WO1999026279A1 - Procede d'exposition et graveur a projection - Google Patents

Procede d'exposition et graveur a projection Download PDF

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Publication number
WO1999026279A1
WO1999026279A1 PCT/JP1998/005184 JP9805184W WO9926279A1 WO 1999026279 A1 WO1999026279 A1 WO 1999026279A1 JP 9805184 W JP9805184 W JP 9805184W WO 9926279 A1 WO9926279 A1 WO 9926279A1
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WO
WIPO (PCT)
Prior art keywords
exposure
optical system
projection optical
conditions
reticle
Prior art date
Application number
PCT/JP1998/005184
Other languages
English (en)
Japanese (ja)
Inventor
Tetsuo Taniguchi
Original Assignee
Nikon Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nikon Corporation filed Critical Nikon Corporation
Priority to AU11734/99A priority Critical patent/AU1173499A/en
Publication of WO1999026279A1 publication Critical patent/WO1999026279A1/fr
Priority to US09/571,685 priority patent/US20030016339A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70216—Mask projection systems
    • G03F7/70241—Optical aspects of refractive lens systems, i.e. comprising only refractive elements
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70425—Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
    • G03F7/70466—Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature

Definitions

  • the present invention relates to an exposure method used for transferring a mask pattern onto a photosensitive substrate when, for example, manufacturing a semiconductor element, a liquid crystal display element, or a thin-film magnetic head using a photolithography technique, and
  • the exposure apparatus is particularly suitable for use in performing multiple exposure.
  • a projection exposure apparatus such as a stepper used for manufacturing a semiconductor device or the like
  • imaging characteristics disortion, best focus position, etc.
  • various correction methods have been proposed.
  • One example of such a correction method is to measure the incident energy to the projection optical system, predict the amount of change in the imaging characteristics according to a previously determined model of the change characteristics of the imaging characteristics, and determine a predetermined amount based on the prediction result. This is a method of driving some optical elements of the projection optical system via the correction mechanism described above.
  • a modified illumination technology or a phase shifter that illuminates a reticle as a mask with illumination light from a secondary light source having an annular shape or a plurality of apertures has been provided.
  • Technology using a reticle has also been proposed.
  • these techniques are used, the intensity distribution of the illumination light in the projection optical system changes greatly, and the fluctuation characteristics of the above-mentioned imaging characteristics change.
  • a technique has been proposed in which a model of the fluctuation characteristic is used after being changed according to exposure conditions.
  • the next lot of wafers may be switched to another exposure condition and exposed.
  • the exposure under the new exposure condition is started while the influence of the previous exposure condition remains in the projection optical system, and the imaging characteristics change discontinuously.
  • Japanese Patent Application Laid-Open No. 6-45217 proposes a method of suspending exposure under new exposure conditions until the influence of the previous exposure conditions is sufficiently reduced.
  • the discontinuity (offset) of the imaging characteristic at the time of the change is measured in advance, and when the imaging characteristic is switched, A method of adding the offset to the imaging characteristic after switching has also been proposed.
  • the conventional method of correcting the imaging characteristics uses a model of the fluctuation characteristics of the imaging characteristics obtained in advance according to the exposure conditions, and performs the offset correction when switching the exposure conditions.
  • the amount of change in the image characteristics is predicted, and the image formation characteristics are corrected so as to offset the predicted amount of change.
  • the imaging characteristics under the two exposure conditions are mixed, and the offset of the imaging characteristics is temporarily considered. Even if a single model of the fluctuation characteristic is used, there is a possibility that a correction error of the imaging characteristic remains.
  • a double exposure method has attracted attention as an exposure method for further improving the imaging performance.
  • This method uses two or more different layers on the same layer (sensitive layer) on the wafer.
  • the dense pattern and the isolated pattern have significantly different states of generation of diffracted light.
  • the numerical aperture (NA), illumination conditions, exposure amount, and best focus position of the projection optical system are different. Therefore, the dense pattern and the isolated pattern are drawn on the first and second reticles different from each other, and the pattern of the two reticles is double-exposed under the optimum exposure conditions, for example, by using both of them.
  • both patterns can be transferred with high resolution.
  • the chemically amplified resist which is a photoresist suitable for excimer laser light, is suitable for forming fine patterns, but the chemical stability after exposure is not very good, so the time between exposure and development is reduced. In order to shorten the time, it is necessary to perform development processing within a certain time after exposure. For this reason, when performing double exposure using a chemically amplified resist, after exposing the pattern of the first reticle for each wafer in one lot, the reticle is exchanged by exchanging the reticle. The reticle pattern must be exposed, and the exposed wafer must be sequentially transferred to a development process.
  • the present invention can reduce the fluctuation of the imaging characteristic due to the absorption of the energy of the illumination light in the projection optical system, even when performing multiple exposure while exchanging patterns for each wafer.
  • a second object is to provide an exposure method that can accurately correct.
  • Another object of the present invention is to provide an exposure apparatus that can use such an exposure method. Disclosure of the invention
  • An exposure method is an exposure method for exposing an image of a mask pattern on a substrate through a projection optical system under a predetermined exposure energy beam, wherein a plurality of different exposure conditions are sequentially applied to the substrate.
  • the image forming characteristic of the projection optical system is corrected in accordance with the switching operation of the exposure condition.
  • the imaging characteristics are substantially mixed with the characteristics under a plurality of exposure conditions. Attention is paid to the fact that the ratio can be regarded as substantially constant according to the switching operation, that is, for example, the ratio of the amount of irradiation energy under each exposure condition, and the like.
  • the imaging characteristics are considered to fluctuate based on the average fluctuation characteristics determined by a ratio corresponding to the switching operation, and the amount of fluctuation of the imaging characteristics is determined according to the average fluctuation characteristics. Is predicted, and the imaging characteristics are corrected based on this result.
  • the correction is performed on the assumption that the imaging characteristic fluctuates according to the average fluctuation characteristic. Therefore, the imaging characteristics can be accurately maintained in a desired state only by performing a simple calculation.
  • the imaging characteristics of the projection optical system it is desirable to correct the imaging characteristics of the projection optical system according to the ratio of the respective exposure times of the plurality of exposure conditions. Since the mixture ratio of the imaging characteristics is determined according to the exposure time ratio, using the exposure time ratio makes it possible to accurately predict the average fluctuation amount of the imaging characteristics with a small amount of calculation. .
  • a plurality of mask patterns may be prepared, and the images of the plurality of mask patterns may be exposed to the same sensitive layer on the substrate under mutually different exposure conditions.
  • a predetermined pattern is exposed by performing multiple exposure while switching the exposure condition on one layer on the substrate.
  • the imaging characteristics are considered to fluctuate based on the average fluctuation characteristics of the plurality of imaging characteristics corresponding to each mask pattern.
  • An example of the exposure condition is any of the illumination condition of the exposure energy beam, the numerical aperture of the projection optical system, and the type of the mask pattern. For example, since the transmittance or the like changes depending on the type of mask pattern, the amount of energy incident on the projection optical system changes.
  • an exposure apparatus is an exposure apparatus that exposes an image of a mask pattern onto a substrate via a projection optical system under a predetermined exposure energy beam. And an image forming characteristic correcting unit for correcting the image forming characteristic of the projection optical system in accordance with the switching operation of the exposure condition.
  • the exposure method of the present invention can be used.
  • the exposure control unit stores in advance a model of a variation characteristic of an imaging characteristic due to absorption of an exposure energy beam of the projection optical system for each of a plurality of exposure conditions, and performs exposure by, for example, a double exposure method.
  • the model obtained by averaging the models of the fluctuation characteristics according to the ratio of the irradiation energy amount under each exposure condition the fluctuation of the imaging characteristics due to the irradiation of the exposure energy beam is corrected. It is desirable to do it.
  • FIG. 1 is a partial view showing a projection exposure apparatus used in an example of an embodiment of the present invention.
  • FIG. 1 is a partial view showing a projection exposure apparatus used in an example of an embodiment of the present invention.
  • FIG. 2 is a diagram for explaining a state of a change in imaging characteristics caused by absorption of illumination light of a projection optical system.
  • FIG. 3 is an explanatory view of patterns of two reticles and corresponding exposure conditions when performing exposure by a double exposure method.
  • FIG. 4 is an explanatory diagram of how to obtain a coefficient of a model _ of a variation amount of an imaging characteristic when performing exposure by a double exposure method in the embodiment.
  • FIG. 5 is a diagram showing a correction amount (change amount) of an imaging characteristic under each exposure condition when performing exposure by a double exposure method in the embodiment.
  • FIG. 6 is an enlarged view showing the correction amount (change amount) of the imaging characteristic in the first part of FIG. BEST MODE FOR CARRYING OUT THE INVENTION
  • FIG. 1 shows the projection exposure apparatus of this example.
  • KrF wavelength 24
  • a r F wavelength 1 9 3 nm
  • F 2 irradiation Meiko IL as an exposure energy beam emitted from the exposure light source 1 consisting of an excimer laser light source 1 5 7 nm
  • the light is incident on a shaping optical system for shaping the cross-sectional shape of light, and an illuminance uniforming optical system 2 including a fly-eye lens for uniforming the illuminance distribution.
  • a mercury lamp, X-ray, or the like can be used as the exposure light source 1.
  • the exit surface of the illumination uniforming optical system 2 is the reticle to be transferred (reticle R in Fig. 1).
  • a turret plate 3 on which various aperture stops for switching the illumination conditions for the reticle are formed is arranged. . That is, around the rotation axis of the turret plate 3, a circular aperture stop for normal illumination, a small circular aperture stop 3a for setting a small ⁇ value as a coherence factor, and an annular illumination are provided. A ring-shaped aperture stop 3b for performing the operation, and a deformed stop composed of four apertures arranged around the optical axis are arranged.
  • the illumination light IL emitted from the illuminance uniforming optical system 2 and having passed through a predetermined aperture stop in the turret plate 3 is further converted into an optical system 4 including a relay lens, a field stop, and the like, a mirror for bending the optical path 5
  • the illumination area on the pattern surface (lower surface) of the reticle R 1 is illuminated via the condenser lens 6.
  • the optical system 4 also includes an integrator sensor 4a for branching a part of the illumination light IL and detecting the amount of the light, and a reflectance monitor 4b for detecting the amount of light reflected from the reticle side. .
  • the image of the pattern in the illumination area of reticle R 1 is projected onto the surface of a semiconductor wafer (hereinafter simply referred to as “wafer”) W at a projection magnification of ⁇ (1 Z 4, 1/5, etc.) via projection optical system PL. Is transferred to the exposure area.
  • wafer semiconductor wafer
  • an illumination system including the illuminance uniforming optical system 2 and the optical system 4 is disclosed in Japanese Patent Application Laid-Open No. Hei 5-2010 (U.S. Pat. No. 5,719,704).
  • An illumination system including a rod-type optical integrator as described above may be used.
  • a variable aperture stop (not shown) is provided on the optical Fourier transform plane (pupil plane) for the pattern surface of the reticle R1 in the projection optical system PL.
  • a pupil filter of a so-called light-blocking type that blocks illumination light in a predetermined area centered on the optical axis as disclosed in Japanese Patent Application Laid-Open No. HEI 6-124870.
  • a phase filter or the like in which a phase member is formed can be installed as needed. Note that the exit surface of the uniform illumination optical system 2 is almost optically conjugate with the pupil plane of the projection optical system PL, and is substantially optically conjugate with the pupil plane of the projection optical system PL due to the rotation of the turret plate 3.
  • the intensity distribution on the pupil plane of the projection optical system PL also changes.
  • a chemically amplified resist is applied to the surface of the wafer W in this example, and the surface is held so as to coincide with the image plane of the projection optical system PL during exposure.
  • the Z axis is taken parallel to the optical axis AX of the projection optical system PL
  • the X axis is taken parallel to the plane of Fig. 1 in a plane perpendicular to the Z axis
  • the Y axis is perpendicular to the plane of Fig. 1.
  • the reticle R 1 is sucked and held on the reticle holder 7, and the reticle holder 7 has three drive elements 8 (two in FIG. Only the driving element 8 appears.
  • the reticle stage RST is mounted on the reticle base 9 movably in the X direction, the Y direction, and the rotation direction by, for example, a linear motor system.
  • the amount of expansion and contraction of the drive element 8 is set by the imaging characteristic control system 16 under the control of the main control system 14.
  • the moving mirror on the reticle holder 7 and the external laser interferometer 10 measure the X coordinate, Y coordinate, and rotation angle of the reticle stage RST (reticle R), and the measured values are used as the reticle stage drive system 11,
  • the reticle stage drive system 11 is supplied to the main control system 14 and controls the operation of the reticle stage RST based on the measured values and control commands from the main control system 14.
  • a reticle exchanging device 12 is installed near the reticle base 9, and a second reticle R 2 is placed on the first slider 13 of the reticle exchanging device 12, and the reticle exchanging device 1 2 Replaces the reticle R 1 on the reticle holder 7 with the second reticle R 2 via the second slider (not shown) and the first slider 13 according to a control command from the main control system 14. . Thereafter, reticle R 1 and reticle R 2 are alternately set on reticle holder 7 by reticle exchange device 12. Reticles R 1 and R 2 in this example are formed with a pattern for double exposure, which will be described later.
  • the wafer W is held by suction on a sample table 23 via a wafer holder (not shown), and the sample table 23 is fixed on a wafer stage WST for positioning the wafer W in the X and Y directions by, for example, a linear motor method. Have been.
  • the sample stage 23 is also provided with a Z leveling drive mechanism for controlling the position (focus position) of the wafer W in the Z direction and the tilt angle within a predetermined range.
  • the moving mirror on the sample stage 23 and the external laser interferometer 25 measure the X coordinate, Y coordinate, and rotation angle of the sample stage 23 (wafer W), and the measured values are used as the wafer stage drive system 26,
  • the wafer stage drive system 26 is supplied to the main control system 14, and controls the operation of the wafer stage WST based on the measured values, control commands from the main control system 14, and the like.
  • the projection exposure apparatus of this embodiment is of a batch exposure type (stepper type), but the present invention is disclosed in Japanese Patent Application Laid-Open No. 6-291106 (US Pat. No.
  • the present invention can also be applied to a scanning exposure type projection exposure apparatus such as a step-and-scan method as disclosed in (1).
  • the reticle stage RST is also provided with, for example, a function of continuously moving in the Y direction. The scanning is performed synchronously with the projection magnification 3 as the speed ratio.
  • a slit image is obliquely placed on the side of the projection optical system PL at a measurement point on the surface of the wafer W near the exposure area.
  • the projection optical system 27 that projects the light, and the reflected light from the surface of the wafer W is received and the slit image is re-imaged, so that the focus signal corresponding to the defocus amount from the image plane at the measurement point is obtained.
  • An oblique incidence type focus position detection system (hereinafter, referred to as “AF sensors 27, 28”) composed of an output light receiving optical system 28 and is provided.
  • the focus signals of the AF sensors 27 and 28 are supplied to the main control system 14 and the wafer stage drive system 26, and the wafer stage drive system 26 has the target value whose focus signal is set from the main control system 14.
  • the operation of the Z repelling drive mechanism in the sample stage 23 is controlled so that the initial value becomes 0.
  • the illumination system and projection optical system including multiple optical components are incorporated into the exposure apparatus main body to perform optical adjustment, and the reticle stage and wafer stage are attached to the exposure apparatus main body to electrically and mechanically By connecting, the projection exposure apparatus of this example is manufactured.
  • the circuit pattern image is, as an example, a butterfly image in which a dense pattern image 32 and an isolated pattern image 33 are mixed, as shown in FIG. 3 (a), and each pattern image is a light shielding pattern. Shall correspond.
  • the dense pattern and the isolated pattern have mutually different optimal exposure conditions (such as the aperture stop of the illumination system, the numerical aperture of the projection optical system PL, and the exposure amount).
  • the corresponding reticle pattern is decomposed into a first reticle R1 pattern shown in FIG. 3 (b) and a second reticle R2 pattern shown in FIG. 3 (d).
  • the pattern of the first reticle R1 is formed by the dense pattern 32A and the light shielding pattern 33A for covering the isolated pattern
  • the pattern of the second reticle R2 is The light-shielding pattern 32B for covering the dense pattern and the isolated pattern 33B are formed.
  • a phase shifter may be provided in the dense pattern 32A
  • the reticle R_l may be a phase shift reticle.
  • the annular aperture stop 3b shown in FIG. 3 (c) is used as the aperture stop of the illumination system
  • the second When exposing the pattern image of the reticle R2 an aperture stop 3a for a small ⁇ value shown in FIG. 3 (e) is used as the aperture stop.
  • the incident energy to the projection optical system PL depends on which reticle is used. Change.
  • the exposure is performed by the double exposure method, but also in this case, the projection optical system PL depends on environmental conditions such as the temperature around the projection optical system PL and the amount of energy incident on the projection optical system PL.
  • the imaging characteristics change gradually. Therefore, the projection exposure apparatus of this example is provided with a sensor for measuring environmental conditions and a mechanism for measuring the amount of energy incident on the projection optical system PL. That is, a detection signal from an environment sensor 30 including an atmospheric pressure sensor, a temperature sensor, and a humidity sensor is supplied to a main control system 14 via a signal processing device 29, and the main control system 14 detects the detection signal.
  • the atmospheric pressure, temperature, and humidity around the projection optical system PL are recognized from the signal.
  • An irradiation monitor 24 composed of a photoelectric detector is installed near the wafer W (wafer holder) on the sample table 23, and a detection signal of the irradiation monitor 24 is supplied to the main control system 14. .
  • a detection signal of the irradiation monitor 24 is supplied to the main control system 14. .
  • reticle R 1 or R 2
  • pattern abundance can be measured. Even during the exposure, the exposure amount to the wafer W (incident energy to the projection optical system PL) is constantly indirectly monitored via the integrator sensor in the optical system 4. And the reflectance monitor of the optical system 4 can be used to determine the reflectivity of the wafer W, and thus the amount of illumination light reflected by the wafer W and returned to the projection optical system PL. .
  • the drive element 8 for driving the reticle R in the optical axis AX direction is used for correcting a symmetric distortion component. If the reticle is non-telecentric, it is used to correct the projection magnification.
  • a lens element L 2 is inserted into a lens frame 20 via three driving elements 19 such as a piezo element which can be extended and contracted on a lens barrel 18 of the projection optical system PL.
  • a lens element L1 is held in the lens frame 22 via three drive elements 21 that can expand and contract in the Z direction on the lens frame 20.
  • the expansion and contraction amounts of the driving elements 19 and 21 are controlled by an imaging characteristic control system 16. For example, by moving the lens elements L 2 and L 1 near the reticle R 1 in the direction of the optical axis AX and tilting them within a predetermined range, for example, the projection is performed. Correction of magnification, field curvature, symmetric distortion components, etc. can be performed.
  • a pressure variable section 15 such as a bellows pump for controlling the pressure inside the sealed space 17 between predetermined lens elements inside the projection optical system PL
  • the imaging characteristic control section 16 includes: By controlling the pressure in the closed space 17 via the pressure variable section 15, for example, magnification, coma aberration, field curvature and the like can be corrected.
  • the main control system 14 detects the wafer stage drive system 26 by the AF sensors 27 and 28. By issuing a command to add the offset corresponding to the variation to the target value of the focus signal, the surface of the wafer W can follow the variation of the image plane.
  • the imaging characteristic control system 16 determines the drive amount of the corresponding correction mechanism and drives each correction mechanism.
  • the main control system 14 measures the energy amount of the illumination light IL incident on the projection optical system PL and the transmittance of the reticle R by the irradiation amount monitor 24 on the wafer stage WST. Also, when monitoring the energy amount of the light beam passing through the projection optical system PL with higher accuracy, the main control system 14 uses the detection signal from the reflectance monitor 4 b provided in the optical system 4 to Calculate the energy of the light beam reflected by the wafer W and returned to the projection optics PL.
  • the main control system 14 determines, for example, at what timing the illumination light IL is incident on the projection optical system PL based on the detection signal of the integrator sensor 4a in the optical system 4, and the illumination light IL for the projection optical system PL. Can be recognized.
  • the internal temperature of the projection optical system PL changes due to the balance between the absorption of the illumination light IL and the heat radiation, and the imaging characteristics change accordingly.
  • FIG. 2 shows how the imaging characteristics of the projection optical system PL change in such a manner.
  • the horizontal axis represents the elapsed time t
  • the vertical axis represents the variation ⁇ ⁇ of the imaging characteristics. I have.
  • the solid curves 31A and 31B represent changes in the imaging characteristics when the reticles R1 and R2 are used, for example.
  • the following describes the exposure conditions (illumination conditions, reticle pattern type, numerical aperture of the projection optical system PL, and the inside of the projection optical system PL) when exposing the patterns of the first reticle R 1 and the second reticle R 2.
  • Filter type; presence / absence, exposure amount, etc.) are referred to as exposure condition A and exposure condition B, respectively.
  • the curves 31 A and 3 IB in FIG. 2 after the irradiation of the projection optical system PL with the illumination light IL is started at time t0, the imaging characteristics gradually change, and the irradiation continues.
  • the absorption and radiation are gradually balanced, and the imaging characteristics are saturated to a certain value.
  • the imaging characteristics gradually return to the original state.
  • the illumination conditions are different under the exposure conditions A and B, and the intensity distribution of the illumination light in the projection optical system PL is different even with the same amount of incident energy as a whole. 3
  • the change characteristics are different. This change characteristic is obtained in advance by an experiment or the like, and is stored in the storage unit in the main control system 14 as a model of the change characteristic of the imaging characteristic.
  • the change amount ⁇ of the imaging characteristic is, for example, the change amount (defocus amount) of the best focus position, the error of the projection magnification / 3, or the amount of distortion.
  • the change amounts ⁇ P under the exposure conditions ⁇ and B are respectively Let ⁇ A and ⁇ B. Then, assuming that the time constants under the exposure conditions A and B are ⁇ A and B, respectively, and the saturation values of the variation ⁇ P under the exposure conditions A and B are PA and PB, respectively.
  • the changes ⁇ PA and ⁇ are each expressed as a function of time t as follows: The following model represents the variation between t O ⁇ t ⁇ tl with the irradiation start time t 0 as 0 in FIG.
  • the main control system 14 By successively substituting the elapsed time t from the irradiation start into these models, the main control system 14 obtains the change amounts ⁇ ⁇ and ⁇ ⁇ of the imaging characteristics at the elapsed time t. be able to. Since the cumulative incident energy during t 0 t ⁇ t 1 is proportional to the elapsed time t, the elapsed time t can be made to correspond to the cumulative incident energy.
  • the saturation values PA and PB are coefficients (usually proportional to energy and change) that indicate how much variation (at saturation level) occurs for a given energy.
  • the time constants ⁇ and ⁇ are coefficients that indicate the speed of change (how long it takes to reach saturation).
  • the saturation values ⁇ , ⁇ ⁇ ⁇ and the time constants A, B vary depending on the amount of incident energy (illuminance) per unit time, their saturation values PA, PB, and the time constant ⁇ , ⁇ The value of It is stored as a function of the illuminance of the illumination light.
  • the storage unit of the main control system 14 stores those environmental conditions. A variation characteristic model for obtaining the amount of change in the imaging characteristic with respect to the variation is also stored. Then, the main control system 14 supplies the change amount of the imaging characteristic according to the change of the environmental condition and the sum of the change amount of the imaging characteristic according to the incident energy amount to the imaging characteristic control system 16. In the imaging characteristic control system 16, imaging is performed via at least one of the driving elements 8, 15, 19, 21 so as to cancel the sum of the supplied changes in the imaging characteristics. Correct the image characteristics. Further, regarding the defocus correction, the main control system 14 changes the offset of the focus signals of the AF sensors 27 and 28 with respect to the target value with respect to the wafer stage drive system 26.
  • the operation of exposing the pattern image of the first reticle R 1 to each wafer in one lot under the exposure condition A is performed in order to shorten the time for putting the chemically amplified resist on the wafer.
  • the operation of exposing the pattern image of the second reticle R 2 under the exposure condition B are alternately repeated.
  • the reticle In order to reduce the frequency of reticle replacement and increase the throughput of the exposure process, after exposing the first wafer, the reticle must not be replaced after the first wafer has been exposed. Exposure of the pattern image of the second reticle R2, and then exchanging the reticle to expose the pattern image of the first reticle R1, and thereafter, it is desirable to perform the reticle exchange at an intermediate point of the exposure of each wafer. .
  • the imaging characteristics change when the fluctuation characteristics of the imaging characteristics under the two exposure conditions A and B are mixed at a constant rate. Can be considered.
  • the projection optical system PL is irradiated in a state where the imaging characteristics of the exposure conditions A and B are mixed, the passing position of the illumination light IL is different between the exposure conditions A and B. Since the change characteristics are different from the change characteristics for exposure condition B, it is necessary to calculate the amount of change in the imaging characteristics using different coefficients (saturation value and time constant) for exposure conditions A and B. is there.
  • FIG. 4 shows the case where it can be considered that the imaging characteristics of exposure conditions A and B are mixed.
  • FIG. 4 is an explanatory diagram of a method of determining a coefficient of a model indicating a variation amount of an imaging characteristic under exposure conditions A and B.
  • a horizontal axis indicates a total irradiation energy under two exposure conditions A and B.
  • the irradiation energy is determined by the transmittance of the reticle and the illuminance on the reticle determined by the exposure conditions of the resist (per unit time with respect to the projection optical system PL monitored by the integrator sensor 4a in the optical system 4). Incident energy) and the irradiation time. If the irradiation energy amounts under the exposure conditions A and B are ⁇ EA and ⁇ EB, respectively, the ratio ⁇ is as follows.
  • the ratio ⁇ can be calculated from the output of the dose monitor 24 in FIG. 1 and parameters (eg, the dose, the number of shots, etc.) that determine the exposure sequence.
  • parameters eg, the dose, the number of shots, etc.
  • the output of the dose monitor 24 is obtained. It is also possible to obtain from the actually measured value of the integrated value.
  • the vertical axis on the left side of FIG. 4 represents the coefficient k A under the exposure condition ⁇
  • the vertical axis on the right side represents the coefficient k B under the exposure condition B
  • the solid curves 34 A and 34 B correspond to the coefficient k A and kB are shown.
  • the coefficients k A and k B are, for example, proportional coefficients for obtaining the saturation values PA and PB (see equations (1A) and (1B)) described with reference to FIG. 2 from the illuminance of the illumination light. It is.
  • the value k A o of the coefficient k A under the exposure condition A when the ratio ⁇ is 0 is the value of the imaging characteristic in the case where one lot of wafers are continuously exposed only under the exposure condition A.
  • the value of the coefficient k ⁇ 0 under the exposure condition B when the ratio ⁇ is 1 is the coefficient representing the fluctuation characteristics.
  • the coefficient k ⁇ ⁇ under the exposure condition ⁇ gradually increases. Conversely, as the ratio ⁇ decreases from 1, the coefficient k ⁇ ⁇ under the exposure condition ⁇ gradually decreases as shown by the curve 34 ⁇ . In this case, the ratio ⁇ is 1
  • the value k Ai of the coefficient k A when it is close to, and the value k of the coefficient k ⁇ ⁇ when the ratio ⁇ is close to 0 may be obtained in advance.
  • the value is a coefficient indicating the amount of change under exposure condition A when greatly affected by exposure condition B.
  • the coefficients kA and kB in the range of 0 ⁇ ⁇ 1 are two It can be regarded as an average coefficient in which the effects of exposure conditions A and B are mixed.
  • an exposure experiment is performed while changing the ratio ⁇ in a predetermined step from 0 to 1 in advance to confirm the values of the coefficients kA and kB.
  • the characteristics of the curves 34A and 34B may be obtained as a function (for example, a quadratic function or the like) relating to the ratio ⁇ , or a table for each predetermined step of the ratio ⁇ .
  • the function or the table may be stored in the storage unit in the main control system 14, and the values of the coefficients k ⁇ and k ⁇ ⁇ may be obtained from the ratio ⁇ during the double exposure.
  • FIG. 5 shows a case where double exposure is performed while the exposure conditions A and B are alternately repeated from the time point t S when the projection optical system PL in FIG. 1 is sufficiently cooled.
  • the horizontal axis represents the elapsed time t, and the vertical axis represents the absolute value of the correction amount C of the imaging characteristic.
  • the correction amount C is a value having the same absolute value and the opposite sign to the change amount ⁇ ⁇ of the imaging characteristic.
  • the exposure period TA under the exposure condition A and the exposure period TB under the exposure condition B alternate alternately at a substantially constant cycle.
  • the ratio ⁇ of the irradiation energy amount between the exposure condition A and the exposure condition B is ⁇ X.
  • the control system 14 obtains the values kAx and kBx of the coefficients kA and kB under the exposure conditions A and B at the ratio ⁇ x from the stored characteristics of the curves 34A and 34B in FIG.
  • the time constant coefficient is obtained from the ratio ⁇ X.
  • the main control system 14 determines the amount of change ⁇ in the imaging characteristic under the exposure condition ⁇ during the period ⁇ ⁇ ⁇ ⁇ by using the model of the variation characteristic represented by the equations (1 ⁇ ) to (2 ⁇ ), for example.
  • the change amount ⁇ ⁇ ⁇ of the imaging characteristic under the exposure condition ⁇ of the period ⁇ ⁇ is sequentially calculated.
  • the change amounts ⁇ ⁇ and ⁇ of the imaging characteristics under the exposure conditions ⁇ and ⁇ are represented by solid-line curves 35 ⁇ and 35 B, respectively.
  • the main control system 14 calculates the change amount ⁇ ⁇ calculated under the exposure condition A.
  • the value of the correction amount C is set so as to offset P A, and in the period TB, the value of the correction amount C is set so as to offset the change amount ⁇ P B calculated under the exposure condition B.
  • FIG. 6 is an enlarged view of a portion corresponding to the first part of the curved line 35A of the exposure condition A in FIG. 5, and in FIG. Shows the actual amount of change ⁇ ⁇ A in the imaging characteristics, and the amount of change ⁇ is large during the exposure period TA under the exposure condition A, and small during the exposure period TB under the exposure condition B. .
  • the curve 36A decreases in the period TC1 and TC2 at the boundary between the period TA and the period TB when the illumination light is not irradiated for the reticle exchange time or the wafer exchange time. Is shown. In FIG. 5, the portion where the variation ⁇ is reduced is omitted. Ideally, it should be corrected according to the change of the solid curve 36A, but it is difficult to calculate exactly the state where the two exposure conditions A and B are mixed.
  • the dotted curve 37A in FIG. And the change amount ⁇ ⁇ ⁇ of the imaging characteristic calculated according to the average coefficient of B and B (the inverse of this sign becomes the correction amount C of the imaging characteristic).
  • the correction amount C of the imaging characteristic is determined based on the curve 35B in FIG.
  • the exposure conditions A and B are switched at a sufficiently short interval compared to the time constant of the change in the imaging characteristics, so that the correction error (the difference between the curves 36A and 37A) is sufficiently small to cause a problem. No.
  • the imaging characteristics based on the change in the incident energy to the projection optical system PL and the environmental conditions are changed. Can be corrected with high accuracy.
  • the pattern image of the first reticle R1 is exposed on the first wafer during the period TA (TA1) starting from the time point tS, and the first half of the next period TB is performed.
  • TA1 the pattern image of the second reticle R2 is exposed on the first wafer.
  • the pattern image of the second reticle R2 is exposed on the second wafer in the second period TB2, and in the first half of the next period TA, the second wafer is exposed in the second period TA2.
  • the pattern image of the first reticle R1 has been exposed.
  • the latter half period TA3 the pattern image of the first reticle R1 is exposed on the third wafer, and thereafter, the reticle is exchanged in the middle of the exposure of each wafer.
  • a step for designing the function and performance of the device For a device such as a semiconductor, a step for designing the function and performance of the device, a step for manufacturing a reticle based on the design step, a step for manufacturing a wafer from a silicon material, a pattern of a reticle by the exposure apparatus of the above-described embodiment. It is manufactured through a step of exposing the wafer to a wafer, a step of assembling devices (including a dicing step, a bonding step, and a package step), and an inspection step.
  • two reticles Rl and R2 are prepared for performing double exposure.
  • the first pattern and the left half of the reticle are provided on the right half of one reticle.
  • the second pattern may be drawn in advance, and the first and second patterns may be alternately exposed.
  • the exposure conditions to be switched are the two conditions A and B, but the same can be applied even when the number of exposure conditions becomes three or more.
  • FIG. A coefficient indicating the amount of change in the imaging characteristics may be obtained from the ratio of the amount of irradiation energy.
  • the effects of the mixture of the two exposure conditions are ignored, and they are calculated independently of each other and simply added, without having to consider the Daraf in FIG. This method is effective when the influence of mixing is small because the calculation load and the coefficient setting load are small.
  • the exposure method of the present invention since the imaging characteristics of the projection optical system are corrected in accordance with the switching operation of the exposure conditions, the exposure is performed when multiple exposures are performed while the plurality of exposure conditions are alternately switched. There is an advantage that a desired imaging state can be accurately maintained by suppressing a change in imaging characteristics without reducing the throughput of the process.
  • a mask (a wafer) is provided for each substrate (wafer).
  • the exposure condition is any one of the illumination condition of the exposure energy beam, the numerical aperture of the projection optical system, and the type of the mask pattern
  • the exposure condition having a large influence on the imaging characteristics is considered. Fluctuations in the imaging characteristics can be corrected more accurately. Further, when performing exposure under a plurality of different exposure conditions, when correcting the imaging characteristics of the projection optical system according to the ratio of the amount of the exposure energy beam incident on the projection optical system under each exposure condition, Variations in image characteristics can be corrected more accurately.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Abstract

La présente invention concerne un graveur à projection tel qu'on peut corriger avec précision la variation d'une caractéristique de formation d'image, provoquée par l'absorption de l'énergie d'une lumière d'exposition, dans un système à projection optique, même lorsqu'on réalise une double exposition lors du changement de motif d'un réticule de chaque plaquette. On expose le motif d'un premier réticule, pendant une durée TA, dans une condition d'exposition A, et on expose le motif d'un second réticule pendant une durée TB, dans une condition d'exposition B. On répète alternativement ces expositions. On détermine un coefficient montrant le motif de la variation de la caractéristique de formation d'image pendant la durée TA, et un coefficient montrant le motif de la variation de la caractéristique de formation d'image pendant la durée TB, en fonction du rapport entre les énergies appliquées dans les conditions d'exposition A et B. On estime la modification Δp de la caractéristique de formation d'image pendant les durées TA et TB en fonction des coefficients et on corrige la caractéristique de formation d'image de manière à annuler la modification Δp.
PCT/JP1998/005184 1997-11-18 1998-11-18 Procede d'exposition et graveur a projection WO1999026279A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU11734/99A AU1173499A (en) 1997-11-18 1998-11-18 Exposure method and aligner
US09/571,685 US20030016339A1 (en) 1997-11-18 2000-05-16 Exposure method and apparatus

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP9316921A JPH11150053A (ja) 1997-11-18 1997-11-18 露光方法及び装置
JP9/316921 1997-11-18

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WO1999026279A1 true WO1999026279A1 (fr) 1999-05-27

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WO (1) WO1999026279A1 (fr)

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Publication number Priority date Publication date Assignee Title
JP4586954B2 (ja) * 2003-04-04 2010-11-24 株式会社ニコン 露光装置及び露光方法、並びにデバイス製造方法
JP4684563B2 (ja) * 2004-02-26 2011-05-18 キヤノン株式会社 露光装置及び方法
US7382438B2 (en) * 2005-08-23 2008-06-03 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method
JP5006762B2 (ja) * 2007-11-05 2012-08-22 キヤノン株式会社 露光装置及びデバイス製造方法
NL2003919A (en) 2008-12-24 2010-06-28 Asml Netherlands Bv An optimization method and a lithographic cell.
DE102011113521A1 (de) * 2011-09-15 2013-01-03 Carl Zeiss Smt Gmbh Mikrolithographische Projektionsbelichtungsanlage
JP7213757B2 (ja) * 2019-05-31 2023-01-27 キヤノン株式会社 露光装置、および物品製造方法
JP2023178029A (ja) 2022-06-03 2023-12-14 キヤノン株式会社 決定方法、露光方法、情報処理装置、プログラム、露光装置、および物品製造方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0794393A (ja) * 1993-09-21 1995-04-07 Nikon Corp 投影露光装置
JPH08288192A (ja) * 1995-04-13 1996-11-01 Nikon Corp 投影露光装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0794393A (ja) * 1993-09-21 1995-04-07 Nikon Corp 投影露光装置
JPH08288192A (ja) * 1995-04-13 1996-11-01 Nikon Corp 投影露光装置

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AU1173499A (en) 1999-06-07

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