JP2004095667A - Method for measuring correction information, exposure method, aligner, exposure system, and method for manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain highly accurate exposure quantity control which is not affected by the linearity of measured values of an integrator sensor to the measured values of a reference illumination meter. <P>SOLUTION: Energy density measurement for receiving an energy beam LB injected from a light source 16 by the integrator sensor 46 and the reference illumination meter in a state that the reference illumination meter is arranged on an image surface (stage 58) of a projecting optical system PL is repeated while sequentially changing the dimming ratio of a dimmer 20. Thus, an output of the reference illumination meter and an output of the sensor 46 are obtained as measured results in each set value of the dimming rate of the dimmer 20. Then correction information for matching the output of the optical sensor 46 and the output of the reference illumination meter is calculated on the basis of the measured results. Consequently, highly accurate exposure quantity control not affected by the linearity of the measured values of the sensor 46 to the measured values of the reference illumination meter can be performed by controlling exposure quantity by using the correction information. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for measuring correction information, an exposure method, an exposure apparatus and an exposure system, and a device manufacturing method. More specifically, the present invention relates to an exposure amount control system including a light amount monitor and a dimming device in an illumination optical system. Measurement method of correction information to be used, exposure method using the measurement method, exposure apparatus for performing the exposure method, exposure apparatus and exposure system including a storage device storing the correction information, and device using the exposure system It relates to a manufacturing method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a lithography process for manufacturing a device such as a semiconductor device, a liquid crystal display device, a plasma display device, or a thin film magnetic head, an exposure apparatus such as a so-called stepper or a so-called scanning stepper has been used.
[0003]
2. Description of the Related Art In recent years, the integration of semiconductor devices has become increasingly higher, and accordingly, device rules (practical minimum line widths) of exposure apparatuses have become finer. In recent exposure apparatuses, it is required to improve the uniformity of the exposure amount (exposure amount control accuracy) to further increase the line width uniformity. Also, as the degree of integration of semiconductors increases, the line width control accuracy (in-plane uniformity, shot-to-shot uniformity, etc.) required of an exposure apparatus has become extremely strict.
[0004]
As such an exposure apparatus for ultra-fine lithography, a scanning stepper using a KrF excimer laser (output wavelength: 248 nm) and the like as a light source having a high luminance and a high output having an oscillation line in a far ultraviolet region may be used. It has become. In this type of exposure apparatus, there are many factors that determine the line width control accuracy, and one of the important factors is to uniformly control the exposure amount on the image plane.
[0005]
In order to uniformly control the exposure amount on the image plane, it is necessary to control the energy of the excimer laser light, which is a pulse laser, well. Therefore, an arbitrary point on the exposure field at the time of exposure is always irradiated with pulse light of a specific pulse number (hereinafter, referred to as “minimum exposure pulse number”) or more, and energy variations of individual pulse lights are averaged. In this way, control is performed such that a uniform exposure amount is always obtained at any point in the exposure field. For example, when the target exposure amount (set exposure amount) is low, it is difficult to irradiate pulse light of the minimum exposure pulse number or more by irradiating a high-energy pulse onto the image plane as it is. In such a case, by reducing the pulse energy, the pulse light of the minimum number of exposure pulses or more is always irradiated onto the image plane at any one point on the exposure field. For this reason, an energy monitor system is indispensable for the exposure amount control system of the exposure apparatus in order to perform the exposure amount control, and the energy monitor system is required to have good measurement reproducibility and output linearity in a use range. . Here, “linearity” means the linearity of the relationship between the illuminance (or energy density) on the image plane and the output of the energy monitor system.
[0006]
In the conventional exposure apparatus, in order to secure the linearity of the output of the above-mentioned energy monitor system, an external reference illuminometer serving as an illuminance reference is installed on an image plane, and the output of the external reference illuminometer and the output of the energy monitor system are output. Were measured, and a relationship between the outputs of the two was found to be close to a linear function, that is, a range in which the linearity of the energy monitor system was good was found, and the exposure amount was controlled using that range as the use range of the energy monitor system. For this reason, for example, a plurality of types of aperture plates having a small aperture for limiting the amount of light incident on the energy monitor system are used, and while the aperture plates are sequentially replaced, the aperture linearity of the output of the energy monitor system is good to some extent or more. Is set so that the linearity of the energy monitor system is not broken by adjusting the amount of light incident on the energy monitor system.
[0007]
[Problems to be solved by the invention]
Recently, the exposure wavelength has been further shortened, and a scanning stepper (hereinafter abbreviated as “ArF scanner”) using an ArF excimer laser (output wavelength: 193 nm) as a light source has been put to practical use. In addition, the types of resists as photosensitizers have been diversified, and relatively high-sensitivity resists such as chemically amplified resists have come to be used relatively frequently. For this reason, for example, when exposing a wafer coated with a chemically amplified resist using an ArF scanner, in order to ensure the minimum number of exposure pulses described above, the extinction ratio which has not been used conventionally is required. It has become necessary to use a neutral density filter or the like having a large size. On the other hand, it is difficult to imagine that the same ArF scanner is always used for exposing a wafer coated with the same type of resist, and the purpose of use and the like are usually different for each user.
[0008]
Against this background, an energy monitor system of an exposure apparatus has been required to have good measurement reproducibility and linearity in a wide energy range that is incomparable with conventional ones. For this reason, the conventional exposure amount control method described above, that is, a method of finding a range in which the linearity of the energy monitor system is good and performing the exposure amount control using the range as a use range of the energy monitor system is becoming difficult to cope with any more. .
[0009]
There is no doubt that the accuracy of exposure dose control will become stricter in the future with the further integration of semiconductor devices, and the linearity of the output of the energy monitor system with respect to the external reference illuminometer will be undoubtedly increased. Further improvement will be required.
[0010]
In addition, since the exposure amount control error (difference between exposure control units) between a plurality of exposure apparatuses causes a decrease in the yield of a device as a final product, the difference between exposure control units is reduced as much as possible. From the viewpoint, the exposure control system of the exposure apparatus used in the same device manufacturing line is usually managed collectively using the same reference illuminometer. However, in order to further reduce the difference between the number of exposure control units, it is assumed that the outputs of the energy monitoring systems of the individual exposure apparatuses have good linearity with respect to the reference illuminometer. However, the energy monitoring system of each exposure apparatus is required to improve the linearity in a wide energy range. It is certain that it is required to further reduce the difference in exposure amount control between the devices.
[0011]
The present invention has been made under such circumstances, and a first object of the present invention is that the output of the reference illuminometer is not affected by the linearity of the output of the optical sensor for energy monitoring in the exposure control system. An object of the present invention is to provide a method for measuring correction information that enables highly accurate exposure amount control.
[0012]
A second object of the present invention is to provide an exposure method and an exposure apparatus capable of accurately transferring a fine pattern onto an object.
[0013]
A third object of the present invention is to provide an exposure system capable of reducing the difference in exposure amount control between the devices.
[0014]
A fourth object of the present invention is to provide a device manufacturing method capable of improving device productivity.
[0015]
[Means for Solving the Problems]
The invention according to claim 1 is an optical sensor (46) for receiving a part of the energy beam (IL) branched from the light source (16) to the mask (R) on the optical path of the energy beam (IL), and the light source. And a dimming device (20) that is disposed between the light source and the branch point and that can set the dimming rate continuously or intermittently within a predetermined range. In a measurement method, the energy beam emitted from the light source in a state where a reference illuminometer serving as a reference for illuminance is arranged on an image plane on which an image of a pattern on the mask is formed, and the light sensor and the reference Repeating the measurement of the energy density received by the illuminometer while sequentially changing the dimming rate of the dimmer; and determining the output of the optical sensor based on the result of the repeatedly performed energy density measurement as the reference. Light meter output It is a measurement method of the correction information including; calculating a correction information for adjusting relative.
[0016]
According to this, an energy beam emitted from a light source is received by an optical sensor and a reference illuminometer while a reference illuminometer serving as an illuminance reference is arranged on an image plane on which an image of a pattern on a mask is formed. The energy density measurement is repeatedly performed while sequentially changing the dimming rate of the dimming device. Thereby, for example, when the dimming rate of the dimming device can be set continuously within a predetermined range, the dimming rate is changed at a predetermined step pitch, for example, within the predetermined range, and the set value of each dimming rate is changed. Each time, the output of the reference illuminometer and the output of the optical sensor are obtained as measurement results. Further, for example, when the dimming rate of the dimming device can be set intermittently within a predetermined range, for example, the dimming rate is changed according to the intermittent setting value, and the dimming rate is changed for each set value of each dimming rate. Then, the output of the reference illuminometer and the output of the optical sensor are obtained as measurement results.
[0017]
Next, correction information for adjusting the output of the optical sensor with respect to the output of the reference illuminometer is calculated based on the measurement result. The calculation of the correction information is performed, for example, as follows.
[0018]
When the output of the optical sensor has no measurement offset depending on the energy value at the time of measurement, that is, when the linearity of the output I of the optical sensor is ideal, the output I of the optical sensor and the output P of the reference illuminometer are The relationship should be proportional, and if the proportionality constant is α, it is expressed as I = α · P. That is, the relationship of P = I / α should be established.
[0019]
However, actually, since the linearity of the output I of the optical sensor is different from the ideal state, the measurement data P, which is the output of the corresponding reference illuminometer, is obtained based on the result of the repeated energy density measurement. _n And the measurement data I which is the output of the optical sensor _n Relationship with α _n = I _n / P _n (N = 1 to N), I _n Every (so P _n Correction information (α) for adjusting the output of the optical sensor with respect to the output of the reference _n ).
[0020]
Alternatively, the measurement data P which is the output of the corresponding reference illuminance meter _n And the measurement data I which is the output of the optical sensor _n (I _n , P _n ) Is plotted on a rectangular coordinate system with the horizontal axis representing the output P of the reference illuminometer. I at each plot point _n And the error (I _n -I) Ratio ΔI to theoretical value _n Approximate curves ΔI = f (P) for all (n = 1 to N) are obtained by the least squares method, and this approximate curve ΔI = f (P) is used as a correction function as correction information.
[0021]
Therefore, according to the measurement method of the present invention, it is possible to obtain correction information capable of correcting the output (measured value) of the optical sensor in a wide energy range in the same manner as in the case where the linearity is ideal. By performing the exposure control using this correction information, a high-precision exposure control that is not affected by the linearity of the output of the optical sensor for energy monitoring in the exposure control system with respect to the measured value of the reference illuminometer. Control becomes possible.
[0022]
In this case, as in the measurement method according to claim 2, the correction information is the correction information α described above. _n And the corresponding P _n However, it may be a second-order or higher-order correction function.
[0023]
According to a third aspect of the present invention, a step of measuring the correction information by the measurement method according to the first or second aspect; correcting the output of the optical sensor using the measured correction information; Transferring the pattern onto an object disposed on the image plane while controlling the integrated energy amount on the image plane based on the output of the optical sensor.
[0024]
According to this, the output (measurement value) of the optical sensor can be corrected in the same manner as in the case where the linearity is ideal, corresponding to the above wide energy range by the measurement method according to claim 1 or 2. Correction information is measured, the output of the optical sensor is corrected using the measured correction information, and the integrated energy amount on the image plane is controlled based on the corrected output of the optical sensor, and the correction is performed on the image plane. The pattern is transferred onto the placed object. Therefore, the controllability of the pattern line width can be improved, and a fine pattern can be accurately transferred onto an object. In the present specification, the controllability of the pattern line width is a concept including the uniformity of the line width between a plurality of partitioned areas, the in-plane uniformity of the line width in a transfer destination area where a pattern is transferred, and the like. is there.
[0025]
The invention according to claim 4 is an exposure apparatus which illuminates a mask (R) with an energy beam (IL) emitted from a light source (16) and transfers a pattern formed on the mask onto an object (W). An optical sensor (46) for receiving a part of the energy beam branched on the optical path of the energy beam from the light source to the mask; and an optical sensor (46) disposed between the light source and the branch point, and having its light dimmed. A dimming device (20) capable of setting a rate continuously or intermittently within a predetermined range; a projection optical system (PL) for projecting an image of a pattern on the mask onto the object; An object stage (WST) on which a reference illuminometer serving as a reference for illuminance can be installed; and a storage device storing correction information for adjusting an output of the optical sensor with respect to an output of the reference illuminometer. (51) and before When transferring the image of the pattern to the object on the object stage via the projection optical system, the output of the optical sensor is corrected using the correction information, and the corrected output of the optical sensor is used as a reference. An exposure control device (50) for controlling the integrated energy amount on the image plane.
[0026]
According to this, when transferring the image of the pattern formed on the mask to the object on the object stage via the projection optical system, the exposure amount control device uses the output of the optical sensor stored in the storage device as the reference illuminance. The output of the optical sensor is corrected using the correction information for adjusting the output of the meter, and the integrated energy amount on the image plane is controlled based on the corrected output of the optical sensor. For this reason, the output (measurement value) of the optical sensor corresponding to a wide energy range can be reduced by storing in advance in the storage device correction information capable of correcting the output (measured value) in the same manner as when the linearity is ideal. Even if the dimming rate of the optical device is set arbitrarily, it is possible to control the exposure amount using the correction information corresponding to the output of the optical sensor at that time, and the reference illuminometer measures the measured value of the optical sensor. High-precision exposure amount control that is not affected by the linearity of the value can be performed. As a result, the controllability of the line width of the pattern transferred onto the object arranged on the image plane is improved, and it becomes possible to transfer a fine pattern onto the object with high accuracy.
[0027]
In this case, the correction information may be a second-order or higher-order correction function.
[0028]
In each of the exposure apparatuses according to claims 4 and 5, as in the exposure apparatus according to claim 6, the energy beam emitted from the light source in a state where the reference illuminometer is installed on the stage is used. The measurement of the energy received by the optical sensor and the reference illuminometer is repeatedly performed while sequentially changing the dimming rate of the dimming device. Based on the result of the repeatedly performed energy measurement, the output of the optical sensor and the reference A measurement control device (50) for obtaining a relationship with an output from the illuminometer; and calculating correction information for adjusting the output of the optical sensor with respect to the output of the reference illuminometer based on the obtained relationship. And a calculating device (50).
[0029]
According to a seventh aspect of the present invention, a plurality of exposure apparatuses (10) in which illuminance is collectively managed using the same reference illuminometer. ₁ -10 _k And an optical sensor (46) for receiving a part of the energy beam (IL) branched from the light source (16) to the mask on the optical path of the energy beam (IL). A dimming device (20) arranged between the light source and the branch point, the dimming rate of which can be set continuously or intermittently within a predetermined range; and the correction information according to claim 1 or 2; A storage device (51) in which correction information measured by the measurement method is stored in advance; and the output of the optical sensor is corrected using the correction information, and the mask based on the corrected output of the optical sensor is used as a reference. A control device (50) for transferring the pattern onto an object arranged on the image surface while controlling the integrated energy amount on the image surface on which the image of the pattern is formed. It is.
[0030]
According to this, each exposure apparatus includes a storage device in which the correction information measured by the correction information measuring method according to claim 1 or 2 is stored in advance. In this case, the storage device of each exposure apparatus stores correction information that can correct the output (measured value) of each optical sensor corresponding to a wide energy range in the same manner as when linearity is ideal. Each is stored. Then, the control device of each exposure apparatus corrects the output of the optical sensor using the correction information, and based on the corrected output of the optical sensor as a reference, the integrated energy on the image plane on which the image of the pattern on the mask is formed. The pattern is transferred onto an object placed on the image plane while controlling the amount. Therefore, in any exposure apparatus, the linearity of the output of the optical sensor with respect to the output of the same reference illuminometer is corrected, so that a plurality of exposure apparatuses in which the illuminance is collectively managed using the same reference illuminometer, for example, the same With a plurality of exposure apparatuses used in the device manufacturing line, it is possible to reduce the difference between the number of exposure control devices.
[0031]
The invention according to claim 8 is a device manufacturing method including a lithography step, wherein in the lithography step, the same plurality of objects are exposed using the exposure system according to claim 7. Device manufacturing method.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
<< 1st Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an exposure apparatus 10 according to the first embodiment. The exposure apparatus 10 is a step-and-scan type scanning exposure apparatus using an excimer laser light source as a pulse light source as an exposure light source.
[0033]
The exposure apparatus 10 includes an illumination system 12 including a pulse light source 16, a reticle stage RST as a mask stage which holds a reticle R illuminated by the illumination system 12 and moves in a predetermined scanning direction, and a reticle R. A projection optical system PL that projects a pattern onto a wafer W as a substrate, an XY stage 14 that holds the wafer W and moves on a horizontal plane (within an XY plane), and a control system for these components are provided.
[0034]
The illumination system 12 is a pulse light source 16, a beam shaping optical system 18, an energy rough adjuster 20 as a dimming device, an optical integrator (a fly-eye lens, an internal reflection type integrator, a diffractive optical element, or the like. Since a fly-eye lens is used, it is also referred to as a “fly-eye lens” hereinafter) 22, an illumination system aperture stop plate 24, a beam splitter 26, a first relay lens 28A, a second relay lens 28B, a fixed reticle blind 30A, a movable A reticle blind 30B, a mirror M for bending the optical path, a condenser lens 32, and the like are provided. In the following, components other than the pulse light source 16 configuring the illumination system 12 are collectively referred to as “illumination optical system” as appropriate.
[0035]
Here, the components of the illumination system 12 will be described. As an example of the pulse light source 16, the pulse energy E per pulse is E _min (For example, 8 mJ / pulse)-E _max (For example, 10 mJ / pulse), and the repetition frequency f of the pulse emission is f _min (For example, 600 Hz) to f _max It is assumed that an ArF excimer laser light source (oscillation wavelength: 193 nm) that can be changed within a range (for example, 2000 Hz) is used. Hereinafter, the pulse light source 16 is referred to as “excimer laser light source 16”.
[0036]
In place of the excimer laser light source 16, a KrF excimer laser light source (oscillation wavelength: 248 nm) or F ₂ Not only a laser light source (oscillation wavelength: 157 nm) but also a pulse light source such as a metal vapor laser light source or a harmonic generation device of a YAG laser can be used. In these cases as well, it is desirable to have a function of changing the pulse energy and the repetition frequency as described above.
[0037]
The beam shaping optical system 18 shapes the cross-sectional shape of the laser beam LB pulsed from the excimer laser light source 16 so that the laser beam LB efficiently enters a fly-eye lens 22 provided behind the optical path of the laser beam LB. , For example, a cylinder lens and a beam expander (both not shown).
[0038]
The energy rough adjuster 20 is disposed on the optical path of the laser beam LB behind the beam shaping optical system 18, and here, two-stage rotating plates 34A and 34B having the same configuration and individually rotating these rotating plates. It is configured to include drive motors 38A and 38B. Around the rotating plate 34A, a plurality (for example, eight) of ND filters (for example, eight) having different transmittances (= 1−dimming ratio) are shown around the circumference (two ND filters are shown in FIG. 1). Is rotated by the drive motor 38A, thereby changing the transmittance of the incident laser beam LB from 100% in geometric progression, for example, in eight steps at a common ratio of 0.85 (85%). It can be switched. The other rotating plate 34B is configured similarly to the rotating plate 34A, and is similarly rotated by the drive motor 38B.
[0039]
The fly-eye lens 22 is disposed on the optical path of the laser beam LB behind the energy rough adjuster 20, and has a surface light source including a large number of point light sources on an emission-side focal plane for illuminating the reticle R with a uniform illuminance distribution. That is, a secondary light source is formed. The laser beam emitted from this secondary light source is hereinafter referred to as “pulse illumination light IL”. It should be noted that a rod (internal reflection type) integrator can be used as an optical integrator instead of the fly-eye lens 22.
[0040]
An illumination system aperture stop plate 24 made of a disc-shaped member is disposed near the exit surface of the fly-eye lens 22, that is, in the present embodiment, near the exit-side focal plane that substantially matches the pupil plane of the illumination optical system. The illumination system aperture stop plate 24 includes, at equal angular intervals, an aperture stop composed of, for example, a normal circular aperture, an aperture stop composed of a small circular aperture, and a σ value that is a coherence factor, and a ring for orbicular illumination. A band-shaped aperture stop, a modified aperture stop in which a plurality of apertures are eccentrically arranged for the modified light source method (only two types of aperture stops are shown in FIG. 1), and the like are arranged. . The illumination system aperture stop plate 24 is configured to be rotated by a driving device 40 such as a motor controlled by a main controller 50 described later, so that one of the aperture stops is positioned on the optical path of the pulse illumination light IL. Is set selectively. Instead of the aperture stop plate 24 or in combination therewith, for example, a plurality of diffractive optical elements which are exchangeably arranged in the illumination optical system, a prism (cone prism, polyhedron, etc.) movable along the optical axis of the illumination optical system An optical unit including at least one of a prism and a zoom optical system is disposed between the light source 16 and the optical integrator 22, and when the optical integrator 22 is a fly-eye lens, illumination light on the incident surface thereof In the case where the optical integrator 22 is an internal reflection type integrator, the intensity distribution of illumination light on the pupil plane of the illumination optical system (2 (The size and shape of the secondary light source), that is, it is desirable to suppress the light amount loss accompanying the change of the illumination condition.
[0041]
A beam splitter 26 having a small reflectance and a large transmittance is arranged on the optical path of the pulse illumination light IL behind the illumination system aperture stop plate 24. Further, on the optical path behind this, a fixed reticle blind 30A and a movable reticle blind 30B are provided. A relay optical system composed of a first relay lens 28A and a second relay lens 28B is disposed interposed therebetween.
[0042]
The fixed reticle blind 30A is arranged on a plane slightly defocused from a conjugate plane with respect to the pattern plane of the reticle R, and has a rectangular opening defining an illumination area 42R on the reticle R. A movable reticle blind 30B having an opening whose position and width in the scanning direction are variable is arranged near the fixed reticle blind 30A, and at the start and end of scanning exposure, the illumination area 42R is provided via the movable reticle blind 30B. Is further restricted, thereby preventing unnecessary portions from being exposed.
[0043]
A bending mirror M that reflects the pulse illumination light IL that has passed through the second relay lens 28B toward the reticle R is disposed on the optical path of the pulse illumination light IL behind the second relay lens 28B that constitutes the relay optical system. A condenser lens 32 is disposed on the optical path of the pulse illumination light IL behind the mirror M.
[0044]
On the other hand, the pulse illumination light IL reflected by the beam splitter 26 is received by an integrator sensor 46 composed of a photoelectric conversion element via a condenser lens 44, and a photoelectric conversion signal of the integrator sensor 46 is supplied to a peak hold circuit (not shown) The signal is supplied to the main controller 50 as an output DS (digit / pulse) via an A / D converter. As the integrator sensor 46, for example, a PIN-type photodiode or the like having sensitivity in the deep ultraviolet region and having a high response frequency for detecting pulse emission of the excimer laser light source 16 can be used.
[0045]
A reticle R is mounted on the reticle stage RST, and is held by suction via a vacuum chuck (not shown). The reticle stage RST can be finely driven in a horizontal plane (XY plane), and is scanned by a reticle stage driving unit 48 in a predetermined stroke range in a scanning direction (here, the Y-axis direction which is the horizontal direction in FIG. 1). It is supposed to be. The position of the reticle stage RST during the scanning is measured by an external laser interferometer 54R via a movable mirror 52R fixed on the reticle stage RST, and the measured value of the laser interferometer 54R is supplied to the main controller 50. It is supposed to be. Note that the end surface of reticle stage RST may be mirror-finished to form a reflection surface of laser interferometer 54R (corresponding to the reflection surface of movable mirror 52R described above).
[0046]
As the projection optical system PL, for example, a bilateral telecentric reduction system, and a refraction system including a plurality of lens elements having a common optical axis AX in the Z-axis direction is used. The projection magnification β of the projection optical system PL is, for example, １ ／ or ５. Therefore, as described above, when the illumination area 42R on the reticle R is illuminated by the pulse illumination light IL, the image formed by reducing the pattern formed on the reticle R by the projection optical system PL at the projection magnification β is obtained. It is formed in a slit-shaped exposure region (a region conjugate to the illumination region 42R) 42W on the wafer W having a surface coated with a resist (photosensitive agent).
[0047]
The XY stage 14 is two-dimensionally driven by a wafer stage driving unit 56 in a Y-axis direction which is a scanning direction in the XY plane and an X-axis direction orthogonal to the scanning direction (a direction orthogonal to the paper surface in FIG. 1). . A Z tilt stage 58 is mounted on the XY stage 14, and a wafer W is held on the Z tilt stage 58 via a wafer holder (not shown) by vacuum suction or the like. The Z tilt stage 58 has a function of adjusting the position (focus position) of the wafer W in the Z direction and adjusting the inclination angle of the wafer W with respect to the XY plane. The position of the XY stage 14 is measured by an external laser interferometer 54W via a movable mirror 52W fixed on a Z tilt stage 58, and the measured value of the laser interferometer 54W is supplied to the main controller 50. It has become so. The end surface of the Z tilt stage 58 (or the XY stage 14) or the like may be mirror-finished to form a reflection surface of the laser interferometer 54 (corresponding to the reflection surface of the above-described movable mirror 52W).
[0048]
A reference illuminometer mounting portion (not shown) for mounting a reference illuminometer is provided on the upper surface of the Z tilt stage 58. It can be attached to.
[0049]
Although not shown, an image pickup device such as a CCD is provided above the reticle R as disclosed in, for example, Japanese Patent Application Laid-Open No. 7-176468. A pair of image processing type reticle alignment microscopes using pulse illumination light IL) as illumination light for alignment is arranged. In this case, the pair of reticle alignment microscopes are installed symmetrically (symmetrically) with respect to the YZ plane including the optical axis AX of the projection optical system PL. The pair of reticle alignment microscopes has a structure capable of reciprocating in the X-axis direction in the XZ plane passing through the optical axis AX.
[0050]
Normally, the pair of reticle alignment microscopes are set at positions where the pair of reticle alignment marks arranged outside the light-shielding band of the reticle R can be observed with the reticle R mounted on the reticle stage RST. I have.
[0051]
The control system is mainly constituted by a main controller 50 as a control means in FIG. The main controller 50 includes a so-called microcomputer (or minicomputer) including a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory) and the like, and performs an exposure operation. For example, synchronous scanning of the reticle R and the wafer W, stepping of the wafer W, exposure timing, and the like are collectively controlled so as to perform the operations accurately.
[0052]
Specifically, for example, at the time of scanning exposure, main controller 50 causes reticle R to move at a speed V in the + Y direction (or -Y direction) via reticle stage RST. _R In synchronization with the scanning, the wafer W moves through the XY stage 14 with respect to the exposure area 42W in the -Y direction (or + Y direction) at the speed β · V. _R (Β is a projection magnification for the wafer W from the reticle R), based on the measurement values of the laser interferometers 54R and 54W, via the reticle stage driving unit 48 and the wafer stage driving unit 56, respectively. The position and speed of the XY stage 14 are controlled. Further, at the time of stepping, main controller 50 controls the position of XY stage 14 via wafer stage driving unit 56 based on the measurement value of laser interferometer 54W. As described above, in the present embodiment, a drive system is configured by the main controller 50, the laser interferometers 54R and 54W, the reticle stage drive unit 48, the wafer stage drive unit 56, the reticle stage RST, and the XY stage 14. .
[0053]
In addition, the main controller 50 controls the light emission timing and the light emission power of the excimer laser light source 16 by supplying the control information TS to the excimer laser light source 16. The main controller 50 controls the energy rough adjuster 20 and the illumination system aperture stop plate 24 via the motor 38 and the driving device 40, respectively, and further opens and closes the movable reticle blind 30B in synchronization with stage system operation information. Control behavior. As described above, in the present embodiment, the main controller 50 also has a role of an exposure amount controller and a stage controller. Of course, these control devices may be provided separately from the main control device 50.
[0054]
Further, in the present embodiment, a storage device 51 formed of, for example, a DRAM or the like is provided in addition to the main control device 50. In the storage device 51, a reference of the ideal state (the output DS (digit / pulse) of the integrator sensor 46) between the output DS of the integrator sensor 46 and the illuminance (exposure amount) of the pulse illumination light IL on the surface of the wafer W Illuminometer output PS (mJ / cm ² / Pulse)), correction information for matching the correlation coefficient α and the output DS of the integrator sensor 46 with the output PS of the reference illuminometer in a state where there is no error in the linearity with respect to (/ pulse)) is obtained and stored in advance for each illumination condition. I have.
[0055]
Next, the configuration of the exposure amount control system of the scanning exposure apparatus 10 of the present embodiment will be described with reference to FIG.
[0056]
FIG. 2 shows components of the scanning exposure apparatus 10 shown in FIG. As shown in FIG. 2, inside the excimer laser light source 16, a laser resonator 16a, a beam splitter 16b, an energy monitor 16c, an energy controller 16d, a high voltage power supply 16e, and the like are provided.
[0057]
In FIG. 2, a laser beam emitted in a pulse form from a laser resonator 16a enters a beam splitter 16b having a high transmittance and a small reflectance, and a laser beam LB transmitted through the beam splitter 16b is emitted to the outside. You. The laser beam reflected by the beam splitter 16b enters an energy monitor 16c composed of a photoelectric conversion element, and a photoelectric conversion signal from the energy monitor 16c is supplied to an energy controller 16d as an output ES via a peak hold circuit (not shown). Have been. The unit of the energy control amount corresponding to the output ES of the energy monitor 16c is (mJ / pulse). During normal light emission, the energy controller 16d operates the high-voltage power supply so that the output ES of the energy monitor 16c becomes a value corresponding to the target value of energy per pulse in the control information TS supplied from the main controller 50. The power supply voltage at 16e is feedback-controlled. The energy controller 16d also changes the oscillation frequency by controlling the energy supplied to the laser resonator 16a via the high voltage power supply 16e. That is, the energy controller 16d sets the oscillation frequency of the excimer laser light source 16 to the frequency specified by the main control device 50 according to the control information TS from the main control device 50, The feedback control of the power supply voltage of the high voltage power supply 16e is performed so that the energy of the high voltage power supply 16e becomes the value specified by the main controller 50.
[0058]
Further, a shutter 16f for shielding the laser beam LB in accordance with control information from the main controller 50 is also provided outside the beam splitter 16b in the excimer laser light source 16.
[0059]
Next, a method of measuring the correlation coefficient α and the correction information in the ideal state described above will be described along the flowchart of FIG. 3 and appropriately referring to other drawings.
[0060]
As a premise, it is assumed that a counter m indicating a number of an illumination condition, which will be described later, and a counter n indicating a target number for setting a transmittance (or a dimming rate) of the energy rough adjuster are both initialized to 1. The illumination conditions to be set include normal illumination (illumination condition number 1), small σ illumination (illumination condition number 2), annular illumination (illumination condition number 3), and modified illumination (illumination condition number 4). It is assumed that the information is specified in advance by the operator via the input / output device 62 and is stored in the RAM of the main control device 50. In addition, the operator sets, via the input / output device 62, the N-stage of, for example, about 0% to about 93% as the dimming rate of the energy rough adjuster, ie, about 100% to about 7% as the transmittance to be set. Are specified in advance and stored in the RAM of main controller 50.
[0061]
First, in step 102, an external reference illuminometer is attached to the reference illuminometer attachment portion on the Z tilt stage 58 by the operator. The operator instructs the main control device 50 via the input / output device 62 to start the measurement at the same time when the attachment of the reference illuminometer is completed.
[0062]
In the next step 104, the main controller 50 sets the m-th (in this case, the first) illumination condition, that is, the normal illumination condition, as the illumination condition by the main controller 50 in response to the instruction to start the measurement. This setting is performed by the main controller 50 selecting and setting the normal illumination stop of the illumination system aperture stop plate 24 via the driving device 40. At this time, if the reference illuminance meter is not substantially below the optical axis of the projection optical system PL, the main controller 50 sets the reference illuminance meter via the wafer stage drive unit 56 based on the measurement value of the interferometer 54W. The XY stage 14 is moved so that the illuminometer is located almost directly below the optical axis of the projection optical system PL.
[0063]
In the next step 106, main controller 50 sets the dimming rate of energy rough adjuster 20 to the n-th (here, the first) target value. This setting is performed by the main controller 50 driving at least one of the rotating plates 34A and 34B via at least one of the corresponding motors 38A and 38B so that the dimming rate matches the target value. You. In this case, an ND filter having a dimming rate of 0% is selected for both the rotating plates 34A and 34B.
[0064]
In the next step 108, main controller 50 starts emission of excimer laser light source 16, proceeds to step 110, and receives light almost simultaneously with integrator sensor 46 and reference illuminometer in synchronization with the trigger of pulse emission, The output DS of the integrator sensor 46 and the output PS of the reference illuminometer are measured. As a result, the output DS (unit “digit / pulse”) and the output PS (unit “mJ / cm”) are stored in a predetermined area in the RAM of the main controller 50. ² / Pulse ") is stored.
[0065]
In the next step 112, main controller 50 determines whether or not capture of outputs DS and PS of a predetermined number of pulses has been completed. If this determination is denied, the process returns to step 110, and output DS of a predetermined number of pulses has been completed. , And PS are fetched repeatedly until the output DS and PS are fetched.
[0066]
Then, when the capture of the outputs DS and PS of the predetermined number of pulses is completed, the routine proceeds to step 114, where it is determined whether or not the value of the counter n is equal to or greater than a value N specified in advance. It is determined whether or not the above-described simultaneous measurement has been completed for each of the dimming rates of the stages. In this case, only when the transmittance at the first stage is 0%, the above-described simultaneous measurement has only been completed, so the determination here is denied, and the process proceeds to step 116.
[0067]
In step 116, the main controller 50 increments the counter n by 1 (n ← n + 1), returns to step 106, and sets the dimming rate of the energy rough adjuster 20 to the n-th (here, the second) target. After the values are set in the same manner as described above, the processing of steps 108 to 112 is repeated, and in step 114, it is determined whether or not the above-described simultaneous measurement has been completed for each of the N-stage dimming rates to be set again as described above. To judge. If this determination is denied, the processing in the loop of steps 116 → 106 to 114 is repeated until the determination in step 114 is affirmed.
[0068]
Then, under the normal lighting condition, when the capture of the outputs DS and PS of the predetermined number of pulses is completed with respect to the designated N-stage dimming rate, the determination in step 114 is affirmed, and the process proceeds to step 118. When the determination in step 114 is affirmed, the measurement data of the output DS and PS of the predetermined number of pulses for the specified N-step dimming rate under the normal lighting condition is stored in the RAM for each value of n. It is stored in a predetermined area.
[0069]
In step 118, main controller 50 determines the average value I of outputs DS and PS for a predetermined number of pulses for each value of n. _n , P _n And calculate a point (P) on a rectangular coordinate system PI (PI coordinate system). _n , I _n ) (N = 1, 2,..., N) are plotted.
[0070]
FIG. 4 shows an example of plot data in the case of N = 8 stages. FIG. 4 shows data when the dimming rate is set to 0%, 15%, 48%, 56%, 62%, 68%, 77%, and 93% (however, 8% of the dimming rate of 93%). The second data is not shown).
[0071]
In the next step 120, main controller 50 calculates an approximate straight line I = α · P (see FIG. 4) passing through the origin (0, 0) by the least squares method based on the plot points in step 118 above. The slope α is stored as a correlation coefficient (conversion coefficient) α in the storage device 51 in association with the value of the counter m at that time. The approximate straight line I = α · P indicates the relationship with the output PS (= P) of the reference illuminometer when the linearity of the output DS (= I) of the integrator sensor 46 under the normal illumination condition is ideal. It is nothing but a straight line.
[0072]
In the next step 124, main controller 50 sets each plot point (P _n , I _n ) For the theoretical value I = α · P _n Error rate ΔI which is the ratio of the deviation (error) of the _n = (I _n -I) / I is calculated respectively. In FIG. 4, some plot points appear to be on the straight line I = α · P due to the drawing convenience. However, since both the straight line and the point have no area, each plot point And even a slight deviation from the straight line, I _n And I do not match.
[0073]
In the next step 126, main controller 50 moves point (P-ΔI) on rectangular coordinate system P-ΔI (P-ΔI coordinate system). _n , ΔI _n ) (N = 1, 2,..., N) are plotted. FIG. 5 shows a point (P _n , ΔI _n )It is shown. In FIG. 5, the error rate ΔI _n The reference line FL = 0 is indicated by a solid line. The error rate Δn is positive in the portion above the reference line FL, that is, the measured value I _n Is larger than the theoretical value I, and the portion below the reference line FL is the error rate ΔI _n Is negative, that is, the measured value I _n Is smaller than the theoretical value I.
[0074]
In the next step 128, the main controller 50 determines the approximate curve ΔI = f by the least squares method based on the plot points in the above step 126. _m (P), and the approximate curve ΔI = f _m (P) is stored in the storage device 51 as a correction function as correction information under normal illumination conditions. FIG. 5 shows a quadratic approximation curve ΔI = f obtained by least squares approximation. _m (P) = bP ² + CP + d is shown.
[0075]
In the next step 132, main controller 50 determines whether or not the value of counter m is equal to or greater than a predetermined M (here, M = 4), thereby determining all the lighting conditions specified. It is determined whether or not the measurement of the correction information has been completed. In this case, since m = 1, the determination here is denied, and the routine proceeds to step 134, where the counter m is incremented by 1 (m ← m + 1), and then returns to step 104.
[0076]
In step 104, the m-th illumination condition (here, the second illumination condition, that is, the small σ illumination condition) is set in the same manner as described above, and then the processing from step 106 onward is repeated. As a result, under the small σ illumination condition, the correlation coefficient α and the correction function f as the correction information ₂ (P) is obtained and stored in the storage device 51.
[0077]
Thereafter, under the annular illumination condition and the modified illumination condition, a correlation coefficient α and a correction function as correction information are obtained and stored in the storage device 51.
[0078]
Next, a basic sequence regarding the exposure amount control of the scanning exposure apparatus 10 of the present embodiment will be described with reference to a flowchart of FIG.
[0079]
As a premise, the above-described measurement method is performed, and the correlation coefficient (conversion coefficient) α and the correction function f for each of the four illumination conditions described above are stored in the storage device 51. _m (P) is assumed to be stored.
[0080]
Prior to the exposure, the output DS of the integrator sensor 46 is indirectly controlled by using the integrator sensor 46 and the energy monitor 16c in the excimer laser light source 16 according to a predetermined procedure disclosed in, for example, Japanese Patent Application Laid-Open No. 10-270345. Exposure on the image plane, ie, the processing amount P of the integrator sensor 46 (mJ / (cm ² .Pulse)) and a predetermined control table showing a correlation between the output ES (mJ / pulse) of the energy monitor 16c in the excimer laser light source 16.
[0081]
However, in the following description, for the sake of simplicity, the correlation between the integrator sensor 46 and the energy monitor 16c is represented by a linear function, the offset of which can be regarded as 0, and the slope thereof can be treated as a conversion coefficient γ. That is, the processing amount P of the integrator sensor 46 (mJ / (cm ² Pulse)) and the conversion coefficient γ, it is assumed that the output ES (mJ / pulse) of the energy monitor 16c can be calculated from the following equation (1).
[0082]
ES = γ · P (1)
[0083]
In particular, when the above-described optical unit is provided, it is preferable that the above-mentioned conversion coefficient γ is obtained for each condition of the illumination light incident on the optical integrator 22 which is variable by the optical unit. Further, it is desirable that the conversion coefficients α and γ be updated by calculation in consideration of the transmittance variation of the pulse illumination light EL of the illumination optical system and the projection optical system PL constituting the illumination system 12.
[0084]
First, in step 202 of FIG. 6, exposure conditions (illumination conditions and set exposure amount S ₀ ), And when the exposure condition is input, the process proceeds to the next step 204 to set the illumination condition and the like designated by the input of the exposure condition. Here, for example, main controller 50 (CPU) loads designated reticle R onto reticle stage RST using a reticle loader (not shown). Further, in accordance with the designation of the illumination condition, an operation such as selecting and setting an illumination aperture stop corresponding to the illumination condition on the optical path via the driving device 40 is performed. In the following, it is assumed that the normal lighting condition is designated as the lighting condition.
[0085]
In the next step 206, the energy E per pulse of the laser beam LB is reduced to the minimum energy value E. _min (8 mJ / pulse), the repetition frequency f _min (600 Hz). That is, the neutral setting of the pulse energy and the repetition frequency is performed in this manner.
[0086]
In the next step 208, the excimer laser light source 16 performs pulse emission a plurality of times (for example, several hundred times) and integrates the output of the integrator sensor 46 to indirectly average the pulse energy density P ( mJ / cm ² / Pulse). This measurement is performed, for example, in a state in which the movable reticle blind 30B is driven to completely close its opening and the illumination light IL is prevented from reaching the reticle R side. Of course, the operation may be performed in a state where the XY stage 14 is driven to retract the wafer W.
[0087]
In the present embodiment, the above average pulse energy density P is obtained as follows.
[0088]
That is, the average value of the output of the integrator sensor 46 corresponding to several hundred pulse emission is expressed by I _mean And the average value I _mean Is defined as an actual measurement value I ′. Then, in the following equation (2), the measured value I ′, the conversion coefficient α corresponding to the normal illumination condition (corresponding to the case of m = 1) stored in the storage device 51, and the correction function ΔI = f _m (P) = f ₁ By substituting the specific function form of (P) and solving equation (2), the average pulse energy density P is calculated.
[0089]
I _m = Α · ｛1 + f _m (P)｝ · P …… (2)
[0090]
Thus, the pulse energy P on the image plane is calculated in a state where the linearity error with respect to the output DS of the integrator sensor 46, that is, the output PS of the reference illuminometer I is corrected.
[0091]
Α · ｛1 + f in equation (2) _m By setting (P)｝ = α ′, equation (2) can be modified as follows.
[0092]
I _m = Α '· P (3)
[0093]
As is apparent from Equation (3), in the present embodiment, the correction function ｛1 + f is substantially obtained. _m The conversion coefficient α is corrected using (P)｝, and a new conversion coefficient (conversion function) α ′ = α · ｛1 + f _m It can be said that (P)｝ has been calculated.
[0094]
In the next step 210, the number N of exposure pulses is calculated by the following equation (4).
[0095]
N = cint (S ₀ / P) …… (4)
Here, the function cint represents the rounding of the value of the first digit after the decimal point. Also, S ₀ Is the set exposure amount input in step 202.
[0096]
In the next step 212, the exposure pulse number N is set to the minimum exposure pulse number N for obtaining the required exposure amount control reproduction accuracy. _min It is determined whether or not this is the case. Here, the minimum exposure pulse number N _min Is, for example, a variation (3σ value) δ of the pulse energy measured in advance and set as a device constant. _p Δ to the average pulse energy density P _p / P. In the present embodiment, for example, N _min = 40.
[0097]
If the determination in step 212 is negative, that is, the number of exposure pulses N is equal to the minimum number of exposure pulses N _min If it is smaller, the process proceeds to step 214, where S is selected from among the transmittances (or dimming rates) that can be set by the energy coarse adjuster 20 in FIG. ₀ / (N _min × P), a transmittance smaller than and closest to the selected one is selected, and a combination of the ND filters having the transmittance is set via at least one of the motors 38A and 38B. Then, the process of step 208 is performed again. Average pulse energy density P = P under selected ND conditions _t Is newly obtained, and the average pulse energy density P _t , The process of step 210 is performed again. In this manner, when the determination in step 212 is affirmative or when the determination in step 212 is affirmative from the beginning (N ≧ N _min ), The process proceeds to step 216. Here, the average pulse energy density P when the determination in step 212 is affirmed from the beginning is the average pulse energy density P under the above-mentioned selected ND condition. _t N ≧ N as in _min Therefore, in the following, P _t Shall be treated as
[0098]
In step 216, the energy density P obtained in step 208 _t Is used to calculate the above-described conversion coefficient γ based on the following equation (5). Of course, the present invention is not limited to this. When the control table described above is obtained in advance, the average pulse density P _t May be calculated.
[0099]
γ = E _min / P _t …… (5)
[0100]
In the next step 218, the energy set value E per pulse of the laser beam LB is calculated by the following equation (6). _t (MJ / pulse) is calculated, and the routine proceeds to step 220.
[0101]
E _t = Γ × S ₀ / N _min ...... (6)
[0102]
In step 220, the energy set value E _t Is supplied to the energy controller 16d to convert the energy E of one pulse to E. _t Set to. The calculated energy set value E _t Is the maximum energy E that can be set _max (10 mJ / pulse) may very rarely occur, but here, the set exposure amount S ₀ Is a reasonable value and E _t Is E _max It is assumed that: Note that E _t Is actually E _max Is exceeded, E _t Is E _max And γ, S ₀ , E _max Is used to recalculate the number N of exposure pulses, but a more detailed description is omitted here.
[0103]
In the next step 222, scan speed V = scan maximum speed (V _max ), The repetition frequency f is calculated by the following equation (7), and the repetition frequency f is set to the calculated value via the energy controller 16d.
[0104]
f = int (V _max × N / Ws) (7)
Here, the function int (a) represents the largest integer that does not exceed the real number a.
[0105]
Then, in the next step 224, the scan target speed (scan speed) is set to the maximum scan speed V. _max Set to.
[0106]
The repetition frequency f calculated in step 222 is the maximum repetition frequency f of the laser. _max May rarely occur, but here, the specified conditions are appropriate, and it is assumed that there is no such case. Note that the repetition frequency f is actually equal to the maximum repetition frequency f _max , The repetition frequency f = f _max To Ws, f _max , N, the scan target speed is calculated, but further detailed description is omitted here.
[0107]
Then, in step 226, the pattern of the reticle R is transferred to the specified shot area on the wafer W by the scanning exposure method under the setting conditions (V, f, E, N) determined in the previous steps.
[0108]
After the above-described scanning exposure is completed, it is determined in step 228 whether or not exposure has been completed for all shot areas. If the determination is negative, that is, if there is a shot area to be exposed, step 228 is performed. Returning to 226, the scanning exposure is performed on the next shot area.
[0109]
In this way, when the shot area to be exposed is exhausted, a series of processing of this routine ends.
[0110]
As is clear from the above description, in this embodiment, the exposure control device, the measurement control device, and the calculation device are realized by the main control device 50, more specifically, by the CPU and the software program. That is, the exposure control device is realized by the processing of steps 206 to 224 performed by the CPU, the measurement control device is realized by the processing of steps 104 to 124 performed by the CPU, and the calculation device is realized by the processing of steps 126 to 128. I have.
[0111]
As described in detail above, according to the exposure apparatus 10 of the present embodiment, the storage device 51 stores the correction function as the correction information for adjusting the output of the integrator sensor 46 with respect to the output of the reference illuminometer in the illumination device. It is measured and stored in advance for each condition. Then, when measuring the correction information, main controller 50 performs a predetermined process according to the above-described flowchart of FIG.
[0112]
Specifically, main controller 50 as a measurement controller emits light from excimer laser light source 16 in a state where a reference illuminometer serving as a reference for illuminance is arranged on an image plane on which a pattern image on reticle R is formed. The energy density measurement of measuring the energy density of the obtained laser beam LB (illumination light IL) with the integrator sensor 46 and the reference illuminometer is repeatedly performed while the extinction rate of the energy rough adjuster 20 is sequentially changed. As a result, the output of the reference illuminometer and the output of the integrator sensor 46 are obtained as measurement results for each set value of the dimming rate of the energy rough adjuster 20.
[0113]
Next, based on the above measurement result, main controller 50 as a calculating device calculates correction information for adjusting the output of integrator sensor 46 with respect to the output of the reference illuminometer as follows. In other words, main controller 50 outputs measurement data P, which is the output of the corresponding reference illuminometer. _n And measurement data I which is the output of the integrator sensor _n (I _n , P _n ) Is plotted on a rectangular coordinate system with the horizontal axis representing the output P of the reference illuminometer. I at each plot point _n (I = α · P) _n -I) Ratio ΔI to theoretical value _n Approximate curves ΔI = f for all (n = 1 to N) _m (P) is obtained by the least square method, and the approximate curve ΔI = f _m Let (P) be a correction function as correction information.
[0114]
In the case of the present embodiment, the measurement of the correction information is performed for each lighting condition.
[0115]
Therefore, according to the above-described measurement method performed by the exposure apparatus 10 of the present embodiment, it is possible to correct the output (measured value) of the integrator sensor 46 corresponding to a wide energy range in the same manner as when the linearity is ideal. Possible correction information can be obtained.
[0116]
Further, according to exposure apparatus 10 of the present embodiment, main controller 50 as an exposure amount controller transfers a pattern image of reticle R onto wafer W on Z tilt stage 58 via projection optical system PL. At this time, the processing is performed according to the above-described flowchart of FIG. 6, and the output of the integrator sensor 46 is software-corrected using the corresponding correction information in the storage device 51 in accordance with the lighting conditions at that time. The integrated energy amount on the image plane is controlled based on the output of the integrator sensor 46. Therefore, the exposure amount control is performed using the correction information that can correct the output (measured value) of the integrator sensor 46 in a wide energy range in the same manner as when the linearity is ideal. . Therefore, regardless of the setting of the transmittance (or the dimming rate) of the energy rough adjuster 20, a high-precision exposure that is not affected by the linearity of the measured value of the integrator sensor 46 to the measured value of the reference illuminometer. The amount control is performed, and the pattern of the reticle R is accurately transferred to a plurality of shot areas on the wafer W arranged on the image plane by the scanning exposure method. At this time, the set exposure amount S ₀ That is, the exposure amount according to the resist sensitivity is given to the wafer W.
[0117]
Therefore, according to the exposure apparatus 10 and the exposure method according to the present embodiment, the controllability of the pattern line width is improved, and a fine pattern can be accurately transferred to each shot area on the wafer W.
[0118]
In the above-described embodiment, a case has been described in which the energy coarse adjuster 20 in which the transmittance (or the light dimming rate) can be set intermittently is used as the dimming device. However, the present invention is not limited to this. Alternatively, a dimming device capable of continuously changing the transmittance (or the dimming rate) within the predetermined energy range may be used together with the energy rough adjuster 20. As an example of such a dimming device, as an example, on a light path of a laser beam LB to be pulsed, a fixed grating plate having a transmitting portion and a light shielding portion formed at a predetermined pitch and a movable movable in the pitch direction of the grating. A double-grating type modulator having a grating plate can be used. By shifting the relative positions of the two grating plates, the transmittance for the laser beam LB can be modulated.
[0119]
When a dimming device capable of continuously changing the transmittance (or the dimming ratio) within a predetermined energy range is used, the main controller 50 sets the predetermined range when measuring the correction information. For example, the extinction ratio may be changed at a predetermined step pitch, and the output of the reference illuminometer and the output of the integrator sensor 46 may be obtained as the measurement result for each set value of the extinction ratio.
[0120]
Further, in the above embodiment, the correction information for each lighting condition is obtained by the correction function f _m (P), but the present invention is not limited to this, and the corresponding measured value I _n And P _n Or I or _n And α _n = I _n / P _n Table data including a combination of the above and the like may be used as the correction information.
[0121]
Alternatively, when obtaining the least-square approximate curve using the plot data of FIG. 5, it is needless to say that a third-order or higher-order approximate curve is obtained and may be used as correction information.
[0122]
<< 2nd Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same reference numerals are used for components that are the same as or equivalent to those of the above-described first embodiment, and detailed descriptions thereof are omitted.
[0123]
FIG. 7 shows an exposure system 100 according to the second embodiment. The exposure system 100 shown in FIG. 1 is installed in a semiconductor factory of a device maker that is a user of an exposure apparatus.
[0124]
The exposure system 100 includes a host computer 70 and a first exposure apparatus 10 connected to each other via a local area network (LAN) 72. ₁ , Second exposure apparatus 10 ₂ ,..., The k-th exposure apparatus 10 _k And so on. Also, the LAN 72 includes the exposure apparatus 10 ₁ -10 _k In addition, other device manufacturing apparatuses such as a coater / developer (not shown) constituting the lithography system are also connected.
[0125]
Exposure device 10 ₁ -10 _k Are managed by the host computer 70, and the illuminance is collectively managed using the same reference illuminometer. Exposure device 10 ₁ -10 _k Are configured similarly to the above-described exposure apparatus 10 of the first embodiment. Therefore, the exposure apparatus 10 ₁ -10 _k Are an integrator sensor 46 that receives a part of the laser beam LB (illumination light IL) branched on the optical path of the laser beam LB from the excimer laser light source 16 to the mask, an excimer laser light source 16 and a beam splitter 26. And an energy rough adjuster 20 whose light reduction rate can be set intermittently within a predetermined range, and correction information (correction function f) for each illumination condition measured by the above-described measurement method. _m (P) The output of the integrator sensor 46 is corrected in the same manner as described above using the storage device 51 stored in advance and the correction information, and the pattern on the reticle R is corrected based on the corrected output of the integrator sensor 46 as a reference. And a main controller 50 that transfers the pattern onto the wafer W disposed on the image surface while controlling the integrated energy amount on the image surface on which the image is formed.
[0126]
In the exposure system 100 of the second embodiment, the exposure apparatus 10 ₁ -10 _k Storage device 51 ₁ ~ 51 _k Each integrator sensor 46 corresponds to a wide energy range. ₁ ~ 46 _k (Correction function f) that can correct the output (measured value) of the reference illuminometer as in the case where the linearity with respect to the output of the reference illuminometer is ideal. _m (P)) are stored.
[0127]
Exposure device 10 ₁ -10 _k Then, each main controller 50 ₁ ~ 50 _k However, similar to the first embodiment, the storage device 51 ₁ ~ 51 _k Using the correction information stored in the integrator sensor 46 ₁ ~ 46 _k And the integrator sensor 46 after the correction ₁ ~ 46 _k The reticle pattern is transferred to a plurality of shot areas on a wafer arranged on the image plane by a step-and-scan method while controlling the integrated energy amount on the image plane of the projection optical system based on the output of the projection optical system.
[0128]
Therefore, in the second embodiment, the linearity of the output of the integrator sensor with respect to the output of the same reference illuminometer is corrected in any of the exposure apparatuses, so that the illuminance is collectively managed using the same reference illuminometer. In addition, it is possible to reduce the difference in exposure amount control between devices with a plurality of exposure apparatuses used in the same device manufacturing line, and as a result, it is possible to reduce the control error of the pattern line width between the devices. .
[0129]
In each of the above embodiments, the case where the present invention is applied to a step-and-scan type scanning exposure apparatus has been described. However, the present invention is not limited to this, and the present invention is applicable to a step-and-repeat type exposure apparatus. (A stepper) or a step-and-stitch type exposure apparatus. For example, when the present invention is applied to a stepper, the integrated energy amount (exposure dose) of the illumination light IL irradiated on the image surface (wafer surface) is estimated based on the output of the integrator sensor, and the integrated energy amount is estimated. Exposure is performed until the energy reaches the set energy amount. At this time, the control device of the stepper corrects the output of the integrator sensor based on the output of the integrator sensor, and on the image plane based on the corrected output of the integrator sensor. Of the energy density of the integrator sensor, or on the image plane in which the linearity of the output of the integrator sensor is corrected based on the output of the integrator sensor and the above-described equation (2), as in the first embodiment. The energy density may be calculated (estimated). As a result, the controllability of the pattern line width is improved, and a fine pattern can be accurately transferred to each shot area on the wafer W. In particular, in the second embodiment, the exposure apparatus 10 ₁ -10 _k If a part of is a stepper, since the control error of the exposure amount among all the exposure apparatuses can be made almost zero, the control error of the pattern line width between the units is reduced. Mix-and-match exposure.
[0130]
The application of the exposure apparatus is not limited to an exposure apparatus for manufacturing a semiconductor, and is, for example, an exposure apparatus for a liquid crystal that transfers a liquid crystal display element pattern onto a square glass plate, and a display such as a plasma display or an organic EL. The present invention can be widely applied to an exposure apparatus for manufacturing an apparatus, a thin film magnetic head, a micromachine, a DNA chip, and the like. In addition to micro devices such as semiconductor elements, glass substrates or silicon wafers for manufacturing reticles or masks used in light exposure equipment, EUV exposure equipment, X-ray exposure equipment, electron beam exposure equipment, etc. The present invention can also be applied to an exposure apparatus that transfers a circuit pattern to a substrate.
[0131]
In each of the above embodiments, as the laser light, for example, single-wavelength laser light in the infrared or visible range oscillated from a DFB semiconductor laser or fiber laser is doped with, for example, erbium (or both erbium and ytterbium). Alternatively, harmonics amplified by a fiber amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used.
[0132]
For example, if the oscillation wavelength of the single-wavelength laser is in the range of 1.51 to 1.59 μm, the 8th harmonic whose generation wavelength is in the range of 189 to 199 nm, or the generation wavelength is in the range of 151 to 159 nm A certain tenth harmonic is output. In particular, if the oscillation wavelength is in the range of 1.544 to 1.553 μm, an 8th harmonic having a generation wavelength in the range of 193 to 194 nm, that is, ultraviolet light having substantially the same wavelength as the ArF excimer laser can be obtained. Is in the range of 1.57 to 1.58 μm, the 10th harmonic whose generation wavelength is in the range of 157 to 158 nm, that is, F ₂ Ultraviolet light having substantially the same wavelength as the laser is obtained.
[0133]
When the oscillation wavelength is in the range of 1.03 to 1.12 μm, a seventh harmonic having a generation wavelength in the range of 147 to 160 nm is output. In particular, the oscillation wavelength is in the range of 1.099 to 1.106 μm. , The seventh harmonic having a generation wavelength in the range of 157 to 158 μm, that is, F ₂ Ultraviolet light having substantially the same wavelength as the laser is obtained. Note that a ytterbium-doped fiber laser is used as the single-wavelength oscillation laser.
[0134]
As a laser light source, Kr having a wavelength of 146 nm is used. ₂ Laser (krypton dimer laser), Ar with a wavelength of 126 nm ₂ A light source that generates vacuum ultraviolet light such as a laser (argon dimer laser) may be used.
[0135]
Further, the magnification of the projection optical system may be not only a reduction system but also any one of an equal magnification and an enlargement system.
[0136]
《Device manufacturing method》
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus in a lithography process will be described.
[0137]
FIG. 8 shows a flowchart of a manufacturing example of a device (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a plasma display, an organic EL, a CCD, a thin-film magnetic head, a micromachine, and the like). As shown in FIG. 8, first, in step 301 (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 302 (mask manufacturing step), a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 303 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.
[0138]
Next, in step 304 (wafer processing step), using the mask and the wafer prepared in steps 301 to 303, an actual circuit or the like is formed on the wafer by a lithography technique or the like as described later. Next, in step 305 (device assembly step), device assembly is performed using the wafer processed in step 304. Step 305 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary.
[0139]
Finally, in step 306 (inspection step), inspections such as an operation confirmation test and a durability test of the device created in step 305 are performed. After these steps, the device is completed and shipped.
[0140]
FIG. 9 shows a detailed flow example of step 304 in the semiconductor device. In FIG. 9, in step 311 (oxidation step), the surface of the wafer is oxidized. In step 312 (CVD step), an insulating film is formed on the wafer surface. In step 313 (electrode forming step), electrodes are formed on the wafer by vapor deposition. In step 314 (ion implantation step), ions are implanted into the wafer. Each of the above steps 311 to 314 constitutes a pre-processing step in each stage of wafer processing, and is selected and executed according to a necessary process in each stage.
[0141]
In each stage of the wafer process, when the above-described pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 315 (resist forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 316 (exposure step), the circuit pattern of the mask is transferred onto the wafer by each of the exposure apparatuses constituting the exposure system 100 described above. Next, in step 317 (development step), the exposed wafer is developed, and in step 318 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 319 (resist removing step), unnecessary resist after etching is removed.
[0142]
By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.
[0143]
If the device manufacturing method of the present embodiment described above is used, each exposure apparatus constituting the exposure system 100 of the second embodiment is sequentially used in the exposure step (step 316). The reticle pattern can be transferred onto the wafer with high precision by controlling the exposure amount accurately, and by improving the pattern line width uniformity between shot areas and the in-plane uniformity of the pattern line width. Further, the exposure apparatus 10 ₁ -10 _k During this period, the exposure is performed in a state where there is almost no difference in the exposure amount control between the devices. As a result, according to the device manufacturing method of the present embodiment, it is possible to improve the productivity (including the yield) of a highly integrated device.
[0144]
【The invention's effect】
As described above, according to the method for measuring correction information according to the present invention, the correction information for accurately correcting the linearity of the output of the optical sensor for energy monitoring in the exposure control system with respect to the output of the reference illuminometer. As a result, by using this correction information, it is possible to control the exposure amount with high accuracy without being affected by the linearity.
[0145]
Further, according to the exposure method and the exposure apparatus according to the present invention, there is an effect that a fine pattern can be accurately transferred onto an object.
[0146]
Further, according to the exposure system of the present invention, there is an effect that the difference in exposure amount control between the devices can be reduced.
[0147]
Further, 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 diagram illustrating a schematic configuration of an exposure apparatus according to a first embodiment.
FIG. 2 is a view showing components extracted from the exposure apparatus of FIG. 1 related to exposure amount control.
FIG. 3 is a flowchart illustrating a method of measuring a correlation coefficient and correction information in an ideal state.
FIG. 4 is a diagram showing an example of plot data when N = 8 stages.
FIG. 5 shows points (P _n , ΔI _n FIG.
FIG. 6 is a flowchart illustrating a control algorithm of a CPU in a main control device for a basic sequence related to exposure amount control of the exposure apparatus in the first embodiment.
FIG. 7 is a diagram illustrating an exposure system according to a second embodiment.
FIG. 8 is a flowchart illustrating a device manufacturing method according to the present invention.
FIG. 9 is a flowchart illustrating a specific example of step 304 in FIG. 8;
[Explanation of symbols]
10, 10 ₁ -10 _k Exposure device, 16 light source, 20 energy rough adjuster (dimming device), 46 integrator sensor (light sensor), 50 main control device (exposure amount control device, measurement control device, calculation device, control device) 51, memory (storage device), IL, illumination light (energy beam), PL, projection optical system, R, reticle (mask), W, wafer (object), WST, wafer stage (object stage).

Claims (8)

An optical sensor that receives a part of the energy beam branched on the optical path of the energy beam from the light source to the mask; and an optical sensor that is disposed between the light source and the branch point, and has a dimming rate continuously within a predetermined range. A method of measuring correction information, which is used in an exposure amount control system including a dimming device that can be set periodically or intermittently,
The energy beam emitted from the light source is received by the optical sensor and the reference illuminometer in a state where a reference illuminometer serving as an illuminance reference is arranged on an image plane on which an image of a pattern on the mask is formed. Repeating energy measurement while sequentially changing the dimming rate of the dimming device;
Calculating correction information for adjusting an output of the optical sensor with respect to an output of the reference illuminometer based on a result of the repeated energy measurement. The method according to claim 1, wherein the correction information is a second-order or higher-order correction function. A step of measuring the correction information by the measurement method according to claim 1 or 2;
The output of the optical sensor is corrected using the measured correction information, and the integrated energy amount on the image surface is controlled based on the corrected output of the optical sensor while being arranged on the image surface. Transferring the pattern onto a damaged object. An exposure apparatus that illuminates a mask with an energy beam emitted from a light source and transfers a pattern formed on the mask onto an object,
An optical sensor for receiving a part of the energy beam branched on the optical path of the energy beam from the light source to the mask;
A dimming device arranged between the light source and the branch point, the dimming rate of which can be set continuously or intermittently within a predetermined range;
A projection optical system for projecting an image of the pattern on the mask onto the object;
An object stage on which the object is placed and on which a reference illuminometer serving as a reference for illuminance can be installed;
A storage device storing correction information for adjusting the output of the optical sensor with respect to the output of the reference illuminometer;
When transferring the image of the pattern to the object on the stage via the projection optical system, correct the output of the optical sensor using the correction information, based on the corrected output of the optical sensor as a reference An exposure controller for controlling the amount of accumulated energy on the image plane. The exposure apparatus according to claim 4, wherein the correction information is a second-order or higher-order correction function. Energy measurement for receiving the energy beam emitted from the light source with the light sensor and the reference illuminometer while the reference illuminometer is installed on the stage, and sequentially measuring the dimming rate of the dimmer A measurement control device that is repeated while changing;
The calculating device according to claim 4, further comprising: a calculating device configured to calculate correction information for adjusting an output of the optical sensor with respect to an output of the reference illuminometer based on a result of the repeatedly performed energy measurement. Exposure equipment. An exposure system including a plurality of exposure apparatuses in which illuminance is collectively managed using the same reference illuminometer,
Each of the exposure apparatuses,
An optical sensor for receiving a part of the energy beam branched on the optical path of the energy beam from the light source to the mask;
A dimming device arranged between the light source and the branch point, the dimming rate of which can be set continuously or intermittently within a predetermined range;
A storage device in which correction information measured by the correction information measurement method according to claim 1 or 2 is stored in advance;
Using the correction information to correct the output of the optical sensor, while controlling the integrated energy amount on the image plane on which an image of the pattern on the mask is formed based on the corrected output of the optical sensor, And a control device for transferring the pattern onto an object arranged on the image plane. A device manufacturing method including a lithography step,
8. A device manufacturing method, wherein the same plurality of objects are exposed using the exposure system according to claim 7 in the lithography step.

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