JP2021039243A - Exposure device and manufacturing method of articles - Google Patents

Abstract

To provide an exposure device advantageous in simultaneously realizing a correction performance of an illuminance distribution on an image surface of an illumination optical system, and an inhibition of deterioration of a luminous intensity on the image surface.SOLUTION: In an exposure device configured to perform scanning exposure of a substrate, an illumination optical system configured to illuminate an illumination target face of an original plate with light from a light source includes: a diffraction optical element configured to convert, with a diffraction action, a light intensity distribution of a light flux from the light source onto a prescribed surface; a first shielding part arranged at a position defocused from a conjugate surface of the illumination target face to the light source side; and a second shielding part arranged at a position defocused from the conjugate surface of the illumination target face to the illumination target face side. The diffraction optical element has diffraction characteristics of reducing a difference between a scan direction of the scanning exposure and a non-scan direction orthogonal to the scan direction with regard to an integration incident angle distribution obtained by integrating an incident angle distribution in a period illuminating a certain point by the scanning exposure, occurring on the illumination target face by the first shielding part and the second shielding part.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exposure apparatus and a method for manufacturing an article.

With the miniaturization of semiconductor devices, the exposure equipment used in the lithography process, which is the manufacturing process of semiconductor devices, is required to have higher resolution. In order to achieve high resolution, the wavelength of the exposure light should be shortened, the numerical aperture (NA) of the projection optical system should be increased (higher NA), and the modified illumination (ring band illumination, bipolar illumination, quadruple illumination) should be achieved. The use of polar lighting, etc.) is effective.

On the other hand, with the recent increase in the number of layers of device structures, exposure devices are also required to have high overlay accuracy. Patent Document 1 discloses a double slit configuration in which a light-shielding portion 103 and a light-shielding portion 105 are arranged before and after the masking unit 104, which is a conjugate surface of the illuminated surface (FIG. 1). This double slit configuration is effective for improving the overlay accuracy.

Further, Patent Document 1 also discloses that a light-shielding portion 401 or a filter 402 for alleviating the asymmetry of the integrated effective light source distribution caused by the double slit configuration is arranged (FIGS. 12 and 14).

Japanese Unexamined Patent Publication No. 2010-73835

However, when a light-shielding portion or a filter for alleviating the asymmetry of the integrated effective light source distribution caused by the double slit configuration is arranged, the image plane illuminance is lowered. Decreasing the image plane illuminance is not preferable because it leads to a decrease in throughput.

The present invention provides, for example, an exposure apparatus that is advantageous in achieving both the correction performance of the illuminance distribution on the image plane of the illumination optical system and the suppression of the decrease in the illuminance on the image plane.

According to one aspect of the present invention, it is an exposure apparatus that scans and exposes a substrate, and has an illumination optical system that illuminates the illuminated surface of the original plate with light from a light source, and the illumination optical system is on a predetermined surface. In addition, a diffractive optical element that converts the light intensity distribution of the light beam from the light source by a diffraction action, a first light-shielding portion arranged at a position defocused from the conjugate surface of the illuminated surface to the light source side, and the subject. It has a second light-shielding portion arranged at a position defocused from the conjugate surface of the illumination surface to the illuminated surface side, and the diffractive optical element is formed by the first light-shielding portion and the second light-shielding portion. With respect to the integrated incident angle distribution that integrates the incident angle distribution during the period in which a certain point is illuminated by the scanning exposure, the difference between the scanning direction of the scanning exposure and the non-scanning direction orthogonal to the scanning direction is calculated. An exposure apparatus characterized by having reduced diffraction characteristics is provided.

According to the present invention, for example, it is possible to provide an exposure apparatus that is advantageous in achieving both the correction performance of the illuminance distribution on the image plane of the illumination optical system and the suppression of the decrease in the illuminance on the image plane.

The schematic cross-sectional view which shows the structure of the exposure apparatus in embodiment. The figure explaining the integration effective light source. The figure explaining the integration effective light source. The figure which shows the structure of the light-shielding part. The figure explaining the design of the diffraction optical element in embodiment. A graph showing the asymmetry of the integrated effective light source for each σ value. A graph showing the line width difference between the vertical pattern and the horizontal pattern for each σ value.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiment, not all of the plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the attached drawings, the same or similar configurations are designated by the same reference numbers, and duplicate explanations are omitted.

<First Embodiment>
FIG. 1 is a schematic cross-sectional view showing the configuration of the exposure apparatus according to the embodiment. This exposure device is a scanning exposure device that exposes a pattern of an original plate (mask) on a substrate by a step-and-scan method. In the step-and-scan method, one shot is exposed while being driven (scanned) relative to the original plate and the substrate, and after the exposure of one shot is completed, the substrate is stepped to move to the next shot area. Will be.

The exposure apparatus includes an illumination optical system that illuminates the reticle 24, which is the original plate, using the light flux from the light source 1, and a projection optical system 26 that projects the pattern of the reticle 24 onto the substrate 27.

As the light source 1, a mercury lamp having a wavelength of about 365 nm, a KrF excimer laser having a wavelength of about 248 nm, an ArF excimer laser having a wavelength of about 193 nm, or the like can be used.

The illumination optical system includes a routing optical system 2, an emission angle preservation optical element 5, a diffraction optical element 6, a condenser lens 7, and a prism unit 10. Further, the illumination optical system further includes a zoom lens unit 11, an optical integrator 12, an aperture 13, a condenser lens 14, a first light-shielding portion 18 and a second light-shielding portion 20, a masking unit 19, a condenser lens 21, and a collimator lens 23. Have.

The routing optical system 2 is provided between the light source 1 and the emission angle conserving optical element 5, and guides the light flux from the light source 1 to the emission angle conserving optical element 5. The emission angle preservation optical element 5 is provided on the light source side of the diffractive optical element 6 and guides the light flux from the light source 1 to the diffractive optical element 6 while keeping the divergence angle constant. The injection angle conserving optical element 5 may be composed of a microlens array or an optical integrator such as a fiber bundle. The injection angle preservation optical element 5 can reduce the influence of the output fluctuation of the light source 1 on the pattern distribution formed by the diffraction optical element 6.

The diffractive optical element 6 is arranged on a surface conjugate with the reticle 24, which is an illuminated surface (image plane), or a surface having a Fourier transform relationship with the pupil surface of the illumination optical system. The diffractive optical element 6 diffracts the light intensity distribution of the light flux from the light source 1 on a predetermined surface such as the pupil surface of the illumination optical system which is a surface conjugate to the pupil surface of the projection optical system 26 and the surface conjugate to the pupil surface of the illumination optical system. Convert to form the desired light intensity distribution. As the diffraction optical element 6, a computer hologram (CGH; Computer Generated Hologram) designed by a computer so that a desired diffraction pattern can be obtained on the diffraction pattern surface may be used. The shape of the light source formed on the pupil surface of the projection optical system 26 is called an effective light source shape. In addition, in this specification, an "effective light source" means a light intensity distribution or a light angle distribution on an illuminated surface and a conjugate surface thereof. The diffractive optical element 6 is provided between the injection angle conserving optical element 5 and the condenser lens 7. The light beam from the emission angle preservation optical element 5 irradiates the diffractive optical element 6, diffracts it with the diffractive optical element 6, and is guided to the condenser lens 7.

In one example, a plurality of diffractive optical elements 6 are provided in the illumination optical system, and each diffractive optical element 6 is attached and mounted in a corresponding one of a plurality of slots of a turret (not shown). The plurality of diffractive optical elements can form different effective light source shapes. Due to these effective light source shapes, the names of the illumination modes are called small σ illumination, large σ illumination, ring zone illumination, double pole illumination, quadrupole illumination, and the like.

The condenser lens 7 is provided between the diffractive optical element 6 and the prism unit 10, collects the light beam diffracted by the diffractive optical element 6, and forms a diffraction pattern on the Fourier transform surface 9. The distribution of the diffraction pattern is constant.

The Fourier transform surface 9 is located between the optical integrator 12 and the diffractive optical element 6, and is a surface that is optically in a Fourier transform relationship with the diffractive optical element 6. By exchanging the diffraction optical element 6 located in the optical path, the shape of the diffraction pattern formed on the Fourier transform surface 9 can be changed.

The prism unit 10 and the zoom lens unit 11 are provided on the light source side with respect to the optical integrator 12, and function as a zoom optical system that expands the light intensity distribution formed on the Fourier transform surface 9. The prism unit 10 can guide the diffraction pattern (light intensity distribution) formed on the Fourier transform surface 9 to the zoom lens unit 11 by adjusting the annular ratio and the like.

Further, the zoom lens unit 11 is provided between the prism unit 10 and the optical integrator 12. The zoom lens unit 11 can guide the diffraction pattern formed on the Fourier transform surface 9 to the optical integrator 12 by adjusting the σ value based on the ratio of the NA of the illumination optical system and the NA of the projection optical system. ..

The optical integrator 12 is provided between the zoom lens unit 11 and the condenser lens 14, and forms a large number of secondary light sources according to the diffraction pattern in which the annular ratio, the aperture angle, and the σ value are adjusted, and the condenser lens 14 is formed. May include fly eye lenses that lead to. However, the fly eye lens portion of the optical integrator 12 may be composed of an optical pipe, a diffractive optical element, a microlens array, or the like. A diaphragm 13 is provided between the optical integrator 12 and the condenser lens 14.

The condenser lens 14 is provided between the optical integrator 12 and the reticle 24. As a result, a large number of light fluxes derived from the optical integrator 12 can be focused to illuminate the reticle 24 in a superimposed manner. The condenser lens 14 includes a half mirror 15, and a part of the exposure light is incident on the light quantity measuring optical system 16. The light amount measurement optical system 16 has a sensor 17 for measuring the light amount. The exposure amount at the time of exposure can be appropriately controlled based on the amount of light measured by the sensor 17.

The masking unit 19 is arranged on the conjugate surface of the non-illuminated surface. The masking unit 19 is arranged to define the illumination range of the reticle 24 and is scanned synchronously with the reticle stage 25 holding the reticle 24 and the substrate stage 28 holding the substrate 27.

Two light-shielding portions are provided at positions defocused from the masking unit 19. Specifically, the first light-shielding portion 18 is arranged at either a position defocused from the illuminated surface to the light source side or a position defocused from the conjugate surface of the illuminated surface to the light source side. Further, the second light-shielding portion 20 is arranged at a position defocused from the conjugate surface of the illuminated surface to the illuminated surface side. In order to reduce the non-uniformity of the illuminance distribution on the illuminated surface, the first light-shielding portion 18 and the second light-shielding portion 20 may be variable slits, respectively.

The light reflected by the mirror 22 having a predetermined inclination with respect to the light flux from the condenser lens 21 illuminates the reticle 24 via the collimator lens 23. The pattern of the reticle 24 is projected onto the substrate 27 via the projection optical system 26.

Next, the integrated effective light source will be described with reference to FIG. FIG. 2A shows the illuminated area 24a of the 24 reticle, which is the illuminated surface. FIG. 2B shows the illumination region 19a of the masking unit 19 surface which is conjugate with the reticle 24 surface. The illumination region 24a is scanned during the exposure. At this time, the incident angle distribution that illuminates a certain point on the exposed surface is the sum of the incident angle distribution that illuminates each point on the straight line 24b parallel to the scanning direction (y direction) in the illumination region 24a. This is called an integrated effective light source. In other words, the integrated effective light source refers to an integrated incident angle distribution that integrates the incident angle distribution during the period in which a certain point in the illumination region is illuminated by scanning exposure.

Next, with reference to FIG. 3, what will happen to the integrated effective light source after scanning when the first light-shielding unit 18 and the second light-shielding unit 20 are used will be described. FIG. 3A is an enlarged view of the vicinity of the first light-shielding portion 18 and the second light-shielding portion 20. FIG. 3B shows an angular distribution of illumination light passing through points A, B, and C on the 19th surface of the masking unit. The luminous flux from the condenser lens 14 toward the point A via the optical integrator 12 is emitted in parallel with the optical axis 1b, and is not eclipsed by a part of the first light-shielding portion 18 and the second light-shielding portion 20. Therefore, the shape of the effective light source 24a at the point A'on the reticle surface is substantially circular.

On the other hand, with respect to the light beam directed from the condenser lens 14 to the point B via the optical integrator 12, a part of the light beam is eclipsed by the light-shielding member 18a of the first light-shielding portion 18 and the light-shielding member 20a of the second light-shielding portion 20. Therefore, the angular distribution of the effective light source 24b at the point B'on the reticle surface becomes asymmetric with respect to the scanning direction (Y direction) of the scanning exposure. The upper side of the effective light source 24b is chipped because it is eclipsed by the light-shielding member 20a of the second light-shielding portion 20, and the lower side is chipped because it is eclipsed by the light-shielding member 18a of the first light-shielding portion 18. As described above, it can be seen that the effective light source 24b has asymmetry with respect to the scanning direction (Y direction) of the scanning exposure due to the two light-shielding portions. Regarding the shape of the effective light source 24c at the point C'on the reticle surface, asymmetry occurs in the Y direction in the same way as the light flux toward the point B.

The integrated effective light source obtained by scanning all the light flux passing on the straight line including the points A, B, and C in the Y direction is as shown in FIG. 3C, and the asymmetry of the integrated effective light source occurs in the scanning direction. You can see that. The asymmetry of the integrated effective light source can cause problems during exposure. For example, when a line-and-space pattern having the same line width is printed in the vertical and horizontal directions, a line width difference occurs between the vertical pattern and the horizontal pattern, which is not preferable. Therefore, it is necessary to correct the asymmetry.

In the embodiment, the third light-shielding portion 8 is arranged on the light source side of the Fourier transform surface 9. The third light-shielding portion 8 is arranged, for example, at a position slightly defocused from the position of the Fourier transform surface 9. The third shading unit 8 can be used to correct the integrated effective light source (integrated incident angle distribution). FIG. 4 shows the configuration of the third light-shielding unit 8. The third light-shielding portion 8 is composed of, for example, four light-shielding plates, and each of the four light-shielding plates can be driven independently in the X direction or the Y direction. For example, in the case of the integrated effective light source shown in FIG. 3, the asymmetry of the integrated effective light source is adjusted by driving the two shading plates in the closing direction in the X direction and partially eclipsing the light in the X direction. can do. A filter may be applied instead of the light-shielding portion for adjustment.

Conventionally, the distribution of the Fourier transform surface 9 was uniform, but in the present embodiment, as shown in FIG. 5A, the diffractive optical element 6 has a non-uniform distribution with respect to the Y direction. Designed to. The diffractive optical element 6 has a non-scanning direction (X) that is orthogonal to the scanning direction (Y direction) of the scanning exposure and the scanning direction with respect to the integrated effective light source generated on the illuminated surface by the first light-shielding unit 18 and the second light-shielding unit 20. It has a diffraction characteristic that reduces the difference from the direction). Specifically, as shown in FIG. 5B, the distribution of the Fourier transform plane and the amount that the effective light source becomes asymmetrical due to the first light-shielding portion 18 and the second light-shielding portion 20 are offset in the Y direction. In addition, the light intensity distribution in the Y direction of the integrated effective light source is made constant. As a result, the X direction and the Y direction of the integrated effective light source become symmetrical. This eliminates the need to apply the third light-shielding portion 8 to adjust the asymmetry. Therefore, the decrease in the image plane illuminance due to the application of the third light-shielding portion 8 is eliminated, which is advantageous from the viewpoint of the throughput of the exposure apparatus.

<Second Embodiment>
The second embodiment is an example in which the zoom lens unit 11 is used and the σ value is changed. When the zoom lens unit 11 is driven to change the zoom, the influence of eclipse on the first light-shielding unit 18 and the second light-shielding unit 20 changes, and the asymmetry of the integrated effective light source changes. Therefore, when one type of diffractive optical element is used, it is difficult to sufficiently reduce the asymmetry of the integrated effective light source in all zooms. Therefore, in the present embodiment, the third shading unit 8 is also used.

FIG. 6 is a graph showing the relationship between the σ value and the asymmetry of the integrated effective light source when the zoom lens unit 11 is driven. As shown in FIG. 6, in the prior art, the integrated effective light source has asymmetry for any σ value. On the other hand, in the present embodiment, the diffractive optical element 6 has a scanning direction (Y direction) and a non-scanning direction (X direction) with respect to the integrated effective light source at the center value in the range of the σ value that can be changed by the zoom lens unit 11. It is designed to have diffraction characteristics that reduce the difference. As a result, the asymmetry of the integrated effective light source in the driving range of the σ value becomes smaller than that of the prior art.

FIG. 7 is a result obtained by optical image simulation of the line width difference between the vertical pattern and the horizontal pattern when exposed with a conventional integrated effective light source having asymmetry as shown in FIG. From this graph, it can be seen that the line width difference between the vertical pattern and the horizontal pattern is smaller in the present embodiment than in the prior art.

When the device is actually used, the asymmetry is adjusted by using the third shading unit 8 according to the σ used, starting from the magnitude of the asymmetry of the integrated effective light source as shown in FIG. That is, the third light-shielding unit 8 is adjusted according to the state (σ value used) of the zoom lens unit. Compared with the conventional example, in the present embodiment in which the asymmetry is small in the range of the σ value to be used, the amount of the asymmetry to be adjusted is small, so that the image plane illuminance for applying the third light-shielding portion 8 is less reduced. , It is advantageous in terms of the throughput of the exposure apparatus.

<Embodiment of article manufacturing method>
The article manufacturing method according to the embodiment of the present invention is suitable for manufacturing articles such as microdevices such as semiconductor devices and elements having a fine structure, for example. In the article manufacturing method of the present embodiment, a latent image pattern is formed on a photosensitive agent applied to a substrate by using the above-mentioned exposure apparatus (a step of exposing the substrate), and a latent image pattern is formed in such a step. Includes a step of developing the substrate. Further, such a manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, flattening, etching, resist peeling, dicing, bonding, packaging, etc.). The article manufacturing method of the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

The invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the invention. Therefore, a claim is attached to make the scope of the invention public.

1: Light source, 6: Diffractive optical element, 11: Zoom lens unit, 18: First light-shielding unit, 19: Masking unit, 20: Second light-shielding unit, 24: Reticle (original plate), 26: Projection optical system, 27: substrate

Claims (9)

An exposure device that performs scanning exposure of a substrate.
It has an illumination optical system that illuminates the illuminated surface of the original plate with the light from the light source.
The illumination optical system is
A diffractive optical element that converts the light intensity distribution of the luminous flux from the light source on a predetermined surface by a diffraction action.
A first light-shielding portion arranged at a position defocused from the conjugate surface of the illuminated surface to the light source side,
It has a second light-shielding portion arranged at a position defocused from the conjugate surface of the illuminated surface to the illuminated surface side.
The diffractive optical element relates to an integrated incident angle distribution obtained by integrating the incident angle distribution during a period in which a certain point is illuminated by the scanning exposure, which is generated on the illuminated surface by the first light-shielding portion and the second light-shielding portion. An exposure apparatus characterized by having a diffraction characteristic that reduces the difference between the scanning direction of scanning exposure and the non-scanning direction orthogonal to the scanning direction. It has a zoom lens unit that changes the σ value,
The exposure apparatus according to claim 1, wherein the diffraction optical element has a diffraction characteristic such that the difference disappears at the center value in the range of the σ value that can be changed by the zoom lens unit. It has a third light-shielding portion that adjusts the integrated incident angle distribution.
The exposure apparatus according to claim 2, wherein the third light-shielding portion is adjusted according to the state of the zoom lens unit. The third aspect of claim 3, wherein the third light-shielding portion is arranged at a position defocused to the light source side from the position of the Fourier transform surface which is optically in a Fourier transform relationship with the diffractive optical element. Exposure device. The first light-shielding portion and the second light-shielding portion each include a variable slit.
The exposure apparatus according to any one of claims 1 to 4, wherein the variable slit is adjusted so as to reduce the difference. The third light-shielding portion includes a variable slit and includes a variable slit.
The exposure apparatus according to claim 3 or 4, wherein the variable slit is adjusted according to the state of the zoom lens unit. The exposure apparatus according to any one of claims 1 to 6, wherein the diffractive optical element includes a computer hologram. The exposure apparatus according to any one of claims 1 to 7, wherein the exposure apparatus is arranged on the conjugate surface and has a masking unit that defines an illumination range of the original plate. A step of exposing a substrate using the exposure apparatus according to any one of claims 1 to 8.
An article manufacturing method comprising a step of developing the exposed substrate and producing an article from the developed substrate.