JP2001284235A - Projection exposure system and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable inert gas which restrains an optical path space from varying in transmittance to be controlled in concentration so as to improve exposure control more in accuracy. SOLUTION: A light volume sensor 91 detects the volume of light emitted from a light source 91 on prescribed timing. When a detected light volume varies, for instance, decreases, the piping 97c system is increased in gas feed rate by a prescribed volume by an instruction issued from a main control device 30. On the other hand, when a detected light volume by the sensor 91 increases, the piping 97c system is decreased in gas feed rate by a prescribed volume. By a gas feed control as mentioned above, a light absorbing material inside a projection optical system 12 can be substantially and very accurately kept constant in concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor device, for example,
In a lithography process for manufacturing various devices such as a liquid crystal element and a thin film magnetic head, a circuit pattern on an original plate (hereinafter, referred to as a reticle) such as a photomask or a reticle is projected and transferred onto a substrate such as a wafer coated with a photosensitive agent. Exposure apparatus, an exposure method using this apparatus, and a device suitable for manufacturing a device.

[0002]

2. Description of the Related Art In order to improve the miniaturization of circuit patterns of semiconductor elements and the like, an exposure apparatus is required to increase the resolution and the transfer fidelity. As one condition for meeting the demand, it is necessary to perform control (exposure amount control) for exposing a photosensitive agent applied on a substrate such as a wafer with an appropriate exposure amount with high accuracy.

There are a step-and-repeat method and a step-and-scan method as an exposure method used in this type of projection exposure apparatus. In the former exposure amount control method, a sensor provided inside the illumination optical system measures the exposure amount during each shot exposure, and the optical system from the sensor to the wafer (part of the illumination optical system and the projection optical system) Is assumed to be a certain value in advance, and is multiplied by this to obtain an estimated exposure amount on the wafer. Based on this, the exposure amount of the next shot is adjusted by light amount adjusting means (for example, a light source output or an ND filter). The method of adjusting is the mainstream.

In the step-and-scan method, each shot is exposed with a plurality of pulses during scanning. During this time, the amount of light is constantly measured by a sensor inside the illumination optical system, and there is an integrated exposure amount in the shot. A method is used in which the output of the light source (for example, energy per pulse or oscillation frequency) is adjusted so as to reach a predetermined value (= optimal exposure amount determined from the resist). In this case, as in the step-and-repeat method, the transmittance of the optical system (part of the illumination optical system and the projection optical system) from the sensor to the wafer is assumed to be a certain value in advance, and the transmittance is multiplied by a certain value. The above exposure is estimated.

FIG. 14 shows a conventional example of the step-and-scan method. 1 is a light source, for example, KrF excimer laser or an ArF excimer laser which emits ultraviolet light having a wavelength of 248 nm (193 nm), and the like _{F 2} laser (157 nm).

Reference numeral 2 denotes a dimming member (ND), for example, a plurality of NDs having different transmittances. Then, the ND driving unit 2 controls the ND driving unit 2 so that the optimum exposure amount is obtained on the surface of the wafer 14.
1 to enable fine adjustment of the dimming rate.

Reference numeral 3 denotes a beam shaping optical system which includes a plurality of optical elements and a zoom lens. The beam shaping optical system 3 is driven by the lens system driving unit 22 to control the intensity distribution and the angle distribution of the light beam incident on the optical integrator 4 at the subsequent stage to a desired distribution. The optical integrator 4 has a configuration in which a plurality of microlenses are two-dimensionally arranged, and forms a secondary light source near the exit surface thereof.

A stop 5 is arranged near the exit surface of the optical integrator 4, and the size and shape of the stop are made variable by a stop driving mechanism 23. Reference numeral 6 denotes a condensing lens which collects light beams emitted from a plurality of secondary light sources formed in the vicinity of the emission surface of the optical integrator 4 and superimposes the light beams on the surface of the scan blade 7b, which is the surface to be irradiated, to make the surface uniform. I have to.

Reference numeral 18 denotes a half mirror which reflects a few% of the light beam emitted from the optical integrator 4 and guides it to the integrated exposure amount sensor 17. 17 is a detector (illuminometer, detector) for constantly detecting the amount of light during exposure
It is arranged at a position optically conjugate with the surface of the wafer 14 and the surface of the reticle 10, and sends a signal corresponding to the output to the main controller 30.

The scan blade 7b is composed of a plurality of movable light-shielding plates, and regulates the exposure range on the surface of the wafer 14 so that an arbitrary opening shape is formed by the scan blade driving device 24.

Further, the scan blade 7b scans and moves in the direction of the arrow in the figure in synchronization with the reticle stage 11 and the wafer stage 15. A variable slit 7a is arranged near the scan blade 7b in order to improve the illuminance uniformity on the exposed surface after the scanning exposure.

Reference numerals 8a and 8b denote imaging lenses, which transfer the opening shape of the scan blade 7b onto the reticle 10 as a surface to be illuminated, and uniformly illuminate a required area on the reticle surface 10.

Here, the reticle 1 is disposed after the laser 1.
The optical systems preceding 0 are collectively referred to as an illumination optical system.

The reticle 10 is held by a reticle stage 11, and the reticle stage 11 is controlled by a reticle stage driving device 25.

Reference numeral 12 denotes a projection optical system for reducing and projecting a circuit pattern on the reticle 10 on the wafer 14 and comprises a plurality of lenses (12a to 12n). Reference numeral 13 denotes an NA stop for limiting a pupil area of the projection optical system, and an NA stop driving device 2
6, the aperture size is changed, and the NA of the projection optical system 12 is changed.
Is variable. Reference numeral 14 denotes a wafer (substrate) on which a circuit pattern on the reticle 10 is projected and transferred, and is located on the exposure surface. Reference numeral 15 denotes a wafer stage that holds the wafer 14 and moves two-dimensionally along a plane orthogonal to the optical axis direction and the optical axis. The wafer stage 15 is controlled by a wafer stage driving device 27.

At the time of exposure, the reticle stage 11 and the wafer stage 15 perform scanning exposure in the direction of the arrow in FIG.

Reference numeral 16 denotes a detector (illuminometer, detector) for detecting the amount of exposure light incident on the surface of the wafer 14, the light receiving portion of which is aligned with the surface of the wafer 14, and the illumination light in the irradiation area is transmitted to the wafer stage. The light receiving unit 15 moves along with the driving of the light receiving unit 15 and receives the light, and sends a signal corresponding to the output to the main control device 30. Reference numeral 30 denotes a main controller, which controls each of the devices 21 to 27.

In the exposure method of the step-and-scan method, the reticle 10 and the wafer 14 perform scanning exposure while synchronizing in the direction of the arrow in FIG. The reduction ratio of the projection optical system is 1
/ Β, the scanning speed of the wafer stage 15 is V (m
m / sec), the scanning speed of the reticle stage 11 is βV (mm / sec). The scanning direction of the wafer stage 15 and the scanning direction of the reticle stage 11 are
The directions are opposite to each other.

Here, a conventional exposure amount control method will be described.

The illuminance on the wafer surface 14 in various illumination modes (NA / σ conditions and annular illumination conditions) is measured by a detector 16 and an integrated exposure amount measuring sensor 17 in an illumination optical system.
Output calibration is performed in advance, and the calibration result is stored. In addition, in various illumination modes, the illuminance distribution of the exposure area is measured by moving the detector 16 two-dimensionally, and the variable slit 7a achieves a shape such that the illuminance distribution becomes uniform when scanning exposure is performed. Keep it.

Next, when an arbitrary illumination mode is designated and the exposure amount at that time is set, the scanning speed V (mm / sec) of the wafer stage 15, the width W (mm) of the variable slit 7a in the scanning direction, The laser oscillation frequency F (Hz) is determined so as to satisfy Expression (1).

V = F × W / n (1) where n is the number of exposure pulses, which is the number of pulses applied during scanning exposure when focusing on one point on the exposure surface.

The minimum value of the number of pulses is determined from the sensitivity of the resist to be used and the pulse energy of the light source, and the exposure requires a pulse number equal to or greater than the minimum value.

In actual exposure, it is necessary to keep the scanning speed V high in order to improve the throughput. Therefore, the width W (mm) of the variable slit in the scanning direction is fixed for each illumination mode, so that the minimum condition of the pulse number n is satisfied.
The output (pulse energy and oscillation frequency F) of the light source 1 and N
The adjustment of D2 is performed, and the feedback control of the exposure amount is performed while constantly monitoring the integrated exposure amount measurement sensor 17.

That is, the exposure amount control during the exposure is always performed by the sensor in the illumination optical system, but the calibration of the output value of the sensor and the illuminance of the actual exposure surface needs to be performed after stopping the exposure. Was.

[0026]

In recent exposure apparatuses, the exposure wavelength is set to i-line (wavelength: 3) in order to further improve the resolution.
65 nm) to KrF excimer laser (248 nm),
It has been shortened to an ArF excimer laser (193 nm). It also considered proceed is _{an F 2} laser (157 nm), such as a further shorter wavelength.

When the exposure wavelength is shortened, the photon energy is increased, so that the possibility of causing a photochemical reaction with an optical member (a glass material or a coating material) or a substance in an atmosphere in an optical path is increased. As a result, there is a concern that the transmittance of the optical system changes.

For example, from the data of basic research on quartz, laser irradiation shows both short-term absorption and long-term deterioration, and furthermore, once the irradiation is stopped, the absorption temporarily drops (recovery of transmittance), and again. It has been found that when irradiation is started, the absorption curve returns to the previous absorption curve (recovery of absorption). Therefore, also in the exposure apparatus, the degree of the transmittance variation depends on the exposure conditions (energy of laser pulse,
It depends on the number of pulses, the illumination mode, the reticle transmittance, the degree of rest of exposure, etc.).

Therefore, in the conventional exposure apparatus as shown in FIG. 14, since the integrated exposure amount sensor 17 which constantly monitors the light amount is arranged in the illumination optical system, the light transmitted through the optical system after the half mirror 18 is transmitted. When the rate change occurs, it becomes impossible to accurately monitor the exposure amount on the surface of the wafer 14, and the accuracy of the exposure amount control is reduced.

In order to improve the accuracy of the exposure control, the exposure is frequently stopped and the illuminance on the exposed surface is measured.
The output of the integrated exposure sensor 17 must be calibrated, which causes a decrease in throughput.

Further, there is also a problem in the variation of the transmittance in the optical path space of the atmosphere in which these lenses are placed.

Accordingly, an object of the present invention is to provide a projection exposure apparatus capable of detecting the transmittance in the optical path space.

Further, the present invention provides a high-performance and high-reliability projection exposure apparatus capable of performing inert gas purge control for suppressing fluctuations in optical path space transmittance and further improving exposure amount control accuracy. The challenge is to do.

[0034]

According to the present invention, there is provided an exposure apparatus for projecting a pattern on an original onto a substrate by using light from a first light source. A second light source; and a light amount detecting unit that detects a light amount of the light from the second light source. The light amount detecting unit detects at least an atmosphere in an exposure optical path from the first light source to the substrate. The amount of light from the second light source that has passed through a part of the atmosphere is detected.

Further, according to the present invention, the change in the gas concentration in at least a part of the exposure light path is detected using light having a larger absorption than the exposure light for a predetermined gas.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram for explaining projection exposure by a first light source, in which a second light source is omitted. This apparatus is modeled on a step-and-scan exposure apparatus used for manufacturing various devices such as a semiconductor element, a liquid crystal element, and a thin-film magnetic head. In this apparatus, the NA stop 1 of the projection optical system 12 is
The photodetector 40 is arranged on the upper part of the three surfaces. Other optical systems and devices correspond to the reference numerals in FIG. here,
The first light source is an F ₂ excimer laser (wavelength 157 nm), but may be an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm).

Since the photodetector 40 receives light transmitted through the entire illumination optical system and a part of the projection optical system, the photodetector 40 monitors the exposure amount on the surface of the wafer 14 more accurately than in the past, and It is possible to control.

During exposure, the reticle 10 is placed on the reticle stage 11 and illuminates the circuit pattern on the reticle 10. The diffracted light of the circuit pattern generated by illumination is
The image is re-imaged on the surface of the wafer 14 by the projection optical system 12. The diffracted light that contributes to the image formation is 0- ± 1st-order (lower-order) diffracted light that is not shaken by the NA diaphragm 13.
On the other hand, the high-order diffracted light flies toward the outside of the NA stop 13 and the projection optical system 12, and does not contribute to image formation.

Accordingly, the photodetector 40 is provided on the surface of the NA stop 13.
By disposing high-order diffracted light and monitoring the change in the amount of light, a change in the transmittance of the optical system up to the vicinity of the surface of the wafer 14 can be detected. Further, by performing feedback control on the output of the light source 1 and the adjustment of the ND 2 by reflecting the detected change in the transmittance in the result of the integrated exposure amount measurement sensor 17, more accurate exposure amount control becomes possible.

FIG. 2 is a flowchart showing an exposure amount control method by the projection exposure apparatus of FIG.

In step 100, the wafer surface 14 for various illumination modes (NA / σ conditions and annular illumination conditions)
The upper illuminance is measured by the detector 16, output calibration with the integrated exposure amount measuring sensor 17 in the illumination optical system is performed in advance, and the calibration result is stored.

In step 200, in various illumination modes, the illuminance distribution on the exposure surface is measured by moving the detector 16 two-dimensionally, and conditions for making the illuminance distribution uniform during scanning exposure are set by the variable slit 7a. Remember.

Next, in step 300, when an arbitrary illumination mode is designated and the exposure amount at that time is set,
The scanning speed V (mm / sec) of the wafer stage 15, the width W (mm) of the variable slit 7a in the scanning direction, and the laser oscillation frequency F (Hz) are determined so as to satisfy the above expression (1). .

Next, in step 400, in order to enter the actual exposure step, the reticle 10 on which an arbitrary pattern is drawn is placed in the exposure area, and the reticle 10 and the wafer 14
Perform scanning exposure in synchronism. When the reduction magnification of the projection optical system is 1 / β, the scanning speed of the wafer stage 15 is V
At (mm / sec), the scanning speed of the reticle stage 11 is βV (mm / sec). The scanning direction is the direction opposite to that of the wafer stage and the reticle stage.

In step 500, the amount of light reaching the photodetector 40 on the NA diaphragm 13 is periodically measured at a certain timing during the scanning exposure.

Further, in step 510, a change in the transmittance of the optical system is sequentially calculated by detecting a change in the measurement signal.

On the other hand, in step 520, the exposure amount is monitored by the integrated exposure amount sensor 17.

Finally, in step 600, the change in the transmittance obtained by the calculation is calculated by the integrated exposure amount measuring sensor 1.
7, the exposure amount is more accurately controlled.

FIG. 3 is a plan view for explaining how a reticle pattern that generates diffracted light is scanned and exposed. It is necessary to pay attention to the fact that the amount of light reaching the photodetector 40 always fluctuates during the exposure because the diffracted light fly according to the reticle transmittance and the pattern changes successively.

Therefore, it is necessary to provide a method for accurately grasping only the change in the transmittance of the optical system in consideration of the timing measured by the photodetector 40.

FIG. 4 shows the result of monitoring the amount of light reaching the detector 40 during scanning exposure for two types of reticles. The detected light amount fluctuates including the influence of the difference in the reticle pattern and the time within the shot (during scanning exposure), but each shot has periodicity. Accordingly, a method of detecting the change in the transmittance of the optical system by acquiring the integrated value (total detected light amount in one shot) or the average value of the detected light amounts in a shot as one data and sequentially detecting a change for each data. Can be considered. Further, a change in the light amount at a specific timing (a specific point in the scanning exposure area) within a shot may be set as one data and the change may be sequentially detected.

FIG. 5 is a flowchart showing another exposure amount control method using the projection exposure apparatus of FIG. The processes from the calibration of the illuminance on the wafer 14 surface for various illumination modes and the output of the integrated exposure amount measuring sensor 17 to the determination of the parameters for realizing the set exposure amount are the same as those in FIG.

The difference from the method shown in FIG. 2 is step 501, in which a special mark for generating diffracted light is provided on the reticle, and a specific timing during non-exposure (for example, between shots, during alignment measurement, Or at the time of wafer replacement), in that the photodetector 40 receives the diffracted light from the dedicated mark.

The special mark drawn on the reticle 10 is designed by assuming the illumination mode to be used in advance, so that the diffracted light reaches the photodetector 40 without fail. Based on the signal thus detected, a change in the transmittance of the optical system is calculated.

The calculated change in the transmittance is reflected on the value from the integrated exposure amount measuring sensor 17 and is fed back to the output of the light source 1 and the adjustment of the ND 2, thereby enabling more accurate exposure amount control.

The transmittance measurement is performed while taking into account the non-exposure time between shots, alignment measurement, wafer exchange, etc., so that there is no need to provide a special measurement time and the exposure is excellent in production efficiency. The amount can be controlled.

Incidentally, as the special mark, a mark provided in advance, such as the reticle reference mark 101 in FIG. 4, may be used.

In this embodiment, the exposure apparatus of the step-and-scan type has been described. However, the same effect can be expected with an exposure apparatus of the step-and-repeat type. In the step-and-repeat method, the reticle pattern that generates the diffracted light is fixed, so that the change in the transmittance of the optical system can be obtained by detecting the change in the integrated value or average value of the detected light amount for each shot as one data. Good.

FIG. 6 is a schematic diagram showing another example of the projection exposure apparatus, in which the second light source is omitted. The model is a step-and-scan exposure apparatus. The difference from the block diagram of the projection exposure apparatus of FIG.
2 is that the photodetector 41 is arranged below the surface of the NA stop 13. Other optical systems and devices correspond to those in FIG.

Focusing on the light scattered on the surface of the wafer 14 during exposure that reaches the photodetector 41 below the NA aperture 13, the photodetector 41 is arranged below the NA aperture 13 to receive light. The detected light quantity change is detected.

A change in the transmittance is calculated from the detected change in the amount of light, and the result is reflected in the value from the integrated exposure amount measuring sensor 17, so that more accurate exposure amount control is executed.

The photodetector 41 receives the light reflected on the surface of the wafer 14 through all of the illumination optical system and the projection optical system, so that the amount of exposure on the surface of the wafer 14 can be more accurately than in the prior art. It is possible to monitor and control the exposure amount.

An exposure control method using the apparatus shown in FIG. 6 will be described with reference to FIG. Wafer 1 for various illumination modes
The process from the calibration of the illuminance on the four surfaces and the output of the integrated exposure amount measurement sensor 17 to the determination of the parameters for realizing the set exposure amount is the same as the first exposure amount control method.

In the subsequent steps, in step 500, during exposure, the amount of light reaching the photodetector 41 below the NA aperture 13 is periodically detected. And step 510
In, the detection results are sequentially compared, and the change in transmittance is calculated.

By reflecting the calculated change in the transmittance on the result of the integrated exposure amount measuring sensor 17 and performing feedback control on the output of the light source 1 and the adjustment of the ND 2, more accurate exposure amount control becomes possible. Become.

In the case of scanning exposure, as shown in FIG. 3, exposure is performed by scanning a reticle pattern that generates diffracted light. Therefore, the light amount changes sequentially according to the reticle transmittance. Also, a pattern in which several types of circuits are stacked in many layers is often formed on the surface of the wafer 14 during exposure, and the direction in which the reflected scattered light travels depends on the pattern shape formed on the wafer 14. Therefore, it is necessary to pay attention to the fact that the amount of light reaching the photodetector 41 always changes during exposure.

Therefore, it is necessary to provide a method for accurately grasping only the change in the transmittance of the optical system in consideration of the timing monitored by the photodetector 41. For example, a method of detecting a change in the transmittance of an optical system by detecting a change in an integrated value detection light amount (a total detection light amount in one shot) or an average value in one shot as one data, and a method of identifying a change in a shot. At the timing (a certain point in the scanning exposure area) as one data, the change may be detected.

Another exposure amount control method using the apparatus of FIG. 6 will be described with reference to FIG. The processes from the calibration of the illuminance on the surface of the wafer 16 for various illumination modes and the output of the integrated exposure amount measuring sensor 17 to the determination of the parameters for realizing the set exposure amount are the same as the first to third exposure methods.

The difference is in step 501, in which a dedicated mark for generating reflected light from the wafer 14 is provided on the wafer stage 15, and during non-exposure (each shot, during alignment measurement, or when replacing the wafer). Another point is that the reflected light from the dedicated mark is received by the photodetector 41.

The special mark drawn on the wafer stage 15 is designed by assuming the illumination mode to be used in advance, so that the reflected light reaches the photodetector 41 without fail.

In step 510, a change in the transmittance of the optical system is calculated based on the signal thus detected.

The calculated change in the transmittance is reflected on the value from the integrated exposure amount measuring sensor 17 and is fed back to the output of the light source 1 and the adjustment of the ND 2, thereby enabling more accurate exposure amount control.

The transmittance is measured at the time of non-exposure such as between shots, alignment measurement, and wafer exchange, so that it is not necessary to provide a special measurement time, and the exposure is excellent in production efficiency. The amount can be controlled.

Note that a mark provided in advance, such as an alignment measurement mark, may be used as the dedicated mark.

As described above, more accurate exposure amount control can be performed in consideration of the transmittance change of the almost entire optical system including the projection optical system.

FIG. 7 is a block diagram of a projection exposure apparatus according to the present invention, which further comprises means for detecting a change in the optical path atmosphere in the projection exposure apparatus of FIG.

The photodetector 40 monitors the total efficiency variation of the optical system after the optical path branching portion of the integrated exposure sensor 17. More specifically, the photodetector 40 combines the efficiency variation of the optical element and the efficiency variation of the optical path space. To monitor.

The apparatus shown in FIG. 7 independently and accurately detects only a change in the light path atmosphere, thereby suppressing a change in the efficiency of the optical system after the light path branching portion of the integrated exposure amount sensor 17 to a smaller extent and further reducing the change. It is intended that the fluctuations can be reflected with high precision by controlling the exposure amount, and that the exposure apparatus can automatically detect only the fluctuations in the efficiency of the optical element. Hereinafter, description will be made with reference to the drawings.

In FIG. 7, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 91 denotes a light source different from the light source 1, and in this embodiment, a case where a deuterium lamp is used as a light source will be described. The light emitted from the light source 91 passes through the lens space in the projection optical system 12 and enters the light amount sensor 92. At this time, the light amount detected by the light amount sensor 92 fluctuates depending on the gas component existing in the optical path from the light source 91 to the light amount sensor 92 and the wavelength of the light from the light source 91. This will be described in detail with reference to FIG.

FIG. 8 is a graph showing light absorption characteristics of oxygen.
Wavelength (unit: nm) on the horizontal axis, absorption coefficient (per cm) on the vertical axis
Is shown. When the absorption coefficient is k, the thickness of the oxygen layer is x, and the gas partial pressure is p, the light transmittance (I / I ₀ ) is expressed by the following equation.

I / I ₀ = exp (−k · p · x) According to FIG. 8, there is a discontinuous strong absorption band from a wavelength around 200 nm to around 180 nm, and a continuous strong absorption band from 180 nm to around 130 nm. It turns out that there is.

Therefore, when detecting a variation in the partial pressure of oxygen gas, when an F ₂ excimer laser having an oscillation wavelength of around 158 nm is used as the light source 1, the light wavelength of the light source 91 is 140 at shorter wavelength than oscillation wavelength
When light having a wavelength longer than nm is used and an ArF excimer laser having an oscillation wavelength near 193 nm is used as the light source 1, the light of the light source 91 is 140 to 170 nm.
By using this wavelength, it is possible to detect the fluctuation of the oxygen partial pressure with higher sensitivity than when using the exposure wavelength.

FIG. 9 is a diagram showing the light absorption characteristics of water vapor, in which the horizontal axis represents the wavelength (unit: nm) and the vertical axis represents the absorption coefficient (per cm).

When detecting a variation in the partial pressure of water vapor from this characteristic, when an F ₂ excimer laser having an oscillation wavelength of around 158 nm is used as the light source 1, the light wavelength of the light source 91 is Longer than the wavelength, 17
By using light having a wavelength shorter than 0 nm, it is possible to detect fluctuations in water vapor partial pressure with higher sensitivity.

FIG. 10 shows the radiation intensity of the deuterium lamp used for the light source 91. The horizontal axis shows the wavelength, and the vertical axis shows the radiation intensity. The presence of radiation is seen for wavelengths from around 120 nm to around 165 nm.

Therefore, a specific wavelength can be extracted from the deuterium lamp having the characteristics shown in FIG.

The configuration inside the light source 91 will be described with reference to FIG.

In the light source 91, a deuterium lamp 100,
The inside of the housing 105 that houses the wavelength selection device 102, the optical path splitting element 103, and the reference light sensor 104, and further covers the entire light source 91, is purged with helium gas or nitrogen gas by an inert gas replacement unit (not shown). .
The light emitted from the deuterium lamp 100 is transmitted to the wavelength selection device 1
02, only the used wavelength is extracted. As the wavelength selection means, a spectroscope using a grating element or a prism may be used, or a wavelength selection filter may be used.
The light of the selected wavelength is split into two by the optical path splitting element 103, one of which is incident on the light quantity sensor 92 and the other is incident on the reference light sensor 104. Outputs of the reference light sensor 104 and the light amount sensor 92 are both subjected to signal processing by the main controller 30.

According to the configuration shown in FIG. 11, the variation in the partial pressure of the light absorbing gas existing in the optical path 106 from the light source 91 to the light quantity sensor 92 is monitored with high accuracy separately from the variation in the output of the deuterium lamp 100. can do.

The wavelength selection device 102 may be configured to be able to select an arbitrary wavelength. For example, a monochromator may be used or a plurality of wavelength selection filters may be arranged and switched. The selection of the wavelength to be used is desirably made according to the type of the light-absorbing gas of interest or according to the distance of the optical path 106, the sensitivity of the light amount sensor 92 and the reference light sensor 104, the output of the deuterium lamp 100, and the like. .

The inert gas supply device 93 shown in FIG. 9 includes pipes 97a, 97b, 97c,
The gas is supplied via 97d.

The closed casing 94 is provided between the light source 1 and the imaging lens 8.
b is housed inside, and the exhaust port 98a
It has.

The closed casing 95 houses the imaging lens 8b, the reticle 10 and the reticle stage 11, and has an exhaust port 98b. The closed casing 96 houses the wafer 14, the wafer stage 15, and the detector 16 therein, and has an exhaust port 98d.

The projection optical system 12 also forms a closed housing, and has an exhaust port 98c.

At the connection between each of the sealed housings and the projection optical system 12, glass (not shown) is arranged in the optical path to allow exposure light to pass therethrough and perform space division.

Next, the operation of the projection exposure apparatus of the present invention shown in FIG. 7 will be described.

The light quantity sensor 92 detects the light quantity from the light source 91 at a predetermined timing. If the detection value fluctuates,
For example, when the detected light amount decreases, the pipe 97c is supplied from the inert gas supply device 93 by a command from the main controller 30.
The gas supply amount of the system is increased by a predetermined amount. On the other hand, when the light amount detected by the light amount sensor 92 increases, the piping 97c
The gas supply amount to the system is reduced by a predetermined amount. By such gas supply control, the concentration of the light absorbing substance in the projection optical system 12 is maintained at a substantially high accuracy and constant. As mentioned above,
If the detected value fluctuates during the exposure, the photodetector 40 controls the exposure amount by reflecting the value from the integrated exposure amount measurement sensor 17. Particularly, as in the present invention, the photodetector 40 is controlled by the projection optical system 12. In the case of being arranged in the middle of the optical path, by maintaining the efficiency of the optical path space after the photodetector 40 constant, more accurate exposure amount control can be achieved.

Next, in the above operation, the light amount sensor 9
In the case where the detected light amount of No. 2 is kept constant and the amount of change in the detection value of the photodetector 40 exceeds a predetermined value, the main controller 30
The exposure operation is stopped in response to a command from the CPU, and a warning is displayed on a display connected to the main controller 30. This is a state where the efficiency of the optical element has decreased by a predetermined amount or more,
The purpose is to prevent adverse effects on exposure performance.

As a measure after stopping the exposure operation, for example, the light source 1 is oscillated at a predetermined timing while the wafer 14 is retracted from the exposure optical path, and at the same time, the optical element efficiency is determined from the detection results of the photodetector 40 and the light amount sensor 92. After returning to the normal state, the warning display on the display 99 may be automatically stopped and the exposure operation may be restarted.

Further, at a predetermined timing during which the exposure operation is stopped, the calibration of the integrated exposure amount sensor 17 is performed by the detector 16.
A confirmation operation such as execution based on the above may be performed.

During the normal exposure operation, based on the detection results of the photodetector 40 and the light amount sensor 92, the display 9
It is also possible to display the optical element efficiency at all times or at any timing.

FIG. 12 shows a light source 91 and a light amount sensor 92.
In the illumination optical system. Since the calibration element and the operation example are the same as those in FIG. 7, the description will be omitted.

As shown in FIG. 12, the arrangement of the light source 91 and the light quantity sensor 92 does not necessarily have to pass through the exposure light path as in the embodiment of FIG. 9, but passes through the atmosphere in the same space as the exposure light path. Then, the effect of the present invention can be obtained.
The amount of gas supplied from the inert gas supply source 93 to the pipe 97a is controlled according to the detection result of the light amount sensor 92.

In FIG. 6, an embodiment further provided with means for detecting a change in the atmosphere of the optical path is also possible.

As described above with reference to FIGS. 7 to 12, the gas permeability detecting portion by the light amount sensor 92 is not limited to one, and the closed casings 94, 95, and 9 are not limited to one.
6 and the projection optical system 12 may be detected at a plurality of positions as necessary, and the present invention is applicable even if the closed housing is divided into configurations other than the above-described four-divided configuration. It is.

Although each of the above embodiments is a step & scan type exposure apparatus, the present invention can also be applied to a step & repeat type exposure apparatus.

When an F ₂ excimer laser is used as an exposure light source, each lens is formed of fluorite (CaF ₂ ) or a material having the same transmittance as this. Further, a diffractive optical element may be used instead of a lens as necessary. Further, as the projection optical system, a catadioptric system may be used in addition to the refractive system.

FIG. 13 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).

In step 1 (circuit design), the circuit of the device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer.

The next step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like.

In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

[0113]

According to the present invention described above, a change in light transmittance in the optical path space can be detected. For example, an inert gas purge control that suppresses a change in the light path spatial transmittance can be performed more than in the prior art. Thus, a highly reliable exposure apparatus can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining projection exposure by a first light source.

FIG. 2 is a flowchart for explaining an exposure amount control method;

FIG. 3 is a plan view of a reticle stage.

FIG. 4 is a waveform diagram of a signal intensity obtained for each shot in a photodetector on an NA stop.

FIG. 5 is a flowchart for explaining another exposure amount control method;

FIG. 6 is a block diagram for explaining another projection exposure by a first light source.

FIG. 7 is a block diagram of a projection exposure apparatus of the present invention to which a second light source is added.

FIG. 8 is a graph showing light absorption characteristics of oxygen.

FIG. 9 is a graph showing light absorption characteristics of water vapor.

FIG. 10 is a graph showing the radiation intensity of a vacuum ultraviolet deuterium lamp.

FIG. 11 is a block diagram of a second light source.

FIG. 12 is a projection exposure apparatus of the present invention including a second light source in an illumination optical system.

FIG. 13 is a flowchart of a device manufacturing process.

FIG. 14 is a block diagram of a conventional projection exposure apparatus.

[Explanation of symbols]

1: Light source 2: Dimming member 3: Beam shaping optical system 4: Optical integrator 5: Aperture 6: Condensing lens 7a: Variable slit 7b: Scan blade 8a, 8b: Imaging lens 9: Mirror 10: Reticle 11: Reticle Stage 12: Projection optical system 12a... 12n: Single lens constituting the projection optical system 13: NA stop 14: Wafer 15: Wafer stage 16: Detector 17: Integrated exposure amount measurement sensor 18: Half mirror 21: ND driving means 22: lens system driving means 23: aperture driving means 24: scan blade movable device 25: reticle stage driving device 26: NA aperture driving device 27: wafer stage driving device 30: main control device 40, 41: photodetector 91: light source 92: Light intensity sensor 93: Inert gas supply device 94: Sealed housing 95 Sealed housing 96: Sealed housing 97a, 97b, 97c, 97d: Piping 98a, 98b, 98c, 98d: Exhaust port 99: Display 100: Deuterium lamp 101: Reticle reference mark 102: Wavelength selector 103: Optical path split Element 104: Reference light sensor 105: Housing 106: Optical path

Claims (18)

[Claims] 1. An exposure apparatus for projecting a pattern on an original onto a substrate using light from a first light source, wherein the second light source is different from the first light source, and the light from the second light source is different from the first light source. Light amount detecting means for detecting the amount of light from the second light source passing through at least a part of the atmosphere of the exposure light path from the first light source to the substrate by the light amount detecting means. A projection exposure apparatus characterized by detecting a light amount. 2. The projection exposure apparatus according to claim 1, wherein the second light source emits light having a wavelength different from the wavelength of light emitted from the first light source. 3. The projection exposure apparatus according to claim 1, wherein the light from the second light source has a wavelength having a larger oxygen absorption coefficient than the light from the first light source. 4. The projection exposure apparatus according to claim 1, wherein the light from the second light source has a wavelength having a larger water vapor absorption coefficient than the light from the first light source. 5. The projection exposure apparatus according to claim 1, wherein a deuterium lamp is used as the second light source. 6. A projection exposure apparatus, wherein a change in gas concentration in at least a part of an exposure optical path is detected by using light having a larger absorption than exposure light for a predetermined gas. 7. The projection exposure apparatus according to claim 6, wherein the light having a large absorption is different from a wavelength of the exposure light. 8. The projection exposure apparatus according to claim 6, wherein the light having a large absorption has a wavelength having a larger oxygen absorption coefficient than the exposure light. 9. The projection exposure apparatus according to claim 6, wherein the light having a large absorption has a wavelength having a larger water vapor absorption coefficient than the exposure light. 10. The projection exposure apparatus according to claim 6, wherein a deuterium lamp is used as a light source of the light having a large absorption. 11. The projection light apparatus according to claim 1, further comprising integrated exposure amount detecting means for constantly detecting the integrated exposure amount on said substrate during pattern projection. 12. The projection exposure apparatus according to claim 11, wherein the light from the second light source passes through at least a part of an optical path atmosphere from the integrated exposure amount detection means to the substrate. 13. An atmosphere control means for controlling an optical path space of at least a part of an optical path from the first light source to the substrate to an inert gas atmosphere, and controlling a detection result of the light receiving means by the atmosphere control means. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus reflects the result. 14. An exposure apparatus comprising both the light receiving means and the light quantity detecting means, stopping an exposure operation of the exposure device and displaying a warning on a display in accordance with a detection result of the light receiving means and the light quantity detecting means. The projection exposure apparatus according to claim 1, wherein: 15. The projection exposure apparatus according to claim 1, wherein the second light source includes a wavelength selection unit that selects a predetermined wavelength. 16. A second light amount detecting means for detecting a light amount of light not used for exposure among diffracted lights generated in the pattern, and detecting a change in transmittance of the optical system based on a detection result of the means. The projection exposure apparatus according to claim 1, wherein: And a third light amount detecting means for detecting light amounts of reflected light, scattered light and diffracted light generated on the substrate,
17. The projection exposure apparatus according to claim 1, wherein a change in transmittance of the optical system is detected based on a detection result of the means. 18. A method comprising: exposing a wafer with a device pattern using the projection exposure apparatus according to claim 1; and developing the exposed wafer. Method of manufacturing devices.