JPH11288870A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner, which is capable of restraining contaminates from adhering to a projection optical system, so as to prevent a photosensitive substrate in exposure or to make a photosensitive substrate undergo irregular exposures. SOLUTION: An optical device 14a is provided detachably between a photosensitive substrate 8 and a lens 7a, which is located nearest to the substrate 8 and included in a projection optical system 7, and when the exposure of the substrate 8 to light is detected by a light volume sensor 9 for detecting a reduction or irregularities in the exposure, a clean optical device 14b is arranged between the photosensitive substrate 8 and the lens 7a, and the contaminated optical device 14a is cleaned with a cleaning device 13. The transmittance of the optical device 14a is monitored with light volume sensors 35 and 36 while it is cleaned, and a cleaning operation is stopped when the transmittance of the device 14a becomes higher than a prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an exposure apparatus used for semiconductor manufacturing and the like.

[0002]

2. Description of the Related Art In a lithography process for manufacturing a semiconductor element or a liquid crystal substrate, an exposure apparatus for exposing a pattern image of a reticle (photomask or the like) onto a photosensitive substrate via a projection optical system is used. In recent years, semiconductor integrated circuits have been developed in the direction of miniaturization, and in the lithography process, a method of shortening the exposure wavelength of a lithography light source has been considered as a means for further miniaturization.
In a semiconductor exposure apparatus called a stepper, the wavelength of light used for exposure has been shortened from visible light to ultraviolet light, and an exposure apparatus using KrF excimer laser light having a wavelength of 248 nm as exposure light has already been developed. . Further, a mercury lamp having a wavelength of about 220 nm or 184 nm, an ArF excimer laser having a wavelength of 193 nm, and the like have been attracting attention as short-wavelength light source candidates.

[0003]

However, in general, when the wavelength is shortened, light causes a chemical reaction or is activated energetically. As a result, when short-wavelength light is used, a problem occurs that does not occur with long-wavelength light. For example, when ArF excimer laser light is used, it reacts with oxygen in the air to generate ozone,
When the wafer is irradiated, a phenomenon occurs in which the resist applied on the wafer evaporates, and a hydrocarbon gas is mainly generated.

When ozone is generated, light utilization efficiency (that is, transmittance) is reduced due to the absorption of exposure light by oxygen molecules, and the performance of the apparatus is deteriorated due to the reaction between ozone and the optical material surface or other components. Particularly problematic is that when the resist evaporates and the gas adheres to the surface of the optical element, the exposure light is absorbed or reflected to lower the transmittance, and furthermore, the heat is absorbed when the light is absorbed. This causes contaminants on the optical element surface to be fixed and difficult to remove.

When such a phenomenon occurs in the exposure apparatus, the exposure amount is reduced and the throughput is reduced, and the position of the exposure amount is uneven, so that the resolution is reduced and the line width control is non-uniform. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus capable of preventing contaminants from adhering to a projection optical system and preventing a decrease in exposure amount and a variation in exposure amount.

[0007]

An embodiment of the present invention will be described with reference to FIGS. (1) The invention according to claim 1 is applied to an exposure apparatus that illuminates a mask 5 on which a pattern is formed with exposure light, and projects the illuminated pattern onto a photosensitive substrate 8 by a projection optical system 7. The above-mentioned object is achieved by providing an optical member 14a which is provided at the position closest to the photosensitive substrate 8 so as to be insertable and removable, and cleaning means 13, 32 and 33 for taking out the optical member 14b from the exposure optical path and cleaning it. I do. Here, a reticle or a mask on which a pattern is formed is generically called a mask. (2) Explaining in association with FIG. 3, the invention according to claim 2 is the exposure apparatus according to claim 1, wherein the optical member comprises:
A plurality of optical elements 14a and 14b provided outside the exposure optical path
The cleaning means 13 includes a plurality of optical elements 14.
a or 14b (optical element 14a in FIG. 3)
Are disposed at a position closest to the photosensitive substrate 8 in the exposure light path, and disposing / discharging means 32 and 33 for discharging the optical element disposed at that position out of the exposure light path are provided. At least one of the plurality of optical elements provided (FIG. 3
Then, the optical element 14b) is cleaned. (3) The exposure apparatus according to claim 2, wherein the cleaning means irradiates the cleaning target optical element 14b with ultraviolet light to remove the contaminant 31 attached to the surface thereof. 13. (4) According to a fourth aspect of the present invention, in the exposure apparatus according to the third aspect, exposure light is used as ultraviolet light. (5) The exposure apparatus according to any one of claims 2 to 4, wherein the sensor 3 detects the transmittance of the optical elements 14a and 14b cleaned by the cleaning means 13.
5 and 36, and a control device 15 for terminating the cleaning of the optical elements 14a and 14b by the cleaning means 13 based on the detection values of the sensors 35 and 36. (6) Explained in connection with FIG. 1, the invention according to claim 6 is the exposure apparatus according to any one of claims 2 to 5, wherein the exposure apparatus transmits the exposure light transmitted through the optical elements 14a and 14b in the exposure optical path. A light quantity sensor 9 for detecting the light quantity, and optical elements 14a, 14a in the exposure optical path based on the detection value of the light quantity sensor 9.
A control device 15 is provided for controlling the cleaning device 13 to take out 4b from the exposure optical path and clean it. (7) Referring to FIGS. 5 and 6, the exposure apparatus according to claim 7 is the exposure apparatus according to claim 1, wherein the optical member 40 is generated by irradiating the photosensitive substrate 8 with exposure light. The cleaning means 13 has at least two adhering surfaces A1 and A2 to which the substance 31 to be adhered can be attached. When the substance 31 adheres to the one adhering surface A2, the cleaning unit 13 moves the one adhering surface A2 to a predetermined position outside the exposure optical path. Moving and the other attachment surface A1
Moving means 33 for moving the optical member 40 so as to dispose the optical member 4 in the exposure optical path, and the optical member 4 moved to a predetermined position.
The substance 31 attached to one of the attachment surfaces A2 is removed. (8) According to an eighth aspect of the present invention, in the exposure apparatus according to the seventh aspect, the optical element 40 is configured as a part of the projection optical system 7 of the exposure apparatus.

In the meantime, in the section of the means for solving the above-mentioned problems which explains the constitution of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easy to understand, but the present invention However, the present invention is not limited to the embodiment.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. FIG.
In the exposure apparatus shown in (1), the excimer laser light source 1 is provided separately from the stepper body S, and is installed on a common floor.
The reason why the light source 1 and the stepper main body S are separately provided in this way is to prevent the size and weight of the stepper main body S from becoming too large, to facilitate maintenance of the light source 1, and to generate the light source 1. This is to reduce the influence of vibration and heat on the stepper body S.

The laser light emitted from the light source 1 is reflected by mirrors M1 and M2 provided in the light transmission system 2 and guided to the illumination optical system 3 of the stepper body S. Reference symbol MS denotes a shutter mirror. When the shutter mirror MS is driven to a state shown by a solid line, laser light is guided from the light transmission system 2 to the illumination optical system 3, and when the shutter mirror MS is driven to a state shown by a broken line, the laser beam is emitted. The light is guided to the light transmission system 4. When the laser light is guided to the light transmission system 4, the laser light is reflected by the mirror M3 and guided to the cleaning device 13. The cleaning device 13
Will be described later in detail. The light transmitting systems 2 and 4 are configured to efficiently guide the laser light.
The internal space of 4 is replaced by nitrogen gas or the like so that the laser beam does not react with oxygen in the air.

The illumination optical system 3 includes optical elements (not shown) such as a beam expander, a fly-eye lens, a relay lens, and a condenser lens. After uniforming to such an intensity, a predetermined area of the reticle 5 placed on the reticle stage 6 is illuminated. A circuit pattern of a semiconductor chip is formed on the reticle 5.
The laser light that has passed through the wafer stage 1
By irradiating the wafer 8 on 0, a reduced image of the pattern of the reticle 5 is transferred onto the wafer 8. An optical element 14a is disposed on an optical path between the projection optical system 7 and the wafer 8, and prevents contamination of the projection optical system.

On the wafer stage 10, a light quantity sensor 9 for measuring the light quantity of the laser light irradiated on the wafer 8 is provided. A control device 15 controls the entire apparatus, and controls a motor 33 described later based on a signal from the light amount sensor 9. The above-described illumination optical system 3, reticle stage 6, projection optical system 7, wafer stage 10, etc.
It is mounted on the vibration isolator 11 so that the vibration transmitted from the device 2 is reduced as much as possible. As shown in FIG. 2, the light source 1 may be placed on a floor 22 different from the stepper main body S in order to improve maintainability. A mechanism is provided for monitoring the optical axis deviation and performing automatic correction.

FIG. 3 is a view showing the wafer 8 and the cleaning device 13 in detail. Since the excimer laser beam from the light source 1 has high energy and easily reacts with oxygen in the air, the internal space of the illumination optical system 3 and the projection optical system 7 is replaced with nitrogen gas or the like as in the light transmission systems 2 and 4. . However, it is difficult to completely replace the vicinity of the wafer 8 with nitrogen gas, and only the flow of nitrogen gas near the wafer can be performed. On the other hand, since a reticle image is formed on the wafer 8 by the laser beam, the energy per unit area on the wafer 8 increases,
The laser beam reacts with oxygen molecules present in the vicinity of the wafer to generate ozone, or resist 3 applied to wafer 8
0 is evaporated. The resist 30 is made of a photosensitive organic substance, and an organic gas 31 is generated by irradiating the resist 30 with a laser beam. Hereinafter, the organic gas 31 is referred to as a pollutant 31.

Reference numeral 7a denotes a lens constituting the projection optical system 7, which is the lens closest to the wafer 8. In FIG. 3, 7a
Is shown by a convex lens having a curvature, but in general, it is often a parallel glass plate for canceling the total aberration of the lens system constituting the projection optical system 7. As previously mentioned,
In the conventional apparatus, the generated contaminant 31 adheres to the surface of the lens 7a, causing a decrease in the exposure amount on the wafer 8, an unevenness in the exposure amount, and the like. In the exposure apparatus of the present embodiment, the optical element 14a is provided between the projection optical system 7 and the wafer 8.
Is disposed, the contaminant 3 is present on the surface of the optical element 14a.
The attachment of 1 prevents the contaminant 31 from adhering to the lens 7a.

FIG. 4 is a view of the portion shown in FIG. 3 viewed from above (projection optical system side). Reference numeral 32 denotes a holder for holding the optical element 14a, and the holder 32 includes a plurality of optical elements (FIG. 4).
In the example shown in FIG. 2, two optical elements 14a and 14b) are held, and one of the optical elements is arranged on the optical path between the projection optical system 7 and the wafer 8 by rotating the holder 32 by the motor 33. can do.

As described above, when the contaminant 31 adheres to the surface of the optical element 14a due to the exposure operation and the decrease in the exposure amount or the unevenness in the exposure amount becomes too large to be ignored, the exposure operation is stopped. The holder 32 is rotated by 180 ° to move the contaminated optical element 14a into the cleaning device 13. At the same time, the clean optical element 14b cleaned by the cleaning device 13 is arranged on the optical path between the projection optical system 7 and the wafer 8, and the exposure operation is restarted. When detecting a decrease in the exposure amount or unevenness in the exposure amount, the light amount sensor 9 (FIG. 3) provided on the wafer stage 10 is moved to a position immediately below the projection optical system 7 to perform the measurement.

The optical elements 14a and 14b are made of, for example, glass plates. 1 and 3, the optical elements 14a, 1
Although the thickness of 4b is drawn thick, it is preferable to make the thickness as thin as possible in order to prevent occurrence of aberration, and it is possible to reduce the absorption of laser light to a negligible level by making it thin. If it is desired to increase the thickness of the optical elements 14a and 14b, SiO ₂ or CaF ₂ may be used as the glass material.
Etc. may be used. The optical elements 14a,
Although 14b may be regarded as a part of the projection optical system, in any case, the optical characteristics of the exposure apparatus are set in consideration of the characteristics of the optical elements 14a and 14b.

Next, the optical element 14 by the cleaning device 13
The cleaning of a and 14b will be described. As described above, the laser light of the light source 1 is guided to the cleaning device 13 by the light transmission system 4 and diffused and uniformized by the lens system 34 to form the optical element 1.
4b. When the optical element 14b is irradiated with ultraviolet light such as excimer laser light, the optical element 14b
The contaminants adhering to the surface of b are separated from the surface.
Such a method of irradiating ultraviolet light to remove a substance adhering to the lens surface is called optical cleaning.

Nitrogen gas or pure air is supplied into the cleaning device 13 from a supply port 13a, and gas in the cleaning device containing the contaminant 31 separated from the optical element 14b is discharged from the discharge port 1a.
3b. From the gas supplied to the cleaning device 13, organic and inorganic ions contained in the gas are removed in advance using an ion filter or the like. By the way, when air is used as the supply gas, oxygen in the air is ozonized by the laser beam, and the ozone decomposes the contaminants attached to the optical element 14b, so that more effective cleaning is expected. it can. Whether or not the optical element 14b has been sufficiently cleaned with light is determined by the control device 15 by monitoring the amount of light incident on the optical element 14b and the amount of light transmitted therethrough with the light amount sensors 35 and 36. For example, if the transmittance exceeds a predetermined value, it is determined that the light cleaning has been sufficiently performed, and the light cleaning is terminated. In the above-described example, the contaminants attached to the optical elements 14a and 14b are removed by light cleaning. However, the cleaning is performed by a physical / chemical cleaning method other than light cleaning so that the contaminants are decomposed by ozone. It may be performed.

In the embodiment described above, the holder 3
2, the optical elements 14a and 14b are held and the holder 32 is rotated to dispose the optical elements in the exposure optical path and discharge the optical elements from the exposure optical path. The optical element is placed in a storage device such as a stocker outside the exposure light path, and the contaminated optical element is discharged from the exposure light path by the arrangement / discharge mechanism and moved into the cleaning device, and any one of the storage devices in the storage device. The optical element may be arranged in the exposure optical path by an arrangement / discharge mechanism.

FIGS. 5 and 6 are views showing a modification of the above-described embodiment, corresponding to FIG. 3 described above, and FIG. 6 is a view of FIG. 5 viewed from the wafer 8 side. In addition. In the following, FIG.
The following description focuses on the differences from the first embodiment. In FIG. 5, reference numeral 40 denotes a disc-shaped optical element, which is rotationally driven by a motor 33 as shown by a reference symbol R in FIG. The areas A1 and A2 are areas to which the contaminant 31 generated when the exposure light is irradiated onto the wafer 8 (the surface 4 of the optical element 40 facing the wafer 8).
0a). Note that the region is also called an attachment surface. Here, the area of the surface 40a needs to be at least twice the area of the area A1 (the area of the area A2 is equal to the area A1).

For example, when exposure is performed by rotating the optical element 40 with the motor 33 so that the area A1 is arranged in the exposure optical path as shown in FIG. 5, the contaminant 31 adheres to the area A1, and the contaminant 31 When the adhesion of the particles increases, the change in the exposure condition exceeds the allowable range. Therefore, if necessary, the change in the exposure condition is measured by using the light amount sensor 9, and if the change in the exposure condition exceeds the allowable range, the area A2 of the optical element 40 is in the exposure light path, and the area A1 is in the cleaning device 13. The optical element 40 is rotated by 180 ° by the motor 33 so as to be inside.
After that, the area A1 of the optical element 40 is cleaned by the cleaning device 13, and the attached contaminants 31 are removed. In addition,
The area A2 arranged in the exposure light path has already been cleaned by the cleaning device 13.

In the above-described embodiment, the laser beam is introduced into the cleaning device 13 by driving the shutter mirror MS (FIG. 1) when the exposure operation is not performed (for example, while replacing the wafer). The light may be guided to the light transmission system 4. In addition to the above-described method using a mirror for the light transmitting system 4, the laser beam reflected by the shutter mirror MS may be condensed by a lens and guided to the cleaning device 13 by an optical fiber. In the above-described example, the light source for exposure 1 is used as light used for light cleaning. However, a light source for light cleaning that generates ultraviolet light different from the exposure light may be provided separately from the light source 1.

As a method of determining when to perform the optical cleaning of the optical elements 14a and 14b, in addition to using the light amount sensor 9 as described above, the number of laser pulses at the time of exposure is counted and a predetermined count is performed. If the number of wafers reaches the specified number, there is a method of performing optical cleaning, or if the number of processed wafers 8 reaches a specified number, a method of performing optical cleaning.

In this embodiment, the light source of the exposure apparatus 1 is illumination light in the ultraviolet wavelength range, for example, F2 laser light (wavelength 1).
It is also possible to use EUVL such as soft X-rays having a shorter wavelength. Further, as the exposure apparatus, a scanning type exposure apparatus that synchronously moves the mask and the substrate to expose the mask pattern, exposes the mask pattern while the mask and the substrate are stationary, and sequentially moves the substrate in steps The present invention can also be applied to a step-and-repeat type exposure apparatus. The type of the exposure apparatus is not limited to an exposure apparatus for manufacturing a semiconductor, and is, for example, an exposure apparatus for a liquid crystal that exposes a liquid crystal display element pattern to a square glass plate, or for manufacturing a thin film magnetic head. It can be widely applied to an exposure apparatus. The projection optical system inspection apparatus and the projection exposure apparatus according to the present invention are composed of the respective components already described in the respective embodiments, and these components are electrically or mechanically operated so as to achieve the functions described above. It is assembled by connecting optically and optically.

In the correspondence between the embodiment described above and the elements of the claims, the wafer 8 constitutes a photosensitive substrate, the holder 32 and the motor 33 constitute arrangement / discharge means, respectively. Means are cleaning device 13, holder 3
The cleaning means of the present invention is constituted by the cleaning device 13.

[0027]

As described above, according to the exposure apparatus of the present invention, an optical element is removably provided at the position closest to the photosensitive substrate in the exposure optical path, and the optical element is placed in the exposure optical path. From the optical substrate closest to the photosensitive substrate, so that even if contaminants adhere to the photosensitive substrate, the contaminants can be easily removed by the cleaning unit. It is possible to keep the above. In the exposure apparatus according to the second aspect of the present invention, a plurality of optical elements that can be disposed at the position closest to the sensitive substrate in the exposure optical path are provided, and at least one of the optical elements outside the exposure optical path is cleaned by the cleaning unit. With this configuration, even while one optical element is being cleaned, the exposure operation can be performed by disposing another optical element cleaned by the cleaning unit in the exposure optical path. In the exposure apparatus according to the fourth aspect of the present invention, a new light source is not required by using the exposure light for cleaning the optical element, so that an increase in cost due to the cleaning can be suppressed. In the exposure apparatus according to the fifth aspect of the present invention, since the transmittance of the optical element is detected and the cleaning by the cleaning unit is terminated, the optical element can be reliably cleaned. In the exposure apparatus according to the sixth aspect of the present invention, whether or not the optical element needs to be cleaned is determined based on the detection value of the light amount sensor, and the cleaning is performed. Generation can be prevented before it occurs.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing another installation example of the light source 1;

FIG. 3 is a diagram showing a wafer 8 portion and a cleaning device 13 in detail.

FIG. 4 is a view of the part shown in FIG. 3 as viewed from the projection optical system side.

FIG. 5 is a diagram showing a modification of the exposure apparatus according to the embodiment of the present invention.

6 is a view of the apparatus shown in FIG. 5 as viewed from the wafer 8 side.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source 2, 4 light transmission system 3 illumination optical system 5 reticle 6 reticle stage 7 projection optical system 7 a lens 8 photosensitive substrate 9, 35, 36 light quantity sensor 10 wafer stage 11 anti-vibration device 13 cleaning device 14 a, 14 b, 40 optical Element 40a Opposing surface 15 Controller 30 Resist 31 Contaminant 32 Holder 33 Motor 34 Lens system A1, A2 area M1, M2, M3 mirror MS Shutter mirror

Claims (8)

[Claims] 1. An exposure apparatus for illuminating a mask on which a pattern is formed with exposure light and projecting the illuminated pattern onto a photosensitive substrate by a projection optical system, the exposure apparatus being closest to the photosensitive substrate in an exposure optical path. An exposure apparatus comprising: an optical member that is removably provided at a position; and a cleaning unit that removes the optical member from an exposure optical path and performs cleaning. 2. The exposure apparatus according to claim 1, wherein the optical member includes a plurality of optical elements provided outside an exposure light path, and the cleaning unit includes one of the plurality of optical elements. Is disposed at a position closest to the photosensitive substrate in the exposure light path, and further includes a disposing / discharging unit that discharges the optical element disposed at the position outside the exposure light path, and is provided outside the exposure light path. An exposure apparatus for cleaning at least one of the plurality of optical elements obtained. 3. An exposure apparatus according to claim 2, wherein said cleaning means is constituted by a light cleaning apparatus for irradiating an optical element to be cleaned with ultraviolet light to remove contaminants adhered to its surface. Exposure equipment characterized. 4. The exposure apparatus according to claim 3, wherein exposure light is used as the ultraviolet light. 5. The exposure apparatus according to claim 2, wherein the sensor detects a transmittance of the optical element to be cleaned by the cleaning unit, and the cleaning unit performs the cleaning based on a detection value of the sensor. An exposure apparatus, comprising: a control device for terminating cleaning of an optical element. 6. The exposure apparatus according to claim 2, wherein a light amount sensor for detecting a light amount of the exposure light transmitted through the optical element in the exposure light path, and a detection value of the light amount sensor. A control device for controlling the optical element in the exposure optical path to be taken out of the exposure optical path and to be cleaned by the cleaning unit. 7. The exposure apparatus according to claim 1, wherein the optical member has at least two attachment surfaces to which a substance generated by irradiation of exposure light from the photosensitive substrate can attach. When the substance is attached to one of the attachment surfaces, the optical member is moved so that the one attachment surface moves to a predetermined position outside the exposure light path, and the other attachment surface is disposed in the exposure light path. An exposure apparatus comprising: a moving unit that moves; and removing the substance attached to the one attachment surface of the optical member moved to the predetermined position. 8. The exposure apparatus according to claim 7, wherein the optical element is configured as a part of a projection optical system of the exposure apparatus.