JPH05259033A - Projection aligner - Google Patents

Abstract

PURPOSE:To manufacture the title projection aligner capable of forming a pattern in high resolving power and focal length by a method wherein the light quantities of respective pulse beams passing through multiple fly-eye lenses are adjusted so that the multiplied light quantities of pulse beams projected from said fly-eye lenses may be almost equalized. CONSTITUTION:A laser controller 32 controls the high tension discharge voltage of a laser beam source 1 corresponding to the energy quantity (light quantity) of the next time irradiating pulse beams. Next, respective beams LBa, LBb emitted from a beam divider 6 are adjusted so that they may be entered into the second fly-eye lenses 7a, 7b through the intermediary of the contrast reducing means 11a, 11b of an interference pattern and then a part of light flux projected from the first fly-eyes lenses 8a, 8b may be led to light quantity sensors 15a, 15b. Finally, a main controller 31 controls a beam position adjusting part 5 per unit pulse so as to equalize the multiplied light quantity values successively computed by light quantity multipiers 30a, 30b for adjusting respective light quantities of the beams LBa, LBb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for manufacturing a semiconductor integrated circuit or a liquid crystal display element, and more particularly, to controlling the exposure amount and uniform illuminance of a projection exposure apparatus equipped with a pulse light source such as an excimer laser as an exposure light source. It is related to the conversion control.

[0002]

2. Description of the Related Art For forming a circuit pattern of a semiconductor element or the like,
Generally, a process called photolithography is required. In this step, a method of transferring a reticle (mask) pattern onto a substrate such as a semiconductor wafer is usually adopted.
A photosensitive photoresist is coated on the substrate,
The circuit pattern is transferred to the photoresist according to the irradiation light image, that is, the pattern shape of the transparent portion of the reticle pattern. Generally, in a projection exposure apparatus (eg stepper), an image of a circuit pattern to be transferred drawn on a reticle is projected and imaged on a substrate (wafer) via a projection optical system.

An optical integrator such as a fly-eye lens is used in the illumination optical system for illuminating the reticle, and the intensity distribution of the illumination light with which the reticle is irradiated is made substantially uniform. In order to perform this homogenization optimally, when using a fly-eye lens, the reticle side focal plane (exit surface side) and the reticle surface (pattern surface) are connected by a Fourier transform relationship. The focal plane and the light source side focal plane (incident surface side) are also connected by a Fourier transform relationship. Therefore, the pattern surface of the reticle and the light source side focal plane of the fly eye lens (more precisely, the light source side focal plane of each lens of the fly eye lens) are connected in an image forming relationship (conjugate relationship). Therefore, on the reticle, the illumination light from each optical element (secondary light source) of the fly-eye lens is added (superposed) by a condenser lens or the like to be averaged, and the illuminance uniformity on the reticle is improved. It is possible.

The above is the principle whether a high-pressure mercury lamp, which is generally used as a light source for exposure at present, or a pulsed laser light source such as a KrF or ArF excimer laser, which has recently received attention. Does not change. However, in a projection exposure apparatus using a pulsed laser as a light source, the laser light has a variation of about ± 10% for each pulse, and the rule on the reticle (or wafer) surface depends on the coherence of the laser light. Interference pattern, and an irregular interference pattern (speckle) in which multiple light beams with different phases overlap due to scratches, dust, surface defects, etc. in the illumination optical system, and these cause illuminance on the reticle surface. Unevenness can occur. Then, for example, JP-A-63-316430
It has been proposed to achieve smoothing of the interference pattern (uniformization of illuminance) by a plurality of pulses and desired exposure amount control accuracy by using the method disclosed in Japanese Patent Laid-Open No. 1-257327 and Japanese Patent Laid-Open No. 1-257327.

By the way, these days, a so-called phase shift reticle, in which the phase of the transmitted light from a specific portion of the transmitted portion of the circuit pattern of the reticle is shifted by π (rad) from the phase of the transmitted light from other transmitted portions, is called a phase shift reticle. Is proposed, for example, in Japanese Examined Patent Publication No. 62-50811. By using this phase shift reticle, it becomes possible to transfer a finer pattern than the conventional one. However, the phase shift reticle has many problems because the manufacturing process is complicated and the cost is high, and the inspection and correction methods have not been established yet.

Therefore, as a projection exposure technique that does not use a phase shift reticle, attempts have been made to improve the transfer resolution by improving the illumination method of the reticle. As one of the illumination methods, a ring-shaped aperture stop (spatial filter) is arranged in the pupil plane (Fourier transform plane) of the illumination optical system, that is, near the exit-side focal plane of the fly-eye lens, and the optical axis of the illumination optical system is By partially cutting the illumination light flux distributed around it and defining the light quantity distribution of the illumination light flux in an annular shape,
A method (annular illumination method) in which an illumination light flux reaching a reticle pattern has a certain inclination has been proposed. Further, in order to achieve projection exposure with high resolution and large depth of focus, a diaphragm having two apertures that are substantially symmetrical with respect to the optical axis of the illumination optical system is arranged near the exit-side focal plane of the fly-eye lens, and the reticle pattern There is also proposed a method (tilt illumination method) of irradiating an illumination light beam with a predetermined angle inclined from a specific direction corresponding to the periodicity.

[0007]

However, in the case of adopting the inclined illumination method as described above, especially when the light source is a pulse laser such as an excimer laser, the energy amount (light amount) and the light intensity distribution vary from pulse to pulse. Beam position (center of gravity position) in the illumination optical path due to mechanical vibration, etc.
Can be slightly shifted in the cross-sectional direction, so that the amount of light emitted from each of the two openings (secondary light sources) for each pulse, and further the integrated value thereof, are different from each other. For this reason, the light amounts of the respective illumination light fluxes gathering at one point on the reticle surface (or wafer surface) deviate, that is, a plurality of reticle patterns are tilted substantially symmetrically with respect to the optical axis of the illumination optical system or the projection optical system. Each of the light quantities (integrated values) of the illumination light flux largely varies, which may cause a problem that a good pattern cannot be formed on the wafer.

The present invention has been made in view of the above problems, and it is possible to obtain a high resolution and a large depth of focus even if a normal reticle is used, and it is excellent in illuminance uniformity and is represented by an excimer laser. An object of the present invention is to provide a projection exposure apparatus capable of forming a good pattern even when a pulse laser is used as a light source.

[0009]

In order to solve such a problem, in the present invention, an optical Fourier transform plane for a mask pattern in an illumination optical system, or in a plane in the vicinity thereof, from the optical axis of the illumination optical system. A plurality of partial areas defined at each of at least two eccentric discrete positions (that is, each exit surface of the plurality of fly-eye lenses (secondary light source image))
The light intensity of the pulsed light emitted from each of the above) is individually measured, and the integrated value of the measured light intensity of the pulsed light is approximately equal in each of the plurality of partial regions (fly eye lens), The light quantity of each pulsed light passing through each of the plurality of partial regions is adjusted for each unit pulse number. Furthermore, when the pulsed light source generates coherent pulsed light, the contrast of interference fringes is also reduced by slightly changing the angle of incidence on the fly-eye lens for each pulse. Also, the integrated value of the amount of passing light for each partial area is
The light amount of the pulsed light emitted from the light source is adjusted in parallel with the above-mentioned light amount adjustment so that the target integrated light amount value corresponding to a predetermined exposure amount (appropriate exposure amount at the time of pattern exposure) is substantially matched. ..

[0010]

In the present invention, when adopting the inclined illumination method,
The integrated value of the light amount of the pulsed light emitted from each of at least two partial regions (for example, the emission surface of the fly-eye lens) defined in the pupil plane (Fourier transform plane) of the illumination optical system or in the vicinity thereof is calculated. It is assumed that they are almost equal to each other. Therefore, the integrated light amount values of the plurality of illumination light beams that reach the mask pattern while being inclined substantially symmetrically with respect to the optical axis of the illumination optical system or the projection optical system are substantially equal to each other, so that a good pattern can be formed on the photosensitive substrate. It will be possible to do. Furthermore, by slightly changing the angle of incidence on the fly-eye lens for each pulse, the contrast of the interference fringes generated by the irradiation of coherent pulsed light is reduced and the illuminance uniformity on the mask (or photosensitive substrate) surface is also improved. It becomes possible. Also, since the integrated value of the amount of light passing through each of the preceding partial areas substantially matches the target integrated light amount value, the total value (exposure amount) of each integrated light amount given to the mask (or the photosensitive substrate) is an appropriate value or a predetermined allowable value. Within the range, it is possible to achieve even a desired exposure amount control accuracy.

[0011]

FIG. 1 is a diagram showing a schematic structure of a projection exposure apparatus (stepper) according to a first embodiment of the present invention. In this embodiment, two polyhedral prisms (see FIG. 3) is used. In addition, here, as the light source for exposure, coherent pulsed light (Ar
A pulsed laser light source that emits F, KrF excimer laser, etc.) is used. Other than coherent pulsed light, for example, incoherent pulsed light may be used.

In FIG. 1, a laser control device 32 controls a high-voltage discharge voltage (corresponding to an applied voltage or a charging voltage) of the laser light source 1 corresponding to the energy amount (light amount) of pulsed light to be irradiated next. Therefore, here, the light amount is adjusted for each pulse. Further, after a predetermined charging time required by the light source 1 has elapsed, an external trigger pulse is sent to the light source 1 to control its oscillation (pulse number, oscillation interval, etc.).
Here, the controller 32 is a main control system 31 for the exposure apparatus main body.
The above-mentioned control is performed based on a command from the above. However, as disclosed in, for example, Japanese Patent Laid-Open No. 294013/1990, the main control system 31 and the control device 32 cooperatively control the exposure apparatus main body and the laser light source 1. You can also do

The laser beam LB emitted from the pulsed laser light source 1 is incident on the dimming unit 2, where the amount of light is continuous between 0% (complete transmission) and 100% (complete light shielding). Or it can be gradually attenuated. Regarding the configuration and control method of the dimming unit 2, for example, Japanese Patent Laid-Open No. 3-17
Since it is disclosed in Japanese Patent No. 9357, its description is omitted here. Further, the laser beam LB is incident on a beam expander (beam cross section shape conversion optical system) 3 in which, for example, two sets (concave and convex) of cylindrical lenses are combined, and the beam expander 3 shapes the beam cross section into an appropriate shape and size. That is, the width of the laser beam LB in the lateral direction is enlarged to convert its cross-sectional shape into a substantially square shape.

The laser beam (parallel light beam) LB emitted from the beam expander 3 is split by a beam splitter 4, and most of it is reflected here and enters a beam position adjusting section (light quantity adjusting means of the present invention) 5. On the other hand, the laser beam LB transmitted through the beam splitter 4 has a light quantity monitor (for example, a pyroelectric power meter, a PIN photodiode, etc.) 3
3, the light amount monitor 33 outputs a signal according to the light amount (light intensity) of each pulse of the laser beam LB to the control device 32. The control device 32 updates the information on the relationship between the applied voltage to the laser light source 1 and the light quantity of the pulsed light oscillated under the applied voltage for each unit pulse, and at the same time, is determined by the main control system 31. The applied voltage corresponding to the light quantity of the pulsed light to be emitted to the is calculated from the updated relationship, and the next pulse is oscillated from the light source 1 under this applied voltage.

FIG. 2 shows an example of a concrete structure of the beam position adjusting section 5. In this embodiment, two parallel flat glass plates 5 are used.
It is composed of a and 5b. In FIG. 2, the parallel plate glasses 5a and 5b are rotatable around two axes (directions parallel to the direction perpendicular to the paper surface) orthogonal to each other and perpendicular to the optical axis AX of the illumination optical system. .. Therefore, the optical axes AX in the plane perpendicular to the optical axis AX of the illumination optical system can be adjusted by adjusting the respective inclination angles of the parallel plate glasses 5a and 5b.
It is possible to arbitrarily change and adjust the position of the laser beam LB with respect to (the position of the center of gravity of the light amount distribution).

The laser beam (parallel light beam) LB that has passed through the beam position adjusting unit 5 is incident on the light splitter 6, where it is split into a plurality of (two in FIG. 1) beams LBa and LBb and emitted. To be done. FIG. 3 shows an example of a specific configuration of the light splitter 6 suitable for the present embodiment. Here, a first polyhedral prism 6a having a V-shaped concave portion and a second polyhedron having a V-shaped convex portion are shown. It is configured by combining with the prism 6b. The beam LB is split into two beams LBa and LBb by the refraction action of these two prisms 6a and 6b.

Further, in this embodiment, the polyhedral prism 6a,
The distance of 6b is adjustable. by this,
Beams LBa, L in a plane perpendicular to the optical axis AX of the illumination optical system
It is possible to change each position of Bb in the direction perpendicular to the optical axis AX (vertical direction in the plane of the drawing). However, in the present embodiment, the dividing position of the beam LB by the light splitter 6 (in other words, the apexes of the concave portions and the convex portions of the V-shaped prisms 6a and 6b) substantially coincides with the optical axis AX of the illumination optical system. I shall. This means that the second fly-eye lens 7a,
When moving 7b, the beam LB follows the movement.
This is effective in accurately causing a and LBb to enter their respective incident surfaces.

Further, in FIG. 3, for example, a parallel plate glass 34 is used as an optical path difference generating member in the optical path of either one of the two beams (beam LBa in the figure) divided by the beam splitters 6a and 6b. It is arranged. Therefore, the beam LBa is delayed by a predetermined amount from the beam LBb, that is, a difference in optical path length occurs between the two beams. The thickness of the parallel plate glass 34 is determined so that the optical path difference between the two beams is longer than the coherent length of the beam LB. As a result, the contrast of the interference pattern due to the beams LBa and LBb is reduced.

In this embodiment, two sets of polyhedral prisms 6a and 6b are used as the light splitter 6, but, for example, an optical fiber, a combination of a V-shaped mirror and two plane mirrors, or a concave type. A combination of a polyhedral prism and a convex lens (or a lens group having a positive power), a diffraction grating (particularly a phase type diffraction grating), or a convex lens array may be used. Further, in the present embodiment, the number of light beams split by the light splitter 6 is two, but the number of splits may be three or more, and the point is the periodicity of the reticle pattern (the number of first and second fly-eye lenses). The number of divisions according to For example, in the case of a two-dimensional periodic pattern, the number of divisions may be four, and as the light splitter 6, a pyramid type (quadratic pyramid type) prism or an optical fiber having four emitting portions may be used.

By the way, in this embodiment, a polyhedral prism (FIG. 3) is used as the light splitter 6, and the light splitter 6 is used.
The beam position adjusting unit 5 is provided closer to the light source. Since the laser beam LB generally has a light intensity distribution as shown in FIG. 4, when the position of the beam LB incident on the light splitter 6 is shifted by the beam position adjusting unit 5, the beam LB by the light splitter 6 is changed. The split ratio changes and the beam LBa,
Each light quantity of LBb will also change. That is, the beam position adjusting unit 5 is capable of adjusting the light amounts of the beams LBa and LBb, and corresponds to the second light amount adjusting means of the present invention. The beam position adjusting unit 5 may be formed of a plate other than the parallel plate glass (FIG. 2), and the light splitter 6 may be movable in a plane perpendicular to the optical axis AX of the illumination optical system. Alternatively, a neutral density filter arranged in each of the optical paths of the beams LBa and LBb between the light splitter 6 and the reticle 19 (a plurality of neutral density filters having different transmissivities are preferably exchangeable). May be used as the second light amount adjusting means.

Returning to the explanation of FIG. 1, each of the beams LBa and LBb from the light splitter 6 is incident on the second fly-eye lenses 7a and 7b via the interference pattern contrast reduction means 11a and 11b. The light fluxes emitted from the second fly-eye lenses 7a and 7b are field lenses 9a and 9b, contrast pattern reduction means 12a and 12b, and field lenses 10a and 10b.
It is incident on the first fly-eye lenses 8a and 8b via b. At this time, only the light flux from the second fly-eye lens 7a enters the first fly-eye lens 8a, and only the light flux from the second fly-eye lens group 7b enters the first fly-eye lens group 8b.

Further, the respective light fluxes emitted from the first fly-eye lenses 8a and 8b are aperture diaphragms (σ diaphragms) 13a and 13b arranged in the vicinity of their emission surfaces, and the beam splitter 1.
Condenser lenses 16, 18 through 4a, 14b,
And the pattern RP formed on the lower surface of the reticle 19 by being guided to the bending mirror 17 is illuminated with a substantially uniform illuminance. The light transmitted through the reticle pattern RP and diffracted is focused by the projection optical system 20 to form an image of the pattern RP on the wafer 22. Here, the diaphragms 13a and 13b are
The numerical aperture of the light beam emitted from the first fly-eye lens, that is, the coherence factor (σ value) is 0.1 to 0.
The opening diameter is determined so as to be about 3.
Reference numeral 21 in the figure denotes an optical Fourier transform plane (hereinafter referred to as a pupil plane of the projection optical system) for the pattern RP in the projection optical system 20, and this pupil plane 21 has a variable aperture stop (NA).
A diaphragm may be provided. In the pupil plane 21, the first fly-eye lens 8a is provided at each of two discrete positions decentered with respect to the optical axis AX (substantially equidistant from the optical axis AX).
A light source image (third light source image) by 8b is formed.

Although there is an optical Fourier transform surface (hereinafter referred to as a pupil plane of the illumination optical system) for the reticle pattern RP in the illumination optical system, each of the above-mentioned first fly-eye lenses 8a and 8b. Is arranged such that its reticle-side focal plane (emission-side focal plane) substantially coincides with the pupil plane of the illumination optical system. In addition, the second fly-eye lenses 7a and 7b
Each exit surface of the field lens (9a, 10a),
(9b, 10b) allows the first fly-eye lens 8a,
It is a Fourier transform surface for the incident surface of 8b. However, it is not necessary to strictly maintain the relationship of Fourier transform, and the point is that the light flux emitted from each lens element forming the second fly-eye lens is superimposed on the incident surface of the first fly-eye lens. It is good if the relationship is maintained.

By the way, in FIG. 1, a part of the luminous flux emitted from each of the first fly-eye lenses 8a and 8b is guided to the light quantity sensors (measuring means of the present invention) 15a and 15b through the beam splitters 14a and 14b. Is configured as follows. The light amount sensors 15a and 15b are photomultipliers, silicon photodiodes, PIN photodiodes, and the like, and are selected (determined) according to the responsiveness to pulsed light, sensitivity, and the like. The light amount sensors 15a and 15b use the light amount (light intensity) of each pulse of the laser beams LBa and LBb.
Is output to the light amount integrators 30a and 30b, where the integrated value of the passing light amount (total value of the light amounts of all pulses) is calculated for each fly-eye lens. The outputs of the light amount sensors 15a and 15b are preliminarily calibrated with the light intensity (illuminance) on the surface of the wafer 22.

The main control system 31 includes light quantity accumulators 30a, 30.
In order that the integrated light quantity values calculated sequentially in b become equal,
The beam position adjusting unit 5 is controlled for each unit pulse (every pulse or every plural pulses) to control the light amounts of the beams LBa and LBb (that is, the beam L by the optical splitter 6 in this embodiment).
B division ratio). As a result, when the pattern exposure by irradiation of a plurality of pulsed lights is completed, the beam LB is
The integrated light amounts of a and LBb substantially match, or the difference therebetween is suppressed within a predetermined allowable range.

In FIG. 1, means (11a, 11b) and (12a, 11a, 11b) for reducing the contrast of interference fringes are shown.
12b) is provided. As an example of a specific configuration of this type of reducing means, for example, Japanese Patent Application Laid-Open No. 1-257732.
As disclosed in Japanese Patent Laid-Open No. 7-27, there is one that changes the incident angle of a light beam incident on a fly-eye lens for each pulse by a vibrating mirror (galvano mirror, polygon mirror, etc.). However, since the vibrating mirror is used in the above method, the illumination optical path must be bent, and a large space is required in the illumination optical system. Therefore, in this embodiment, as a reducing means, as shown in FIG. 5, the wedge prism 27 is configured to be finely rotatable about a rotation axis in a direction perpendicular to the optical axis AX (a direction perpendicular to the paper surface in the figure). Is desirable. Further, although not shown in FIG. 5, on the reticle side of the rotatable wedge prism 27 in FIG.
If a wedge-shaped prism having the same shape as the prism 27 is arranged (fixed) in the opposite direction, each of the beams LBa and LBb incident on the first or second fly-eye lens does not tilt with respect to the optical axis AX, and It only needs to shift relatively in the plane perpendicular to the optical axis AX while keeping parallel to AX.

In this embodiment, the interference fringe contrast reducing means (11a, 11b), (12a, 12b) are arranged for each of the first and second fly-eye lenses, but either one of them is arranged. Only the reducing means may be arranged only in this case. However, it is more effective to improve the illuminance uniformity that the incident angle of the light flux incident on the first fly-eye lenses 8a and 8b is changed.
It is desirable to provide 2b). Further, the folding mirror 4 may be used as the reduction means, and the contrast of the interference fringes is similarly changed by vibrating the mirror 4 to change the incident angle of the light flux incident on the second fly-eye lenses 7a and 7b. It can be reduced.

Here, in the apparatus according to this embodiment (FIG. 1), the laser beam LB is made incident on the optical splitter 6 via the beam position adjusting unit 5, but the beam position adjusting unit 5 and The arrangement with the divider 6 may be reversed. That is, the beam position adjusting unit 5, that is, the parallel plate glass 5 is provided in the optical path of each of the plurality of light beams split by the light splitter 6.
It is also possible to arrange a and 5b and shift the incident position of the light flux with respect to the second fly-eye lens so as to change the incident efficiency, and it is possible to adjust the respective light amounts of the beams LBa and LBb in the same manner as described above. is there.

By the way, in the present embodiment, when adopting the tilted illumination method, each position of the first fly-eye lens (a surface perpendicular to the optical axis is determined according to the fineness (pitch) of the reticle pattern to be exposed and the cycle direction). Position within) determined (changed)
To do. At this time, each position of the first fly-eye lens has an optimum resolution and depth-of-focus improvement effect with respect to the fineness (pitch) of the pattern to be transferred by each illumination light flux from the first fly-eye lens group. As described above, the position (incident angle) of incidence on the reticle pattern may be set (details are disclosed in Japanese Patent Application No. 3-2331531 previously filed by the applicant of the present application). Therefore, for each reticle, the first fly-eye lens 8a, 8b, and further the first fly-eye lens 8a, 8b, and Are field lenses (9a, 10a), (9b, 10b), second fly-eye lenses 7a, 7b, and reduction means (11a, 1).
2a) and (11b, 12b) are preferably configured so as to be able to follow (interlock) with each other, and these may be integrally fixed to the holding member. The driving is performed based on an operation command from the main control system 31, and the setting conditions such as the position at this time are input / output device (keyboard, etc.) 35.
Enter more. Alternatively, the barcode pattern on the reticle may be read by a barcode reader and the setting may be performed based on the information.

Next, the operation of the apparatus according to this embodiment will be described. Normally, the energy amount (light amount) of the pulsed light emitted from the pulsed light source varies from pulse to pulse with reference to an average value, and the variation is about 15% (3σ).
On the other hand, the target control accuracy required for the exposure amount control is as high as ± 1%. Therefore, it is necessary to use a plurality of pulsed light for one shot of exposure, and the exposure must be performed with the minimum exposure pulse number Nmin or more corresponding to the variation of energy amount for each pulse and the exposure control logic. Therefore, when the sensitivity of the resist layer formed on the wafer 22 is high to some extent, the energy amount of the pulsed light from the pulsed light source 1 is attenuated by the light attenuating section 2 to
The number of pulses required for shot exposure must be Nmin or more.

Here, FIG. 6 shows an example of a specific configuration of the dimming unit 2. In FIG. 6, mesh-shaped neutral density (ND) filters 2a to 2f having six kinds of different transmittances are provided on the turret plate, and the transmittances of the respective filters are determined as shown in FIG. .. In FIG. 7, the rotation amount π / 3 corresponds to the ND filter 2b, and the rotation amount 2π corresponds to the ND filter 2a. The ND filter may have a shape other than the mesh shape, and may be, for example, a transparent optical member coated with dielectric films having different reflectances or an energy absorbing ND filter.

Next, a specific exposure sequence will be described with reference to FIG. In FIG. 8, first, the operator responds to the sensitivity of the resist layer by the input / output device 35 or by reading the exposure condition corresponding to the identification code of the wafer (or the loader cassette) from the memory.
The target (optimal) exposure amount S of the shot is input to the apparatus main body (main control system 31) (step 100). Next, the main control system 31 oscillates the pulsed light from the pulsed light source 1 for one pulse or several pulses prior to the exposure operation, and the energy amount (average value) P _AV (mJ) per pulse on the wafer 22 surface.
/ cm ² · pulse) is measured (step 101). The average energy amount P _AV is calibrated with the energy amount (light amount) on the wafer surface in advance, and the light amount sensors 15 a, 15
It is obtained as a total value of values obtained by multiplying each output value of b by the calibration values αa and αb. At this time, it is assumed that an appropriate ND filter, for example, 2e, is set in the optical path in the dimming unit 2. Further, the output values of the light amount sensors 15a and 15b are compared, and if the difference is significantly different (exceeds a predetermined allowable range), the beam position adjusting unit 5 is set so that the difference becomes zero. Controlled beam LBa, LBb
It is desirable to adjust the amount of energy (division ratio of the beam LB by the light splitter 6) of the above.

In the next step 102, the main control system 3
1 is the number of pulses N (N = S / P) required for one-shot exposure
After calculating _AV ), it is determined whether or not the relationship of N ≧ Nmin is satisfied with respect to the minimum exposure pulse number Nmin for achieving the desired exposure amount control accuracy (step 10).
3). Here, if N <Nmin, step 1
04, the main control system 31 determines the average pulse energy amount P
_{In order} to reduce _AV and increase the number of pulses N, the above relationship (N
An optimum ND filter satisfying ≧ Nmin) is selected, and the ND filter is replaced in the light reduction unit 2. Then, steps 101 to 103 are executed again, and it is confirmed whether the exposure pulse N satisfies N ≧ Nmin.

When it is determined in step 103 that the relation N ≧ Nmin is satisfied, a predetermined shot area on the wafer 22 is moved to the exposure position, and then exposure is started according to a predetermined exposure control logic. To be done. In step 105, the main control system 31 oscillates one pulse from the pulse light source 1, and then determines in step 106 according to the exposure control logic whether or not the exposure for one shot area is completed. Since only one pulse is oscillated here, the routine proceeds to step 107.

At step 107, the main control system 31
From the output values of the light quantity integrators 30a and 30b, the beam LBa,
The (integrated) light amount ratio of LBb is checked, and the division ratio of the beam LB, that is, the driving amount of the beam position adjusting unit 5, is calculated so that the integrated values of the light amounts of the beams LBa and LBb are substantially equal by the irradiation of the next pulse. Thereafter, the beam position adjusting unit 5 is controlled according to the calculated driving amount, and the beam LB is adjusted.
The light quantity ratio of a and LBb is changed (step 108). After completion of step 108, the process returns to step 105 again, and the pulse light source 1 oscillates only one pulse. At this time, the main control system 31 (laser control device 32) is operated by the beam position adjusting unit 5
A light emission trigger pulse is given to the pulsed light source 1 in synchronization with the driving of. Hereinafter, steps 105 to 108 are repeatedly executed until the exposure for one shot area is completed, that is, the pulse oscillation for the exposure pulse number N is completed. As a result, when the exposure is completed, the integrated values of the light amounts of the beams LBa and LBb emitted from the first fly-eye lenses 8a and 8b become substantially the same.

When it is determined in step 106 that the exposure for one shot is completed, the main control system 31 causes the wafer 22 to be exposed.
It is determined whether or not there is a shot area to be exposed next (step 109), and if exposure of the next shot is to be continuously executed, the process proceeds to step 110 and the wafer 22 is moved. Then, in the same manner as the above operation, step 105
By repeating the steps up to 108, the exposure for the next shot is completed. Hereinafter, steps 105 to 110 are repeatedly executed until the exposure for all the shot areas on the wafer 22 is completed, and the exposure operation for one wafer is completed when it is determined in step 109 that the exposure is completed. ..

In the above embodiments, the sequence for adjusting the position of the beam position adjusting section 5 (adjusting the light amount of the beams LBa and LBb) for each pulse has been described as an example. this is,
The light amount (light intensity) and the light intensity distribution are different for each pulse, and the beam L to the light splitter 6 is caused by mechanical vibration or the like.
This is because the incident position of B may slightly fluctuate in the cross-sectional direction, so that the light amounts of the two beams LBa and LBb split by the light splitter 6 do not always match. Further, in steps 107 and 108, even if the respective integrated light amounts of the beams LBa and LBb up to a predetermined pulse number are substantially equal or the respective integrated light amounts are different, the beam position adjusting section 5
If it is determined that it is not necessary to drive, the beam position adjusting unit 5 need not be controlled prior to the irradiation of the next pulse. Further, it is not necessary to perform the adjustment operation for each pulse, and the operation is performed for every plurality of pulses depending on the degree of variation in the pulse energy amount, the control accuracy of the light amount ratio of the beams LBa and LBb by the beam position adjusting unit 5, and the like. May be performed.

Further, in order to further improve the exposure amount control accuracy, a method of finely adjusting the average pulse energy amount P _AV emitted from the pulse light source 1 (that is, the dimming unit 2) for each pulse (Japanese Patent Laid-Open No. 3-3003). (Disclosed in Japanese Patent No. 179357) is also proposed. When this kind of exposure amount control logic is adopted, the light amount ratio of the beams LBa and LBb, that is, the drive amount of the beam position adjusting unit 5 is taken into consideration by taking into consideration the average pulse energy amount (correction value) P _AV of the next pulse. It is desirable to decide. At this time, the final beams LBa, LB
To make the integrated light amounts of b substantially equal, the energy amount of the pulsed light emitted from the pulsed light source 1 (that is, incident on the light splitter 6) and the first fly-eye lens 8a are generated for each pulse or a plurality of pulses. At least one of the respective energy amounts of the pulsed light emitted from each of 8b will be adjusted by controlling the applied voltage applied to the pulsed light source 1 and the driving amount of the beam position adjusting unit 5.

Further, in the above embodiment, nothing is mentioned about the uniformity of illuminance, but when coherent pulsed light is used, it is also important to reduce the contrast of the interference fringes. However, even in the case of performing the above reduction, it is sufficient to determine the exposure pulse number N in consideration of the minimum pulse number Nmin and the minimum pulse number Nsp required for the reduction. The reduction means (11a, 11b), (12a, 12)
It suffices to drive b) to change the incident angle of the light beam incident on the fly-eye lens.

Further, in the above embodiment, an example in which the laser beam LB is split into two beams by the light splitter 6 has been described, but when the reticle pattern is a two-dimensional periodic pattern, for example, the illumination optical system The number of secondary (or tertiary) light source images (emission surface of the fly-eye lens) to be formed on the pupil plane is four. In such a case, four sets of synthetic fly-eye lens groups (first and second fly-eye lenses,
And a field lens), and four sets of light quantity sensors (and light quantity integrators) corresponding to each, and a pyramid prism or the like may be used as the light splitter. Further, in adjusting the light amount of the four beams, each output value from the four light amount sensors (light amount integrators) is Pa to Pd, and each calibration for performing calibration with the actual energy amount on the wafer surface. The value is αa ~
Let αd be αa × Pa + αb × Pb = αc × Pc + αd × Pd αa × Pa + αc × Pc = αb × Pb + αd × Pd αa × Pa + αd × Pd = αb × Pb + αc × Pc. Alternatively, the beam position adjusting unit 5 may be controlled for each plurality of pulses. As a result, when the exposure for one shot is completed, the integrated light amounts of the respective beams can be made substantially equal to each other within a predetermined allowable range.

However, in the case of adjusting the respective light amounts of the beams divided into four by using the two sets of parallel plate glasses 5a and 5b and the pyramid prism shown in FIG. 2, the respective light amounts of the four beams are individually adjusted. It is difficult to adjust accurately. Therefore,
When it is necessary to accurately adjust the light amount, for example, a pyramid prism is not used as the light splitter 6, but two sets of V-shaped prisms (6a, 6b) shown in FIG. It is desirable to drive the prism to adjust the light amount. At this time, two sets of V-type prisms are arranged in series substantially along the optical axis AX of the illumination optical system so that the dividing directions of the beam LB (directions perpendicular to the paper surface in FIG. 3) are orthogonal to each other.

Next, a second embodiment of the present invention will be described with reference to FIG. As described above, in the first embodiment, 1
The one pulsed light is split into two light beams by the light splitter 6 and is made incident on each of the second fly-eye lenses 7a and 7b. In the present embodiment, the pulsed light from the pulsed light source 1 is supplied to the second fly-eye lens 7 in pulse units.
The only difference is that the light is distributed and incident on each of a and 7b. Therefore, the structural difference from the device according to the first embodiment (FIG. 1) is that the light beam deflecting members (28, 29a, 29b) as shown in FIG. Therefore, only this difference will be described here.

In FIG. 9, the second fly-eye lens 7
The movable mirror 28 for distributing the pulsed light to each of a and 7b is configured to be rotatable about the optical axis AX of the illumination optical system as a rotation axis, and the distributed pulsed light of the fixed mirrors 29a and 29b is here. It is guided to the second fly-eye lenses 7a and 7b via each of them. When four sets of second fly-eye lenses are provided, it is only necessary to add two fixed mirrors corresponding thereto.

In the present embodiment, the main control system 31 outputs a light emission trigger signal to the pulse light source 1 in synchronization with the rotation of the movable mirror 29. Further, the main control system 31
Alternatively, the beam position adjusting unit 5 is controlled for every plural pulses,
The incidence efficiency of each pulsed light on each of the second fly-eye lenses 7a and 7b is changed. Thereby, also in the present embodiment, it is possible to make the integrated values of the light amounts of the pulsed lights emitted from the first fly-eye lenses 8a and 8b substantially coincide with each other within a predetermined allowable range. In this embodiment, the same exposure amount control logic as in the first embodiment can be used. The beam LB may be distributed to each of the second fly-eye lenses 7a and 7b by the movable mirror 28 by driving the movable mirror 28 for each pulse, or may be driven for each plurality of pulses. You may also do it. Further, the light beam deflecting member is not limited to the configuration shown in FIG. 9 and may have any configuration.

In the present embodiment, the integrated light amount is controlled by using only the beam position adjusting unit 5, but, for example, the beam position adjusting unit 5 is not provided and the light reducing unit 2 or the pulse light source 1 is provided. By controlling the applied voltage, the light amount of the light beam itself incident on the light beam deflecting member (28, 29a, 29b) may be adjusted, or the light amount adjustment and the beam position adjusting unit 5 may be used together. May be. Further, the number of pulsed lights incident on each of the second fly-eye lenses 7a and 7b is equal to or greater than the number of pulses Nmin necessary to achieve a desired exposure amount control accuracy (further, for coherent pulsed lights). , So that the desired illuminance uniformity is achieved, that is, the minimum number of pulses Nsp required to reduce the contrast of interference fringes is satisfied). At this time, the number of pulsed lights to be incident on each of the second fly-eye lenses 7a and 7b may be different from each other, but in practice, the number of pulses of both is set to be the same, in other words, the exposure pulse number N is set to the first or It is desirable to set it to an integral multiple of the number of second fly-eye lenses.

In the apparatus according to the first and second embodiments described above, the method of irradiating the pulsed light (average pulse energy amount P _AV ) with the minimum exposure pulse number Nmin or more is adopted as the exposure amount control logic. Any control logic can be applied to the projection exposure apparatus according to the present invention. Various types of control logics have been proposed as this type of control logic, and one of them is a modified exposure system. This modified exposure method is particularly effective as a method for reducing the number of exposure pulses per shot (that is, reducing the minimum pulse number Nmin) for highly sensitive resists, and the details thereof are described in, for example, JP-A-63-316.
No. 430 is disclosed. Hereinafter, the correction exposure method will be briefly described with reference to FIG.

As shown in FIG. 10, it is 1 in the correction exposure method.
The exposure for one shot area is divided into rough exposure and correction exposure, and when the integrated exposure amount on the wafer reaches a certain level with respect to the target exposure amount by rough exposure, it is suitable for correction exposure according to a predetermined control logic. The transmittance and the number of correction exposure pulses are selected (determined), and the correction exposure is performed by irradiating several pulses of pulsed light in which the amount of energy per pulse is significantly reduced. As the pulse energy amount adjusting means for the correction exposure, the dimming unit for adjusting the exposure pulse number shown in FIG. 6 may be used also, or another adjusting means (ND filter or the like) dedicated to the correction exposure may be used. It may be provided.

From the above, in the apparatus according to the first embodiment, the correction exposure method can be applied as it is, but in the apparatus according to the second embodiment, the correction exposure pulse number n is set to the first value in consideration of the exposure amount control accuracy. Alternatively, it is desirable to set it to an integral multiple of the number of second fly-eye lenses. In each of the above embodiments, in order to improve the illuminance uniformity, a two-stage integrator structure in which two sets of fly-eye lenses are provided for each of the plurality of light beams split by the light splitter 6 is used. A prismatic rod-type integrator may be used as the integrator, or two sets of rod-type integrators or a combination of a rod-type integrator and a fly-eye integrator may be used to form the two-stage integrator structure as described above. Incidentally, such a configuration is disclosed in, for example, Japanese Patent Laid-Open No. 1-271718.

In addition to the two-stage integrator structure,
For example, each of the plurality of light beams divided by the light splitter 6 is further divided into a plurality of light beams by using a polyhedral prism, a mirror or the like, and each of the divided plurality of light beams is divided into one fly-eye lens group ( Alternatively, it may be a rod-type integrator) and may be configured to be incident on the incident surface in a superimposed manner. According to such a configuration, even if only one optical integrator is used, the effect of improving the illuminance uniformity can be obtained to some extent.

Further, for example, if the size (cross-sectional area) of each element forming the fly-eye lens is reduced, it is possible to use only one mesh-shaped fly-eye lens without adopting a two-stage integrator structure. It is possible to improve the illuminance uniformity to some extent. Further, in the above-described embodiment, 2 is set for each of the plurality of light beams split by the light splitter 6.
Fly eye lens group (7a, 8a), (7b, 8)
b) is arranged, for example, at least one of the first fly-eye lens group and the second fly-eye lens group is provided on the entire surface of the area through which each light flux passes in the plane perpendicular to the optical axis AX of the illumination optical system. It may be used as one large fly-eye lens that spreads out. At this time, it is desirable to determine the size of the fly-eye lens in consideration of the moving range of each light beam in the plane perpendicular to the optical axis AX depending on the periodicity and fineness of the reticle pattern. This also applies when only one set of fly-eye lenses is used.

Although the light quantity monitor 33 is provided in FIG. 1, it is not particularly necessary in the apparatus according to the first and second embodiments, and if not provided, the total value of the outputs of the light quantity sensors 15a and 15b may be used instead. good. Further, the present invention can be applied to any projection exposure apparatus provided with a pulse oscillation type light source. Further, if an apparatus similar to the above embodiment is constituted by an electromagnetic lens or the like, pulse energy other than light such as an electron beam can be generated. What is generated can also be used as a light source.

[0052]

As described above, according to the present invention, a plurality of two
The integrated values of the pulse energy amounts emitted from the next (or tertiary) light sources are made to substantially coincide with each other within a predetermined allowable range, and each integrated value is also set as a target integrated light amount determined from a predetermined exposure amount (appropriate exposure amount). It was decided that they would almost coincide with each other within a predetermined allowable range. For this reason, a good pattern exposure can be performed on the photosensitive substrate, and the exposure amount given to the photosensitive substrate (corresponding to the total value of the integrated values of the pulse energy amounts emitted from each of the plurality of secondary light sources) is appropriate. It is possible to achieve a desired exposure amount control accuracy that substantially matches the exposure amount. Further, even when a coherent pulse light source is used, the contrast of interference fringes can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a specific configuration of a beam position adjusting unit shown in FIG.

FIG. 3 is a diagram showing an example of a specific configuration of the optical splitter shown in FIG.

FIG. 4 is a diagram showing a light intensity distribution of pulse energy emitted from a pulse light source.

5 is a diagram showing an example of a specific configuration of the reducing means shown in FIG.

FIG. 6 is a diagram showing an example of a specific configuration of the dimming unit shown in FIG.

7 is a diagram showing a transmittance characteristic of the ND filter shown in FIG.

FIG. 8 is a flowchart for explaining the operation of the apparatus according to the first embodiment.

FIG. 9 is a diagram illustrating a configuration of an apparatus according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating a modified exposure method applied to exposure amount control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 dimming unit 5 beam position adjusting unit 6 light splitters 7a, 7b second fly-eye lenses 8a, 8b first fly-eye lenses 15a, 15b light quantity sensor 19 reticle 20 projection optical system 21 pupil plane 22 wafers 30a, 30b Light quantity integrator 31 Main control system

Claims (10)

[Claims] 1. A pulse light source that emits pulsed light with a fluctuation in light amount within a predetermined range each time of oscillation, an illumination optical system that irradiates the mask with a fine pattern with the pulsed light, and an image of the pattern of the mask. A projection optical system for image-forming and projecting on a photosensitive substrate, and transferring a pattern of the mask onto the photosensitive substrate with a predetermined exposure amount by irradiating a plurality of pulsed lights, in the optical path of the illumination optical system. The exit side focal plane is arranged on the Fourier transform surface of the mask pattern or in the vicinity thereof, and the center is arranged at each of a plurality of discrete positions decentered from the optical axis of the illumination optical system. A plurality of first fly-eye lenses; and an exit-side focal plane disposed on a Fourier transform plane for each incident end of each of the plurality of first fly-eye lenses, or in a plane in the vicinity thereof. Moni,
A plurality of second fly-eye lenses provided corresponding to each of the first fly-eye lenses; splitting the pulsed light from the pulsed light source into a plurality of light beams for each of the plurality of second fly-eye lenses A light splitter for making incident light; a light quantity adjusting means for adjusting the light quantity of each pulsed light emitted from each of the plurality of first fly-eye lenses; each pulse emitted from each of the plurality of first fly-eye lenses Measuring means for individually measuring the light quantity of the light; and the light quantity adjustment for each unit pulse number so that the integrated value of the measured light quantity of the pulsed light becomes substantially equal in each of the plurality of first fly-eye lenses. A projection exposure apparatus comprising: a control unit that controls the unit. 2. The light quantity adjusting means includes a movable member that changes a relative positional relationship between the pulsed light from the pulsed light source and the light splitter in a plane perpendicular to the optical axis of the illumination optical system. The projection exposure apparatus according to claim 1, wherein: 3. The movable member is a parallel plate glass which is arranged between the pulse light source and the light splitter and changes the incident position of the pulsed light with respect to the light splitter. Item 3. The projection exposure apparatus according to item 2. 4. The movable member is the light splitter, at least a part of which makes the split position of the pulsed light from the pulsed light source variable, and which is movable in a plane perpendicular to the optical axis of the illumination optical system. The projection exposure apparatus according to claim 2, wherein: 5. The pulsed light source emits coherent pulsed light, and the illumination optical system includes a plurality of first fly-eye lenses,
The projection exposure apparatus according to claim 1, further comprising a light beam deflection member that changes an incident angle of the pulsed light with respect to each of the plurality of second fly-eye lenses. 6. The light flux deflecting member is a wedge-shaped prism disposed between each of the plurality of first fly-eye lenses and each of the plurality of second fly-eye lenses. Item 6. The projection exposure apparatus according to item 5. 7. A pulse light source that emits pulsed light with a light amount variation within a predetermined range each time of oscillation, an illumination optical system that irradiates the mask with a fine pattern with the pulsed light, and an image of the pattern of the mask. A projection optical system for image-forming and projecting on a photosensitive substrate, and transferring a pattern of the mask onto the photosensitive substrate with a predetermined exposure amount by irradiating a plurality of pulsed lights, in the optical path of the illumination optical system. The exit side focal plane is arranged on the Fourier transform surface of the mask pattern or in the vicinity thereof, and the center is arranged at each of a plurality of discrete positions decentered from the optical axis of the illumination optical system. A plurality of first fly-eye lenses; and an exit-side focal plane disposed on a Fourier transform plane for each incident end of each of the plurality of first fly-eye lenses, or in a plane in the vicinity thereof. Moni,
A plurality of second fly-eye lenses provided corresponding to each of the first fly-eye lenses; pulse light from the pulse light source is sequentially incident on each of the plurality of second fly-eye lenses for each unit pulse number Luminous flux deflecting means for making: a measuring means for individually measuring the light quantity of each pulsed light emitted from each of the plurality of first fly-eye lenses; and each pulse emitted from each of the plurality of first fly-eye lenses A light quantity adjusting means for adjusting the light quantity of the light; and the light quantity adjusting means for each unit pulse number so that the integrated value of the measured light quantity of the pulsed light becomes substantially equal in each of the plurality of first fly-eye lenses. And a control means for controlling the projection exposure apparatus. 8. A pulse light source that emits pulsed light with a variation in light amount within a predetermined range each time of oscillation, an illumination optical system that irradiates the mask having a fine pattern with the pulsed light, and an image of the pattern of the mask. A projection optical system for imaging and projecting onto a photosensitive substrate, and transferring a pattern of the mask to the photosensitive substrate with a predetermined exposure amount by irradiating a plurality of pulsed lights, wherein the illumination optical system includes: Discrete eccentric with respect to the optical axis of the illumination optical system or the projection optical system by an amount determined according to the periodicity of the mask pattern on an optical Fourier transform plane for the pattern of the mask or in the vicinity thereof. A light beam splitting member that splits and concentrates the pulsed light from the pulsed light source into each of at least two partial regions; Light quantity adjusting means for adjusting the light quantity of each pulsed light concentrated on each of the two partial areas; measuring means for individually measuring the light quantity of each pulsed light passing through each of the at least two partial areas; And a control means for controlling the light quantity adjusting means for each unit pulse number so that the integrated value of the passing light amount for each partial area becomes substantially equal in each of the at least two partial areas. Projection exposure device. 9. A pulse light source that emits pulsed light with a fluctuation in light amount within a predetermined range each time of oscillation, an illumination optical system that irradiates the mask with a fine pattern with the pulsed light, and an image of the pattern of the mask. A projection optical system for imaging and projecting onto a photosensitive substrate, and transferring a pattern of the mask to the photosensitive substrate with a predetermined exposure amount by irradiating a plurality of pulsed lights, wherein the illumination optical system includes: Discrete eccentric with respect to the optical axis of the illumination optical system or the projection optical system by an amount determined according to the periodicity of the mask pattern on an optical Fourier transform plane for the pattern of the mask or in the vicinity thereof. Beam deflecting means for deflecting the pulsed light from the pulsed light source for each unit pulse number so that the pulsed light sequentially passes through each of the at least two partial regions. ; And measuring means for measuring the light intensity of each pulse light passing through each of the at least two partial regions individually; at least 2
Light quantity adjusting means for adjusting the light quantity of each pulsed light passing through each of the two partial areas; and the integrated value of the measured quantity of passing light for each of the partial areas is substantially equal in each of the at least two partial areas. A projection exposure apparatus comprising: a control unit that controls the light amount adjustment unit for each unit pulse number. 10. A pulsed light source that emits pulsed light with a variation in light amount within a predetermined range each time of oscillation, and an illumination optical system that irradiates the pulsed light to a mask having a fine pattern.
A projection exposure system, comprising: a projection optical system for image-forming and projecting an image of the pattern of the mask onto a photosensitive substrate, wherein the pattern of the mask is transferred onto the photosensitive substrate at a predetermined exposure amount by irradiation with a plurality of pulsed lights. First light amount adjusting means for adjusting the light amount of each pulsed light emitted from the pulse light source; a Fourier transform plane for the pattern of the mask in the optical path of the illumination optical system, or a plane near the exit side of the Fourier transform plane. Being placed,
A plurality of first fly-eye lenses whose centers are respectively arranged at a plurality of discrete positions decentered from the optical axis of the illumination optical system; and a Fourier transform plane for each incident end of the plurality of first fly-eye lenses. Or a plurality of second fly-eye lenses provided in correspondence with each of the first fly-eye lenses while the exit-side focal plane is arranged in the vicinity thereof; and each of the plurality of second fly-eye lenses. An optical splitter that splits the pulsed light from the pulsed light source into a plurality of luminous fluxes for incidence; and a second light quantity that adjusts the amount of each pulsed light emitted from each of the plurality of first fly-eye lenses. Adjusting means; measuring means for individually measuring the light quantity of each pulsed light emitted from each of the plurality of first fly-eye lenses; and an integrated value of the measured light quantity of the pulsed light, fly The first light amount adjusting means and the second light amount adjusting means are set for each unit pulse number so that they are substantially equal to each other and substantially match the target integrated light amount value corresponding to the predetermined exposure amount. A projection exposure apparatus, comprising: a control unit that controls at least one of them.