JPH06224107A - Method and device for projection aligner - Google Patents

Abstract

PURPOSE:To decrease the effect of standing wave generated when a projection aligning operation is conducted using a single projection aligner by providing a means to move to axial direction at least one of a means, which changes the wavelength of light source, a glass substrate, a wafer and a projection optical system. CONSTITUTION:The image-forming position of a light 3 of wavelength (lambda0) and the image-forming position of a light 4 of wavelength (lambda1) are separated in the amount DELTAz. A wafer 1 on the stage of a projection exposing device is shifted to the direction of optical axis in order to compensate the variation of the above-mentioned focul position. Besides, a mask or a projection optical system may be shifted instead of shifting the stage. In order to effectively decrease the effect of standing wave, the reflected light, sent from a resit 2 by exposure using the light of wavelength (lambda1), is brought to the minimum by the variation of resist film thickness when the light sent from the resist 2 by the exposure using the light of wavelength (lambda2) becomes the maximum by the variation. As a result, a plurality of wavelength can be exposed using a single projection exposure device, and the dimensional variation of the resist pattern due to the effect of standing wave can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method and apparatus capable of reducing the standing wave effect generated during projection exposure in the production of semiconductors and the like.

[0002]

2. Description of the Related Art A projection exposure apparatus with high production efficiency is widely used for processing fine patterns such as semiconductor integrated circuits. In the above apparatus, a refraction optical system may be used as the projection optical system, but in this case, if the wavelength band width of the light source is wide, chromatic aberration occurs and the resolution is lowered. Therefore, in order to obtain high resolution, when a high-pressure mercury lamp is used as a light source, light from the light source is passed through a filter having an extremely narrow bandwidth, and when a laser is used as a light source, a diffraction grating, a prism,
Narrow band using etalon. When light with a narrow band is used as a light source in this way, due to the effect of standing waves due to the interference between the light incident on the resist and the light reflected from the resist / wafer interface, there is a slight change in the resist film thickness The effective amount of light absorbed by the light fluctuates greatly. This causes variations in resist pattern size and defective resolution. If a catadioptric system is used as the projection optical system instead of the dioptric system, the problem of chromatic aberration is reduced, and the wavelength of the light source can be in a wide band. When the wavelength of the light source is in a wide band, the standing wave effect is reduced because the standing waves are generated differently in light of different wavelengths. Such a catadioptric optical system is disclosed in, for example, JP-A-63-163319 (reference 1).
Further, Japanese Patent Laid-Open No. 63-198324 (reference 2) discloses a method of reducing the standing wave effect by irradiating a light having a wavelength λ ₀ through a glass substrate (mask) having an exposed pattern with a dose D _0.
A method of irradiating the entire surface of a resist or a pattern formation region with a light beam having a wavelength λ ₁ different from λ ₀ with a dose D ₁ smaller than D ₀ is described before and after exposure.

[0003]

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
The catadioptric optical system described in (1) has the problems that alignment of the optical system is difficult and it is difficult to increase the numerical aperture in terms of design. Also, the method of Reference 2 can be applied to a refraction optical system, but when the entire surface of the resist is irradiated with light,
There is a problem that the image contrast is lowered and the resolution is deteriorated. If selectively irradiated with light of wavelength lambda ₁ only in the pattern formation region deterioration of contrast prevented, but concrete method of irradiating lambda ₀ different wavelengths lambda ₁ of light only in the pattern formation region is in the literature 2 Not mentioned in. The number of man-hours increases when two exposures are performed by using a projection exposure apparatus simply designed for the wavelength λ ₀ and a projection exposure apparatus designed for the wavelength λ ₁ , and a resist-coated wafer is exposed in two different types. There is a problem in that alignment becomes difficult when moving between devices. An object of the present invention is to provide a projection exposure method and a projection exposure apparatus that realize exposure with a plurality of wavelengths to reduce the standing wave effect with a single projection exposure apparatus.

[0004]

According to a first aspect of the present invention, an exposed pattern on a glass substrate illuminated by light emitted from a light source is formed on a resist-coated wafer by using a projection optical system. In the projection exposure method of forming an image, a first step of forming an image of the exposed pattern illuminated by light of a first wavelength emitted from the light source on the wafer, and the glass substrate, the wafer, and the projection optical system. A second step of moving at least one of them in the optical axis direction to form an image of the exposed pattern illuminated with the light of the second wavelength emitted from the light source on the wafer. It is a characteristic projection exposure method.

A second invention according to the present invention comprises at least a glass substrate having a pattern to be exposed, a resist-coated wafer, a light source and a projection optical system, means for changing the wavelength of the light source, the glass substrate, A projection exposure apparatus comprising: means for moving at least one of a wafer and a projection optical system in an optical axis direction.

A third invention according to the present invention is to expose an exposed pattern on a glass substrate illuminated by light emitted from a light source,
In a projection exposure method for forming an image on a resist-coated wafer using a projection optical system, a first method for forming an image on the wafer by exposing the exposed pattern illuminated with light of a first wavelength emitted from the light source. A step of inserting a substance having a refractive index different from that of air between the glass substrate and the wafer, and forming an image of the exposed pattern illuminated by the light of the second wavelength emitted from the light source on the wafer. A projection exposure method comprising a second step.

According to a fourth aspect of the present invention, there is provided a glass substrate having a pattern to be exposed, a resist-coated wafer, a light source and a projection optical system, and means for changing the wavelength of the light source, and the glass substrate. A projection exposure apparatus comprising a means for inserting a substance having a refractive index different from that of air between the wafer and the wafer.

According to a fifth aspect of the present invention, the exposed pattern on the glass substrate illuminated by the light emitted from the light source,
In a projection exposure method for forming an image on a resist-coated wafer by using a projection optical system, a multifocal lens for forming images at a plurality of positions on the projection optical system is used, and different first wavelengths emitted from the light source and The multi-focal lens forms an image on the wafer at the first wavelength and an image on the wafer at the second wavelength as well, by performing exposure once or plural times with light of the second wavelength. Projection exposure method.

A sixth invention according to the present invention comprises at least a glass substrate having a pattern to be exposed, a resist-coated wafer, a light source and a projection optical system, wherein the wavelength of the light source is different from the first wavelength or the first wavelength. A projection exposure apparatus, which is provided with a unit for setting a wavelength of 2 and the projection optical system is composed of a multifocal lens that forms an image on a wafer at both the first wavelength and the second wavelength. Is.

[0010]

When the exposure with a plurality of wavelengths is performed by a single refracting optical system to reduce the standing wave effect, the focal position moves due to the influence of chromatic aberration. In the first and second inventions, the movement of the focal position is compensated by moving at least one of the mask, the wafer and the projection optical system in the optical axis direction.
In the third and fourth aspects of the invention, the movement of the focal position is compensated by inserting a substance having a refractive index different from that of air between the mask and the wafer. In the fifth and sixth inventions, a multifocal lens is used as the projection optical system so that an image is formed on the wafer even if the focal position moves due to chromatic aberration.

[0011]

EXAMPLES Next, examples of the present invention will be described. An embodiment of the first invention is shown in FIG. A KrF excimer laser is used as the light source of the projection exposure apparatus. The KrF excimer laser oscillates with a center wavelength of 248.3 nm and a half width of 350 pm, but has a narrow band to a half width of 3 pm to suppress chromatic aberration. The center wavelengths λ ₀ = 248.4 nm and λ ₁ = 248.2n are obtained by finely rotating the band-narrowing element.
Oscillation at m becomes possible. Focus position variation Δz at this time
Is given by

[0012]

[Equation 1]

Here, m and f are the magnification and focal length of the projection optical system, which are ⅕ and 100 mm, respectively. Further, n and dn / dλ are the refractive index and the refractive index dispersion at λ = 248.3 nm of the synthetic quartz used for the lens, which are 1.51 and 0.24 μm ⁻¹ , respectively. Substituting the wavelength difference Δλ = −200 pm between λ ₁ and λ ₀ into the above equation, the focal position fluctuation becomes 10.5 μm. In FIG. 1, the image forming position of the light 3 having the wavelength λ _{0 and} the image forming position of the light 4 having the wavelength λ ₁ are separated by Δz. In order to compensate for this focus position fluctuation, in the embodiment shown in FIG. 1, the wafer 1 on the stage of the projection exposure apparatus is moved in the optical axis direction. The mask or the projection optical system may be moved instead of moving the stage.
The most effective way to reduce the standing wave effect by using light of two wavelengths is when the reflected light from the resist 2 due to exposure to light of wavelength λ ₀ becomes maximum (minimum) due to fluctuations in the resist film thickness. The light reflected from the resist 2 due to the exposure with the light having the wavelength λ ₁ may be minimized (maximum). The resist film thickness d satisfying such a condition is given by the following equation.

[0014]

[Equation 2]

Where l is 0 or any positive integer, n _r
Is the refractive index of the resist 2. In order to select the thinnest resist film thickness, the refractive index n _{r of the} resist is set to n _r = 1.6
Is substituted, the resist film thickness becomes 48 μm. Since the resist film thickness desired to remain after resist development is about 1 μm, the resist is a two-layer resist as shown in FIG. 2, and the lower layer photosensitive agent containing portion 5 (1 μm thick) and the upper transparent resin portion 6 are used.
(47 μm thick).

The reflectance on the resist surface under the above conditions is shown in FIG. Wavelength λ ₀ due to slight variation in resist film thickness
The reflectance 7 of and the reflectance 8 of the wavelength λ ₁ vary greatly,
The fluctuation of the average value 9 is extremely small. Like this first
When the exposure method of the invention is used, the effective light amount absorbed in the resist becomes substantially constant regardless of the film thickness, and the standing wave effect can be greatly reduced.

FIG. 4 shows an embodiment of the projection exposure apparatus of the second invention for realizing the exposure method of the first invention. Kr
The F excimer laser light source 10 is band-narrowed by a wavelength band narrowing element 11 made of a diffraction grating, a prism, an etalon, or the like. The central wavelength of the light source 10 is the wavelength narrowing element 11
It can be changed by rotating a minute. Since the light reflected by the reflecting mirror 12 has a spatially non-uniform distribution, the homogenizer 13 makes the light intensity distribution uniform. The light emitted from the illumination optical system 14 becomes parallel light and illuminates the mask 15.
After being reduced through the projection optical system 16, an image is formed on the resist-coated wafer 17. By moving the stage 18 up and down, it is possible to compensate the fluctuation of the focus position due to the wavelength fluctuation of the light source 10.

An embodiment of the third invention is shown in FIG. In the first invention, the focus position variation due to the wavelength variation is compensated by the movement of the stage or the like, but in the third invention, the thin film 19 having a refractive index different from that of air is inserted between the mask and the wafer to obtain the optical path length. Compensate by extending. Since it is not necessary to move the stage or the like, there is no displacement due to movement. The thickness t of the thin film required to extend the optical path length by Δz is given by the following equation.

[0019]

[Equation 3]

Here, n _f is the refractive index of the thin film 19. If synthetic quartz is used as the thin film 19, the film thickness is 20.6 μm.
m. As shown in FIG. 5, the light 3 of the first wavelength λ ₀
By the exposure by (1), the thin film 19 is not inserted, and the thin film 19 is inserted in the second exposure, and the same effect as the first invention can be obtained. As the thin film 19, not only synthetic quartz but various inorganic thin films, organic thin films, or gases having a refractive index different from that of air may be inserted instead.

FIG. 6 shows an embodiment of the projection exposure apparatus of the fourth invention for realizing the exposure method of the third invention. Second
The difference from the projection exposure apparatus of the invention is that it is not necessary to move the stage 18 during a plurality of exposures, and a mechanism for inserting the thin film 19 between the projection optical system 16 and the wafer 17 is added instead. The thin film 19 is the projection optical system 16
And the wafer 17 as well as between the mask 15 and the wafer 17
You can place it anywhere between.

An embodiment of the fifth invention is shown in FIG. In the fifth invention, a multifocal lens is used in the projection optical system. In the present embodiment, a bifocal lens is used as the multifocal lens, and the distance between the two focal points is made equal to the focal point moving distance Δz due to wavelength fluctuation. In this way, in the first exposure, there are light 20 which forms an image on the wafer and light 21 which forms an image in the air above the wafer with the light having the wavelength λ ₀ . In the second exposure, the focus position moves due to wavelength fluctuations,
Light 20 which has been imaged on the wafer becomes light 22 that no wavelength lambda ₁ for imaging, light of the wavelength lambda ₁ to the light 21 which has been imaged wafer above the air is imaged on the wafer 23. Incidentally, it is not necessary to divide the exposure into two, and if the laser light source that oscillates at two wavelengths is used, only one exposure is required. When this exposure method is used, the time required for moving the stage and the like required in the first invention is reduced, but the contrast of the image is deteriorated because there is light that does not form an image.

FIG. 8 shows an embodiment of the projection exposure apparatus of the sixth invention for realizing the exposure method of the fifth invention. Second
The difference from the projection exposure apparatus of the invention is that the stage 18 does not need to be moved during a plurality of exposures, and the projection optical system 16 is replaced with a multifocal lens 24.

Although the KrF excimer laser is used as the light source in the above-mentioned first to sixth embodiments, an ArF excimer laser, an i-line of a high pressure mercury lamp or the like may be used instead. Further, the exposure wavelength is not limited to two wavelengths, and the same effect can be obtained by exposing a plurality of wavelengths or continuous wavelengths a plurality of times or continuously.

[0025]

As described in detail above, according to the projection exposure method and apparatus of the present invention, it is possible to perform exposure with a plurality of wavelengths with a single projection exposure apparatus even if a refractive optical system is used as the projection optical system. As a result, the undeveloped resist and the dimensional variation of the resist pattern due to the standing wave effect can be significantly reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first invention.

FIG. 2 is a cross-sectional view of a wafer coated with a resist used in the first invention.

FIG. 3 is a diagram showing a reflectance from a resist and an average value thereof when a resist-coated wafer is irradiated with light having wavelengths λ ₀ and λ ₁ .

FIG. 4 is a configuration diagram of a projection exposure apparatus according to a second invention.

FIG. 5 is an explanatory diagram of a third invention.

FIG. 6 is a configuration diagram of a projection exposure apparatus according to a fourth invention.

FIG. 7 is an explanatory diagram of a fifth invention.

FIG. 8 is a configuration diagram of a projection exposure apparatus according to a sixth invention.

[Explanation of symbols]

1 Wafer 2 Resist 3 Light of wavelength λ ₀ 4 Light of wavelength λ ₁ 5 Photosensitive agent containing portion 6 Transparent resin portion 7 Reflectivity of wavelength λ ₀ 8 Reflectivity of wavelength λ ₁ 9 Average value 10 KrF excimer laser light source 11 Narrow wavelength Band-passing element 12 Reflector 13 Homogenizer 14 Illumination optical system 15 Mask 16 Projection optical system 17 Wafer 18 Stage 19 Thin film 24 Multifocal lens

Claims (6)

[Claims] 1. A projection exposure method for forming an image of a pattern to be exposed on a glass substrate illuminated by light emitted from a light source on a resist-coated wafer using a projection optical system. A first step of forming an image of the exposed pattern illuminated with light of wavelength on the wafer, and moving at least one of the glass substrate, the wafer, and the projection optical system in the optical axis direction. A second step of forming an image of the exposed pattern illuminated with light of a second wavelength emitted from a light source on the wafer. 2. A glass substrate having an exposed pattern,
A wafer coated with a resist, at least a light source and a projection optical system, means for changing the wavelength of the light source, and means for moving at least one of the glass substrate, the wafer and the projection optical system in the optical axis direction. A projection exposure apparatus, which comprises: 3. A projection exposure method for forming an image of a pattern to be exposed on a glass substrate, which is illuminated by light emitted from a light source, on a resist-coated wafer by using a projection optical system. From the light source by inserting a substance having a refractive index different from that of air between the glass substrate and the wafer; And a second step of forming an image of the exposed pattern illuminated by the emitted light of the second wavelength on the wafer. 4. A glass substrate having an exposed pattern,
A resist coated wafer; a light source and a projection optical system; and means for changing the wavelength of the light source; and means for inserting a substance having a refractive index different from air between the glass substrate and the wafer. A projection exposure apparatus characterized in that 5. A projection exposure method for forming an image of an exposed pattern on a glass substrate illuminated by light emitted from a light source on a resist-coated wafer by using a projection optical system, wherein a plurality of projection optical systems are provided. Of the first wavelength and the second wavelength of light emitted from the light source, which are different from each other, and the multifocal lens is exposed once or a plurality of times. A projection exposure method, wherein an image is formed on a wafer with a wavelength and an image is formed on a wafer with a second wavelength. 6. A glass substrate having an exposed pattern,
A resist-coated wafer, at least a light source and a projection optical system, and means for setting the wavelength of the light source to different first wavelengths or second wavelengths, wherein the projection optical system includes the first wavelength and the second wavelength. A projection exposure apparatus comprising a multifocal lens that forms an image on a wafer at any of the second wavelengths.