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

Abstract

Provided are a charged particle beam drawing device, a discharge detection method, and a discharge detection device that detect a discharge in which a pattern error has occurred. A charged particle beam drawing device according to an embodiment of the present invention is provided with: a discharge unit that discharges a charged particle beam; a high-voltage power supply that applies an acceleration voltage for charged particles to the discharge unit; a deflector that deflects the emitted charged particle beam; a mounting table which is irradiated with the charged particle beam and on which a substrate on which a pattern is to be drawn is mounted; a discharge sensor whose output value varies when discharge occurs in a lens barrel in which the discharge unit and the deflector are disposed or in the high-voltage power supply; and a discharge detection control unit that converts an output value of the discharge sensor to a converted value having the same sign at all times, calculates an integrated value of the converted value within a certain time, and determines whether or not a discharge that causes a pattern error has occurred on the basis of the integrated value.

Description

[0001] Related Applications

[0002] This application claims priority based on Japanese Patent Application No. 2023-120081 (filing date: July 24, 2023). This application incorporates the entire contents of the basic application by reference. Technical Field

[0003] The present invention relates to a charged particle beam delineation device, a discharge detection method and a discharge detection device. Background Art

[0004] With the high integration of LSI, the circuit line width of semiconductor devices is becoming smaller and smaller year by year. In order to form the desired circuit pattern on the semiconductor device, a method is adopted in which a high-precision original pattern (mask, or especially a stepper exposure device, also called an intermediate mask used in a scanner) formed on quartz is reduced and transferred on a wafer using a reduced projection exposure device. The high-precision original pattern is drawn by an electron beam drawing device, using the so-called electron beam lithography technology.

[0005] In electron beam lithography equipment, abnormal discharge may occur due to dust attached to components, column walls, etc. If such abnormal discharge occurs, the trajectory of the electron beam is bent and the beam cannot be irradiated to the desired position, or the electron beam disappears, resulting in pattern errors and reduced lithography accuracy.

[0006] In order to detect such discharge, a discharge detection device is used. The discharge detection device includes, for example, an antenna such as a metal plate, and an insulating member that electrically insulates the antenna from the housing and holds the antenna in the housing. The change in the electric field generated during the discharge affects the potential of the antenna, causing a voltage change in the output of the discharge detection device.

[0007] In the past, the output voltage of the discharge detection device was monitored, and if the output voltage became above a predetermined threshold, a pattern error caused by the discharge was reported and the drawing process was stopped. However, it is actually difficult to determine whether a pattern error has occurred by simply comparing the output voltage with the threshold.

[0008] For example, when the output voltage is above the threshold for a very short time, the drawing process may be stopped even though no pattern error actually occurs. Alternatively, even if the output voltage is less than the threshold, discharge continues for a long time, sometimes causing a pattern error, but because the output voltage is less than the threshold, the drawing process is continued in a state where a pattern error occurs, sometimes reducing the yield. Summary of the invention

[0009] The present invention provides a charged particle beam drawing device, a discharge detection method and a discharge detection device for detecting discharge causing pattern errors.

[0010] A charged particle beam drawing device according to one embodiment of the present invention comprises: an emission unit that emits a charged particle beam; a high-voltage power supply that applies an accelerating voltage for the charged particles to the emission unit; a deflector that deflects the emitted charged particle beam; a mounting table that is irradiated with the charged particle beam and mounts a substrate on which a pattern is to be drawn; a discharge sensor whose output value changes when a discharge occurs in a lens barrel in which the emission unit and the deflector are arranged or in 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 within a certain period of time, and determines whether a discharge that causes a pattern error has occurred based on the integral value. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of an electron beam imaging device according to an embodiment of the present invention.

[0012] Figure 2 This is a schematic diagram for explaining beam forming.

[0013] Figure 3 It is a diagram showing an example of the time integration of voltage.

[0014] Figure 4 It is a diagram showing an example of the time integration of voltage.

[0015] Figure 5A , Figure 5B It is a diagram for explaining a conventional discharge detection method. DETAILED DESCRIPTION

[0016] 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.

[0017] Figure 1 This is a schematic diagram of an electron beam imaging device according to an embodiment of the present invention. Figure 1 The electron beam drawing device shown is a deformable drawing device including a drawing section W, a drawing control section 40 , and a discharge detection section 60 .

[0018] The drawing section W includes an electron optical lens barrel 100 and a drawing chamber 200. 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 in the electron optical lens barrel 100.

[0019] An XY stage 20 is disposed in the drawing chamber 200. A substrate 30 to be drawn is disposed on the XY stage 20. The substrate 30 is a mask substrate in which a metal light shielding film such as chromium is provided on a quartz substrate and a resist is applied on the metal light shielding film.

[0020] The electron beam B emitted from the electron gun 1 (emission unit) has its excess electrons cut off when passing through the limiting aperture 3. When passing through the blanker 4 (blanking deflector), the electron beam B that has passed through the limiting aperture 3 is controlled by the blanker 4 to pass through the blanking aperture 6 in the beam-on state, and in the beam-off state, the entire beam is deflected so as to be blocked by the blanking aperture 6. The electron beam B that changes from the beam-off state to the beam-on state and then passes through the blanking aperture 6 before changing to the beam-off state is emitted as a single electron beam.

[0021] The blanker 4 controls the deflection of the electron beam B passing through, and generates a beam-on state and a beam-off state alternately. 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 irradiation amount of each shot of the electron beam B irradiated to the substrate 30 is adjusted by the irradiation time of each shot.

[0022] Each emitted electron beam B generated by the blanker 4 and the blanking aperture 6 is irradiated by the illumination lens 5 to an opening 8a having a rectangular shape (see Figure 2 ) as a whole of the first shaping aperture 8. The electron beam B is shaped into a rectangular shape by the opening 8a of the first shaping aperture 8.

[0023] The electron beam B having passed through the first aperture image of the first shaping aperture 8 is projected by the projection lens 11 onto a surface having an opening 12a (see Figure 2 ) on the second forming aperture 12. At this time, the first aperture image projected onto the second forming aperture 12 is deflected and controlled by the forming deflector 9, so that the shape and size of the electron beam passing through the opening 12a can be changed (variable forming can be performed).

[0024] The electron beam B of the second aperture image having 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 to a target position of the substrate 30 disposed on the XY stage 20. The deflector 13 may be a two-stage structure including a main deflector and a sub-deflector, or a three-stage structure including a sub-sub-deflector.

[0025] Figure 2 This 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.

[0026] A variable shaping opening 12a for shaping the electron beam B having passed through the opening 8a of the first shaping opening 8 into a desired shape is formed in the second shaping aperture 12. The variable shaping opening 12a is an octagonal shape having a hexagonal portion and a quadrilateral portion connected to the hexagonal portion.

[0027] The electron beam B irradiated from the electron gun 1 and passed through the opening 8a of the first shaping aperture 8 is deflected by the shaping deflector 9 and becomes an electron beam of a desired size and shape through the variable shaping opening 12a. The electron beam of a desired size and shape that has passed through a part of the variable shaping opening 12a is irradiated to the substrate 30 mounted on the XY stage 20 that moves continuously in a predetermined direction (for example, set to the X direction). That is, the beam shape F of both the opening 8a of the first shaping aperture 8 and the variable shaping opening 12a of the second shaping aperture 12 can be drawn on the drawing area of ​​the substrate 30 mounted on the XY stage 20 that moves continuously in the X direction.

[0028] exist Figure 2 In the example, the electron beam B is first formed into a rectangle by passing through the opening 8a of the first forming aperture 8, and then passes through the variable forming opening 12a of the second forming hole 12, thereby being formed into an isosceles right triangle in cross section perpendicular to the beam axis direction.

[0029] The storage device 50 stores drawing data for drawing a pattern on the substrate 30. The drawing data is obtained by converting design data (layout data) into a format for the drawing device, and is input from an external device and stored in the storage device 50.

[0030] The drawing control unit 40 performs, for example, multi-stage data conversion processing on the drawing data stored in the storage device 50, divides each graphic pattern to be drawn into a shot pattern of a size that can be irradiated with one irradiation, and generates shot data in a format inherent to the drawing device. The shot data includes, for example, a graphic code indicating the type of the graphic of each shot pattern, a graphic size, a shot position, an irradiation time, etc. for each shot. The generated shot data is temporarily stored in a memory (not shown).

[0031] The drawing control unit 40 applies a deflection voltage to the blanker 4 so as to achieve the irradiation time set in the emission data. The drawing control unit 40 applies a deflection voltage to the shaping deflector 9 so as to achieve the pattern type and pattern size set in the emission data. The drawing control unit 40 applies a deflection voltage to the deflector 13 so as to irradiate the electron beam to the emission position set in the emission data.

[0032] In the drawing section W, scattered electrons may be generated by collision of the electron beam B with the forming aperture, etc., thereby charging the insulating material and causing discharge. In order to detect such discharge, the electron beam drawing device is provided with a discharge detection section 60 (discharge detection device).

[0033] 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.

[0034] The sensor 62 (discharge sensor) is used as an antenna or an electrode. The antenna mentioned here is made of a conductive material such as metal, and captures electromagnetic waves or changes in electric fields or magnetic fields (electromagnetic noise) in space and converts them into voltage signals or current signals and outputs them. Such an antenna can capture signals related to discharge. In this embodiment, the case where the sensor 62 is a metal plate is described, but the shape of the sensor 62 is not limited to a plate shape, and can also be a cable, a single copper wire, etc. formed into a coil shape.

[0035] The sensor 62 is provided, for example, near and above the electron gun 1 in the electron optical lens column 100. The sensor 62 is not limited to this arrangement, and can be arranged at any position in the housing of the electron beam imaging device as long as it is not on the path of the electron beam B.

[0036] The signal processing unit 63 is, for example, an oscilloscope, which is electrically connected to the sensor 62 and obtains a signal related to the sensor 62. Below, an example of a case where the signal processing unit 63 is an oscilloscope is described, but the signal processing unit 63 can also be an ammeter or a voltmeter. The signal processing unit (digital converter) 63 obtains, 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 causes the storage unit 64 to store the data generated by the processing (hereinafter also referred to as voltage data. In addition, the voltage data can be regarded as current value data that changes the strength of the resistance). The voltage data, for example, represents the relationship between the output voltage of the sensor 62 and time.

[0037] The discharge detection control unit 61 reads the voltage data stored in the storage unit 64, performs a discharge detection process for detecting a change in the electric field from the discharge based on the voltage data, and stores the result of the process in the storage unit 64. The result of the process stored in the storage unit 64 is displayed on the monitor 65, for example. Alternatively, the relationship between the voltage and time represented by the voltage data stored in the storage unit 64 may be displayed on the monitor 65. The discharge detection process may also be executed based on the display on the monitor 65.

[0038] The electron beam drawing apparatus detects discharge that causes drawing pattern error using the discharge detection device 60 while performing drawing processing on the substrate 30 .

[0039] For example, the discharge detection control unit 61 always reads the voltage data stored in the storage unit 64 at a certain time interval during the drawing process, and detects the discharge that may cause the drawing pattern error based on the voltage data.

[0040] For example, the discharge detection control unit 61 monitors the voltage variation measured by the sensor 62 and calculates the time integral of the absolute value of the voltage within a certain period of time. When the calculated integral value is greater than a predetermined value, the discharge detection control unit 61 determines that a discharge causing a drawing pattern error is detected. On the other hand, when the integral value is less than a predetermined value, the discharge detection control unit 61 determines that a discharge causing a drawing pattern error is not detected.

[0041] The specified value (threshold) used for comparison with the integrated value can be determined by several examples, or an experiment can be conducted artificially to produce discharges of various sizes. While the discharge is measured and recorded by a sensor, the irradiated electron beam is detected by a Faraday cup (not shown) set on the XY stage 20, and the increase or decrease of the beam is determined based on whether the desired accuracy is met.

[0042] Figure 3 FIG. 6 shows an example of a graph plotting voltage data. In this graph, the horizontal axis corresponds to time, and the vertical axis corresponds to the voltage measured by the sensor 62. The time integral of the absolute value of the voltage within a certain time T calculated by the discharge detection control unit 61 is equivalent to Figure 3 When the sensor 62 captures the electromagnetic noise of the discharge using the antenna, the reference potential becomes the ground potential.

[0043] like Figure 4 As shown, the discharge detection control unit 61 continuously calculates the integral value of the absolute value of the voltage while shifting the interval for integration.

[0044] When the integrated value is equal to or greater than a predetermined value, the drawing control unit 40 stops the drawing process or issues an alarm. After the drawing process is stopped, the substrate 30 can be carried out to the outside, the resist can be peeled off, and the substrate can be used for the drawing process again.

[0045] In the conventional discharge detection method, the voltage measured by the sensor 62 is compared with a threshold value. Figure 5A As shown in FIG. 1 , when the time for which the voltage is above the threshold is extremely short, a pattern error may be determined to have occurred even though no pattern error actually occurred, and the drawing process may be stopped. On the other hand, in this embodiment, in order to obtain the integral value of the absolute value of the voltage, Figure 5A In the case of the voltage variation pattern shown, it is determined that the discharge causing the drawing pattern error is not detected and the drawing process is continued, thereby suppressing erroneous detection.

[0046] In addition, in a conventional discharge detection method in which the voltage measured by the sensor 62 is compared with a threshold value, as shown in FIG. Figure 5B As shown, although the voltage is less than the threshold value, when the voltage remains high to a certain level for a long time and a pattern error occurs, the discharge is sometimes not detected, and the drawing process is continued in the state where the pattern error occurs, which reduces the yield. For example, when the pattern error is performed on one irradiation area n times (for example, 4 times), even if the voltage change (amplitude) does not become a pattern error in one shot, the voltage change time is long, and sometimes the voltage change time for each shot up to the nth shot to enter the discharge occurs. On the other hand, in this embodiment, in order to obtain the integral value of the absolute value of the voltage, Figure 5B In the case of the voltage variation pattern shown, it is determined that a discharge causing a drawing pattern error has occurred, and the drawing process can be stopped.

[0047] Furthermore, for example, the operation of the high voltage power supply for applying the acceleration voltage to the electron gun 1, the floating capacitance of the electron gun 1, the series impedance, and the voltage stabilization circuit in the high voltage power supply may be used. Figure 3 As shown in FIG. 1 , the voltage variation caused by discharge is not in a constant direction, but sometimes varies in both positive and negative directions. In the conventional discharge detection method of comparing the time integral value of the voltage measured by the sensor 62 with the threshold value, as shown in FIG. Figure 3 As shown in FIG. 1 , when the voltage fluctuation is not in a constant direction but fluctuates in both positive and negative directions, and the time integral values ​​of the positive and negative fluctuations are close to each other, the time integral value is small despite the long voltage fluctuation and time, so sometimes the discharge cannot be detected, and the drawing process is continued in a state where a pattern error occurs, which reduces the yield. On the other hand, in this embodiment, in order to obtain the integral value of the absolute value of the voltage, Figure 3 In the case of the voltage variation pattern shown, it is determined that a discharge causing a drawing pattern error has occurred, and the drawing process can be stopped.

[0048] As described above, according to the present embodiment, it is possible to accurately detect a discharge in which a pattern error occurs.

[0049] In the above embodiment, a structure for continuously calculating the time integral of the absolute value of the voltage within a certain time T is described, but in this structure, multiple digital converters or complex digital converters are required, and calculations are always required. Therefore, only when the voltage (or the absolute value of the voltage) measured by the sensor 62 becomes greater than a predetermined reference value, the voltage data for a certain time T thereafter may be recorded, and the time integral of the absolute value of the voltage within the certain time T may be calculated, and whether a discharge that causes a drawing pattern error has occurred may be determined based on the integral value. Thus, a digitizer may be one or a simple digitizer for one sensor, and calculations do not need to be performed all the time, so the cost required for the calculation of the integral value can be greatly reduced.

[0050] In the above embodiment, as a discharge sensor, a structure using the sensor 62 that captures the change of the electric field and magnetic field caused by the discharge is described, but various sensors that measure the physical quantity that changes due to the discharge can be used. For example, a light sensor that converts the light emitted by the discharge into an electrical signal can also be used as a discharge sensor. In addition, the voltage value and current value of the high-voltage power supply (not shown) that applies a high voltage to the electron gun 1 change due to the discharge, so a sensor that monitors the voltage value and current value can also be used as a discharge sensor. In addition, a sensor that monitors the change in the beam current on the electron gun 1 side can also be used as a discharge sensor.

[0051] The integration processing time is appropriately determined according to the type of discharge sensor used ( Figure 3 time T), and a specified value (threshold) to be compared with the integral value.

[0052] The discharge detection unit control unit 61 may identify the cause of the discharge based on the waveform pattern of the voltage fluctuation. In addition, maintenance may be performed based on the identified cause.

[0053] In the above-mentioned embodiment, an example of an image drawing apparatus using a single beam is described, but the present invention is also applicable to an image drawing apparatus using multiple beams.

[0054] The discharge detection unit 60 (discharge detection device) can be applied not only to the drawing device but also to other devices that generate discharge in the housing. The discharge detection unit 60 monitors the voltage change measured by the sensor 62, calculates the time integral of the absolute value of the voltage within a certain period of time, and determines whether an error that affects the processing of the device has occurred based on the integral value.

[0055] In the above embodiment, an example is described in which the discharge sensor (first discharge sensor) of the discharge detection unit is set in the electron optical lens barrel 100 to detect the discharge generated in the electron optical lens barrel 100, but it is also possible to connect the cathode of the electron gun 1 (discharge unit) and set a discharge sensor (second discharge sensor) to the high-voltage power supply that applies the acceleration voltage of the electrons to detect the discharge generated in the high-voltage power supply. In this case, the circuit that extracts the variation (pulsation) of the output voltage or output current of the high-voltage power supply has the function of the discharge sensor. The discharge detection control unit 61 calculates the integral value of the absolute value of the output of the pulsation extraction circuit within a certain period of time, and when the calculated integral value is greater than a specified value, it is determined that the discharge that causes the drawing pattern error is detected. The discharge sensor is preferably set on both the electron optical lens barrel 100 and the high-voltage power supply, but it can also be set on only one side.

[0056] In the above embodiment, an example of calculating the integral value of the absolute value of the output voltage of the discharge sensor within a certain period of time is described, but the integration is not limited to the absolute value, and the output voltage of the discharge sensor can be converted into a discharge intensity signal that always has the same sign and the converted value can be integrated. For example, the square value of the output voltage of the discharge sensor can also be integrated.

[0057] In addition, the present invention is not limited to the above-mentioned embodiments intactly. In the implementation stage, the structural elements can be deformed and concretized within the scope of the main purpose. In addition, various inventions can be formed by appropriate combinations of multiple structural elements disclosed in the above-mentioned embodiments. For example, several structural elements can also be deleted from all the structural elements shown in the embodiments. Furthermore, the structural elements of different embodiments can also be appropriately combined.

[0058] [Explanation of Reference Numerals]

[0059] 1 Electron gun

[0060] 3 Limiting aperture

[0061] 4 Blanker

[0062] 5 Illumination lens

[0063] 6 Blanking Aperture

[0064] 8. First forming aperture

[0065] 9 Forming Deflector

[0066] 11 Projection lens

[0067] 12 Second forming aperture

[0068] 13 Deflector

[0069] 14 Objective lens

[0070] 20 XY stage

[0071] 30 substrate

[0072] 40 Drawing control unit

[0073] 50 Storage device

[0074] 60 Discharge detection unit

[0075] 62 Sensors

[0076] 100 Electron optical tube

[0077] 200 Drawing Room

Claims

1. A charged particle beam mapping device, comprising: An emission unit for emitting a charged particle beam; a high voltage power supply for applying an accelerating voltage of the charged particles to the discharge portion; a deflector for deflecting the emitted charged particle beam; a mounting table, which is irradiated with the charged particle beam and on which a substrate on which a pattern is to be drawn is mounted; a discharge sensor whose output value changes when discharge occurs in a barrel in which the discharge section and the deflector are arranged or in the high voltage power supply; as well as The discharge detection control unit converts the output value of the discharge sensor into a conversion value having the same sign at all times, calculates an integral value of the conversion value within a certain period of time, and determines whether a discharge causing a pattern error has occurred based on the integral value.

2. The charged particle beam mapping device according to claim 1, wherein: The charged particle beam drawing device further includes a drawing control unit configured to perform control to stop pattern drawing processing when the discharge detection control unit determines that a discharge causing a pattern error has occurred.

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

4. The charged particle beam mapping device according to claim 1, wherein: The discharge sensor is a sensor that detects electromagnetic noise of discharge generated in the barrel, or a sensor that detects light generated by the discharge.

5. The charged particle beam mapping device according to claim 1, wherein: The discharge sensor is a circuit that extracts a variation in the output voltage or output current of the high-voltage power supply.

6. The charged particle beam mapping device according to claim 1, wherein: The discharge sensor includes: a first discharge sensor whose output value changes when discharge occurs in the barrel; and a second discharge sensor whose output value changes when discharge occurs in the high-voltage power supply.

7. The charged particle beam mapping device according to claim 1, wherein: The discharge sensor is arranged above the discharge portion.

8. The charged particle beam mapping device according to claim 1, wherein: The discharge detection control unit specifies a cause of discharge based on a waveform of a change in an output value of the discharge sensor.

9. A discharge detection method, comprising: A step of applying an accelerating voltage for charged particles to an emission section in a column using a high voltage power supply, emitting a charged particle beam from the emission section, and drawing a pattern on a substrate; A step of obtaining an output value of a discharge sensor whose output value changes when discharge occurs in the lens barrel or in the high voltage power supply; The step of converting the output value into a conversion value having the same sign all the time, and calculating an integral value of the conversion value within a certain period of time; and A step of determining whether or not a discharge causing a pattern error has occurred is performed based on the integrated value.

10. The discharge detection method according to claim 9, wherein: When it is determined that a discharge causing a pattern error has occurred, the pattern drawing process is stopped.

11. The discharge detection method according to claim 9, wherein: When the output value is equal to or greater than a predetermined reference value, the output value for the certain period of time is recorded and the integrated value is calculated.

12. The discharge detection method according to claim 9, wherein: The discharge sensor detects electromagnetic noise of discharge occurring in the barrel or light emitted by the discharge.

13. A discharge detection device comprising: a discharge sensor whose output value changes when discharge occurs; and The discharge detection control unit converts the output value of the discharge sensor into a conversion value having the same sign at all times, calculates an integral value of the conversion value within a certain period of time, and determines whether a discharge causing an error has occurred based on the integral value.

14. The discharge detection device according to claim 13, wherein: The discharge detection control unit records the output value for the certain period of time and calculates the integrated value when the output value becomes equal to or greater than a predetermined reference value.

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