JPH11106901A - Optical thin film deposition equipment - Google Patents

Abstract

(57) [Problem] To provide an optical thin film deposition apparatus capable of suppressing unevenness in film thickness even in the case of a lens having a large curvature. SOLUTION: An optical thin film forming apparatus is provided in a film forming chamber, wherein an element supporting mechanism for supporting a lens L to revolve or revolve and a plurality of vapor deposition sources 11 and 12 for generating vapor deposition particles for forming a thin film are provided. A membrane device is configured. If a plurality of evaporation sources 11 and 12 are provided in this manner, a thin film is formed by causing evaporation particles to enter the revolving or revolving lens L from a plurality of directions, so that the lens L has a large curvature. It is possible to uniform the film thickness distribution on the surface of even an optical element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an optical thin film (for example, a reflection film, an antireflection film, etc.) on the surface of an optical element such as an optical lens or a mirror.

[0002]

2. Description of the Related Art Generally, such optical thin films are formed by vacuum evaporation. FIG. 4 shows an example of a conventionally-used vacuum evaporation apparatus (optical thin film deposition apparatus). This apparatus 100 includes an evaporation source 102 and a correction plate 105 in a closed deposition chamber 101 capable of evacuating. And a plurality of optical elements (lenses) L rotatably supported by a support mechanism (not shown). The optical element L revolves as indicated by arrow B by the support mechanism and the arrow C
It is rotated as shown by.

In the film forming process, the heater or the electron gun 1 in the vapor deposition source 102 is evacuated while the inside of the film forming chamber 101 is evacuated.
The evaporation is performed by heating and evaporating the evaporation material 102b by 02a, and the evaporation particles are diffused as shown by an arrow A, and the evaporation particles are attached to the surface of the optical element L to form a thin film. At this time, the correction plate 105 is provided as shown in the drawing so that the film thickness distribution of the formed film does not become uneven due to the distance of the particles from the evaporation source 102 and the like.
As can be clearly understood from the drawing, this correction plate restricts to some extent the evaporation particles attached to the optical element L in the direction close to normal incidence (the amount of adhesion to the central part of the optical element), and oblique incidence directions. The restriction on the adhesion of the evaporated particles (in the vicinity of the optical element) is reduced to uniform the film thickness distribution.

[0006] In addition to rotating the optical element L on its own axis, the optical element L is also swung to change the angle formed between the evaporation source 102 and the optical element L to achieve a uniform film thickness distribution. Note that, conventionally, the correction plate 105 is an optical element L
Has a flat surface or a curved surface with a large radius of curvature (curved surface with a small curvature), and the shape is set so as not to cause unevenness in film thickness.

[0005]

However, recently, in an optical lithography apparatus called a stepper, an excimer laser beam having a short wavelength is used, and the refractive index of a lens used for such a short wavelength light is small. ,
An optical element having a small radius of curvature (a lens having a large curvature) has been increasingly used. If a conventional optical thin film forming apparatus is used as it is for forming a lens having such a large curvature as a film-forming target, there is a problem that vapor deposition particles are insufficiently adhered to an end portion (peripheral portion) of the lens and uneven film thickness occurs. There is. For this reason, film peeling occurs, and film weakness and a decrease in the refractive index around the lens occur remarkably, causing a change in the characteristics around the lens, and the optical system using these deteriorates the optical performance. There was a problem.

In view of such a problem, an object of the present invention is to provide an optical thin film forming apparatus capable of suppressing uneven film thickness even in a case of a lens having a large curvature.

[0007]

In order to achieve the above object, according to the present invention, there is provided, in a film forming chamber, an element supporting portion for supporting an optical element to revolve or revolve, and vapor deposition particles for forming a thin film. An optical thin film forming apparatus is configured by providing a vapor deposition source for generating the vapor deposition. At this time, a plurality of vapor sources are provided. If a plurality of evaporation sources are arranged in this way, a thin film is formed by causing the evaporation particles to enter the orbiting or revolving optical element from a plurality of directions.
Even with an optical element such as a lens having a large curvature, the film thickness distribution on the surface can be made uniform.

That is, when the film forming apparatus of the present invention is used, a film is not formed on the entire surface of the optical element by evaporation particles diffused and emitted from a single evaporation source as in the related art, but is diffused from a plurality of directions. A film is formed by the evaporating particles that fly. Here, on each part of the surface of the optical element, evaporation particles from an evaporation source whose incident angle is close to vertical incidence in a plurality of directions are most efficiently attached to form a film, but the surface shape has a large curvature. Even in the case of an optical element having the above, it is possible to have an evaporation source whose incident angle is close to vertical incidence at almost all positions on the surface, and the film thickness distribution is made uniform.

Preferably, the plurality of evaporation sources are arranged at different distances from the orbital axis of the element support.
Thus, the evaporated particles can be made to enter the optical element in different directions and at different incident angles and adhere to the optical element surface, and the film thickness distribution can be made more uniform.

From the same point of view, it is preferable to provide a throttle member between each evaporation source and the optical element supported by the element support for limiting the diffusion direction angle of the evaporated particles from each evaporation source. With this aperture member, it is possible to control the thickness distribution of the thin film formed on the optical element surface by limiting the incident angle of the evaporating particles reaching the optical element from each of the plurality of evaporation sources. The film thickness distribution can be made more uniform by limiting the incident angle in the direction of Further, a correction plate (a correction plate similar to the conventional one, which is close to normal incidence) for adjusting the unevenness of attachment of the evaporated particles to the surface of the optical element is provided between the aperture member and the optical element supported by the element supporting portion. By providing a correction plate for limiting the amount of adhesion of the portion, the film thickness distribution can be made more uniform.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a first embodiment of the optical thin film forming apparatus according to the present invention. This device 1
Reference numeral 0 denotes a configuration in which two evaporation sources 11 and 12 are provided in a film forming chamber (not shown) similar to that shown in FIG. Further, a support mechanism (not shown) for supporting the lens L so as to be able to rotate (arrow C) is provided in the film forming chamber, and aperture plates 15 and 16 are provided between the lens L and the evaporation sources 11 and 12. Is provided.

The lens L supported by the support mechanism is rotated about a vertically extending rotation axis X as shown by an arrow C.
The evaporation sources 11 and 12 are respectively evaporating substances 11b and 12b
Is heated and evaporated by the electron guns 11a and 12a to diffuse the evaporated particles. The evaporation source 11 is disposed immediately below the lens L (below the rotation axis X), and the evaporation source 12 is disposed obliquely below the lens L. The aperture plates 15 and 16 have circular or elliptical openings 15a and 16a, respectively.
Reference numeral 6a faces the center and periphery of the lower surface of the lens L as viewed from the evaporation sources 11 and 12, respectively.

Using such a film forming apparatus 10, a lens L
In order to form an optical thin film on the surface of the film, first, the film forming chamber is evacuated to a vacuum, and then the evaporating substance
1b and 12b are heated and evaporated to diffuse. The evaporated particles thus diffused are diffused as indicated by arrows A1 to A4. However, the evaporated particles diffused in the directions indicated by arrows A2 and A4 are blocked by the diaphragm plates 15 and 16, and the arrows A1 and A3. Only the evaporating particles diffused in the direction shown by the arrow pass through the openings 15a and 16a and reach and adhere to the surface of the lens L to form an optical thin film.

In the case of this example, the arrow A
The evaporating particles diffused in one direction are directed toward the central portion of the lower surface of the lens L, and reach the surface of the lens L in a state substantially near normal incidence and adhere thereto. On the other hand, the evaporated particles diffused from the evaporation source 12 in the direction of the arrow A3 obliquely enter the periphery of the lower surface of the lens L, and in this case also reach and adhere to the periphery of the lower surface of the lens L in a state almost nearly perpendicular. That is, the evaporation source 1
1 to the central part of the lower surface of the lens, and from the evaporation source 12 to the peripheral part of the lower surface of the lens. Good thin film formation is performed, and the film thickness distribution becomes uniform.

FIG. 2 shows a second embodiment of the optical thin film forming apparatus according to the present invention. This apparatus 20 is also configured by disposing two evaporation sources 21 and 22 in a film forming chamber (not shown). A support mechanism (not shown) for supporting the plurality of lenses L so that they can revolve (arrow B) and rotate (arrow C) is further provided in the film forming chamber, and is provided between the lens L and each of the evaporation sources 21 and 22. Are provided with aperture plates 25 and 26. Evaporation source 21,
Reference numeral 22 has the same configuration as the evaporation sources 11 and 12 of the first embodiment. The evaporation source 21 is disposed below the orbit of the lens L, and the evaporation source 22 is disposed obliquely below the lens L. The aperture plates 25 and 26 are formed with circular or elliptical openings 25a and 26a, respectively, and these openings 25a and 26a face the lower surface side and the peripheral side of the lens L as viewed from the evaporation sources 21 and 22, respectively.

Using such a film forming apparatus 20, a lens L
In order to form an optical thin film on the surface of the film, first, the film forming chamber is evacuated to a vacuum, and then evaporated particles are diffused from the evaporation sources 21 and 22. The evaporating particles diffused in this manner are indicated by arrows A
Diffusion as indicated by 1 to A4, but arrows A2 and A4
The vaporized particles diffused in the directions indicated by the arrows are blocked by the diaphragm plates 25 and 26, and only the vaporized particles diffused in the directions indicated by the arrows A1 and A3 pass through the openings 25a and 26a and adhere to the surface of the lens L. Then, an optical thin film is formed.

In the case of this example, the arrow A
The vaporized particles diffused in one direction are directed upward in the vertical direction with respect to the lower surface of the revolving lens L, and reach and adhere to the central portion of the lower surface of the lens L in a state almost nearly perpendicularly incident. On the other hand, the evaporated particles diffused from the evaporation source 22 in the direction of the arrow A3 obliquely enter the self-revolving lens L, and arrive and adhere to the peripheral portion of the lens in a state almost nearly perpendicularly incident. Here, since the attachment efficiency and the attachment density of the vertically incident evaporating particles are the highest, the optical thin film is mainly formed by the evaporating particles from the evaporation source 21 at the central portion of the lens lower surface, and the peripheral portion of the lens lower surface is formed. The optical thin film is formed mainly by the evaporated particles from the evaporation source 22, the efficient thin film formation is performed in any part, and the film thickness distribution becomes uniform.

FIG. 3 shows a third embodiment of the optical thin film forming apparatus according to the present invention. This apparatus 30 is obtained by adding a correction plate 31 to the film forming apparatus shown in FIG. 2, and the same members as those shown in FIG. The correction plate 31 is configured to detect the evaporation particles from the evaporation source through the lens L.
In view of the fact that the attachment efficiency is highest when the light is perpendicularly incident on the surface and the attachment efficiency becomes lower as the incident angle increases toward the oblique incidence side, a plurality of blades 32 are provided to limit the incident particles near the normal incidence.

Using such a film forming apparatus 30, the lens L
In order to form an optical thin film on the surface of the film, first, the film forming chamber is evacuated to a vacuum, and then evaporated particles are diffused from the evaporation sources 21 and 22. The evaporating particles diffused in this manner are indicated by arrows A
Evaporated particles diffused as indicated by 1 to A4 and diffused in the directions indicated by arrows A2 and A4 are blocked by the diaphragm plates 25 and 26, and only the evaporated particles diffused in the directions indicated by arrows A1 and A3 are opened. , 26a.

The evaporated particles that have passed through the openings 25a and 26a pass through the correction plate 31, and after the passing particles are partially restricted by the blades 32, they reach the surface of the lens L and adhere to the lens L. Form a thin film. The restriction of the passing particles by the blades 32 is such that the portion which is perpendicularly incident on the surface of the lens L is the largest and becomes smaller on the oblique incidence side, thereby further uniforming the film thickness distribution of the optical thin film to be formed. I do.

As can be understood from the above description, the diaphragm plate prevents the oblique incident component from entering the evaporation particles diffused from each evaporation source, and uses only the vertical incidence component having good adhesion efficiency to achieve the film thickness distribution. Is intended to be uniform, but for this reason,
A plurality of evaporation sources are provided so that a film can be formed at the center and the periphery of the lens (optical element) using particles evaporated from different evaporation sources. On the other hand, the correction plate is for restricting the incidence of the vertical incidence component to some extent in order to eliminate the difference between the normal incidence component and the oblique incidence component with respect to the attachment of the evaporation particles from the predetermined evaporation source. The correction plate and the correction plate have the same purpose in terms of making the film thickness distribution uniform, but their methods are greatly different.

In each of the above embodiments, two evaporation sources are used. However, three or more evaporation sources may be provided. In this case, three or more diaphragm plates are used. Further, the disposition position of the evaporation source can be appropriately set according to the surface shape of the optical element. In addition, although an electron gun is used as a means for heating the evaporated substance in the evaporation source, a resistance heating or induction heating method may be used. Further, a gas such as oxygen or argon may be introduced into the film formation chamber during film formation.

[0023]

As described above, according to the present invention,
Since a plurality of evaporation sources are provided in the film forming chamber, thin films are formed by making evaporation particles incident on the revolving or revolving optical element from a plurality of directions, and an optical element such as a lens having a large curvature is formed. Even in this case, the film thickness distribution on the surface can be made uniform. That is, since the film is formed by evaporating particles that diffuse and fly from a plurality of directions, even in the case of an optical element having a surface shape with a large curvature, an evaporation source whose incident angle is close to normal incidence at almost all positions on the surface is considered. It is possible to form an optical thin film having a uniform film thickness distribution even on the surface of an optical element having a large curvature.

Preferably, the plurality of evaporation sources are arranged at different distances from the revolution axis of the element support.
Thus, the evaporated particles can be made to enter the optical element in different directions and at different incident angles and adhere to the optical element surface, and the film thickness distribution can be made more uniform.

From the same point of view, it is preferable to provide a throttle member between each evaporation source and the optical element supported by the element support for limiting the diffusion direction angle of the evaporated particles from each evaporation source. With this aperture member, it is possible to control the thickness distribution of the thin film formed on the optical element surface by limiting the incident angle of the evaporating particles reaching the optical element from each of the plurality of evaporation sources. The film thickness distribution can be made more uniform by limiting the incident angle in the direction of Further, by providing a correction plate between the aperture member and the optical element supported by the element support for adjusting the unevenness of the evaporation of particles on the surface of the optical element, the film thickness distribution can be made more uniform.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical thin film forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of an optical thin film forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a configuration of an optical thin film forming apparatus according to a third embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a conventional optical thin film forming apparatus.

[Explanation of symbols]

 10, 20, 30 Film forming apparatus 11, 12, 21, 22 Evaporation source 15, 16, 25, 26 Aperture plate 31 Correction plate

Claims (4)

[Claims] An element supporting portion for supporting an optical element and revolving or revolving the optical element and vapor deposition particles for forming a thin film on the surface of the optical element are provided in a film-forming chamber formed so as to be sealable. An optical thin film forming apparatus comprising a plurality of vapor deposition sources to be generated. 2. The optical thin film forming apparatus according to claim 1, wherein the plurality of evaporation sources are arranged at different distances from a revolution axis of the element support. 3. An aperture member for limiting an angle of diffusion of evaporation particles from each of the evaporation sources is provided between each of the evaporation sources and the optical element supported by the element support. The optical thin film forming apparatus according to claim 1, wherein a thickness distribution of a thin film formed on the surface of the optical element is controlled by limiting an incident angle of the evaporated particles reaching the optical element. . 4. A correction plate is provided between the stop member and the optical element supported by the element support, for adjusting unevenness in attachment of evaporated particles to the surface of the optical element. Item 4. The optical thin film deposition apparatus according to Item 3.