Multi-charged particle beam drawing method and multi-charged particle beam drawing apparatus

Abstract

The invention provides a multi-charged particle beam drawing method and a multi-charged particle beam drawing device which can suppress the influence of coulomb effect and improve drawing precision. The multi-charged particle beam drawing method comprises: a step for grouping a plurality of beams into a plurality of beam groups; a step for determining the irradiation time for each beam emitted each time; and an emission division step for dividing each emission into a plurality of irradiation steps including irradiation steps of different irradiation times, grouping a plurality of irradiation steps of a predetermined first irradiation time into a first group in a part of the divided plurality of irradiation steps, and dividing the plurality of irradiation steps into a second group in a part of the divided plurality of irradiation steps. A group of irradiation steps for the irradiation time for each beam, in which the total of the irradiation times for each irradiation step has been determined, is selected. In the emission division step, the timing of a first group of irradiation steps belonging to the irradiation steps of each of the plurality of beam groups is determined on the basis of a predetermined distribution order and the number of irradiation steps to be turned on, so that the timing differs for each beam group.

Description

[0001] Related Application

[0002] This application claims the priority of Japanese Patent Application No. 2023-138217 (filing date: August 28, 2023) as a basic application. The present application incorporates the entire contents of the basic application by reference. Technical Field

[0003] The invention relates to a multi-charged particle beam drawing method and a multi-charged particle beam drawing device. Background Art

[0004] With the high integration of LSI, the circuit line width used for semiconductor devices is miniaturized year by year. In order to form a desired circuit pattern as a semiconductor device, a method is adopted in which a high-precision original pattern (also called an intermediate mask used in a mask, or particularly in a stepper or scanner) formed on a light-shielding film on a glass substrate is reduced and transferred to a wafer using a reduced projection exposure device. In the production of the high-precision original pattern, the so-called electron beam lithography technology in which a resist pattern is formed by an electron beam drawing device is adopted. In addition, there is also a case of a so-called wafer direct drawing method in which a pattern is formed on a resist coated on a wafer using an electron beam.

[0005] In a multi-beam drawing device using a blanking aperture array substrate as one form of a multi-beam drawing device, for example, an electron beam emitted from one electron gun is passed through a forming aperture array component having a plurality of openings to form a plurality of beams (a plurality of electron beams). A blanking aperture array substrate is provided downstream of the forming aperture array component. The blanking aperture array substrate has an electrode pair (blanker) for deflecting the beam individually and an opening for beam passage formed between the electrode pairs for each of the multi-beams, and these are arranged in an array on the blanking aperture array substrate. The blanking aperture array substrate switches the blanking deflection of the beam passing through between the electrode pairs corresponding to each of the multi-beams to be the same potential or to be different potentials from each other. The multi-beams formed by the forming aperture array component pass through the passing holes between the corresponding blankers of the blanking aperture array substrate. The optical lens barrel of the multi-beam drawing device is configured to shield the electron beam deflected by the blanker and irradiate the electron beam that is not deflected onto the substrate.

[0006] Compared with the case of drawing with a single electron beam, the drawing device using multiple beams can significantly improve the production capacity because more beams can be irradiated at one time. On the other hand, since the total beam current can be set larger, the drawing accuracy may be deteriorated due to the Coulomb effect. Specifically, the repulsion between electrons may cause a deterioration in the resolution of the beam, a beam position deviation on the sample surface, or a focus deviation. The Coulomb effect occurs significantly in places where the density of electron beams is high in the optical system, such as the crossover where multiple beams are focused to a point, but the Coulomb effect at the crossover on the downstream side of the blanking aperture array substrate is not constant, and varies depending on the total current of the connected beams in the multiple beams.

[0007] As a countermeasure for the deterioration of the drawing accuracy due to the Coulomb effect, for example, a method of reducing the total current of the connected beam has been proposed (see Japanese Patent Application Laid-Open No. 2007-329220). This method is effective when the waiting time for the beam not to be connected in the emission cycle is longer than the time for the beam to be connected because the beam control is not high-speed, etc. However, if the drawing system is optimized to shorten the waiting time for the beam not to be connected, the effect becomes smaller. Summary of the invention

[0008] A technical solution of the present invention provides a multi-charged particle beam drawing method and a multi-charged particle beam drawing device that suppress the influence of the Coulomb effect and improve the drawing accuracy.

[0009] A multi-charged particle beam drawing method according to one technical solution of the present invention comprises: a process of emitting multiple beams of charged particles; a process of grouping the multiple beams constituting the multiple beams into multiple beam groups; a process of determining the irradiation time of each beam of each emission of the multiple beams according to drawing pattern data; an emission division process of dividing the above-mentioned each emission into multiple irradiation steps including irradiation steps with different irradiation times, and in a part of the multiple irradiation steps after division, grouping multiple irradiation steps with a predetermined first irradiation time into a first group, selecting a group of irradiation steps whose total irradiation time of each irradiation step is determined to be the irradiation time of each beam; and a process of switching each beam of the multiple beams on and off to execute the group of the multiple irradiation steps to perform multiple beam emission; in the above-mentioned emission division process, based on the predetermined allocation order and the number of the above-mentioned irradiation steps that become turned on, the timing of the irradiation step of the above-mentioned first group of the above-mentioned multiple irradiation steps belonging to each of the multiple beam groups is determined so that the timing of the irradiation step of the above-mentioned first group is different for each of the above-mentioned beam groups. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of a multi-charged particle beam imaging device according to an embodiment of the present invention.

[0011] Figure 2 is a top view of the shaped aperture array component.

[0012] Figure 3 is a cross-sectional view showing the structure of a blanking aperture array substrate.

[0013] Figure 4 This is a schematic diagram of the control circuit in the blanking aperture array substrate.

[0014] Figure 5 It is a structural diagram of the input and output circuit and the unit array circuit.

[0015] Figure 6 This is a schematic structural diagram of a separate blanking mechanism.

[0016] Figure 7 This is a diagram showing an example of irradiation steps within one emission cycle.

[0017] Figure 8 1 is a diagram showing an example of beam-on timing.

[0018] Fig. 9 It is a diagram showing the order of allocating irradiation steps.

[0019] Fig.10 1 is a diagram showing an example of beam-on timing.

[0020] Fig.11 1 is a diagram showing an example of beam-on timing.

[0021] Fig.12 (a)~ Fig.12 (c) is a diagram showing an example of grouping of beam arrays.

[0022] Fig.13 This is a flowchart illustrating the drawing method.

[0023] Fig.14 This is a diagram that explains the drawing action.

[0024] Fig.15 It is a diagram showing the order of allocating irradiation steps.

[0025] Fig.16 1 is a diagram showing an example of beam-on timing.

[0026] Fig.17 It is a diagram showing the order of allocating irradiation steps.

[0027] Fig.18 1 is a diagram showing an example of beam-on timing.

[0028] Fig.19Graphs showing examples of beam currents in a case where the beam turning-on timing is shifted and a case where the beam turning-on timing is not shifted. DETAILED DESCRIPTION

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a configuration using an electron beam as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and may be an ion beam.

[0030] Figure 1 1 is a schematic diagram of the structure of a drawing device according to an embodiment of the present invention. Figure 1 As shown, the drawing device 100 includes a drawing unit 150 and a control unit 160. The drawing device 100 is an example of a multi-charged particle beam drawing device. The drawing unit 150 includes an electron lens barrel 102 and a drawing chamber 103. In the electron lens barrel 102, an electron gun 201, an illumination lens 202, a shaping aperture array component 203, a blanking aperture array substrate 204, a reduction lens 205, a limiting aperture component 206, an objective lens 207 and a deflector 208 are arranged.

[0031] An XY stage 105 is arranged in the drawing chamber 103. On the XY stage 105, a substrate 101 of a drawing object is arranged. A resist for electron beam exposure is applied to the upper surface of the substrate 101. The substrate 101 is, for example, a mask blank or a semiconductor substrate (silicon wafer) processed by a semiconductor device. In addition, a reflector 210 for measuring the stage position is arranged on the XY stage 105.

[0032] The control unit 160 includes a control computer 110, a deflection control circuit 130, a table position detector 139, and a storage unit 140. In the storage unit 140, drawing data is input from the outside and stored. In the drawing data, information of a plurality of graphic patterns used for drawing is defined. Specifically, a graphic code, coordinates, and size are defined for each graphic pattern. In the drawing data, other information, such as control information of the irradiation amount, may also be additionally defined.

[0033] The control computer 110 includes an area density calculation unit 111, an irradiation time calculation unit 112, a data processing unit 113, and a drawing control unit 114. Each unit of the control computer 110 may be composed of hardware such as circuits, or software such as programs that execute these functions. Alternatively, it may be composed of a combination of hardware and software.

[0034] The stage position detector 139 irradiates the reflection mirror 210 with laser light, receives the reflected light from the reflection mirror 210 , and detects the position of the XY stage 105 by laser interferometry.

[0035] Figure 22 is a conceptual diagram showing the structure of the shaping aperture array component 203. The shaping aperture array component 203 is a plate-shaped component such as Figure 2 As shown, a plurality of openings 203a are formed along the longitudinal direction (y direction) and the transverse direction (x direction) in the plane of the shaping aperture array component 203. Each opening 203a is preferably formed in a rectangular shape of the same or substantially the same size. The shape of each opening 203a may also be circular.

[0036] The electron beam 200 emitted from the electron gun 201 (emission unit) illuminates the shaping aperture array component 203 through the illumination lens 202. The electron beam 200 illuminates the region including all the openings 203a in the shaping aperture array component 203. A portion of the electron beam 200 passes through the plurality of openings 203a of the shaping aperture array component 203, and the remaining beam is blocked by the shaping aperture array component 203, thereby forming a plurality of electron beams, i.e., multi-beams 20a to 20e. The shape of each multi-beam is in accordance with the shape of the opening 203a of the shaping aperture array component 203, for example, a rectangular shape.

[0037] like Figure 3 As shown, the blanking aperture array substrate 204 has a support platform 204a and a semiconductor substrate 204b made of silicon or the like disposed on the support platform 204a. The central portion of the semiconductor substrate 204b is cut thinner from the back side and processed into a diaphragm region 204c with a thinner film thickness. The area surrounding the diaphragm region 204c is a peripheral region with a thicker film thickness, and the semiconductor substrate 204b is held on the support platform 204a through the back side of the peripheral region. The central portion of the support platform 204a is open, and the position of the diaphragm region 204c is located in the region of the opening of the support platform 204a.

[0038] In the diaphragm region 204c, a plurality of beam passing holes H are formed to match the respective arrangement positions of the plurality of openings 203a of the aperture array component 203. In each passing hole H, a blanker 50 composed of a pair of two electrodes 51 and 52 is arranged, and one of the plurality of beams passes between the electrode pair and through the passing hole H. The blanker 50 switches the deflection of the beam passing through the passing hole H between on and off by grounding one electrode 52 and maintaining it at the ground potential and switching the other electrode 51 to the ground potential or a potential other than the ground potential. Thus, the blanker 50 performs blanking control to set the plurality of beams to a certain state of beam on and beam off. The principle of blanking control is described below.

[0039] When one of the multiple beams is controlled to be in the beam-on state, the opposing electrodes 51 and 52 of the blanker 50 are controlled to be at the same potential, and the blanker 50 does not deflect the beam passing through the through hole H. When controlled to be in the beam-off state, the opposing electrodes 51 and 52 of the blanker 50 are controlled to be at different potentials from each other, and the blanker 50 deflects the beam passing through the through hole H.

[0040] The multiple beams 20 a to 20 e that have passed through the blanking aperture array substrate 204 are reduced by the reduction lens 205 and travel toward the central opening formed on the limiting aperture component 206 .

[0041] Here, the beam controlled to be in the beam-off state is deflected by the blanker 50, and is shielded by the limiting aperture component 206 because it leads to a track outside the opening of the limiting aperture component 206. On the other hand, the beam controlled to be in the beam-on state passes through the opening of the limiting aperture component 206 because it is not deflected by the blanker 50. The trajectory of the beam is pre-adjusted by the calibration coil (not shown) so that the beam controlled to be in the beam-on state is located within the opening of the limiting aperture component 206. Figure 1 In the embodiment, the orbits of the multiple beams are adjusted so that the multiple beams in the beam-on state are concentrated at one point at the position of the limiting aperture member 206, but it is preferable to adjust the calibration coil so that the one point is located at the center of the opening of the limiting aperture member 206. In this way, the on / off state of each beam of the multiple beams is controlled by the combination of the on / off operation of the deflection of the blanker 50 and the shielding of the beam by the limiting aperture. That is, blanking control is performed.

[0042] As described above, the blanking aperture array substrate 204 uses a plurality of blankers 50 to perform blanking control on each of the multiple beams 20 individually. That is, for each of the multiple beams 20, the beam-on and beam-off states can be switched independently. In the irradiation process described later, from the state where all the beams of the multiple beams are controlled to be in the beam-off state, only the specified beam is blanked and controlled to be in the beam-on state, and after a specified time, all the beams are controlled to be in the beam-off state. Through such blanking control, only the selected beam among the multiple beams can be controlled to be in the beam-on state for a specified time.

[0043] The multiple beams that have passed through the limiting aperture member 206 are focused by the objective lens 207 and are imaged as a pattern image of a desired reduction ratio on the substrate 101. Ideally, the multiple beams are arranged on the substrate 101 at a pitch obtained by multiplying the arrangement pitch of the multiple openings 203a of the shaping aperture array member 203 by the desired reduction ratio. The beams (the entire beams in the beam-on state among the multiple beams) that have passed through the limiting aperture member 206 are deflected together in the same direction by the deflector 208 and irradiated on a desired position on the substrate 101 in a state of focusing on the surface of the substrate 101.

[0044] The irradiation of the substrate 101 by the multi-beam can be performed when the XY stage 105 is stationary or when it is continuously moving. When the XY stage 105 is continuously moving, the stage position detector 139 measures the change in the stage position, and using the result, the deflector 208 is used to continuously change the position of the multi-beam so that it follows the movement of the XY stage 105. This is called stage tracking deflection. By stage tracking deflection, the position of the multi-beam on the substrate 101 can be fixed. At least during the period of irradiating the substrate 101 with beams, the stage tracking deflection is controlled to be performed so that the position of each beam of the multi-beam on the substrate 101 becomes stationary.

[0045] In addition to the blanker 50 and the through hole H described above, the blanking aperture array substrate 204 also includes a control circuit for applying a desired voltage to the blanker 50. The control circuit is as follows: Figure 4 As shown, an input-output circuit 31 and a unit array circuit 34 are provided.

[0046] like Figure 5 As shown in FIG. 1 , a plurality of units constituting the individual blanking mechanism 40 for driving the blanking device 50 are provided on the unit array circuit 34. Figure 5 , an example of a blanking aperture array substrate having 262144 unit array circuits and blankers composed of 512 rows and 512 columns is shown. One individual blanking mechanism 40 drives one blanker 50. The input-output circuit 31 outputs data received from the deflection control circuit 130 to the unit array circuit 34. For example, the input-output circuit 31 includes an input-output circuit 31a that outputs data to the individual blanking mechanism 40 arranged on one half side of the unit array circuit 34 and an input-output circuit 31b that outputs data to the individual blanking mechanism 40 arranged on the other half side.

[0047] The input / output circuit 31 is provided with a plurality of selectors 320 (multiplexers). The selectors 320 receive irradiation time control data defining the on / off of each beam via the amplifier 310 and output the data from the corresponding output line. A plurality of individual blanking mechanisms 40 are connected in series to each output line.

[0048] The selector 320 has, for example, eight output lines row1 to row8, each of which is connected to 256 individual blanking mechanisms 40. By configuring 64 selectors 320 in each of the input and output circuits 31a and 31b, the irradiation time control data can be transferred to 512×512 individual blanking mechanisms 40 constituting the unit array circuit 34.

[0049] like Figure 6As shown, the individual blanking mechanism 40 includes a shift register 41, a pre-buffer 42, a buffer 43, a data register 44, a NAND circuit 45, and an amplifier 46. The shift register 41 transfers data output from the shift register of the preceding unit to the shift register of the succeeding unit according to a clock signal (SHIFT).

[0050] The pre-buffer 42 stores the irradiation time control data for the unit output from the shift register 41 in accordance with the clock signal (LOAD1).

[0051] The buffer 43 takes in and holds the output value of the pre-buffer 42 in accordance with the clock signal (LOAD2).

[0052] The data register 44 takes in and holds the output value of the buffer 43 in accordance with the clock signal (LOAD3).

[0053] To the NAND circuit 45, the output signal of the data register 44 and the shot enable signal (SHOT_ENABLE) are inputted. The output signal of the NAND circuit 45 is given to an electrode 51 of a blanker 50 via an amplifier 46 (driver amplifier).

[0054] When both the output signal of the data register 44 and the emission enable signal are high, the output of the NAND circuit 45 becomes low, the electrode 51 and the electrode 52 become the same potential, and the blanker 50 does not deflect the beam, so the beam is turned on. When at least one of the output signal of the data register 44 and the emission enable signal is low, the output of the NAND circuit 45 becomes high, the electrode 51 and the electrode 52 become different potentials, the blanker 50 deflects the beam, and the beam is turned off.

[0055] The emission enable signal is input to the NAND circuits 45 of all the individual blanking mechanisms 40 . By setting the emission enable signal to a low potential (Low), all the bundles can be turned off regardless of the output signal of the data register 44 .

[0056] When the emission enable signal is maintained at a high potential (High), the beam is switched on / off by the output of the data register 44. That is, the beam is turned on when the irradiation time control data is 1 (High), and the beam is turned off when the irradiation time control data is 0 (Low).

[0057] In order to form a resist pattern in a desired size by exposure of the resist, it is necessary to control the exposure amount to an appropriate value. That is, in blanking control, it is necessary not only to switch the on / off of the beam, but also to control the time when the beam is on. Since the blanking control is performed by a logic circuit, i.e., a digital circuit, the exposure time is represented by an integer value. For example, the exposure time T is divided by the quantization unit Δ to calculate the stepped (Japanese: stepped) exposure time N. The quantization unit Δ can be set in various ways, but it is set so that the maximum exposure time obtained by multiplying the maximum value of the stepped exposure time N by the quantization unit Δ is greater than the maximum value of the exposure time required for exposure. The quantization unit Δ is set to 1ns, for example.

[0058] In multi-beam drawing, since some of the beams are positioned inside the pattern and other beams are positioned at the end of the pattern or in a region without a pattern, the irradiation time control data assigned to each of the beams is not the same for all the beams. Therefore, it is necessary to independently control the irradiation time of each of the beams. As one method of such control, the irradiation time of each beam is controlled by using Figure 4 The circuit of the blanking plate 204 shown divides one emission into a plurality of irradiation steps of different lengths, and controls each beam so that each beam is turned on at the irradiation step required to obtain the desired exposure time. Therefore, the step value N is converted into a binary number of n digits, and the length of the irradiation step corresponding to each digit of the binary number of n digits, that is, the time when the beam is turned on, is set to the time obtained by multiplying the decimal number corresponding to each digit of the binary number by Δ.

[0059] For example, if the step-wise irradiation time N = 50 and the number of digits n = 8, then according to the relationship of expressing the decimal number as the sum of powers of 2, 50 = 2 5 +2 4 +2 1 , the irradiation time control data is uniquely determined to be "00110010". Similarly, if the stepwise irradiation time N = 100 and the number of bits n = 8, the irradiation time control data becomes "01100100".

[0060] The first bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 1Δ. The second bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 2Δ. The third bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 4Δ. The fourth bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 8Δ. The fifth bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 16Δ. The sixth bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 32Δ. The seventh bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 64Δ. The eighth bit from the lower order of the irradiation time control data corresponds to the irradiation step of irradiation time 128Δ. That is, one emission is divided into the same number of irradiation steps as the number of bits (number of bits) n of the irradiation time control data, and each irradiation step has Δ×2 k－1 (k=1, 2, ..., n) irradiation time.

[0061] Figure 7 The following is an example of an irradiation step of 1 shot when the number of bits n=8 and the quantization unit Δ=1ns. In this example, the irradiation steps are performed in sequence starting from the irradiation step with the longer irradiation time. The first irradiation step is an irradiation with an irradiation time of 128ns. The second irradiation step is an irradiation with an irradiation time of 64ns. The third irradiation step is an irradiation with an irradiation time of 32ns. The fourth irradiation step is an irradiation with an irradiation time of 16ns. The fifth irradiation step is an irradiation with an irradiation time of 8ns. The sixth irradiation step is an irradiation with an irradiation time of 4ns. The seventh irradiation step is an irradiation with an irradiation time of 2ns. The eighth irradiation step is an irradiation with an irradiation time of 1ns. In addition, since the total irradiation time does not change even if the irradiation steps are replaced, it is also possible to replace them with the same irradiation time. Figure 7 Different order implementation.

[0062] In the case of N=100, the irradiation time control data is "01100100", such as Figure 8 As shown, the beam is controlled to be on in the 2nd (64ns), 3rd (32ns), and 6th (4ns) irradiation steps, and the beam is controlled to be off in the 1st, 4th, 5th, 7th, and 8th irradiation steps.

[0063] As described above, the required irradiation time is set for each of the multiple beams. In a certain emission, when a certain staged irradiation time, for example, N=100, is set for a certain beam, a different staged irradiation time, for example, N=50, is also set for other beams. Multiple irradiation processes in one emission cycle are implemented simultaneously for all multiple beams, but each beam is independently controlled to be beam-on or beam-off in each irradiation process. That is, for a beam with a staged irradiation time of N=100 and a beam with N=50, the beam-on and beam-off in each irradiation process are controlled with different irradiation time data, that is, with different combinations of beam-on and beam-off corresponding to each irradiation process. In this way, the irradiation time of each of the multiple beams in one emission cycle is independently controlled for each beam.

[0064] In the drawing by electron beam irradiation, when the pattern is irradiated with a uniform irradiation amount, the so-called proximity effect occurs, in which the pattern size becomes thicker at a location where the pattern density is high. This is because the electrons that pass through the resist coated on the upper surface of the substrate of the drawing object are backscattered by the substrate and re-injected into the resist, causing secondary resist exposure. In order to correct this proximity effect, a method of correcting the irradiation amount based on the pattern density around the beam irradiation position is used.

[0065] In this method, the higher the pattern density, the smaller the irradiation amount is, so that the photosensitivity of the resist, that is, the sum of the primary photosensitivity caused by irradiation and the secondary photosensitivity caused by backscattering, becomes constant regardless of the pattern density. As a result, the pattern size can be made constant regardless of the pattern density. The secondary photosensitivity caused by backscattering is about half the size of the primary photosensitivity caused by irradiation. In this case, in a pattern with a density of 100%, half the irradiation amount of a pattern with a density of 0% is used. The proximity effect correction irradiation amount D is given by the following formula, for example.

[0066]

[0067] Here, D base is the reference irradiation amount, η is the backscattering coefficient, and U is the average pattern density at the irradiation position.

[0068] In multi-beam drawing, especially multi-beam drawing using many multi-beams, there may be a case where there are both high-density areas and low-density areas in the area drawn by the multi-beams. Therefore, it is necessary to set the maximum time of emission and the cycle time of emission to a time longer than the irradiation time after the proximity effect correction of the area with zero density, so that even if there is an area with zero density, that is, the area with the longest irradiation time after the proximity effect correction, it can be drawn. In addition, in order to simplify the control, the workbench speed that can draw in the cycle time of emission in the area with zero density is calculated, and the so-called constant speed of the workbench is used to fix the workbench speed at this speed.

[0069] As a result, the multiple beams exposing the area with lower pattern density are in the on state for most of the emission cycle, while the multiple beams exposing the area with higher pattern density are in the on state only for a part of the emission cycle. In particular, the multiple beams exposing the area with 100% pattern density are in the on state only for about half of the emission cycle, and are controlled to be in the off state for the rest of the time.

[0070] The multi-beam drawing device is characterized in that by using many beams, the total current of the multiple beams becomes larger, and low-sensitivity resist can be drawn at a high speed. On the other hand, if the total current of the multiple beams becomes larger, there is a fundamental problem that the resolution of the beams or the resolution of the drawn pattern deteriorates due to the Coulomb effect. In this embodiment, in order to alleviate the deterioration of the drawing accuracy caused by the Coulomb effect without reducing the drawing speed, the timing of each beam of the multiple beams being turned on is staggered during the emission cycle. In addition, by utilizing the fact that the beam turn-on time in the emission cycle is shorter in an area with a higher density of proximity effects as described above, and performing one emission through multiple irradiation steps, it is possible to perform blanking control of the multiple beams without significantly extending the emission cycle or significantly reducing the drawing speed, so as to reduce the total current of the multiple beams in the turned-on state.

[0071] In this embodiment, multiple (m) irradiation steps with an irradiation time of T1 and multiple irradiation steps with an irradiation time less than T1 are set within one emission cycle. If the irradiation time of each irradiation step is proportional to the power of 2, the irradiation time control becomes simple, which is preferred, so an example in this case is described. The irradiation steps with an irradiation time less than T1 have different irradiation times. In addition, multiple beams are grouped into m groups, and in each group, the allocation order of the irradiation steps with an irradiation time of T1 is changed, and irradiation is performed in the allocation order. Group information indicating which group each beam belongs to is stored in the storage unit 140.

[0072] Such an irradiation step can be generated by dividing a part of the irradiation steps from a group of multiple irradiation steps with irradiation times that are powers of 2. Figure 7The multiple irradiation steps shown in the figure are divided into two irradiation steps with irradiation time of 64ns. The number of irradiation steps increases by this division, but in order not to reduce the drawing speed, it is preferable to delete the irradiation step with the shortest irradiation time (irradiation time of 1ns) in a way that does not increase the number of bits of the irradiation time control data. Fig. 9 As shown, the irradiation steps of the first to third times are 64ns. The irradiation step of the fourth time is 32ns. The irradiation step of the fifth time is 16ns. The irradiation step of the sixth time is 8ns. The irradiation step of the seventh time is 4ns. The irradiation step of the eighth time is 2ns. In order to delete the irradiation step with the shortest irradiation time (irradiation time of 1ns), the quantization unit Δ can be set to 2ns, which is twice of 1ns.

[0073] Furthermore, in order to stagger the timing of turning on the multiple beams, the multiple beams are classified into multiple groups, and blanking control is performed using different methods for each group. Fig. 9 In the example of , the multiple beams are classified into three groups A to C. The beams of group A have the allocation order of the first irradiation step set to No. 1, the allocation order of the second irradiation step set to No. 2, and the allocation order of the third irradiation step set to No. 3. The beams of group B have the allocation order of the third irradiation step set to No. 1, the allocation order of the first irradiation step set to No. 2, and the allocation order of the second irradiation step set to No. 3. The beams of group C have the allocation order of the second irradiation step set to No. 1, the allocation order of the third irradiation step set to No. 2, and the allocation order of the first irradiation step set to No. 3.

[0074] For example, when the irradiation time for one shot is 80 ns, since the quantization unit is 2 ns, the stepwise irradiation time is 40. According to the relationship of expressing a decimal number as the sum of numbers raised to the power of 2, 40=2 5 +2 3 relationship, in Fig. 9 In the example, the desired exposure time of 80 ns can be obtained by performing exposure in one of the three irradiation steps with a 64 ns irradiation time and the irradiation step with a 16 ns irradiation time. Fig.10 As shown in FIG. 1 , the beams of group A to C are turned on in the first irradiation step and the fifth irradiation step. The beams of group B are turned on in the third irradiation step and the fifth irradiation step. The beams of group C are turned on in the second irradiation step and the fifth irradiation step. The beams of groups A to C are turned on at different timings with respect to the irradiation step of irradiation time 64 ns, so the current amount of the turned-on beams can be reduced.

[0075] For example, when the irradiation time for one shot is 180 ns, the stepwise irradiation time is 90 because the quantization unit is 2 ns. 6 +2 4 +2 3 +2 1 In one transmission cycle, Fig. 9 The beam is turned on in two of the three irradiation steps with an irradiation time of 64 ns and in the irradiation steps with irradiation times of 32 ns, 16 ns, and 4 ns. When the allocation order is set as described above, the beam of group A is as follows: Fig.11 As shown in FIG. 1 , the beams of group B are turned on in the first, second, fourth, fifth and seventh irradiation steps. The beams of group C are turned on in the second, third, fourth, fifth and seventh irradiation steps. In the irradiation step with an irradiation time of 64 ns, two groups are turned on at the same time, and three groups are not turned on at the same time, so the current amount of the turned-on beam can be reduced.

[0076] Specifically, when all the multiple beams are irradiated for 180ns, the total current of the average connected beam in the emission cycle can be reduced to a value obtained by weighting the number of beams that are turned on in each irradiation step by the irradiation time of each irradiation step and averaging it (64×2+64×2+64×2+32×3+16×3+4×3) / (64+64+64+32+16+4) / 3=73%. Fig.11 In the example, when the irradiation time after the proximity effect correction is set to 250ns in the area with a pattern density of 0, the irradiation time in the area with a pattern density of 40% becomes about 180ns. That is, in the area with a pattern density of 40% or more, since the pattern density is high, the number of multiple beams controlled by beam connection and the current amount of the multiple beams controlled by connection are large, but in this embodiment, the average value of the total current of the connected beam in the emission cycle can be reduced by 30%.

[0077] In this way, by setting the allocation order of the irradiation steps to be different for each group, the timing of turning on multiple beams can be staggered between groups, the average value of the total current of the turned-on beams of the multiple beams in the emission cycle can be reduced, the influence of the Coulomb effect can be reduced, and the drawing accuracy can be improved. Figure 7 and Fig. 9 As shown, since the number of irradiation steps constituting one shot and the total irradiation time of each irradiation step remain unchanged, the emission cycle and the drawing time will not be extended. In other words, the average value of the total current of the multiple on-beams in the emission cycle can be reduced without extending the drawing time.

[0078] exist Fig.12(a)~ Fig.12 (c) shows an example in which a plurality of beams are grouped into groups A to C. Fig.12 (a)~ Fig.12 (c) shows an 8×8 beam array for the sake of convenience. It is preferable to group the beams so that there is no bias in the beam current of the switched-on beams. Fig.12 Compared with the grouping shown in (c), it is preferred that Fig.12 (a) Fig.12 As shown in (b), the groups A to C are grouped in sequence. Fig.12 In (a), the bundles adjacent in the x-direction and the y-direction belong to different groups. Fig.12 In (b), the bundles adjacent in the x direction belong to different groups.

[0079] Next, along Fig.13 The flowchart shown in the figure illustrates the pattern drawing method related to the present embodiment. In the pattern area density calculation process (step S1), the area density calculation unit 111 virtually divides the drawing area of ​​the substrate 101 into a plurality of grid areas. The size of the grid area is, for example, the same size as the size of each beam constituting the multi-beam, and each grid area becomes a pixel (unit irradiation area). The area density calculation unit 111 reads the drawing data from the storage unit 140, and uses the pattern defined by the drawing data to calculate the pattern area density ρ of each pixel.

[0080] In the irradiation time calculation process (step S2), the irradiation time calculation unit 112 calculates the irradiation amount of the beam irradiated to each pixel by multiplying the pattern area density ρ by the reference irradiation amount D0 and a correction coefficient for correcting the proximity effect, etc. The irradiation time calculation unit 112 divides the irradiation amount by the current density to calculate the irradiation time.

[0081] In the irradiation time control data generation process (step S3), the data processing unit 113 considers the allocation order of the irradiation steps, allocates the irradiation time to multiple irradiation steps, and generates the irradiation time control data. For example, the data processing unit 113 divides the irradiation time by the quantized unit and calculates the stage value t (integerized irradiation time). Fig. 9 In the example shown, the data processing unit 113 generates the sequence T as the irradiation time control data. k (2 5 , 2 5 , 2 5 , 2 4 , 2 3 , 2 2 , 2 1 , 2 0 ) Find the value of k Column b of the corresponding ON / OFF flagk (k=1, 2,…, 7).

[0082] As high-order bits b1, b2, b3 are determined by the corresponding time T M =T1=T2=T3=2 5 The obtained m=FLOOR(t / T M ) and the order of allocation of irradiation steps for each group. However, m is a number not exceeding 3. The lower bits b4, b5, b6, b7, b8 correspond to the integer value t-m×T M More generally, in the sequence T k When part of is not a power of 2, the irradiation amount control data b can be obtained from t using the following formula or the like: k .

[0083]

[0084] If the quantization unit Δ of the irradiation time is determined so that the irradiation time is shorter than the total value of each irradiation time in each irradiation step, the bit sequence b is determined according to the step value t of the irradiation time. k .

[0085] In the data transfer process (step S4), the drawing control unit 114 outputs the irradiation time control data to the deflection control circuit 130. The deflection control circuit 130 outputs the irradiation time control data to the blanking aperture array substrate 204. The input / output circuit 31 of the blanking aperture array substrate 204 transfers the irradiation time control data to the corresponding individual blanking mechanism 40.

[0086] In the individual blanking mechanism 40, the irradiation time control data is transferred to the buffer of the subsequent stage 1 bit at a time according to the clock signal. The data corresponding to the irradiation time of each irradiation step is transferred, and the on / off of the beam in each irradiation step is switched according to the irradiation time control data stored in the buffer 44 of the final stage. When one irradiation of the irradiation step is implemented, the irradiation time control data of the next irradiation step is transferred to each buffer and the buffer 44 of the final stage. In this way, the on / off of each beam is switched according to the irradiation time control data of each beam in each irradiation step for each irradiation step.

[0087] In the drawing process (step S5), the drawing control unit 114 controls the drawing unit 150 to perform the drawing process. The drawing control unit 114 controls the deflector 208 using the deflection control circuit 130 to position the multiple beams so that each of the corresponding multiple beams irradiates each pixel corresponding to the transferred data. After the positioning is completed, the drawing control unit uses the deflection control circuit 130 to implement the irradiation process so that each of the multiple beams irradiates with a prescribed irradiation amount of the corresponding pixel and performs blanking control. When the irradiation process constituting one shot is completed, the data transfer process and the drawing process are implemented to irradiate the next group of pixels.

[0088] In this way, by repeatedly Fig.13 In each process, the drawing unit 150 uses a plurality of beams to perform a drawing operation for drawing a drawing area in a raster scanning manner.

[0089] Fig.14 It is a conceptual diagram used to illustrate the action. Fig.14 As shown, the drawing area 80 of the substrate 101 is virtually divided into a plurality of short stripe areas 82 with a predetermined width, for example, in the y direction (first direction). First, the XY table 105 is moved and adjusted so that the irradiation area 84 that can be irradiated by a single multi-beam irradiation is located at the left end of the first stripe area 82, and drawing is started.

[0090] When depicting the first stripe area 82, the depiction is relatively advanced in the +x direction by moving the XY worktable 105 in the -x direction. During the depiction, the multiple beams are deflected at least in the Y direction by the deflector, thereby switching the pixels to be exposed by the multiple beams. By repeatedly switching the exposure pixels and the exposure action, the multiple beams expose all the pixels defined in the stripe area 82. The XY worktable 105 is moved continuously at a specified speed. At this time, the worktable speed is set within the range in which the above-mentioned depiction action can be performed. After the depiction of the first stripe area 82 is completed, the worktable position is moved in the -y direction, and adjustment is performed so that the beam array 84 is located at the right end of the second stripe area 82. Next, the depiction is performed in the -x direction by moving the XY worktable 105 in the +x direction.

[0091] In the third stripe region 82, the pattern is drawn in the +x direction, and in the fourth stripe region 82, the pattern is drawn in the -x direction. By drawing while changing the direction alternately, the drawing time can be shortened. The stripe regions 82 may also be drawn in the same direction.

[0092] In this embodiment, the number of irradiation steps is not changed, but multiple irradiation steps with the same irradiation time are set in one emission cycle, and multiple beams are classified into multiple groups, and the allocation order of the irradiation steps is changed between the groups. As a result, in at least a part of the irradiation steps in one emission cycle, the timing at which the beams are controlled to be turned on is staggered between multiple groups of multiple beams, so that the average total current of the turned-on beams in the emission cycle can be reduced, the influence of the Coulomb effect is reduced, and the drawing accuracy is improved.

[0093] In this embodiment, the number of groups into which the multiple beams are grouped may not be set to Fig. 9 In this case, the allocation order of the first irradiation step is set to 1, the allocation order of the second irradiation step is set to 2, instead of 3. In this case, the group A and the group B are set, and the group A sets the allocation order of the first irradiation step to 1, the allocation order of the second irradiation step to 2, and the allocation order of the third irradiation step to 3; the group B sets the allocation order of the third irradiation step to 1, the allocation order of the first irradiation step to 2, and the allocation order of the second irradiation step to 3. When using the irradiation time of one or two of the first, second, and third irradiation steps, control is performed so that the timing of a part of the irradiation steps of the group A and the group B is staggered.

[0094] The number of bits of the irradiation time control data may be increased to increase the number of irradiation steps with the same irradiation time, thereby efficiently shifting the timing at which the beam is turned on.

[0095] In this embodiment, for example, Fig.15 As shown, the number of bits (number of bits) of the irradiation time control data is changed from Figure 7 The 8 bits are increased to 10 bits, the quantization unit Δ is set to 2ns, the first irradiation step is set to 64ns irradiation, and the second to sixth irradiation steps are set to 32ns irradiation. The seventh irradiation step becomes 16ns irradiation. The eighth irradiation step becomes 8ns irradiation. The ninth irradiation step becomes 4ns irradiation. The tenth irradiation step becomes 2ns irradiation. These 10 irradiation steps are equivalent to Figure 7 The first irradiation step with an irradiation time of 128 ns is decomposed into four irradiation steps with an irradiation time of 32 ns. Fig.15 The total irradiation time of each irradiation step is 255ns, which is Figure 7 However, since the number of drawing steps increases and the amount of exposure time data transferred to the blanking aperture during drawing increases, the drawing overhead time such as data transfer time increases, and the drawing time is longer than when the exposure time control data is 8 bits.

[0096] In this embodiment, a plurality of beams are classified into two groups A and B, and the allocation order of the 2nd to 6th irradiation steps is changed between group A and group B. For example, the allocation order of the 2nd irradiation step of the beam of group A is set to No. 1, the allocation order of the 3rd irradiation step is set to No. 2, the allocation order of the 4th irradiation step is set to No. 3, the allocation order of the 5th irradiation step is set to No. 4, and the allocation order of the 6th irradiation step is set to No. 5. The allocation order of the 6th irradiation step of the beam of group B is set to No. 1, the allocation order of the 5th irradiation step is set to No. 2, the allocation order of the 4th irradiation step is set to No. 3, the allocation order of the 3rd irradiation step is set to No. 4, and the allocation order of the 2nd irradiation step is set to No. 5.

[0097] For example, when the irradiation time of one emission is 180ns, within one emission cycle, the beam is turned on in an irradiation step with an irradiation time of 64ns, three irradiation steps with an irradiation time of 32ns, an irradiation step with an irradiation time of 16ns, and an irradiation step with an irradiation time of 4ns.

[0098] When the allocation order of the irradiation steps is set as described above, the beams of group A are as follows: Fig.16 As shown in FIG. 1 , the beams of group A and B are turned on in the 1st to 4th irradiation steps, the 7th irradiation step, and the 9th irradiation step. The beams of group B are turned on in the 1st irradiation step, the 4th to 7th irradiation step, and the 9th irradiation step. The beams of group A and B are turned on at the same time only once in the irradiation step with an irradiation time of 32ns, and are turned on at different timings otherwise, so the current of the turned-on beams can be reduced. In this example, the number of groups into which the multiple beams are grouped is set to 2, but it can also be set to 3. For example, for Fig.15 Add group C to groups A and B. For the beams of group C, just set the allocation order of the second irradiation step to No. 4, the allocation order of the third irradiation step to No. 5, the allocation order of the fourth irradiation step to No. 1, the allocation order of the fifth irradiation step to No. 2, and the allocation order of the sixth irradiation step to No. 3.

[0099] It is also possible to increase the number of bits in the illumination time control data and extend the emission period to more efficiently stagger the timing at which the beam is turned on.

[0100] For example, Fig.17As shown, the number of bits (number of bits) of the irradiation time control data is set to 14, the quantization unit Δ is set to 2ns, and the irradiation steps from the 1st to the 6th are set to 32ns irradiation. The 7th and 11th irradiation steps become 16ns irradiation. The 8th and 12th irradiation steps become 8ns irradiation. The 9th and 13th irradiation steps become 4ns irradiation. The 10th and 14th irradiation steps become 2ns irradiation. In other words, two sets of 4 irradiation steps with irradiation times of 16ns, 8ns, 4ns, and 2ns are set. Therefore, the total value of the irradiation time of each irradiation step is changed from Figure 7 The 255ns is increased by 14ns. That is, the transmission period is lengthened by 14ns, and the drawing time is extended.

[0101] The multiple beams are classified into two groups A and B, and the allocation order of the irradiation steps of the first to sixth times is changed between the groups A and B. For example, the allocation order of the irradiation step of the first time is set to No. 1, the allocation order of the irradiation step of the second time is set to No. 2, the allocation order of the irradiation step of the third time is set to No. 3, the allocation order of the irradiation step of the fourth time is set to No. 4, the allocation order of the irradiation step of the fifth time is set to No. 5, and the allocation order of the irradiation step of the sixth time is set to No. 6. The allocation order of the irradiation step of the sixth time is set to No. 1, the allocation order of the irradiation step of the fifth time is set to No. 2, the allocation order of the irradiation step of the fourth time is set to No. 3, the allocation order of the irradiation step of the third time is set to No. 4, the allocation order of the irradiation step of the second time is set to No. 5, and the allocation order of the irradiation step of the first time is set to No. 6.

[0102] In addition, only group A is used in the set of irradiation steps from the 7th to the 10th time, and only group B is used in the set of irradiation steps from the 11th to the 14th time.

[0103] For example, when the irradiation time of one shot is 140 ns, the beam is turned on in four irradiation steps of 32 ns, 8 ns, and 4 ns in one shot cycle.

[0104] When the allocation order of the irradiation steps is set as described above, the beams of group A are as follows: Fig.18 As shown, the beam of group B is turned on in the 1st to 4th irradiation steps, the 8th irradiation step, and the 9th irradiation step. The beam of group B is turned on in the 3rd to 6th irradiation steps, the 12th irradiation step, and the 13th irradiation step.

[0105] The beams of groups A and B are turned on simultaneously only twice in the irradiation step with an irradiation time of 32 ns, and are turned on at different timings otherwise, so the average value of the total current of the beams turned on in the emission cycle can be reduced. Fig.16 and Fig.18 It is known that in Fig.18 In the irradiation step, since a set of irradiation steps with shorter irradiation time is set for groups A and B respectively, it is possible to Fig.16 The irradiation step more efficiently shortens the time during which the beams of group A and group B are simultaneously turned on.

[0106] exist Fig.19 It was stated in Fig. 9 , Fig.15 , Fig.17 The average value of the total current of the turned-on beam in the transmission cycle when the beam turning-on timing is staggered and when the beam turning-on timing is not staggered as shown. It is confirmed that the average value of the total current of the turned-on beam in the transmission cycle is reduced by staggering the beam turning-on timing.

[0107] In addition, it was confirmed that the higher the pattern area density, the greater the decrease in the average value of the total current of the on-beam in the emission cycle. This is because the higher the pattern area density, the less irradiation is caused by the proximity effect correction, the more irradiation steps are made to turn off the beam in one emission cycle, and the beam on timing can be efficiently staggered between the irradiation steps.

[0108] In the above-mentioned embodiment, the beam shaping and blanking control can also be performed by using the openings of the blanking aperture array substrate, and the shaping aperture array component can be removed.

[0109] In addition, the present invention is not limited to the above-mentioned embodiments as it is, and the constituent elements can be deformed and concretized in the implementation stage without departing from the scope of its purpose. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-mentioned embodiments. For example, some constituent elements can also be removed from all constituent elements represented in the embodiments. Furthermore, constituent elements across different embodiments can also be appropriately combined.

[0110] Description of Reference Numerals

[0111] 40 separate blanking mechanism; 50 blanker; 100 drawing device; 110 control computer; 111 area density calculation unit; 112 irradiation time calculation unit; 113 data processing unit; 114 drawing control unit.

Claims

1. A multi-charged particle beam characterization method, characterized in that: have: The process of emitting multiple beams of charged particles; The step of grouping the plurality of bundles constituting the plurality of bundles into a plurality of bundle groups; a step of determining the irradiation time of each of the plurality of beams emitted at each time according to the drawing pattern data; an emission division step of dividing each of the above-mentioned emissions into a plurality of irradiation steps including irradiation steps of different irradiation times, grouping a plurality of irradiation steps of a predetermined first irradiation time into a first group in a part of the above-mentioned plurality of irradiation steps after division, and selecting a group of irradiation steps that becomes the irradiation time of each of the above-mentioned beams after the total irradiation time of each irradiation step is determined; and A process of performing the plurality of irradiation steps by switching each of the plurality of beams on and off to emit the plurality of beams; In the emission splitting process, the timing of the irradiation steps of the first group of the plurality of irradiation steps belonging to each of the plurality of beam groups is determined based on a predetermined allocation order and the number of the irradiation steps to be turned on, so that the timing of the irradiation steps of the first group is different for each beam group.

2. The multi-charged particle beam drawing method according to claim 1, characterized in that: The plurality of irradiation steps each include the first group and a second group of irradiation steps consisting of irradiation steps having an irradiation time shorter than the first irradiation time.

3. The multi-charged particle beam drawing method according to claim 2, characterized in that: The first irradiation time is the longest irradiation time among the irradiation times in the plurality of irradiation steps.

4. The multi-charged particle beam drawing method according to claim 1, characterized in that: The irradiation time of each of the plurality of irradiation steps is determined so that the irradiation time is proportional to a power of 2.

5. The multi-charged particle beam drawing method according to claim 2, characterized in that: In the second group, the timing at which the beams are turned on in the plurality of irradiation steps of the second irradiation time differs for each of the beam groups.

6. The multi-charged particle beam drawing method according to claim 1, characterized in that: Among the plurality of bundles, bundles adjacent to each other in a drawing progress direction or a direction linearly independent from the drawing progress direction are classified into different groups.

7. A multi-charged particle beam mapping device, characterized in that: have: an emission unit that emits multiple beams of charged particles; and A drawing control unit switches on and off for each of the plurality of beams to control the irradiation time of each of the plurality of beams obtained based on the drawing pattern data; The above-mentioned depiction control unit grouped the multiple beams constituting the above-mentioned multiple beams into multiple beam groups, divided the above-mentioned each emission into multiple irradiation steps including irradiation steps with different irradiation times, and in a part of the above-mentioned multiple irradiation steps after being divided, grouped multiple irradiation steps with a predetermined first irradiation time into a first group, selected a group of irradiation steps that becomes the irradiation time of each of the above-mentioned beams after the total irradiation time of each irradiation step is determined, and determined the timing of the irradiation step of the above-mentioned first group of the above-mentioned multiple irradiation steps belonging to each of the above-mentioned multiple beam groups based on a predetermined allocation order and the number of the above-mentioned irradiation steps that become connected, so that the timing of the irradiation step of the above-mentioned first group is different for each of the above-mentioned beam groups.

8. The multi-charged particle beam imaging device according to claim 7, characterized in that: The plurality of irradiation steps each include the first group and a second group of irradiation steps consisting of irradiation steps having an irradiation time shorter than the first irradiation time.

9. The multi-charged particle beam drawing device according to claim 8, characterized in that: The first irradiation time is the longest irradiation time among the irradiation times in the plurality of irradiation steps.

10. The multi-charged particle beam drawing device according to claim 7, characterized in that: The irradiation time of each of the plurality of irradiation steps is determined so that the irradiation time is proportional to a power of 2.

11. The multi-charged particle beam imaging device according to claim 8, characterized in that: In the second group, the timing at which the beams are turned on in the plurality of irradiation steps of the second irradiation time differs for each of the beam groups.

12. The multi-charged particle beam drawing device according to claim 7, characterized in that: The drawing control unit classifies, among the plurality of bundles, bundles that are adjacent to each other in a drawing progress direction or a direction linearly independent of the drawing progress direction into different groups.

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