JP2002203762A - Exposure amount setting method, exposure system and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily set a proper exposure amount. SOLUTION: A control unit irradiates a measurement mark PM on a reticle R with illuminating light IL and scans a slit plate 90, in such a way that a slit 22 is relatively scanned with respect to a space image of the mark which is formed on the image surface and measures the light intensity distribution of the space image according to the photoelectric transfer signal from a photosensor in each of several positions in the direction of the optical axis (in the direction of the Z axis) of the slit plate 90. The control unit finds a peak value of the photoelectric transfer signal corresponding to the best focus position, and sets the exposure amount for pattern transfer according to the result of comparison between the peak value and the reference intensity value. The exposure amount can be properly set according to the result of comparison by determining the reference intensity value with a specified relation with the best exposure amount for exposing the measurement mark PM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure setting method,
The present invention relates to an exposure apparatus and a device manufacturing method, and more particularly, to an exposure amount setting method for setting an exposure amount when a mask pattern is transferred onto a substrate via a projection optical system, which is suitable for implementing the exposure amount setting method. The present invention relates to an exposure apparatus and a device manufacturing method using the exposure apparatus.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor element or a liquid crystal display element is manufactured by a photolithography process, a pattern of a photomask or a reticle (hereinafter, collectively referred to as “reticle”) is formed on a surface through a projection optical system. Exposure apparatus for transferring onto a substrate such as a wafer or a glass plate on which a photosensitive agent such as a photoresist is coated, for example, a step-and-repeat type reduction projection exposure apparatus (so-called stepper), a step-and-scan method (A so-called scanning stepper) or the like is used.

However, when a semiconductor device or the like is manufactured using a projection exposure apparatus, an exposure region (a region irradiated with illumination light) on a substrate is required to minimize the occurrence of exposure failure due to defocus. ) Must be within the range of the depth of focus of the best imaging plane of the projection optical system. For this purpose, a focus position detection system (focus) that accurately measures the best imaging plane or the best focus position of the projection optical system and detects the position of the substrate in the optical axis direction of the projection optical system based on the measurement result. It is important to calibrate the detection system).

As a method of measuring the best focus position of the projection optical system, a predetermined measurement mark on the reticle, for example, a line and space mark, is changed while changing the position of the substrate in the optical axis direction of the projection optical system at predetermined step intervals. The resist is sequentially transferred to different regions on the substrate via a projection optical system, and the line width of a resist image formed on the substrate after the substrate is developed is measured using an SEM (scanning electron microscope) or the like, and the line width is measured. Conventionally, a method of setting a position in the optical axis direction of a substrate corresponding to a resist image having a desired line width as a best focus position (hereinafter, referred to as a “printing method”) has been mainly performed.

In addition, a measurement mark formed on a reticle, for example, a line and space mark is illuminated with illumination light, and a spatial image (projection image) of the measurement mark formed by the projection optical system is used by using a spatial image measuring device. A method of measuring and calculating the best focus position based on the measurement result (hereinafter, referred to as “aerial image measurement method”) is also performed.

However, it is difficult to transfer a fine pattern onto a substrate with high accuracy only by suppressing the occurrence of defocus by focus calibration. Particularly, a fine pattern is formed on a substrate with a desired line width. It is important that the exposure amount at the time of exposure is adjusted to the best exposure amount (best dose amount) determined according to the resist sensitivity.

Conventionally, the setting of the best exposure amount has been performed by the above-described printing method. That is, the above-described printing method is repeatedly performed under a plurality of exposure conditions that differ only in the exposure amount, and the line width of the resist image corresponding to the best focus is obtained for each exposure condition. The exposure condition when a predetermined line width is determined from the value, that is, the exposure amount is determined as the best exposure amount.

[0008]

In an exposure apparatus, the exposure amount is feedback-controlled using the above-mentioned best exposure amount as an exposure amount control target value based on a measurement value of a light amount detector arranged in an illumination optical system. I have. On the other hand, in an exposure apparatus, due to cloudiness of an optical system such as an illumination optical system and a projection optical system,
The illumination light transmittance in the illumination light path decreases with time. However, when cloudiness occurs behind the light path of the light amount detector, it is difficult to detect the cloudiness.

In such a case, if the exposure is performed using the initially determined best exposure amount as the exposure amount control target value, an exposure defect due to an insufficient exposure amount occurs. For this reason, in the conventional exposure apparatus, it is necessary to update the best exposure amount (exposure amount control target value) by measuring the best exposure amount by the above-described printing method at a constant interval.

However, in the measurement of the best exposure amount by the printing method, it is necessary to go through a series of procedures of exposure, development, and line width measurement, so that the measurement takes too much time and causes a decrease in throughput. For this reason, the best exposure amount cannot be frequently measured, and the measurement interval of the best exposure amount has inevitably increased. However, with the recent miniaturization of patterns, a decrease in the exposure amount (insufficient illuminance on the image plane) due to the deterioration of the best exposure amount in the time between two successive measurement of the best exposure amount is becoming negligible. is there.

By the way, the best focus position of the projection optical system changes due to irradiation of the projection optical system with illumination light. Conventionally, the fluctuation of the best focus position (irradiation fluctuation of the best focus position) due to this illumination light irradiation is
In order that the projection optical system is continuously irradiated with illumination light so as not to cause defocusing at the time of exposure, it is necessary to sequentially transfer marks to different regions on the substrate while step-moving the substrate in the optical axis direction. Repeatedly, a time change curve of the irradiation variation at the best focus position is obtained from the line width measurement results of the resist images of those marks, and the focus detection system is calibrated at predetermined intervals based on the time change curve.

However, it takes a long time to measure the above-described time change curve of the irradiation fluctuation at the best focus position by the printing method.

On the other hand, it is conceivable to obtain a time change curve of the irradiation fluctuation at the best focus position by simulation. However, it is inevitable that the measurement accuracy is reduced as compared with the case where actual measurement is performed. The probability of occurrence of focus increases.

The present invention has been made under such circumstances, and a first object of the present invention is to provide an exposure setting method and an exposure apparatus capable of easily setting an appropriate exposure. is there.

It is a second object of the present invention to provide an exposure apparatus capable of suppressing a decrease in exposure accuracy due to defocusing when exposure is continuously repeated.

A third object of the present invention is to provide a device manufacturing method capable of improving device productivity.

[0017]

According to a first aspect of the present invention, there is provided an exposure amount setting method, comprising the steps of:
L) is an exposure setting method for setting an exposure when transferring onto a substrate (W) via a predetermined measurement mark (P).
M) is illuminated with illumination light (IL), a spatial image (PM ') of the measurement mark is formed on the image plane via the projection optical system, and the measurement arranged on the image plane side of the projection optical system Pattern for scanning relative to the aerial image, and converting a photoelectric conversion signal corresponding to the intensity of the illumination light via the measurement pattern into a plurality of signals in the optical axis direction of the measurement pattern. An actual measurement step for each of the positions; determining a best focus position of the projection optical system based on the photoelectric conversion signals obtained for each of the plurality of positions in the actual measurement step; A calculating step of calculating a target intensity value based on the photoelectric conversion signal; comparing the calculated target intensity value with a reference intensity value obtained in advance, and calculating an exposure amount during the pattern transfer based on the comparison result. Exposure setting to be set And a setting step.

According to this, a predetermined measurement mark is illuminated by the illumination light, a spatial image of the measurement mark is formed on an image plane via a projection optical system, and a measurement pattern is relatively formed on the spatial image. And a photoelectric conversion signal corresponding to the intensity of the illumination light via the measurement pattern is obtained for each of a plurality of positions in the optical axis direction of the measurement pattern. Then, a best focus position of the projection optical system is obtained based on the photoelectric conversion signals obtained for each of the plurality of positions, and a target intensity value is calculated based on the photoelectric conversion signal corresponding to the best focus position. The target intensity value is compared with a predetermined reference intensity value, and an exposure amount at the time of pattern transfer is set based on the comparison result. Here, by setting the reference intensity value to a value having some relationship with the best exposure amount when exposing the measurement mark, based on the result of comparing the calculated target intensity value with the reference intensity value, Exposure can be set appropriately. Therefore, it is possible to easily set an appropriate exposure amount by aerial image measurement without going through a process such as printing and development as in the related art.

In this case, various methods for determining the reference intensity value are conceivable. For example, as in the exposure setting method according to the second aspect, the reference intensity value is set at a target light amount for the predetermined measurement mark. The peak value of the photoelectric conversion signal corresponding to the best focus position measured in advance under the reference measurement condition in which is set, or the exposure setting method according to claim 3. The reference intensity value is the photoelectric conversion signal corresponding to the best focus position measured in advance under the reference measurement condition in which the light amount is set to the target light amount for the predetermined measurement mark, and a line forming the measurement mark The intensity value may be set based on the line width of the pattern. In the latter case, for example, a slice level at which a distance between two intersections between the photoelectric conversion signal waveform and a predetermined slice level matches a value obtained by multiplying the line width of the line pattern by a projection magnification can be used as a reference intensity value. .

In the exposure amount setting method according to the first aspect, as in the exposure amount setting method according to the fourth aspect, under the reference measurement condition in which the light amount is set to the target light amount for the predetermined measurement mark, The predetermined measurement mark is illuminated with illumination light, a spatial image of the measurement mark is formed on an image plane via the projection optical system, and the measurement pattern is scanned relative to the spatial image. A reference measurement step of obtaining a photoelectric conversion signal corresponding to the intensity of the illumination light via the measurement pattern for each of a plurality of positions in the optical axis direction of the measurement pattern; and a reference measurement step for each of the plurality of positions. The best focus position of the projection optical system under the reference measurement condition is obtained based on the photoelectric conversion signal, and the reference intensity is obtained based on the photoelectric conversion signal corresponding to the best focus position. The reference measurement step and the reference intensity value determination step are repeatedly performed for a plurality of different exposure conditions, and the actual measurement step and the calculation step Is performed under any one of the exposure conditions selected from the exposure conditions, and in the exposure amount setting step, the reference intensity value corresponding to the selected exposure condition and the target intensity value calculated in the calculation step are The exposure amount at the time of the pattern transfer can be set based on the comparison result.

In each of the exposure setting methods according to the first to fourth aspects, as in the exposure setting method according to the fifth aspect,
The target light amount is determined as the light amount at which the line width of the resist image obtained by transferring the predetermined measurement mark onto the substrate via the projection optical system becomes the predetermined line width at the time of best focus. be able to. In this case, for example, a light amount in which the line width of the resist image substantially coincides with the line width of the line width of the line pattern forming the measurement mark times the projection magnification can be set as the target light amount.

In the exposure setting method according to the fourth aspect, as in the exposure setting method according to the sixth aspect, the exposure conditions include an illumination condition, a pattern type to be exposed, a target line width, and the projection optical system. It may include at least one of the numerical apertures of the system.

According to a seventh aspect of the present invention, there is provided an exposure apparatus for transferring a pattern of a mask (R) onto a substrate (W) via a projection optical system (PL).
An illumination device (10) for illuminating an object by means of; a pattern forming member (90) arranged on the image plane side of the projection optical system and having a measurement pattern (22) formed thereon; A photoelectric conversion element (24) for outputting a photoelectric conversion signal according to the intensity of the illumination light; and a measurement mark (R) arranged on substantially the same plane as the plane on which the mask is arranged.
M) is illuminated by the illumination device, and the measurement pattern is relatively scanned with respect to the aerial image in a state where the aerial image (PM ′) of the measurement mark is formed on the image plane. A measurement process for scanning the pattern forming member and measuring a light intensity distribution corresponding to the aerial image at each of a plurality of positions in the optical axis direction of the pattern forming member based on a photoelectric conversion signal from the photoelectric conversion element. Apparatus (20)
Obtaining a best focus position of the projection optical system based on a photoelectric conversion signal corresponding to the aerial image measured for each of the plurality of positions by the measurement processing device, and obtaining the photoelectric conversion signal corresponding to the best focus position While calculating the target intensity value based on, the calculated target intensity value is compared with a predetermined reference intensity value, based on the comparison result,
An exposure setting device (20) for setting an exposure at the time of pattern transfer.

According to this, the measurement mark arranged on substantially the same surface as the surface on which the mask is arranged is illuminated by the illumination device by the measurement processing device, and a spatial image of the measurement mark is formed on the image plane. In this state, the pattern forming member is scanned so that the measurement pattern is relatively scanned with respect to the aerial image, and the light intensity distribution corresponding to the aerial image is formed based on the photoelectric conversion signal from the photoelectric conversion element. It is measured at each of a plurality of positions in the optical axis direction of the member. Then, the exposure setting device determines the best focus position of the projection optical system based on the photoelectric conversion signal corresponding to the aerial image measured at each of the plurality of positions, and obtains the photoelectric conversion signal corresponding to the best focus position. Is calculated based on the target intensity value, and an exposure amount at the time of pattern transfer is set based on a result of comparing the calculated target intensity value with a predetermined reference intensity value. Here, by setting the reference intensity value to a value having some relationship with the best exposure amount when exposing the measurement mark, based on the result of comparing the calculated target intensity value with the reference intensity value, Exposure can be set appropriately. Therefore, it is possible to easily set an appropriate exposure amount by aerial image measurement without going through a process such as printing and development as in the related art.

In this case, an intensity value determined by various standards can be used as the reference intensity value. For example, as in the exposure apparatus according to claim 8, the reference intensity value is determined by the predetermined measurement. 10. The exposure apparatus according to claim 9, wherein a peak value of the photoelectric conversion signal corresponding to the best focus position under a reference measurement condition in which a light amount is set to a target light amount for a mark can be obtained. The reference intensity value is the photoelectric conversion signal corresponding to the best focus position under the reference measurement condition in which the light amount is set to the target light amount for the predetermined measurement mark, and the line width of a line pattern forming the measurement mark The intensity value may be set based on the above. In the latter case, for example, a slice level at which a distance between two intersections between the photoelectric conversion signal waveform and a predetermined slice level matches a value obtained by multiplying the line width of the line pattern by a projection magnification can be used as a reference intensity value. .

[0026] In the exposure apparatus according to claim 7,
As in the exposure apparatus according to claim 10, under a reference measurement condition in which a light amount is set to a target light amount for the measurement mark,
Measurement of the light intensity distribution corresponding to the aerial image of the measurement mark for each of the plurality of positions in the optical axis direction of the pattern forming member is performed under a plurality of different exposure conditions, and is determined based on the measurement result. A storage device (51) that stores a reference intensity value for each exposure condition determined based on the photoelectric conversion signal corresponding to the best focus position of the projection optical system under the determined reference measurement condition. In the case, the measurement processing device performs the measurement under the set exposure condition of the plurality of exposure conditions, and the exposure amount setting device is measured by the measurement processing device for each of the plurality of positions. Calculating a target intensity value corresponding to the aerial image, and comparing the calculated target intensity value with a reference intensity value corresponding to the set exposure condition. Based on the compare result, he is possible to setting the exposure amount at the time of the pattern transfer.

In each of the exposure apparatuses according to the seventh to tenth aspects, as in the exposure apparatus according to the eleventh aspect, the target light amount is obtained by transferring the measurement mark onto the substrate via the projection optical system. It can be assumed that the line width of the obtained resist image is determined as the amount of light that becomes a predetermined line width at the time of best focus. In this case, for example, a light amount in which the line width of the resist image substantially coincides with the line width of the line width of the line pattern forming the measurement mark times the projection magnification can be set as the target light amount.

In the exposure apparatus according to the tenth aspect, as in the exposure apparatus according to the twelfth aspect, the exposure conditions include an illumination condition, a pattern type to be exposed, a target line width, and a numerical aperture of the projection optical system. May be included.

In each of the exposure apparatuses according to the seventh to twelfth aspects, as in the exposure apparatus according to the thirteenth aspect, the photoelectric conversion that constitutes a signal processing system (50) having a predetermined dynamic range together with the photoelectric conversion elements. The signal processing circuit further includes a signal processing circuit to which a signal is input, and the measurement processing device includes a signal sensitivity setting device configured to set a signal sensitivity of the signal processing system. When measuring the light intensity distribution corresponding to the aerial image based on the signal, based on the integral value of the photoelectric conversion signal, the signal processing system so that the dynamic range of the signal processing system can be utilized most effectively. Can be set.

An exposure apparatus according to claim 14 illuminates a mask (R) with illumination light (IL) and transfers the pattern of the mask onto a substrate (W) via a projection optical system (PL). An illumination device (10) for illuminating an object with illumination light; a pattern forming member (90) disposed on an image plane side of the projection optical system and having a measurement pattern (22) formed thereon; A photoelectric conversion element (24) for outputting a photoelectric conversion signal according to the intensity of the illumination light via the measurement pattern; and a measurement mark (RM) arranged on substantially the same plane as the plane on which the mask is arranged Is illuminated by the illumination device, and the spatial image (R
In the state in which M ′) is formed, the pattern forming member is scanned so that the measurement pattern is relatively scanned with respect to the aerial image, and based on a photoelectric conversion signal from the photoelectric conversion element, A measurement processing device (20) for measuring a light intensity distribution corresponding to an aerial image at each of a plurality of positions in the optical axis direction of the pattern forming member; and detecting a position of the substrate in the optical axis direction of the projection optical system. A position detection system (60a, 60b); a relationship between a change in the irradiation amount of the illumination light to the projection optical system and a change in the best focus position of the projection optical system is measured in advance using the measurement processing device; The storage device (5) in which the relationship information is stored
And 1) a correction device (20, 81) for correcting a detection offset of the position detection system when transferring the mask pattern based on the information on the relationship.

According to this, the measurement mark arranged substantially on the same plane as the surface on which the mask is arranged is illuminated by the illumination device, and the spatial image of the measurement mark is formed on the image plane. While scanning the pattern forming member so that the measurement pattern is relatively scanned, the light intensity distribution corresponding to the aerial image in the optical axis direction of the pattern forming member is determined based on the photoelectric conversion signal from the photoelectric conversion element. A measurement processing device for measuring at each of a plurality of positions is provided. In the storage device,
The relationship between the change in the irradiation amount of the illumination light to the projection optical system and the change in the best focus position of the projection optical system is measured in advance using a measurement processing device, and information on the relationship is stored. Here, for example, the relationship is that the measurement pattern is relatively scanned with respect to the spatial image of the measurement mark formed on the image plane in a state where the projection optical system is continuously irradiated with the illumination light. By scanning the pattern forming member such that the light intensity distribution corresponding to the aerial image is measured at each of a plurality of positions in the optical axis direction of the pattern forming member based on the photoelectric conversion signal from the photoelectric conversion element, it changes every moment. The best focus position of the projection optical system to be measured can be obtained by measuring continuously or intermittently at predetermined intervals. The correction device corrects the detection offset of the position detection system that detects the position of the substrate in the optical axis direction of the projection optical system when transferring the mask pattern, based on the information on the relationship. Therefore, when exposure (transfer of a mask pattern onto a substrate) is repeatedly performed continuously, a decrease in exposure accuracy due to defocus is suppressed, and the mask pattern is accurately transferred onto the substrate via a projection optical system. It is possible to do.

An exposure apparatus according to claim 15 illuminates a mask (R) with illumination light (IL) and transfers the pattern of the mask onto a substrate (W) via a projection optical system (PL). An illumination device (10) for illuminating an object with illumination light; a pattern forming member (90) disposed on an image plane side of the projection optical system and having a measurement pattern (22) formed thereon; A photoelectric conversion element (24) that outputs a photoelectric conversion signal according to the intensity of the illumination light via the measurement pattern; and a signal processing circuit (42) that receives the photoelectric conversion signal from the photoelectric conversion element. A measurement system for measuring the optical characteristics of the projection optical system based on the output of the signal processing system; and setting the signal sensitivity of the signal processing system for each of a plurality of different exposure conditions. Signal sensitivity setting device (2 ) And; comprises.

According to this, a photoelectric conversion element for outputting a photoelectric conversion signal corresponding to the intensity of illumination light through the measurement pattern of the pattern forming member arranged on the image plane side of the projection optical system, and the photoelectric conversion element And a signal processing circuit to which the photoelectric conversion signal from the element is input. Then, the measuring device measures the optical characteristics of the projection optical system based on the output of the signal processing system. Here, the signal sensitivity setting device sets the signal sensitivity of the signal processing system for each of a plurality of different exposure conditions. For this reason, it is possible to measure the optical characteristics of the projection optical system by setting the signal sensitivity of the signal processing system appropriately, for example, so that the dynamic range of the signal processing system can be used most effectively regardless of the exposure conditions. Becomes

In this case, as in the exposure apparatus according to the sixteenth aspect, the signal sensitivity setting apparatus has storage means for storing signal sensitivity information of the signal processing system corresponding to the plurality of different exposure conditions. It can be.

A device manufacturing method according to claim 17 is
A device manufacturing method including a lithography step, wherein exposure is performed in the lithography step using each of the exposure apparatuses according to claims 7 to 16.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. FIG. 1 shows a schematic configuration of an exposure apparatus 100 according to one embodiment. The exposure apparatus 100 is a step-and-scan type scanning projection exposure apparatus, that is, a so-called scanning stepper.

The exposure apparatus 100 holds an illumination system 10 as an illumination device including a light source and an illumination optical system, a reticle stage RST for holding a reticle R as a mask, a projection optical system PL, and a wafer W as a substrate. A wafer stage WST as a substrate stage that can move freely in the XY plane and a control system for controlling these are provided.

As shown in FIG. 2, the illumination system 10 includes a light source 1, a beam shaping optical system 2, an energy rough adjuster 3,
A fly-eye lens 4 as an optical integrator, an illumination system aperture stop plate 5, a beam splitter 6, a first relay lens 7A, a second relay lens 7B, a fixed reticle blind 11, a movable reticle blind 12, and the like are provided.

Here, the components of the illumination system 10 will be described. As the light source 1, a KrF excimer laser (oscillation wavelength 248 nm), an ArF excimer laser (oscillation wavelength 193 nm) or an F ₂ laser (oscillation wavelength 15 nm) is used.
7 nm) and the like are used. The light source 1 is actually installed on a floor surface in a clean room where the exposure apparatus main body is installed, or on a room (service room) having a low degree of cleanness different from the clean room, and is connected via a drawing optical system (not shown). Connected to the incident end of the beam shaping optical system 2.

The beam shaping optical system 2 shapes the cross-sectional shape of the laser beam LB pulsed from the light source 1 so that the laser beam LB efficiently enters a fly-eye lens 4 provided behind the optical path of the laser beam LB. And includes, for example, a cylinder lens and a beam expander (both not shown).

The energy rough adjuster 3 is arranged on the optical path of the laser beam LB behind the beam shaping optical system 2, and here, a plurality of light sources having different transmittances (= 1−dimming ratio) are provided around the rotating plate 31. (For example, six) ND filters (only two ND filters 212A and 21D are shown in FIG. 1), and the rotating plate 31 is driven by a driving motor 33.
, The transmittance for the incident laser beam LB can be switched from 100% in a geometric progression in a plurality of steps. Drive motor 33
Is controlled by the main controller 20.

The fly-eye lens 4 is arranged on the optical path of the laser beam LB behind the energy rough adjuster 3, and has a surface composed of a number of point light sources (light source images) for illuminating the reticle R with a uniform illuminance distribution. Form a light source, a secondary light source. Hereinafter, the laser beam emitted from the secondary light source is referred to as “illumination light IL”. Note that, instead of the fly-eye lens 4, a rod-type (internal reflection type) integrator may be used as an optical integrator.

An illumination system aperture stop plate 5 made of a disc-shaped member is arranged near the exit surface of the fly-eye lens 4. The illumination system aperture stop plate 5 is provided at substantially equal angular intervals, for example, an aperture stop composed of a normal circular aperture, an aperture stop composed of a small circular aperture, and a small coherence factor σ value (small σ stop); A ring-shaped aperture stop (ring stop) for annular illumination, and a modified aperture stop formed by eccentrically arranging a plurality of apertures for the modified light source method (only two of these aperture stops are shown in FIG. 2). Etc.) are arranged. The illumination system aperture stop plate 5 is configured to be rotated by a drive device 37 such as a motor controlled by the main controller 20, whereby any one of the aperture stops is selectively placed on the optical path of the illumination light IL. Is set to

A beam splitter 6 having a small reflectance and a large transmittance is disposed on the optical path of the illumination light IL behind the illumination system aperture stop plate 5, and a reticle blind 8 is interposed on the optical path behind the reticle blind 8. 1 relay lens 7A and 2nd
A relay optical system including a relay lens 7B is provided.

The reticle blind 8 comprises a fixed reticle blind 11 having a fixed opening and a movable reticle blind 12 having a variable opening. The fixed reticle blind 11 is disposed in the vicinity of the pattern surface of the reticle R or on a surface slightly defocused from the conjugate plane thereof, and a rectangular slit-shaped illumination area on the reticle R (the X-axis direction which is a direction orthogonal to the plane of FIG. 1). A rectangular opening defining a rectangular slit-shaped illumination area (IAR) having a predetermined width in the Y-axis direction, which is the horizontal direction in the plane of the paper of FIG. 1, is formed. The movable reticle blind 12 is disposed on a conjugate plane with respect to the pattern surface of the reticle R, and corresponds to a scanning direction (here, Y-axis direction) and a non-scanning direction (X-axis direction) at the time of scanning exposure. It has an opening whose position and width in the direction of movement are variable.
In FIG. 2, for simplicity of description, the movable reticle blind 12 is shown as being disposed near the illumination system side with respect to the reticle R.

On the optical path of the illumination light IL behind the second relay lens 7B constituting the relay optical system, a bending mirror 9 for reflecting the illumination light IL passing through the second relay lens 7B toward the reticle R is arranged. Have been.

The operation of the illumination system 10 constructed as described above will be briefly described. A laser beam LB pulsed from a light source 1 enters a beam shaping optical system 2 where a rear fly-eye lens is provided. After its cross-sectional shape is shaped so as to be incident on the energy rough adjuster 4 efficiently, it is incident on the energy rough adjuster 3. Then, any one of N
The laser beam LB transmitted through the D filter enters the fly-eye lens 4. Thereby, the fly-eye lens 4
A surface light source composed of a number of point light sources (light source images), that is, a secondary light source is formed at the exit end of the light source. The illumination light IL emitted from the secondary light source passes through one of the aperture stops on the illumination system aperture stop plate 5 and reaches a beam splitter 6 having a large transmittance and a small reflectance. The illumination light IL as exposure light transmitted through the beam splitter 6 passes through the first relay lens 7A, passes through the rectangular opening of the reticle blind 8, then passes through the second relay lens 7B, and the optical path is changed by the mirror 9. After being bent vertically downward, a rectangular (for example, square) illumination area IAR on the reticle R held on the reticle stage RST is illuminated with a uniform illuminance distribution.

On the other hand, the illumination light IL reflected by the beam splitter 6 is received by the integrator sensor 53 composed of a photoelectric conversion element via the condenser lens 29, and the photoelectric conversion signal of the integrator sensor 53 is converted into a peak hold signal (not shown). The output DS is supplied to the main controller 20 via the circuit and the A / D converter. As the integrator sensor 53, for example, a PI having sensitivity in the deep ultraviolet region and having a high response frequency for detecting the pulse emission of the light source 1 is used.
An N-type photodiode or the like can be used.

The movable reticle blind 12 is controlled by the main controller 20 at the start and end of the scanning exposure, and further restricts the illumination area IAR.
Exposure of unnecessary portions is prevented. In the present embodiment, the movable reticle blind 12 is
It is also used for setting an illumination area when measuring an aerial image by an aerial image measuring device described later.

A reticle R is fixed on the reticle stage RST by, for example, vacuum suction (or electrostatic suction). Here, reticle stage RST is driven by an unillustrated reticle stage drive system including a linear motor or the like, and XY perpendicular to optical axis AX of projection optical system PL described later.
It can be finely driven two-dimensionally in the plane (in the X-axis direction, the Y-axis direction, and the rotation direction (θz direction) around the Z-axis orthogonal to the XY plane), and Y is driven on a reticle base (not shown).
It can move at a specified scanning speed in the axial direction.
The reticle stage RST has a movement stroke in the Y-axis direction that allows the entire surface of the reticle R to cross at least the optical axis AX of the projection optical system PL.

On reticle stage RST, a reticle laser interferometer (hereinafter, referred to as “reticle interferometer”) 13
The movable mirror 15 that reflects the laser beam from the reticle stage RST is fixed, and the position of the reticle stage RST in the XY plane (including the rotation in the θz direction, which is the rotation direction about the Z axis) is, for example, 0 by the reticle interferometer 13. It is always detected with a resolution of about 0.5 to 1 nm. Here, actually, the scanning direction (Y-axis direction) at the time of scanning exposure is on the reticle stage RST.
And a moving mirror having a reflecting surface orthogonal to the non-scanning direction (X-axis direction). The reticle interferometer 13 has at least two axes in the Y-axis direction and at least two axes in the X-axis direction. Although one axis is provided, these are typically shown as a movable mirror 15 and a reticle interferometer 13 in FIG.

The position information of the reticle stage RST from the reticle interferometer 13 is sent to a main controller 20 comprising a workstation (or a microcomputer).
Main controller 20 drives and controls reticle stage RST via a reticle stage drive system based on position information of reticle stage RST.

The projection optical system PL is disposed below the reticle stage RST in FIG. 1 and the direction of the optical axis AX thereof is the Z-axis direction. A refractive optical system including a plurality of lens elements arranged at predetermined intervals along the optical axis is used. Here, the projection magnification of the projection optical system PL is, for example, 1/5. Therefore, when the slit-shaped illumination area IAR on the reticle R is illuminated by the illumination light IL from the illumination system 10, this reticle R
Of the reticle R in the slit-shaped illumination area IAR through the projection optical system PL, the reduced image (partially inverted image) of the illumination light IL passing through the wafer W on the surface of which the photoresist has been coated. It is formed in an exposure area IA conjugate to the illumination area IAR.

The wafer stage WST is freely driven along an upper surface of the stage base 16 in an XY two-dimensional plane (including θz rotation) by a wafer stage drive system (not shown) composed of, for example, a magnetic levitation type two-dimensional linear actuator. It has become so. Here, since the two-dimensional linear actuator also has a Z drive coil in addition to the X drive coil and the Y drive coil, the wafer stage WST
The micro drive can be performed in three degrees of freedom, Z, θx (rotation direction around the X axis), and θy (rotation direction around the Y axis).

A wafer holder 25 is mounted on wafer stage WST, and wafer W is held by wafer holder 25 by vacuum suction (or electrostatic suction).

Incidentally, instead of wafer stage WST, XY is driven by a drive system such as a linear motor or a planar motor.
When a two-dimensional moving stage driven only in a two-dimensional plane is used, the wafer holder 25 is set to three of Z, θx, and θy.
What is necessary is just to mount it on the two-dimensional movement stage via a Z leveling table that is minutely driven by, for example, a voice coil motor in the direction of freedom.

A movable mirror 27 for reflecting a laser beam from a wafer laser interferometer (hereinafter, referred to as "wafer interferometer") 31 is fixed on the wafer stage WST. 5 degrees of freedom directions (X, Y, θz,
(θx and θz directions) are always detected at a resolution of, for example, about 0.5 to 1 nm.

Here, actually, wafer stage WST
A moving mirror having a reflecting surface orthogonal to the Y-axis direction, which is the scanning direction at the time of scanning exposure, and a moving mirror having a reflecting surface orthogonal to the X-axis direction, which is the non-scanning direction, are provided on the upper side. A plurality of shafts 31 are provided in the Y-axis direction and the X-axis direction, respectively.
Shown as wafer interferometer 31. The position information (or speed information) of wafer stage WST is sent to main controller 20. Main controller 20 controls the position of wafer stage WST via a wafer stage drive system (not shown) based on the position information (or speed information). The position in the XY plane is controlled.

Further, inside wafer stage WST,
A part of an optical system constituting an aerial image measuring instrument 59 used for measuring the optical characteristics of the projection optical system PL is arranged. Here, the configuration of the aerial image measuring device 59 will be described in detail. As shown in FIG. 3, the aerial image measuring device 59 includes a stage-side component provided on the wafer stage WST, that is, a slit plate 90 as a pattern forming member and a lens 8.
4, 86, a relay optical system, a mirror 88 for bending the optical path, a light transmitting lens 87, and a component outside the stage provided outside the wafer stage WST, ie, a mirror M,
A light receiving lens 89, an optical sensor 24 as a photoelectric conversion element,
And a signal processing circuit 42 for the photoelectric conversion signal from the optical sensor 24.

This will be described in more detail.
As shown in FIG. 3, is fitted from above into a protruding portion 58a provided on the upper surface of one end of wafer stage WST and having an open top, in a state of closing the opening.
The slit plate 90 has a rectangular light receiving glass 82 in a plan view.
A reflection film 83 also serving as a light-shielding film is formed on the upper surface of the substrate, and a part of the reflection film 83 has a predetermined width (2
D) slit-shaped opening pattern (hereinafter, “slit”)
22) is formed by patterning.

As a material of the light-receiving glass 82, synthetic quartz, fluorite, or the like, which has good transmittance of KrF excimer laser light or ArF excimer laser light, is used here.

Wafer stage WST below slit 22
Inside, a mirror 8 for horizontally bending the optical path of the illumination light beam (image light beam) that has entered vertically downward through the slit 22.
8, a relay optical system (84, 86) composed of lenses 84, 86 is arranged, and the relay optical system (84, 86) is arranged.
A light transmitting lens 87 for transmitting the illumination light beam relayed by a predetermined optical path length by the relay optical system (84, 86) to the outside of the wafer stage WST is provided on the side wall on the + Y side of the wafer stage WST behind the optical path 86). Fixed.

The light transmission lens 87 causes the wafer stage W
A mirror M having a predetermined length in the X-axis direction is inclined at an inclination angle of 45 ° on the optical path of the illumination light beam sent out of the ST. The mirror M allows the wafer stage W
The optical path of the illumination light beam sent to the outside of the ST is bent 90 ° vertically upward. A light receiving lens 89 having a larger diameter than the light transmitting lens 87 is arranged on the bent optical path. Above the light receiving lens 89, the optical sensor 24 is arranged. The light receiving lens 89 and the optical sensor 24 are housed in a case 92 while maintaining a predetermined positional relationship. The case 92 is located near an upper end of a support 94 implanted on the upper surface of the base 16 via a mounting member 93. Fixed.

As the optical sensor 24, a photoelectric conversion element (light receiving element) capable of accurately detecting weak light, for example, a photomultiplier tube (PM)
T, photomultiplier tube, etc. are used. The signal processing circuit 42 for the output signal of the optical sensor 24 is configured to include an amplifier, an A / D converter (usually, one having a resolution of 16 bits is used) (see FIG. 9). In this embodiment,
The signal sensitivity (detection sensitivity) is set by setting the applied voltage between the cathode and the anode of the optical sensor 24. This will be described later.

As described above, the slits 22 are formed in the reflection film 83, but hereinafter, the description will be made assuming that the slits 22 are formed in the slit plate 90 for convenience.

According to the aerial image measuring device 59 configured as described above, when measuring a projection image (aerial image) of the measurement mark formed on the reticle R via the projection optical system PL, which will be described later. Light IL transmitted through the projection optical system PL
When the slit plate 90 constituting the aerial image measuring device 59 is illuminated by the illumination light IL transmitted through the slit 22 on the slit plate 90, the illumination light IL is transmitted through the lens 84, the mirror 88, the lens 86, and the light transmitting lens 87 to the wafer. Stage WST
It is led outside. Then, the wafer stage W
The light guided to the outside of the ST has its optical path bent vertically upward by the mirror M, is received by the optical sensor 24 via the light receiving lens 89, and is subjected to a photoelectric conversion signal (light amount) corresponding to the amount of light received from the optical sensor 24. The signal P is output to the main controller 20 via the signal processing circuit 42.

In the case of the present embodiment, the measurement of the projection image (spatial image) of the measurement mark is performed by the slit scan method.
9 and the optical sensor 24. Therefore, in the aerial image measuring device 59, the size of each lens and the mirror M is set such that all light passing through the light transmitting lens 87 moving within a predetermined range enters the light receiving lens 89.

As described above, in the aerial image measuring device 59, the light deriving section for guiding the light passing through the slit 22 to the outside of the wafer stage WST by the slit plate 90, the lenses 84 and 86, the mirror 88, and the light transmitting lens 87. Is formed, and the light receiving lens 89 and the optical sensor 24 are used to set the wafer stage W
A light receiving unit that receives the light led out of the ST is configured. In this case, the light guiding section and the light receiving section are mechanically separated. Then, only at the time of aerial image measurement, the light deriving unit and the light receiving unit are optically connected via the mirror M.

That is, in the aerial image measuring device 59, since the optical sensor 24 is provided at a predetermined position outside the wafer stage WST, the heat generation of the optical sensor 24 adversely affects the measurement accuracy of the laser interferometer 31 and the like. Or give. Further, since the outside and inside of wafer stage WST are not connected by a light guide or the like, the driving accuracy of wafer stage WST is adversely affected as in the case where the outside and inside of wafer stage WST are connected by a light guide. Not even.

Of course, if the influence of heat can be eliminated, optical sensor 24 may be provided inside wafer stage WST. The shape, dimensions, and the like of the slit 22 on the slit plate 90 constituting the aerial image measuring device 59, and the aerial image measuring method and the optical characteristic measuring method performed using the aerial image measuring device 59 will be described in detail later. I do.

Returning to FIG. 1, on the side of the projection optical system PL,
Alignment mark (alignment mark) on wafer W
Off-axis alignment system ALG for detecting the In the present embodiment, the alignment system AL
As G, an image processing type alignment sensor, so-called FIA (Field Image Alignment) system is used. As shown in FIG. 3, the alignment system ALG includes an alignment light source 32, a half mirror 34, a first
Objective lens 36, second objective lens 38, image sensor (CC
D) 40 and the like. Here, the light source 32
For example, a halogen lamp that emits broadband illumination light is used. In this alignment system ALG, as shown in FIG. 4, the alignment mark Mw on the wafer W is illuminated by the illumination light from the light source 32 via the half mirror 34 and the first objective lens 36, and Reflected light of the first objective lens 3
6. The light is received by the image sensor 40 via the half mirror 34 and the second objective lens 38. As a result, a bright field image of the alignment mark Mw is formed on the light receiving surface of the image sensor. Then, a photoelectric conversion signal corresponding to the bright-field image, that is, a light intensity signal corresponding to a reflection image of the alignment mark Mw is supplied from the image sensor 40 to the main controller 20. Main controller 20 calculates the position of alignment mark Mw based on the detection center of alignment system ALG based on the light intensity signal, and calculates the calculation result and wafer stage which is the output of wafer interferometer 31 at that time. WS
The coordinate position of the alignment mark Mw in the stage coordinate system defined by the optical axis of the wafer interferometer 31 is calculated based on the position information of T.

Further, in the exposure apparatus 100 of the present embodiment,
As shown in FIG. 1, an imaging light flux having a light source whose on / off is controlled by main controller 20 and for forming an image of a slit (or pinhole) toward an imaging surface of projection optical system PL. 60a for irradiating the wafer W obliquely with respect to the optical axis AX, and a light receiving system 60b for receiving the reflected light flux of the imaging light flux on the surface of the wafer W.
An oblique incident light type focus position detection system is provided as a position detection system for detecting a position in the optical axis AX direction (Z-axis direction).

FIG. 5 shows a focus position detection system (60a, 60a).
b) and the configuration of a processing drive unit 56 (see FIG. 1) that processes output signals of the focus position detection systems (60a, 60b) and drives plane parallel described later. In FIG. 5, it is assumed that the best imaging plane of the projection optical system PL and the surface of the wafer W match.

As shown in FIG. 5, the irradiation system 60a includes a light emitting diode (LED) 62, a condenser lens 64, a slit plate 66, a mirror 68, an irradiation objective lens 70 including a reduction lens, and the like. The light receiving system 60b includes a light receiving objective lens 7 composed of a magnifying lens.
2. Parallel plate glass (plane parallel) 74, slit plate 78 via vibrating mirror 76, and photoelectric detector 80
Etc. are provided.

Here, the operation and the like of each of the above components constituting the irradiation system 60a and the light receiving system 60b will be briefly described. Light having a wavelength that does not expose the photoresist generated from the light emitting diode (LED) 62 is condensed by the condenser lens 64 and illuminates the slit plate 66 having the elongated rectangular slit 66a. The light transmitted through the slit 66a is reflected by the mirror 68, converged by the irradiation objective lens 70, and is located near the optical axis AX on the surface of the wafer W.
Is formed as a light image SI. Then, the reflected light from the wafer W is received by the light receiving objective lens 72, the plane parallel 74,
The light is guided to the slit plate 78 via the vibration mirror 76, and an enlarged image of the optical image SI is formed on the slit plate 78. The slit plate 78 is provided with a slit 78 a, and the light transmitted through the slit 78 a is received by the photoelectric detector 80. The vibrating mirror 76 is driven by the driving unit 91 such that the enlarged image of the optical image SI vibrates on the slit plate 78 in a single vibration in a direction parallel to the slit 78a and in a direction orthogonal to the longitudinal direction.

The photoelectric signal from the photoelectric detector 80 is supplied to the amplifier 8
After being amplified by 5, a synchronous rectification (synchronous detection) circuit (hereinafter, referred to as
(Called “PSD”) 71. The PSD 71 determines a vibration frequency of the vibration mirror 76 (hereinafter referred to as “O”).
SC "), and outputs a focus signal FPS by synchronously rectifying the photoelectric signal with the reference frequency signal.

The plane parallel 74 includes a driving unit 81
Are rotatable within a certain angle range.
Due to the rotation (tilt) of the plane parallel 74, the center of vibration of the enlarged image of the optical image SI formed on the slit plate 78 is shifted in a direction orthogonal to the longitudinal direction of the slit 78a (the horizontal direction in FIG. 5). . The shift of the vibration center with respect to the slit 78a is equivalent to shifting the position of the wafer W in the Z-axis direction when the focus signal FPS is determined to be in focus (zero point on the S-curve signal waveform). In the present embodiment, the focus variation is corrected by the plane parallel 74 and the drive unit 81.

In the above configuration, as can be seen from FIG. 1, the processing driver 56 is composed of the amplifier 85, the PSD 71, the OSC 73, the driving unit 91 of the oscillating mirror 76, and the driving unit 81 of the plane parallel 74.

FIG. 6 shows a specific configuration of the plane parallel 74 and the drive section 81 in a partial cross section. As shown in FIG. 6, the plane parallel 74 is held by a holder 75 having a rotation center 75a perpendicular to the paper surface, and a lever 77 is fixed to the holder 75. A female screw 77 a is formed at the tip of the lever 77, and a male screw 54 that rotates by driving a motor 79 is screwed into the female screw 77 a. The rotation amounts of the motor 79 and the male screw 54 are read by the rotary encoder 55.

In such a configuration, when the motor 79 is driven, the plane parallel 74 rotates around the center 75a, and the rotation angle (the amount of tilt) is changed by the rotary encoder 55.
, The pitch of the male screw 54 and the length of the lever 77 (more precisely, the length from the female screw 77a to the center 75a)
Can be calculated from Since the pitch of the male screw 54 and the length of the lever 77 are constant values, the rotation angle of the plane parallel 74 can be obtained as long as the read value of the rotary encoder 55 is known.

That is, in the present embodiment, the main controller 2
0 performs a simple proportional calculation using the pitch of the male screw 54 and the length of the lever 77 based on the read value ENS of the rotary encoder 55,
4 is calculated.

For example, when the focus fluctuation occurs in the projection optical system PL, the main controller 20 sets an offset command value (OFS) corresponding to the focus fluctuation in order to correct a detection offset caused by the focus fluctuation. By providing the drive signal to the motor driver MD to control the tilt amount (rotation angle θ) of the plane parallel 74, the center of vibration of the enlarged image of the optical image SI formed on the slit plate 78 is aligned with the longitudinal direction of the slit 78a. Focus calibration is performed, in which the optical axis of the light beam reflected from the surface of the wafer W is shifted so as to coincide with the center (zero point) in the direction orthogonal to the wafer.

In this embodiment, for example, instead of the focal position detecting system (60a, 60b), for example,
A multipoint focal position detection system disclosed in, for example, Japanese Patent No. 3403 can also be used.

The main controller 20 operates a wafer stage drive system (not shown) so that the focus shift from the light receiving system 60b, for example, the S-curve signal FPS becomes zero at the time of scanning exposure to be described later. Via wafer stage WST
Of the illumination light IL by controlling the movement of the
Of the projection optical system PL and the surface of the wafer W in the irradiation area (the image formation relationship with the illumination area IAR).

When using the multi-point focal position detection system, the main controller 20 uses a wafer stage drive system (not shown) based on a focus signal from the light receiving system 60b at the time of scanning exposure, which will be described later. In addition to the movement of wafer stage WST in the Z-axis direction, two-dimensional inclination (that is, θx, θ
By controlling the rotation of the wafer stage WST using the multi-point focal position detection system, the projection optics can be controlled within the irradiation area of the illumination light IL (the imaging relation with the illumination area IAR). Auto-focus (auto-focusing) and auto-leveling that substantially match the imaging plane of the system PL with the surface of the wafer W can be performed.

The control system is mainly composed of a main controller 20 comprising a work station (or a microcomputer), and comprises a signal processing circuit 42, a processing drive section 56 and the like. As shown in FIG. 1, the main control device 20 is provided with a storage device 51 and an input / output device 30.

Next, the operation of the exposure step in the exposure apparatus 100 of this embodiment will be briefly described.

First, the reticle R is transported by a reticle transport system (not shown), and is held by suction at the reticle stage RST at the loading position. Next, the positions of wafer stage WST and reticle stage RST are controlled by main controller 20, and a projection image (spatial image) of a reticle alignment mark (not shown) formed on reticle R is read using aerial image measuring device 59. The measurement is performed as described later (see FIG. 3), and the projection position of the reticle pattern image is obtained. That is, reticle alignment is performed.

Next, main controller 20 moves wafer stage WST such that aerial image measuring device 59 is positioned immediately below alignment system ALG, and alignment system ALG serves as a position reference for aerial image measuring device 59. The slit 22 is detected. Main controller 20 aligns the projection position of the pattern image of reticle R with the projection position of the reticle pattern image based on the detection signal of alignment system ALG, the measurement value of wafer interferometer 31 at that time, and the projection position of the reticle pattern image obtained earlier. A relative position with respect to the system ALG, that is, a baseline amount of the alignment system ALG is obtained.

When the baseline measurement is completed, main controller 20 performs wafer alignment such as EGA (Enhanced Global Alignment) disclosed in detail in, for example, Japanese Patent Application Laid-Open No. 61-44429. The positions of all shot areas on W are determined. At the time of this wafer alignment, the wafer alignment mark Mw of a predetermined sample shot among a plurality of shot areas on the wafer W is measured as described above using the alignment system ALG (FIG. 3). reference).

Next, main controller 20 monitors wafer stage WST while monitoring position information from interferometers 31 and 13 based on the position information of each shot area on wafer W and the base line amount obtained above. Are positioned at the scanning start position of the first shot area, the reticle stage RST is positioned at the scanning start position, and scanning exposure of the first shot area is performed.

That is, main controller 20 starts relative scanning of reticle stage RST and wafer stage WST in the Y-axis direction opposite to each other. When both stages RST and WST reach their respective target scanning speeds, illumination light IL Then, the pattern area of the reticle R starts to be illuminated, and the scanning exposure is started. Prior to the start of the scanning exposure, the light source 1
However, since the movement of each blade of the movable blind 12 constituting the reticle blind is controlled in synchronization with the movement of the reticle stage RST by the main controller 20, the light emission to the pattern area on the reticle R The shielding of the irradiation of the illumination light IL is the same as in a normal scanning stepper.

In main controller 20, moving speed Vr of reticle stage RST in the Y-axis direction particularly during the scanning exposure described above.
Reticle stage RST and wafer stage WS such that the speed ratio of wafer stage WST in the X-axis direction is maintained at a speed ratio corresponding to the projection magnification of projection optical system PL.
T is controlled synchronously.

Then, the different areas of the pattern area of the reticle R are sequentially illuminated with the ultraviolet pulse light, and the illumination of the entire pattern area is completed, thereby completing the scanning exposure of the first shot area on the wafer W. Thereby, the circuit pattern of the reticle R is changed to the first pattern via the projection optical system PL.
It is reduced and transferred to the shot area.

When the scanning exposure of the first shot area is completed, a stepping operation between shots for moving wafer stage WST to the scanning start position of the second shot area is performed. Then, the scanning exposure of the second shot area is performed in the same manner as described above. Thereafter, the same operation is performed in the third shot area and thereafter.

In this way, the stepping operation between shots and the scanning exposure operation for shots are repeated, and the pattern of the reticle R is transferred to all shot areas on the wafer W by the step-and-scan method.

During the scanning exposure, the focus sensor (60) integrally attached to the projection optical system PL is used.
a, 60b), the above-described autofocus (or autofocus / autoleveling) is performed.

By the way, in order for the pattern of the reticle R and the pattern already formed in the shot area on the wafer W to be accurately overlapped during the above-mentioned scanning exposure, the optical characteristics of the projection optical system PL and the baseline are required. It is important that the amount is accurately measured and that the optical characteristics of the projection optical system PL are adjusted to a desired state.

In the present embodiment, an aerial image measuring device 59 is used for measuring the above-mentioned imaging characteristics. Hereinafter, the aerial image measurement by the aerial image measuring device 59 and the measurement of the optical characteristics of the projection optical system PL will be described in detail.

FIG. 3 shows a state where the aerial image of the measurement mark formed on the reticle R is being measured using the aerial image measuring device 59. As the reticle R,
A dedicated aerial image measurement device or a device reticle having a dedicated measurement mark formed on a device reticle used for manufacturing a device is used. Instead of these reticles,
A reticle stage RST may be provided with a fixed mark plate (also called a reticle fiducial mark plate) made of a glass material of the same material as the reticle, and a mark plate having measurement marks formed thereon may be used.

Here, it is assumed that a measurement mark PM composed of a line and space mark having periodicity in the Y-axis direction is formed at a predetermined position on the reticle R, as shown in FIG. Further, it is assumed that the slit plate 90 of the aerial image measuring device 59 is formed with a slit 22 having a predetermined width 2D extending in the X-axis direction, as shown in FIG. Here, the predetermined width 2D is assumed to be about the half pitch of a line and space pattern with a duty ratio of 1: 1 at the resolution limit, for example, 2D = 0.2 μm. In the following, the line and space are abbreviated as “L / S” as appropriate.

In measuring the aerial image, the movable reticle blind 12 is driven by the main controller 20 via the blind driving device, and the illumination area of the illumination light IL of the reticle R is defined only at the measurement mark PM (FIG. 3). In this state, when illumination light IL is applied to reticle R, light (illumination light IL) diffracted and scattered by measurement mark PM is refracted by projection optical system PL, as shown in FIG. Measurement mark PM on the image plane of system PL
Is formed. At this time, it is assumed that wafer stage WST is set at a position where the aerial image PM 'is formed on the + Y side (or -Y side) of slit 22 on slit plate 90 of aerial image measuring device 59. FIG. 7A is a plan view of the aerial image measuring device 59 at this time.
Is shown in

Then, main controller 20 moves wafer stage WST through a wafer stage drive system as shown in FIG.
When driven in the + Y direction as shown by an arrow F in (A), the slit 22 scans the aerial image PM ′ along the Y-axis direction. During this scanning, the light (illumination light IL) passing through the slit 22 is received by the optical sensor 24 via the light guide portion in the wafer stage WST and the light receiving lens 89, and the photoelectric conversion signal is transmitted to the signal processing circuit 42. The power is supplied to the main controller 20 via the main controller 20. Main controller 20 measures the light intensity distribution corresponding to aerial image PM ′ based on the photoelectric conversion signal.

FIG. 7B shows an example of a photoelectric conversion signal (light intensity signal) P obtained at the time of the aerial image measurement.

In this case, the spatial image PM ′ is averaged due to the width (2D) of the slit 22 in the scanning direction (Y-axis direction).

Therefore, assuming that the slit is p (y), the intensity distribution of the aerial image is i (y), and the observed light intensity signal is m (y), the intensity distribution of the aerial image is i (y). The relationship between the intensity signals m (y) can be expressed by the following equation (1).
In the equation (1), the intensity distribution i (y) and the intensity signal m
The unit of (y) is the intensity per unit length.

[0107]

(Equation 1)

[0108]

(Equation 2)

That is, the observed intensity signal m (y) is a convolution of the slit p (y) and the intensity distribution i (y) of the aerial image.

Therefore, from the viewpoint of measurement accuracy, the smaller the slit width 2D is, the better. When the PMT is used as the optical sensor 24 as in the present embodiment, the scanning speed is reduced even if the slit width is extremely small. It is possible to detect the light amount (light intensity) if the measurement is delayed and time is taken for the measurement. However, in reality, the scanning speed at the time of measuring the aerial image has a certain restriction from the viewpoint of throughput. Therefore, if the slit width 2D is too small, the amount of light transmitted through the slit 22 becomes too small, and the measurement becomes impossible. It will be difficult.

According to the knowledge obtained by the inventor through simulations and experiments, the optimum value of the slit width 2D is about half the resolution limit pitch of the exposure apparatus (the pitch of the L / S pattern having a duty ratio of 1: 1). Therefore, in the present embodiment, it is set as such.

The aerial image measuring device 59 and the aerial image measuring method using the same are described in a. Detection of the best focus position, b. Detection of the image forming position of the pattern image in the XY plane,
c. Used for baseline measurement of the alignment system ALG.

In exposure apparatus 100 of the present embodiment, c.
Baseline measurement has already been described. B.
Since the detection of the image forming position of the pattern image in the XY plane is not closely related to the present invention, the following a. The detection of the best focus position will be described.

The detection of the best focus position is used, for example, for the purpose of detecting the best focus position of the projection optical system PL and detecting the best image plane (image plane).

In the present embodiment, as an example, the best focus position of the projection optical system PL is detected as follows.

For detecting the best focus position, for example, a line width of 0.15 μm on a wafer (0.75 μm on a reticle) and a pitch of 1.5 μm (duty ratio 1:
The reticle R in which the L / S mark of 9) is formed as the measurement mark PM is used.

First, reticle R is loaded on reticle stage RST by a reticle loader (not shown).
Next, main controller 20 sets measurement mark P on reticle R at a predetermined point (here, on the optical axis of projection optical system PL) at which the best focus position is to be measured in the field of view of projection optical system PL.
The reticle stage RST is moved so that M is positioned.

Next, the main controller 20 controls the driving of the movable reticle blind 12 so as to irradiate only the measurement mark PM with the illumination light IL, thereby defining an illumination area.
In this state, main controller 20 irradiates reticle R with illumination light IL, and performs wafer stage W
While scanning ST in the Y-axis direction, the aerial image measurement of the measurement mark PM is performed by the slit scan method using the aerial image measuring device 59 in the same manner as described above. At this time, main controller 20 repeats a plurality of times while changing the position of slit plate 90 in the Z-axis direction (that is, the Z position of wafer stage WST) at, for example, about 15 steps at a pitch of 0.1 μm.
The light intensity signal (photoelectric conversion signal) of each time is stored in the internal memory. The step range is performed, for example, in a range around the design best focus position.

Here, at the time of the aerial image measurement described above, the slit plate 90 is scanned at the first Z position, and the measurement mark P
When the light intensity signal corresponding to the aerial image of M is captured,
The detection sensitivity is set (calibrated) so as to make the best use of the dynamic range of the signal processing circuit 42 at the subsequent stage of the optical sensor 24. This will be described later.

In this case, for example, the measurement mark is an L / S mark (L / S pattern) having a duty ratio of 1: 1.
In the case of, each of the above light intensity signals is Fourier transformed,
A contrast, which is an amplitude ratio between the first-order frequency component and the zero-order frequency component, is obtained. Since this contrast changes sensitively depending on the focus position, it is convenient to determine the best focus position from the intensity signal. But,
In the case of a measurement mark PM composed of an L / S pattern (pseudo-isolated line) having a duty ratio of 1: 9, focus detection using a primary frequency component is inaccurate due to a large pattern repetition pitch. This is because the DOF of the dull pattern is large. However, since the amplitude of a high-order frequency component is not sufficiently large, even if focus detection is performed using only the amplitude of a high-order single frequency component, accuracy is still poor.

Therefore, in the present embodiment, main controller 20
Calculates the best focus position by the following first and second methods based on a plurality of light intensity signals (photoelectric conversion signals) obtained by the repetition.

A. First Method This first method uses an area corresponding to a light intensity signal corresponding to an aerial image of an isolated line (or a single line pattern of a pseudo isolated line) in an XY plane of a design pattern. The center area of the design line width centered on the imaging position (center position) (first area)
Area) and peripheral areas (second areas) on both sides thereof, and the best focus position is obtained using the area ratio of the two as an evaluation amount. Hereinafter, the detection principle of the first method will be described with reference to FIGS.

FIG. 8A shows the slit transmitted light intensity in the best focus state obtained as a result of a simulation in which a measurement mark having the same size as the above-mentioned measurement mark PM and a slit width are set. Position (or Y position of wafer stage WST),
FIG. 8B shows the slit transmitted light intensity in a state where the focus is 1 μm defocused, with the horizontal axis representing the Y position of the slit 22 (or the Y position of the wafer stage WST).

In FIG. 8A, the image forming position (center position) on the designed XY plane of one line pattern of the measurement mark PM surrounded by the light intensity signal P ₁ and the horizontal axis is set as the center. Assuming that the area ratio of the area A = A ₁ of the area of the design line width to the area B = B ₁ (= b ₁ + b ₂ ) of the area on both sides thereof is α ₁ ,
α ₁ can be expressed as in the following equation (3). α ₁ = A ₁ / B ₁ (3)

On the other hand, in FIG. 8B, the light intensity signal P
Area A = A ₂ of the area of the design line width centered on the designed image forming position (center position) in the XY plane of one line pattern of the measurement mark PM surrounded by ₂ and the horizontal axis; Assuming that the area ratio of the area B = B ₂ (= b ₃ + b ₄ ) of the regions on both sides is α ₂ , α ₂ can be expressed as the following equation (4). α ₂ = A ₂ / B ₂ (4) As is clear from comparison between FIG. 8A and FIG. 8B, α ₁ > α ₂ .

Therefore, if the area ratio α in the following equation (5) is used as the evaluation amount, the best focus position can be detected with high accuracy. Area ratio α = A / B (5)

Various methods for obtaining the best focus position using the above-described area ratio α as an evaluation amount are conceivable. For example, as shown in FIG. 9, each position of the slit plate 90 in the optical axis direction (Z position) is determined. The area ratio α calculated based on the obtained light intensity signal is plotted on an orthogonal coordinate system having the horizontal axis as the Z position (see the crosses in FIG. 9). Then, each plot point is approximated by a curve (curve fit). For example, a fourth-order approximate curve is obtained by the least square method. Then, the approximate curve is sliced at an appropriate threshold level (slice level) SL, and the slice level SL
The intersections J and K of the curve and the approximate curve are obtained, and the intersections J and K
The intersection G between the axis parallel to the vertical axis (the axis of the evaluation amount α) passing through the middle point (the point at a distance L / 2 from each of the points J and K) O is defined as the peak point of the approximate curve, and the peak point G _{Is set} as the best focus position.

As described above, when measuring the best focus position, the aerial image measurement is usually performed by the slit scan method while changing the Z position by about 15 steps at a pitch of about 0.1 μm. In this case, in order to improve the measurement reproducibility, it is important to determine the peak position from information on as many measurement points (Z positions) as possible. FIG. 9 shows an example in which the best focus position is obtained from the area ratio α at 13 points.

B. Second Method In the second method, a region corresponding to a light intensity signal corresponding to an aerial image of an isolated line (or a single line pattern of a pseudo isolated line) is divided into two by a predetermined threshold level as a boundary. , A region above the threshold level (first region) and a region below the threshold level (second region).
This is a method of obtaining the best focus position using the area ratio of the (area) as an evaluation amount. Hereinafter, the detection principle of the second method will be described with reference to FIGS. 10 (A) and 10 (B).

FIGS. 10 (A) and 10 (B) show FIG.
8A and 8B, the horizontal axis indicates the Y-position of the slit 22 (or the Y-position of the wafer stage WST).
It is shown as

[0131] In FIG. 10 (A), the in the region surrounded by the light intensity signal P ₁ and the horizontal axis, the area C = C of the upper regions bisected with respect to a boundary of a predetermined slice level (threshold level) SL ' _1, when the area ratio between the area E = E ₁ in the lower region is gamma _1, gamma _{1 is, γ 1 = C 1 / E} 1 ......... represented by the following formula (6) (6)

Here, the slice level SL 'is obtained by, for example, previously obtaining the light intensity at the peak point in the best focus state by an experiment or the like, and is set to, for example, a level of about 50% thereof.

[0133] On the other hand, in FIG. 10 (B), the in the region surrounded by the light intensity signal P ₄ and the horizontal axis, because the area C = 0 in the upper region of a predetermined slice level (threshold level) SL ' , And the slice level (threshold level) SL '
Assuming that the area ratio of the lower area E = E ₂ to γ ₂ is γ _2
2 can be expressed as in the following equation (7). γ ₂ = 0 / E ₂ = 0 (7) In this case, obviously, γ ₁ > γ ₂ .

Therefore, the area ratio γ represented by the following equation (8)
Is used as the evaluation amount, the best focus position can be detected with high accuracy. Area ratio γ = C / E (8)

Also in this case, when determining the best focus position using the area ratio γ as the evaluation amount, the best focus position is calculated based on the light intensity signal obtained for each position (Z position) of the slit plate 90 in the optical axis direction. The plotted area ratio γ is plotted on an orthogonal coordinate system having the horizontal axis as the Z position, each plot point is approximated by a curve, and the peak point of the approximate curve is obtained based on the slice midpoint method described above. The method of setting the coordinate of the horizontal axis corresponding to the point as the best focus position can be adopted as it is.

The image plane shape of the projection optical system PL can be detected as follows.

First, reticle R is loaded on reticle stage RST by a reticle loader (not shown).
Next, main controller 20 controls reticle stage RST such that measurement mark PM is positioned at the first detection point (here, on the optical axis of projection optical system PL) in the field of view of projection optical system PL. Moving. Next, main controller 20 drives and controls movable reticle blind 12 so that illumination light IL is emitted only to measurement mark PM, and defines an illumination area. In this state, the main controller 20 controls the illumination light I
L is irradiated onto the reticle R, and in the same manner as described above, the aerial image measurement of the measurement mark PM and the detection of the best focus position Z ₁ of the projection optical system PL are performed using the aerial image measurement device 59 by the slit scan method. The result is stored in the internal memory.

When the detection of the best focus position at the first detection point in the field of view of projection optical system PL is completed, main controller 20 sets measurement mark PM at the second detection point in the field of view of projection optical system PL. The reticle stage RST is moved so that is positioned. Next, main controller 20 drives and controls movable reticle blind 12 so that illumination light IL is emitted only to measurement mark PM, and defines an illumination area. In this state, similarly to the above, the aerial image measurement and projection optical system P of the measurement mark PM is performed by the slit scan method.
Performs detection of the best focus position Z ₂ of the L, and the result is stored in the internal memory.

Thereafter, the main controller 20 changes the detection point in the field of view of the projection optical system PL while measuring the aerial image of the measurement mark PM and changing the projection optical system PL in the same manner as described above.
Is repeatedly detected.

[0140] This the best focus position obtained by Z _1, Z _2, ......, based on Z _n, by performing a predetermined statistical processing, to calculate the image plane shape of the projection optical system PL. At this time, the field curvature may be calculated separately from the image plane shape. Here, the measurement marks PM are arranged at a plurality of points where the reticle R should be moved to measure the best focus position. However, a plurality of measurement marks PM are formed on the reticle R, and the movable reticle blind 1 is formed.
The measurement focus PM at each point may be detected by sequentially irradiating each measurement mark PM with the illumination light IL according to 2.

The image plane of the projection optical system PL, that is, the best image formation plane, has innumerable points (that is, different points from the optical axis).
Since it is a surface composed of a set of best focus points at so-called countless points having different image heights, the image surface shape can be easily and accurately obtained by such a method.

By the way, as in this embodiment, the photo
When a multiplier tube (PMT, photomultiplier tube) is used as the optical sensor 24, when measuring an aerial image, for example, L / with a duty ratio of 1: 1 is used as a measurement mark.
Even when the S pattern is used, the optical sensor 2
It is desirable to set the signal sensitivity (detection sensitivity) of the signal processing system including the signal processing circuit 4 and its signal processing circuit so that the dynamic range can be effectively used. In particular, when a pseudo-isolated line having a duty ratio of 1: 9 is used as a measurement mark as in the present embodiment, the L / S having a duty ratio of 1: 1 is used.
The adjustment of the signal sensitivity is important because the amplitude of the fundamental wave tends to be smaller than in the case of the pattern and the measurement accuracy is inferior.

Next, a method of setting the signal sensitivity (calibration method) of the signal processing system for processing the signal light (slit transmitted light) performed by the exposure apparatus 100 of the present embodiment will be described.

In general, the sensitivity of the PMT is set by the applied voltage. That is, assuming that the number of dynodes in the electron multiplying section (dynode section) is n and the applied voltage between the anode and the cathode is V, the current multiplication factor μ corresponding to the sensitivity is substantially proportional to the nth power of the applied voltage V. The sensitivity of the PMT is set so that the anode sensitivity is such that the dynamic range of the subsequent signal processing circuit can be used without waste.

However, in the case of the present embodiment, since the aerial image measurement aims to detect the best focus position,
At the time of measurement, the best focus position is unknown. For this reason, the sensitivity setting requires some contrivance. That is, the peak level of the intensity signal is maximum during the best focus. However, since the best focus position is unknown, if the applied voltage is set with a higher peak level, the dynamic range is used as efficiently as possible. It is difficult to make full use of the resolution of the / D converter (usually 16 bits). On the other hand, if the applied voltage is set with a low peak level, the possibility of exceeding the dynamic range is high.

Therefore, in exposure apparatus 100 of the present embodiment, main controller 20 performs best focus control based on a light intensity signal (photoelectric conversion signal) obtained in a defocused state (or a state in which the best focus position is unknown). The applied voltage V is set so that the maximum peak value of the signal processing circuit 42 substantially falls within the dynamic range of the signal processing circuit 42. Hereinafter, this will be described specifically.

FIG. 11 is a simplified block diagram showing the configuration of a signal processing system 50 for processing signal light (slit transmitted light).

This signal processing system 50 includes an optical sensor (PM
T) 24 and an analog amplifier 4 composed of an operational amplifier circuit
4. Signal processing circuit 42 including A / D converter 48, D / A converter 46, DC / DC converter 52, etc.
And In this signal processing system 50, the optical sensor 2
4 is amplified by an analog amplifier 44, and the amplified analog signal is converted into a digital signal by an A / D converter 48.
Input to main controller 20. The main controller 20 gives a voltage command value (0 to FFFF) to, for example, a 16-bit D / A converter 46. As a result, a DC voltage signal of, for example, 1 to 10 V corresponding to the voltage command value is output from the D / A converter 46, and the DC voltage signal is
The voltage is boosted by the 0-times DC / DC converter 52,
A high voltage of about 100 to 1000 V is applied between the anode and the cathode of the optical sensor 24. In the present embodiment, a voltage command value for determining the applied voltage V is set by the main controller 20 based on the output of the A / D converter 48 in accordance with the principle described below, whereby the signal sensitivity of the signal processing system 50 is set. Is set.

FIGS. 12A to 12C schematically show how the intensity signal of the aerial image of the pseudo isolated line pattern changes according to the focus position. These figures show examples where the slit width (2D) is sufficiently small (substantially infinitesimal). FIG. 12A shows the best focus state, and the defocus amount increases in the order of FIGS. 12B and 12C. Since the total amount (integrated light amount) of signal light (slit transmitted light) should be constant regardless of the defocus amount, FIGS. 12 (A) to 12 (C)
, The area s and the total area S of each mountain should be the same value. Here, since there are five peaks, the integrated light amount S = 5 × s. The signal capture width is 5
Since it is equal to the pitch, the pitch is 5p, where p is the pitch. FIG.
2 (A) to FIG. 12 (C), the average signal intensity a
ve are equally constant (5s / 5p = s / p) (see FIG. 12D). Therefore, the applied voltage V, that is, a voltage command value for determining the applied voltage V (hereinafter, appropriately referred to as “applied voltage V”) is adjusted until the average value of the signal obtained at the unknown focus position reaches the target value.

From FIG. 12A, PEAK = s / w (9), where s is the line width in design, and s = ave × p (10).

Therefore, the following equation (11) is established. PEAK = s / w = ave × p / w (11)

That is, the peak value PEAK at the best focus in the case of a pseudo isolated line is converted by the above equation (11) based on the target average value ave. Therefore, by determining the applied voltage V such that the peak value PEAK calculated by the above equation (11) substantially falls within the dynamic range of the signal processing circuit 42, the signal sensitivity of the dynamic range can be effectively utilized. Setting is possible.

However, since the slit actually has a finite width, the above setting is actually used in a special case (for example, when the slit width (0.2 μm) and the line width coincide with each other). Other than ()) are not considered applicable. If the slit has a finite width, the signal will be dull at the width of the slit. In order to effectively utilize the dynamic range, it is necessary to match the peak value of the dull signal with the peak before dulling. Therefore, a method for matching the signal peak value when the signal is dull to the signal peak value when the slit width is sufficiently small will be described below.

First, as shown in FIG. 13A, a case where the width MARK of the target mark in the scanning direction of the spatial image PM ′ is larger than the width 2D of the slit 22 will be described.

FIG. 13B shows an intensity signal of an aerial image PM ′ having a sufficiently small slit width (infinitely small).
FIG. 3 (C) shows the intensity signal of the aerial image PM ′ when the slit width is 2D finite. In these figures, if both the peak values are PEAK, the area SA can be approximated to the area SB. Therefore, the following equation (12)
Holds. PEAK = SA / MARK = SB / MARK (12)

According to the above equation (12), the integrated value of one peak of the photoelectric conversion signal obtained by scanning the slit 22 having a finite width and the width (design value) of the spatial image PM ′ of the measurement mark in the scanning direction. Based on the above, the signal peak value when the width of the slit 22 is sufficiently small (when it is almost close to the best focus state) can be calculated. This equation (12) can be regarded as the equation (11) in which s and w are replaced with SB and MARK, respectively, and are substantially equivalent.
That is, the peak value PEAK when the slit width is sufficiently small can be calculated by dividing the integral value (area) of one peak of the photoelectric conversion signal by the mark width. Therefore, by determining the applied voltage V such that the peak value PEAK calculated based on the equation (12) substantially falls within the dynamic range of the signal processing circuit 42, the signal sensitivity is set so that the dynamic range is effectively used. Becomes possible.

Next, as shown in FIG. 14A, the case where the width of the spatial image PM ′ of the target mark in the scanning direction is smaller than the width 2D of the slit will be described.

FIG. 14B shows an intensity signal of an aerial image PM ′ having a sufficiently small slit width (infinitely small), and FIG.
4 (C) shows an aerial image P when the slit width 2D is finite.
The intensity signal of M 'is shown. In these figures,
Assuming that both peak values are PEAK, the following equation (13) holds. PEAK = SC / MARK = SD / 2D (13)

According to the above equation (13), the slit 22 is calculated based on the integral value of one peak of the photoelectric conversion signal obtained by scanning the slit 22 having a finite width and the slit width 2D.
Can be calculated when the width is sufficiently small (when it is almost close to the best focus state). That is, the peak value PEAK when the slit width is sufficiently small can be calculated by dividing the integral value (area) of one peak of the photoelectric conversion signal by the slit width 2D. Therefore, the PEAK calculated based on the equation (13) is the signal processing circuit 4
By determining the applied voltage V so as to substantially fall within the dynamic range of 2, the signal sensitivity can be set while making the most of the dynamic range.

As is apparent from the above relationship, the integral value of one peak of the photoelectric conversion signal obtained by scanning the slit 22 having a finite width is determined by the line width (design value) of the aerial image PM ′ of the measurement mark. : Line width of measurement mark x projection magnification) and the value obtained by dividing by the larger dimension of slit width 2D.
It is possible to set the signal sensitivity of the signal processing system 50 so that the dynamic range of the signal processing system 50 can be effectively used as much as possible.

The applied voltage V for setting the signal sensitivity of the signal processing system 50 so that the dynamic range of the signal processing system 50 determined as described above can be utilized most effectively, that is, the applied voltage V The voltage command value to be determined is normally a value that should not change once it is set, so it is desirable to store it in the storage device 51 once the optimum value has been obtained. However, this applied voltage V depends on the type of the target measurement mark (the duty ratio in the case of the L / S mark,
Line width), illumination conditions (including illumination types of normal illumination, small σ illumination, annular illumination, deformed illumination, coherence factor σ value, annular ratio in the case of annular illumination, etc.), and projection optical system P
It depends on exposure conditions in a broad sense including the numerical aperture of L, the wavelength of illumination light, and the like.

Therefore, in this embodiment, under various exposure conditions that are normally assumed, focus measurement by the above-described slit scan type aerial image measurement and setting of signal sensitivity are performed, and an optimal voltage command is set for each exposure condition. Value (applied voltage V)
Are obtained in advance and stored in the storage device 51. And
When performing aerial image measurement for focus calibration or the like during normal operation of the exposure apparatus, the main controller 2
In the case of 0, a voltage command value corresponding to the exposure condition (illumination condition, type of target measurement mark, numerical aperture, wavelength, etc.) at that time is read from the storage device 51, and the voltage command value is set to D.
/ A converter 46 is provided as a voltage command value.

Incidentally, in order to maintain good performance of the exposure apparatus, it is necessary to periodically perform focus calibration and also perform calibration of a dose amount (exposure amount). Here, the calibration of the dose performed by the exposure apparatus of the present embodiment will be described.

In the present embodiment, the reference intensity values obtained under various exposure conditions, that is, the best focus position and the best dose under various exposure conditions, are stored in the storage device 51 for the calibration of the exposure amount. The peak value of the light intensity signal (photoelectric conversion signal) corresponding to the aerial image in the amount is stored.

Here, a method of obtaining (determining) the reference intensity value will be described.

First, at the time of device adjustment in the manufacturing stage of the exposure device 100 or at the time of periodic device adjustment, under the at least one exposure condition, the best exposure amount is obtained by using the predetermined measurement mark PM by the printing method described above. Is measured. In this case, the best exposure amount is determined as a light amount at which the line width of the resist image obtained by transferring the measurement mark PM onto the wafer W via the projection optical system PL becomes a predetermined line width at the time of best focus. Specifically, the best light amount can be the light amount at which the line width of the resist image substantially coincides with the line width of the line width of the line pattern constituting the measurement mark PM times the projection magnification.

Then, the operator inputs the best exposure amount obtained as described above as a target light amount to the main controller 20 via the input / output device 30. Next, when the operator instructs the start of measurement, in response to the instruction, the main controller 20 sets the measurement mark PM as the target mark under the exposure condition (reference measurement condition) in which the target light amount is set to the light amount. The best focus position is measured as described above. That is, the main controller 20 irradiates the reticle R with the illumination light IL in a state where the illumination area is defined so that the illumination light IL is emitted only to the measurement mark PM, and measures the spatial image of the measurement mark PM. This is performed by the slit scan method as described above. At this time, main controller 20 repeats a plurality of times while changing the position of slit plate 90 in the Z-axis direction (ie, the Z position of wafer stage WST) at, for example, about 15 steps at a pitch of 0.1 μm. The intensity signal (photoelectric conversion signal) is stored in an internal memory (reference measurement step).

Then, based on the photoelectric conversion signal obtained at each position of the slit plate 90 in the Z-axis direction, the first
Or the second method, the best focus position of the projection optical system PL under this reference measurement condition is determined. FIG.
5 shows an example of the photoelectric conversion signal PS corresponding to the best focus position thus obtained.
Therefore, the main controller 20 determines, for example, the peak value PK (the level indicated by the dotted line in FIG. 15) of the photoelectric conversion signal PS as the reference intensity value and stores it in the storage device 51 (reference intensity value determination step).

In this case, in order to improve the measurement accuracy and the measurement reproducibility, the above-described reference measurement step and reference intensity value determination step are repeated a plurality of times, and the average value of the peak values obtained in each time is calculated. , A reference intensity value.

Since the best exposure amount determined as described above also varies depending on the exposure conditions, it is desirable to determine the reference intensity value accordingly. Therefore, in the present embodiment, a plurality of different exposure conditions (types of target measurement marks (duty ratio and line width in case of L / S mark, line width)) and illumination conditions (normal illumination, small σ illumination, annular illumination, deformation In addition to the illumination type of illumination, it also includes a coherence factor σ value, an annular ratio in the case of annular illumination, and the like), a numerical aperture of the projection optical system PL,
With respect to exposure conditions in a broad sense including the wavelength of illumination light, etc., the best exposure amount is determined in advance by a printing method. Then, the above-described reference measurement step and reference intensity value determination step are repeatedly performed using the best exposure amount as a target exposure amount, and a reference intensity value (peak value of a photoelectric conversion signal) under each exposure condition is obtained. Then, the reference intensity value obtained in this way is stored in the storage device 51.

When the exposure apparatus 100 is used, the main controller 20 sets the exposure condition set at that time (the one selected from the plurality of exposure conditions for which the above-described reference intensity value determination is performed). The best focus of the projection optical system PL using the aforesaid slit scan aerial image measurement every time exposure of a predetermined number of wafers (including one wafer) is completed under a predetermined interval, for example, under one exposure condition). The position is measured by the same method as described above (actual measurement step), and the peak value of the photoelectric conversion signal corresponding to the measured best focus position is set as the target intensity value (calculation step). Then, the main controller 20 reads the reference intensity value under the exposure condition set at that time from the storage device 51, compares the reference intensity value with the target intensity value, and based on the result of the comparison. Then, a change in the illumination light transmittance in the illumination optical path (a change in image plane illuminance) is calculated, and an exposure amount at the time of reticle pattern transfer is set according to the calculation result (exposure amount setting step).

For example, main controller 20 can monitor the deterioration of the image plane illuminance by determining whether or not the target intensity value matches the reference intensity value within a predetermined allowable range.

Further, main controller 20 easily calculates the correction amount of the exposure amount (image surface illuminance) at the time of exposure by calculating what percentage of the target intensity value is lower than the reference intensity value. The exposure amount can be appropriately set immediately before the start of the exposure. When the correction amount is small, for example, the main controller 20 adjusts the repetition frequency of the pulse emission from the light source 1 (the number of pulses per unit time) when the correction amount is small. When the correction amount is large, for example, the main controller 20 changes the dimming rate of the ND filter (dimming filter) (see FIG. 2) in the illumination system 10 and adjusts the repetition frequency of the light source 1. It is performed by performing in combination.

As described above, in the exposure apparatus 100,
The irradiation of the illumination light IL onto the projection optical system PL changes the best focus position of the projection optical system PL. Therefore,
In the exposure apparatus 100 of the present embodiment, the projection optical system PL
In order to suppress the occurrence of defocus due to the variation in irradiation at the best focus position, correction of the detection offset of the focus position detection system (60a, 60b), that is, calibration is performed according to the variation in irradiation at the best focus position. It has become. In the case of the present embodiment, this calibration is performed by the plane parallel 74 in the light receiving system 60b.
This is done by adjusting the rotation angle of.

The focus position detecting system (60a, 60
The principle of correction of the detection offset in b) will be described.

That is, in the present embodiment, at least under the exposure condition, the illumination optical system PL is continuously irradiated with the illumination light IL for a predetermined time, and the measurement mark PM is set as the target pattern and the above-described best focus position is determined. By measuring the measurement continuously or intermittently at predetermined intervals, the best focus position of the projection optical system that changes every moment is obtained. When the data of each best focus position obtained as a result is plotted on a coordinate system in which the horizontal axis is time t and the vertical axis is the Z position, and fitted with an appropriate function,
For example, as shown in the section at time t ₀ ~t ₂ in FIG. 16, the change indicating the irradiation amount of change of the illumination light IL, the relationship between the change in the best focus position of projection optical system PL with respect to the projection optical system PL A curve is obtained. When the initial best focus position of the projection optical system PL is set to Z ₀ and illumination light is incident on the projection optical system PL from time t ₀ , the best focus position fluctuates exponentially with time, and a constant position Z at time t ₁ . Stabilizes at ₁ . The position Z ₁ is the saturation point of the variation corresponding to the incident energy at that time.

Next, after a lapse of sufficient time that the best focus position of the projection optical system PL returns to the initial value Z ₀ , the projection optical system PL is irradiated with the illumination light IL for a time (t ₂ -t ₀ ). Then, after the irradiation is stopped for the time Δt, the above-described best focus position is measured. Next, the projection optical system PL
After a lapse of time sufficient for the best focus position to return to the initial value Z ₀ , the projection optical system PL is irradiated with the illumination light IL for the time (t ₂ −t ₀ ), and the irradiation is performed for the time 2 · Δt. After stopping, the above-described best focus position is measured. In this way, the same measurement is repeated n times such that t ₃ −t ₂ = n · Δt. Then, the measurement result of the best focus position of the obtained n times plotted on the coordinate system, the fitting of these plotted points with a suitable function, as shown in a section in FIG. 16 time t ₂ ~t ₃ Here, a change curve indicating a time change of the best focus position of the projection optical system PL while the irradiation of the illumination light IL is stopped is obtained.
This change curve Then stop the irradiation of the illumination light IL at the time t ₂ (canceled), return to the original from exponentially Z ₁ with the best focus position is time, reaches the initial position Z ₀ is at time t ₃ It shows that.

The magnitude of the variation ΔZ _S of the best focus position up to the saturation point with the characteristic shown in FIG. 16 naturally changes proportionally according to the incident energy (the transmittance of the reticle R and the illumination light intensity). time from t ₀ t ₁ may become both the projection optical system PL specific constant value to the constant Td when falling from the constant Tu and time t ₂ when rising up t ₃ to, various reticle and illumination condition This was confirmed by repeating the same experiment as above. This time constant varies depending on the type and structure of the projection optical system.
It is about 00 seconds.

In this embodiment, the irradiation fluctuation characteristic curve at the best focus position as shown in FIG. 16 is stored in the storage device 51 as table data.

During normal use of the exposure apparatus 100, the main controller 20 controls the integrated value of the measured value of the integrator sensor 53 in the illumination system 10 (or the integrated value of the energy monitor in the light source 1). Value or the product of the total number of light emission pulses of the light source 1 and the pulse energy value per pulse)
And the elapsed time, the irradiation history of the illumination light energy from the initial time to the present time on the projection optical system PL is always obtained, and at regular intervals in accordance with the irradiation fluctuation of the best focus position corresponding to the irradiation history. Immediately before the start of exposure, the rotation angle of the plane parallel 74 is adjusted to correct the detection offset of the focus detection system (60a, 60b), that is, focus calibration is performed.

If the storage device 51 has only the irradiation fluctuation characteristic curve of the best focus position measured under a single exposure condition (reticle transmittance and illumination light intensity), the main controller 20 controls the actual Irradiation variation may be calculated by proportional calculation based on the transmittance of the reticle R, the illumination light intensity, and the reticle transmittance and the illumination light intensity at the time of measurement.

As is clear from the above description, in the present embodiment, the measurement processing device,
An exposure amount setting device and a signal sensitivity setting device are configured, and
The main control device 20 and the drive section 81 constitute a correction device.

As described above in detail, according to the exposure apparatus 100 of the present embodiment, during actual exposure, the main controller 20 performs the above-described slit scan type aerial image measurement under the exposure conditions. The best focus position is measured by the method, and the target intensity value which is the peak value of the photoelectric conversion signal of the aerial image corresponding to the measured best focus position corresponds to the exposure condition stored in the storage device 51. The exposure amount can be appropriately set based on the result of comparison with the reference intensity value. Therefore, it is possible to easily set an appropriate exposure amount by aerial image measurement without going through a process such as printing and development as in the related art. Moreover, since the main controller 20 can perform the measurement for setting the exposure amount, for example, every time the exposure of a predetermined number of wafers W is completed, the exposure can always be performed with an appropriate exposure amount. Becomes possible.

In the main controller 20, the above-mentioned focus calibration is repeatedly performed at predetermined intervals according to the irradiation fluctuation of the best focus position of the projection optical system PL. A pattern of the reticle R is projected onto the wafer W through the projection optical system PL while suppressing a decrease in exposure accuracy due to defocus.
It is possible to transfer the image with high accuracy.

According to the signal sensitivity setting method of the signal processing system 50 performed by the exposure apparatus 100 of the present embodiment, a linear pattern having a predetermined line width extending in the X-axis direction on the object plane of the projection optical system PL, for example. Measurement mark) Illumination light I via PM
L is irradiated onto the image plane via the projection optical system PL, and the slit 22 having a predetermined width extending in the X-axis direction on the image plane is scanned with the illumination light IL along the Y-axis direction, for example. The illumination light IL passing through the slit 22 is received by the optical sensor 24 and converted into a photoelectric conversion signal corresponding to the intensity of the received light. Then, based on the integrated value of the photoelectric conversion signal, the signal processing system 5 is used in such a manner as described above so that the dynamic range of the signal processing system 50 can be utilized as effectively as possible.
Set a signal sensitivity of 0. Thus, the signal processing system 50
As a result, the signal sensitivity is set so that the dynamic range of the illumination light IL can be used as effectively as possible.
, That is, in the case of the above embodiment, the light intensity distribution corresponding to the aerial image PM ′ of the measurement mark PM can be measured.

In the above embodiment, the peak value of the photoelectric conversion signal corresponding to the best focus position under the reference measurement condition where the light amount is set to the target light amount for the predetermined measurement mark PM is used as a reference for setting the exposure amount. The case where the reference intensity value is determined has been described, but the present invention is not limited to this. That is, the reference intensity value is
The value may be set to a value that has some relationship with the best exposure amount when exposing the measurement mark. For example, the photoelectric conversion signal of the spatial image of the measurement mark PM corresponding to the best focus position under the reference measurement condition in which the light amount is set to the target light amount for the predetermined measurement mark PM, and the line width of the line pattern forming the measurement mark PM May be determined as the reference intensity value. Specifically, for example, a slice level at which a distance between two intersections between the photoelectric conversion signal waveform and a predetermined slice level matches a value obtained by multiplying a line pattern line width by a projection magnification can be used as a reference intensity value. .

Note that the signal sensitivity (detection sensitivity) described above is used.
Is applied not only to the case where the PMT is used as an optical sensor, but also to the case where the detection sensitivity of another photoelectric conversion element is set, for example, the case where the gain of an amplifier constituting an output amplifier of the photoelectric conversion element is set. It is possible.

FIG. 17A shows a circuit configuration in which a silicon photodiode (SPD) 24 ′ is used as an optical sensor and the gain of a variable gain amplifier (variable gain amplifier) 144 is set by main controller 20. Is shown in FIG. In this case, main controller 20
The gain of the variable gain amplifier 144 is calculated and set in the same manner as the setting of the applied voltage V to the PMT in the above-described embodiment. As a result, the photoelectric conversion signal from the SPD 24 'is amplified by the variable gain amplifier 144 with the gain according to the set gain, and the A / D converter 1
The digital signal digitally converted at 46 is input to main controller 20 as an aerial image intensity signal. Also in this case, the signal processing system (SPD2) is used so that the dynamic range of the A / D converter 146 can be utilized as effectively as possible.
4 ', variable gain amplifier 144, A / D converter 14
6) is set.

As the variable gain amplifier 144, for example, an operational amplifier 148 as shown in FIG.
An inverting amplifier composed of a variable feedback resistor 152 is used. In the inverting amplifier (variable gain amplifier) of FIG. 17B, the non-inverting input of the operational amplifier 148 is grounded (G). The input signal (In) from the SPD and the feedback signal via the variable feedback resistor 152 are input to the inverting input. Here, the variable feedback resistor 1
As 52, it is desirable to use a ladder type D / A converter with an accuracy of, for example, about 16 bits. Ladder type D
The / A converter has a switch and a resistor, and has a capability of changing a resistance value with a 16-bit dynamic range and accuracy.

In the above embodiment, the optimal voltage command value (applied voltage V) and the reference intensity value are obtained in advance for each exposure condition, and these are stored in the storage device 51. The present invention is not limited to this,
The storage device only needs to store a reference intensity value or the like for at least one exposure condition.

In the above embodiment, the projection optical system PL
To correct the detection offset of the focus detection system (60a, 60b) according to the irradiation variation of the best focus position of
The case where focus calibration is performed by adjusting the inclination angle of the plane parallel 74 in the light receiving system 60b has been described. However, the present invention is not limited to this, and an electrical offset is added to the detection signal of the focus detection system (60a, 60b). May be added. Alternatively, a focus detection system (60a, 60
The detection value itself in b) may be corrected by calculation. The point is that the exposure may be performed in a state where the detection offset of the focus detection systems (60a, 60b) is corrected as a result.

Further, in the above embodiment, even when the measurement mark is a mark composed of an isolated line or a pseudo isolated line, in order to accurately measure the best focus position, the photoelectric conversion signal of the spatial image of the measurement mark is required. Although a method of detecting the best focus position using a predetermined area ratio as an evaluation criterion is adopted, it is a matter of course that the present invention is not limited to this. For example, when the measurement mark is an L / S mark having a duty ratio of 1: 1 and the like, the photoelectric conversion signal is subjected to Fourier transform.
It is possible to adopt a method of detecting the best focus position using the contrast, which is the amplitude ratio between the next component and the zero-order component, and other evaluation criteria.

In the above embodiment, the case where the present invention is applied to the projection exposure apparatus of the step-and-scan method has been described. However, the present invention is not limited to this. The present invention can be applied to a step-and-repeat type exposure apparatus in which the substrate is transferred stepwise while the substrate is sequentially moved.

In the above embodiment, the case where the present invention is applied to an exposure apparatus for manufacturing a semiconductor has been described. However, the present invention is not limited to this. The present invention can be widely applied to an exposure apparatus for manufacturing, a thin film magnetic head, an image sensor, a micromachine, a DNA chip, and an exposure apparatus for manufacturing a reticle, a mask, and the like.

Further, in the above embodiment, the case where KrF excimer laser light (248 nm), ArF excimer laser light (193 nm), or the like is used as the exposure illumination light has been described. i
A line (365 nm), an F ₂ laser beam (157 nm), a harmonic of a copper vapor laser, a YAG laser, or the like can be used as exposure illumination light.

Further, in the above embodiment, the case where the reduction system and the refraction system are used as the projection optical system has been described.
The invention is not limited to this, and an equal magnification or magnification system may be used as the projection optical system, and any of a refraction system, a catadioptric system, and a reflection system may be used.

The illumination optical system and the projection optical system PL composed of a plurality of lenses are incorporated in the main body of the exposure apparatus for optical adjustment, and the reticle stage RST and the wafer stage WST composed of a number of mechanical parts are mounted on the main body of the exposure apparatus. The exposure apparatus 100 of the present embodiment can be manufactured by attaching and connecting wires and pipes, and further performing overall adjustment (electric adjustment, operation confirmation, and the like). It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.

<< Device Manufacturing Method >> Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 100 in a lithography process will be described.

FIG. 18 shows devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads,
The flowchart of the example of manufacture of a micromachine etc. is shown. As shown in FIG.
In 1 (design step), a function / performance design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, in step 202 (mask manufacturing step)
A mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 203 (wafer manufacturing step)
A wafer is manufactured using a material such as silicon.

Next, in step 204 (wafer processing step), using the mask and the wafer prepared in steps 201 to 203, an actual circuit or the like is formed on the wafer by a lithography technique or the like as described later. . Next, in step 205 (device assembly step), device assembly is performed using the wafer processed in step 204. In this step 205,
Steps such as a dicing step, a bonding step, and a packaging step (chip encapsulation) are included as necessary.

Finally, step 206 (inspection step)
In step S205, inspections such as an operation check test and a durability test of the device created in step 205 are performed. After these steps, the device is completed and shipped.

FIG. 19 shows a detailed flow example of step 204 in the semiconductor device. In FIG. 19, in step 211 (oxidation step), the surface of the wafer is oxidized. Step 212 (CV
In step D), an insulating film is formed on the wafer surface. In step 213 (electrode formation step), electrodes are formed on the wafer by vapor deposition. Step 214
In the (ion implantation step), ions are implanted into the wafer. Each of the above steps 211 to 214 constitutes a pre-processing step in each stage of wafer processing, and is selected and executed according to a necessary process in each stage.

In each stage of the wafer process, when the above-mentioned pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 2
In 15 (resist forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 216 (exposure step), the circuit pattern of the mask is transferred onto the wafer by the lithography system (exposure apparatus) and the exposure method described above. Next, in step 218 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 219 (resist removing step), unnecessary resist after etching is removed.

By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.

If the device manufacturing method of this embodiment described above is used, the exposure apparatus of the above embodiment is used in the exposure step (step 216), so that defocusing and inaccurate setting of the target exposure amount occur. The reticle pattern can be transferred onto the wafer with high accuracy by preventing the occurrence of exposure failure due to these. As a result, it is possible to improve the productivity (including the yield) of a highly integrated device.

[0206]

As described above, according to the exposure amount setting method and the first exposure apparatus of the present invention, there is an effect that an appropriate exposure amount can be easily set.

According to the second exposure apparatus of the present invention,
When repeating exposure continuously, there is an effect that a decrease in exposure accuracy due to defocus can be suppressed.

According to the device manufacturing method of the present invention, there is an effect that the productivity of the device can be improved.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a specific configuration of an illumination system.

FIG. 3 is a diagram showing an internal configuration of an aerial image measuring device and an alignment system of FIG. 1;

FIG. 4 is a diagram showing a state where an alignment mark on a wafer is detected by an alignment system.

FIG. 5 is a diagram schematically illustrating a configuration of a focus position detection system and a processing drive unit that processes an output signal of the focus position detection system and drives a plane parallel.

FIG. 6 is a diagram partially showing a specific configuration of a plane parallel and a driving unit thereof.

FIG. 7A is a plan view showing an aerial image measuring device in a state where an aerial image PM ′ is formed on a slit plate at the time of aerial image measurement, and FIG. FIG. 7 is a diagram showing an example of a photoelectric conversion signal (light intensity signal) P obtained at that time.

8A and 8B are diagrams for explaining a first method for detecting a best focus position, and FIG. 8A is a graph showing the slit transmitted light intensity in the best focus state obtained as a result of simulation on the horizontal axis. FIG. 8B is a diagram illustrating the slit transmitted light intensity in a state where the focus is 1 μm defocused, with the horizontal axis as the Y position of the slit.

FIG. 9 is a diagram for explaining a method of obtaining a best focus position using an area ratio as an evaluation amount.

10A and 10B are diagrams for explaining a second method for detecting a best focus position, and FIG. 10A is a graph showing the slit transmitted light intensity in the best focus state obtained as a result of simulation on the horizontal axis. FIG. 10B is a diagram showing the slit transmitted light intensity in a state where the focus is 1 μm defocused, with the horizontal axis as the Y position of the slit.

FIG. 11 is a simplified block diagram showing the configuration of a signal processing system that processes signal light (slit transmitted light).

FIGS. 12A to 12D are diagrams for explaining a method of setting signal sensitivity when the slit width (2D) is sufficiently small (substantially infinitely small).

FIGS. 13A to 13C illustrate a method of setting signal sensitivity when the slit width (2D) is finite and the width of the aerial image of the mark is wider than the slit width. FIG.

FIGS. 14A to 14C illustrate a method of setting signal sensitivity when the slit width (2D) is finite and the width of the aerial image of the mark is smaller than the slit width. FIG.

FIG. 15 is a diagram illustrating an example of a photoelectric conversion signal corresponding to a best focus position obtained by the first method or the second method.

FIG. 16 is a diagram showing irradiation fluctuation characteristics at a best focus position of the projection optical system.

FIG. 17 (A) is a diagram showing a simplified configuration of a control system when a signal sensitivity (detection sensitivity) setting technique is applied to the setting of the detection sensitivity of a photoelectric conversion element other than a PMT. FIG. 17B is a diagram showing the variable gain amplifier of FIG. 17A in more detail.

FIG. 18 is a flowchart illustrating an embodiment of a device manufacturing method according to the present invention.

FIG. 19 is a flowchart showing details of step 204 in FIG. 18;

[Explanation of symbols]

10: illumination system (illumination device), 20: main controller (measurement processing device, exposure amount setting device, signal sensitivity setting device, part of correction device), 22: slit (measurement pattern), 24 ...
Optical sensor (photoelectric conversion element), 42 ... signal processing circuit, 50
... Signal processing system, 51 ... Storage device, 60a ... Irradiation system (part of position detection system), 60b ... Light receiving system (part of position detection system), 81 ... Drive unit (part of correction device), 90 ... Slit plate (pattern forming member), 100 ... Exposure device, PL ...
Projection optical system, IL: illumination light, PM: measurement mark, PM '
... aerial image, W: wafer (substrate), R: reticle (mask), WST: wafer stage (substrate stage).

Continuing from the front page (72) Inventor, Harumi Shunmi 3-2-2, Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation (72) Inventor Naoto Kondo 2-3-2, Marunouchi, Chiyoda-ku, Tokyo Co., Ltd. Inside Nikon (72) Inventor Eiji Takane 3-2-3 Marunouchi, Chiyoda-ku, Tokyo F-term in Nikon Corporation (reference) 5F046 DA02 DA13 DB01 DB05 DB10

Claims (17)

[Claims] 1. An exposure amount setting method for setting an exposure amount when a mask pattern is transferred onto a substrate via a projection optical system, wherein a predetermined measurement mark is illuminated with illumination light, and the measurement mark Forming an aerial image on an image plane via the projection optical system,
While relatively scanning the measurement pattern arranged on the image plane side of the projection optical system with respect to the aerial image, a photoelectric conversion signal according to the intensity of the illumination light through the measurement pattern, An actual measurement step of obtaining a measurement pattern at each of a plurality of positions in the optical axis direction; and a best focus position of the projection optical system based on the photoelectric conversion signals obtained at the plurality of positions in the actual measurement step. Calculating and calculating a target intensity value based on the photoelectric conversion signal corresponding to the best focus position; comparing the calculated target intensity value with a reference intensity value obtained in advance; An exposure setting step of setting an exposure at the time of pattern transfer. 2. The reference intensity value is a peak value of the photoelectric conversion signal corresponding to the best focus position measured in advance under a reference measurement condition in which a light amount is set to a target light amount for the predetermined measurement mark. 2. The exposure setting method according to claim 1, wherein: 3. The photoelectric conversion signal corresponding to the best focus position measured in advance under a reference measurement condition in which a light amount is set to a target light amount for the predetermined measurement mark, and the measurement mark 2. The exposure amount setting method according to claim 1, wherein the intensity value is set based on a line width of a line pattern constituting. 4. A method according to claim 1, wherein the predetermined measurement mark is illuminated by the illumination light under a reference measurement condition in which a light amount is set to a target light amount for the predetermined measurement mark. Formed on the image plane through the measurement pattern relative to the aerial image, the photoelectric conversion signal according to the intensity of the illumination light through the measurement pattern, for the measurement A reference measurement step for obtaining a plurality of positions in the optical axis direction of the pattern; and obtaining a best focus position of the projection optical system under the reference measurement conditions based on the photoelectric conversion signals obtained for the plurality of positions. A reference intensity value determining step of determining the reference intensity value based on the photoelectric conversion signal corresponding to the best focus position, the reference measuring step and the reference intensity value determining step. The step is repeatedly performed for a plurality of different exposure conditions, the actual measurement step and the calculation step are performed under any one exposure condition selected from the plurality of exposure conditions, In the exposure amount setting step, The reference intensity value corresponding to the selected exposure condition is compared with the target intensity value calculated in the calculation step, and the exposure amount at the time of pattern transfer is set based on the comparison result. Claim 1
Exposure amount setting method described in 1. 5. The target light amount is determined as a light amount at which a line width of a resist image obtained by transferring the predetermined measurement mark onto a substrate via the projection optical system becomes a predetermined line width at the time of best focus. 2. The method according to claim 1, wherein
The exposure amount setting method according to any one of items 1 to 4, above. 6. The exposure amount setting according to claim 4, wherein the exposure condition includes at least one of an illumination condition, a pattern type to be exposed, a target line width, and a numerical aperture of the projection optical system. Method. 7. An exposure apparatus for transferring a pattern of a mask onto a substrate via a projection optical system, comprising: an illumination device for illuminating an object with illumination light; A pattern forming member on which a measurement pattern is formed; a photoelectric conversion element that outputs a photoelectric conversion signal corresponding to the intensity of the illumination light via the measurement pattern; Illuminate the measurement mark arranged in the by the illumination device, in a state where a spatial image of the measurement mark is formed on the image plane,
Scanning the pattern forming member so that the measurement pattern is scanned relative to the aerial image,
A measurement processing device that measures a light intensity distribution corresponding to the aerial image at each of a plurality of positions in the optical axis direction of the pattern forming member based on a photoelectric conversion signal from the photoelectric conversion element;
The best focus position of the projection optical system is obtained based on the photoelectric conversion signal corresponding to the aerial image measured for each of the plurality of positions by the measurement processing device, and based on the photoelectric conversion signal corresponding to the best focus position. An exposure amount setting device that calculates the target intensity value, calculates the target intensity value, compares the calculated target intensity value with a predetermined reference intensity value, and sets the exposure amount at the time of pattern transfer based on the comparison result;
An exposure apparatus comprising: 8. The method according to claim 8, wherein the reference intensity value is a peak value of the photoelectric conversion signal corresponding to the best focus position under a reference measurement condition in which a light amount is set to a target light amount for the predetermined measurement mark. The exposure apparatus according to claim 7, 9. The photoelectric conversion signal corresponding to the best focus position under a reference measurement condition in which a light amount is set to a target light amount for the predetermined measurement mark, and a line forming the measurement mark. The exposure apparatus according to claim 7, wherein the intensity value is set based on a line width of the pattern. 10. A light intensity distribution corresponding to an aerial image of the measurement mark at each of a plurality of positions in the optical axis direction of the pattern forming member under a reference measurement condition in which a light amount is set to a target light amount for the measurement mark. Is measured under a plurality of different exposure conditions, and is determined based on the photoelectric conversion signal corresponding to the best focus position of the projection optical system under the reference measurement condition determined based on the measurement result. The measurement processing device further performs a measurement under a set exposure condition of the plurality of exposure conditions, the storage device storing a reference intensity value for each exposure condition to be performed. The amount setting device calculates a target intensity value corresponding to the aerial image measured for each of the plurality of positions by the measurement processing device, and calculates the calculated target intensity value. Together with a reference intensity value corresponding to the set exposure conditions, based on the comparison result, the exposure apparatus according to claim 7, characterized in that setting the exposure amount at the time of the pattern transfer. 11. The target light amount is determined as a light amount at which a line width of a resist image obtained by transferring the measurement mark onto the substrate via the projection optical system becomes a predetermined line width at the time of best focus. 7. The method according to claim 7, wherein
The exposure apparatus according to any one of items 0 to 10. 12. The exposure apparatus according to claim 10, wherein the exposure condition includes at least one of an illumination condition, an exposure target pattern type, a target line width, and a numerical aperture of the projection optical system. 13. A signal processing circuit for receiving the photoelectric conversion signal constituting a signal processing system having a predetermined dynamic range together with the photoelectric conversion element, wherein the measurement processing device has a signal sensitivity of the signal processing system. Including a signal sensitivity setting device, the signal sensitivity setting device,
When measuring the light intensity distribution corresponding to the aerial image based on the photoelectric conversion signal, based on the integral value of the photoelectric conversion signal, the signal so that the dynamic range of the signal processing system can be utilized most effectively. 13. The exposure apparatus according to claim 7, wherein a signal sensitivity of a processing system is set. 14. An exposure apparatus for illuminating a mask with illumination light and transferring a pattern of the mask onto a substrate via a projection optical system, wherein the illumination apparatus illuminates an object with the illumination light; A pattern forming member disposed on the image plane side of the system and having a measurement pattern formed thereon; a photoelectric conversion element that outputs a photoelectric conversion signal corresponding to the intensity of the illumination light via the measurement pattern; The measurement mark arranged on substantially the same plane as the surface to be arranged is illuminated by the illumination device, and the measurement pattern is positioned relative to the aerial image in a state where the aerial image is formed on the image plane. While scanning the pattern forming member so as to be scanned, the light intensity distribution corresponding to the aerial image based on the photoelectric conversion signal from the photoelectric conversion element is set in the optical axis direction of the pattern forming member. A measurement processing device that measures each of a plurality of positions; a position detection system that detects a position of the substrate in the optical axis direction of the projection optical system; a change in an irradiation amount of the illumination light to the projection optical system; A storage device in which a relationship with a change in the best focus position of the optical system is measured in advance using the measurement processing device, and a storage device in which the information on the relationship is stored; and a storage device that transfers the mask pattern based on the information on the relationship. A correction device for correcting a detection offset of the position detection system. 15. An exposure apparatus for illuminating a mask with illumination light and transferring a pattern of the mask onto a substrate via a projection optical system, wherein the illumination apparatus illuminates an object with the illumination light; A pattern forming member disposed on the image plane side of the system and having a measurement pattern formed thereon; a photoelectric conversion element that outputs a photoelectric conversion signal corresponding to the intensity of the illumination light via the measurement pattern; A signal processing system including a signal processing circuit to which the photoelectric conversion signal is input from an element; a measuring device that measures optical characteristics of the projection optical system based on an output of the signal processing system; A signal sensitivity setting device for setting signal sensitivity for each of a plurality of different exposure conditions. 16. The exposure apparatus according to claim 15, wherein the signal sensitivity setting device has storage means for storing signal sensitivity information of the signal processing system in accordance with the plurality of different exposure conditions. . 17. A device manufacturing method including a lithography step, wherein in the lithography step, exposure is performed using the exposure apparatus according to any one of claims 7 to 16. .