JPH10289860A - Method for adjusting beam of projection optical system and projection optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system in which beam adjustment can be easily operated and aberration or the like can be reduced, and the beam adjusting method of the projection optical system. SOLUTION: This projection optical system is provided with lens 2 and 3 in two stages, four deflectors 8-11, and cross-over opening 4a, and a charged beam passing through a rectile 1 is allowed to pass through the cross-over opening 4a, and projected on a sample 5. An electron beam is two-dimensionally scanned on an aperture plate 7 by the deflector 8, and currents generated on the aperture plate 7 are detected by a detector 21. A controller 20 controls the deflecting amount of the deflector 8 so that a main light beam 6 can pass through the center of an opening 7a of the aperture plate 7 provided at the deflection central position of the deflector 9 based on the detected result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection optical system used for a charged particle beam exposure apparatus and the like, and a beam adjusting method for the projection optical system.

[0002]

2. Description of the Related Art In a charged particle beam projection exposure apparatus, it is known that a projection optical system having a low aberration can be obtained by configuring a projection optical system with a lens and a deflector. By the way, when designing the projection optical system of the exposure apparatus, a computer is simulated using a computer, and design values are determined so that low aberration can be obtained.

[0003]

However, when an optical system is actually manufactured, it is very difficult to manufacture an optical component in accordance with the theoretical design values obtained by simulation, and a certain degree of error in the manufacturing is required. Is inevitable. In particular, when this error affects the performance of the optical system,
It is necessary to compensate for errors in these optical components by adjusting the beam (adjusting the excitation current and deflection current of the lens and deflector constituting the optical system). However, in the past,
Since a beam adjustment method and procedure for a reduced projection optical system that projects a large area have not been clarified, how to perform beam adjustment has been a problem. Especially,
In the case of a deflector, since its structure is not axially symmetric, a manufacturing error is likely to occur, and beam adjustment has been a problem.

An object of the present invention is to provide a projection optical system which can easily perform beam adjustment and has small aberration and the like, and a beam adjustment method for the projection optical system.

[0005]

The present invention will be described with reference to FIG. 1 showing an embodiment of the invention. (1) The invention of claim 1 is a two-stage lens 2 and 3, and at least four deflectors 8 to And a crossover opening 4a, a beam adjusting method for a projection optical system for projecting a charged beam passing through the reticle 1 through the crossover opening 4a onto a sample 5. The deflector 8 closest to the reticle 1 Is the first deflector, the deflector 9 closer to the reticle 1 than the crossover and closest to the crossover is the second deflector, and the deflector 10 closer to the sample 5 than the crossover and closest to the crossover. Is the third deflector, and the deflector 11 closest to the sample 5 is the fourth deflector, the principal ray 6 of the charged beam intersects the optical axis AX at the deflection center position of the second deflector 9 So the first deflector It has to adjust the amount of deflection of the charged particle beam by the achieve the above object. (2) The invention according to claim 2 is provided with two-stage lenses 2 and 3, at least four deflectors 8 to 11 and a crossover opening 4a, and allows the charged beam passing through the reticle 1 to pass through the crossover opening 4a. A beam adjusting method for a projection optical system for projecting onto a sample 5, wherein a deflector 8 closest to the reticle 1 is a first deflector, and a deflector 9 closer to the reticle 1 than the crossover and closest to the crossover. The second
The deflector 10 on the sample 5 side of the crossover and closest to the crossover is a third deflector, the deflector 11 closest to the sample 5 is a fourth deflector, and the reticle surface is xy. The second deflector 9 is arranged such that the charged beam passes through the center of the crossover opening 4a when the coordinate plane is set.
The above-mentioned object is achieved by adjusting the x and y deflection amounts of. (3) The invention according to claim 3 is provided with two-stage lenses 2 and 3, at least four deflectors 8 to 11 and a crossover opening 4a, and allows the charged beam passing through the reticle 1 to pass through the crossover opening 4a. A beam adjusting method for a projection optical system for projecting onto a sample 5, wherein a deflector 8 closest to the reticle 1 is a first deflector, and a deflector 9 closer to the reticle 1 than the crossover and closest to the crossover. The second
The deflector 10 closer to the sample 5 than the crossover and closest to the crossover is the third deflector, the deflector 11 closest to the sample 5 is the fourth deflector, and the reticle surface is xy. When the coordinate plane is set, the absolute values of the x and y deflection angles of the third deflector 10 are respectively equal to the corresponding x and y deflection angles of the second deflector 9, and the deflection direction is 180 degrees. The above-mentioned object is achieved by making different adjustments. (4) The invention according to claim 4 is provided with two-stage lenses 2 and 3, at least four deflectors 8 to 11 and a crossover opening 4a, and allows the charged beam passing through the reticle 1 to pass through the crossover opening 4a. A method of adjusting a beam of a projection optical system for projecting onto a sample 5 at a reduction rate of 1 / M, wherein a deflector 8 closest to the reticle 1 is used as a first deflector, and is located closer to the reticle 1 than the crossover. Is used as the second deflector, and the sample 5
When the deflector 10 on the side closest to the crossover is the third deflector, the deflector 11 closest to the sample 5 is the fourth deflector, and the reticle surface is an xy coordinate plane, The x and y deflection amounts of the fourth deflector 11 are adjusted so that the pattern at the coordinates (x0, y0) is projected onto the coordinates (-x0 / M, -y0 / M) on the sample surface. Thus, the above-mentioned object is achieved. (5) The beam adjustment method according to any one of claims 2 to 4, wherein the deflection amount of the first deflector 8 is calculated by computer simulation, and the deflection amount of the first deflector 8 is calculated. The deflection is adjusted so as to be equal to the deflection amount. (6) The invention according to claim 6 is provided with a two-stage lens 2 and 4, at least four deflectors 8 to 11 and a crossover opening 4a, and allows the charged beam passing through the reticle 1 to pass through the crossover opening 4a. The deflector 8 which is applied to the projection optical system for projecting onto the sample 5 and is closest to the reticle 1
The deflector 9 on the reticle 1 side of the crossover and closest to the crossover is a second deflector,
When the deflector 10 closest to the crossover and closer to the sample 5 than the crossover is the third deflector, and the deflector 11 closest to the sample 5 is the fourth deflector, the second deflector 9 Beam detecting means 7 and 21 which are arranged at the center of the deflection of the optical axis and generate a signal when an aperture 7a is formed about the optical axis AX and are irradiated with a charged beam; The above-mentioned object is achieved by providing a controller 20 for controlling the amount of deflection of the first deflector 8 so that the chief ray 6 of the charged beam intersects the optical axis AX at the deflection center position of the deflector 9.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easier to understand. However, the present invention is not limited to the embodiment.

[0007]

Embodiments of the present invention will be described below with reference to FIG. FIG. 1 is a view showing an embodiment of a projection optical system according to the present invention, and is a schematic view showing a schematic configuration of a projection optical system (reduction ratio of 1/4) of an electron beam projection exposure apparatus. A reticle 1 is irradiated with an electron beam from above in the figure by an illumination optical system (not shown). Reference numeral 6 denotes a principal ray of the electron beam emitted from the reticle 1 in parallel with the optical axis AX.
4 and projected onto the sample 5. At this time, the aberration of the optical system is reduced by controlling the trajectory of the electron beam by the deflectors 8, 9, 10, and 11. Reference numeral 20 denotes a control device for controlling the deflectors 8 to 11. Reference numeral 4 denotes an aperture plate provided at the crossover 16 position, and a crossover opening 4a is formed at the optical axis position. Reference numeral 7 denotes an aperture plate provided at a deflection center position of the deflector 9 and having a circular opening 7a centered on the optical axis AX. The aperture plate 7 is connected to a detector 21 for detecting a current generated when an electron beam is irradiated. I have. 22
Is a backscattered electron detector for detecting backscattered electrons generated when the sample 5 is irradiated with the electron beam. Detectors 21 and 2
2 are connected to the control device 20, respectively.

The deflectors 8 to 11 have the following functions. The deflector 8 has a function of moving the optical axis of the lens 2 and a function of deflecting the chief ray 6 in the x and y directions so that the trajectory of the chief ray 6 passes through the center of the opening 7 a of the aperture plate 7. I have. The deflector 9 deflects the obliquely incident chief ray 6 to travel along the optical axis AX. As a result, the electron beam passes on the axes of the lenses 2 and 3 from the center of deflection of the deflector 9 to the center of deflection of the deflector 10 below the lens 2 and above the lens 3. The generated aberration can be reduced. The deflector 10 deflects the chief ray 6 traveling along the optical axis AX so that the trajectory of the chief ray 6 becomes similar to the crossover 16. The deflector 11 deflects the electron beam so that the chief ray 6 enters the sample 5 perpendicularly. Further, the insulator spacer 13 and the ferrite 12
Are alternately stacked so that eddy currents are not generated in the pole pieces of the lenses 2 and 3 made of a ferromagnetic material such as iron or permalloy by the magnetic field of the deflectors 8 and 9. 14a and 14b are members made of ferrite. Similar cylinders 23 were provided for the deflectors 10 and 11 on the lens 3 side. Therefore, the deflectors 8 to 11 can be operated at high speed.

First, a method of adjusting the deflector 8 will be described. The control device 20 uses the deflector 8 to convert the chief ray 6 into x, y
The beam is deflected in the direction and scanned on the aperture plate 7.
At this time, when the electron beam is incident on the aperture plate 7, a current is detected by the detector 21, and when the electron beam completely passes through the opening 7a, no current is detected. Based on the signal from the detector 21, the control device 20 obtains a deflection range in which the current becomes zero, and when the deflection amount of the deflector 8 is at the center of the deflection range, the chief ray 6 changes the aperture 7.
Assuming that the current passes through the center of a, the deflection current of the deflector 8 is adjusted to a current value corresponding to the center of the deflection range.

The optimum value of the deflection amount of the deflector 8 is calculated in advance by computer simulation. If the accuracy of the deflector 8 is sufficiently high, the above adjustment is not performed, and The deflection amount may be set to the calculated optimum value. In this case, there is no need to provide the aperture plate 7.

When adjusting the deflector 9, the electron beam is deflected in the x and y directions by the deflector 9 and two-dimensionally scanned near the crossover opening 4 a on the aperture plate 4, and The reflected electrons are detected by the reflected electron emitter 22. At this time, if the electron beam passes through the crossover opening 4a, reflected electrons from the sample 5 are detected. On the other hand, if the electron beam is blocked by the aperture plate 4, the electron beam does not enter the sample 15. Backscattered electrons are not detected. Therefore, the control device 20 obtains a deflection range in which reflected electrons are detected, and considers that the principal ray 6 passes through the center of the crossover opening 4a when the deflection amount of the deflector 9 is at the center of the deflection range. The deflection current of the deflector 9 is adjusted to a current value corresponding to the center of the deflection range. In the case of the deflector 10, the adjustment is performed utilizing symmetry. That is, the deflection angle of the deflector 10 in the x direction is adjusted so that the absolute value of the deflection angle of the deflector 9 in the x direction is equal to that of the deflection direction and the deflection direction is different by 180 degrees. The deflection angle in the y direction is adjusted similarly.

When adjusting the deflector 11, the coordinates (x0, y0) of the reticle 1 and the coordinates (-x0,
/ 4, −y0 / 4), respectively, marks M1 and M5 are formed, and an image of the mark M1 is projected on the sample 5 and deflected on the sample so that the image of the mark M1 and the mark M5 just overlap. The deflection current of the device 11 is adjusted. At this time, the electron beam is deflected in the x and y directions by the deflector 10, and the reflected electron at that time is detected by the reflected electron detector 22, thereby detecting the positional deviation between the image of the mark M1 and the mark M5. , Electron beam deflection center (center of mark M1 image)
And the displacement of the center of the mark M1 is measured. Note that x0,
y0 may be zero.

In this way, the deflection amount (that is, beam adjustment) can be adjusted for each of the deflectors 8 to 11. Therefore, even if there is a manufacturing error in the deflector, it can be easily corrected by the above-described beam adjustment, and aberrations and the like of the optical system can be reduced.

In the correspondence between the embodiment of the invention described above and the constituent elements in the claims, the deflector 8 is the first deflector, the deflector 9 is the second deflector, and the deflector 10 is the The third deflector and the deflector 11 constitute a fourth deflector, and the aperture plate 7 and the detector 21 constitute a beam detecting means.

[0015]

As described above, according to the present invention,
Beam adjustment for compensating for a manufacturing error of the deflector constituting the projection optical system can be easily performed, and a projection optical system with small aberration can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a projection optical system according to the present invention, and is a schematic diagram showing a schematic configuration of a projection optical system (reduction ratio of １ ／) of an electron beam projection exposure apparatus.

[Explanation of symbols]

 Reference Signs List 1 reticle 2, 3 lens 4, 7 aperture plate 4a crossover aperture 5 sample 6 principal ray 7a aperture 8-11 deflector 20 controller 21 detector 22 backscattered electron detector

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01L 21/30 541B

Claims (6)

[Claims] 1. A beam adjusting method for a projection optical system comprising a two-stage lens, at least four deflectors, and a crossover aperture, wherein a charged beam passing through a reticle passes through the crossover aperture and is projected onto a sample. The deflector closest to the reticle is the first deflector, the deflector on the reticle side of the crossover and closest to the crossover is the second deflector, and the deflector on the sample side of the crossover is crossover. When the deflector closest to the sample is a third deflector and the deflector closest to the sample is a fourth deflector, the principal ray of the charged beam at the center of deflection of the second deflector is aligned with the optical axis. A beam adjusting method for a projection optical system, wherein an amount of deflection of a charged beam by the first deflector is adjusted so as to intersect. 2. A beam adjusting method for a projection optical system comprising a two-stage lens, at least four deflectors, and a crossover aperture, wherein a charged beam passing through a reticle is projected through a crossover aperture onto a sample. The deflector closest to the reticle is the first deflector, the deflector on the reticle side of the crossover and closest to the crossover is the second deflector, and the deflector on the sample side of the crossover is crossover. The charged beam passes through the center of the crossover aperture when the deflector nearest to the sample is the third deflector, the deflector closest to the sample is the fourth deflector, and the reticle surface is the xy coordinate plane. The method of adjusting the beam of the projection optical system, wherein the x and y deflection amounts of the second deflector are adjusted as described above. 3. A beam adjusting method for a projection optical system comprising a two-stage lens, at least four deflectors, and a crossover aperture, wherein a charged beam passing through a reticle is projected through the crossover aperture onto a sample. The deflector closest to the reticle is the first deflector, the deflector on the reticle side of the crossover and closest to the crossover is the second deflector, and the deflector on the sample side of the crossover is crossover. When the deflector nearest to the sample is a third deflector, the deflector closest to the sample is a fourth deflector, and the reticle surface is an xy coordinate plane, the x and y deflection angles of the third deflector Are adjusted so that their absolute values are equal to the corresponding x and y deflection angles of the second deflector, and the directions of deflection differ by 180 degrees. Over-time adjustment method. 4. Projection optics comprising a two-stage lens, at least four deflectors, and a crossover aperture, and projecting a charged beam passing through a reticle through the crossover aperture onto a sample at a reduction rate of 1 / M. A beam deflector closest to the reticle as a first deflector, a deflector closer to the reticle than the crossover and closer to the crossover as a second deflector, and a sample deflector from the crossover. When the deflector closest to the crossover on the side is the third deflector, the deflector closest to the sample is the fourth deflector, and the reticle surface is the xy coordinate plane, the coordinates on the reticle surface ( The pattern at (x0, y0) is the coordinates (-x0
/ M, -y0 / M), wherein the x and y deflection amounts of the fourth deflector are respectively adjusted so as to be projected onto the projection optical system. 5. The beam adjustment method according to claim 2, wherein the deflection amount of the first deflector is calculated by computer simulation, and the deflection amount of the first deflector is calculated. A beam adjusting method for a projection optical system, wherein the beam is adjusted to be equal to 6. A projection optical system, comprising a two-stage lens, at least four deflectors, and a crossover aperture, for projecting a charged beam passing through the reticle through the crossover aperture and projecting onto a sample. The deflector closer to the reticle than the crossover and closest to the crossover is the second deflector, and the deflector closer to the sample than the crossover and closest to the crossover is the first deflector. When the third deflector is used and the deflector closest to the sample is the fourth deflector, the deflector is disposed at the deflection center position of the second deflector, and an opening about the optical axis is formed. Beam detecting means for generating a signal when the charged beam is irradiated; and the first deflection unit so that a chief ray of the charged beam intersects an optical axis at a deflection center position of the second deflector based on the signal. A projection optical system, characterized in that it comprises a control device for controlling the amount of deflection of.