Charged particle beam drawing device, discharge detection method, and discharge detection device

Abstract

To correctly detect discharge that generates a pattern error.SOLUTION: A charged particle beam drawing device according to one embodiment of the present invention, comprises: a discharge part that discharges a charged particle beam; a high-voltage power supply that applies an accelerating voltage of a charged particle to the discharge part; a deflection device that deflects the charged particle beam to be discharged; a stage to which the charged particle beam is radiated, and a substrate onto which a pattern is drawn is mounted; a discharge sensor of which an output value is modulated when the discharge occurs in a lens tube or the high-voltage power supply to which the discharge part and the deflection device are arranged; and a discharge detection control part that converts an output value of the discharge sensor into a conversion value that becomes usually a same coding, calculates an integration value in a constant time of the conversion value, and determines whether the discharge generating the pattern error occurs on the basis of the integration value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a charged particle beam drawing apparatus, a discharge detection method, and a discharge detection apparatus. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width of semiconductor devices becomes 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 (a mask, or a mask used in steppers and scanners in particular is 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 equipment, abnormal discharges can occur due to dust adhering to components, column walls, etc. When such abnormal discharges occur, the trajectory of the electron beam is bent, making it impossible to irradiate the beam at the desired position, or the electron beam disappears, causing pattern errors and reducing lithography accuracy.

[0004] In order to detect such discharges, a discharge detection device is used. The discharge detection device includes an antenna, which is, for example, a metal plate, and an insulating member that holds the antenna within the housing while electrically insulating it from the housing. Fluctuations in the electric field that occur during discharge affect the potential of the antenna, causing voltage fluctuations in the output of the discharge detection device.

[0005] Conventionally, the output voltage of the discharge detection device is monitored, and when the output voltage exceeds a predetermined threshold, a notification is issued that a pattern error has occurred due to discharge, and the drawing process is stopped. However, it is difficult to determine whether a pattern error has actually occurred by only comparing the output voltage with the threshold.

[0006] For example, when the time during which the output voltage is equal to or greater than the threshold is extremely short, the drawing process may be stopped even though no pattern error has actually occurred.Alternatively, even if the output voltage is less than the threshold, discharge may continue for a long time, causing a pattern error. However, since the output voltage is less than the threshold, the drawing process may continue even though a pattern error has occurred, resulting in a decrease in yield. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-333297 [Patent Document 2] Japanese Patent Application Publication No. 11-352178 [Patent Document 3] JP 2003-107122 A [Patent Document 4] JP 2015-75482 A [Patent Document 5] JP 2016-3989 A [Patent Document 6] JP 2017-152341 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a charged particle beam drawing apparatus, a discharge detection method, and a discharge detection apparatus that can accurately detect discharges that cause pattern errors. [Means for solving the problem]

[0009] A charged particle beam drawing apparatus according to one embodiment of the present invention comprises an emitter that emits a charged particle beam, a high-voltage power supply that applies an acceleration voltage of the charged particles to the emitter, a deflector that deflects the emitted charged particle beam, a stage on which a substrate is placed on which the charged particle beam is irradiated and a pattern is drawn, a discharge sensor whose output value fluctuates when a discharge occurs within a lens barrel in which the emitter and the deflector are arranged or within the high-voltage power supply, and a discharge detection control unit that converts the output value of the discharge sensor into a conversion value that always has the same sign, calculates an integral value of the conversion value over a certain period of time, and determines whether a discharge that causes a pattern error has occurred based on the integral value.

[0010] A discharge detection method according to one embodiment of the present invention comprises the steps of applying an acceleration voltage for charged particles to an emitter in a lens barrel using a high-voltage power supply, causing the emitter to emit a charged particle beam, and drawing a pattern on a substrate; acquiring an output value of a discharge sensor whose output value fluctuates when a discharge occurs in the lens barrel or in the high-voltage power supply; converting the output value into a conversion value that always has the same sign, calculating an integral value of the conversion value over a certain period of time; and determining whether a discharge that causes a pattern error has occurred based on the integral value.

[0011] A discharge detection device according to one embodiment of the present invention comprises a discharge sensor whose output value fluctuates when a discharge occurs, and a discharge detection control unit that converts the output value of the discharge sensor into a conversion value that always has the same sign, calculates an integral value of the converted value over a certain period of time, and determines whether a discharge causing an error has occurred based on the integral value. Effect of the Invention

[0012] According to the present invention, discharges that cause pattern errors can be accurately detected. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of an electron beam drawing apparatus according to an embodiment of the present invention. [Diagram 2]FIG. 1 is a schematic diagram illustrating beam shaping. [Diagram 3] FIG. 13 is a diagram showing an example of a time integral of a voltage. [Figure 4] FIG. 13 is a diagram showing an example of a time integral of a voltage. [Diagram 5] 5A and 5B are diagrams for explaining a conventional discharge detection method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a configuration using an electron beam as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and may be an ion beam or the like.

[0015] 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 lithography unit W, a lithography control unit 40, and a discharge detection unit 60.

[0016] The drawing unit W includes an electron optical column 100 and a drawing chamber 200. In the electron optical column 100, an electron gun 1, a limiting aperture 3, a blanker 4, an illumination lens 5, a blanking aperture 6, a first shaping aperture 8, a shaping deflector 9, a projection lens 11, a second shaping aperture 12, a deflector 13, an objective lens 14, and a sensor 62 are arranged.

[0017] An XY stage 20 is disposed in the writing chamber 200. A substrate 30 to be written is disposed on the XY stage 20. The substrate 30 is, for example, a mask substrate in which a metal light-shielding film such as chromium is provided on a quartz substrate and a resist is applied to the metal light-shielding film.

[0018] Electron beam B emitted from electron gun 1 (emitter) has excess electrons cut off when it passes through limiting aperture 3. When electron beam B passes through limiting aperture 3 and passes inside blanker 4 (blanking deflector), it is controlled by blanker 4 so that in the beam-on state it passes through blanking aperture 6, and in the beam-off state it is deflected so that the entire beam is blocked by blanking aperture 6. The electron beam B that passes through blanking aperture 6 from the beam-off state to the beam-on state until the beam is subsequently turned off constitutes one electron beam shot.

[0019] The blanker 4 controls the deflection of the passing electron beam B to alternately generate a beam-on state and a beam-off state. For example, in the beam-on state, no deflection voltage is applied to the blanker 4, and in the beam-off state, a deflection voltage is applied to the blanker 4. The dose of the electron beam B irradiated onto the substrate 30 per shot is adjusted depending on the irradiation time of each shot.

[0020] The electron beam B of each shot, generated by passing through the blanker 4 and the blanking aperture 6, is irradiated onto the entire first shaping aperture 8 having a rectangular opening 8a (see FIG. 2) by the illumination lens 5. By passing through the opening 8a of the first shaping aperture 8, the electron beam B is shaped into a rectangle.

[0021] The electron beam B of the first aperture image having passed through the first shaping aperture 8 is projected onto a second shaping aperture 12 having an opening 12a (see FIG. 2) by the projection lens 11. At that time, the first aperture image projected onto the second shaping aperture 12 is deflection-controlled by the shaping deflector 9, and the shape and dimensions of the electron beam passing through the opening 12a can be changed (variable shaping can be performed).

[0022] The electron beam B of the second aperture image that has passed through the opening 12a of the second shaping aperture 12 is focused by the objective lens 14, deflected by the deflector 13, and irradiated onto a target position on the substrate 30 placed on the XY stage 20. The deflector 13 may be a two-stage configuration including a main deflector and a sub-deflector, or may be a three-stage configuration further including a sub-sub-deflector.

[0023] 2 is a schematic perspective view for explaining beam shaping by the first shaping aperture 8 and the second shaping aperture 12. The first shaping aperture 8 has a rectangular (rectangular or square) opening 8a for shaping the electron beam B.

[0024] Further, a variable shaping aperture 12a is formed in the second shaping aperture 12 for shaping the electron beam B that has passed through the opening 8a of the first shaping aperture 8 into a desired shape. The variable shaping aperture 12a is an octagonal shape that shares a hexagonal portion and a square portion that is continuous with the hexagonal portion.

[0025] Electron beam B, which is irradiated from electron gun 1 and passes through opening 8a of first shaping aperture 8, is deflected by shaping deflector 9 and passes through variable shaping aperture 12a to become an electron beam of desired dimensions and shape. The electron beam of desired dimensions and shape that has passed through a part of variable shaping aperture 12a is irradiated onto substrate 30 mounted on XY stage 20 that moves continuously in a predetermined direction (for example, X direction). That is, beam shape F that can pass through both opening 8a of first shaping aperture 8 and variable shaping aperture 12a of second shaping aperture 12 is drawn in a drawing region of substrate 30 mounted on XY stage 20 that moves continuously in the X direction.

[0026] In the example of Figure 2, electron beam B is first shaped into a rectangle by passing through opening 8a of first shaping aperture 8, and then, by passing through variable shaping opening 12a of second shaping aperture 12, is shaped so that its cross-sectional shape perpendicular to the beam axis direction becomes a right-angled isosceles triangle.

[0027] The storage device 50 stores drawing data for drawing a pattern on the substrate 30. This drawing data is data obtained by converting design data (layout data) into a format for the drawing device, and is input to the storage device 50 from an external device and stored therein.

[0028] The writing control unit 40 performs, for example, a multi-stage data conversion process on the writing data stored in the storage device 50, divides each figure pattern to be written into shot figures of a size that can be irradiated in one shot, and generates shot data in a format specific to the writing device. The shot data includes, for each shot, for example, a figure code indicating the figure type of each shot figure, figure size, shot position, irradiation time, etc. The generated shot data is temporarily stored in a memory (not shown).

[0029] The writing control unit 40 applies a deflection voltage to the blanker 4 so as to achieve the irradiation time set in the shot data. The writing control unit 40 applies a deflection voltage to the shaping deflector 9 so as to achieve the figure type and figure size set in the shot data. The writing control unit 40 applies a deflection voltage to the deflector 13 so that the electron beam is irradiated to the shot position set in the shot data.

[0030] In the drawing section W, electron beam B collides with a shaping aperture or the like to generate scattered electrons, which may cause insulators to become charged and discharge. In order to detect such discharges, the electron beam drawing apparatus is provided with a discharge detection section 60 (discharge detection device).

[0031] The discharge detection unit 60 includes, for example, a discharge detection control unit 61, a sensor 62, a signal processing unit 63, a storage unit 64, and a monitor 65. The discharge detection control unit 61 performs control related to the detection of discharge.

[0032] The sensor 62 (discharge sensor) is used as an antenna or an electrode. The antenna referred to here is made of a conductive material such as metal, and is capable of capturing electromagnetic waves or fluctuations in an electric field or fluctuations in a magnetic field (electromagnetic noise) in space, converting them into a voltage signal or a current signal, and outputting the signal. Such an antenna is capable of capturing a signal related to discharge. In this embodiment, the sensor 62 is described as being a metal plate, but the shape of the sensor 62 is not limited to a plate shape, and may be a coiled cable or a single copper wire.

[0033] The sensor 62 is provided, for example, near and above the electron gun 1 in the electron optical column 100. The location of the sensor 62 is not limited thereto, and the sensor 62 can be provided at any position in the housing of the electron beam drawing apparatus as long as it is not in the path of the electron beam B.

[0034] The signal processing unit 63 is, for example, an oscilloscope, electrically connected to the sensor 62, and acquires a signal related to the sensor 62. An example in which the signal processing unit 63 is an oscilloscope will be described below, but the signal processing unit 63 may be an ammeter, a voltmeter, or the like. The signal processing unit (digitizer) 63 acquires, for example, analog data of a current based on the potential of the sensor 62, performs analog-to-digital conversion processing on the analog data, and stores data generated by the processing (hereinafter also referred to as voltage data. Note that the voltage data can be considered as current value data with a changed resistance strength) in the storage unit 64. The voltage data represents, for example, the relationship between the output voltage of the sensor 62 and time.

[0035] The discharge detection control unit 61 reads out the voltage data stored in the memory unit 64, performs a discharge detection process to detect a fluctuation in the electric field resulting from a discharge based on the voltage data, and stores the results of the process in the memory unit 64. The results of the process stored in the memory unit 64 are displayed, for example, on the monitor 65. Alternatively, the relationship between voltage and time represented by the voltage data stored in the memory unit 64 may be displayed on the monitor 65. It is also possible to execute the discharge detection process based on the display on the monitor 65.

[0036] While performing a drawing process on the substrate 30, the electron beam drawing apparatus uses the discharge detection device 60 to detect discharges that cause drawing pattern errors.

[0037] For example, the discharge detection control unit 61 constantly reads out the voltage data stored in the memory unit 64 at certain time intervals while drawing is being performed, and detects discharge that may cause a drawing pattern error based on the voltage data.

[0038] For example, the discharge detection control unit 61 monitors the voltage fluctuation measured by the sensor 62, and calculates the time integral of the absolute value of the voltage over a certain period of time. If the calculated integral value is equal to or greater than a predetermined value, the discharge detection control unit 61 determines that a discharge that will cause a drawing pattern error has been detected. On the other hand, if the integral value is less than the predetermined value, the discharge detection control unit 61 determines that a discharge that will cause a drawing pattern error has not been detected.

[0039] The predetermined value (threshold value) used for comparison with the integral value may be determined from several actual examples, or may be determined by conducting an experiment in which discharges of various magnitudes are artificially generated, measuring and recording the discharges with a sensor while detecting the irradiated electron beam with a Faraday cup (not shown) provided on the XY stage 20, and determining whether the increase and decrease in the beam satisfies the desired precision.

[0040] Fig. 3 shows an example of a graph in which voltage data is plotted. In this graph, the horizontal axis corresponds to time, and the vertical axis corresponds to the voltage measured by sensor 62. The time integral of the absolute value of the voltage over a certain time T calculated by discharge detection control unit 61 corresponds to the shaded area in Fig. 3. When sensor 62 captures electromagnetic noise of discharge with an antenna, the reference potential is the ground potential.

[0041] As shown in FIG. 4, the discharge detection control section 61 continuously calculates the integral value of the absolute value of the voltage while shifting the interval for integration.

[0042] When the integral value becomes equal to or exceeds a predetermined value, the drawing control unit 40 stops the drawing process or issues a warning. After the drawing process is stopped, the substrate 30 is taken out, the resist is peeled off, and the substrate 30 can be used again for drawing.

[0043] In a conventional discharge detection method in which the voltage measured by the sensor 62 is compared with a threshold value, when the time during which the voltage is equal to or greater than the threshold value is extremely short, it may be determined that a pattern error has occurred, even though no pattern error has actually occurred, and the drawing process may be stopped, as shown in Fig. 5A. On the other hand, in this embodiment, since the integral value of the absolute value of the voltage is obtained, in the case of a voltage fluctuation pattern as shown in Fig. 5A, it is determined that a discharge that would cause a drawing pattern error has not been detected, and the drawing process is continued, thereby making it possible to suppress erroneous detection.

[0044] In addition, in the conventional discharge detection method in which the voltage measured by the sensor 62 is compared with a threshold value, when the voltage is below the threshold value but a relatively high voltage state continues for a long time, causing a pattern error, as shown in Fig. 5B, the discharge is not detected and the drawing process is continued with the pattern error occurring, which may result in a decrease in yield. On the other hand, in the present embodiment, since the integral value of the absolute value of the voltage is obtained, in the case of a voltage fluctuation pattern as shown in Fig. 5B, it is possible to determine that a discharge that causes a drawing pattern error has occurred and stop the drawing process.

[0045] In this manner, according to this embodiment, discharges that cause pattern errors can be accurately detected.

[0046] In the above embodiment, a configuration for continuously calculating the time integral of the absolute value of the voltage for a certain time T has been described, but this configuration requires multiple digitizers or a complex digitizer, and constant calculation is required. Therefore, only when the voltage (or the absolute value of the voltage) measured by the sensor 62 becomes equal to or greater than a predetermined reference value, the voltage data for the following certain time T may be recorded, the time integral of the absolute value of the voltage for the certain time T may be calculated, and based on the integral value, it may be determined whether or not a discharge that causes a drawing pattern error has occurred. This allows one digitizer or a simple digitizer to be sufficient for one sensor, and constant calculation is not required, so that the cost required for calculating the integral value can be significantly reduced.

[0047] In the above embodiment, a configuration has been described in which the sensor 62 that detects the variations in the electric field and magnetic field due to the discharge is used as the discharge sensor, but various sensors that measure physical quantities that change due to the discharge can be used. For example, an optical sensor that converts the light emitted by the discharge into an electric signal can be used as the discharge sensor. Furthermore, since the voltage value and current value of a high-voltage power supply (not shown) that applies a high voltage to the electron gun 1 change due to the discharge, a sensor that monitors this voltage value and current value can be used as the discharge sensor. Furthermore, a sensor that monitors the amount of change in the beam current on the electron gun 1 side relative to the blanker 4 can be used as the discharge sensor.

[0048] The integration process time (time T in FIG. 3) and the predetermined value (threshold value) to be compared with the integration value are appropriately determined depending on the type of discharge sensor used.

[0049] The cause of the discharge may be identified from the waveform pattern of the voltage fluctuation, and maintenance may be performed.

[0050] Although the above embodiment has been described as an example of a drawing apparatus using a single beam, the present invention can also be applied to a drawing apparatus using multiple beams.

[0051] The discharge detection unit 60 (discharge detection device) can be applied not only to a drawing device but also to other devices in which discharge occurs inside a housing. The discharge detection unit 60 monitors the voltage fluctuation measured by the sensor 62, calculates the time integral of the absolute value of the voltage over a certain period of time, and determines whether or not an error that affects the processing of the device has occurred based on the integral value.

[0052] In the above embodiment, an example has been described in which the discharge sensor (first discharge sensor) of the discharge detection unit is installed in the electron optical column 100 to detect discharge occurring in the electron optical column 100, but a discharge sensor (second discharge sensor) may be installed in a high-voltage power supply that is connected to the cathode of the electron gun 1 (emitter) and applies an accelerating voltage for electrons, to detect discharge occurring in the high-voltage power supply. In this case, a circuit that extracts fluctuations (ripples) in the output voltage or output current of the high-voltage power supply has the function of a discharge sensor. The discharge detection control unit 61 calculates an integral value of the absolute value of the output of the ripple extraction circuit over a certain period of time, and when the calculated integral value is equal to or greater than a predetermined value, it determines that a discharge that causes a drawing pattern error has been detected. The discharge sensor is preferably installed in both the electron optical column 100 and the high-voltage power supply, but may be installed in only one of them.

[0053] In the above embodiment, an example is described in which the integral value of the absolute value of the output voltage of the discharge sensor over a certain period of time is calculated, but the value to be integrated is not limited to the absolute value, and it is sufficient if the output voltage of the discharge sensor is converted into a discharge intensity signal that always has the same sign, and the converted value is integrated. For example, the square value of the output voltage of the discharge sensor may be integrated.

[0054] 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]

[0055] 1 Electron gun 3 Limiting Aperture 4. Blanka 5 Lighting lens 6 Blanking Aperture 8 First Shaping Aperture 9 Molded deflector 11 Projection lens 12 Second Shaping Aperture 13 Deflector 14 Objective Lens 20 XY Stage 30 Substrate 40 Drawing control unit 50 Storage device 60 Discharge detection unit 62 Sensors 100 Electron optical tube 200 drawing room

Claims

1. an emission section that emits a charged particle beam; a high-voltage power supply that applies an acceleration voltage of the charged particles to the emission section; a deflector for deflecting the emitted charged particle beam; a stage for supporting a substrate on which the charged particle beam is irradiated and a pattern is drawn; a discharge sensor whose output value fluctuates when a discharge occurs in a lens barrel in which the emission unit and the deflector are disposed or in the high-voltage power supply; a discharge detection control unit that converts an output value of the discharge sensor into a converted value that always has the same sign, calculates an integral value of the converted value over a certain period of time, and determines whether or not a discharge that causes a pattern error has occurred based on the integral value; A charged particle beam writing apparatus comprising:

2. 2. The charged particle beam drawing apparatus according to claim 1, further comprising a drawing control unit that performs control so as to stop a pattern drawing process when the discharge detection control unit determines that a discharge causing a pattern error has occurred.

3. 2. The charged particle beam drawing apparatus according to claim 1, wherein the discharge detection control unit records the output value for the certain period of time and calculates the integral value when the output value becomes equal to or greater than a predetermined reference value.

4. 2. The charged particle beam drawing apparatus according to claim 1, wherein the discharge sensor is a sensor that detects electromagnetic noise caused by discharge occurring within the lens barrel, or a sensor that detects light emitted by discharge.

5. 2. The charged particle beam drawing apparatus according to claim 1, wherein the discharge sensor is a circuit for extracting a fluctuation in an output voltage or an output current of the high voltage power supply.

6. 2. The charged particle beam drawing apparatus according to claim 1, wherein the discharge sensor includes a first discharge sensor whose output value fluctuates when a discharge occurs in the lens barrel, and a second discharge sensor whose output value fluctuates when a discharge occurs in the high-voltage power supply.

7. applying an acceleration voltage of the charged particles to an emission section in the lens barrel using a high-voltage power supply to emit a charged particle beam from the emission section, thereby drawing a pattern on a substrate; acquiring an output value of a discharge sensor whose output value fluctuates when a discharge occurs in the lens barrel or the high-voltage power supply; converting the output value into a converted value that always has the same sign, and calculating an integral value of the converted value over a certain period of time; determining whether or not a discharge causing a pattern error has occurred based on the integral value; A discharge detection method comprising:

8. 8. The discharge detection method according to claim 7, further comprising the step of: stopping the pattern drawing process when it is determined that a discharge causing a pattern error has occurred.

9. 8. The discharge detection method according to claim 7, further comprising the steps of: recording the output value for the certain period of time and calculating the integral value when the output value becomes equal to or greater than a predetermined reference value.

10. a discharge sensor whose output value fluctuates when a discharge occurs; a discharge detection control unit that converts an output value of the discharge sensor into a converted value that always has the same sign, calculates an integral value of the converted value over a certain period of time, and determines whether or not a discharge that causes an error has occurred based on the integral value; A discharge detection device comprising:

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