JP2008219037A - Electron gun, and device and method of electron beam drawing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an electron gun equipped with a plurality of cathodes to provide a method of adjusting each electron beam in order to improve throughput of an electron beam drawing device. <P>SOLUTION: A deflector (408) and rotation coil (409) acting on all electron beams are installed in an acceleration space. The deflector (410) acting on each electron beam is installed outside the acceleration space. An electron beam shielding board (411) having a heat dissipation mechanism is installed outside the acceleration space. Each cathode is used in a temperature limited area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electron beam drawing technique including an electron gun used in a semiconductor process or the like.

  In recent years, an electron beam drawing apparatus that draws a desired pattern on a sample in a semiconductor process or the like is required to have higher drawing accuracy and throughput, but further improvement in performance of the electron gun is also required.

  First, looking at the electron gun from the viewpoint of the drawing method, conventionally, the number of elements (hereinafter referred to as cathodes) capable of emitting electrons provided in the electron gun is one, and the emitted electron beam is also Although it is one, it is desirable to use a plurality of cathodes in order to improve the throughput. In this regard, an electron beam drawing apparatus including an electron gun capable of emitting a plurality of electron beams from a plurality of cathodes and a plurality of columns corresponding to the plurality of electron beams has been proposed (for example, non-patent literature). 1).

  On the other hand, looking at the electron gun from the viewpoint of the type of cathode and the method of using the same, conventionally, in an electron beam drawing apparatus, a thermal field emission electron gun or a thermal electron gun is often used. In particular, in a high-throughput electron beam lithography apparatus used in semiconductor device mask manufacturing or semiconductor device manufacturing processes, a triode type thermoelectron gun that can easily obtain a large current and has stable electron emission may be used. Many.

  FIG. 1 is a schematic diagram of a general triode type thermoelectron gun. By energizing and heating the heater 102, the cathode 101 made of a material having a low work function is heated, and energy sufficient to overcome the barrier on the cathode surface is given to the electrons, so that the anode 104 having a high potential with respect to the cathode. Accelerate towards. Reference numeral 105 denotes an electron trajectory.

  The current density at the cathode surface (hereinafter referred to as cathode emission current density) is determined by (1) work function of the cathode material, (2) cathode temperature, (3) electric field strength at the cathode surface, (4) vacuum quality, and the like. Of these, (1) the work function of the cathode material and (4) the quality of the vacuum are difficult to manipulate freely, and (2) the temperature of the cathode and (3) the electric field strength at the cathode surface, To control. The cathode temperature is controlled by adjusting the current supplied to the heater for heating the cathode, and the electric field strength at the cathode surface is controlled by adjusting the voltage applied to the Wehnelt electrode 103 placed between the cathode and the anode. I do. In the figure, reference numeral 106 denotes an electron beam crossover. Crossover is an image formed when electron beams emitted in the same direction from different positions in the same cathode intersect. The size (diameter) of the crossover is called the crossover diameter, and the position where the crossover is formed (on the beam axis) is called the crossover position. The crossover diameter and the crossover position vary depending on the structure of the electron gun and the voltage applied to each electrode.

On the other hand, FIG. 2 schematically shows a typical example of the relationship between the cathode temperature (T) and the cathode emission current density with respect to the electric field intensity on the cathode surface. As shown in the figure, the space charge limiting region 201 in which the cathode emission current density rapidly changes with respect to the electric field intensity, and the change in the cathode emission current density with respect to the electric field intensity is gradual and the temperature (T). On the other hand, it is divided into a temperature limit region 202 that varies greatly (in the drawing, T ₁ > T ₂ > T ₃ ). In a conventional electron beam drawing apparatus, a thermionic gun is used in a space charge limited region.

"Proceedings of the 62nd JSAP Scientific Lecture Meeting (Lecture No. 11a-C-5)"

  In order to improve the throughput of an electron beam drawing apparatus, an electron beam drawing apparatus having an electron gun capable of emitting a plurality of electron beams from a plurality of cathodes and a plurality of columns corresponding to the plurality of electron beams is realized. For this purpose, an electron gun capable of emitting electron beams with uniform characteristics from a plurality of cathodes is required.

  For this purpose, it is necessary to select an electron gun configuration with high beam intensity and high stability. In this respect, it can be said that a thermoelectron gun having a triode structure that has been used conventionally is a desirable form. On the other hand, in order to draw simultaneously on the same sample using a plurality of cathodes, it is desirable that the distance between the cathodes is several tens mm to about 100 mm at the longest, and the plurality of cathodes are mounted in the same vacuum apparatus.

In the following, regarding a new problem when a number of electron beams equal to the number of cathodes are generated using a thermoelectron gun equipped with a plurality of cathodes, a thermoelectron gun using a single cathode is used. In contrast to the case where one electron beam is generated, the following is listed.
(1) Since the number of electron beams becomes plural, it is necessary to control the arrangement (position, distance, direction) of each electron beam.
(2) Since the electron beam is also a heat source in the drawing apparatus, the problem of heat generation in the electron optical column becomes serious due to the increase in the number of electron beams.
(3) One electron optical system is provided for each of a plurality of electron beams emitted from an electron gun, as in the drawing method proposed in the conventional example “62nd JSAP Scientific Lecture”. In the case of assignment, it is important to make the system of the entire drawing apparatus as simple as possible by making the conditions of a plurality of electron optical systems installed downstream (downstream) from the electron gun as much as possible. For this reason, the characteristics (probe current, crossover diameter, crossover position) of the electron beam emitted from the electron gun need to be made uniform.

  The present invention has been made in view of the above-described conventional problems, and has realized an electron gun capable of emitting a plurality of electron beams from a plurality of cathodes in order to improve the throughput of an electron beam lithography apparatus. It is an object of the present invention to provide an electron beam drawing technique using.

  A first aspect for achieving the object of the present invention relates to adjustment of the arrangement (position, distance, direction) of each electron beam. For this purpose, the present invention provides an electromagnetic deflector or electrostatic deflector having eight or more poles in the acceleration space to act on all the electron beams, and corrects the shift of the beam arrangement and the gain and distortion. It is characterized by.

  In addition, the present invention is characterized in that a rotating coil is installed in the acceleration space, and acts on all electron beams to correct the rotation of the beam arrangement.

  Further, the present invention is characterized in that a plurality of deflectors are installed downstream of the anode and individually act on each beam to perform high-order positional deviation correction of the beam arrangement.

  A second aspect for achieving the object of the present invention relates to a heat generation problem caused by an increase in the total current, and for this purpose, the present invention is characterized by installing a diaphragm provided with a heat dissipation mechanism downstream of the anode. To do.

  A third aspect for achieving the object of the present invention relates to a method for adjusting a thermionic gun. For this purpose, the present invention is characterized in that the cathode is used in a temperature limited region.

  In addition, the present invention is characterized in that the current reaching the sample is adjusted by controlling the cathode temperature after adjusting the crossover diameter or the crossover position by controlling the voltage applied to the Wehnelt electrode.

  In addition, the present invention is characterized in that the current discharged from the cathode is adjusted by controlling the cathode temperature after adjusting the crossover diameter or the crossover position by controlling the voltage applied to the Wehnelt electrode.

As described above in detail, according to the present invention, when a number of electron beams equal to the number of cathodes are generated using a thermionic gun equipped with a plurality of cathodes,
(1) Control the arrangement of electron beams,
(2) Resolving the heat generation problem in the electron optical column due to the increase in the number of electron beams,
(3) It is possible to suppress variations in the characteristics of each electron beam.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Example 1)
FIG. 3 is a block diagram showing an embodiment of an electron beam drawing apparatus according to the present invention. In this embodiment, as an example, electron guns each having 4 × 4 cathodes and Wehnelt electrodes are used, and 4 × 4 electron beams are emitted.

  Electrons emitted from the cathodes 301a, 301b, 301c, and 301d are subjected to the action of the electric field generated by the Wehnelt electrodes 302a, 302b, 303c, and 303d, toward the anode 304 while forming the crossovers 303a, 303b, 303c, and 303d. Accelerated. All cathodes and all Wehnelt electrodes and anodes are mounted in the same vacuum apparatus, which is called an electron gun. A region to which an acceleration electric field from the cathode to the anode is applied is called an acceleration space.

  The 4 × 4 electron beams emitted from the electron gun pass through the 4 × 4 holes 314 penetrating the anode, and then are subjected to the action of the magnetic field generated by the electromagnetic lens groups 305, 306, 307, and 308. , A reduced image of the crossover is projected onto the sample 310 mounted on the movable stage 309. Reference numeral 311 denotes a blanker group that determines whether or not each electron beam is irradiated onto the sample. Reference numeral 312 denotes a beam calibration mark. Reference numeral 313 denotes a semiconductor detector. In FIG. 3, the diaphragm for blocking part or all of the electron beam and the deflector for changing the traveling direction of the electron beam are omitted.

  FIG. 4 shows a cross-sectional view of the electron gun portion. In the figure, 401 shown by a dotted line is a cathode and a Wehnelt electrode part. Reference numeral 402 denotes an electron beam emitted from each cathode. Reference numeral 403 denotes an anode. Reference numeral 404 denotes an anode hole, and the accelerated electron beam passes through this hole. The number of cathodes, Wehnelt electrodes, and anode holes is the same, and in this embodiment, 4 × 4 each.

  The voltage applied to the cathode and Wehnelt electrode is supplied from a power source (not shown) via a high voltage cable 405. The same current and cable are used to supply current to the heater that heats the cathode. All cathodes are at the same potential (50 KV in this embodiment), and 4 × 4 anodes are also at the same potential (earth potential in this embodiment).

On the other hand, the voltages applied to each Wehnelt electrode are controlled independently of each other, and the currents flowing through the heaters are also controlled independently of each other. SF ₆ (sulfur hexafluoride) gas is sealed in the high voltage space 406 including the end portion of the high voltage cable 405 to prevent discharge. Ceramics having a low coefficient of thermal expansion were used for the chip holding part 407. This is to prevent the tip holding portion, which is several tens of degrees Celsius to several hundred degrees Celsius, from expanding due to heating of the cathode and the distance between the cathodes from changing. An electromagnetic deflector 408 and a rotating coil 409 are installed in the acceleration space. Further, an electron blocking plate 411 and an electrostatic deflector 410 are installed downstream of the anode.

  Next, in order to describe the cathode and Wehnelt electrode in detail, the cathode and Wehnelt electrode portion 401 is enlarged and displayed in FIG.

  In order to align the central axes of the cathode 501 and the Wehnelt electrode 503, the cathode 501 and the Wehnelt electrode 503 also include a heater 502 for heating the cathode and a terminal 504 for supplying voltage or current to the Wehnelt electrode 503, the cathode 501 and the heater 502. And integrated. The Wehnelt electrode 503 and the terminal 504 are insulated by, for example, an insulator 505 made of alumina.

  When 4 × 4 electron beams were emitted from the electron gun described above, the position of each electron beam sometimes deviated from the ideal position. The main causes are manufacturing errors and installation errors of cathodes, Wehnelt electrodes, and anodes. Therefore, the position of the electron beam was measured by irradiating the beam calibration mark (312 in FIG. 3) with the electron beam and detecting the reflected electrons with the semiconductor detector (313 in FIG. 3).

  FIG. 6 shows an example of the measurement result. In the figure, a lattice 601 drawn by a dotted line indicates an ideal position of each electron beam, and 602 indicates a measurement result of the position of each electron beam.

  In FIG. 6A, all 4 × 4 electron beams are shifted with respect to the ideal position.

  In FIG. 6B, the relative distance between 4 × 4 electron beams is larger than the ideal relative distance.

  In FIG. 6C, the projected electron beam is distorted with respect to the ideal lattice.

  In FIG. 6D, the relative distance of the electron beam is large in the vertical direction and the magnification is small in the horizontal direction.

  In order to correct these, an electromagnetic deflector (408 in FIG. 4) was installed in the acceleration space. Two poles of the electromagnetic deflector are taken out and shown in FIG. By winding the coil 701 in a saddle shape surrounding a region through which all electron beams pass, a magnetic field perpendicular to the traveling direction 702 of the electron beam acts on all the electron beams and deflects them. In the present embodiment, as shown in FIG. 7B, four sets of coils with a 45 ° (degree) interval and a total of eight poles were installed in the acceleration space. Note that by performing correction in the acceleration space, correction can be performed before the electron beam is completely accelerated, so that the correction amount can be kept small. In this embodiment, a saddle type electromagnetic deflector is used, but an electrostatic deflector may be used. On the other hand, the number of poles of the deflector needs to be 8 or more in order to correct the relative position of each electron beam.

  On the other hand, in FIG. 6E, the projected electron beam is rotated with respect to an ideal position. In order to correct this, a rotating coil (409 in FIG. 4) was installed in the acceleration space.

  The rotating coil used in the present example is shown in FIG. By winding the coil 703 in a plane perpendicular to the beam traveling direction 704 surrounding the region through which all the beams pass, a magnetic field in a direction parallel to the beam axis acts on all the electron beams. The image formed by the beam is rotated.

  As described above, the position of the electron beam can be brought close to the ideal position by correcting the position of the electron beam using the electromagnetic deflector and the rotating coil.

  In this embodiment, both the electromagnetic deflector and the rotating coil are installed in a vacuum. However, if an electromagnetic field can be created in a region through which electrons pass, the same effect can be obtained even if installed outside the vacuum.

  Further, when the position of the electron beam is detected, the beam calibration mark and the semiconductor detector installed on the stage are used, but further upstream with respect to the beam traveling direction, for example, the electromagnetic lens group 306 in FIG. Even if the detection means is installed between the electromagnetic lens groups 307, the same effect can be obtained. Further, the detection means is not limited to the combination of the mark and the semiconductor detector.

  Further, even when the positional deviation of the electron beam is a combination of the positional deviation of the beam shown in FIGS. 6A to 6E, it can be corrected in the same manner as in this embodiment.

(Example 2)
In the present embodiment, the remainder of the correction performed in the first embodiment is handled. In Example 1, since electromagnetic deflectors and rotating coils that act on all electron beams were used, shift, magnification, distortion, astigmatism, rotation, and their combination could be corrected. Aberrations and individual beam variations could not be corrected.

  FIG. 8 shows a measurement example of the deviation that cannot be completely removed in the first embodiment. In the figure, a lattice 801 drawn by a dotted line indicates an ideal position of each electron beam, and 802 indicates a measurement result of the position of each electron beam.

  In this embodiment, a deflector (410 in FIG. 4) acting on each electron beam is used. The position of the electron beam is an ideal position by individually correcting the position and traveling direction of the 4 × 4 electron beams using an 8-pole, two-stage electrostatic deflector 410 installed downstream of the anode. We were able to move to.

  In this embodiment, an electrostatic deflector is used, but an electromagnetic deflector may be used. Further, the number of poles of the deflector is not limited to eight. The number of stages of deflectors is not limited to two.

(Example 3)
In this embodiment, a plurality of electron beams are generated using a plurality of cathodes to solve a serious heat generation problem.

  The configuration of this embodiment will be described with reference to FIG. 9 in which a portion 412 (dotted line portion in the drawing) relating to the cathode and Wehnelt electrode portion 401, the anode 403, and the electron shielding plate 411 shown in FIG. In addition, the thing using the same code | symbol as FIG. 4 has shown the same thing.

  In the electron beam lithography system, only the portion of the electron beam accelerated from the cathode that can be projected onto the sample is capable of obtaining high and uniform brightness, and the remaining unnecessary portions are placed in the electron optical column. The sample is blocked before reaching the sample by the diaphragm or the like. Further, since the repulsive force acting between the electrons may increase the spatial and energy dispersion between the time when the electron beam is emitted from the cathode and the time when it reaches the sample, the unnecessary electron beam may be as upstream as possible. It is desirable to be blocked.

  However, when electrons are blocked, heat is generated by collision and scattered electrons are scattered, which may adversely affect nearby electron optical elements. Therefore, it is necessary to block the electron beam as upstream as possible as long as heat generation and reflected electrons do not adversely affect the electron optical element.

  Therefore, in the present invention, the size of the anode hole 404 is made larger than the electron beam when passing through the anode hole. When the diameter of the anode hole 404 is smaller than the electron beam, electrons scattered on the anode 403 may be charged up to the insulating portion in the electron gun, disturbing the electric field in the acceleration space or causing discharge. Because. On the other hand, in order to keep the electron gun portion in a high vacuum, it is advantageous that the anode hole is small. Therefore, in this embodiment, the electron beam size (half width) when passing through the anode hole is 1.2 mm. The anode hole was 2 mm in diameter. The optimum size of the anode hole varies depending on the optical structure of the electron gun and the structure as a vacuum device.

  On the other hand, when the electrostatic deflector 410 is irradiated with a large amount of electron beams, heat generation of the electrostatic deflector becomes a problem. Therefore, an electron blocking plate 411 is installed between the anode 403 and the electrostatic deflector 410. A diaphragm 902 made of, for example, molybdenum is attached to the electron blocking plate, and these two blocks the portion of the electron beam 901 except for the central portion where the luminance is high and uniform. A water-cooled tube 903 was passed through the inside of the electronic shielding plate, and for example, water was allowed to flow therethrough to suppress heat generation of the shielding plate.

Example 4
In the electron beam drawing apparatus according to the present embodiment, a plurality of electron guns having a plurality of cathodes and the same number of Wehnelt electrodes (4 × 4 in FIG. 3) as shown in FIG. (4 × 4 in FIG. 3) is emitted, and an electron optical system such as a lens and a deflector is assigned to each electron beam downstream from the electron gun. In such an electron beam drawing apparatus, in order to simplify the system of the entire drawing apparatus, it is desirable to make the conditions of the electron optical system downstream (downstream) from the electron gun the same. For this purpose, the characteristics of a plurality of electron beams emitted from the electron gun must be uniform.

  Here, the characteristics of the electron beams to be aligned are the probe current, the crossover diameter, and the crossover position. The probe current is the current of an electron beam that reaches the sample among the electron beams emitted from the cathode. In the present embodiment, measurement is performed using a Faraday cup (not shown) mounted on a stage (309 in FIG. 3).

  The crossover is an image formed when electron beams emitted in the same direction from different positions in the same cathode intersect as indicated by 106 in FIG. The size (diameter) of the crossover is called the crossover diameter, and the position where the crossover is formed (relative to the beam traveling direction) is called the crossover position. In this embodiment, the size of the reduced image of the crossover projected on the stage is measured using a knife edge (not shown) installed on the stage (309 in FIG. 3). The crossover position can be obtained from the focal length of the lens when the reduced image of the crossover is formed on the sample.

  In order to obtain an electron beam with the same probe current, crossover diameter, and crossover position, it is necessary to align the cathode and Wehnelt electrode and anode hole shape and relative position. It is not always easy to obtain an electron beam with uniform characteristics due to the installation error, the resistance error of the heater for heating the cathode, and the non-uniformity of the surface state of the cathode.

  In this embodiment, the cathode current is applied by the voltage applied to the Wehnelt electrode so that the probe current, the crossover diameter, and the crossover position of the electron beams emitted from all the cathodes are between preset upper and lower limits. The intensity of the electric field on the surface is adjusted, and the cathode temperature is adjusted by the current passed through the filament.

Here, the one of the 4 × 4 electron beams as an example, illustrates the behavior for Wehnelt voltage and the filament current I _F of the characteristics of the beam.

First, the behavior of the probe current is shown in FIG. The probe current is closely related to the cathode emission current density. Therefore, in the space charge limited region where the cathode emission current density changes rapidly with respect to the Wehnelt voltage, the probe current also changes sensitively. Further, in this area, since the cathode emission current density does not depend on the cathode temperature, probe current is also not dependent on the filament current I _F. On the other hand, cathode emission current density gently changes with respect to the strength of the electric field of the cathode surface, in the temperature limited region varies greatly with respect to the cathode temperature, the probe current changes greatly with respect to the filament current I _F (In the figure, I ₁ > I ₂ > I ₃ ).

  As an example of the upper limit value and the lower limit value of the probe current, as shown in FIG. 10A, the upper limit value 1001 is 1.6 μA, and the lower limit value 1002 is 1.4 μA. The lower limit value was obtained from the throughput that the drawing apparatus should achieve. The reason why the upper limit value is set is that if the cathode temperature is set too high, the deterioration of the cathode may be accelerated.

  Next, the behavior of the crossover diameter is shown in FIG. The crossover diameter is closely related to the trajectory of electrons after being emitted from the cathode, rather than the cathode emission current density. Therefore, there is no dependence on the cathode temperature, and the crossover diameter varies due to the change in electric field distribution near the cathode accompanying the change in Wehnelt voltage.

  For the crossover diameter, an upper limit value and a lower limit value were determined from the required drawing accuracy. As an example, as shown in FIG. 10B, the upper limit value 1003 of the crossover diameter was 11 μm, and the lower limit value 1004 was 9 μm. In this embodiment, since the reduction ratio of the optical system is 1/500, the reduced image of the crossover on the stage needs to be between 22 nm and 18 nm.

  FIG. 10C shows the behavior of the crossover position. Similarly to the crossover diameter, the crossover position has very little dependence on the cathode temperature, and fluctuates when the Wehnelt voltage is changed.

  For the crossover position, an upper limit value and a lower limit value were determined from the focal length of the lens installed downstream. As an example, as shown in FIG. 10C, the upper limit value 1006 is set to 10 mm and the lower limit value 1007 is set to 0 mm with the beam traveling direction from the cathode tip as a positive direction.

  In a conventional electron beam drawing apparatus, it is common to use a cathode in a space charge limited region and control the probe current only by adjusting the Wehnelt voltage. In the space charge limited region, the probe current does not depend on the cathode temperature, and the dependency of the crossover diameter and the crossover position on the cathode temperature is extremely small. Therefore, there is only one parameter for adjusting the characteristics of the electron beam. In order to handle a plurality of electron beams and make their characteristics uniform, it is desirable to use a parameter called cathode temperature for adjustment. Therefore, in this embodiment, the cathode is used in the temperature limited region.

  In this temperature limited region, the probe current changes slowly with respect to the Wehnelt voltage, and the sensitivity to the cathode temperature is high. On the other hand, the crossover diameter and the crossover position depend on the voltage applied to each electrode regardless of the cathode temperature. It is determined. Focusing on this point, in order to perform the adjustment efficiently, first, the Wehnelt voltage is set so that the crossover diameter and the crossover position become the desired values, and then the probe current becomes the desired value. What is necessary is just to set a heater current.

  By performing this independently for all the electron beams, the cathode emission current density, the crossover diameter, and the crossover position of all the electron beams can be set to desired values.

  On the other hand, from the viewpoint of throughput, it is desirable to obtain a higher cathode emission current density. As is apparent from the relationship between the cathode temperature and the cathode field current density at the cathode surface shown in FIG. 2, in order to obtain a high cathode emission current density, the cathode temperature is increased or the electric field applied to the cathode is increased. Should be strengthened. However, when the cathode temperature is increased, the degree of vacuum in the electron gun may be lowered and the cathode may be deteriorated. In other words, it is a good idea to obtain a high cathode emission current density at the lowest possible cathode temperature. For this purpose, the electric field strength on the cathode surface is increased as compared with the prior art, and it is used in a temperature limited region or a region close to the temperature limited region. It is desirable. That is, it can be said that the use of an electron gun in the temperature limited region is desirable from the viewpoint of throughput.

  In the above description, the Wehnelt voltage is adjusted so that both the crossover diameter and the crossover position are between the set upper limit value and lower limit value. However, in this embodiment, (b) in FIG. ) And (c), it was found that the appropriate range 1005 of the electric field strength with respect to the crossover position completely includes the proper range 1008 of the electric field strength with respect to the crossover diameter. Therefore, it was sufficient to adjust the Wehnelt voltage so as to be between the upper limit value and the lower limit value set based on only the crossover diameter.

  Depending on the structure of the electron gun and the design of the downstream electron optical system, contrary to this embodiment, the appropriate range of the electric field strength with respect to the crossover diameter completely includes the appropriate range of the electric field strength with respect to the crossover position. In some cases. In that case, the Wehnelt voltage may be adjusted based on the crossover position. The same effect can be obtained by adjusting the Wehnelt voltage based on both the crossover diameter and the crossover position.

  Next, the configuration of this embodiment will be described in detail using the flowchart shown in FIG.

  In step 1, reference current values are set for all heaters that heat a plurality of cathodes, and reference voltage values are set for all Wehnelt electrodes.

  In step 2, the crossover diameter is individually measured for all electron beams emitted from the plurality of cathodes.

  In Step 3, based on the measurement in Step 2, it is individually determined whether or not the crossover diameter is between the upper limit value and the lower limit value for all the electron beams.

  If it is determined in step 3 that there is one of all the electron beams whose crossover diameter is not between the upper limit value and the lower limit value, the Wehnelt voltage corresponding to the corresponding electron beam is set. Reset and return to step 2. Steps 2 to 3 were repeated until it was determined in step 3 that the crossover diameters of all electron beams were between the upper limit value and the lower limit value. If it is determined in step 3 that the crossover diameters of all electron beams are between the upper limit value and the lower limit value, the process proceeds to step 4.

  In step 4, the probe current of each electron beam is measured.

  In step 5, it is determined whether or not the probe current measured in step 4 is between the upper limit value and the lower limit value.

  If it is determined in step 5 that any one of all the electron beams does not have the probe current between the upper limit value and the lower limit value, the current to be supplied to the heater corresponding to the corresponding electron beam is determined. Reset and go back to step 4. Steps 4 to 5 are repeated until it is determined in step 5 that the probe currents of all electron beams satisfy the lower limit value.

  If it is determined in step 5 that the probe currents of all the electron beams satisfy the lower limit value, the process proceeds to step 6.

  In step 6, the electromagnetic deflector and the rotating coil are adjusted in the same manner as in the first embodiment.

  In step 7, each electrostatic deflector is adjusted in the same manner as in the second embodiment.

  Beam calibration according to the above procedure was performed at the time of replacing the cathode, and the calibration was performed once a week with regular calibration. As a result, good drawing results could be maintained without reducing the throughput.

In this embodiment, a thermoelectron gun having a triode structure composed of a cathode, an anode, and a Wehnelt electrode is used. For example, two or more electrodes are provided between a cathode and an anode for one beam. Even if one is used, the same effect as the present embodiment can be obtained if the same cathode emission current density characteristic as that of the triode structure can be obtained.
In this example, a heater was used to heat the cathode, and the cathode temperature was controlled by adjusting the current applied to the cathode. However, when heating the cathode using a heater of a different form, For example, the voltage applied to the heater may be adjusted.

  Further, in this embodiment, in order to measure the crossover diameter, the electrons reflected on the knife edge placed on the stage are detected by the semiconductor detector, but the measuring means is not limited to this combination. For example, a cross wire or a beam calibration mark may be used instead of the knife edge, or a photomultiplier tube may be used instead of the semiconductor detector. Also, a combination of a fine diaphragm and a semiconductor detector for measuring the current passing through the diaphragm may be used.

  In this example, the probe currents of a plurality of electron beams were measured, and the cathode temperature was adjusted so as to obtain a desired value. However, the relationship between the probe current and the current emitted from the cathode was good. If known, the current emitted from each cathode may be measured and the cathode temperature adjusted to bring them to the desired value.

  The present invention includes the following configuration examples.

  (1) In an electron gun having a plurality of cathodes and means for generating an electric field for accelerating a plurality of electron beams generated from the plurality of cathodes, the plurality of electron beams are included in an electric field for accelerating the plurality of electron beams. An electron gun having a deflector composed of eight or more coils or eight or more electrodes that act on all of the above.

  (2) In an electron gun having a plurality of cathodes and means for generating an electric field for accelerating a plurality of electron beams generated from the plurality of cathodes, the plurality of electron beams are included in the electric field for accelerating the plurality of electron beams. An electron gun having a rotating coil that acts on

  (3) An electron beam drawing apparatus comprising the electron gun according to any one of the items (1) to (2).

  (4) Electron beam drawing provided with an electron gun having a plurality of cathodes and an anode that has a positive potential with respect to the plurality of cathodes and generates an electric field that accelerates a plurality of electron beams generated from the plurality of cathodes. An apparatus according to claim 1, further comprising a plurality of deflectors that individually act on the plurality of electron beams downstream of the anode in the traveling direction of the electron beam.

  (5) In an electron beam lithography apparatus comprising a plurality of cathodes and an electron gun having a positive potential with respect to the plurality of cathodes and generating an electric field for accelerating a plurality of electron beams generated from the cathodes An electron beam drawing apparatus comprising: means for blocking electrons having a heat dissipation mechanism downstream of the anode with respect to the traveling direction of the electron beam.

  (6) A plurality of cathodes, temperatures of the plurality of cathodes are individually adjusted, the same number of heaters as the cathodes, and an electric field intensity in the vicinity of the surfaces of the plurality of cathodes are individually adjusted, the same number as the cathodes An electron gun having a positive electrode potential with respect to the plurality of cathodes and generating an electric field for accelerating a plurality of electron beams generated from the plurality of cathodes; An electron beam drawing method, wherein a movable stage capable of mounting a target object is used to operate at least a part of each cathode in a temperature limited region.

(7) In item (6) above,
(A) setting a voltage to be applied to the plurality of Wehnelt electrodes and a parameter for determining a temperature of the plurality of heaters to a reference value;
(B) a step of individually measuring the magnitude of crossover for all electron beams emitted from the plurality of cathodes;
(C) Based on the measurement in (b), determining whether or not the magnitude of the crossover is a desired value individually for all electron beams;
(D) In the step (c), when there is one or more electron beams that are determined to have no desired crossover magnitude, the Wehnelt voltage corresponding to the corresponding electron beam is reset. And returning to the step (b),
(E) In the step (c), when it is determined that the magnitude of the crossover of all the electron beams is a desired value, all of the plurality of cathodes Measuring the current individually,
(F) determining whether the current of the emitted electron beam has a desired value individually for all the cathodes based on the measurement of (e);
(G) In the step (f), if there is one or more cathodes for which the current of the emitted electron beam is determined not to have a desired value, the temperature of the heater for heating the corresponding cathode is determined. Resetting the parameters to be performed and returning to the step (e),
An electron beam drawing method comprising:

(8) In item (6) above,
(A) setting a voltage to be applied to the plurality of Wehnelt electrodes and a parameter for determining a temperature of the plurality of heaters to a reference value;
(B) a step of individually measuring the magnitude of crossover for all electron beams emitted from the plurality of cathodes;
(C) Based on the measurement in (b), determining whether or not the magnitude of the crossover is a desired value individually for all electron beams;
(D) In the step (c), when there is one or more electron beams that are determined to have no desired crossover magnitude, the Wehnelt voltage corresponding to the corresponding electron beam is reset. And returning to the step (b),
(E) In the step (c), when it is determined that the magnitude of crossover of all electron beams is a desired value, for all electron beams emitted from the plurality of cathodes, Individually measuring the current that has reached the stage;
(F) determining whether or not the current reached on the stage has a desired value individually for all electron beams based on the measurement in (e);
(G) In the step (f), when there is one or more electron beams determined that the current reached on the stage is not a desired value, the cathode corresponding to the corresponding electron beam is heated. Resetting the parameter for determining the temperature of the heater and returning to the step (e),
An electron beam drawing method comprising:

Schematic diagram of a general three-electrode type thermoelectron gun. The figure explaining the relationship of the cathode emission current density with respect to the cathode temperature and the electric field strength on the cathode surface. The figure explaining the structure of one Example of the electron beam drawing apparatus by this invention. Sectional drawing of the electron gun part in FIG. The enlarged view of the cathode and Wehnelt electrode part in FIG. The figure which shows an example of the measurement result of the position of an electron beam. The figure which shows the specific example of an electromagnetic deflector (a) in FIG. 3, (b), and a rotating coil (c). The figure which shows the other example of the measurement result of the position of an electron beam. The enlarged view of the part concerning a cathode and a Wehnelt electrode in FIG. The figure explaining the relationship between the probe current, the crossover diameter, and the crossover position with respect to the cathode temperature and the electric field strength on the cathode surface. The flowchart explaining the adjustment method of the electron gun in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Cathode, 102 ... Heater, 103 ... Wehnelt electrode, 104 ... Anode, 105 ... Crossover, 201 ... Space charge limited area, 202 ... Temperature limited area,
301a, 301b, 301c, 301d ... cathode, 302a, 302b, 302c, 302d ... Wehnelt electrode, 303a, 303b, 303c, 303d ... crossover, 304 ... anode, 305 ... electromagnetic lens group, 306 ... electromagnetic lens group, 307 ... Electromagnetic lens group, 308 ... Electromagnetic lens group, 309 ... Stage, 310-Sample, 311 ... Blanker group, 312 ... Beam calibration mark, 313 ... Semiconductor detector, 401 ... Cathode and Wehnelt electrode section, 402 ... Electron beam, 403 ... Anode, 404 ... Anode hole, 405 ... High voltage cable, 406 ... High voltage space, 407 ... Chip holding part, 408 ... Electromagnetic deflector, 409 ... Rotary coil, 410 ... Electrostatic deflector, 411 ... Electronic blocking plate, 412 ... Cathode, Wehnelt electrode and anode and electron blocking plate, 501 ... Cathode, 502 ... He -503 ... Wehnelt electrode, 504 ... Terminal, 505 ... Insulator, 601 ... Ideal position of each electron beam, 602 ... Measurement result of position of each electron beam, 701 ... Coil, 702 ... Direction of travel of electron beam, 703 ... Coil, 704 ... Electron beam traveling direction, 801 ... Ideal position of each electron beam, 802 ... Measurement result of position of each electron beam, 901 ... Electron beam, 902 ... Aperture, 903 ... Water-cooled tube, 1001 ... Upper limit value of probe current, 1002 ... Lower limit value of probe current, 1003 ... Upper limit value of crossover diameter, 1004 ... Lower limit value of crossover diameter, 1005 ... Appropriate range of electric field strength with respect to crossover position, 1006 ... Crossover Upper limit value of position, 1007 ... Lower limit value of crossover position, 1008 ... Electric field strength with respect to crossover diameter The proper range.

Claims (2)

  A plurality of cathodes, a plurality of Wehnelt electrodes for individually adjusting the electric field strength in the vicinity of the surfaces of the plurality of cathodes, and a plurality of cathodes having a positive potential with respect to the plurality of cathodes and generated from the plurality of cathodes. A step of drawing a desired pattern on a sample using an electron gun including an anode for generating an electric field for accelerating an electron beam, and controlling the voltage applied to the Wehnelt electrode to control the voltage from the plurality of cathodes For all of the plurality of emitted electron beams, the crossover diameter or the crossover position is individually adjusted, and then the temperature of the plurality of cathodes is controlled to control the current emitted from the plurality of cathodes or the sample. An electron beam drawing method characterized by adjusting an electric current reaching the top.   The electron gun is disposed in an electric field for accelerating the plurality of electron beams so as to surround a region through which the plurality of electron beams pass, and has a deflector and a rotating coil that act on all of the plurality of electron beams. 8. The electron beam writing method according to claim 7, wherein the arrangement of the plurality of electron beams is corrected using the deflector and the rotating coil.

Images