Electron beam drawing apparatus and electron beam drawing method

Abstract

To suppress an influence of a secondary electron on a beam trajectory while detecting a beam current by using an aperture substrate.SOLUTION: An electron beam drawing apparatus according to an aspect of the present invention includes: a discharge part that discharges an electron beam; an aperture substrate in which an opening through which the electron beam passes is formed and that shields a part of the electron beam; a deflector that deflects the electron beam that has passed through the opening of the aperture substrate and irradiates a drawing target substrate with the electron beam to draw a pattern; a wiring that is connected to the aperture substrate and through which a current based on the electron beam shielded by the aperture substrate flows; a current detector that is connected to the wiring and detects the current; and a voltage drop element that is connected in series to the wiring that connects the aperture substrate and the current detector and applies a negative potential to the aperture substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electron beam writing apparatus and an electron beam writing method. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer every year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (called a mask, or a reticle, especially when used in steppers and scanners) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure system. The high-precision original pattern is drawn using an electron beam drawing system, using so-called electron beam lithography technology.

[0003] As shown in FIG. 8, in the electron beam lithography apparatus, an electron gun 200 is provided in a grounded electron optical column 102, and a high voltage is applied to the electron gun 200 using a high-voltage power supply P to emit an electron beam B, which is then deflected by a deflector (not shown) to write a pattern on a sample S. The electron beam B emitted from the electron gun 200 passes through multiple aperture substrates AS installed in the electron optical column 102 and is irradiated onto the sample S. The multiple aperture substrates AS include an aperture substrate that cuts the beam amount to an appropriate amount, an aperture substrate that cuts the electron beam B from the sample surface, an aperture substrate for monitoring the beam amount, an aperture substrate for beam shaping, and the like. The electron beam B passes through the multiple aperture substrates AS, and thereby its beam current amount and beam shape are adjusted.

[0004] Some of the multiple aperture substrates AS constitute part of the beam current detection mechanism, and are connected to a current detector 400 via a coaxial cable L. Electrons (electron beam B) emitted from the electron gun 200 and irradiated onto the sample S return via the electron optical column 102 to the high-voltage power supply P that supplies power to the electron gun 200. Electrons irradiated onto the aperture substrates AS return to the high-voltage power supply P via the coaxial cable L, the current detector 400, the electron optical column 102, etc.

[0005] The current detector 400 detects the beam current of the electron beam irradiated onto the aperture substrate AS. Based on the detection results of the current detector 400, fluctuations in the beam current and the occurrence 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 the aperture substrate AS is irradiated with the electron beam, secondary electrons including reflected electrons are generated, and there is a possibility that the secondary electrons remaining on the beam trajectory may affect the trajectory of the electron beam B. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-174774 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-114127 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-70944 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an electron beam writing apparatus and an electron beam writing method that can suppress the influence of secondary electrons on the beam trajectory while detecting the beam current using an aperture substrate. [Means for solving the problem]

[0009] An electron beam writing apparatus according to one aspect of the present invention comprises: an emission section that emits an electron beam; an aperture substrate in which an opening through which the electron beam passes is formed and that blocks a portion of the electron beam; a deflector that deflects the electron beam that has passed through the opening in the aperture substrate and irradiates a writing target substrate with the electron beam to write a pattern; wiring connected to the aperture substrate and through which a current flows based on the electron beam that has been blocked by the aperture substrate; a current detector connected to the wiring and that detects the current; and a voltage drop element that is connected in series to the wiring connecting the aperture substrate and the current detector and that applies a negative potential to the aperture substrate.

[0010] An electron beam writing method according to one aspect of the present invention includes: an emitter emits an electron beam; as the electron beam passes through an opening in an aperture substrate, the aperture substrate shields a portion of the electron beam; a deflector is used to deflect the electron beam that has passed through the opening in the aperture substrate; the electron beam is irradiated onto a substrate to be written to write a pattern; a current based on the electron beam that has been shielded by the aperture substrate flows through wiring connecting the aperture substrate and a current detector; the current is detected by the current detector; and a negative potential is applied to the aperture substrate as the current flows through a voltage drop element connected in series to the wiring. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress the influence of secondary electrons on the beam trajectory while detecting the beam current using the aperture substrate. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a drawing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a conceptual diagram showing a main deflection region and a sub-deflection region. [Figure 3] FIG. 10 is a diagram illustrating a voltage drop caused by a resistor. [Figure 4A] FIG. 10 is a diagram illustrating an example of a voltage drop element. [Figure 4B] FIG. 10 is a diagram illustrating an example of a voltage drop element. [Figure 4C] FIG. 10 is a diagram illustrating an example of a voltage drop element. [Figure 5] FIG. 10 is a diagram showing a configuration for applying a negative potential to an aperture substrate according to a comparative example. [Figure 6] FIG. 10 is a diagram showing a beam current detection configuration according to a comparative example. [Figure 7] FIG. 1 illustrates a beam current detection configuration according to an embodiment. [Figure 8] FIG. 10 is a diagram showing a beam current detection configuration according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. In the embodiment, a variable shaping type electron beam lithography apparatus 100 will be described as an example of an electron beam lithography apparatus.

[0014] FIG. 1 is a schematic diagram of a drawing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the drawing apparatus 100 includes a drawing unit W and a control unit C. The drawing unit W includes a grounded electron optical column 102 and a drawing chamber 103. The electron optical column 102 contains an electron gun 200, a first illumination lens 202, a current-limiting aperture substrate 204, a blanking deflector 206, a second illumination lens 208, a blanking aperture substrate 210, a first shaping aperture substrate 212, a projection lens 214, a shaping deflector 216, a second shaping aperture substrate 218, a main deflector 220, a sub-deflector 222, and an objective lens 224. A sub-sub-deflector may be further provided below the main deflector 220.

[0015] An XY stage 105 that is movable at least in the X and Y directions is placed in the patterning chamber 103. A substrate 101 to be patterned is placed on the XY stage 105. The substrate 101 includes an exposure mask, a silicon wafer, etc. for manufacturing a semiconductor device. The mask includes a mask blank.

[0016] The control unit C includes a control computer 110, a deflection control circuit 120, a digital-to-analog conversion (DAC) amplifier unit 130, a current detector 140, etc. Although one DAC amplifier unit 130 is shown in Fig. 1, DAC amplifier units corresponding to each deflector such as the blanking deflector 206, the shaping deflector 216, the main deflector 220, and the sub-deflector 222 are provided.

[0017] A high-voltage power supply circuit (see Figure 8) is connected to the electron gun 200, and an acceleration voltage is applied from the high-voltage power supply circuit between a filament (cathode) and an extraction electrode (anode) (not shown) inside the electron gun 200.In addition, a voltage is applied to another extraction electrode (Wehnelt) and the cathode is heated, which accelerates the group of electrons emitted from the cathode and causes them to be emitted as electron beam B.

[0018] The electron beam B emitted from the electron gun 200 (emitter) travels with a certain degree of divergence and is illuminated by the first illumination lens 202 onto a current-limiting aperture substrate 204 in which an aperture is formed. When the electron beam B passes through the aperture of the current-limiting aperture substrate 204, electrons (electron beam) in the peripheral region are blocked by the current-limiting aperture substrate 204, and only electrons (electron beam) in the central region pass through the aperture. 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-chargeable metal such as tantalum. The current-limiting aperture substrate 204 is rectangular in plan view, with a circular aperture formed in its center. It is preferable that the center of the current-limiting aperture substrate 204 and the center of the circular aperture coincide with each other.

[0019] The electron beam B that has passed through the current-limiting aperture substrate 204 is controlled by the blanking deflector 206 so that in the beam-on state it passes through the blanking aperture substrate 210, and in the beam-off state it is deflected so that the entire beam is shielded by the blanking aperture substrate 210. The electron beam B that passes through the blanking aperture substrate 210 from the beam-off state until it is turned on and then turned off constitutes one electron beam shot.

[0020] The blanking 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 in the beam-on state, and a voltage is applied to the blanking deflector 206 when the beam is off. The irradiation amount per shot of the electron beam B irradiated onto the substrate 101 is adjusted depending on the irradiation time of each shot.

[0021] The electron beam B of each shot, generated by passing through the blanking deflector 206 and blanking aperture substrate 210 as described above, illuminates a first shaping aperture substrate 212 with a rectangular opening by a second illumination lens 208. Here, the electron beam B is first shaped into a rectangle.

[0022] Then, electron beam B of the aperture image that has passed through the first shaping aperture substrate 212 is projected onto a second shaping aperture substrate 218 by a projection lens 214. The aperture image on the second shaping aperture substrate 218 is deflection-controlled by a shaping deflector 216, making it possible to change the beam shape and dimensions. Such variable shaping is performed for each shot, and typically, the beam is shaped into a different shape and dimensions for each shot.

[0023] The electron beam B that has passed through the second shaping aperture substrate 218 is focused by the objective lens 224, deflected by the main deflector 220 and the sub-deflector 222, and irradiated onto a desired position on the substrate 101 that is placed on the continuously moving XY stage 105. As described above, multiple shots of the electron beam B are deflected sequentially onto the substrate 101 by each deflector.

[0024] 2 is a conceptual diagram showing a main deflection region and a sub-deflection region. As shown in FIG. 2, when a desired pattern is drawn using the drawing device 100, the drawing region on the substrate 101 is divided into a plurality of stripe-shaped drawing regions (stripes) 1 in the Y direction, for example, with a width that can be deflected by the main deflector 220. Each stripe 1 is then partitioned in the X direction with a width that is the same as the width of the stripe in the Y direction. These partitioned regions become main deflection regions 2 that can be deflected by the main deflector 220. Regions obtained by further dividing this main deflection region 2 become sub-deflection regions 3 (also called sub-fields).

[0025] The sub-deflector 222 is used to control the position of the electron beam B for each shot at high speed and with high precision. Therefore, the deflection range of the sub-deflection area 3 is limited to the sub-deflection area 3, and deflection beyond that area is performed by the main deflector 220. The main deflector 220 is used to determine the sub-deflection area 3 to be written, and performs beam deflection within a range (main deflection area 2) that includes multiple sub-deflection areas 3. Furthermore, since the XY stage 105 moves continuously in the X direction during writing, the writing origin of the sub-deflection area 3 can be moved (tracked) by the main deflector 220 as needed to follow the movement of the XY stage 105.

[0026] The control computer 110 reads the drawing data from a storage unit (not shown) and performs multiple stages of data conversion processing to generate shot data. The shot data includes information such as the shot shape, shot size, shot position, and shot time.

[0027] The control computer 110 transfers the shot data to the deflection control circuit 120 in shot order. The deflection control circuit 120 uses the shot data to output deflection signals that control the deflection amounts of the blanking deflector 206, the shaping deflector 216, the main deflector 220, and the sub-deflector 222. The DAC amplifier unit 130 digital-to-analog converts the deflection signals output from the deflection control circuit 120, amplifies them, and outputs deflection voltages to be applied to each deflector.

[0028] As described above, when the electron beam B passes through the aperture formed in the current-limiting aperture substrate 204, a portion of the electron beam B is blocked by the current-limiting aperture substrate 204. In other words, a portion of the electron beam B is irradiated onto the current-limiting aperture substrate 204. The current detector 140 detects the current value of the beam current irradiated onto the current-limiting aperture substrate 204 (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 fluctuations in the beam current of the electron beam emitted from the electron gun 200, the occurrence of discharge within the electron optical column 102, and the like.

[0029] In this embodiment, a resistor 142 is connected in series to a wiring that connects a current-limiting aperture substrate 204 having a circular opening formed in its center to the current detector 140. Specifically, one end of the resistor 142 is connected to the current-limiting aperture substrate 204 via a wiring such as a coaxial cable, and the other end of the resistor 142 is connected to a terminal of the current detector 140 via a wiring such as a coaxial cable.

[0030] The electrons irradiated onto the current-limiting aperture substrate 204 flow toward the current detector 140 via the wiring and resistor 142. At this time, the flow of electrons and the flow of current are in opposite directions, so a current flows from the current detector 140 toward the current-limiting aperture substrate 204.

[0031] When a current flows from the current detector 140 to the current-limiting aperture substrate 204, a voltage drop occurs across the resistor 142, and the current-limiting aperture substrate 204 becomes at a lower potential than the current detector 140. As shown in Figure 3, when the current detector 140 is operated at ground potential (0 V), a negative potential (for example, -1 V) is applied to the current-limiting aperture substrate 204.

[0032] 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 toward the upstream side of the optical path (beam traveling direction) and diffuse upward. As a result, the density of secondary electrons remaining on the beam trajectory is reduced compared to when the aperture substrate AS is at ground potential as shown in Fig. 8, thereby suppressing the influence of secondary electrons on the beam trajectory and improving the accuracy of the beam irradiation position.

[0033] The resistance value of the resistor 142 is determined according to the potential to be applied to the current-limiting aperture substrate 204. In other words, by adjusting the resistance value of the resistor 142, a desired negative potential can be applied to the current-limiting aperture substrate 204.

[0034] In the above embodiment, a configuration using resistor 142 as a voltage drop element has been described, but semiconductor elements such as diode 144 shown in FIG. 4A, constant voltage circuit 146 including a transistor shown in FIG. 4B, and shunt regulator 148 (or Zener diode) shown in FIG. 4C may also be used. By using a semiconductor element, a constant negative potential can be applied to current-limiting aperture substrate 204. The characteristics of the semiconductor element to be used are determined depending on the potential to be applied to current-limiting aperture substrate 204.

[0035] 5, a configuration may be considered in which a negative potential is applied to the current-limiting aperture substrate 204 using an external power supply 300. However, in such a configuration, current flows from the external power supply 300 to the current detector 140, making it impossible for the current detector 140 to detect the beam current of the beam irradiated onto the current-limiting aperture substrate 204 with high accuracy.

[0036] 6, a configuration is conceivable in which a voltage detector 500 is used to detect a voltage generated when the beam current of the beam irradiated onto the current-limiting aperture substrate 204 flows through a resistor R. However, in such a configuration, a negative potential is applied to the current-limiting aperture substrate 204, and the voltage detector 500 becomes susceptible to voltage noise. Furthermore, when detecting voltage, a semiconductor element cannot be used in place of the resistor R.

[0037] On the other hand, as shown in FIG. 7, in this embodiment, the current detector 140 is operated at ground potential (0 V), and separately from the internal resistance r of the current detector 140 for current detection, i.e., while maintaining the function of the current detector, a resistor 142 (external resistor) is connected in series between the current-limiting aperture substrate 204 and the current detector 140 to drop the voltage and apply a negative potential to the current-limiting aperture substrate 204.

[0038] In the configuration shown in Figure 7, even if resistor 142 is omitted and a resistor R as shown in Figure 6 is provided between the current detector 140 and ground, the current detector 140 operates at ground potential and resistor R is connected to ground, so no voltage drop occurs on the wiring and a negative potential cannot be applied to the current-limiting aperture substrate 204.

[0039] In the above embodiment, a configuration has been described in which a negative potential is applied to the current-limited aperture substrate 204, which is arranged upstream of the blanking deflector 206 in the optical path, but a similar configuration can also be applied to other aperture substrates with circular openings formed in the center that block (part of) the beam and are provided inside the electron optical lens barrel 102. If a circular opening is formed in the center, the passing beam will not be affected by the lens action of the electric field.

[0040] In the above embodiment, a single-beam drawing apparatus has been described, but the present invention can also be applied to a multi-beam drawing apparatus.

[0041] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0042] 100 drawing device 101 Substrate 102 Electron Optical Tube 103 Drawing room 110 Control computer 140 Current Detector 142 Resistor 204 Current Limiting Aperture Board 206 Blanking Deflector 210 Blanking aperture board

Claims

1. an emission section that emits an electron beam; an aperture substrate having an aperture through which the electron beam passes and which blocks a part of the electron beam; a deflector that deflects the electron beam that has passed through the opening of the aperture substrate and irradiates the electron beam onto a target substrate to write a pattern; a wiring connected to the aperture substrate and through which a current flows based on the electron beam shielded by the aperture substrate; a current detector connected to the wiring and detecting the current; a voltage drop element connected in series to the wiring connecting the aperture substrate and the current detector, and applying a negative potential to the aperture substrate; An electron beam lithography apparatus comprising:

2. 2. The electron beam writing apparatus according to claim 1, wherein the voltage drop element is a resistor.

3. 2. The electron beam writing apparatus according to claim 1, wherein said voltage drop element is a semiconductor element.

4. 4. The electron beam writing apparatus according to claim 3, wherein the semiconductor element is a diode or a constant voltage circuit.

5. The emitter emits an electron beam, When the electron beam passes through an opening in an aperture substrate, a portion of the electron beam is blocked by the aperture substrate; deflecting the electron beam that has passed through the opening of the aperture substrate using a deflector, and irradiating the electron beam onto a substrate to be patterned to write a pattern; a current based on the electron beam shielded by the aperture substrate flows through a wiring connecting the aperture substrate and a current detector; Detecting the current with the current detector; a negative potential is applied to the aperture substrate by causing the current to flow through a voltage drop element connected in series to the wiring;

Images