JPH10340846A - Aligner, its manufacture, exposing method and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuous correction of imaging performance without vibration, by installing a refractive index adjusting means for adjusting the refractive index of liquid. SOLUTION: A refractive index adjusting means consists of the following; electrodes D1, ion exchange films 11, 12, bulkheads K1, K2, exhaust pipes H1, H2, a mixer K, an electromagnetic valve DV, an introducing pipe LD, a power source supply part and a second control part. The second control part sends a command to the power source supply part, and applies 8 specified voltage for a specified period across the two electrodes D1. From one electrode turning to an anode, oxygen gas is generated. From the other electrode turning to a cathode, mixed gas of hydrogen and chlorine is generated. Since the concentration of hydrogen chloride in liquid LQ is decreased, the refractive index of the liquid LQ is decreased. The second control part sends a command to the electromagnetic valve DV, in order to open the valve DV and add high concentration admixture aqueous solution to the liquid LQ. Thereby the refractive index of the liquid LQ is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure apparatus having a projection optical system for projecting a device pattern provided on a reticle onto a photosensitive substrate, an exposure method using the exposure apparatus, and a device manufacturing method. . More specifically, the present invention relates to an immersion type exposure apparatus in which an optical path between a projection optical system and a photosensitive substrate is filled with a liquid. The present invention is suitable for manufacturing a semiconductor device, an imaging device (such as a CCD), a liquid crystal display device, or a thin-film magnetic head.

[0002]

2. Description of the Related Art A space between a final surface of an optical system and an image surface is defined as:
Although it is called a working distance, the working distance is filled with air in a projection optical system of a conventional exposure apparatus. By the way, in the process of manufacturing an IC or an LSI, it is always desired to miniaturize a pattern to be exposed on a silicon wafer. To this end, it is necessary to shorten the wavelength of light used for exposure or to set a numerical aperture on the image side. Need to be larger. As the wavelength of light becomes shorter, the number of glass materials having a transmittance sufficient to secure a sufficient amount of light for exposure while obtaining satisfactory imaging performance decreases.

[0003] Therefore, it has been proposed to increase the numerical aperture on the image side by making the final medium up to the image plane a liquid having a higher refractive index than air, thereby increasing the projection optical system using such a liquid. The exposure apparatus provided is called an immersion type exposure apparatus. Now, in the exposure apparatus, in order to correct the imaging performance of the projection optical system, an imaging performance correction for adjusting the imaging performance in the optical path closest to the object or the optical path closest to the image of the projection optical system. There is known a technique in which members are exchangeably provided.

[0004]

However, in the immersion type exposure apparatus, since the optical path (working distance) between the projection optical system and the photosensitive substrate is filled with liquid, it is necessary to correct the imaging performance. Is difficult to dispose. In addition, since only a limited number of such imaging performance correcting members can be prepared in consideration of a finite number and a realistic device configuration, there is a problem that the imaging performance can be corrected only discretely. .

Further, the imaging performance of the projection optical system needs to be within a predetermined allowable range, but if the correction of the imaging performance can be performed only discretely as described above, it is within this predetermined allowable range. It becomes difficult. In particular, when the miniaturization of the exposure pattern and the increase of the exposure area are required, the allowable range of the imaging performance is narrowed, and when performing the scanning exposure method of performing the exposure while scanning the reticle and the photosensitive substrate. Also, the allowable range of the fluctuation width of the imaging performance characteristic is narrow, and discrete correction cannot cope with it.

Further, when the imaging performance correcting member is replaced as described above, the projection optical system itself vibrates.
The imaging performance may be adversely affected. Therefore, a first object of the present invention is to enable continuous correction of imaging performance without vibration. It is a second object of the present invention to achieve both the increase in the numerical aperture of the projection optical system and the correction of the imaging performance.

[0007]

In order to achieve the first object described above, an exposure apparatus according to the present invention comprises an illumination optical system for illuminating a pattern provided on a reticle, and an image of the pattern formed by a photosensitive element. A projection optical system formed on the substrate,
An exposure apparatus that performs exposure via a liquid located at least in a part of an optical path between a projection optical system and a photosensitive substrate, and has a refractive index adjusting unit for adjusting a refractive index of the liquid. .

Here, according to a preferred aspect of the present invention, the refractive index adjusting means adjusts the refractive index of the liquid so as to correct the imaging performance of the projection optical system. According to a preferred aspect of the present invention, based on this configuration, the apparatus further includes an imaging performance measuring unit that measures the imaging performance of the projection optical system, and the refractive index adjusting unit includes the imaging performance. Is to adjust the refractive index of the liquid so as to correct.

According to a preferred aspect of the present invention, there is further provided a fluctuation factor detecting means for detecting a state of a factor of a fluctuation of the imaging performance of the projection optical system, wherein the refractive index adjusting means comprises: The refractive index of the liquid is adjusted so as to correct the imaging performance according to the state of the factor. Based on this configuration, according to a preferred aspect set forth in claim 5,
The illumination optical system is configured to be able to change the illumination condition with respect to the reticle, the variation factor detection means detects the state of the illumination condition, and the refractive index adjustment means according to the change in the illumination condition,
This is to adjust the refractive index of the liquid so as to correct the imaging performance.

According to a preferred aspect of the present invention, the fluctuation factor detecting means determines the type of the reticle, and the refractive index adjusting means adjusts the imaging performance according to the type of the reticle. This is to adjust the refractive index of the liquid so as to make correction. In order to achieve the second object, it is preferable that the entire optical path between the projection optical system and the photosensitive substrate be filled with liquid. At this time, the exposure apparatus according to the present invention includes a side wall for filling the optical path between the projection optical system and the photosensitive substrate with the liquid, and supplies the liquid to the photosensitive substrate holder and collects the liquid from the photosensitive substrate holder. It is preferable to further include a photosensitive substrate holder for holding the photosensitive substrate, which is provided with a supply / recovery unit for performing the operation.

[0011] The refractive index adjusting means may include an additive supply unit for supplying an additive for adjusting the refractive index to the liquid, and an additive recovery unit for recovering the additive from the liquid. preferable.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention having the above-described structure, the refractive index of a liquid located in an optical path between a projection optical system and a photosensitive substrate can be adjusted. Thus, the imaging performance of the projection optical system can be corrected. Here, as a method of adjusting the refractive index, assuming that the liquid is a mixed liquid of multiple substances, the refractive index n of the mixed liquid is calculated according to the Lorentz-Lorenz equation.

[0013]

(Equation 1)

## EQU1 ## However,

[0015]

(Equation 2)

## EQU1 ## For example, when the liquid is an aqueous solution, the refractive index of the aqueous solution changes according to the concentration of the aqueous solution itself, and thus the concentration of the substance added to the aqueous solution may be increased or decreased. With this, if the refractive index of the liquid is changed so that the refractive index value can compensate for the imaging performance of the projection optical system,
The imaging performance of the projection optical system is good.

Here, the refractive index may be adjusted by, for example, measuring the imaging performance of the projection optical system, such as aberration, and adjusting the refractive index according to the result. May be detected, and the refractive index may be adjusted according to the result. In the former method of measuring the imaging performance of the projection optical system, the aberration of the projection optical system is measured at the time of manufacturing the exposure apparatus, and the value of the refractive index for compensating the aberration is set to the initial value of the refractive index of the liquid. You may. If the refractive index is adjusted as a part of the adjustment at the time of manufacturing as described above, there is an advantage that manufacturing and adjustment are facilitated. Further, an aberration measuring mechanism or the like may be provided in the exposure apparatus itself, and the refractive index of the liquid may be changed according to the aberration measurement result by the aberration measuring mechanism.

On the other hand, fluctuations in factors corresponding to the latter fluctuations in imaging performance include the type of reticle, the state of illumination conditions,
The exposure energy amount that passes through the projection optical system is exemplified. Here, the illumination conditions (σ value,
The optimal illumination is determined depending on the type of pattern provided on the reticle, and when the illumination condition changes, the imaging performance including aberration of the projection optical system changes. Therefore, for example, for each factor such as the type of the reticle and the illumination condition, the value of the refractive index for compensating the imaging performance that changes with the variation of this factor is stored in a memory or the like in advance, and the variation of this factor is stored. May be detected, and the refractive index of the liquid may be adjusted based on the stored relationship. Also,
The imaging performance of the projection optical system changes according to the magnitude of the exposure energy passing through the projection optical system, that is, there is a so-called irradiation fluctuation. In this case, too, the exposure energy and the magnitude of the exposure energy vary. The value of the refractive index for compensating the image performance may be stored in a memory or the like in advance, a change in the factor may be detected, and the refractive index of the liquid may be adjusted based on the stored relationship. In this method, instead of storing the data in the memory, the data may be calculated by a predetermined calculation formula.

By adjusting the refractive index of the liquid in this way, it is effective to correct, among other things, spherical aberration and curvature of field in the imaging performance of the projection optical system. Hereinafter, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1 schematically shows an exposure apparatus according to a first embodiment of the present invention. still,
In FIG. 1, an XYZ coordinate system is adopted.

In FIG. 1, a light source S has a wavelength of 24, for example.
8 nm exposure light is supplied, and the exposure light from the light source S is
The reticle R is illuminated through the illumination optical system IL and the reflecting mirror M under substantially uniform illumination distribution. Here, in this example, a KrF excimer laser light source is used as the light source S, but instead, an Ar that supplies exposure light of 193 nm is used.
An F excimer laser light source, a high-pressure mercury lamp for supplying g-line, i-line, or the like may be used. Although not shown in FIG. 1, the illumination optical system IL includes an optical integrator for forming a surface light source and a light for condensing light from the surface light source to uniformly illuminate the irradiated surface in a superimposed manner. It has a condenser optical system and a variable aperture stop arranged at the position of a surface light source formed by an optical integrator to change the shape of the surface light source. Here, as the shape of the surface light source, there are a shape having a plurality of surface light sources eccentric from the optical axis, an annular shape, a circular shape having a different size, and the like. Such an illumination optical system IL
For example, those disclosed in US Pat. No. 5,329,094 and US Pat. No. 5,576,801 can be used.

The exposure light that has passed and diffracted through the reticle R reaches the wafer W via the projection optical system T, and an image of the reticle R is formed on the wafer. Here, the reticle R is held by the reticle loader RL, and the reticle loader RL is configured to be able to move on the loader table LT at any time on the X axis and the Y axis at an arbitrary speed by the driving device T1. . Here, the moving speed of the reticle loader RL on the loader table LT is detected by the speed sensor SS, and an output from the speed sensor SS is transmitted to the first control unit CPU1.

The wafer W is held by a wafer table WT. The wafer table WT is provided with a side wall for storing the liquid LQ. In this example, the side wall has a configuration in which the entire optical path from the wafer W to the projection optical system T is filled with the liquid LQ.
The wafer table WT is configured to be able to move at an arbitrary speed in the X-axis direction and the Y-axis direction on the holder table HT by the driving device T2.

Here, the first controller CPU1 calculates the moving speed of the wafer table WT on the holder table from the moving speed of the reticle loader RL on the loader table LT and the exposure magnification β of the projection optical system T. Is calculated and transmitted to the driving device T2. The driving device is a first control unit CPU
The wafer table WT is moved on the basis of the moving speed transmitted from Step 1.

FIG. 2 is a diagram showing the configuration of the wafer table WT in detail. In FIG. 2, the optical member closest to the wafer W of the projection optical system T and the metal frame of the projection optical system T are in close contact with each other or are packed so that the liquid LQ does not permeate. Further, the wafer table W
At the bottom of T, a plurality of openings are provided, and by reducing the pressure from a pipe V connected to these openings,
The wafer W is attracted to the wafer table WT. Then, electrodes D1 and D2 are provided on wafer table WT, and ion exchange membranes I1 and I2 are provided around these electrodes D1 and D2, respectively. These ion exchange membranes I1 and I2 separate the periphery of the electrodes D1 and D2 from the region where the exposure light passes through the liquid LQ. Here, the atmosphere around the electrode D1 is the ion exchange membrane I
1 and a partition K1 form a closed space, and an exhaust pipe H1 is connected to this closed space. The electrode D2
Is surrounded by an ion exchange membrane I2 and a partition K2, and an exhaust pipe H2 is connected to the enclosed space. These exhaust pipes H1, H2 are both connected to the mixer K. One end of an inlet tube LD provided with an electromagnetic valve DV is connected to the mixer K, and the other end of the inlet tube LD is located near the wafer table WT.

The voltage applied to the electrodes D1 and D2 is supplied from a power supply unit (not shown), and the voltage supplied from the power supply unit is controlled by the second control unit CPU2. Also, the opening and closing of the solenoid valve DV is controlled by the second control unit CPU2. In this example, these electrodes D1, D2, ion exchange membranes I1, I2, partition walls K1, K2, exhaust pipes H1, H2, mixer K, solenoid valve DV, introduction pipe LD, power supply unit not shown, second control The unit CPU2 constitutes a refractive index adjusting unit.

The operation of the refractive index adjusting means will be described below. In the following description, it is assumed that the liquid LQ is obtained by adding hydrogen chloride as an additive to pure water. First,
When lowering the refractive index of the liquid LQ, the second control unit CPU2
Sends a command to the power supply unit and applies a predetermined voltage between the electrode D1 and the electrode D2 for a predetermined time. At this time,
An oxygen gas is generated from the electrode serving as the anode, and a mixed gas of hydrogen and chlorine is generated from the electrode serving as the cathode. At this time, since the concentration of hydrogen chloride in the liquid LQ decreases, the refractive index of the liquid LQ decreases as can be seen from the above equation (1). Here, the gas generated in the vicinity of each of the electrodes D1 and D2 does not pass through the ion exchange membranes I1 and I2, and can be recovered through the exhaust pipes H1 and H2. The recovered gas is sent to the mixer K. In the mixer K, the recovered gases (oxygen gas, hydrogen gas, hydrogen chloride gas) are mixed, whereby an additive aqueous solution having a higher concentration than the liquid LQ is generated.

When increasing the refractive index of the liquid LQ, the second control unit CPU2 sends a command to the solenoid valve DV to open the solenoid valve DV and to add a high-concentration additive aqueous solution to the liquid LQ. Thereby, the refractive index of the liquid LQ increases. With this configuration, the refractive index of the liquid LQ can be made variable. Now, the memory M1 connected to the second control unit CPU2
In the table, values of the refractive index are stored in the form of a table corresponding to various illumination conditions. Here, the value of the refractive index is a value of the refractive index of the liquid LQ necessary for correcting the aberration generated in the projection optical system T under a certain illumination condition. Also,
The value of the additive concentration in the liquid LQ at a certain point in time is stored in the memory M1 in a form that is constantly updated.

The illumination optical system IL described above stores information on the shape of the surface light source formed by the illumination optical system IL in a second form.
In order to transmit to the control unit CPU2, the second control unit CPU2
Is connected to Here, when the illumination conditions—in this example, the shape of the surface light source—change, this information is stored in the second control unit CPU2.
Is transmitted to At this time, the second control unit CPU2 searches the value of the refractive index corresponding to the transmitted illumination condition from the memory M1, and calculates the concentration of the additive for realizing the refractive index from the above equation (1). . Next, the second control unit CPU2
The electrodes D1 and D2 are used to set the current additive concentration to the calculated additive concentration according to the current additive concentration stored in the memory M1 and the calculated additive concentration.
2 or the solenoid valve DV is controlled.

Thus, the value of the refractive index of the liquid LQ is such that the aberration of the projection optical system T including the liquid LQ is corrected. [Second Embodiment] The second embodiment is significantly different from the first embodiment in that the additive is ethyl alcohol. This ethyl alcohol does not dissolve the resist layer of the wafer W coated with the resist as the photosensitive substrate, and is applied to the optical member closest to the wafer W in the projection optical system T (the optical member in contact with the liquid LQ) and the optical member. There is an advantage that the influence on the applied optical coat is small.

Further, in the second embodiment, the configuration of the refractive index adjusting means is different from that of the first embodiment. Hereinafter, the configuration of the refractive index adjusting means will be described with reference to FIG. In FIG. 3, members having the same functions as those shown in FIG. 2 are denoted by the same reference numerals. Second
FIG. 3 showing the wafer table WT according to the second embodiment differs from that of the first embodiment in that an additive supply pipe LS for supplying an additive to the liquid LQ and pure water is supplied to the liquid LQ. Pure water supply pipe WS for supplying liquid L
It has a discharge pipe L for discharging the liquid LQ so that Q does not overflow from the wafer table WT.

Here, the additive supply pipe LS and the pure water supply pipe W
S and the discharge pipe L are provided with solenoid valves DVLS and DVWS for adjusting the supply amount of the additive and the pure water, and a solenoid valve DVL for adjusting the discharge amount of the liquid LQ, respectively. Opening and closing of the valves DVLS, DVWS, DVL is controlled by the second control unit CPU2. Second
The operation at the time of adjusting the refractive index in the embodiment will be described.

First, when increasing the refractive index of the liquid LQ, the second control unit CPU2 controls the solenoid valve DVLS to add a predetermined amount of additive to the liquid LQ. At this time, the discharge pipe L
, The liquid LQ is discharged by a predetermined amount. The amount of the liquid LQ to be discharged is preferably the same as the amount of the added additive. Thereby, the additive concentration in the liquid LQ increases, and the refractive index increases.

When lowering the refractive index of the liquid LQ, the second controller CPU2 controls the solenoid valve DVWS to add a predetermined amount of pure water to the liquid LQ. At this time, the liquid LQ is discharged from the discharge pipe L by a predetermined amount. It is preferable that the amount of the liquid LQ to be discharged is the same as the amount of the pure water added. Thereby, the concentration of the additive in the liquid LQ decreases, and the refractive index decreases.

Here, the amount of additive and pure water to be added,
The amount of the liquid LQ to be discharged is controlled by the second control unit CPU2. The point that the value of the refractive index is stored in the memory M1 corresponding to the type of the illumination condition and the value of the additive concentration of the liquid LQ at a certain point in time are stored in the first memory described above.
Is the same as the embodiment described above, and based on this information,
The calculation of the additive concentration for realizing a refractive index capable of correcting the aberration of the projection optical system T is also the same as in the first embodiment.

As described above, the second control unit CPU2 in the second embodiment determines the current additive concentration according to the current additive concentration stored in the memory M1 and the calculated additive concentration. And the opening and closing of the solenoid valves DVLS, DVWS, and DVL are controlled so that is the calculated additive concentration. Thereby, the value of the refractive index of the liquid LQ becomes
Is corrected, the aberration of the projection optical system T is corrected. [Third Embodiment] Next, a third embodiment will be described with reference to FIG. The exposure apparatus according to the third embodiment is different from the above-described first and second embodiments in that the exposure apparatus includes an aberration measuring apparatus. In FIG. 4, members having the same functions as those in the examples of FIGS. 1 to 3 described above are denoted by the same reference numerals, and employ the same XYZ coordinate system as in FIG. 1.

In FIG. 4, the light source S has a wavelength of 248 nm.
After the exposure light from the light source S is adjusted to a cross section of a predetermined shape by the beam shaping optical system 11,
The light enters the first fly-eye lens 12. On the emission side of the first fly-eye lens 12, a secondary light source composed of a plurality of light source images is formed. Exposure light from the secondary light source passes through the relay lens systems 13F and 13R, and then passes through the second fly-eye lens 1
5 is incident. This relay lens system includes a front group 13F and a rear group 13R.
Between the 3Rs, a vibrating mirror 14 for preventing speckle on the surface to be irradiated is arranged.

On the exit surface side of the second fly-eye lens 15, a plurality of images of the secondary light source by the first fly-eye lens are formed, and this becomes the tertiary light source. At a position where the tertiary light source is formed, a variable aperture stop 16 capable of setting a plurality of aperture stops having a predetermined shape or a predetermined size is disposed. As shown in FIG. 5, the variable aperture stop 16 is provided with six aperture stops 16a to 16e patterned on a transparent substrate made of quartz or the like in a turret shape. Here, the two aperture stops 16a and 16b having a circular aperture are apertures for changing a value (numerical aperture of the illumination optical system with respect to the numerical aperture of the projection optical system), and have two annular apertures. Aperture 16c, 16d
Are diaphragms having different ring zone ratios. The remaining two aperture stops 16e and 16f are aperture stops having four eccentric apertures. The variable aperture stop 16 is provided with a plurality of aperture stops 16 a by a variable aperture stop drive unit 17.
-16f is driven so as to be located in the optical path.

Returning to FIG. 4, the exposure light from the variable aperture stop 16 is condensed by the condenser lens system 18 and illuminates the reticle blind 19 in a superimposed manner. The reticle blind 19 is disposed conjugate with the pattern forming surface of the reticle R with respect to the relay optical systems 20F and 20R.
The shape of the illumination area on the reticle R is determined by the opening shape of the reticle blind 19. Exposure light from the reticle blind 19 passes through the front group 20F of the relay optical system, the reflecting mirror M and the rear group 20R of the relay optical system to form a reticle R.
An illumination area having a substantially uniform illumination distribution is formed at a predetermined position on the upper side.

The illumination optical system IL according to the first and second embodiments can employ the beam shaping optical system 11 to the relay optical systems 20F and 20R described in this embodiment. Now, the reticle R is mounted on the reticle loader RL, and the reticle loader R
L is movable on the holder table LT in the XY directions and the rotation direction (θ direction) around the Z axis in the figure. The reticle loader RL is provided with a movable mirror RIM, and the reticle interferometer RI detects the position of the reticle loader RL in the XY direction and the θ direction. Also,
The reticle loader RL is driven in the XY direction and the θ direction by a reticle loader drive unit RLD. Here, the output from the reticle interferometer RI is the first control unit CP
The signal is transmitted to U1, and the first control unit CPU1 controls the reticle loader-drive unit RLD.

A bar code reader BR for reading a bar code provided on the reticle R is provided in the middle of a transport path from a reticle stocker (not shown). Information on the type of the reticle R read by the barcode reader BR is transmitted to the second control unit CPU2. Here, in the memory M1 connected to the second control unit CPU2, information on the optimum illumination condition for each type of the reticle R and the value of the refractive index of the liquid LQ optimum for each type of the reticle R are stored. Have been.

Below the reticle R, a predetermined reduction magnification |
A projection optical system T having β | is provided, and a liquid LQ is interposed between the wafer W and the optical member closest to the wafer surface of the projection optical system T. The projection optical system T forms a reduced image of the reticle R on the wafer surface via the liquid LQ. The wafer W is suction-fixed to the wafer table WT. The wafer table WT has Z actuators ZD1 and ZD for moving the wafer table WT itself in the Z-axis direction and tilting (tilting with respect to the Z-axis).
The wafer stage WTS is mounted on the wafer stage WTS that can move in the XY directions with respect to the surface plate via the ZD3 and ZD3. The wafer stage WTS includes a wafer stage drive unit W
D driven. The side wall of the wafer table is mirror-finished, and this portion serves as a moving mirror of the wafer interferometer WI. Here, the drive of the wafer stage drive unit WD is controlled by the above-described first control unit CPU1, and the output from the wafer interferometer WI is output by the first control unit CPU1.
It is configured to be transmitted to.

The projection optical system T is provided with a focus sensor AF for measuring a distance in the Z direction between the projection optical system T and the wafer W. The focus sensor AF irradiates light onto the wafer surface via an optical element close to the wafer W in the projection optical system T, receives light reflected by the wafer via the optical element, and receives the light at the light receiving position. Is used to measure the distance in the Z direction between the projection optical system T and the wafer W. Such a focus sensor A
The configuration of F is disclosed, for example, in Japanese Patent Application Laid-Open No. 6-66543.

Now, also in the third embodiment, the additive supply pipe LS for supplying the high-concentration additive aqueous solution stored in the additive storage unit LST to the liquid LQ and the pure water storage unit WST A pure water supply pipe WS for supplying the stored pure water to the liquid LQ; and adjusting the supply amounts of the additive aqueous solution and the pure water to the additive supply pipe LS and the pure water supply pipe WS. Solenoid valves DVLS and DVWS are provided. The wafer table WT is provided with a discharge pipe L for discharging the liquid LQ so that the liquid LQ does not overflow from the wafer table. The discharge pipe L is used to adjust the discharge amount of the liquid LQ. Are provided. Opening and closing of these solenoid valves DVLS, DVWS, DVL is performed by the second control unit CP, as in the above-described second embodiment.
It is controlled by U2.

On the wafer table WT, an aberration measuring unit AS for measuring the aberration of the projection optical system and a liquid L
Additive concentration detector DS for detecting additive concentration of Q
Are provided. Here, as the aberration measuring unit AS, for example, the one disclosed in JP-A-6-84757 can be used. Here, the outputs from the aberration measurement unit AS and the additive concentration detection unit DS are output from the second control unit CPU2.
Is transmitted to The output from the additive concentration detection unit DS is stored as a value of the additive concentration of the liquid LQ at a certain point in time in the memory M1 via the second control unit CPU2.

Next, the operation of the third embodiment will be described. First, while the reticle R is taken out from a reticle stocker (not shown) and placed on the reticle loader RL, the barcode reader BR reads a barcode provided on the reticle R, and the information is read by the second control. To the CPU 2. The second control unit CPU2 reads information related to the illumination condition corresponding to the type of the reticle R stored in the memory M1, and according to the information,
The variable aperture stop drive unit 17 is controlled to control the aperture stop 16
A predetermined one of a to 16f is located in the optical path.
Further, based on the value of the refractive index of the liquid LQ stored in the memory M1, the second control unit CPU2 calculates the concentration of the additive for realizing the refractive index from the above equation (1). Thereafter, the current additive concentration is set to the calculated additive concentration according to the current additive concentration detected by the additive concentration detecting unit DS and stored in the memory M1 and the calculated additive concentration. And the solenoid valves DVLS and DV
Controls opening and closing of WS and DVL.

Thus, the value of the refractive index of the liquid LQ is such that the aberration of the projection optical system T including the liquid LQ is corrected. Thereafter, the position and tilt of the wafer W in the Z direction are detected by the focus sensor AF, and the wafer W is detected.
So that the Z actuators ZD1 and Z
D2 and ZD3 are driven. In this state, the exposure light from the light source S is guided to the reticle R via the illumination optical system, and the first control unit CPU1 detects the positions of the reticle R and the wafer W by the reticle interferometer RI and the wafer interferometer WI. Then, the reticle loader-driving unit RLD and the wafer stage driving unit WD are driven to move the reticle R and the wafer W under the speed ratio of the projection optical system T at the projection magnification | β |. As a result, the pattern on the reticle R is transferred onto the wafer W under a good image formation state.

The image forming performance (aberration etc.) of the projection optical system T is not always constant, but changes due to temperature change, atmospheric pressure change, temperature rise due to the projection optical system T absorbing exposure light, and the like. There is. Therefore, in the third embodiment, the aberration (imaging performance) of the actual projection optical system T is measured by the aberration measurement unit AS, and the liquid L is measured based on the measurement result.
It is configured to adjust the value of the refractive index of Q.

More specifically, in the third embodiment, the value of the refractive index of the liquid LQ capable of correcting the aberration is stored in the memory M1 in a form corresponding to the aberration value of the projection optical system. . Then, the aberration of the projection optical system T detected by the aberration measurement unit AS is transmitted to the second control unit CPU2. The second control unit CPU2 reads the value of the refractive index of the liquid LQ stored in the memory M1, obtains the additive concentration from the above equation (1) so as to obtain the value of the refractive index, and obtains the liquid LQ.
Is set to the additive concentration so that the solenoid valves DVLS, DVW
The opening and closing of S and DVL are controlled.

With this configuration, even if there is an environmental change (a change in temperature, a change in atmospheric pressure, a change due to exposure light absorption) of the projection optical system T, it is possible to maintain good imaging performance. The measurement by the aberration measuring unit AS does not need to be performed at all times, but may be performed at predetermined intervals. [Fourth Embodiment] Next, a fourth embodiment will be described with reference to FIG. In the fourth embodiment, the optical path between the projection optical system and the wafer is not entirely filled with liquid, but a part of the optical path is filled with liquid.

6 (a) and 6 (b), members having the same functions as those of the first and second embodiments shown in FIGS. In the fourth embodiment shown in FIGS. 6A and 6B, instead of storing the liquid LQ by the side wall of the wafer holder WT, the containers C1, C2 made of a material (for example, quartz or the like) that transmits exposure light are used. The configuration in which the liquid LQ is filled in C2 is different from the above-described first and second embodiments. With this configuration, among the effects of the first and second embodiments described above, although there is no effect of increasing the numerical aperture or increasing the effective depth of focus, the aberration of the projection optical system T is continuously increased. This has the effect of enabling adjustment of image performance).

In the fourth embodiment, the containers C1 and C2 containing the liquid LQ are connected to the projection optical system T.
And may be provided integrally. In the above-described first to fourth embodiments, pure water is used as the liquid LQ, but the liquid LQ is not limited to pure water.

[0052]

As described above, according to the present invention, the imaging performance of the projection optical system can be continuously adjusted without vibration. In addition, it is possible to achieve both an increase in the numerical aperture (or an effective increase in the depth of focus) and adjustment of the imaging performance.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an entire exposure apparatus according to first and second embodiments of the present invention.

FIG. 2 is a sectional view showing a main part of the exposure apparatus according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of an exposure apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic view showing an exposure apparatus according to a third embodiment of the present invention.

FIG. 5 is a schematic view showing a part of an exposure apparatus according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a main part of an exposure apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

S: Light source T2: Drive unit IL: Illumination optical system M1: Memory M: Reflector V: Decompression tube T: Projection optical system D1, D2: Electrode W: Wafer I1, I2: Ion exchange membrane LQ: Liquid K1, K2 Partition wall R ... Reticle H1, H2 ... Piping RL ... Reticle loader L ... Discharge pipe LT ... Loader table LD ... Introducing pipe SS ... Sensor WS ... Pure water supply pipe WT ... Wafer table LS ... Additive supply pipe T1 ... Drive device

Claims (11)

[Claims] An illumination optical system for illuminating a pattern provided on a reticle, and a projection optical system for forming an image of the pattern on a photosensitive substrate, wherein the projection optical system, the photosensitive substrate, An exposure apparatus for performing exposure via a liquid located at least in a part of an optical path between the liquid and an exposure apparatus, comprising: a refractive index adjusting unit for adjusting a refractive index of the liquid. 2. An exposure apparatus according to claim 1, wherein said refractive index adjusting means adjusts the refractive index of said liquid so as to correct the imaging performance of said projection optical system. 3. An apparatus according to claim 1, further comprising an imaging performance measuring unit for measuring an imaging performance of said projection optical system, wherein said refractive index adjusting unit adjusts a refractive index of said liquid so as to correct said imaging performance. 3. The method according to claim 2, wherein
Exposure apparatus according to the above. 4. The image forming apparatus according to claim 1, further comprising: a fluctuation factor detecting unit configured to detect a state of a factor of a change in the imaging performance of the projection optical system, wherein the refractive index adjusting unit adjusts the image forming performance in accordance with the state of the factor. 2. The exposure apparatus according to claim 1, wherein a refractive index of the liquid is adjusted so as to make a correction. 5. The illumination optical system is configured to be able to change an illumination condition for the reticle, the variation factor detecting means detects a state of the illumination condition, and the refractive index adjusting means is configured to change the illumination condition. Depending on the change,
The exposure apparatus according to claim 4, wherein a refractive index of the liquid is adjusted so as to correct the imaging performance. 6. The variation factor detecting means determines a type of the reticle, and the refractive index adjusting means determines a type of the reticle according to the type of the reticle.
The exposure apparatus according to claim 4, wherein a refractive index of the liquid is adjusted so as to correct the imaging performance. 7. A photosensitive substrate holder for holding the photosensitive substrate, wherein the photosensitive substrate holder has a side wall for filling an optical path between the projection optical system and the photosensitive substrate with the liquid. The exposure apparatus according to any one of claims 1 to 6, further comprising a supply / recovery unit for supplying the liquid to the photosensitive substrate holder and recovering the liquid from the photosensitive substrate holder. 8. An additive supply unit for supplying an additive for adjusting a refractive index to the liquid, and an additive recovery unit for recovering the additive from the liquid. 8. The method according to claim 1, further comprising:
The exposure apparatus according to claim 1. 9. A projection optical system comprising: a step of illuminating a reticle under predetermined illumination conditions; and a step of transferring a pattern provided on the reticle to a photosensitive substrate using a projection optical system. An exposure method for directing light from the substrate to the photosensitive substrate via a predetermined liquid, comprising a step of adjusting a refractive index of the liquid in order to correct an imaging performance of the projection optical system. Exposure method. 10. A projection optical system comprising: a step of illuminating a reticle under predetermined illumination conditions; and a step of transferring a device pattern provided on the reticle to a photosensitive substrate using a projection optical system. In a device manufacturing method for guiding light from a system to the photosensitive substrate through a predetermined liquid, a refractive index of the liquid is changed when at least one of the reticle and the illumination condition is changed. Device manufacturing method. 11. An illumination optical system for illuminating a pattern provided on a reticle, and a projection optical system for forming an image of the pattern on a photosensitive substrate, wherein the projection optical system, the photosensitive substrate, In a method of manufacturing an exposure apparatus that performs exposure via a liquid located at least in a part of an optical path between, a step of measuring the imaging performance of the projection optical system, based on the measured imaging performance, Determining an initial value of the refractive index of the liquid.