JPH08330225A - Lighting optical device, exposure device, and exposure method - Google Patents

Abstract

PURPOSE: To reduce speckle with a simple control by providing an optical member for rocking a plurality of fluxes of light which are applied to a second optical integrator for distributing pulse light from a first optical integrator two-dimensiomlly at least for half period while applying a minimum number of pulses between both integrators. CONSTITUTION: A fly-eye lens 3 which is a first optical integrator receives pulse light from a light source device 10 to generate a plurality of point light sources distributed two-dimensionally. A fly-eye lens 5 which is a second optical integrator receives pulse light from the first optical integrator to generate a plurality of point light sources distributed two-dimensiomlly. A scanning mirror 17 is provided between the fly-eye lens 3 which is a first optical integrator and the fly-eye lens 5 which is a second optical integrator as an optical member for rocking a plurality of fluxes of light entering the second optical integrator 5 at least for half period while applying a minimum number of pulses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical apparatus, an exposure apparatus, and an exposure method, and more particularly, an illumination optical apparatus, an exposure apparatus, and an exposure method suitable for using a coherent beam such as excimer laser light. It is about.

[0002]

2. Description of the Related Art In an exposure apparatus for semiconductor manufacturing, high resolution is achieved by shortening the wavelength of exposure light from a light source. The most dominant short wavelength light source at present is the excimer laser. FIG. 2 is a diagram schematically showing an optical path when an excimer laser light source is placed in an illumination system (optimally designed when used as a light source) of a conventional mercury lamp. Beam LB from laser light source
Is incident on the fly-eye lens 1 as an optical integrator from the left in the figure as a substantially parallel light beam. The fly-eye lens 1 is indispensable for uniformly illuminating the reticle R.

The fly-eye lens 1 is composed of three element lenses 1a, 1b, and 1c here, and a secondary light source (focused spot of laser light) is placed in the spaces a, b, and c on the exit end side of each element lens. ) Is formed. The light diffused from each of the points a, b, and c is collected by the condenser lens 2 and illuminates the reticle R with a uniform illuminance distribution. The pattern on the reticle is projected and exposed on the wafer W by the projection lens PL. The secondary light sources a, b and c are imaged on the pupil plane ep of the projection lens PL.

Normally, the number of element lenses constituting the fly-eye lens is a two-dimensional array of 10 × 10 = 100, but here, for simplification, three lenses 1a, 1b, 1c are arranged in a one-dimensional array. Shown as a representative. However, this illumination system has the following problems. That is, unlike the case of the mercury lamp, when the laser light is incident on the fly-eye lens 1, the secondary light sources a, b, and c become spots with extremely high brightness. Therefore, when the secondary light source forms an image (focuses) on an optical component (lens or the like) in the optical path, there is a problem that the optical component is destroyed. Further, even if the secondary light source is imaged in the vicinity of the reticle even by extremely weak reflection from the surface of the lens, etc., the light source images are reflected by the reticle and re-imaged on the wafer, which causes a ghost. It was

However, it has been confirmed that such a problem can be easily solved by a new method developed by the applicant of the present application. It is disclosed in, for example, JP-A-58-14770.
As disclosed in Japanese Patent Publication No. 8, the method using two sets of fly-eye lenses is a further improved method. This method is shown in FIG. As shown in the drawing, the light from the secondary light sources a, b, and c formed by the first fly-eye lens 3 is condensed by the condenser lens 4 and is incident on the second fly-eye lens 5. Tertiary light sources (spot lights) a1, b1 and c1 are formed on the exit ends of the element lenses 5-1, 5-2 and 5-3 of the lens 5. This tertiary light source is 2
Since the number is larger than that of the next light source, the intensity of each point is very weak.

In FIG. 3, the first fly-eye lens 3
On the incident side of the beam LB of, the element lenses (square rods made of quartz) 3a, 3b, 3c are formed into spherical surfaces, and the exit end side is formed into a flat surface.
It is specified to make b and c in space. The condensing lens 4 allows the divergent light from each of the secondary light sources a, b, and c to effectively enter the second fly-eye lens 5, so that the focus (f) of the lens 4 from the incident end of the fly-eye lens 5 The secondary light sources a are arranged at positions separated by a distance,
The light sources b, c are arranged slightly apart from the secondary light sources a, b, c so that they are not located inside the condenser lens 4. The entrance ends of the element lenses (square rods made of quartz) 5-1, 5-2, 5-3 of the fly-eye lens 5 are formed into spherical surfaces having a curvature R1, and the exit ends thereof have a curvature R smaller than the curvature R1.
It is formed on the spherical surface of 2 and has a third-order light source a1, b1, c1.
Is defined to be created in space. Each tertiary light source a1, b
The light diverging from each of 1 and c1 is simultaneously superposed on the reticle R via the condenser lens 2 shown in FIG. 2 to obtain a uniform illuminance distribution. Here, the third light source a1
, B1 and c1 are formed on the surface ep 'which is the projection lens PL.
Of the secondary light sources a, b, c
It is also conjugated to the plane on which is created.

FIG. 4 is a plan view of the exit surface side of the second fly-eye lens 5, showing a case where the element lenses of the fly-eye lens 5 are arranged in a matrix, for example, 3 × 3 (9 pieces). . Here, assuming that the first fly-eye lens 3 is also composed of 3 × 3 (9) element lenses, there are nine fly-eye lenses 5 on the exit end side of one element lens. A third light source is created. Then, one secondary light source, for example, a is made as a tertiary light source a1 at the same position on each exit end face of the nine element lenses of the fly-eye lens 5. Therefore, a total of 9 × 9 (81) tertiary light sources (spot light) are aligned on the exit side of the fly-eye lens 5. The illuminance distribution uniformizing optical system itself shown in FIG. 3 is a technique which is the basis of the present invention and is not necessarily known.

In FIG. 3, the number of element lenses of the fly-eye lens is 3 × 3 (9) for both the first and second stages, but in a typical example, it is about 10 × 10 (100). Good. Therefore, the number of tertiary light sources is increased to 100 × 100 with respect to 100 secondary light sources, and the intensity of each spot of the tertiary light source is reduced to about 1/100 as compared with the one-stage fly-eye lens. To be done.

As a result, all problems such as destruction and ghost can be solved. In FIG. 3, it is also effective to arrange a lens close to the incident end of the fly-eye lens 5 to minimize the loss due to the diffusion of light. Further, between the pupil conjugate plane ep ′ and the condenser lens 2, the tertiary light source a
It is also effective to provide a field lens at a position close to 1, b1 and c1 so as to suppress loss due to divergence of light.

[0010]

However, it has been found that the structure shown in FIG. 3 causes a new problem. That is, fine illumination unevenness such as interference fringes called speckle occurs. In FIG. 2, the optical companions advancing from the respective secondary light sources a, b, and c and overlapping with each other on the reticle R may interfere with each other to generate interference fringes. This is roughly determined by the pitch in the arrangement direction of the element lenses 1a, 1b, 1c of the fly-eye lens 1 and the coherence of the beam LB. In general, an excimer laser has a poor coherence and has a characteristic that optical beams separated by a distance within a beam diameter do not interfere with each other. Since this distance is shorter than the arrangement pitch of the element lenses 1a, 1b, and 1c of the fly-eye lens 1, the lights from the secondary light sources a, b, and c in FIG. 2 do not interfere with each other after all. .

However, the story is different in the double integrator system shown in FIG. With the same idea,
The light traveling from each of the secondary light sources a, b, and c does not interfere with each other, but the light traveling from the secondary light source a is each element lens 5-1 and 5-by the second fly-eye lens 5.
Each of the light sources 2 and 5-3 serves as a tertiary light source a1 and is focused. In FIG. 3, for example, assuming that the element lenses (rods) of the first and second fly-eye lenses 3 and 5 have the same diameter and 10 (10 × 10) elements are arranged in one direction of the arrangement pitch, the secondary The beam diameter passing through the element lens 3a that makes up the light source a will be enlarged by about 10 times when reaching the second fly-eye lens 5. This means that the distance that does not cause the above-mentioned interference is also expanded by about 10 times. Therefore, the distance at which the fly-eye lens 5 does not interfere is larger than the pitch of the element lenses, so that the element lenses 5-1, 5-2, 5-
Tertiary light sources a1 that can be formed in the emission part such as 3 will interfere with each other. In reality, the fly-eye lens 5
Among them, the tertiary light sources a1 comrades, the tertiary light source b1 comrades, or the tertiary light source c1 comrades made of the element lenses adjacent to each other cause strong interference.

As a result, one-dimensional or two-dimensional interference fringes (speckle) corresponding to the arrangement direction of the element lenses 5-1, 5-2, 5-3 of the fly-eye lens 5 are generated on the reticle R, It is directly transferred onto the wafer W through the projection lens PL, which hinders accurate pattern transfer.

[0013]

In order to solve the above problems, an exposure apparatus according to claim 1 is a light source device for illuminating a reticle on which a circuit pattern is formed with pulsed light, and the light source device. From a first optical integrator that generates a plurality of point light sources that are two-dimensionally distributed by receiving the pulsed light from the optical fiber, and a plurality of points that are two-dimensionally distributed by receiving the pulsed light emitted from the first optical integrator. A second optical integrator for generating a light source and the second optical integrator.
And a condensing optical system for irradiating light from each of a plurality of point light sources generated by an optical integrator as pulsed illumination light onto the reticle in a superimposed manner, and forming an image of a circuit pattern of the illuminated reticle on a photosensitive substrate. In the exposure apparatus for projecting onto the upper surface, the second optical integrator is composed of a plurality of two-dimensionally arranged optical elements, and the number of the optical elements arranged in one specific direction among the plurality of optical elements. Is n (n is an integer), and the minimum pulse number of the pulsed light from the light source device required to expose the image of the circuit pattern on the photosensitive substrate is N equal to or more than N, the second optical An optical member that swings the plurality of light beams incident on the integrator for a half cycle or more during the irradiation of the pulse number N is provided in the first optical integrator and the first optical integrator. It is provided between the Optical integrator.

An exposure apparatus according to a second aspect of the present invention comprises a plurality of optical elements in which the first optical integrators are two-dimensionally arranged, and the plurality of optical elements of the first optical integrator and the second optical elements. The arrangement direction of the optical integrator and the plurality of optical elements is different. An illumination optical apparatus according to claim 3 comprises a light source for generating a coherent beam, and an illuminance distribution uniformizing means for irradiating the illuminated object with light having a uniform illumination distribution. An illumination optical device,
The light source generates a beam whose spatial coherence in a predetermined first direction in a cross section of the beam is higher than spatial coherence in a second direction substantially orthogonal to the first direction, and the illuminance distribution uniformizing means, A first optical integrator for injecting a beam from the light source, and a second for injecting a beam emitted from the first optical integrator.
An optical integrator, and swings a beam incident on the second optical integrator between at least the first optical integrator and the second optical integrator at least in a direction intersecting the second direction. First swing means is provided.

An exposure method according to a fourth aspect is an exposure method of illuminating a mask with light beams from first and second optical integrators that generate a plurality of point light sources, and exposing a pattern image of the mask onto a substrate. Irradiating the first optical integrator with a coherent beam whose spatial coherence in a predetermined first direction in the cross section of the beam is higher than spatial coherence in a second direction substantially orthogonal to the first direction. And between the first optical integrator and the second optical integrator,
Oscillating the beam incident on the second optical integrator at least in a direction intersecting the second direction.

The swing angle of the light beam by the above-mentioned optical member or the first swing means is sufficient to move the interference fringes formed on the reticle R (or wafer W) by one pitch. Further, in the case where the coherent beam emits pulses like excimer laser light, it is effective to synchronize the change of the swing angle and the timing of pulse emission. With a continuous wave laser beam, there is no particular need for synchronization, but if the rate of change of the swing angle, that is, the speed of movement in the direction orthogonal to the fringes of the interference fringes formed on the illuminated object, is almost constant, it will be uniform. The accuracy of is increased.

In the present invention, by using either a pulsed light emission or a continuous light emission beam, the object to be illuminated is made to have a uniform illuminance distribution for a certain fixed time (in the case of pulsed light emission, a plurality of pulses are required). Any device that needs to be illuminated can be widely used as an optical processing device, an illumination device for alignment, and the like. As described above with reference to FIG. 3, speckles (interference fringes) are generated by the interference of the third light sources with each other by the second fly-eye lens 5. Therefore, while illuminating the reticle R (or the wafer W), the wavefront of the light beam incident on the second fly-eye lens 5 is tilted to form a third-order light source a1 (or b) which can be an adjacent element lens of the fly-eye lens 5.
1, c1) give each other a phase difference of 2mπ (m = 1, 2, 3 ...). In other words, a phase difference of 2 mπ is given to the light (wavefront) incident on the adjacent element lenses, that is, an optical path difference of mλ (λ is the wavelength of the beam) is given. The speckle has a periodic structure corresponding to the distance between the element lenses of the fly-eye lens. When the phase difference of light from adjacent third light sources a1 changes, the speckle moves and the phase difference changes by 2π. Each time, the speckle moves exactly one cycle and becomes the same state as the original.

That is, if the phase of the object is continuously or stepwise changed by 2π or 2mπ during illumination, the speckles will be smoothed when illumination for a certain period of time is completed. By the way, since the excimer laser is a pulse laser, the phase change is not continuous.
It will be scattered. However, if the number of pulses is larger than a certain amount, the same result as a continuous change can be obtained. This is schematically shown in FIG. FIG. 5 (a)
Is a one-dimensional schematic drawing of the intensity distribution of periodic speckles (interference fringes). While increasing the phase difference by 2π / 4 in the element lens of the fly-eye lens, which is a close neighbor, the speckle of each pulse generated when four pulses of excimer laser light were irradiated to the illuminated object was shown to overlap. Is FIG. 5 (b). Add this (addition)
Then, the speckles are smoothed and disappear as shown in FIG. Strictly speaking, the ripple component is superimposed on a certain intensity distribution. The larger the number of pulses, the better, but usually several tens of pulses will provide a sufficient effect.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a first embodiment of the present invention will be described with reference to FIG. In FIG. 1, members having the same functions as those used in FIG. 3 are designated by the same reference numerals. In FIG. 1, the beam emitted from the excimer laser light source 10 is incident on the optical system 11 including the cylindrical lens through the ultraviolet reflection mirrors M1, M2, M3, and M4, and the beam LB0 having a rectangular cross section is almost square. Beam L
Shaped as B. The beam LB is an ultraviolet reflection mirror M.
The light beam is bent at 5 and enters the beam expander 15, is expanded to a predetermined beam diameter, and then enters the first fly-eye lens 3 shown in FIG.

Now, regarding the relationship between the structure of the excimer laser light source 10 and the characteristics of the oscillated laser beam,
This will be described with reference to FIGS. 6, 7, and 8. Excimer laser light sources are roughly classified into two types. One is called a stable resonator type, and as shown in FIG. 6, two resonator mirrors 102a and 102b are arranged at both ends of a discharge tube 100 that causes stimulated emission to form a resonator.
When the light reciprocates between the resonator mirrors (102a, 102b), the amplitude of the stimulated emission light is strengthened and the laser beam LB0 is emitted. The laser beam emitted from the laser light source of this type. Is characterized by low spatial and temporal coherence. In other words, the low temporal coherence means that the half-width of the spectrum is wide (Δλ≈0.4 nm), and such a light source can be used in an exposure apparatus for manufacturing an integrated circuit.
Achromaticity (chromatic aberration correction) is required in the projection lens PL, and it is difficult to make a practical lens in this wavelength range.

Another type of laser light source is called an injection lock type, and is divided into an oscillator and an amplifier as shown in FIG. In the oscillator, the resonator mirrors (102a, 102b) are arranged in the same manner as in the stable resonance type described above, but in this type, an etalon for selecting a wavelength in a predetermined region, a diffraction grating, etc. in the oscillator are used. The wavelength selection element (106) is provided, and the apertures (104a, 104a) for blocking the laser beam in a predetermined region are provided at both ends of the discharge tube 100.
b) is arranged, and the half width of the spectrum of the emitted laser beam is narrow (Δλ≈0.001 nm), that is, the monochromaticity is improved. Further, the oscillated laser beam is bent by the mirror (108) and is incident on the amplifier.
Mirrors (112a, 11a) for unstable resonators provided with convex and concave surfaces facing each other on both ends of the discharge tube (110).
It is amplified and emitted by 2b). One of the characteristics of the laser beam emitted from this type of laser light source is that the oscillator has enhanced monochromaticity and high temporal coherence, and there is no need for achromatization in the projection lens PL.

Therefore, there is an advantage that the lens can be made from only a single glass material (quartz), which is easy to design and manufacture. However, another feature of the injection-lock type laser light source is that it has an extremely high spatial coherence because it is amplified by an unstable resonator.When such a laser light source is used, strong interference fringes occur in the exposure area. Will end up.

Then, as a new type of laser light source developed to solve such inconvenience, there is one as shown in FIG. In this type of laser light source, a wavelength selection element 114 for narrowing the wavelength band, such as an etalon, a prism, and a diffraction grating, is provided in the above-mentioned stable resonator type laser light source, and the spectrum of the emitted laser beam is obtained. The width is narrow (Δλ≈0.003 nm). The characteristic of the laser beam emitted from such a laser light source is that the wavelength selection element 1
By providing 14, the temporal coherence is improved and the spatial coherence is lower than that of the injection locking type.

Although three laser light sources have been described above, the laser light source 10 used in this embodiment is the stable resonance type laser light source of FIG. 8 provided with a wavelength selection element, that is, a means for enhancing temporal coherence, and a projection lens. PL chromatic aberration correction is unnecessary. Further, since the spatial coherence is lower than that of the injection lock type, the speckle contrast generated by the beam emitted from the laser light source is extremely low.

However, the cross-sectional shape of the beam emitted from the excimer laser light source generally has an aspect ratio of 1: 2.
It has a 1: 5 rectangular shape, and the spatial coherence is not isotropic, and is higher in the lateral direction than in the longitudinal direction of the beam cross section. Therefore, speckles are likely to occur in the lateral direction of the beam cross section, and the speckle pattern generated by the beam emitted from the laser light source 10 shown in FIG. 1 is a one-dimensional interference pattern with low contrast. As described above, the pitch and arrangement direction of the interference fringes correspond to the interval and arrangement direction of the lens elements such as the fly-eye lens arranged in the illumination system as the intensity distribution uniformizing means.

Returning to the explanation of FIG. 1, the parallel beam emitted from the beam expander 15 and having a substantially square cross section is shown in FIG.
Scanning mirror 1 via fly's eye lens 3 and lens 4
It is incident on 7. Since the laser light source 10 of the present embodiment oscillates a stable resonator type KrF excimer laser light having a wavelength selection element therein as shown in FIG.
The spatial coherence is high in the lateral direction of the beam cross section, and the oscillation of the beam by the scanning mirror 17 is one-dimensionally performed in accordance with the lateral direction. Therefore, in the present embodiment, the scanning mirror 17 has the beam LB0 before being shaped by the optical system 11 including the cylindrical lens.
Is arranged so that the central axis of vibration coincides with the longitudinal direction of the cross section, that is, the longitudinal direction, and is connected to a vibration source (deflection source) 19 such as a galvano, piezo or torsional vibrator.

Here, it is not always necessary that the direction in which the beam is vibrated is completely aligned with the lateral direction of the beam, and it may be one direction appropriately selected from the directions intersecting the longitudinal direction of the beam. . That is, the direction of the vibration center axis of the scanning mirror 17 is not fixedly set, but the beam LB may be changed depending on the state of the speckle pattern to be removed.
It is preferable to appropriately incline the longitudinal direction of 0 and the center axis of vibration relative to about 45 degrees.

Further, in this embodiment, the beam is vibrated a predetermined number of times. However, since the speckle (interference fringe) to be removed in this embodiment has a low contrast from the beginning, the beam is not always regularly formed. There is no need to vibrate back and forth. That is, a resist layer (not shown) formed on the wafer W during one scan
In the case of ending the pulse for obtaining an appropriate exposure amount set in consideration of the sensitivity of the speckle, it is assumed that the speckle can be eliminated by swinging the scanning mirror 17 in a predetermined direction by a predetermined amount. It The beam oscillation is preferably performed in synchronism with the oscillation of the laser beam LB0.
In this embodiment, for example, the condition may be set so that one scan has about 50 pulses.

Next, the beam oscillated in the lateral direction by the scanning mirror 17 passes through the lens 21 and is incident on the second fly-eye lens 5, and as shown in FIG. After being condensed as spot light), it is diverged, condensed again by the condenser lens 25, bent by the ultraviolet reflection mirror 27, and enters the main condenser lens 2. Light from each of a large number of tertiary light sources, which are properly condensed by the main condenser lens 2, are all superimposed on the reticle R, and the reticle R is illuminated with a uniform illuminance distribution. As a result, the circuit pattern on the reticle R is projected and exposed on the wafer W by the projection lens PL made of, for example, quartz.

Here, the projection lens PL is one side (wafer side) or both sides telecentric, and the tertiary light source image formed on the emission surface side of the second fly-eye lens 5 is a condenser lens 25 and a main condenser lens 2. Pupil e by etc.
It is almost conjugate with p. That is, the point source (converging point of the beam) of the tertiary light source is located on the pupil ep and the fly-eye lenses 3 and 5
Will be formed by the product of the respective lens element numbers.

In the present embodiment, the longitudinal direction of the rectangular cross section of the beam LB0 oscillated by the laser light source 10 is the arrangement direction of one of the element lenses of the fly-eye lenses 3 and 5 (the optical axis AX is Z in FIG. 1). The axis is defined so as to coincide with the Y-axis direction). Further, the arrangement of the element lenses of the two fly-eye lenses 3 and 5 is assumed to be the same in the X direction and the Y direction, but this is not always necessary, and the fly-eye lens 3 shown in FIG. The fly-eye lens 5 may be relatively rotated about the optical axis AX from the state shown in the figure.

Next, the operation and operation of this embodiment will be described. In the case of the laser light source 10 of this embodiment, since the spatial coherence of the beam LB0 is originally low, the secondary light sources a, b, c produced by the first fly-eye lens 3 are used as described above with reference to FIG. It is possible to manufacture a fly-eye lens with a practical size and number while setting the intervals of the element lenses 3a, 3b, 3c so that they do not interfere with each other. However, with the second fly-eye lens 5, 3
When the dimensions of the element lenses 5-1, 5-2 and 5-3 are determined so that the next light sources a1 (or b1 and c1) do not interfere with each other, especially with respect to the arrangement direction which coincides with the lateral direction of the cross section of the beam LB0. In an extreme case, the size becomes about 10 times as large as the outer size of the first fly-eye lens 3. This is extremely inconvenient in terms of the structure of the apparatus, and therefore interference between the third light sources a1 (or b1 and c1) is unavoidable. Therefore, the scanning mirror 17 shown in FIG. 1 is swung to generate a tertiary light source a1 (or b) formed by the element lenses adjacent to the fly-eye lens 5.
1, c1) A phase difference of 2 mπ is given to each other and the interference fringes are smoothed as shown in FIG. The secondary light sources a, b, c
If there is no coherence between the comrades, the fly eye lens 5 1
Tertiary light sources a1 and b1 created in one element lens
, C1 They have no interference with each other. Here, considering the interference caused by the tertiary light source, as shown in FIG. 9, for example, the respective element lenses 5a and 5a of the fly-eye lens 5 are
When b, 5c, 5d, 5e, 5f, 5g, and 5h are regularly arranged in the X and Y directions, and the longitudinal direction of the cross section of the laser beam LB0 from the laser light source 10 coincides with the Y direction, the Y direction. (3), since the spatial coherence of the beam LB0 is originally low, the elemental lenses arranged in the Y direction, for example, the tertiary light sources Aa, Ad and Ag from the secondary light source a which can be 5a, 5d and 5g, respectively, interfere with each other. Conditions that do not occur are satisfied. However, regarding the X direction,
Since the spatial coherence is relatively high, for example, each of the element lenses 5c, 5d, 5e, and 5f arranged in the X direction is formed by the light from the secondary light source a and the tertiary light sources Ac and A are formed.
d, Ae, and Af interfere with each other.

The interference due to the tertiary light sources Ac, Ad, Ae, and Af also changes depending on the system conditions. For example, the tertiary light sources Ac and A of the two adjacent element lenses 5c and 5d.
d only interferes with each other, and the tertiary light sources Ae and A of the element lenses 5e and 5f that are two or more away from the tertiary light source Ac
If there is no interference between each of f, or 3
In some cases, only three of the secondary light sources Ac, Ad, and Ae interfere with each other, and in addition, all of the tertiary light sources Ac, Ad, Ae, and Af formed at the same position of the element lens in the X direction interfere with each other. FIG. 10 shows that when only tertiary light sources (eg, Ac and Ad, Ad and Ae, Ae and Af) that can be formed at the same position in two adjacent element lenses interfere with each other on the reticle R (or wafer W). The intensity distribution Fr1 of the interference fringes shown in FIG.

Therefore, in such a case, the phase difference between the tertiary light sources that interfere with each other is π (or K = 0, 1, 2, 3).
Assuming that the laser light source 10 oscillates two pulses by changing the angle of the scanning mirror 17 so as to deviate by 2Kπ + π), the intensity distribution Fr2 of the interference fringes due to the second pulse deviates by exactly 1/2 pitch. The mathematical result is a flat intensity distribution Fr3. However, in general, some tertiary light sources arranged in the X direction interfere with each other, so that the intensity distribution becomes complicated as shown in FIG. However, even if n third-order light sources (eg, Ac, Ad, Ae, or Ad, Ae, Af, etc.) arranged in the X direction interfere with each other, mathematical analysis shows that n third light sources Each secondary light source is 2π / n
When the beam of n pulses is irradiated in synchronism with the angle change of the scanning mirror 17 so that the phase difference is changed each time, that is, the interference fringes on the reticle R are moved by 1 / n pitch in the pitch direction, they are superposed. It is known that the intensity distribution can be made flat. Therefore, fly eye lens 5
When the number of element lenses in the X direction is n, for example, if n pulses are irradiated with the same intensity while the scanning mirror 17 vibrates in half cycles (corresponding to movement of one pitch of interference fringes), the exposure on the wafer W is performed. The uneven exposure due to the interference fringes generated in the area can be eliminated.

However, in this case, it is necessary to keep the angle change of the scanning mirror 17 and the timing of the oscillation trigger for each pulsed light extremely accurate. As another way of thinking,
It is also possible to perform exposure with a pulse number sufficiently larger than n pulses while the scanning mirror 17 vibrates in a half cycle. As described above, assuming that the number of element lenses of the fly-eye lens 5 in the X direction is 10, n = 10. Therefore, about 50 pulses (100 pulses for reciprocation) during the half-cycle vibration of the scanning mirror 17. ) To oscillate the degree. In this case, it is not necessary to maintain the angle change of the scanning mirror 17 and the oscillation trigger for each pulsed light so accurately, which is advantageous from the viewpoint of device implementation. In addition, the experiment shows that the minimum number of pulses N required during the half period of the scanning mirror for smoothing the interference fringes.
If min is obtained and the light quantity of each pulsed light is adjusted so that the total number of pulses required for exposure of a certain shot is m · Nmin (m = 1, 2, 3, ...) The control can be easily realized.

As described above, in the present embodiment, the scanning mirror 17 is oscillated only in one dimension according to the short-side direction (direction orthogonal to the long-side direction) of the cross section of the beam LB0. This is made by the fly-eye lens 5. This is because one-dimensional interference fringes are generated only by the arrangement of the tertiary light sources in the X direction (short direction of the beam LB0), and if they are arranged along the longitudinal direction (Y direction) of the cross section of the beam LB0. When the interference is caused by the third light sources, the scanning mirror 17 may be two-dimensionally swung in the same way. In this case, each of the tertiary light sources changes its position on the pupil ep by a minute amount at the same time as in the raster scanning. In addition, one scanning mirror 17
Instead of dimensional vibration, two scanning mirrors for the X direction and the Y direction may be provided to share the vibration direction of the beam.

Further, in the present embodiment, the longitudinal direction of the cross section of the beam LB0 emitted from the laser light source 10 and the arrangement direction (Y direction) of one of the element lenses of the fly-eye lenses 3 and 5 are made to coincide with each other. , This may be any relationship and is not a requirement. However, no matter what the relationship is, the oscillation direction of at least one of the beams due to the oscillation of the scanning mirror 17 is the same as the original beam L.
The direction intersects the longitudinal direction of the B0 cross section.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 11 shows only the illuminance distribution uniformizing means, and other configurations are the same as those in FIG. Further, the same members as those shown in FIG. 1 are designated by the same reference numerals. In the present embodiment, the scanning mirror 16 for oscillating the beam and the vibration source 1 thereof are also provided in front of the first fly-eye lens 3.
8 is different from that of the first embodiment.

Also in the present embodiment, the laser light source 10 is a stable cavity excimer laser (KrF) light source having a wavelength selection element therein, the oscillated beam LB0 has a rectangular cross section, and the spatial coherence in the longitudinal direction is. It is assumed that the double integrator is low enough not to cause interference fringes and the spatial coherence in the lateral direction is considerably high.

In the first embodiment, a large number of secondary light source images (spot lights) formed by the first fly-eye lens 3 on the surface SP2 in space do not interfere with each other, but depending on the conditions. May interfere. In this case,
As described above, the third-order light sources a1 (or b1, c1) composing the element lenses 5-1, 5-2, and 5-3 of the second fly-eye lens 5 at the same position naturally interfere with each other. Furthermore, the tertiary light sources a1, b1, and c1 formed in one element lens also interfere with each other.

As is clear from FIG. 11 (also in FIG. 3), the surface SP2 on which the secondary light source image is formed and the surface SP3 on which the tertiary light source image is formed are conjugate with each other. And the second
Since one element lens of the fly-eye lens 5 re-images all the secondary light source images formed on the exit side of the first fly-eye lens 3, a relatively large magnification is applied. As a typical example, assuming that the element lenses of the fly-eye lenses 3 and 5 have the same diameter dimension and the number in the arrangement direction is 10, the magnification is 10
Double.

Therefore, as in the first embodiment, the scanning mirror 1 necessary for smoothing the speckle pattern due to the interference of the tertiary light sources Ac, Ad, Ae and Af shown in FIG.
With only the minimum angle change range of 7, the influence of interference by the secondary light sources remains. Therefore, it is conceivable that the angle change range of the scanning mirror 17 is set to about 10 times or more as a typical example. However, shaking the scanning mirror 17 greatly increases the possibility that a part of the light beam incident on the fly-eye lens 5 is eclipsed, and is not very preferable. If a part of the light beam incident on the fly-eye lens 5 is eclipsed at the beginning and the end of the large deflection angle of the scanning mirror 17, it is left as it is on the wafer W.
This is an inconvenience because of an error with respect to an appropriate exposure amount to the light or a decrease in throughput.

Therefore, in the present embodiment, the scanning mirror 16 oscillates the beam incident on the first fly-eye lens 3 to change the phase difference between the secondary light sources between 2 mπ and generate a plurality of pulsed lights. I tried to irradiate. of course,
The swinging of the beam by the scanning mirror 17 is also performed at the same time as in the first embodiment. The appearance of the interference fringes formed on the reticle R (or the wafer W) by the interference of the secondary light sources is exactly the same as that described above with reference to FIG. 10, but between the first and second fly-eye lenses. So, for example, 10
Because of the double magnification, the pitch of the interference fringes on the reticle R is about 10 times larger than the pitch of the interference fringes created by the interference of the tertiary light sources a1. Therefore, for example, when only the secondary light sources of the adjacent element lenses of the first fly-eye lens 3 interfere with each other, as shown in FIG. 12, a sinusoidal intensity distribution Fr0 with a long pitch and a short pitch with a short pitch. Interference fringes in which the intensity distribution Fr4 is superimposed appear.

In the case of the interference fringes as shown in FIG. 12, the scanning mirror 16 may be moved to at least two angular positions so as to give a phase difference of π to two secondary light sources which interfere with each other. That is, when the scanning mirror 16 is at an angular position,
While oscillating the scanning mirror 17 for a half cycle (or about one cycle), light emission of several tens of pulses is performed, and then the scanning mirror 1
In a state in which 6 is angularly changed (giving a phase difference π) by a predetermined amount, the scanning mirror 17 may be similarly oscillated for a half cycle (or about 1 cycle) and light emission of several tens of pulses may be performed.

Of course, if the spatial coherence of the beam LB0 becomes high, three or more of the secondary light sources a, b, and c will interfere with each other, and accordingly, the rate of change in the angle of the scanning mirror 16 will change. It becomes fine. Therefore, after changing the angle of the scanning mirror 16 by a certain amount, the scanning mirror 17 is repeatedly shaken for a half cycle (or one cycle).

If, for example, light emission of about 50 pulses is performed within the half cycle of the scanning mirror 17,
The number of times the angle of the scanning mirror 16 is changed is at least about 10 times (the number of elements in the fly-eye lens 3 in the interference direction)
It may be necessary, and at least 50 × 10 = 500 pulses are required to expose one area (one shot) on the wafer. This means that in consideration of the proper exposure amount, 1
The amount of light per pulse is 1/5 to that of the first embodiment.
This means that the exposure is performed by narrowing down to about 1/10. A typical repetitive emission frequency of an excimer laser light source is 100 to
Since the frequency is about 200 Hz, the exposure time for one shot reaches 2.5 to 5 seconds, which may cause a significant decrease in throughput. Therefore, as described above, the scanning mirror 17
The angle change of the scanning mirror 16 and the timing of the oscillation trigger for each pulse are synchronized as accurately as possible to minimize the number of pulses emitted during the half cycle of the scanning mirror 17 and the angle change of the scanning mirror 16 is performed as accurately as possible. To In this way, the throughput is not significantly reduced as compared with the embodiment of FIG.

As described above, according to this embodiment, the speckle pattern can be satisfactorily smoothed even if the laser light source having a high spatial coherence, for example, the injection lock type laser shown in FIG. 7 is used. Of course, scanning mirror 1
If both 6 and 17 are made to vibrate two-dimensionally, the two-dimensional interference fringes or random speckles can be smoothly smoothed.

In this embodiment, the vibration sources 18, 1
9 and the trigger circuit of the laser light source 10 are simultaneously cycle-controlled by appropriate control means. Next, a third embodiment of the present invention will be described with reference to FIG. Fig. 13 shows a square pillar rod 3 made of quartz for the first stage optical integrator.
An example of the illuminance distribution uniforming means when 0 is used will be shown. The beam LB0 from the laser light source 10 is converted into a condensed beam LB 'by using an appropriate optical system. The focused beam LB 'enters the entrance end of the rod 30 at a position slightly diverging from the focusing point (spot) SP0. The beam LB ′ repeats multiple reflection inside the rod 30, and becomes the light diverging from the other end of the rod 30 and enters the lens 4. The light flux that has passed through the lens 4 is reflected by the scanning mirror 17, becomes a large number of secondary light sources on the surface SP2 in the space, is condensed again, and then diverges again and enters the lens 21, and is emitted from each secondary light source. The light beams become substantially parallel light fluxes (slightly different angles from each other) and enter the fly-eye lens 5 as the second optical integrator. In this embodiment, one converging point SP0 is generated by multiple reflection of the beam LB 'inside the rod 30.
Are apparently re-imaged on the surface SP2 so as to be present in large numbers.

Although the respective embodiments of the present invention have been described above, the optical integrator may be a combination in which the first stage is a bundle of thin optical fibers and the second stage is a fly-eye lens. Further, the element lens of the fly-eye lens may have a honeycomb shape (regular hexagonal shape) and an integrated quartz material may be processed. Further, the present invention can be directly applied not only to the reduction projection type exposure apparatus as shown in FIG. 1 but also to all apparatuses that must perform illumination with a uniform illuminance distribution.
Further, in each of the embodiments of the present invention, the scanning mirror is swung between the first-stage optical integrator and the second-stage optical integrator. May be vibrated in a cycle of.

[0050]

As described in detail above, according to the first and second aspects of the present invention, it is not necessary to precisely control the angle change of the optical member and the oscillation trigger of each pulse, so that the control can be performed. It has the effect of being simple. Also,
According to the first and second aspects of the invention, the number of beam spot images (third-order light sources) formed on the pupil of the projection optical system can be made extremely large by the two-stage optical integrator. Also, there is an effect that extremely large energy is not concentrated on a specific lens element inside the projection optical system and damage to the projection optical system is prevented. According to the third aspect of the invention, the optical integrator is provided in two stages to make the illuminance distribution on the illuminated object uniform, and the speckle pattern (interference fringe) generated by using the optical integrator is good. Since it can be smoothed to a uniform level, even if a coherent beam such as a laser beam is used, uniform illumination light without ghost, speckle, etc. can be obtained. (Optical CVD, etc.), alignment observation, etc. are achieved with extremely high accuracy.

According to the fourth aspect of the present invention, between the one optical integrator and the second optical integrator, the beam incident on the second optical integrator is oscillated at least in a direction intersecting the second direction. As a result, speckles do not occur and the pattern of the wafer can be accurately exposed on the substrate.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration when an illumination optical device according to a first embodiment of the present invention is applied to a projection type exposure apparatus.

FIG. 2 is a diagram showing a relationship between a fly-eye lens and a projection exposure system in a conventional apparatus.

FIG. 3 is a diagram illustrating the configuration of a double fly-eye lens that is the basis of the present invention.

FIG. 4 is a plan view showing an array of light source images (spot light) obtained by the configuration of FIG.

5 (a), (b), and (c) are intensity distributions of interference fringes generated by illumination light of one pulse on an illuminated object, and position shifts of interference fringes when smoothing with illumination light of multiple pulses. , And a diagram showing the intensity distribution after smoothing.

FIG. 6 is a diagram showing a typical structure of a laser light source.

FIG. 7 is a diagram showing a typical structure of a laser light source.

FIG. 8 is a diagram showing a typical structure of a laser light source.

FIG. 9: 3 that can be formed at the exit end of the second-stage fly-eye lens
The top view which shows the arrangement | sequence of a secondary light source (spot light).

FIG. 10 is a view for explaining how interference fringes are smoothed.

FIG. 11 is a diagram showing a configuration of an illumination optical device according to a second embodiment of the present invention.

FIG. 12 is a diagram showing an example of an intensity distribution of interference fringes generated on an illuminated object when a beam having strong coherence is incident on a double fly-eye lens.

FIG. 13 is a diagram showing a configuration of an illumination optical device according to a third embodiment of the present invention.

[Explanation of symbols for main parts]

1, 3, 5 ... Fly-eye lens, 2 ... Condenser lens, 10 ... Laser light source, 16, 17 ...
Scanning mirror, 30 ... Rod, R ... Reticle, P
L ... Projection lens, W ... Wafer, LB0 ... Oscillation beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/30 515D

Claims (4)

[Claims] 1. A light source device for illuminating a reticle on which a circuit pattern is formed with pulsed light, and a first optical for generating pulsed light from the light source device to generate a plurality of point light sources distributed two-dimensionally. An integrator, a second optical integrator that generates pulse light emitted from the first optical integrator to generate a plurality of two-dimensionally distributed point light sources, and a plurality of the plurality of optical integrators generated by the second optical integrator In an exposure apparatus that has a condensing optical system that irradiates the light from each of the point light sources as pulsed illumination light onto the reticle in a superimposed manner, and projects an image of the circuit pattern of the illuminated reticle onto a photosensitive substrate. The second optical integrator is composed of a plurality of optical elements arranged two-dimensionally, and a specific optical element among the plurality of optical elements is arranged. The number of optical elements arranged in the direction is n (n is an integer), and the minimum pulse number of the pulsed light from the light source device required to expose the image of the circuit pattern on the photosensitive substrate is N which is n or more. Then, an optical member that swings the plurality of light beams incident on the second optical integrator for a half cycle or more during the irradiation of the pulse number N is provided between the first optical integrator and the second optical integrator. An exposure apparatus characterized by being provided between them. 2. The first optical integrator is 2
It consists of multiple optical elements arranged in a dimension,
2. The exposure apparatus according to claim 1, wherein the plurality of optical elements of the first optical integrator and the plurality of optical elements of the second optical integrator are arranged in different array directions. 3. An illumination optical apparatus comprising: a light source for generating a coherent beam; and an illuminance distribution uniformizing means for irradiating the illuminated object with light having a uniform illumination distribution. The light source generates a beam in which a spatial coherence in a predetermined first direction within a cross section of the beam is higher than a spatial coherence in a second direction substantially orthogonal to the first direction,
The illuminance distribution uniformizing means includes a first optical integrator that receives a beam from the light source and a second optical integrator that receives a beam emitted from the first optical integrator, and the first optical integrator. A first rocking means for rocking a beam incident on the second optical integrator at least in a direction intersecting the second direction, between the integrator and the second optical integrator. Illumination optical device. 4. An exposure method for illuminating a mask with light beams from first and second optical integrators, which generate a plurality of point light sources, and exposing a pattern image of the mask onto a substrate. Irradiating the first optical integrator with a coherent beam having a spatial coherence in a first direction substantially higher than a spatial coherence in a second direction substantially orthogonal to the first direction; and the first optical integrator. A step of oscillating a beam incident on the second optical integrator with at least the second optical integrator in a direction intersecting at least the second direction.