JP3415251B2 - Illumination optical system for projection exposure equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system used in a projection exposure apparatus.

[0002]

2. Description of the Related Art With the recent increase in the degree of integration of semiconductors, the resolution required for projection exposure apparatuses is increasing year by year.
In order to improve the resolution, various methods such as shortening the wavelength of the light source, adopting the phase shift method, adopting the modified illumination method, etc. are being researched and developed. Among them, the modified illumination method makes significant changes to the conventional device. It has the advantage of not being necessary.
As a typical example of the modified illumination method, when the light flux passes through the aperture stop of the illumination optical system, it is referred to as quadrupole illumination or four-point illumination in which the passage position of the light flux is limited to four positions separated from the optical axis. And a method called annular illumination in which the passing position of the light flux passing through the aperture stop of the illumination optical system is restricted to an annular shape concentric with the optical axis. It is known that the quadrupole illumination is particularly effective in improving the resolution and increasing the depth of focus for a pattern composed of vertical and horizontal lines. On the other hand, the annular illumination has the effect of improving the resolution and increasing the depth of focus by 4.
Although not as remarkable as the polar illumination, it has a feature that it does not depend on the direction of the reticle pattern.

As a conventional example of quadrupole illumination, for example, FIG.
And FIG. 43. In the conventional example shown in FIG. 42, an illumination light flux from a light source unit having an elliptic mirror 102, a mercury lamp 103, and a lens 104 is incident on a fly-eye lens 108, and an opening having four circular openings is provided immediately after the fly-eye lens. The illumination beam is divided into four by the diaphragm 109a. The conventional example shown in FIG. 43 is disclosed in Japanese Patent Laid-Open No. 4-225357, and the elliptical mirror 102, the mercury lamp 103 and the lens 1 are used.
The illumination light flux from the light source unit having 04 is divided into four by the optical fiber 121 branched into four.

On the other hand, conventional examples of annular illumination include those shown in FIGS. 44 and 45, for example. In the conventional example of FIG. 44, the elliptical mirror 102, the mercury lamp 103 and the lens 10 are used.
Fly-eye lens 1 for illuminating luminous flux from a light source unit having 4
The aperture stop 109b having a ring-shaped aperture provided immediately after the fly-eye lens is used to limit the illumination light flux to a ring-shaped state. Further, in the conventional example of FIG. 45, the illumination light flux from the light source unit having the elliptical mirror 102, the mercury lamp 103 and the lens 104 is reflected by the lens 104.
An axicon lens 122 provided immediately after is converted into an annular shape. In each of the conventional examples described above, the illumination light flux divided into four or the illumination light flux converted into the annular shape is converted into the condenser lens 110 and the reticle 1.
11 and reaches the wafer 113 via the imaging optical system 112.

[0005]

In the conventional example of FIG. 42 described above, since only the illumination light flux that can reach the aperture provided in the aperture stop 109a can be transmitted, the utilization efficiency of the light flux from the light source unit is improved. The illuminance is significantly reduced and the illuminance is significantly uneven. Further, in the conventional example of FIG. 43 described above, although the utilization efficiency of the light flux from the light source unit can be improved, a large number of optical fibers are required, which complicates the configuration, makes the manufacturing difficult, and increases the mechanical reliability. Sex is reduced. Further, in the conventional example of FIG. 44, since only the illumination light flux that can reach the aperture provided in the aperture stop 109b can be transmitted, the utilization efficiency of the light flux from the light source unit is significantly reduced. Further, in the conventional example of FIG. 45 described above, although the utilization efficiency of the light flux from the light source unit can be improved, an axicon lens which is difficult to manufacture is required, and therefore an increase in cost cannot be avoided.

The present invention has been made in view of the above problems, and provides an illumination optical system for a projection exposure apparatus which has a high utilization efficiency of light from a light source and a simplified structure which can be easily realized. The purpose is to do.

[0007]

To this end, the structure of claim 1 of the present invention comprises a light beam splitting optical system for splitting a light beam from a light source, and a light beam split by the light beam splitting optical system on a reticle. In the illumination optical system for a projection exposure apparatus, the first light diffusing optical unit has a diffraction grating pattern for separating the light beam from the light source into four, and The second diffractive optical means is provided at a position corresponding to four light beams generated by the first diffractive optical means, and has a diffractive grating pattern.

According to a second aspect of the present invention, in the above, the diffraction grating pattern of the first diffractive optical means is a linear grating pattern, and the boundary of the linear grating pattern is substantially cross-shaped. Are four linear grid patterns that are arranged in a line and have a substantially equal grid pitch,
It is characterized in that the lattice directions of the linear lattice patterns adjacent to each other are substantially orthogonal to each other.

Further, in the structure of claim 3 of the present invention, in the above, the first diffractive optical means is m ₁ , m ₂ , m.
_A first diffractive optical surface having a groove-shaped linear grating pattern in which the diffraction efficiencies of + m _1st-order diffracted light and −m _1st- order diffracted light are substantially equal when ₃ is an arbitrary natural number; In the optical axis direction, the area where the + m _1st-order diffracted light from the first diffractive optical surface is incident and the diffraction efficiencies of the + m _2nd-order diffracted light and the −m _2nd- order diffracted light become substantially equal. A first diffractive region having a groove cross-sectional shape and a linear grating pattern in a grating direction substantially orthogonal to the grating direction of the first diffractive optical surface and the -m _1st-order diffracted light by the first diffractive optical surface are incident. And a linear grating pattern in a grating direction substantially orthogonal to the grating direction of the first diffractive optical surface in a groove cross-sectional shape in which the diffraction efficiencies of the + m _third-order diffracted light and the −m _third- order diffracted light are substantially equal. Have Second comprising a second diffraction region
And two diffractive optical surfaces.

According to a fourth aspect of the present invention, in the above structure, the first diffractive optical means is a diffractive optical element in which substantially square regions having different depths are alternately arranged in a checkered pattern. It is characterized by having.

Further, according to a fifth aspect of the present invention, a luminous flux separation optical system for converting a luminous flux from a light source into an annular light flux, and a condenser for guiding the annular light flux converted by the luminous flux separation optical system onto a reticle. An illumination optical system for a projection exposure apparatus having an optical system, wherein the light beam splitting optical system comprises diffractive optical means having a concentric ring grating pattern.

According to a sixth aspect of the present invention, in the above configuration, the concentric ring grating pattern of the diffractive optical means has grating pitches substantially equal to each other, and the concentric ring grating pattern is emitted from the light source incident on the diffractive optical means. The cross-sectional shape of the groove is blazed with respect to the wavelength of the luminous flux of.

[0013] The configuration according to claim 7 of the present invention, in the above, the diffractive optical means, when the m ₁ and any natural number, the grating pitch of the concentric rings grid pattern with a substantially equal intervals + m _First-order diffracted light and -m ₁
It is characterized in that it has a diffractive optical element having a groove cross-sectional shape in which the diffraction efficiency of the second-order diffracted light is substantially equal. Further, the structure of claim 8 of the present invention is for a projection exposure apparatus having a light beam separating optical system for separating a light beam from a light source and a condenser optical system for guiding the light beam separated by the light beam separating optical system onto a reticle. In the illumination optical system, the light beam splitting optical system includes diffractive optical means having a linear grating pattern that splits the light beam from the light source into four, and the diffractive optical means includes m ₁ ,
a first diffractive optical surface having a linear grating pattern having a groove cross-sectional shape in which the diffraction efficiencies of + m _1st-order diffracted light and −m _1st- order diffracted light are substantially equal to each other when m ₂ and m ₃ are arbitrary natural numbers; Of the + m _2nd-order diffracted light and the −m _2nd- order diffracted light, which is arranged apart from the diffractive optical surface in the optical axis direction and into which the + m _1st-order diffracted light is incident. A first diffraction region having a groove cross-sectional shape with substantially the same and having a linear grating pattern in a grating direction substantially orthogonal to the grating direction of the first diffractive optical surface, and the -m ₁ by the first diffractive optical surface. In the region where the second diffracted light is incident, the groove cross-sectional shape is such that the diffraction efficiencies of the + m _third-order diffracted light and the −m _third- order diffracted light are substantially equal to each other, and the grating direction is substantially orthogonal to the grating direction of the first diffractive optical surface. Straight grid putter Characterized by comprising comprises two diffractive optical surface and second diffractive optical surface comprising a second diffraction area having. In addition, claim 9 of the present invention
In the above configuration, the diffraction grating patterns of the first diffractive optical means and the second diffractive optical means have a cross-sectional shape that is a blazed shape or a shape that approximates the blazed shape to a stepped shape.

[0014]

In the case of using the quadrupole illumination, the illumination light beam is divided into four beams, and each of them is made incident on the reticle at an inclined angle (in the prior art, a reflection member (mirror) and refraction are used to separate the illumination light beam). Members (prism) etc. are used). According to the structure of claim 1 of the present invention, the light beam from the light source is separated into four by the first diffractive optical means having the diffraction grating pattern provided in the light beam separation optical system. The light beams separated into the four light beams are respectively arranged at positions corresponding to the four light beams generated by the first diffractive optical means, and are incident on the second diffractive optical means having a diffraction grating pattern. And
The light flux emitted from the second diffractive optical means is guided onto the reticle by the condenser optical system. At this time, since the first and second diffractive optical means are used to separate the illumination light flux, the thickness required for the diffractive surface to exert a diffractive action when, for example, primary light is used as diffracted light. Since the wavelength is at most about the wavelength of the illumination optical system, compared to the conventional example in which the illumination light beam is divided by using a reflecting member, a refracting member, etc.
The illumination optical system can be reduced in size and weight.

According to the second aspect of the present invention,
When the light flux from the light source is incident on the linear grating pattern which is the diffraction grating pattern of the first diffractive optical means provided in the light beam splitting optical system, the linear grating pattern has four grating pitches with substantially equal intervals. Consists of a linear grid pattern,
Since the lattice directions of the linear lattice patterns adjacent to each other are substantially orthogonal to each other, the light flux from the light source is diffracted in the direction corresponding to the lattice direction of the incident linear lattice pattern, Four light beams are separated from the light beam from the light source. Therefore, since the first diffractive optical means can be realized by one diffractive optical surface, the configuration is simplified and the alignment is facilitated.

According to the structure of claim 3 of the present invention,
For example, in the case of m ₁ = m ₂ = m ₃ = 1, the light flux from the light source incident on the first diffractive optical surface is
The linear grating pattern separates the + 1st-order diffracted light, the -1st-order diffracted light, and the diffracted light of other orders, and at this time, the + 1st-order diffracted light and the -1st-order diffracted light have substantially the same intensity. The + 1st order diffracted light diffracted by the first diffractive optical surface is
+ 1st order diffracted light by the linear grating pattern formed on the second diffractive optical surface in a direction substantially orthogonal to the grating direction of the first diffractive optical surface after entering the first diffractive region of the diffractive optical surface of It is separated into the diffracted light of the next order and the diffracted light of other orders. Similarly, -1 diffracted by the first diffractive optical surface
The secondary diffracted light is incident on the second diffractive region of the second diffractive optical surface, and then, by the linear grating pattern formed on the second diffractive optical surface in a direction substantially orthogonal to the grating direction of the first diffractive optical surface. It is separated into + 1st-order diffracted light, -1st-order diffracted light, and diffracted light of other orders.

In this case, the + 1st-order diffracted light formed by the first diffractive optical surface is diffracted into the + 1st-order diffracted light and the -1st-order diffracted light in the second diffractive region and the first diffractive optical surface. -1st order diffracted light is +1 in the second diffraction area
A total of four light fluxes including the diffracted light of the first-order diffracted light and the one diffracted to the -1st-order diffracted light are formed and used as the illumination light flux. According to the structure of claim 3, since the diameter of the light flux does not change due to the diffractive optical surface, if the light flux having the same diameter is finally formed, the light flux is divided into wavefronts.
The diameter of the light beam incident on the first diffractive optical means can be made smaller than that of the above configuration. Therefore, the first diffractive optical means can be brought close to the light source, and the total length of the illumination optical system can be shortened.

According to the fourth aspect of the present invention,
The light beam from the light source is incident on the diffractive optical element provided in the first diffractive optical means of the light beam separating optical system, and the diffractive optical element is arranged in a checkerboard pattern in which substantially square regions having different depths are alternately arranged. Therefore, considering the X and Y directions shown in FIG. 40A, the incident light beam is diffracted into diffractable orders determined by the pitch and depth of the diffraction grating. Therefore, considering the whole, the light beam incident on the diffractive optical elements arranged in a checkerboard pattern in a substantially square region is diffracted to the positions of the grid points of the grid pattern as shown in FIG. 41. Of these luminous fluxes, four luminous fluxes which are usually high in intensity and arranged in a substantially square shape can be selected and used as illumination luminous fluxes.

On the other hand, in the case of using the annular illumination, an annular luminous flux is formed from the illumination luminous flux and is incident on the reticle at an inclined angle (in the prior art, the axial luminous flux is formed to form the annular luminous flux. Uses a lens, etc.). According to the configuration of claim 5 of the present invention, the light flux from the light source is converted into the annular light flux by the diffractive optical means having the concentric ring grating pattern provided in the light beam separation optical system, and these annular light fluxes are respectively condensed. It is guided onto the reticle by the optical system. At this time, a concentric ring grating pattern that is easier to manufacture than an axicon lens or the like can be used to form the annular light flux.

According to the structure of claim 6 of the present invention,
When the light beam from the light source enters the concentric ring grating pattern, the groove cross-sectional shape of the concentric ring grating pattern is blazed with respect to the light beam from the light source, so that the loss due to the concentric ring grating pattern does not occur. It is possible to convert the luminous flux from the light into a ring-shaped luminous flux with high efficiency.

According to the structure of claim 7 of the present invention,
The luminous flux from the light source is diffracted into diffractive orders determined by the grating pitch of the concentric ring grating pattern and the groove depth. Therefore, a plurality of annular light fluxes corresponding to the respective orders are formed, and an appropriate one is used as the illumination light flux. At that time, for example, if m ₁ = 1
Since the diffraction efficiencies of the + m _1st- order light and the −m _1st- order light are substantially equal to each other, it is possible to form a uniform illumination light flux. Further, if a light flux having the same annular zone width is finally formed, the diameter of the light flux can be reduced to about half that of the structure of claim 5. Therefore, the diffractive optical means can be brought close to the light source, and the total length of the illumination optical system can be shortened. Further, according to the structure of claim 8 of the present invention, the light flux from the light source is split into four by the diffractive optical means having the linear grating pattern provided in the light flux splitting optical system, and the light flux split into these four light fluxes. Are each guided onto the reticle by the condenser optics. At this time, since the diffractive optical means is used to separate the illumination light flux, the thickness required for the diffractive surface to exhibit a diffractive action when the first-order light is used as the diffracted light is at most an illumination optical system. Since the wavelength is about the same wavelength, it is possible to reduce the size and weight of the illumination optical system, as compared with the conventional example in which the illumination light flux is divided by using a reflecting member, a refracting member, or the like. Further, in the structure of claim 8 of the present invention, since the diameter of the light flux does not change due to the diffractive optical surface, if the light flux of the same diameter is finally formed, the light flux is wavefront-divided. The diameter of the light beam incident on the diffractive optical means can be made smaller than that of the configuration. Therefore, the diffractive optical means can be brought close to the light source, and the total length of the illumination optical system can be shortened. According to the configuration of claim 9 of the present invention, the diffraction grating patterns of the first diffractive optical means and the second diffractive optical means have a blazed cross-sectional shape or a blazed shape approximated to a stepped shape. Since it has a shape and uses a blazed diffractive optical element for the light beam splitting optical system, it is possible to efficiently use the illumination light generated by the light source, which leads to an effect such as an improvement in throughput. Become.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of a first embodiment of an illumination optical system for a projection exposure apparatus of the present invention. Reference numeral 1 in the figure denotes a light source unit, which includes an elliptical mirror 2, a mercury lamp 3 and a lens 4.
Further, reference numeral 51 in the figure denotes a light beam separating section, which is composed of transmissive diffractive optical elements 61 and 71.

The diffractive optical element 61 is made of, for example, quartz,
As shown in the plan view of FIG. 2A, the side view of FIG. 2B, and the detailed view of part A of FIG. Equally spaced linear diffraction grating 6
1a is formed, and the directions of the lattice patterns of the respective areas are orthogonal to each other between the adjacent areas. The cross-sectional shape of the linear diffraction grating 61a is blazed with respect to the first-order diffracted light. On the other hand, the diffractive optical element 71 is made of, for example, quartz, and as shown in FIG. 3, the linear diffraction gratings 71a at equal intervals are formed in four separated regions corresponding to the four regions of the linear diffraction grating 61a. ing. Linear diffraction grating 7
The cross-sectional shape of 1a is blazed with respect to the primary light, but the direction of blazing is opposite to that of the linear diffraction grating 61a. The other surface of the diffractive optical gratings 61 and 71 on which the linear diffraction grating is not formed is coated with an antireflection film (not shown) for the light of the light source.

In the figure, reference numeral 8 is a fly-eye lens, which is decentered from the optical axis according to the light beam separated by the light beam separating section 51.
It is placed in the place. Immediately after the fly-eye lens 8, an aperture stop 9 having four circular apertures is arranged. Further, in the figure, 10 is a condenser lens, 11 is a reticle, and an imaging projection system 12 is arranged between the reticle 11 and the wafer 13. When actually constructing the illumination optical system using the first embodiment of the present invention, other optical elements (not shown) (wavelength selection filter, etc.) are required, which are not disclosed in the prior art. The description is omitted because it is the same as that described above.

Next, the flow of the illumination luminous flux of the first embodiment will be described with reference to FIGS. The substantially parallel light flux formed by the light source unit 1 is incident on the diffractive optical element 61 (at this time, when the shape of the diffraction grating region of the diffractive optical element 61 is rectangular as shown in FIG. A stop (not shown) corresponding to the shape of the region may be installed closer to the light source section than the diffractive optical element 61). The illumination light beam 14 is separated (wavefront divided) into four illumination light beams 15 by the diffractive optical element 61, as shown in FIG. 4, which is a perspective view near the diffractive optical elements 61 and 71. The wavefront is divided in this way
A linear diffraction grating 61a is formed in the diffractive optical element 61 so that the grating direction or the blazed direction is different from each other.
This is because the light flux is diffracted at a desired angle for each of the incident areas.

The illumination light beam 15 is converted into a direction substantially parallel to the optical axis by the diffractive optical element 71, and then enters the fly-eye lens 8. At this time, the linear diffraction grating 61
Since the sectional shapes of a and 71a are blazed, a diffraction efficiency of almost 100% can be obtained, so that the utilization efficiency of the light from the light source is improved. Since the exit-side end surface of the fly-eye lens 8 has a function of a secondary light source, four aperture stops 9 having circular openings are arranged at that position. The shape of the four openings can be square according to the shape of the separated light flux, but may be circular. In the case of a circular shape, a part of the light beam is cut off, but the utilization efficiency of the light source is much higher than that in the case of simply providing such an aperture stop without using the technique of the present invention. Become. The illumination light fluxes that have passed through the four apertures of the aperture stop 9 each illuminate the reticle 11 with four poles through the condenser lens 10, and the image of the reticle 11 is formed on the wafer 13 by the image forming optical system 12. To be done.

By the way, linear diffraction grating 61a, the grating pitch p of 71a, ₁ the incident angle theta, ₂ the emission angle theta, the diffraction order m, and the wavelength of light and _{λ, p (sinθ 1 -sinθ 2} ) = Mλ. However, when the linear diffraction gratings 61a and 71a have different orders, the grating pitches of the linear diffraction gratings 61a and 71a do not necessarily have to be the same. Further, the grating pitches do not necessarily have to be evenly spaced, and it is only necessary to take out the parallel light flux divided into four by the combination of the diffractive optical elements 61 and 71, so that the diffractive optical elements 61 and 71 have an appropriate pitch distribution. It may be added, but in practice, it is easier to manufacture if the intervals are equal.

As a method of manufacturing the diffractive optical elements 61 and 71, a conventionally known method, for example, blazing by oblique ion beam irradiation and four identical partial elements corresponding to each of the four regions are performed. A method of manufacturing and combining them can be used. On the other hand, as a method for producing one element from the beginning, the lattice pattern shown in FIG. 2A is divided into four lattice patterns 61b as shown in FIG. Method, or as disclosed in Japanese Patent Laid-Open No. 2-1109, prepare n (n is a natural number) masks corresponding to the lattice pattern of FIG.
It is also possible to employ a method of approximating the blazed shape as a stepped shape of 2 ⁿ steps by repeating the etching process once. In this case, if the blazed shape is approximated by a staircase shape, whether or not the diffraction efficiency is deteriorated becomes a problem. For example, when n = 4, a 16-step staircase shape is obtained.
Since a diffraction efficiency of 9% is obtained, there is no practical problem.

As described above, in this first embodiment, since the blazed diffractive optical element is used in the light beam splitting optical system, the illumination light generated by the light source can be efficiently used. This brings about an effect such as an improvement in throughput.

In the above, the diffractive optical element 6 is used.
2 (a) to (c) and FIG. 3 are shown as examples of arrangement of the linear diffraction gratings 61a and 71a on the Nos. 1 and 71, but the present invention is not limited to these and various modifications or changes may be made. Can be added. For example, as shown in FIG. 6A, the linear diffraction grating 61c, which is divided into four substantially squares on the diffractive optical element 61, is arranged so that the grating direction is substantially perpendicular or substantially parallel to the boundary. Figure 6
A linear diffraction grating 71c is arranged on the diffractive optical element 71 as shown in FIG. 7B, or a linear diffraction grating divided into four approximately isosceles triangles on the diffractive optical element 61 as shown in FIG. 7A. The grid direction of 61d is approximately 45 ° to the boundary
Alternatively, a linear diffraction grating 71d may be arranged on the diffractive optical element 71 as shown in FIG. 7B. Alternatively, as shown in FIG. 8, the diffractive optical elements 61 and 71 are integrally provided with two diffractive surfaces facing each other, and each diffractive surface has a linear diffraction grating 61a shown in FIG.
Even if 71a is formed, the same effect as the first embodiment can be obtained. Further, although the diffraction order of the linear diffraction gratings 61a and 71a is set to the first order, other orders may be used. Furthermore, although the mercury lamp 3 is used as the light source in the above, other light sources such as an excimer laser can be used. Furthermore, it is needless to say that instead of quartz as the material of the diffractive optical gratings 61 and 71, other optical materials having a high transmittance can be used.

FIG. 9 is a view showing the arrangement of the second embodiment of the illumination optical system for a projection exposure apparatus of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and their description is omitted. 52 in the figure
Is a light beam separating section, and is composed of diffractive optical elements 62 and 72. In the first embodiment, the diffractive optical element 61 having a small area is arranged on the light source 1 side and the diffractive optical element 71 having a large area is arranged on the fly eye lens 8 side. The large diffractive optical element 72 is attached to the light source unit 1.
It is arranged so that the lens 4 is arranged between the diffractive optical elements 72 and 62.

As shown in the plan view of FIG. 10A, the side view of FIG. 10B, and the detailed view of the portion B in FIG. 10C, the diffractive optical element 62 has a boundary having a substantially cross shape on one surface thereof. Arranged 4
A reflection type linear diffraction grating 62a is formed in one area, and the directions of the grating patterns in the areas are orthogonal to each other. The cross-sectional shape of the linear diffraction grating 62a is blazed for a specific reflection diffraction order, for example, + 1st order. On the other hand, the diffractive optical element 72 is shown in FIG.
As shown in FIG. 1, the linear diffraction grating 62a on one surface thereof is
Reflective linear diffraction grating 72a is formed in each of the four separated regions corresponding to the four regions, and the sectional shape of the linear diffraction grating 72a has a specific reflection diffraction order, for example, −
Blazed for the first order. Further, a region 72b near the center of the diffractive optical element 72 is hollowed out to be wider than the passing range of the illumination light beam at the position of the diffractive optical element 72.

Next, the flow of the illumination luminous flux of the second embodiment will be described with reference to FIG. The substantially parallel illumination light flux 14 formed by the light source unit 1 is reflected by the diffractive optical element 6 as shown in FIG. 12 which is a perspective view of the vicinity of the diffractive optical elements 72 and 62.
It is incident on 2. During this time, the light flux emitted from the mercury lamp 3 penetrates the region 72b of the diffractive optical element 72. After that, the illumination light beam 14 is reflected and diffracted by the linear diffraction grating 62 a of the diffractive optical element 62 in different directions for each incident region, and is separated into four light beams 15. After that, the light beam 15 is converted into a direction substantially parallel to the optical axis by the linear diffraction grating 72a of the diffractive optical element 72, and four separated light beams are formed. The light flux divided into these four rays enters the fly-eye lens 8. For convenience of explanation of the drawings, some of the light fluxes 14 and 15 are omitted.

The linear diffraction grating 62a is formed on a quartz substrate by using, for example, the method described in the first embodiment, and metal such as aluminum is vapor-deposited in order to improve the reflectance. Alternatively, a linear diffraction grating may be formed by vapor-depositing metal on substantially parallel flat plates and directly processing the metal with a ruling engine. Further, metal can be used as the material of the diffractive optical elements 62 and 72, and in that case, it is only necessary to form the linear diffraction grating by the ruling engine.

In the second embodiment, the light beam splitting optical system has two components.
Since the optical path is folded back by using one reflection type diffraction grating, the length of the projection exposure apparatus in the optical axis direction can be shortened.

In the second embodiment, the lens 4
Instead of providing the diffractive optical element 72 as shown in FIG.
A transmission type diffraction grating 4a having the same function as that of the lens 4 is provided in the central portion of the
And the lens 4 can be integrated with the diffractive optical element 72. In that case, by configuring the illumination optical system as shown in FIG. 14, the number of parts can be reduced and the alignment can be facilitated. In the case of the configuration of FIG. 14, since the transmission type diffraction grating 4a is formed, the material of the diffractive optical element 72 is preferably an optical material such as quartz. Further, as in the first embodiment, a light source other than the mercury lamp 3 such as an excimer laser is used as the light source, or four circular apertures are provided at the position where the aperture stop is to be arranged (immediately after the fly-eye lens 8). Aperture stop 9
Can be placed.

FIG. 15 is a diagram showing the structure of a third embodiment of the illumination optical system for a projection exposure apparatus of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. 5 in the figure
Reference numeral 3 denotes a light beam separating section, which includes diffractive optical elements 63 and 73 and a light beam deflecting member 16. The diffractive optical element 63 is made of, for example, quartz, and as shown in the plan view of FIG. 16A and the side view of FIG. Is a duty ratio of 1: 1
And has a depth t ₁ optimized so that the total value of the diffraction efficiencies of the + _{1st order} diffracted light and the −1st order diffracted light is maximized. At this time, the depth t ₁ is t ₁ =
λ / {2 (n ₁ −1)}, and the + 1st order diffracted light and −
The total value of the diffraction efficiency of the first-order diffracted light is about 81%. Where λ is the wavelength of the light source and n ₁ is the refractive index of the substrate of the diffractive optical element 63.

On the other hand, the diffractive optical element 73 is made of, for example, quartz, and as shown in the plan view of FIG. 17A and the side view of FIG. 17B, one surface thereof is separated by a linear diffraction grating 63a. The linear diffraction gratings 73a and 73b are formed in the two separated regions corresponding to the light flux, and the linear diffraction grating 73
The grating patterns a and 73b are formed in a direction orthogonal to the grating direction of the linear diffraction grating 63a when viewed from the optical axis direction. At this time, the cross-sectional shape of each groove of the linear diffraction gratings 73a and 73b is a rectangular shape with a duty ratio of 1: 1 like the linear diffraction grating 63a, and the depth t ₂ thereof is + 1st-order diffracted light and -1st-order diffracted light. The diffraction efficiencies of the folded light are optimized so as to be equal to each other and maximized. When the mercury lamp 3 is used as the light source, the linear diffraction gratings 63a, 73a, and 73b have a square area whose one side is longer than the diameter of the light flux because the cross-sectional shape of the light flux emitted from the light source unit 1 is circular. It may be formed in. It is needless to say that a circular region may be used instead of the square region, but a square region is generally easier to manufacture.

The light beam deflecting member 16 is made of, for example, quartz,
As shown in FIG. 18, one surface thereof is divided into four regions corresponding to the + 1st-order light and the -1st-order light from the linear diffraction gratings 73a and 73b of the diffractive optical element 73, which are separated from each other. The linear diffraction gratings 16a are formed at intervals, and the cross-sectional shape of the linear diffraction grating 16a is blazed for a specific diffraction order light, for example, first-order light.

Next, the flow of the illumination luminous flux of the third embodiment will be described with reference to FIG. The light beam incident on the diffractive optical element 63 is +1 by the linear diffraction grating 63a as shown in FIG. 19 which is a perspective view in the vicinity of the diffractive optical elements 63 and 73.
The light is diffracted into the second-order light 14a, the −1st-order light 14b, and other orders of diffracted light. At this time, as described above, the + 1st order light,
Since the depth t ₁ of the linear diffraction grating 63a is optimized for the −1st order light, about 40.5% of the incident light flux is + 1st order light and about 40.5% is −1st order light. In 14b, the rest (about 19%) is split into other order lights. The + 1st order light 14a and the −1st order light 14b are incident on the linear diffraction gratings 73a and 73b of the diffractive optical element 73, respectively.

The light beam incident on the linear diffraction grating 73a is
The light flux diffracted into the + 1st order light 15a, the −1st order light 15b and other orders of diffracted light and similarly incident on the linear diffraction grating 73b has a + 1st order light 15c, a −1st order light 15d and other orders. Diffracted into diffracted light. These four light beams 15a, 15b, 15c, 15d are incident on the light beam deflecting member 16, are converted into light beams substantially parallel to the optical axis by the linear diffraction grating 16a, and are then incident on the fly-eye lens 8.

In the third embodiment, since a diffractive optical element having a rectangular cross section with a duty ratio of 1: 1 is used in the light beam splitting optical system, there is no need for blazing.
It has an advantage that it can be easily manufactured. Therefore, as a method of manufacturing the diffractive optical elements 63 and 73, a conventionally known method, for example, a method of manufacturing a rectangular shape by a photolithography technique and a dry etching technique can be used. Further, although a loss occurs due to a light beam other than the + 1st order light and the −1st order light diffracted by the diffractive optical elements 63 and 73, the light loss due to each diffraction grating is about 19%. Also, a utilization efficiency of about 65% can be obtained for the light beam incident on the diffractive optical element 63. This utilization efficiency is much higher than in the case where the aperture stop is simply provided with a diaphragm having four apertures without using the technique of the present invention. Further, since the diameter of the light flux does not change due to the diffractive optical element 63, if four light fluxes of the same diameter are finally formed, the illumination light flux is divided into four wavefronts in the first embodiment. In comparison, the diameter of the light flux 14 can be halved, and the lens 4 can be brought closer to the light source. As a result, the total length of the illumination optical system is shortened.

Although the blazed diffractive optical element is used as the light beam deflecting member in the third embodiment, the same effect can be obtained by using other members such as four triangular prisms and mirrors. it can. However, the use of the diffractive optical element as shown in FIG. 18 makes it possible to integrally manufacture the light beam deflecting member, so that the alignment is easy and the cost is low. Further, the groove cross-sectional shape of the diffraction grating that equalizes the diffraction efficiency of the + 1st-order diffracted light and the -1st-order diffracted light is not limited to the rectangular shape with the duty ratio of 1: 1 described above, and should be a symmetrical trapezoidal shape or a sine wave shape. You can also However, +1
The maximum value of the diffraction efficiencies of the first-order diffracted light and the −1st-order diffracted light is maximum in the case of the rectangular shape of the present embodiment.

Further, the diffractive optical elements 63 and 73 are shown in FIG.
It is also possible to combine them into one diffractive optical element as shown in FIG. In that case, the linear diffraction grating 63 is provided on one surface.
a is formed, and a linear diffraction grating 73c is formed on the other surface in a direction orthogonal to the linear diffraction grating 63a.
The cross-sectional shape of 3a and 73c is a rectangular shape with a duty ratio of 1: 1 and the depth thereof is optimized so that the total value of the diffraction efficiency of the + 1st order diffracted light and the −1st order diffracted light is maximized.
At this time, since the light beam can be separated by one diffractive optical element, there is an advantage that the configuration is simplified and the alignment is facilitated.

FIG. 21 is a diagram showing the structure of a fourth embodiment of the illumination optical system for a projection exposure apparatus of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. 5 in the figure
Reference numeral 4 denotes a light beam separation unit, which includes transmissive diffractive optical elements 64 and 74. The diffractive optical element 64 is made of, for example, quartz, and as shown in the plan view of FIG. 22A and the side view of FIG. 22B, concentric ring pattern diffraction gratings 64a are formed on one surface thereof at equal intervals and at equal pitches. Has been done. Diffraction grating 64
The cross-sectional shape of a is blazed with respect to the primary light.
On the other hand, the diffractive optical element 74 is made of, for example, quartz, and
As shown in the plan view of (a) and the side view of (b), the diffraction pattern has concentric ring pattern diffraction gratings 74a at equal intervals in annular zones corresponding to the light flux from the diffraction grating 64a. Are formed. The cross-sectional shape of the diffraction grating 74a is blazed with respect to the primary light. However, the blazing direction is opposite to that of the diffraction grating 64a. The fly-eye lens 8 is arranged in an annular shape so as to correspond to the luminous flux formed by the luminous flux separating section 54. Also,
As shown in FIG. 24, the aperture stop 9 has a ring-shaped aperture corresponding to the fly-eye lens 8.

As a method for producing a blazed substantially concentric ring pattern diffraction grating such as the diffractive optical elements 64 and 74, a conventionally known method, for example, Japanese Laid-Open Patent Publication No. 2-1109 or JP-B-63-63. The method disclosed in 21171 can be used.

Next, the flow of the illumination luminous flux of the fourth embodiment will be described with reference to FIG. A substantially parallel illumination light flux 14 is emitted from the light source unit 1 and is incident on the diffractive optical element 64.
The illumination light beam 14 incident on the diffractive optical element 64 is converted into an annular illumination light beam 15 by the diffraction grating 64a of the diffractive optical element 64, as shown in FIG. 25 which is a perspective view of the vicinity of the diffractive optical elements 64 and 74. The annular illumination light beam 15 is converted into a direction substantially parallel to the optical axis by the diffractive optical element 74, and then is incident on the Philaye lens 8. At this time, since the end surface of the fly-eye lens 8 on the exit side functions as a secondary light source, the light flux that has passed through the ring-shaped aperture of the aperture stop 9 arranged immediately after that passes through the condenser lens 10 and the reticle 11. To illuminate the zone.

In the fourth embodiment, since the blazed diffractive optical element is used in the light beam splitting optical system, the illumination light generated by the light source can be used efficiently.
This results in improved throughput. Also,
Since the diffractive optical element of the light beam splitting portion can be easily manufactured and only two flat plates need to be arranged as the diffractive optical element, the configuration is simplified and the alignment is facilitated as compared with the conventional example.

FIG. 26 is a view showing the arrangement of the fifth embodiment of the illumination optical system for a projection exposure apparatus of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and their description is omitted. 5 in the figure
Reference numeral 5 denotes a light beam separation unit, which includes transmissive diffractive optical elements 65 and 75. As shown in the plan view of FIG. 27A and the side view of FIG. 27B, the diffractive optical element 65 has, on one surface thereof, a concentric ring pattern diffraction grating 65 at equal intervals and pitches.
a is formed. The cross-sectional shape of the diffraction grating 64a is a rectangular shape with a duty ratio of 1: 1 and its depth t ₃
Are optimized so that the diffraction efficiencies of the + 1st-order light and the -1st-order light are equal and maximized. At this time, t ₃ = λ /
The fact that {2 (n-1)} is obtained is the same as in the third embodiment. On the other hand, on the surface of the diffractive optical element 75, FIG.
Of the diffraction grating 65 as shown in the plan view of FIG.
Concentric ring pattern diffraction gratings 75a are formed at equal intervals and pitches in a ring-shaped region corresponding to the light flux from a. The cross-sectional shape of the diffraction grating 75a has a specific diffraction order light,
For example, it is blazed for the primary light.

Next, the flow of the illumination luminous flux of the fifth embodiment will be described with reference to FIG. First, for simplicity of explanation,
The light flux 14 from the light source unit 1, which is considered in the plane including the optical axis, is incident on the diffractive optical element 65. At this time,
Although the diffraction grating 65a of the diffractive optical element 65 has a concentric pattern, it can be said that it is almost equivalent to a linear diffraction grating in a region minute in the angular direction. Therefore, the light beam incident on the diffractive optical element 65 is +1 by the diffraction grating 65a.
The light is diffracted into second-order light, −1st-order light and other order lights. As described above, since the depth t ₃ of the diffraction grating 65a is optimized for the + 1st order light and the −1st order light, about 40.5% of the incident luminous flux is about the + 1st order light and about 40. 5% is separated into -1st-order light, and the rest (about 19%) is separated into other-order light. The + 1st-order light and the -1st-order light are incident on the diffraction grating 75a of the diffractive optical element 75 and are converted into a direction substantially parallel to the optical axis.

Next, the whole will be considered. Considering the minute area in the angle direction as described above, as shown in FIG. 29, which is a perspective view of the vicinity of the diffractive optical elements 65 and 75, the light flux incident on the diffraction grating 65a is + 1st order light and −1st order light. It will be separated into light. Therefore, if this idea is applied to the entire circumference, it will be understood that the light beam 14 incident on the diffractive optical element 65 is converted into the annular light beam 15 by the diffraction grating 65a. The converted light flux 15 is incident on the diffractive optical element 75, and its traveling direction is converted by the diffraction grating 75a in the form of a ring. The subsequent flow of the luminous flux is the same as that in the fourth embodiment, and the description thereof will be omitted.

The fifth embodiment uses the diffractive optical element having a rectangular shape with a duty ratio of 1: 1 in the light beam splitting optical system, and therefore has the advantage of being easy to manufacture. Further, if the light flux having the same annular zone width is finally formed, the diameter of the light flux may be about half of that in the fourth embodiment.
The lens 4 can be brought close to the light source, and the total length of the illumination optical system can be shortened.

FIG. 30 is a diagram showing the structure of the sixth embodiment of the illumination optical system for a projection exposure apparatus of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. 5 in the figure
Reference numeral 6 denotes a light beam separation unit, which includes transmissive diffractive optical elements 66 and 76. In the fourth and fifth embodiments, the diffractive optical element having a small area is arranged on the light source section 1 side and the diffractive optical element having a large area is arranged on the fly eye lens 8 side. Diffractive optical element 76 with large
Is arranged on the light source section 1 side, and the lens 4 is arranged between the diffractive optical elements 76 and 66.

As shown in the plan view of FIG. 31A and the side view of FIG. 31B, the diffractive optical element 66 has concentric ring pattern diffraction gratings 66a formed on one surface thereof at equal intervals and pitches. The cross-sectional shape is blazed for a specific reflected diffraction order light, for example, + 1st order light. On the other hand, the diffractive optical element 76 is made of, for example, quartz, and as shown in the plan view of FIG. 32 (a) and the side view of FIG. 32 (b), the diffraction grating 76a is concentrically formed in the ring-shaped region on one surface thereof. Has been formed. The cross-sectional shape of the diffraction grating 76a is blazed for a specific reflected diffraction order light, for example, -1st order light. Further, the area 76b near the center of the diffractive optical element 76 is hollowed out to be wider than the passing range of the illumination light beam at the position of the diffractive optical element 76.

Next, the flow of the illumination luminous flux of the sixth embodiment will be described with reference to FIG. A substantially parallel illumination light flux 14 is formed by the light source unit 1 and is incident on the diffractive optical element 66. Meanwhile, the light flux emitted from the mercury lamp 3 penetrates the area 76b of the diffractive optical element 76. Diffractive optical element 66
The illumination light flux 14 incident on the diffractive optical elements 66, 76
As shown in FIG. 33, which is a perspective view of the vicinity of, the light is reflected and diffracted by the diffraction grating 66a of the diffractive optical element 66 and converted into the annular illumination light beam 15. After that, the annular illumination luminous flux 15 is
After being reflected and diffracted by the diffraction grating 76 a of the diffractive optical element 76 and converted into a direction substantially parallel to the optical axis, the light is incident on the Philaye lens 8. The subsequent flow of the luminous flux is the same as that in the fourth embodiment, and the description thereof will be omitted.

By the way, in the sixth embodiment, the optical system can be changed as shown in FIG. In this case, the light beam splitting unit is changed to a light beam splitting unit 156 including reflective diffractive optical elements 166 and 167. Diffractive optical element 166
As shown in the plan view of FIG. 35 (a) and the side view of FIG. 35 (b), concentric ring pattern diffraction gratings 166a are formed on one surface thereof at equal intervals and pitches, and the sectional shape thereof has a duty ratio of 1 : 1 has a rectangular shape and its depth t ₄
Are optimized so that the diffraction efficiencies of the + 1st-order reflected diffracted light and the -1st-order reflected diffracted light are equal and maximum.
At this time, t ₄ = λ / 4. However, λ is the wavelength of the light source. On the other hand, the diffractive optical element 176 is shown in FIG.
As shown in the plan view and the side view of (b), ring pattern diffraction gratings 176a are formed concentrically at equal intervals and in a ring-shaped region on one surface thereof, and the cross-sectional shape has a specific reflection diffraction order. It is blazed with respect to light, for example, primary light. Further, a region 176b near the center of the diffractive optical element 176 is coated with an antireflection film (not shown) for the wavelength of the light source.

In the case of the configuration shown in FIG. 34, the flow of the illumination luminous flux is as follows. That is, the illumination light flux 14 that is incident on the diffractive optical element 166 in the same manner as described above is reflected and diffracted by the diffraction grating 166a of the diffractive optical element 166, and is the annular illumination light flux by the + 1st-order light and the -1st-order light that are reflected and diffracted. 15 is formed. The operation of the diffraction grating 166a in this case is basically the same as that of the fifth embodiment except the difference between the transmission type and the reflection type. After that, the annular illumination light beam 15 enters the diffractive optical element 176 and is reflected and diffracted. The reflected and diffracted annular illumination light beam 15 is converted into substantially parallel to the optical axis and is incident on the fly-eye lens 8. The subsequent flow of the luminous flux is the same as that in the fourth embodiment, and the description thereof will be omitted.

In the sixth embodiment, the light beam splitting optical system has two elements.
Since the optical path is folded back by using one reflective diffractive optical element, the length of the projection exposure apparatus in the optical axis direction can be shortened.

In the sixth embodiment, the lens 4
Instead of providing the diffractive optical element 76 as shown in FIG.
A transmission type diffraction grating 4a having the same function as that of the lens 4 is provided in the central portion of the
And the lens 4 can be integrated with the diffractive optical element 72. In that case, the configuration of the illumination optical system is as shown in FIG. 38, and the number of parts can be reduced and the alignment is facilitated.

FIG. 39 is a diagram showing the structure of a seventh embodiment of the illumination optical system for a projection exposure apparatus of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. 5 in the figure
Reference numeral 7 denotes a light beam separating section, which includes a transmission type diffractive optical element 67 and a light beam deflecting member 16. The diffractive optical element 67 is made of, for example, quartz, and has a plan view of FIG.
As shown in the side view of (c), a diffraction grating 67a is formed on one surface thereof. In the diffraction grating 67a, a square portion shaded in FIG. 40 is higher than the other square portions by a height t _S in a large number of square regions partitioned by straight lines that are vertically and horizontally equidistant like graph paper. It has a structure. When viewed in a direction parallel to straight lines extending at equal intervals in the vertical and horizontal directions, its sectional shape is a rectangular shape with a duty ratio of 1: 1 and its depth t _S is + 1st order diffracted light and −
It is optimized so that the total value of the diffraction efficiencies of the first-order diffracted light is maximized.

The light beam deflecting member 16 is made of, for example, quartz,
As shown in FIG. 18 described above, one of the surfaces is
The linear diffraction gratings 16a at equal intervals are formed in four mutually separated regions corresponding to the + 1st order light and the -1st order light from the diffractive optical element 67, and the cross-sectional shape of the linear diffraction grating 16a is specified. Is blazed with respect to the diffraction order light of, for example, the first-order light.

Next, the flow of the illumination luminous flux of the seventh embodiment will be described. The light beam incident on the diffractive optical element 67 is diffracted by the diffraction grating 67a, and considering the x direction in FIG. 40A, it is separated into + 1st order light, −1st order light and other order lights, and also in the y direction. Similarly, + 1st order light, -1
It is split into second and other orders. Of these,
A total of four luminous fluxes of + 1st-order light and -1st-order light in both x and y directions 1
5 are respectively incident on the four linear diffraction gratings 16 a formed on the light beam deflecting member 16. The light beam 15 incident on the linear diffraction grating 16a is converted into a direction substantially parallel to the optical axis.

In the seventh embodiment, since a diffractive optical element having a rectangular cross section with a duty ratio of 1: 1 is used in the light beam splitting optical system, there is no need for blazing.
It has an advantage that it can be easily manufactured. Therefore, as a method of manufacturing the diffractive optical element 67, a conventionally known method, for example, a method of manufacturing a rectangular shape by a photolithography technique and a dry etching technique can be used. Further, since the diameter of the light beam is not changed by the diffractive optical element 67, if the final four light beams having the same diameter are formed, the illumination light beam is divided into four wavefronts in the first embodiment. In comparison, the diameter of the light flux 14 can be halved, and the lens 4 can be brought closer to the light source. As a result, the total length of the illumination optical system is shortened. In addition, in the seventh embodiment, since the two diffractive surfaces are combined into one as a result, a comparison with the third embodiment using the + 1st order light and the −1st order light as in the above is made. When manufacturing a diffractive optical element, there is an advantage that the manufacturing process is shortened.

Although the blazed diffractive optical element is used as the light beam deflecting member in the seventh embodiment, the same effect can be obtained by using other members such as four triangular prisms and mirrors. it can. However, the use of the diffractive optical element as shown in FIG. 18 makes it possible to integrally manufacture the light beam deflecting member, so that the alignment is easy and the cost is low.

[0065]

As described above, according to the present invention, in order to separate the illumination luminous flux into four or convert it into an annular shape,
Since the diffractive optical element is used, the structure is simplified and the mechanical reliability is improved. Further, since a known method can be used for manufacturing the diffraction grating, it is easy to realize. Further, it has an advantage that the illumination light flux can be used with high efficiency and the utilization efficiency of the light source light is increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of an illumination optical system for a projection exposure apparatus of the present invention.

2 (a), (b), and (c) are a plan view, a side view, and a detailed view of a portion A showing a diffractive optical element 61, respectively.

3A and 3B are a plan view and a side view showing a diffractive optical element 71.

FIG. 4 is a perspective view of the vicinity of diffractive optical elements 61 and 71.

FIG. 5 is a diagram for explaining a method of manufacturing the diffractive optical elements 61 and 71.

6A and 6B are diagrams showing another configuration example of the diffractive optical elements 61 and 71.

7A and 7B are diagrams showing another configuration example of the diffractive optical elements 61 and 71.

FIG. 8 is a diagram showing another configuration example of the diffractive optical elements 61 and 71.

FIG. 9 is a diagram showing a configuration of a second example of the illumination optical system for the projection exposure apparatus of the present invention.

10A, 10B, and 10C are a plan view, a side view, and a detailed view of a B part, respectively, showing a diffractive optical element 62.

FIG. 11 is a plan view showing a diffractive optical element 72.

FIG. 12 is a perspective view of the vicinity of diffractive optical elements 62 and 72.

FIG. 13 is a diagram showing another configuration example of the diffractive optical element 72.

14 is a diagram showing a configuration of an illumination optical system for a projection exposure apparatus corresponding to FIG.

FIG. 15 is a diagram showing the configuration of a third example of the illumination optical system for a projection exposure apparatus of the present invention.

16A and 16B are a plan view and a side view showing a diffractive optical element 63, respectively.

17A and 17B are a plan view and a side view showing a diffractive optical element 73, respectively.

FIG. 18 is a plan view showing a light beam deflecting member 16.

FIG. 19 is a perspective view near the diffractive optical elements 63 and 73.

FIG. 20 is a diagram showing another configuration example of the diffractive optical elements 63 and 73.

FIG. 21 is a diagram showing the configuration of a fourth example of the illumination optical system for a projection exposure apparatus of the present invention.

22A and 22B are a plan view and a side view, respectively, showing the diffractive optical element 64.

23A and 23B are respectively a plan view and a side view showing the diffractive optical element 74.

FIG. 24 is a plan view showing an aperture stop 9.

FIG. 25 is a perspective view of the vicinity of diffractive optical elements 64 and 74.

FIG. 26 is a diagram showing the configuration of a fifth example of the illumination optical system for a projection exposure apparatus of the present invention.

27A and 27B are a plan view and a side view, respectively, showing the diffractive optical element 65.

28A and 28B are a plan view and a side view, respectively, showing the diffractive optical element 75.

FIG. 29 is a perspective view near the diffractive optical elements 65 and 75.

FIG. 30 is a diagram showing the configuration of a sixth example of the illumination optical system for a projection exposure apparatus of the present invention.

31A and 31B are a plan view and a side view, respectively, showing the diffractive optical element 66.

32A and 32B are a plan view and a side view showing a diffractive optical element 76, respectively.

FIG. 33 is a perspective view of the vicinity of the diffractive optical elements 66 and 76.

FIG. 34 is a diagram showing another configuration of the illumination optical system for the projection exposure apparatus of the sixth example.

35A and 35B are diffractive optical element 166, respectively.
3A and 3B are a plan view and a side view, respectively.

36A and 36B are diffractive optical element 176, respectively.
3A and 3B are a plan view and a side view, respectively.

FIG. 37 is a diagram showing another configuration example of the diffractive optical element 76.

FIG. 38 is a diagram showing a configuration of an illumination optical system for a projection exposure apparatus corresponding to FIG. 37.

FIG. 39 is a diagram showing the configuration of a seventh example of the illumination optical system for a projection exposure apparatus of the present invention.

40 (a), (b) and (c) are a plan view and a side view showing a diffractive optical element 67, respectively.

41 is a plan view showing the operation of the diffractive optical element 67. FIG.

FIG. 42 is a diagram for explaining a conventional technique.

FIG. 43 is a diagram for explaining a conventional technique.

FIG. 44 is a diagram for explaining a conventional technique.

FIG. 45 is a diagram for explaining a conventional technique.

[Explanation of symbols]

1 light source 2 elliptical mirror 3 Mercury lamp 4 lenses 8 fly eye lens 9 Aperture stop 10 Condenser lens 11 reticle 12 Imaging projection system 13 wafers 51 Light flux separation unit 61 Diffractive optical element 61a Linear diffraction grating 71 Diffractive optical element 71a Linear diffraction grating

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-4-225514 (JP, A) JP-A-5-188577 (JP, A) JP-A-5-326366 (JP, A) JP-A-62- 294202 (JP, A) JP-A-6-310396 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G02B 27/42 G03F 7/20 521

Claims (9)

(57) [Claims] 1. An illumination optical system for a projection exposure apparatus, comprising: a light beam separating optical system for separating a light beam from a light source; and a condenser optical system for guiding the light beam separated by the light beam separating optical system onto a reticle. A separation optical system, which is arranged at a position corresponding to four light beams generated by the first diffractive optical means, which has a diffraction grating pattern for separating the light beam from the light source into four An illumination optical system for a projection exposure apparatus, comprising: a second diffractive optical means having a diffraction grating pattern. 2. The diffraction grating pattern of the first diffractive optical means is a linear grating pattern, and the linear grating pattern is arranged so as to form a boundary in a substantially cross shape and has a grating pitch of substantially equal intervals. 2. The illumination optical system for a projection exposure apparatus according to claim 1, wherein the linear grating patterns are four linear grating patterns, and the grating directions of adjacent linear grating patterns are substantially orthogonal to each other. 3. The first diffractive optical means comprises m ₁ , m
₂ , a first diffractive optical surface having a linear grating pattern having a groove cross-sectional shape in which the diffraction efficiencies of + m _1st-order diffracted light and −m _1st- order diffracted light are substantially equal to each other when ₂ and m ₃ are arbitrary natural numbers; A region which is arranged apart from the diffractive optical surface in the optical axis direction and into which the + m _1st-order diffracted light from the first diffractive optical surface is incident, and which is + m _2nd-order diffracted light and −m ₂
A first diffractive region having a groove cross-sectional shape in which the diffraction efficiency of the second-order diffracted light is substantially equal and having a linear grating pattern in a grating direction substantially orthogonal to the grating direction of the first diffractive optical surface; and the first diffractive optical surface. Is a region into which the -m _1st-order diffracted light is incident, and has a groove cross-sectional shape in which the diffraction efficiencies of the + m _3rd-order diffracted light and the -m _3rd- order diffracted light are substantially equal to each other, and is substantially the same as the grating direction of the first diffractive optical surface. Projection exposure according to claim 1, characterized in that it comprises two diffractive optical surfaces, a second diffractive optical surface comprising a second diffractive area having a linear grating pattern in orthogonal grating directions. Lighting optics for equipment. 4. The projection according to claim 1, wherein the first diffractive optical means has diffractive optical elements in which substantially square regions having different depths are alternately arranged in a checkered pattern. Illumination optical system for exposure equipment. 5. A projection exposure apparatus illumination having a light beam splitting optical system for converting a light beam from a light source into an annular light beam, and a condenser optical system for guiding the annular light beam converted by the light beam splitting optical system onto a reticle. In the optical system, the illumination optical system for a projection exposure apparatus, wherein the light beam splitting optical system includes diffractive optical means having a concentric ring grating pattern. 6. The concentric ring grating pattern of the diffractive optical means is such that the grating pitches are substantially equal and the groove cross-sectional shape is blazed with respect to the wavelength of the light beam from the light source incident on the diffractive optical means. The illumination optical system for a projection exposure apparatus according to claim 5, wherein: 7. The diffractive optical means is such that when m ₁ is an arbitrary natural number, the grating pitches of the concentric ring grating patterns are substantially equal, and the diffraction efficiency of + m _1st-order diffracted light and −m _1st- order diffracted light is high. The illumination optical system for a projection exposure apparatus according to claim 5, further comprising a diffractive optical element having a groove cross-sectional shape that is substantially equal. 8. An illumination optical system for a projection exposure apparatus, comprising: a light beam separating optical system for separating a light beam from a light source; and a condenser optical system for guiding the light beam separated by the light beam separating optical system onto a reticle. The separation optical system comprises a diffractive optical means having a linear grating pattern for separating the light flux from the light source into four, and the diffractive optical means is + m when m ₁ , m ₂ and m ₃ are arbitrary natural numbers. _{A first} diffractive optical surface having a linear grating pattern having a groove cross-sectional shape in which the diffraction efficiencies of the _first-order diffracted light and the -m _first- order diffracted light are substantially equal to each other, and the first diffractive optical surface is spaced apart from the first diffractive optical surface in the optical axis direction. Is a region where the + m _1st-order diffracted light is made incident by the first diffractive optical surface, and the + m _2nd-order diffracted light and −m ₂
A first diffractive region having a groove cross-sectional shape in which the diffraction efficiency of the second-order diffracted light is substantially equal and having a linear grating pattern in a grating direction substantially orthogonal to the grating direction of the first diffractive optical surface; and the first diffractive optical surface. Is a region into which the -m _1st-order diffracted light is incident, and has a groove cross-sectional shape in which the diffraction efficiencies of the + m _3rd-order diffracted light and the -m _3rd- order diffracted light are substantially equal, and is substantially the same as the grating direction of the first diffractive optical surface. An illumination optical system for a projection exposure apparatus, comprising: two diffractive optical surfaces, a second diffractive optical surface having a second diffractive area having a linear grating pattern in orthogonal grating directions. . 9. The first diffractive optical means and the second diffractive optical means.
2. The illumination optical system for a projection exposure apparatus according to claim 1, wherein the diffraction grating pattern of the diffractive optical means has a blazed shape or a shape in which the blazed shape is approximated to a stepped shape.