JPH05251310A - Exposure controller - Google Patents

Abstract

PURPOSE:To shorten the time required for adjusting exposing energy when exposure is controlled by using a beam attenuating filter plate. CONSTITUTION:A beam attenuating section 6 for corrective exposure is constituted of slide type beam attenuating filter plates 23 and 24 each of which has two kinds of transmittance. Upon completing rough exposure, corrective exposure is performed after adjusting the transmittance by bringing out and in the filter plates 23 and 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device for controlling the irradiation energy of a photosensitive object, and more particularly, for controlling the exposure amount of an exposure device using pulsed laser light such as excimer laser as the exposure light. The present invention relates to an exposure control device that is suitable for use in.

[0002]

2. Description of the Related Art Conventionally, an exposure apparatus using a pulse laser as a light source has been developed. However, in general, pulse laser light has a variation of about ± 10% for each pulse, and in the short and long term. There is a phenomenon that the laser power decreases. Therefore, exposure control in such an exposure apparatus has been performed by a method of detecting and integrating the light amount for each pulse and continuing light emission until the integration result reaches a desired value. The conventional exposure control methods are roughly divided into
For example, a modified exposure method as disclosed in Japanese Patent Laid-Open No. 60-169136 and a method of making the exposure energy substantially equal to a predetermined average light intensity value over the entire pulsed light required for one shot exposure are available. is there. The present invention can be applied to any method, but the modified exposure method will be described below as an example.

As shown in FIG. 5 (a), in the case of the correction exposure method, the exposure to the photoconductor (such as a wafer coated with a resist) is a rough exposure in which the exposure energy is slightly lower than the proper exposure amount. It is performed in two stages, RE and modified exposure CE that gives the remaining exposure energy. That is, FIG.
As shown in (b), when the proper exposure amount is EG, the rough exposure RE gives exposure energy which is smaller than the proper exposure amount EG by ΔE, and the remaining exposure energy ΔE
Is less than the exposure energy for one pulse in the period of rough exposure RE, for example. Therefore, in the correction exposure CE, the exposure energy per pulse of the laser light is attenuated by the neutral density filter plate, and the attenuated laser light is irradiated by the number of pulses corresponding to the remaining exposure energy ΔE. In this case, since the rough exposure RE is performed to a level slightly lower than the appropriate exposure amount EG, the throughput does not decrease, and the exposure energy per pulse in the corrected exposure CE is set to be small, so that the final exposure It is possible to easily suppress the variation of the total integrated exposure amount from the appropriate exposure amount EG within the allowable error range.

Further, when the correction exposure is performed, the power of the laser light is conventionally attenuated by using, for example, a neutral density filter plate 1 shown in FIG. In FIG. 6A, six mesh filter plates 2A to 2F each having a different attenuation rate (transmittance) at 60 ° intervals are incorporated in the peripheral portion of the neutral density filter plate 1, and these mesh filter plates 2A to The transmittance of 2F is set as shown in FIG. Then, the neutral density filter plate 1 is rotated about the axis 1a to allow the pulse laser light LB to pass through the filter plate 2.
The power of the pulsed laser beam LB can be set to a desired level by passing through the center part of the desired mesh filter plate in A to 2F.

[0005]

However, in the conventional exposure control method, the rough exposure RE stage shown in FIG.
The mesh filter plate 2A of the neutral density filter plate 1 is used, and in the modified exposure CE, for example, the mesh filter plate 2D 180 ° apart from the mesh filter plate 2A.
However, it takes time to rotate and position the neutral density filter plate 1. If it takes time to rotate and position the neutral density filter plate 1 as described above, the time required to switch from the rough exposure RE to the correction exposure CE in FIG. 5A becomes long, and as a result, the exposure time becomes long as a whole. Throughput decreases.

Since a large number of mesh filter plates 2A to 2F are incorporated in the conventional neutral density filter plate 1, the size of each mesh filter plate 2A to 2F is a pulse in order to miniaturize the entire apparatus. It is necessary to make it as small as possible within the range exceeding the cross-sectional area of the laser beam LB.
Therefore, the positioning accuracy of the neutral density filter plate 1 becomes strict, which is one of the factors that lengthen the positioning time.

Further, not only in the correction exposure method but also in the method in which the power of all the pulsed light of the laser light is set near a certain average level, the neutral density filter plate is used to attenuate the power of the laser light. When using, it is desirable to set the transmittance of the neutral density filter plate as quickly and accurately as possible. In view of such a point, the present invention is
When controlling the amount of exposure using a neutral density filter plate,
An object of the present invention is to provide an exposure control device capable of reducing the time required for adjusting the exposure energy and improving the throughput.

[0008]

An exposure control apparatus according to the present invention is, for example, as shown in FIGS. 1 and 2, a pulse for emitting a coherent pulsed light with a light amount variation within a predetermined range at each oscillation. A light source (3) and an illumination optical system (8, 12) for irradiating the first object R with this pulsed light are provided, and the pattern formed on the first object R is exposed in a predetermined manner by irradiation with a plurality of pulsed lights. In an exposure control device that controls the exposure amount of the second object W to a predetermined exposure amount, the exposure optical system (8, 12) has an illumination optical system (8, 12). Has a plurality of neutral density filter plates (23, 24) arranged in series along the optical axis and having a plurality of filter portions (25A, 25B) having different transmittances for the pulsed light LB2. However, the filter part (25A) is, for example, a 100% transmission filter,
There are four types of transmittance obtained by the two neutral density filter plates having two types of filter parts. Furthermore, the present invention provides a plurality of these neutral density filter plates (23, 2).
Driving means (2) for changing the transmittance of the plurality of neutral density filter plates for the pulsed light LB2 as a whole by individually moving (4) in the illumination optical system.
0), monitor means (9, 11, 22) for detecting the light quantity of the pulsed light from the pulse light source (3), and the exposure amount to the second object W based on the light quantity detected by the monitor means. Calculation means (14) for obtaining a combination of the transmittances of the plurality of neutral density filter plates (23, 24) such that the predetermined exposure amount is obtained, and a driving means (20) thereof.
And a control means (14) for setting the combination of the transmittances of the plurality of neutral density filter plates to the combination obtained by the calculation means (14).

In this case, an even number of the plurality of light-reducing filter plates (23, 24) are provided, and the even-numbered light-reducing filter plates are arranged two by two in a wedge shape, and the driving means (2
In 0), it is desirable to move the even number of neutral density filter plates while maintaining the wedge-shaped arrangement.

[0010]

According to the present invention, when a plurality of neutral density filter plates (27, 28) are used for attenuating the pulsed light LB2, according to the present invention, a plurality of neutral density filter plates (27, 28) are used. , 28) to realize nine different transmittances. Therefore, when the types of the filter parts (27A, 27B, 27C) having different transmittances are the same as those in the conventional case in each of the neutral density filter plates (23, 24), the total number of types is larger than that in the conventional case. Can be obtained. In this case, the transmittance can be switched at high speed in each of the neutral density filter plates (27, 28). Further, the size of the plurality of filter portions (27A, 27B, 27C) having different transmittances in the respective neutral density filter plates (27, 28) can be made larger than the conventional one, and the positioning accuracy can be made rough, so that the overall positioning is reduced. The time required for adjusting the exposure energy can be further shortened.

Further, an even number of neutral density filter plates (23,
24) are arranged two by two in a wedge shape, and the driving means (20)
However, when moving the even number of neutral density filter plates while maintaining the wedge-shaped arrangement, there should be no positional deviation between the optical axis of the incident pulsed light LB2 and the optical axis of the emitted pulsed light LB3. You can Therefore, even when the neutral density filter plates (23, 24) are arranged, the pulse light source (3)
It is not necessary to adjust the optical axes of the illumination optical system (8, 12).

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the exposure control apparatus according to the present invention will be described below with reference to FIGS. In this embodiment, the present invention is applied to an exposure control system of a step-and-repeat type reduction projection type exposure apparatus (stepper) that performs exposure by a correction exposure method. FIG. 1 shows the entire configuration of the stepper of this example. In FIG. 1, 3 is a pulse laser light source such as an excimer laser. The pulsed laser light source 3 has a narrowed wavelength stabilization mechanism composed of an etalon or a dispersive element, etc., in a part between two resonant mirrors arranged between both ends with a laser tube interposed therebetween. It is configured as a laser light source with a stable resonator. Further, in the pulsed laser light source 3, a high-voltage discharge is generated between two electrodes provided in parallel along the optical axis of the laser light, so that an ultraviolet pulse that sensitizes a resist layer of a wafer described later is obtained. Laser light, eg wavelength 2
A 48 nm KrF excimer laser beam is emitted.

The cross-sectional shape of the laser beam LB0 emitted from the pulse laser light source 3 is a rectangle having an aspect ratio of about 1/2 to 1/5 depending on the arrangement of the two electrodes. The laser beam LB0 is incident on a beam expander 4 configured by combining, for example, two concavo-convex cylindrical lenses, and the beam expander 4
From, a laser beam LB1 whose cross-sectional shape is converted into a substantially square shape by expanding the width of the cross-sectional shape in the short side direction is emitted.

The laser beam LB1 is incident on a rough exposure light reducing section 5 which is composed of, for example, a conventional light reduction filter plate 1 shown in FIG. ) Is emitted from 100% (complete transmission) in a stepwise manner to a predetermined rate. The laser beam L in the light-attenuating section 5 for rough exposure
The transmittance for B1 is set so that the average number of laser pulses exposed during rough exposure to a level slightly lower than an appropriate exposure amount for a wafer, which is a photosensitive substrate, becomes a predetermined minimum value N _MIN or more. To be selected. The minimum value N _MIN is set on the basis that the influence of the interference fringes formed on the resist by the laser light as the exposure light is below the allowable value. Further, when sequentially performing exposure on each shot area of one wafer, the setting of the transmittance in the rough exposure dimming unit 5 is the same for all shot areas of the one wafer. Therefore, the coarse exposure dimming unit 5
In addition, even if the neutral density filter plate 1 of FIG. 6A, which requires a long time for positioning, is used, the throughput of the whole exposure hardly decreases.

The laser beam LB2 emitted from the rough exposure dimming unit 5 enters the correction exposure dimming unit 6. The modified exposure light-reducing portion 6 of this example is composed of two slide-type light-reducing filter plates 23 and 24 arranged in a wedge shape on the optical axis of the laser beam LB2. As shown in FIG. 2A, the former neutral density filter plate 23 includes a filter plate 25A having a transmittance of 100% for the laser beam LB2 and a filter plate 25B having a transmittance of, for example, 20%.
And are arranged in parallel to the R direction. The filter plate 25B is composed of a mesh filter plate or a dielectric having a predetermined transmittance. Similarly, the latter neutral density filter plate 24 is configured by arranging a filter plate having a transmittance of 100% for the laser beam LB2 and a filter plate having a transmittance of, for example, 30% in parallel with the R direction.
In addition, R in the neutral density filter plates 23 and 24
The direction is the same as the direction perpendicular to the paper surface of FIG. 1, and the slide type neutral density filter plates 23 and 24 are taken in and out in the direction perpendicular to the paper surface of FIG. 1 to increase the transmittance for the laser beam LB2. Can be changed.

In FIG. 1, a laser beam LB3 having an exposure energy obtained by multiplying the incident laser beam LB2 by its transmittance is emitted from the correction exposure dimming unit 6. In this case, since the two neutral density filter plates 23 and 24 have the same refractive index and the same thickness and the two neutral density filter plates 23 and 24 are arranged in a wedge shape, the laser beam The optical axis of LB3 matches the optical axis of the laser beam LB2.

The laser beam LB3 is reflected by the ultraviolet reflection mirror 7 and enters the fly-eye lens 8, and a large number of secondary light sources are formed on the focal plane on the rear side (reticle side) of the fly-eye lens 8. .. The laser light from these secondary light sources is transmitted through a beam splitter 9 having a small reflectance, which is obliquely installed at an inclination angle of 45 ° with respect to the optical axis, and then is appropriately condensed by a condenser lens 12 to form a reticle R. Illuminate the top in a superimposed manner. As a result, the image of the circuit pattern on the reticle R is transferred to the resist layer of the wafer W held on the wafer stage 13 via the projection optical system PL.

Further, a part of the laser beam split by the beam splitter 9 is received by the light receiving element 11 by the condensing optical system 10.
Is condensed on the light receiving surface of. The light receiving element 11 accurately outputs a photoelectric conversion signal corresponding to the light amount (light intensity) of each pulse of laser light, has a sufficient sensitivity in the ultraviolet region, and has a sufficiently fast response speed. It is composed of a diode and the like.

Reference numeral 14 denotes a main control system for controlling the operation of the entire apparatus. The main control system 14 is a memory 15 for storing various information and an input / output device for receiving commands from the operator and outputting information to the operator. Has 16. Reference numeral 17 denotes a trigger control unit that controls the oscillation of the pulse laser light source 1, and 18 denotes a first light amount control unit that controls the high-voltage discharge voltage of the light source 1, and the main control system 1
Reference numeral 4 controls oscillation of the pulsed laser light source 3 (number of light emission pulses, oscillation interval, etc.) via the trigger controller 17,
The pulse energy of the pulse laser light source 1 is controlled via the light quantity control unit 18.

Reference numeral 19 is a second light amount control section for controlling the rotation of the light reduction filter plate inside the rough exposure light reduction section 5, and 20 is two slide type light reductions inside the correction exposure light reduction section 6. The third light amount control unit for switching the transmittance of the filter plates 23 and 24 is shown, and the main control system 14 includes the light amount control units 19 and 20.
The transmittances of the rough exposure light-reducing portion 5 and the correction exposure light-reducing portion 6 are set to the values calculated in the procedure described later via the. In addition, the photoelectric conversion signal of the light receiving element 11 is supplied to the light amount monitor unit 22 via the amplifier 21, and the light amount monitor unit 22 outputs 1
During the shot exposure, the signals supplied in pulse form from the light receiving element 11 are sequentially integrated, and the integrated signal thus obtained is supplied to the main control system 14. Further, the conversion ratio between the photoelectric conversion signal from the light receiving element 11 and the exposure energy amount on the wafer W is previously obtained by actual measurement, and this conversion ratio is stored in the memory 15.
Stored in the main control system 14 while performing exposure.
Can monitor the actual integrated exposure amount on the wafer W.

Next, the exposure operation of this example will be described.
In the initial state, a filter plate is set on the optical axis of the laser beam LB2 such that the two neutral density filter plates 23 and 24 of the modified exposure light reducing unit 6 have a transmittance of 100%. Then, before starting the exposure of one wafer W,
The main control system 14 fixes the exposure energy per pulse of the pulse laser light source 3 to a predetermined value via the first light quantity control unit 18, and starts the pulse emission of the pulse laser light source 3 via the trigger control unit 17. Let Then, the main control system 14 obtains the average exposure energy EP per pulse via the light amount monitor unit 22, and thereafter divides the appropriate exposure amount EG of the wafer W by the average exposure energy EP to obtain an integer of this quotient. The minimum value N required for the part to reduce interference fringes
_The transmittance of the rough exposure dimming unit 5 is adjusted via the second light amount control unit 19 so as to be _MIN or more.

Thereafter, the main control system 14 places the wafer W on the wafer stage 13, starts the pulsed light emission of the pulsed laser light source 3 to perform rough exposure on the first shot area of the wafer W, and the light quantity monitor unit. When the exposure amount corresponding to the integrated signal obtained from 22 exceeds a predetermined exposure amount slightly lower than the proper exposure amount EG of the wafer W, the rough exposure is stopped. Then, the main control system 14 calculates the total transmittance and the number of correction pulses in the correction exposure dimming unit 6 based on the remaining exposure amount ΔE up to the appropriate exposure amount EG. In order to improve the throughput, it is desirable that the number of correction pulses is as small as possible. The overall transmittance of the modified exposure light reducing section 6 is selected from the transmittances obtained by combining the transmittances of the two slide type neutral density filter plates 23 and 24. For example, if the transmittance of the neutral density filter plate 23 is 100% and 20%, and the transmittance of the neutral density filter plate 24 is 100% and 30%, the obtained transmittances are 100%, 20%, 30% and 6%. % Of 4
It is a kind.

The main control system 14 depends on the selected transmittance.
After positioning the neutral density filter plates 23 and 24 in the direction perpendicular to the paper surface of FIG. 1 via the third light amount control unit 20, the correction exposure is performed by the calculated number of pulses and then the exposure is stopped. After that, the transmittance of the light-reducing portion 6 for correction exposure is set to 1
After performing the rough exposure for the next shot area of the wafer W after returning to 00%, the main control system 14 determines the correction exposure dimming unit 6 based on the remaining exposure amount ΔE ′ up to the proper exposure amount EG.
Calculate the total transmittance and the number of correction pulses in. Then, the transmittance of the correction exposure light-reducing unit 6 is set to the transmittance, and after the correction exposure is performed for the calculated number of pulses, the exposure is stopped. The exposure is sequentially performed. In this way, it is necessary to select the transmittance of the light reducing section 6 for correction exposure for each shot.
This is because the exposure energy of each pulse of the pulse laser light source 1 fluctuates to some extent during the exposure of each shot.

As described above, according to the present example, the correction exposure is performed after the rough exposure by setting the transmittance of the correction-exposure dimming unit 6 in order to obtain an appropriate exposure amount for the wafer W.
In this case, the setting of the transmittance in the correction exposure light-reducing unit 6 is performed only by inserting and removing the two slide-type light-reducing filter plates 23 and 24 and setting either one of the two types of filter plates. It Therefore, the transmittance of the light-attenuating portion for correction exposure 6 is set extremely quickly, the time required for switching from the rough exposure to the correction exposure is shortened, and the exposure throughput can be improved.

Further, as shown in FIG. 2A, the neutral density filter plate 23 (similarly to the neutral density filter plate 24) has only two kinds of filter plates 25A and 25B, which are different from those of the conventional example. The shape of the filter plates 25A and 25B can be set larger than the sectional shape of the laser beam LB2. Therefore, the neutral density filter plate 23
The positioning accuracy of Nos. 24 and 24 can be made coarser than before, and the transmittance can be switched at higher speed.

In the example shown in FIG. 1, the correction exposure dimming unit 6 is used.
Is composed of two slide type neutral density filter plates 23 and 24, but the number of modified exposure neutralization parts 6 is N (integer).
It may be configured by a slide type neutral density filter plate having two kinds of transmittances. In this case, each neutral density filter plate has a filter plate with a transmittance of 100%. Further, assuming that there is no overlap in the transmittance, the number of types of transmittance that can be switched is 2 ^N. Therefore, an odd number of neutral density filter plates may be used, but when an even number of neutral density filter plates are used, two wedge-shaped (line symmetrical) patterns are used.
By arranging in the above, it is possible to eliminate the deviation of the optical axis between the incident light and the emitted light. In the case of an odd number of sheets, it is desirable to separately arrange a parallel plate glass for optical path correction.

Further, as a neutral density filter plate, as shown in FIG.
As shown in (b), using a slide type neutral density filter plate 26 in which filter plates 27B and 27C having different transmittances are arranged on the left and right (R direction) around the filter plate 27A having 100% transmittance. May be. In this case, in the rough exposure stage, the filter plate 27A having a central transmittance of 100% is used, and in the correction exposure, either the left or right filter plate 27B or 27C is selected even if the slide amount is the largest. The quantity is small. Therefore, it is possible to switch the transmittance in the correction exposure dimming section at an extremely high speed. Also, each filter plate 2
The shape of 7A to 27C can be made larger than the sectional shape of the laser beam LB2, and the positioning accuracy can be roughened.

Further, as the neutral density filter plate, as shown in FIG. 3, a rotary neutral density filter plate in which three filter plates 29A to 29C having different transmittances are arranged in the peripheral portion at equal angular intervals. 28 can also be used.
Also in this example, for example, the transmittance of the filter plate 29A is 10
It is 0%. The transmittance is 100 at the rough exposure stage.
%, The filter plate 29A is used, and even when the rotation angle is the largest at the time of correction exposure, the neutral density filter plate 28 is rotated by 120 ° about the axis 28a and either the left or right filter plate 29B or 29C is selected. Therefore, the rotation angle is small. Therefore, it is possible to switch the transmittance in the correction exposure dimming section at an extremely high speed. Further, the shape of each of the filter plates 29A to 29C can be made larger than the sectional shape of the laser beam LB2,
The positioning accuracy can be roughened.

Next, another embodiment of the present invention will be described with reference to FIG. In this example, the rough exposure light-reducing portion 5 of FIG. 1 is also configured by an even number of slide-type light-reducing filter plates. In FIG. 4, portions corresponding to those in FIG. Detailed description is omitted.

FIG. 4 shows a rough exposure light reducing section 5 and a correction exposure light reducing section 6 of this example. The rough exposure light reducing section 5 is composed of four slide type light reducing filter plates 30 to 33. Constitute.
Each of the neutral density filter plates 30 to 33 is shown in FIG.
Like the neutral density filter plate 23, one has a transmittance of 100.
% With two filter plates. Then, the laser beam LB1 from the beam expander 4 shown in FIG.
The laser beam LB2 that has passed through 33 is supplied to the correction exposure dimming unit 6. In this case, the four neutral density filter plates 30 to 33 are arranged in a wedge shape by two, and the optical axis of the incident laser beam LB1 and the emitted laser beam LB.
The optical axis of 2 is not displaced. In addition, the second light amount adjusting unit 34, in response to an instruction from the main control system 14, includes the four light reducing filter plates 30 to 33 of the rough exposure light reducing unit 5.
4 are individually put in and taken out in a direction perpendicular to the paper surface of FIG. 4 to set the transmittance of the rough exposure dimming unit 5 as a whole. Other configurations are similar to those in FIG.

The operation at the time of exposure in the example of FIG. 4 will be described.
First, in the initial state, the transmittances of the light-reducing filter plates 30 to 33 of the rough-exposure light-reducing unit 5 are set to 100%.
Then, the average pulse number of the rough exposure calculated from the average pulse energy of the pulse laser light source 3 of FIG. 1 and the proper exposure amount to the wafer W becomes smaller than the minimum pulse number N _MIN required for reducing interference fringes. In this case, the coarse exposure dimming unit 5 is adjusted so that the average pulse number of the coarse exposure becomes larger than N _MIN.
Calculate the transmittance at. The main control system 14 sets the calculated transmittance in the rough exposure dimming unit 5 via the second light amount control unit 34. After that, the main control system 14 places the wafer W on the wafer stage 13 to perform rough exposure, and then sets the transmittance of the correction exposure dimming unit 6 to perform correction exposure. As described above, according to the example of FIG. 4, since the coarse exposure light reducing unit 5 is also configured by the slide type light reduction filter plate whose transmittance can be switched at high speed, the overall exposure time is further shortened and the throughput is reduced. Can be further improved.

Although the above-mentioned embodiment applies the present invention to the exposure control system of the stepper of the correction exposure type, the present invention does not perform the correction exposure and uses the neutral density filter plate to adjust the level of each laser pulse light. Can also be applied to the method of adjusting the average. The present invention can be applied not only to a step-and-repeat type projection exposure apparatus but also to a collective exposure type exposure apparatus. In the case of the batch exposure method, the exposure light is applied to the entire wafer through the reticle in one shot. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0033]

According to the present invention, when the exposure amount is controlled using the neutral density filter plate, there is an advantage that the time required for adjusting the exposure energy can be shortened and the throughput can be improved. In particular, when applied to the correction exposure method, it is possible to shorten the switching time from the rough exposure to the correction exposure and significantly improve the throughput. Further, when two even-numbered neutral density filter plates are arranged in a wedge shape, it is possible to eliminate the deviation between the optical axis of the incident pulsed light and the optical axis of the emitted pulsed light.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a stepper to which an embodiment of an exposure control apparatus according to the present invention is applied.

2A is a plan view showing a slide type neutral density filter plate 23 used in FIG. 1, and FIG. 2B is a plan view showing a modified example of the slide type neutral density filter plate.

FIG. 3 is a plan view showing a rotary neutral density filter plate.

FIG. 4 is a configuration diagram showing a dimming unit of another embodiment of the present invention.

FIG. 5 is a diagram used for explaining correction exposure.

6A is a plan view showing a conventional rotary type neutral density filter plate, and FIG. 6B is a diagram showing the transmittance of the neutral density filter plate of FIG. 6A.

[Explanation of symbols]

 3 pulse laser light source 5 light-attenuating section for rough exposure 6 light-attenuating section for correction exposure 9 beam splitter 10 condensing optical system 11 light-receiving element 12 condenser lens R reticle PL projection optical system W wafer 13 wafer stage 14 main control system 19 second Light intensity control unit 20 Third light intensity control unit 22 Light intensity monitor unit 23, 24 Dark filter plate 25A, 25B Filter plate

Claims (2)

[Claims] 1. A pulsed light source that emits pulsed light with a fluctuation in light amount within a predetermined range each time it oscillates;
And an illumination optical system for irradiating an object, wherein the exposure device transfers the pattern formed on the first object by irradiation of a plurality of pulsed lights to a photosensitive second object with a predetermined exposure amount. In an exposure control device for controlling the exposure amount of two objects to the predetermined exposure amount, a plurality of filters arranged in series along the optical axis in the illumination optical system and having different transmittances for the pulsed light, respectively. A plurality of attenuating filter plates, and a plurality of the attenuating filter plates are individually moved in the illumination optical system to transmit the pulsed light as a whole of the plurality of attenuating filter plates. Drive means for changing the rate, monitor means for detecting the light quantity of the pulsed light from the pulsed light source, and the exposure amount for the second object based on the light quantity detected by the monitor means. The calculating means for obtaining a combination of the transmittances of the plurality of light-reducing filter plates so as to obtain a constant exposure amount, and the calculating means for calculating the combination of the transmittances of the plurality of light-reducing filter plates via the driving means. And an exposure control device for setting the combination obtained by the above. 2. An even number of the light-reducing filter plates are provided, and the even-numbered light-reducing filter plates are arranged two by two in a wedge shape, and the driving means maintains the wedge-shaped arrangement. The exposure control apparatus according to claim 1, wherein an even number of neutral density filter plates are moved.