JP2002189113A - Diffraction optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorite diffraction optical element improved in workability. SOLUTION: A fluorite (CaF2) substrate having 100 mm (4 inches) diameter and 4 mm thickness is used as a BO(binary optics) substrate 11, on which a fluorine-containing quartz film 12 having 0.17 μm thickness is formed in a sputtering type vapor deposition system by using amorphous fluorine-containing quartz (SiO2:F) as the sputtering target and a mixture gas prepare by mixing fluorine by 10% in argon as the sputtering gas. Then the fluorine-containing quartz film 12 is worked with plasma by using chromium masks 21 to 23 and formed into a step-like shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorite diffractive optical element which is effective as an optical system for far ultraviolet rays and an optical system for vacuum ultraviolet rays.

[0002]

2. Description of the Related Art A diffraction grating is used as a light-splitting element of a spectroscope, and its cross-sectional shape is a so-called blazed type having a sawtooth shape.

On the other hand, in recent years, a binary optics (BO) element having a step-like lattice cross section has attracted attention as an optical element utilizing a diffraction phenomenon, and is also called a BO lens, and has an achromatic effect, an aspheric surface. Therefore, there is great expectation for the development of a new optical system.

An optical element applied to a lens optical system for photographing with a general steel camera or the like can be manufactured by a molding method of plastic and glass by molding using a metal mold. In order to apply to light rays with short wavelengths such as UV transmittance, finer processing and higher precision are required, the conventional mold processing method,
Techniques such as molding method and lens material have not been established.

[0005] With conventional lens materials and processing methods, it is difficult to produce a BO element that can be applied to ultraviolet light and far ultraviolet light, that is, a BO lens. The required specifications of this BO element, that is, the BO lens, greatly exceed the current blazed-type cutting limit, but high-precision fine processing can be achieved by using a photolithography method that is a semiconductor processing method. To some extent it has become possible.

Therefore, a quartz substrate is used, an i-line stepper (reduction exposure baking apparatus) is used for exposure baking, a photolithography technique using ultraviolet rays for semiconductor manufacturing, and a dry etching process using a parallel plate type RIE apparatus. Techniques using technology have been devised, which allow micro-machining to a certain extent and make it possible to produce eight-stage BO lenses.

[0007]

However, in the conventional example described above, the BO element has been processed by directly processing the quartz substrate.
There is a major problem that contraction is caused by irradiation of a powerful energy beam of a laser beam such as F or KrF. Therefore, fluorite is attracting attention as a substrate material in place of quartz. Fluorite can be said to be an excellent material because it can also be expected to have an achromatizing effect, but it has difficulties in processing and handling. That is, there is a big problem that dry etching processing which is possible with quartz is difficult.

On the other hand, optical lithography tends to be used in the vacuum ultraviolet region, that is, at a wavelength of 200 nm or less. Quartz has insufficient performance as a glass material constituting an optical system capable of performing such a process. It is the only glass material that can be used instead.

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 using a fluorite substrate.

[0010]

According to a first aspect of the present invention for achieving the above object, the present invention uses fluorite as a substrate material,
A diffractive optical element, wherein a stepped shape made of an amorphous fluorine-containing quartz film is formed on the surface of the substrate.

The present invention according to claim 2 is the diffractive optical element according to claim 1, wherein the fluorine-containing quartz film is a thin film formed by a vacuum deposition method.

According to a third aspect of the present invention, there is provided the diffractive optical element according to the first aspect, wherein the stepped shape made of the fluorine-containing quartz film is formed by a photolithography method and a dry etching method. .

According to a fourth aspect of the present invention, there is provided the diffractive optical element according to the first aspect, wherein the stepped shape made of the fluorine-containing quartz film is formed by a photolithography method and a lift-off method. .

According to a fifth aspect of the present invention, the fluorine-containing quartz film is formed by sputtering, ion beam sputtering, CVD,
3. The diffractive optical element according to claim 2, wherein the film is formed by any one of B sputtering.

According to a sixth aspect of the present invention, one of the thin film forming means used in the photolithography method and the lift-off method is a sputtering method, an ion beam sputtering method, or an electron beam sputtering method.
5. A vacuum deposition method such as B deposition.
Is a diffractive optical element described in 1. above.

According to a seventh aspect of the present invention, there is provided a diffractive optical lens comprising an antireflection film provided on the front surface and the back surface of the substrate of the diffractive optical element according to the first to sixth aspects.

An eighth aspect of the present invention is an optical system having the diffractive optical lens according to the seventh aspect.

According to a ninth aspect of the present invention, there is provided an exposure printing apparatus for semiconductor manufacturing incorporating the optical system according to the eighth aspect.

According to a tenth aspect of the present invention, there is provided a semiconductor device manufactured by using the exposure printing apparatus for manufacturing a semiconductor according to the ninth aspect.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a perspective view of the BO lens 1, and FIG. 2 is a cross-sectional view.
assuming for F ₂ lasers m, has about 1800 annular zone on a circle having a diameter of 20mm have been engraved, the stepped BO shape of 8 stages each annular zone, respectively.

FIG. 3 is a schematic diagram of an eight-step staircase BO element unit. The outermost ring zone is a design value, and the width of each step is 0.1 mm.
The width is 35 μm, the height is 0.024 μm, the width of each annular zone is 2.8 μm, and the height is 0.17 μm.

FIG. 4 shows B in the process of the first embodiment.
FIG. 2 shows a cross-sectional view of an O substrate, in which a fluorite (CaF
₂ ) Using a substrate, an amorphous fluorine-containing quartz (SiO ₂ : F) is used as a sputtering target on the substrate 11, and a mixed gas of 10% fluorine mixed with argon is used as a sputtering gas. BO substrate 1 in a vacuum deposition system
A fluorine-containing quartz film 12 having a thickness of 0.17 μm is formed on the film 1. The fluorine-containing quartz film 12 may be formed by an ion beam evaporation method, a CVD film formation method, or the like, in addition to the sputtering method.

FIG. 5 is a cross-sectional view of the BO substrate and the mask. In manufacturing the BO lens, chrome masks 21 to 23 are arranged above the BO substrate 11. i-line (wavelength λ = 3
65nm) stepper and use chrome masks 21-
After the pattern 23 is reduced and baked on a negative photoresist on the BO substrate 11, the fluorine-containing quartz film 12 on the substrate 11 is formed by dry etching (RIE) using the developed resist pattern as a mask. Plasma etching. In addition, a mixed gas of argon and CF ₄ is used as an etching gas used at this time.

Generally, metal fluoride represented by fluorite has difficulty in handling due to physical and mechanical properties, and chemical etching using a halogen-based dry etching gas cannot be applied to processing. Therefore, it is necessary to use physical sputter etching using an inert gas.

However, a conventionally known chemical dry etching method can be applied to the fluorine-containing quartz film 12 in the present embodiment, and fluorite (CaF ₂ )
Since the BO substrate 11 made of is inert to the reaction gas, the BO substrate 11 serves as a stopper, which is a great advantage for improving the accuracy.

In the present embodiment, three masks are used.
Using the disks 21 to 23, the above-described photolithography
Process and etching process three times
, F _TwoHigh-precision 8 applicable to laser lithography
Stepped BO lenses can be manufactured.

As an antireflection film on both surfaces of the eight-stage BO lens manufactured as described above, a film thickness of 2 was formed by vacuum evaporation.
A 67 ° magnesium fluoride (MgF ₂ ) film can be formed. By forming this antireflection film,
When the diffraction efficiency was measured using KrF laser light,
An average of 12 compared to the case where no anti-reflection film is formed
%improves.

Further, through a process similar to that of the first embodiment, a BO lens having a diameter of 200 mm is manufactured by split exposure of a stepper, and a KrF laser stepper equipped with a lens optical system incorporating the BO lens is used. A high-performance semiconductor device can be manufactured by reduced baking on a silicon substrate and a series of semiconductor manufacturing processes.

FIG. 6 is a cross-sectional view of a BO substrate according to the second embodiment.
A fluorite substrate having a thickness of 0 mm (4 inches) and a thickness of 4 mm was used. The calcium fluoride (CaF ₂ ) film 32 is laminated, and the total is 240
The composite film 33 having a thickness of about 0.17 μm is formed by performing continuous vapor deposition repeatedly seven times with Å as a unit.

Then, as shown in FIG. 7, a BO lens is manufactured by using an i-line stepper in the same manner as in the first embodiment, and the pattern of the chrome masks 21 to 23 is formed on the BO substrate 11. After reduced baking on a negative type photoresist, dry etching (RI) using a mixed gas of argon and CF ₄ with the developed resist pattern as a mask.
E) method, fluorine-containing quartz film 3 on BO substrate 11
1 is etched.

In the present embodiment, three masks 2
By repeating the above process three times using Nos. 1 to 23, an eight-stage BO lens can be obtained. In addition, it is possible to manufacture a highly accurate BO element in which each step is clear.

FIG. 8 is a sectional view of a BO substrate and a mask according to the third embodiment. A circular BO lens having a diameter of 20 mm is manufactured by applying a lift-off process. A fluorite substrate having a diameter of 100 mm (4 inches) and a thickness of 4 mm was used as the BO substrate 11, and a 0.5 μm thick film was formed on the BO substrate 11 using a resist coating device (spinner).
An m-line negative resist for i-line is formed.

Subsequently, the first resist is used to cover the first resist.
After the pattern of the chrome mask 21 is reduced and printed using an i-line stepper, a resist pattern corresponding to the first chrome mask 21 is manufactured by a known resist developing process. Next, a 560 ° -thick fluorine-containing quartz film 41 is formed using a sputtering-type film forming apparatus. continue,
By removing the resist pattern with acetone, B
The second stage fluorine-containing quartz film 41 of the O lens can be formed.

Similarly, the same process is repeated using the second chromium mask 22 and the third chromium mask 23, and the fluorine-containing quartz film 41 is laminated on the substrate 11. The width of each step of the outermost annular zone is 0.35μ
m, the height is 0.056 μm, and the width is 2.
Four-stage BO lenses of 8 μm and 0.17 μm can be manufactured.

[0035]

As described above, in the fluorite diffractive optical element according to the present invention, the processability can be improved by forming a fluorine-containing quartz film on a fluorite substrate.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a BO lens.

FIG. 3 is a schematic view of a step-like BO element.

FIG. 4 is a cross-sectional view of the BO substrate according to the first embodiment.

FIG. 5 is a cross-sectional view of a BO substrate and a mask.

FIG. 6 is a sectional view of a BO substrate according to a second embodiment.

FIG. 7 is a sectional view of a BO substrate and a mask.

FIG. 8 is a sectional view of a BO substrate according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 1 BO lens 11 BO substrate 12, 31, 41 Fluorine-containing quartz film 21, 22, 23 Chromium mask 32 Calcium fluoride film 33 Composite film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/027 H01L 21/30 515D

Claims (10)

[Claims] 1. A diffractive optical element, wherein fluorite is used as a material of a substrate, and a stepped shape made of an amorphous fluorine-containing quartz film is formed on the surface of the substrate. 2. The diffractive optical element according to claim 1, wherein the fluorine-containing quartz film is a thin film formed by a vacuum deposition method. 3. The diffractive optical element according to claim 1, wherein the stepped shape made of the fluorine-containing quartz film is formed by a photolithography method and a dry etching method. 4. The diffractive optical element according to claim 1, wherein the stepped shape made of the fluorine-containing quartz film is formed by a photolithography method and a lift-off method. 5. The diffractive optical element according to claim 2, wherein the fluorine-containing quartz film is formed by any one of sputtering, ion beam sputtering, CVD, and EB sputtering. 6. The method according to claim 4, wherein one of the thin film forming means used for the photolithography method and the lift-off method is a vacuum deposition method such as sputtering, ion beam sputtering, and EB deposition. Diffractive optical element. 7. A diffractive optical lens, wherein an anti-reflection film is provided on the front surface and the back surface of the substrate of the diffractive optical element according to claim 1. 8. An optical system having the diffractive optical lens according to claim 7. 9. An exposure printing apparatus for manufacturing a semiconductor, incorporating the optical system according to claim 8. 10. A semiconductor device manufactured by using the exposure printing apparatus for manufacturing a semiconductor according to claim 9.