JPH1020107A - Diffraction optical element, projection optical system. illumination optical system, optical apparatus, exposure device and production of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffraction optical element capable of effectively preventing the reflection of the light made incident from a prescribed direction. SOLUTION: The diffraction optical element 1 of a binary type approximating a lens 3 constituting a Fresnel lens by a staircase 4 is so constituted that the number L of the steps of this staircase and the height (h) of one step satisfy the conditions of the equations, L=1-k=λ/ (ns -ni )h}, h=λ/(2pni ), 0<k<=1, where the wavelength of incident light I is defined as λ, the refractive index of a substrate 1 inscribed with the staircase 4 as ns , the refractive index of the medium 2 on the light incident side of the staircase as ni and (p) as a natural number of >=2. Reflected light rays R1, R3 and reflected light rays R2, R4 are thereby made into antitheses from each other and the intensity over the entire part of the reflected light rays is made substantially zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diffractive optical element, and more particularly to a binary diffractive optical element, an optical system having the binary diffractive optical element, and an optical device having the optical system.

[0002]

2. Description of the Related Art In order to manufacture a diffractive optical element with high precision, a binary element has recently attracted attention. The binary element is manufactured by approximating a diffractive optical element having a blazed cross-sectional shape as shown in FIG. 12A with a step-like shape as shown in FIG. 12B. Here, reference numerals 100 and 101 in FIG. 12 denote transparent substrates, on which a diffraction grating having a fine shape is formed. By approximating the shape of the diffraction grating in a step shape, L
Since a semiconductor process used for manufacturing an SI or the like can be applied, high-precision processing can be easily performed even with a fine pitch.

FIG. 13 shows a process of manufacturing a diffractive optical element (binary element) having a four-step structure using a semiconductor process. In FIG. 13, reference numeral 110 denotes a transparent substrate on which a diffraction grating is carved, 111 denotes a resist applied on the substrate 110, and 112 denotes a mask for forming a grating pattern.
In the process of FIG. 11A, the register 111 is exposed by the exposure light 113 via the mask 112, and a latent image of a mask pattern is formed thereon. In the process of FIG.
The resist in the exposed portion (latent image portion) is removed by development (here, a positive type resist is assumed). FIG.
In the process (c), the substrate 110 is dug down to a predetermined depth vertically by reactive ion etching. After that, the remaining resist is removed to form a two-step shape as shown in FIG. Next, in the process of FIG. 13E, a resist 114 is newly applied to the substrate surface, and then exposure is performed using a mask 115 on which a grid pattern having a half pitch of the pattern on the mask 112 is formed.
In FIGS. 13F and 13G, the resist is removed and etched in 12 exposed portions in the same manner as in the previous exposure to remove the residual resist, and finally the four-step staircase of FIG. 13H is obtained. . To further increase the number of steps, a similar process may be repeated using a mask having a pattern having a half cycle of the pattern on the mask 115. In the method described above, the number of steps that can be produced is 2 ⁿ (n:
Although the number is limited to a (natural number), by freely selecting the number of masks to be used and the pattern line width, a step having an arbitrary number of steps can be obtained.

A method of obtaining a desired step shape by etching a substrate by etching has been described above. A film having a thickness corresponding to one step is selectively deposited (deposited) at a predetermined position on a flat substrate. A technique for forming a similar shape by repeating the step of forming the same shape is also known.

Although the diffraction efficiency is slightly lowered by approximating the shape in a stepwise manner, about 95% is obtained by approximation of 8 steps and about 99% by approximation of 16 steps, and there is no practical problem.

FIG. 14 is an enlarged view of a part of the diffractive optical element for explaining the details of the staircase shape.
Here the refractive index n _s of the substrate 120, the refractive index of the side of the medium 121 on which light is incident and n _i. A dotted line 122 indicates an ideal shape of the element, and a solid line 123 indicates a shape of the element obtained by approximating the dotted line 122 by steps. In order to give a discontinuous phase change of 2π to the light beam incident on the boundary of each pitch of the element (line B in the figure), the height D with respect to the ideal shape 122 is

[0007]

[Outside 1] It is necessary that (Λ is the wavelength of the incident light)
Assuming that the height of one step is h and the number of steps is L (in FIG. 14, six steps are shown for convenience), the height E with respect to the step shape 123 is E = (L−1) h. In the figure, α is the difference between D and E,

[0008]

[Outside 2] Holds. Usually, α = h,

[0009]

[Outside 3] Is imposed to determine the height of each step of the stairs, but this is not necessary. With this method, the height h of one stair is automatically determined when the number L of steps is determined.
Is determined, and h cannot be adjusted to control the characteristics of the element.
It is often more convenient to leave a degree of freedom in the value of α in the range of < h and freely determine the value of h. Therefore, if the above equation (1) is rewritten as α = kh (0 <k < 1),

[0010]

[Outside 4] Is a condition relating to the height h and the number L of one staircase of the element. Here, k takes an arbitrary value in the range of 0 <k < 1.

Incidentally, an antireflection film for suppressing reflected light is usually provided on the surface of the optical element. In the case of a refractive lens, since the surface shape is smooth, an antireflection film can be easily formed. On the other hand, regarding binary devices, reports that an antireflection film was formed on the surface have been reported, for example, in "E. Pawlowski and B. Kuhl."
ow, “Antireflection-coated
diffractive optical element
ents fabricated by thin-f
ilm deposition, "Opt. Eng.
3 (11), 3537-3546 (1994) ". The method disclosed therein uses an ion beam sputtering technique, as shown in FIG.
A thin film 132 is formed by depositing a substance 131 for an anti-reflection film perpendicularly on the substrate 130 from above the stepped substrate 130.

[0012]

FIG. 16 shows a state in which an antireflection film is formed on a fine step by a sputtering technique. In the prior art, the steps are fine, so that the thickness of the antireflection film on the steps becomes uneven, and the effect of antireflection is reduced.

Further, when antireflection is performed by an antireflection film, a film formation step is included in the fabrication of the device, so that the production time and the production cost increase.

[0014]

SUMMARY OF THE INVENTION A first object of the present invention is to:
An object of the present invention is to provide a diffractive optical element capable of effectively preventing reflection of light incident from a predetermined direction.

A second object of the present invention is to provide a method for manufacturing a projection optical system, an illumination optical system, an optical apparatus, and an exposure apparatus having the above-described diffractive optical element.

According to a first mode of the diffractive optical element of the present invention, in a diffractive optical element in which a plurality of step-like elements are arranged, the intensity of reflected light from the entire element due to interference between reflected lights from different areas of the element. Is set to substantially zero, and the number of steps of the step-like element and the height of one step are determined.

According to a second aspect of the diffractive optical element of the present invention, in a diffractive optical element in which a plurality of step-like elements are arranged, the wavelength of incident light is λ, the refractive index of the step-like element is n _s , When the refractive index of the medium on the light incident side of the step-like element is n _i and p is a natural number of 2 or more, the number L of steps and the height h of one step satisfy the following conditions. .

[0018] L = 1-k + λ / {(n s -n i) h} h = λ / (2pn i) 0 <k ≦ 1

According to a third aspect of the diffractive optical element of the present invention, in a diffractive optical element in which a plurality of step-like elements are arranged, the wavelength of incident light is λ, the refractive index of the step-like element is n _s , When the refractive index of the medium on the light emission side of the step-like element is n _j and p is a natural number of 2 or more, the number L of steps and the height h of one step satisfy the following conditions. Diffractive optical element.

[0020] L = 1-k + λ / {(n s -n j) h} h = λ / (2pn s) 0 <k ≦ 1

According to a fourth aspect of the present invention, in a binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a staircase structure, interference between reflected lights from different regions of the element causes interference from the entire element. A diffractive optical element wherein the number of steps and the height of one step are determined so that the intensity of reflected light is substantially zero.

According to a fifth aspect of the present invention, in a binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step structure, the wavelength of incident light is λ, the refractive index of the step is n _s , When the refractive index of the medium on the light incident side of the steps is n _i and p is a natural number of 2 or more, the number L of steps and the height h of one step satisfy the following conditions: element.

[0023] L = 1-k + λ / {(n s -n i) h} h = λ / (2pn i) 0 <k ≦ 1

According to a sixth aspect of the present invention, in a binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step structure, the wavelength of incident light is λ, the refractive index of the step is n _s , When the refractive index of the medium on the light exit side of the stairs is n _j and p is a natural number of 2 or more, the number of steps L of the stairs
And the height h of one step satisfies the following condition.

[0025] L = 1-k + λ / {(n s -n j) h} h = λ / (2pn s) 0 <k ≦ 1

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a part of a diffractive optical element (binary element) in which light reflected from a surface is suppressed by using the present invention. In FIG. 2, reference numeral 1 denotes a transparent substrate (refractive index: n _S ) formed of glass or plastic on which a binary element is formed, and reference numeral 2 denotes a medium (refractive index: n _i ) on the light incident side. A dotted line 3 shows an ideal shape of the element, that is, a so-called Fresnel lens shape. A solid line 4 indicates the actual binary element shape obtained by approximating the lens shape of the ideal shape 3 with a step shape. Here, the stairs have an eight-stage structure composed of regions K1 to K8, each having a width of r1, r2,... R8. The heights per stair are all equal and are h as shown in the figure. .. Denote incident light incident on the regions K1, K2,..., Respectively, and R1, R2,.
The reflected light from 2,. In FIG. 1, the incident lights I5 to I8 and the reflected lights R5 to R8 for the portions K5 to K8 are omitted. Here, the incident lights I1 to I8 are plane waves whose phases are aligned with each other, and the reflected lights R1 to R8 are plane waves whose phases are changed as a whole and whose phases are changed by each step of the height h of the steps. It is well known that the reflected light from the entire region K1 to K8 is calculated by adding R1 to R8 in consideration of the phase. In the embodiment shown in FIG. 1, the shape of the binary element is determined so that the reflected lights from the respective stages cancel each other out by interference and the intensity of the reflected light from the whole becomes zero as a result.

Here, the conditions under which the intensity of the reflected light becomes zero due to interference from the whole will be described with reference to FIG.
In FIG. 2, 10 is a region having a width a ₁ and 11 is a region having a width a _2. These regions are formed with a step having a height d, and plane waves J 1 and J 2 having the same phase are incident on each region. When the refractive index of the light incident-side medium and n _i, the difference in optical path length in the reflected light S2 from the reflection light S1 and the area 11 is generated from the region 10, the value of the optical path length difference is given by 2n _i d. Here, in order for the reflected light S1 and the reflected light S2 to cancel each other and become zero as a whole, the phases of the reflected light S1 and the reflected light S2 are inverted with each other (that is, shifted by 180 °) and are mutually shifted. The condition is that the amplitudes are equal.
The wavelength of the incident light in a vacuum (hereinafter referred to as wavelength) is λ
Then, in order to satisfy the phase condition,

[0028]

[Outside 5] Is required, and the width a ₁ and the width a ₂ need to be equal in order to satisfy the condition of the amplitude.

Although FIG. 2 has been described using a two-step staircase structure composed of two regions, FIG. 3 and FIG. 4 will be used to explain other conditions for satisfying the above conditions regarding the phase and amplitude of the reflected light. The staircase structure will be described.

[0030] Figure 3 is a width of b _1, b _2, 3 a region of b ₃ 20, 21, 22

[0031]

[Outside 6] Fig. 2 shows a staircase structure arranged with steps. J1 to J3 indicate incident lights having the same phase with each other, and S1 to S3 indicate reflected lights whose phases are shifted from each other due to each step. When the step is determined as described above, the phases of the reflected light S2 and the reflected light S1 are inverted,
Similarly, the phases of the reflected light S2 and the reflected light S3 are also inverted. Therefore, the reflected light S1 and the reflected light S3 have the same phase. Therefore, if b ₂ = b ₁ + b ₃ is satisfied with respect to the width of the region, the intensity of the entire reflected light becomes zero as a result of interference between the reflected lights.

[0032] Figure 4 four regions 30, 31, 32 and 33 of width _{c 1, c 2, c 3} , c 4

[0033]

[Outside 7] Fig. 2 shows a staircase structure arranged with steps. J1 to J4 indicate incident lights having the same phase with each other, and S1 to S4 indicate reflected lights having different phases with each other due to a step. When the step is determined as described above, the phases of the reflected light S1 and the reflected light S3 are inverted with respect to the reflected light S2 based on the reflected light S2,
Has the same phase as the reflected light S2. Therefore, in order for the intensity of the entire reflected light to become zero as a result of interference between the reflected lights, the condition of c ₁ + c ₃ = c ₂ + c ₄ may be satisfied with respect to the width of the region. In the case of a staircase structure with five steps, six steps, seven steps or more,

[0034]

[Outside 8] By forming a staircase structure with the steps described above, it is possible to achieve an antireflection effect.

From the above discussion, in the binary device of FIG.
Since the reflected lights R1 to R8 interfere with each other and the reflected light intensity becomes zero, the step h of the stairs becomes

[0036]

[Outside 9] Is determined to satisfy the conditions. By the way, as for the height per one step of the binary optical element, the above-mentioned relation (2) needs to be satisfied. Therefore

[0037]

[Outside 10] Substituting into equation (2) gives

[0038]

[Outside 11] Becomes As actual values, when the refractive index of the substrate on which the binary element is formed is n _s = 1.52 and the medium on the light incident side is air (n _i = 1.0), L = 8 and k = 0.
69. Since the value of k can be any value of 0 <k < 1, as described above, as shown in FIG.
The condition in which the reflected lights actually cancel each other is realized by the eight-step structure. However, in order for the intensity of the reflected light to be actually zero, a set of the reflected lights R1 to R8 having the same phase, that is, (R1, R3, R5, R7) and (R
2, R4, R6, and R8) need to be equal. Therefore, in the present embodiment shown in FIG. 1, the widths r1 to r8 correspond to r ₁ + r ₃ + r
So that _{5 + r 7 = r 2 +} r 4 + r 6 + r 8 determines the width of each step. Although FIG. 1 uses the expression “width” of the stairs because the cross section of the binary element is drawn two-dimensionally,
In an element having an actual three-dimensional shape, the “width” of each step corresponds to the “area” of each step.

In the example shown in FIG. 1, the intensity of the entire reflected light is made zero in the range of K1 to K8, that is, in the range of one pitch as a binary element, but the coherence of the incident light is maintained. If it is a range, it is possible to adopt a structure in which a wider range is regarded as one region and reflected light therefrom is zero.

The anti-reflection condition of the element when light enters the binary element from the air has been described above. The anti-reflection condition when light is emitted from the binary element to the air will be considered below. The refractive index of the substrate on which the binary element is formed is n _s , the refractive index of the medium on the light emission side is n _j, and the height of each step is

[0041]

[Outside 12] The expression corresponding to the above expression (2) is

[0042]

[Outside 13] Becomes (4)

[0043]

[Outside 14] Substituting

[0044]

[Outside 15] Becomes Here, when calculations are performed for the case of n _s = 1.52 and n _j = 1.0, L = 12 and k = 0.69, and it can be seen that the antireflection effect can be realized by the 12-step stair structure. .

[Second Embodiment] In the first embodiment, the steps of the stairs are

[0046]

[Outside 16] The antireflection condition was derived under the condition that the phase of the reflected light from the adjacent stage is inverted (that is, the phase is different by 180 °). Here, a configuration in the case where the phase difference of the reflected light from the first adjacent stage is 120 ° will be described. FIG. 5 shows a staircase composed of three regions 40, 41, and 42, where the step difference per one stage is t. Here, E1
E3 is incident light incident on each area and having the same phase with each other, and G1 to G3 indicate reflected light from each area. As described above, when two reflected lights having the same amplitude and a phase different from each other by 180 ° interfere with each other, the intensity becomes zero as a whole, but the three reflected lights having the same amplitude and the phase different from each other by 120 ° interfere with each other. Even if it does, the intensity as a whole will be zero. And the reflected light G1 reflected light G2, since the optical path length difference between the reflected light G2 reflected light G3 is 2n _i t, condition their phase difference becomes 120 ° is

[0047]

[Outside 17] As a result, the condition for the height per stair is

[0048]

[Outside 18] Becomes Substituting this result for h in equation (2) above, n _s
= 1.52, n _i = 1.0, L = 12
Is obtained and the step

[0049]

[Outside 19] A binary element that does not generate reflected light can be realized with a 12-step stair structure having

Next, a case where the phase difference of the reflected light from the adjacent stage becomes 90 ° will be described with reference to FIG.
FIG. 6 shows a staircase composed of four regions 50, 51, 52, and 53 with a step difference u per step. F1
F4 to F4 are incident lights incident on the respective regions and having the same phase with each other, and H1 to H4 represent reflected lights from the respective regions. Here, the phases of the four reflected lights having the same amplitude are set to 0 °,
The intensity is changed by 90 °, such as 90 °, 180 °, and 270 °, so that the intensity becomes zero as a whole. Specifically, the phase of the reflected light H2 is delayed by 90 ° with respect to the reflected light H1, the phase of the reflected light H3 is delayed by 180 °, and the phase of the reflected light H4 is delayed by 270 °. Since the optical path difference between adjacent reflected lights is 2n _i u, the condition that their phase difference is 90 ° is

[0051]

[Outside 20] As a result, the condition for the height of the stairs per step is

[0052]

[Outside 21] Becomes Substituting this result for h in equation (2) above, n _s
= 1.52, n _i = 1.0, L = 16
Is obtained and the step

[0053]

[Outside 22] A binary element that does not generate reflected light can be realized with a 16-step stair structure having the following.

When the same consideration is given hereafter, the height per stair is

[0055]

[Outside 23] Obviously, the condition is that no reflected light is generated when p is a natural number of 2 or more.

Summarizing the above results, the conditions under which reflected light does not occur as a whole are as follows.

[0057] (1) a medium binary elements from (refractive index: n _s) of the refractive index n _i in a one-stage step-when light is incident height:

[0058]

[Outside 24] Number of stairs:

[0059]

[Outside 25]

(2) A case where light is emitted from a binary element (refractive index: n _s ) to a medium having a refractive index of n _j One step height:

[0061]

[Outside 26] Number of stairs:

[0062]

[Outside 27] (However, in each case, p is a natural number of 2 or more, and k is 0 <k
< Real number of 1)

In the description so far, the condition for minimizing the reflectance of light that is perpendicularly incident on the surface of the binary element is as follows:
The height and number of stairs were determined. Using the present invention, the height and the number of steps can be determined so that the reflectance of light incident at an angle other than perpendicular is minimized.

Next, an example in which a conventional antireflection film is combined with a binary diffractive optical element (binary element) according to the present invention will be described with reference to FIG. In FIG. 7, reference numeral 60 denotes a binary element to which the present invention is applied, and the height h per one step is determined as described in the first embodiment. The anti-reflection effect at that time is optimized for the light beam 61 that is perpendicularly incident on the element 60. When an ordinary optical element is used in an optical system, the angle of incidence of a light beam on the element usually has a predetermined range as well as being perpendicular. In FIG. 7, reference numerals 62 and 63 indicate incident light beams from oblique directions. In the anti-reflection technology using the conventional anti-reflection film, reflection is performed by a very large number of layers of about 10 layers so that the anti-reflection effect is realized not only for the incident light beam in the vertical direction but also for the incident light beam in the oblique direction. A protective film was formed. On the other hand, in the binary element 60 to which the present invention is applied, a sufficient anti-reflection effect for incident light 61 from the vertical direction is realized without the anti-reflection film.
By providing an anti-reflection film 64 having optimized anti-reflection characteristics for incident light beams 62 and 63 from oblique directions, a binary device having good anti-reflection characteristics over a wide reflection angle range with a small number of layers. Is obtained. Since there is no need to provide a large number of layers in manufacturing such an antireflection film, the problem described with reference to FIG. 16 can be relatively easily avoided. Here, the height and the number of steps of each step of the binary element are set so that the reflectance for the incident light beams 62 and 63 from the oblique direction is minimized.
The same effect can be obtained even if the reflectance for 1 is set to be the minimum.

The diffractive optical element described above has a configuration in which a step structure is formed on one surface of a transparent substrate and a flat surface or a spherical surface is formed on the other surface, or a step structure is formed on one surface of the transparent substrate. Then, an aspherical surface may be formed on the other surface, or a staircase structure may be formed on both surfaces of the transparent substrate.

FIG. 8 is a view showing a projection optical system having any of the above-mentioned diffractive optical elements. 8, reference numeral 81 denotes a normal lens having a spherical or aspherical surface, and reference numeral 82 denotes a diffractive optical element of the present invention. The diffractive optical element 82 corrects various system aberrations (chromatic aberration and Seidel's five aberrations) in cooperation with the ordinary lens 81. Note that an antireflection film is formed on the surface of the normal lens 81.

Such a projection optical system includes various cameras,
Interchangeable lenses attached to single-lens reflex cameras, office machines such as copiers, projection exposure equipment for manufacturing liquid crystal panels, ICs,
It is used for a projection exposure apparatus for manufacturing a semiconductor chip such as an LSI.

FIG. 9 is a schematic diagram showing the projection exposure apparatus. 9, reference numeral 91 denotes an illumination optical system for supplying exposure light; 92, a mask illuminated by the illumination optical system; 93, a projection optical system for projecting an image of a device pattern drawn on the mask 92; 1 shows a glass substrate or a silicon substrate that has been etched. The projection optical system 93 has the diffractive optical element of the present invention, and the illumination optical system 91 also has the diffractive optical element of the present invention. The lens constituting the illumination optical system 91 and the projection optical system has an anti-reflection film formed on the surface thereof.

Next, an embodiment of a method for manufacturing a semiconductor device using the above-described exposure apparatus will be described. FIG. 10 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. Step 3
In (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 11 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated device which has been conventionally difficult to manufacture.

[0072]

As described above, according to the present invention, it is possible to effectively prevent reflection of light incident on a diffractive optical element from a predetermined direction. As a result, the manufacturing time and manufacturing cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a binary diffractive optical element according to the present invention.

FIG. 2 is an explanatory diagram for explaining conditions under which reflected light disappears.

FIG. 3 is an explanatory diagram for explaining another condition under which reflected light disappears.

FIG. 4 is an explanatory diagram for explaining another condition under which reflected light disappears.

FIG. 5 is an explanatory diagram for explaining another condition under which reflected light disappears.

FIG. 6 is an explanatory diagram for explaining another condition under which reflected light disappears.

FIG. 7 is an explanatory view showing an example in which an antireflection film is combined.

FIG. 8 is a diagram showing a projection optical system.

FIG. 9 is a view showing a projection exposure apparatus.

FIG. 10 is a diagram showing a manufacturing flow of the semiconductor device.

FIG. 11 is a view showing a wafer process of FIG. 10;

FIG. 12 is a diagram comparing cross sections of a conventional diffraction element and a binary diffraction element.

FIG. 13 is an explanatory diagram for describing a method for manufacturing a binary diffraction element.

FIG. 14 is an explanatory diagram for explaining how to determine the height of one step of the binary element.

FIG. 15 is an explanatory diagram for explaining a conventional method for manufacturing an antireflection film.

FIG. 16 is an explanatory diagram for explaining a state of an antireflection film provided to a binary element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Medium 3 Ideal shape (Fresnel lens shape) 4 Step shape (binary one element shape) I Incident light R Reflected light

Claims (22)

[Claims] In a diffractive optical element in which a plurality of step-like elements are arranged, the intensity of reflected light from the entire element becomes substantially zero due to interference between reflected lights from different regions of the element. A diffractive optical element wherein the number of steps and the height of one step are determined. 2. A diffractive optical element in which a plurality of step-like elements are arranged, wherein the wavelength of the incident light is λ, the refractive index of the step-like elements is n _s , and the refraction of the medium on the light incident side of the step-like elements. A diffractive optical element characterized in that, when the ratio is n _i and p is a natural number of 2 or more, the number L of steps and the height h of one step satisfy the following conditions. L = 1-k + λ / {(n s -n i) h} h = λ / (2pn i) 0 <k ≦ 1 3. A diffractive optical element in which a plurality of step-like elements are arranged, wherein the wavelength of the incident light is λ, the refractive index of the step-like elements is n _s , and the refraction of the medium on the light exit side of the step-like elements. A diffractive optical element characterized in that when the ratio is n _j and p is a natural number of 2 or more, the number L of steps and the height h of one step satisfy the following conditions. L = 1-k + λ / {(n s -n j) h} h = λ / (2pn s) 0 <k ≦ 1 4. In a binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a stepped structure, the intensity of reflected light from the entire element is substantially increased due to interference between reflected lights from mutually different regions of the element. A diffractive optical element, wherein the number of steps and the height of one step are determined so as to be zero. 5. A binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step structure, wherein the wavelength of the incident light is λ, the refractive index of the step is n _s , and the medium on the light incident side of the step. Where n _i and p are natural numbers of 2 or more, the number L of steps and the height h of one step
Satisfies the following condition. L = 1-k + λ / {(n s -n i) h} h = λ / (2Pn i) 0 <k ≦ 1 6. A binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step structure, wherein the wavelength of the incident light is λ, the refractive index of the step is n _s , and the medium on the light exit side of the step. When the refractive index n is n _j and p is a natural number of 2 or more, the number L of steps and the height h of one step satisfy the following conditions. L = 1-k + λ / {(n s -n j) h} h = λ / (2pn s) 0 <k ≦ 1 7. The diffractive optical element according to claim 4, wherein the incident light is light that is perpendicularly incident on a surface of the element. 8. The diffractive optical element according to claim 7, wherein an antireflection film optimized for light obliquely incident on the element surface is provided on the number of steps. 9. The diffractive optical element according to claim 4, wherein the incident light is light obliquely incident on the element surface. 10. The diffractive optical element according to claim 9, wherein an antireflection film optimized for light vertically incident on the element surface is provided on the stairs. 11. The diffractive optic according to claim 4, wherein the step structure is formed on one surface of the transparent substrate, and an aspherical surface is formed on the other surface of the transparent substrate. element. 12. The diffractive optical element according to claim 4, wherein the step structure is formed on both surfaces of a transparent substrate. 13. The diffraction according to claim 4, wherein the step structure is formed on one surface of the transparent substrate, and a flat surface or a spherical surface is formed on the other surface of the transparent substrate. Optical element. 14. The diffractive optical element according to claim 11, wherein said transparent substrate is made of glass. 15. The diffractive optical element according to claim 11, wherein said transparent substrate is made of plastic. 16. A projection optical system comprising the diffractive optical element according to claim 1. 17. An optical apparatus comprising the projection optical system according to claim 16. 18. An exposure apparatus comprising the projection optical system according to claim 16. 19. An illumination optical system comprising the diffractive optical element according to claim 1. Description: 20. An optical apparatus comprising the illumination optical system according to claim 19. 21. An exposure apparatus comprising the illumination optical system according to claim 19. 22. A device manufacturing method, comprising a step of transferring a device pattern onto a substrate by the exposure apparatus according to claim 18.