Electron beam adjusting method, electron beam writing apparatus, and program

Abstract

PURPOSE: To provide a method capable of obtaining a necessary incident irradiation amount in the whole irradiation region of an electron beam.CONSTITUTION: According to another aspect of the present invention, there is provided an electron beam adjustment method including: measuring a current density distribution of an electron beam reaching a sample; calculating a feature amount of the measured current density distribution; and increasing a temperature of an electron beam emission source when the feature amount is out of a threshold range.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] One aspect of the present invention relates to an electron beam adjustment method, an electron beam writing apparatus, and a program, and relates to, for example, a technique for adjusting the operating conditions of a cathode of a thermionic gun that emits an electron beam. [Background technology]

[0002] Lithography technology, which is responsible for the advancement of miniaturization of semiconductor devices, is the only extremely important process in semiconductor manufacturing that generates patterns. In recent years, with the increasing integration density of LSIs, the circuit line width required for semiconductor devices has been getting finer year by year. Here, electron beam (EB) lithography technology has inherently excellent resolution, and mask patterns are written onto mask blanks using an electron beam.

[0003] For example, there is a lithography system that uses multiple beams. Compared to lithography using a single electron beam, using multiple beams allows for the irradiation of many beams at once, thereby significantly improving throughput. In such a lithography system, for example, an electron beam emitted from a thermal electron gun is passed through a mask with multiple holes to form multiple beams, each of which is blanked and each beam that is not blocked is reduced in size by an optical system, the mask image is reduced, and the beam is deflected by a deflector to be irradiated at the desired position on the sample.

[0004] In electron beam lithography, the electron beam emitted from the electron gun is periodically adjusted so that the current density of the entire electron beam is within an allowable range. For example, conventionally, the current density of the entire electron beam is periodically measured, and if it is insufficient, the emission current is increased, and if it is still insufficient, the cathode temperature is increased, thereby adjusting the current density of the entire electron beam to a desired value (see, for example, Patent Document 1).

[0005] However, when adjusting an electron beam using conventional methods, there was a problem in that when the adjusted electron beam was irradiated onto a sample surface, the desired incident irradiation dose was not obtained in some parts of the irradiated area. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-165075 Summary of the Invention [Problem to be solved by the invention]

[0007] One aspect of the present invention provides a method and apparatus that can obtain a required incident dose over the entire irradiation area of ​​the electron beam. [Means for solving the problem]

[0008] An electron beam adjusting method according to one aspect of the present invention includes: measuring the current density distribution of the electron beam reaching the sample; calculating a feature amount of the measured current density distribution; increasing the temperature of the electron beam source when the feature value falls outside the threshold range; The present invention is characterized by the following.

[0009] In addition, the cathode of an electron gun is used as the electron beam emission source. This is preferable.

[0010] In addition, the sample is irradiated with an electron beam, measuring a current density of the electron beam for each of a plurality of sub-regions into which an irradiation region of the electron beam reaching the sample is divided; A current density distribution is measured using the current density for each sub-region of the plurality of sub-regions. This is preferable.

[0011] Furthermore, the ratio of the current density of each sub-region to the maximum current density of each sub-region of the current density distribution is used as the feature amount. This is preferable.

[0012] The method further comprises the step of measuring the brightness of the entire electron beam, The current density distribution is measured when the brightness is above a threshold value. This is preferable.

[0013] The temperature is increased by a predetermined reference temperature interval. This is preferable.

[0014] An electron beam lithography apparatus according to one aspect of the present invention comprises: a current density distribution measurement unit for measuring the current density distribution of the electron beam reaching the sample; a feature amount calculation unit that calculates a feature amount of the measured current density distribution; a temperature increasing unit that increases the temperature of the electron beam emission source when the feature value falls outside a threshold range; a drawing mechanism that draws a pattern on a sample using an electron beam; The present invention is characterized by the following.

[0015] A program according to one aspect of the present invention comprises: measuring the current density distribution of the electron beam reaching the sample; storing the measured current density distribution in a storage device; A process of reading out the current density distribution from the storage device and calculating a feature amount of the current density distribution; a process of increasing the temperature of the electron beam source when the feature amount falls outside the threshold range; to be executed by the computer. [Effects of the Invention]

[0016] According to one aspect of the present invention, a required incident irradiation amount can be obtained over the entire irradiation area of ​​the electron beam. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a conceptual diagram showing a configuration of a drawing device according to a first embodiment. [Figure 2] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate according to the first embodiment. [Figure 3] 2 is a cross-sectional view showing the configuration of a blanking aperture array mechanism in the first embodiment. FIG. [Figure 4] FIG. 3 is a diagram showing an example of the current density distribution of an electron beam that reaches a sample surface in the first embodiment. [Figure 5] FIG. 2 is a flowchart showing an example of main steps of the writing method according to the first embodiment. [Figure 6] FIG. 3 is a diagram showing an example of a transition over time of a feature amount in the first embodiment. [Figure 7] FIG. 3 is a diagram showing an example of a path of an operating point of an electron gun due to electron beam adjustment in the first embodiment. [Figure 8] FIG. 4 is a diagram showing an example of a transition of a current density distribution due to adjustment of an electron beam in the first embodiment. [Figure 9] FIG. 2 is a conceptual diagram for explaining an example of a drawing operation in the first embodiment. [Figure 10] 3 is a diagram showing an example of a multi-beam irradiation area and a pixel to be written in the first embodiment. FIG. [Figure 11] FIG. 2 is a diagram for explaining an example of a multi-beam writing method according to the first embodiment. [Figure 12] FIG. 10 is a conceptual diagram showing the configuration of a drawing device according to a second embodiment. [Figure 13] FIG. 10 is a diagram for explaining a method for measuring a current density distribution in the second embodiment. [Figure 14] FIG. 10 is a diagram illustrating a procedure for measuring a current density distribution in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following embodiments, the electron beam may be a multi-beam or a single beam. Although the following description will be given of a drawing apparatus, the invention may be applied to any apparatus other than a drawing apparatus, such as an image acquisition apparatus or an inspection apparatus, as long as the apparatus uses an electron beam emitted from an electron emission source.

[0019] Embodiment 1 FIG. 1 is a conceptual diagram showing the configuration of a lithography apparatus according to the first embodiment. In FIG. 1, the lithography apparatus 100 includes a lithography mechanism 150 and a control circuit 160. The lithography apparatus 100 is an example of a multi-electron beam lithography apparatus. The lithography apparatus 100 is also an example of an electron beam lithography apparatus. The lithography mechanism 150 includes an electron lens barrel 102 (multi-electron beam column) and a lithography chamber 103. The electron lens barrel 102 includes an electron gun 201 (thermal electron gun, thermionic emission source), an illumination lens 202, a shaping aperture array substrate 203, a blanking aperture array mechanism 204, a reduction lens 205, a limiting aperture substrate 206, an objective lens 207, a deflector 208, and a deflector 209. The lithography chamber 103 includes an XY stage 105. A sample 101, such as a resist-coated mask blank, which serves as a target substrate for lithography, is placed on the XY stage 105. The sample 101 includes an exposure mask used in manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which the semiconductor device is manufactured, etc. A mirror 210 for measuring the position of the XY stage 105 is also placed on the XY stage 105. A Faraday cup 106 is also placed on the XY stage 105.

[0020] The electron gun 201 (a thermionic electron gun, an example of an electron beam emission source) has a cathode 222 (another example of an electron beam emission source), a Wehnelt 224 (Wehnelt electrode), and an anode 226 (anode electrode). The anode 226 is grounded (earthed). The anode 226 is controlled to have a positive potential relative to the cathode 222. The Wehnelt 224 is controlled to have a negative potential relative to the cathode 222. The electron gun 201 emits an electron beam 200 from the cathode 222 toward the anode 226.

[0021] The control system circuit 160 includes a control computer 110, a memory 112, a monitor 114, an electron gun power supply device 120, a deflection control circuit 130, digital-to-analog (DAC) amplifier units 132 and 134, a current detection circuit 136, a stage position detector 139, and a storage device 140 such as a magnetic disk drive. The control computer 110, the memory 112, the monitor 114, the electron gun power supply device 120, the deflection control circuit 130, the DAC amplifier units 132 and 134, the current detection circuit 136, the stage position detector 139, and the storage device 140 are connected to one another via a bus (not shown).

[0022] The deflection control circuit 130 is connected to DAC amplifier units 132 and 134 and a blanking aperture array mechanism 204. The output of the DAC amplifier unit 132 is connected to a deflector 209. The output of the DAC amplifier unit 134 is connected to a deflector 208. The deflector 208 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via a DAC amplifier 134. The deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via a DAC amplifier 132. The stage position detector 139 irradiates a mirror 210 on the XY stage 105 with laser light and receives the light reflected from the mirror 210. The position of the XY stage 105 is measured using the principle of laser interference based on information about the reflected light. The output of the Faraday cup 106 is connected to a current detection circuit 136.

[0023] The control computer 110 includes a judgment unit 51, a brightness measurement unit 52, a brightness judgment unit 54, a current density distribution measurement unit 56, a feature calculation unit 58, a judgment unit 59, a drawing data processing unit 40, and a drawing control unit 42. Each of the "units" such as the determination unit 51, the luminance measurement unit 52, the luminance determination unit 54, the current density distribution measurement unit 56, the feature calculation unit 58, the determination unit 59, the writing data processing unit 40, and the writing control unit 42 has a processing circuit. Such a processing circuit may include, for example, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each of the "units" may use a common processing circuit (the same processing circuit) or different processing circuits (separate processing circuits). Information input to and output from the determination unit 51, the luminance measurement unit 52, the luminance determination unit 54, the current density distribution measurement unit 56, the feature calculation unit 58, the determination unit 59, the writing data processing unit 40, and the writing control unit 42, as well as information being calculated, are stored in the memory 112 each time.

[0024] The electron gun power supply device 120 includes a control computer 232, a memory 78, a storage device 79 such as a magnetic disk device, an acceleration voltage power supply circuit 236, a bias voltage power supply circuit 234, a filament power supply circuit 231 (filament power supply unit), and an ammeter 238. The control computer 232 is connected to the memory 78, the storage device 79, the acceleration voltage power supply circuit 236, the bias voltage power supply circuit 234, the filament power supply circuit 231, and the ammeter 238 by a bus (not shown).

[0025] The control computer 232 is arranged with a cathode temperature addition unit 60, a cathode temperature determination unit 62, a cathode temperature determination unit 63, a cathode temperature correction unit 64, a cathode temperature setting unit 70, an emission current setting unit 72, a bias voltage control unit 74, and a cathode temperature control unit 76. Each of the "~ units" such as the cathode temperature summing unit 60, the cathode temperature determination unit 62, the cathode temperature determination unit 63, the cathode temperature correction unit 64, the cathode temperature setting unit 70, the emission current setting unit 72, the bias voltage control unit 74, and the cathode temperature control unit 76 has a processing circuit. Such a processing circuit may include, for example, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each of the "~ units" may use a common processing circuit (the same processing circuit) or different processing circuits (separate processing circuits). Information input to and output from the cathode temperature summing unit 60, the cathode temperature determination unit 62, the cathode temperature determination unit 63, the cathode temperature correction unit 64, the cathode temperature setting unit 70, the emission current setting unit 72, the bias voltage control unit 74, and the cathode temperature control unit 76, as well as information being calculated, is stored in memory 78 each time.

[0026] The cathode (-) side of the acceleration voltage power supply circuit 236 is connected to both electrodes of the cathode 222 in the electron microscope column 102. The anode (+) side of the acceleration voltage power supply circuit 236 is grounded (connected to ground) via an ammeter 238 connected in series. The cathode (-) of the acceleration voltage power supply circuit 236 is also branched and connected to the anode (+) of the bias voltage power supply circuit 234. The cathode (-) of the bias voltage power supply circuit 234 is electrically connected to the Wehnelt 224, which is arranged between the cathode 222 and the anode 226. In other words, the bias voltage power supply circuit 234 is arranged so as to be electrically connected between the cathode (-) of the acceleration voltage power supply circuit 236 and the Wehnelt 224. The filament power supply circuit 231, controlled by the cathode temperature control unit 76, passes a current between both electrodes of the cathode 222 to heat the cathode 222 to a predetermined temperature. In other words, the filament power supply circuit 231 supplies filament power W to the cathode 222. A fixed relationship can be defined between the filament power W and the cathode temperature T, and the cathode can be heated to a desired cathode temperature T by the filament power W. Therefore, the cathode temperature T is controlled by the filament power W. The filament power W is defined as the product of the current flowing between the two electrodes of the cathode 222 and the voltage applied between the two electrodes of the cathode 222 by the filament power supply circuit 231. The acceleration voltage power supply circuit 236 applies an acceleration voltage between the cathode 222 and the anode 226. The bias voltage power supply circuit 234, controlled by the bias voltage control unit 74, applies a negative bias voltage to the Wehnelt 224.

[0027] Furthermore, drawing data is input from outside the drawing device 100 and stored in the storage device 140. The drawing data usually defines information on a plurality of graphic patterns to be drawn. Specifically, for each graphic pattern, for example, the coordinates of the vertices that make up the graphic are defined in the order in which the graphic is formed. Alternatively, for each graphic pattern, for example, a graphic code, reference position coordinates, size, etc. are defined.

[0028] 1 shows the configuration necessary for explaining the first embodiment. The drawing device 100 may also include other configurations that are normally required.

[0029] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate 203 according to the first embodiment. In FIG. 2, holes (openings) 22 are formed in a matrix of p columns (x direction) by q columns (y direction) (p, q≧2) at a predetermined pitch on the shaping aperture array substrate 203. In FIG. 2, for example, 512×512 columns of holes 22 are formed in the x and y directions. Each hole 22 is formed as a rectangle of the same size and shape. Alternatively, they may be circles of the same diameter. The shaping aperture array substrate 203 (beam forming mechanism) forms multiple beams 20. Specifically, multiple beams 20 are formed by portions of an electron beam 200 passing through each of the multiple holes 22. The arrangement of holes 22 is not limited to the grid-like arrangement shown in FIG. 2. For example, the holes in the kth column and the k+1th column in the y direction may be offset by a dimension a in the x direction. Similarly, the holes in the k+1th column and the k+2th column in the vertical direction (y direction) may be arranged with a shift of dimension b in the horizontal direction (x direction).

[0030] FIG. 3 is a cross-sectional view showing the configuration of the blanking aperture array mechanism 204 according to the first embodiment. In the blanking aperture array mechanism 204, as shown in FIG. 3, a semiconductor substrate 31 made of silicon or the like is placed on a support base 33. The central portion of the substrate 31 is removed, for example, from the backside, to form a membrane region 330 (first region) with a thin film thickness h. The area surrounding the membrane region 330 is a peripheral region 332 (second region) with a thick film thickness H. The upper surfaces of the membrane region 330 and the peripheral region 332 are formed to be at the same height position or substantially at the same height position. The substrate 31 is held on the support base 33 at the backside of the peripheral region 332. The central portion of the support base 33 is open, and the membrane region 330 is located in the open region of the support base 33.

[0031] In the membrane region 330, passage holes 25 (openings) for passing through each beam of the multibeam 20 are opened at positions corresponding to the holes 22 of the shaping aperture array substrate 203 shown in FIG. 2. In other words, a plurality of passage holes 25 for passing through corresponding beams of the multibeam 20 using electron beams are formed in an array in the membrane region 330 of the substrate 31. A plurality of electrode pairs, each having two electrodes, are arranged on the membrane region 330 of the substrate 31 at positions facing each other across a corresponding passage hole 25 among the plurality of passage holes 25. Specifically, on the membrane region 330, as shown in FIG. 3, pairs of a control electrode 24 for blanking deflection and a counter electrode 26 (blankers: blanking deflectors) are arranged in positions near each passage hole 25 on either side of the corresponding passage hole 25. Furthermore, a control circuit 41 (logic circuit) for applying a deflection voltage to the control electrode 24 for each passage hole 25 is arranged inside the substrate 31 and near each passage hole 25 on the membrane region 330. The counter electrode 26 for each beam is connected to ground.

[0032] The control circuit 41 includes an amplifier (an example of a switching circuit, not shown), such as a CMOS inverter circuit. The amplifier output line (OUT) is connected to the control electrode 24. On the other hand, a ground potential is applied to the counter electrode 26. A control signal is applied to the input (IN) of the amplifier, either an L (low) potential (e.g., ground potential) that is lower than the threshold voltage, or an H (high) potential (e.g., 1.5 V) that is equal to or higher than the threshold voltage. In the first embodiment, when an L potential is applied to the input (IN) of the amplifier, the output (OUT) of the amplifier is at a positive potential (Vdd). The corresponding beam is deflected by an electric field due to a potential difference with the ground potential of the counter electrode 26, and is controlled so that the beam is turned OFF by being blocked by the limiting aperture substrate 206. On the other hand, when an H potential is applied to the input (IN) of the amplifier (active state), the output (OUT) of the amplifier is at ground potential. Since the potential difference with the ground potential of the counter electrode 26 disappears, the corresponding beam is not deflected, and the beam is controlled so that it is turned ON by passing through the limiting aperture substrate 206.

[0033] The pairs of control electrode 24 and counter electrode 26 individually blank and deflect the corresponding beams of multi-beam 20 by the potentials switched by the amplifiers that serve as the corresponding switching circuits. In this way, the multiple blankers perform blanking deflection of the corresponding beams of multi-beam 20 that have passed through the multiple holes 22 (openings) of shaping aperture array substrate 203.

[0034] Next, the operation of the drawing mechanism 150 in the drawing apparatus 100 will be described. An electron beam 200 emitted from an electron gun 201 (electron emission source) illuminates the entire shaping aperture array substrate 203 via an illumination lens 202. A plurality of rectangular holes 22 (openings) are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area including all of the holes 22. Portions of the electron beam 200 irradiated onto the positions of the holes 22 pass through the holes 22 in the shaping aperture array substrate 203, thereby forming a plurality of electron beams (multibeams 20), each having a rectangular shape, for example. The multibeams 20 pass through corresponding blankers (first deflectors: individual blanking mechanisms) in a blanking aperture array mechanism 204. Each blanker individually deflects the passing electron beam (performs blanking deflection).

[0035] The multi-beams 20 that pass through the blanking aperture array mechanism 204 are reduced by the reduction lens 205 and travel toward the central hole formed in the limiting aperture substrate 206. Here, among the multi-beams 20, the electron beams that are deflected by the blankers of the blanking aperture array mechanism 204 are positioned away from the central hole of the limiting aperture substrate 206 and are blocked by the limiting aperture substrate 206. On the other hand, the electron beams that are not deflected by the blankers of the blanking aperture array mechanism 204 pass through the central hole of the limiting aperture substrate 206, as shown in FIG. 1. Blanking control is performed by turning on / off these individual blanking mechanisms, and the on / off of the beams is controlled. Then, the beams that are formed for each beam from when the beam is turned on until when the beam is turned off and that pass through the limiting aperture substrate 206 form a beam for one shot. The multibeams 20 that have passed through the limiting aperture substrate 206 are focused by the objective lens 207 to form a pattern image with the desired reduction ratio, and the individual beams that have passed through the limiting aperture substrate 206 (the entire multibeams 20 that have passed through) are deflected collectively in the same direction by the deflectors 208 and 209, and each beam is irradiated onto its respective irradiation position on the sample 101. Ideally, the multibeams 20 that are irradiated at one time are aligned at a pitch obtained by multiplying the arrangement pitch of the plurality of holes 22 in the shaping aperture array substrate 203 by the desired reduction ratio described above.

[0036] As described above, in the electron gun 201 that emits the electron beam, in order to obtain an emission current that will result in an electron beam of desired brightness at the lowest possible cathode temperature, the operating point of the electron gun 201 is often set near the boundary between the space charge limited region and the temperature limited region, but not within the temperature limited region.

[0037] FIG. 4 is a diagram showing an example of the current density distribution of the electron beam reaching the sample surface in the first embodiment. As shown in FIG. 4, even when the current density of the entire electron beam satisfies a desired value, the current density varies depending on the position within the entire beam. Therefore, even when the sample 101 is irradiated with the electron beam, the incident irradiation amount (dose amount) varies depending on the position within the irradiated area. In the example of FIG. 4, it can be seen that the current density decreases toward the outer periphery. In the multi-beam 20, the electron beams near the four corners of the beam array constituting the multi-beam 20 tend to have a lower current density than the electron beams in the center.

[0038] Conventionally, in electron beam lithography, the electron beam emitted from the electron gun has been periodically adjusted so that the current density of the entire electron beam is within an acceptable range. For example, conventionally, the current density of the entire electron beam has been periodically measured, and if it is insufficient, the emission current has been increased, and if it is still insufficient, the cathode temperature has been increased to adjust the current density of the entire electron beam to a desired value.

[0039] However, when adjusting an electron beam using conventional methods, the current density of the entire beam is monitored, but the position-dependent current density distribution within the beam irradiation area is not monitored. Therefore, even if the adjusted electron beam is irradiated onto a sample surface, the desired incident irradiation dose cannot be obtained at some locations within the irradiated area, such as the outer periphery. Therefore, in the first embodiment, not only the current density of the entire beam but also the current density distribution of the irradiating electron beam is measured, and the electron beam is adjusted in accordance with the current density distribution. This will be explained in detail below.

[0040] Fig. 5 is a flowchart showing an example of main steps of the writing method according to Embodiment 1. In Fig. 5, the writing method according to Embodiment 1 carries out a series of steps including a brightness measurement step (S102), a determination step (S110), an emission current determination step (S111), an emission current increase step (S112), a cathode temperature determination step (S113), a cathode temperature increase step (S114), a cathode temperature determination step (S116), a cathode temperature correction step (S118), a cathode component replacement step (S119), a current density distribution measurement step (S120), a feature calculation step (S130), a determination step (S132), and a writing step (S140). In the flowchart of FIG. 5, the electron beam adjustment method includes a brightness measurement step (S102), a determination step (S110), an emission current determination step (S111), an emission current increase step (S112), a cathode temperature determination step (S113), a cathode temperature increase step (S114), a cathode temperature determination step (S116), a cathode temperature correction step (S118), a cathode component replacement step (S119), a current density distribution measurement step (S120), a feature calculation step (S130), and a determination step (S132). The electron beam is adjusted periodically, for example, once a week. While the cathode component replacement step (S119) is preferably performed, it may be omitted.

[0041] In the brightness measurement step (S102), the brightness measurement unit 52 measures the brightness of the entire multibeam 20. Here, the current density J of the entire multibeam 20 is measured as a parameter indicating the brightness. A more detailed explanation will be given below. First, the XY stage 105 is moved to a position where the multibeam 20 can be incident on the Faraday cup 106. Then, the Faraday cup 106 detects the current value of the entire multibeam 20, which is formed from the electron beam 200 emitted from the electron gun 201 and reaches the sample surface position. The signal detected by the Faraday cup 106 is output to the current detection circuit 136, converted into digital data, and output to the control computer 110. Within the control computer 110, the brightness measurement unit 52 calculates the current density J of the entire multibeam 20. The current density J can be calculated by dividing the measured current value by the sum of the opening areas of the multiple holes 22 in the shaping aperture array substrate 203.

[0042] In the determination step (S110), the brightness determination unit 54 determines whether the adjusted brightness is equal to or greater than a threshold. If the brightness is equal to or greater than the threshold, the process proceeds to a current density distribution measurement step (S120). If the brightness is not equal to or greater than the threshold, the process proceeds to an emission current determination step (S111).

[0043] In the emission current determination step (S111), the determination unit 51 determines whether the current emission current Emi is equal to or greater than the maximum value Emax. The value of the emission current Emi can be obtained as a current value detected by the ammeter 238. The maximum value Emax of the emission current Emi is preferably set in advance for each cathode temperature T. If the current emission current Emi is equal to or greater than the maximum value Emax, the process proceeds to the cathode temperature increase step (S114). If the current emission current Emi is less than the maximum value Emax, the process proceeds to the emission current increase step (S112).

[0044] In the emission current increasing step (S112), the emission current setting unit 72 increases the emission current Emi to increase the current density J (luminance) of the entire multi-beam 20. Specifically, the operation is as follows. First, the emission current setting unit 72 sets a new emission current Emi by adding a preset current width ΔEmi to the current emission current Emi. The bias voltage control unit 74 changes the bias voltage V so as to obtain the new emission current Emi. The bias voltage control unit 74 controls the bias voltage power supply circuit 234, for example, to change the current bias voltage V to the positive side (ground potential side). The bias voltage power supply circuit 234 applies the new bias voltage V to the Wehnelt 224. Here, the bias voltage V indicates the potential difference between the negative potential applied to the cathode 222 and the negative potential applied to the Wehnelt 224 .

[0045] Then, the process returns to the brightness measurement step (S102), and the steps from the brightness measurement step (S102) to the emission current increase step (S112) are repeated until the brightness becomes equal to or greater than the threshold value or the emission current Emi becomes equal to or greater than the maximum value Emax.

[0046] This adjusts the current density J (brightness) of the entire multi-beam 20 to the current density threshold Jth. Alternatively, the current density J (brightness) of the entire multi-beam 20 is adjusted to approach the current density threshold Jth within a range in which the emission current Emi can be increased.

[0047] In addition to adjusting the brightness, it is more preferable to adjust electromagnetic lenses such as the illumination lens 202, reduction lens 205, and objective lens 207 so that the half angle of each beam on the surface of the sample 101 falls within a predetermined range.

[0048] In the cathode temperature determination step (S113), the cathode temperature determination unit 63 determines whether the set cathode temperature T is a preset maximum cathode temperature Tmax. If the set cathode temperature T is not the preset maximum cathode temperature Tmax, the process proceeds to a cathode temperature increase step (S114). If the set cathode temperature T is the preset maximum cathode temperature Tmax, the process proceeds to a cathode part replacement step (S119).

[0049] In the cathode temperature increasing step (S114), the cathode temperature adding unit 60 adds ΔT to the current cathode temperature T. The cathode temperature setting unit 70 sets the new cathode temperature T to a cathode temperature that is increased by ΔT from the current cathode temperature T. The cathode temperature T is increased by a predetermined reference temperature width ΔT. The cathode temperature control unit 76 (temperature increasing unit) controls the filament power supply circuit 231 so that the cathode temperature becomes the set cathode temperature T. This controls the cathode temperature to a newly set cathode temperature T that is increased by ΔT. The reference temperature width ΔT is preferably set in the range of 10 to 50°C, for example. For example, it is set to 20°C. Then, the bias voltage control unit 74 changes the bias voltage V so that the set emission current Emi is obtained at the cathode temperature T. For example, the bias voltage V is changed to the negative side.

[0050] In the cathode temperature determination step (S116), the cathode temperature determination unit 62 determines whether the set cathode temperature T exceeds a preset maximum cathode temperature Tmax. If the set cathode temperature T exceeds the maximum cathode temperature Tmax, the process proceeds to a cathode temperature correction step (S118). If the set cathode temperature T does not exceed the maximum cathode temperature Tmax, the process returns to the brightness adjustment step (S102), and the steps from the brightness adjustment step (S102) to the determination step (S116) are repeated until the brightness becomes equal to or greater than the threshold value or until the set cathode temperature T exceeds the maximum cathode temperature Tmax.

[0051] In the cathode temperature correction step (S118), if the set cathode temperature T exceeds the maximum cathode temperature Tmax, the cathode temperature correction unit 64 corrects the current cathode temperature T to the maximum cathode temperature Tmax. The cathode temperature setting unit 70 sets the corrected cathode temperature as the new cathode temperature T. The cathode temperature control unit 76 controls the filament power supply circuit 231 so that the cathode temperature T becomes the set cathode temperature T. This controls the cathode temperature T to the maximum cathode temperature Tmax. Then, the bias voltage control unit 74 changes the bias voltage V so that the set emission current Emi is obtained at this cathode temperature T. Because it is difficult to increase the cathode temperature any further, the process returns to the brightness measurement step (S102) at this temperature, and it is confirmed whether the desired brightness and desired current density distribution are obtained.

[0052] If the cathode temperature T set in the cathode temperature determination step (S113) is determined to be the preset maximum cathode temperature Tmax, this means that the desired brightness or current density distribution was not obtained even if the set cathode temperature T was the maximum cathode temperature Tmax. Therefore, in the cathode component replacement step (S119), the cathode component is replaced with a new one, and the process returns to the brightness measurement step (S102) and adjustment is started again. For example, if the cathode component deteriorates, it may become impossible to satisfy the current density or current density distribution even if the cathode temperature is raised to the upper limit temperature. In this case, the cathode component is replaced and adjustment is started again. In such a case, it is preferable to start the cathode temperature from an initial value that is sufficiently lower than the maximum cathode temperature Tmax.

[0053] In the current density distribution measuring step (S120), the current density distribution measuring unit 56 measures the current density distribution U of the multi-beam 20 (electron beam). In other words, the current density distribution measuring unit 56 measures the current density distribution U of the multi-beam 20 that reaches the sample 101. First, the current density distribution measurement unit 56 measures the electron beam current density J(i,j) for each of the subregions into which the irradiation region of the electron beam reaching the sample 101 is divided. (i,j) indicates the index of the subregion. In the first embodiment, a multibeam 20 is used as the electron beam, so the current density distribution measurement unit 56 divides the multibeam 20 into multiple beam array groups (subregions) in which neighboring beam groups are grouped together. For example, the beam array region of the multibeam 20 is divided into k × k subregions, and each subregion is divided into multiple beam array groups in which the beam groups in the subregion are grouped together. Then, the Faraday cup 106 detects the current value for each beam array group. First, the XY stage 105 is moved to a position where the target beam array group can be incident on the Faraday cup 106. Then, the Faraday cup 106 detects the current value of the target beam array group that has reached the sample surface position. The signal detected by Faraday cup 106 is output to current detection circuit 136, converted into digital data, and output to control computer 110. Within control computer 110, current density distribution measurement unit 56 measures (calculates) the current density J of the target beam array group for each beam array group. The current density J of the target beam array group can be calculated by dividing the measured current value by the total opening area of ​​the multiple holes 22 for each beam array group in shaping aperture array substrate 203.

[0054] Next, the current density distribution measurement unit 56 measures (calculates) the current density distribution U using the current density J for each sub-region of the plurality of sub-regions. Specifically, the current density distribution measurement unit 56 calculates the current density distribution U using the current density J for each beam array group. The current density distribution U is measured when the brightness is equal to or greater than a threshold value. The measured current density distribution U is stored in, for example, the storage device 140.

[0055] In the feature calculation step (S130), the feature calculation unit 58 calculates the feature K(i, j) of the measured current density distribution U. The feature K(i, j) is calculated for each beam array group (sub-region). The feature K(i, j) is the ratio of the current density J(i, j) of each beam array group to the maximum value Jmax of the current density J(i, j) for each beam array group (sub-region) of the current density distribution U. The feature K can be defined by the following equation (1): (1) K(i,j)=J(i,j) / Jmax

[0056] 6 is a diagram showing an example of the transition of feature quantities over time in the first embodiment. FIG. 6 shows an example of the transition of feature quantities over time at the four corners (top right corner, top left corner, bottom right corner, and bottom left corner) of the rectangular multi-beam 20. As described above, in the current density distribution U of the electron beam, the current density J tends to decrease at the outer periphery. In the example of FIG. 6, it can be seen that the feature quantities for each beam array group at the bottom right corner and bottom left corner decrease significantly over time.

[0057] In the determination step (S132), the determination unit 59 determines whether or not there is a feature amount K(i, j) that falls outside the threshold range. Specifically, the determination unit 59 determines whether or not there is a feature amount K(i, j) that is equal to or less than a threshold value Kth. The threshold value Kth is preferably set in the range of 0.95 to 0.99 (95% to 99%), for example. If there is no feature amount K(i,j) that is equal to or less than the threshold value Kth, the electron beam adjustment is terminated and the process proceeds to the drawing step (S140). If there is a feature amount K(i,j) that is equal to or less than the threshold value Kth, the process proceeds to a cathode temperature increasing step (S114), and the steps from the brightness adjusting step (S102) to the determining step (S132) are repeated until there is no feature amount K(i,j) that is equal to or less than the threshold value Kth. In this way, the cathode temperature control unit 76 (temperature increasing unit) increases the temperature of the cathode 222 (electron beam emission source) when the feature amount K(i,j) is outside the threshold range.

[0058] In the example of Figure 6, when the feature value K(i, j) of the beam array group in the lower left corner reaches the threshold value Kth, the process proceeds to the cathode temperature increase step (S114) and the cathode temperature T is increased, which increases the feature value in each sub-region and restores it to nearly the state immediately after the previous electron beam adjustment.

[0059] FIG. 7 is a diagram showing an example of a path of the operating point of the electron gun due to electron beam adjustment in the first embodiment. FIG. 8 is a diagram showing an example of a transition of a current density distribution due to adjustment of an electron beam in the first embodiment. FIG. 7 shows an example of the relationship between the emission current Emi, bias voltage V, and cathode temperature T. The vertical axis represents the emission current Emi, and the horizontal axis represents the bias voltage V. FIG. 7 shows characteristic curves of the emission current and bias voltage for each cathode temperature. The cathode temperatures T have the relationship T3>T2>T1. The boundary between the space charge limited region and the temperature limited region is indicated by a dotted line. The bias voltage value at the boundary between the space charge limited region and the temperature limited region varies depending on the cathode temperature. Generally, the lower the cathode temperature, the smaller the negative bias voltage at the boundary. The operating point for driving the electron gun 201 is generally set near the boundary between the space charge limited region and the temperature limited region, but not within the temperature limited region.

[0060] When an electron beam is emitted in the temperature-limited region, the beam's current density distribution U has a steep, non-uniform shape, resulting in localized areas of high intensity in the beam's current density distribution U. On the other hand, when an electron beam is emitted in the space-charge-limited region, the beam's current density distribution U has a highly uniform shape. At the same emission current, the locally high intensity of the beam's current density distribution U in the temperature-limited region may be higher than the intensity of the uniform portion of the beam's current density distribution U in the space-charge-limited region.

[0061] When the electron gun 201 is driven at an operating point at cathode temperature T1, if the brightness (here, the current density of the entire multi-beam) is below the threshold, the emission current Emi is increased. As a result, the operating point enters, for example, a temperature-limited region, resulting in a current density distribution U with low uniformity and a steep slope (distribution A in FIG. 8). In this state, the brightness (here, the current density of the entire multi-beam) satisfies the threshold, but the current density distribution U does not satisfy the condition (here, a feature value K(i, j) below the threshold Kth exists). Therefore, the cathode temperature T is increased to T2. The bias voltage control unit 74 then changes the bias voltage V so that the set emission current Emi is obtained. As a result, the operating point returns to, for example, a space-charge-limited region, resulting in a highly uniform current density distribution U (distribution B in FIG. 8). As a result, the current density distribution U satisfies the condition. However, this time the brightness is insufficient. The emission current Emi is then increased at cathode temperature T2. As a result, the operating point enters, for example, the temperature limited region, resulting in a current density distribution U with low uniformity and steepness (distribution C in FIG. 8). As a result, the luminance satisfies the threshold value, but the current density distribution U does not satisfy the condition. Therefore, the cathode temperature T is raised to T3. Then, the bias voltage control unit 74 changes the bias voltage V so that the set emission current Emi is obtained. As a result, the operating point returns to, for example, the space charge limited region, resulting in a current density distribution U with high uniformity (distribution D in FIG. 8). As a result, the current density distribution U satisfies the condition while satisfying the luminance condition (here, there are no feature quantities K(i, j) below the threshold Kth).

[0062] As a result, the electron beam can be adjusted so that the current density distribution U satisfies the conditions.

[0063] Next, the method of drawing processing will be described.

[0064] In the writing step (S140), first, the writing data processing unit 40 reads out writing data stored in the storage device 140 and generates writing time data for writing with the multi-beams. The writing control unit 42 rearranges the irradiation time data in shot order according to the writing sequence. Then, the irradiation time data is transferred to the deflection control circuit 130 in shot order. The deflection control circuit 130 outputs a blanking control signal to the blanking aperture array mechanism 204 in shot order, and also outputs a deflection control signal to the DAC amplifier units 132 and 134 in shot order. The writing mechanism 150, controlled by the writing control unit 42, writes a pattern on the sample 101 using the electron beam emitted from the electron gun 201 and subjected to beam adjustment. In other words, the writing mechanism 150 writes a pattern on the sample 101 using the multi-beams 20 whose feature amount K(i, j) is within a threshold range.

[0065] FIG. 9 is a conceptual diagram illustrating an example of the writing operation in the first embodiment. As shown in FIG. 9, the writing region 30 on the sample 101 is virtually divided into a plurality of stripe regions 32, each having a predetermined width in the y direction. First, the XY stage 105 is moved to adjust the irradiation region 34 that can be irradiated with one shot of the multi-beam 20 to be located at the left end of the first stripe region 32 or further to the left, and writing begins. When writing the first stripe region 32, the XY stage 105 is moved, for example, in the −x direction to relatively write in the x direction. The XY stage 105 is moved continuously, for example, at a constant speed. After writing the first stripe region 32, the stage position is moved in the −y direction to adjust the irradiation region 34 to be located at the right end of the second stripe region 32 or further to the right in the y direction. Then, the XY stage 105 is moved, for example, in the x direction to similarly write in the −x direction. The writing time can be reduced by alternately changing the writing direction, such as writing in the x direction in the third stripe region 32 and writing in the -x direction in the fourth stripe region 32. However, writing is not limited to alternately changing the writing direction, and writing in each stripe region 32 may proceed in the same direction. In one shot, multiple shot patterns, up to the same number as the number of holes 22 formed in the shaping aperture array substrate 203, are formed at once by the multi-beams formed by passing through each hole 22 in the shaping aperture array substrate 203. Furthermore, while the example in FIG. 9 shows a case where each stripe region 32 is written once, this is not limiting. Multiple writing, in which the same region is written multiple times, is also suitable. When performing multiple writing, it is suitable to set the stripe regions 32 for each pass while shifting their positions.

[0066] FIG. 10 is a diagram showing an example of a multibeam irradiation area and target pixels for writing in the first embodiment. In FIG. 10, a stripe area 32 is set with a plurality of control grids 27 (design grids) arranged in a grid pattern at a beam size pitch of the multibeams 20 on the surface of the sample 101. For example, an arrangement pitch of approximately 10 nm is preferable. These control grids 27 are the designed irradiation positions of the multibeams 20. The arrangement pitch of the control grids 27 is not limited to the beam size, and may be any size that can be controlled as the deflection position of the deflector 209 regardless of the beam size. A plurality of pixels 36 are virtually divided into a mesh shape with the same size as the arrangement pitch of the control grids 27, centered on each control grid 27. Each pixel 36 is an irradiation unit area for one beam of the multibeams. The example of FIG. 16 shows a case where the writing area of ​​the sample 101 is divided into a plurality of stripe areas 32, for example, in the y direction, with a width substantially equal to the size of the irradiation area 34 (writing field) that can be irradiated by one irradiation of the multibeams 20. The x-direction size of the irradiation area 34 can be defined by the inter-beam pitch of the multibeam 20 in the x-direction multiplied by the number of beams in the x-direction. The y-direction size of the irradiation area 34 can be defined by the inter-beam pitch of the multibeam 20 in the y-direction multiplied by the number of beams in the y-direction. Note that the width of the stripe area 32 is not limited to this. It is preferable that the size be n times the size of the irradiation area 34 (n is an integer greater than or equal to 1). In the example of FIG. 17, for example, a 512×512 array of multibeams is simplified to an 8×8 array of multibeams. Furthermore, within the irradiation area 34, a plurality of pixels 28 (beam drawing positions) that can be irradiated with one shot of the multibeam 20 are shown. In other words, the pitch between adjacent pixels 28 is the pitch between each beam of the multibeam in the design. In the example of FIG. 10, one sub-irradiation area 29 is formed by an area surrounded by the inter-beam pitch. In the example of FIG. 10, each sub-irradiation area 29 is formed by 4×4 pixels.

[0067] FIG. 11 is a diagram illustrating an example of a multi-beam writing method according to the first embodiment. FIG. 11 illustrates a portion of the sub-irradiation region 29 written by the beams at coordinates (1,3), (2,3), (3,3), . . . , (512,3) in the third row in the y direction among the multi-beams that write the stripe region 32 shown in FIG. 9 . The example in FIG. 11 illustrates a case in which, for example, four pixels are written (exposed) while the XY stage 105 moves a distance equivalent to eight beam pitches. While writing (exposing) these four pixels, the entire multi-beam 20 is deflected collectively by the deflector 208 to prevent the relative position of the irradiation region 34 with respect to the sample 101 from shifting due to the movement of the XY stage 105, thereby causing the irradiation region 34 to follow the movement of the XY stage 105. In other words, tracking control is performed. The example in FIG. 18 illustrates a case in which one tracking cycle is performed by writing (exposing) four pixels while shifting the pixel 36 to be irradiated with the beam in the y direction for each shot while moving a distance equivalent to eight beam pitches.

[0068] Specifically, the writing mechanism 150 irradiates each control grid 27 with a corresponding ON beam of the multi-beam 20 for a writing time (irradiation time or exposure time) corresponding to each control grid 27 within the maximum irradiation time Ttr among the irradiation times of each beam of the multi-beam in the shot. The maximum irradiation time Ttr is set in advance. In reality, the shot cycle is the maximum irradiation time Ttr plus the settling time of beam deflection. However, here, the settling time of beam deflection is omitted and the maximum irradiation time Ttr is shown as the shot cycle. Then, when one tracking cycle is completed, the tracking control is reset and the tracking position is swung back to the start position of the next tracking cycle.

[0069] Since drawing of the first pixel row from the right in each sub-irradiation area 29 has been completed, after tracking reset, in the next tracking cycle, the deflector 209 first deflects the beam so as to align (shift) the drawing position of the corresponding beam with the control grid 27 of the pixel in the first row from the bottom and second from the right in each sub-irradiation area 29.

[0070] As described above, during the same tracking cycle, the deflector 208 controls the irradiation region 34 so that its relative position with respect to the sample 101 remains the same, and the deflector 209 shifts the irradiation region 34 by one control grid 27 (pixel 36) to perform each shot. After one tracking cycle is completed, the tracking position of the irradiation region 34 is returned, and then, as shown in the lower part of Figure 11, the first shot position is adjusted to a position shifted by, for example, one control grid (one pixel), and each shot is performed while the deflector 209 shifts the irradiation region 34 by one control grid (one pixel) while performing the next tracking control. By repeating this operation during the writing of the stripe region 32, the position of the irradiation region 34 moves sequentially from 34a to 34o, as shown in the lower diagram of Figure 9, and the stripe region is written.

[0071] Which beam of the multi-beam irradiates which control grid 27 (pixel 36) on the sample 101 is determined by the drawing sequence. If the sub-irradiation area 29 is an area of ​​n×n pixels, n control grids (n pixels) are drawn in one tracking operation. In the next tracking operation, n pixels are drawn in the same way using a beam different from the beam described above. In this way, n pixels are drawn in n tracking operations, each with a different beam, and all pixels in one n×n pixel area are drawn. Similar operations are performed at the same time on other n×n pixel sub-irradiation areas 29 within the multi-beam irradiation area, and drawing is performed in the same way.

[0072] The beam adjustment described above is performed when writing is not being performed on the sample 101. For example, it is performed after writing on one sample is completed and before writing on the next sample is started. Alternatively, it is performed after writing on the sample is started or before it is completed, for example, after writing on a stripe 32 is completed and before writing on the next stripe region 32 is started.

[0073] As described above, according to the first embodiment, in multi-beam writing, it is possible to improve the uniformity of the current density distribution in the irradiation area of ​​the irradiated multi-beams 20. Therefore, it is possible to obtain the necessary incident irradiation amount in the entire irradiation area of ​​the multi-beams 20.

[0074] Embodiment 2 In the first embodiment, a configuration using multiple beams has been described, but the present invention is not limited to this. In the second embodiment, a configuration using a single beam will be described. The contents other than those specifically described below are the same as those of the first embodiment.

[0075] FIG. 12 is a conceptual diagram showing the configuration of a drawing device according to the second embodiment. 12, a drawing apparatus 400 includes a drawing mechanism 450. The drawing apparatus 400 is an example of an electron beam drawing apparatus. The drawing mechanism 450 includes an electron lens barrel 402 and a drawing chamber 403. Inside the electron lens barrel 402, an electron gun 201, an illumination lens 502, a first shaping aperture substrate 503, a projection lens 504, a deflector 505, a second shaping aperture substrate 506, an objective lens 507, and a deflector 508 are arranged.

[0076] A movably arranged XY stage 405 is disposed within the writing chamber 403. A sample 401 is disposed on the XY stage 405. As in the first embodiment, the sample 401 includes a photomask substrate or the like. These mask substrates include, for example, mask blanks on which no pattern has yet been formed. A Faraday cup 406 is disposed on the XY stage 405.

[0077] Also, the control system circuitry is omitted in Fig. 12. The drawing apparatus 400 in the second embodiment has a configuration equivalent to the control system circuitry 160 shown in Fig. 1. For example, it has a control computer 110, a memory 112, a monitor 114, an electron gun power supply device 120, a deflection control circuit 130, DAC amplifier units 132 and 134, a current detection circuit 136, a stage position detector 139, and a storage device 140.

[0078] 12 omits the illustration of components other than those necessary for explaining the present embodiment 2. It goes without saying that the drawing device 400 may include other components that are normally required.

[0079] An electron beam 200 emitted from an electron gun 201 (electron emission source) is illuminated by an illumination lens 502 over the entire first shaping aperture substrate 503, which has a rectangular hole, e.g., a rectangular hole. Here, the electron beam 200 is first shaped into a rectangle. Then, the electron beam 200 as a first aperture image having passed through the first shaping aperture substrate 503 is projected onto a second shaping aperture substrate 506 by a projection lens 504. The position of the first aperture image on the second shaping aperture substrate 506 is deflection-controlled by a deflector 505, thereby changing the beam shape and size. As a result, the electron beam 200 is variably shaped. Typically, the beam shape and / or size are changed for each shot. Then, the electron beam 200 as a second aperture image having passed through the second shaping aperture substrate 506 is focused by an objective lens 507 and deflected by a deflector 508. As a result, a shot of the shaped electron beam 200 is irradiated onto a desired position of the sample 401 on the XY stage 405. The XY stage 105 moves continuously. That is, the drawing device 400 draws while the XY stage 405 moves continuously. Alternatively, step-and-repeat movement may be performed. In that case, the drawing device 400 draws while the XY stage 405 is stopped while moving in a step-and-repeat manner.

[0080] Even in the case of such a single beam, a current density distribution occurs in the emitted electron beam 200, as shown in Fig. 4. In the example of Fig. 4, this corresponds to, for example, the first aperture image that has passed through the first shaping aperture substrate 503. In the second embodiment, the electron beam is variably shaped for each shot, so that the electron beam that reaches the surface of the sample 401 usually uses some of the four corners of the first aperture image. Therefore, the current density distribution U becomes an issue.

[0081] A flowchart showing an example of the main steps of the writing method according to the second embodiment is similar to that shown in FIG.

[0082] In the brightness measurement step (S102), the brightness measurement unit 52 measures the brightness of the electron beam 200. Here, as a parameter indicating brightness, the current density J of the entire electron beam 200 that can reach the sample 101 is measured. A more detailed explanation will be given below. First, the XY stage 105 is moved to a position where the electron beam 200 can be incident on the Faraday cup 106. Then, the Faraday cup 106 detects the overall current value of the electron beam 200 that is emitted from the electron gun 201, passes through the first shaping aperture substrate 503, and reaches the sample surface position. The signal detected by the Faraday cup 106 is output to the current detection circuit 136, converted into digital data, and output to the control computer 110. Within the control computer 110, the brightness measurement unit 52 calculates the current density J of the entire electron beam 200. The current density J can be calculated by dividing the measured current value by the opening area of ​​the first shaping aperture substrate 503. Here, the deflector 505 is controlled so that the entire electron beam 200 that has passed through the first shaping aperture substrate 503 passes through the shaping aperture of the second shaping aperture substrate 506 .

[0083] The contents of each of the determination step (S110), emission current determination step (S111), emission current increase step (S112), cathode temperature increase step (S114), cathode temperature determination step (S116), and cathode temperature correction step (S118) are the same as those in the first embodiment.

[0084] In the current density distribution measuring step (S120), the current density distribution measuring unit 56 measures the current density distribution U of the electron beam 200 (electron beam). In other words, the current density distribution measuring unit 56 measures the current density distribution U of the electron beam 200 that reaches the sample 101. First, the current density distribution measurement unit 56 measures the current density J(i, j) of the electron beam for each of a plurality of sub-regions into which the irradiation region of the electron beam reaching the sample 101 is divided. (i, j) indicates the index of the sub-region. In the second embodiment, a single beam is used as the electron beam, so the current density distribution measurement unit 56 divides the single beam into a plurality of sub-regions.

[0085] FIG. 13 is a diagram illustrating a method for measuring the current density distribution in the second embodiment. In FIG. 13, a rectangular opening 411 is formed in the first shaping aperture substrate 503. A shaping aperture 421 is formed in the second shaping aperture substrate 506. In the example of FIG. 13, the shaping aperture 421 is rectangular, but this is not limiting. Other shapes are also possible. Furthermore, a subregion opening 423 is formed in the second shaping aperture substrate 506 at a position different from the shaping aperture 421. The shaping aperture 421 is sized to allow the entire first aperture image to pass therethrough, whereas the subregion opening 423 is formed to have the size of a subregion obtained by dividing the rectangular irradiation region of the first aperture image on the second shaping aperture substrate 506 into k × k subregions. Therefore, the subregion opening 423 passes only a partial beam within one of the subregions of the first aperture image.

[0086] FIG. 14 is a diagram illustrating a procedure for measuring a current density distribution in the second embodiment. As shown in FIG. 14, the deflector 505 deflects the electron beam 200 to move the subregion that irradiates the subregion aperture 423, allowing the partial beam of each subregion to pass through individually. The Faraday cup 106 then detects the current value for each subregion. First, the XY stage 405 is moved to a position where the partial beam of the target subregion can be incident on the Faraday cup 106. The Faraday cup 106 then detects the current value of the partial beam of the target subregion that has reached the sample surface. The signal detected by the Faraday cup 106 is output to the current detection circuit 136, converted into digital data, and output to the control computer 110. Within the control computer 110, the current density distribution measurement unit 56 measures (calculates) the current density J of the partial beam of the target subregion for each subregion. The partial beam current density J in the target subregion can be calculated by dividing the measured current value by the aperture area of ​​the subregion aperture 423.

[0087] Next, the current density distribution measurement unit 56 uses the current density J for each of the plurality of sub-regions to measure (calculate) the current density distribution U. The measured current density distribution U is stored in the storage device 140, for example.

[0088] In the feature calculation step (S130), the feature calculation unit 58 calculates the feature K(i, j) of the measured current density distribution U. The feature K(i, j) is calculated for each sub-region. The feature K(i, j) is the ratio of the current density J(i, j) of each beam array group to the maximum value Jmax of the current density J(i, j) for each sub-region of the current density distribution U. The feature K can be defined by the above-mentioned formula (1).

[0089] The example of the transition of feature amounts over time shown in Fig. 6 may also produce similar results in the case of a single beam. The result in Fig. 6 corresponds to an example of the transition of feature amounts over time at the four corners (upper right corner, upper left corner, lower right corner, and lower left corner) of the electron beam 200 that has passed through the first shaping aperture array substrate 503. Here too, for example, the feature amounts of the sub-regions at the lower right corner and the lower left corner may decrease significantly over time.

[0090] The contents of the determination step (S132) are the same as those in the first embodiment.

[0091] In the writing step (S140), the writing mechanism 150 controlled by the writing control unit 42 writes a pattern on the sample 101 using the electron beam 200 that has been adjusted and emitted from the electron gun 201. In other words, the writing mechanism 150 writes a pattern on the sample 101 using the electron beam 200 whose feature amount K(i, j) is within a threshold range.

[0092] As described above, according to the second embodiment, the uniformity of the current density distribution within the irradiation area of ​​the irradiated beam can be improved in single beam writing, and therefore the required incident irradiation amount can be obtained over the entire irradiation area of ​​the electron beam 200.

[0093] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples.

[0094] Furthermore, the processing functions described in embodiment 1 may be executed by a computer, and a program for causing a computer to execute such processing functions may be stored in a non-transitory, tangible readable recording medium such as a magnetic disk device.

[0095] Although the description of the device configuration, control method, and other parts not directly necessary for the explanation of the present invention have been omitted, the required device configuration and control method can be appropriately selected and used. For example, the description of the control unit configuration that controls the drawing device 100 has been omitted, but it goes without saying that the required control unit configuration can be appropriately selected and used.

[0096] In addition, all electron beam adjustment methods, electron beam writing apparatuses, and programs (or readable recording media on which programs are non-temporarily recorded) that include elements of the present invention and that can be appropriately modified by a person skilled in the art are included in the scope of the present invention. [Explanation of symbols]

[0097] 20 Multibeam 22 holes 24 control electrode 25 Passing hole 26 Counter electrode 27 Control Grid 28 pixels 29 Sub-irradiation area 30 drawing area 32 stripe area 31 PCB 33 Support stand 34 Irradiation area 36 pixels 40 Drawing data processing unit 41 Control circuit 42 Drawing control unit 51 Judgment section 52 Luminance measurement unit 54 Luminance judgment unit 56 Current density distribution measurement section 58 Feature calculation unit 59 Judgment section 60 Cathode temperature adder 62,63 Cathode temperature determination unit 64 Cathode temperature correction unit 70 Cathode temperature setting unit 72 Emission current setting section 74 Bias voltage control section 76 Cathode temperature control unit 78 memory 79 Storage device 100 drawing device 101 Sample 102 Electron Telescope 103 Drawing room 105 XY stage 106 Faraday Cup 110 Control computer 112 memory 114 Monitor 120 Electron gun power supply 130 Deflection control circuit 132,134 DAC amplifier unit 136 Current detection circuit 139 Stage Position Detector 140 Storage device 150 Drawing mechanism 160 Control Circuits 200 electron beam 201 Electron Gun 202 Lighting lens 203 Shaped Aperture Array Substrate 204 Blanking Aperture Array Mechanism 205 Reduction Lens 206 Limiting Aperture Substrate 207 Objective Lens 208,209 Deflector 210 Mirror 222 cathode 224 Wehnelt 226 Anode 231 Filament power supply circuit 232 Control Computer 234 Bias voltage power supply circuit 236 Accelerating voltage power supply circuit 238 Ammeter 330 Membrane Region 332 Outer area 400 Drawing device 450 Drawing mechanism 402 Electron Telescope 403 Drawing room 502 Lighting lens 503 First shaping aperture substrate 504 Projection Lens 505 Deflector 506 Second shaping aperture substrate 507 Objective Lens 508 Deflector

Claims

1. measuring the current density distribution of the electron beam reaching the sample; calculating a feature amount of the measured current density distribution; increasing the temperature of the electron beam source when the characteristic amount falls outside a threshold range; 1. An electron beam adjusting method comprising:

2. The cathode of an electron gun is used as the electron beam emission source.

2. The method for adjusting an electron beam according to claim 1.

3. a sample is irradiated with the electron beam; measuring a current density of the electron beam for each of a plurality of sub-regions into which an irradiation region of the electron beam reaching the sample is divided; The current density distribution is measured using a current density for each sub-region of the plurality of sub-regions.

3. The electron beam adjusting method according to claim 1 or 2.

4. As the feature amount, a ratio of the current density of each sub-region to a maximum current density of each sub-region of the current density distribution is used.

4. The electron beam adjusting method according to claim 3.

5. measuring the brightness of the entire electron beam; The current density distribution is measured when the luminance is equal to or greater than a threshold value.

3. The electron beam adjusting method according to claim 1 or 2.

6. The temperature is increased by a predetermined reference temperature width.

3. The electron beam adjusting method according to claim 1 or 2.

7. a current density distribution measurement unit for measuring the current density distribution of the electron beam reaching the sample; a feature amount calculation unit that calculates a feature amount of the measured current density distribution; a temperature increasing unit that increases the temperature of the electron beam emission source when the characteristic amount falls outside a threshold range; a writing mechanism that writes a pattern on a sample using the electron beam whose feature amount is within a threshold range; 1. An electron beam lithography apparatus comprising:

8. measuring the current density distribution of the electron beam reaching the sample; a process of storing the measured current density distribution in a storage device; a process of reading the current density distribution from the storage device and calculating a feature amount of the current density distribution; a process of increasing the temperature of the electron beam source when the characteristic amount falls outside a threshold range; A program that causes a computer to execute the following.

Images