JP4473798B2 - Drawing method of electron beam drawing apparatus - Google Patents

Description

  The present invention relates to a drawing method of an electron beam drawing apparatus.

  An electron beam drawing apparatus is widely used for drawing a fine pattern on a drawing target such as a mask blank for forming a photomask.

  In the electron beam drawing apparatus, an objective lens is provided above a mounting table (movable stage) on which a drawing target is placed, and an electron beam image is formed on the surface of the drawing target by the objective lens. As the objective lens, an electromagnetic lens using a static magnetic field is usually used. Therefore, if a conductive region is provided on the surface of the mounting table, an eddy current is induced in the conductive region by the magnetic field of the objective lens when the mounting table moves. The trajectory of the electron beam is bent by the magnetic field generated by this eddy current, and as a result, there arises a problem that the irradiation position of the electron beam deviates from the desired position (target position). Such a problem becomes a big problem as a drawing pattern is miniaturized.

  In order to solve the above-described problem, Patent Document 1 discloses a method of correcting an irradiation position of an electron beam by controlling an electric field or a magnetic field generated by an objective deflector. However, in this method, it is necessary to perform control in real time according to the position and moving speed of the mounting table, and there is a problem that the control system becomes complicated.

  Another possible method is to suppress the effect of eddy currents by sufficiently lowering the moving speed of the mounting table. However, such a method has a problem that the drawing time becomes very long and the processing efficiency is lowered.

As described above, in the electron beam drawing apparatus, there is a problem that the irradiation position of the electron beam deviates from a desired position due to the eddy current induced by the magnetic field of the objective lens, and an effective solution to such a problem. Is desired. However, the conventional solution has a problem that the control for correcting the beam irradiation position becomes complicated and a problem that the drawing time is long and the processing efficiency is lowered. Therefore, conventionally, the problem that the irradiation position of the electron beam deviates from the desired position cannot be solved by an effective method.
Japanese Examined Patent Publication No. 6-28232

  An object of the present invention is to provide a drawing method of an electron beam drawing apparatus that can effectively prevent the problem that the irradiation position of the electron beam is shifted from a desired position.

The drawing method of the electron beam drawing apparatus according to one aspect of the present invention includes a step of defining a maximum moving speed of the mounting table according to an electron beam irradiation position on a mounting table on which a drawing target is mounted, and the electron beam while moving the table at a rate not exceeding the maximum moving speed defined in accordance with the irradiation position, comprising the steps of performing drawing by an electron beam, the drawing object which is placed on the mounting table, before A conductive region is provided on a part of the surface of the mounting table, and the maximum moving speed is defined so that the deflection amount of the electron beam based on the eddy current induced in the mounting table is smaller than the allowable deflection amount. Is done .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to prevent effectively the problem that the irradiation position of an electron beam shifts | deviates from a desired position.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing a configuration example of an electron beam drawing apparatus according to an embodiment of the present invention.

  The basic configuration of this electron beam drawing apparatus is the same as that of a normal electron beam drawing apparatus, and is an electron source 11, a condenser lens 12, a blanking electrode 13, a first shaping aperture 14, a shaping deflector 15, and a projection lens 16. , A second shaping aperture 17, a blanking aperture 18, a reduction lens 19, an objective lens 20, an objective deflector 21, and a mounting table (movable stage) 30 on which a drawing target is placed. In the present embodiment, a mask blank for forming a photomask is used as a drawing target. The mounting table 30 is connected to a control unit 40 for controlling the movement of the mounting table.

  FIG. 2 is a plan view schematically showing the configuration of the mounting table 30. The mounting table 30 includes a conductive portion (conductive region) 31 provided in a frame shape along the outer periphery of the mounting table 30 and a non-conductive portion (non-conductive region) inside the conductive portion 31 in the same manner as a normal mounting table. 32. The conductive portion 31 is provided to allow the electron beam charge to escape from the surface of the mounting table 30. The non-conductive part 32 is formed of an insulator or is in a state where a hole is opened.

  FIG. 3 is a plan view showing a state in which a drawing target (mask blanks in this embodiment) 50 is placed on the mounting table 30. The drawing target 50 is disposed on the non-conductive portion 32 of the mounting table 30. Accordingly, the drawing target 50 is surrounded by the conductive portion 31 of the mounting table 30.

  As described in the section “Background Art”, the objective lens 20 is an electromagnetic lens using a static magnetic field. Therefore, as shown in FIGS. 2 and 3, if the conductive part 31 is provided on the surface of the mounting table 30, an eddy current is induced in the conductive part 31. That is, as shown in FIG. 4, an eddy current is induced in the conductive portion 31 by the magnetic field of the objective lens 20 as the mounting table 30 moves. Due to the magnetic field generated by this eddy current, the trajectory of the electron beam is bent in a direction perpendicular to the moving direction of the mounting table 30 (the electron beam is deflected). By deflecting the electron beam in this way, the irradiation position of the electron beam is shifted from the desired position (target position).

  The following simulation was performed on the deflection of the electron beam caused by the eddy current described above. FIG. 5 is a diagram showing a planar configuration of the mounting table used in the simulation. The size of the mounting area of the mounting table (the mounting area for drawing) is 150 mm × 150 mm, the conductive area (conductive part) of the mounting table is set on the upper side and the right side of the mounting area, and the size of each conductive area is 150 mm. X30 mm. The magnetic field distribution of the objective lens assumed a Gaussian distribution. Further, the mounting table is assumed to be moving in the x direction (−x direction in FIG. 5) at a speed of 40 mm / sec. Therefore, the electron beam is deflected in the y direction. The origin of the xy coordinates (x = 0, y = 0) is the upper right corner of the placement area.

  FIG. 6 shows the amount of deflection of the electron beam (the amount of deflection on the surface of the mounting region) obtained by simulation. The left column in FIG. 6 shows the electron beam irradiation position (x position or y position). That is, the beam irradiation position on the A line or the beam irradiation position on the B line in FIG. The center column of FIG. 6 shows the deflection amount dy in the y direction on the A line of the electron beam. The right column of FIG. 6 shows the deflection amount dy in the y direction on the B line of the electron beam.

  As shown in FIG. 6, for example, at x = 0 mm, that is, at the boundary between the placement region and the conductive region, the deflection amount dy is 58.3 nm, and the deflection amount dy is a large value. Even at the position of x = −5 mm, the deflection amount dy is a large value of 30.1 nm. The deflection amount dy decreases as the beam irradiation position moves away from the x-coordinate origin (x = 0), and at the position where x = −20 mm, the deflection amount dy is 1 nm or less. Similarly, when y = 0, the deflection amount dy is a large value of 16.8 nm. The deflection amount dy decreases as the beam irradiation position moves away from the y coordinate origin (y = 0), and y = −15 mm. At the position, the deflection amount dy is 1 nm or less. Therefore, on both the A line and the B line, the deflection amount dy is large in the vicinity of the boundary between the placement region and the conductive region, and the deflection amount dy is greatly reduced when the distance from the boundary exceeds a certain extent.

  As can be seen from the above, the deflection amount of the electron beam changes according to the irradiation position of the electron beam, and the deflection amount is large because the influence of the eddy current is large in the region close to the conductive region. Since the influence of eddy current is small in the region, the deflection amount is small. On the other hand, the eddy current depends on the moving speed of the mounting table, and the higher the moving speed of the mounting table, the larger the value of the eddy current, and the larger the deflection amount of the electron beam. Therefore, when the electron beam irradiation position is close to the conductive region, the movement speed of the mounting table is slowed down, and when the electron beam irradiation position is far from the conductive region, control is performed to increase the movement speed of the mounting table. For example, the amount of deflection of the electron beam can be set to a certain value or less regardless of the irradiation position of the electron beam, and an increase in writing time can be suppressed.

  Therefore, in this embodiment, the maximum movement speed of the mounting table is defined in advance according to the position on the mounting table corresponding to the electron beam irradiation position of the drawing target mounted on the mounting table, and the mounting table is mounted on the mounting table. When performing drawing by irradiating the drawn object with an electron beam, the moving speed of the mounting table is limited so as not to exceed the prescribed maximum moving speed.

  FIG. 7 is a flowchart showing an operation for performing the control as described above, and FIG. 8 is a block diagram showing a configuration of a control unit (corresponding to the control unit 40 of FIG. 1). Hereinafter, description will be given with reference to these flowcharts and block diagrams.

  First, necessary data is acquired in order to determine the maximum moving speed of the mounting table 30 according to the electron beam irradiation position (S1). Data acquisition may be performed by simulation, but preliminary measurement may be performed using an actually used electron beam drawing apparatus, and data may be acquired from the measurement result. For example, there is a method in which test drawing is performed at a plurality of movement speeds, the distribution of the beam deflection amount in the drawing area is obtained for each movement speed, and the measurement result thus obtained is reflected in the setting of the maximum movement speed. Conceivable.

  Next, based on the acquired data, the maximum moving speed of the mounting table 30 corresponding to the irradiation position of the electron beam is defined (S2). The allowable value (allowable deflection amount) of the deflection amount of the electron beam (deviation amount from the desired irradiation position (target position) of the electron beam) is determined by the dimensional accuracy of the device to be manufactured. Also, the maximum moving speed is defined so that the beam deflection amount becomes small. For example, as shown in FIG. 9, the drawing area is divided into a plurality of sub areas A1 to A3, and the maximum moving speed of the mounting table 30 is defined for each sub area. In the example of FIG. 9, the region A3 is closest to the conductive region 31 of the mounting table 30, and the region A1 is farthest from the conductive region 31 (see FIGS. 2 and 3). Therefore, if the maximum movement speeds related to the sub-regions A1, A2, and A3 are M1, M2, and M3, respectively, “M1> M2> M3”. That is, the maximum moving speed is defined so as to decrease as the electron beam irradiation position is closer to the conductive region 31. FIG. 9 is an example of the division method, and the division method and the number of divisions can be changed as appropriate. Information on the maximum moving speed of the mounting table obtained in this way is stored in the maximum moving speed defining unit 41 shown in FIG.

  After the maximum moving speed of the mounting table 30 corresponding to the irradiation position of the electron beam is defined as described above, a drawing target (in this embodiment, a mask blank with resist is formed on the mounting table 30 as shown in FIG. ) 50 is placed (S3).

  Next, drawing is performed by irradiating the drawing target 50 placed on the mounting table 30 with the electron beam while moving the mounting table 30 at a speed that does not exceed the maximum moving speed defined according to the electron beam irradiation position. (S4). That is, drawing is performed on the sub-region A1 shown in FIG. 9 while moving the mounting table 30 at a speed that does not exceed the maximum movement speed M1. Similarly, drawing is performed while moving the mounting table 30 at a speed that does not exceed the maximum moving speed M2 for the sub-region A2, and mounting table is performed at a speed that does not exceed the maximum moving speed M3 for the sub-region A3. Drawing is performed while moving 30. In this example, the drawing position information is grasped by the drawing position information acquisition unit 42 shown in FIG. Therefore, the moving speed control unit 43 controls the moving speed of the mounting table 30 based on the drawing position information and the maximum moving speed information of each sub-area stored in the maximum moving speed defining unit 41. Note that the maximum moving speed defines the maximum speed during drawing, that is, during electron beam irradiation. If the mounting table 30 is simply moved without drawing to move the drawing position, the maximum moving speed is maximum. The mounting table 30 may be moved at a speed higher than the moving speed. Further, if the speed is lower than the maximum moving speed, the mounting table 30 may be moved while changing the moving speed according to the drawing pattern or the like.

  As described above, in this embodiment, the maximum moving speed of the mounting table 30 is defined according to the position on the mounting table corresponding to the electron beam irradiation position. Therefore, the maximum moving speed is set relatively small for a region close to the conductive region 31 where the influence of eddy current is large, and the maximum moving speed is set relative to a region far from the conductive region 31 where the influence of eddy current is small. Can be set large. Therefore, by performing drawing while moving the mounting table at a speed that does not exceed the maximum moving speed set in such a manner, the deflection amount of the electron beam can be made less than the allowable value regardless of the irradiation position of the electron beam. In addition, an increase in drawing time can be suppressed. Therefore, according to the present embodiment, it is possible to effectively solve the problem that the irradiation position of the electron beam deviates from the desired position.

  In the embodiment described above, the shape of the conductive portion 31 of the mounting table 30 is not particularly mentioned. However, as shown in FIG. 10, the conductive portion 31 is provided with a slit 33, and the conductive portion 31 is formed into a plurality of portions. You may make it divide | segment. By dividing the conductive portion 31 into a plurality of portions in this manner, the eddy current is divided into a plurality of small eddies, so that the influence of the eddy current can be reduced. In particular, the conductive portion 31 is divided in a direction perpendicular to the moving direction of the mounting table 32 with respect to the conductive portion 31 extending in a direction perpendicular to the moving direction of the mounting table 32 (the moving direction of the mounting table 32 and By making the extension direction of the slit 33 parallel, it is possible to further reduce the influence of the eddy current.

  In order to demonstrate the effect of the above-described division, a simulation was performed. The basic conditions for the simulation are the same as the simulation conditions described with reference to FIGS. The influence of the eddy current at the position of x = 0 was calculated for the case where the conductive region on the right side of the placement region shown in FIG. As a result, the influence of the eddy current was reduced by 24% in the case of three divisions and 1/2 or less in the case of five divisions compared with the case where no division was performed.

  Moreover, as shown in FIG. 11 (cross-sectional view along the line AA in FIG. 10), the slit 33 is formed in an oblique direction with respect to the surface of the mounting table (the surface of the conductive portion 31). desirable. When the slits are formed obliquely in this way, the ends of the adjacent divided portions overlap each other when viewed from a direction perpendicular to the surface of the mounting table, that is, when viewed from the electron beam irradiation direction. become. For example, when an insulating part is provided below the conductive part 31, if a vertical slit is formed, the electron beam directly reaches the insulating part. Will be accumulated. By forming the slits obliquely as shown in FIG. 11, the electron beam can be effectively shielded, and the charge of the electron beam can be prevented from accumulating in the insulating portion.

  In the above-described embodiment, the mask blank for forming a photomask has been described as an example of the drawing target. However, the method of the above-described embodiment can be applied to a case where a circuit pattern or a device pattern is directly drawn on a semiconductor substrate. It is possible to apply the same method.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent elements. For example, even if several constituent requirements are deleted from the disclosed constituent requirements, the invention can be extracted as an invention as long as a predetermined effect can be obtained.

It is the figure which showed typically the structural example of the electron beam drawing apparatus which concerns on embodiment of this invention. FIG. 4 is a plan view schematically showing the configuration of the mounting table according to the embodiment of the present invention. FIG. 4 is a plan view showing a state in which a drawing target is placed on a placement table according to the embodiment of the present invention. It is explanatory drawing which showed the eddy current induced in a conductive area according to the embodiment of the present invention. FIG. 6 is a diagram illustrating a configuration used for simulation according to the embodiment of the present invention. It is a figure showing a result of simulation concerning an embodiment of the present invention. It is the flowchart which showed the control operation of the electron beam drawing device which relates to the execution form of this invention. It is the block diagram which showed the structure of the control part of the electron beam drawing apparatus which concerns on embodiment of this invention. FIG. 6 is a diagram illustrating a sub-region of a drawing region according to the embodiment of the present invention. FIG. 6 is a plan view showing a modification example of the conductive portion of the mounting table according to the embodiment of the present invention. It is sectional drawing which concerns on embodiment of this invention and showed the example of a change of the electroconductive part of a mounting base.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Electron source 12 ... Condenser lens 13 ... Blanking electrode 14 ... 1st shaping | molding aperture 15 ... Molding deflector 16 ... Projection lens 17 ... 2nd shaping | molding aperture 18 ... Blanking aperture 19 ... Reduction lens 20 ... Objective lens 21 ... Objective Deflector 30 ... Place 31 ... Conductive area 32 ... Non-conductive area 33 ... Slit 40 ... Control part 41 ... Maximum moving speed defining part 42 ... Drawing position information acquiring part 43 ... Moving speed control part 50 ... Drawing target

Claims (4)

Defining the maximum moving speed of the mounting table according to the electron beam irradiation position on the mounting table on which the drawing target is mounted ;
A step of drawing is performed by irradiating said electron beam while moving the table at a rate not exceeding the maximum moving speed defined in accordance with the irradiation position, the electron beam drawing object placed on the mounting table,
Equipped with a,
A conductive region is provided on a part of the surface of the mounting table,
The drawing method of the electron beam drawing apparatus, wherein the maximum moving speed is defined such that the deflection amount of the electron beam based on the eddy current induced in the mounting table is smaller than the allowable deflection amount . The drawing method of the electron beam drawing apparatus according to claim 1 , wherein the maximum moving speed is defined such that the closer the electron beam irradiation position is to the conductive region, the smaller the moving speed. The drawing method of the electron beam drawing apparatus according to claim 2 , wherein the conductive region is provided in a frame shape along the outer periphery of the mounting table. The drawing method of the electron beam drawing apparatus according to claim 2 , wherein the conductive region is divided into a plurality of portions.

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