JP2695795B2 - Charged beam drawing equipment - Google Patents

Description

Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to a charged beam drawing apparatus, and more particularly to a charged beam drawing apparatus of a variable shaped beam system. (Prior Art) In recent years, a variable shaped beam type electron beam writing apparatus has been developed for the purpose of improving the writing throughput. In this type of apparatus, when an image of the first aperture is formed at the same magnification on the second aperture, two stages of projection lenses 23 and 24 are arranged between the aperture masks 21 and 22 as shown in FIG. cage, crossover image P ₁ is imaged in an intermediate position of the two-stage lens 23 and 24. Therefore, a deflector 25 for changing the beam size is provided between these two lenses 23 and 24. Here, the distance from the first aperture mask 21 to the target (not shown) needs to be as short as possible in order to reduce the beam blur due to the space charge effect. Since the length of the deflector 25 for changing the beam size in the optical axis direction needs to be driven at a high speed and needs to be driven at a low voltage, there is a demand that the length be as long as possible. However, since the deflector 25 is disposed between the two-stage lenses 23 and 24, if the length of the deflector 25 in the optical axis direction is increased, it is necessary to increase the lens interval. As a result, the two aperture intervals are reduced. growing. As the aperture interval becomes longer, the space charge effect between them becomes larger, and a large difference occurs between the resolution of the beam edge corresponding to the first aperture image and that corresponding to the second aperture image, which deteriorates the connection between the formed beams. It is a factor to make it. In addition, the length of the deflector 25 in the optical axis direction is generally set to be about 40% of the aperture interval because it is necessary to avoid interference with the magnetic poles of the lenses 23 and 24 and the surrounding structures. . (Problems to be Solved by the Invention) As described above, conventionally, there is a so-called trade-off relationship between the length of the deflector in the optical axis direction and the distance between two apertures. If the length of the deflector in the direction of the optical axis is increased, the aperture interval must be increased, and the difference in beam edge resolution corresponding to the first and second apertures due to the space charge effect increases. There were problems such as a decrease in connection accuracy. The present invention has been made in consideration of the above circumstances, and an object thereof is to make it possible to sufficiently increase the length of the deflector in the optical axis direction and to sufficiently reduce the interval between two apertures. Another object of the present invention is to provide a charged beam writing apparatus which can change the beam size with a small voltage and improve the connection accuracy between beams. [Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to insert a deflector inside a lens by reducing the magnetic gap between two projection lenses and increasing the bore diameter. Is provided to increase the length of the deflector in the optical axis direction without increasing the aperture interval. That is, the present invention comprises at least two projection lenses and a deflector for changing the beam size between the shaping aperture masks shown in FIGS. 1 and 2, and forms a variable shaping beam to irradiate the sample with a charged beam. In the beam writing apparatus, the deflector is installed inside the two-stage lens and over a region longer than the lens interval. (Operation) According to the present invention, since the deflector is disposed inside the lens, the deflector, which was conventionally only inserted between the projection lenses, is further extended vertically, and is extended to the vicinity of the upper and lower apertures. Can be. In addition, since the deflector is not arranged between the lenses, the distance between the lenses can be shortened regardless of the length of the deflector, and the aperture interval can be shortened. Therefore, the beam size can be changed with a small voltage, and the connection accuracy between the beams can be improved. Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a schematic diagram showing an optical system configuration of an electron beam writing apparatus according to one embodiment of the present invention. In the figure, reference numeral 10 denotes an electron gun. An electron beam emitted from the electron gun 10 is applied to a first aperture mask 11. The rectangular beam formed by the mask 11 is imaged on the second aperture mask 12 by the two-stage projection lenses 13 and 14. Lens 1
A deflector 15 for changing the beam size is disposed inside the beam splitters 3 and 14, and the length of the deflector 15 in the optical axis direction is set longer than the lens interval. The size of the rectangular beam is variably set by changing the optical overlap of the apertures 11a and 12a of the masks 11 and 12 by the deflector 15. The lens 13 images the cross-over P of the electron gun 10 in an intermediate position P ₁ of the lenses 13 and 14. Deflection center of the deflector 15 is in this crossover image position P _1. Also,
Since the focal lengths of the lenses 13 and 14 are relatively large, if the magnetic gap G between the magnetic poles is reduced to some extent, the bore diameter can be increased and a space for providing the deflector 15 therein is secured. Furthermore, the excitation current of the lens 13 and 14 to thereby prevent movement of which is reverse direction to each other, thereby the other deflection direction of the crossover image P ₁ at the time of deflecting the beam. The deflector 15 can deflect the beam in both x and y directions with 4 poles or 8 poles. When using an electrostatic deflector, 1
A stage may be provided in the x direction, and two stages above and below it in the y direction. The beams formed by the aperture masks 11 and 12 and the deflector 15 are imaged on a target 18 via a reduction lens 16 and an objective lens 17. A desired pattern is drawn on the target 18 by scanning the shaped beam with a scanning deflector (not shown) or the like. Thus, according to the present embodiment, the deflector 15 is
Since it is arranged inside the lenses 13 and 14, it is arranged inside the lenses 13 and 14, so the length of the deflector 15 in the optical axis direction can be increased without increasing the lens interval. it can. Therefore, the beam can be deflected with a small deflection voltage,
High-speed response is possible. In this embodiment, the length of the deflector 15 in the optical axis direction is set to two aperture masks 11 and 1.
The interval can be reduced to about 80% of the interval of 2, and the length can be extended to about twice as long as the conventional one. Further, when it is not necessary to lengthen the deflector 15, since the lens interval can be shortened, the aperture interval can be shortened, and the beam blur due to the space charge effect is reduced. For this reason, the beam edge resolution corresponding to the edges of the first aperture and the second aperture is reduced, and the connection accuracy between the beams can be improved.
Further, since the total length of the optical lens barrel is shortened, it is possible to reduce the size and weight and realize the optical lens at low cost. The present invention is not limited to the embodiments described above. For example, the lens placed between the apertures is 2
The number is not limited to three, and may be three or more. Further, the size of the magnetic gap of the lens may be determined as appropriate according to the electrode spacing of the deflector arranged inside the lens.
Further, the present invention is not limited to the electron beam writing apparatus, and can be applied to an ion beam writing apparatus. In addition, various modifications can be made without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an optical system configuration of an electron beam writing apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic view showing an optical system configuration of a conventional apparatus. 10 ... electron gun, 11 ... first aperture mask, 11a ...
1st aperture, 12 ... second aperture mask, 12a ...
... Second aperture, 13, 14 Projection lens, 15 Deflector, 16 Reduction lens, 17 Objective lens, 18 Target.

Claims (1)

(57) [Claims] A charged beam lithography system, comprising a two-stage projection lens and a beam size variable deflector between FIG. 1 and a second shaping aperture mask, for forming a variable shaping beam and irradiating the beam onto a sample, A charged beam is disposed inside the two-stage lens over a region longer than the lens interval, and the exciting currents of the two-stage lens are set in opposite directions to each other. Drawing device. 2. 2. The charged beam drawing apparatus according to claim 1, wherein said deflector comprises an electrostatic deflecting plate. 3. 3. The charged beam drawing apparatus according to claim 2, wherein a bore diameter of said two-stage lens is longer than an interval between said electrostatic deflecting plates facing each other.