JPS61221722A - Lighting system using rectangular luminous flux - Google Patents

Abstract

PURPOSE:To utilize luminous flux effectively by guiding rectangular luminous flux emitted by a light source to a lighting system through an optical conversion system which is different in the conversion ratio of luminous flux shape size on a section containing the optical axis and a section perpendicular to it, and irradiating an object surface. CONSTITUTION:When the focal lengths of the 1st and the 2nd lenses are denoted as f1 and f2 and the interval between their principal points if denoted as l, an arrangement is so made that f1+f2 is nearly equal to l. The luminous flux from an excimer laser 1 is in such a shape that its size is (b) in the direction of a section H and (a) (>b) in the direction of a section V perpendicular to the section H. At this time, when the luminous flux is diverged by the 1st lens 21 in the direction of the section H and travels by the distance l, the refracting power and distance l of the 1st lens 21 are so set that the luminous flux size in the section H is the luminous flux size (a) of the section V. Then, the luminous flux is shaped to the luminous flux size (a) in the section H and then converged by the 2nd lens L and the luminous flux sizes in the sections H and V are both (a), so that parallel luminous flux is projected. At this time, the refracting power values of the 1st and the 2nd lenses are so set that af1+bf2=0 holds.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an illumination system using a rectangular light beam, and in particular, the present invention relates to an illumination system that uses a rectangular light beam, and in particular an excimer laser that oscillates a rectangular light beam as a light source to form a pattern of an electronic circuit or the like. The present invention relates to an illumination system using a rectangular light beam, which is designed to make effective use of a suitable light beam when transferring and exposing a mask pattern onto a wafer surface.

(Conventional technology) Recent semiconductor manufacturing technology includes high integration of electronic circuits.
There is a need for a lithographic technique that can form high-density circuit patterns.

Generally, when a circuit pattern on a mask or reticle surface is transferred onto a wafer surface via a projection optical system, the resolved line width of the circuit pattern transferred onto the wafer surface is proportional to the wavelength of the light source. Further, in the case of the contact/proxycity method, it is proportional to the square root of the wavelength. For this reason, the wavelength is 200~3
For example, a high-pressure mercury lamp, a xenon mercury lamp, or the like, which oscillates a short wavelength of 00 nIn in the far ultraviolet (deep UV region), is used.

However, these light sources have low brightness and no directivity, and the photoresist coated on the wafer surface has low photosensitivity, resulting in long exposure times and reduced throughput.

On the other hand, recently, a light source called an excimer laser, which has an oscillation wavelength in the deep UV region, has been developed, and various reports have shown that it is effective as a lithography technology due to its high brightness, monochromaticity, and directivity. .

Most of these excimer lasers use a transverse discharge excitation method, and discharge electrodes are arranged on both sides of the laser oscillation tube, so the cross-sectional shape of the oscillated laser beam is rectangular or nearly rectangular. ing. Generally, when constructing an illumination system using a light source that oscillates an arc-shaped luminous flux, many illumination optical systems are configured rotationally symmetrically, so unless the luminous flux is used with a circular or square shape, it will not work. cannot make effective use of the luminous flux.

In the illumination system of exposure equipment that uses the step-and-rebead method or contact/proxy method for semiconductor manufacturing, the shape of the light flux used is circular due to the shape of one chip of the circuit pattern and the need for uniform illumination of the mask pattern. Alternatively, it is desirable that the shape be square.

In particular, when an excimer laser that emits a rectangular beam is used as a light source in the illumination system of an exposure device, the characteristics of the excimer laser, such as high brightness and directivity, cannot be fully utilized unless the beam shape is shaped. It's gone.

(Objective of the Present Invention) An object of the present invention is to provide an illumination system using a rectangular light beam that can effectively utilize a light beam from a light source that oscillates a rectangular light beam.

A further object of the present invention is to use a light source such as an excimer laser that oscillates a rectangular light beam in an exposure apparatus for semiconductor manufacturing to uniformly illuminate a mask pattern and align the mask and wafer with high accuracy. An object of the present invention is to provide an illumination system using a bare-shaped luminous flux that can be used.

(Main feature of the present invention) After the image-shaped light beam emitted from the light source is passed through a conversion optical system that changes the conversion ratio of the shape and dimension of the light beam between a cross section including the optical axis and a cross section H perpendicular to the cross section. The light was guided to the illumination system and the illuminated surface was illuminated.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a schematic diagram of an optical system of an embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing.

In the figure, reference numeral 1 denotes an excimer laser, and a part of a rectangular beam from the excimer laser 1 is divided into two beams by a beam splitting means 2. Among these, the image-shaped light beam reflected by the light beam splitting means 2 is converted by the conversion optical system 17 so that the shape and dimensions of the light beam are, for example, the same in length and width, and then illuminates the mask pattern 4 by the illumination thread 6. Thereby, uniform illumination of the mask pattern 4 is performed. Mask pattern 4 is projected onto wafer 6 by projection system 5 .

The illumination system 3 includes a light integrator or other means for spatially uniformizing the amount of light, an incoherent means for reducing coherence, etc., as necessary.

On the other hand, the image-shaped light beam that has passed through the light beam splitting means 2 is reflected by a reflecting mirror 8.
The light is reflected by the alignment optical system 11 through the semi-transmissive mirror 92 and the reflecting mirror 1o, and irradiates the mask alignment mark provided on the mask pattern 4 surface. The mask alignment mark is projected by the projection system 5 near the wafer alignment mark provided on the surface of the wafer 6 .

The mask pattern 4 and the wafer 6 are aligned by detecting the relative positional relationship between the mask alignment mark and the wafer alignment mark projected onto the wafer surface by the detection means 14. . To align the mask alignment mark and the wafer alignment mark at this time, in principle, it is possible to use the method already proposed by the present applicant in Japanese Unexamined Patent Publication No. 135654/1983.

That is, both the mask alignment mark and the wafer alignment mark on the wafer 6 surface are optically scanned with a party-shaped light beam by a scanning means (not shown), and the specularly reflected light is sent to the projection system 5.
．． The alignment optical system 11 is blocked by a stopper 12 after passing through the semi-transmissive mirror 9, and only the scattered light and diffracted light generated from the edges of both alignment marks are collected by the condensing lens 16 and detected by the detection means 14. Then, based on the output signal from the detection means 14, the relative positional relationship between both alignment marks is determined by the calculation means 15, and the drive means 16 drives the XY stage 7 on which the wafer 6 is placed to form the mask pattern 4. The wafer 6 is aligned with the wafer 6.

In this way, in this embodiment, the alignment mark is irradiated with a rectangular light beam from the excimer laser 1, and the scattered light and diffracted light from the edges of the alignment mark are detected, so the S/N ratio is improved and high precision is achieved. It becomes possible to harmonize the following.

FIGS. 2(4), 2(B), and 2(C) are explanatory views of one embodiment of the conversion optical system 17 shown in FIG. 1, respectively. Same figure (4)
is a perspective view, ) is a side view, and ((i) is a plan view. FIG. 2(4)).

CB), (0), 21 is a cylindrical divergent lens, 22 is a cylindrical convergent second lens, and both are within the cross section H that includes the optical axis, that is, the meridional cross section (Figure 2 CB) (in a cross section in a side view). And the first. If the focal length of the second lens is 8, f2, and the distance between the principal points of the second lens and the second lens is l, approximately 11+h-
1. Now, the shape of the light flux of excimer laser 1 is shown in Figure 2 (6) t (B), (C)
As shown in , a cross section V perpendicular to b1 cross section H in the cross section H direction
Assume that it has a rectangular shape with the dimensions of ``pa (a) b).At this time, as shown in FIG. The refractive power and distance l of the second lunches 21 are set so that the luminous flux dimension in section H is a, which is the same as the luminous flux dimension in section V.Then, after setting the luminous flux dimension in section H to a,
The light is converged by the lens 22, the light beam dimensions of both the cross sections H and V are set to a, and the light beams are emitted as parallel light beams. At this time, the first . The refractive power of the second lens is set. In this embodiment, the object of the present invention can be achieved even if the above two equations are not completely satisfied.

In this embodiment, as shown in FIG. 2(C), since none of the 1° and 2nd lenses has refractive power in the cross-sectional direction 2, the luminous flux dimension a remains unchanged.

As described above, in this embodiment, by appropriately selecting the parameters of each lens constituting the conversion optical system, a rectangular light beam can be shaped into an arbitrary light beam shape and guided to the illumination system.

As the conversion optical system in this embodiment, a toric lens may be used in addition to a cylindrical lens, and with this, a single lens can convert the beam size of the aspect ratio.

Furthermore, the shape of the rectangular beam may be changed by using the rectangular beam at an angle of 17 relative to the optical axis, or the optical system may be decentered to change the state of use of the beam in the horizontal and vertical directions. The shape of the luminous flux may be changed by making the values different.

The present invention can also be applied to exposure apparatuses of the so-called hand-touch method, in which a mask and a wafer are placed in close contact with each other for transfer exposure, and to the so-called proximity method, in which a mask and a wafer are arranged with a slight distance from each other for transfer exposure. Further, the light source is not limited to an excimer laser, but any light source that emits a rectangular light beam can be used.

(Effects of the Present Invention) According to the present invention, it is possible to convert a light beam from a light source that emits a rectangular light beam into an arbitrary light beam shape, and to achieve an illumination system that effectively utilizes the light beam. In particular, exposure equipment for semiconductor manufacturing uses an excimer laser that oscillates a G-E-shaped beam as a light source, uses a rod-shaped beam for aligning the mask and wafer, and uses a beam whose beam shape is converted into an approximately square beam for the illumination system. By using this, it is possible to uniformly illuminate the mask, and also to achieve highly accurate alignment, making it possible to achieve an illumination system that takes advantage of the features of excimer lasers, such as high brightness and high directivity.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment in which the present invention is applied to an exposure apparatus for semiconductor manufacturing, and FIG. 2 (4) and (B). (0) is an explanatory diagram of a conversion optical system according to the present invention. In the figure, 1 is an excimer laser, 12 is a beam splitting means, 6 is an illumination system, 4 is a mask, 5 is a projection system, 6 is a wafer, 17 is a conversion optical system, and 21 and 22 are cylindrical lenses.

Claims (4)

[Claims] (1) A rectangular light beam emitted from a light source is guided to the illumination system through a conversion optical system that changes the conversion ratio of the shape and dimension of the light beam between a cross section L including the optical axis and a cross section H perpendicular to the cross section L. An illumination system using a rectangular light beam, characterized in that it emits light and illuminates an irradiated surface. (2) The conversion optical system converts the incident rectangular light beam so that the outgoing light beam has substantially the same dimensions at the cross section L and the cross section H. An illumination system using the rectangular light beam according to item 1. (3) An illumination system using a rectangular light beam according to claim 1, wherein the light source is an excimer laser. (4) An excimer laser that emits a rectangular beam is used as the light source, the rectangular beam from the excimer laser is split into at least two beams by a light splitting means, and one of the rectangular beams is sent to the conversion optical system. 4. An illumination system using a rectangular light beam according to claim 3, wherein the other rectangular light beam is guided to the illuminated surface in a rectangular state.