JP2002050558A - Projection aligner and method for manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deteriorations of an image due to aberrations occurring at a pellicle. SOLUTION: In a projection aligner, a leans group 114 is moved in the direction of an optical axis by a drive unit 150, so that the group 114 is positioned at a position for correcting the aberrations occurring at the pellicle 104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection exposure apparatus and a device manufacturing method.

[0002]

2. Description of the Related Art The wave of miniaturization of semiconductor devices is rapid.
The design rule is also trying to achieve 130nm in the mass production process. The mainstream processing technology is optical lithography using a projection exposure apparatus, and various measures have been taken to extend the life. The wavelength of the exposure light (hereinafter, "exposure wavelength")
) Is an effective means for that. At present, KrF excimer laser (wavelength 248 nm) and ArF excimer laser (wavelength 193 nm) are used as exposure light sources, and in the near future, F2 excimer laser (157 nm) will be used as exposure light source. it is conceivable that.

[0003] The problem of shortening the exposure wavelength is that when the wavelength is shortened, the light absorption of the optical material (glass material, film material) increases and the transmittance of the optical system is extremely reduced.

For example, when an F2 excimer laser is used, a pellicle film having a thickness of 1 μm or less for preventing dust from contaminating a circuit pattern due to dust (foreign matter such as dust and dirt) provided on a reticle is exposed to light having a wavelength of 157 nm. Absorbs a lot of light,
In addition to the deterioration of the protective film itself, the transmittance of the protective film is reduced, and the gas generated at that time may contaminate the lens of the projection optical system.

As one means for solving this problem, a wavelength of 157 nm is used instead of the above-mentioned optical thin film conventionally used.
There is a method using a flat glass material (hereinafter, referred to as “hard pellicle”) having a high transmittance to the exposure light of m.

[0006]

However, when a reticle provided with a hard pellicle on the projection optical system side is mounted on a reticle stage of a projection exposure apparatus and its circuit pattern is projected and exposed on a wafer, the following problems arise. There is.

That is, since the glass material forming the hard pellicle cannot be processed as thin as a conventional pellicle film, its thickness is as large as 200 to 300 μm. If placed between optical systems, the circuit pattern image will be blurred or distorted due to aberrations generated in the hard pellicle, and as a result, the line width of the resist pattern on the developed wafer will be thin or the position will be shifted. As a result, the production yield of semiconductor devices is reduced.

It is an object of the present invention to provide a projection exposure apparatus and a device manufacturing method which can accurately project a circuit pattern image on a wafer even when a reticle with a hard pellicle is used.

[0009]

According to a first aspect of the present invention, there is provided an illumination optical system for illuminating a reticle with light from a light source, and a projection optical system for projecting the reticle pattern onto a wafer. A projection exposure apparatus having a dust proof film or plate provided on the projection optical system side and capable of installing the reticle, further comprising a correction unit for correcting aberrations generated in the dust proof film or plate.

According to a second aspect of the present invention, in the projection exposure apparatus according to the first aspect, the reticle having the dustproof film or plate and the reticle having no dustproof film or plate can be installed. It is characterized by the following.

According to a third aspect of the present invention, in the projection exposure apparatus according to the first aspect, a plurality of types of reticles having different thicknesses of the dustproof film or plate can be installed. .

According to a fourth aspect of the present invention, in the projection exposure apparatus according to any one of the first to third aspects, thickness detection means for detecting information on the thickness of the dust-proof film or plate before the reticle is set on the reticle stage. It is characterized by having.

According to a fifth aspect of the present invention, in the projection exposure apparatus according to the fourth aspect, the thickness detecting means is located inside a reticle transport system.

According to a sixth aspect of the present invention, in the projection exposure apparatus according to the fifth aspect, the thickness detecting means has means for reading a bar code recorded on the reticle, the information of the thickness being recorded. Features.

According to a seventh aspect of the present invention, in the projection exposure apparatus according to the fifth aspect, the thickness detecting means has a measuring device for measuring the thickness of the dust-proof film or plate.

According to an eighth aspect of the present invention, in the projection exposure apparatus according to any one of the first to seventh aspects, the correction means includes one or more of the projection optical systems according to a thickness of the dust-proof film or plate. It is characterized by having means for moving the lens in the optical axis direction.

According to a ninth aspect of the present invention, in the projection exposure apparatus according to any one of the first to eighth aspects, the correction means is provided in the projection optical system according to the thickness of the dust-proof film or plate. It is characterized by having a transparent plate that can be attached and detached in the optical path.

According to a tenth aspect of the present invention, in the projection exposure apparatus according to the ninth aspect, the correcting means is provided when the thickness of the dust-proof film or plate is smaller than a predetermined thickness or when the dust-proof film or plate is thinner. When there is no, a plurality of transparent plates having different thicknesses can be inserted between the dustproof film or plate and the projection optical system by inserting a transparent plate having a thickness equal to the predetermined thickness. It is characterized by.

According to an eleventh aspect of the present invention, in the projection exposure apparatus according to any one of the first to tenth aspects, the correcting means includes a predetermined lens and a lens of the projection optical system according to the thickness of the dust-proof film or plate. And means for changing the pressure of the gas in the space between them.

According to a twelfth aspect of the invention, in the projection exposure apparatus according to the first to eleventh aspects, the correction means changes the wavelength of light from the light source in accordance with the thickness of the dust-proof film or plate. It is characterized by having.

According to a thirteenth aspect of the present invention, in the projection exposure apparatus according to the first to twelfth aspects, the correcting means are opposite to each other in a direction orthogonal to the optical axis according to the thickness of the dust-proof film or plate. Characterized by having a pair of aspherical plates that are displaced in a plane.

According to a fourteenth aspect of the present invention, in the projection exposure apparatus according to the first to thirteenth aspects, the correcting means has means for changing a shape of a refracting surface of the lens.

According to a fifteenth aspect of the present invention, in the projection exposure apparatus according to any one of the first to fourteenth aspects, the correction means includes the projection optical system.

According to a sixteenth aspect of the present invention, in the projection exposure apparatus according to the first to fifteenth aspects, the dust-proof film or plate is formed of any one of quartz, fluorine-doped quartz, and fluorite. And

According to a seventeenth aspect, in the projection exposure apparatus according to any one of the first to sixteenth aspects, the light source is an F2 excimer laser.

According to an eighteenth aspect of the present invention, there is provided a device manufacturing method comprising the steps of: exposing a wafer with a device pattern using the projection exposure apparatus according to any one of claims 1 to 17; and developing the exposed wafer. Is the way.

It is difficult to control the thickness of the glass material of the hard pellicle, and a thickness tolerance of 10 μm or more occurs when the hard pellicle is made in a normal manufacturing process. However, according to each embodiment described below, it is possible to cope with a case where a plurality of types of reticles having different thicknesses of hard pellicles are installed in the projection exposure apparatus. Further, according to the present invention, it is possible to cope with a case where a reticle with a hard pellicle, a reticle without a pellicle film, and a conventional reticle with a pellicle film are mixed and carried into one projection exposure apparatus.

[0028]

FIG. 1 is a schematic view showing a scanning type reduced projection exposure apparatus according to a first embodiment of the present invention.

In FIG. 1, a laser beam having a wavelength of 157 nm emitted from a light source 110 composed of an F2 excimer laser is converted into an exposure light beam having a uniform cross-sectional shape and a uniform illuminance distribution by an illumination system 111, and is fixed to a reticle stage 102. The circuit pattern of the reticle 103 is illuminated.

The exposure light beam that has passed through the circuit pattern of the reticle 103 travels inside the reduction projection lens 120 with a magnification of 1/2, 1/4 or 1/5 as an image light beam (hatched portion in the figure). This imaging light flux forms an image with almost no aberration on the resist of the wafer 121 held on the XY stage by the lens group 114 to 118 made of fluorine-doped quartz and fluorite of the projection lens 120 and the stop 116. Then, a reduced image of the circuit pattern on the lower surface of the reticle 103 is formed and transferred (exposed).

In the case of the scanning type projection exposure apparatus of this embodiment, a slit-like good image area (aberration-free area) intersecting with the optical axis of the reduction projection lens 120 is used. A part of the reticle 103 is illuminated by the exposure light beam having the shape, and the reticle 103 and the wafer 121 are scanned in synchronization with the exposure light beam and the lens 120 in directions A and AR opposite to each other so that the entire circuit pattern of the reticle 103 Is transferred to the resist on the wafer 121. (In the figure, arrows A and AR indicate the scanning directions of the reticle and the wafer, respectively.)

It is to be noted that a reduced catadioptric optical system having a lens and a concave mirror may be used instead of the reduced projection lens 120, and an off-axis circular slit-like good image area of the optical system may be used. Whatever type of projection optics you use,
It is desirable that both the reticle stage side (object side) and the wafer stage side (image side) are telecentric systems, but only the wafer stage side may be telecentric. The projection optical system is placed in an atmosphere of an inert gas such as nitrogen or helium.

The light source 110 may employ an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm).

A plurality of reticles 101 are loaded in the reticle library 100 in advance and stacked in the direction of arrow C. Reticle library 10 of the present embodiment
In 0, a reticle having a relatively thick pellicle, a reticle having a relatively thin pellicle, and a reticle having no pellicle can be stored. The reticle transport system 140 pulls out the reticle 101 used for the next exposure from the reticle library 100 and transports the reticle 103 to the reticle stage 102. Arrow B in FIG. 1 indicates the route.

The exposure apparatus of the present embodiment has a reticle transport system
A thickness capable of measuring the thickness of a pellicle (a transparent member for dust prevention) provided on the lower side of the reticle 101 (on the side of the projection lens 120 at the time of exposure) to protect a circuit pattern in the middle of the transport path of the reticle 101. The hard pellicle 104 of the reticle 101 being transported is measured by the measuring means 130, and the thickness information is sent to the controller 160. The thickness of the hard pellicle 104 was measured using the reticle 1
It is possible whether 01 is stationary or moving.
Further, the presence or absence of the pellicle can be determined by the measuring means 130.

The controller 160 controls the sequence of the entire exposure apparatus. Here, only the sequence particularly related to the present invention will be described.

The controller 160, which has received the information on the thickness of the pellicle 104, sets a plurality of lens groups (each lens group) of the projection lens 120 in accordance with the calculated sensitivity of the lens to the pellicle thickness in advance. Is composed of one or a plurality of refraction lenses or diffraction lenses), and calculates the amount of movement of a specific lens group 114, and moves the lens group 114 in the optical axis direction H of the projection lens 120.
A command is issued to 50 to move the lens group 114 to a position where aberrations (spherical aberration, coma, distortion, etc.) generated in the pellicle 104 can be corrected. In the present embodiment, the lens group 114 closest to the reticle stage 102 is used for aberration correction. However, the present invention is not limited to this, and correction sensitivity to projection lens aberrations (specifically, spherical aberration, coma aberration, distortion, etc.) is provided. Any one or a plurality of lens groups having power may be used.

FIG. 2 is an explanatory view showing an example of the reticle 103 with the pellicle 104. The upper side of FIG. 2 is a plan view, and the lower side is a side view. The pellicle 104, which is a dust-proof protective member, is a glass plate (or film) made of either fluorine-doped quartz or fluorite.

As shown in FIG. 2, a pellicle frame 107 on which a pellicle 104 is stretched is mounted below the reticle 103. Since the pellicle frame 107 has a height of several mm, even if an image of a foreign substance on the pellicle 104 is projected onto the wafer 121 by the projection lens 120, the pellicle frame 107 is blurred, so that the resist on the wafer 121 is not substantially exposed. It has become.

The reticle 103 shown in FIG. 2 has a bar code 200 on which information relating to exposure conditions is recorded on a lower surface (circuit pattern side) of a substrate made of fluorine-doped quartz or fluorite.
Is formed. In order to cope with the case where such a barcode is formed, usually, a barcode reading device is installed in the reticle transport path of the exposure device.

Now, when detecting the pellicle thickness information of the reticle on which such a barcode 200 is formed,
When making the reticle, measure the thickness of the pellicle,
A method of recording the result in a barcode and obtaining the pellicle thickness information recorded in the barcode in advance by a barcode reader instead of the pellicle thickness measuring means 120 can be adopted.

The present invention is also effective for reticles on which no barcode is formed.

FIG. 3 is a flowchart showing a sequence up to the start of exposure in the exposure apparatus of FIG.

A reticle 103 to be used for the next exposure is selected from the reticle library 100 and transported toward the reticle stage 102.

During the conveyance, the thickness of the pellicle 104 of the reticle 103 is measured, or the thickness information of the pellicle 104 is read from the barcode of the reticle 103. If the reticle 103 does not have a pellicle, the information is also obtained and the controller
Send to 160.

Under the control of the controller 160, adjustment of the projection optical system for correcting the aberration caused by the pellicle is performed. It is desirable from the viewpoint of throughput that this adjustment work is completed before the reticle 103 is held by the reticle stage 102 and set at the exposure position, but from the viewpoint of throughput, the reticle 103 is adjusted by the reticle stage 102 after adjustment of the projection optical system. It may be held and set at the exposure position.

Exposure starts when the reticle is set at the exposure position.

In the above embodiment, the aberration generated in the pellicle is corrected by moving one lens group 114. However, a plurality of lens groups may be independently moved according to the number of types of aberration to be corrected. .

FIG. 4 is a schematic view showing a scanning type reduced projection exposure apparatus according to a second embodiment of the present invention. In FIG. 4, the same members as those in the exposure apparatus in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and description thereof is omitted. Although not shown, a drive unit for the lens 114 for correcting aberrations generated in the pellicle is mounted.

The feature of this embodiment is that, in comparison with the above-described first embodiment, an adjustment plate (a transparent parallel plane plate or an aspherical plate) for correcting aberration is provided between the projection lens 120 and the reticle stage 102. ) Can be inserted. The projection lens 120 itself is designed in advance so that a relatively thick pellicle (hard pellicle) -attached reticle can be formed with no aberration in a state where the reticle is inserted into the optical path.
In such an exposure apparatus, when a reticle with a relatively thin pellicle (soft pellicle) is carried in, or a reticle without a pellicle is selected, the reticle stage 102
If the adjustment plate having a thickness different from the thickness of the relatively thick pellicle is inserted just below the reticle 103, a constant glass thickness is always maintained for the projection lens 120 therebelow. Therefore, the aberration-free state in which the aberration is corrected can be maintained. Although the apparatus shown in FIG. 4 has two adjustment plates (the adjustment plate 1 and the adjustment plate 2), a configuration having three or more adjustment plates having different thicknesses and aspherical shapes from each other can be adopted. This embodiment utilizes the fact that the material of the soft pellicle is the same as the material of the adjustment plate (the two have the same refractive index). According to the present embodiment,
Regardless of the pellicle of any thickness (including the case without the pellicle), the optimal state of the projection lens 120 (a state designed in advance and having no aberration) can be maintained.

FIG. 5 shows an embodiment of the pellicle thickness measuring means 130. In FIG. 5, a laser beam from a laser light source 400 is incident on a pellicle 104 at a predetermined opening angle by an incident optical system 401.
Incident on. Light reflected from the upper and lower surfaces of the pellicle 104 is captured by the light receiving optical system 402, and the two reflected lights are collected on the position sensor 403 by the optical system 402. The processing system 404 processes a signal corresponding to the condensing position of each reflected light from the position sensor 403 to create pellicle thickness information. This thickness information is transmitted to the controller 160 shown in FIGS.

In each of the above embodiments, the aberration generated in the pellicle is corrected by moving the lens group 114, inserting the adjustment plate, or designing the lens. Any known device applicable to the device can be used. Examples of this device include a device that changes the atmospheric pressure (pressure of an inert gas such as nitrogen and helium) in a space between a specific lens and a lens of a projection optical system, or a device that applies stress to a lens to change the refractive surface of the lens. A device for deforming, a device for changing an oscillation wavelength of an excimer laser, that is, a wavelength of an exposure light beam, and a device for driving a pair of aspherical plates that are displaced in directions opposite to each other in a direction perpendicular to the optical axis (Japanese Patent Application Laid-Open No. 10-24048) See also), and any combination of these with a lens drive.

Although the embodiment described above is a scanning projection exposure apparatus, the present invention is naturally applicable to a so-called stepper which does not scan a reticle and a wafer during exposure of one shot area.

Next, the device manufacturing process of the present invention will be described. In a flow of an overall manufacturing process of a device such as a semiconductor chip, a circuit of a semiconductor device is designed in step 1 (circuit design). Step 2 (mask production)
Then, a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (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 of forming a semiconductor chip using the wafer produced in step 4, and assembly such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Process. 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). The pre-process and the post-process are performed in separate dedicated factories, and maintenance is performed for each of these factories by the above-described remote maintenance system. Further, information for production management and apparatus maintenance is also communicated between the pre-process factory and the post-process factory via the Internet or a dedicated line network.

In the detailed flow of the wafer process, in step 11 (oxidation), the surface of the wafer is oxidized. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16
In (exposure), a circuit pattern of a mask (reticle) is printed and exposed on a wafer by the projection exposure apparatus of each embodiment described with reference to FIGS. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. Since the manufacturing equipment used in each process is maintained by the remote maintenance system described above, troubles can be prevented beforehand, and if troubles occur, quick recovery is possible. Productivity can be improved.

[0056]

As described above, according to the present invention, even if a reticle with a dustproof film or plate having a thickness that cannot be ignored is used,
An object of the present invention is to provide a projection exposure apparatus and a device manufacturing method capable of accurately projecting a circuit pattern image on a wafer because the apparatus has a correction unit for correcting aberration caused by the dust-proof film or plate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

FIG. 2 is a plan view and a side view of a reticle with a pellicle.

FIG. 3 is a view showing a sequence up to the start of exposure in the exposure apparatus of FIG. 1;

FIG. 4 is a schematic diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a pellicle thickness measuring means.

[Explanation of symbols]

 103 reticle 104 pellicle 111 illumination optical system 114 movable lens 120 projection lens 130 pellicle thickness measuring means 150 lens drive unit

Claims (18)

[Claims] An illumination optical system for illuminating a reticle with light from a light source and a projection optical system for projecting a pattern of the reticle onto a wafer, wherein a dust-proof film or plate is provided on the projection optical system side. A projection exposure apparatus in which the reticle can be installed, wherein the projection exposure apparatus further comprises a correction unit configured to correct aberration generated in the dust-proof film or plate. 2. The projection exposure apparatus according to claim 1, wherein the reticle having the dust-proof film or plate and the reticle without the dust-proof film or plate can be installed. 3. The projection exposure apparatus according to claim 2, wherein a plurality of types of reticles having different thicknesses of the dust-proof film or plate can be installed. 4. The apparatus according to claim 1, further comprising a thickness detector for detecting information on a thickness of said dust-proof film or plate before said reticle is mounted on a reticle stage.
The projection exposure apparatus according to any one of the above. 5. The projection exposure apparatus according to claim 4, wherein said thickness detecting means is located inside a reticle transport system. 6. The projection exposure apparatus according to claim 5, wherein said thickness detecting means includes means for reading a barcode formed on said reticle and recording information on its thickness. 7. The projection exposure apparatus according to claim 5, wherein said thickness detecting means has a measuring device for measuring the thickness of said dust-proof film or plate. 8. The apparatus according to claim 1, wherein said correction means includes means for moving one or more lenses of said projection optical system in an optical axis direction according to a thickness of said dust-proof film or plate. The projection exposure apparatus according to any one of claims 1 to 7. 9. The apparatus according to claim 1, wherein said correction means has a transparent plate which is detachably mounted on an optical path of said projection optical system according to a thickness of said dust-proof film or plate. Item 2. The projection exposure apparatus according to item 1. 10. The correction means, when the thickness of the dust-proof film or plate is smaller than a predetermined thickness, or when there is no dust-proof film or plate, has a thickness corresponding to the predetermined thickness. 10. The projection exposure apparatus according to claim 9, comprising a plurality of transparent plates having different thicknesses into which a transparent plate can be inserted between the dustproof film or plate and the projection optical system. 11. The apparatus according to claim 1, wherein the correction unit includes a unit that changes a pressure of gas in a space between the predetermined lenses of the projection optical system according to a thickness of the dustproof film or plate. The projection exposure apparatus according to claim 1. 12. The apparatus according to claim 1, wherein said correction means has means for changing a wavelength of light from said light source in accordance with a thickness of said dust-proof film or plate.
The projection exposure apparatus according to item 9. 13. The apparatus according to claim 1, wherein said correcting means includes a pair of aspherical plates which are displaced in directions opposite to each other in a direction perpendicular to an optical axis in accordance with a thickness of said dustproof film or plate. 13. The projection exposure apparatus according to any one of claims 12 to 12. 14. The apparatus according to claim 1, wherein said correcting means has means for changing a shape of a refractive surface of the lens.
4. The projection exposure apparatus according to claim 3. 15. The projection exposure apparatus according to claim 1, wherein the correction unit includes the projection optical system. 16. The projection exposure apparatus according to claim 1, wherein the dust-proof film or plate is formed of any one of quartz, fluorine-doped quartz, and fluorite. . 17. The projection exposure apparatus according to claim 1, wherein the light source is an F2 excimer laser. 18. A device manufacturing method, comprising: exposing a wafer with a device pattern using the projection exposure apparatus according to claim 1; and developing the exposed wafer.