JP2926241B2 - Exposure apparatus and method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for manufacturing a semiconductor using a laser such as an excimer laser or the like that requires gas exchange, gas charging, or the like as an exposure light source.

[Conventional technology]

In recent years, as the degree of integration of a semiconductor integrated circuit has increased, the minimum pattern size of the circuit has tended to be smaller. Therefore, an exposure apparatus using an excimer laser as an exposure light source has been developed instead of a conventional mercury lamp. ing. An excimer laser exposure apparatus is generally composed of an excimer laser light source and an exposure apparatus main body, and at the present time, a reduction projection type sequential movement system, a so-called stepper, is mainly used because the exposure apparatus main body has excellent resolution and mask manufacturability. is there. In such an excimer laser exposure apparatus, a system is generally used in which the excimer laser and the exposure apparatus main body are connected by an electric cable or an optical fiber interface cable, and emits a laser according to a sequence of a main computer in the exposure apparatus main body. Interface signals include, for example, a light emission trigger from the exposure apparatus main body to the excimer laser, a signal indicating high voltage charging start, oscillation start, oscillation stop, etc., an oscillation standby completion from the excimer laser to the exposure apparatus main body, an internal shutter position. , A signal indicating that the interlock is in operation or the like.

Excimer lasers are generally halogen gases such as fluorine,
Krypton, inert gas such as argon, and helium,
A mixed gas of three kinds of rare gases such as neon is sealed in a laser chamber, and the halogen gas and the inert gas react with each other due to discharge in the chamber to emit laser light (pulse light on the order of nsec). However, as the laser light emission is repeated, the halogen gas combines with impurities generated in the chamber or is adsorbed inside the chamber, so that the concentration of the halogen gas decreases and the pulse energy of the laser decreases. . On the other hand, when an excimer laser is used as a light source of a semiconductor exposure apparatus, if the pulse energy fluctuates, (1) the control accuracy of the energy (exposure amount) reaching the object to be exposed (a wafer or the like) decreases.

(2) The function of reducing interference fringes on the object to be exposed due to the optical system is reduced.

(3) The S / N ratio of the signal of the photoelectric detection system of the pulse energy monitor system and the alignment system is reduced. And the like. For this reason, the excimer laser monitors the pulse energy that decreases due to the decrease in the halogen gas concentration, feeds back the pulse energy to the discharge application voltage, and keeps the pulse energy constant by gradually increasing the discharge application voltage. . However, since the discharge applied voltage has an upper limit, when the applied voltage reaches the upper limit, a halogen gas injection (HI) operation is performed to return the halogen gas concentration to an appropriate value, and the voltage is applied accordingly. It was necessary to keep the pulse energy constant by reducing the voltage.

 This HI operation is shown in FIG.

FIG. 3 (A) shows the pulse energy emitted from the excimer laser on the vertical axis and the time t on the horizontal axis, and FIG. 3 (B) shows the pulse energy to the electrode in the laser chamber on the vertical axis. The discharge applied voltage is taken, and the time t is plotted on the horizontal axis. As shown in FIG. 3A, when the upper limit and the lower limit are determined centering on the set value of the pulse energy required on the exposure apparatus side, the excimer laser light source is provided with an energy monitor (light receiving element) provided therein. , Etc.), and the magnitude relationship with the set value is compared for each pulse. When the pulse energy decreases, the discharge applied voltage is gradually increased as shown in FIG. 3 (B). An upper limit value and a lower limit value are also set for the discharge application voltage, and the actual voltage range varies depending on the internal structure of the excimer laser light source, the manufacturer, and the like. Now, the discharge voltage applied at time t ₁ reaches the upper limit, the control processor which is provided in the excimer laser light source
It is determined that HI operation is necessary, and a predetermined amount of halogen gas is injected into the laser chamber. Immediately after the injection, the concentration of the halogen gas returns to its original value, but the voltage applied to the discharge cannot be rapidly restored (decreased), and it is necessary to take some time. HI operates in the same manner as any subsequent time t ₂ is performed.

Such a gradual decrease in the discharge applied voltage is caused by the HI
Immediately after the operation, the gas in the laser chamber cannot be said to be sufficiently homogeneously mixed, and the pulse energy is highly likely to vary. This is because light may not be oscillated and a power monitor may not be able to be performed.

However, as the halogen gas injection is repeated, impurities in the laser chamber increase.

Even if halogen gas is injected along with the increase of the impurities, the halogen gas is combined with these impurities (decrease of the halogen gas concentration), and the minimum applied voltage for keeping the pulse energy constant increases. As a result, the period of the halogen gas injection is shortened, and it becomes impossible to keep the pulse energy constant even when the halogen gas is injected.

FIGS. 4 (A) and 4 (B) show the state and correspond to the graph of FIG. As shown in FIG. 4 (B), slowly injected cycle is shortened and the time _{t 1, t 2 ... t 6} , at the time t ₆ after despite discharge the applied voltage is in the upper limit value, the pulse energy It gradually decreases.

As described above, when the effect of the halogen gas injection is lost or reduced to a predetermined condition, the three kinds of mixed gases are partially replaced, that is, the partial gas exchange (PG
R: Partial Gas Replacement) operation was required to maintain the pulse energy. FIG. 5 shows an example of a state when the partial gas exchange is executed. Changes in pulse energy and discharge applied voltage when partial gas exchange is performed with reference to FIG. 5 will be described below.

FIGS. 5 (A) and (B) show FIGS. 4 (A) and
4B, times t ₃ , t ₄ and t ₅ are the same as those in FIG. 4 and represent the timing of the HI operation. And time
PGR operates in the time Ta after t ₅ is executed.

Generally, in the PGR operation, in order to extract a part of the gas in the laser chamber, if pulse emission is performed as it is, the pulse energy temporarily decreases as shown in FIG. 5 (A). At this time, since the discharge applied voltage is already near the upper limit as described above, it is difficult to increase the applied voltage to return the pulse energy to the set value. Thereafter, a predetermined amount of a new mixed gas is injected into the laser chamber. Since the pulse energy increases and becomes larger than a set value (allowable upper limit value) by this injection, the applied voltage is gradually lowered to return the pulse energy to the set value. Thereafter, the halogen gas injection (HI operation) is repeated as in FIG. 3 until the partial gas exchange is required again.

The reason for gradually lowering the applied voltage during the PGR operation is the same as in the previous HI operation.

The above HI operation and PGR operation were almost automatically performed by the instruction of the control processor in the excimer laser light source.

[Problems to be solved by the invention]

On the other hand, when the excimer laser light source is viewed from the exposure apparatus main body side, it is desirable that the pulse energy is constant as described above. It is difficult to make it constant. Therefore, the exposure apparatus main body sets a permissible value of the pulse energy fluctuation to satisfy the function and the specification, and the excimer laser side implements various measures so that the pulse energy always enters the set value.

One of the methods is the HI described in FIGS.
Operation and PGR operation, but from the perspective of the exposure apparatus,
There was a problem that the pulse energy exceeded the allowable value in the sections indicated by times a and b in FIG. 5 (A). The times a and b vary depending on the structure of the laser light source, the maker, and the like, but currently require several seconds to several minutes.
Further, a serious drawback on the exposure apparatus side is that these periods a and b, that is, the HI operation and the PGR operation occur exclusively by the control of the laser light source.

Therefore, when the wafer is exposed by the step-and-repeat method, if the HI operation or the PGR operation is performed asynchronously during the exposure of one shot region (usually several thousand pulses or more are required), the exposure after the shot region is performed. Exposure to most shots, up to many shots or even shot areas on the next wafer, will be severely damaged.

Of course, even if the excimer laser beam is used for other purposes, for example, for relative positioning between the reticle (original plate) and the wafer, alignment errors may occur if HI operation or PGR operation occurs during the alignment period. become.

The present invention has been made in view of such problems,
In an exposure apparatus that uses a laser light source that requires partial gas exchange, partial gas injection, etc., such as an excimer laser light source, the purpose is to minimize the decrease in the function and accuracy of the exposure apparatus. is there.

[Means for solving the problem]

Therefore, in the present invention, the operations of the laser light sources (10, 12) such as gas exchange and gas injection, and the exposure main unit (M1 to M6, PL, 32X, 3
2Y, 34, FM, ...).

[Action]

In the present invention, the operation of the laser light source and the processing operations such as exposure and alignment of the exposure main body are coordinated so that the performance of the exposure apparatus does not deteriorate due to the maintenance operation performed asynchronously by the laser light source. For example, the maintenance of the laser light source can be performed without impairing the performance of the exposure apparatus by performing the maintenance operation of the laser light source such as gas exchange or gas injection at the timing when the laser light is not used in the exposure main body.

〔Example〕

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

Reference numeral 10 denotes a main body of an excimer laser light source, in which 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 for resonance, and a wavelength for narrowing the wavelength band. A selection element (diffraction grating, prism, etalon, etc.), a spectroscope for monitoring the absolute value of the oscillation wavelength, a detector for monitoring laser power, a shutter SH, and the like are provided. The HI operation and the PGR operation for the laser chamber are performed by the control system 12, but in the present embodiment, independent control is not performed only by the processor in the control system 12, but cooperative control is performed in cooperation with the exposure apparatus main body. The control system 12 also performs control for wavelength stabilization, control of a discharge applied voltage, and the like.

The pulse light from the excimer laser light source 10 enters the beam shaping optical system 14 via the movable mirror M ₁ and the fixed mirror M ₂ and is shaped into a predetermined cross-sectional shape and size. After the pulse light from the beam shaping optical system 14 is reflected by the oscillating mirror M ₃ to swing within a predetermined angle by the drive unit 16 enters the fly-eye lens FL functioning as an optical integrator, a number of secondary It is converted to a light source (spot light).
Each spot light of the excimer beam formed on the exit side of each element lens of the fly-eye lens FL passes through the beam splitters BS ₁ and BS ₂ and is condensed by the condenser lens system 24.
The reticle blinds (illumination field stop) RB are superimposed so as to have a substantially uniform intensity distribution. Excimer light passing through reticle blind RB is lens system 26, fixed mirror
M _4, a main condenser lens 28, and via a fixed mirror M ₅ illuminates the circuit pattern area of the reticle R. Here, the reticle blind RB is conjugated to the reticle R by the lens system 26 and the main condenser lens 28. The reticle R is positioned in the X, Y, and θ directions with respect to the apparatus main body by dedicated reticle alignment systems 30X, 30Y. The image of the circuit pattern of the reticle R is reduced and projected on the wafer W by the projection lens PL. The wafer W is mounted on an X stage 32X, and the X stage 32X
It moves in the X direction on the Y stage 32Y that moves in the direction.
As a result, the wafer W moves two-dimensionally along the projection image plane, and the step-and-repeat exposure or the like is performed. On the X stage 32X, a fiducial mark plate FM having a transmissive fiducial slit at substantially the same height as the wafer W is provided. A mirror (not shown) fixed to the X stage 32X is provided below the reference mark plate FM. The reference mark plate FM, when the movable mirror M ₁ is retracted from the position shown, the pulse light from an excimer laser light source 10, from the bottom surface via a mirror M ₆ fixed on a plurality of mirrors and the Y stage 32Y It is arranged to receive. The excimer beam incident on the mirror M ₆ with substantially parallel light flux is parallel to the Y axis, is reflected at a right angle in the X-direction by the mirror M _6, are 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.

Incidentally, alignment (mark detection) of the wafer W
This is performed by a wafer alignment system 34 of an off-axis system. 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. Further, 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 projection of the circuit pattern of the reticle R Since the relative positional relationship with the center of the image slightly changes each time the reticle R is replaced, the reference mark plate FM
Is used to measure the relative positional relationship. For this purpose, the pulse light from the light emitting slit of the reference mark plate FM is partially branched via the beam splitter BS ₂ arranged in the optical path of the illumination system, and received by the photoelectric element (photomultiplier or the like) 22 through the lens system 20. I do. This photoelectric element 22
The light-receiving surface of the projection lens by the lens system 24, 26, 28, etc.
It is arranged almost conjugate with the pupil plane (entrance pupil or exit pupil) of the PL. Further, Koehler illumination is performed by forming images of a large number of secondary light sources formed by the fly-eye lens FL on the entrance pupil of the projection lens PL.

Now, in the above configuration, between the movable mirror M ₁ and the laser light source 10, there is thermal chamber partition wall for accommodating the exposure apparatus (stepper) body, the laser light source 10 is disposed outside the thermal chamber . The main body of the stepper is controlled by the main controller 40 to move the XY stages 32X and 32Y, and the reticle alignment systems 30X and 30Y.
Of reticle R by means of wafer alignment system 34
Detection and operation of wafer W by reticle blind
RB setting, checking the operation of a series of relative positions using the photoelectric element 22 and the reference mark plate FM, exposure using a photoelectric device 18 that receives a portion of the reflected pulse light at the beam splitter BS ₁ control operation or speckle due to vibration of the vibration mirror M ₃ (excimer beam interference fringes caused by coherent etc.) executing a reduction operation or the like.

The positions of the XY stages 32X and 32Y are sequentially measured as coordinate values by a laser interferometer (interferometer), and the coordinate values are also input to the main controller 40 and used for various position measurements. .

The configuration on the stepper side described above is merely an example in the present invention, and is not limited thereto.

In the present embodiment, four new interface signals are provided between the main controller 40 on the stepper side and the control system 12 on the laser light source side to enable cooperative control. Of course, other interface signals are of course provided, but are shown only for the invention. The names and functions of the four interface signals are as follows.

Signal PGR.REQ. (PGR REQUEST) This is a signal from the excimer laser light source side to the main body of the exposure apparatus. Partial gas exchange (PGR operation) or halogen gas injection (H
This is for notifying the exposure apparatus main body that the need to perform the (I operation) is imminent by changing the signal level (Lo → Hi in this embodiment). In addition, it has a function of notifying the exposure apparatus main body that the operation of the partial gas exchange or the halogen gas injection is completed by changing the signal level from Hi to Lo.

Signal STEP.ST. (STEPPER STATUS) This is a level signal that commands the operation mode from the exposure apparatus body to the excimer laser light source. When Lo, the excimer laser light source 10 is synchronized with the EXT.TRG. Signal from the exposure apparatus body. Then, laser light is emitted one pulse at a time. The operation mode of the excimer laser when this signal is Hi has the following two modes. If this signal changes from Lo to Hi while the excimer laser light source sets the signal PGR.REQ. To Lo, that is, while there is no request to perform partial gas exchange or halogen gas injection to the exposure apparatus main body, the excimer laser light source changes to laser. The shutter SH at the light emission port is closed, and self-oscillation is performed at an appropriate low frequency to lock the pulse energy, the absolute wavelength, and the like. Also, the signal PG
When this signal changes from Lo to Hi when R.REQ. Is Hi, the excimer laser light source closes the shutter SH and executes partial gas exchange or halogen gas injection.

Signal SHUT.ST. (SHUTTER STATUS) This is a level signal indicating the shutter position in the excimer laser from the excimer laser light source to the exposure apparatus main body. In this embodiment, the signal is Hi when open and Lo level when closed. The timing for changing the level is such that when the shutter SH is closed, the shutter SH is completely closed and then changes from Hi to Lo, and when the shutter is opened, the shutter is completely opened and then changed from Lo to Hi.

Signal EXT.TRG. (EXTERNAL TRIGGER) This is a trigger signal for laser light emission from the exposure apparatus body to the excimer laser light source. The laser light source emits laser light by detecting the edge of this signal. One trigger signal corresponds to one pulse of laser light emission.

As described above, in this embodiment, the cooperative control between the laser light source side and the stepper body side is performed based on the four interface signals.

Therefore, the control operation of this embodiment will be described next.
Before that, each of the exposure operation using the excimer laser beam and the alignment operation in the stepper will be briefly described.

One shot area on the wafer W is exposed with several thousand pulses or more due to the relationship between speckle reduction and exposure amount control accuracy. Speckle reduction, the interference fringes on the image plane caused by the use of fly-eye lenses FL, the oscillating mirror M ₃ by oscillating the laser pulse while deflected by a small angle, the fine motion in the pitch direction of interference fringes After the exposure of one shot is completed, the contrast of the interference fringes on the wafer is suppressed to a level that does not affect practically (about ± 1% as a contrast value). In this case, the number of image plane deflection angle of the oscillating mirror M ₃ required to reduce the contrast of the interference fringes on (wafer surface) (half cycle) alpha laser pulse light required between the deflection angle alpha the N _P, are uniquely determined by experiment or the like.

On the other hand, the proper exposure amount Ev for one shot also depends on the type of resist,
Since the naturally determined by the thickness or the like, in view of the speckle pulse number K · N _P required reduction (K is a natural number incremented by 1 for every half cycle of the oscillation angle α of the oscillating mirror M _3),
Average pulse energy E _P of each pulse set in dimming filter or the like need to be exposed. At the time of exposure, the actual energy of each pulse light detected by the photoelectric element 18 is integrated to monitor whether or not an appropriate exposure amount has been reached. Alternatively, a high-speed variable neutral density filter is provided in front of the fly-eye lens FL to integrate the energy detected by the photoelectric element 18 for each pulse emission while satisfying the conditions of the number of pulses K · N _P and the deflection angle α. Compare the value to the current target integration value,
A method of finely adjusting the energy of the next pulse emission by a high-speed variable neutral density filter may be used.

As described above, since the number of pulses K · N _P required for speckle reduction is predetermined, any one of the pulses K · N _P (K = 1, 2, 3,. Or 1
Before reaching the One), the time a shown in FIG. 5 (A) is started, since the average energy E _P of the pulsed light from that point increases, proper before sufficient reduction of speckle contrast is performed Inconvenience such as reaching the exposure amount occurs. In particular, at the time of the PGR operation, the fluctuation amount of the pulse energy becomes large as at the time b in FIG.
This is extremely inconvenient for speckle reduction and exposure control.

In the alignment operation using excimer laser light, the transmission slit of the fiducial mark plate FM is run in a direction crossing the slit longitudinal direction one-dimensionally on the projection image plane by the XY stage, and the slit image is transmitted through the transmission slit on the reticle R. is bound to the mark, mirror M ₅ excimer light transmitted through the slit mark, the condenser lens 28, a mirror
M _4, the lens system 26 and 24, received by the photoelectric element 22 via the beam splitter BS _2, recognizes the projection position of the slit mark of the reticle R on the movement coordinate system of the XY stage. At this time, the excimer laser light source 10 emits a pulse signal in response to a measurement pulse from the laser interferometer on the stepper side.
Outputs EXT.TRG. Laser interferometer, XY stage 32
Since a measurement pulse (up / down pulse) is output each time X and 32Y move, for example, by 0.01 μm, the main controller 40
Generates the signal EXT.TRG. By appropriately dividing this measurement pulse. Then, the level of the photoelectric signal from the photoelectric element 22 is digitally sampled by the A / D converter after the oscillation of the pulse light, and is stored in the memory in address order for each pulse emission. This address uniquely corresponds to the coordinate position of the XY stage. However, since the energy of the excimer laser light has a variation of about ± several% to several tens% for each pulse, for example, a photoelectric signal from a power detector in the excimer laser light source 10 is taken in every pulse emission, and It is necessary to standardize the levels of the 22 photoelectric signals with a divider or the like. Note that detector for normalization may be provided in the stepper 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 Can be

With the above operation, the projection position of the slit mark (or the reticle center point) of the reticle R is defined as a value of the moving coordinate system of the XY stage. Further reference mark plate
By using a laser interferometer to read the position of the XY stage when a slit or the like on the FM is taken at the detection center of the wafer alignment system 34, the movement coordinates between the center of the projected image of the reticle R and the detection center of the wafer alignment system 34 The relative positional relationship in the system is defined.

During such an alignment operation, particularly when a PGR operation or the like is started while the photoelectric signal from the photoelectric element 22 is being acquired, the S / N ratio of the acquired signal waveform is reduced, and the alignment is reduced. There is a disadvantage that the accuracy is reduced.

Next, the operation of this embodiment will be described with reference to FIG. 2 (A), (C), (D) and (E) show a signal STEP.ST, a signal SHUT.ST, a signal EXT.TRG and a signal PGR.RE, respectively.
FIG. 2B shows the state of Q. The position of the shutter SH in the excimer laser light source 10 is shown. FIGS. 2 (F) and 2 (G) show the time change of the pulse energy and the time change of the discharge applied voltage, respectively. Now, in FIG. 2 (A), the signal
When STEP.ST. is Lo, the normal wafer exposure is performed. During Hi, the stepper body is exposed to the excimer laser light source for several seconds or more.
This shows a state in which operations such as wafer exchange, reticle alignment by the reticle alignment systems 30X and 30Y, and wafer alignment by the wafer alignment system 34 are being performed without sending out a light emission trigger. In the period, 1
Exposure is repeated for each shot in a step-and-repeat manner for a single wafer. At this time, FIG. 2 (D)
Each set S of the trigger pulse train of the signal EXT.TRG. Shown in FIG.

When the stepper completes the exposure (period) for one wafer, it changes from Lo to Hi as indicated by the signal STEP.ST. The excimer laser light source that recognizes this starts closing the shutter SH (), sets the signal SHUT.ST. to Lo when the shutter is completely closed, and then starts self-oscillation at a low frequency of several Hz or less. (), Lock (feedback control) of pulse energy, absolute wavelength, etc. is performed. During this period, the stepper body performs an operation (period) in which the above-described light emission trigger is not transmitted, and then outputs the signal STEP.ST.
Change from Hi to Lo (). The excimer laser light source that recognizes this stops self-oscillation and then starts opening the shutter SH (). When the shutter is fully opened, the signal SH
Change UT.ST. from Lo to Hi (). The stepper body recognizing this, as a signal EXT.TRG., Sets a set of trigger pulse trains S ₁ , S ₂ ,.
Is output. XY stages 32X, 3 between pulse trains S ₁ and S ₂
2Y stepping.

The excimer laser light source needs to perform partial gas exchange or halogen gas injection asynchronously with the operation sequence of the stepper body. Here, a case where a partial gas exchange (PGR operation) is performed will be described. Before starting the exposure of each shot area on the wafer, the stepper body checks the state of the signal PGR.REQ. If it is Lo, as shown in the pulse trains S, S ₁ and S ₂ in FIG. 2 (D). Is exposed. On the other hand, during delivery of the trigger pulse train S _2, that is, during the exposure of the second shot of the second wafer, the excimer laser light source is detected that the discharge voltage applied is close to the upper limit value (), partial gas conversion The signal PGR.REQ. Is changed from Lo to Hi as a request to execute (). This signal PGR.RE
The timing at which Q. is changed from Lo to Hi is, for example, a margin for the longest expected exposure time required to expose one shot area (or the photoelectric signal capturing time at the time of photoelectric detection using an excimer beam). Required time Tm, required for final start of partial gas exchange or halogen gas injection Ta
It may be set before.

Well, here for signal PGR.REQ. Is changed during the exposure the second shot area (during delivery of the trigger pulse train S _2), after the exposure of the stepper body second shot, the third following After the XY stages 32X and 32Y are stepped on the shot area of (1), the signal PGR.REQ. Is checked to recognize that the signal PGR.REQ. Is Hi (). As a result, the sequence of the stepper body becomes 3
The exposure start to the second shot area is interrupted, and the signal STEP.S
Change T. from Lo to Hi (). When the signal STEP.ST. changes from Lo to Hi while the signal PGR.REQ. Is Hi, the excimer laser light source recognizes this as a partial gas exchange or halogen gas injection start command, closes the shutter SH ( ), Signal SHUT.S
After changing T. from Hi to Lo (), partial gas exchange is performed while self-oscillating at an appropriate frequency (for example, a higher frequency than in the case) ().

Thereafter, the excimer laser light source monitors the pulse energy, and when it returns to within the allowable value (), stops self-oscillation and changes the signal PGR.REQ. From Hi to Lo (). The stepper body recognizing this sends the signal STEP.ST.
Is changed from Hi to Lo (). When the excimer laser light source recognizes this, it opens the shutter SH () and outputs the signal SHU.
Set T.ST. to Hi (). After recognizing this, the stepper body sends trigger pulse trains S ₃ , S _4, ... As a signal EXT.TRG. And starts exposing the third and subsequent shot areas ().

As described above, the PGR operation has been described in the present sequence, but the HI operation is executed in the same manner. further,
Even when excimer laser light is used in the alignment operation, the state of the signal PGR.REQ. Is monitored on the stepper main body immediately before the photoelectric light detection operation of the pulse light is started. If so, the excimer laser light source side starts the PGR operation or the HI operation, and the stepper side preferentially executes other operations (wafer replacement, wafer alignment, etc.) not using the excimer laser light. .

By the way, in FIG. 2 (D), pulse light is oscillated at a low frequency with the shutter SH closed, which is caused by the excimer laser light source 10.
This is because it is necessary to cause the spectroscope inside the device to detect a change in the wavelength of the oscillation pulse light after the band narrowing. The other is for adjusting the discharge voltage applied with PGR operation, the HI operation, or for pulse energy settings for the next shot S _1, a power monitor provided in the excimer laser light source 10 in (photoelectric element) This is because it is necessary to receive the pulse light at a time.

Further, since the signal PGR.REQ. In the present embodiment means interruption or resumption of exposure to the stepper, the excimer laser light source 10
Absolute wavelength control and spectral half width control (bandwidth narrowing) are to be detected by a spectroscope or the like during partial gas exchange or halogen gas injection, indicating an unfavorable behavior of the stepper. If .REQ. Is set to Hi, the inconvenience can be avoided. Also, in response to the execution request generation (Lo → Hi) by the signal PGR.REQ. Of the present embodiment, the sequence being executed by the stepper body can tolerate pulse energy fluctuation due to partial gas exchange or halogen gas injection. In this case, the partial gas exchange or the halogen gas injection may be executed without interrupting the sequence and closing the shutter SH. In addition, using the partial gas exchange request and the halogen gas injection request as separate signal lines, the sequence of the exposure apparatus body determines whether or not to execute each request by closing the shutter SH for each execution request. You may do it.

Note that the shutter SH may be provided on the exposure apparatus main body side. In addition, in response to the execution request generated by the signal PGR.REQ., The trigger of laser generation when the shutter SH is closed and the partial gas exchange or the halogen gas injection is performed is self-oscillation on the excimer laser light source side in the present embodiment. Alternatively, the light may be emitted by a trigger signal (EXT.TRG.) From the exposure apparatus body.

By the way, in the sequence shown in FIG. 2, the stepper checks at a timing whether the signal PGR.REQ. Is Hi or Lo.

However, in the case of an object to be exposed which requires a long exposure, for example, as shown in FIGS. 2 (E) and 2 (F), after a certain time Tm has elapsed since the signal PGR.REQ. Since the PGR (or HI) operation starts, time T
m must be set quite long. Increasing the time Tm means that the pulse energy of the laser beam decreases from the set value before the PGR and HI operations are started.

Therefore, a timer or the like is provided on the stepper main body side, and during the exposure operation of a certain shot, for example, between the pulse light and the pulse light emission timing, the state of the signal PGR.REQ.
If it is at the Hi level, start the timer and measure the time Tm. At the end of the time Tm, it is checked whether or not the exposure operation is still continuing. If the exposure operation is interrupted, the PGR and HI operations are executed as in the previous embodiment. If the exposure operation continues at the end of time Tm,
Exposure operation (irradiation of pulse light) with the accumulated exposure amount and pulse energy (average value) etc. up to that time stored
Is forcibly interrupted and PGR and HI operations are started. After the completion of the PGR and HI operations, the exposure is restarted until a proper exposure is continuously obtained from the stored integrated exposure. As described above, in the present invention, the state in which the exposure operation is interrupted in the sequence of the exposure apparatus includes an extremely short time between pulsed light emission and pulsed light emission.

Further, a function for outputting a signal (shot status) indicating a shot exposure state is provided on the stepper side, and the AND signal (theoretical product) of the shot status signal and the PGR.REQ. .ST. May be set to Hi level. That is, the shot status signal is set to the Lo level during the exposure of a certain shot, and set to the Hi level at a timing not using the excimer laser, such as during stepping between shots or during wafer exchange. Therefore, when the signal PGR.REQ. Becomes Hi level during the shot exposure, the signal STEP.ST. becomes Hi immediately after the exposure of the shot is completed, and the PGR and HI operations are started.

Now, in the case of the PGR operation and the HI operation, the pulse energy tends to momentarily exceed the allowable upper limit and considerably increase as shown in FIG. 5 (A) or FIG. 2 (F). By utilizing this tendency, a method of further shortening the time until the restart of exposure can be considered.

Generally, in the PGR operation, when the pulse energy is determined to be too high by the power monitor, the discharge application voltage is gradually reduced in small steps. For this reason, it is difficult to detect whether or not the light emission is equal to or more than the allowable upper limit value by the emission of one pulse, and to suddenly decrease the discharge applied voltage from the second pulse onward.

Therefore, as shown in FIGS. 2 (F) and 2 (G), the PGR operation on the excimer laser light source side is left as it is, and a variable neutral density filter is further provided on the stepper side to change the attenuation rate of this filter with time. To the time T _P in FIG. 2 (F).
The control is performed so as to substantially match the pulse energy fluctuation characteristics in the above.

This variable neutral density filter gradually decreases the attenuation rate (that is, increases the transmittance) from the point when the pulse energy peaks during PGR operation, so that the original pulse energy before entering the filter falls within the allowable value. When this happens, automatic control is performed so that the attenuation factor becomes zero (the maximum transmittance of the filter).

In this way, even if signal PGR.REQ. Is Hi, exposure can be restarted somewhat earlier. To this end, it is needless to say that the opening / closing timing (SHUT.ST.) of the shutter SH needs to be changed accordingly.

When using a variable neutral density filter for large fluctuations in pulse energy, the shutter SH should be installed after the variable neutral density filter, and control the attenuation rate while monitoring the energy of the pulsed light passing through the variable neutral density filter. And opening of the shutter SH may be executed.

In FIGS. 2 (F) and 2 (G), the time Tm is estimated based on the longest exposure time of one shot. Depending on the number of remaining unexposed shots, wait for the PGR operation and HI operation until the exposure processing of one wafer is completed.
It may be determined whether to start the PGR operation or the like during the processing of a single wafer.

Furthermore, when PGR operation is required, the discharge applied voltage has also reached near the upper limit, but even if the upper limit value is maintained, the pulse energy can maintain the allowable lower limit value or more for a certain number of pulses. The interruption timing of the exposure operation or the like may be determined in consideration of the amount.

In this embodiment, an exposure apparatus for printing a reticle (or mask) pattern on a resist layer of a wafer is illustrated. However, a processing apparatus (laser annealing, laser repair, or the like) using a laser light source of this type may be used. Since a similar problem occurs, a similar effect can be obtained by the same configuration of the present invention.

As described above, the stepper using the projection lens has been described in the present embodiment. However, the present invention can be applied to exposure apparatuses of any other types and types in the same manner. Furthermore, although an excimer using a rare gas halide is used as the laser light source, the same 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.

〔The invention's effect〕

As described above, according to the present invention, the laser light source can execute partial gas exchange or gas injection (replenishment) asynchronously with the sequence of the exposure apparatus main body, and can also prevent the performance of the exposure apparatus from being impaired. is there.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the configuration of an exposure apparatus and a laser light source according to an embodiment of the present invention, FIG. 2 is a chart diagram illustrating an example of the operation of the configuration shown in FIG. 1, and FIG. FIG. 4 is a chart illustrating an operation at the time of execution, FIG. 4 is a chart illustrating an operation at the time of injecting a halogen gas when impurities in the laser chamber increase, and FIG. It is a chart figure. [Explanation of Signs of Main Parts] 10: Excimer laser light source, 12: Control system, 18, 22: Photoelectric element 28: Main condenser lens 30X, 30Y: Reticle alignment system 32X, 32Y: XY stage 34 … Wafer alignment system 40… Control device R… Reticle W… Wafer SH… Shutter M ₃ … Swing mirror PL… Projection lens FM… Reference mark plate

Claims (47)

(57) [Claims] A laser light source requiring a gas maintenance operation; an exposure main body for exposing a sensitive substrate with an image of a mask pattern using the laser light emitted from the laser light source; A control system for instructing the laser light source to perform a gas maintenance operation on the basis of information on a maintenance operation from the apparatus and an operation state of the exposure main body. 2. An exposure apparatus according to claim 1, wherein said laser light source is an excimer laser light source. 3. The exposure apparatus according to claim 1, wherein the information on the maintenance operation is information on gas exchange or gas injection of the laser light source. 4. A control system according to claim 1, wherein when a signal requesting a gas maintenance operation is output from said laser light source as information relating to said maintenance operation, a gas is supplied to said laser light source in accordance with an operation state of said exposure main body. 4. The exposure apparatus according to claim 1, wherein a maintenance operation is commanded. 5. The exposure according to claim 4, wherein the request signal from the laser light source is output when a voltage applied to a discharge electrode inside the laser light source becomes higher than a predetermined level. apparatus. 6. A request signal from the laser light source is required to start a maintenance operation of the gas for a time obtained by adding a predetermined margin to a time required for exposing the sensitive substrate with an image of the pattern of the mask. The exposure apparatus according to claim 4, wherein the output is performed before a time when the exposure is not performed. 7. A time required for exposing the sensitive substrate with an image of the pattern of the mask is a time required for exposing one of a plurality of regions on the sensitive substrate. The exposure apparatus according to claim 6, wherein 8. The method according to claim 6, wherein the time required for exposing the sensitive substrate with the image of the pattern of the mask is the time required for exposing an unexposed area on the sensitive substrate. Exposure apparatus according to the above. 9. The control system instructs the laser light source to perform a gas maintenance operation when the exposure main body is in an operation state in which laser light from the laser light source is not used. The exposure apparatus according to any one of claims 1 to 3. 10. The operation state in which the laser beam is not used is the replacement operation of the sensitive substrate.
3. The exposure apparatus according to claim 1. 11. The exposure apparatus according to claim 9, wherein the operation state without using the laser beam is a positioning operation of the mask or the sensitive substrate. 12. The exposure main unit has an alignment system for detecting an alignment mark on the sensitive substrate, and determines a relative positional relationship between a detection center of the alignment system and a projection center of a pattern image of the mask. The exposure apparatus according to claim 1, wherein detection is performed using laser light from the laser light source. 13. The exposure apparatus according to claim 1, wherein the laser light source is installed outside a chamber that houses the exposure main body. . 14. The apparatus according to claim 1, further comprising an opening / closing shutter in an optical path of the laser beam, wherein the opening / closing shutter is closed when a maintenance operation of the gas is performed.
The exposure apparatus according to any one of claims 4 to 9, or the exposure apparatus according to claim 9. 15. A laser light source requiring a maintenance operation; an exposure main body for performing processing on an object to be processed using laser light emitted from the laser light source; and a laser light source performing a maintenance operation. A control system for causing the exposure main body to execute a processing operation that does not use the laser light from the laser light source when the exposure is performed. 16. The exposure apparatus according to claim 15, wherein the operation that does not use the laser light is an operation of exchanging the object to be processed. 17. The operation without using a laser beam is a positioning operation of the object to be processed.
16. The exposure apparatus according to 15. 18. The exposure system according to claim 15, wherein the control system controls the exposure main body unit to continue the operation state without using the laser light until the output of the laser light is stabilized at a predetermined state. 3. The exposure apparatus according to claim 1. 19. The exposure apparatus according to claim 15, wherein the maintenance operation of the laser light source is gas exchange or gas injection. 20. The exposure apparatus according to claim 15, wherein the maintenance operation of the laser light source is an adjustment for stabilizing the wavelength of the laser light or an adjustment of a discharge applied voltage. 21. An apparatus according to claim 15, further comprising an opening / closing shutter in an optical path of said laser beam, wherein said opening / closing shutter is closed during a maintenance operation of said gas.
3. The exposure apparatus according to claim 1. 22. A laser light source requiring maintenance; an exposure main body for processing an object to be processed using laser light emitted from the laser light source; and information based on maintenance information from the laser light source. A control system for coordinating maintenance of the laser light source and processing operation of the exposure main body. 23. The exposure apparatus according to claim 22, wherein the information on maintenance of the laser light source is a request for gas exchange or gas injection. 24. The exposure apparatus according to claim 22, wherein the control system issues a maintenance command to the laser light source when the exposure main body is in an operation state in which the laser light is not used. 25. The apparatus according to claim 22, wherein the control system causes the exposure main body to execute an operation not using laser light from the laser light source when maintenance is being performed by the laser light source. Exposure apparatus according to the above. 26. The exposure apparatus according to claim 25, wherein the operation without using the laser beam is an operation for replacing the object to be processed. 27. The operation not using a laser beam is a positioning operation of the object to be processed.
26. The exposure apparatus according to 25. 28. The apparatus according to claim 28, wherein the control system determines a time when the processing in the exposure main body is interrupted based on information on maintenance from the laser light source, and instructs the laser light source to perform maintenance. Item 23. The exposure apparatus according to item 22, wherein 29. The control system according to claim 29, wherein after the maintenance of said laser light source is completed, the output of said laser beam is stabilized to a predetermined state, and then the processing in said exposure main body is restarted. 29. The exposure apparatus according to 28. 30. An exposure method for exposing an object to be processed by an exposure main body using laser light from a laser light source requiring maintenance, wherein information on maintenance from the laser light source is checked; Instructing the laser light source to perform maintenance based on an operation state of the exposure main body; after the maintenance of the laser light source, performing exposure of the object using laser light from the laser light source. Exposure method. 31. The exposure method according to claim 30, wherein the information on maintenance of the laser light source is a request for gas exchange or gas injection. 32. The exposure apparatus according to claim 30, wherein when the object to be processed is being exposed by the exposure main body, maintenance is instructed to the laser light source after the exposure of the object to be processed is completed. Method. 33. The information related to maintenance of the laser light source,
31. The exposure method according to claim 30, wherein the exposure method includes energy of laser light of the laser light source and operating conditions of the laser light source. 34. The exposure method according to claim 33, wherein the operating condition of the laser light source is a voltage applied to a discharge electrode inside the laser light source. 35. An exposure method for exposing a sensitive substrate with an image of a pattern of a mask in an exposure main body portion using a laser beam from a laser light source requiring a maintenance operation, wherein the maintenance operation of the laser light source is performed during the maintenance operation. An exposure method, wherein an operation not using the laser beam is performed in an exposure main body. 36. The exposure method according to claim 35, wherein the operation without using the laser beam is an operation for replacing the sensitive substrate. 37. The exposure method according to claim 35, wherein the operation without using a laser beam is an alignment operation of the mask or the sensitive substrate. 38. A laser light source for generating a laser light; an exposure main body for exposing a sensitive substrate with a pattern image of a mask using the laser light from the laser light source; A control system for causing the exposure main body to execute an operation not using laser light from the laser light source. 39. The control system according to claim 39, wherein when the maintenance operation is being performed by the laser light source, the exposure main unit performs an operation not using the laser light from the laser light source. 39. The exposure apparatus according to 38. 40. The exposure apparatus according to claim 38, wherein the operation without using the laser beam is an operation for replacing the sensitive substrate. 41. The exposure apparatus according to claim 38, wherein the operation not using the laser light is an operation of positioning the mask or the sensitive substrate. 42. A laser light source for generating a laser beam; an exposure main unit for processing an object to be exposed using the laser light from the laser light source; and an exposure control system for controlling the operation of the exposure main unit. And a laser control system that controls the operation of the laser light source and outputs a request for a predetermined processing operation of the laser light source to the exposure control system. The exposure control system is requested by the laser control system. An exposure apparatus for determining whether or not the laser light source performs the processing operation. 43. An exposure apparatus according to claim 40, wherein the processing operation required from said laser control system is gas exchange or gas injection of said laser light source. 44. The exposure apparatus according to claim 42, wherein the exposure control system makes the determination based on an operation state of the exposure main body. 45. A laser light source for generating a laser light; a laser control system for controlling the operation of the laser light source; and an exposure main body for processing an object to be exposed using the laser light from the laser light source. An exposure control system for controlling the operation of the exposure main unit and outputting information on the operation state of the exposure main unit to the laser control system, wherein the laser control system is output from the exposure control system An exposure apparatus, wherein an operation of the laser light source is controlled based on an operation state of the exposure main body. 46. The exposure apparatus according to claim 45, wherein the laser control system causes the laser light source to perform adjustment when the exposure main body is in an operation state in which laser light from the laser light source is not used. apparatus. 47. The laser control system, wherein when the exposure main body is in an operation state in which laser light from the laser light source is not used, a shutter of the laser light source is closed to self-oscillate the laser light. 47. The exposure apparatus according to claim 46, wherein: