JP3359292B2 - Optical element and optical system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element and an optical system using the same, for example, a semiconductor exposure apparatus, a camera,
In an optical device such as a telescope or a microscope, the optical device is suitable when a plurality of optical members among optical elements such as a lens and a prism constituting the optical system are joined and used.

[0002]

2. Description of the Related Art An optical system constituting an optical apparatus includes a single lens, a cemented lens in which a plurality of lenses are cemented, a prism, and the like.
An optical element in which a plurality of optical members are bonded is often used. Of these, an adhesive such as balsam is mainly used for bonding a plurality of lenses. Also,
Recently, various proposals have been made to use a phase type diffractive optical element (binary optics) having a blazed shape as a new optical element in an optical system.

[0003] A diffractive optical element is used as an optical element for converting an incident wavefront into a predetermined wavefront. This diffractive optical element has features not found in refraction lenses. For example, it has features such as having a dispersion value opposite to that of a refraction lens, and having a compact optical system because it has substantially no thickness.

In general, when a diffractive optical element is formed into a binary shape, a semiconductor element manufacturing technique can be applied to its manufacture, and a fine pitch can be realized relatively easily. For this reason, research on a binary diffractive optical element in which a blazed shape is approximated by a step shape has been actively pursued recently.

FIGS. 9 and 10 are explanatory views of a diffractive optical element. In the figure, reference numeral 50 denotes a Fresnel lens, 51 denotes a blazed diffraction grating, 52 denotes a binary diffractive optical element, and 53 denotes a diffraction grating having a stepped cross-sectional shape.

As a diffractive optical element, for example, a Fresnel lens 50 has a blazed shape 51 as shown in FIG.
Is ideal, and the diffraction efficiency with respect to the design wavelength can be theoretically set to 100%. However, since it is actually difficult to process the complete blazed shape 51, the blazed shape 51 is usually quantized and approximated to form a stepped cross-sectional shape 53 as shown in FIG. Are used. Although the binary diffractive optical element 52 is an approximation of the Fresnel lens 50, the diffraction efficiency of the first-order diffracted light is 90%.
% Or more can be secured.

Here, in order to increase the degree of approximation or to give the diffractive optical element as an optical element a large power, it is desirable that the minimum line width of the diffractive optical element be as small as possible. Therefore, a lithography process cultivated in a semiconductor manufacturing apparatus is used to obtain a high-performance diffractive optical element.

[0008] The apparatus for the lithography process currently used here is designed on the assumption that a wafer having a thickness of less than 1 mm is handled. For this reason, the diffractive optical element 55 created using the lithography process
As shown in FIG. 10, it was formed on a wafer-shaped optical material.

Next, consider the case where the diffractive optical element obtained by the above-described manufacturing method is used for an illumination system of a semiconductor exposure apparatus. FIG. 11 shows a conventional exposure apparatus for manufacturing a semiconductor device. In FIG. 11, 61 is a light source, 62 is a reticle, 6
Reference numeral 3 denotes a reticle holding table, 64 denotes a projection optical system, 65 denotes a lens, 66 denotes a wafer, and 67 denotes a wafer stage. The wafer 66 is positioned at a desired position by the wafer stage 67, and the focus of the wafer
6 is adjusted to the focus position. A shutter (not shown) is opened to illuminate the reticle 62 with illumination light from the light source 61, and the circuit pattern on the reticle 62 is projected onto the projection optical system 6.
4 onto the wafer 66. Lens 65
Is capable of moving up and down slightly in order to cope with expansion and contraction of the wafer 66 due to thermal distortion and the like, and performs magnification correction and aberration correction of the projection optical system 64. In a projection lens system of a semiconductor exposure apparatus, since the required accuracy is strict, it is general to set an optical axis in a vertical direction in consideration of gravity. When a diffractive optical element is used for the projection lens system, the diffractive optical element is arranged in the projection optical system in a horizontal state.

[0010]

When a diffractive optical element is manufactured through a lithography process, the semiconductor manufacturing apparatus is manufactured within the standard range of the Si wafer, and the precision is maintained most within the range. Designed to lean. If it is modified to use outside the range, it is difficult to maintain accuracy.

Further, the lithography step will be described in detail, including a resist pattern formation and an etching step. With resist pattern formation, applying an organic resist, exposing using light through a reticle on which the surface shape to be processed is formed, baking, developing process,
A resist pattern having a desired surface shape is formed. In applying the resist, a device called a spinner, which rotates the substrate at a high speed and applies the resist to a uniform film thickness, is used.As the weight of the substrate increases, the load of rotation increases, making it difficult to control. It is becoming.

A bake is performed using a hot plate having a high temperature controllability and is controlled on a second-by-second basis. However, it is very difficult to control the temperature on a thick substrate such as a material having poor thermal conductivity such as quartz. Difficult. In the etching step, etching is performed using a chemical with the resist pattern as a mask, or processing is performed using a dry etching apparatus using plasma or the like, and dry etching with high precision is mainly used. In the dry etching equipment,
Although substrate cooling or the like is required, it is very difficult to control the temperature of a thick substrate with a material having low thermal conductivity, as in the case of resist baking.

Therefore, the diffractive optical element has a size of several hundred μm to several m.
It is manufactured on a substrate having a thickness of m.

The thin diffractive optical element having an outer shape of 10
When an optical element having a length of 0 to 200 mm is prepared and mounted on a projection optical system, if the optical element is held in a lens barrel by a conventional holding method, a contact portion due to its own weight deformation of the diffractive optical element and processing accuracy of the lens barrel is obtained. They are easily deformed due to non-uniformity, distortion at the time of mounting due to a force applied at the time of fixing, pressure fluctuations, and temperature fluctuations, surface deformation occurs, and performance at the time of design cannot be exhibited, and image performance may deteriorate. As one of the solutions to such a problem, a method of joining and integrating with a thick member having a strength capable of withstanding its own weight deformation by the respective insertion bonding methods is considered. At this time, the adhesive wraps around the optical element surface and
The generation of the gap and the deterioration of the flatness due to the adhesion become problems. In addition, stress remains due to the force applied at the time of joining, and deformation or breakage due to the distortion also poses a problem.

An object of the present invention is to provide an optical element and an optical system capable of preventing deformation of an optical member when joining optical members and preventing surface contamination with an adhesive. I do.

[0016]

According to a first aspect of the present invention, there is provided an optical element in which two or more optical members are joined by using an adhesive, wherein two or more of the two or more optical members are adjacent to each other. The two opposing surfaces of the two optical members are both flat or convex and concave curved surfaces of the same shape, and the center of the two surfaces is bonded by Optical Contact, and of the two adjacent optical members, One or both optical members are characterized in that one or more grooves around the adhesive are provided nearer to the center of the optical member than the adhesive and outside the effective diameter of the optical member.

According to a second aspect of the present invention, in the first aspect of the present invention, the two adjacent optical members have different thicknesses from each other, and the optical member having a smaller thickness is provided with the groove. I have.

According to a third aspect of the present invention, in the first or second aspect, at least one optical member constituting the optical element is a refractive optical element.

According to a fourth aspect of the present invention, in the first or second aspect, at least one optical member constituting the optical element is a diffractive optical element.

According to a fifth aspect of the present invention, in the fourth aspect, the diffractive optical element is a phase type diffractive optical element having a quantized blazed shape.

According to a sixth aspect of the present invention, in the first or the second aspect of the present invention, in joining the optical members, a peripheral portion of the optical member is joined.

According to a seventh aspect of the present invention, in the first or second aspect, the two optical members are joined by using an adhesive, and the adhesive is an organic adhesive.

According to an eighth aspect of the present invention, in the first aspect, the two optical members are joined by using an adhesive, and the adhesive is an inorganic adhesive.

An optical system according to a ninth aspect of the present invention is characterized by employing at least one optical element according to any one of the first to eighth aspects.

According to a tenth aspect of the present invention, there is provided the projection exposure apparatus, wherein the pattern on the first object plane disposed on the surface to be irradiated is projected on the second object plane using the optical system of the ninth aspect. And

According to an eleventh aspect of the invention, there is provided a device manufacturing method, wherein a pattern on a reticle surface is projected and exposed on a wafer surface by a projection optical system using the projection exposure apparatus according to the tenth aspect, and then the wafer is subjected to a developing process. It is characterized in that devices are manufactured through processes.

[0027]

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, in an optical element used by joining two or more optical members, a groove is formed in one or both of the joints in order to prevent the occurrence of a gap and the deterioration of flatness due to an adhesive. Provided. The grooves reduce the residual stress generated by the force applied during bonding. In addition, the grooves prevent the occurrence of the gap and the deterioration of the flatness due to the protrusion of the adhesive, and at the same time, are bonded only at the grooves to solve the problem.

Further, a diffractive optical element having a fine structure is manufactured by a lithography process, and is integrated with a thick optical member. Is prevented from becoming worse.

Next, a specific configuration of the optical element of the present invention will be described.

FIG. 1 is a sectional view of a main part of a first embodiment of the present invention. In the figure, reference numeral 1 denotes a parallel plate member made of quartz, and its thickness is 10 to 30 mm. 2 denotes a diffractive optical element formed on a quartz wafer, 3 denotes an adhesive,
FIG. 2 shows a sectional view in the diametric direction passing through the center of the parallel plane member 1.

FIG. 2 is an enlarged schematic view of a main portion of a region indicated by A in FIG. In FIG. 2, reference numeral 3 denotes an adhesive, and 4 denotes a groove (groove for wrapping around the adhesive). FIG. 2 (A),
In (B), the diffractive optical element 2 is shown as four-stage binary optics obtained by quantizing and approximating a kinoform, but the effect of the present invention does not depend on the quantization number (the number of stages) of the binary optics. Therefore, even if a Fresnel lens having a blazed shape is adopted, the effect of the present invention is not impaired.

FIG. 5 is a view showing a joining operation, wherein 1 is a parallel plate substrate, 2 is a diffractive optical element formed on a quartz wafer, 31 is a parallel plate holder, 32 is a diffractive optical element chuck, 33 Is an annular projection a, 34 is an annular projection b, 35 is an exhaust port, and 36 is a scope. Times
The folding optical element 2 is placed on the diffractive optical element chuck 32 on which the position measuring mark is formed, and adjusted by the scope 36 so that the center of the diffractive optical element 2 and the center of the chuck 32 are located. A negative pressure is introduced to adsorb. The centering of the diffractive optical element 2 may be performed using the pattern of the diffractive optical element itself, or a dedicated mark may be provided. After the measurement, the scope 36 is moved from the joining apparatus to a place where it does not interfere with the joining. Due to the annular projections a and b, the diffractive optical element 2 is deformed into a convex shape. The amount is actually small, but is exaggerated for clarity in the figure. The parallel plate holder 31 is provided with three butting portions 37 so that the center of the diffractive optical element chuck 32 and the center of the substrate set in the holder are aligned. Diffractive optical element 2 and parallel plate 1
After the center alignment is completed, the parallel plate 1 is
First touch the center of the By gradually returning the pressure of the exhaust port 35 to the atmosphere, the deformation is released, and the diffractive optical element 2 and the parallel flat plate 1 gradually come into contact and are directly joined.

Diffractive optical element 2 formed on quartz wafer
Denotes an optical contact with the parallel plane member 1. Here, Optical Contact refers to a case where substrates are directly bonded to each other without using an adhesive or the like, apart from the pretreatment (including vacuum bonding and the like). Here, AR
(Anti-reflection) In some cases, a coating is applied to suppress reflection on the adhesive surface.

As shown in FIG. 2, the periphery of the parallel plane member 1 and the diffractive optical element 2 are adhered to each other. An epoxy-based adhesive is used as the adhesive 3. In the present invention, an epoxy-based adhesive is used as the adhesive 3, but a methacrylic or polyester-based adhesive, or an organic or inorganic adhesive may be used. For bonding the diffractive optical element 2, an ultraviolet curing type or the like can be applied. Since the diffractive optical element 2 formed on the quartz wafer has a small thickness of several mm or less, a groove 4 is formed around the diffractive optical element 2 so that the adhesive does not flow around the diffraction pattern.

In this embodiment, depending on the amount of the adhesive 3, FIG.
The adhesive may enter the groove 4 as shown in FIG.
The adhesive does not have to enter the groove 4 as shown in FIG.

In the case of Optical Contact, a non-adhesive portion may be generated (especially at the outermost peripheral portion).
In order to prevent the adhesive from seeping into the cal contacted surface,
The groove 4 may be formed closer to the center than the adhesive and outside the effective diameter as shown in FIG.

Also, as shown in FIG.
The non-adhered portion generated at the time of t may be adhered by an adhesive.

At this time, the groove 4 may be formed closer to the center than the adhesive and outside the effective diameter.

Here, bonding and fixing the periphery in the above configuration gives basic fixing strength between the diffractive optical element 2 and the parallel plane member 1. In addition, when vacuum bonding is used, it also serves to seal the vacuum atmosphere. Also, diffractive optical element 2
The surface having the blazed shape may be used as the contact surface. Making the space a vacuum guarantees close contact of the center portion of the diffractive optical element with the optical material even when the diffractive optical element is disposed below the optical material in the projection optical system.

In the present embodiment, the optical member is bonded at the central portion by optical contact, and only the peripheral portion is coated with an adhesive.
It shows an example of bonding by using the above.

In the case of bonding only at the periphery, as shown in FIG. 2C, the groove 4 is required closer to the center than the adhesive and outside the effective area.

By using the above-described bonding method, it is possible to secure a sufficient bonding strength when the diffractive optical element in a wafer state is integrated with other optical members, and to protect the element surface of the diffractive optical element.

FIG. 3 is a schematic view of a main part of a second embodiment of the present invention. In FIG. 3 (A), 5 is a plano-convex lens made of quartz, 2 is a diffractive optical element formed on a quartz wafer, 3
Represents an adhesive. FIG. 3A shows a cross-sectional view in the diameter direction passing through the center. The plano-convex lens 5 and the diffractive optical element 2 are optically contacted as in the first embodiment. Further, FIG. 4 is an enlarged view of the area indicated by B in FIG. 3, as in the first embodiment. As the adhesive 3, an inorganic adhesive low-melting glass is used. Low-melting glass has good compatibility with the bonding between the glasses as in the present invention in terms of the coefficient of thermal expansion and the like, and when the temperature changes due to the environmental temperature change / light absorption of the lens itself together with the suction force of the vacuum atmosphere. Also,
The generation of unnecessary stress is suppressed.

As shown in FIG. 4, a groove 4 forming an adhesive portion may be formed in both the plano-convex lens 5 and the diffractive optical element 2.
Eutectic of metals (Au and Al) as one of the inorganic bonding methods
Is used, a groove having a thickness (for example, about 0.1 μm) is formed on both the diffractive optical element 2 and the plano-convex lens 5 to deposit Au or Al which is one metal forming a eutectic. A metal film is formed in each groove, and eutectic bonding is performed. Another bonding method is anodic bonding. The plano-convex lens 5 or the diffractive optical element 2 which is formed by depositing a conductive film and a glass having ions and bonding them by applying an electric field may be a glass having ions. FIG.
4A, the groove on the plano-convex lens 5 side may be made wider as shown in FIG. 4B.

In this embodiment, the adhesive at the center is Optica.
l The example of contact is shown, but the whole surface may be bonded or only the periphery may be bonded. When the entire surface is bonded, as an inorganic bonding method, fusion using a material that is optically easy to use is used. As a material used for fusion, not only quartz but also CAF ₂ , MgF, LiF or the like may be used.

Further, as shown in FIG. 3B, the same applies to the case where the diffractive optical element 2 is bonded to a plano-convex lens 5 made of quartz.

By using the above-described bonding method, it is possible to secure a sufficient bonding strength when the diffractive optical element in a wafer state is integrated with another optical member, and to protect the element surface of the diffractive optical element.

Further, by performing inorganic bonding, it is possible to prevent a decrease in efficiency due to deterioration of the adhesive. or,
In the above configuration, the use of the optical material for securing the intensity as the lens constituting the projection optical system also reduces the total thickness of the optical material as a whole of the projection optical system and minimizes the absorption of illumination light. ing.

FIG. 6 is a sectional view of a main part of a third embodiment of the present invention. In the figure, 7 is a plano-concave lens made of quartz,
Reference numeral 2 denotes a diffractive optical element formed on a quartz wafer, and reference numeral 3 denotes an adhesive, and a cross-sectional view in a diameter direction passing through the center. The plano-concave lens 7 and the diffractive optical element 2 are the same as in the first embodiment.
Optical Contact has been.

At this time, as shown in FIG. 6A, a groove 4 is formed on the side of the diffractive optical element 2 in order to alleviate the distortion generated at the time of bonding.
Is formed. When performing bonding using an adhesive, FIG.
As shown in (B), a groove 4 is formed on the diffractive optical element 2 side to reduce distortion generated during bonding, and a groove 4 is formed on the plano-concave lens 7 so that the adhesive does not flow around. For example, a plurality of grooves may be provided for each application. The residual stress generated by the force applied at the time of bonding can be reduced, and the element surface of the diffractive optical element can be protected. As a result, the bonding strength increases.

FIGS. 7A and 7B show a fourth embodiment of the present invention.
FIG. FIG. 7A shows the bonding between the lenses L1 and L2, and FIG. 7B shows the bonding between the prisms P1 and P2. As the bonding method, both organic and inorganic bonding as described in the first and second embodiments, Optical Contact, and the like are used. A groove for an adhesive is provided outside the effective diameter, and the adhesive strength is improved by the adhesive. Depending on the bonding method, the configuration as shown in FIG. 8 can be applied to the shape of the groove of the bonding portion and the state of the adhesive. Further, as shown in FIG. 8 (F), a groove for preventing the adhesive from flowing around may be provided.

By providing the grooves as described above, the grooves can prevent the generation of the gap due to the protrusion of the adhesive and the deterioration of the flatness, and can also solve the problem by bonding only at the groove portions. .

In the present invention, a device is manufactured by applying the above optical members such as the diffractive optical element to a part of the optical system of the exposure apparatus shown in FIG.

[0055]

According to the present invention, as described above, when an optical element having a structure in which at least two optical members such as a diffractive optical element are bonded with an adhesive or an optical contact is used in an optical system, By providing a groove at or near the joining portion of at least one optical member, it is possible to prevent the surface deformation of the optical member and prevent the surface from being stained, and accurately hold the optical member in a favorable state in the lens barrel. And an optical system using the same.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a structure and effects according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged view illustrating a structure and effects according to the first and second embodiments of the present invention.

FIG. 3 is a diagram illustrating a structure and effects according to a second embodiment of the present invention.

FIG. 4 is a partially enlarged view illustrating a structure and effects according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a bonding step according to the first and second embodiments of the present invention.

FIG. 6 is a partially enlarged view illustrating a structure and effects according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a structure and effects according to a fourth embodiment of the present invention.

FIG. 8 is a partially enlarged view illustrating a structure and effects according to a fourth embodiment of the present invention.

FIG. 9 is a diagram illustrating a conventional diffractive optical element.

FIG. 10 is a diagram illustrating a conventional diffractive optical element.

FIG. 11 is an explanatory view of a conventional exposure apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Parallel plate member 2 Diffractive optical element 3 Adhesive 4 Groove 5 Plano-convex lens 6 Convex lens 7 Plano-concave lens 50 Fresnel lens 51 Blazed shape 52 Binary type diffractive optical element 53 Stepwise cross-sectional shape 55 Diffractive optical element 61 Light source 62 Reticle 63 Reticle Holder 64 Projection optical system 65 Lens 66 Wafer 67 Wafer stage 31 Parallel plate holder 32 Diffractive optical element chuck 33 Annular projection a 34 Annular projection b 35 Exhaust port 36 Scope 37 Butting section

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Claims (11)

(57) [Claims] 1. An optical element in which two or more optical members are bonded using an adhesive, wherein two opposing surfaces of two adjacent optical members of the two or more optical members are both flat or It is a convex and concave curved surface of the same shape, and the center of the two surfaces is Opti
the one or both optical members of the two adjacent optical members closer to the center of the optical member than the adhesive and
An optical element, wherein one or more grooves for sneaking in an adhesive are provided outside the effective diameter of the optical member . Wherein said adjacent two optical members have different thicknesses from each other, the optical element according to claim 1, wherein the thinner the groove in the optical member of the thicknesses is provided. 3. The optical element according to claim 1, wherein at least one optical member constituting the optical element is a refractive optical element. 4. The optical element according to claim 1, wherein at least one optical member constituting the optical element is a diffractive optical element. 5. The optical element according to claim 4, wherein said diffractive optical element is a phase type diffractive optical element having a quantized blazed shape. 6. The optical element according to claim 1, wherein, in joining the optical members, a peripheral portion of the optical member is joined. 7. The optical element according to claim 1, wherein the two optical members are joined using an adhesive, and the adhesive is an organic adhesive. 8. The optical element according to claim 1, wherein the two optical members are joined using an adhesive, and the adhesive is an inorganic adhesive. 9. An optical system comprising at least one optical element according to claim 1. 10. A projection exposure apparatus using the optical system according to claim 9 to project a pattern on a first object plane disposed on a surface to be irradiated onto a second object plane. 11. A device is manufactured by projecting a pattern on a reticle surface onto a wafer surface by a projection optical system using the projection exposure apparatus according to claim 10, and then subjecting the wafer to a development process. A method for manufacturing a device, comprising: