JPH0550848B2 - - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a variable optical path length optical device.

[Prior art] When matching the relative shift between the focus of an optical system and a target object for the purpose of focusing an optical system of semiconductor manufacturing equipment, etc., it is necessary to move either the optical system or the target object in the optical axis direction. It is well known that there are two types of methods: a method of displacement and a method of moving a part of the optical system to change its focal length.

In the former method of displacing the optical system or target object, if the optical system or target object mounting table is large,
In order to guarantee the accuracy of movement, including the parallelism of the feed direction and optical axis for displacement, not only must the displacement guide mechanism be large and highly rigid, but the feed speed cannot be very high. There are drawbacks. Particularly when high-speed operation is required for the purpose of increasing the efficiency of inspection work, etc., the drawback that the drive actuator and transmission mechanism become extremely large is unavoidable. For example, in an apparatus such as a projection exposure apparatus for manufacturing semiconductor devices, which requires a strict relative positional relationship between the projection optical system, the original plate, and the object to be exposed in the plane direction perpendicular to the optical axis, The deviation in other direction components relative to the movement in the optical axis direction must be on the order of 1 μm or less, and there is not much time for this focusing, and it is necessary not only for the optical system but also for the object mounting table to be exposed. on top of that
Since it is equipped with an XY stage, it is large in size, and therefore, in order to guarantee the accuracy of the above order, a guide mechanism for movement in the optical axis direction, a drive actuator,
Also, it is inevitable that the transmission mechanism will become larger.

On the other hand, in the method of moving part of the optical system to change its focal length, although the mass to be driven is smaller, it requires precision in the direction perpendicular to the optical axis between the fixed optical system and the optical system. In addition to increasing the design burden, the movement of each optical element becomes complicated, requiring the use of a cam, and the accuracy of this cam becomes important.

[Object of the invention] The present invention eliminates the drawbacks of the prior art described above, and
Only the optical path length can be changed by simply linearly feeding at least two simple optical components with small mass such as two pieces of glass, and the optical path can be easily fine-tuned without requiring any special design changes to other optical systems. The present invention aims to provide a length variable optical device.

[Means and Actions for Achieving the Object] In order to achieve the above-mentioned object, the present invention provides a variable optical path length optical device interposed in the optical path of an optical system, in which a cross section along the optical axis of the optical system is has a plurality of wedge-shaped translucent optical components (glass components 1A, 1B), and the translucent optical components are arranged complementary to each other with a space in the optical path of the optical system, Each inner surface (surfaces 2A, 3B) is inclined and parallel to the optical axis of the optical system, and each outer surface (surfaces 2B, 3A) is parallel to the optical axis of the optical system in the space. The present invention is characterized in that one of the translucent optical components moves relative to the other in a direction intersecting the optical axis of the optical system while maintaining a constant distance in the optical axis direction.

Further, in a variable optical path length optical device interposed in an optical path of an optical system, the first, second, and third translucent optical components each have a wedge-shaped cross section along the optical axis of the optical system. (Glass parts 1C, 1D, 1E)
in the optical path of the optical system, the first and third
The second light-transmitting optical component (glass component 1D) is disposed oppositely between the light-transmitting optical components (glass components 1C, 1E) with a space therebetween, and One surface of the optical component (surface 3
D) and the inner surface (surface 2) of the first translucent optical component
The pair C), the other surface (surface 2D) of the second light-transmitting optical component, and the inner surface (surface 3E) of the third light-transmitting optical component are located on the optical axis of the optical system, respectively. The outer surfaces (surfaces 3C, 2E) of the first and third translucent optical components are parallel to each other while being inclined in opposite directions, and the second translucent optical component is parallel to the outer surface of the first and third translucent optical components. It is characterized in that it moves in a direction intersecting the optical axis of the optical system with respect to the first and third translucent optical components.

In the variable optical path length optical device of the present invention, when at least one optical component is displaced relative to the others, only the total optical path length for the light beam at a certain transmission position changes correspondingly, and the degree of this change changes. is a function of the amount of displacement of the optical component and the cross-sectional shape of the optical component, regardless of the transmission position. Therefore, by predetermining the cross-sectional shape of the optical component in the displacement direction, it is possible to adjust the optical path length using the amount of displacement, and it is possible to reduce the rate of change in the cross-sectional shape in the displacement direction. Since the ratio between the amount of displacement and the amount of change in optical path length can be increased, fine adjustment is easy, and deviations in other directional components do not occur.

[Example] Fig. 1 shows a first example of the present invention, in which glass components 1A and 1B each having a wedge-shaped cross-section and having mutually symmetrical cross-sectional shapes are used as translucent optical components.
, a feed screw device 10 as a displacement means, a drive motor 11 thereof, and the like. One glass component 1A is fixed, while the other glass component 1B
is disposed so as to be displaceable by the feed screw device 10. Each outer surface 3A, 2B of glass parts 1A and 1B
are always kept parallel to the direction of displacement of the feed screw device 10, and the opposing surfaces 2A and 3B of both glass parts are kept parallel so that the gap between them does not shift due to displacement. Glass parts 1B
Therefore, it is guided on a plane 12 parallel to the inclined surface 2A of the fixed side glass component 1A, and can be moved in parallel against the spring 14 by the feed screw device 10 via the bearing 13, and by this movement, the outer surface 2B
It is possible to change only the optical path length without changing the relative position and angle of the incident light on the outer surface 3A (or 3A) and the output light from the outer surface 3A (or 2B).

FIG. 2 shows a second embodiment of the present invention, in which the translucent optical section consists of three glass parts 1C, 1D, and 1E each having a wedge-shaped cross section. The intermediate glass component 1D has a double-sided inclined shape in which the upper and lower surfaces are symmetrical with respect to the center surface 4D, and the upper surface 2D and the lower surface 3D have a lower surface (sloped surface) 3E and a lower surface (slanted surface) of the upper glass component 1E, respectively. The upper surface (slanted surface) 2C of the lower glass component 1C faces each other through a parallel gap.
The upper and lower glass components 1E and 1C are fixedly arranged, and their outer surfaces, the upper surface 2E of the component 1E and the lower surface 3C of the component 1C, are parallel to the center plane 4D along the moving direction of the component 1D. The intermediate glass component 1D is attached to a frame 26 that is slidably supported on guide surfaces 22 and 25 parallel to the center plane 4D, and this frame 26 is rotated by a feed screw device 20 via a bearing 23. It can be displaced against the spring 24, and this movement changes only the optical path length without changing the relative position and angle of the incident light on the outer surface 2E (or 3C) and the exit light from the outer surface 3C (or 2E). Is possible.

The variable optical path length optical device of the present invention is used by being inserted into the optical path of an observation optical system in an inspection device for IC manufacturing wafers, etc., or a projection optical system of a projection exposure device, etc., and is suitable for use in these applications. Typical examples are shown in FIGS. 3 and 4.

That is, FIG. 3 shows an example in which a variable optical path length optical device 32 according to the present invention is incorporated between an observation optical system 30 and an object (wafer) 31, and the observation optical system 30 itself is Measure the position of the object surface,
The position of the object 31 to be inspected is measured using an air sensor 33 or the like, the amount of positional deviation between the object surface and the object 31 is calculated, and one wedge-shaped glass 32A of the optical device 32 is connected to the other wedge. The object surface is made to coincide with the surface of the object 31 by moving it relative to the shaped glass 32B.

FIG. 4 shows an example in which a variable optical path length optical device 42 according to the present invention is incorporated between an exposure optical system 40 and a photosensitive plate (wafer) 41 in a projection exposure apparatus. When illuminating the mask 46 through the lens 45 and forming a projected image of the mask 46 on the photosensitive plate 41 using the optical system 40, the position of the image plane of the exposure optical system 40 is measured in advance. The position of the photosensitive plate 41 is measured using an air sensor 43 or the like, and the amount of positional deviation between the image plane and the photosensitive plate 41 is calculated.
2, one wedge-shaped glass 42A is moved relative to the other wedge-shaped glass 42B to align the image plane with the photosensitive plate.

Although not shown in the drawings, the device of the present invention can be used in place of the optical path length converter C of the optical system shown in, for example, Japanese Patent Laid-Open No. 19320/1983, and can be used to control the optical system in response to changes in the position of the wafer surface in a stepper or the like. It can also be used to perform optical path length correction.

Further, the variable optical path length optical device of the present invention is preferably used by being interposed between the imaging optical system and the target object as shown in FIGS. 3 and 4. When the optical device 42 of the present invention is installed on the side opposite to the target object, for example, in the case where the optical device 42 of the present invention is placed between the mask 46 and the optical system 40 in FIG. 4, the reduction magnification of the exposure optical system can be When it is 1/n,
In this arrangement position, the change in optical path length on the mask side is 1/n ² times that on the wafer side, and a large change in optical path length must be applied, making it unsuitable for purposes other than fine adjustment. Further, in this case, unless the exposure optical system 40 is configured to be telecentric toward the mask side, the magnification will change due to a change in the optical path length, resulting in a magnification error in the exposure pattern.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a variable optical path length optical device in which only the optical path length can be changed by simply linearly feeding a simple translucent optical component. It can be installed without requiring any special design changes to the observation or projection optical system to which it is applied, and
Fine adjustment can be easily achieved, and for example, when used in the projection optical system of a projection exposure apparatus for semiconductor device manufacturing, it is possible to correct the positional deviation (focal deviation) of the wafer in the Z direction without moving the wafer, its stage, or the projection optical system. This also contributes to improving throughput.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the first embodiment of the present invention, Fig. 2 is a block diagram showing the second embodiment, Fig. 3 is a block diagram showing an example of application to an observation optical system, and Fig. 4 is a block diagram showing the second embodiment. FIG. 2 is a configuration diagram showing an example of application to a projection optical system. 1A, 1B, 1C, 1D, 1E: wedge-shaped glass parts (translucent optical parts), 10, 20: feed screw device (displacement means), 11, 21: drive motor.

Claims (1)

[Scope of Claims] 1. A variable optical path length optical device interposed in the optical path of an optical system, which includes a plurality of translucent optical components each having a wedge-shaped cross section along the optical axis of the optical system. In the optical path of the optical system, the translucent optical components are arranged complementary to each other with a space between them, and each inner surface is inclined and parallel to the optical axis of the optical system. The outer surfaces of the optical components are parallel to each other, and one of the translucent optical components is arranged relative to the other in a direction intersecting the optical axis of the optical system while maintaining a constant distance in the space in the optical axis direction of the optical system. A variable optical path length optical device characterized by being movable. 2. In a variable optical path length optical device interposed in the optical path of an optical system, first, second, and third translucent optical components each having a wedge-shaped cross section along the optical axis of the optical system are provided. and the second light-transmitting optical component is disposed oppositely between the first and third light-transmitting optical components in the optical path of the optical system such that the second light-transmitting optical component is positioned with a space therebetween, and a set of one surface of the second light-transmitting optical component and the inner surface of the first light-transmitting optical component; and a set of the other surface of the second light-transmitting optical component and the inner surface of the third light-transmitting optical component. The sets of side surfaces are parallel to each other while being inclined in opposite directions to the optical axis of the optical system, and the outer surfaces of each of the first and third translucent optical components are parallel to each other, and the outer surfaces of the first and third translucent optical components are parallel to each other. 2
A variable optical path length optical device, wherein a light-transmitting optical component moves relative to the first and third light-transmitting optical components in a direction intersecting an optical axis of the optical system.