 4. The multi-charged particle beam drawing apparatus according to claim 3, wherein the second correction lens is a magnetic field correction lens arranged upstream of the two or more stages of objective lenses and outside of a lens magnetic field.

5. 4. The multi-charged particle beam writing apparatus according to claim 3, wherein the second correction lens is a magnetic field correction lens disposed outside a lens magnetic field between the two or more stages of objective lenses.

6. The multi-charged particle beam writing apparatus according to claim 3 , wherein the third correction lens is an electrostatic correction lens.

7. 4. The multi-charged particle beam writing apparatus according to claim 3, wherein the third correction lens is a magnetic field correction lens.

8. the second correction lens is a magnetic field correction lens disposed within a lens magnetic field of any one of the objective lenses of the two or more stages of objective lenses, 2. The multi-charged particle beam drawing apparatus according to claim 1, wherein the third correction lens is an electrostatic correction lens arranged within a lens magnetic field of any one of the objective lenses of the two or more stages of objective lenses.

9. the second correction lens is a magnetic field correction lens disposed within a lens magnetic field of any one of the objective lenses of the two or more stages of objective lenses, 2. The multi-charged particle beam drawing apparatus according to claim 1, wherein the third correction lens is a magnetic field correction lens disposed within a lens magnetic field of any one of the objective lenses of the two or more stages.

10. 2. The multi-charged particle beam writing apparatus according to claim 1, wherein a mutual relationship between the excitation amounts of the three or more correction lenses is set to correct an imaging state of the multi-charged particle beam.

11. 11. The multi-charged particle beam writing apparatus according to claim 10, wherein the correction of the imaging state is a correction for changing the imaging height without changing the magnification and without rotating the beam.

12. 11. The multi-charged particle beam writing apparatus according to claim 10, wherein the correction of the imaging state is a correction for changing a magnification without rotation and without changing an imaging height.

13. 11. The multi-charged particle beam writing apparatus according to claim 10, wherein the correction of the imaging state is a correction that changes rotation while keeping the imaging height and magnification constant.

Images