JP2000056111A - Diffraction optical device and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffraction optical device easily producible and having high diffraction efficiency and excellent basic properties such as a small aberration as an optical element, and its prepn. method. SOLUTION: Thin films 12a of respective layers consisting of a diffractive Fresnel lens are collectively formed in batch by forming a releasing layer 11 on a substrate 10, depositing an Al thin film 12A on the releasing layer 11 and patterning the Al thin film 12 by photo-lithography method. The diffractive Fresnel lens 16A having a four-stage structure to laminate three-layer thin films 12a on an Al layer 14 is prepd. by peeling the plural thin films 12a from the releasing layer 11 and joining after laminating it on an Al layer 14 formed on a stage 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffractive optical element having a stepped cross section and a method of manufacturing the same, and more particularly, to an optical element having high diffraction efficiency, low aberration, etc., having excellent basic characteristics and easy manufacturing. And a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, diffractive optical elements such as microgratings and micro Fresnel lenses have attracted attention as optical elements that are small and lightweight and have various functions. As a method of manufacturing the diffractive optical element, an ultra-precision lathe method and a lithography method using an electron beam or an ion beam are generally used. However, in such a method, it is difficult to manufacture the diffractive optical element to have an ideal triangular cross-sectional shape.
Only a low diffraction efficiency of at most 40% can be obtained. Therefore, in order to improve this, a diffractive optical element having a multi-stepped shape has been conventionally proposed. For example, the diffraction efficiency is improved to 80% in the four-stage structure and to 95% in the eight-stage structure.

As a method of manufacturing such a conventional diffractive optical element having a multi-stage structure, for example, Japanese Patent Application Laid-Open No. 5-333204
And the literature "SPIE Vol. 1992, p9
0 to p101 ”.

FIGS. 6 (a) to 6 (d) show Japanese Patent Application Laid-Open No. 5-33320.
No. 4 discloses a method of manufacturing a conventional diffractive optical element (first conventional example). This manufacturing method is a typical method using electron beam exposure. First, as shown in FIG. 3A, an electron beam resist is applied as a photosensitive medium 102a to a substrate 101 and prebaked at 170 ° C. for 20 minutes. Subsequently, as shown in FIG. 3B, the same photosensitive medium 102b is applied on the photosensitive medium 102a, and prebaking is performed at a temperature (90 ° C.) lower than the initial prebaking temperature for 20 minutes. As a result, a photosensitive medium 102a having low sensitivity to the electron beam and a photosensitive medium 102b having good sensitivity are formed. Next, as shown in FIG. 3C, an electron beam lithography apparatus (not shown) applies an electron beam 103 having an irradiation amount corresponding to the sensitivity to the photosensitive media 102a and 102b, thereby forming a step-like shape of a target diffractive optical element. Draw corresponding to. Finally, a developing process is performed to produce a diffractive optical element having a desired shape in which the film thicknesses of the photosensitive media 102a and 102b are changed stepwise as shown in FIG.
In this example, a three-stage diffractive optical element is manufactured.

FIGS. 7 (a) to 7 (f) show the reference "SPIE Vo".
l. 1992, p90 to p101 ”(second conventional example). First,
As shown in FIG. 1A, a quartz substrate 201 having a chromium film 202 is prepared as a substrate, and a photoresist 2
03 is applied. Next, as shown in FIG. 3B, the photoresist 203 is exposed to ultraviolet rays 205 through a photomask 204 and developed, so that the photoresist 203 is patterned into the same shape as the opening 204a of the photomask 204. Further, using the pattern of the photoresist 203 as a mask, FIG.
When the chromium film 202 is patterned by wet etching as shown in (c) and the photoresist 203 is stripped, the chromium film 202 is patterned into the same shape as the opening 204a of the photomask 204 as shown in FIG. You. When the quartz substrate 201 is further etched by dry etching using the chromium film 202 as a mask as shown in FIG.
a is formed. When the chromium film 202 is removed,
As shown in (f), a quartz substrate 20 having a step 201a is formed.
1 is formed. Thereafter, in the same manner as described above, the quartz substrate 201 is etched using the second photomask, so that a further step can be formed in the step 201a, and a multi-step diffractive optical element is manufactured. . According to this method, since the diffractive optical element of the two-stage structure in a single patterning step it can be produced by n times of patterning process the diffractive optical element 2 ⁿ stages can be manufactured. An almost similar method is described in the document “MEMS97 (p360-p36)”.
5) ", and in this document, a Fresnel lens for infrared rays is manufactured using a Si substrate.

[0006]

However, according to the first conventional example, after a multi-stage lens shape is formed on a photosensitive medium, the photosensitive medium and the substrate are simultaneously etched by a dry etching method to form the lens. Need to be transferred to the substrate. Therefore, it is necessary to select an etching condition in which the selectivity (the ratio of the etching rate of the photosensitive medium to the etching rate of the substrate) is extremely close to 1, and it is difficult to control the etching conditions and to secure uniformity within the substrate. It is not always possible to accurately transfer the shape of the photosensitive medium to the substrate. Therefore, there is a problem that the finally obtained lens shape of the substrate is inferior in shape accuracy. Further, since it is difficult to form a three-layer photosensitive medium having different sensitivities, there is a problem that it is difficult to manufacture a diffractive optical element having four or more steps.

According to the second conventional example, the etching depth is controlled by the etching conditions and the etching time in each stage of the etching process, but the microloading effect (a phenomenon in which the etching rate varies locally depending on the etching area). Therefore, the etching depth often depends on the pattern shape, and it is difficult to obtain a uniform etching depth over the entire surface of the substrate. In addition, predetermined depth (time)
There is a disadvantage that the surface roughness of the bottom surface of the etching is poor because the etching is stopped only after the etching. Further, when trying to fabricate a multi-stage structure by repeating patterning, there is a disadvantage that the resist coating film thickness varies depending on the location due to the unevenness of the already formed substrate, and accurate patterning becomes difficult. Therefore, the diffractive optical element manufactured by this method has a problem that the more steps, the lower the shape accuracy, and the surface roughness of each step portion is poor, so that light is scattered and diffraction efficiency is poor.

Accordingly, an object of the present invention is to provide a diffractive optical element which is excellent in basic characteristics as an optical element having high diffraction efficiency and small aberration, and which is easy to manufacture, and a method of manufacturing the same.

[0009]

In order to achieve the above object, the present invention provides a diffractive optical element having a stepped cross-section having a plurality of steps, wherein the diffractive optical element has a predetermined two-dimensional pattern corresponding to the steps. And a diffractive optical element comprising a plurality of thin films that form the staircase shape by being stacked and joined to each other. According to the above configuration, by increasing the number of laminated thin films, a cross-sectional shape having four or more steps is obtained, and the diffraction efficiency is improved. In addition, since an easy-to-manufacture patterning method such as a photolithography method can be used for forming a plurality of thin films, an accurate two-dimensional pattern can be obtained, and shape accuracy is improved, thereby reducing aberration. Further, since the surface roughness of the thin film is small, light scattering is reduced, and the diffraction efficiency is further improved in combination with the increase in the number of laminated thin films.

In order to achieve the above object, the present invention provides a method of manufacturing a diffractive optical element having a cross-sectional shape having a plurality of steps, wherein a first release layer is formed on a substrate.
And a second step of forming a plurality of thin films having a predetermined two-dimensional pattern corresponding to the step on the release layer formed on the substrate, and releasing the plurality of thin films from the mold. A third step of forming a structure having the staircase shape by peeling from the layer, laminating and joining, and a fourth step of transferring a diffractive optical element using the structure as a mold. And a method for manufacturing a diffractive optical element. According to the above configuration, by forming the release layer between the substrate and the plurality of thin films, the plurality of thin films can be easily separated from the substrate.

In order to achieve the above object, the present invention provides a method for manufacturing a diffractive optical element having a cross-sectional shape having a plurality of steps, the first step of forming a release layer on a substrate; A second step of forming a plurality of thin films having a predetermined two-dimensional pattern corresponding to the step on the release layer formed on the substrate, and peeling the plurality of thin films from the release layer A third step of forming a structure having the step shape by stacking and joining, and a fourth step of transferring a diffractive optical element using the structure as a mold. Provided is a method for manufacturing a device. According to the above configuration, the diffractive optical element is mass-produced by repeatedly manufacturing the diffractive optical element using the same structure as a mold.

[0012]

FIG. 1 shows a manufacturing apparatus according to an embodiment of the present invention. The manufacturing apparatus 1 has a vacuum chamber 2 in which a laminating step described later is performed. Inside the vacuum chamber 2, a substrate holder 3 on which a substrate is placed and a thin film formed on the substrate are transferred. A high-speed atomic beam of argon (FAB: fast) is provided on the stage 13 and the substrate holder 3.
The first F that irradiates atom beam 15 to clean the surface
An EB source 4A, a second FEB source 4B for irradiating the stage 13 with the FAB 15 to clean the surface, an X-axis table 5A for moving the stage 13 in the X-axis direction (left-right direction in FIG. 1), and a stage 13 Is moved in the Y-axis direction (the direction perpendicular to the plane of FIG. 1). In addition, the manufacturing apparatus 1 includes a Z-axis table 5C for moving the substrate holder 3 in the Z-axis direction (vertical direction in FIG. 1) outside the vacuum chamber 2, and a rotation of the substrate holder 3 around the Z-axis during alignment adjustment. And a θ table 5D that rotates the table. Note that the first and second F
When the EB sources 4A and 4B press the substrate holder 3 against the stage 13, the EB sources 4A and 4B can be retracted by a motor (not shown) so as not to interfere.

Hereinafter, a case where a diffractive Fresnel lens as a diffractive optical element is manufactured using the manufacturing apparatus 1 configured as described above will be described. The target diffraction type Fresnel lens has a circular surface shape and a stepped grating (diffraction grating) having a four-step cross section. The surface shape of the grating may be elliptical.

FIGS. 2A to 2F show a method for manufacturing a diffractive optical element according to the first embodiment of the present invention. The first embodiment is directed to a reflection type diffraction type Fresnel lens made of aluminum (Al). First, as shown in FIG. 1A, a substrate 10 made of, for example, a Si wafer is prepared, and polyimide is applied to the substrate 10 by 5 μm by a spin coating method, which is cured, and the surface is fluorinated. To form the release layer 11. The surface of the release layer 11 can easily have a surface roughness of Ra <2 nm by using the spin coating method. Further, an Al thin film 12A made of Al is deposited to a thickness of 0.2 μm on the release layer 11 by a sputtering method.

The thickness of the Al thin film 12 is determined in consideration of the used wavelength λ of the Fresnel lens, the form of the Fresnel lens (transmission type or reflection type), the refractive index of the Fresnel lens and its surroundings, and the number of steps L of the Fresnel lens. . In the case of the reflection type, assuming that the entire thickness is T, the thickness t of one layer is given by the following equation (1). t = T / L = λ / 2n / L (1) where n is the refractive index of the surrounding medium and is 1 when used in air. The thickness of the Al thin film 12A can be accurately set by monitoring with a quartz oscillator.

Next, as shown in FIG. 1B, the Al thin film 12A is patterned using a normal photolithography method to form a thin film 1 of each layer constituting a diffraction Fresnel lens.
2a is collectively formed. The radius of each thin film 12a is determined in consideration of the wavelength used, the focal length, the brightness, the number of steps, and the like of the diffractive Fresnel lens. The etching of the Al thin film 12A is more dry etching than wet etching, preferably reactive ion etching (RIE).
hing) is preferable because the corners of the thin film 12a are not rounded and the end face is perpendicular to the surface of the substrate 10.

FIG. 3A shows a patterned thin film 12.
FIG. 4B shows an example of the thin film 12a of each pattern.
Shows the state of lamination. This example shows a diffractive Fresnel lens having four steps and two zones, and the top row is a thin film 12 corresponding to the pattern of the second step (first layer) of the Fresnel lens.
a, the second row is the thin film 12a corresponding to the pattern of the third step (second layer), and the bottom row is the thin film 12a corresponding to the pattern of the fourth step (third layer). Assuming that the wavelength of the thin film 12a in each pattern is λ, the focal length is f, the zone number of the Fresnel lens is m, the step number is g, and the number of steps is L, the radius is given by the following equation (2). r _{(m, g)} = (2λf (m-1 + g / L)) ^1/2 (2) Note that the zone number increases from the center of the thin film 12a to 1, and increases to 2,3,. . When the wavelength is in the range from visible light to the near infrared region and the focal length is about several mm to several tens of mm, the radius of the thin film 12a is several tens μm to several hundreds of μm, which is convenient for manufacturing by the photolithography method. In order to manufacture two Fresnel lenses of the same shape at a time, two patterns of the same layer (step) are arranged side by side. Since the diameter of one lens is 100 μm to tens of mm, it is possible to simultaneously pattern the patterns of each stage of a large number of lenses using a normal Si wafer or glass substrate.

Next, as shown in FIG. 2C, the substrate 10 on which a plurality of thin films 12a are formed is introduced into the vacuum chamber 2 of the manufacturing apparatus 1 shown in FIG. It is evacuated to a high vacuum, preferably an ultra-high vacuum, facing the stage 13. It is preferable that the surface of the stage 13 is coated with an Al layer 14 having a thickness of about 0.1 μm, because it has the same reflectance as the thin film 12a to be laminated. Then, both surfaces of the thin film 12a and the stage 13 are irradiated with the FAB 15 to clean the surfaces. FAB15 is an argon gas source, 1.5 kV acceleration voltage, 15 mA
At a current value of 5 minutes. Although the oxide film and the contaminant layer on the surface are removed by the FAB 15, the thickness thereof is at most about 5 nm, so that the influence on the thickness accuracy is small. It is also possible to add the removal amount to the film thickness of the Al thin film 12A in consideration of the removal amount in advance.

Subsequently, as shown in FIG. 1D, when the substrate holder 3 is raised by the Z-axis stage 5C and the substrate 10 is pressed against the stage 13, the thin film 12a and the stage 13 are pressed.
Is strongly bonded by room-temperature bonding. This bonding strength can be made very strong by optimizing the irradiation conditions and press-contact conditions of the FAB 15 and is therefore sufficient for forming a structure such as a lens.

Further, as shown in FIG. 2E, when the substrate 10 is separated from the stage 13, the thin film 12a on the substrate 10 is transferred to the stage 13. This is because the adhesion between the release layer 11 and the thin film 12a is smaller than the bonding force between the thin film 12a and the stage 13. By this step, a two-stage diffractive optical element is formed on the stage 13.
The surface of the transferred thin film 12a is the surface that has been in contact with the release layer 11, and the surface roughness is almost the same as the surface roughness of the polyimide release layer 11 (Ra <2 nm), which is very good. It is. If the surface roughness is good, light scattering on the surface can be reduced, so that the light collection efficiency as an optical element can be increased. The loss due to scattering at the surface increases exponentially with increasing surface roughness. For example, a loss of only 0.07% at a surface roughness of 2 nm is 20 n
When it becomes m, it is extremely deteriorated to 12%. Therefore, a diffractive Fresnel lens using this surface as an optical surface has a feature that loss due to scattering is small.

Then, each of the above steps (c) to (e) is repeated twice, as shown in FIG.
A reflection type diffractive Fresnel lens 16A having a four-stage structure in which three thin films 12a are stacked on the Al layer 14 is manufactured.
When bonding the second and subsequent layers, it is necessary to position the first layer of the thin film 12a already transferred onto the stage 13 and the second and subsequent layers of the thin film 12a on the substrate 10.
It can be easily realized by precise positioning using the alignment mechanism and the stages 5A to 5D.

According to the above-described first embodiment, a diffraction type Fresnel lens having a cross-sectional shape having four steps can be manufactured, so that a diffraction efficiency of 80% can be obtained. In a similar manner, a diffraction efficiency of 95% can be obtained in an eight-stage structure (repeated transfer of the lamination of seven thin films is repeated). As described above, even the diffraction type Fresnel lens having the multi-stage structure can be easily manufactured by repeating the lamination transfer of the thin film. Further, since each stage of the diffraction type Fresnel lens is made of Al, it has a high reflectance with respect to visible light and infrared light, and can be used as a favorable reflection type optical element. Further, the diffraction type Fresnel lens manufactured by the present manufacturing method has excellent shape accuracy, and thus has excellent basic characteristics as an optical element, such as high diffraction efficiency and small aberration. Particularly, in a diffraction type Fresnel lens having a multi-stage structure aimed at high diffraction efficiency, since the film thickness of each stage is good and the surface roughness of each stage is small, high diffraction efficiency and low scattering loss can be realized.

FIGS. 4A to 4F show a method of manufacturing a diffractive optical element according to a second embodiment of the present invention. The second embodiment is directed to a transmission type diffractive Fresnel lens made of silicon (Si). First,
As shown in FIG. 1A, a substrate 10 made of a Si wafer is prepared, and a chemical vapor deposition (CVD:
Silicon oxide film (SiO ₂ ) or silicon oxyfluoride film (SiOF) by Chemical Vapor Deposition method
Is deposited to form a release layer 11. Since the surface of the release layer 11 was formed by the CVD method, the surface roughness was Ra <1n.
m is easily possible. Further, a 0.5 μm thick Si thin film 12B made of amorphous silicon or polycrystalline silicon is applied on the release layer 11 by sputtering or CVD. After depositing the Si thin film 12B,
An appropriate heat treatment may crystallize amorphous silicon or improve the crystallinity of polycrystalline silicon. Also,
The surface of the Si thin film 12 </ b> B may become conspicuous due to the heat treatment at this time. In such a case, the surface may be flattened by a chemical mechanical polishing (CMP) method.

Next, as shown in FIG. 2B, the Si thin film 12B is patterned by using a normal photolithography method to collectively form the thin films 12a of the respective layers of the diffractive Fresnel lens. The etching of Si is preferably dry etching, preferably RIE, rather than wet etching because the corners of the thin film 12a are not rounded and the end faces are perpendicular to the surface of the substrate 10.

The thickness of the Si thin film 12B is determined in consideration of the used wavelength λ of the Fresnel lens, the form of the Fresnel lens (transmission type or reflection type), the refractive index of the Fresnel lens and its surroundings, and the number of steps L of the Fresnel lens. . In the case of the transmission type, when the entire thickness is T, the thickness t of one layer is
It is given by the following equation (4). t = T / L = λ / Δn / L (4) where Δn is a refractive index difference between the lens and the surrounding medium. λ is from visible light to near infrared region, Δn is about 0.5, L
Is about several steps to several tens steps, t is 0.1 to 0.5 μm
This is a convenient range for forming the Si thin film 12B.

Next, as shown in FIG.
The substrate 10 on which is formed is introduced into a vacuum chamber, and another S
It is evacuated to a high vacuum, preferably an ultra-high vacuum, facing the substrate 10 ′ made of an i-wafer. The opposing Si wafer substrate 10 ′ is a substrate serving as a base for the diffractive optical element, and is preferably a double-side polished substrate polished not only on the front surface but also on the back surface. Subsequent steps are the same as in the first embodiment, and the patterned S
i, the thin film 12a is transferred by bonding at room temperature,
The transmission type diffraction type Fresnel lens 16B having the step structure is completed. In the present embodiment, the substrate 10 ′ and the thin film 12
Since a is made of Si, the substrate 10 'and the thin film 1
The whole 2a is transparent to infrared rays, and becomes a transmission type infrared diffractive optical element.

FIGS. 5A to 5G show a method of manufacturing a diffractive optical element according to a third embodiment of the present invention. The difference between the third embodiment and the first embodiment is that in the present embodiment, a mold for forming a diffractive Fresnel lens is manufactured. First, as shown in FIG. 1A, a substrate 10 made of a Si wafer or a glass substrate is prepared, and a fluorinated polyimide is formed on the substrate 10 as a release layer 11, and on the release layer 11, Al as a mold for diffractive Fresnel lens
The thin film 12A is deposited. As the thin film, in addition to Al, tantalum (Ta) having a higher mechanical strength is preferably used. These materials are selected from materials that can be easily formed into a thin film by a vacuum deposition method and can be bonded at room temperature. Al thin film 12
The film thickness of A is determined in consideration of the wavelength used for the diffraction type Fresnel lens, the molding material (refractive index of plastic), the number of steps, and the like.

Next, as shown in FIG. 1B, the thin film 12a of each layer of the diffractive Fresnel lens is collectively patterned by photolithography or the like on the Al thin film 12A. The RIE method was used for the etching. Thin film of each layer 1
The radius of 2a is determined in consideration of the focal length, brightness, number of steps, and the like of the Fresnel lens, as in the first embodiment.

The steps (c) to (f) are the same as in the first embodiment, and the thin film 12a of each layer is sequentially laminated to produce a mold 17 of a diffractive Fresnel lens. This mold 17
Has a shape obtained by inverting the diffraction type Fresnel lens to be manufactured, but is similar to the first embodiment in that the pattern of each layer is transferred by lamination.

Finally, as shown in FIG. 3G, a plastic material such as ZEONEX (registered trademark of Nippon Zeon Co., Ltd.) is injection-molded using a mold 17 to produce a diffractive Fresnel lens 16B having a desired shape. it can. In the present embodiment, since the optical element finally obtained is made of transparent plastic, it can be used as a transmission type diffractive Fresnel lens.

According to the above-described third embodiment, once the mold is manufactured, the subsequent molding step is a manufacturing method with a very high productivity, so that the cost of the diffractive Fresnel lens can be reduced. Become. In addition, since a high-strength metal material such as A1 or Ta can be used for the mold, the mold has excellent durability.
In addition, since a mold having a multi-stage structure can be manufactured using a hard material such as a metal, a diffraction Fresnel lens manufactured using the same has excellent shape accuracy. In the third embodiment, the injection molding method is used as the mold shape transfer method. However, another transfer method, for example, a casting method or a molding method may be used.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in each of the above embodiments, a diffractive Fresnel lens is described as a diffractive optical element, but the present invention can be applied to other diffractive optical elements such as a diffraction grating, a hologram, a holographic lens, and a holographic optical element. .

[0033]

As described above, according to the present invention, by adopting a patterning method such as a photolithography method for a plurality of thin films, it is possible to easily manufacture a stepped shape having four or more steps, thereby improving the diffraction efficiency. Since the shape accuracy is improved, aberration is reduced, and the surface roughness is reduced, so that light scattering is reduced, and an effect such as a further improvement in diffraction efficiency in combination with a step shape having four or more steps is obtained. As a result,
A diffractive optical element excellent in basic characteristics as an optical element having high diffraction efficiency and small aberration can be easily manufactured. Further, by repeatedly manufacturing the diffractive optical element using the same structure as a mold, mass production of the diffractive optical element becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus for manufacturing a diffractive optical element according to an embodiment of the present invention.

FIGS. 2A to 2F are diagrams illustrating a method for manufacturing a diffractive optical element according to the first embodiment of the present invention.

3A is a diagram showing a thin film pattern patterned by the manufacturing method according to the first embodiment, and FIG. 3B is a cross-sectional view showing a laminated state of a thin film of each pattern.

FIGS. 4A to 4F are diagrams illustrating a method for manufacturing a diffractive optical element according to a second embodiment of the present invention.

FIGS. 5A to 5G are diagrams illustrating a method for manufacturing a diffractive optical element according to a third embodiment of the present invention.

FIGS. 6A to 6D are diagrams showing a method of manufacturing a first conventional diffractive optical element.

FIGS. 7A to 7F are diagrams showing a method of manufacturing a second conventional diffractive optical element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Vacuum chamber 3 Substrate holder 4A 1st FEB source 4B 2nd FEB source 5A X axis table 5B Y axis table 5C Z axis table 5D Theta table 10 Substrate 11 Release layer 12A Al thin film 12a thin film 12B Si thin film 13 Stage 14 Al layer 15 FAB 16A Reflection type diffraction type Fresnel lens 16B Transmission type diffraction type Fresnel lens 17 type

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hidenori Yamada 430 Border, Nakai-cho, Ashigara-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. F-term (reference) 2H049 AA08 AA33 AA37 AA46 AA51 AA63 AA68

Claims (12)

[Claims] 1. A diffractive optical element having a stepped cross section having a plurality of steps, having a predetermined two-dimensional pattern corresponding to the steps, forming the step by laminating and joining together. A diffractive optical element comprising a plurality of thin films. 2. The diffractive optical element according to claim 1, wherein said plurality of thin films are made of a material reflecting light at a desired wavelength. 3. The diffractive optical element according to claim 1, wherein said plurality of thin films are made of a material that transmits light at a desired wavelength. 4. The plurality of thin films have a surface roughness of 2 Ra.
The diffractive optical element according to claim 1, wherein the diffractive optical element has a configuration of not more than nm. 5. A method for manufacturing a diffractive optical element having a stepped shape having a plurality of steps in cross section, comprising: a first step of forming a release layer on a substrate; and a step of forming the release layer on the substrate. A second step of forming a plurality of thin films having a predetermined two-dimensional pattern corresponding to the step on a mold layer, and peeling the plurality of thin films from the release layer, stacking and joining the thin films, And a third step of forming a step-like shape. 6. The method of manufacturing a diffractive optical element according to claim 5, wherein said plurality of thin films are made of a material reflecting light at a desired wavelength. 7. The method of manufacturing a diffractive optical element according to claim 5, wherein said plurality of thin films are made of a material that transmits light at a desired wavelength. 8. The plurality of thin films have a surface roughness of 2 Ra.
6. The method for manufacturing a diffractive optical element according to claim 5, wherein the structure is not more than nm. 9. A method for manufacturing a diffractive optical element having a cross-sectional shape having a stepped shape including a plurality of steps, comprising: a first step of forming a release layer on a substrate; and the step of forming a release layer on the substrate. A second step of forming a plurality of thin films having a predetermined two-dimensional pattern corresponding to the step on a mold layer, and peeling the plurality of thin films from the release layer, stacking and joining the thin films, A method for manufacturing a diffractive optical element, comprising: a third step of forming a structure having a stepped shape; and a fourth step of transferring a diffractive optical element using the structure as a mold. 10. The method for manufacturing a diffractive optical element according to claim 9, wherein said plurality of thin films are made of a material reflecting light at a desired wavelength. 11. The method according to claim 9, wherein the plurality of thin films are made of a material that transmits light at a desired wavelength. 12. The method according to claim 9, wherein the plurality of thin films have a surface roughness of 2 nm or less in Ra value.