JP6403045B2 - Multi-beam drawing method and multi-beam drawing apparatus - Google Patents

Description

  The present invention relates to a multi-beam drawing method and a multi-beam drawing apparatus, for example, a technique for controlling irradiation time of each beam when drawing a pattern by irradiating a sample on a stage with multi-beams.

  Lithography technology, which is responsible for the progress of miniaturization of semiconductor devices, is an extremely important process for generating a pattern among semiconductor manufacturing processes. In recent years, with the high integration of LSI, circuit line widths required for semiconductor devices have been reduced year by year. Here, the electron beam (electron beam) drawing technique has an essentially excellent resolution, and drawing is performed on a wafer or the like using an electron beam.

  For example, there is a drawing apparatus using a multi-beam. Compared with the case of drawing with one electron beam, the use of multi-beams enables irradiation with many beams at a time, so that the throughput can be significantly improved. In such a multi-beam type 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, and each of the unshielded beams is blanked. Irradiation to a desired position on the sample (see, for example, Patent Document 1).

  In a thermionic emission electron gun used for electron beam writing, the cathode (cathode) material evaporates during operation. Therefore, the shape of the cathode material changes with time, and the current density distribution of the electron beam irradiated onto the sample also changes with time. Therefore, the current amount of each beam of the multi-beam formed from the electron beam having such a current density distribution changes with time. When a multi-beam is formed from an electron beam having a non-constant current density distribution, the current density is different between the central portion and the end portion, and therefore the irradiation time is different even when a beam having the same irradiation amount is irradiated. Therefore, conventionally, the current amounts of all the beams are measured before drawing, and the irradiation time (exposure time) of each beam is determined based on the measured current amounts. However, even if the irradiation time of each beam is determined, as described above, as the drawing time becomes longer due to the deterioration of the cathode material over time, an error occurs in the exposure time. Therefore, there is a problem that the dimensional accuracy of the drawn pattern is deteriorated. Therefore, in order to recalculate the current density for each beam accompanying the deterioration of the cathode material, it is necessary to remeasure the current amounts of all the beams every predetermined period. When the multi-beam is composed of n × m beams, it is necessary to measure the current amount n × m times. For example, the amount of current needs to be measured again for tens of thousands of beams. Such a measurement operation has a problem that the throughput of the drawing apparatus is remarkably deteriorated.

JP 2006-261342 A

  Accordingly, an object of one aspect of the present invention is to provide a drawing apparatus and method capable of overcoming the above-described problems and suppressing the deterioration of throughput caused by the multi-beam current density distribution.

The multi-beam drawing method of one embodiment of the present invention includes:
Measuring a current value of at least one representative beam among the multi-beams formed by each of a part of the electron beams emitted from an electron gun having a planar photocathode passing through a plurality of openings;
Using a measured current value of at least one representative beam to calculate a representative current density representative of the multi-beam;
Calculating the current density of each beam of the multi-beam using the representative current density;
Calculating the irradiation time of the multi-beam using the current density of each beam calculated using the representative current density;
Drawing a pattern on the sample using a multi-beam of the irradiation time of each calculated beam;
It is provided with.

The drawing area of the sample is virtually divided into a plurality of stripe areas,
Each time at least one of the plurality of stripe regions is drawn, the representative current density is recalculated,
After the representative current density is recalculated, the irradiation time of each beam is preferably calculated using the current density of each beam calculated using the recalculated representative current density.

  In addition, it is preferable to use a central beam and an end beam of the multi-beam as at least one representative beam.

A multi-beam drawing apparatus according to one embodiment of the present invention includes:
An illumination device that generates illumination light having a substantially uniform light intensity distribution;
An electron gun having a planar photocathode that emits an electron beam by irradiation of illumination light;
An aperture plate that is formed with a plurality of openings, receives an electron beam in a region including the whole of the plurality of openings, and forms a multi-beam by passing a part of the electron beams through each of the openings;
A blanking plate in which a plurality of blankers that perform blanking deflection of the corresponding beams among the multi-beams that have passed through the plurality of openings are arranged,
An opening is formed, and each beam that is deflected so as to be in the beam OFF state by a plurality of blankers among the multi-beams is shielded at a position outside the limiting opening, and each beam that is in the beam ON state is limited. A blanking aperture member that passes through the opening;
A multi-beam using a current value of at least one representative beam among multi-beams formed by passing a part of electron beams emitted from an electron gun having a planar photocathode through a plurality of openings. A representative current density calculation unit for calculating a representative current density representative of
An individual current density calculation unit that calculates the current density of each beam of the multi-beam using the representative current density,
An irradiation time calculation unit that calculates the irradiation time of the multi-beam using the current density of each beam calculated using the representative current density,
A controller that controls the plurality of blankers so that the beam is in an ON state during the irradiation time of each beam of the multi-beam;
It is provided with.

  According to one embodiment of the present invention, it is possible to suppress deterioration in throughput due to multi-beam current density distribution.

1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to Embodiment 1. FIG. FIG. 4 is a flowchart showing main steps of the drawing method according to Embodiment 1. 3 is a conceptual diagram illustrating a configuration of an aperture member according to Embodiment 1. FIG. FIG. 3 is a conceptual diagram showing a configuration of a blanking plate in the first embodiment. 6 is a diagram illustrating an example of the position of a representative beam in Embodiment 1. FIG. 6 is a conceptual diagram for explaining a drawing operation in Embodiment 1. FIG. 3 is a conceptual diagram illustrating an example of a configuration of a lighting device and a planar photocathode according to Embodiment 1. FIG. FIG. 5 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. 3 is a diagram showing an example of the current density of an electron beam emitted from a planar photocathode in Embodiment 1. FIG. FIG. 5 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. FIG. 5 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. 6 is a diagram illustrating an example of an installation configuration of a lighting device in Embodiment 1. FIG. FIG. 5 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. FIG. 5 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. FIG. 5 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. 6 is a diagram for explaining a change in current density distribution accompanying evaporation of a cathode in a comparative example of Embodiment 1. FIG.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to the first embodiment. In FIG. 1, the drawing apparatus 100 includes a drawing unit 150 and a control unit 160. The drawing apparatus 100 is an example of a multi charged particle beam drawing apparatus. The drawing unit 150 includes an electron column 102 and a drawing chamber 103. In the electron column 102, an illumination device 212, an electron gun 201, an illumination lens 202, an aperture member 203, a blanking plate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, and a deflector 208 are arranged. ing. An XY stage 105 is disposed in the drawing chamber 103. On the XY stage 105, a sample 101 such as a mask to be a drawing target substrate at the time of drawing is arranged. The sample 101 includes an exposure mask for manufacturing a semiconductor device, or a semiconductor substrate (silicon wafer) on which the semiconductor device is manufactured. Further, the sample 101 includes mask blanks to which a resist is applied and nothing is drawn yet. On the XY stage 105, the Faraday cup 106 is arranged at a position different from the position where the sample 101 is arranged.

  The reduction lens 205 and the objective lens 207 are both configured by electromagnetic lenses, and are arranged so that the magnetic field is in the reverse direction and the magnitude of excitation is equal, for example. The reduction lens 205 and the objective lens 207 constitute a reduction optical system.

  The electron gun 201 has a planar photocathode 10, Wehnelt 12, and an anode 14. The Wehnelt 12 is disposed between the planar photocathode 10 and the anode 14. The anode 14 is grounded and the potential is set to the ground potential. An electron gun power supply device 130 is connected to the electron gun 201. The electron gun power supply device 130 applies an acceleration voltage between the planar photocathode 10 and the anode 14. As the acceleration voltage, a negative potential is applied to the planar photocathode 10 with respect to the anode 14 having the ground potential. In addition, the electron gun power supply device 130 applies a negative bias voltage to the Wehnelt 12.

  In the conventional thermionic emission type cathode, the current density distribution of the emitted electron beam changes with time. However, in the planar photocathode 10, when the planar photocathode 10 is irradiated with substantially uniform illumination light, the current density distribution of the emitted electron beam becomes substantially uniform (substantially uniform). In the planar photocathode 10, the quantum efficiency at the photocathode surface deteriorates with time, but the deterioration rate does not depend on the position of the photocathode surface. Therefore, even if the quantum efficiency deteriorates with time, the current density distribution of the emitted electron beam can be maintained substantially uniform (substantially uniform). Quantum efficiency is defined by the ratio of the number of electrons emitted to the number of incident photons. Therefore, in the first embodiment, the electron gun 201 using the planar photocathode 10 forms the electron beam 200 having a substantially uniform current density distribution. The wavelength of the illumination light may be appropriately adjusted according to the material of the planar photocathode 10. The wavelength of the illumination light may be ultraviolet light or visible light depending on the material of the planar photocathode 10.

  The control unit 160 includes a control computer 110, a memory 112, a control circuit 120, an electron gun power supply circuit 130, an amplifier 132, and storage devices 140, 142, and 144 such as a magnetic disk device. The control computer 110, the memory 112, the control circuit 120, the electron gun power supply circuit 130, the amplifier 132, and the storage devices 140, 142, and 144 are connected to each other via a bus (not shown).

In the control computer 110, a drawing data processing unit 50, an irradiation amount calculation unit 52, a representative beam current (I ₀ ) measurement unit 54, a representative beam current density (J ₀ ) calculation unit 56, and an individual beam current density (Jk) calculation. A unit 58, an individual beam irradiation time (Tk) calculation unit 60, a drawing control unit 62, a setting unit 64, and determination units 66 and 68 are arranged. Drawing data processing unit 50, irradiation amount calculation unit 52, representative beam current (I ₀ ) measurement unit 54, representative beam current density (J ₀ ) calculation unit 56, individual beam current density (Jk) calculation unit 58, individual beam irradiation time (Tk) Each function such as the calculation unit 60, the drawing control unit 62, the setting unit 64, and the determination units 66 and 68 may be configured by software such as a program. Alternatively, it may be configured by hardware such as an electronic circuit. Alternatively, a combination thereof may be used. Necessary input data or calculated results in the control computer unit 110 are stored in the memory 112 each time. Further, the drawing data processing unit 50, the dose calculation unit 52, the representative beam current (I ₀ ) measurement unit 54, the representative beam current density (J ₀ ) calculation unit 56, the individual beam current density (Jk) calculation unit 58, the individual beam When at least one of the irradiation time (Tk) calculation unit 60, the drawing control unit 62, the setting unit 64, and the determination units 66 and 68 is configured by software, a calculator such as a CPU or a GPU is arranged.

  Here, FIG. 1 shows a configuration necessary for explaining the first embodiment. The drawing apparatus 100 may normally have other necessary configurations.

FIG. 2 is a flowchart showing main steps of the drawing method according to the first embodiment. In FIG. 2, the drawing method according to the first embodiment includes a representative beam setting step (S102), an opening area measuring step (S104), a representative beam current (I ₀ ) measuring step (S106), and a representative beam current density. (J ₀ ) calculation step (S108), individual beam current density (Jk) calculation step (S110), dose calculation step (S112), individual beam irradiation time (Tk) calculation step (S114), and drawing step A series of steps of (S116), determination step (S118), and determination step (S120) are performed.

  FIG. 3 is a conceptual diagram showing the configuration of the aperture member in the first embodiment. In FIG. 3A, the aperture member 203 has vertical (y direction) m rows × horizontal (x direction) n rows (m, n ≧ 2) holes (openings) 22 in a matrix form with a predetermined arrangement pitch. Is formed. In the example of FIG. 2A, for example, 512 × 8 rows of holes 22 are formed. Each hole 22 is formed of a rectangle having the same size and shape. Alternatively, it may be a circle having the same outer diameter. Here, an example is shown in which eight holes 22 from A to H are formed in the x direction for each row in the y direction. When a part of the electron beam 200 passes through each of the plurality of holes 22, the multi-beam 20 is formed. Here, an example in which two or more holes 22 are arranged in both the vertical and horizontal directions (x and y directions) is shown, but the present invention is not limited to this. For example, either one of the vertical and horizontal directions (x and y directions) may be a plurality of rows and the other may be only one row. Further, the arrangement of the holes 22 is not limited to the case where the vertical and horizontal directions are arranged in a grid pattern as shown in FIG. As shown in FIG. 3B, for example, the holes in the first row in the vertical direction (y direction) and the holes in the second row are shifted by a dimension a in the horizontal direction (x direction). Also good. Similarly, the holes in the second row in the vertical direction (y direction) and the holes in the third row may be arranged shifted by a dimension b in the horizontal direction (x direction).

  FIG. 4 is a conceptual diagram showing the configuration of the blanking plate in the first embodiment. Passing holes are formed in the blanking plate 204 in accordance with the arrangement positions of the respective holes 22 of the aperture member 203, and a pair of two electrodes 24 and 26 (blankers: first deflection) is formed in each passing hole. Are arranged respectively. The electron beam 20 passing through each through hole is deflected by a voltage applied to the two electrodes 24 and 26 that are paired independently. Blanking is controlled by such deflection. In this manner, the plurality of blankers perform blanking deflection of the corresponding beams among the multi-beams that have passed through the plurality of holes 22 (openings) of the aperture member 203.

  The drawing apparatus 100 operates according to the control of the drawing control unit 62. In particular, the drawing unit 150 operates as follows. The planar photocathode 10 is irradiated with the illumination light 16 from the illuminating device 212 to the planar photocathode 10 in a state where the set voltages are respectively applied to the planar photocathode 10 and the Wehnelt 12 by the electron gun power supply device 130. The electron beam 200 is emitted from. The electron beam 200 emitted from the planar photocathode 10 whose emission amount is controlled by the bias voltage of the Wehnelt 12 spreads after forming a crossover (C.O.), is accelerated by the anode 14, and is accelerated by the electron gun 201. It is emitted from (emission part).

  The emitted electron beam 200 illuminates the entire aperture member 203 almost vertically by the illumination lens 202. A plurality of rectangular holes (openings) are formed in the aperture member 203, and the electron beam 200 illuminates a region including all of the plurality of holes. Each part of the electron beam 200 irradiated to the positions of the plurality of holes passes through the plurality of holes of the aperture member 203, thereby forming, for example, a plurality of rectangular electron beams (multi-beams) 20a to 20e. Is done. The multi-beams 20a to 20e pass through the corresponding blankers (first deflectors) of the blanking plate 204, respectively. Each of these blankers deflects the electron beam 20 that individually passes (performs blanking deflection). The multi-beams 20 a to 20 e that have passed through the blanking plate 204 are refracted and condensed by the reduction lens 205, and travel toward a central hole formed in the limiting aperture member 206. Here, the electron beam 20 deflected by the blanker of the blanking plate 204 is displaced from the hole at the center of the limiting aperture member 206 (blanking aperture member), and is blocked by the limiting aperture member 206. On the other hand, the electron beam 20 that has not been deflected by the blanker of the blanking plate 204 passes through the central hole of the limiting aperture member 206. Blanking control is performed according to ON / OFF of the blanker, and ON / OFF of the beam is controlled. Thus, the limiting aperture member 206 shields each beam deflected so as to be in a beam OFF state by a plurality of blankers. A beam of one shot is formed by the beam that has passed through the limiting aperture member 206, which is formed from when the beam is turned on to when the beam is turned off. The pattern image of the multi-beam 20 that has passed through the limiting aperture member 206 is focused by the objective lens 207, deflected collectively by the deflector 208, and irradiated to each irradiation position on the sample 101.

  The drawing apparatus 100 performs a drawing operation by a raster scan method in which the XY stage 105 moves and sequentially irradiates the shot beam sequentially, and when drawing a desired pattern, a necessary beam is blanked according to the pattern. The beam is controlled by control.

Here, each beam of the multi-beam irradiates a necessary position with a beam having a necessary irradiation amount. In electron beam drawing, for example, dimensional variations such as proximity effects occur according to the shape of the pattern to be drawn. In the drawing apparatus 100, the dimensional variation such as the proximity effect is corrected by the dose. Therefore, the necessary irradiation amount D (x, y) varies depending on the irradiation position (x, y). The irradiation amount D (x, y) is controlled by the beam irradiation time Tk. Hereinafter, k represents an identification number or coordinates (vector) of an individual beam. The irradiation time Tk can be obtained by dividing the irradiation amount D (x, y) by the beam current density Jk as shown in the equation (1).
(1) Tk = D (x, y) / Jk

Therefore, it is necessary to accurately grasp the current density Jk of each beam. If there is an error in the current density Jk of each beam, an error occurs in the dose. As a result, pattern misalignment or the like occurs. In a conventional electron gun using a heat emitting cathode, the current density Jk of each beam individually changes with the passage of time. Therefore, the current density Jk for all the beams every predetermined period. It was necessary to confirm. Therefore, it is necessary to measure the current amount Ik for all the beams. The throughput that takes time to measure the current amount Ik is deteriorated. Therefore, in the first embodiment, by emitting the substantially uniform electron beam 200 from the planar photocathode 10, the current density Jk of each beam of the formed multi-beam 20 can be made substantially uniform. Therefore, every predetermined period, for all beam, there is no need to measure the amount of current Ik respectively, to measure only the amount of current I ₀ for the representative beam. And the current density Jk of each beam of the multi-beam 20 is calculated | required from the result. Thereby, the measurement time can be greatly shortened.

  As the representative beam setting step (S102), the setting unit 64 sets at least one representative beam among the multi-beams.

  FIG. 5 is a diagram illustrating an example of the position of the representative beam in the first embodiment. In the example of FIG. 5, a plurality of holes 22 in the aperture member 203 that forms 9 × 9 multi-beams are shown. In the first embodiment, the central beam and the end beam of the multi-beam are used as the representative beams. In the example of FIG. 5, a beam formed by passing through the hole 23a at the center of the plurality of holes 22 and 4 formed by passing through the holes 23b, 23c, 23d, and 23e at the four corners that are the end portions. A total of five beams are set as representative beams. However, the present invention is not limited to this. There may be at least one representative beam representing the multi-beam. For example, one beam formed by passing through the center hole 23a of the plurality of holes 22 may be set as the representative beam.

  In the opening area measurement step (S104), each hole 22 of the aperture member 203 is imaged using a scanning electron microscope (SEM), and the opening area Sk of the opening that forms each beam of the multi-beam is determined from the captured image. calculate. Alternatively, each hole 22 of the aperture member 203 is irradiated with a laser, and the opening area Sk of the opening that forms each beam is calculated using the amount of transmitted laser light for each hole 22. If all the holes 22 can be manufactured uniformly in the same shape, not only all the holes 22 but only the representative beam holes 23 may be imaged using the SEM to calculate the opening area Sk.

As a representative beam current (I ₀ ) measurement step (S106), the I ₀ measurement unit 54 is configured such that a part of the electron beam 200 emitted from the electron gun 201 using the planar photocathode 10 passes through a plurality of openings. Thus, the current value I ₀ of at least one representative beam among the multi-beams 20 formed is measured. Here, the current value I ₀ of the set representative beam is measured. Specifically, it operates as follows. Only the representative beam to be measured is turned on, and other beams are deflected by a blanker in the blanking plate 204 so that the beam is turned off. When a plurality of representative beams are set, control is performed so that the beams are turned on one by one. Thereby, only the representative beam 20 can be guided to the stage. At that time, the XY stage 105 is moved so that the representative beam 20 applied to the Faraday cup 106 is irradiated. Thereby, the current value of the representative beam 20 can be detected. The remaining beam is shielded by the limiting aperture member 206. Therefore, the beam is blocked before reaching the drawing chamber 103. Therefore, the beam does not reach the stage 105 or the sample 101. Information measured by the Faraday cup 106 is converted into a digital signal by the amplifier 132 and output to the I ₀ measurement unit 54. Thereby, the I ₀ measuring unit 54 can measure the current value I ₀ of the representative beam. Such an operation is performed for all representative beams. As a result, the beam current value I ₀ for each representative beam can be measured.

In the representative beam current density (J ₀ ) calculation step (S108), the J ₀ calculation unit 56 uses the measured current value I ₀ of at least one representative beam to calculate the representative current density J ₀ representing the multi-beam. Calculate. When a plurality of representative beams are set, the representative current density J ₀ is calculated for each beam. Specifically, the calculation is performed as follows. The J ₀ calculation unit 56 calculates the current density J ₀ of the representative beam by dividing the measured current value I ₀ of the representative beam by the opening area Sk of the corresponding hole 22 of the aperture member 203. Such an operation is performed for all representative beams. This allows calculation of the current density J ₀ of each representative beam.

As an individual beam current density (Jk) calculation step (S110), Jk calculation unit 58 (individual current density calculation unit) calculates the current density Jk of each beam of the multi-beam using a representative current density _{J 0.} First, the obtained current density J ₀ for each representative beam is fitted (approximate) with a polynomial to obtain an approximate expression. Here, since the form a multi-beam 20 from the electron beam 200 emitted from the planar photocathode 10, if the opening area Sk is the same, the current density J ₀ of the representative beams operations substantially uniform Become. Therefore, the approximate polynomial may be defined by a first-order polynomial shown in the following formula (2) without using a higher-order function. In the equation (2), the position coordinate k of the beam is indicated by (x, y).
(2) J (x, y) = ax + by + c

In the example of FIG. 5, the current densities J ₀ of five representative beams are obtained. Therefore, for approximation, for example, the least square method is used based on the current densities J ₀ of these five representative beams. Thus, it is preferable to obtain an approximate expression. In other words, it is preferable to obtain the coefficients a, b, and c of the approximate expression using the least square method. And the Jk calculating part 58 calculates the current density Jk of each beam of a multi-beam by substituting the position coordinate (x, y) of each beam into Formula (2). In the case of only one representative beam current density J ₀ of the representative beam as it is, or may be the current density Jk other beam. In the above-described example, approximation is performed using a first-order polynomial, but the present invention is not limited to this. A second or higher order polynomial may be used. When the aperture area Sk is different from the aperture area Sk of the representative beam, when calculating the current density Jk of each beam, the ratio between the aperture area Sk of the target beam and the aperture area Sk of the representative beam is expressed by the equation (2). It is also preferable to correct by multiplying the value obtained from (1). Specifically, the value obtained by dividing the aperture area Sk of the representative beam by the aperture area Sk of the target beam may be multiplied and corrected by the value obtained from Expression (2). When a plurality of representative beams are set, for example, a value obtained by dividing the average value of the aperture area Sk of the representative beam by the aperture area Sk of the target beam may be corrected by multiplying the value obtained from Expression (2). .

As described above, by measuring the current value I ₀ of a very small number of representative beams with respect to one or the number of multi beams, the current density Jk of each beam of a large number of multi beams can be obtained. Therefore, the measurement time can be greatly shortened as compared with the case where the current values Ik of all the beams of the multi-beams are measured.

  As the dose calculation step (S112), the dose calculation unit 52 reads the drawing data from the storage device 140 and calculates the dose for each irradiation position of the sample 101. In the drawing data, for example, an arrangement position, a figure type, and a figure size of each figure pattern are defined. In addition, a reference dose is defined.

  As will be described later, the drawing area of the sample 101 is virtually divided into a plurality of strip-like stripe areas with a predetermined width in the y direction, for example. In multi-beam drawing, a drawing region (or stripe region) is meshed with a size of 1 / n (for example, n is an integer of 1 or more) of one of a plurality of beams constituting the multi-beam. Virtually split. A pattern is drawn by irradiating a mesh on which a graphic pattern exists and irradiating a non-existent mesh with a beam. However, when the end of the graphic pattern is located within the mesh, the position of the end of the graphic pattern is controlled by adjusting the irradiation amount. Further, when a plurality of graphic patterns are drawn, the dose may be modulated by the graphic pattern. The modulation factor data may be separately stored in the storage device 140 or the like and read from the storage device 140. In addition, it is necessary to adjust the dose in order to correct dimensional variations such as proximity effects. The proximity effect correction calculation may be performed by a conventional method. Irradiation amount data for each mesh position (beam irradiation position) is created, for example, as an irradiation amount map and stored in the storage device 142. Thus, the dose data for each irradiation position is often different. Of course, the case of the same dose is not excluded. The calculation of the irradiation amount is preferably performed for each stripe region in real time as the drawing process proceeds. For example, it is preferable to perform an operation on a stripe region one or two steps ahead of the stripe region being drawn.

As an individual beam irradiation time (Tk) calculation step (S114), Tk calculation unit 60 uses the respective beam current density Jk multibeam computed using the representative current density J _0, of each beam of the multi-beam The irradiation time Tk is calculated. The irradiation time Tk of each beam can be obtained by the above equation (1). The Tk calculator 60 may read the dose map from the storage device 142 and use it for calculating the irradiation time Tk of each beam. The calculation of the irradiation time for each mesh position (beam irradiation position) is preferably performed for each stripe region in real time as the drawing process proceeds. For example, it is preferable to perform an operation on a stripe region one or two steps ahead of the stripe region being drawn. The calculated irradiation time Tk of each beam is created, for example, as an irradiation time T map and stored in the storage device 144.

  As the drawing step (S116), first, the drawing data processing unit 50 generates shot data in accordance with the irradiation order of irradiation positions where multi-beams are irradiated for each stripe region described later. In multi-beam drawing, not all irradiation positions in an irradiation region that can be irradiated with a multi-beam at a time can be drawn at a time. While shifting the position of the irradiation region, the entire stripe region is sequentially drawn using the multi-beam. Therefore, shot data in which irradiation time Tk data of the irradiation positions of the corresponding beams is sequentially arranged for each shot of the entire multi-beam is generated. The drawing data processing unit 50 may read the irradiation time T map from the storage device 144 and generate shot data. Then, the control circuit 120 controls and drives the drawing unit 150 based on a control signal from the drawing control unit 62. The drawing unit 150 draws a pattern on the sample 101 using multi-beams with the irradiation times Tk of the respective beams calculated along the shot data. The control circuit 120 controls a plurality of blankers corresponding to the blanking plate 204 so as to be in the beam ON state during the irradiation time Tk of each beam of the multi-beam.

  FIG. 6 is a conceptual diagram for explaining a drawing operation in the first embodiment. As shown in FIG. 6A, the drawing area 30 of the sample 101 is virtually divided into a plurality of strip-shaped stripe areas 32 having a predetermined width in the y direction, for example. Each stripe region 32 is a drawing unit region. First, the XY stage 105 is moved and adjusted so that the irradiation region 34 that can be irradiated by one irradiation of the multi-beam 20 is positioned at the left end of the first stripe region 32 or further on the left side. Is started. When drawing the first stripe region 32, the drawing is relatively advanced in the x direction by moving the XY stage 105 in the −x direction, for example. For example, the XY stage 105 is continuously moved at a predetermined speed. After drawing of the first stripe region 32, the stage position is moved in the -y direction, and the irradiation region 34 is relatively positioned in the y direction at the right end of the second stripe region 32 or further to the right side. Next, as shown in FIG. 6B, the XY stage 105 is moved in the x direction, for example, so that the drawing is similarly performed in the −x direction. In the third stripe region 32, drawing is performed in the x direction, and in the fourth stripe region 32, drawing is performed while alternately changing the orientation, such as drawing in the −x direction. Can be shortened. However, the drawing is not limited to the case of alternately changing the direction, and when drawing each stripe region 32, the drawing may be advanced in the same direction. In one shot, as shown in FIG. 6C, the same number of shot patterns 36 as the holes 22 are formed at once by the multi-beams formed by passing through the holes 22 of the aperture member 203. Is done. For example, the beam that has passed through one hole A of the aperture member 203 is irradiated to a position “A” shown in FIG. 6C, and a shot pattern 36 is formed at that position. Similarly, for example, the beam that has passed through one hole B of the aperture member 203 is irradiated to a position “B” shown in FIG. 6C, and a shot pattern 36 is formed at that position. Hereinafter, the same applies to C to H. Then, when drawing each stripe 32, while the XY stage 105 moves in the x direction, the deflector 208 deflects all the beams (multi-beams) at once, and continuously irradiates the shot beam sequentially. Draw with the raster scan method.

  Here, the drawing apparatus 100 places the sample 101 on the XY stage 105 and draws a pattern on the sample 101 while continuously moving the XY stage 105 or performing a step-and-repeat operation.

  As a determination step (S118), the determination unit 66 determines whether drawing of the entire drawing region 30 of the sample 101 is finished each time drawing of one stripe region 32 is finished. If the drawing of the entire drawing area 30 has been completed, the drawing process ends. If the drawing of the entire drawing area 30 has not been completed, the process proceeds to the determination step (S120).

In the determination step (S120), the determination unit 68 determines whether or not drawing of the L stripe regions 32 set in advance has been completed since the last measurement of the representative beam current. The L stripe regions 32 may be at least one stripe region 32. If the drawing of the L stripe regions 32 has not been completed, the process returns to the dose calculation step (S112), and the dose at each irradiation position in the remaining stripe region 32 is calculated. Then, each process from the dose calculation step (S112) to the determination step (S120) is repeated until drawing of the L stripe regions 32 is completed. Note that, in the irradiation amount calculation step (S112), for example, one or two stripe regions 32 of the stripe region 32 for which drawing has been completed is calculated in advance, so the remaining stripe region for which drawing has not been completed. Even if there is, there is a case where the irradiation amount calculation has already been completed. In that case, the irradiation amount calculation step (S112) may be omitted and the process proceeds. The same applies to the individual beam irradiation time (Tk) calculation step (S114). Further, when the drawing of the preset L stripe regions 32 is completed, the process returns to the representative beam current (I ₀ ) measurement step (S106). Then, the I ₀ measuring unit 54 again measures the current value I ₀ of the set representative beam. Then, the representative current density J ₀ is recalculated from the current value I ₀ of the latest representative beam. Then, each beam of current density Jk from representative current density J ₀ of such latest representative beam is re-computed. Then, the irradiation time Tk of each beam is calculated from the latest current density Jk of each beam, which has been recalculated, from the latest current density Jk of each beam.

As described above, the drawing area 30 of the sample 101 is virtually divided into a plurality of stripe regions 32, each at least one drawing of the plurality of stripe regions 32 is completed, representative current density J ₀ is re-computed . After the representative current density J ₀ is re-computed, the irradiation time of each beam is calculated using the individual current density Jk computed using the representative current density J ₀ which are re-computed. Since the quantum efficiency degradation rate of the planar photocathode 10 is considered not to advance enough to update the current density J ₀ of the representative beam only by drawing one stripe region 32, each time a plurality of stripe regions 32 are drawn. it may be updated to the current density J ₀ of the representative beam. However, it does not exclude the case of updating the current density J ₀ of the representative beam for each drawing one stripe region 32. Further, by updating the current density J ₀ of the representative beam stripe region 32 units, since the inside of the stripe region 32 are not able to stop the drawing operation in the drawing, the position of the pattern in the stripe region 32 in the drawing process Misalignment can be prevented.

  FIG. 7 is a conceptual diagram showing an example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 7, the illumination device 212 includes a light source 214 and an illumination optical system 216. In the example of FIG. 7, the illumination light 16 irradiated from the light source 214 is refracted by the illumination optical system 216 and irradiated as parallel light onto the back surface of the planar photocathode 10 with a substantially uniform intensity distribution. As a result, the planar photocathode 10 emits an electron beam 200 having a substantially uniform current density from the surface opposite to the surface irradiated with the illumination light 16.

  FIG. 8 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 8, the illumination device 212 includes a light source 214 and an illumination optical system 216. In the example of FIG. 8, the illumination light 16 irradiated from the light source 214 may be refracted by the illumination optical system 216 and irradiated as parallel light onto the surface of the planar photocathode 10 with, for example, a substantially uniform intensity distribution from an oblique direction. . As a result, an electron beam 200 having a substantially uniform current density is emitted from the planar photocathode 10 from the same surface as the surface irradiated with the illumination light 16.

  FIG. 9 is a diagram showing an example of the current density of the electron beam emitted from the planar photocathode in the first embodiment. As shown in FIG. 9, the current density distribution of the electron beam emitted from the planar photocathode 10 can be made substantially uniform. Therefore, the aperture member 203 can be irradiated with an electron beam having a substantially uniform current density distribution.

  FIG. 10 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 10, the lighting device 212 includes a light source 214 (laser light source) and an optical fiber 218. In the example of FIG. 10A, the illumination light 16 irradiated from the light source 214 is propagated through the optical fiber 218 and irradiated on the back surface of the planar photocathode 10. By propagating through the optical fiber 218, the laser intensity distribution of the illumination light 16 can be made substantially uniform as shown in FIG. As a result, the planar photocathode 10 emits an electron beam 200 having a substantially uniform current density from the surface opposite to the surface irradiated with the illumination light 16.

  FIG. 11 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 11, the lighting device 212 includes a light source 214 (laser light source) and an optical fiber 218. In the example of FIG. 11A, the illumination light 16 irradiated from the light source 214 is propagated through the optical fiber 218 and irradiated onto the surface of the planar photocathode 10 from an oblique direction, for example. By propagating through the optical fiber 218, the laser intensity distribution of the illumination light 16 can be made substantially uniform as shown in FIG. 11B, as in FIG. 10B. As a result, an electron beam 200 having a substantially uniform current density is emitted from the planar photocathode 10 from the same surface as the surface irradiated with the illumination light 16.

  FIG. 12 is a diagram illustrating an example of an installation configuration of the lighting device in the first embodiment. In the example of FIG. 1, the case where the illumination device 212 is disposed in the electronic lens barrel 102 is shown, but the present invention is not limited to this. A light source 214 may be disposed outside the electron column 102. By using the optical fiber 218, the degree of freedom of the propagation path of the illumination light 16 can be increased, and the light source 214 can be easily disposed outside the electron column 102. Note that the light source 214 may be arranged outside the electron column 102 and the arrangement position of the illumination optical system 216 may be adjusted to irradiate the planar photocathode 10 in the electron column 102 with the illumination light 16. Absent.

  FIG. 13 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 13A, the illumination device 212 includes an LED (Light Emitting Diode) light source 314 and an illumination optical system 216. In the example of FIG. 13A, the illumination light 18 irradiated from the LED light source 314 is refracted by the illumination optical system 216 and irradiated as parallel light on the back surface of the planar photocathode 10 with a substantially uniform intensity distribution. By irradiating the illumination light 18 from the LED light source 314, the LED light intensity distribution of the illumination light 18 can be made substantially uniform over a wide range, as shown in FIG. Therefore, what is necessary is just to irradiate the planar photocathode 10 with LED light in a range where the LED light intensity distribution is substantially uniform. As a result, the planar photocathode 10 emits the electron beam 200 having a substantially uniform current density from the surface opposite to the surface irradiated with the illumination light 18.

  FIG. 14 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 14A, the illumination device 212 has an LED light source 314 and an illumination optical system 216. In the example of FIG. 14A, the illumination light 16 irradiated from the LED light source 314 is refracted by the illumination optical system 216 and irradiated as parallel light onto the surface of the planar photocathode 10 with a substantially uniform intensity distribution from an oblique direction, for example. May be. By irradiating the illumination light 18 from the LED light source 314, as shown in FIG. 14B, the LED light intensity distribution of the illumination light 18 can be made substantially uniform over a wide range, as in FIG. 13B. Therefore, what is necessary is just to irradiate the planar photocathode 10 with LED light in a range where the LED light intensity distribution is substantially uniform. As a result, the planar photocathode 10 emits an electron beam 200 having a substantially uniform current density from the same surface as the surface irradiated with the illumination light 18.

  FIG. 15 is a conceptual diagram showing another example of the configuration of the illumination device and the planar photocathode in the first embodiment. In FIG. 15, the illumination device 212 includes a light source 214, an illumination optical system 316, and a slit 318. In order to obtain a uniform current density from the planar photocathode 10, it depends on how the uniformity of the light intensity of the illumination light 16 is increased. For this purpose, for example, the light 15 from the light source 214 having a Gaussian distribution of light intensity is refracted by the illumination optical system 316 and spread as much as possible, and a portion of the light 15 having a uniform light intensity near the center of the Gaussian distribution. It is desirable to cut out with the slit 318 at the position as close as possible to the planar photocathode 10. In other words, it is desirable to cut light other than the portion where the light intensity near the center of the Gaussian distribution is uniform at the slit 318. Then, it is preferable to irradiate the planar photocathode 10 as illumination light 16 with a portion of light having a uniform light intensity near the center of the Gaussian distribution that has passed through the slit 318. Thereby, the illuminating device 212 can generate illumination light having a substantially uniform light intensity distribution. Note that the smaller the light to be cut, the better the efficiency. Therefore, it is desirable that the output of the light source 214 has a more uniform light intensity. Therefore, it is more preferable to use the above-described optical fiber 218 or LED light source 314 as the light source 214.

  FIG. 16 is a diagram for explaining a change in the current density distribution accompanying the evaporation of the cathode in the comparative example of the first embodiment. Here, as a comparative example of the first embodiment, cathode deterioration of a heat emission electron gun will be described. In FIG. 16A, in the state before the cathode deterioration, the electron beam emitted from the cathode (cathode) spreads after forming a crossover, and is refracted into a substantially vertical beam by the illumination lens (collimator lens). And proceed to the mask (sample) surface side. When the cathode evaporates (deteriorates) over time, the area of the cathode emission surface becomes narrower. However, since the Wehnelt voltage has not changed, the current density is increased. Therefore, the spread of the beam after crossover is also small. FIG. 16B shows the current density distribution in each state before and after the cathode deterioration. When the cathode evaporates (deteriorates) as compared with the state before the cathode deterioration, the beam spread becomes small as described above, and the peak value of the current density distribution becomes high. Thus, the shape of the current density distribution changes greatly before and after the cathode deterioration. On the other hand, in the first embodiment, the current density is obtained by using the planar photocathode 10 that can emit a substantially uniform electron beam regardless of the position of the current density distribution even when time passes. Distribution can be maintained substantially uniform. Therefore, the number of beams for current measurement can be greatly reduced, and the throughput can be improved.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. The raster scan operation described above is an example, and a raster scan operation using a multi-beam and other operation methods may be used.

  In addition, although descriptions are omitted for parts and the like that are not directly required for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used. For example, although the description of the control unit configuration for controlling the drawing apparatus 100 is omitted, it goes without saying that the required control unit configuration is appropriately selected and used.

  In addition, all charged particle beam writing methods and charged particle beam writing apparatuses that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Planar type photocathode 12 Wehnelt 14 Anode 20 Multi beam 22, 23 Hole 24, 26 Electrode 30 Drawing area 32 Stripe area 34 Irradiation area 36 Shot pattern 50 Drawing data processing part 52 Irradiation amount calculation part 54 I ₀ measurement part 56 J ₀ Calculation unit 58 Jk calculation unit 60 Tk calculation unit 62 Drawing control unit 64 Setting unit 66, 68 Judgment unit 100 Drawing device 101, 340 Sample 102 Electron barrel 103 Drawing chamber 105 XY stage 110 Control computer 112 Memory 120 Control circuit 130 Electron gun Power supply circuit 132 Amplifier 140, 142, 144 Storage device 150 Drawing unit 160 Control unit 200 Electron beam 201 Electron gun 202 Illumination lens 203 Aperture member 204 Blanking plate 205 Reduction lens 206 Limiting aperture member 207 Objective lens 2 8 deflector 212 illumination device 214 light source 216, 316, the illumination optical system 218 fibers 314 LED light source 318 slit

Claims (4)

Measuring a current value of at least one representative beam among the multi-beams formed by each of a part of the electron beams emitted from an electron gun having a planar photocathode passing through a plurality of openings;
Calculating a representative current density representative of the multi-beam using a measured current value of at least one representative beam;
Calculating the current density of each beam of the multi-beam using the representative current density;
Calculating the irradiation time of the multi-beam using the current density of each beam calculated using the representative current density;
Drawing a pattern on the sample using a multi-beam of the irradiation time of each calculated beam;
A multi-beam drawing method comprising: The drawing area of the sample is virtually divided into a plurality of stripe areas,
Each time at least one of the plurality of stripe regions is drawn, the representative current density is recalculated,
After the representative current density is recalculated, the irradiation time of each beam is calculated using the current density of each beam calculated using the recalculated representative current density. The multi-beam drawing method according to claim 1 . 3. The multi-beam drawing method according to claim 1, wherein a beam at a center portion and a beam at an end portion of the multi-beam are used as the at least one representative beam. An illumination device that generates illumination light having a substantially uniform light intensity distribution;
An electron gun having a planar photocathode that emits an electron beam by irradiation of the illumination light;
A plurality of openings are formed, a region including the whole of the plurality of openings is irradiated with the electron beam, and a part of the electron beam passes through the plurality of openings to form a multi-beam. Aperture plate,
Among the multi-beams that have passed through the plurality of openings, a blanking plate in which a plurality of blankers that perform blanking deflection of the corresponding beam is disposed,
A limiting opening is formed, and each of the multi-beams deflected so as to be in a beam OFF state by the plurality of blankers is shielded at a position outside the limiting opening, and the beam is in an ON state. A blanking aperture member that allows each beam to pass through the limiting aperture;
Using the current value of at least one representative beam among the multi-beams formed by each of a part of the electron beams emitted from the electron gun having the planar photocathode passing through a plurality of openings, A representative current density calculator for calculating a representative current density representative of a multi-beam;
Using the representative current density, an individual current density calculation unit that calculates the current density of each beam of the multi-beam,
An irradiation time calculation unit that calculates the irradiation time of the multi-beam using the current density of each beam calculated using the representative current density;
A controller that controls the plurality of blankers so that the beam is in an ON state during the irradiation time of each beam of the calculated multi-beam;
A multi-beam drawing apparatus comprising:

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