JP2020088276A - Settling time acquisition method and multi charged particle beam drawing method - Google Patents

Abstract

To control an irradiation amount with high accuracy while preventing a drawing accuracy and throughput from lowering.SOLUTION: A settling time acquisition method according to an embodiment comprises the steps of: performing on/off control for each beam of a multi-beam using a plurality of individual blankers; performing on/off control collectively for the multi-beam using a common blanker; drawing an evaluation pattern for each beam on a substrate; drawing an evaluation pattern at each settling time while varying a settling time that is a difference between output timings of individual amplifiers, which apply voltages to the individual blankers, and an output timing of a common amplifier, which applies a voltage to the common blanker; measuring a size and roughness of the evaluation pattern; obtaining, for each beam, a shortest first settling time at which the size and roughness become constant; and obtaining, from the first settling time for each beam, a second settling time to be set in a drawing device at the time of actual drawing.SELECTED DRAWING: Figure 1

Description

The present invention relates to a settling time acquisition method and a multi-charged particle beam writing method.

With the high integration of LSIs, the circuit line width required for semiconductor devices has been miniaturized year by year. In order to form a desired circuit pattern on a semiconductor device, a reduction projection type exposure apparatus is used, and a high-precision original image pattern formed on quartz (a mask, or especially a stepper or scanner is also called a reticle). .) is reduced and transferred onto the wafer. A high-precision original image pattern is drawn by an electron beam drawing device, and so-called electron beam lithography technology is used.

For example, there is a drawing device using a multi-beam. As compared with the case of writing with one electron beam, by using a multi-beam, a large number of beams can be irradiated at one time, so that the throughput can be significantly improved. In a multi-beam drawing apparatus, for example, an electron beam emitted from an electron gun is passed through a mask having a plurality of holes to form a multi-beam, which is blanked and is not shielded by an optical system. The image is reduced, deflected by a deflector, and irradiated to a desired position on the sample.

In multi-beam writing, the irradiation amount of each beam is individually controlled by the irradiation time. In order to control the irradiation amount of each beam with high accuracy, it is necessary to perform blanking control for turning the beam ON/OFF at high speed. In a conventional multi-beam drawing apparatus, a blanking control circuit for each beam is mounted on a blanking plate on which blanking electrodes of the multi-beam are arranged. A control signal was sent to the blanking control circuit to control the irradiation time of each beam.

However, because the circuit installation space on the blanking plate and the amount of usable current are limited, it is unavoidable to use a simple circuit for the amount of information of the control signal, and blanking that enables high-speed and highly accurate operation. It was difficult to mount the control circuit. Therefore, Patent Document 1 discloses a drawing apparatus including an individual blanking mechanism for switching ON/OFF of each beam and a common blanking mechanism for collectively performing ON/OFF control of beams for the entire multi-beam. Has been done.

In the drawing device of Patent Document 1, in order to accurately control the irradiation amount, when the output of the individual amplifier that applies a voltage to the individual blanking control deflector is stable, the common blanking control deflector is stable. A common amplifier that applies a voltage to ON switches the output ON/OFF. For example, the common amplifier is turned on after a predetermined settling time elapses after the individual amplifier is turned on.

The same number of individual amplifiers as the number of deflectors for individual blanking control, that is, the number of multi-beams are provided. Although the time required for the output to stabilize is different for each individual amplifier, conventionally, the settling time was set without considering the difference. Therefore, a beam with insufficient irradiation amount is generated, which may affect the pattern size and roughness. If the settling time is set to be sufficiently long, there is a problem that throughput is reduced.

JP, 2014-112639, A JP, 2009-88202, A JP, 2014-183267, A JP, 2005-153873, A Japanese Patent Publication No. 2006-505124 JP, 10-289843, A

An object of the present invention is to provide a settling time acquisition method and a multi-charged particle beam drawing method for controlling the irradiation amount with high accuracy while preventing a decrease in drawing accuracy and throughput.

A method of acquiring a settling time according to an aspect of the present invention includes a step of forming a multi-beam by passing a charged particle beam through a plurality of openings provided in a shaping aperture plate, and using a plurality of individual blankers, Of the multi-beams, a step of individually performing on/off control of beams corresponding to each of the multi-beams, and a step of collectively performing beam on/off control of the entire multi-beams using a common blanker A step of deflecting the multi-beams using a deflector and drawing an evaluation pattern for each beam on a substrate, output timing of an individual amplifier that applies a voltage to the individual blanker, and applying a voltage to the common blanker While varying the settling time which is the difference between the output timing of the common blanker, a step of drawing an evaluation pattern on the substrate for each settling time, a step of measuring the dimensions or roughness of the evaluation pattern, and for each beam , A step of obtaining the shortest first settling time among the settling times when the evaluation pattern in which the measurement result of the dimension or the roughness is within a predetermined range is drawn, and from the first settling time of each beam, in actual writing And a step of acquiring a second settling time set in the drawing apparatus.

The settling time acquisition method according to an aspect of the present invention acquires the longest first settling time among the first settling times of each beam as the second settling time.

The method for acquiring the settling time according to one aspect of the present invention is to divide the shaping aperture plate into a plurality of regions, measure the sum or average size of the areas of the evaluation patterns drawn by a beam corresponding to each region, and for each region. , A step of obtaining the shortest third settling time of the settling times when the evaluation pattern is drawn such that the sum of the areas or the measurement result of the average dimension falls within a predetermined range, and the third settling time is set to the longest area. The first settling time is obtained for each included beam, and the second settling time is obtained from the obtained first settling time.

The method for obtaining the settling time according to one aspect of the present invention is the settling time that is the shortest and the longest settling time among the settling times when the evaluation pattern is drawn such that the measurement result of the dimension or roughness falls within a predetermined range. And the difference is used to determine the interval at which the read signal for reading data is output to the individual register that outputs the signal to the individual amplifier.

A multi-charged particle beam drawing method according to an aspect of the present invention is a multi-charged particle beam drawing method using a drawing apparatus in which the second settling time acquired in the above method is set. The drawing process is performed without using a beam whose settling time is longer than the second settling time.

According to the present invention, it is possible to control the irradiation amount with high accuracy while preventing the drawing accuracy and the throughput from decreasing.

It is a schematic block diagram of the drawing apparatus which concerns on embodiment of this invention. It is a schematic block diagram of a shaping aperture plate. It is a schematic block diagram of a blanking plate. It is a schematic block diagram of a blanking plate. It is a schematic block diagram of a blanking control circuit. It is a figure which shows an example of irradiation time array data. It is a timing chart of each signal. It is a flow chart explaining the settling time acquisition method concerning the embodiment. It is a figure which shows the example of an evaluation pattern. It is explanatory drawing of the dimension measurement location of an evaluation pattern. It is a graph which shows the example of the measurement result of the size and roughness for every settling time. (A) (b) is a graph which shows the example of the cumulative distribution of the beam with respect to the optimal settling time. It is a figure which shows the example of a division of a blanking plate. It is a graph which shows the relationship between the settling time for every area|region and the sum of the area of an evaluation pattern.

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

FIG. 1 is a schematic configuration diagram of a drawing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the drawing apparatus 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 electronic 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 plate 203, a blanking plate 204, a reduction lens 205, a common blanking deflector (common blanker) 212, a limiting aperture member 206, an objective lens 207, And a deflector 208 are arranged.

An XY stage 105 is arranged in the drawing chamber 103. The substrate 101 to be drawn is arranged on the XY stage 105. The substrate 101 includes a mask for exposure when manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured, and the like. In addition, the sample 101 includes mask blanks on which a resist is applied and on which nothing is drawn. A mirror 210 for measuring the position of the XY stage 105 is arranged on the XY stage 105.

The control unit 160 includes a control computer 110, a memory 112, a deflection control circuit 130, a logic circuit 132, a stage position measuring unit 139, and storage devices 140 and 142 such as a magnetic disk device. The control computer 110, the memory 112, the deflection control circuit 130, the stage position measuring unit 139, and the storage devices 140 and 142 are connected to each other via a bus (not shown). Drawing data is externally input and stored in the storage device 140 (storage unit). The storage device 140 also stores settling time information calculated by the method described later.

An area density calculator 60, an irradiation time calculator 62, a gradation value calculator 64, a bit converter 66, a transfer processor 68, and a drawing controller 72 are arranged in the control computer 110. Each function of the area density calculation unit 60, the irradiation time calculation unit 62, the gradation value calculation unit 64, the bit conversion unit 66, the transfer processing unit 68, and the drawing control unit 72 may be configured by hardware such as an electric circuit. It may be configured by software such as a program that executes these functions. The information input/output to/from each unit and the information being calculated are stored in the memory 112 each time.

In FIG. 1, the configuration necessary for explaining the embodiment is described. The drawing apparatus 100 may be provided with other necessary configurations.

FIG. 2 is a schematic configuration diagram of the shaping aperture plate 203. As shown in FIG. 2, in the forming aperture plate 203, m (vertical) (y direction)×n (horizontal (x direction) n) openings (m, n≧2) are formed in a matrix at a predetermined array pitch. Has been done. Each of the openings 22 is a rectangle or a circle having the same size and shape. A part of the electron beam 200 passes through the plurality of openings 22 to form the multi-beam 20.

As shown in FIGS. 3 and 4, passage holes (openings) H are formed in the blanking plate 204 in accordance with the arrangement positions of the openings 22 of the shaping aperture plate 203. An individual blanker consisting of a pair of two electrodes 24, 26 is arranged. The voltage output from the individual amplifier 46 is applied to one of the two electrodes 24 and 26 (for example, the electrode 24) for each beam. The individual amplifier 46 is provided for each individual blanker.

The logic circuit 41 is independently arranged in each individual amplifier 46. The other of the two electrodes 24, 26 for each beam (eg electrode 26) is grounded. The electron beam 20 passing through each of the passage holes H is independently deflected by the voltage applied to the pair of two electrodes 24 and 26, and blanking control is performed. In this way, the plurality of individual blankers perform blanking deflection of corresponding beams among the multi-beams that have passed through the plurality of openings 22 of the shaping aperture plate 203.

As shown in FIG. 5, in each logic circuit 41 arranged on the blanking plate 204, a shift register 40, a register 42, and an AND calculator 44 (logical product calculator) are arranged. The AND operator 44 may be omitted. In this embodiment, the individual blanking control for each beam is controlled by a 1-bit control signal. That is, a 1-bit control signal is input to and output from the shift register 40, the register 42, and the AND operator 44. Since the information amount of the control signal is small, the installation area of the control circuit can be reduced. In other words, even when the logic circuit 41 is arranged on the blanking plate 204 having a small installation space, more beams can be arranged with a smaller beam pitch.

A common amplifier 54 is connected to the common blanker 212. The logic circuit 132 is connected to the common amplifier 54. A register 50 and a counter 52 (an example of a shot time control unit) are arranged in the logic circuit 132. This does not perform a plurality of different controls at the same time, but requires only one circuit that performs ON/OFF control. Therefore, even if a circuit for quick response is placed, there is a problem of installation space and limitation of the current used by the circuit. Does not happen. Therefore, the common amplifier 54 operates significantly faster than the individual amplifier 46 mounted on the blanking plate 204. The common amplifier 54 is controlled by a 10-bit control signal, for example. That is, for example, a 10-bit control signal is input to and output from the register 50 and the counter 52.

The drawing apparatus 100 includes a beam ON/OFF control by each logic circuit 41 for individual blanking control, and a beam ON/OFF control by a common blanking control logic circuit 132 for blanking control of the entire multi-beam at once. Both are used to perform blanking control of each beam.

The area density calculation unit 60 reads the drawing data from the storage device 140, and for each mesh area of the plurality of mesh areas in which the drawing area of the substrate 101 is virtually divided into meshes, the area density of the pattern arranged therein is calculated. calculate. For example, first, the drawing area of the substrate 101 is divided into strip-shaped stripe areas with a predetermined width. Then, each stripe area is virtually divided into the plurality of mesh areas described above. The size of the mesh area is, for example, the beam size. The area density calculation unit 60 reads the corresponding drawing data from the storage device 140 for each stripe area, and allocates a plurality of graphic patterns defined in the drawing data to the mesh area. Then, the area density of the graphic pattern arranged for each mesh region is calculated.

The irradiation time calculation unit 62 calculates the irradiation time T of the electron beam per shot (also referred to as shot time or exposure time) for each mesh region. When performing multiple writing, the irradiation time T of the electron beam per shot in each layer may be calculated. The irradiation time T is preferably set to a time corresponding to the corrected irradiation amount obtained by correcting the dimensional fluctuation amount due to a phenomenon that causes dimensional fluctuations such as a proximity effect, a fogging effect, and a loading effect, which are not shown, by the irradiation amount. The irradiation time T for each mesh area is defined in the irradiation time map, and the irradiation time map is stored in, for example, the storage device 142.

The gradation value calculation unit 64 calculates an integer gradation value N when the irradiation time T for each mesh area defined in the irradiation time map is defined using a predetermined quantization unit Δ. The irradiation time T is defined by the equation T=ΔN. The gradation value N is defined as an integer value obtained by dividing the irradiation time T by the quantization unit Δ. The quantization unit Δ can be set variously, but can be defined by, for example, 1 ns (nanosecond). Δ means a quantization unit for control such as a clock cycle when controlling with a counter.

The bit conversion unit 66 converts, for each shot, the irradiation time of each beam of the multi-beam (here, the gradation value N) into a binary value of a preset digit number n. For example, if N=50, then 50=2 ¹ +2 ⁴ +2 ⁵ , which is “0000110010” when converted to a 10-digit binary number. For example, if N=500, the value will be “0111110100” as well. If N=700, it becomes "1010111100". The irradiation time of each beam corresponds to the irradiation time defined in the mesh area to be irradiated by each beam for each shot.

The shot of each beam is divided into irradiation of the number of binary digits (n times). When the number of digits n=10, one shot is divided into 10 irradiation steps.

For example, when the number of digits n=10 and N=700 (“1010111100”), the irradiation time at the tenth digit (10th bit) is Δ×512×1. The irradiation time of the 9th digit (9th bit) is Δ×256×0=0. The irradiation time of the 8th digit (8th bit) is Δ×128×1. The irradiation time of the 7th digit (7th bit) is Δ×64×0=0. The irradiation time of the sixth digit (6th bit) is Δ×32×1. The irradiation time of the fifth digit (fifth bit) is Δ×16×1. The irradiation time of the 4th digit (4th bit) is Δ×8×1. The irradiation time of the third digit (third bit) is Δ×4×1. The irradiation time of the second digit (second bit) is Δ×2×0=0. The irradiation time of the first digit (first bit) is Δ×1×0=0.

Then, for example, when irradiation is performed in order from the one with the largest number of digits, for example, if Δ=1 ns, the first irradiation step is irradiation for 512 ns (beam ON). The second irradiation step is 0 ns (beam OFF) irradiation. The third irradiation step is irradiation for 128 ns (beam ON). The fourth irradiation step is irradiation for 0 ns (beam OFF). The fifth irradiation step is irradiation for 32 ns (beam ON). The sixth irradiation step is irradiation for 16 ns (beam ON). The seventh irradiation step is irradiation for 8 ns (beam ON). The 8th irradiation step is irradiation for 4 ns (beam ON). The ninth irradiation step is 0 ns (beam OFF) irradiation. The 10th irradiation step is irradiation of 0 ns (beam OFF). The substrate 101 is sequentially irradiated with a beam having an irradiation time corresponding to each digit.

The transfer processing unit 68 outputs the irradiation time array data converted into binary number data to the deflection control circuit 130 for each shot of each beam.

The deflection control circuit 130 outputs irradiation time array data to the logic circuit 41 for each beam for each shot. Further, in synchronization with this, the deflection control circuit 130 outputs timing data of each irradiation step to the logic circuit 132 for common blanking.

FIG. 6 is a diagram showing an example of a part of the irradiation time array data. FIG. 6 shows a part of irradiation time array data of predetermined shots of, for example, the beams #1 to #5 among the beams forming the multi-beam. In the example of FIG. 6, the irradiation time array data from the irradiation step of the k-th bit (k-th digit) to the irradiation step of the k-3th bit (k-3rd digit) is shown for beams #1 to #5. There is.

In the example of FIG. 6, data “1101” is shown for the irradiation step from the kth bit (kth digit) to the k-3rd bit (k-3rd digit) for beam #1. Similarly, data "1100" is shown for beam #2. Data “0110” is shown for beam #3. Data "0111" is shown for beam #4. Data "1011" is shown for beam #5.

As shown in FIG. 5, since the shift register 40 is used in the logic circuit 41, the deflection control circuit 130 transfers the data of the same bit (same digit) of the blanking plate 204 in the beam arrangement order during data transfer. Data is transferred to each logic circuit 41. It also outputs a clock signal (CLK1) for synchronization, a read signal (read) for reading data, and a gate signal (BLK). In the example of FIG. 6, for example, as the k-th bit (k-th digit) data of beams #1 to #5, each 1-bit data “10011” is transferred from the subsequent beam side.

The shift register 40 of each beam transfers data to the next shift register 40 in order from the higher order side according to the clock signal (CLK1). For example, for the k-th bit (k-th digit) data of beams #1 to #5, 1-bit data “1” is stored in the shift register 40 of beam #1 in response to five clock signals. 1-bit data "1" is stored in the shift register 40 of the beam #2. 1-bit data "0" is stored in the shift register 40 of the beam #3. 1-bit data "0" is stored in the shift register 40 of the beam #4. 1-bit data "1" is stored in the shift register 40 of the beam #5.

Next, the individual register 42 of each beam reads the k-th bit (k-th digit) data of each beam from the shift register 40 in response to the input of the read signal (read). In the example of FIG. 6, 1-bit data “1” is stored in the individual register 42 of the beam #1 as the k-th bit (k-th digit) data. As the kth bit (kth digit) data, 1-bit data “1” is stored in the individual register 42 of the beam #2. As the k-th bit (k-th digit) data, 1-bit data “0” is stored in the individual register 42 of the beam #3. As the k-th bit (k-th digit) data, 1-bit data “0” is stored in the individual register 42 of the beam #4. As the k-th bit (k-th digit) data, 1-bit data "1" is stored in the individual register 42 of the beam #5.

When the k-th bit (k-th digit) data is input, the individual register 42 of each beam outputs an ON/OFF signal to the AND calculator 44 according to the data. If the kth bit (kth digit) data is "1", an ON signal is output, and if it is "0", an OFF signal is output. In the AND operator 44, if the BLK signal is the ON signal and the signal of the individual register 42 is ON, the ON signal is output to the individual amplifier 46, and the individual amplifier 46 outputs the ON voltage to the electrode 24 of the individual blanker. Apply. Otherwise, the AND calculator 44 outputs an OFF signal to the individual amplifier 46, and the individual amplifier 46 applies the OFF voltage to the electrode 24 of the individual blanker.

While the k-th bit (k-th digit) data is being processed, the deflection control circuit 130 sets the next k−1-th bit (k−1-th digit) data on the blanking plate 204 in the beam arrangement order. Data is transferred to each logic circuit 41. In the example of FIG. 6, for example, 1-bit data of "01111" is transferred from the subsequent beam side as the k-1th bit (k-1st digit) data of beams #1 to #5. The shift register 40 of each beam transfers data to the next shift register 40 in order from the higher order side according to the clock signal (CLK1).

For example, the k-1th bit (k-1st digit) data of the beams #1 to #5 is "1" which is 1-bit data in the shift register 40 of the beam #1 by the clock signal of five times. Is stored. 1-bit data "1" is stored in the shift register 40 of the beam #2. 1-bit data "1" is stored in the shift register 40 of the beam #3. 1-bit data "1" is stored in the shift register 40 of the beam #4. 1-bit data "0" is stored in the shift register 40 of the beam #5. Then, in response to the k-1 bit (k-1 digit) read signal, the individual register 42 of each beam outputs the k-1 bit (k-1 digit) data of each beam from the shift register 40. Just read it. Hereinafter, similarly, it is sufficient to proceed to the data processing of the first bit (first digit).

As a drawing step based on the irradiation time of the target digit, the irradiation time of the target digit (for example, the k-th bit (k-th digit)) of the irradiation divided into a plurality of irradiation steps is performed for each beam shot.

FIG. 7 is a flowchart showing the beam ON/OFF switching operation for a part of the irradiation step in one shot. In FIG. 7, for example, one beam (beam #1) is shown among a plurality of beams forming a multi-beam. The irradiation time array data from the kth bit (kth digit) to the k-3rd bit (k-3rd digit) of the beam #1 is indicated by "1101" in the example of FIG. First, when the kth bit (kth digit) read signal is input, the individual register 42 (individual register 1) outputs an ON/OFF signal in accordance with the stored kth bit (kth digit) data. In FIG. 7, it is an ON output. In the individual register 42, the data output is maintained only for the time corresponding to the irradiation time of the kth bit.

Since the kth bit (kth digit) data is ON data, the individual amplifier 46 outputs an ON voltage and applies the ON voltage to the blanking electrode 24 for beam #1. On the other hand, in the common blanking logic circuit 132, ON/OFF is switched according to the timing data of each irradiation step of 10 bits. The common blanking mechanism outputs an ON signal for the irradiation time of each irradiation step. For example, if Δ=1 ns, the irradiation time of the first irradiation step (for example, the 10th digit (10th bit)) is Δ×512=512 ns. The irradiation time of the second irradiation step (for example, the 9th digit (9th bit)) is Δ×256=256 ns. The irradiation time of the third irradiation step (for example, the eighth digit (8th bit)) is Δ×128=128 ns. Thereafter, similarly, it is turned on only for the irradiation time of each digit (each bit).

In the logic circuit 132, when the timing data of each irradiation step is input to the register 50 and the register 50 outputs the ON data of the kth digit (kth bit), the counter 52 irradiates the kth digit (kth bit). The time is counted and controlled to be turned off when a predetermined irradiation time elapses.

Further, in the common blanking mechanism, the ON/OFF switching of the individual blanking mechanism is performed after the voltage stabilization time (settling time) of the individual amplifier 46 has elapsed. In the example of FIG. 7, after the read signal is input to the individual register 42 (after the read signal is output from the deflection control circuit 130), the common amplifier 54 is turned on after the settling time S1 has elapsed. As a result, it is possible to eliminate beam irradiation with an unstable voltage when the individual amplifier 46 rises. Then, the common amplifier 54 is turned off after the irradiation time of the k-th digit (k-th bit) has elapsed. As a result, the actual beam is turned on when the individual amplifier 46 and the common amplifier 54 are both turned on, and the substrate 101 is irradiated with the beam. Therefore, the ON time of the common amplifier 54 is controlled to be the actual beam irradiation time.

In other words, the common blanking mechanism will define the irradiation time. The common amplifier 54 and the common blanker 212 are controlled by the counter 52 (irradiation time control unit) so as to define the irradiation time.

When a read signal (read) is input after a lapse of a predetermined time S2 from the output of the individual register 42 being turned off, the individual register 42 reads the k−1th bit (k−1th digit) data from the shift register 40. ..

As described above, in the individual beam ON/OFF switching step, the plurality of individual blanking mechanisms (logic circuit 41, electrodes 24, 26) individually turn the beams ON/OFF for the corresponding beams of the multi-beams. Take control.

Then, as the common beam ON/OFF switching step, after the beam is switched ON/OFF by the individual blanking mechanism for the irradiation step (irradiation) of the k-th digit (k-th bit), the common blanking mechanism (logic The circuit 132, the common blanker 212, etc.) are used to collectively control the ON/OFF of the beams for the entire multi-beam, and only the irradiation time corresponding to the irradiation step (irradiation) of the kth digit (kth bit) Blanking control is performed so that the beam is turned on.

The drawing control unit 72 controls the data transfer of the irradiation time array data.

The electron beam 200 emitted from the electron gun 201 (emitter) illuminates the entire shaping aperture plate 203 almost vertically by the illumination lens 202. A plurality of rectangular openings 22 are formed in the shaping aperture plate 203, and the electron beam 200 illuminates a region including all the openings 22. A part of the electron beam 200 passes through the plurality of openings 22 to form a plurality of rectangular electron beams (multi-beams) 20, for example. The multi-beams 20 pass through the corresponding blankers of the blanking plate 204. The individual blankers individually deflect the electron beam 20 (perform blanking deflection).

The multi-beam 20 that has passed through the blanking plate 204 is reduced by the reduction lens 205 and advances toward the central hole formed in the limiting aperture member 206. Here, the electron beam deflected by the individual blanker of the blanking plate 204 is displaced from the central hole of the limiting aperture member 206, and is blocked by the limiting aperture member 206. On the other hand, the electron beam 20 which is not deflected by the individual blankers of the blanking plate 204 passes through the central hole of the limiting aperture member 206 unless deflected by the common blanker 212.

The blanking control is performed by a combination of ON/OFF of the individual blanking mechanism and ON/OFF of the common blanking mechanism to control ON/OFF of the beam. In this way, the limiting aperture member 206 blocks each beam deflected by the individual blanking mechanism or the common blanking mechanism to be in the beam OFF state. Then, the beam that has passed through the limiting aperture member 206, which is formed from the time the beam is turned on to the time the beam is turned off, forms a beam for an irradiation step in which one shot is further divided.

The multi-beam 20 that has passed through the limiting aperture member 206 is focused by the objective lens 207 to form a pattern image with a desired reduction ratio, which is collectively deflected by the deflector 208 in the same direction and irradiated onto the substrate 101. When the XY stage 105 continuously moves, the beam irradiation position is controlled by the deflector 208 so as to follow the movement of the XY stage 105. Ideally, the multi-beams 20 irradiated at one time are arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of openings 22 of the shaping aperture plate 203 by the above-mentioned desired reduction rate.

As described above, the output of the common amplifier 54 turns ON after the settling time S1 has elapsed after the read signal was output from the deflection control circuit 130. The individual amplifiers 46 have individual differences in the time required for the output to stabilize. If the settling time S1 is too short, a beam with an insufficient dose may be generated. On the other hand, if the settling time S1 is too long, the throughput decreases. Therefore, in the present embodiment, a suitable settling time S1 is determined in consideration of the output characteristics of each individual amplifier 46.

FIG. 8 is a flowchart showing a settling time determination method. First, the settling time S1 is set to t1 (step S102), and an evaluation pattern is drawn on the evaluation substrate 101 (step S104). An evaluation pattern is drawn using each individual beam of the multi-beam.

That is, one evaluation pattern is drawn with one individual beam. The evaluation pattern is, for example, a contact hole (rectangular pattern). The settling time S1 is changed (changed) j times from t1 to tj, and an evaluation pattern is drawn (steps S104 to S108).

As shown in FIG. 9, when the number of individual beams included in the multi-beam is M, M×j evaluation patterns are drawn on the substrate 101.

The dimension (CD) and roughness (LER: Line Edge Roughness) of the evaluation pattern are measured (step S110). Specifically, development, etching, etc. are performed after the drawing process, and the dimensions and roughness of the pattern formed on the substrate 101 are measured. As for the dimension, as shown in FIG. 10, it is preferable to measure the dimension in the direction along the blanking direction.

Focusing on one individual beam, a graph in which the horizontal axis represents the settling time and the vertical axis represents the measured line width and roughness is as shown in FIG. If the settling time is short, the output of the common amplifier 54 becomes ON before the output of the individual amplifier 46 stabilizes, the irradiation amount becomes insufficient, the size becomes small, and the roughness becomes large.

On the other hand, if the settling time is too long, the value of the individual register falls before the output of the common amplifier 54 is turned off. As a result, the output of the individual amplifier 46 is turned off, the irradiation amount is insufficient, the size is small, and the roughness is large.

As shown in FIG. 11, the shortest settling time in the region where the size and roughness are constant (within a desired range) is the optimum settling time (first settling time) of the individual amplifier 46 corresponding to this individual beam. ). The optimum settling time is obtained for each of the multi-beams by the same method (step S112).

FIG. 12A is an example of a graph in which the horizontal axis represents the optimum settling time T and the vertical axis represents the yield (cumulative distribution) of the number of beams. For example, as shown in FIG. 12A, the longest optimum settling time among the optimum settling times of all the beams is determined as the settling time (second settling time) set in the drawing device when the product pattern is actually drawn ( Step S114). As a result, it is possible to suppress the settling time and prevent a decrease in throughput while accurately drawing patterns for all the beams.

As shown in FIG. 12B, when the optimum settling time of some (a small number of) beams is long, setting the longest optimum settling time in the drawing apparatus may cause a decrease in throughput. Therefore, in such a case, as shown in FIG. 12B, a settling time advantageous for throughput is selected, and an individual beam having an optimal settling time longer than that is set not to be used for writing.

If there is an individual beam that is not used for writing, a known defect correction technique may be applied separately.

As described above, according to the present embodiment, the settling time S1 is set in consideration of the output characteristics of each individual amplifier 46, so that it is possible to prevent the occurrence of a beam with an insufficient irradiation amount and suppress a decrease in drawing accuracy. Further, it is possible to prevent a decrease in throughput.

The area in which the dimensions and the roughness are constant shown in FIG. 11 corresponds to a margin of time S2 from when the output of the individual register 42 is turned off until the next read signal is input. Therefore, the size of the region where the dimensions and roughness are constant (the difference between the shortest settling time and the longest settling time where the dimensions and roughness are constant) is calculated from the measurement results of the dimensions and roughness, and the time S2 is set accordingly. By shortening the delay time and advancing the timing of the read signal, the throughput can be further improved.

Both the dimensions and the roughness may be measured, or only one of them may be measured.

In the above embodiment, the example in which the dimensions and the like are measured for all of the evaluation patterns drawn by each beam has been described, but the measurement time becomes long when the number of beams is large. Therefore, as shown in FIG. 13, the blanking plate 204 (or the shaping aperture plate 203) is divided into a plurality of regions R1 to Rx, and the sum of the areas of the evaluation patterns drawn by the beams included in each region is measured. Good.

FIG. 14 shows an example of a graph in which the sum of the areas of the evaluation patterns drawn by the beams of the regions R1, R2, and R3 is plotted for each settling time. An optimum settling time (first settling time) for each beam in the region is obtained for a region where the settling time (third settling time) at which the sum of areas starts to be constant is long. For example, the optimum settling time (first settling time) of each beam in the region R3 is obtained, and the longest optimum settling time is determined as the settling time (second settling time) set in the drawing apparatus. Since it is not necessary to obtain the optimum settling time for all beams, the measurement time can be shortened.

It may not be the sum of the areas of the evaluation patterns, and some evaluation patterns in the region may be measured to obtain the average value of the dimensions. Also, fitting may be performed using some measurement results to perform interpolation.

In the above embodiment, the individual register 42 falls after a lapse of a predetermined time after the input of the read signal, and the output of the individual amplifier 46 is turned off each time even when the beam is turned on in consecutive bits. However, considering the output stability of the individual amplifier 46, the circuit may be designed so that the output of the individual amplifier 46 remains ON when the beam is turned ON with consecutive bits.

In such a case, when the evaluation pattern is drawn, the irradiation time is set so that only the odd-numbered bits or even-numbered bits of the irradiation time array data are set to 1 (beam ON). As a result, the individual amplifier 46 switches ON/OFF for each bit, so that the settling time S1 can be evaluated.

Even when the common blanker cannot exhibit the desired performance and the irradiation amount is controlled by the individual blanker, the method according to the above embodiment can be applied.

The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements within a range not departing from the gist of the invention in an implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements of different embodiments may be combined appropriately.

20 multi-beam 44 AND calculator 46 individual amplifier 54 common amplifier 204 blanking plate 212 common blanker

Claims (5)

Forming a multi-beam by passing the charged particle beam through a plurality of openings provided in the shaping aperture plate;
A step of individually performing on/off control of beams corresponding to each of the multi-beams using a plurality of individual blankers;
A step of collectively performing on/off control of beams for the entire multi-beam using a common blanker;
Deflecting the multi-beam using a deflector, and drawing an evaluation pattern for each beam on the substrate,
While varying the settling time, which is the difference between the output timing of the individual amplifier that applies the voltage to the individual blanker and the output timing of the common blanker that applies the voltage to the common blanker, the evaluation pattern on the substrate for each settling time And the process of drawing
A step of measuring the dimensions or roughness of the evaluation pattern,
For each beam, a step of obtaining the shortest first settling time of the settling time when the evaluation pattern in which the measurement result of the dimension or the roughness falls within a predetermined range is drawn,
Obtaining a second settling time to be set in the drawing apparatus during actual drawing from the first settling time of each beam;
A method of acquiring settling time, comprising: The settling time acquisition method according to claim 1, wherein the longest first settling time among the first settling times of each beam is acquired as the second settling time. Dividing the shaping aperture plate into a plurality of regions, measuring the sum or average dimension of the area of the evaluation pattern drawn by the beam corresponding to each region,
For each region, the step of obtaining the shortest third settling time of the settling time when drawing the evaluation pattern in which the measurement result of the sum of the areas or the average dimension is within a predetermined range,
The said 1st settling time is calculated|required about each beam contained in the area|region where the said 3rd settling time is the longest, and the said 2nd settling time is acquired from the calculated|required 1st settling time. How to get the settling time. Of the settling time when the measurement result of the dimension or the roughness is drawn within a predetermined range, the difference between the shortest settling time and the longest settling time is obtained,
4. The difference is used to determine an interval at which a read signal for reading data is output to an individual register that outputs a signal to the individual amplifier. How to get settling time. A multi-charged particle beam drawing method using a drawing apparatus in which the second settling time set by the method according to claim 1 is set,
The multi-charged particle beam writing method, wherein the writing process is performed without using a beam having the first settling time longer than the second settling time among the multi-beams.

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