Charged particle beam writing equipment

Abstract

To simultaneously resolve spatial residence of secondary electrons and fluctuation in beam position due to deflector electrode charging.SOLUTION: A charged particle beam drawing device includes a positioning deflector that adjusts the irradiation position of a charged particle beam with which a substrate to be drawn is irradiated, a fixed deflector arranged downstream of the positioning deflector in the traveling direction of the charged particle beam and having a fixed amount of deflection, a focus correction lens that corrects the focus of the charged particle beam according to the surface height of the substrate, and an objective lens for focusing the charged particle beam.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a 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 original pattern (mask, or particularly one used in steppers and scanners, called a reticle) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is drawn by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

[0003] In electron beam lithography systems, the objective lens focuses the beam for each shot onto the sample surface, which is the surface of the substrate, while an electrostatic lens is used to dynamically correct the focus (dynamic focus) during lithography to accommodate the unevenness of the sample surface. If this electrostatic lens is operated in the negative voltage range, secondary electrons generated by electron beam lithography return to the sample surface, causing the resist to become charged, which hinders the improvement of the positional accuracy of the lithography pattern.

[0004] In order to suppress the effects of return of secondary electrons, etc., it is preferable to operate the electrostatic lens in a positive voltage range relative to the sample surface and guide the secondary electrons upward from the sample. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO 99 / 46798 [Patent Document 2] JP 2001-357808 A [Patent Document 3] JP 2007-141488 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the electrostatic lens is operated in the positive voltage range, secondary electrons from the sample surface suddenly decelerate after passing through the electrostatic lens and remain on the beam trajectory at a high density. In addition, the secondary electrons become charged by non-conductive dirt (contamination) on the inner surface of the deflector electrodes, which changes the electric field near the electron beam, changing the electron beam trajectory and degrading the beam position accuracy.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a charged particle beam drawing apparatus that can simultaneously solve the problems of spatial retention of secondary electrons and fluctuations in beam position due to charging of deflector electrodes. [Means for solving the problem]

[0008] A charged particle beam drawing apparatus according to one embodiment of the present invention comprises a positioning deflector that adjusts the irradiation position of the charged particle beam irradiated onto a substrate to be drawn on, a fixed deflector that is arranged downstream of the positioning deflector in the direction of travel of the charged particle beam and has a fixed deflection amount, a focus correction lens that corrects the focus of the charged particle beam in accordance with the surface height of the substrate, and an objective lens that focuses the charged particle beam. Effect of the Invention

[0009] According to the present invention, it is possible to simultaneously solve the problems of spatial retention of secondary electrons and fluctuations in beam position due to charging of deflector electrodes. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of an electron beam writing apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of a first shaping aperture and a second shaping aperture. [Diagram 3] FIG. 2 is a cross-sectional view of an objective lens. [Figure 4]13A and 13B are diagrams illustrating the trajectories of secondary electrons according to a comparative example. [Diagram 5] 5A and 5B are diagrams illustrating the trajectory of secondary electrons according to the embodiment. [Figure 6] FIG. 13 is a diagram showing an example of a voltage applied to a fixed deflector. [Figure 7] FIG. 13 is a diagram showing an example of a voltage applied to a fixed deflector. [Figure 8] 1A and 1B are diagrams illustrating an example of the configuration of a fixed deflector. [Figure 9] FIG. 13 is a diagram showing an example in which a plurality of fixed deflectors are arranged. [Figure 10] FIG. 13 is a schematic configuration diagram of a fixed deflector according to a modified example. [Figure 11] 13A and 13B are diagrams illustrating an example of the arrangement of an aperture plate. [Figure 12] 13(a) and 13(b) are diagrams for explaining the trajectory of secondary electrons. [Figure 13] FIG. 13 is a diagram showing a configuration in which a fixed deflector is disposed below a focus correction lens. [Figure 14] FIG. 2 is a diagram illustrating an example of the configuration of a fixed deflector. [Figure 15] 15 is a cross-sectional view taken along line XV-XV of FIG. 14. [Figure 16] FIG. 13 is a diagram showing a configuration in which an electron detector is disposed above a fixed deflector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 1 is a schematic diagram of an electron beam lithography apparatus according to an embodiment of the present invention. The electron beam lithography apparatus shown in FIG. 1 is a variable shaping type lithography apparatus including a control unit 100 and a lithography unit 200.

[0013] The drawing unit 200 includes an electron optical column 220 and a drawing chamber 230. In the electron optical column 220, an electron gun 201, an illumination lens 202, a blanker 203, a first shaping aperture member 204, a projection lens 205, a shaping deflector 206, a second shaping aperture member 207, an objective lens 208, a positioning deflector 209, a focus correction lens 210, and a fixed deflector 212 are arranged.

[0014] An XY stage 232 is disposed in the drawing chamber 230. A substrate 240 to be drawn is placed on the XY stage 232. A Z sensor 250 for detecting the position of the substrate 240 in the height direction (Z direction) is disposed in the upper part of the drawing chamber 230. The Z sensor 250 is composed of a combination of a light projector and a light receiver, and can measure the surface height of the substrate 240 by reflecting light irradiated from the light projector on the surface of the substrate 240 and receiving this reflected light with the light receiver. The substrate 240 is fixed to earth potential.

[0015] The height data detected by the Z sensor 250 is converted into digital data by the detection circuit 150 and then transferred to the control computer 110.

[0016] An electron beam B emitted from an electron gun 201 (emission section) provided in an electron optical column 220 is switched by a blanker (blanking deflector) 203 as it passes through the blanker 203 as to whether or not the electron beam is irradiated onto a substrate.

[0017] The electron beam B is irradiated onto the entire first shaping aperture member 204 having a rectangular opening 32 (see FIG. 2) by the illumination lens 202. By passing through the opening 32 of the first shaping aperture member 204, the electron beam B is shaped into a rectangle.

[0018] The electron beam B of the first aperture image having passed through the first shaping aperture member 204 is projected by the projection lens 205 onto a second shaping aperture member 207 having a variable shaping aperture 34 (see FIG. 2). At that time, the shaping deflector 206 controls the deflection of the first aperture image projected onto the second shaping aperture member 207, making it possible to change the shape and dimensions of the electron beam passing through the variable shaping aperture 34 (perform variable shaping).

[0019] The electron beam B of the second aperture image that passes through the variable shaping aperture 34 of the second shaping aperture member 207 is deflected by the positioning deflector 209, focused by the objective lens 208 and the focus correction lens 210, and irradiated onto the substrate 240 placed on the continuously moving XY stage 232.

[0020] The positioning deflector 209 deflects and irradiates the electron beam to a desired position, and may be a single-stage deflector or may be configured with multiple stages of deflectors with different sizes of deflection areas. For example, it may be a two-stage configuration of a main deflector and a sub-deflector, or a three-stage configuration of a main deflector, a sub-deflector, and a sub-sub-deflector.

[0021] Electromagnetic lenses (magnetic field type lenses) are used for the illumination lens 202, the projection lens 205, and the objective lens 208, but some or all of them may be electrostatic lenses. The focus correction lens 210 performs dynamic focus adjustment in response to height variations of the surface of the substrate 240, and an electrostatic lens is used, but an electromagnetic lens (including a coil that generates an axially symmetric magnetic field) may also be used. In addition, it may be configured as a multi-stage lens system in which the applied voltages and excitation currents change in conjunction with each other in a certain relationship. Alternatively, the objective lens 208 may also have the function of the focus correction lens 210, or the objective lens 208 and the focus correction lens 210 may be configured to perform focus adjustment by interlocking with each other in a certain relationship.

[0022] The fixed deflector 212 is disposed downstream of the positioning deflector 209 in the traveling direction of the electron beam B. The fixed deflector 212 is an electrostatic deflector. The focus correction lens 210 is disposed downstream of the fixed deflector 212 in the traveling direction of the electron beam B.

[0023] 2 is a schematic diagram for explaining beam shaping by the first shaping aperture member 204 and the second shaping aperture member 207. In the first shaping aperture member 204, a rectangular opening 32 for shaping the electron beam B is formed.

[0024] Furthermore, a variable shaping aperture 34 is formed in the second shaping aperture member 207 for shaping the electron beam B having passed through the aperture 32 of the first shaping aperture member 204 into a desired shape. The shape of the beam having passed through both the aperture 32 of the first shaping aperture member 204 and the variable shaping aperture 34 of the second shaping aperture member 207 is drawn in a drawing region of a substrate 240 mounted on an XY stage 232 which moves continuously.

[0025] 1, the control unit 100 has a control computer 110, a deflection control circuit 120, a storage unit 130, a lens control circuit 140, and a detection circuit 150. Drawing data, which becomes layout data, is input from the outside and stored in the storage unit 130.

[0026] The control computer 110 has a shot data generation unit 111 and a drawing control unit 112. Each unit of the control computer 110 may be configured with hardware such as an electric circuit, or may be configured with software. When configured with software, a program that realizes at least some of the functions of the control computer 110 may be stored in a recording medium and read and executed by a computer including a CPU. The recording medium is not limited to removable ones such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory.

[0027] The shot data generator 111 reads out the drawing data from the storage unit 130, and generates shot data by performing multiple stages of data conversion processing. The shot data includes information such as the shot shape, shot size, shot position, and shot time.

[0028] The writing control unit 112 transfers the shot data in the order of shots to the deflection control circuit 120. The deflection control circuit 120 uses the shot data to control the deflection amounts of the blanker 203, the shaping deflector 206, and the positioning deflector 209, and performs writing processing.

[0029] Moreover, the deflection control circuit 120 applies a constant (fixed) voltage to the fixed deflector 212 during the drawing process.

[0030] The lens control circuit 140 controls each lens provided in the drawing unit 200. For example, the lens control circuit 140 controls the amount of current applied to the coil of the objective lens 208. In addition, the lens control circuit 140 controls the voltage applied to the focus correction lens 210 based on the surface height of the substrate 240 detected by the Z sensor 250.

[0031] Objective lens 208 is an electromagnetic lens, and has coil 208a and yoke 208b that houses coil 208a, as shown in Fig. 3. Yoke 208b is made of a material with high magnetic permeability such as iron, and has a notch (pole piece 208c) formed in a part of it.

[0032] Magnetic field lines created by passing a current through coil 208a leak into space via pole piece 208c, creating a magnetic field.

[0033] The focus correction lens 210 is disposed, for example, inside the objective lens 208, for example, at the same height as the pole piece 208c. The focus correction lens 210 is an electrostatic lens having a ring-shaped electrode. A positive voltage is applied to this electrode, and the focus correction lens 210 is operated in the positive voltage range. This attracts secondary electrons to the electrode side, making it possible to suppress positional fluctuations caused by charging the resist.

[0034] When the electron beam B (primary beam) is irradiated onto the substrate 240, secondary electrons are emitted from the substrate surface. The secondary electrons travel upward within the electron optical column 220.

[0035] In the writing process, the resist on the surface of the substrate 240 evaporates due to the beam irradiation, and contamination (dirt) adheres to the electrode surface of the positioning deflector 209. If the fixed deflector 212 is not provided, the secondary electrons reach and charge the contamination on the electrode surface of the positioning deflector 209, as shown in FIG. 4(a), and change the trajectory of the electron beam B.

[0036] 4(b), when the beam deflection position (beam irradiation position on the substrate 240) is changed by changing the voltage applied to the electrodes of the positioning deflector 209, the strength and direction of the electric field in the positioning deflector 209 change, and the arrival position of the secondary electrons, i.e., the charged position, changes significantly across the electrodes. The large change in the charged position causes a large change in the electric field near the beam, which results in a large fluctuation (drift) in the beam irradiation position.

[0037] Therefore, in this embodiment, a fixed deflector 212 is installed between the focus correction lens 210 and the positioning deflector 209, and a fixed voltage is applied to the fixed deflector 212. Since the voltage applied to the fixed deflector 212 is not changed during the drawing process, the amount of deflection by the fixed deflector 212 is fixed. As shown in FIG. 5(a), the secondary electrons are deflected laterally toward the fixed deflector 212 side and removed from the vicinity of the trajectory of the electron beam B, and hardly reach the positioning deflector 209.

[0038] The secondary electrons deflected by the fixed deflector 212 reach the electrodes of the fixed deflector 212, causing the electrodes to become charged. As shown in Fig. 5(b), even if the beam irradiation position is changed by changing the voltage applied to the positioning deflector 209, the deflection voltage (deflection excitation) of the fixed deflector 212 is constant, so there is no change in the arrival position of the secondary electrons (charged position) and the change in the electric field (electric field change including the direction) in the vicinity of the electron beam becomes small, so the fluctuation in the beam irradiation position is also small. This makes it possible to improve the beam position accuracy.

[0039] Generally, the energy of secondary electrons (a few tens of eV or less) is extremely low compared to the energy of the electron beam B used for drawing (about 50 kV). Therefore, even if the secondary electrons are deflected, the electron beam B is hardly deflected at all, and there is almost no effect on the optical characteristics.

[0040] 6 shows an example of a voltage applied to the fixed deflector 212. As shown in FIG. 6, when the fixed deflector 212 is an electrostatic quadrupole deflector having four electrodes 212a to 212d, a fixed deflection voltage V D , -V D is applied to the electrodes 212b and 212d, and the remaining electrodes 212b and 212d are fixed at the ground potential. D , -V D is determined by a numerical simulation taking into account the specifications of the fixed deflector 212. For example, the deflection voltage V D The voltage is 20 V or more. The space surrounded by the four electrodes 212a to 212d is the area through which the electron beam B passes.

[0041] 7, a positive common voltage Vc may be further added to the voltages applied to the electrodes 212a to 212d. The common voltage Vc is set to a value equal to or greater than the upper limit of the voltage applied to the focus correction lens 210. A constant (fixed) value of the common voltage Vc is applied from the deflection control circuit 120 during the drawing process. This allows secondary electrons that have passed through the focus correction lens 210 to move to the fixed deflector 212 without decelerating, thereby preventing secondary electrons from staying between the focus correction lens 210 and the fixed deflector 212 and improving the accuracy of the beam irradiation position.

[0042] The fixed deflector 212 is not limited to a quadrupole deflector, and may be an octupole deflector. Alternatively, as shown in Fig. 8(a), it may be a dipole deflector in which the electrodes 212b and 212d are omitted. The pair of opposing electrodes 212a and 212c may have a flat plate structure as shown in Fig. 8(a), or may have a curved structure in which the surface on the beam passing region side is convex outward as shown in Fig. 8(b).

[0043] The voltage applied to the electrode 212a is V D , the voltage applied to the electrode 212c is −V D When a positive common voltage Vc is added to the applied voltage, the voltage applied to the electrode 212a is Vc+V D , the voltage applied to the electrode 212c is Vc-V D Here, Vc=V D Then, the voltage applied to the electrode 212a is 2V. D Therefore, the voltage applied to the electrode 212c becomes zero, and a power supply for applying a voltage to the electrode 212c can be omitted, thereby reducing costs.

[0044] In the above embodiment, an example in which one fixed deflector 212 is provided has been described, but multiple fixed deflectors may be provided. By combining multiple fixed deflectors, it is possible to reduce distortion and aberration of the electron beam B (primary beam for drawing).

[0045] The multiple fixed deflectors may include both electrostatic and magnetic deflectors. Fig. 9 shows an example of a configuration in which an electrostatic fixed deflector 212 and magnetic field fixed deflectors 213 and 214 are arranged.

[0046] 10, a recess R1 may be formed on the surface of the electrode of the fixed deflector 212 on the side of the beam passing region. A region where the secondary electrons hit is calculated by trajectory simulation of the secondary electrons, and the recess R1 is formed in the calculated region. The recess R1 may also be formed in an electrode where the secondary electrons do not hit.

[0047] By forming the recess R1, the bottom surface of the recess R1 becomes the charging position due to secondary electrons, and compared to a case where the recess R1 is not formed, the charging position is farther from the trajectory of the electron beam B, and even if charging occurs, the deflection sensitivity of the beam decreases, so the beam can be more stabilized. Therefore, the accuracy of the beam irradiation position can be improved.

[0048] As shown in FIG. 11, an aperture plate 260 having a beam passage hole 262 may be provided between the positioning deflector 209 and the fixed deflector 212, and the voltage applied to the fixed deflector 212 may be adjusted so that the secondary electrons hit the aperture plate 260 instead of the fixed deflector 212.

[0049] A recess R2 may be formed on the lower surface of the aperture plate 260 (the surface downstream in the traveling direction of the electron beam B). The area where the secondary electrons hit is calculated by simulating the trajectory of the secondary electrons, and the recess R2 is formed in the calculated area. The upper surface of the recess R2 becomes the charged position by the secondary electrons, and compared to a case where the recess R2 is not present, the charged position is farther from the trajectory of the electron beam B. Even if charging occurs, the deflection sensitivity of the beam decreases, and the beam can be more stabilized. This improves the accuracy of the beam irradiation position.

[0050] The recess R2 may be formed circumferentially so as to surround the beam passing hole 262, or may be formed only partially.

[0051] In some cases, the inner diameter of the magnetic pole of the objective lens 208 on the upstream side in the beam travel direction is increased to widen the lens focusing magnetic field distribution in the upstream direction, thereby reducing aberration and distortion. In this case, the lens focusing magnetic field reaches the fixed deflector, so the secondary electrons move in a direction perpendicular to the deflection electric field, as shown in Figures 12(a) and 12(b). In other words, the deflection voltage V D , -V D The magnetic field moves approximately parallel to the surfaces of the electrodes 212a and 212c to which the magnetic field is being applied.

[0052] By making the length L1 of the electrodes 212a and 212c longer than the length L2 of the electrodes 212b and 212d, the charged position by the secondary electrons becomes farther from the trajectory of the electron beam B, and the deflection sensitivity of the beam decreases, so that the beam can be more stabilized. Therefore, the accuracy of the beam irradiation position can be improved.

[0053] In the above embodiment, a configuration has been described in which the fixed deflector 212 is disposed between the focus correction lens 210 and the positioning deflector 209. However, as shown in FIG. 13, the fixed deflector 212 may also be disposed between the focus correction lens 210 and the substrate 240 (downstream of the focus correction lens 210 in the beam propagation direction).

[0054] When the distance between the substrate 240 and the focus correction lens 210 is short, the electrodes of the fixed deflector 212 may be in the form of divided rings formed by dividing a thin ring, as shown in FIGS.

[0055] As shown in FIG. 16, an aperture h through which electrons reflected by a substrate 240 pass may be formed in a divided annular electrode, and an electron detector 270 for detecting the mark position may be disposed above the aperture h.

[0056] In the above embodiment, a configuration using an electron beam has been described as an example of a charged particle beam, but the charged particle beam is not limited to an electron beam, and may be a beam using charged particles such as an ion beam.

[0057] In the above embodiment, a configuration using a single beam has been described, but a configuration using multiple beams may also be used.

[0058] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0059] 100 Control section 110 Control computer 208 Objective Lens 209 Positioning deflector 210 Focus correction lens 212 Fixed deflector

Claims

1. a positioning deflector that adjusts an irradiation position of the charged particle beam irradiated onto a substrate to be written; a fixed deflector that is disposed downstream of the positioning deflector in a traveling direction of the charged particle beam and has a fixed deflection amount; a focus correction lens for correcting the focus of the charged particle beam in accordance with the surface height of the substrate; an objective lens for focusing the charged particle beam; Equipped with The fixed deflector has an electrostatic deflector, and fixed deflection voltages V D and -V D are applied to at least one pair of opposing electrodes among a plurality of electrodes constituting the electrostatic deflector, for deflecting secondary electrons emitted when the substrate is irradiated with the charged particle beam toward the fixed deflector.

2. 2. The charged particle beam writing apparatus of claim 1, wherein the focus correction lens is an electrostatic lens and operates in a positive voltage range with respect to the surface of the substrate.

3. A positioning deflector that adjusts an irradiation position of a charged particle beam that is irradiated onto a substrate to be written; a fixed deflector that is disposed downstream of the positioning deflector in a traveling direction of the charged particle beam and has a fixed deflection amount; a focus correction lens for correcting the focus of the charged particle beam in accordance with the surface height of the substrate; an objective lens for focusing the charged particle beam; Equipped with The fixed deflector has an electrostatic deflector, and a voltage obtained by adding a positive common voltage with respect to the surface of the substrate to fixed deflection voltages V D and -V D for deflecting secondary electrons emitted when the substrate is irradiated with the charged particle beam toward the fixed deflector is applied to at least one pair of opposing electrodes among a plurality of electrodes constituting the electrostatic deflector, in a charged particle beam drawing device.

4. 4. The charged particle beam writing apparatus according to claim 3, wherein the focus correction lens is an electrostatic lens, and the positive common voltage is equal to or greater than a voltage applied to the focus correction lens.

5. 5. The charged particle beam drawing apparatus according to claim 4, wherein a voltage twice as high as said common voltage is applied to one of said pair of opposing electrodes, and a voltage applied to the other electrode is set to zero.

6. 6. The charged particle beam drawing apparatus according to claim 1, wherein the focus correction lens is disposed downstream of the positioning deflector in the traveling direction of the charged particle beam.

7. 7. The charged particle beam drawing apparatus according to claim 6, wherein the fixed deflector is disposed downstream of the focus correction lens in the traveling direction of the charged particle beam.

8. 7. The charged particle beam drawing apparatus according to claim 6, wherein the fixed deflector is disposed upstream of the focus correction lens in the traveling direction of the charged particle beam.

9. 9. The charged particle beam drawing apparatus according to claim 1, wherein the fixed deflector is composed of a plurality of stages of deflectors.

10. 10. The charged particle beam writing apparatus according to claim 9, wherein the fixed deflector includes an electrostatic deflector and a magnetic deflector.

11. A charged particle beam drawing apparatus as described in any one of claims 1 to 10, wherein a recess is provided on the surface of at least one of the multiple electrodes constituting the electrostatic deflector on the beam passing region side.

12. 12. The charged particle beam writing apparatus according to claim 1, further comprising an aperture plate provided between the positioning deflector and the fixed deflector.

13. 13. The charged particle beam drawing apparatus according to claim 12, wherein a recess is provided on a surface of the aperture plate on a downstream side in a traveling direction of the charged particle beam.

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