Adjustment method for multi-charged particle beam irradiation device and beam detector

Abstract

To align holes of a two-stage aperture with high precision.SOLUTION: A beam detector has a first aperture substrate with a first passage hole smaller than the inter-beam pitch of the multiple charged particle beams, a second aperture substrate with a second passage hole through which one detection target beam that has passed through the first passage hole can pass, and a sensor detecting a beam current of the detection target beam that has passed through the second passage hole. The second aperture substrate is transparent to light and includes a conductive material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a beam detector, a multi-charged particle beam irradiation apparatus, and a method for adjusting a beam detector.

Background Art

[0002] With the increasing integration of LSIs, the circuit line widths of semiconductor devices have been further miniaturized. As a method for forming an exposure mask (also referred to as a reticle when used in a stepper or scanner) for forming a circuit pattern on these semiconductor devices, an electron beam lithography technique having excellent resolution is used.

[0003] As an electron beam lithography apparatus, the development of a lithography apparatus using multi-beams has been underway. By using multi-beams, more beams can be irradiated compared to the case of irradiating with a single electron beam, so that the throughput can be significantly improved. In a multi-beam type lithography apparatus, for example, an electron beam emitted from an electron gun is passed through an aperture member having a plurality of holes to form multi-beams, blanking control of each beam is performed by a blanking aperture array, and the unshielded beam is reduced by an optical system and irradiated onto a substrate placed on a movable stage.

[0004] In order to maintain the irradiation position of multi-beams on a substrate with high precision, it is important to accurately grasp the position of each beam constituting the multi-beams on the substrate. In a configuration where the number of beams is small, for example, several, and the pitch between beams is sufficiently wide, the position of each beam can be measured by arranging the same number of marks as the number of beams for each beam on the stage and scanning the corresponding marks with each beam (see, for example, Patent Document 1).

[0005] However, as circuit patterns become smaller, a multi-beam system with a greater number of beams is required to significantly improve throughput. As the number of beams increases, the beam diameter decreases and the beam pitch narrows. Thus, as the number of beams increases and the beam pitch narrows, it becomes difficult to detect each beam individually from among the irradiated multi-beams using marks placed on the stage.

[0006] Individual beam detectors have been proposed that use a thin film aperture with a single through-hole smaller than the beam pitch of a multi-beam system but larger than the beam diameter, and detect a single target beam that passes through this through-hole with a sensor such as a photodiode. However, with such individual beam detectors, scattered electrons generated when beams near the target beam pass through the thin film aperture can enter the sensor, potentially becoming a noise source and reducing detection accuracy. To shield against scattered electrons, it is conceivable to provide a second aperture between the thin film aperture (first aperture) and the sensor, but both the holes in the thin film aperture and the holes in the second aperture are very small, making alignment difficult. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2009-9882 [Patent Document 2] Japanese Patent Publication No. 2005-340229 [Patent Document 3] Japanese Patent Application Publication No. 10-261566 [Patent Document 4] Japanese Patent Application Publication No. 6-275500 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a beam detector and a multi-charged particle beam irradiation device in which the holes of the two-stage aperture are precisely aligned. Furthermore, the present invention aims to provide a method for adjusting a beam detector that enables highly precise alignment of the holes of the two-stage aperture. [Means for solving the problem]

[0009] A beam detector according to one aspect of the present invention is This is used in a device that irradiates with a multi-charged particle beam, and the above The system comprises a first aperture substrate having a first through-hole smaller than the beam-to-beam pitch of a multi-charged particle beam, a second aperture substrate having a second through-hole through which one target beam that has passed through the first through-hole can pass, and a sensor for detecting the beam current of the target beam that has passed through the second through-hole, wherein the second aperture substrate is transparent to light and contains a conductive material.

[0010] A multi-charged particle beam irradiation apparatus according to one aspect of the present invention comprises a stage on which a substrate to be drawn is placed, an emission unit for emitting a charged particle beam, a molded aperture array substrate that receives irradiation from the charged particle beam and forms a multi-beam by allowing a portion of the charged particle beam to pass through each of the substrates, an optical system for irradiating the substrate to be drawn with the multi-beam, and a beam detector disposed on the stage for individually detecting each of the multi-beams, wherein the beam detector comprises a first aperture substrate having a first through-hole smaller than the beam-to-beam pitch of the multi-beam, a second aperture substrate having a second through-hole through which one detection target beam that has passed through the first through-hole can pass, and a sensor for detecting the beam current of the detection target beam that has passed through the second through-hole, wherein the second aperture substrate contains a material that is transparent to light and conductive.

[0011] A beam detector adjustment method according to one aspect of the present invention involves a first through hole in a first aperture substrate, which has a first through hole smaller than the inter-beam pitch of a multi-charged particle beam, and the multi Charged particleA beam detector adjustment method for aligning a second aperture substrate, through which one of the target beams to be detected can pass, with the second aperture, comprising the steps of: irradiating the first aperture substrate with light emitted from a light source via the second aperture substrate, focusing the objective lens on the first aperture substrate, observing the image of reflected light incident through the objective lens using an image sensor, and setting the position of the first aperture to a reference mark; and focusing the objective lens on the second aperture substrate, observing the image of reflected light incident through the objective lens using an image sensor, and moving the second aperture substrate so that the position of the second aperture coincides with the reference mark. [Effects of the Invention]

[0012] According to the present invention, the holes of the two-stage aperture for multi-beam beam detection can be aligned with high precision. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of a multi-charged particle beam lithography apparatus according to an embodiment of the present invention. [Figure 2] This is a schematic diagram of a molded aperture array substrate. [Figure 3] This is a schematic diagram of the individual beam detector configuration. [Figure 4] This diagram illustrates the alignment method for the holes in a two-stage aperture. [Figure 5] This diagram illustrates the alignment method for the holes in a two-stage aperture. [Figure 6] This is a schematic diagram of the individual beam detector configuration. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0015] FIG. 1 is a schematic diagram of a multi-charged particle beam lithography apparatus according to an embodiment of the present invention. In this embodiment, as an example of the charged particle beam, a configuration using an electron beam will be described. However, the charged particle beam is not limited to the electron beam, and other charged particle beams such as an ion beam may also be used.

[0016] This lithography apparatus includes a drawing unit W that irradiates an electron beam onto a substrate 24 to be drawn to draw a desired pattern, and a control unit C that controls the operation of the drawing unit W.

[0017] The drawing unit W has an electron beam column 2 and a drawing chamber 20. Inside the electron beam column 2, an electron gun 4, an illumination lens 6, a shaping aperture array substrate 8, a blanking aperture array substrate 10, a reduction lens 12, a limiting aperture member 14, an objective lens 16, and a deflector 17 are arranged.

[0018] An XY stage 22 is arranged inside the drawing chamber 20. A substrate 24 to be drawn is placed on the XY stage 22. The substrate 24 to be drawn includes, for example, a wafer, or a mask for exposure that transfers a pattern using a reduction projection exposure apparatus such as a stepper or a scanner using an excimer laser as a light source on the wafer, or an extreme ultraviolet exposure apparatus (EUV).

[0019] Further, a transmission mark type individual beam detector 40 is arranged at a position different from the position where the substrate 24 is placed on the XY stage 22. The height of the individual beam detector 40 can be adjusted by an adjustment mechanism (not shown). The upper surface of the individual beam detector 40 is preferably installed at the same height position as the surface of the substrate 24.

[0020] The control unit C has a control computer 32 and a deflection control circuit 34.

[0021] The control computer 32 includes a drawing data processing unit 60, a drawing control unit 61, and a measurement unit 62. Each part of the control computer 32 may be composed of hardware such as electrical circuits, or it may be composed of software such as programs that perform these functions. If it is composed of software, the programs that realize these functions may be stored on a recording medium and loaded into a computer including a CPU and executed.

[0022] A storage device (not shown) stores drawing data, which is the design data (layout data) converted into a format for the drawing device. The drawing data processing unit 60 reads the drawing data from this storage device and performs multiple stages of data conversion processing to generate shot data. Shot data is generated for each pixel, and the drawing time (irradiation time) is calculated. For example, if no pattern is formed on the target pixel, there is no beam irradiation, so an identification code for zero drawing time or no beam irradiation is defined. Here, the maximum drawing time T (maximum exposure time) for one multi-beam shot is set in advance. The irradiation time of each beam actually irradiated is preferably determined in proportion to the calculated area density of the pattern. Furthermore, the irradiation time of each beam finally calculated is preferably the time corresponding to the corrected irradiation amount, which is corrected for dimensional changes due to phenomena that cause dimensional changes, such as proximity effect, flicker effect, and loading effect (not shown), by the irradiation amount. Therefore, the irradiation time of each beam actually irradiated may differ from beam to beam. The drawing time (irradiation time) of each beam is calculated using a value within the maximum drawing time T. Furthermore, the drawing data processing unit 60 generates irradiation time array data for each multi-beam shot, which is arranged in the order of the beams in the multi-beam, using the calculated irradiation time data for each pixel as data for the beam that will draw that pixel.

[0023] The drawing control unit 61 uses irradiation time sequence data (shot data) to output control signals for performing drawing processing to the deflection control circuit 34 and the control circuit (not shown) that drives the drawing unit W. Based on the control signals, the drawing unit W uses a multi-beam to draw the desired pattern on the substrate 24. Specifically, it operates as follows.

[0024] The electron beam 30 emitted from the electron gun 4 illuminates the entire molded aperture array substrate 8 almost vertically through the illumination lens 6. Figure 2 is a conceptual diagram showing the configuration of the molded aperture array substrate 8. The molded aperture array substrate 8 has m rows (vertical y-direction) × n rows (horizontal x-direction) (m,n≧2) of apertures 8a formed in a matrix at a predetermined arrangement pitch. For example, 512 rows × 512 rows of apertures 8a are formed. Each aperture 8a is formed as a rectangle of the same dimensions and shape. Each aperture 8a may also be a circle of the same diameter.

[0025] The electron beam 30 illuminates the region of the molded aperture array substrate 8 that includes all of the apertures 8a. As a portion of the electron beam 30 passes through each of these multiple apertures 8a, a multi-beam system 30a to 30e is formed as shown in Figure 1.

[0026] The blanking aperture array substrate 10 has through-holes formed in accordance with the positions of each aperture 8a of the molded aperture array substrate 8, and a blanker consisting of a pair of electrodes is placed in each through-hole. The electron beams 30a to 30e passing through each through-hole are deflected independently by the voltage applied to the blanker. This deflection controls the blanking of each beam. The blanking aperture array substrate 10 performs blanking deflection on each beam of the multi-beam that has passed through the multiple apertures 8a of the molded aperture array substrate 8.

[0027] The multi-beams 30a to 30e that have passed through the blanking aperture array substrate 10 have their respective beam sizes and array pitches reduced by the reduction lens 12 and proceed toward the central aperture formed in the limiting aperture member 14. The electron beams deflected by the blanking aperture array substrate 10 have their trajectories displaced and move away from the central aperture of the limiting aperture member 14, where they are shielded. On the other hand, the electron beams that have not been deflected by the blanking aperture array substrate 10 pass through the central aperture of the limiting aperture member 14.

[0028] The limiting aperture member 14 shields each electron beam that has been deflected by the blanker of the blanking aperture array substrate 10 to the beam-off state. The beam that passes through the limiting aperture member 14 from the time the beam is turned ON until it is turned OFF constitutes one shot of electron beam.

[0029] The electron beams 30a to 30e that have passed through the limiting aperture member 14 are focused by the objective lens 16, forming a pattern image with the desired reduction ratio on the substrate 24. Each electron beam (the entire multi-beam system) that has passed through the limiting aperture member 14 is deflected in the same direction by the deflector 17 and irradiated onto the substrate 24.

[0030] Ideally, the multi-beams irradiated at once will be arranged at a pitch obtained by multiplying the array pitch of the multiple openings 8a of the aperture member 8 by the desired reduction ratio described above. This drawing device performs drawing operations using a raster scan method in which shot beams are irradiated sequentially, and when drawing a desired pattern, the necessary beams are controlled to be turned ON by blanking control according to the pattern. When the XY stage 22 is moving continuously, the beam irradiation position is controlled by the deflector 17 so that it follows the movement of the XY stage 22.

[0031] In such a drawing device, it is necessary to individually determine the irradiation position of each beam constituting the multi-beam system in order to improve drawing accuracy. Therefore, an individual beam detector 40 is used to detect the position of each beam.

[0032] Figure 3 is a schematic diagram of a transmission mark type individual beam detector 40. The individual beam detector 40 includes a first aperture substrate 41, a support base 43, a second aperture substrate 46, a sensor 48, and a housing 49.

[0033] The first aperture substrate 41 (thin film) has one microhole 42 (first through hole) formed in the center. The first aperture substrate 41 is formed of a thin film with a thickness that allows multi-beams to pass through. Specifically, the first aperture substrate 41 is formed using a heavy metal material, for example, as a thin film plate with a thickness of 300 to 1000 nm. More preferably, it is formed to a thickness of about 500 nm ± 50 nm. For example, an electron beam emitted at an accelerating voltage of 50 keV cannot be completely absorbed by the aperture substrate 41 and passes through.

[0034] By making the first aperture substrate 41 a thin film structure, when the first aperture substrate 41 is heated, heat transfer from the heated area to the surroundings is made difficult, thereby reducing heat dissipation. Suitable heavy metal materials include, for example, platinum (Pt), gold (Au), or tungsten (W). Even when the film thickness is thin, using a heavy metal can reduce the amount of electrons transmitted when irradiated with a multi-beam.

[0035] The micropores 42 are formed with a diameter size φ1 that is larger than the beam diameter of the individual beams of the multi-beam system composed of electron beams, and smaller than the inter-beam pitch. If the inter-beam pitch of the multi-beam system is, for example, around 150-200 nm, the holes are formed with a diameter φ1 of, for example, around 80-120 nm. By making the diameter of the micropores 42 larger than the beam diameter of the individual beams and smaller than the inter-beam pitch, it is possible to prevent multiple beams from passing through the micropores 42 simultaneously, even when scanning the multi-beam system.

[0036] The first aperture substrate 41 is supported by a support base 43. The support base 43 has an opening 44 formed below the region containing the micropores 42 in the first aperture substrate 41. In the example shown in Figure 3, the opening 44 is formed in the center. The diameter size φ2 (width size) of the opening 44 is formed such that when the first aperture substrate 41 is irradiated with a multi-beam, the temperature at the periphery of the micropores 42 in the first aperture substrate 41 is higher than the evaporation temperature of impurities (contaminants) adhering to the periphery. For example, it is preferable to use a temperature of 100°C or higher as the evaporation temperature of the contaminants.

[0037] Suitable materials for the support base 43 include, for example, molybdenum (Mo), platinum (Pt), tantalum (Ta), or silicon (Si). The thickness of the support base 43 is such that it can shield the electron beams constituting the irradiated multibeam without allowing them to pass through. For example, a thickness of 15 μm or more is sufficient to shield an electron beam accelerated at 50 keV.

[0038] By further providing an opening 45 around the periphery of the opening 44 on the back side of the support base 43, which is carved to a thickness that prevents electrons from passing through, it becomes more difficult for heat transferred horizontally from the first aperture substrate 41 to the support base 43 near the periphery of the opening 44. As a result, the temperature drop in the region near the micro-holes 42 of the first aperture substrate 41 above the opening 44 can be further suppressed.

[0039] The outer circumference of the support base 43 is formed to be the same size as, for example, the outer circumference of the first aperture substrate 41, or larger than the outer circumference of the first aperture substrate 41. The bottom surface of the support base 43 is supported by the housing 49.

[0040] A second aperture substrate 46 is positioned between the first aperture substrate 41 and the sensor 48. The second aperture substrate 46 has one minute hole 47 (second through hole) formed in the center. The outer periphery of the second aperture substrate 46 is fixed by the housing 49.

[0041] When the first aperture substrate 41 is scanned with multiple beams, for the beams irradiated onto the region above the aperture 44, one detection target beam passes through the micro-hole 42, while the other beams pass through the first aperture substrate 41 and are scattered from the back side of the first aperture substrate 41. On the other hand, the beams irradiated onto regions other than the region above the aperture 44 are shielded by the support base 43.

[0042] The detection target beam that passes through the micro-hole 42 passes through the micro-hole 47 of the second aperture substrate 46 and reaches the light-receiving surface of the sensor 48. On the other hand, scattered electrons from the back side of the first aperture substrate 41 are shielded by the second aperture substrate 46, and their arrival at the light-receiving surface of the sensor 48 is suppressed.

[0043] Sensor 48 is, for example, an SSD (solid-state detector) and detects the beam current of the beam to be detected. The detection result from sensor 48 is notified to control computer 32. By scanning the first aperture substrate 42 with multiple beams, the measurement unit 62 obtains the beam current of each beam from sensor 48. The measurement unit 62 converts the beam current into brightness, creates a beam image based on the deflection amount of the deflector 17, and obtains information such as the overall shape of the multi-beam. Based on this information, corrections are made to the irradiation amount of each beam.

[0044] When the imaging landing angle of the beam to be detected is α [radians] and the distance between the surface of the first aperture substrate 41 and the surface of the second aperture substrate 46 is L, it is preferable that the diameter of the micro-hole 47 be 2 × α × L or greater so that the beam that passes through the micro-hole 42 passes through the micro-hole 47 and reaches the light-receiving surface of the sensor 48.

[0045] From the viewpoint of antistatic properties, the material of the second aperture substrate 46 is preferably conductive. It is preferable that the material has conductivity such that the charged particles Ii incident on the second aperture substrate 46 and the emitted charged particles Io satisfy the condition Ii = Io. Here, Io includes backscattered electrons and secondary electrons.

[0046] Furthermore, the material of the second aperture substrate 46 is preferably a transparent material with a flat surface that transmits observation light used for the alignment process of the hole positions between the micropores 42 of the first aperture substrate 41 and the micropores 47 of the second aperture substrate 46, as described later. The observation light may be visible light, infrared light, or ultraviolet light. The thickness of the second aperture substrate 46 is sufficient to shield scattered electrons.

[0047] Next, the method for aligning the hole positions (axial alignment) between the micro-holes 42 of the first aperture substrate 41 and the micro-holes 47 of the second aperture substrate 46 will be described. The alignment process is performed outside the drawing device.

[0048] As shown in Figure 4, the alignment process uses an incident illumination unit having a light source (light irradiation unit) 71, a half mirror 72, an objective lens 73, an imaging lens 74, and an image sensor 75.

[0049] For example, when the light source 71 emits visible light with a wavelength of 400 to 800 nm, the second aperture substrate 46 can be made of a material that allows visible light to pass through, such as quartz, crown glass, or borosilicate glass, with a conductive film that allows observation light to pass through deposited on it. This conductive film may be a non-magnetic conductor.

[0050] Observation light emitted from the light source 71 is reflected by a half-mirror 72 positioned at a 45° angle to the optical axis, passes through the objective lens 73, and illuminates the object to be observed (first aperture substrate 41 and second aperture substrate 46). The second aperture substrate 46 is located between the objective lens 73 and the first aperture substrate 41. A support base 43 is attached to the first aperture substrate 41.

[0051] Light reflected from the object being observed passes through the objective lens 73, then through the half-mirror 72, and is imaged by the image sensor 75 via the imaging lens 74. The image sensor 75 is, for example, a CMOS image sensor.

[0052] First, the position of the objective lens 73 is adjusted to focus on the first aperture substrate 41. Then, the image detected by the image sensor 75 is observed to identify the imaging position of the micro-hole 42, and this identified position is set as a reference mark. The second aperture substrate 46 only needs to be transparent enough to allow visible light to pass through to the extent necessary to identify the imaging position of this micro-hole 42.

[0053] Next, as shown in Figure 5, the position of the objective lens 73 is adjusted to focus on the second aperture substrate 46. Then, using a moving mechanism (not shown), the second aperture substrate 46 is moved in a planar direction perpendicular to the optical axis so that the imaging position of the micro-hole 47 in the second aperture substrate 46 coincides with the above-mentioned reference mark.

[0054] When the imaging position of the microhole 47 in the second aperture substrate 46 coincides with the reference mark, the positions of the microhole 42 in the first aperture substrate 41 and the microhole 47 in the second aperture substrate 46 are precisely aligned.

[0055] Once the alignment is complete, the first aperture substrate 41 and support base 43, the second aperture substrate 46, and the sensor 48 are fixed together in the housing 49 to create an individual beam detector 40 with the micro-holes 42 and 47 aligned. This individual beam detector 40 is then mounted on the lithography device.

[0056] Thus, according to this embodiment, the micro-holes 42 and 47 of the two-stage aperture substrates, the first aperture substrate 41 and the second aperture substrate 46, can be aligned with high precision.

[0057] In the above embodiment, an example was described in which the material for the second aperture substrate 46 is made of optical glass through which visible light, which is the observation light emitted from the light source 71, is transmitted, and a conductive film that transmits observation light is deposited on the optical glass. However, as shown in Figure 6, the periphery of the micro-holes 47 of the second aperture substrate 46 may be made of a non-magnetic conductor 90. In other words, micro-holes may be machined into the non-magnetic conductor 90. Examples of non-magnetic conductors 90 include titanium, copper, titanium alloys, copper alloys, etc. Titanium, in particular, is a material that is easy to machine and FIB process, and allows for precise control of the hole diameter when processing the micro-holes 47.

[0058] When the observation light emitted from the light source 71 is infrared light (wavelength 1100-1500 nm), the material of the second aperture substrate 46 can be silicon crystal, sapphire crystal, etc. In this case, for example, an InGaAs image sensor is used for the image sensor 75.

[0059] In the above embodiment, a multi-beam lithography system was described as an example of a device equipped with individual beam detectors, but it is not limited to this. For example, any device that irradiates multiple beams, such as an inspection device for checking defects in patterns, can be similarly equipped with these detectors. It is also applicable to devices that irradiate single beams.

[0060] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Moreover, components from different embodiments may be appropriately combined. [Explanation of Symbols]

[0061] 2 Electron beam tube 4. Electronic gun 6. Illumination Lens 8. Molded aperture array substrate 10 Blanking aperture array substrate 12 Reduction lens 14 Restrictive Aperture Member 16 Objective lenses 17 Deflector 20 Drawing room 22 XY Stages 32 Control Computer 34 Deflection control circuit 40 Individual beam detectors 60 Drawing Data Processing Unit 61 Drawing Control Unit 62 Measuring part

Claims

1. A stage on which the substrate to be drawn is placed, An emission unit that emits a charged particle beam, A molded aperture array substrate that receives irradiation from the charged particle beam and forms multiple beams by allowing a portion of the charged particle beam to pass through each, An optical system for irradiating the multi-beam onto the substrate to be drawn, A beam detector is placed on the stage and detects each of the multi-beams individually, Equipped with, The beam detector is A first aperture substrate having first through holes smaller than the beam-to-beam pitch of the multi-beam, A second aperture substrate having a second through-hole formed therein, through which one detection target beam that has passed through the first through-hole can pass, A sensor for detecting the beam current of the target beam that has passed through the second through hole, It has, The second aperture substrate is a multi-charged particle beam irradiation device containing a material that is transparent to light and conductive.

2. A method for adjusting a beam detector, which involves aligning a first through-hole in a first aperture substrate, which has a first through-hole smaller than the beam-to-beam pitch of a multi-charged particle beam, with a second through-hole in a second aperture substrate, which has a second through-hole through which one of the detection target beams of the multi-charged particle beam can pass, The process involves irradiating the first aperture substrate with light emitted from a light source via the second aperture substrate, focusing the objective lens on the first aperture substrate, observing the image of the reflected light incident through the objective lens using an image sensor, and setting the position of the first through-hole to a reference mark. The process involves focusing the objective lens on the second aperture substrate, observing the image of reflected light incident through the objective lens using the image sensor, and moving the second aperture substrate so that the position of the second through-hole coincides with the reference mark. A method for adjusting a beam detector equipped with [a specific feature / feature].

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