JPH10284410A - Exposure apparatus and exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner and exposure which can realize reliable and continuous output light control. SOLUTION: An aligner transfers a predetermined pattern 75 onto a substrate 77 through optical system elements 71, 72, 73, 74 and 75 with use of light emitted from a light source. The aligner includes a light source 10 for emitting light having a central wavelength of 20 nm or less, an oxygen-contained closed container 12 through which the light received from the light source 10 is passed, a device 33 for adjusting a concentration of oxygen in the container 12, a light receiving element 31 for detecting a quantity of light emitted from the light source 10, and a device 32 for controlling the oxygen concentration adjusting device 33 on the basis of a detected result of the light quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for transferring a circuit pattern onto a photosensitive substrate such as a semiconductor wafer or a glass plate by using light having a center wavelength of 200 nm or less in order to manufacture a semiconductor device or a liquid crystal display device. The present invention relates to an apparatus and an exposure method.

[0002]

2. Description of the Related Art In an exposure apparatus, when a pulse oscillation discharge type gas laser such as an excimer laser is used as a light source, the output of the light source has a large fluctuation, which causes an error in the irradiation amount on the photosensitive substrate at the time of exposure. As a countermeasure, the number of irradiation pulses at the time of exposure is set to be plural to reduce the error of the irradiation amount. In this case, as the number of pulses increases, the error decreases, but the exposure time increases, thereby lowering the productivity. On the other hand, when the output per oscillation is increased, the exposure time is reduced, but the error of the irradiation amount is increased. In order to prevent this, it is necessary to control the output per oscillation and to set the error and the productivity within appropriate ranges. Until now, the output control per one oscillation has been performed by controlling input energy to a laser oscillation circuit, controlling output light by an ND filter, and the like.

[0003]

However, the change of the input energy to the laser oscillation circuit in the above-mentioned prior art is as follows.
There is a disadvantage that a control error is increased because the discharge state of the laser is changed.

The method of changing the ND filter each time has a drawback that continuous control cannot be performed.
There is a drawback that the filter itself is damaged by the laser beam, and thus the transmittance changes with time.
In addition, when a mesh filter is used, there is a disadvantage that the illumination intensity at the time of exposure may be uneven.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus and an exposure method capable of solving the drawbacks of the prior art and performing reliable and continuous output light control.

[0006]

According to the present invention, there is provided an exposure apparatus for transferring a predetermined pattern onto a substrate by using light from a light source via an optical system.
A light source that outputs light having the following center wavelengths, and a sealed oxygen-containing optical path through which light output from the light source passes.
Means for adjusting the number of oxygen molecules in the sealed oxygen-containing optical path, means for detecting the amount of light output from the light source, and means for controlling the oxygen molecule number adjusting means based on the detection result of the amount of light. Is provided.

When light has a center wavelength of less than 200 nm, it is absorbed by oxygen. Therefore, according to the exposure apparatus of the present invention, light having a center wavelength of 200 nm or less is output from the light source and is absorbed by oxygen when passing through the sealed oxygen-containing optical path, so that the energy of the light is reduced. . The absorption by oxygen depends on the number of oxygen molecules in the oxygen-containing optical path. Therefore, the amount of light absorbed by oxygen in the oxygen-containing optical path can be adjusted by adjusting the number of oxygen molecules in the oxygen-containing optical path by the oxygen molecule number adjusting means. This makes it possible to continuously change the energy of light.

By controlling the oxygen molecule number adjusting means by the control means based on the light amount detected by the light amount detecting means, the energy of light required for exposure on the substrate can be continuously controlled. Therefore, it is possible to provide an exposure apparatus capable of performing reliable and continuous output light control.

Further, when the oxygen-containing optical path is disposed between the light source and the light amount detecting means, the light amount of the light passing through the oxygen-containing optical path is detected, and the oxygen molecule number adjusting means is controlled based on the detection result. Can be controlled.

If the oxygen-containing optical path is formed in a sealed container, a closed optical path can be formed, and the number of oxygen molecules can be easily adjusted in the container. For example, the number of oxygen molecules in the oxygen-containing optical path can be changed by providing an oxygen concentration adjusting means as the oxygen molecule number adjusting means in communication with the closed vessel and changing the oxygen concentration in the closed vessel. Incidentally, the oxygen molecule number adjusting means may have another configuration, for example, may be provided with a means for adjusting the length of the container so as to be able to expand and contract in the optical path length direction of the container. It can also be configured by controlling the air pressure. Also,
A plurality of such containers may be provided in the optical axis direction.

According to the present invention, in an exposure method for transferring a predetermined pattern onto a substrate by light from a light source via an optical system, a step of detecting a light amount of the light output from the light source; Changing the number of oxygen molecules in a closed optical path through which the light passes based on According to this exposure method, the energy of light for exposing the substrate can be continuously controlled by changing the number of oxygen molecules in the closed optical path based on the detected light amount. Therefore, it is possible to provide an exposure method capable of performing reliable and continuous output light control.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram schematically showing an example of an exposure apparatus according to the present invention. In the exposure apparatus shown in FIG. 1, laser light having a center wavelength of 200 nm or less output from the laser light source 10 passes through the oxygen-containing closed container 12, and then passes through the half mirror 71 and the light intensity uniforming illumination unit 72. After being folded by the reflection mirror 73, the light passes through the condenser lens 74 and irradiates the reticle 75. The reticle 75 is a mask on which a circuit pattern or the like is drawn. The laser light passing through the reticle 75 forms an image of the circuit pattern on the wafer substrate 77 via the projection lens 76. Although not shown, these optical systems of the exposure apparatus are hermetically sealed to prevent light energy reduction due to oxygen and ozone gas diffusion since the light has a wavelength of 200 nm or less, and the inside thereof is made of nitrogen or the like. It has been replaced by gas. Further, the projection lens 76
It is composed of a lens whose chromatic aberration has been corrected.

The laser light output from the laser light source 10 passes through the oxygen-containing closed container 12, and a part of the laser light is reflected by the half mirror 71 and enters the light receiving element 31 to detect the amount of the laser light. To the control device 32. When the amount of laser light changes and the detection signal fluctuates, a signal is sent from the control device 32 to the oxygen concentration adjusting device 33, and the adjusting device 33 is configured to change the oxygen concentration in the oxygen-containing closed container 12. ing.

FIG. 2 shows a laser light source 10 of the exposure apparatus shown in FIG.
FIG. 3 is a diagram for explaining the oxygen-containing closed container 12 in more detail. The laser light source 10 shown in FIG. 2 includes a laser-excited discharge unit 11 having a pair of discharge electrodes 11c and 11d sealed inside a laser medium gas, and a pair of resonators arranged so as to sandwich both end surfaces of the laser excitation unit 11. 13a and 13b, and each component 11, 13a and 13b is a laser light source 10
Are arranged on the optical axis p. An enclosed oxygen-containing container 12 containing oxygen gas therein is hermetically disposed close to the resonator 13a. An oxygen-containing optical path through which laser light passes is formed in the oxygen-containing closed container 12, and the optical path length is determined by the optical axis. corresponds to the length of the container 12 along p.

The laser excitation discharge section 11 of the laser light source 10
Has light transmission windows 11a and 11b on both end faces in the optical axis p direction. A predetermined voltage is applied to the discharge electrodes 11c and 11d from a power supply (not shown) during laser oscillation. The sealed container 12 has light transmitting windows 12a on both end surfaces in the optical axis p direction,
12b. These light transmission windows can be made of a material such as synthetic quartz, but may be any material that can transmit light having a center wavelength of 200 nm or less.

One of the resonators 13a constitutes an output mirror, and the output mirror 13a is sandwiched between the light transmission window 11a of the laser excitation discharge section 11 and the light transmission window 12b of the closed casing 12. Are located in The other resonator 13b constitutes a reflection mirror, and this reflection mirror 13b
Is disposed so as to be close to and opposed to the light transmission window 11b of the laser excitation discharge unit 11.

The oxygen-containing closed container 12 has a tube 12d and an oxygen sensor 12c for measuring oxygen concentration inside.
The oxygen concentration adjusting device 3 shown in FIG.
3 is provided and communicated with the inside of the container 12 by a pipe 12d. Based on a signal from the control device 32 shown in FIG. 1, the oxygen concentration control device 33 supplies oxygen gas for adjusting the oxygen concentration in the container 32, and supplies a gas other than oxygen such as nitrogen. Thereby, the oxygen concentration in the container 12 can be increased or decreased. The oxygen concentration in the container 12 can be measured by the oxygen sensor 12c, and the oxygen concentration in the container 12 can be kept constant based on a signal from the oxygen sensor 12c.

The operation of the exposure apparatus including the laser light source 10 and the oxygen-containing closed optical path 12 will be described. Laser light source 1
Assuming that the laser medium gas in the 0 laser excitation discharge unit 11 is, for example, ArF, an ArF excimer laser light source is configured. FIG. 8 shows a curve (a) showing the intensity distribution with respect to the wavelength of the laser light emitted from the ArF excimer laser light source, and a curve (b) showing the light absorption characteristics of oxygen gas in the intensity distribution of the laser light. This laser beam has a wavelength of 19 as shown in the intensity distribution curve (a).
It has a center wavelength in the vicinity of 3.4 to 193.5 nm. The light absorption characteristic curve (b) has a plurality of peaks and valleys, and in the valley corresponding to the predetermined wavelength, the intensity of the laser beam is reduced due to absorption by oxygen, but the peak corresponds to the predetermined wavelength. It can be seen that there is almost no absorption by oxygen at the peak.

When a predetermined voltage is applied between the discharge electrodes 11c and 11d of the laser excitation discharge unit 11 to excite the laser light source 10, a discharge is generated between the electrodes and stimulated emission of the excited excimer caused by the discharge. By laser light source 1
0 causes pulse oscillation. Thereby, the laser beam is reflected and reciprocates between the pair of resonators 13a and 13b in the optical axis p direction.
When the laser light source 10 reaches the critical oscillation state, pulsed laser light is emitted from the output mirror 13a.

When the laser light passes through the oxygen-containing closed container 12 when the light source is an ArF excimer laser light source, for example, as shown in a light absorption characteristic curve by oxygen (b) in FIG. It can be seen that the intensity of the laser light decreases at the wavelength of, and that the energy of the laser light as a whole decreases in the frequency band shown in FIG. The degree of decrease in the intensity of the laser light at a plurality of specific wavelengths depends on the number of oxygen molecules in the optical path through which the laser light passes.

Light emitted from the light transmission window 12a of the oxygen-containing closed container 12 passes through the half mirror 71 and reaches the wafer substrate 77 as described above. At this time, if the output of the laser light deviates from a predetermined value, the amount of light detected by the light receiving element 31 on which the light reflected by the half mirror 71 is incident fluctuates. A signal is sent from the control device 32 to the oxygen concentration adjusting device 33 in accordance with the fluctuation of the light amount, and the adjusting device 33
Increase or decrease the oxygen concentration in 2. The number of oxygen molecules also changes according to the increase or decrease of the oxygen concentration, and the degree of decrease in the intensity of the laser beam in the container 12 changes according to the change. For example, when the oxygen concentration increases and the number of oxygen molecules increases, the laser light is more absorbed and the intensity of the laser light decreases. Therefore, the relationship between the oxygen concentration in the oxygen-containing closed container 12, the light amount at the light receiving element 31, and the final light amount on the wafer substrate 77 is determined in advance, and the final light amount is set to a predetermined value. By adjusting the oxygen concentration in the container 12, the light amount can be controlled continuously, not stepwise.

Next, a modification of the oxygen-containing closed container in FIG. 2 will be described with reference to FIGS.

The oxygen-containing closed container 22 shown in FIG. 3 is provided with light transmitting windows 22a and 22b at both ends, and has bellows 23 so that the optical path length formed in the longitudinal direction L of the container can be changed.
Is provided. The bellows 23 is driven by a driving device 24 and is configured to be able to expand and contract in the L direction. The driving device 24 controls the bellows 2 based on a signal from the control device 32 in FIG.
3 can be expanded or contracted to change the optical path length, thereby changing the number of oxygen molecules in the optical path.

The closed container 25 shown in FIG. 4 has light transmitting windows 25a and 25b at both ends, contains air therein, and has a pipe 25d.
And a pressure sensor 25c for measuring pressure therein. An air pressure control device 26 is provided outside the container 25, and communicates with the inside of the container 25 by a pipe 25d. The air pressure control device 26 can increase or decrease the air pressure in the container 25 based on a signal from the control device 32 shown in FIG. This change in air pressure changes the number of oxygen molecules in the container. An ozone gas adsorbent 25e made of activated carbon or the like is provided on the inner surface of the container 25. Even if ozone gas is generated in the container 25 due to photolysis of oxygen by laser light, the ozone gas is adsorbed. Can be reduced. In particular, when the amount of ozone gas in the container increases, the light absorption characteristics in the container 25 change and there is a possibility that the wavelength of light fluctuates, but this can be prevented. The ozone gas adsorbent can be provided also in the containers 12 and 22 shown in FIGS.

FIG. 5 shows another example of the laser light source and the oxygen-containing container according to the present invention. The basic configuration of the laser light source shown in FIG. 5 is the same as that of FIG. 1 except that both the pair of resonators are arranged in the oxygen-containing closed vessel. FIG.
The laser-excited discharge unit 41 of the laser light source 40 has a pair of discharge electrodes 41c and 41d that hermetically seals the laser medium gas inside, and is on both sides of the light transmission windows 41a and 41b of the discharge unit 41 and on the optical axis p. Oxygen-containing closed containers 42 and 44 are arranged in the container.

A light transmitting window 42a is provided on one end surface of the container 42, and the light transmitting window 4a of the laser excitation discharge section 41 is provided on the other end surface.
1a is directly joined to the surface. One end of the container 44 is directly joined to the surface of the light transmitting window 41b of the laser excitation discharge unit 41, and the other end is closed. An output mirror 43a is arranged inside the container 42 so as to be close to and opposed to the light transmission window 41a of the laser excitation discharge unit 41. Also,
Inside the container 44, a reflection mirror 43b is arranged so as to be close to and opposed to the light transmission window 41b of the discharge unit 41. The laser light is emitted from the light transmission window 42a of the container 42.

In the configuration shown in FIG. 5, the same effect as in FIG. 2 can be obtained. In this example, the oxygen molecule number adjusting means is not shown, but may be the same as that shown in FIG. 2 or the one shown in FIGS.

FIG. 6 shows still another example of the laser light source and the oxygen-containing closed container according to the present invention. The basic configuration of the laser light source shown in FIG. 6 is the same as that of FIG. 5 except that the laser excitation discharge part and the pair of resonators are arranged in one oxygen-containing closed container. A laser light source 50 shown in FIG. 6 includes a laser excitation discharge section 51 having a pair of discharge electrodes 51c and 51d in which a laser medium gas is sealed and a pair of resonators 53a and 5d.
3b, and the oxygen-containing closed container 52 includes a discharge unit 51 and a pair of resonators 53a and 53b therein.

A light transmitting window 52a is provided at one end of the container 52.
Is provided, and the other end face is closed. The laser-excited discharge unit 51 includes light transmitting windows 51a and 51a at both end surfaces in the optical axis p direction.
b, the light transmitting window 51a and the light transmitting window 5 of the container 52 are provided.
2a is arranged in the container 52 so as to be separated by a predetermined distance. A pair of resonators 5 sandwich the discharge section 51 therebetween.
3a and 53b are also arranged in the container 52. The output mirror 53a is disposed so as to be close to and opposed to the light transmission window 51a of the discharge unit 51. Also, the reflection mirror 53b
Are disposed so as to be close to and opposed to the light transmission window 51b of the discharge unit 51. The laser beam is transmitted through the light transmitting window 52 of the container 52.
Released from a. An oxygen-containing optical path is formed between the output mirror 53a and the light transmission window 52a in the oxygen-containing closed vessel 52 when laser light is output.

In the configuration shown in FIG. 6, the same effect as in FIG. 2 can be obtained. In this example, the oxygen molecule number adjusting means is not shown, but may be the same as that shown in FIG. 2 or the one shown in FIGS. In addition, in the examples shown in FIGS. 5 and 6, a cover may be provided on an optical part such as a resonator or a portion that comes into contact with oxygen, such as an inner surface of a container, to prevent damage.

In the exposure apparatus shown in FIG. 1, a plurality of the above-mentioned oxygen-containing closed containers may be arranged on the optical axis p. In this case, the container in which the oxygen concentration is fixed and the container in which the oxygen molecule number adjusting means is provided may be separately arranged.

Next, another example of the exposure apparatus of the present invention will be described with reference to FIG. FIG. 7 is a schematic diagram showing a schematic configuration of the exposure apparatus. The basic configuration is the same as that of the exposure apparatus shown in FIG. 1, but a means for detecting the amount of light in the optical system of the apparatus is added. is there. In the exposure apparatus shown in FIG. 7, a half mirror 81 is disposed between a reflection mirror 73 and a condenser lens 74, light reflected by the half mirror 81 is incident on a light receiving element 82, and the amount of laser light is detected. The detection signal is sent to the control device 32. When the detection signal of the light amount of the laser beam fluctuates, a signal is sent from the control device 32 to the oxygen concentration adjusting device 33, and the adjusting device 33 increases or decreases the oxygen concentration in the container 12. Therefore, according to the configuration of the exposure apparatus shown in FIG. 7, the same effect as in the case of FIG. 1 can be obtained. The position where the light amount is detected is not limited to this example, but may be another position in the optical system.

[0033]

According to the present invention, by controlling the number of oxygen molecules in the oxygen-containing optical path through which light having a center wavelength of 200 nm or less passes based on the detected light amount, the light required for the exposure on the substrate is reduced. Energy can be controlled continuously. Therefore, it is possible to provide an exposure apparatus and an exposure method capable of performing reliable and continuous output light control.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an exposure apparatus according to the present invention.

FIG. 2 is a schematic side sectional view showing an example of a laser light source, an oxygen-containing closed container, and an oxygen molecule number adjusting means that can be used in the exposure apparatus of FIG.

FIG. 3 is a schematic side sectional view showing another example of the oxygen-containing closed container and the oxygen molecule number adjusting means which can be used in the exposure apparatus of FIG.

FIG. 4 is a schematic side sectional view showing another example of the oxygen-containing closed container and the oxygen molecule number adjusting means that can be used in the exposure apparatus of FIG.

5 is a schematic side sectional view showing another example of a laser light source and an oxygen-containing closed container that can be used in the exposure apparatus of FIG.

6 is a schematic side sectional view showing another example of a laser light source and an oxygen-containing closed container that can be used in the exposure apparatus of FIG.

FIG. 7 is a schematic diagram showing another example of the exposure apparatus according to the present invention.

FIG. 8 shows an intensity distribution curve (a) of light output from an ArF excimer laser and a light absorption characteristic curve (b) of oxygen.

[Explanation of symbols]

10, 40, 50 Laser light source 12, 22, 25, 42, 52, 44 Oxygen-containing closed container 25e Ozone adsorbing means 31, 82 Light receiving element 32 Control device 33 Oxygen concentration control device 24 Drive device 26 Air pressure control device 71, 81 Half Mirror 75 reticle 76 projection lens 77 wafer substrate

Claims (4)

[Claims] 1. An exposure apparatus for transferring a predetermined pattern onto a substrate by light from a light source via an optical system, wherein the light source outputs light having a central wavelength of 200 nm or less, and the light output from the light source passes through the light source. A sealed oxygen-containing optical path, a means for adjusting the number of oxygen molecules in the sealed oxygen-containing optical path, a means for detecting the amount of light output from the light source, and the oxygen molecule based on a detection result of the light amount Means for controlling the number adjusting means. 2. An exposure apparatus according to claim 1, wherein said oxygen-containing optical path is disposed between said light source and said light amount detecting means. 3. The exposure apparatus according to claim 1, wherein the oxygen-containing optical path is formed in a closed container. 4. An exposure method for transferring a predetermined pattern onto a substrate by light from a light source via an optical system, wherein the step of detecting a light amount of light output from the light source; Changing the number of oxygen molecules in a closed optical path through which the light passes.