JP3099815B2 - 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 method using a laser requiring maintenance such as gas exchange and gas charge of an excimer laser or the like as an exposure light source.

[0002]

2. Description of the Related Art 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, as an exposure light source, an excimer laser has been used instead of a mercury lamp which has conventionally been mainstream. Devices have been developed. An excimer laser exposure apparatus is generally composed of an excimer laser light source and an exposure apparatus main body, and at present, 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.

An excimer laser generally encloses a mixed gas of three kinds of gases, such as a halogen gas such as fluorine, an inert gas such as krypton and argon, and a rare gas such as helium and neon, and discharges the halogen in the chamber. The gas reacts with the inert gas 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, when the pulse energy fluctuates, (1) an object to be exposed (a wafer, etc.)
Control accuracy of the energy (exposure amount) reaching the laser beam decreases.
(2) The function of reducing interference fringes on the object to be exposed due to the optical system is reduced. (3) Pulse energy monitor system,
Inconveniences such as a reduction in the S / N ratio of the signal of the photoelectric detection system of the alignment system occur.

[0004] For this reason, the excimer laser monitors the pulse energy that decreases due to the decrease in the halogen gas concentration, feeds it back to the discharge application voltage, and keeps the pulse energy constant by gradually increasing the discharge application voltage. I have to. However, since the discharge applied voltage has an upper limit, when the applied voltage reaches the upper limit, a halogen gas injection (HI: Halogen Injection) operation is performed.
It was necessary to return the halogen gas concentration to an appropriate value, thereby reducing the applied voltage and keeping the pulse energy constant.

FIG. 3 shows the state of the HI operation. FIG.
3A shows the pulse energy emitted from the excimer laser on the vertical axis and the time t on the horizontal axis, and FIG. 3B shows the discharge applied voltage to the electrodes in the laser chamber on the vertical axis. The time t is plotted on the horizontal axis. FIG.
As shown in (A), when the upper limit value and the lower limit value are determined centering on the set value of the pulse energy required on the exposure apparatus side, the excimer laser light source turns on an energy monitor (light receiving element or the like) provided therein. By comparing the magnitude with the set value 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. When the discharge application voltage reaches the upper limit value at time t1, the control processor provided inside the excimer laser light source determines that the HI operation is necessary, and injects a predetermined amount of halogen gas 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. At the subsequent time t2, the HI operation is performed similarly.

The reason for gradually decreasing the discharge applied voltage in this manner is that the gas in the laser chamber is not sufficiently uniformly mixed immediately after the HI operation, and there is a great possibility that the pulse energy varies. For this reason, if the discharge application voltage is rapidly lowered immediately after the HI operation, a disadvantage may occur that the pulsed light is not oscillated and even the power monitor cannot 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. 4A and 4B show the state, and correspond to the graph of FIG. As shown in FIG. 4 (B), the injection period gradually becomes shorter at times t1, t2... T6, and after time t6, the pulse energy gradually decreases despite the discharge applied voltage being at the upper limit. I will do it. As described above, when the effect of the halogen gas injection is lost, or when the effect of the halogen gas injection is reduced to a predetermined condition, the three kinds of mixed gases are partially replaced, that is, a partial gas replacement (PGR) operation is performed. It was necessary to maintain 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. 5A and 5B respectively show FIGS.
(A) and (B) corresponding to time t3, t4, t5
Is the same as that in FIG. 4 and indicates the timing of the HI operation. Then, at time Ta after time t5, the PGR operation is performed. In general, in the PGR operation, first, a part of the gas in the laser chamber is first extracted, so that if pulse emission is performed as it is, the pulse energy once decreases as shown in FIG. 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. HI above
The operation and the PGR operation were almost automatically performed by a command of a control processor in the excimer laser light source.

[0011]

On the other hand, when the excimer laser light source is viewed from the exposure apparatus main body, it is desirable that the pulse energy be constant as described above. It is difficult to make it completely constant due to factors such as partial gas exchange. Therefore, set the allowable value of pulse energy fluctuation to satisfy the function and specification on the exposure apparatus main body side,
The excimer laser side implements various measures so that the pulse energy always reaches the set value.

One of the methods is the HI operation and the PGR operation described with reference to FIGS. 3 to 5, but from the viewpoint of the exposure apparatus, the sections indicated by the times a and b in FIG. However, there is a problem that the pulse energy exceeds the allowable value. 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 the section between the times a and b, that is, the HI operation and the PGR operation occur exclusively by the control of the laser light source.

Therefore, when exposing a wafer by the step-and-repeat method, the HI operation or the PGR is performed during the exposure of one shot area (usually several tens or more pulses are required).
If the operation is performed asynchronously, the exposure of most shots will be greatly damaged up to many shots after the shot area or to the shot area on the next wafer.

Of course, excimer laser light is used for other purposes,
For example, even when used for relative positioning between a reticle (original) and a wafer, an alignment error will occur if an HI operation or a PGR operation occurs during the alignment period. The present invention has been made in view of such a problem, and an exposure apparatus using an exposing method using a laser light source requiring maintenance such as partial gas exchange and partial gas injection, such as an excimer laser light source, is disclosed. Function degradation,
The purpose is to minimize the decrease in accuracy.

[0015]

SUMMARY OF THE INVENTION The present invention provides an exposure method for exposing a sensitive substrate with a mask pattern image using a laser beam from a light source system. Timed. Further, in the present invention, in an exposure method for transferring a pattern onto a substrate using a beam from a beam source, information on maintenance of the beam source is checked before performing a predetermined operation using the beam from the beam source. The maintenance of the beam source is controlled based on the result of the check. The present invention also relates to an exposure method for transferring a pattern onto a substrate using an exposure beam from a beam source, wherein an operation using the exposure beam from the beam source for performing gas exchange or gas injection as maintenance of the beam source. Is interrupted, the exposure information at that time is stored, and the operation using the exposure beam from the beam source is restarted based on the stored exposure information.

[0016]

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. Selective element (diffraction grating, prism, etalon, etc.), spectroscope to monitor absolute value of oscillation wavelength,
A detector for monitoring the laser power, a shutter SH, and the like are provided. Although the HI operation and the PGR operation for the laser chamber are performed by the control system 12, 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 stabilizing the wavelength, control of the 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 M1 and the fixed mirror M2, and is shaped into a predetermined cross-sectional shape and size. The pulse light from the beam shaping optical system 14 is reflected by a swinging mirror M3 that swings within a predetermined angle by a driving unit 16, and then is incident on a fly-eye lens FL functioning as an optical integrator, and a number of secondary light sources are provided. (Spot light). Fly Eye Lens FL
Each spot light of the excimer beam formed on the exit side of each element lens passes through the beam splitters BS1 and BS2, and has a substantially uniform intensity distribution on the reticle blind (illumination field stop) RB by the condenser lens system 24. Are superimposed. Reticle blind RB
The excimer light passing through the lens system 26, the fixed mirror M4,
The circuit pattern area of the reticle R is illuminated via the main condenser lens 28 and the fixed mirror M5. Here, the reticle blind RB is conjugated with the reticle R by the lens system 26 and the main condenser lens 28. Reticle R is a dedicated reticle alignment system 30
It is positioned in the X, Y, and θ directions with respect to the apparatus main body by X, 30Y.

The image of the circuit pattern of the reticle R is reduced and projected on the wafer W by the projection lens PL. Wafer W
Is mounted on the X stage 32X, and the X stage 32
X moves in the X direction on a Y stage 32Y that moves in the Y direction on the base. 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. When the movable mirror M1 retreats from the position shown in the figure, the reference mark plate FM transmits the pulse light from the excimer laser light source 10 to a plurality of mirrors and a Y mirror.
It is arranged to receive from the lower surface via a mirror M6 fixed on the stage 32Y. The excimer beam incident on the mirror M6 is a substantially parallel light beam, parallel to the Y axis, reflected at right angles in the X direction by the mirror M6, and vertically reflected upward by the 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 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)
Since the relative positional relationship between the reticle R and the center of the projected image of the circuit pattern slightly changes each time the reticle R is exchanged, the relative positional relationship can be measured using the reference mark plate FM. It is. For this purpose, via a beam splitter BS2 arranged in the optical path of the illumination system,
The pulse light from the light emitting slit of the reference mark plate FM is partially branched, and is received by a photoelectric element (such as a photomultiplier) 22 through a lens system 20. The light receiving surface of the photoelectric element 22 is arranged almost conjugate with the pupil plane (the entrance pupil or the exit pupil) of the projection lens PL by the lens systems 24, 26, 28 and the like.

On the entrance pupil of the projection lens PL, Koehler illumination is performed by forming images of a large number of secondary light sources formed by the fly-eye lens FL. Now, in the above configuration, there is a partition of a thermal chamber for housing the exposure apparatus (stepper) main body between the movable mirror M1 and the laser light source 10, and the laser light source 10 is installed outside the thermal chamber. Further, the main body of the stepper is controlled by the main controller 40 to move the XY stages 32X and 32Y and to control the reticle alignment system 3.
Positioning of reticle R by 0X and 30Y, position detection of wafer W by wafer alignment system 34, setting of reticle blind RB, checking of a series of relative positional relationships using photoelectric element 22 and reference mark plate FM, beam splitter BS1 Control operation using the photoelectric element 18 that receives a part of the pulse light reflected by the light source, or operation to reduce speckles (interference fringes caused by excimer beam coherence) due to vibration of the vibrating mirror M3, etc. I do.

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 to measure various positions. Used for 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 so that cooperative control can be performed. 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 signal is a signal from the excimer laser light source side to the exposure apparatus main body, and changes the signal level to indicate that the necessity of performing partial gas exchange (PGR operation) or halogen gas injection (HI operation) is imminent (in this embodiment, L0 → Hi) to notify the exposure apparatus main body. Further, it has a function of notifying the exposure apparatus main body that the operation of the partial gas exchange or the halogen gas injection has been completed by changing the signal level from Hi to L0. [Signal STEP. ST. (STEPPER STATU
S)] This is a level signal for instructing the operation mode from the exposure apparatus main body to the excimer laser light source. When L0, the excimer laser light source 10 outputs the EXT. TR
G. FIG. 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 excimer laser light source is a signal PGR. R
EQ. When this signal changes from L0 to Hi while L is set to L0, that is, there is no request to execute partial gas exchange or halogen gas injection to the exposure apparatus body, the excimer laser light source closes the shutter SH at the laser light emission port. And self-oscillates at an appropriate low frequency to lock the pulse energy, the absolute wavelength, and the like. The signal PGR. REQ. Is H
When this signal changes from L0 to Hi at the time of i, the excimer laser light source closes the shutter SH and executes partial gas exchange or halogen gas injection. [Signal SHUT. ST. (SHUTTER STATU
S)] a level signal indicating a shutter position in the excimer laser from the excimer laser light source to the exposure apparatus body;
In this embodiment, the level is Hi when open and L0 level when closed. The timing of changing the level is such that when the shutter SH is closed, the shutter SH is completely closed and then changes from Hi to L0, and when it is opened, the shutter is completely opened and then changed from L0 to Hi. [Signal EXT. TRG. (EXTERNAL TRIG
GER)] is a trigger signal for emitting a laser beam from the exposure apparatus body to the excimer laser light source, and the laser light source emits a laser beam by detecting an edge of this signal. One trigger signal corresponds to one pulse of laser light emission.

As described above, in this embodiment, 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 the present embodiment will be described next, but 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 tens of pulses or more due to the relationship between speckle reduction and exposure amount control accuracy. The speckle reduction is achieved by finely moving the interference fringes in the pitch direction by oscillating laser pulses while deflecting the oscillating mirror M3 by a small angle at a time by using the fly-eye lens FL to deflect the interference fringes on the image plane. , 1
After the exposure of the shot is completed, the contrast of interference fringes on the wafer is practically unaffected (contrast value ± 1
%). In this case, the oscillation angle (half cycle) α of the oscillating mirror M3 required to reduce the contrast of the interference fringes on the image plane (wafer surface) and the number Np of laser pulse lights required between the oscillation angles α Is uniquely determined by experiments and the like.

On the other hand, since the proper exposure amount Ev for one shot is also determined by the type and thickness of the resist,
Number of pulses K · Np required for speckle reduction (K is a natural number that increases by 1 every half cycle of the swing angle α of the oscillating mirror M3)
Average pulse energy E per pulse
It is necessary to set p with a neutral density filter or the like for exposure.
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, and the integrated value of the energy detected by the photoelectric element 18 for each pulse emission in a state where the conditions of the number of pulses K · Np and the deflection angle α are satisfied. May be compared with the target integrated value at that time, and the energy of the next pulse emission may be finely adjusted by a high-speed variable neutral density filter.

As described above, since the number of pulses K · Np required for speckle reduction is determined in advance, 1
During exposure of the shot, the pulse K · Np (K = 1, 2, 3,
..), The average energy Ep of the pulsed light increases from that point on, and the speckle contrast is sufficiently reduced. There is a disadvantage that the proper exposure amount is reached before the operation is performed. In particular, during the PGR operation, the fluctuation amount of the pulse energy becomes large as at the time b in FIG. 5A, which is extremely inconvenient for speckle reduction and exposure amount control.

In the alignment operation using the excimer laser beam, the transmission slit of the fiducial mark plate FM is
The stage is one-dimensionally run in the direction crossing the longitudinal direction of the slit in the projection image plane, the slit image is formed on a transmission slit mark on the reticle R, and the excimer light transmitted through the slit mark is reflected by a mirror M5 and a condenser lens. The projection position of the slit mark on the reticle R is recognized on the moving coordinate system of the XY stage by receiving the light from the photoelectric element 22 through the mirror 28, the mirror M4, the lens systems 26 and 24, and the beam splitter BS2. At this time, the excimer laser light source 10
Signal EXT. Generates a pulse oscillation in response to a measurement pulse from the laser interferometer on the stepper side. TRG. Is output. The laser interferometer has XY stages 32X, 32
Y outputs a measurement pulse (up-down pulse) every time it moves, for example, 0.01 μm. Therefore, main controller 40 appropriately divides this measurement pulse to obtain signal EXT. TRG. make. 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 the order of addresses for each pulse emission. This address uniquely corresponds to the coordinate position of the XY stage.

However, the energy of the excimer laser light is
Since there is 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 captured for each pulse emission, and the level of the photoelectric signal of the photoelectric element 22 is divided. It is necessary to standardize with equipment. Incidentally, the detector for normalization may be provided in the stepper body, and more specifically, the pulse light split by the beam splitter near the mirror M6 on the stage in FIG. 1 may be received. .

With the above operation, the projection position of the slit mark (or the center point of the reticle) of the reticle R becomes XY.
It is defined as the value of the movement coordinate system of the stage. Further, the position of the XY stage when the slit or the like on the fiducial mark plate FM is taken at the detection center of the wafer alignment system 34 is read by a laser interferometer, so that the center of the projected image of the reticle R and the detection center of the wafer alignment system 34 are obtained. Is defined in the moving coordinate system.

During such an alignment operation, in particular, while the photoelectric signal from the photoelectric element 22 is being taken, P
When the GR operation or the like is started, the S / S
There is a disadvantage that the N ratio is reduced and the alignment accuracy is reduced. Next, the operation of this embodiment will be described with reference to FIG. 2 (A), (C), (D),
(E) shows signals STEP. ST, SHUT. S
T, signal EXT. TRG, signal PGR. REQ. FIG. 2B shows the position of the shutter SH in the excimer laser light source 10. 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. 2A, the signal STE
P. ST. Is a period A when L0 indicates normal wafer exposure, and a period B when Hi indicates that the stepper body does not emit a light emission trigger for several seconds or more with respect to the excimer laser light source. For example, a state is shown in which operations such as wafer exchange, reticle alignment by reticle alignment systems 30X and 30Y, and wafer alignment by wafer alignment system 34 are being performed.
In the period A, exposure is repeated for each shot in a step-and-repeat manner for one wafer, and at this time, the signal EXT. Shown in FIG. TRG. Of the trigger pulse trains correspond to one-shot exposure.

When the stepper completes exposure (period A) for one wafer, the signal STEP. ST. (1)
Is changed from L0 to Hi. The excimer laser light source that recognizes this starts closing the shutter SH ((2)),
When the shutter is completely closed, the signal SHUT. ST.
Is set to L0 ((3)), self-oscillation is started at a low frequency of several Hz or less ((4)), and locking (feedback control) of pulse energy, absolute wavelength, and the like is performed. During this time, the stepper body performs the operation (period B) not sending out the above-mentioned light emission trigger, and then outputs the signal STEP. ST. Is changed from Hi to L0 ((5)). The excimer laser light source that recognizes this stops the self-oscillation and then starts opening the shutter SH ((6)). When the shutter is completely opened, the signal SHUT. ST. Is changed from L0 to Hi ((7)). After recognizing this, the stepper body transmits the signal EXT. To start the exposure operation for the next wafer. TRG. Are output as a set of trigger pulse trains S1, S2,. Note that the pulse train S
Between 1 and S2, the XY stages 32X and 32Y are stepped.

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 in which a partial gas exchange (PGR operation) is performed will be described. Before the stepper body starts exposing each shot area on the wafer, the signal PGR. REQ. Is checked, and if it is L0, exposure is performed as in the pulse trains S, S1, and S2 in FIG. 2D. On the other hand, during the transmission of the trigger pulse train S2, that is, during the exposure of the second shot of the second wafer, the excimer laser light source detects that the discharge applied voltage has approached the upper limit ((8)), and The signal PGR. REQ. Is changed from L0 to Hi ((9)). This signal PGR. REQ. Is changed from L0 to Hi is, for example, the longest expected exposure time necessary to expose one shot area.
(Or a time Tm obtained by adding a margin to (or a photoelectric signal capturing time at the time of photoelectric detection using an excimer beam))
The timing may be set before the necessary start time Ta of the partial gas exchange or the halogen gas injection.

Here, during exposure of the second shot area (during transmission of the trigger pulse train S2), the signal PGR. R
EQ. Has changed, the stepper body moves to the next third shot area after the end of the exposure of the second shot.
After the Y stage 32X, 32Y is stepped,
The signal PGR. REQ. Is checked, and the signal PGR. R
EQ. Is Hi ((10)). As a result, the sequence of the stepper body interrupts the start of exposure to the third shot area, and the signal STEP. ST.
Is changed from L0 to Hi ((11)). The excimer laser light source is a signal PGR. REQ. During the signal STEP. S
T. Is changed from L0 to Hi, it is recognized as a partial gas exchange or halogen gas injection start command, and the shutter S
H is closed ((12)) and the signal SHUT. ST from Hi to L
After changing to 0 ((13)), the partial gas exchange is performed while self-oscillating at an appropriate frequency (for example, higher frequency than in (4)) ((14)).

Thereafter, the excimer laser light source monitors the pulse energy. When the pulse energy returns to the allowable value ((15)), the self-oscillation is stopped and the signal PGR. REQ. Is changed from Hi to L0 ((16)). After recognizing this, the stepper body issues a signal STEP. As a command to restart exposure to the excimer laser light source. ST. Is changed from Hi to L0 ((17)). When recognizing this, the excimer laser light source opens the shutter SH ((18)) and outputs the signal SHUT. S
T. Is set to Hi ((19)). After the stepper body recognizes this, the signal EXT. TRG. , And the exposure of the third and subsequent shot areas is started ((20)).

As described above, the PGR operation has been described in the present sequence, but the HI operation is executed in exactly the same manner. Further, when excimer laser light is used in the alignment operation, the signal PGR. REQ. Is monitored, and if it is L0, the photoelectric detection operation is started as it is; if Hi, the excimer laser light source side starts the PGR operation or HI operation, and the stepper side is in the standby state or does not use the excimer laser light. Other operations (wafer replacement, wafer alignment, etc.) are executed with priority.

By the way, in (4) and (14) of FIG. 2D, pulse light is oscillated at a low frequency in a state where the shutter SH is closed. This is because it is necessary to cause the spectroscope inside the excimer laser light source 10 to detect the wavelength change of the oscillation pulse light after the band narrowing. The other is to adjust the discharge application voltage in accordance with the PGR operation and the HI operation, or to set the pulse energy for the next shot S1.
This is because it is necessary to make the power monitor (photoelectric element) provided therein receive the pulse light.

The signal PGR. REQ.
Means interrupting or resuming exposure to the stepper,
The absolute wavelength control of the excimer laser light source 10 and the control of the spectrum half width (narrowing of the band) are performed by using a spectroscope or the like to detect that the stepper exhibits unfavorable behavior during partial gas exchange or halogen gas injection. Is the signal P
GR. REQ. Is set to Hi, the inconvenience can be avoided. Further, the signal PGR. RE
Q. If the sequence being executed by the stepper body is acceptable for the pulse energy fluctuation due to the partial gas exchange or the halogen gas injection, the sequence is interrupted and the shutter SH is executed. Without closing the gas supply, partial gas exchange or halogen gas injection may be executed. In addition, the partial gas exchange request and the halogen gas injection request are set as different signal lines, 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. You may make it.

Incidentally, the shutter SH may be provided on the exposure apparatus main body side. The signal PGR. REQ. In this embodiment, the self-oscillation on the excimer laser light source side is performed when the shutter SH is closed and the partial gas exchange or the halogen gas injection is performed in response to the execution request generated by the shutter SH. Signal (EX
T. TRG. ) May be used to emit light.

By the way, in the sequence shown in FIG.
The stepper side receives the signal PGR. REQ.
Was checked to see if it was Hi or L0. However, in the case of an object to be exposed which requires a long exposure, the signal PGR. REQ.
Has risen to Hi at timing (9) for a certain period of time T
Since the PGR (or HI) operation is started after the lapse of m, the time Tm must be set considerably long.
Increasing the time Tm means that the pulse energy of the laser light decreases from the set value before the PGR and HI operations are started.

Therefore, a timer or the like is provided on the side of the stepper, and during the exposure operation of a certain shot, for example, between the pulse light and the light emission timing of the pulse light, the signal PGR. REQ. Is checked, and if it is at the Hi level, the timer is started to measure the time Tm. And time T
At the end of m, 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 is continued at the end of the time Tm, the exposure operation (irradiation of pulse light) is forcibly interrupted with the accumulated exposure amount, pulse energy (average value) and the like up to that time stored, P
Enter GR and HI operation. 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 shot status signal and the PGR. REQ. By AND (theoretical product) with the signal, the signal STE of FIG.
P. ST. May be set to the Hi level. That is, the shot status signal is set to L0 during exposure of a certain shot, and is set to the Hi level at a timing not using an excimer laser, such as during stepping between shots or during wafer exchange. Therefore, the signal PG
R. REQ. Becomes high during shot exposure,
As soon as the exposure of the shot is completed, the signal STE
P. ST. Becomes Hi, 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 exceed the allowable upper limit instantaneously as shown in FIG. 5A or FIG. By utilizing this tendency, a method of further shortening the time until the restart of exposure can be considered. In general, during the PGR operation, if the pulse energy is determined to be too high by the power monitor, the discharge applied 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. 2F and 2G, 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.
The change over time of the attenuation factor of this filter is shown in FIG.
The control is performed so as to substantially match the pulse energy fluctuation characteristics within the middle time Tp. This variable neutral density filter gradually decreases the attenuation rate (that is, increases the transmittance) from the time when the pulse energy reaches a peak during the PGR operation, so that the original pulse energy before entering the filter falls within an allowable value. When this happens, automatic control is performed so that the attenuation factor becomes zero (the maximum transmittance of the filter).

By doing so, the signal PGR. REQ.
, The 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 provided after the variable neutral density filter to control the attenuation rate while monitoring the energy of the pulsed light passing through the variable neutral density filter. And the shutter SH may be opened.

Incidentally, in FIGS. 2F and 2G, the time T
m was estimated based on the longest exposure time of one shot,
In addition, set the length to allow for the exposure time for several shots,
PGR operation and HI until the exposure processing of one wafer is completed in consideration of the number of remaining unexposed shots on one wafer
It may be determined whether to wait for the operation or to start the PGR operation or the like while processing one wafer.

Further, when the PGR operation is required, the applied voltage of the discharge also approaches the upper limit. However, even if the upper limit value is maintained, the pulse energy must maintain the allowable lower limit value or more for a certain number of pulses. Therefore, 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.

[0048]

As described above, according to the present invention, maintenance of the laser light source can be performed without deteriorating the performance of the exposure apparatus itself.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of an exposure apparatus and a laser light source according to an embodiment of the present invention.

FIG. 2 is a chart illustrating an example of an operation by the configuration shown in FIG. 1;

FIG. 3 is a chart illustrating an operation at the time of executing halogen gas injection.

FIG. 4 is a chart illustrating an operation at the time of injecting a halogen gas when impurities in a laser chamber increase.

FIG. 5 is a chart illustrating an operation at the time of executing a partial gas exchange.

[Explanation of symbols]

 Reference Signs List 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 controller R reticle W wafer SH shutter M3 vibrating mirror PL projection lens FM reference mark plate

Claims (13)

(57) [Claims] 1. An exposure method for exposing a sensitive substrate with a pattern image of a mask using a laser beam from a light source system, wherein a time from when a maintenance request is output from the light source system is measured. Exposure method. 2. The method according to claim 1, wherein said maintenance includes gas exchange or gas injection of said light source system. 3. The method according to claim 1, wherein maintenance of the light source system is started based on a result of the timing. 4. The maintenance of the light source system is started based on an operation state of an exposure main body system for exposing a sensitive substrate with a pattern image of the mask and a result of the clocking. 3. The method according to 3. 5. The method according to claim 4, wherein an operation of an exposure system for exposing the sensitive substrate with a pattern image of the mask is determined based on a result of the timing. 6. The method according to claim 5, wherein the operation of the exposure system is interrupted when a predetermined time has elapsed since the maintenance request was output from the light source system. 7. An exposure method for transferring a pattern onto a substrate using a beam from a beam source, wherein information on maintenance of the beam source is checked before performing a predetermined operation using the beam from the beam source. An exposure method, wherein maintenance of the beam source is controlled based on a result of the check. 8. The method according to claim 7, wherein said predetermined operation includes exposing said substrate. 9. The method according to claim 7, wherein said predetermined operation includes exposing a shot area on said substrate. 10. The method according to claim 7, wherein the predetermined operation includes an alignment operation using the beam. 11. The apparatus according to claim 7, wherein said exposure beam is a pulse beam, and information on maintenance of said beam source is checked each time said pulse beam is emitted.
The method according to any one of 8, 9, and 10. 12. The method according to claim 7, wherein said maintenance includes gas exchange or gas injection of said beam source. 13. An exposure method for transferring a pattern onto a substrate using an exposure beam from a beam source, wherein gas exchange or gas injection is performed as maintenance of the beam source.
When the operation using the exposure beam from the beam source is interrupted, the exposure information at that time is stored. Based on the stored exposure information, the exposure beam from the beam source is used. An exposure method, wherein the operation is restarted.