Charged particle beam drawing device

Abstract

The present application provides a charged particle beam drawing device capable of simultaneously solving the spatial retention of secondary electrons and the variation of beam position caused by the charging of deflector electrodes. The charged particle beam drawing device of the present embodiment includes a positioning deflector that adjusts the irradiation position of a charged particle beam irradiated to a substrate of a drawing object; a fixed deflector disposed at a position downstream of the positioning deflector in the traveling direction of the charged particle beam, with a fixed deflection amount; a focus correction lens that performs focus correction of the charged particle beam in accordance with the surface height of the substrate; and an objective lens that focuses the focus of the charged particle beam.

Description

[0001] Related applications

[0002] This application enjoys priority based on Japanese Patent Application No. 2021-067803 (filed on April 13, 2021). This application includes all contents of the basic application by reference to that basic application. Technical Field

[0003] This invention relates to a charged particle beam mapping apparatus. Background Technology

[0004] With the increasing integration of LSI (Light Silicon Integrated Systems), the required linewidths for semiconductor devices are becoming smaller year by year. To form the desired circuit patterns on semiconductor devices, the following method is used: a reduction projection exposure device is used to reduce and transfer a high-precision original pattern (mask, or especially the original pattern used in steppers and scanners, also called a mask reticle) formed on quartz onto the wafer. The high-precision original pattern is drawn by an electron beam lithography device, using what is known as electron beam lithography.

[0005] In an electron beam mapping apparatus, an objective lens is used to focus each emitted beam onto the sample surface, which serves as the substrate. An electrostatic lens is used to dynamically correct the focus during mapping in a manner that corresponds to the unevenness of the sample surface (dynamic focusing). When this electrostatic lens is used within a negative voltage range, secondary electrons generated by electron beam mapping return to the sample surface, thereby charging the resist and hindering the improvement of the positional accuracy of the mapped pattern.

[0006] To suppress the effects of the return of secondary electrons, it is preferable to use an electrostatic lens with a positive (plus) voltage range over the sample surface to guide the secondary electrons upward from the sample.

[0007] However, when using an electrostatic lens within a positive voltage range, secondary electrons from the sample surface decelerate rapidly after passing through the electrostatic lens and remain in the beam trajectory at a high density, or cause non-conductive dirt (contamination) on the inner surface of the deflector electrodes to become charged, thereby causing changes in the electric field near the electron beam, changes in the electron beam trajectory, and deterioration of the beam position accuracy. Summary of the Invention

[0008] The present invention provides a charged particle beam mapping device that can simultaneously solve the problems of spatial retention of secondary electrons and beam position variation caused by the charging of deflector electrodes.

[0009] One aspect of the charged particle beam painting apparatus of the present invention includes: a positioning deflector for adjusting the irradiation position of a charged particle beam irradiating a substrate onto which the beam is to be painted; a fixing deflector disposed at a position downstream of the positioning deflector in the direction of travel of the charged particle beam, and having a fixed deflection amount; a focus correction lens for performing focus correction of the charged particle beam at a height relative to the surface of the substrate; and an objective lens for focusing the charged particle beam. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of an electron beam mapping apparatus according to an embodiment of the present invention.

[0011] Figure 2 It is a three-dimensional view of the first forming aperture and the second forming aperture.

[0012] Figure 3 This is a cross-sectional view of the objective lens.

[0013] Figure 4 A, Figure 4 B is a diagram illustrating the orbitals of the secondary electrons in the comparative example.

[0014] Figure 5 A, Figure 5 B is a diagram illustrating the orbitals of the secondary electrons in this embodiment.

[0015] Figure 6 This is a diagram illustrating an example of the applied voltage of a fixed deflector.

[0016] Figure 7 This is a diagram illustrating an example of the applied voltage of a fixed deflector.

[0017] Figure 8 A, Figure 8 B is a diagram showing an example of the configuration of a fixed deflector.

[0018] Figure 9 This is a diagram illustrating an example of configuring multiple fixed deflectors.

[0019] Figure 10 This is a schematic diagram of the fixed deflector in a modified example.

[0020] Figure 11 This is a diagram showing an example of a perforated plate configuration.

[0021] Figure 12 A, Figure 12 B is a diagram illustrating the orbital pattern of the secondary electron.

[0022] Figure 13 This diagram shows a configuration where a fixed deflector is positioned below the focal correction lens.

[0023] Figure 14 This is a diagram showing an example of the configuration of a fixed deflector.

[0024] Figure 15 yes Figure 14 XV-XV line cross-section diagram.

[0025] Figure 16 This diagram shows a configuration in which an electronic detector is positioned above a fixed deflector.

[0026] Explanation of reference numerals in the attached figures

[0027] 100 Control Department

[0028] 110 Control Computer

[0029] 208 Objective Lens

[0030] 209 Positioning Deflector

[0031] 210 Focus Correction Lens

[0032] 212 Fixed deflector Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic diagram of an electron beam mapping apparatus according to an embodiment of the present invention. Figure 1 The electron beam drawing apparatus shown is a shape-changing drawing apparatus equipped with a control unit 100 and a drawing unit 200.

[0035] The drawing unit 200 includes an electron optical lens barrel 220 and a drawing chamber 230. The electron optical lens barrel 220 is equipped with an electron gun 201, an illumination lens 202, a blanking device 203, a first forming aperture component 204, a projection lens 205, a forming deflector 206, a second forming aperture component 207, an objective lens 208, a positioning deflector 209, a focus correction lens 210, and a fixed deflector 212.

[0036] An XY stage 232 is arranged inside the drawing chamber 230. A substrate 240, on which the drawing object is to be drawn, is placed on the XY stage 232. A Z-sensor 250, which detects the height (Z-direction) position of the substrate 240, is arranged at the top of the drawing chamber 230. The Z-sensor 250 is a combination of a projector and a receiver, causing light irradiated from the projector to be reflected on the surface of the substrate 240, and the receiver receives the reflected light, thereby enabling the determination of the surface height of the substrate 240. The substrate 240 is fixed to a ground potential.

[0037] The height data detected by the Z sensor 250 is converted into digital data by the detection circuit 150 and then transmitted to the control computer 110.

[0038] The electron beam B emitted from the electron gun 201 (release section) located in the electron optical lens barrel 220 passes through the blanking device (blanking deflector) 203, and the blanking device 203 switches whether to irradiate the substrate with the electron beam.

[0039] Electron beam B illuminates the rectangular opening 32 (see reference 202) through illumination lens 202. Figure 2 The first forming aperture component 204 is integral. The electron beam B passes through the opening 32 of the first forming aperture component 204, thereby being formed into a rectangle.

[0040] The electron beam B, having passed through the first aperture image of the first forming aperture component 204, is projected by the projection lens 205 onto a surface having a variable forming opening 34 (see reference). Figure 2 The first aperture image projected onto the second forming aperture component 207 is deflected and controlled by the forming deflector 206, which enables the shape and size of the electron beam passing through the variable forming opening 34 to change (perform variable forming).

[0041] The electron beam B of the second aperture image, which has passed through the variable forming opening 34 of the second forming aperture component 207, is deflected by the positioning deflector 209, focused by the objective lens 208 and the focus correction lens 210, and irradiates the substrate 240 placed on the continuously moving XY stage 232.

[0042] The positioning deflector 209 deflects the irradiated electron beam to the desired location. It can be a single-stage deflector or a multi-stage deflector composed of deflection regions of different sizes. For example, it can be a two-stage structure consisting of a main deflector and a secondary deflector, or a three-stage structure consisting of a main deflector, a secondary deflector, and a secondary secondary deflector.

[0043] Although electromagnetic lenses (magnetic field type lenses) are used in the illumination lens 202, projection lens 205, and objective lens 208, some or all of them can also be electrostatic lenses. The focus correction lens 210 performs dynamic focusing adjustment for height variations on the surface of the substrate 240. Although an electrostatic lens is used, an electromagnetic lens (including a coil that generates an axisymmetric magnetic field) can also be used. Alternatively, it can be constructed as a multi-stage lens system where the applied voltage and excitation current change in a specific relationship. Alternatively, the objective lens 208 can also possess the function of the focus correction lens 210, and the objective lens 208 and focus correction lens 210 can be configured to perform focusing adjustment in a specific relationship.

[0044] The fixed deflector 212 is positioned downstream of the positioning deflector 209 in the direction of travel of the electron beam B. The fixed deflector 212 is an electrostatic deflector. The focus correction lens 210 is positioned downstream of the fixed deflector 212 in the direction of travel of the electron beam B.

[0045] Figure 2 This is a schematic diagram illustrating beam shaping based on the first forming aperture component 204 and the second forming aperture component 207. A rectangular opening 32 for shaping the electron beam B is formed in the first forming aperture component 204.

[0046] Furthermore, a variable forming opening 34 is formed in the second forming aperture component 207 for shaping the electron beam B, after passing through the opening 32 of the first forming aperture component 204, into a desired shape. The beam shapes passing through both the opening 32 of the first forming aperture component 204 and the variable forming opening 34 of the second forming aperture component 207 are depicted on the depiction area of ​​the substrate 240 mounted on the continuously moving XY stage 232.

[0047] like Figure 1 As shown, the control unit 100 includes a control computer 110, a deflection control circuit 120, a storage unit 130, a lens control circuit 140, and a detection circuit 150. Depiction data, which becomes layout data, is input from an external source into the storage unit 130 and stored.

[0048] The control computer 110 includes a data transmission generation unit 111 and a rendering control unit 112. Each part of the control computer 110 can be constructed using hardware such as electronic circuits or software. In the case of software construction, a program implementing at least a portion of the functions of the control computer 110 can be stored in a recording medium, which can then be read and executed by a computer containing a CPU. The recording medium is not limited to removable recording media such as disks or optical discs, but can also be a fixed recording medium such as a hard disk drive or a memory.

[0049] The launch data generation unit 111 reads the depiction data from the storage unit 130 and performs multi-level data conversion processing to generate launch data. The launch data includes information such as launch shape, launch size, launch location, and launch time.

[0050] The drawing control unit 112 transmits the launch data to the deflection control circuit 120 according to the launch sequence. The deflection control circuit 120 uses the launch data to control the deflection amount of the blanking deflector 203, the shaping deflector 206, and the positioning deflector 209, and performs drawing processing.

[0051] In addition, the deflection control circuit 120 applies a certain (fixed) voltage to the fixed deflector 212 during the drawing process.

[0052] 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.

[0053] Objective lens 208 is an electromagnetic lens, such as Figure 3 As shown, there is a coil 208a and a yoke 208b that houses the coil 208a. The yoke 208b is made of a material with high magnetic permeability, such as iron, and has a notch (pole 208c) in a portion.

[0054] The magnetic field lines generated by the current flowing through the coil 208a leak into the space through the pole piece 208c, generating a magnetic field.

[0055] The focus correction lens 210 is configured, for example, to fit closely to the interior of the objective lens 208, such as the electrode 208c. The focus correction lens 210 is an electrostatic lens with an annular electrode. A positive voltage is applied to this electrode, and the focus correction lens 210 is used within the positive voltage range. As a result, secondary electrons are attracted to the electrode side, suppressing positional changes caused by the charge on the resist.

[0056] If the electron beam B (primary beam) irradiates the substrate 240, secondary electrons are released from the substrate surface. The secondary electrons enter upwards within the electron optical lens barrel 220.

[0057] During the painting process, the resist on the surface of the substrate 240 evaporates due to beam irradiation, leaving contaminants (dirt) adhering to the electrode surface of the positioning deflector 209. Without the fixing deflector 212, as... Figure 4 As shown in Figure A, the secondary electrons become charged by the contamination on the electrode surface of the positioning deflector 209, causing the trajectory of the electron beam B to change.

[0058] like Figure 4 As shown in Figure B, if the voltage applied to the electrodes of the positioning deflector 209 is changed, causing a change in the beam deflection position (beam irradiation position in the substrate 240), the intensity and direction of the electric field within the positioning deflector 209 change, and the arrival position of the secondary electrons, i.e., their charged position, changes significantly across the electrodes. Due to this significant change in the charged position, a large change in the electric field near the beam occurs, resulting in a large variation (drift) in the beam irradiation position.

[0059] Therefore, in this embodiment, a fixed deflector 212 is provided between the focus correction lens 210 and the positioning deflector 209, and a fixed voltage is applied to the fixed deflector 212. During the drawing process, since the applied voltage to the fixed deflector 212 is not changed, the deflection amount of the fixed deflector 212 is fixed. Figure 5 As shown in Figure A, the secondary electrons are laterally deflected toward the fixed deflector 212 and removed from the vicinity of the electron beam B's trajectory, barely reaching the positioning deflector 209.

[0060] Secondary electrons deflected by the fixed deflector 212 reach the electrodes of the fixed deflector 212, generating a charge on the electrodes. For example... Figure 5 As shown in Figure B, even when the beam irradiation position is changed by altering the applied voltage to the positioning deflector 209, the arrival position (charged position) of the secondary electrons remains unchanged because the deflection voltage (deflection excitation) of the fixed deflector 212 is constant. Therefore, the change in the electric field near the electron beam (including the change in direction) is small, and consequently, the variation in the beam irradiation position is also small. Thus, the beam position accuracy can be improved.

[0061] Generally speaking, the energy of secondary electrons (below tens of eV) is extremely low compared to the energy of the electron beam B used for mapping (around 50kV). Therefore, even if the secondary electrons are deflected, the electron beam B will hardly be deflected, and it will have almost no effect on the optical properties.

[0062] Figure 6 An example of an applied voltage to a fixed deflector 212 is shown. Figure 6 As shown, when the fixed deflector 212 is an electrostatic quadrupole deflector with four electrodes 212a to 212d, a fixed deflection voltage V is applied to the opposing pair of electrodes 212a and 212c respectively. D -V D The remaining electrodes 212b and 212d are fixed at ground potential. Considering the specifications of the fixed deflector 212, the deflection voltage V is determined through numerical simulation. D -V D For example, the deflection voltage V D It is above 20V. The space surrounded by the four electrodes 212a to 212d becomes the passage region of electron beam B.

[0063] like Figure 7As shown, a positive common voltage Vc can also be added to the voltage applied to electrodes 212a-212d. The common voltage Vc is set to a value above the upper limit of the voltage applied to the focus correction lens 210. The common voltage Vc is applied at a certain (fixed) value from the deflection control circuit 120 during the drawing process. As a result, the secondary electrons passing through the focus correction lens 210 move towards the fixed deflector 212 without deceleration, thus preventing the retention of secondary electrons between the focus correction lens 210 and the fixed deflector 212 and improving the beam irradiation position accuracy.

[0064] The fixed deflector 212 is not limited to a four-pole deflector; it can also be an eight-pole deflector. Additionally, as... Figure 8 As shown in A, it can also be a diode deflector with electrodes 212b and 212d omitted. The opposing pair of electrodes 212a and 212c can be... Figure 8 The flat plate structure shown in Figure A can also be... Figure 8 As shown in B, it becomes a structure that bends outward from the surface on the side where the beam passes through.

[0065] Let the voltage applied to electrode 212a be V. D The applied voltage to electrode 212c is set to -V. D When a positive common voltage Vc is applied to the applied voltage, the applied voltage to electrode 212a is Vc + Vc. D The voltage applied to electrode 212c is Vc - V D Here, if Vc = V D The voltage applied to electrode 212a is 2V. D The voltage applied to electrode 212c is 0, which eliminates the need for a power supply to apply voltage to electrode 212c and reduces costs.

[0066] In the above embodiment, an example of setting one fixed deflector 212 was described, but multiple fixed deflectors can also be set. By combining multiple fixed deflectors, distortion and aberrations of the electron beam B (the primary beam used for mapping) can be reduced.

[0067] Multiple fixed deflectors can also include both electrostatic deflectors and magnetic field deflectors. Figure 9 An example of a configuration is shown, which includes an electrostatic type fixed deflector 212 and magnetic field type fixed deflectors 213 and 214.

[0068] like Figure 10 As shown, a recess R1 can also be formed on the surface of the electrode of the fixed deflector 212 on the side of the beam passage region. The area of ​​secondary electron collision is calculated by means of secondary electron trajectory simulation, etc., and the recess R1 is formed in the calculated area. The recess R1 can also be formed on the electrode where secondary electrons do not collide.

[0069] By forming a recess R1, the bottom surface of the recess R1 becomes a charged position brought about by secondary electrons. Compared with the case without a recess R1, the charged position is far away from the trajectory of the electron beam B. Even if a charge is generated, the deflection sensitivity of the beam decreases, thus making the beam more stable. As a result, the accuracy of the beam irradiation position can be improved.

[0070] like Figure 11 As shown, an aperture plate 260 with a beam passage hole 262 can also be provided between the positioning deflector 209 and the fixed deflector 212, and the applied voltage of the fixed deflector 212 can be adjusted so that the secondary electrons collide with the aperture plate 260 instead of the fixed deflector 212.

[0071] Alternatively, a recess R2 can be formed on the lower surface of the aperture plate 260 (the surface downstream of the electron beam B's travel direction). The collision area of ​​secondary electrons is calculated through simulations of secondary electron trajectories, and the recess R2 is formed within this calculated area. The upper surface of the recess R2 becomes the charged position resulting from the secondary electrons. Compared to the case without the recess R2, the charged position is farther from the electron beam B's trajectory. Even with the generated charge, the beam deflection sensitivity decreases, thus making the beam more stable. This improves the accuracy of the beam irradiation position.

[0072] The recess R2 can be formed in a circumferential shape to surround the beam through hole 262, or it can be formed only in a part of it.

[0073] Sometimes, aberrations and distortions are reduced by increasing the inner diameter of the magnetic pole on the upstream side of the objective lens 208 in the beam-tracing direction, thereby expanding the lens-gathering magnetic field distribution in the upstream direction. In this case, since the lens-gathering magnetic field reaches the fixed deflector, secondary electrons, such as Figure 12 A, Figure 12 As shown in Figure B, it moves in a direction perpendicular to the deflection electric field. In other words, it moves in a direction perpendicular to the applied deflection voltage V. D -V D The surfaces of electrodes 212a and 212c move approximately parallel to each other.

[0074] By making the length L1 of electrodes 212a and 212c longer than the length L2 of electrodes 212b and 212d, the charged position brought about by secondary electrons is moved away from the trajectory of electron beam B, reducing the beam deflection sensitivity and thus making the beam more stable. This improves the accuracy of the beam irradiation position.

[0075] In the above embodiments, a configuration in which the fixed deflector 212 is disposed between the focus correction lens 210 and the positioning deflector 209 has been described, but as Figure 13As shown, a fixed deflector 212 can also be disposed between the focus correction lens 210 and the substrate 240 (at a position downstream of the focus correction lens 210 in the beam travel direction).

[0076] When the distance between the substrate 240 and the focus correction lens 210 is short, it is also possible to... Figure 14 , Figure 15 The electrodes of the fixed deflector 212 are formed into a segmented ring shape, as shown.

[0077] like Figure 16 As shown, an opening h can also be formed on the segmented annular electrode to allow electrons reflected by the substrate 240 to pass through, and an electron detector 270 for detecting the mark position can be disposed above the opening h.

[0078] In the above embodiments, an example of a charged particle beam is described using an electron beam, but the charged particle beam is not limited to an electron beam, and may also be a beam using charged particles such as an ion beam.

[0079] In the above embodiments, a configuration using a single beam was described, but multiple beams can also be used.

[0080] Furthermore, this invention is not limited to the embodiments described above. During implementation, the constituent elements can be modified and embodied by variations without departing from its spirit. Additionally, various inventions can be formed through appropriate combinations of the multiple constituent elements disclosed in the above embodiments. For example, several constituent elements may be deleted from all the constituent elements shown in the embodiments. Moreover, constituent elements from different embodiments may be appropriately combined.

Claims

1. A charged particle beam mapping device, comprising: Positioning deflector to adjust the irradiation position of the charged particle beam irradiating the substrate of the object being depicted; A fixed deflector is positioned downstream of the positioning deflector in the direction of travel of the charged particle beam, and the deflection amount of the fixed deflector is fixed during the drawing process. A focus correction lens is used in conjunction with the surface of the substrate to perform focus correction on the charged particle beam. as well as The objective lens focuses the charged particle beam. The focus-correcting lens is an electrostatic lens that operates within a positive voltage range relative to the surface of the substrate. The fixed deflector includes an electrostatic deflector, wherein the voltage applied to each of the plurality of electrodes constituting the electrostatic deflector is supplemented with a common voltage that is positive relative to the surface of the substrate. The positive common voltage is greater than or equal to the voltage applied to the focus correction lens. The focus correction lens is positioned downstream of the positioning deflector in the direction of travel of the charged particle beam. The fixed deflector is positioned upstream of the charged particle beam in the direction of travel, relative to the focal correction lens.

2. The charged particle beam mapping device according to claim 1, One of the opposing electrodes in the plurality of electrodes is subjected to a voltage twice the common voltage, while the applied voltage to the other electrode is set to zero.

3. The charged particle beam mapping device according to claim 1, The fixed deflector consists of multiple deflectors.

4. The charged particle beam mapping device according to claim 3, The fixed deflector includes an electrostatic deflector and a magnetic field deflector.

5. The charged particle beam mapping apparatus according to claim 1, A recess is provided on the surface of at least one electrode of the plurality of electrodes constituting the electrostatic deflector on the beam-passing area side.

6. The charged particle beam mapping apparatus according to claim 1, It also includes a perforated plate located between the positioning deflector and the fixed deflector.

7. The charged particle beam mapping apparatus according to claim 6, A recess is provided on the downstream side of the aperture plate in the direction of travel of the charged particle beam.

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