JP4257440B2 - Prism-type modified illumination device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a prism type modified illumination device used in a photolithography process in the manufacture of a semiconductor integrated circuit.
[0002]
[Prior art]
Conventionally, this type of optical stepper has the following configuration.
[0003]
FIG. 9 is a block diagram of such a conventional optical stepper.
[0004]
In this figure, 1 is an Hg lamp, 2 is an elliptical mirror, 3 is an integrator (fly eye lens), 4 is an aperture, 5 is a condenser lens, 6 is a reticle, 7 is a reduction lens, and 8 is a wafer.
[0005]
In a conventional exposure technique, exposure is performed using a super-resolution technique such as modified illumination as a technique for obtaining an effect such as an improvement in limit resolution or an increase in DOF (depth of focus). In order to obtain modified illumination, a light shielding plate called an aperture is used in the prior art.
[0006]
[Problems to be solved by the invention]
However, in this method using a light shielding plate, since only the light is blocked, the conditions of the illumination system have not been optimally set. There is also a method of arranging a prism in front of the modified illumination, but this is a completely different structure from the present invention, and therefore a light shielding plate is required or intended for light shielding in a square shape.
[0007]
An object of the present invention is to provide a prism type modified illumination device that can eliminate the above-mentioned problems and optimize the condition setting of the modified illumination.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[1] In the prism-type modified illumination device, the cross-sectional shape parallel to the bottom surface is such that the circular portion is divided by eight cycloid curves, and the hemispherical curved surface is formed by a curved surface having two curvatures. the hemispherical prism and circular cone shaped prism having a cross-section of the cycloid shape are arranged in parallel on the optical axis, respectively, by using this combination was placed in the middle of the fly-eye lens and the exposure lens, and incident on the hemispherical prism The light is dispersed and transmitted in four directions, and after passing through the conical prism, is dispersed radially, and all exposure light is obliquely incident on the mask to expose the mask pattern on the wafer.
[0009]
[2] The prismatic modified illumination device above SL [1], wherein the upper surface Ri is Do and the hemispherical prism and the lower surface is convex downward with the cross-sectional surface of the cycloid shape, from said conical prism bottom surface faces upward Thus, the bottom surface of the hemispherical prism and the top surface of the conical prism are bonded together and formed integrally.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0011]
FIG. 1 is a schematic diagram of a prism type modified illumination device showing a first embodiment of the present invention, FIG. 1 (a) is a perspective view of a cycloid prism, FIG. 1 (b) is a plan view of the cycloid prism, FIG. 1 (c) is a perspective view of a conical prism. FIG. 2 is a diagram showing an optical path of the prism type modified illumination. Here, a modified illumination using two types of prisms shown in FIG. 1, which is one of the prism-type modified illuminations, will be described. In FIG. 1B, the curvature differs between the curved surface A (11A) and the curved surface B (11B).
[0012]
As shown in FIG. 1, the prism type modified illumination includes a hemispherical prism (hereinafter referred to as a cycloid prism) 11 and a conical prism (hereinafter referred to as a conical prism) 12 each having a cycloidal cross section, as shown in FIG. The direction in which the hem narrows is arranged parallel to the outside or inside, and using this combination, the mask pattern is placed on the wafer (not shown) between the fly-eye lens (not shown) and the exposure lens (not shown). ) The top exposure method is the basic configuration.
[0013]
When exposure is performed, as shown in FIG. 2, after the exposure light from the light source passes through the fly-eye lens, the exposure light from the light source 10 passes through the cycloid prism 11 of the prism type modified illumination shown in FIG. The light is dispersed and transmitted in the four cross-sectional directions, and the light is dispersed and transmitted radially by passing through the conical prism 12. As a result, the exposure light becomes a plurality of light beams dispersed in an arbitrary direction. By obliquely incident on the mask, the light emitted from the mask is interfered with the two light beams and passes through the exposure lens (not shown) and passes through the wafer ( In this case, a good resolution pattern can be obtained.
[0014]
As described above, according to the first embodiment, the prism-shaped modified illumination shown in FIGS. 1 and 2 is used to disperse light in an arbitrary direction, and unlike the conventional technique, all exposure light is obliquely applied on the mask. Since it can enter, a very favorable resolution pattern can be obtained. At this time, by reducing the area of the semicircular cross-sectional portion of the cycloid prism, it is possible to further disperse the light with an angle in an oblique direction.
[0015]
In addition, an angle can be given in an oblique direction by increasing the angle of the cross section, but this angle is limited to an angle at which the four semicircles do not intersect each other.
[0016]
Next, a first reference example of the present invention will be described.
[0017]
FIG. 3 is a schematic diagram of a prism-type modified illumination device showing a first reference example of the present invention. FIG. 3 (a) is a perspective view of the first dome prism, and FIG. 3 (b) is a second dome prism. FIG. 3C is a perspective view of a conical prism. FIG. 4 is a diagram showing an optical path of the prism type modified illumination.
[0018]
In this embodiment, the three prisms 21, 22, and 23 shown in FIG. 3 are used, and the first dome-shaped prism 21 having a semicircular cross section arranged in a target shape is directed laterally from the light source 20. Similarly, the second dome-shaped prism 22 is arranged in the longitudinal direction with the cross section thereof being narrowed, and the light is arranged in parallel with the direction in which the skirt is narrowed outward or inward. Furthermore, the conical prism 23 can be arranged in the direction in which the skirt narrows, and a total of three prisms can be arranged in parallel to the optical axis.
[0019]
In the second embodiment, the light is transmitted through the three prisms 21, 22, and 23 in order to perform exposure. After the exposure light from the light source passes through the fly-eye lens (not shown), it passes through the dome-shaped prism 21 of the prism-type modified illumination shown in FIG. By passing through the dome-shaped prism 22, the light is dispersed and transmitted in the longitudinal direction, which is the two cross-sectional directions of the prism, and further, by passing through the conical prism 23, the light is dispersed radially. Then penetrate. As a result, the exposure light becomes a plurality of light fluxes dispersed in an arbitrary direction. By obliquely incident on the mask, the light emitted from the mask is interfered by two light fluxes and passes through an exposure lens (not shown) to be on the wafer. Then, a good resolution pattern can be obtained.
[0020]
As described above, according to the first reference example, the prism-shaped modified illumination shown in FIGS. 3 and 4 is used to disperse light in an arbitrary direction, and unlike the conventional technique, all exposure light is obliquely applied on the mask. Since it can enter, a very favorable resolution pattern can be obtained. At this time, by reducing the area of the semicircular cross section, it is possible to disperse the light with an angle in an oblique direction. In addition, an angle can be given in an oblique direction by increasing the angle of the cross section, but this angle is limited to an angle at which the four semicircles do not intersect each other. Although three prisms are used, unlike the first embodiment, this wide range of limiting angles is a feature of the second embodiment.
[0021]
Next, a second reference example of the present invention will be described.
[0022]
FIG. 5 is a schematic diagram of a prism type modified illumination device showing a second reference example of the present invention, and FIG. 5A is a perspective view of a pyramid-shaped prism (hereinafter referred to as a pyramid prism), FIG. ) Is a plan view of the pyramid prism, and FIG. 5C is a perspective view of the conical prism. FIG. 6 is a diagram showing an optical path of the prism type modified illumination device.
[0023]
Here, only one prism is used, and a configuration example of a variable aperture is shown. In this embodiment, a modified illumination using prism type modified illumination will be described.
[0024]
In this prism type modified illumination, the pyramid prism 31 shown in FIG. 5 and the cone prism 32 shown in FIG. The basic configuration is a method in which a mask pattern is exposed on a wafer by placing the mask pattern between a fly-eye lens (not shown) and an exposure lens (not shown).
[0025]
In the second reference example, light is transmitted through the two prisms 31 and 32 in order to perform exposure. After the exposure light from the light source 30 passes through the fly-eye lens (not shown), the light passes through the pyramid prism 31 of the prism-type modified illumination shown in FIG. The light is dispersed and transmitted, and is transmitted through the conical prism 32 so that the light is radially dispersed and transmitted. As a result, the exposure light becomes a plurality of light fluxes dispersed in an arbitrary direction. By obliquely incident on the mask, the light emitted from the mask is interfered by two light fluxes and passes through an exposure lens (not shown) to be on the wafer. Then, a good resolution pattern can be obtained.
[0026]
As described above, according to the second reference example, the prism-shaped modified illumination shown in FIGS. 5 and 6 is used to disperse light in an arbitrary direction, and unlike the conventional technique, all exposure light is obliquely applied on the mask. Since it can be made incident, a very good resolution pattern can be obtained. At this time, by reducing the area while keeping the apex of the triangular cross section of the pyramid prism 31, the light can be further dispersed at an angle in an oblique direction. In addition, an angle can be given in an oblique direction by increasing the angle of the cross section, but this angle is limited to an angle at which the four triangles do not intersect each other.
[0027]
Next, a second embodiment of the present invention will be described.
[0028]
FIG. 7 is a configuration diagram of a cycloid conical prism type modified illumination device showing a second embodiment of the present invention, and FIG. 8 is a diagram showing an optical path of the prism type modified illumination device.
[0029]
In this embodiment, a modified illumination using one type of prism shown in FIG. 7, which is one of the prism-type modified illuminations, will be described.
[0030]
This prism type modified illumination is characterized by a shape in which the bottom surfaces of the cycloid prism 41 of FIG. 7 and the conical prism 42 are bonded together.
[0031]
This is a method in which a mask pattern is exposed on a wafer (not shown) by being arranged between a fly-eye lens (not shown) and an exposure lens (not shown).
[0032]
When performing exposure, after the exposure light from the light source passes through the fly-eye lens (not shown), the exposure light from the light source 40 passes through the cycloid prism 41 of the prism-type deformed illumination, and is thus light in the four cross-sectional directions of the prism. Are dispersed and transmitted, and the light is dispersed and transmitted radially by passing through the conical prism 42. As a result, the exposure light becomes a plurality of light beams dispersed in an arbitrary direction. By obliquely incident on the mask, the light emitted from the mask is interfered with the two light beams and passes through the exposure lens (not shown) and passes through the wafer ( In this case, a good resolution pattern can be obtained.
[0033]
In this way, according to the second embodiment, the prism-type modified illumination device shown in FIGS. 7 and 8 is used to disperse light in an arbitrary direction, and unlike the prior art, all exposure light is placed on the mask. Since oblique incidence can be performed, a very good resolution pattern can be obtained. At this time, by reducing the area of the semicircular cross-sectional portion of the cycloid prism 41, it is possible to disperse the light with an angle in an oblique direction. In addition, an angle can be given in an oblique direction by increasing the angle of the cross section, but this angle is limited to an angle at which the four semicircles do not intersect each other. Further, unlike the first embodiment, it is not necessary to prepare two prisms, and further, no optical path is required between the prisms, so that the optical design can be easily made precise.
[0034]
In addition, prism-type modified illumination is applicable to various types of modified illumination as shown in FIGS. 1, 2, and 3, and the shape of the prism may be other shapes.
[0035]
In the present invention, by using a prism type modified illumination device characterized by a certain shape, the condition setting of the modified illumination can be optimized, so that an illumination system that can obtain a better exposure result than the conventional technique can be obtained. . Further, unlike conventional prisms, three light beams can be formed into two light beams, which can also be precisely controlled, so that good resolution characteristics can be obtained.
[0036]
The present invention is not limited to the above-described embodiments, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.
[0037]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0038]
(1) Since light can be dispersed in an arbitrary direction and all exposure light can be obliquely incident on the mask, unlike the prior art, a very good resolution pattern can be obtained. At this time, by reducing the area of the semicircular cross-sectional portion of the cycloid prism, it is possible to further disperse the light with an angle in an oblique direction.
[0039]
( 2 ) A very good resolution pattern can be obtained. At this time, by reducing the area of the semicircular cross-sectional portion of the cycloid prism, it is possible to further disperse the light with an angle in an oblique direction. Further, unlike the above (1), it is not necessary to prepare two prisms, and further, since no optical path is required between the prisms, the optical design can be easily made precise.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of prism-type modified illumination showing a first embodiment of the present invention.
FIG. 2 is a diagram showing an optical path of prism type modified illumination according to the first embodiment of the present invention.
FIG. 3 is a schematic diagram of prism-type modified illumination showing a first reference example of the present invention.
FIG. 4 is a diagram showing an optical path of prism-type modified illumination showing a first reference example of the present invention.
FIG. 5 is a schematic diagram of prism-type modified illumination showing a second reference example of the present invention.
FIG. 6 is a diagram showing an optical path of prism type modified illumination showing a second reference example of the present invention.
FIG. 7 is a configuration diagram of a cycloidal conical prism type modified illumination showing a second embodiment of the present invention.
FIG. 8 is a diagram showing an optical path of prism type modified illumination showing a second embodiment of the present invention.
FIG. 9 is a configuration diagram of a conventional optical stepper.
[Explanation of symbols]
10, 20, 30, 40 Light source 11, 41 A hemispherical prism having a cycloidal cross section (cycloidal prism)
12, 23, 32, 42 Conical prism (conical prism)
21 First dome-shaped prism 22 Second dome-shaped prism 31 Pyramid prism (pyramid prism)

Claims (2)

Bottom surface parallel to the cross-sectional shape, is divided by eight cycloid circular portion, and a hemispherical curved surface, and a hemispherical prism having a cross section of a cycloid shape, which is formed by a curved surface with two curvatures circular cone prism and arranged in parallel on the optical axis, respectively, by using this combination was placed in the middle of the fly-eye lens and the exposure lens, the hemispherical light incident on the prism dispersed in four directions, transmitted, Further , the prism-type modified illumination device, wherein the prism-shaped modified illumination device is configured such that after passing through the conical prism, it is radially dispersed and all exposure light is obliquely incident on the mask to expose the mask pattern on the wafer. In prismatic modified illumination apparatus according to claim 1, the upper surface Ri is Do and the hemispherical prism and the lower surface is convex downward with the cross-sectional surface of the cycloid shape, it consists of a said conical prism bottom surface facing up, the hemispherical A prism type modified illumination device , wherein a bottom surface of a prism and an upper surface of the conical prism are bonded together and formed integrally.

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