JP2001042505A - Mask and exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and easily control quantity of exposure light while a mask is mounted. SOLUTION: The mask R having a pattern to be illuminated with exposure light has measurement regions 38a, 38b to be used to measure changes in the quantity of exposure light and to transmit a part of the exposure light. Since the changes in the light quantity can be measured by passing the light in the measurement regions of the mask, it is not necessary to exchange the masks for every measurement. Moreover, the real quantity of exposure light passing the mask can be measured so that the quantity of exposure light can be controlled with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a mask having a pattern to be transferred to a semiconductor device, a liquid crystal display device or the like, and an exposure apparatus for exposing and transferring the pattern of the mask onto a substrate by using photolithography technology.

[0002]

2. Description of the Related Art Generally, when a semiconductor device or a liquid crystal display device is manufactured by using a photolithography technique, a reticle (mask) pattern is coated with a photosensitive agent by reducing or enlarging the pattern directly or at a predetermined magnification. An exposure apparatus that exposes the substrate thus exposed is used. Since an appropriate exposure amount is determined for this photosensitive agent, in a conventional exposure apparatus,
Arrange the beam splitter in the illumination optical system of the exposure light,
By monitoring the amount of exposure light branched by the beam splitter, the amount of exposure on a substrate, for example, a wafer, is monitored. Then, the exposure amount is controlled so that the above-mentioned appropriate exposure amount is obtained according to the monitored result.

[0003] In recent years, as semiconductor devices and the like have been miniaturized, the line width of circuit patterns has also been miniaturized. For this reason, for example, in a reduction projection type exposure apparatus, an exposure apparatus having a larger numerical aperture has been developed, but in order to cope with further miniaturization of semiconductor devices and the like, the wavelength of exposure light is further shortened. There is a need.

Therefore, excimer laser light, which is light having a shorter wavelength, has been employed instead of g-line (wavelength: 436 nm) and i-line (wavelength: 365 nm) exposure light of a mercury lamp that is currently widely used. . Excimer laser light has a different wavelength depending on the type of gas of the oscillation medium of the laser light source. For example, krypton fluoride (Kr
Excimer laser light having a wavelength of 248 nm using F) and a wavelength of 19 using argon fluoride (ArF) as an oscillation medium.
The use of a 3 nm excimer laser beam or the like is being studied.

However, when excimer laser light is used as the exposure light, the optical characteristics (eg, transmittance) of the glass material and the coating film of optical elements such as an illumination optical system and a projection optical system for the exposure light are changed. Has been found to gradually change with irradiation. FIG. 5 shows a time change characteristic of the transmittance of the optical system. As shown in this figure, KrF
In the wavelength range shorter than the wavelength of the excimer laser light,
Immediately after the irradiation of the laser beam, the transmittance of the optical system temporarily decreases.
This is because the transmittance of the optical element itself changes due to the irradiation of the laser beam.

[0006] The transmittance, which has greatly decreased immediately after the irradiation of the laser beam, gradually increases thereafter, and becomes substantially saturated after a certain period of time. This is because so-called light cleaning occurs in which moisture and organic substances attached to the optical element are removed from the surface of the optical element by irradiation with laser light.

On the other hand, a change in transmittance when the exposure processing is interrupted due to a wafer exchange operation or the like is shown by a dashed line in the figure. When the laser beam irradiation is interrupted at time t1, the optical cleaning of the optical element is also interrupted, and the suspended contaminants in the optical system once removed adhere to the surface of the optical element again, or the transmittance of the optical element itself fluctuates. And drop. When the irradiation of the laser beam is restarted at the time t2, the optical element is optically cleaned again and the transmittance increases. Thus, when excimer laser light is used as the exposure light, the transmittance of the optical element fluctuates even in a short time.

Accordingly, the ratio between the light amount (energy amount) of the excimer laser light branched by the beam splitter and the light amount of the excimer laser light reaching the wafer also varies, and it is assumed that this ratio is constant. When the above exposure amount control is performed, the difference between the actual exposure amount and the appropriate exposure amount may exceed a predetermined allowable value. In order to avoid such a problem, there is known an exposure apparatus that corrects the sensitivity of a light amount monitor in an illumination optical system by using a second light receiving element disposed near a wafer.

[0009]

However, the above-described conventional mask and exposure apparatus have the following problems. When correcting the sensitivity of the light amount monitor in the illumination optical system, the reticle (mask) actually used for exposure
Needs to be replaced with a dedicated test reticle having a pattern for sensitivity correction, or the reticle needs to be removed from the reticle stage. However, if the sensitivity correction of the light amount monitor is frequently performed in response to the fluctuation of the transmittance even in a short time as described above, the production efficiency decreases.
The timing of the correction has been practically limited when the reticle is replaced.

Therefore, as a technique for solving this problem,
For example, JP-A-9-96908 is disclosed.
According to this technique, a reticle stage for holding a reticle is provided with a transmission portion through which exposure light is transmitted, so that the amount of exposure light transmitted through the transmission portion can be reduced without changing or removing the reticle. It is possible to monitor with.

However, although the wafer is irradiated with the exposure light transmitted through the reticle, the above technique monitors the exposure light not transmitted through the reticle. Since the amount of exposure light reaching the wafer differs between the case where light passes through the reticle and the case where light does not pass therethrough, there is a problem that accurate exposure amount control cannot be performed only by monitoring exposure light that does not pass through the reticle.

It is conceivable to monitor the amount of light by transmitting the exposure light to a reticle actually used for exposure. However, since the pattern formed for each reticle is different, depending on the pattern at the place where the light is transmitted, the reticle may be exposed. The amount fluctuates. Further, as in the case of a reticle for forming a contact hole, the pattern area may be shielded from light over substantially the entire surface, and it is not easy to monitor the exposure light transmitted through the reticle.

Further, in the above technique, since the reticle stage needs to be moved so that the transmitting portion is located in the optical path of the exposure light, the moving stroke of the reticle stage must be increased, which results in an increase in size and height of the apparatus. There was also the problem of inviting price increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a mask capable of performing exposure amount control accurately and easily with a mask mounted thereon without increasing the stage movement stroke. An object of the present invention is to provide an exposure apparatus.

[0015]

In order to achieve the above object, the present invention employs the following structure corresponding to FIGS. 1 to 4 showing an embodiment. The mask of the present invention is a mask (R) having a pattern illuminated with exposure light.
In the measurement area (38a, 38b, 40a-4), which is used for measuring the change in the amount of exposure light and through which a part of the exposure light passes.
0f).

Therefore, in the mask of the present invention, even if the pattern is different for each mask (R), a part of the exposure light used for the light quantity change measurement is measured in the measurement area (38a, 38a, 38b, 40a to 40f). The measurement area (38a,
38b, 40a to 40f) are set outside the pattern region (36), so that the exposure light is transmitted even when the light is shielded over almost the entire surface of the pattern region (36) like a mask for forming a contact hole. can do. In this case, by setting the measurement areas (38a, 38b, 40a to 40f) on both sides of the pattern area (36), the measurement areas (38a, 38b,
40a to 40f), the exposure light can be transmitted. Further, it is preferable to set the measurement area (38a, 38b, 40a to 40f) near the center of the pattern area (36) because measurement can be performed near the center of the optical system. Measurement area (3
8a, 38b, 40a to 40f) in the pattern area (3
By setting a plurality of values along 6), it is also possible to perform measurement by averaging the amounts of exposure light transmitted through the respective measurement areas (38a, 38b, 40a to 40f).

Further, the exposure apparatus of the present invention provides a mask stage (23) for holding a mask (R) having a pattern.
And an illumination optical system that illuminates the mask (R) with the exposure light, and wherein the mask stage (23) is configured to transfer a pattern of the mask (R) to the substrate (W). The mask (R), wherein the mask (R) according to any one of claims 1 to 5 is held, the first light receiving means (15) receiving a part of exposure light illuminating the mask (R), and the mask (R). A second light receiving means (33) for receiving the exposure light transmitted through the measurement area, a first light receiving means (15) and a second light receiving means (15).
And a light quantity correcting means (16) for correcting the light quantity of the exposure light based on the output signal of the light receiving means (33).

Therefore, in the exposure apparatus of the present invention, the mask (R) is moved in the optical path of the exposure light by moving the mask stage (23).
Are positioned so that even if the mask (R) is mounted on the mask stage (23), a part of the exposure light is masked (R).
Can be transmitted. Then, the light amount correction means (1
6) exposure light for illuminating the mask (R) and measurement areas (38a, 38b, 40a to 40f) of the mask (R)
The amount of exposure light can be corrected based on the exposure light that has passed through.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a mask and an exposure apparatus according to the present invention will be described with reference to FIGS. Here, a description will be given using an example in which the substrate is a wafer for manufacturing a semiconductor device, and the exposure apparatus is a scanning type exposure apparatus that scans and exposes the reticle pattern onto the wafer by synchronously moving the reticle and the wafer.

FIG. 2 is a schematic structural view of the exposure apparatus 1 according to the present invention. As shown in this figure, a laser light (exposure light) as a substantially parallel light beam is emitted from an ArF excimer laser light source 3 provided outside the exposure apparatus main body 2 and oscillating a pulse light having an output wavelength of, for example, 193 nm. Is guided to the light transmission window 5 on the side of the exposure apparatus main body 2.

Here, the exposure apparatus main body 2 includes a chamber 6
And is controlled so that the temperature is kept constant. The laser beam that has passed through the light transmission window 5 is shaped into a laser beam having a predetermined cross-sectional shape by a beam shaping optical system 7, and a plurality of ND filters provided on a turret plate TP having different transmittances (light reduction ratios) from one another. (In FIG. 2, ND1)
, And is reflected by a reflection mirror 8 and guided to a fly-eye lens 9 as an optical integrator. The fly-eye lens 9 is configured by bundling a large number of lens elements, and on the exit surface side of this lens element, a large number of light source images (secondary light sources) corresponding to the number of lens elements constituting the lens element are provided. It is formed.

The turret plate TP holds six ND filters ND1 to ND6 (only ND1 and ND2 are shown). When the turret plate TP is rotated by the motor 35, the six ND filters are selectively illuminated. It is arranged in the optical system. The ND filters ND1 to ND6 are used to determine the sensitivity of the resist
The number of pulse lights (the number of exposure pulses) to be applied to one point on the wafer W during scanning exposure is determined by the variation in the oscillation intensity of the light source 3 and the control accuracy of the exposure amount (exposure dose) on the wafer W. ) Is selected as appropriate. The number of exposure pulses is such that one point on the wafer W corresponds to an illumination area on the reticle R defined by the variable field stop (reticle blind) 10 and a conjugate area with respect to the projection optical system 11 in the scanning direction (synchronous movement direction). It is expressed by the number of pulsed lights radiated to one point while traversing along.

In place of the turret plate TP shown in FIG. 2, for example, two plates each having a plurality of slits are arranged to face each other, and the two plates are relatively moved in the direction in which the slits are arranged, so that pulsed light is emitted. The strength may be adjusted.

The light source 3 oscillates pulsed light in response to a trigger pulse sent from a light source control circuit (not shown), and the light source control circuit adjusts a voltage applied to the light source 3 (charging voltage). The intensity of the pulse light emitted from the light source 3 is adjusted. In the present embodiment, the reticle R, that is, the wafer W, is adjusted by at least one of the adjustment of the oscillation intensity of the light source 3 by the light source control circuit and the adjustment of the transmittance (dimming rate) of the pulse light by the turret plate TP. , The intensity of the pulse light, that is, the integrated light amount can be adjusted. The light source control circuit controls the light source 3 in accordance with a command from a main controller (light amount correction unit) 16 that controls the entire exposure apparatus 1.

At the positions of a number of secondary light sources formed by the fly-eye lens 9, a turret plate 12 having a plurality of aperture stops having different shapes and sizes from each other is provided. The turret plate 12 is rotatably driven by a motor 13, and according to the pattern of the reticle R to be transferred onto the wafer W,
One of the aperture stops is selected and inserted into the optical path of the illumination optical system. Turret plate 12 and motor 1
Reference numeral 3 denotes a variable aperture stop for an illumination system.

The light beam from the secondary light source formed by the fly-eye lens 9 passes through the variable aperture stop of the turret plate 12, is split into two light paths by the beam splitter 14, and the reflected light as a part of the light beam is The light is received by the integrator sensor (first light receiving means) 15 and the illuminance (intensity) of the illumination system is detected. The integrator sensor 15
Are arranged on a plane conjugate with the wafer W. The signal S1 corresponding to the detected illuminance is input to the main controller 16.

On the other hand, the transmitted light transmitted through the beam splitter 14 is reflected by a reflection mirror 19 through a relay lens 17, a variable field stop 10 defining a rectangular aperture, and a relay lens 18, and then is reflected by a plurality of lenses. The light is condensed by a condenser optical system 20 composed of a refractive optical element. As a result, the illumination area on the reticle R defined by the opening of the variable field stop 10 is illuminated almost uniformly in a superimposed manner. Then, the image of the circuit pattern on the reticle R is formed on the wafer W by the projection optical system 11, the resist applied on the wafer W is exposed, and the circuit pattern image is transferred onto the wafer W.

The variable field stop 10 is controlled by the motor 21.
By moving at least one of the blades, the shape and size of the rectangular aperture of the variable field stop 10 can be changed. In particular, by changing the width of the rectangular opening in the short direction, the width of the illumination area on the reticle R in the scanning direction changes. This makes it possible to adjust the integrated light amount (exposure dose) of a plurality of pulsed lights irradiated to one point on the wafer W by the scanning exposure. Also, by changing the scanning speed of the wafer W and the reticle R, it is possible to adjust the integrated light amount of the pulse light applied to one point on the wafer W during the scanning exposure. this is,
This is because the number of pulsed lights applied to one point on the wafer W changes while the point crosses the projection area conjugate to the illumination area of the reticle R along the scanning direction.

That is, in the present exposure apparatus 1, the intensity of the pulse light on the wafer W is adjusted by changing at least one of the oscillation intensity of the light source 3 and the transmittance (dimming rate) of the pulse light, or The width of the pulse light on the wafer W in the scanning direction,
By changing at least one of the transmission frequency of the light source 3 and the scanning speed of the wafer W to adjust the number of pulsed lights applied to each point on the wafer W, the wafer W exposed with the pattern image of the reticle R The integrated light amount of the pulse light applied to each point in the upper region can be controlled to an appropriate value according to the sensitivity of the resist on the wafer W.

As shown in FIG. 1, a pattern area 36 for forming a pattern (not shown) to be transferred to the wafer W is set on the reticle R.
A light-shielding band 37 for blocking exposure light is formed of Cr or the like around the periphery. Outside the pattern area 36, rectangular measurement areas 38a and 38b in a plan view through which a part of the exposure light passes are located on both sides of the pattern area 36 in the scanning direction (vertical direction in FIG. 1). Set to a specific location. The measurement areas 38a and 38b are used for measuring the change in the amount of exposure light, and are set near the center of the pattern area 36 in the non-scanning direction (the horizontal direction in FIG. 1).

When the light-shielding portion is entirely formed outside the pattern region 36, the measurement regions 38a and 38b are set so that the exposure light can be transmitted by removing the light-shielding portion at the specific position. You. When the entire area outside the pattern area 36 is not a light-shielding portion as in the present embodiment, the measurement areas 38a and 38b are set as virtual areas.

On the other hand, outside the pattern area 36, the reticle alignment marks 3 used at the time of alignment are located on both sides of the pattern area 36 in the non-scanning direction.
9 to 39 are formed respectively. And
Above the reticle R, a reticle alignment system (not shown) for detecting the reticle alignment marks 39... 39 is provided.

The reticle R is held and fixed to a reticle stage (mask stage) 23 by a reticle holder 22. The reticle stage 23 has a pattern area 3
A through hole 23a (only a part is shown) is formed so that the exposure light transmitted through 6 and the measurement regions 38a and 38b can pass therethrough. The reticle stage 23 is provided on the base 24 so as to move along a plane orthogonal to the plane of FIG. A movable mirror 25 is arranged on the reticle holder 22. The position of the reticle stage 23 is measured when the laser light emitted from the laser interferometer 26 is reflected by the movable mirror 25 and enters the laser interferometer 26.
The measured position information is input to the main controller 16. The main controller 16 drives the reticle stage driving motor 27 based on the input position information, and the position of the reticle R and the reticle R during the scanning exposure.
Is controlled.

The wafer W is held and fixed on a wafer stage 29 by a wafer holder 28. The wafer stage 29 is provided so as to move along a plane orthogonal to the plane of FIG. A movable mirror 30 is provided on the wafer stage 29. The position of the wafer stage 29 is
The laser light emitted from the laser interferometer 31 is
Is measured by being reflected by and entering the laser interferometer 31. The measured position information is transmitted to the main controller 16.
Is input to The main controller 16 drives the wafer stage driving motor 32 based on the input position information to control the position of the wafer W, the speed of the wafer W during scanning exposure, and the like.

On the wafer stage 29, an illuminance sensor (second light receiving means) 33 composed of a photoelectric conversion element and an irradiation amount monitor 34 are provided so that the light receiving surface thereof substantially coincides with the surface of the wafer W. . Illuminance sensor 33
Is for detecting the illuminance of the exposure light applied to the wafer W and specifically detecting the exposure energy per unit area, and is provided at two places corresponding to the measurement areas 38a and 38b. I have. A signal corresponding to the illuminance detected by the illuminance sensor 33 is output to the main controller 16. The irradiation amount monitor 34 detects the total energy amount of the exposure light, and a detected signal is output to the main controller 16. When the illuminance sensor 33 is arranged corresponding to one of the measurement areas 38a and 38b and receives the exposure light passing through the other of the measurement areas 38a and 38b, the illuminance sensor 33 is moved via the stage 29. It should be done.

The operation of the reticle (mask) and the exposure apparatus having the above configuration will be described. First, the illuminance sensor 33 is calibrated using the irradiation amount monitor 34 in advance. Specifically, the irradiation amount monitor 34 is moved on the optical axis of the projection optical system 11 while the reticle R is not set on the reticle stage 23, and the laser light source 3 is driven. Then, the exposure light from the laser light source 3 is applied to the beam splitter 14.
At the same time, the integrator sensor 15 receives the light and measures its output signal S1. At the same time, the irradiation amount monitor 34 receives the exposure light transmitted through the projection optical system 11 and measures the output signal S2. Next, the coefficient α is set so that the measured signals S1 and S2 satisfy the following equation. S1 × α = S2 Further, the illuminance sensor 33 is moved on the optical axis of the projection optical system 11, and the output signal S3 is measured by receiving the exposure light. Then, the calibration of the illuminance sensor 33 is completed by adjusting the gain of the output signal S3 of the illuminance sensor 33 using the above-mentioned coefficient α so that the following equation is satisfied. S1 × α = S3

Note that this calibration procedure is merely an example, and the output signal S1 is compared with the fixed coefficient α and the output signal S2.
After adjusting the gain of the illuminance sensor 33, the gain of the output signal S3 of the illuminance sensor 33 is adjusted with reference to the output signal S1, or the output signal of the illuminance sensor 33 is firstly used by using the output signal S2 using a fixed coefficient α. And then adjust the gain of the output signal S1 of the integrator sensor 15 with reference to the output signal S2.

When the calibration of the illuminance sensor 33 is completed, the illuminance sensor 33 is used to measure the illuminance unevenness on the wafer W. Specifically, the illuminance sensor 33 scans the entire projection area of the projection optical system 11 by driving the wafer stage 29. At that time, the illuminance sensor 3
Read the coordinates of 3. At the same time, exposure light emitted from the laser light source 3 is received by the integrator sensor 15 and the illuminance sensor 33. The main controller 16 calculates a ratio LW / L1 between the output L1 of the integrator sensor 15 and the output LW of the illuminance sensor 33, and stores the ratio in a format corresponding to the coordinates.

Next, the reticle R on which the pattern to be transferred is formed is transported and placed on the reticle stage 23 by a reticle loading mechanism (not shown).
At this time, the reticle alignment mark 39 is detected by the reticle alignment system so that the reticle R is set at a predetermined position, and the position of the reticle R is set by a reticle position control circuit (not shown) based on the detection result.

Subsequently, before the exposure step is started, a transmittance time change prediction straight line (transmittance time change characteristic) of the projection optical system 11 as shown by reference numeral C1 in FIG. 3 is calculated. FIG.
5 is a graph in which the horizontal axis represents exposure time and the vertical axis represents transmittance. The transmittance shown in FIG.
From the beam splitter 14 that splits the exposure light to the wafer W
This is the transmittance of an optical system up to the surface (hereinafter, referred to as a transmittance measurement optical system).

First, the reticle stage 23 and the wafer stage 29 are moved and the measurement area 38 of the reticle R is moved.
a, 38b and the illuminance sensors 33, 33, which are closer to the optical axis of the projection optical system 11 (referred to as 38a and 33), are positioned on the optical axis of the projection optical system 11, and the laser light source 3 is driven.
For example, idle driving of 20,000 pulses is performed. This allows
A part of the exposure light emitted from the laser light source 3 is input to the integrator sensor 15, and the other part is transmitted to the transmittance measurement optical system and the measurement area 38 a of the reticle R and input to the illuminance sensor 33. Here, for example, the integrator sensor 15 and the illuminance sensor 33 are synchronized with the first pulse.
1 and 2 respectively receive the exposure light and capture the illuminance.
At this time, the ratio LW / L1 of the output L1 of the integrator sensor 15 and the output LW of the illuminance sensor 33 is calculated.
This is the transmittance P0 at the start of exposure in FIG.

Next, for example, in synchronism with the 200001-th pulse, the integrator sensor 15 and the illuminance sensor 33
And the exposure light is received, and its illuminance is captured. At this time, the ratio LW / L1 of the output L1 of the integrator sensor 15 and the output LW of the illuminance sensor 33 is calculated.
This is the transmittance P1 at the exposure time t1 in FIG.

The moisture and organic substances adhering to the surface of the transmittance measuring optical system including the projection optical system 11 are peeled off from the lens surface by the light cleaning effect by the idle firing of the laser pulse, and the transmittance of the transmittance measuring optical system is changed. Is improved, and the transmittance P1> P0. By connecting these two transmittances P0 and P1 with a straight line, a transmittance time change prediction straight line C1 can be calculated. This straight line C1 is stored as a linear function,
Alternatively, it is stored as a table of the transmittance with respect to the exposure time. Note that the above calculation and storage are performed by the main controller 16.

When the transmittance time change line C1 is determined,
The first wafer W is opposed to the optical axis of the projection optical system 11. A resist, which is a photosensitive agent, is previously applied to the surface of the wafer W. In this state, the wafer W is transported by a wafer loading mechanism (not shown), and
It is installed at an upper predetermined position, for example, based on the outer diameter. The wafer W is aligned and held and fixed on the wafer stage 29.

Thereafter, the pattern on the reticle R is selectively illuminated by the variable field stop 10 with, for example, slit-shaped exposure light extending in the non-scanning direction, and the reticle stage 2
3 moves the reticle R relative to this illumination area. At the same time, the wafer W
Is moved relative to the projection area conjugate to the illumination area with respect to the projection optical system 11. In other words, the reticle R and the wafer W are synchronously moved in the scanning direction with respect to the exposure light. Thereby, the pattern formed on reticle R is sequentially transferred to the projection area on wafer W.

At the start of the above-mentioned exposure, the reticle R has a constant speed after the run-in, and the variable field stop 10 is opened immediately before the pattern area 36 of the reticle R reaches the illumination area, so that a predetermined area on the reticle R is illuminated. Upon completion of the exposure, when the light-shielding band 37 of the reticle R reaches the illumination area, the variable field stop 10 closes to shield the exposure light.

Here, when the exposure is started, the main controller 16 controls the integrator sensor 15.
Of the output L1 of the illuminance sensor 33 to the output L1 of the illuminance sensor 33 (LW /
L1) is multiplied by a predetermined coefficient K1 to calculate a gain G1. During the exposure operation, the integrator sensor 15
Is multiplied by the gain G1 to output the estimated actual illuminance L on the wafer W. This gain G1 is set as an optimal value when there is no change in transmittance.

The estimated actual illuminance L is further multiplied by a gain G2 to calculate the estimated actual illuminance LC on the corrected wafer W. The gain G2 is calculated by calculating the transmittance from the elapsed time from the start of exposure and the stored transmittance time change prediction straight line C1, and multiplying the obtained transmittance by a predetermined coefficient K2. It is assumed that a pattern image is projected on the wafer W between the time points t1 and t2 in FIG.
Is used from the transmittance time change prediction line C1 based on the elapsed time (exposure time) during the exposure. The main controller 16 calculates a deviation between a preset target illuminance on the wafer W and the calculated estimated actual illuminance LC, and corrects the deviation by using a laser light source control circuit via a light source control circuit. The oscillation intensity of No. 3, that is, the light amount is adjusted. Thus, it is possible to predict the time change characteristic of the light amount with respect to the exposure light, and correct the light amount based on the prediction result.

When the exposure to the predetermined projection area on the first wafer W is completed at time t2 in FIG. 3, as described above,
The reticle R is moved by moving the reticle stage 23 and the wafer stage 29 while closing the variable field stop 10.
Of the measurement areas 38a and 38b and the illuminance sensors 33 and 33, the one closer to the optical axis of the projection optical system 11 (referred to as 38b and 33) is positioned on the optical axis of the projection optical system 11. And
By the same procedure as described above, the transmittance P2 is calculated and stored from the ratio LW / L1 of the output L1 of the integrator sensor 15 and the output LW of the illuminance sensor 33 at the time t2, and the transmittance P1 at the time t1 and the time t2 are calculated. To calculate the transmittance time change prediction straight line C2.

Next, the wafer W is exchanged by the wafer loading mechanism, and when the second wafer W is set at a predetermined position on the wafer stage 29, exposure of the wafer W is started. For this exposure, similarly to the first exposure, the transmittance is calculated from the elapsed time from time t2 to t3 based on the transmittance time change prediction line C2, and the gain G2 calculated from this transmittance is used. Thus, the exposure amount is controlled.

In the case of the second and subsequent transfer of the pattern to the wafer W, since the pattern exists on the wafer W, the mark attached to the previously transferred pattern is measured by a wafer alignment system (not shown). By doing so, the positions of the reticle stage 23 and the wafer stage 29 are controlled such that the pattern to be transferred has a predetermined positional relationship with respect to the pattern previously transferred on the wafer W.

When exposing the third and subsequent wafers W, a transmittance time change prediction straight line is calculated in the same procedure as that for the second wafer W. , For example, the transmittance time change prediction line C
1, a transmittance time change prediction straight line may be calculated from the change in the slope of C2. That is, the next prediction line may be obtained by calculation from the change in the slopes of the two previous prediction lines.

In the mask and exposure apparatus of the present embodiment, the exposure light is transmitted through the measurement areas 38a and 38b set on the reticle R. Therefore, when the illuminance sensor 33 measures the amount of light, In addition to eliminating the need for replacement, it is also possible to measure the amount of exposure light that has actually passed through the reticle R, and to perform highly accurate exposure control. Therefore, the light quantity measurement can be performed frequently, and the target illuminance on the wafer W can be easily and reliably maintained even if the transmittance of the transmittance measurement optical system changes due to the optical cleaning. Also, the reticle stage 23 originally has a stroke for approaching, and if the measurement areas 38a and 38b are provided on the reticle R,
Since the exposure light can be transmitted through the measurement areas 38a and 38b within this stroke, it is not necessary to make the stroke unnecessarily large, and it is possible to prevent the apparatus from becoming large and expensive.

In the mask and exposure apparatus of the present embodiment, since the measurement areas 38a and 38b are set outside the pattern area 36, the pattern area is almost entirely formed like a reticle for forming a contact hole. , The light amount of the exposure light can be surely corrected without interfering with the measurement of the light amount by the illuminance sensor 3.

Further, in the mask and exposure apparatus of the present embodiment, the measurement areas 38a and 38b are
Is set on both sides in the scanning direction with respect to the reticle stage 23 after scanning exposure, it is possible to select a measurement area close to the optical axis of the projection optical system 11 even when the reticle stage 23 is moved to measure the amount of light. Therefore, the moving distance of the reticle stage 23 can be shortened, and the tact time of the exposure process can be increased. In addition, the measurement area 38a,
Since 38b is set at the center of the pattern area 36 in the non-scanning direction, it is possible to measure the amount of exposure light transmitted through the vicinity of the center, which is most important in the projection optical system 11, and to achieve a more accurate exposure Control is realized. Note that the same result can be obtained even when only one of the measurement areas 38a and 38b is used.

In addition, in the mask and the exposure apparatus according to the present embodiment, the time change characteristic of the light quantity of the exposure light is predicted by calculating the transmittance time change prediction line, and the light quantity is corrected based on the prediction result. Therefore, the wafer W can be properly exposed even if the transmittance of the transmittance measurement optical system of the illumination optical system or the projection optical system 11 changes during exposure or when the apparatus is stopped. For example, the illuminance on the wafer W can be corrected to an appropriate value, and the integrated light amount (exposure dose) of the exposure light on the wafer W can always be corrected to an appropriate value according to the sensitivity of the wafer W.

FIGS. 4 and 5 are views showing a mask and an exposure apparatus according to a second embodiment of the present invention. In these figures, the same components as those of the first embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted. The difference between the second embodiment and the first embodiment is the configuration of the measurement area on the reticle R and the method of calculating the transmittance.

That is, as shown in FIG.
Outside the pattern region 36, the measurement regions 40a to 40c are located on both sides in the scanning direction with the pattern region 36 interposed therebetween.
And 40d to 40f are set in the non-scanning direction along the pattern area 36, respectively. Measurement area 40b, 4
0e are arranged near the center of the pattern area 36 in the non-scanning direction. Measurement areas 40a, 40c, 40
d and 40e are respectively arranged near the end of the pattern area 36 in the non-scanning direction. Also, the wafer stage 29
Are provided with six illuminance sensors 33... 33 corresponding to the measurement areas 40a to 40f, respectively.

On the other hand, the main controller 16
Is a table corresponding to the exposure condition obtained by combining the transmittance time change characteristic as indicated by the solid line with the pattern type of the reticle R, the illumination condition according to the type of the reticle R, and the numerical aperture of the projection optical system 11. It is measured and stored in advance. Other configurations are the same as those of the first embodiment.

In the reticle and the exposure apparatus having the above-described structures, the table according to the set exposure condition is referred to.
The transmittance is read based on the elapsed time from the start of the exposure operation. Then, using this transmittance, the light amount of the laser light source 3 is adjusted in the same procedure as in the first embodiment.

When the amount of exposure light is measured each time the wafer W is replaced, the reticle stage 23 and the wafer stage 29 are moved to measure the reticle measurement area 40a.
To 40c, 40d to 40f and illuminance sensors 33 ... 33
Of which is closer to the optical axis of the projection optical system 11 (40a-40
c, 33... 33) on the optical axis. Then, the exposure light emitted from the laser light source 3 is received by the integrator sensor 15 and the measurement area 40 a
The light is received by the illuminance sensors 33... Next, by averaging the outputs of the respective sensors, it is possible to obtain a light amount in which the influence of distortion or the like of the optical element is reduced.

Then, the transmittance of the transmittance measuring optical system is calculated from these light amounts, and the transmittance is referred to the transmittance time change curve set in the table. If the transmittance obtained from this curve is different from the transmittance actually measured and calculated, the curve set in the table is offset-corrected and stored so that the calculated transmittance is positioned on the curve. I do. Thereafter, the transmittance is read from the offset-corrected curve and used until the next light quantity measurement.

In the mask and the exposure apparatus of the present embodiment, the same effects as those of the first embodiment can be obtained, and the optical element can receive the exposure light transmitted through the plurality of measurement areas 40a to 40c. In this case, the amount of light in which the influence of distortion or the like is reduced can be obtained, and more accurate exposure amount control can be performed. Further, since the transmittance change during the exposure is stored in the table in advance, the transmittance corresponding to the elapsed time can be quickly determined.

In the above embodiment, the measurement areas 38a, 38b, and 40a to 40f are set outside the pattern area 36. However, the present invention is not limited to this. If it is possible and at a specific position determined in advance, it may be set inside the pattern area 36. In this case, the exposure light does not need to pass through the entire measurement area, and a part of the pattern may be included in the measurement area.

The measurement areas 38a, 38b, 40a-
Although 40f is set on both sides in the scanning direction with the pattern region 36 interposed therebetween, it may be set on only one side, and if the moving stroke of the reticle stage 23 in the non-scanning direction is secured, it may be provided on both sides in the non-scanning direction. You may.
Also, it is not always necessary to set near the center in the non-scanning direction, and it may be set near the end. When a plurality of settings are made in the non-scanning direction, the setting is not limited to three, but may be a setting of two or four or more. When the projection optical system 11 is a so-called multi-lens system using a plurality of projection lenses, setting a measurement area for each projection lens enables more accurate exposure amount control.

In the above embodiment, the time t0
Although the idle firing of 20001 pulses is performed during the period from to t1, the number of pulses is not limited to 20001 pulses. In addition, the transmittance is predicted by calculating the transmittance time change prediction line by connecting the two transmittances at the time points t0 and t1 and the time points t1 and t2. However, even if three or more transmittances are used. Good. The approximation method is not linear approximation,
A regression line or regression curve that does not directly connect the calculated transmittance may be used. In addition, any method such as polynomial approximation, power approximation, and modified exponential approximation may be used.

In the above embodiment, the oscillation intensity of the laser light source 3 is adjusted in order to correct the deviation between the target illuminance and the estimated actual illuminance. However, the present invention is not limited to this. As described above, the turret plate TP To adjust the transmittance of the laser light source 3 for the pulse light, or the width of the pulse light on the wafer W in the scanning direction, the transmission frequency of the laser light source 3, the wafer W
By changing at least one of the scanning speeds of the laser light and adjusting the number of pulsed lights applied to each point on the wafer W, the integrated light amount of the exposure light applied to the wafer W can be reduced. It may be controlled to an appropriate value according to the sensitivity.

On the other hand, in the above-described embodiment, in order to improve the throughput, the sequence in which the exposure amount is measured by the illuminance sensor 33 every time when the wafer W is replaced, but the transmittance fluctuates greatly during the exposure. If it is not negligible, the exposure amount is measured for each shot even for one wafer W in order to perform the exposure amount correction with higher accuracy.
Depending on the type of light source, the exposure amount may be measured for each pulse. Further, in order to perform the exposure amount measurement, the illuminance sensor 33 for measuring the illuminance unevenness is commonly used.
A configuration in which a sensor for measuring the amount of exposure is separately provided may be employed.

Further, when the transmittance of the projection optical system 11 does not fluctuate or is small, it is only necessary to determine the time-dependent characteristics of the transmittance of the illumination optical system only. In this case, the illuminance sensor 33 is disposed on the reticle stage 23, and the transmittance is measured based on the output values of the integrator sensor 15 and the illuminance sensor 33. Conversely, when the transmittance of the illumination optical system does not fluctuate or is small, the time change characteristic of the transmittance of only the projection optical system 11 may be obtained. In this case, the illuminance may be measured by splitting the exposure light from between the illumination optical system and the projection optical system 11.

Although the variable field stop 10 is used as a means for blocking the exposure light illuminated on the reticle R, the present invention is not limited to this. For example, a shutter is provided between the laser light source 3 and the chamber 6 and the shutter is provided. The exposure light may be blocked or released by opening and closing.

The substrate of the present embodiment is not limited to a semiconductor wafer for a semiconductor device, but also a glass plate for a liquid crystal display device, a ceramic wafer for a thin film magnetic head, or a mask or reticle used in an exposure apparatus. (Synthetic quartz, silicon wafer) and the like are applied.

As the exposure apparatus 1, only a step-and-scan type scanning projection exposure apparatus (US Pat. No. 5,473,410) for exposing the pattern of the reticle R by synchronously moving the reticle R and the wafer W, a so-called scanning stepper However, the present invention can also be applied to a step-and-repeat type exposure apparatus (stepper) that exposes the pattern of the reticle R while the reticle R and the wafer W are stationary and sequentially moves the wafer W stepwise. The adjustment of the exposure amount by the stepper adjusts at least one of the intensity of the exposure light on the wafer W (such as the oscillation intensity of a pulse light source) and the number of pulses. When continuous light is used as the exposure light, at least one of the intensity of the exposure light on the wafer W (emission intensity of the light source, etc.) and the irradiation time is adjusted. Further, the exposure apparatus 1 can also be applied to a proximity exposure apparatus that exposes the pattern of the reticle R to the wafer W by bringing the reticle R and the wafer W into close contact without using the projection optical system 11.

The application of the exposure apparatus 1 is not limited to an exposure apparatus for manufacturing semiconductors. For example, an exposure apparatus for a liquid crystal for exposing a liquid crystal display element pattern to a square glass plate, a thin film magnetic head, The present invention can be widely applied to an exposure apparatus for manufacturing a device (CCD) or a reticle R.

Although the description has been given of the ArF laser as the exposure light, the present invention can be applied to an exposure apparatus using a KrF laser or EUVL such as soft X-ray having a shorter wavelength. Further, the transmittance of the optical system is measured at a plurality of times using the exposure light, but another light source that emits light having substantially the same wavelength as the wavelength of the exposure light may be used.

The magnification of the projection optical system 11 may be not only a reduction system but also any one of an equal magnification and an enlargement system. Further, as the projection optical system 11, when using a far ultraviolet rays such as an excimer laser using a material which transmits far ultraviolet rays such as quartz and fluorite as glass material, a catadioptric or refractive system when using a F ₂ laser An optical system (a reticle R of a reflection type is also used), and when an electron beam is used, an electron optical system including an electron lens and a deflector may be used as the optical system. It is needless to say that the optical path through which the electron beam passes is in a vacuum state.

The wafer stage 29 and the reticle stage 2
When a linear motor (see US Pat. No. 5,623,853 or US Pat. No. 5,528,118) is used for 3, either an air levitation type using an air bearing or a magnetic levitation type using Lorentz force or reactance force may be used. In addition, each stage 2
9, 23 may be of a type that moves along a guide,
A guideless type without a guide may be used.

As a driving device for the stages 23 and 29, a planar motor that drives a stage by electromagnetic force with a magnet unit having a two-dimensionally arranged magnet and an armature unit having a two-dimensionally arranged coil opposed thereto is used. You may. In this case, one of the magnet unit and the armature unit may be connected to the stage, and the other of the magnet unit and the armature unit may be provided on the moving surface side of the stage.

The reaction force generated by the movement of the wafer stage 29 is disclosed in Japanese Patent Application Laid-Open No. 8-166475 (US Pat. No. 5,528,11).
As described in 8), the frame member may be mechanically released to the floor (ground). The reaction force generated by the movement of the reticle stage 23 is disclosed in
As described in Japanese Patent Publication No. 24 (US S / N 08 / 416,558), a frame member may be used to mechanically escape to the floor (ground).

The illumination optical system and the projection optical system 11 composed of a plurality of optical elements are respectively incorporated in the exposure apparatus main body 2 to perform optical adjustment, and the reticle stage 23 and the wafer stage 29 composed of many mechanical parts are exposed. The exposure apparatus 1 according to the present embodiment can be manufactured by attaching to the apparatus main body 2, connecting wiring and piping, and performing overall adjustment (electrical adjustment, operation confirmation, and the like). In addition,
It is desirable to manufacture the exposure apparatus 1 in a clean room in which the temperature, cleanliness, and the like are controlled.

In the semiconductor device, a step of designing the function and performance of each device, a step of manufacturing a reticle R based on the design step, a step of manufacturing a wafer W from a silicon material, and the exposure apparatus 1 of the above-described embodiment. To expose the pattern of the reticle R on the wafer W, to assemble each device (including a dicing process, a bonding process, and a package process), and to perform an inspection step.

[0081]

As described above, the mask according to the first aspect is used for measuring a change in the amount of exposure light, and has a measurement area through which a part of the exposure light passes. As a result, with this mask, the light quantity change measurement can be performed by transmitting the light through the measurement area, so that it is not necessary to replace the mask each time the measurement is performed. Can be measured,
Highly accurate exposure amount control can be performed. Further, it is possible to frequently measure the light quantity, and it is possible to obtain the effect that the target illuminance on the substrate can be easily and reliably maintained even if the transmittance changes due to the light cleaning.

The mask according to claim 2 has a configuration in which the measurement region is set outside the pattern region. As a result, with this mask, the effect of reliably measuring the amount of exposure light can be obtained even when the pattern region is almost completely shielded from light, as in the case of a contact hole forming mask.

The mask according to claim 3 is configured such that the measurement area is set on both sides of the pattern area.
As a result, in this mask, even when the mask is moved to measure the amount of light, a measurement area close to the optical axis of the exposure light can be selected, so that the movement distance of the mask can be shortened. The advantage is that the tact time of the exposure process can be increased.

The mask according to claim 4 is configured such that the measurement region is set near the center of the pattern region. As a result, with this mask, it is possible to measure the amount of light near the center of the exposure light, and the effect of achieving more accurate exposure amount control is obtained.

The mask according to claim 5 has a configuration in which a plurality of measurement areas are set along the pattern area. Thus, with this mask, it is possible to obtain an amount of light in which the influence of distortion or the like of the optical element is reduced, and it is possible to obtain an effect that more accurate exposure amount control can be performed.

The exposure apparatus according to claim 6, wherein the first light receiving means receives a part of the exposure light illuminating the mask, the second light receiving means receives the exposure light transmitted through the measurement area of the mask,
The light quantity correcting means corrects the light quantity of the exposure light based on the output signals of the first and second light receiving means. This eliminates the need to change the mask each time the exposure apparatus is used, and allows the amount of exposure light that has actually passed through the mask to be measured. can do. In addition, the light amount measurement can be performed frequently, and even if the transmittance changes due to light cleaning, the target illuminance on the substrate can be easily and reliably maintained, and the stroke needs to be increased more than necessary. In addition, an excellent effect that an increase in the size and cost of the apparatus can be prevented can be obtained.

The exposure apparatus according to claim 7 is configured such that the light quantity correction means predicts the time change characteristic of the light quantity of the exposure light, and corrects the light quantity based on the prediction result. Thus, in this exposure apparatus, even if the transmittance of the illumination optical system or the projection optical system fluctuates during the exposure or when the apparatus is stopped, the illuminance on the substrate is corrected to an appropriate value, and the exposure on the substrate is not performed. The effect is obtained that the integrated light quantity (exposure dose) of the light can always be corrected to an appropriate value according to the sensitivity of the substrate.

The exposure apparatus according to claim 8 is configured such that the measurement areas are set on both sides in the synchronous movement direction with the pattern area interposed therebetween. This allows the exposure apparatus to select a measurement area close to the optical axis of the exposure light even when the mask stage is moved to measure the amount of light after the scanning exposure. It is possible to shorten the length, and to achieve an effect that the tact time of the exposure process can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, and is a plan view of a reticle in which a measurement region is set outside a pattern region.

FIG. 2 is a diagram illustrating a first embodiment of the present invention, and is a schematic configuration diagram of an exposure apparatus.

FIG. 3 is a diagram illustrating the first embodiment of the present invention, and is a relationship diagram illustrating a relationship between exposure time and transmittance.

FIG. 4 is a view showing a second embodiment of the present invention, and is a plan view of a reticle in which a plurality of measurement regions are set outside a pattern region along a non-scanning direction.

FIG. 5 is a time change characteristic diagram showing a relationship between an elapsed time from the start of exposure and a transmittance.

[Explanation of symbols]

 R Reticle (mask) W Wafer (substrate) 1 Exposure device 15 Integrator sensor (first light receiving means) 16 Main controller (light amount correction means) 23 Reticle stage (mask stage) 33 Illuminance sensor (second light receiving means) 36 pattern Area 38a, 38b, 40a-40f Measurement area

Claims (8)

[Claims] 1. A mask having a pattern illuminated with exposure light, the mask having a measurement region used for measuring a change in the amount of light of the exposure light and transmitting a part of the exposure light. 2. The mask according to claim 1, wherein the measurement area is set outside a pattern area where the pattern is formed. 3. The mask according to claim 2, wherein the measurement area is set on both sides of the pattern area. 4. The mask according to claim 3, wherein the measurement areas are respectively set near the center of the pattern area. 5. The mask according to claim 3, wherein a plurality of the measurement areas are set along the pattern area. 6. An exposure apparatus, comprising: a mask stage for holding a mask having a pattern; and an illumination optical system for illuminating the mask with exposure light, and transferring the pattern of the mask to a substrate. A mask for holding the mask according to any one of claims 1 to 5, and receiving a part of the exposure light for illuminating the mask.
A light-receiving means, a second light-receiving means for receiving the exposure light transmitted through the measurement area of the mask, and an amount of the exposure light based on output signals of the first light-receiving means and the second light-receiving means. An exposure apparatus, comprising: a light amount correction unit that corrects the light amount. 7. The exposure apparatus according to claim 6, wherein the light quantity correction unit predicts a time change characteristic of the light quantity of the exposure light from the output signal, and corrects the light quantity based on the prediction result. Exposure equipment characterized. 8. The exposure apparatus according to claim 6, further comprising: a synchronous movement unit configured to synchronously move the mask and the substrate with respect to the exposure light, wherein the measurement area includes a pattern on which the pattern is formed. An exposure apparatus, wherein the exposure apparatus is set on both sides of the synchronous movement direction across an area.