JP2002110502A - Illumination device and exposure device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to illuminate an illumination area such as a rectangular mask surface uniformly and effectively (that is, at a desired illuminance) in a conventional illumination apparatus using annular illumination. A lighting device is provided. An illumination device for illuminating an illuminated surface having an aspect ratio not equal to 1 using a light beam emitted from a light source, the illumination device being arranged between the light source and the illuminated surface to uniformly illuminate the illuminated surface. A light integrator for illuminating, a first integrator disposed between the light source and the light integrator, including a circular arc in a part of a cross-sectional shape, and an aspect ratio of the cross-sectional shape approximates an aspect ratio of the illumination region; An optical rod.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an illuminating device and an exposing device, and more particularly, to exposing an object to be processed such as a single crystal substrate for a semiconductor wafer and a glass substrate for a liquid crystal display (LCD). The present invention relates to an illumination device used and an exposure device. The present invention is suitable for, for example, an illumination device for an exposure apparatus that exposes a single crystal substrate for a semiconductor wafer by a step-and-scan projection method in a photolithography process. However, the application of the illumination device of the present invention is not limited to an exposure device, and can be widely applied to optical equipment such as photolithography, projection inspection, a projector, and a projector.

[0002] Here, the "step-and-scan projection system" refers to a method in which a wafer is continuous with respect to a mask or a reticle (in the present application, "mask" collectively refers to these) unless otherwise specified. This is a projection exposure method in which a mask pattern is exposed on a wafer by scanning the wafer, and after the exposure of one shot is completed, the wafer is step-moved to an exposure area of the next shot.

[0003]

2. Description of the Related Art In recent years, demands for miniaturization and thinning of electronic devices have increased the demand for miniaturization of semiconductor elements mounted on electronic devices. For example, the line and space is less than 0.15 μm, and it is expected that the line and space will be further reduced in the future. Line-and-space refers to an image projected on a wafer with the widths of lines and spaces being equal in exposure, and is a measure of exposure resolution.
In exposure, resolution, overlay accuracy, and throughput
One parameter is important. The resolution is the minimum dimension that can be transferred accurately, the overlay accuracy is the accuracy when several patterns are overlaid on the workpiece, and the throughput is the number of sheets processed per unit time.

[0004] Basically, there are two types of exposure methods: a 1: 1 transfer method and a projection method. The equal-size transfer includes a close contact method in which a mask is brought into contact with an object to be processed and a close method in which the mask is slightly separated. However, although the close contact method can provide high resolution, dust and fragments of silicon are pressed into the mask, resulting in damage to the mask, scratches and defects on the object to be processed. The proximity method has solved such a problem, but if the distance between the mask and the object to be processed becomes smaller than the maximum size of the dust particles, the mask may be damaged as well.

Therefore, a projection method for further increasing the distance between the mask and the object has been proposed. Among the projection methods, there is known a scan exposure method in which a part of a mask is exposed to improve resolution and to enlarge an exposure area, and a wafer is continuously or intermittently scanned. An exposure apparatus employing such a method may be particularly referred to as a scanning projection exposure apparatus.

[0006] The projection exposure apparatus generally has an illumination optical system for illuminating the mask and a projection optical system arranged between the mask and the object to be processed. In the illumination optical system, in order to obtain a uniform illumination area, the light flux from the light source is introduced into a light integrator such as a fly-eye lens composed of a plurality of rod lenses, and the light integrator exit surface is used as a secondary light source surface for a condenser. Koehler illumination of the mask surface with a lens.

The resolution R of the projection exposure apparatus is given by the following equation using the wavelength λ of the exposure light source and the numerical aperture (NA) of the exposure apparatus.

[0008]

(Equation 1)

Therefore, the shorter the wavelength and the higher the NA, the better the resolution. In recent years, the wavelength of the exposure light source is going to be from KrF excimer laser (wavelength: about 248 nm) to ArF excimer laser (wavelength: about 193 nm), and the numerical aperture is going to be about 0.6 to about 0.75.

On the other hand, a focal range in which a certain imaging performance can be maintained is called a depth of focus, and the depth of focus DOF is given by the following equation.

[0011]

(Equation 2)

Therefore, the shorter the wavelength and the higher the NA, the smaller the depth of focus. As the depth of focus becomes smaller, focusing becomes difficult, and it is required to increase the flatness (flatness) and focus accuracy of the substrate.

From both formulas, it is desired to increase the numerical aperture by shortening the wavelength for further miniaturization, but there is a problem that this cannot be realized because the depth of focus becomes small. Therefore, the proportional constant k
Super-resolution technology for miniaturization by reducing the value of ₁ (RET: Resolution Enhanced)
Tecology) has recently been proposed. One of the RETs is called a modified illumination method (or an oblique incidence illumination method). As a modified illumination method, a method is generally used in which an aperture stop having a light-shielding plate on the optical axis of an optical system is disposed near the exit surface of a light integrator, and an exposure light beam is obliquely incident on a mask. Depending on the shape of the aperture stop, there are annular illumination, quadrupole illumination, and the like. For example, Japanese Patent Application Laid-Open No. Hei 5-21312 discloses an exposure method using an aperture stop for annular illumination. According to the method disclosed in the publication, k ₁ , which is usually 0.5 or more, can be reduced to about 0.3.

Further, the scanning projection exposure apparatus has a feature that it is preferable because aberration of a projection lens for projecting a mask onto a substrate can be reduced. Here, the aberration indicates a degree of blur at a conjugate point on the image plane when a point on the object plane of the lens is projected, and a lens having a large aberration has less resolving power than a lens having a small aberration. Lens design becomes more difficult as the numerical aperture increases, and aberrations are related to numerical aperture. For example, spherical aberration is proportional to the third order of the numerical aperture in the third order aberration theory. Therefore, as the numerical aperture increases, it becomes very difficult to design a lens. In addition to the numerical aperture, the angle of view (the area in which the projection lens can project) is also related to the aberration. For example, distortion is third-order proportional to the angle of view in the third-order aberration theory. Therefore, even if the angle of view becomes large, it becomes very difficult to design a lens. Therefore, the projection lens of the scanning projection exposure apparatus having a smaller angle of view than the exposure area is easier to design and reduces aberrations than the projection lens of the collective projection exposure apparatus having the same angle of view in the exposure area. it can.

[0015]

Non-uniform illumination causes insufficient pattern transfer to a resist, and makes it impossible to provide high-quality semiconductor wafers, LCDs, thin-film magnetic heads, and the like. Therefore, it is necessary to uniformly and effectively illuminate an illumination area such as a generally rectangular mask surface (that is, at a desired illuminance). In addition, if illumination cannot be performed with high illuminance, the throughput decreases.

However, in a conventional illumination device using annular illumination, an aperture stop for annular illumination is arranged on the exit surface of the light integrator due to a demand for uniform illumination.
However, simply arranging the aperture stop blocks some light, so that the illuminance is reduced and the throughput is reduced. For example, in the case of an aperture stop for 1/2 annular illumination in which the ratio of the outer opening diameter to the inner opening diameter is 2: 1, 25 is used.
%, And the ratio of the outer opening diameter to the inner opening diameter is 3: 2, 2/3.
In the case of an aperture stop for annular illumination, 44% of the light is vignetted by the aperture stop. Therefore, conventionally, some illumination devices have been proposed that reduce vignetting due to an aperture stop, increase light use efficiency, and achieve high illuminance.

Japanese Patent Application Laid-Open No. Hei 5-283317 proposes an illuminating device using a method in which a prism is arranged closer to a light source than a fly-eye lens, and the vignetting light is reduced by an aperture stop. If the light rays incident on the prism can be regarded as parallel light, this method can be expected to improve the light use efficiency. However, when the angle between the light beam incident on the prism and the optical axis is large and cannot be regarded as parallel light, the light beam cannot be bent in a desired direction by the prism, and the light use efficiency does not increase so much. On the other hand, even if it can be regarded as parallel light, if the light source is a laser, vibration occurs between the laser and the illumination optical system, and if the positions are shifted, the center of light quantity of the annular effective light source is shifted, resulting in axial symmetry. It does not provide an effective light source and cannot achieve uniform illumination.

Japanese Patent Application Laid-Open No. 11-54426 teaches that a fly-eye lens or an internal reflection member is inserted between a light source and a prism in order to prevent a problem due to vibration. However, in this method, the light incident on the prism cannot be regarded as parallel light, so that the light use efficiency does not increase much as described above.

Japanese Patent Application Laid-Open No. 4-225514 proposes a method of increasing the light use efficiency by using a diffractive optical element. However, if the parallel light is not incident on the diffractive optical element, the light beam cannot be bent in a desired direction as in the case of the above-described prism, and the light use efficiency does not increase much. The diffraction efficiency of the diffractive optical element is determined by the number of stages of the element, but it is difficult to obtain a diffraction efficiency of 100% by the current processing method. This also does not significantly increase the light use efficiency.

[0020]

SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide a new and useful illuminating device and exposure device which solve such conventional problems.

More specifically, the present invention illuminates an illumination area, such as a rectangular mask surface, uniformly and effectively (ie, with a desired illuminance) in a conventional illumination device that uses annular illumination. It is an exemplary purpose to provide a lighting device.

Also, the present invention provides a high-quality semiconductor, LCD, CC using an illuminating device for illuminating uniformly and with high illuminance.
D, Another exemplary object is to provide an exposure apparatus that exposes a device such as a thin-film magnetic head at a desired throughput.

In order to achieve the above object, an illuminating device as an exemplary embodiment of the present invention is an illuminating device for illuminating a surface to be illuminated having an aspect ratio other than 1 using a light beam emitted from a light source, A light integrator arranged between the light source and the illuminated surface to uniformly illuminate the illuminated surface, and arranged between the light source and the light integrator, includes a circular arc in a part of the cross-sectional shape. And a first optical rod whose cross-sectional shape has an aspect ratio that approximates the aspect ratio of the illumination area. Such an illuminating device uses an arc-shaped first optical rod, so that the shape of the effective light source for illuminating the incident surface of the light integrator does not change even if the optical axis of the illuminating optical system deviates from the light source. Even if the optical axis of the device shifts, the center of gravity of the effective light source does not shift. Further, by setting the aspect ratio of the cross-sectional shape of the first optical rod to be substantially equal to the aspect ratio of the light integrator, the amount of vignetting by the light integrator can be reduced and the light use efficiency can be increased. Further, the first optical rod can realize annular illumination in which an aperture stop is provided downstream of the light integrator, thereby contributing to an improvement in resolution.

An exposure apparatus as one exemplary embodiment of the present invention has such an illuminating apparatus and an optical system for projecting a pattern formed on a reticle or a mask onto an object to be processed. Since such an exposure apparatus uses the above-described illumination device, it has a similar effect.

A device manufacturing method according to an exemplary aspect of the present invention includes a step of projecting and exposing an object to be processed by using the above-described exposure apparatus, and a step of performing a predetermined process on the object to be exposed and projected. Having. The device manufacturing method having the same operation as that of the above-described lighting apparatus extends to the device itself as an intermediate and final product. Such devices include semiconductor chips such as LSI and VLSI, CCDs, LCDs, magnetic sensors, thin-film magnetic heads, and the like.

[0026] Other objects and further features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same members. Here, FIG. 1 is a schematic configuration diagram of an exemplary exposure apparatus 1 of the present invention and an illumination apparatus 100 as a part thereof.

The exposure apparatus 1 has an illumination device 100, a mask 200, and a projection optical system 300, as shown in FIG. The exposure apparatus 1 is a scanning projection exposure apparatus that exposes a pattern formed on a mask 200 onto a plate W by a step-and-scan projection exposure method.

The illumination device 100 illuminates the mask 200 on which the transfer pattern has been formed. As shown in FIG. 1, the illumination device 100 includes a laser 110 as a light source and an illumination optical system.

The laser 110 is a light source for emitting illumination light, for example, a KrF excimer laser having a wavelength of about 248 nm. The laser 110 has an ArF wavelength of about 193 nm.
It may be replaced with an excimer laser. The light source is
For example, an ultra-high pressure mercury lamp, a xenon lamp, or the like generally having an output of 500 W or more may be used.

When a laser is used, a light beam shaping optical system for shaping a parallel light beam from a laser light source into a desired beam shape, or an incoherent optical system for making a coherent laser light beam incoherent may be used.
The light beam shaping optical system can use, for example, a plurality of cylindrical lenses, beam expanders, or the like, and converts the aspect ratio of the cross-sectional shape of the laser light into a desired value. The incoherent optical system is disclosed in, for example,
As disclosed in FIG. 1 of Japanese Patent No. 15930, after splitting an incident light beam into at least two light beams (for example, p-polarized light and s-polarized light) at a light splitting surface, one light beam is split via an optical member into the other light beam. Use of an optical system having at least one folding system in which an optical path difference greater than the coherence length of a laser beam is given to a light beam and then re-guided to a split surface so as to be superimposed and emitted with the other light beam Can be.

Further, a first bent lens 11 which will be described later
A collimator lens may be disposed between the laser beam 5 and the laser 110 to convert a laser beam emitted from the light source so as to diverge and spread to parallel light.

The illumination optical system is an optical system for irradiating the mask 200 with a light beam, and includes a first bending mirror 115, a prism 120, an optical rod 125, a first condenser lens 130, and a second bending mirror. 135,
Fly-eye lens 140 and second condenser lens 1
45, the aperture 150, and the imaging optical systems 155a and 155
b and a third bending mirror 160.

The first bending mirror 115 is a laser 1
The light beam L1 emitted from the optical rod 125 is transmitted to an optical rod 125 to be described later.
Are deflected so as to be parallel to the longitudinal direction (also referred to as an axial direction in this specification). If the emitted light of the laser 110 and the longitudinal direction of the optical rod 125 are arranged in parallel in advance, the first bending mirror 1
15 can be omitted. However, referring to FIG. 1, by using the first folding mirror 115,
By deflecting the light beam of the laser 110, the size of the illumination device 100 and the exposure device 1 can be reduced. Note that the first bending mirror 115 deflects the light beam from the laser 110 at an angle such that the light beam is optimally incident on a component located behind.

The prism 120 converts the light beam L1 deflected by the first bending lens 115 into an optical rod 12 to be described later.
5 is used for incidence at an angle to the axial direction. The prism 120 is a polyhedron formed of glass or the like. The prism 120 may be formed from, for example, quartz or fluorite. The prism 120 used in the exposure apparatus 1 of the present invention is a triangular prism having a triangular cross section. Note that the prism 120 has a configuration in which the incident surface of the light beam and the emission surface of the light beam opposed thereto are relatively inclined.
There is no limitation on the shape.

Referring to FIG. 2, the light beam L 1 deflected by the first bending mirror 115 is perpendicularly incident on the prism 120. Here, FIG. 2 shows the lighting device 10 shown in FIG.
FIG. 4 is a simple optical path diagram passing through a prism 120 used for zero. The light beam L2 passing through the prism 120 exits from the opposite surface inclined by an angle e2 with respect to the incident surface of the prism 120. At this time, the light beam L2 becomes a light beam L3 refracted by the angle e1 with respect to the light beam L2. Here, luminous fluxes L2 and L3 have n × sin (e2) = sin (e1 +
e2), where n is the absolute refractive index of the prism 120. That is, the angle e1 of the light beam L3 with respect to the light beam L2 depends on the absolute refractive index n of the prism 120 and the inclination angle e2 of the exit surface. Thereby, the light beam L3 is
The light can be incident at an angle e1 with respect to the longitudinal direction of the optical rod 125. In this embodiment, since the light beam L1 is perpendicularly incident on the incident surface of the prism 120,
An angle change due to refraction does not occur between the light beams L1 and L2. However, the prism 120 may be arranged so that refraction occurs between the light beams L1 and L2. Furthermore, prism 1
It is also conceivable to arrange 20 on a turret so as to be freely rotatable. With such a configuration, the optical rod 1
The angle of the light beam L3 incident on the light rod 25 with respect to the axial direction of the optical rod 125 can be arbitrarily changed. In addition, it is preferable that the incident angle e1 with respect to the optical rod 125 be adjusted according to the required exit angle of the optical rod 125 as described later.

Further, referring to FIG.
Can be replaced with a prism 121. Here, FIG. 3 is a diagram showing another exemplary form of the prism 120 used in the lighting device 100 shown in FIG. The prism 121 is formed into a wedge shape by diagonally dividing a quadrangular prism having a rectangular cross section, so that the upper prism 121a is
It is rotated by degrees. In the prism 121, the prism 121a is disposed lower than the prism 121b with respect to the traveling direction of the light beam. Further, it is preferable that the incident surface of the light beam of the prism 121b is disposed perpendicular to the incident light beam, but the present invention is not limited to this. The prism 121 is shifted from the state shown in (a) of the prism 121a with respect to the prism 121b (b).
By shifting the arrangement to an arbitrary position between the states shown in (1) and (2), the incident angle of the light beam incident on the optical rod 125 can be arbitrarily changed.

The first folding mirror 11 described above
5 may be adjusted so that the light is incident at an angle to the longitudinal direction of the optical rod 125. In such a configuration, it is not necessary to dispose the prism 120. Whether the light is incident on the optical rod 125 by using the bending mirror 115 or the light flux having an angle with respect to the longitudinal direction of the optical rod 125 by adjusting the bending mirror 115 is optional.

The optical rod 125 is used to obtain a light beam having a uniform angular distribution symmetrical with respect to the optical axis at the light exit surface. First, a cylindrical rod 500 as an example of an optical rod
Will be described with reference to FIG. Here, FIG. 13 is a simplified optical path diagram when the parallel light L is put into the cylindrical rod 500. Such a cylindrical rod 5
00 is already disclosed in Japanese Patent Publication No. 2767235. The cylindrical rod 500 has a property that the parallel light L is made uniform by skew reflection at the exit surface in an axially symmetric manner with respect to the optical axis.

Referring to FIG. 13, the polar coordinate system is (r, θ) with respect to the axial coordinate system (x, y, z) in which the axis of the cylindrical rod 500 is the z axis and the x axis and the y axis are perpendicular to the z axis. , Φ). At this time, the light ray L (θ = e, φ = 0) incident on the incident end 502 of the rod changes only in the φ direction component. This change in φ differs depending on how the rod hits the side surface of the cylindrical rod 500. Also, if the incident light beam has a large thickness, it changes differently from place to place. Therefore, if the columnar rod is sufficiently long in the z-axis direction, φ has various values. The light beam L has an angle e with the z-axis at the emission end 504, and becomes a light beam L 'having an angular distribution symmetrical with respect to the z-axis. As shown in FIG. 13, when the screen is placed at a position distant from the emission end 504, an annular light distribution is observed.

Therefore, referring to FIG. 14, if the exit surface 504 of the cylindrical rod 500 is used as a secondary light source to illuminate the entrance surface of the fly-eye lens 510 using the Koehler illumination method, the fly-eye lens 510 As in the case where a ring-shaped aperture stop is arranged at the subsequent stage, a ring-shaped effective light source distribution can be obtained. Here, FIG. 14 is a simplified optical path diagram of a part of an optical system using the cylindrical rod 500 shown in FIG. Further, Koehler illumination is an illumination method in which the angular distribution of light in a light source is replaced by the positional distribution of an illumination surface, and the positional distribution of light in a light source is replaced by the angular distribution of an illumination surface. In the present application, such a relationship may be referred to as a Fourier transform relationship. Even if the position where the incident light beam L enters the rod rises and falls, the angle e on the emission surface does not change. Therefore, the shape of the effective light source does not change even if the optical axis of the illumination optical system deviates from the optical axis of the laser in the illumination device. As a result, the cylindrical rod 500 can provide uniform illumination to the surface to be illuminated, and can provide an illumination device that is resistant to vibration.

However, the cylindrical rod 50 is attached to the lighting device 100.
When 0 is used, there arises a problem that the non-uniformity of the effective light source and the light use efficiency are not compatible. As described above, Koehler illumination is an illumination method in which the angular distribution of light in a light source is replaced by the positional distribution of an illumination surface, and the positional distribution of light in a light source is replaced by the angular distribution of an illumination surface. Referring to FIG. 14, the angle distribution of light on the incident surface 512 of the fly-eye lens 510 has the shape of the exit surface 504 of the cylindrical rod, that is, a circular distribution.

The fly-eye lens 510 is a kind of light integrator that converts an angle distribution of incident light into a position distribution and emits the light, and the incident surface 512 and the emission surface 514 have a Fourier transform relationship. The fly-eye lens is formed by arranging a plurality of lenses (lens elements) on the other surface having different focal positions from each other. In the case of an optical system using the cylindrical rod 500 as shown in FIG.
Since the angle distribution of the light on the zero incidence surface 512 is circular, the position distribution of the light on the emission surface 514 of each lens element of the fly-eye lens is circular. Further, when the cross-sectional shape of each lens element constituting the fly-eye lens is substantially similar to the illumination area of the illumination device when the lens surface of each lens element is spherical, the utilization efficiency of the illumination light is higher. This is because the fly-eye lens and the illumination area have a pupil-image relationship (Fourier transform relationship).

In the case of the exposure apparatus 1, since the illumination area as the mask 200 surface is rectangular, for example, 26 mm × 13 mm, the fly-eye lens has an aspect ratio of about 2:
It is preferably 1. As described above, in the optical system shown in FIG. 14, the position distribution of light on the exit surface 514 of the fly-eye lens 510 is circular. Therefore, the fly's eye lens 51
The light intensity distribution on the zero emission surface 514 is as shown in FIG. 15 or FIG. Here, FIGS. 15 and 16
FIG. 7 is a plan view of a light intensity distribution when an emission surface 514 of a fly-eye lens 510 is viewed from a mask side. In FIG. 15, the image of the exit surface of the cylindrical rod 500 forming the effective light source distribution is smaller than the cross section of each lens element of the fly-eye lens 510, and the effective light source cannot be regarded as a surface light source. In FIG. 16, even if the light enters the incident surface 512 of the fly-eye lens 510, it cannot be emitted from the exit surface 514, and there is light vignetting by the fly-eye lens 510.

Therefore, the present inventor has set the fly-eye lens 140 shown in FIG. 1 to be an effective light source that can sufficiently simulate the surface light source, and that the exit surface of the fly-eye lens 140 described later is used.
The shape of the optical rod 125 is designed so that the amount of vignetting is reduced by 40 and the light use efficiency is increased.

The optical rod 125 is an optical element formed by a transparent columnar member. Generally, a step index optical fiber may be used as the optical rod. Referring to FIG. 4, the optical rod 125 has a semicircular cross-sectional shape, and the aspect ratio of the cross-sectional shape is substantially equal to the aspect ratio of each lens element constituting the fly-eye lens 140, and thus the aspect ratio of the illumination area. It is formed. Here, FIG. 4 is an exemplary sectional view of the optical rod 125. However, the optical rod 125 only needs to have a part of a circular cross section and an aspect ratio of the cross section substantially equal to an aspect ratio of the illumination area. The optical rod 125 can realize annular illumination similarly to the cylindrical rod 500 shown in FIG. 13 due to the cross-sectional shape including the arc. Further, the optical rod 125 can obtain a preferable light use efficiency with a predetermined aspect ratio. 5 and 6, the optical rod has, for example, a sectional shape obtained by cutting both sides of a circle (125).
a) or a shape (125b) composed of a common portion of a circle whose center is shifted. Here, FIGS. 5 and 6
Is a cross-sectional view of another exemplary optical rod 125a and 125b in the axial direction.

Referring to FIG. 9, the light beam L3 incident on the optical rod 125 is refracted at the end of the incident surface 126 and becomes a light beam L4 having an angle e3 with respect to the rod axis. Here, FIG. 9 is a simple optical path diagram of a light beam passing through the optical rod 125 used in the illumination device 100 shown in FIG. Luminous flux L
4 propagates toward the emission end face while being reflected several times inside. At this time, regarding the axial direction, the optical rod 1
At 25, the rod is flat and has no power. Therefore, the light beam L4 is reflected while maintaining the angle e3 with respect to the axis of the optical rod. At the end of the exit surface 127, the light beam L4 is refracted in the opposite direction to the end of the entrance surface 126. That is, the emission surface 12
The angle of the light beam L5 emitted from 7 with respect to the rod axis is e1
Remains. On the other hand, in the portion of the optical rod 125 having a curvature, the optical rod 12 is perpendicular to the axial direction.
5 has power. Therefore, the angle of the light beam L4 incident on the optical rod 125 in the direction perpendicular to the optical rod 125 axis is not preserved. That is, the light beam L4 is mixed in the spiral direction. Thus, the optical rod 125 can obtain a light flux having a uniform annular zone angle distribution axially symmetric with respect to the optical axis on the light exit surface 127. Optical rod 1
25 has the same cross-sectional shape as the aspect ratio of the illumination area, so that the fly-eye lens 140 does not cause vignetting.

It is preferable that the light beam L 4 is totally reflected on the inner surface of the optical rod 125. This is made possible by causing the light beam L3 to be incident on the optical rod 125 such that the light beam L4 is reflected at an acute angle with the rod side surface. Further, by forming a reflective film on the side surface of the optical rod 125, total reflection can be effectively performed.

As described above, the lighting device 100 of the present invention
The optical rod 125 used in the above-mentioned method can make the angular distribution axially symmetric about the optical axis by skew reflection by making a part of the cross-sectional shape an arc. Further, the optical rod 125 has an aspect ratio of the cross-sectional shape of the fly-eye lens 14.
By setting the cross-sectional shape to be substantially equal to the aspect ratio of the cross section of each lens element constituting 0, and thus the aspect ratio of the illumination area, the effective light source distribution can be regarded as a surface shape in the fly-eye lens 140 described below, and The luminous flux can be prevented from vignetting.

In the optical rod 125, the light flux L
3 is formed perpendicular to the rod axis. However, an optical rod 125c having a configuration in which the end on the incident side is obliquely formed as shown in FIG. 7 is also conceivable. Referring to FIG. 7, in such a configuration,
When the light beam L10 parallel to the rod axis is made incident on the optical rod 125c, the light beam L10 is refracted at the end formed obliquely (L11). Here, FIG. 7 is a diagram showing a simple optical path diagram from the side of another exemplary form of the optical rod 125c used in the lighting device 100 shown in FIG. Therefore, the light beam L1 incident on the optical rod
1 has an angle with respect to the rod axis direction. The above-described configuration can obtain the same effect as the optical rod 125 using the above-described prism 120 without using a prism.

Referring again to FIG. 1, the first condenser lens 130 is arranged so that the exit surface of the optical rod 125 and the entrance surface of the fly-eye lens 140 have a Fourier transform relationship. The bending mirror 135 deflects the light beam.

The fly-eye lens 140 is a type of light integrator that converts an angle distribution of incident light into a position distribution and emits the light, and the incident surface and the emission surface have an optical Fourier transform relationship. However, as will be described later, the (optical) integrator that can use the present invention is not limited to the fly-eye lens. In this embodiment, the fly-eye lens 140 is a lens element (that is, a minute lens) 1 having a rectangular cross section.
37, but the present invention
This does not exclude lens elements having a circular, square, hexagonal or other cross-sectional shape.

As shown in FIG. 8, the fly-eye lens 140 has a total of 18 lens elements 137 having a rectangular cross section, that is, six rows vertically and three rows horizontally. Here, FIG. 8 is a plan view of the effective light source viewed from the exit surface of the fly-eye lens 140 used in the illumination device 100 shown in FIG. The semicircle of each lens element 137 of the fly-eye lens 140 shown in FIG. Thus, the optical rod 1
By approximating the aspect ratio of the cross-sectional shape of the optical lens 125 to the aspect ratio of each lens element constituting the fly-eye lens 140 corresponding to the shape of the illuminated area, the images of the exit surfaces of the many optical rods 125 are The mask 200 can be regarded as an effective light source close to a surface light source without vignetting, and the mask 200 can be efficiently and uniformly illuminated.

The second condenser lens 145 collects as much of the light beam L7 from the fly-eye lens 140 as possible and superimposes the light beam L7 on the stop 150 so as to illuminate the stop 150 with Koehler illumination (L8). That is, the aperture 150 and the exit surface of the fly-eye lens 140 are arranged in a Fourier transform relationship.

A part of the optical system shown in FIG. 1 may be replaced with the optical system shown in FIG. Here, FIG. 10 is a schematic configuration diagram of the exposure apparatus 1 shown in FIG. 1 and another example of an illumination apparatus 100a which is a part thereof. FIG. 10 illustrates a first condenser lens 130, a second folding mirror 135, and a second condenser lens 130 of the illumination device 100 that is a part of the exposure device 1 of FIG.
Fly-eye lens 140 and second condenser lens 1
45 is a first collimator lens 170, a second folding mirror 175, and a second collimator lens 18
0 and a second optical rod 185.

The first collimator lens 170 converts the light beam L5 into a substantially parallel light beam L10. The light beam L10 is the second
Is deflected by the bending mirror 175 and enters the second collimator lens. The second collimator lens 180 converts the parallel light beam L10 into a condensed light beam L11 that converges on the incident surface end of the second optical rod 185. With this configuration, the exit surface of the optical rod 125 (hereinafter, referred to as a first optical rod for convenience in the embodiment of FIG. 10) and the entrance surface of the second optical rod 185 are optically positioned between the object plane and the image plane. In a relationship. Such a relationship may be referred to as a conjugate relationship in the present application. The first optical rod 125
When the second optical rod 185 described later is arranged in series, the first collimator lens 170, the second bending mirror 175, and the second collimator lens 18
0 may be omitted.

In the present embodiment, the image forming system including the first and second collimator lenses 170 and 180 is configured such that the exit surface of the first optical rod 125 is the first collimator lens 1.
At the focal position of 70, the incident surface of the second optical rod 185 is arranged at the focal position of the second collimator lens 180, respectively. With such a configuration, the light beam L10 that has passed through the first collimator lens 170 becomes a substantially parallel light beam, and the effective diameter required by the second bending mirror 175 is required even if the position of the second bending mirror 175 is changed. Does not change much, so the degree of freedom in designing the mirror arrangement increases.

The second optical rod 185 makes the illuminance distribution, which was not uniform on the entrance surface, uniform on the exit surface. The second optical rod 185 is a rectangle whose cross-sectional shape perpendicular to the rod axis has almost the same aspect ratio as the illumination area. If the second optical rod 185 has power in a cross-sectional shape perpendicular to the rod axis, the illuminance on the exit surface is not uniform. Therefore, the cross-sectional shape of the second optical rod 185 perpendicular to the rod axis is a polygon formed by only straight lines. Except for such a configuration, the optical rod 125 is the same as the optical rod 125 described above, and thus a detailed description is omitted.

The stop 150 is used to limit the illumination area on the mask 200. The stop 150 has a substantially rectangular light transmitting portion when the projection optical system 300 is a lens type projection system. When the projection optical system 300 is an Offner-type reflection mirror projection system, the second condenser lens 145 is used.
An arc-shaped light transmitting portion and a light shielding portion are provided in a region that is uniformly illuminated. The light beam transmitted through the light transmitting portion of the aperture 150 is used as illumination light for the mask 200. Imaging optical system 160
Re-images the aperture image of the stop 150 on the mask 200 again.

As shown, the image forming optical system includes a plurality of optical systems 155a and 155b and a third folding mirror 160.
Having. However, if the mask 200 and the stop 150 are arranged in parallel, the folding mirror 160 can be omitted, and either one of the optical systems 155a and 155b may be used.

A pattern is formed on the mask 200, and the diffracted light emitted from the mask 200 passes through the projection optical system 300 to form a pattern image on the plate W. The plate W is an object to be processed such as a wafer or a liquid crystal substrate, on which a resist is applied. The stop 150 and the mask 200 are arranged in a conjugate relationship. The exit surface of the fly-eye lens 140 and the mask 200 have a Fourier transform relationship. Further, the mask 200 and the plate W have a conjugate relationship.

In the case of a scanning projection exposure apparatus, the mask 20
By scanning 0 and the plate W, the pattern of the mask 200 is transferred onto the plate W. In the case of a stepper (an exposure apparatus of a step-and-repeat exposure method), exposure is performed with the relative position between the mask 200 and the plate W fixed (still).

The projection optical system 300 includes an optical system including only a plurality of lens elements, an optical system including a plurality of lens elements and at least one concave mirror, and a diffractive optical system such as a plurality of lens elements and at least one kinoform. An optical system having an element can be used. When it is necessary to correct chromatic aberration, a plurality of lens elements made of glass materials having different dispersion values (Abbe values) are used, or a diffractive optical element is used.

The plate W is coated with a photoresist. The photoresist coating step includes a pretreatment, an adhesion improving agent coating process, a photoresist coating process, and a pre-bake process. Pretreatment includes washing, drying, and the like. The adhesion improver application treatment is a surface modification (that is, making the surface hydrophobic by applying a surfactant) treatment to increase the adhesion between the photoresist and the base, and is applied to HMDS (Hexameth).
An organic film such as yl-disilazane) is coated or steamed. Prebaking is a baking (firing) step, but is softer than that after development, and removes the solvent. The mask 200 and the plate W move in opposite directions synchronously at a predetermined speed.

In the exposure, the light beam emitted from the laser 110 is deflected by the first bending mirror 115.
Thereafter, the light flux changes its angle at the slit 120 and is obliquely incident on the optical rod 125. By repeating the skew reflection of the light beam on the optical rod 125, a uniform angular distribution symmetrical with respect to the optical axis on the exit surface is obtained. Such a light beam is made substantially parallel by the first condenser lens 130, deflected by the bending mirror 135, and combined at the entrance surface of the fly-eye lens 140. At this time, the light emitted from the optical rod 125 may be combined by the second optical rod 185.

The light beam emitted from the fly-eye lens 140 and the like passes through the second condenser lens 145, and then illuminates the stop 150. The light beam that has passed through the stop 150 passes through the imaging optical system 160, and then illuminates the irradiation surface of the mask 200. The second condenser lens 145 uses the light emitted from the integrator to stop the aperture 150 and the mask 200.
Is uniformly illuminated by Koehler illumination.

Since the exposure apparatus 1 using the illumination apparatus 100 can perform illumination with a uniform effective light source, pattern transfer to a resist is performed with high accuracy and high-quality devices (semiconductor element, LCD element, image pickup element (CCD) Etc.), thin film magnetic heads, etc.).

Next, with reference to FIGS. 11 and 12, an embodiment of a device manufacturing method using the above-described exposure apparatus 1 will be described. FIG. 11 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, and the like). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the circuit of the device is designed. Step 2 (mask fabrication)
A mask on which the designed circuit pattern is formed is manufactured. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is referred to as a preprocess, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). . In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 12 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD)
Then, an insulating film is formed on the surface of the wafer. Step 13
In (electrode formation), electrodes are formed on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a circuit pattern on the mask onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) removes portions other than the developed resist image. Step 19
In (resist removal), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. According to the manufacturing method of this embodiment, it is possible to manufacture a high-quality device which has conventionally been difficult to manufacture.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the invention.

[0071]

According to the illumination apparatus and the exposure apparatus of the present invention, the incident surface of the light integrator is illuminated even if the optical axis of the light source and the illumination optical system deviate since the optical rod having a cross section including an arc is used. Therefore, even if the shape of the effective light source does not change and the optical axis of the light source and the illuminating device shift, the center of gravity of the effective light source does not shift. As a result, the illumination device can provide uniform illumination to the surface to be illuminated even if the optical axis of the light source and the illumination device are shifted. Therefore, the present invention can provide a lighting device that is resistant to vibration.

Further, by making the aspect ratio of the sectional shape of the optical rod approximately equal to the aspect ratio of the surface to be illuminated, and furthermore, the aspect ratio of the sectional shape of the light integrator, the amount of vignetting by the light integrator is reduced and the light is reduced. Usage efficiency can be increased. As a result, the exposure apparatus can maintain a desired throughput.

Further, it is possible to realize annular illumination in which an aperture stop is provided downstream of the light integrator by the optical rod. As a result, the exposure apparatus can realize a high resolution by increasing the proportionality constant k ₁ in Equation 1.

Further, since the present invention does not use a diffractive optical element or the like, a relatively inexpensive illumination device and exposure device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an exemplary exposure apparatus of the present invention and an illumination apparatus that is a part of the exposure apparatus.

FIG. 2 is a simple optical path diagram passing through a prism used in the lighting device shown in FIG.

FIG. 3 is a cross-sectional view showing another exemplary form of a prism used in the illumination device shown in FIG.

FIG. 4 is an exemplary sectional view of an optical rod used in the lighting device shown in FIG. 1;

5 is a vertical cross-sectional view of another exemplary optical rod used in the lighting device shown in FIG.

6 is a vertical cross-sectional view of another exemplary optical rod used in the lighting device shown in FIG.

7 shows a simplified optical path diagram from the side of another exemplary optical rod used in the lighting device shown in FIG. 1;

FIG. 8 is a plan view of an effective light source viewed from an exit surface of a fly-eye lens used in the illumination device shown in FIG. 1;

9 is a simple optical path diagram of a light beam passing through an optical rod used in the lighting device shown in FIG.

10 is a schematic configuration diagram of the exposure apparatus shown in FIG. 1 and a lighting device of another exemplary embodiment which is a part thereof.

FIG. 11 is a flowchart illustrating the manufacture of a device.

FIG. 12 is a detailed flowchart of a wafer process shown in FIG. 11;

FIG. 13 is a simplified optical path diagram for explaining the properties of the optical rod of the illumination device shown in FIG. 1 when parallel light is injected into a cylindrical rod.

14 is a simplified optical path diagram of a part of an optical system using the cylindrical rod shown in FIG.

FIG. 15 is a plan view of the light intensity distribution when the emission surface of the fly-eye lens is viewed from the mask side.

FIG. 16 is a plan view of the light intensity distribution when the emission surface of the fly-eye lens is viewed from the mask side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exposure apparatus 100 Illumination apparatus 110 Laser 125 Optical rod 140 Fly-eye lens 150 Aperture 160 Imaging optical system 185 Second optical rod 200 Mask 300 Projection optical system

Claims (10)

[Claims] 1. An illumination device for illuminating an illuminated surface having an aspect ratio not equal to 1 using a light beam emitted from a light source, wherein the illuminated device is arranged between the light source and the illuminated surface to make the illuminated surface uniform. A light integrator for illuminating the light source; a light integrator disposed between the light source and the light integrator, the cross sectional shape including a circular arc, and the aspect ratio of the sectional shape approximates the aspect ratio of the illumination area. An illumination device having an optical rod. 2. The illumination device according to claim 1, wherein the cross-sectional shape of the first optical rod is a shape obtained by cutting off a part of a circle. 3. The lighting device according to claim 1, wherein the light integrator has a fly-eye lens. 4. The lighting device according to claim 1, wherein the light integrator has a plurality of cylindrical lens arrays in which each set is orthogonal. 5. The illumination device according to claim 1, wherein an exit surface of the first optical rod and an entrance surface of the light integrator have an optical relationship between a pupil and an image. 6. The illumination device further includes a second optical rod having a cross section substantially similar to the surface to be illuminated, and an exit surface of the first optical rod and an entrance of the second optical rod. The lighting device according to claim 1, wherein the surface is substantially optically conjugate. 7. The lighting device according to claim 1, further comprising a prism between the light source and the optical rod. 8. An exposure apparatus comprising: the illumination device according to claim 1; and an optical system configured to project a pattern formed on a reticle or a mask onto an object to be processed. 9. A device manufacturing method, comprising: a step of projecting and exposing an object to be processed using the exposure apparatus according to claim 8; and a step of performing a predetermined process on the object to be exposed and projected. 10. A device manufactured from an object to be projected and exposed by using the exposure apparatus according to claim 8.