JP3125307B2 - Exposure apparatus and exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus (such as a stepper) for manufacturing a semiconductor device using an excimer laser or the like which requires partial gas exchange, gas injection, or the like as an exposure light source.

[0002]

2. Description of the Related Art In recent years, in an exposure apparatus used in a photolithography process for manufacturing a semiconductor device, the minimum pattern size of a circuit has been reduced along with the high integration of the device.
An exposure apparatus using an excimer laser has been developed as a light source for exposure, instead of a mercury lamp that has conventionally been mainstream. The excimer laser and the exposure apparatus main body are connected by an electric wire or an optical fiber interface cable,
A method of emitting a laser according to a sequence of a main computer in an exposure apparatus main body is generally used. Interface signals include, for example, a light emission trigger from the exposure apparatus main body to the excimer laser, a signal indicating the start of high-voltage charging, oscillation start and stop, an oscillation standby completion from the excimer laser to the exposure apparatus main body, an internal shutter position, an A signal indicating that the lock operation is being performed is exemplified.

In this type of exposure apparatus, the laser light has a variation of about ± 10% for each pulse, and the exposure surface (reticle or wafer) is regularly arranged due to the coherence of the laser light. Interference patterns (speckles) resulting from the superposition of a large number of light beams having different phases caused by scratches, dust, surface defects, etc. in the illumination optical system. Can occur. The above two interference patterns, particularly regular interference patterns, have a significant effect on controlling the pattern line width in the photolithography process. Therefore, for example, Japanese Patent Application Laid-Open No. 59-226317 or Japanese Patent Application Laid-Open
It is also considered to smooth regular interference patterns and speckles (hereinafter collectively referred to as interference patterns) by a method equivalent to the method disclosed in Japanese Patent No. 59533.
The smoothing (incoherent) of the interference pattern disclosed in the above publication is performed by moving a laser beam one-dimensionally or two-dimensionally (raster scan) at a constant period by a vibrating mirror (galvano mirror, polygon mirror), and spatially. This is to reduce coherency. In other words, illuminance equalization means for each pulse (optical integrator)
By changing the incident angle of the laser beam on the reticle, the interference pattern is moved on a reticle every pulse, and finally the interference pattern is smoothed, in other words, the illuminance uniformity is improved. At this time, a plurality of pulses are emitted in synchronization with one-dimensional or two-dimensional scanning by the vibrating mirror. Usually, the oscillation pulse width of an excimer laser is 20
Since the vibration mirror is extremely short at about nsec, even if the vibration mirror is vibrated at about 10 Hz, the vibration mirror behaves as if it is stationary during one pulse of the excimer laser.

Accordingly, in order to achieve the smoothing of the interference pattern by a plurality of pulses (uniform illuminance) and the desired accuracy of exposure amount control, (1) the energy amount per pulse is kept substantially constant during exposure. (2) It is important to obtain the target exposure with an integral number of pulses of a half cycle of the mirror vibration in one-dimensional or two-dimensional scanning by the vibrating mirror. By the way, the laser light source also has a phenomenon that the laser density decreases in a short term and a long term. This phenomenon of a decrease in laser density is remarkable in a gas laser, and the output decreases with the deterioration of the mixed gas of the active medium sealed in the chamber. For example, an excimer laser encloses three kinds of mixed gas of a halogen gas such as fluorine, an inert gas such as krypton and argon, and a rare gas such as helium and neon in a laser chamber, and discharges the halogen gas and the inert gas by discharge in the chamber. The active gas reacts with the active gas and emits laser light.As the laser light is emitted repeatedly, the halogen gas is combined with impurities generated in the chamber or adheres to the inside of the chamber. As a result, the pulse energy of the laser light decreases. In general, the relationship between the applied voltage (or charging voltage) applied to an excimer laser light source and the energy amount of an exposure pulse emitted under the applied voltage changes over time, for example, deterioration of a mixed gas of an active medium (halogen gas). When the output of the laser light source decreases with the decrease in the density, the desired oscillation energy cannot be obtained even if the applied voltage corresponding to the pulse energy to be emitted next is determined from the above relationship.

Generally, laser light sources include a constant applied voltage mode and a constant energy amount mode. In particular, when the output decreases due to a decrease in the concentration of halogen gas, etc. in the constant energy mode, it is necessary to receive part of the laser beam, detect the energy amount, and feed back the detected value to the applied voltage. Thus, a device has been devised so as to gradually increase the applied voltage between two electrodes inside the chamber and reduce the decrease in output. However, since the applied voltage has an upper limit, when the applied voltage reaches the upper limit, halogen gas injection (HI: Halogen Injection) is performed.
ion) operation to return the halogen gas concentration to an appropriate value and reduce the applied voltage. In addition, the impurities in the laser chamber increase while the HI operation is repeated. Therefore, even if the HI operation is performed, the halogen gas is combined with these impurities, and the applied voltage increases due to a decrease in the gas concentration. As a result, the cycle of the HI operation is gradually shortened, and the pulse energy amount is gradually reduced even though the applied voltage is near the upper limit. Therefore, when the effect of the HI operation is lost or reduced to a predetermined condition, so-called partial gas exchange (PGR: Partial Gas Repl
acement) needed to perform the action. Note that the above HI operation is repeatedly executed until the PGR operation is required again. The above-described HI operation and PGR operation were almost automatically performed by a command from a control processor in the excimer laser light source.

[0006]

However, in the conventional exposure apparatus as described above, a substantially constant oscillation energy can always be obtained by oscillating the excimer laser light source in the constant energy mode. It is impossible to obtain a desired oscillation energy amount (that is, an applied voltage corresponding to the oscillation energy amount) in the entire control range. In other words, there is a problem in that fine adjustment of the oscillation energy amount cannot be accurately performed for each pulse, and high-precision exposure amount control cannot be achieved, thereby lowering the yield and the like. Furthermore, since the HI operation and the PGR operation are exclusively controlled by the laser light source alone, during exposure of one shot area during exposure of a wafer by the step-and-repeat method (typically several tens or more pulses are required) HI
If the operation and the PGR operation are performed asynchronously, there is a possibility that the shot and the next shot will be significantly damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points. In an exposure apparatus using a laser light source requiring partial gas exchange, gas injection, etc., highly accurate exposure amount control can be achieved. It is intended to prevent a decrease in yield due to factors such as the above.

[0008]

In order to solve the above-mentioned problems, the present invention requires partial gas exchange or gas injection, and emits pulsed light with energy fluctuation within a predetermined range every time oscillation occurs. Excimer laser light source 1
And a means for adjusting the applied voltage to the laser light source (applied voltage control unit 11). In an apparatus for exposing the formed pattern on a sensitive substrate [wafer W] with a predetermined exposure amount, a signal corresponding to the necessity of partial gas exchange of a laser light source or gas injection [ A first control means [main control system 9] for outputting a request signal SA and a prohibition signal SB]; a signal [request corresponding to the necessity of partial gas exchange or gas injection according to the oscillation state of the laser light source] Signal LA and prohibition signal LB], and based on the generated signal and the signal input from the first control means, perform partial gas exchange or gas Second executing the timing of injection by detecting
And control information [control system 25] for storing information relating to the relationship between the voltage applied to the laser light source and the amount of energy of the pulse light emitted from the laser light source under this applied voltage on the reticle or wafer. Storage means [memory 7];
Energy amount measuring means [light receiving element 4 and light amount monitoring unit 5] for detecting the amount of energy of the pulse light actually emitted from the laser light source on the reticle or wafer; and at a predetermined unit pulse number or unit time, or An operation for updating the information stored in the storage unit based on the applied voltage applied to the laser light source and the energy amount detected by the energy amount measurement unit each time partial gas exchange or gas injection is performed. Means [arithmetic unit 6]; and deciding means [arithmetic unit 6] for determining an applied voltage to the laser light source corresponding to the energy amount of the pulse light to be emitted next based on this updated information.

[0009]

In the present invention, during exposure of at least one shot area, the oscillation state of the laser light source and the sensitive substrate are avoided in order to avoid fluctuations in laser output caused by asynchronous partial gas exchange and gas injection on the laser light source side. Corresponding to the exposure state with respect to each of the laser light source and the exposure apparatus body, having the required conditions and the prohibited conditions of the above operation,
The laser light source is cooperatively controlled with the exposure apparatus main body so that the above operation is performed only when at least one of the two required conditions is satisfied and the two prohibition conditions are not both satisfied. Further, in controlling the applied voltage to the laser light source for each pulse for controlling the exposure amount, data on the applied voltage to the laser light source (or the actual charging voltage at the time of energy oscillation) and the pulse energy amount are stored in a unit pulse. The relational expression between the applied voltage and the pulse energy amount stored in the storage means in advance is taken in every several or unit time, or every time the partial gas exchange or the gas injection operation is executed, and is sequentially updated.

Therefore, during the exposure of one shot area, the execution of the partial gas exchange and gas injection operations can be avoided, and even if the relationship between the applied voltage and the pulse energy amount changes over time, it is expressed. Since the relational expression is appropriately updated in accordance with the change with time, it is possible to always achieve good exposure amount control.

[0011]

FIG. 1 is a perspective view showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of a control system of the exposure apparatus shown in FIG. Hereinafter, the configuration of the apparatus according to the present embodiment will be described with reference to FIGS. In FIG. 1, an excimer laser light source 1 has a laser chamber in which a mixed gas such as a rare gas halide is sealed, a front mirror (semi-transmissive) and a rear mirror disposed at both ends of the laser chamber with the two resonators. A wavelength selection element (diffraction grating, prism, etalon, etc.) for narrowing the wavelength band, a spectroscope for monitoring the absolute value of the oscillation wavelength, and a detector for monitoring the laser power , A shutter SH and the like, and is configured as a laser light source having a stable resonator. Then, a high-voltage discharge is generated between two electrodes provided in parallel along the optical axis of the laser light, so that a deep ultraviolet light having a wavelength such that the resist layer is exposed, for example, a KrF excimer laser light (wavelength 248 nm).

The PGR operation and the HI operation for the excimer laser light source 1 are controlled by a control system 25 (second control means of the present invention).
However, in the present embodiment, independent control is not performed only by the control system 25, and cooperative control is performed in cooperation with the exposure apparatus main body (main control system 9). Here, as shown in FIG. 2, after a predetermined charging time required in the excimer laser light source 1 has elapsed, the trigger control unit 10 sends an external trigger pulse to the excimer laser light source 1 and oscillates (pulse number, oscillation interval). Control). The applied voltage control unit 11
The high-voltage discharge voltage (corresponding to the applied voltage) of the excimer laser light source 1 is controlled. By changing the applied voltage in accordance with a command from the main control system 9, the energy amount of the pulse light to be irradiated next is changed. Fine adjustment of. Gas supply control unit 2
4 is a PGR operation for the excimer laser light source 1 and HI
The execution of the operation is controlled, and the cooperative control is performed in cooperation with the exposure apparatus main body as described above. The above trigger control unit 1
A control system 25 (FIG. 1) is configured by 0, the applied voltage control unit 11 and the gas supply control unit 24, and the control system 25 also performs control for stabilizing the wavelength of the excimer laser light source 1.

The laser beam ExB emitted from the excimer laser light source 1 has a rectangular cross section corresponding to the arrangement of the two electrodes, that is, an aspect ratio of the beam cross section of 1/2 to 1.
It is a rectangle of about / 5. Therefore, the laser beam ExB is incident on the beam expander 14 (beam cross-sectional shape conversion optical system) combining two sets (concavities and convexities) of cylindrical lenses via the movable mirror M ₁ and the fixed mirror M ₂ , where a predetermined cross section is formed. Shaped and shaped. That is, the beam expander 14 enlarges the width of the laser beam in the lateral direction, converts the beam cross section into a substantially square shape, and emits the beam.

Further, the beam emitted from the beam expander 14 is incident on the dimming unit 15, where the light intensity (energy) is continuously between 0% (complete transmission) and 100% (complete light shielding), or It is attenuated stepwise. As shown in FIG. 2, the dimming unit 15 controls the dimming rate (transmittance) to a predetermined value by the dimming control unit 12.
As will be described later, the dimming rate of the dimming unit 15 is determined by a desired number of pulses Nsp for smoothing an interference pattern generated on the reticle R or the wafer W and an integrated light amount given to the wafer W. This is determined from the pulse number Nexp required for actual pattern exposure determined from the pulse number Ne required for control with the exposure amount control accuracy, and the appropriate exposure amount.

Here, for example, if the dimming rate of the dimming section 15 is set to six discrete steps, the dimming rate is selected based on the pulse number Nexp and the proper exposure amount before the start of exposure. , During exposure of at least one shot. In other words, the dimming unit 15 does not change the exposure condition for the wafer W (for example, an appropriate exposure amount per shot according to the sensitivity characteristic of the resist).
The light amount of all the pulse lights is always attenuated uniformly at a predetermined light reduction rate, and a light amount adjustment mechanism having a relatively low response speed (light reduction rate switching speed) may be used.

A light reduction unit 15 suitable for use in the present embodiment.
For example, a method is used in which six types of mesh filters having different attenuation rates (transmittances) are attached to a turret plate and the turret plate is rotated. FIG. 3 shows an example of the structure of the rotating turret plate 16 as the light reduction unit 15 and the six types of mesh filters 16a to 16f.
(That is, 100% transmittance). Each of the filters 16a to 16f is arranged at about six positions along a circle centered on the rotation axis of the rotating turret plate 16 at approximately 60 ° intervals. It is configured to be located in the optical path of ExB.

FIG. 4 shows the rotary turret plate 1 shown in FIG.
6 shows the relationship between the rotation amount and the transmittance. Here, the amount of rotation when the filter 16a is positioned in the optical path of the laser beam is set to zero, and the rotary turret plate 16 is rotated counterclockwise in FIG. In FIG. 4, the rotating turret plate 16 is set at about 60 °.
When rotated by (π / 3), the laser beam is dimmed at a predetermined rate. Note that the rotation amount is 2π (360 ° or 0 °).
In the case of (°), since the filter 16a is selected, the transmittance becomes 100%.

Here, as the dimming element attached to the rotating turret plate 16, a dielectric mirror having a different transmittance may be used other than the mesh filter. Further, two sets of rotating turret plates 16 are provided so as to be relatively rotatable at a predetermined interval, and for example, the transmittance of the dimming element of the first rotating turret plate is set to 100%, 90%, 80%, 7%.
0%, 60%, and 50%, and the transmittance of the dimming element of the second rotating turret plate is 100%, 40%, 30%, 20%,
If they are set to 10% and 5%, a total of 36 different transmittances can be realized by a combination of the two.

It is to be noted that a predetermined short aperture and a zoom lens system are combined as the dimming unit 15 to continuously dimm the light by changing the zoom ratio and the aperture diameter.
A method of rotating a so-called etalon in which two glass plates (quartz or the like) are held substantially in parallel at a predetermined interval, a method of relatively moving two phase gratings or light and dark gratings, or a linearly polarized laser beam as exposure light When using a method, a method of rotating a polarizing plate or the like may be adopted.

[0020] Returning to the description of FIG. 1, the substantially parallel beam subjected to a predetermined attenuation in the light reducing portion 15, after being reflected by the oscillating mirror M ₃ as an interference pattern reducing member for smoothing an interference pattern Then, a vibrating beam that swings one-dimensionally (or two-dimensionally) at a small angle is incident on the fly-eye lens 19 that functions as an optical integrator. The oscillating mirror M ₃ (galvanometer mirror, polygon mirror, etc.) is vibrated one-dimensionally (or two-dimensionally) within a predetermined angle by a driving unit MT including an actuator (for example, a piezo element), and a fly-eye lens is provided for each pulse. By changing the angle of incidence of the laser beam on the reticle 19, the interference pattern is moved one-dimensionally (or two-dimensionally) on the reticle and finally smoothed, in other words, the illuminance uniformity is improved.

Therefore, the angle of incidence of the laser beam incident on the fly-eye lens 19 at the plane of incidence on the fly-eye lens 19 changes every moment. Here, the fly-eye lens 19 is formed by bundling a plurality of rod-shaped element lenses, and the exit end thereof has as many secondary light source images as the number of element lenses (here, the respective condensed spots of the partial luminous flux of the laser beam). ) Is formed.

FIG. 5 shows the relationship between the incident beam of the fly-eye lens 19 and the secondary light source image (spot light).
FIG. 9 is a schematic explanatory diagram according to the principle disclosed in Japanese Patent Application Laid-Open No. 9-226317. Each rod lens 19a of the fly-eye lens 19 is a quadrangular prism made of quartz glass having convex spherical surfaces formed at both ends. When the beam LBb (parallel light beam) is incident on the fly-eye lens 19 in parallel with the optical axis AX, the exit end of each rod lens 19a of the fly-eye lens 19, or a position where a predetermined amount of the light exits from the exit end into the air, The spot light SPb is collected. This spot light SPb is 1 in FIG.
Although only one rod lens is shown, the beam LBb is actually formed on all the exit sides of the irradiated rod lens. Moreover, each spot light SPb is focused on the beam LBb substantially at the center of the exit surface of the rod lens. On the other hand, when the parallel beam LBc inclined rightward with respect to the optical axis AX enters the fly-eye lens 19, it is collected as a spot light SPc on the left side of the exit surface of each rod lens 19a. Similarly, the parallel beam LBa inclined leftward with respect to the optical axis AX is transmitted to the rod lens 19a.
Is condensed as spot light SPa on the right side of the exit surface of.
Therefore, all of the plurality of spot lights generated on the exit side of the fly-eye lens 19 by the one-dimensional vibration of the parallel beam by the interference pattern
9 (optical axis AX) in one direction.

As described above, a plurality of beams forming each spot light formed on the exit side of the fly-eye lens 19 pass through the beam splitters BS ₁ and BS ₂ as shown in FIG.
The condenser lens system 21 overlaps the reticle blind (illumination field stop) RB so as to have a substantially uniform intensity distribution. The laser beam having passed through the reticle blind RB illuminates the circuit pattern area of the reticle R with a substantially uniform illuminance distribution via the lens system 22, the fixed mirror M ₄ , the condenser lens CL, and the fixed mirror 2. Here, the reticle blind RB is conjugated with the reticle R by the lens system 22 and the condenser lens CL. The reticle R is moved to the main body of the apparatus by dedicated reticle alignment systems 30X and 30Y.
It is positioned in the θ direction.

As described above, the oscillating mirror M ₃ oscillates the beam incident on the fly-eye lens 19 to move the interference fringes generated on the reticle surface or wafer surface by a very small amount. This is intended to smooth the light and dark fringes transferred to the resist layer, thereby reducing the visibility of interference fringes. In the present embodiment, the laser light incident on the fly-eye lens 19 is vibrated when the interference pattern is smoothed. In addition, for example, the rotating diffuser may be rotated in synchronization with the emission of the pulse light. Is also good.

The image of the circuit pattern of the reticle R is transferred by the projection lens PL onto the wafer W on which the resist layer has been formed at a predetermined exposure amount. At this time, a plurality of spot lights (secondary light source images) formed at the exit end of the fly-eye lens 19 are re-formed on at least the pupil plane (entrance pupil) of the image-side (wafer-side) telecentric projection lens PL,
A so-called Koehler illumination system is configured. The wafer W is mounted on an X stage 32X, and the X stage 32X moves in the X direction on a Y stage 32Y that moves on the base in the Y direction. As a result, the wafer W moves two-dimensionally along the projection image plane, and exposure by a step-and-repeat method or the like is performed.

On the X stage 32X, there is provided a reference mark plate FM having a transmission type reference slit at substantially the same height as the wafer W. Below the reference mark plate FM, a mirror (not shown) fixed to the X stage 32X is provided. The reference mark plate FM is a movable mirror M ₁
There when retracted from the position shown, the pulse light from an excimer laser light source 1 is arranged to receive from the lower surface via a mirror M ₆ fixed on a plurality of mirrors and the Y stage 32Y. Excimer beam is substantially parallel beam, and is parallel to the Y axis, the mirror M ₆ incident on the mirror M ₆
Is reflected at right angles in the X direction, and is reflected vertically upward by a mirror below the reference mark plate FM. Therefore, no matter how the X stage 32X and the Y stage 32Y move, the excimer beam always enters the lower surface of the reference mark plate FM.

Alignment of wafer W (mark detection)
Is performed by an off-axis type wafer alignment system 34. The wafer alignment system 34 photoelectrically detects an alignment mark at a specific position on the wafer W using illumination light (uniform illumination or spot light) in a wavelength range that does not expose the resist layer on the wafer W. The wafer alignment system 34 is fixed in a fixed positional relationship with respect to the projection lens PL, but the detection center of the mark on the wafer W (index or spot light in the alignment system) and the projected image of the circuit pattern of the reticle R Is slightly different every time the reticle R is exchanged, so that the reference line can be measured using the reference mark plate FM. Therefore, by partially branched pulsed light from the light-emitting slit of the reference mark plate FM by the beam splitter BS ₂ which is disposed in the optical path of the illumination optical system, photoelectric elements through a lens system 23 (photomultiplier, etc.)
At 26, light is received. The light receiving surface of the photoelectric element 26 is arranged almost conjugate with the pupil plane (the entrance pupil or the exit pupil) of the projection lens PL by the lens systems CL, 21, 23 and the like.

[0028] Now, in the apparatus having the above structure, between the movable mirror M ₁ and the excimer laser light source 1, there is thermal chamber partition wall for accommodating the exposure apparatus (stepper) body, laser light source 1 is the thermal chamber outer It is installed in. Further, the main body of the stepper is integrally controlled by the main control system 9, and moves the XY stages 32X and 32Y, positions the reticle R by the reticle alignment systems 30X and 30Y, detects the position of the wafer W by the wafer alignment system 34, operates, and performs reticle blind RB. Setting, a series of relative positional check operations using the photoelectric element 26 and the reference mark plate FM, the beam splitter BS ₁
Element 4 (for example, a pyroelectric power meter, a PIN photodiode, or the like) that receives a part of the pulse light reflected by the light source
Exposure control operation using, or to perform a smoothing operation, etc. of the interference pattern due to vibration of the vibration mirror M _3. still,
The positions of the XY stages 32X and 32Y are sequentially measured as coordinate values by a laser interferometer (interferometer) (not shown). These coordinate values are also input to the main control system 9 and used for various position measurements. Is

The above configuration on the stepper side is merely an example in the present invention, and is not limited to the above configuration. Now, as shown in FIG. 2, the light receiving element 4 accurately outputs a photoelectric signal corresponding to the light quantity (light intensity) of each pulse of the laser beam emitted from the excimer laser light source 1, and is sufficient in the ultraviolet region. Composed of a PIN photodiode having high sensitivity. The photoelectric signal output from the light receiving element 4 is input to a light amount monitor 5, and is converted into an actual light amount for each pulse by the light amount monitor 5. Therefore, the light receiving element 4 and the light amount monitor 5 constitute the energy amount measuring means of the present invention, and the energy amount measured in this way (a value corresponding to the actually measured energy amount is sufficient, and the energy amount itself is required. Is sent to the arithmetic unit 6, where the light amounts of the respective pulses are sequentially integrated. Further, the actual measurement value (light amount) in the arithmetic unit 6 is controlled by the exposure amount control, the applied voltage of the excimer laser light source 1 and the exposure pulse energy amount (or the actual energy amount given to the wafer W,
This is basic data for updating information relating to the relationship with a so-called dose amount, and controlling the oscillation of the trigger pulse oscillated from the trigger control unit 10 for each shot.

In the light receiving element 4, the relationship between the actual light amount of the laser beam irradiated on the wafer W by the power meter and the sensitivity of the light receiving element 4 is obtained in advance. 7 is stored. Alternatively, the light quantity monitor unit 5 may sequentially integrate the light quantity for each pulse, and the integrated light quantity and the light quantity for each previous pulse may be output to the calculator 6.

The arithmetic unit 6 updates the information on the relationship between the applied voltage (or charging voltage) and the exposure pulse energy amount (or dose amount) in the present invention, and updates the energy amount of the next exposure pulse to be irradiated. Means for determining an applied voltage corresponding to. For example, when the above information is updated every unit number of pulses or every unit time while exposing one wafer, the applied voltage at the time of oscillating a plurality of pulses up to the previous pulse, the light amount monitoring unit 5 Then, the exposure pulse energy amount detected at step (1) is fetched, and the information is updated and stored in the memory 7 by a predetermined arithmetic processing (details will be described later) based on these data. Therefore,
Even during the exposure of one shot, the information can be updated without interrupting the exposure.

The above information is obtained when the stepper is started, when the pulse oscillation is stopped for a long time and the oscillation is restarted, or when the PGR operation and the HI operation are executed, the information is updated. When the wafer W is mounted on the XY stage, prior to the exposure operation, for example, the XY stage is moved to a predetermined retreat position so that the wafer W is not exposed, and then the excimer laser is switched while changing the applied voltage. Oscillation may be performed a plurality of times, and the information may be calculated or updated from the relationship between the applied voltage and the amount of exposure pulse energy.

The arithmetic unit 6 irradiates the next exposure light in accordance with a predetermined exposure amount control logic based on the integrated energy amount obtained by sequentially integrating the exposure pulse energy amounts detected by the light amount monitor unit 5 for each pulse. After calculating the energy amount of the pulse light to be applied, the applied voltage corresponding to the pulse energy amount to be irradiated next is determined by calculation based on the relationship between the previously updated applied voltage and the exposure pulse energy amount. Send to control system 9. Although the exposure amount control logic will be described later in detail, in this embodiment, the interference pattern is also smoothed (illumination uniformity).

Here, the excimer laser light source 1 is shown in FIG.
(A charging voltage measuring means of the present invention) for detecting the charging voltage between the two electrodes during pulse oscillation in (1) (corresponding to the voltage applied to the excimer laser light source 1) is not shown. In this embodiment, the case where there is no charging voltage measuring means will be described. When the charging voltage measuring means is provided in the excimer laser light source 1, the measurement result by the charging voltage measuring means is taken into the calculator 6, and the information on the relationship between the charging voltage and the exposure pulse energy amount is updated instead of the applied voltage. Therefore, the description is omitted here.

Main control system 9 (first control means of the present invention)
The control system 25 (trigger control unit 1) stores information on the applied voltage, oscillation trigger pulse, and the like determined by the arithmetic unit 6 and the like.
0, output to the applied voltage controller 11). Further, in accordance with the exposure state of the wafer on the exposure apparatus main body side, signals (request signals SA and inhibition signals SB described later) corresponding to the necessity of the HI operation and the PGR operation of the excimer laser light source 1 are generated. The two signals are also supplied to the control system 25 (gas supply control unit 2).
Output to 4). Further, in addition to giving predetermined command signals relating to the dimming degree and the interference pattern control to each of the control units 12 and 13 in accordance with various calculation results, it also controls the overall operation of the apparatus. Further, the final integrated light amount (total exposure amount to the wafer W) is output to the input / output device 8 as necessary.

As will be described in detail later, the gas supply control unit 24 responds to the oscillation state of the excimer laser light source 1 by
Signals corresponding to the necessity of the HI operation and the PGR operation (a request signal LA and a prohibition signal LB to be described later) are generated. The operation and the execution time of the HI operation are detected and executed.

The input / output device 8 is a man-machine interface between the operator and the main body of the stepper. The input / output device 8 receives various parameters required for exposure and pulse oscillation from the operator, and informs the operator of the operation state of the stepper and the excimer laser light source. . Also, the energy amount of the final pulse is notified to the operator as needed.

The memory 7 stores parameters (constants) and tables necessary for the exposure and oscillation operations input from the input / output device 8 and various operations, or the light receiving element 4.
Are stored. In particular, in this embodiment, while the laser beam by the swinging mirror M ₃ is vibrated by the half-period, information is stored for determining the minimum necessary number of pulses for smoothing a good interference pattern (Nvib below) Have been. Here, the half cycle of the beam means the swing angle of the beam in the order of LBa → LBb → LBc (or the reverse) to move the spot light in the order of SPa → SPb → SPc (or the reverse) in FIG. It corresponds to tilting by α °. Note that the actual amount of tilt of the oscillating mirror is α from the double angle theorem.
° / 2.

The arithmetic unit 6 has a pulse number Nsp necessary for smoothing the interference pattern stored in the memory 7 in advance, and an arithmetic unit 6 necessary for achieving a desired exposure amount control accuracy in one-shot exposure. Based on the pulse number Ne and data on the proper exposure amount S per shot according to the sensitivity characteristics of the resist, the light reduction rate β of the light reduction unit 15 and the average light amount per pulse (Pav · β) described later. ) Is calculated. The calculator 6 calculates a target integrated light amount to be given to the wafer W when each pulse is irradiated with the average light amount value, and then calculates the target integrated light amount and the light amount monitor unit 5 described above.
, The difference D from the actual integrated light amount obtained by sequentially integrating the actually measured values (energy amounts) sent from the computer is calculated. Then, an applied voltage of the excimer laser light source 1 is calculated based on the difference D, and information on the applied voltage is stored in the main control system 9.
Output to

In other words, based on the difference D, the arithmetic unit 6 calculates the light quantity of the pulse light to be irradiated next to the average light quantity (P
av · β) and sends it to the main control system 9. Then, based on this correction value, the excimer laser control system 25
Means that the applied voltage of the excimer laser light source 1 is controlled by the applied voltage control unit 11, that is, the applied voltage is corrected by the amount corresponding to the above-mentioned correction value and applied to the excimer laser light source 1. An example of the relationship between the voltage applied to the excimer laser light source 1 and the light quantity (pulse energy) of the emission pulse is as shown in FIG. In the present embodiment, the above relationship is updated in accordance with gas deterioration or the like, which will be described later in detail.

The main control system 9 includes the excimer laser light source 1.
As the deflection angle of the beam due to pulse emission and oscillating mirror M ₃ of sync, and outputs a drive signal to the interference pattern control unit 13. Note that this synchronization follows the output of a detector that monitors the beam deflection angle with high accuracy, and sends an oscillation start and stop signal to the trigger control unit 10 so as to trigger a pulse emission to the excimer laser light source 1. You may make it output.

Here, the dimming unit 15 described above is not limited to the position shown in FIG. 1, but may be a cavity mirror between the excimer laser light source 1 and the beam expander 14, or inside the excimer laser light source 1. The same effect can be obtained even if it is inserted between the two. Furthermore, if the oscillating mirror M ₃ described above does not take the system to vibrate small angle of beam may be placed between the oscillating mirror M ₃ and the fly-eye lens 19. However, in any case, the dimming unit 15 needs to be placed in a stage before the laser light is incident on the fly-eye lens 19. This is because a dimming element such as a mesh filter often causes deterioration of illuminance uniformity in a beam cross section, and it is necessary to eliminate this by the fly-eye lens 19.

Next, the minimum number of pulses Nsp required for smoothing the interference pattern (uniform illuminance) will be described. The smoothing of the interference pattern is disclosed, for example, in Japanese Patent Application Laid-Open No. 1-257327. Therefore, a brief description will be given here. In the above publication, when an optical integrator, particularly an illumination optical system having a fly-eye lens is employed, a plurality of pulsed light beams are irradiated while moving an interference pattern formed on a reticle (or wafer) within a certain range. Therefore, when performing the smoothing, the minimum number of pulses to be irradiated during the movement of the interference pattern by one pitch is limited to a certain fixed value in advance, and the pulse light of the number equal to or more than the minimum number of pulses must be irradiated. It uses the principle that it must be.

Now, as shown in FIG. 5, the interference pattern is generated by the interference of the spot lights formed by the rod lenses of the fly-eye lens 19 with each other. At this time, a case where only the spot lights of two rod lenses adjacent to each other interfere with each other or a case where three spot lights in the arrangement direction of the rod lenses interfere with each other may be used. What is necessary is just to consider a case where a number of spot lights interfere with each other.

Therefore, theoretically, the minimum necessary for smoothing an excellent interference pattern depends on the number of the rod lenses constituting the fly-eye lens 19 in the arrangement direction and the number of spot lights that interfere with each other. a pulse number Nsp, more minimum number of pulses to be irradiated during the half period of the beam oscillating by oscillating mirror M ₃ required one pitch movement of the interference pattern N
vib (Nvib is an arbitrary integer satisfying Nvib ≧ Nsp) is also determined.

For example, when only two adjacent spot lights interfere with each other, the intensity distribution of the interference pattern is mathematically and theoretically a simple sine wave. In order to smooth this interference pattern, two pulses, one pulse before and after shifting the phase difference between the two spot lights by π (movement of a half cycle of the interference pattern), are required. . In general, when n spot lights interfere with each other, theoretically, it is possible to irradiate one pulse while moving the interference pattern by 1 / n period, and to smooth it with a total of n pulses. .

Here, when considering the intensity distribution in one direction (for example, Y direction) of an interference pattern generated upon emission of one pulse on the reticle, generally, bright stripes and dark stripes are formed at a predetermined pitch Yp in the Y direction. Are alternately arranged. However, depending on the configuration of the fly-eye lens in two stages or the like, in addition to the basic component of the pitch Yp determined by the arrangement pitch of the rod lenses of the fly-eye lens, the wavelength of the laser beam, and the like, a weak interference fringe whose intensity changes at a finer pitch is also generated. It may appear superimposed. Therefore, in practice, complete smoothing is rarely achieved under the above conditions, and the optimum value of the minimum pulse number Nsp required for smoothing the interference pattern needs to be determined by experiments or the like.

[0048] In this embodiment, based on the minimum number of pulses Nsp obtained by experiments, set the angle change of the oscillating mirror M ₃ and the light emitting pulse interval (frequency) of n · ΔY ≧ Yp become involved in Mitsurusu so I do. Then, the interference pattern is sequentially shifted in the Y direction by a minute amount ΔY (ΔY <Yp) on the resist layer for each emission of one or more pulses, so that the interference pattern is smoothed (illuminance uniformity) at the completion of exposure. This is intended to obtain a substantially constant illuminance distribution including a minute amount of ripple so as not to affect the accuracy.

Considering the conditions required for uniform illuminance, the following two conditions can be given. (1) Half period of mirror oscillation (beam oscillation angle is 0 ° to α °
), Pulse light emission of a certain number Nsp or more is performed almost uniformly. Here, the pulse number Nsp is determined by the visibility of the interference pattern, and the larger the visibility, the larger the value of Nsp. Further, the pulse number Nsp is determined in advance by experiments such as trial printing, and the numerical value differs between apparatuses having different optical systems. Therefore, when the pulse light emission of a number smaller than Nsp is almost uniformly distributed within the half cycle of the beam swing angle change (0 ° → α °), it is desirable in terms of uniform illuminance (illumination unevenness on the image plane). It will not be within the precision of.

(2) The average exposure energy per pulse at a predetermined angle of the oscillating mirror should be substantially constant at any angle within the beam oscillating range (0 ° → α °). The second condition is that the total number of pulses Nexp actually required for one-shot exposure is equal to the number of pulses N in a half cycle of beam oscillation.
vib, and the first pulsed light is emitted at the maximum angle of the mirror oscillation (0 ° to α ° / 2) (for example, 0 ° at which the beam LBa in FIG. 5 is obtained). Is achieved in. Also, the pulse number Nexp is equal to the mirror oscillation (0 ° to
When the pulse number is an integral multiple of the number of pulses in one cycle of (α ° / 2), the first pulse light is transmitted through mirror oscillation (0 ° to α ° /
Light emission may be started at an arbitrary angle in 2).

From the above, the above two conditions (1)
By adjusting the average exposure energy per pulse and simultaneously determining the optimal number of pulses so as to simultaneously satisfy (2), it is possible to achieve both illuminance uniformity and exposure amount control extremely efficiently. . In addition to the exposure energy,
If the oscillation cycle (oscillation speed) of the oscillating mirror is also changed, the number of exposure pulses is not increased more than necessary, which is advantageous in throughput.

The voltage applied to the excimer laser light source 1 is set to a value slightly smaller than the maximum applied voltage Vmax to the excimer laser light source 1 in consideration of the variation in exposure energy for each oscillation pulse. In one-shot exposure, after emitting the first pulse light under the above set value, the main control system 9 sends information on the voltage value calculated by the arithmetic unit 6 to the applied voltage control unit 11. The applied voltage is sequentially controlled to the above-mentioned voltage value for every second and subsequent pulses. Therefore, the exposure energy control range by controlling the applied voltage of the excimer laser light source 1 will be described next. The average exposure energy per pulse is Pav (under the dimming rate of the dimming unit 15 is 1), the variation between the exposure energy pulses is ΔPav, and pulse emission is performed N times in one shot exposure. At the same time, the accumulated light amount (target value) up to the k-th pulse is calculated by Pav · k for each pulse after the second pulse.
(K ≦ N), the variation of the actual integrated light amount I with respect to the target integrated light amount Pav · N (S = Pav · N with the appropriate exposure amount S) is calculated by the following equation 1. expressed.

[0053]

(Equation 1)

As is apparent from the above equation 1, the control ratio of the light amount by the applied voltage control is 0 <ΔPav / Pav <1,
Assuming that the number of pulses N is a somewhat large integer, ｛1 ± (ΔP
av / Pav) / (1−ΔPav / Pav)｝. Therefore,
In order that the maximum value {1 / (1−ΔPav / Pav)} of the control ratio does not exceed the maximum value of the exposure energy control range, the average exposure energy control value set before the exposure should be The maximum value of the control range (1−ΔPav / Pa)
v) It should be less than twice.

Actually, a desired exposure energy is obtained based on the relationship shown in FIG. 6 such that the average exposure energy Pav is not more than (1−ΔPav / Pav) times the maximum output of the excimer laser light source. What is necessary is just to set the applied voltage (discharge voltage between electrodes) to the laser light source 1. In the case of an excimer laser, since (ΔPav / Pav) = about 10%, if the exposure energy at the maximum applied voltage of the laser light source 1 is 10 mJ / cm ² , the average exposure energy Pav is 9 mJ / cm ^2.
The applied voltage may be set so as to be J / cm ² or less. Actually, the applied voltage is set so that the average exposure energy Pav is, for example, 5 mJ / cm ² or less in consideration of the phenomenon of the decrease in the laser density (the decrease in output due to the deterioration of the mixed gas) and the life of the optical components. It is desirable to do.

In the present embodiment, the light reduction section 15 is set in accordance with the exposure conditions (type of resist, appropriate exposure amount, etc.) on the wafer W.
, The exposure energy of the second and subsequent pulsed light is finely adjusted only to correct an error in the integrated light amount due to variation between pulses. Therefore, there is no need to greatly change the discharge voltage between the electrodes in the excimer laser light source 1, and the dynamic range of the applied voltage control unit 11 can be reduced. Therefore, 1
The relationship between the applied voltage and the amount of exposure pulse energy in the exposure of the shot only needs to use a very small portion of the graph shown in FIG. .

Next, a brief description will be given of the pulse number Ne required to achieve the desired exposure amount control accuracy A (Equation 19) in one-shot exposure.

[0058]

[Equation 19]

The exposure amount control in this embodiment is to adjust the exposure energy for each pulse while making the actual integrated light amount I substantially equal to the target integrated light amount Pav · N. The error in the light quantity results in a variation in the exposure energy of the final pulse light. Therefore, in order to achieve the exposure amount control accuracy, the variation in the exposure energy of the final pulse light must be within the tolerance of the exposure amount control accuracy. That is, the average exposure energy Pav must be set to a small value, and the number of pulses N (N = S / Pav) required for one-shot exposure must be a relatively large number. From this, in the above equation 1, (ΔPav / P
av) Since ^N can be regarded as zero, if each side is divided by Pav · N and arranged, the exposure amount control accuracy A is expressed by the following equation (2).

[0060]

(Equation 2)

Here, in equation 2, the exposure amount control accuracy A
Is the maximum allowable error, that is, when the following equation 3 is satisfied, the number of pulses N required to achieve the exposure amount control accuracy becomes the smallest.

[0062]

(Equation 3)

Thus, the pulse number Ne is expressed by the following equation (4).

[0064]

(Equation 4)

Therefore, if the exposure is performed with at least the pulse number Ne equal to or larger than the pulse number Ne represented by the above equation 4, the final integrated light amount I is ± A with respect to the target integrated light amount Pav · N.
(For example, in the case of 1%, A = 0.01), the control accuracy is guaranteed. Next, the number of exposure pulses N for one shot
Here is how to determine exp. Generally, the number of exposure pulses Nexp is Nexp = int (S / Pav). However, int (ω) indicates that the decimal point of the real value ω is rounded up and converted to an integer value.

The pulse light oscillated from the excimer laser light source 1 has a predetermined dimming rate β (0 ≦
Irradiated on the reticle R after being uniformly attenuated by β ≦ 1). For this reason, the number Nexp of exposure pulses is required to satisfy the following conditional expression (Equation 5).

[0067]

(Equation 5)

In order to achieve the exposure amount control accuracy A described above, it is necessary to satisfy the following expression (6).

[0069]

(Equation 6)

In order to further smooth the interference pattern, the number of exposure pulses Nexp must be an integral multiple of the number of pulses Nvib in a half cycle of the oscillating mirror. Therefore, the number of exposure pulses Nexp is represented by the following equation (7).

[0071]

(Equation 7)

Therefore, the extinction ratio β of the extinction section 15 is given by
From Equations (5) and (6), the following Equation 8 is used.

[0073]

(Equation 8)

The integer m is represented by the following equation (9) from equations (4), (6) and (7).

[0075]

(Equation 9)

Further, since the extinction ratio β is 1 or less, it is expressed by the following Expression 10 from Expressions 5 and 7.

[0077]

(Equation 10)

From the above, in the present embodiment, first, the extinction ratio of the extinction section is determined so as to satisfy Expression 8.
That is, the filter of the rotating turret plate 16 is selected. Next, under the extinction rate of this selected filter,
The number of pulses Nexp calculated from Expression 5 is expressed by Expressions 6 and 7
Check whether or not is satisfied. If you are not satisfied,
A filter that satisfies Expression 8 and has a smaller dimming rate is selected so that the number Nexp of exposure pulses satisfies Expressions 6 and 7. When the number Nexp of the exposure pulses is determined in this way, m and Nvib may be determined so as to simultaneously satisfy Expressions 9 and 10.

As an example, the variation ΔPav / Pav between pulses of the average exposure energy is reduced by 10% (ΔPav / Pav =
0.1), assuming that the exposure amount control accuracy A is 1% (A = 0.01), the number of pulses Ne is 12 from Equation 4.
On the other hand, when the dimming rate β of the dimming section 15 is 1, the average exposure energy Pav is ² mJ / cm ² , and the appropriate exposure S is 80 mJ.
/ cm ² , the number of pulses Nsp required for smoothing the interference pattern is 5
If the number of exposure pulses is 0, the number of exposure pulses Nexp
Is 40 pulses, but this pulse number Nexp does not satisfy Expression 7. Therefore, the dimming rate of the dimming unit 15 is set to be smaller than 1, so that the dimming rate, that is, the number of exposure pulses Nexp calculated from Equation 5 under the average exposure energy Pav · β satisfies Equation 7. I do.

Here, if the extinction ratio β of the extinction section 15 can be set continuously, Ne = 12 and Nsp = 50 pulses, so that m and Nvib are calculated based on equations 9 and 10. Set. At this time, the combination of (m, Nvib)
Various methods such as (1, 50), (1, 60), (2, 100), etc. can be considered. Here, in order to minimize the number of exposure pulses Nexp (Nexp = mNvib) in consideration of throughput, The number of exposure pulses Nexp is set to 50 by setting m = 1 and Nvib = 50. If exposure is performed with Nexp = 50, it is possible to optimize the exposure amount and smooth the interference pattern with the minimum number of pulses Nexp.

As a result, from equation (5), the dimming rate β of the dimming unit 15 is set to 0.80. Also, ΔPav /
From Pav = ± 10%, ΔPav becomes ± 0.2 mJ / cm ^2, and the variation ΔPav · β of the average light amount Pav · β is ± 0.
It is 160 mJ / cm ² . Therefore, the variation of the average light amount of the final pulse light, that is, the error of the final integrated exposure amount can be considered to be about ± 0.160 mJ / cm ² , and the exposure amount control accuracy (1%) is sufficiently achieved. It is understood that it is done.

On the other hand, as in the present embodiment, the extinction ratio β
Is discontinuous, first, a mesh filter of the rotating turret plate 16 that satisfies the expression 8 is selected. It is checked whether the calculated pulse number Nexp satisfies Equation 7. Here, in order to minimize the above-mentioned Nexp, a filter that satisfies Expression 8 is selected from the filter having the largest dimming rate. β
= 0.50 (i.e. ^{Pav · β = 1mJ / cm 2} ) in the case of become Nexp = 80 pulses, thus satisfying the formula 6,7. By determining the number of pulses Nexp in this way,
After that, since Nexp = 80, it is only necessary to determine m and Nvib which simultaneously satisfy Expressions 9 and 10. Here, m = Nvib.
1, Nvib = 80.

As is clear from the above, if the setting of the dimming rate of the dimming section 15 is discontinuous, the dimming rate cannot always be set to the optimum value obtained from the calculation.
The number of pulses Nexp becomes larger than in the case where continuous setting is possible, which may be disadvantageous in throughput. For this reason, the light-attenuating section is one that can continuously set the light-attenuation rate, or one that can set the attenuation rate (transmittance) finely even if it is discontinuous (for example, two rotating turrets). It is desirable to use a combination of plates).

Next, a method of updating information relating to the relationship between the voltage applied to the excimer laser light source 1 and the amount of exposure pulse energy will be described in detail. FIG. 6 is a diagram showing an example of the relationship between the applied voltage and the energy amount of the emission pulse, and has a quadratic function here. In FIG. 6, black circles represent actual data, and solid lines represent curves obtained by applying the data to a quadratic function by the least squares method. Generally, in a processing apparatus such as a stepper using a laser light source that requires a PGR operation and an HI operation, the above relationship (FIG. 6)
For example, fitting a quadratic function by the least squares method (fitting)
Need to do. However, as described above, since the dimming unit 15 is provided in the present embodiment, the dynamic range of the applied voltage control unit 11 can be small. For this reason,
The relationship between the applied voltage and the amount of exposure pulse energy in one-shot exposure uses a small part of the relationship shown in FIG. Therefore, the relationship between the applied voltage and the exposure pulse energy can be sufficiently approximated by a linear function.
In this embodiment, the least squares method is used for fitting a linear function. However, other than the least squares method described below, for example, a method of minimizing the maximum deviation from data may be adopted. Therefore, if the applied voltage is V and the pulse energy amount is P, the model function of the above relationship is expressed by the following equation (11).

[0085]

[Equation 11]

Here, s and t are unknowns obtained by the least squares method. In addition, each data regarding the actual applied voltage and the exposure pulse energy amount is set as V _i and P _i . The subscript i represents the newness of the data, i = 1 is the latest data,
Hereinafter, past data becomes larger as i becomes larger. Further, the evaluation function E is expressed as in the following Expression 12. However,
γ _i is a weight (described later) for the data (V _i , P _i ).

[0087]

(Equation 12)

Now, the unknown s that minimizes the evaluation function E,
t is given by 最小 E / ∂s = 0, ∂
By solving the system of binary equations with E / ∂t = 0,
It can be obtained from the following Expression 13.

[0089]

(Equation 13)

Incidentally, γ _i is a weight for the data (V _i , P _i ). As described above, the relationship between the applied voltage V and the exposure pulse energy amount P gradually changes according to the temporal change (deterioration of the mixed gas or the like). Therefore, by setting the weight γ _i to γ ₁ > γ ₂ > γ ₃ ..., It is necessary to make the weight of the latest data the heaviest and to gradually reduce the weight as the data becomes older. Therefore, the weight γ _i
Is defined as in the following Expression 14.

[0091]

[Equation 14]

Here, ε is a constant that satisfies 0 <ε <1. Specifically, the applied voltage V and the exposure pulse energy amount P
Is a value determined in advance according to a change rate of the relationship with time due to a change with time. For example, if ε = 0.995, about 92
The contribution (weight) to the evaluation function E of the data (V _i , P _i ) relating to the oscillating pulse before 0 is 1 compared to the latest pulse.
%. Therefore, when the value of the constant ε approaches 1,
As is apparent from the above equation 13, a large number of data (V _i ,
Since the unknowns s and t are determined from P _i ), it is possible to prevent a decrease in the accuracy of determining the unknowns s and t due to a variation (about ± 10%) in the energy amount of each pulse.

However, if the relationship between the applied voltage V and the exposure pulse energy amount P fluctuates more than the above-mentioned fluctuation due to some reason, the past data (V _i ,
Since there are many P _i ), it may be difficult to calculate the unknowns s, t by following the fluctuation without delay. Conversely, when the value of the constant ε approaches 0, the unknowns s and t are determined from a small amount of data (V _i , P _i ).
It is greatly affected by the variation of the energy amount for each pulse. Therefore, in practice, it is desirable to determine the value of the constant ε by experiment or the like in consideration of the balance between the two depending on the stability of the excimer laser light source 1 and the like.

Next, each element of the matrix on the right side of Expression 13 is represented as Expression 15 below.

[0095]

(Equation 15)

At this time, the above elements, that is, the parameters G _{1 to} G ₃ , H ₁ , and H ₂ are stored in the memory 7 as information relating to the relationship between the applied voltage and the exposure pulse energy amount. Then, when new data (V _i , P _i ), that is, the latest data (V ₁ , P ₁ ) is obtained, the computing unit 6 fetches the parameters G _{1 to} G ₃ , H ₁ , H ₂ from the memory 7. , G ₂ , G ₃ and H ₁ , H ₂ are updated using the recurrence formula (Equation 16) shown below except for G ₁ (G ₁ = 1 / (1−ε ² )) which is a constant. I do. As a result, by applying the recurrence formula, the calculation time required for updating the information on the relationship between the applied voltage V and the exposure pulse energy amount P can be reduced, and the arithmetic unit 6 newly stores the updated information in the memory 7. Will be stored.

[0097]

(Equation 16)

[0098] Thus, the unit number of pulses, or a predetermined time every, every time a further executes PGR operation or HI operation, appropriate G ₂ in the formula 16, G ₃ and H _1, H ₂
Is updated, and the unknowns s and t are calculated by calculating Expression 13, the relational expression (Expression 11) between the applied voltage V and the exposure pulse energy P is updated, and the exposure pulse energy P to be irradiated next is updated. Can be obtained by the following equation (11). In the present embodiment, the relationship between the applied voltage and the amount of exposure pulse energy (FIG. 6) was applied in the form of a linear function (Equation 11), but it is needless to say that the function may be applied in the form of a quadratic function. No.

Next, the exposure operation of this embodiment will be described with reference to FIG. FIG. 7 is a schematic flowchart showing an example of the exposure operation of the present embodiment. First, the computing unit 6 in step 200, it is determined whether or not to initialize the parameters G ₁ ~G ₃ and H _1, H ₂ stored in the memory 7, the parameters G ₁ ~G ₃ and H _1, H ₂ If it is sufficiently reliable, proceed to step 203. on the other hand,
If initialization is necessary, for example, when the excimer laser light source 1 is started up or its oscillation has been stopped for a long time, or immediately after executing the PGR operation or the HI operation, the process proceeds to step 201, where the applied voltage V Is changed several times within the range of use (in a range where Equation 11 can be sufficiently approximated by a linear function), and the light amount of each pulse oscillated under each voltage value is taken in from the light amount monitoring unit 5. Thereafter, in step 202, the arithmetic unit 6 executes step 201
Based on the data (V _i , P _i ) obtained in
, The parameters G _{1 to} G ₃ and H ₁ , H ₂ are calculated and stored in the memory 7. At the time of initialization, ε = 1 may be set so that equal weights are given to all data.

In the next step 203, the arithmetic unit 6 calculates the target integrated light amount S from the input / output device 8, the exposure amount control accuracy A, the variation between the average exposure energy pulses (ΔPav / Pav), the maximum applied voltage from the memory 7. Vmax and the number of pulses Nsp required for smoothing the interference pattern are fetched. still,
The above variation (ΔPav / Pav) is calculated by
May be values obtained from the actual data (V _i , P _i ) obtained in step (1). Next, the arithmetic unit 6 performs step 203
Based on the data captured in step (1), the light emission rate β of the light reduction unit 15 (average light amount value Pav · β), that is, the exposure pulse under the light reduction rate of the filter of the rotating turret plate and the selected filter. The number Nexp, the number of pulses Nvib in a half cycle of the oscillating mirror, and an integer m are calculated (step 20).
4). Subsequently, in step 205, the rotating turret plate 16 is rotated to set the dimming rate of the dimming section to β, and in step 206, the average exposure energy P
The applied voltage V for obtaining av is calculated. Here, the average exposure energy Pav is the exposure energy (Pa) oscillated from the excimer laser light source 1 under the maximum applied voltage Vmax.
v) It is desirable to set it to (1-ΔPav / Pav) times or less of max (maximum value).

In the next step 207, the pulse counter n and the integrated light amount I are set to Nexp and zero, respectively. In the following step 208, the main control system 9
Determines whether the pulse counter n is zero, and if not, proceeds to the next step 209. Then, in step 209, after the excimer laser control system 25 sets the applied voltage of the excimer laser light source 1 by the applied voltage control unit 11, the trigger control unit 10 sends a trigger pulse to the excimer laser light source 1 to emit one pulse. In the following step 210, a value (Pav) a corresponding to the actual light quantity of the pulsed light oscillated by using the light receiving element 4 is detected and sent to the arithmetic unit 6 via the light quantity monitoring unit 5. Next, step 2
At 11, the computing unit 6 calculates the integrated light amount I, sets the integrated light amount to I = I + (Pav) a, and sets the pulse counter to (Nexp-1).

Next, at step 212, the target integrated light amount to be given by the average light amount value (Pav · β) determined at the previous step 204, and the target integrated light amount and A difference D from the obtained actual integrated light amount I is obtained.

[0103]

[Equation 17]

Subsequently, in step 213, based on the difference D, the light amount Pav ′ of the pulse light to be irradiated next is calculated as
It is obtained by correcting from the average light amount Pav · β determined in step 204 by the following equation (18).

[0105]

(Equation 18)

In the next step 214, the arithmetic unit 6 sets the data of the previous pulse, that is, the applied voltage V applied to the excimer laser light source 1 in step 209 and the step 2
Based on the light amount (Pav) a for one pulse detected at 10, the parameters G _{1 to} G ₃ and H ₁ , H ₂ are updated from the above equation (16) and stored in the memory 7. Then, in the next step 215, the arithmetic unit 6 calculates the applied voltage corresponding to the light amount Pav ′ by using the equation 11, and returns to step 208. In this step 208, it is determined whether or not the pulse counter n is zero as in the operation described above. If not zero, go to step 209,
After performing the same operation as described above in Steps 9 to 215, the process returns to Step 208 again, and repeats Steps 209 to 215 until the pulse counter n becomes zero. When the pulse counter n becomes zero, the exposure operation is started. finish.

Next, the state of exposure control in the apparatus according to the present embodiment will be described with reference to FIG. FIG. 8 is a graph showing the relationship between the number of pulses and the integrated exposure amount when exposing one shot. Here, the case where the exposure is completed by eight pulses is shown. For simplicity of explanation, it is assumed that the dimming rate β of the dimming unit 15 is set to 1. FIG.
In FIG. 7, the straight line indicated by the two-dot chain line indicates the target value of the integrated exposure amount to be given by the pulse light having the average light amount value (Pav · β) determined in step 204. Therefore,
In the present embodiment, the light amount is adjusted for each of the second and subsequent pulses so that the exposure amount control is performed according to the target value.

Now, assuming that the _first pulse light is emitted with an exposure amount of Pav _{1 as} a target, and that the actually detected exposure amount after light emission is Pav ₁ ′, the second pulse light is emitted. the difference between the target exposure amount 2Pav ₁ and Pav ₁ '(2Pav ₁ -P
av ₁ ′) = Pav ₂ and light emission is performed. At this time, the applied voltage control unit 11
_The applied voltage corresponding to ₂ may be applied to the excimer laser light source 1. Similarly, the actually measured value of the second pulse light amount is Pav
₂ ′, the third pulse light is (3Pav ₁
−Pav ₁ ′ −Pav ₂ ′) = Pav ₃ is set, and light emission is performed.

Therefore, by repeating the above operation, the exposure is completed at the eighth pulse while the deviation from the target line of the two-dot chain line is small. At this time, the final exposure control accuracy (variation of the measured value with respect to the appropriate exposure)
Is apparently a light amount error (variation) of the eighth pulse light. Here, in this embodiment, when one shot is exposed with a plurality of pulsed lights, the (i + 1) th
The target value and the past value of the integrated exposure amount up to the first exposure (until the i-th exposure)
(I) to be irradiated next based on the difference between
+1) The light amount of the first pulse light was set. However, if there is any tendency in the variation method for each pulse, the ratio between the target value for each unit pulse and the actually measured value for each unit pulse is averaged over a plurality of past pulses, and the target value is calculated based on this ratio. A new target value may be set by dividing by the average value.

Incidentally, in the exposure apparatus having the above configuration (FIG. 1), the operation in which the applied voltage control for the excimer laser light source 1 is effective (necessary) is performed by the wafer exposure and the relational expression between the applied voltage and the exposure pulse energy (Equation 11). (Step 201 in FIG. 7). Usually, the oscillation of the excimer laser light source 1 in the exposure apparatus is also required at the time of the above-described baseline measurement.

The operation of measuring the baseline in an exposure apparatus using an excimer laser as a light source is disclosed in, for example, JP-A-64-10105, and will be briefly described here. In FIG. 1, a laser beam transmitted from an excimer laser light source 1 by a plurality of reflecting members (or optical fibers) illuminates a transmission slit of a fiducial mark plate FM from below (inside a stage).
The Y-stages 32X and 32Y are driven one-dimensionally in a direction crossing the longitudinal direction of the transmission slit in the projection image plane, and scan the transmission slit mark with the slit image formed on the pattern surface of the reticle R. Then, the laser beam transmitted through the slit mark is reflected by the mirror 2 and the condenser lens C.
L, mirror M ₄ , lens systems 22 and 21, and light received by photoelectric element 26 via beam splitter BS ₂ , and by detecting the stage position when the slit image matches the slit mark, the projection of the slit mark is performed. Position X
It is recognized on the moving coordinate system of the Y stage.

By the above operation, the projection position of the slit mark (or the center of the reticle) of the reticle R is defined as the value of the moving coordinate system of the XY stage. Further, a bar mark (chrome) or the like on the reference mark plate FM is detected by using the wafer alignment system 34, and the position of the XY stage when the mark detection center position matches the mark is read by the laser interferometer. As a result, the relative positional relationship in the moving coordinate system between the center of the projected image of the reticle R and the detection center of the wafer alignment system 34 is defined, and the interval between these two points is used as the baseline.

However, since the pulse energy of the excimer laser beam has a variation of ± several% to several tens% for each pulse, for example, a photoelectric signal from a power detector in the laser light source 1 is captured for each pulse emission. , Photoelectric element 2
It is necessary to normalize the level of the photoelectric signal of No. 6 with a divider or the like. Note that detector for normalization may be provided in the exposure apparatus body, specifically provided to receive pulsed light branched by the beam splitter in the vicinity of the mirror M ₆ on the stage in FIG. 1 You may do it.

As described above, it is not always necessary to control the applied voltage to the excimer laser light source 1 at the time of the baseline measurement as described above. Therefore, the oscillation mode of the excimer laser light source 1 is changed according to the operation mode of the exposure apparatus.
It is desirable to be able to switch between the applied voltage control mode and the constant energy amount mode, and to use the constant energy amount mode in operations other than wafer exposure and data collection in step 201.

Now, as described above, one shot area on the wafer W is exposed with several tens of pulses or more due to the relationship between the smoothing of the interference pattern and the exposure amount control accuracy. Therefore, when the PGR operation and the HI operation are started during the exposure of one shot,
Even if the voltage applied to the excimer laser light source 1 is adjusted for each pulse in accordance with the exposure amount control logic described above, the relationship between the applied voltage (or charging voltage) and the amount of exposure pulse energy fluctuates drastically during the above operation. However, it is difficult to satisfactorily update the relational expression expressing the above-mentioned relation in accordance with the fluctuation, and thus it is impossible to achieve a desired exposure amount control accuracy. Therefore, next, the PGR operation in the device of the present embodiment,
A method for determining the timing for executing the HI operation and the exposure operation in the above apparatus will be described with reference to FIGS.

In this embodiment, the signals corresponding to the necessity of the PGR operation and the HI operation on the excimer laser light source 1 (control system 25) side and the exposure apparatus main body (main control system 9) side, that is, A signal for requesting the execution of the operation and a signal for inhibiting the execution are created, and the timing for executing the operation is determined based on these four signals. Therefore, first, a request signal and a prohibition signal generated by each of the control system 25 and the main control system 9 will be described.

The control system 25 constantly generates a signal LA for requesting the execution of the PGR operation or the HI operation and a signal LB for inhibiting the execution, in accordance with the oscillation state of the excimer laser light source 1. In this embodiment, the signals LA, LB
By changing each signal level of Hi to Lo or Lo to Hi, it is necessary to execute the above-mentioned operation on the excimer laser light source side, and it is necessary to prohibit the above-mentioned operation. A determination circuit (to be described later) for determining a timing (timing) for executing the above operation is notified.

For example, when the oscillation mode of the excimer laser light source 1 is the constant energy mode, the gas supply control unit 24 monitors the applied voltage applied to the excimer laser light source 1, and the monitored value is set to a predetermined upper limit value. (Eg, a value slightly lower than the maximum applied voltage), the signal level of the request signal LA is changed to (Lo → in the present embodiment).
Hi). Alternatively, the number of pulses (or oscillation time) oscillated after the start-up of the laser or the previous PGR operation or HI operation is counted, and the total number of pulses (or total oscillation time) is a predetermined value (depending on oscillation conditions and the like). , The signal level of the request signal LA may be changed. The gas supply control unit 2
4 changes the signal level of the request signal LA from Hi to Lo when the above operation is completed.

On the other hand, when the oscillation mode of the excimer laser light source 1 is the applied voltage control mode, the gas supply control unit 24
Monitors the output of a laser power monitor detector provided in the body of the excimer laser light source 1, and applies the applied voltage to the excimer laser light source 1 and the energy of the pulse light actually emitted under the applied voltage. Try to find the relationship with the quantity (or the relational expression that expresses it). Then, the relationship (expression) changes due to deterioration of the internal gas and the like, and when the relationship (expression) serving as a predetermined determination criterion is reached, the signal level of the request signal LA may be changed. It should be noted that even if the above relation (expression) is updated sequentially,
It may be updated every unit number of pulses or every unit time.

Further, the control system 25 also generates a signal LB for prohibiting the execution of the above operation in order to prevent an excessive amount of halogen gas inside the laser chamber which may occur after the PGR operation or the HI operation. That is, the gas supply control unit 24 determines the energy amount of the pulsed light oscillated under a predetermined applied voltage, or the total number of pulses (or the total oscillation time) oscillated after the PGR operation, the HI operation, or the gas inside the chamber. While monitoring any one of the densities, the signal level of the prohibition signal LB is set to Hi in this embodiment until the monitored value reaches a predetermined value.
Execution of the above operation is prohibited. Then, the pulse oscillation is continued, and when the monitor value reaches the predetermined value, the signal level is changed from Hi to Lo to notify that the prohibition state of the operation has been released.

Here, since the prohibition signal LB is for preventing an excessive amount of halogen gas, its signal level is usually Lo, and a predetermined oscillation time elapses immediately after the above operation is executed. The signal level can become Hi only during this period. The pulse energy amount, the total number of pulses (total oscillation time), and the gas concentration are monitored, and when one or all of them reach a predetermined value, the signal level is monitored. To Hi →
It may be changed to Lo.

On the other hand, the main body of the exposure apparatus also constantly generates a signal SA for requesting the execution of the PGR operation or the HI operation and a signal SB for inhibiting the execution of the PGR operation or the HI operation. Transmits these signals SA and SB to the control system 25.
(The gas supply control unit 24). In other words, the main control system 9 determines the exposure state of the wafer W on the exposure apparatus main body side, for example, the applied voltage and the reticle ( The gas supply control unit 24 (a determination circuit to be described later) corresponds to each of the relationship with the pulse energy amount on the (wafer) surface (FIG. 6) and the operation state in the exposure sequence on the exposure apparatus main body side. The above signal S to be input
The signal levels of A and SB are changed. by this,
The gas supply control unit 24 is notified that the operation needs to be performed on the exposure apparatus main body side or that the operation needs to be prohibited.

For example, when the oscillation mode of the excimer laser light source 1 is the applied voltage control mode, the main control system 9 monitors the energy amount (output of the light amount monitor unit 5) of the pulse light actually irradiated on the reticle surface. Meanwhile, the relation between the applied voltage and the amount of pulse energy on the reticle surface (or a relational expression expressing the relation) is appropriately checked,
When the relationship (expression) reaches the relationship (expression) serving as a predetermined criterion, the signal level of the request signal SA is changed from Lo to Hi in the present embodiment.

Here, FIG. 9 shows an example of the relationship between the voltage applied to the excimer laser light source 1 and the amount of energy of the pulse light actually oscillated under the applied voltage on the reticle (or wafer) surface. In the figure, the relationship immediately after executing the PGR operation or the HI operation is indicated by a solid line, and the above-described relationship serving as a criterion is indicated by a dotted line. As is clear from FIG. 9, the relationship shown by the solid line gradually changes with the deterioration of the internal gas, and finally reaches the relationship of the criterion (dotted line). Will be changed. Note that the main control system 9 changes the signal level of the request signal SA to H
Change from i to Lo.

In this embodiment, the oscillation mode of the excimer laser light source 1 is changed to the applied voltage control mode only at the time of wafer exposure and data collection (initialization) for creating or updating the relationship (FIG. 6). In this case, the request signal SA is output only when the oscillation mode is the applied voltage control mode, and particularly when the exposure operation for the wafer W is being performed or when the initialization operation is completed (the signal level is Lo → Hi). To change). This is because, in the constant energy amount mode, the necessity of execution of the PGR operation and the HI operation can be sufficiently determined only by the previous request signal LA without using the request signal SA, and during the initialization operation, This is because the relationship (FIG. 6) is being created or updated. Further, for the above reason, the main control system 9 does not need to always obtain the above relationship (FIG. 6) from the output of the light amount monitoring unit 5, and when the relationship is updated according to the previous exposure amount control logic during the exposure operation. The request signal S based on this updated relationship
It is only necessary to determine whether or not to change the signal level of A.

Further, the main control system 9 responds to the operation state in the exposure sequence on the exposure apparatus main body side, for example, in order to prevent the PGR operation and the HI operation from being started during the exposure of one shot area. , The level of the signal SB input to the gas supply control unit 24 for inhibiting the execution of the above operation is changed. In the present embodiment, information (FIG. 6) relating to wafer exposure in an applied voltage control mode in accordance with an exposure amount control logic, and the relationship between the applied voltage and the energy amount of pulsed light irradiated on a reticle (or wafer) surface is described. During execution of data collection (initialization) for creating or updating, the signal level of the inhibition signal SB is set to, for example, Hi so as to inhibit execution of the above operation, and one shot area or one shot is set. Exposure operation on the wafer,
Alternatively, when the initialization operation is completed, the signal level is changed from Hi to Lo. The inhibition signal SB is set at the time when the exposure operation or the initialization operation is started.
The signal level changes from Lo to Hi.

Now, the above four signals LA, LB, S
A and SB are input to a gas supply control unit 24, that is, a determination circuit provided therein in the present embodiment.
It is determined whether to execute the operation and the HI operation. The gas supply control unit 24 executes the PGR operation or the HI operation when the execution of the above operation is determined by the determination circuit, that is, when the level of the output signal changes. FIG. 10 is a block diagram showing an example of a determination circuit for determining the timing (timing) for executing the PGR operation or the HI operation. The request signals LA and SA are input to the OR circuit 51, while the inhibition signal LB is input. , SB are input to a NOR circuit 52. Therefore, the request signal LA,
Only when at least one of the signal levels of SA becomes Hi and the signal levels of the inhibit signals LB and SB both become Lo, the signal REQ. Level is L
It changes from o to Hi, and at this time, the gas supply control unit 24 starts the PGR operation or the HI operation. Here, the signal REQ. Level is Lo → H
i, the shutter SH of the excimer laser light source 1 is driven, and the gas supply control unit 24
When H is closed, the above operation, that is, gas injection into the laser chamber or the like is started.

Next, the operation of the exposure apparatus according to the present embodiment will be described with reference to FIG. FIG. 11 shows an example of a time chart of the operation in the present embodiment. First, functions of signals not described above will be briefly described. (1) The signal EXT. TRG. (EXTERNAL TR
IGGER) This is a trigger signal for laser light oscillation from the exposure apparatus main body to the excimer laser light source 1. The laser light source oscillates laser light upon detection of this signal. One trigger signal corresponds to one pulse of laser light oscillation. (2) The signal STEP. ST. (STEPPER STA
TUS) This is a level signal for instructing the operation mode from the exposure apparatus main body to the excimer laser light source. TRG. Laser light is emitted one pulse at a time in synchronization with the signal. The operation mode of the excimer laser when this signal is Hi has the following two modes. The signal REQ. Is Lo, that is, PG for the excimer laser light source 1
If this signal changes from Lo to Hi while there is no execution instruction of the R operation or the HI operation, the excimer laser light source 1 closes the shutter SH at the laser light emission port and self-oscillates at an appropriate low frequency to expose the exposure pulse. Locks energy, absolute wavelength, etc. The signal REQ. When this signal changes from Lo to Hi when is High, the excimer laser light source 1 closes the shutter SH and performs the PGR operation or the HI operation.

The initialization operation (or PGR,
If the wafer W is below the projection lens PL when performing the HI operation), the main control system 9 changes the signal SD applied to the stage controller (not shown) from Lo to Hi,
The XY stages 32X and 32Y are moved to a predetermined retreat position. Here, FIGS. 11A, 11C, 11H and 11J show the signal EXT. TRG, request signal LA, inhibit signal LB, request signal SA, inhibit signal SB, signal REQ. ,
The signal STEP. ST and state of signal SD, FIG. 11 (B)
Represents the oscillation mode of the excimer laser light source 1. FIG. 11I shows the position of the shutter SH of the excimer laser light source 1, and FIG. 11K shows the XY stages 32X and 32Y.
3 shows the position state of. Note that, as is apparent from the inhibition signal SB shown in FIG. 11F, the PGR operation or the HI operation is not executed during the exposure of at least one shot area. In this sequence, a case where only the HI operation is performed will be described.

Incidentally, the signal ST in FIG.
EP. ST. Is Lo during the normal wafer exposure execution, and during the Hi period, the exposure apparatus main body does not send out the light emission trigger to the excimer laser light source 1 for several seconds or more. Operation, for example, wafer exchange, reticle alignment by reticle alignment systems 30X and 30Y, or wafer alignment system 3
4 shows a state where an operation such as wafer alignment is performed. During the period in which the signal is Lo, exposure of one shot is repeated for each shot area in a step-and-repeat manner. At this time, the signal EXT. Shown in FIG. TRG. , Each set S ₁ , S ₂ , S ₃ of the trigger pulse train corresponds to one shot exposure.

As shown in FIG. 11A, when the exposure apparatus main body (main control system 9) finishes exposing the _first wafer W1, the signal STEP. ST. Is changed from Lo to Hi (a). The excimer laser light source (control system 25) recognizing this starts closing the shutter SH (b), and when the shutter SH is completely closed, starts self-oscillation at a low frequency of several Hz or less (c). Lock (feedback control) such as wavelength. The exposure apparatus main body performs the operation of not sending out the above-mentioned light emission trigger while the excimer laser light source is self-oscillating, and then outputs the signal STEP. S
T. Is changed from Hi to Lo (d). The excimer laser light source that recognizes this stops the self-oscillation and then starts opening the shutter SH (e). The exposure apparatus main body, when the shutter SH is completely opened, so as to start an exposure operation for the next wafer W _2, signal EXT. TRG. And outputs the set S ₂ of the trigger pulse train as. The steps between the trigger pulse trains S ₁ , S ₂ , and S ₃ are stepping of the XY stages 32X and 32Y.

By the way, the excimer laser light source 1 is not synchronized with the exposure sequence of the exposure apparatus body as described above.
There is a need to perform an R operation or an HI operation. Therefore, before the exposure apparatus body starts exposing each shot area on the wafer, the signal REQ. Is checked, and if the signal level is Lo, exposure of the next shot is executed. On the other hand, during delivery of the trigger pulse train S _2, i.e. the change in the exposure of the second sheet of the second shot area of the wafer W _2, request signal LA of the excimer laser light source side to the Lo → Hi shown in FIG. 11 (C) (F), the excimer laser light source HI is synchronized with the signal LA.
Instead of starting the operation, the signal REQ. Is Lo → Hi
, That is, when the exposure of the second shot area is completed, execution of the HI operation is started (g).
Here, when the request signal LA changes from Lo to Hi, FIG.
The prohibition condition LB shown in FIG. 1 (D) is Lo, but the prohibition condition SB shown in FIG. 11 (F) is Hi.

Here, since the request signal LA changes from Lo to Hi during exposure of the second shot area,
After the exposure of the second shot area is completed (3.
Before stepping the XY stages 32X and 32Y to the second shot area), the signal REQ. To recognize that the level is Hi. As a result, the sequence of the exposure apparatus main body interrupts the stepping to the third shot area, and the signal STEP. ST. To L
Change from o to Hi (h). Excimer laser light source is signal R
EQ. Is changed from Lo to Hi, it is recognized as an HI operation start command, and the signal STEP.
ST. To start closing the shutter SH (i). At this time, the exposure apparatus main body also changes the signal SD from Lo → Hi (j), and moves the XY stages 32X and 32Y to a predetermined retreat position (k). After the shutter SH is completely closed, the excimer laser light source self-oscillates at an appropriate frequency (for example, a higher frequency than in the case of (c)), and
The I operation is performed (l).

Thereafter, when the HI operation (halogen gas injection) is completed, the excimer laser light source stops self-oscillation and outputs the signal REQ. Is changed from Hi to Lo (m).
When recognizing this, the exposure apparatus main body issues a signal ST as a command to start an initialization operation to the excimer laser light source.
EP. ST. Is changed from Hi to Lo (n). Further, the excimer laser light source that recognizes this starts opening the shutter SH (o), and when the shutter SH is completely opened,
The exposure apparatus body starts an initialization operation (data collection for creating the relationship shown in FIG. 6) (p). When the above operation is completed, the exposure apparatus main body outputs the signal SD.
Was changed to Hi → Lo (q), after moving the wafer W ₂ to a predetermined exposure position by driving the XY stage (r),
The signal EXT. TRG. It sends out a trigger pulse train S ₂ as to initiate the exposure of the third and subsequent shot area.

In this case, since the halogen gas concentration in the laser chamber has become equal to or higher than the predetermined value after the end of the HI operation, the prohibition signal LB changes from Lo to Hi in FIG. 11D. In the above sequence, the shutter S
The XY stage also starts to move to the retreat position at the same time when H is closed (i), but the XY stage may be moved to the retreat position before the initialization operation is started.

When the exposure of the _second wafer W2 is completed, the exposure apparatus main body receives the signal ST in the same manner as the above operation.
EP. ST. Is changed from Lo to Hi (s). The excimer laser light source that recognizes this starts closing the shutter SH (t), and when the shutter SH is completely closed, a few Hz.
Self-oscillation is started at the following low frequency (u) to lock the absolute wavelength and the like. During this period, the main body of the exposure apparatus replaces the reference mark plate F
After performing operations such as detection of a bar mark on M, the signal ST
EP. ST. Is changed from Hi to Lo (v). The excimer laser light source that recognizes this stops the self-oscillation, and then starts opening the shutter SH (w). The exposure apparatus main body is configured to drive the movable mirror M ₁ at the time the shutter SH is completely opened, the excimer laser light source changes the oscillation mode from the application voltage control mode to the energy amount constant mode (x). Thus, the main body of the exposure apparatus illuminates the reference mark plate FM with the excimer laser from below, thereby measuring the projection position of the slit mark of the reticle R (y). A baseline amount is calculated from the mark detection position.

[0137] Thereafter, an excimer laser light source switches the oscillation mode to the applied voltage control mode (z), the exposure apparatus main body so as to start an exposure operation for the next wafer W _3, signal EXT. TRG. (Set S ₃ of the trigger pulse train) is output. Hereinafter, during the exposure of the _third wafer W3, the signal RE is output.
Q. Is changed from Lo to Hi, the excimer laser light source may execute the HI operation in exactly the same operation as described above.

Although the HI operation has been described in the above sequence, it is needless to say that the PGR operation can be executed in the same manner. The excimer laser light source is
Even if only the HI operation is performed a plurality of times during the entire exchange of the mixed gas in the laser chamber, the operation of performing the PGR operation after performing the HI operation only a plurality of times is repeated. I do not care. Further, when the excimer laser light source side starts the PGR operation or the HI operation, the exposure apparatus body side preferentially executes a waiting state or another operation (wafer replacement, wafer alignment, etc.) not using the excimer laser light. I do.

As described above, in this embodiment, the request signal and the prohibition signal for determining whether or not to execute the PGR operation or the HI operation are generated on each of the excimer laser light source side and the exposure apparatus main body side. The timing at which the determination circuit 50 executes the above operation is determined from these four signals.
Therefore, the above operation is not executed during exposure of one shot area or in a state where the halogen gas is excessive, and the above operation can be executed at an optimal timing without lowering the yield and the like. Has become.

Here, (c), (l), and (c) of FIG.
In (u), the pulse light is oscillated at a low frequency with the shutter SH closed, but this is because
One reason is that it is necessary to cause a spectroscope inside the excimer laser light source to detect a change in the wavelength of the oscillation pulse light after the band is narrowed. Another reason is that it is necessary to cause a power monitor (photoelectric element) provided in the excimer laser light source 1 to receive pulsed light in order to set pulse energy for exposure of the next shot area. Further, the signal REQ. Means that the exposure to the exposure apparatus main body is interrupted or resumed, so that the absolute wavelength control and the spectrum half-width control (narrowing of the band) of the excimer laser light source 1 cause inconvenient behavior for the exposure main body during PGR operation and HI operation. Is detected by a spectroscope or the like.
Q. Is set to Hi, the inconvenience can be avoided.

The signal REQ. If the sequence being executed by the exposure apparatus main body in response to the execution command (Lo → Hi) is acceptable for the pulse energy fluctuation due to the PGR operation or the HI operation, the sequence is interrupted and the shutter SH is closed. Without any
The PGR operation or the HI operation may be executed. Further, the PGR operation or the HI operation request is used as another signal line, and the sequence of the exposure apparatus body determines whether or not to execute each request by closing the shutter SH for each execution request. May be.

Note that the shutter SH may be provided on the exposure apparatus main body side. The signal REQ. The shutter SH is closed and the PGR operation or H
In this embodiment, the laser generation trigger for performing the I operation is self-oscillation on the side of the excimer laser light source. However, light emission may be performed by a trigger signal (EXT.TRG.) From the exposure apparatus main body. In addition the sequence, but the XY stage during initializing operation had to be moved to a predetermined retracted position, the shutter in the optical path between the beam splitter BS ₁ and the reticle R arranged in FIG. 1, the shutter during initialization operation May be used to close the optical path.

Next, another exposure sequence of the apparatus having the above configuration will be briefly described with reference to FIG. 12, but here, only operations that are not included in the sequence shown in FIG. 11 will be described. In FIG. 12, the PGR operation or the HI operation is not performed during the exposure of one wafer. In other words, during the exposure of one wafer, the inhibition signal SB on the exposure apparatus main body side shown in FIG.

Now, during the exposure of the _second wafer W2, the request signal S on the side of the exposure apparatus main body shown in FIG.
Since A changes from Lo to Hi, the exposure apparatus main body is 2
After the exposure of the _second wafer W2 is completed, the signal REQ. To recognize that the level is Hi.
As a result, the exposure apparatus main body receives the signal STEP. ST. To L
with changing the o → Hi, by changing the signal SD to the Lo → Hi, XY stage 32X, 32Y move to a predetermined position for performing wafer exchange, keep out the wafer W ₂ from the XY stage. Excimer laser light source is signal R
EQ. Is changed from Lo to Hi, it is recognized as an HI operation start command, and the signal STEP.
ST. To start closing the shutter SH. Further, the excimer laser light source, after the shutter SH is completely closed,
The HI operation is executed while self-oscillating at an appropriate frequency.

Thereafter, when the HI operation (halogen gas injection) is completed, the excimer laser light source stops self-oscillation and outputs the signal REQ. Is changed from Hi to Lo. After recognizing this, the exposure apparatus main body issues a signal STEP. As a command to start an initialization operation to the excimer laser light source.
ST. Is changed from Hi to Lo. Further, the excimer laser light source recognizing this starts opening the shutter SH, and when the shutter SH is completely opened, the exposure apparatus body starts an initialization operation (data collection for creating the relationship shown in FIG. 6). . And when the operation is completed, the exposure apparatus main body in conjunction with changing the signal SD to Hi → Lo, after loading the third wafer W ₃ on the XY stage, exposing the wafer W ₃ given by the XY stage Move to the position. Thereafter, the exposure apparatus main body outputs the signal EXT. TRG. It sends a trigger pulse train S ₃ as to start exposure of the shot area. It should be noted that the throughput may be allowed to loading in advance of the third piece of the wafer W ₃ on the XY stage during the initialization operation in consideration of the. However, since such may then exposed wafer W ₃ pulse light irradiated through the projection lens PL along with the initializing operations, as stray light in the case, XY stage wafer W ₃ after initializing operation as described above It is desirable to load on top.

When the exposure of the _third wafer W3 is completed, the exposure apparatus main body outputs the signal STEP. ST. To L
Change from o to Hi. The excimer laser light source recognizing this starts closing the shutter SH, and when the shutter SH is completely closed, starts self-oscillation at a low frequency of several Hz or less to lock the absolute wavelength or the like. The exposure apparatus main body performs operations such as wafer exchange and bar mark detection on the reference mark plate FM by the wafer alignment system 34 while the excimer laser light source is self-oscillating.
TEP. ST. Is changed from Hi to Lo. The excimer laser light source that recognizes this stops the self-oscillation and then starts opening the shutter SH. The exposure apparatus body has a shutter S
H drives the movable mirror M ₁ when fully open, the excimer laser light source changes the oscillation mode from the application voltage control mode to the energy amount constant mode. by this,
The main body of the exposure apparatus illuminates the reference mark plate FM from below with an excimer laser to measure the projection position of the slit mark of the reticle R, and obtains a baseline from the measured value and the mark detection position of the wafer alignment system 34 previously obtained. Calculate the amount.

Here, when measuring the projection position of the slit mark of the reticle R in the constant energy amount mode,
That is, when the exposure apparatus main body outputs the trigger pulse train S 'shown in FIG. 12A, the request signal LA on the excimer laser light source side shown in FIG. 12C changes from Lo to Hi. At this time, the prohibition signal L shown in FIGS.
Both B and SB are Lo. Therefore, the request signal L
A changes from Lo to Hi when the signal REQ. Is Lo
Since it changes to Hi, the excimer laser light source immediately executes the HI operation even during the baseline measurement.
At this time, of course, the excimer laser light source is the shutter S
Do not close H. Then, the HI operation is completed and the signal RE is output.
Q. Is changed from Hi to Lo, the request signal LA on the excimer laser light source side also changes from Hi to Lo. Thereafter, the excimer laser light source switches the oscillation mode to the applied voltage control mode at the time of baseline measurement has been completed, perform the initializing operation, the exposure apparatus main body so as to start an exposure operation for the next wafer W _4, signal EXT . TR
G. FIG. (Set S ₄ of the trigger pulse train) is output.

As described above, even in the above sequence, the above operation is not executed during exposure of one wafer or in a state in which the amount of halogen gas is excessive, so that the yield and the like are not reduced and the optimal timing is obtained. The above operation can be performed. In the time charts shown in FIGS. 11 and 12, the baseline measurement was performed before the exposure of the wafers W ₃ and W ₄ was started. However, the baseline measurement was performed every time the wafer was replaced. Alternatively, it may be performed only when the reticle is replaced.

In the above embodiment, as shown in FIG. 9, the relationship between the voltage applied to the excimer laser light source 1 and the amount of energy of the pulse light actually oscillated under the applied voltage on the reticle surface is as follows. At the point in time when a predetermined reference criterion is reached, the request signal SA on the exposure apparatus main body side is changed from Lo to Hi. Here, in the above embodiment, since the number Nexp of exposure pulses per shot, the extinction rate β, and the like are determined in advance, if the extinction rate is β <1, the number of exposure pulses Nexp is constant. The applied voltage can be reduced by increasing the dimming rate β when the above relationship approaches the determination standard. That is, PGR operation or HI
The operation interval can be extended. Therefore, as long as the dimming rate is β <1, the dimming rate β may be increased stepwise (or continuously) when the above-mentioned relationship approaches the determination standard. In the above embodiment, the number of exposure pulses Nexp and the extinction ratio β are both constant.
Needless to say, when changing the extinction ratio β, it is necessary to adjust the pulse energy Pav (that is, the applied voltage) again. Further, even when the extinction ratio β is 1, if the number of exposure pulses Nexp is increased, the same effect as in the case of changing the extinction ratio β can be obtained.
However, if the number of exposure pulses Nexp is increased, the throughput is reduced. Therefore, when the dimming rate β actually becomes 1 and the above-mentioned relationship reaches the determination criterion, the request signal SA is changed from Lo to Hi. Is desirable. When the extinction ratio β and the number of exposure pulses Nexp are changed as described above, the extinction ratio β and the pulse energy Pav (applied voltage), and again the PGR operation or the HI operation are executed. Needs to be reset to the number of exposure pulses Nexp.

Further, in this embodiment, the oscillation mode of the excimer laser light source 1 is always the applied voltage control mode during wafer exposure. However, the number of pulses is smaller in the applied voltage control mode (the number of pulses required to achieve the smoothing of the interference pattern and the desired exposure amount control accuracy).
Exposure of one shot is effective when exposure is performed on a resist having relatively high sensitivity. For a resist with relatively low sensitivity, a sufficient number of pulses are required for one-shot exposure. Therefore, even if exposure is not performed in the applied voltage control mode, sufficient exposure is achieved by averaging by irradiation with a large number of pulsed lights. Amount control accuracy can be achieved. Therefore, the oscillation mode may be switched between the applied voltage control mode and the constant energy amount mode according to the sensitivity of the resist.

In the above embodiments, an exposure apparatus using a projection lens, that is, a so-called stepper has been described. However, the present invention can be applied to exposure apparatuses of any other types and systems in the same manner. Furthermore, although an excimer laser using a rare gas halide is used as the laser light source, a similar effect can be obtained by using another laser light source that requires partial gas exchange, gas injection, gas circulation, and the like in the laser chamber.

[0152]

As described above, in the present invention, the timing for executing the partial gas exchange and the gas injection is determined based on the operation states of the laser light source and the exposure apparatus main body, and therefore, at least one shot area is required. During the exposure, no gas injection is performed, and the applied voltage (charging voltage)
And information on the relationship between the amount of energy (dose amount) of the pulsed light emitted under the applied voltage and the mask or the sensitive substrate surface, is updated each time gas injection or the like is performed. Even after gas injection etc. is performed,
The advantage that good exposure dose control can always be performed is obtained.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a control system of the exposure apparatus shown in FIG.

FIG. 3 is a configuration diagram showing an example of a rotating turret plate suitable for being applied to a dimming unit.

FIG. 4 is a diagram showing a relationship between a rotation amount of a dimming element and transmittance when dimming is performed by the rotating turret plate shown in FIG. 3;

FIG. 5 shows a beam incident on an optical integrator (fly-eye lens) and its secondary light source image (spot light).
The figure which shows the relationship typically with.

FIG. 6 is a diagram illustrating an example of a relationship between an applied voltage to an excimer laser light source and the amount of light (pulse energy) on a reticle (or wafer) surface of pulsed light emitted under the applied voltage.

FIG. 7 is a schematic flowchart showing an example of the operation of the exposure apparatus according to the embodiment of the present invention.

FIG. 8 is a graph showing a state of exposure amount control in the embodiment of the present invention.

FIG. 9 is a diagram illustrating generation of a signal requesting execution of partial gas exchange or gas injection on the exposure apparatus main body side.

FIG. 10 is a block diagram showing an example of a determination circuit for determining a timing (timing) at which partial gas exchange or gas injection is performed.

FIG. 11 is a time chart illustrating an example of an operation of the exposure apparatus according to the embodiment of the present invention.

FIG. 12 is a time chart illustrating another operation of the exposure apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Excimer laser light source 5 ... Light amount monitor 6 ... Calculator 7 ... Memory 8 ... I / O device 9 ... Main control system 10 ... Trigger control unit 11 ... Applied voltage control unit 12 ... Dimming control unit 13 ... Interference pattern control unit 15: Attenuator 16: Rotating turret 17: Interference pattern reducer 19: Fly-eye lens 24: Gas supply controller 34: Wafer alignment system 50: Judgment circuit R: Reticle PL: Projection lens W: Wafer SH: Shutter FM … Fiducial mark plate

Claims (11)

(57) [Claims] 1. requires partial gas exchange or gas injection,
A light source that oscillates pulsed light whose energy amount fluctuates with each oscillation, and a unit that adjusts a control parameter for the light source that determines the energy amount of the pulsed light, wherein a plurality of energy amounts are controlled by the adjusting unit. An exposure apparatus that irradiates a mask with pulsed light and transfers a pattern formed on the mask onto a sensitive substrate, wherein a partial gas exchange or gas injection of the light source is required according to an exposure state of the sensitive substrate. A first control means for outputting a first signal corresponding to the necessity, and a second signal corresponding to the necessity of partial gas exchange or gas injection of the light source corresponding to the oscillation state of the light source. A second control means for detecting and executing a timing of partial gas exchange or gas injection of the light source based on the first and second signals, and a control parameter of the light source. And storage means for storing information relating to the relationship between the amount of energy of the pulse light oscillated from the light source under the control parameter and the amount of energy on the mask or the sensitive substrate; and the pulse light actually oscillated from the light source. Detection means for detecting the amount of energy on the mask or sensitive substrate of the above, every predetermined unit number of pulses or per unit time, or every time the partial gas exchange or gas injection is performed, the control parameters of the light source and Calculating means for updating the information stored in the storage means based on the detected energy amount; and the light source corresponding to the energy amount of the pulse light to be emitted next based on the updated information And an deciding means for deciding the control parameters. 2. A function representing a relationship between an applied voltage applied to the light source during oscillation of the pulse light, or a charging voltage of the light source during oscillation of the pulse light, and an energy amount of the pulse light. 2. An exposure apparatus according to claim 1, wherein said parameter is stored. 3. The determining means determines an applied voltage to the light source as the control parameter so that the adjusting means adjusts an applied voltage to the light source to control an energy amount of the pulsed light. 3. The method according to claim 1, wherein
Exposure apparatus according to the above. 4. A light source that oscillates pulsed light applied to a mask, a photodetector that receives the pulsed light and detects an energy amount thereof, and a control parameter for the light source that determines the energy amount of the pulsed light. Means for exposing a sensitive substrate with the pulsed light through the mask, comprising: a control parameter for the light source; and an energy amount of the pulsed light oscillated from the light source under the control parameter. Storage means for storing information about the relationship between the light source, and a control parameter for the light source when a plurality of pulsed lights are oscillated from the light source and weighting the energy amount detected by the photodetector, and the storage Computing means for updating the updated information, wherein the adjusting means utilizes the updated information to determine the energy of the pulsed light. Exposure apparatus characterized by controlling the amount. 5. An exposure apparatus according to claim 4, wherein said calculating means makes the weight given to the energy amount of the pulse light initially oscillated out of said plurality of pulse lights the lightest. 6. The exposure apparatus according to claim 4, wherein the control parameter is a voltage applied to the light source or a charging voltage of the light source when the pulsed light oscillates. 7. A method of irradiating a mask with pulsed light oscillated from a light source and exposing a sensitive substrate with the pulsed light through the mask, wherein a partial gas exchange or gas injection of the light source is performed. After the partial gas exchange, or gas injection, oscillate a plurality of pulsed light from the light source, sequentially measure the energy amount of the pulsed light in association with a control parameter for the light source that determines the energy amount of the pulsed light, Determining a parameter representing a relationship between the control parameter used for controlling the energy amount of the pulsed light and the energy amount of the pulsed light. 8. In the exposure of the sensitive substrate after the partial gas exchange or the gas injection, a control parameter for the light source is adjusted according to the determined parameter to control an energy amount of the pulse light. The exposure method according to claim 7, wherein 9. The timing of the partial gas exchange or gas injection is determined according to the energy amount of the pulsed light or the number of pulses required to transfer the pattern of the mask onto the sensitive substrate. 8. The method according to claim 7, wherein
Or the exposure method according to 8. 10. A method of irradiating a mask with pulsed light oscillated from a light source, and exposing a sensitive substrate with the pulsed light via the mask, wherein a control parameter for the light source is set according to sensitivity characteristics of the sensitive substrate. The first mode of controlling the energy amount of pulsed light oscillated from the light source by adjusting the control parameter, or the second mode of oscillating the pulsed light from the light source with the control parameter or the energy amount constant. An exposure method, comprising selecting and exposing the sensitive substrate using the selected mode. 11. The method according to claim 7, wherein the control parameter is a voltage applied to the light source or a charging voltage of the light source when the pulsed light oscillates. Exposure method.