JP2006351994A - Charged particle beam lithographic apparatus and method for beam correction thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of beam correction where a difference is not generated between line widths in (x) direction and (y) direction, regardless of deflection coma aberrations and deflection chromatic aberrations, and to provide a charged particle beam lithographic apparatus. <P>SOLUTION: The charged particle beam lithographic device carries out dynamic focal correction and dynamic astigmatic correction regarding a beam. The device is provided with a beam correction means for carrying out the dynamic focal correction (110) and the dynamic astigmatic correction (120), by adding (323, 323) a focal deviation amount (312) and astigmatic deviation amount (322) for eliminating the difference between the (x) direction and the (y) direction of beam blurring, caused by the deflection coma aberration and the deflection chromatic aberration, respectively, to a correction value (321) for the dynamic focal correction and a correction value (321) for the dynamic astigmatic correction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a beam correction method and a charged particle beam drawing apparatus for a charged particle beam drawing apparatus, and more particularly, to a method for performing dynamic focus correction and dynamic astigmatism correction for a beam of the charged particle beam drawing apparatus, and to dynamic for the beam. The present invention relates to a charged particle beam drawing apparatus that performs focus correction and dynamic astigmatism correction.

In a charged particle beam lithography system that draws a predetermined pattern on a semiconductor wafer or mask material using an electron beam or ion beam, in order to correct beam blur due to deflection field curvature aberration and deflection astigmatism due to beam deflection, Focus correction and dynamic astigmatism correction are performed (see, for example, Patent Document 1). Since these aberrations depend on the deflection position of the beam, a correction value for dynamic focus correction and a correction value for dynamic astigmatism correction are prepared for each deflection position and are used corresponding to the deflection position at the time of drawing.
JP 2003-347188 A (page 2-3, FIG. 1-3)

  Deflection aberrations further include deflection coma and chromatic aberration, which depend on the deflection position, but cannot be corrected by dynamic focus correction or dynamic astigmatism correction, so beam blur based on these aberrations cannot be removed. . Further, since the beam blur amount due to the deflection aberration and the deflection coma aberration is different in the x direction and the y direction, a difference is generated in the drawn line width between the x direction and the y direction.

  Accordingly, an object of the present invention is to realize a beam correction method and a charged particle beam drawing apparatus that do not cause a difference in line width between the x direction and the y direction regardless of deflection coma and chromatic aberration.

  The invention according to claim 1 for solving the above-described problem is related to the x direction of beam blur due to deflection coma and deflection chromatic aberration when performing dynamic focus correction and dynamic astigmatism correction on a beam of a charged particle beam drawing apparatus. The focus shift amount and the astigmatism shift amount for eliminating the difference between the y-direction and the y-direction are added to the correction value for dynamic focus correction and the correction value for dynamic astigmatism correction, respectively. A beam correction method for a charged particle beam drawing apparatus, characterized in that point correction is performed.

  The invention according to claim 2 for solving the above-mentioned problem is a charged particle beam drawing apparatus for performing dynamic focus correction and dynamic astigmatism correction on a beam, and x of beam blur caused by deflection coma aberration and deflection chromatic aberration. Dynamic focus correction and dynamic by adding the focus shift amount and astigmatism shift amount for eliminating the difference between the direction and the y direction to the correction value for dynamic focus correction and the correction value for dynamic astigmatism correction, respectively. A charged particle beam drawing apparatus comprising beam correction means for performing astigmatism correction.

  In the invention according to claim 3 for solving the above-mentioned problem, the beam correction means stores a correction value for dynamic focus correction and a correction value for dynamic astigmatism correction corresponding to the deflection position, respectively. The first and second storage means, and the focal shift amount and the astigmatism shift amount for eliminating the difference between the x direction and the y direction of the beam blur caused by the deflection coma aberration and the deflection chromatic aberration are stored corresponding to the deflection position, respectively. Third and fourth storage means; first addition means for adding the output value of the first storage means and the output value of the third storage means; the output value of the second storage means; The charged particle beam drawing apparatus according to claim 2, further comprising: a second addition unit that adds the output value of the fourth storage unit.

  According to the first aspect of the present invention, when performing dynamic focus correction and dynamic astigmatism correction on the beam of the charged particle beam drawing apparatus, the difference between the x direction and the y direction of the beam blur due to deflection coma aberration and chromatic aberration is calculated. Since the focus shift amount and the astigmatism shift amount for canceling are respectively added to the correction value for dynamic focus correction and the correction value for dynamic astigmatism correction, dynamic focus correction and dynamic astigmatism correction are performed. A beam correction method that does not cause a difference in line width between the x direction and the y direction regardless of the deflection coma aberration and the deflection chromatic aberration can be realized.

  According to the second aspect of the invention, the charged particle beam drawing apparatus that performs dynamic focus correction and dynamic astigmatism correction on a beam eliminates the difference between the x direction and the y direction of the beam blur caused by deflection coma and chromatic aberration. Beam correcting means for performing dynamic focus correction and dynamic astigmatism correction by adding the focus shift amount and the astigmatism shift amount for adjusting to the dynamic focus correction value and the dynamic astigmatism correction value, respectively Therefore, it is possible to realize a charged particle beam drawing apparatus in which there is no difference in line width between the x direction and the y direction regardless of the deflection coma aberration and the deflection chromatic aberration.

  According to the invention of claim 3, the beam correcting means stores the first and second dynamic focus correction values and dynamic astigmatism correction values corresponding to the deflection positions, respectively. The third and fourth storage units store the focal shift amount and the astigmatism shift amount corresponding to the deflection position for eliminating the difference between the x direction and the y direction of the beam blur caused by the deflection coma aberration and the deflection chromatic aberration, respectively. Storage means, first addition means for adding the output value of the first storage means and the output value of the third storage means, the output value of the second storage means, and the fourth storage means Since the second adding means for adding the output values is provided, dynamic beam correction can be easily performed.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention. FIG. 1 is a block diagram showing a configuration of an example of a charged particle beam drawing apparatus. An example of the best mode for carrying out the invention relating to the charged particle beam drawing apparatus is shown by the configuration of the apparatus. An example of the best mode for carrying out the invention relating to the beam correction method of the charged particle beam drawing apparatus is shown by the operation of this apparatus.

As shown in FIG. 1, the charged particle beam drawing apparatus has an electron gun 1. The electron beam EB generated from the electron gun 1 is irradiated onto the first shaping aperture 3 via the illumination lens 2.
The aperture image of the first shaping aperture is formed on the second shaping aperture 6 by the shaping lens 4, and the position of the imaging can be changed by the shaping deflector 5. The image formed by the second shaping aperture 6 is irradiated onto the material 10 through the reduction lens 7 and the objective lens 8. The irradiation position on the material 10 can be changed by the positioning deflector 9.

  The computer 11 transfers the pattern data from the memory 12 to the shot divider 14 through the data transfer circuit 13. The pattern data is shot divided by the shot divider 14.

  A signal corresponding to the drawing data from the shot divider 14 is supplied to an amplifier 16 that supplies a deflection voltage to the shaping deflector 5 via a DA converter 15. Further, the voltage is supplied to an amplifier 18 that supplies a deflection voltage to the positioning deflector 9 via the deflector control circuit 28 and the DA converter 17. Further, it is supplied via a DA converter 19 to a blanking control circuit 21 that controls a blanking electrode 20 for blanking an electron beam generated from the electron gun 1. Further, it is supplied to the beam corrector 100 via the beam correction circuit 300.

  The computer 11 controls the drive mechanism 23 of the stage 22 on which the material 10 is placed for the movement of the material for each field. The amount of movement of the stage 22 is measured by the laser length measuring device 24, and the measurement result is supplied to the computer 11.

  Secondary electrons and reflected electrons are generated by irradiating the material 10 with the electron beam EB. For example, the reflected electrons are detected by the pair of reflected electron detectors 25. The detection signals of the backscattered electron detector 25 are added by the adder 26 and then supplied to the computer 11 through the mark signal processing device 27.

  A Faraday cup 202 is provided on the stage 22, and the current of the electron beam EB can be measured by moving the stage 22 to a position where the electron beam EB enters the Faraday cup 202. The measurement result is supplied to the computer 11 through the current signal processing circuit 29.

  The drawing operation of this apparatus will be described. The pattern data stored in the memory 12 is sequentially read out and supplied to the shot divider 14 via the data transfer circuit 13. Based on the data divided by the shot divider 14, the electron beam shaping data is supplied to the amplifier 16 via the DA converter 15, and the signal amplified by the amplifier 16 is supplied to the shaping deflector 5. The deflection signal of the electron beam corresponding to the drawing pattern is supplied to the amplifier 18 via the deflector control circuit 28 and the DA converter 17, and the signal amplified by the amplifier 18 is supplied to the positioning deflector 9.

  As a result, the cross section of the electron beam is formed into a rectangular or trapezoid having a desired area by the shaping deflector 5 based on the divided pattern data, and the beam having such a cross section is supplied to the positioning deflector 9. Shots are sequentially made on the material according to the signal, and a pattern having a desired shape is drawn. At this time, blanking of the electron beam is executed in synchronization with the shot of the electron beam on the material 10 by a blanking signal from the blanking control circuit 21 to the blanking electrode 20.

  Such a drawing operation by deflection of the electron beam is performed in units of fields, and after the drawing in one field is completed, the stage 22 is moved by the length of the field by the drive mechanism 23 to draw the next field. Is done. The amount of movement of the stage 22 is measured by the laser length measuring device 24, and the measured value is supplied to the computer 11. The computer 11 controls the drive mechanism 23 based on the movement amount measurement value, so that the stage 22 is accurately moved.

  In the process of performing such drawing, the beam correction circuit 300 causes the beam corrector 100 to perform dynamic focus correction and dynamic correction for correcting beam blur due to deflection field curvature aberration and deflection astigmatism due to beam deflection. Astigmatism correction is performed. The portion composed of the beam corrector 100 and the beam correction circuit 300 is an example of the beam correction means in the present invention.

  To these correction values for dynamic focus correction and dynamic astigmatism correction, a focus shift amount and an astigmatism shift amount for eliminating the difference between the x direction and the y direction of the beam blur due to deflection coma aberration and chromatic aberration are added. The Hereinafter, beam correction will be described.

  FIG. 2 is a block diagram showing the main part of the apparatus related to beam correction. As shown in FIG. 2, the beam corrector 100 includes a dynamic focus corrector 110 and a dynamic astigmatism corrector 120. The beam correction circuit 300 includes a focus correction amount map 311, a focus shift amount map 312, an adder 313 and a focus correction control circuit 314 corresponding to the dynamic focus corrector 110. Correspondingly, an astigmatism correction amount map 321, an astigmatism shift amount map 322, an adder 323 and an astigmatism correction control circuit 324 are provided.

  The focus correction amount map 311, the focus shift amount map 312, the astigmatism correction amount map 321 and the astigmatism shift amount map 322 may be provided in the memory 12. Further, the adders 313 and 323 may be realized by the function of the computer 11.

  The focus correction amount map 311 is an example of a first storage unit in the present invention. The defocus amount map 312 is an example of a third storage unit in the present invention. The adder 313 is an example of a first addition unit in the present invention.

  The astigmatism correction amount map 321 is an example of a second storage unit in the present invention. The astigmatism shift amount map 322 is an example of a fourth storage unit in the present invention. The adder 323 is an example of the second adding means in the present invention.

  The focus correction amount map 311 stores a correction value for dynamic focus correction for each beam position, the focus shift amount map 312 stores a focus shift amount for each beam position, and these stored values correspond to the beam position data. Read out. The two values read out are added by the adder 313 and input to the focus correction control circuit 314. The focus correction control circuit 314 controls the dynamic focus corrector 110 based on the input signal. Thus, dynamic beam correction can be easily performed by reading out correction values stored in correspondence with beam positions and performing beam correction.

  The astigmatism correction map 321 stores dynamic astigmatism correction values for each beam position, the astigmatism shift map 322 stores astigmatism shifts for each beam position, and these stored values are stored as beam values. Read according to the position data. The two read values are added by the adder 323 and input to the astigmatism correction control circuit 324. The astigmatism correction control circuit 324 controls the dynamic astigmatism corrector 120 based on the input signal. Thus, dynamic beam correction can be easily performed by reading out correction values stored in correspondence with beam positions and performing beam correction.

  Dynamic focus correction and dynamic astigmatism correction will be described with reference to FIG. FIG. 3 is a graph in which the focal position is the horizontal axis and the amount of beam blur is the vertical axis. FIG. 3A shows a state before dynamic focus correction and dynamic astigmatism correction, and FIG. 3B shows a state after correction.

  As shown in (a), the average focal point of the deflected beam is moved from the focal position f0 to f ′ without change due to the deflection field curvature aberration and the deflection astigmatism, and the focal positions fx and y in the x direction. A difference occurs in the focal position fy. Also, the amounts of blur at the respective focal positions x and fy are different. The difference in blur amount is caused by deflection coma and deflection chromatic aberration.

  The deflection field curvature aberration and the deflection astigmatism are corrected by dynamic focus correction and dynamic astigmatism so that fx = fy = f0 as shown in FIG. Realizing fx = fy is dynamic astigmatism correction, and adjusting fx and fy to f0 is dynamic focus correction. A focus correction value and an astigmatism correction value that enable such correction are stored in the focus correction amount map 311 and the astigmatism correction amount map 321 for each beam position.

  Due to deflection coma and deflection chromatic aberration, the amount of blur at the focal position f0 of the beam after correction differs between the x direction and the y direction. Such a difference in blur amount is eliminated by a focus shift amount and an astigmatism shift amount added to the focus correction value and the astigmatism correction value.

  The focus shift amount and astigmatism shift amount will be described with reference to FIG. FIG. 4 is a graph in which the focal position is the horizontal axis and the amount of beam blur is the vertical axis. FIG. 4 shows a state in which the focus is shifted by Δf from the beam correction state shown in FIG. 3B and the astigmatism is shifted by Δa.

  By such focal shift and astigmatism shift, the average focal position of the beam moves to f ″, but the focal position in the y direction remains at f0, and only the focal position in the x direction moves to fx. The movement amount fx of the focal position in the x direction is such a movement amount that the blur amount in the x direction at the focal position f0 is the same as that in the y direction. As a result, the amount of blur at the focal position f0 is equalized in the x and y directions, and the difference between the two is eliminated.

  The equalization of the blur amount at the focal position f0 is performed in the beam correction state shown in FIG. 3B in which the blur amount at the focal position f0 is larger in the x direction and the y direction and the blur amount is smaller. It is done by increasing and matching. Therefore, when the amount of blur in the x direction is large at the focal position f0, the amount of blur in the y direction is increased and matched.

  Such focus shift amount and astigmatism shift amount are stored in the focus shift amount map 312 and astigmatism shift amount map 322 for each beam position, respectively, and a correction value and dynamic astigmatism for dynamic focus correction are stored. It is used by adding to the correction value for correction. Therefore, dynamic focus correction and dynamic astigmatism correction in which the difference in beam blur between the x direction and the y direction is eliminated can be performed.

  The optimum values of the focus shift amount and the astigmatism shift amount are specified through a drawing trial using a plurality of candidate values prepared in advance. The optimum values of the focus shift amount and the astigmatism shift amount are values that minimize the drawn line width and minimize the difference between the line widths in the x and y directions.

The trial of drawing with a plurality of candidate values is performed for the focus shift amount Δf and the astigmatism shift amount Δa.
± Δf = Δa / 2
Efficient trials can be performed by limiting to only those having the above relationship.

  FIG. 5 shows an example of a drawing result using the optimum values of the focus shift amount and the astigmatism shift amount. FIG. 5A is a graph showing a two-dimensional distribution of line widths in a drawing field when single drawing is performed, with the line width X on the left side and the line width Y on the right side. Distribution. The two-dimensional distribution of the line width in both graphs is the same, indicating that there is no difference between the line width in the x direction and the line width in the y direction.

  However, since there is a single drawing, there is a variation in the line width in the field, but the variation in the line width is reduced as shown in FIG. Double drawing is performed by shifting the field by 1/2 field. Since there is no difference between the line width in the x direction and the line width in the y direction, variation can be sufficiently reduced even if the multiple drawing is limited to double drawing.

  FIG. 6 shows an example of the effect of equalizing the blur in the x direction and the y direction by comparison with the case where no equalization is performed. FIG. 6A is a graph in which the horizontal axis represents the number of times of multiple drawing and the vertical axis represents the line width variation within the field, the solid line is not equalized and the broken line is equalized. (B) is a graph in which the horizontal axis represents the number of times of multiple drawing and the vertical axis represents the in-field variation of the XY difference of the line width, where the solid line is not equalized and the broken line is equalized. From these graphs, the remarkable effect of equalizing the blur in the x direction and the y direction is clear. The above is an example of a drawing apparatus using an electron beam, but the same effect can be obtained for a drawing apparatus using an ion beam.

1 is a block diagram showing a configuration of a charged particle beam drawing apparatus as an example of the best mode for carrying out the present invention. It is a block diagram which shows the structure of the principal part of the charged particle beam drawing apparatus of an example of the best form for implementing this invention. It is a figure which shows an example of the relationship between a focus position and beam blur. It is a figure which shows an example of the relationship between a focus position and beam blur. It is a figure which shows an example of the two-dimensional distribution of the line | wire width in a field. It is a figure which shows an example of a beam correction effect.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron gun 2 Illumination lens 3 2nd shaping | molding aperture 4 Molding lens 5 Molding deflector 6 2nd shaping | molding aperture 7 Reduction lens 8 Objective lens 9 Positioning deflector 10 Material 11 Computer 12 Memory 13 Data transfer circuit 14 Shot dividers 15 and 17 , 19 DA converter 16, 18 amplifier 20 blanking electrode 21 blanking control circuit 22 stage 23 drive mechanism 24 laser length measuring device 25 backscattered electron detector 26 adder 27 mark signal processing circuit 28 deflector control circuit 29 current signal processing Circuit 202 Faraday cup 100 Beam corrector 110 Dynamic focus corrector 120 Dynamic astigmatism corrector 300 Beam correction circuit 311 Focus correction amount map 312 Focus shift amount map 313 Adder 314 Focus corrector control circuit 321 Astigmatism correction amount map Flop 322 astigmatic shift amount map 323 adder 324 astigmatism corrector control circuit

Claims (3)

In performing dynamic focus correction and dynamic astigmatism correction for the beam of the charged particle beam drawing apparatus,
The focus shift amount and the astigmatism shift amount for eliminating the difference between the x direction and the y direction of the beam blur due to the deflection coma aberration and the deflection chromatic aberration are set as a correction value for dynamic focus correction and a correction value for dynamic astigmatism correction. Add each to perform dynamic focus correction and dynamic astigmatism correction,
A beam correction method for a charged particle beam drawing apparatus. A charged particle beam drawing apparatus for performing dynamic focus correction and dynamic astigmatism correction on a beam,
The focus shift amount and the astigmatism shift amount for eliminating the difference between the x direction and the y direction of the beam blur due to the deflection coma aberration and the deflection chromatic aberration are set as a correction value for dynamic focus correction and a correction value for dynamic astigmatism correction. Beam correction means for performing dynamic focus correction and dynamic astigmatism correction by adding each,
A charged particle beam drawing apparatus comprising: The beam correcting means includes
First and second storage means for storing a correction value for dynamic focus correction and a correction value for dynamic astigmatism correction corresponding to each deflection position;
Third and fourth storage means for storing a focus shift amount and an astigmatism shift amount corresponding to the deflection position, respectively, for eliminating the difference between the x direction and the y direction of beam blur caused by deflection coma and chromatic aberration;
First addition means for adding the output value of the first storage means and the output value of the third storage means;
Second addition means for adding the output value of the second storage means and the output value of the fourth storage means;
The charged particle beam drawing apparatus according to claim 2, further comprising: