JP2003307763A - Optical diaphragm device and aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical diaphragm device by which nearly a round aperture shape is obtained by a less number of light shielding plates in the wide variable range of an optical diaphragm, and an aligner provided with the optical diaphragm and used for manufacturing a semiconductor or the like. <P>SOLUTION: In the optical diaphragm device by which a prescribed aperture can be obtained successively variably by arranging several light shielding plates so as to mutually overlap one area and sliding several light shielding plates with each other, an outline part constituting the prescribed aperture is constituted of several circular arcs in several light shielding plates. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical diaphragm apparatus and an exposure apparatus used for manufacturing semiconductors including the optical diaphragm apparatus.

[0002]

2. Description of the Related Art In a conventional manufacturing process of a semiconductor device formed from an ultrafine pattern, a reduced projection exposure is performed in which a circuit pattern drawn on a mask is reduced and projected onto a substrate coated with a photosensitizer to be printed. The device is being used.
In order to further miniaturize the pattern, at the same time as the development of the resist process, the miniaturization of the exposure apparatus is being promoted.

A typical method for improving the resolving power of the exposure apparatus is to increase the NA (numerical aperture) of the projection optical system. Recently, with the progress of design and manufacturing techniques, an exposure apparatus equipped with a projection optical system having a higher NA, for example, NA = 0.70 has been put into practical use. Further, it is necessary to secure the depth of focus of the projection optical system while improving the resolution. Since the depth of focus decreases as the NA increases, in the actual process, the conditions for NA optimization are performed to secure the depth of focus and improve the resolution. Therefore, in a normal projection optical system, an optical diaphragm device that can change the NA almost steplessly is incorporated so that the NA can be selectively used. Conventionally,
As an optical diaphragm device for changing the NA, Japanese Patent Application Laid-Open No. 7-242242
As described in JP-A-301845, there is used an iris diaphragm device in which a plurality of light-shielding plates are overlapped with each other and each light-shielding plate is rotated while sliding to change the aperture diameter.

[0004]

By the way, in recent years, in order to improve the resolving power of an exposure apparatus, while increasing the NA of the projection optical system, the exposure apparatus compatible with the same high NA can also be used for pattern exposure of a middle layer. There is a demand for a device specification that can be used even with a low NA so that it can be handled.

As a typical optical diaphragm device for changing the NA of the projection optical system, as shown in the above-mentioned conventional example, a plurality of light shielding plates are laminated on each other and each light shielding plate is slid. An iris diaphragm device is used which is rotated while being rotated to change the aperture diameter. In general, a conventional iris diaphragm device uses a plurality of light-shielding plates 31 as shown in FIG. 10, and as shown in FIG. The rotary shaft 33 is driven around 32 to obtain a predetermined diaphragm aperture.

In this iris diaphragm device, since a plurality of light-shielding plates are used as described above, the shape of the diaphragm aperture is not necessarily close to a perfect circle, as is apparent from FIG. The greater the degree of narrowing down,
That is, the smaller the opening diameter, the closer the shape becomes to a regular polygon.

Therefore, when the projection lens is used at a high NA, there is no particular problem, but when the projection lens is used at a lower NA, the shape of the diaphragm deviates from a perfect circle, so that the optical axis direction of the projection lens is increased. As seen from the above, an azimuth difference occurs in the substantial NA size. Therefore, the resolution may be slightly different depending on the arrangement direction of the circuit pattern drawn on the mask.

In order to make the opening shape close to a perfect circle even when the opening diameter is reduced, it can be solved by increasing the number of the light shielding plates. However, increasing the number of light-shielding plates in the mechanism in which the respective light-shielding plates are superposed increases the drive load of the mechanism and increases the possibility that the light-shielding plates will be worn or damaged due to sliding between the light-shielding plates. Cause problems.

In order to solve the above-mentioned problems, the present invention provides an optical diaphragm device and an optical diaphragm which can obtain an aperture shape closer to a perfect circle with a smaller number of light shielding plates in a wide variable range of the optical diaphragm. It is an object of the present invention to provide an exposure apparatus used for manufacturing a semiconductor including the above.

[0010]

In order to achieve the above-mentioned object, the present invention is used for manufacturing an optical diaphragm device configured as described in (1) to (7) below and a semiconductor having the optical diaphragm. The present invention provides an exposure apparatus. (1) In an optical diaphragm device in which a plurality of light-shielding plates are overlapped with each other in one region and a plurality of light-shielding plates are slid on each other so that a predetermined aperture is continuously variable, The light-shielding plate is an optical diaphragm device, wherein a contour portion forming the predetermined opening is composed of a plurality of arcs. (2) The optical diaphragm device according to (1), wherein the plurality of arcs have different curvatures. (3) In the optical diaphragm device, wherein a plurality of light-shielding plates are made to overlap each other in one area, and the plurality of light-shielding plates are slid on each other so that a predetermined opening is continuously variable. The light-shielding plate is an optical diaphragm device, wherein a contour portion forming the predetermined opening is formed by one or more conical curves. (4) In the optical diaphragm device in which a plurality of light-shielding plates are overlapped with each other in one area, and the plurality of light-shielding plates are slidable with each other so that a predetermined opening is continuously variable. The light-shielding plate is an optical diaphragm apparatus, wherein a contour portion forming the predetermined opening is composed of one or more arcs and one or more conic curves. (5) The optical diaphragm device according to (3) or (4), wherein the conic curve is an elliptic arc. (6) The optical diaphragm device according to any one of the above (1) to (5), wherein the plurality of light shielding plates are driven by a cam mechanism. (7) An exposure apparatus comprising the optical diaphragm device according to any one of (1) to (6) above.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION By applying the above configuration,
With a wide optical aperture variable range, with fewer light shields,
It is possible to realize an optical diaphragm device that can obtain an aperture shape that is closer to a perfect circle and an exposure device that includes the optical diaphragm device.

[0012]

The actual command of the present invention will be described below. [Embodiment 1] FIG. 1 is a schematic view of an optical diaphragm apparatus and an exposure apparatus using the same in Embodiment 1 of the present invention. In the figure, reference numeral 101 is a reticle on which a pattern serving as an original is drawn and is held by a reticle chuck 107. Reference numeral 103 denotes a semiconductor wafer coated with a photosensitive agent, which is supported via a wafer chuck 107 on a wafer stage 108 having precise positioning performance.
A projection optical system 102 projects and exposes a pattern on the surface of the reticle 101 illuminated by the exposure light from the illumination optical system 104 at a predetermined magnification (for example, 1/4 or 1/5) onto the wafer surface. Reference numeral 105 denotes an optical diaphragm device, which is a projection optical system 1
It is arranged near the pupil position of No. 02.

A surface plate 109 supports the projection optical system 102 and also supports an optical diaphragm driving device 106 for driving the optical diaphragm device 105. FIG. 2 shows a schematic configuration of the optical diaphragm device 105. Reference numeral 1 denotes a light shielding plate, and in this embodiment, a plurality of light shielding plates having the same shape are used. Each of the light shielding plates 1 is arranged on a base plate 8 and has a cam shaft 2 and a cam shaft 3 attached to each light shielding plate. Reference numeral 4 denotes a cam plate, which is fixed to the base plate 8 via a bearing 9 and is rotatable about the optical axis O.

Reference numeral 6 denotes a gear connected to the cam plate 4 and meshes with a gear 7 attached to the motor 11. By driving the motor 11, the cam groove 5 provided in the cam plate 4 is rotated, and the guide groove 1 provided in the base plate 8 is rotated.
The cam shaft 2 is driven along 3 and the cam shaft 3 is driven to position the light shielding plate 1 at a predetermined position.

Reference numeral 12 is a lens barrel for holding an optical element (not shown) formed in the projection optical system. The optical diaphragm device 105 is held by the lens barrel 12. The gear 6 can be driven from the outside of the lens barrel 12 through an opening 10 provided in the lens barrel 12.

With reference to FIG. 3 and FIG.
A method of forming the aperture opening will be described. FIG. 3 shows the shape of the light shielding plate. In the light-shielding plate 1, a contour for obtaining a predetermined diaphragm aperture is formed with a radius R2 (R2 <R1) centered on a point Q different from arcs L1 and P formed with a radius R1 centered on the point P. Arc L2
It is composed of

FIG. 4 shows a state in which the light shield plates 1 are equally divided around the optical axis O to form an aperture stop. Figure 4
In FIG. 4A, a relatively large aperture (when the aperture diameter exceeds 2 × R2) is formed by using the arc L1 portion of the light shield plate 1. In FIG. 4B, the arc L2 portion of the light shield plate 1 is formed. With a relatively small aperture (when the aperture diameter is 2 x R2 or less)
Is formed. The arcs are used separately by changing the driving method of the light shielding plate 1. In FIG. 4A, the arc L1 is driven by simultaneously driving the camshaft 2 and the camshaft 3 in the same direction as the radial direction centered on O. In FIG. 4B, the camshaft 2 is driven. By rotating the cam shaft 3 around the center, the arc L2 is driven.

Here, as shown in FIG. 5, the predetermined opening diameter is φC, and the maximum portion and the minimum portion of the diameter formed by the light shielding plate are φCmax and φCmin, respectively.
The opening diameter φC is the average value of φCmax and φCmin, and the error rate from a perfect circle is defined as (φCmax−φC) / φC.

FIG. 6 shows the error rate in the case where the maximum aperture diameter obtained by the mechanism of this embodiment is φD and R1 = D / 2, R2 = R1 × 0.7. For comparison, FIG. 12 shows the error rate when the conventional type light-shielding plate shown in FIGS. 10 and 11 is used. Here, the opening ratio is a diameter ratio of a predetermined opening diameter φC to the maximum opening diameter φD obtained by this mechanism. In the diaphragm device using the conventional type light-shielding plate, the aperture ratio is about 2% at 0.5, whereas in the present embodiment, the maximum aperture ratio is in the range of 1 to 0.5. However, it can be suppressed to about 1.2%.

As described above, in the present embodiment, the case where the contour portion of the light shielding plate for obtaining the predetermined aperture opening is composed of two arcs having different sizes, but three or more different sizes are used. The circularity of the opening can be further improved by using a circular arc and arbitrarily setting the driving method of the light shielding plate. The number of light-shielding plates is not limited to eight, and the number of light-shielding plates may be optimized if necessary.

In this embodiment, the case where the optical diaphragm device is configured as the aperture diaphragm (NA diaphragm) portion of the projection optical system has been described, but it is similarly used for the aperture diaphragm (σ diaphragm) portion of the illumination optical system. May be.

[Embodiment 2] Next, an optical diaphragm apparatus according to Embodiment 2 of the present invention will be described. In this embodiment, the overall configuration of the optical diaphragm device is almost the same as that of the first embodiment, and the shape and operation of the light shielding plate forming the diaphragm opening will be described. FIG. 7 shows the shape of the light shielding plate. In the light shielding plate 21, a contour portion for obtaining a predetermined opening is formed by an elliptic arc L21 centered on the point R. Here, the major axis of the ellipse is A and the minor axis is B.

FIG. 8 shows a state in which eight light shield plates 21 are equally divided around the optical axis O to form an aperture stop. Here, a cam shaft 22 and a cam shaft 23 are attached to the light shielding plate 21, and each light shielding plate moves in a radial direction with respect to the optical axis O along a guide groove 24 provided in the base plate 8. Is possible. In addition, the cam groove 25 provided in the cam plate 4
By the rotation of, the light shielding plate 21 is positioned at a predetermined position, and a predetermined opening can be obtained by the contour portion L21. In FIG. 8A, a relatively large aperture stop is formed by using a large curvature portion of the elliptic arc of the light shielding plate 21, and in FIG. 8B, a small curvature portion is used. A relatively small aperture stop is formed.

The error rate from the perfect circle when the maximum aperture diameter obtained by the mechanism of this embodiment is φD and B = D and A = B × 1.2 is designed is the same as that of the first embodiment. In Fig. 9
Shown in. At the maximum aperture (aperture ratio 1), the error rate is inferior to that of the conventional type, but when the aperture ratio is about 0.84, the error rate approaches 0, and the error rate increases as the aperture is further reduced. Even if is 0.5, it can be suppressed to about 1.5%. In this embodiment, the error rate can be averaged as compared with the conventional type diaphragm, and the roundness can be brought to a state close to 0 at a predetermined aperture.

As described above, in the present embodiment, the case where the contour portion of the light shielding plate for obtaining the predetermined opening is the elliptic arc is explained, but the contour shape is not limited to the elliptic arc, and is constituted by other conical curves or continuous curvatures. The curved line may be used. Also,
The number of light-shielding plates and the driving method are not limited to those shown in this embodiment, and may be optimized as needed.

[0026]

According to the present invention, an optical diaphragm apparatus and an exposure apparatus including the same that can obtain an aperture shape closer to a perfect circle with a smaller number of light shielding plates in a wide optical diaphragm variable range are realized. can do.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an outline of an exposure apparatus used for manufacturing a semiconductor according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an optical diaphragm device according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating an optical diaphragm device according to a first embodiment of the present invention.

FIG. 4 is a diagram illustrating an optical diaphragm device according to a first embodiment of the present invention.

FIG. 5 is a diagram illustrating effects of the optical diaphragm device according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating effects of the optical diaphragm device according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating an optical diaphragm device according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating an optical diaphragm device according to a second embodiment of the invention.

FIG. 9 is a diagram illustrating effects of the optical diaphragm device according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating an embodiment of a conventional type optical diaphragm device.

FIG. 11 is a diagram illustrating an embodiment of a conventional type optical diaphragm device.

FIG. 12 is a diagram illustrating the accuracy of a conventional type optical diaphragm device.

[Explanation of symbols]

1: Light shield 2, 3: Cam shaft 4: Cam plate 5: Cam groove 12: lens barrel 101: Reticle 102: Projection optical system 103: Wafer 104: Illumination optical system 105: Optical diaphragm device

Claims (7)

[Claims] 1. An optical diaphragm device in which a plurality of light-shielding plates are arranged so that their areas overlap with each other, and a predetermined opening is continuously variable by sliding the plurality of light-shielding plates. The optical diaphragm device, wherein the plurality of light-shielding plates has a plurality of arcs in a contour portion forming the predetermined opening. 2. The optical diaphragm apparatus according to claim 1, wherein the plurality of arcs are arcs having different curvatures. 3. An optical diaphragm device, wherein a plurality of light-shielding plates are overlapped with each other in one region, and a predetermined aperture is continuously variable by sliding the plurality of light-shielding plates. An optical diaphragm device, wherein a plurality of light-shielding plates has a contour portion forming one of the predetermined openings formed by one or more conical curves. 4. An optical diaphragm device in which a plurality of light-shielding plates are made to overlap each other in one area, and a predetermined opening is continuously variable by sliding the plurality of light-shielding plates. An optical diaphragm device, wherein a plurality of light-shielding plates has a contour portion that constitutes the predetermined opening and is configured by one or more arcs and one or more conic curves. 5. The optical diaphragm device according to claim 3, wherein the conic curve is an elliptic arc. 6. The optical diaphragm device according to claim 1, wherein the plurality of light shielding plates are driven by a cam mechanism. 7. An exposure apparatus comprising the optical diaphragm device according to any one of claims 1 to 6.