Electron beam mapping apparatus and electron beam mapping method

Abstract

The objective of this invention is to suppress the influence of secondary electrons on the beam trajectory while detecting beam current using an aperture substrate. The electron beam drawing apparatus includes: an emitting unit that emits an electron beam; an aperture substrate having an opening through which the electron beam passes and partially shielding the electron beam; a deflector that deflects the electron beam passing through the opening of the aperture substrate, irradiating a substrate to be drawn with the electron beam to draw a pattern; a wiring connected to the aperture substrate for current flow based on the electron beam shielded by the aperture substrate; a current detector connected to the wiring for detecting the current; and a voltage reduction element connected in series with the wiring connecting the aperture substrate and the current detector to apply a negative potential to the aperture substrate. This invention also provides an electron beam drawing method.

Description

Technical Field

[0001] This invention relates to an electron beam mapping apparatus and an electron beam mapping method. Prior Technology

[0002] With the increasing integration of Large Scale Integration (LSI), the required linewidths for semiconductor devices are becoming smaller year by year. To form the desired circuit pattern on a semiconductor device, the following method is used: a reduction projection exposure device is used to reduce and transfer a high-precision original pattern (mask, or, especially, reticles in steppers or scanners) formed on a quartz wafer onto the wafer. The high-precision original pattern is then drawn using an electron beam lithography device, employing a technique known as electron beam lithography.

[0003] As shown in Figure 8, in the electron beam mapping apparatus, an electron gun 200 is installed inside a grounded electron optical lens barrel 102. A high voltage is applied to the electron gun 200 using a high-voltage power supply P, and an electron beam B is emitted. A deflector (not shown) is used to deflect the electron beam B and draw a pattern on the sample S. The electron beam B emitted from the electron gun 200 irradiates the sample S through multiple aperture substrates AS disposed in the electron optical lens barrel 102. The multiple aperture substrates AS include aperture substrates for appropriately cutting the beam amount, aperture substrates for cutting the electron beam B from the sample surface, aperture substrates for monitoring the beam amount, and aperture substrates for beam shaping. By passing the electron beam B through the multiple aperture substrates AS, the beam current or beam shape is adjusted.

[0004] A portion of the multiple aperture substrates AS constitutes part of the beam current detection mechanism and is connected to the current detector 400 via a coaxial cable L. Electrons (electron beam B) emitted from the electron gun 200 and irradiating the sample S return to the high-voltage power supply P that powers the electron gun 200 via the electron optical lens 102. Additionally, electrons irradiating the aperture substrates AS return to the high-voltage power supply P via the coaxial cable L, the current detector 400, the electron optical lens 102, etc.

[0005] The current detector 400 detects the beam current of the electron beam irradiating the aperture substrate AS. Based on the detection results of the current detector 400, variations in the beam current or the presence or absence of discharge are monitored. The beam current detection mechanism (current detector 400, aperture substrate AS) operates at or near ground potential (0 V).

[0006] When an electron beam is irradiated onto the aperture substrate AS, secondary electrons, including reflected electrons, are generated. These secondary electrons, which may remain on the beam track, could potentially affect the track of the electron beam B. [Existing Technical Documents] [Patent Literature]

[0007] Patent Document 1: Japanese Patent Application Publication No. 5-174774 Patent Document 2: Japanese Patent Application Publication No. 2012-114127 Patent Document 3: Japanese Patent Application Publication No. 2009-70944 Summary of the Invention

[0008] [The problem that the invention aims to solve] The objective of this invention is to provide an electron beam mapping apparatus and method that can suppress the influence of secondary electrons on the beam trajectory while detecting beam current using an aperture substrate. [Methods for solving problems]

[0009] An electron beam drawing apparatus according to the present invention includes: an emitting unit for emitting an electron beam; an aperture substrate having an opening through which the electron beam passes and partially shielding the electron beam; a deflector for deflecting the electron beam passing through the opening of the aperture substrate and irradiating a substrate to be drawn with the electron beam to draw a pattern; a wiring connected to the aperture substrate for supplying current based on the electron beam shielded by the aperture substrate; a current detector connected to the wiring for detecting the current; and a voltage drop element connected in series with the wiring connecting the aperture substrate and the current detector to apply a negative potential to the aperture substrate. [The effects of the invention]

[0010] This invention enables the detection of beam current using an aperture substrate while suppressing the influence of secondary electrons on the beam trajectory. Simple Explanation of the Diagram

[0011] Figure 1 is a schematic structural diagram of the drawing device in an embodiment of the present invention. Figure 2 is a conceptual diagram representing the primary deflection region and the secondary deflection region. Figure 3 is a diagram illustrating the voltage drop caused by the resistor. Figure 4A is a diagram showing an example of a voltage drop element. Figure 4B is a diagram showing an example of a voltage drop element. Figure 4C is a diagram showing an example of a voltage drop element. Figure 5 is a diagram showing the structure of applying a negative potential to an aperture substrate based on a comparative example. Figure 6 is a diagram showing the beam current detection structure based on the comparative example. Figure 7 is a diagram showing the beam current detection structure based on the implementation configuration. Figure 8 is a diagram showing the beam current detection structure based on the comparative example. Implementation

[0012] Hereinafter, embodiments of the present invention will be described based on the drawings. In this embodiment, as an example of an electron beam drawing apparatus, a drawing apparatus 100 with a variable shape will be described.

[0013] Figure 1 is a schematic structural diagram of the drawing apparatus according to an embodiment of the present invention. As shown in Figure 1, the drawing apparatus 100 includes a drawing unit W and a control unit C. The drawing unit W includes a grounded electron optical lens barrel 102 and a drawing chamber 103. An electron gun 200, a first illumination lens 202, a current limiting aperture substrate 204, a blocking deflector 206, a second illumination lens 208, a blocking aperture substrate 210, a first forming aperture substrate 212, a projection lens 214, a forming deflector 216, a second forming aperture substrate 218, a main deflector 220, a secondary deflector 222, and an objective lens 224 may also be provided below the main deflector 220.

[0014] An XY stage 105 capable of moving along the XY direction is disposed within the drawing chamber 103. A substrate 101, which is the object to be drawn, is disposed on the XY stage 105. The substrate 101 includes a mask or silicon wafer for exposure in the manufacture of semiconductor devices. The mask includes mask blanks.

[0015] The control unit C includes a control computer 110, a deflection control circuit 120, a digital-to-analog converter (DAC) amplifier unit 130, a current detector 140, etc. Figure 1 shows a DAC amplifier unit 130, but it is equipped with DAC amplifier units corresponding to each deflector, such as the masking deflector 206, the shaping deflector 216, the main deflector 220, and the secondary deflector 222.

[0016] The electron gun 200 is connected to a high-voltage power supply circuit (see Figure 8). By applying an accelerating voltage from the high-voltage power supply circuit to the filament (cathode) and the lead-out electrode (anode) inside the electron gun 200 (not shown), applying voltage to other lead-out electrodes (Wehnelt), and heating the cathode, the electron group emitted from the anode is accelerated and becomes an electron beam B and emitted.

[0017] The electron beam B emitted from the electron gun 200 (emitting section) propagates while exhibiting a certain degree of diffusion, illuminating the current-limiting aperture substrate 204 with an opening formed by the first illumination lens 202. When the electron beam B passes through the opening of the current-limiting aperture substrate 204, electrons (electron beams) in the peripheral region are blocked by the current-limiting aperture substrate 204, and only electrons (electron beams) in the central region pass through the opening. The current-limiting aperture substrate 204 limits the amount of electron beam B passing through. The current-limiting aperture substrate 204 is a metal plate made of a non-magnetic, non-charged metal such as tantalum. The current-limiting aperture substrate 204 has a rectangular shape in top view, and a circular opening is formed in its center. Preferably, the center of the current-limiting aperture substrate 204 coincides with the center of the circular opening.

[0018] The electron beam B passing through the current-limiting aperture substrate 204 is controlled by the shielding deflector 206 so that it passes through the shielding aperture substrate 210 in the beam-on state, and is deflected by the shielding deflector 206 so that the entire beam is shielded by the shielding aperture substrate 210 in the beam-off state. From the beam-off state to the beam-on state, and then before the beam is turned off, the electron beam B passing through the shielding aperture substrate 210 constitutes an electron beam exposure.

[0019] The deflector 206 controls the trajectory of the passing electron beam B to alternately generate a beam-on state and a beam-off state. For example, no voltage is applied when the beam is on, and a voltage is applied to the deflector 206 when the beam is off. The irradiation amount of the electron beam B irradiating the substrate 101 for each exposure time is adjusted.

[0020] As described above, the electron beams B generated by the shielding deflector 206 and the shielding aperture substrate 210 are used to illuminate the first shaped aperture substrate 212 with a rectangular opening using the second illumination lens 208. Here, the electron beams B are first shaped into rectangles.

[0021] Then, the electron beam B, which has passed through the aperture image of the first forming aperture substrate 212, is projected onto the second forming aperture substrate 218 by the projection lens 214. The aperture image on the second forming aperture substrate 218 can be deflected and controlled by the forming deflector 216 to change the beam shape and size. This variable forming is performed for each exposure, typically with different beam shapes and sizes for each exposure.

[0022] The electron beam B, having passed through the second-shaped aperture substrate 218, is focused by the objective lens 224, deflected by the main deflector 220 and the sub-deflector 222, and irradiates the substrate 101 disposed on the continuously moving XY stage 105 at the desired position. As described above, multiple exposures of the electron beam B are sequentially deflected onto the substrate 101 by the respective deflectors.

[0023] Figure 2 is a conceptual diagram showing the main deflection region and the sub-deflection region. As shown in Figure 2, when the desired pattern is drawn using the drawing device 100, the drawing area of ​​the substrate 101 is divided into multiple drawing areas (stripes) 1 in the Y direction with a width that can be deflected by the main deflector 220. Moreover, each stripe 1 is also divided in the X direction with the same width as the stripe in the Y direction. The divided area becomes the main deflection region 2 that can be deflected by the main deflector 220. The area after further subdividing the main deflection region 2 becomes the sub-deflection region 3 (or subdomain).

[0024] The secondary deflector 222 is used to control the position of the electron beam B for each exposure at high speed and with high precision. Therefore, the deflection range of the secondary deflector 222 is limited to the secondary deflection region 3, and deflection outside this region is performed by the primary deflector 220. The primary deflector 220 is used to determine the secondary deflection region 3 of the object being depicted, and performs beam deflection within a range (primary deflection region 2) that includes multiple secondary deflection regions 3. In addition, since the XY stage 105 moves continuously along the X direction during depiction, the movement of the XY stage 105 can be tracked by moving the depiction origin of the secondary deflection region 3 at any time using the primary deflector 220.

[0025] The control computer 110 reads the drawing data from the storage unit (not shown) and performs multiple data conversion processes to generate exposure data. The exposure data includes information such as exposure shape, exposure size, exposure position, and exposure time.

[0026] The control computer 110 transmits exposure data to the deflection control circuit 120 according to the exposure sequence. The deflection control circuit 120 uses the exposure data to output deflection signals that control the deflection amounts of the masking deflector 206, the shaping deflector 216, the main deflector 220, and the secondary deflector 222. The DAC amplifier unit 130 performs digital-to-analog conversion on the deflection signals output from the deflection control circuit 120, amplifies them, and outputs the deflection voltage applied to each deflector.

[0027] As described above, when electron beam B passes through the opening formed in the current-limiting aperture substrate 204, a portion of electron beam B is blocked by the current-limiting aperture substrate 204. In other words, a portion of electron beam B irradiates the current-limiting aperture substrate 204. The current detector 140 detects the current value of the beam current irradiating the current-limiting aperture substrate 204 (which is blocked by the current-limiting aperture substrate 204) and outputs the detection result to the control computer 110. Based on the detection result of the current detector 140, the control computer 110 monitors changes in the beam current of the electron beam emitted from the electron gun 200, or the generation of discharge within the electron optical tube 102.

[0028] In this embodiment, a resistor 142 is connected in series with the wiring that connects the current limiting aperture substrate 204, which has a circular opening at its center, and the current detector 140. Specifically, one end of the resistor 142 is connected to the current limiting aperture substrate 204 via a coaxial cable or other wiring, and the other end of the resistor 142 is connected to the terminal of the current detector 140 via a coaxial cable or other wiring.

[0029] Irradiated electrons that irradiate the current-limiting aperture substrate 204 flow toward the current detector 140 via wiring and resistor 142. At this time, the flow of electrons is opposite to the flow of current, so current flows from the current detector 140 toward the current-limiting aperture substrate 204.

[0030] When current flows from the current detector 140 toward the current limiting aperture substrate 204, a voltage drop is generated by the resistor 142, so that the potential of the current limiting aperture substrate 204 is lower than that of the current detector 140. As shown in FIG3, when the current detector 140 is operated at ground potential (0 V), a negative potential (e.g., -1 V) is applied to the current limiting aperture substrate 204.

[0031] When a negative potential is applied to the current-limiting aperture substrate 204, secondary electrons emitted from the current-limiting aperture substrate 204 are accelerated towards the upstream side of the optical path (beam travel direction) and diffuse upwards. Therefore, compared to the case where the aperture substrate AS is at ground potential as shown in Figure 8, the density of secondary electrons remaining on the beam track is reduced, thus suppressing the influence of secondary electrons on the beam track and improving the accuracy of beam irradiation position.

[0032] The resistance value of resistor 142 is determined based on the potential applied to the current-limiting aperture substrate 204. In other words, by adjusting the resistance value of resistor 142, a desired negative potential can be applied to the current-limiting aperture substrate 204.

[0033] In the described embodiment, a structure using resistor 142 as a voltage reduction element has been presented. However, semiconductor elements such as diode 144 shown in FIG. 4A, constant voltage circuit 146 containing transistor shown in FIG. 4B, and shunt regulator 148 (or Zener diode) shown in FIG. 4C can also be used. By using semiconductor elements, a certain negative potential can be applied to the current limiting aperture substrate 204. The characteristics of the semiconductor element to be used are determined based on the potential applied to the current limiting aperture substrate 204.

[0034] Furthermore, as shown in Figure 5, a structure could be considered where an external power supply 300 applies a negative potential to the current-limiting aperture substrate 204. However, in this structure, current flows from the external power supply 300 to the current detector 140, making it impossible to use the current detector 140 to detect the beam current of the beam irradiating the current-limiting aperture substrate 204 with high precision.

[0035] Alternatively, as shown in Figure 6, a structure could be considered that uses a voltage detector 500 to detect the voltage generated by the beam current flowing through the resistor R from the beam irradiating the current-limiting aperture substrate 204. However, in this structure, a negative potential is applied to the current-limiting aperture substrate 204, but the voltage detector 500 is susceptible to voltage noise. Furthermore, in the case of voltage detection, a semiconductor element cannot be used to replace the resistor R.

[0036] On the other hand, as shown in FIG7, in this embodiment, while the current detector 140 is operated at ground potential (0 V), a resistor 142 (external resistor) is connected in series between the current limiting aperture substrate 204 and the current detector 140, separately from the internal resistor r of the current detector 140 used for current detection, that is, while maintaining the function of the current detector, and the voltage is reduced to apply a negative potential to the current limiting aperture substrate.

[0037] Furthermore, in the structure shown in Figure 7, even if resistor 142 is omitted and resistor R as shown in Figure 6 is placed between it and ground, the current detector 140 will operate at ground potential. Since resistor R is connected to ground, no voltage drop will occur on the wiring, thus making it impossible to apply a negative potential to the current limiting aperture substrate 204.

[0038] In the described embodiment, a structure is shown that applies a negative potential to the current-limiting aperture substrate 204, which is positioned upstream of the optical path, closer to the deflector 206. However, the same structure can also be applied to other aperture substrates disposed within the electron optical lens barrel 102 that shield the beam (partially) and have a circular opening formed at the center. If the circular opening is formed at the center, it will not have the effect of lensing caused by the electric field on the passing beam.

[0039] In the described embodiment, a single-beam drawing device was described, but it can also be applied to a multi-beam drawing device.

[0040] The invention has been described in detail using specific examples, but those skilled in the art will understand that various modifications can be made within the scope of achieving the effects of the invention. This application is based on Japanese Patent Application No. 2024-084090, filed on May 23, 2024, the entire contents of which are incorporated herein by reference.

[0041] 1: Delineate the area (stripes) 2: Main deflection region 3: Secondary deflection region 100: Depicting device 101:Substrate 102: Electron Optical Lens Tube 103: Drawing Room 105:XY platform 110: Control computer 120: Deflection control circuit 130: DAC Amplifier Unit 140, 400: Current detector 142: Resistor 144: Diode 146: Constant Voltage Circuit 148: Branch Regulator 200: Electron Gun 202: First Illumination Lens 204: Current-limiting aperture substrate 206: Deflector 208: Second illumination lens 210: Substrate with obscured aperture 212: First forming aperture substrate 214: Projection Lens 216: Forming deflector 218: Second forming aperture substrate 220: Main deflector 222: Sub-deflector 224: Objective lens 300: External power supply 500: Voltage Detector AS: Aperture substrate B: Electron beam C: Control Department L: Coaxial cable P: High-voltage power supply R: Resistance S: Sample W: Depiction Department X, Y: Direction

Claims

1. An electron beam mapping apparatus, comprising: The transmitter emits an electron beam; An aperture substrate having an opening for the electron beam to pass through and partially shielding the electron beam; a deflector deflecting the electron beam passing through the opening of the aperture substrate to illuminate a substrate for patterning; a wiring connected to the aperture substrate for current flow based on the electron beam shielded by the aperture substrate; and a ground potential supply unit connected to the wiring. And a voltage reduction element, connected in series with the wiring that connects the aperture substrate and the ground potential supply unit, applies a negative potential to the aperture substrate.

2. The electron beam mapping apparatus as claimed in claim 1, wherein, The voltage drop element is a resistor.

3. The electron beam mapping apparatus as claimed in claim 1, wherein, The voltage drop element is a semiconductor element.

4. The electron beam mapping apparatus as claimed in claim 3, wherein, The semiconductor element is a diode or a constant voltage circuit.

5. The electron beam mapping apparatus as claimed in claim 1, wherein, A circular opening is formed at the center of the aperture substrate.

6. The electron beam mapping apparatus as claimed in claim 5, wherein, The aperture substrate is a current-limiting aperture substrate disposed upstream of the optical path, closer to the shielding deflector.

7. An electron beam mapping method, wherein, An electron beam is emitted from an emitting unit. When the electron beam passes through an opening in an aperture substrate, a portion of the electron beam is blocked by the aperture substrate. A deflector is used to deflect the electron beam that has passed through the opening in the aperture substrate, and the electron beam is used to irradiate the substrate to be patterned to draw a pattern. A current based on the electron beam blocked by the aperture substrate flows in the wiring that connects the aperture substrate to the ground potential supply unit. The current flows in a voltage drop element connected in series with the wiring to apply a negative potential to the aperture substrate.

8. The electron beam mapping method as described in claim 7, wherein, The voltage drop element is a resistor.

9. The electron beam mapping method as described in claim 7, wherein, The voltage drop element is a semiconductor element.

10. The electron beam mapping method as described in claim 9, wherein, The semiconductor element is a diode or a constant voltage circuit.

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