JP2000028812A - Diffractive optical element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffraction optical element which is good in workability at the time of manufacture and a process for producing the same. SOLUTION: The thickness of a substrate 1' is 40 mm and the weight thereof is about 2.8 kg. A groove 5 for handling is formed to a U-shape in cross section and is formed circumferentially on the flank of this substrate 1' at a width of 14 mm and a depth of 10 mm. The groove 5 formed in such a manner is exceedingly effective in preventing flaw, stain and dirt accompanying the handling at the time of moving and storing the substrate 1' during the respective stages from rough polishing to finish polishing.

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 and a method for manufacturing the same.

[0002]

2. Description of the Related Art A diffraction grating has been conventionally used as a spectral element of a spectroscope. The cross-sectional shape is a sawtooth shape, which is called a so-called phrased type, and some have diffraction efficiency as high as 100%.

On the other hand, in recent years, a step-like BO (Binary Optics) element has attracted attention as an optical element utilizing diffraction. That is, the BO element is also called a BO lens, and is expected to have an achromatic effect and an aspherical effect. Therefore, there is great expectation for the development of a new optical system.

[0004] In order to apply this BO lens to a lens optical system for photographing with a general steel camera, it is possible to produce a plastic and glass by a molding method using a mold using a mold. However, finer processing and accuracy are required for application to light having a short wavelength such as ultraviolet light, and thus, techniques such as a mold processing method, a molding method, and a lens material have not been established at present.

As described above, it is difficult to produce a diffractive optical element, that is, a BO lens applicable to ultraviolet rays and far-ultraviolet rays. Therefore, it is necessary to use a photolithography technique using ultraviolet rays for semiconductor manufacturing and a dry etching technique. It is proposed that this be done by

[0006]

In the production of a BO lens, glass, quartz, fluorite and ceramics are used as a substrate. When the aperture of the lens is small, the thickness of the substrate is small and there is almost no problem, but the thickness increases as the aperture increases. For example, a lens having a diameter of 300 mm requires a thickness of at least 40 to 50 mm. Assuming that the specific gravity of the substrate is 2.2 g / cm ³ , the weight of the substrate is about 6 to
It can be as much as 8 kg. To process the substrate, it is necessary to perform a manufacturing process by sufficiently pressing down the end surface, the front surface, and the rear surface of the substrate by hand and moving and fixing the substrate.

However, when this conventional manufacturing method is applied, a serious problem occurs. That is, since the weight of the substrate is heavy, work and handling are difficult, and scratches and stains due to the suppression of the surface are likely to occur, and spin coating in the photolithography process is likely to be difficult.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a diffractive optical element having good workability at the time of manufacturing and a method of manufacturing the same.

[0009]

A diffractive optical element according to the present invention for achieving the above object is characterized in that a locking portion for use in handling and fixing is formed on a side surface of a substrate.

Further, a method of manufacturing a diffractive optical element according to the present invention is characterized in that a diffractive optical element is manufactured by handling and fixing the substrate using a locking portion provided on the substrate.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. 1 is a perspective view of the BO lens 1, FIG. 2 is a schematic view thereof, and FIG. 3 is an enlarged sectional view of an 8-stage BO element unit. The BO lens 1 is designed on the basis of quartz and used for a KrF laser beam having a diameter of 200 mm and a working wavelength of 248 nm using quartz as a substrate. The number of BO element units, that is, the number of annular zones is about 18,000. Each annular zone has an eight-step staircase BO shape. The outermost annular zone has a design value of 0.35 μm in width and 0.061 μm in height at each step.
And the width and height of each annular zone, that is, the element unit, are 2.8.
μm and 0.427 μm.

The BO lens 1 is made of an i-line (λ = 365n).
m), the pattern of the chrome mask is reduced and baked on the photoresist on the BO substrate by using the stepper for m), and the substrate is etched using the developed resist pattern as a mask by dry etching.

FIG. 4 is a sectional view of an eight-stage BO lens 1 formed by repeating the above process three times by divided exposure using three masks 2, 3, and 4.

The substrate cut out from the raw material is cut into a disk having a predetermined size, and then a groove is formed on a side surface. FIG. 5 is a cross-sectional view of the BO lens 1 provided with a groove for handling according to the first embodiment. The thickness of the substrate 1 'is 40 mm and the weight is about 2.8 kg. The groove 5 for handling has a U-shaped cross section, and is provided on the side surface of the substrate 1 'in a circumferential shape with a width of 14 mm and a depth of 10 mm.

By providing the groove 5, handling and handling during movement and storage of the substrate 1 'during each process from rough polishing to finish polishing, and prevention of scratches, dirt and dust attached to handling are remarkable. effective.

The processing of the groove 5 provided on the side surface of the substrate 1 'is suitably performed as a step prior to the processing of the surface shape of the substrate 1'. The shape of the groove 5 will be determined according to the shape of the handling device.

By applying this embodiment, handling can be performed mechanically without relying on human hands, and (1) automation of the manufacturing process, (2) cleaning, and (3) It offers countless advantages such as automation of assembly, (4) clean and automated storage, and simplification of storage.

In the second embodiment shown in the plan view of FIG. 6 and the sectional view of FIG. 7, a hole is formed instead of the groove 5 on the substrate 1 '. That is, the diameter 1 is provided on the side surface of the substrate 1 '.
Four 4 mm holes 5 are provided symmetrically from the center, and the depth of the hole 6 is 20 mm.

By the handling by the four arms using the holes 6, in a series of polishing steps and the like, as in the previous embodiment, B with much less scratches and dirt than in the prior art.
The O lens 1 can be manufactured.

Various shapes such as U-shape, V-shape and U-shape can be applied to the shape of the groove 5 and the hole 6. These are handling,
It can be used properly depending on the form of chucking.

FIG. 8 is a sectional view of the third embodiment, and FIG. 9 is a plan view. A convex protrusion 7 for handling is provided in a ring shape around the substrate 1 'with a width of 14 mm and a depth of 10 mm. ing.

In the fourth embodiment shown in FIGS. 10 and 11,
A straight cutting process is performed on the side surface of the substrate 1 ', and the width 2
An orifice-shaped step portion 8 having a length of 8 mm and a maximum depth of 10 mm is symmetrically formed at four places from the center.

By handling with four arms using the stepped portion 8, a series of polishing steps and a step of forming a BO element are performed.
The O lens 1 can be manufactured. Further, since the present embodiment has the orientation flat vertical surfaces on all sides, it can be used for positioning when abutting and measuring.

As a fifth embodiment, in order to improve the diffraction efficiency of the BO lens 1, an enhancement film, that is, an antireflection film is provided on the surface of the BO lens 1. 12, FIG. 13 is a second cross-sectional view of a cross section when attached, respectively ZoTorumaku 9 by vapor deposition on the back surface of the BO element 1 of the third embodiment, respectively, MgF ₂ and A1 ₂ O _A permeation increasing film 9 made of a _three- layered film ₃ is sputter-deposited. The thickness of the permeable film 9 is 272 nm, and the average thickness of each layer is 68 nm. When the diffraction efficiency was measured, an improvement of 18% was found.

At the time of deposition and measurement of the permeability-enhancing film 9, a holding mark of a mounting tool may have remained in the past. However, handling holes 6 and projections provided at four positions for holding the substrate 1 ′ were provided. The use of No. 7 results in a very good finish without traces.

Through the same steps as in the first to fourth embodiments,
The BO lens 1 having a diameter of 200 mm can be formed by the division exposure of the stepper. Utilizing a handling locking portion provided on the side surface of the BO lens 1, a KrF laser stepper equipped with a lens optical system incorporated in a lens barrel is used to perform reduction baking onto a silicon substrate and a series of semiconductors. By a manufacturing process, a high-performance semiconductor device can be manufactured.

[0027]

As described above, the diffractive optical element and the manufacturing method according to the present invention can improve the manufacturing process and quality by forming the locking portion on the side surface of the substrate. In particular, since problems such as scratches, dirt, and adhesion of dust can be remarkably improved, not only diffractive optical elements in the visible, infrared, and ultraviolet regions,
The performance of the diffractive optical element and the diffractive optical lens used in the far ultraviolet and vacuum ultraviolet regions can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a BO lens.

FIG. 2 is a conceptual diagram of a BO lens.

FIG. 3 is an enlarged sectional view of a BO lens.

FIG. 4 is a diagram illustrating the production of a BO lens.

FIG. 5 is a sectional view of the first embodiment.

FIG. 6 is a plan view of the second embodiment.

FIG. 7 is a sectional view.

FIG. 8 is a plan view of a third embodiment.

FIG. 9 is a sectional view.

FIG. 10 is a plan view of a fourth embodiment.

FIG. 11 is a sectional view.

FIG. 12 is a sectional view of a BO lens provided with a permeable film.

FIG. 13 is a cross-sectional view of a BO lens provided with a permeable film.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 BO lens 1 ′ substrate 5 groove 6 hole 7 protrusion 8 step 9 permeable membrane

Claims (8)

[Claims] 1. A diffractive optical element, wherein a locking portion for use in handling and fixing is formed on a side surface of a substrate. 2. The diffractive optical element according to claim 1, wherein the locking portion is a groove or a hole. 3. The diffractive optical element according to claim 1, wherein the locking is a projection. 4. A method for manufacturing a diffractive optical element, wherein the diffractive optical element is manufactured by handling and fixing the substrate using a locking portion provided on the substrate. 5. The method of manufacturing a diffractive optical element according to claim 4, wherein the steps of manufacturing the diffractive optical element include polishing, cleaning, bonding, photolithography, installation of an antireflection film, and processing of the substrate. 6. An optical system comprising the diffractive optical element according to claim 1 as a component. 7. The exposure printing apparatus according to claim 6, wherein the optical system is incorporated. 8. A semiconductor device manufactured by using the exposure printing apparatus for manufacturing a semiconductor according to claim 7.