TWI798581B - Exposure device and article manufacturing method - Google Patents

Abstract

An exposure device for performing scanning exposure of a substrate, an illumination optical system for illuminating an illuminated surface of an original plate with light from a light source includes: a diffractive optical element that directs light from a beam of light from the light source on a predetermined surface The intensity distribution is transformed through the effect of diffraction; the first light shielding part is arranged at a position defocused from the conjugate surface of the aforementioned illuminated surface toward the light source side; and the second light shielding part is arranged at a position from the conjugate surface of the aforementioned illuminated surface The aforementioned conjugate plane is defocused towards the side of the aforementioned illuminated plane. The diffractive optical element is in terms of an integrated incident angle distribution obtained by integrating incident angle distributions during the scanning exposure period for illuminating a certain point on the illuminated surface that has passed through the first light-shielding portion and the second light-shielding portion. , has a diffraction characteristic that reduces the difference between the scanning direction of the aforementioned scanning exposure and the non-scanning direction perpendicular to the scanning direction.

Description

Exposure device and article manufacturing method

The invention relates to an exposure device and an article manufacturing method.

With the miniaturization of semiconductor devices, further higher resolution is required in exposure devices used in photolithography processes of semiconductor device manufacturing. 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 modification of illumination (ring zone illumination, double pole illumination, quadruple pole illumination, etc.) Use as valid.

On the other hand, with the multilayering of device structures in recent years, exposure devices are also required to have high overlay accuracy. Patent Document 1 discloses a double-slit structure in which a light shielding portion 103 and a light shielding portion 105 are arranged in front and rear of a shielding unit 104 that is a conjugate surface of the illuminated surface ( FIG. 1 ). This double slit configuration is effective in order to improve the superposition accuracy.

In addition, Patent Document 1 also discloses that a light shielding portion 401 or a filter 402 is disposed for alleviating the asymmetry of the integrated effective light source distribution caused by the double slit structure (FIGS. 12 and 14). [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2010-73835

[Problem to be solved by the invention]

However, if a light shielding unit or a filter is arranged for alleviating the asymmetry of the integrated effective light source distribution due to the double-slit configuration, the image plane illuminance may decrease. The decrease in the illumination of the image plane leads to a decrease in the throughput, so it is not preferred.

For example, the present invention provides an exposure apparatus that is advantageous in both correction performance of an illuminance distribution on an image plane of an illumination optical system and suppression of a decrease in illuminance on an image plane. [Technical means to solve the problem]

According to one aspect of the present invention, an exposure device is provided, which performs scanning exposure of a substrate, and has an illumination optical system for illuminating an illuminated surface of an original plate with light from a light source, and the illumination optical system has: diffractive optics An element, which converts the light intensity distribution of the light beam from the light source on a predetermined surface through diffraction; the first light shielding part, which is arranged at a position defocused from the conjugate surface of the surface to be illuminated toward the light source side; and a second light-shielding part, which is arranged at a position defocused from the aforementioned conjugate plane of the aforementioned illuminated surface toward the side of the aforementioned illuminated surface; In terms of the cumulative incident angle distribution obtained from the incident angle distribution during the illumination of a certain point on the illuminated surface through the aforementioned scanning exposure, it has a scanning direction that reduces the aforementioned scanning exposure and a non-scanning direction that is perpendicular to the scanning direction. poor diffraction properties. [compared to the effect of prior art]

According to the present invention, for example, it is possible to provide an exposure device that is advantageous in 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.

Other features and advantages of the present invention will be clarified through the following description with reference to the drawings. In addition, in the drawings, the same or similar configurations are denoted by the same reference signs.

Embodiments will be described in detail below with reference to the drawings. In addition, the following embodiments do not limit the inventors of the claims. Although plural features are described in the embodiments, all of these plural features are not limited to those necessary for the invention, and the plural features may be combined arbitrarily. In addition, in the drawing, the same reference numerals are assigned to the same or similar configurations, and overlapping explanations are omitted.

<First Embodiment> FIG. 1 is a schematic cross-sectional view showing the configuration of an exposure apparatus in the embodiment. This exposure apparatus is a scanning type exposure apparatus which exposes the pattern of the original plate (mask) to a board|substrate by a step-and-scan method. In the step-and-scan method, one exposure is performed while driving (scanning) the original plate and the substrate relative to each other. After the exposure of one exposure is completed, the stepping movement of the substrate moves to the next exposure area.

The exposure device has an illumination optical system for illuminating a reticle 24 serving as an original plate with a light beam from the light source 1 , and a projection optical system 26 for projecting the pattern of the reticle 24 on a substrate 27 .

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

The illumination optical system has a guiding optical system 2 , an emission angle preserving optical element 5 , a diffractive optical element 6 , a focusing lens 7 , and a prism unit 10 . In addition, the illumination optical system further includes a zoom lens unit 11 , an optical integrator 12 , a diaphragm 13 , a focus lens 14 , a first shield 18 and a second shield 20 , a shield 19 , a focus lens 21 , and a collimator lens 23 .

The guiding optical system 2 is arranged between the light source 1 and the exit angle preserving optical element 5 , and guides the light beam from the light source 1 to the exit angle preserving optical element 5 . The emission angle preserving optical element 5 is provided on the light source side of the diffractive optical element 6 , and guides the light beam from the light source 1 to the diffractive optical element 6 while keeping the divergence angle constant. The emission angle preserving optical element 5 can be constituted by an optical integrator such as a microlens array or a fiber bundle. The output angle preservation optical element 5 can reduce the influence of the output variation of the light source 1 on the pattern distribution formed by the diffractive optical element 6 .

The diffractive optical element 6 is disposed on a plane conjugate to the magnifier 24 which is an illuminated plane (image plane) or a plane having a Fourier transform relationship with the pupil plane of the illumination optical system. The diffractive optical element 6 responds to the light intensity distribution of the light beam from the light source 1 on a predetermined plane such as the pupil plane of the illumination optical system, which is a plane conjugate to the pupil plane of the projection optical system 26, and the plane conjugate thereto. Transformation is performed by diffraction to form the desired light intensity distribution. A computer generated hologram (CGH: Computer Generated Hologram) designed with a computer may also be used for the diffractive optical element 6 in order to obtain a desired diffraction pattern on the diffraction pattern surface. The light source shape formed on the pupil plane of the projection optical system 26 is called an effective light source shape. In addition, in this specification, "effective light source" refers to the light intensity distribution or the angular distribution of light on the illuminated surface and its conjugate surface. The diffractive optical element 6 is provided between the emission angle preserving optical element 5 and the focusing lens 7 . The light beam from the emission angle preserving optical element 5 is irradiated on the diffractive optical element 6 , diffracted by the diffractive optical element 6 , and guided to the focusing lens 7 .

In one example, a plurality of diffractive optical elements 6 are provided in the illumination optical system, and individual diffractive optical elements 6 are mounted in corresponding ones of a plurality of slots of a turntable (not shown). A plurality of diffractive optical elements can form individually different effective light source shapes. According to these effective light source shapes, the name of the lighting mode is called small σ lighting, big σ lighting, ring lighting, double pole lighting, quadruple pole lighting, etc.

The focusing lens 7 is disposed between the diffractive optical element 6 and the prism unit 10 , and focuses the beam diffracted by the diffractive optical element 6 to form a diffraction pattern on the Fourier transform plane 9 . The distribution of the diffraction pattern is fixed.

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

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 amplifies the light intensity distribution formed on the Fourier transform plane 9 . The prism unit 10 can guide the diffraction pattern (light intensity distribution) formed on the Fourier transform plane 9 to the zoom lens unit 11 by adjusting the ring rate and the like.

Furthermore, the zoom lens unit 11 is provided between the prism unit 10 and the optical integrator 12 . The zoom lens unit 11 adjusts the σ value based on the ratio of the NA of the illumination optical system to the NA of the projection optical system with respect to the diffraction pattern formed on the Fourier transform plane 9 , and guides the diffraction pattern to the optical integrator 12 .

The optical integrator 12 is arranged between the zoom lens unit 11 and the focusing lens 14, and may include fly-eyes that form a plurality of secondary light sources according to the diffraction pattern after adjusting the ring rate, aperture angle, and σ value and lead to the focusing lens 14. lens. Wherein, the fly-eye lens part of the optical integrator 12 may be composed of an optical tube, a diffractive optical element, a microlens array, and the like. An aperture 13 is provided between the optical integrator 12 and the focusing lens 14 .

The focusing lens 14 is disposed between the optical integrator 12 and the reticle 24 . Thereby, a plurality of light beams guided from the optical integrator 12 can be condensed to illuminate the reticle 24 overlappingly. The focus lens 14 includes a half mirror 15 , and a part of the exposure light enters a light quantity measuring optical system 16 . The light quantity measuring optical system 16 has a sensor 17 for measuring the light quantity. According to the amount of light measured through the sensor 17, the exposure amount during exposure can be properly controlled.

On the conjugate surface of the non-illumination surface, the shielding unit 19 is arranged. The masking unit 19 is arranged to define the illumination range of the reticle 24 , and is scanned in synchronization with the reticle stage 25 holding the reticle 24 and the substrate stage 28 holding the substrate 27 .

At positions defocused from the shielding unit 19, two light shielding portions are provided. Specifically, the first light shielding portion 18 is arranged at any one of a position defocused from the illuminated surface toward the light source side and a position defocused from the conjugate surface of the illuminated surface toward the light source side. In addition, the second light shielding portion 20 is arranged at a position defocused from the conjugate plane of the illuminated surface toward the illuminated surface side. In order to reduce the non-uniformity of the illuminance distribution on the surface to be illuminated, the first light shielding part 18 and the second light shielding part 20 can be respectively variable slits.

The light reflected by the mirror 22 having a predetermined inclination with respect to the light beam from the focusing lens 21 illuminates the magnification mask 24 via the collimator lens 23 . The pattern of the reticle 24 is projected on the substrate 27 through the projection optical system 26 .

Next, the integrated effective light source will be described with reference to FIG. 2 . The illumination area 24a is an illumination area of the surface of the reticle 24 which is the surface to be illuminated. The illumination area 19 a is an illumination area on the surface of the shielding unit 19 that is in a conjugate relationship with the surface of the reticle 24 . The illuminated area 24a is scanned during exposure. In this case, the incident angle distribution for illuminating one point on the exposure surface is obtained by integrating the incident angle distribution for illuminating each point on the straight line 24b parallel to the scanning direction (y direction) in the illumination area 24a. This is called the cumulative effective light source. In other words, the integrated effective light source refers to the integrated incident angle distribution obtained by integrating the incident angle distribution during the period of illuminating a certain point in the illumination area by scanning exposure. The straight line 19b is a straight line parallel to the scanning direction (y direction) in the illuminated area 19a, corresponding to the straight line 24b.

Next, with reference to FIG. 3 , how the integrated effective light source after scanning becomes when the first light shielding unit 18 and the second light shielding unit 20 are used will be described. Reference numeral 3 a shows an enlarged view of the vicinity of the first light shielding portion 18 and the second light shielding portion 20 . Symbol 3b shows the angular distribution of the illumination light passing through the points A, B, and C on the surface of the shielding unit 19 . The light beam directed toward the point A from the focusing lens 14 through the optical integrator 12 is emitted parallel to the optical axis 1b, and is not partially obscured by the first light shielding portion 18 and the second light shielding portion 20 . For this reason, the shape of the effective light source 24a at point A' on the reticle surface becomes substantially circular.

On the other hand, as for the light beam going from the focusing lens 14 to the point B through the optical integrator 12, part of the light is dimmed by the light shielding member 18a of the first light shielding unit 18 and the light shielding member 20a of the second light shielding unit 20. For this reason, the angular distribution of the effective light source 24b in terms of point B' on the reticle surface is asymmetrical in the scanning direction (Y direction) of the scanning exposure. The upper side of the effective light source 24b is missing because the light shielding member 20a of the second light shielding unit 20 is darkened, and the lower side is missing because the light shielding member 18a of the first light shielding unit 18 is darkened. In this manner, it can be seen that asymmetry occurs in the scanning direction (Y direction) of the scanning exposure with respect to the effective light source 24b due to the presence of 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 from the same viewpoint as the light beam heading to the point B.

It can be seen that the integrated effective light source obtained by scanning all the light beams on the straight line including point A, point B, and point C in the Y direction has a light intensity distribution as represented by symbol 3c, and the integrated effective light source occurs in the scanning direction. Asymmetry of the light source. Problems with exposure can occur when there is an asymmetry in the integration of the effective light source. For example, when printing line and space patterns with the same line width in the vertical and horizontal directions, a difference in line width occurs between the vertical pattern and the horizontal pattern, which is not preferable. For this, the asymmetry needs to be corrected.

In the embodiment, the third light shielding portion 8 is disposed on the light source side of the Fourier transform plane 9 . The third light shielding portion 8 is arranged, for example, at a position slightly defocused from the position of the Fourier transform plane 9 . In order to correct the integrated effective light source (integrated incidence angle distribution), the third light shielding portion 8 can be used. In FIG. 4, the structure of the 3rd light shielding part 8 is shown. The third light shielding unit 8 is constituted by, for example, four light shielding plates, and each of the four light shielding plates can be independently driven 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 can be adjusted by driving the two shading plates in the direction of closing in the X direction to partially dim the light in the X direction. It can also be adjusted by applying a filter instead of the light-shielding part.

Conventionally, the distribution of the Fourier transform plane 9 is the same, but in this embodiment, as shown in FIG. 5A , the diffractive optical element 6 is designed to have a different distribution with respect to the Y direction. The diffractive optical element 6 has a scanning direction (Y direction) for reducing scanning exposure and a non-scanning direction orthogonal to the scanning direction in terms of the integrated effective light source generated on the illuminated surface through the first light shielding part 18 and the second light shielding part 20. Poor diffraction characteristics in the X direction (X direction). Specifically, with respect to the Y direction, the distribution of the Fourier transform plane and the asymmetric part of the effective light source due to the first light shielding part 18 and the second light shielding part 20 are offset, so that as shown in FIG. 5B, the Y direction of the effective light source is integrated. The light intensity distribution becomes constant. As a result, the X direction and the Y direction of the integrated effective light source become symmetrical. Thereby, it is not necessary to adjust the asymmetry by applying the third light shielding portion 8 . For this reason, the fall of the image plane illuminance by applying the 3rd light shielding part 8 does not generate|occur|produce, and it is advantageous from the viewpoint of the throughput of an exposure apparatus.

<Second Embodiment> The second embodiment is an example of changing the σ value using the zoom lens unit 11 . When the zoom lens unit 11 is driven to change the zoom, the influence of shading on the first light shielding portion 18 and the second light shielding portion 20 changes, and the asymmetry of the integrated effective light source changes. Therefore, in the case of using one type of diffractive optical element, it is difficult to sufficiently reduce the asymmetry of the integrated effective light source in all zooms. Therefore, also in this embodiment, the 3rd light shielding part 8 is used together.

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, there is an asymmetry in the cumulative effective light source for any value of σ. On the other hand, in the present embodiment, the diffractive optical element 6 is designed to have a scanning direction (Y direction) and a non-scanning direction ( X direction) to reduce the diffraction characteristics of the difference. Thereby, the asymmetry of the integrated effective light source in the driving range of the σ value becomes smaller compared with the prior art.

FIG. 7 is the result of calculating the line width difference between the longitudinal pattern and the transverse pattern when exposing by the integrated effective light source having the conventional asymmetry shown in FIG. 6 through an optical image simulation. From the figure, it can be seen that the line width difference between the vertical pattern and the horizontal pattern is smaller in this embodiment than in the prior art.

In actual use of the device, the asymmetry is adjusted using the third light shielding portion 8 in accordance with the σ used, starting from the magnitude of the asymmetry of the integrated effective light source as shown in FIG. 6 . 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 where the asymmetry is small within the range of the σ value used, the amount of adjusting the asymmetry is small, so the reduction of the image plane illuminance by applying the third light-shielding part 8 becomes less, and the It is advantageous from the viewpoint of the throughput of the exposure apparatus.

<Embodiments of the article manufacturing method> The article manufacturing method according to the embodiment of the present invention is suitable for, for example, manufacturing articles such as microdevices such as semiconductor devices and elements having a fine structure. The article manufacturing method of this embodiment includes a process of forming a latent image pattern on the photosensitive agent applied to the substrate using the above-mentioned exposure device (a process of exposing the substrate) and a process of developing the substrate on which the latent image pattern is formed by this process. program. Furthermore, such manufacturing methods include other well-known procedures (oxidation, film formation, evaporation, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method of this embodiment is advantageous in at least one of article performance, quality, productivity, and production cost compared to conventional methods.

The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the scope of the patent application is drafted to disclose the scope of the invention.

1: light source 1b: optical axis 2: Guide optical system 3a: Zoom in 3b: Angle distribution 3c: Light intensity distribution 5: Shooting angle saves optical components 6: Diffractive optical element 7: Focusing lens 8: The third shading part 9: Fourier transform plane 10: Prism unit 11:Zoom lens unit 12: Optical integrator 13: Aperture 14: Focusing lens 15: half mirror 16: Light quantity measurement optical system 17: Sensor 18: The first shading part 18a: Shading member 19: Masking unit 19a: Lighting area 19b: straight line 20: The second shading part 20a: Shading member 21: Focusing lens 22: Mirror 23: Collimating lens 24: double shrink mask 24a: Lighting area 24b: Effective light source 24c: Effective light source 25: Reticle stage 26: Projection optical system 27: Substrate 28: Substrate carrier A: Points on the surface of masking unit 19 A': point on the mask surface B: point on the surface of masking unit 19 B': point on the mask surface C: Points on the surface of the masking unit 19 C’: point on the surface of the doubled photomask y: scanning direction

The drawings are described in the specification, constitute a part thereof, show embodiments of the present invention, and are used for explaining the principle of the present invention together with the description. [ Fig. 1] Fig. 1 is a schematic cross-sectional view showing the configuration of an exposure apparatus in an embodiment. [ Fig. 2 ] A diagram illustrating an integrated effective light source. [ Fig. 3 ] A diagram explaining the integration of effective light sources. [ Fig. 4 ] A diagram showing the configuration of a light-shielding unit. [FIG. 5A] A diagram illustrating the design of the diffractive optical element in the embodiment. [ Fig. 5B ] A diagram explaining the design of the diffractive optical element in the embodiment. [ Fig. 6 ] A graph plotting the asymmetry of the integrated effective light source for each value of σ. [ FIG. 7 ] A graph plotting the difference in line width between a vertical pattern and a horizontal pattern for each value of σ.

1: light source

2: Guide optical system

5: Shooting angle saves optical components

6: Diffractive optical element

7: Focusing lens

8: The third shading part

9: Fourier transform plane

10: Prism unit

11:Zoom lens unit

12: Optical integrator

13: Aperture

14: Focusing lens

15: half mirror

16: Light quantity measurement optical system

17: Sensor

18: The first shading part

19: Masking unit

20: The second shading part

21: Focusing lens

22: Mirror

23: Collimating lens

24: Double shrink mask

25: Reticle stage

26: Projection optical system

27: Substrate

28: Substrate carrier

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 light from the light source, The aforementioned illumination optical system has: a diffractive optical element, which transforms the light intensity distribution of the light beam from the aforementioned light source on a predetermined surface through diffraction; a first light-shielding portion disposed at a position defocused from a conjugate surface of the illuminated surface toward the light source side; and a second light-shielding portion disposed at a position defocused from the conjugate plane of the illuminated surface toward the illuminated surface; The above-mentioned diffractive optical element is in terms of an integrated incident angle distribution obtained by integrating the incident angle distribution during the period of illuminating a certain point on the illuminated surface that has passed through the first light-shielding portion and the second light-shielding portion through the scanning exposure. , has a diffraction characteristic that reduces the difference between the scanning direction of the aforementioned scanning exposure and the non-scanning direction perpendicular to the scanning direction. The exposure device according to claim 1, which has a zoom lens unit that changes the value of σ, The above-mentioned diffractive optical element has a diffraction characteristic in which the above-mentioned difference disappears in the center value of the range of the σ value that can be changed by the above-mentioned zoom lens unit. The exposure device according to claim 2, which has a third light-shielding section for adjusting the aforementioned cumulative incidence angle distribution, The third light-shielding portion is adjusted according to the state of the zoom lens unit. The exposure apparatus according to claim 3, wherein the third light shielding portion is disposed at a position defocused toward the light source from a position of a Fourier transform plane optically in a Fourier transform relationship with the diffractive optical element. Such as the exposure device of claim 1, wherein, The first light-shielding portion and the second light-shielding portion each include a variable slit, The aforementioned variable seams are adjusted in such a way as to reduce the aforementioned difference. Such as the exposure device of claim 3, wherein, The aforementioned third light-shielding portion includes variable slits, The aforementioned variable slit is adjusted according to the state of the aforementioned zoom lens unit. The exposure device according to claim 1, wherein the diffractive optical element includes a computerized hologram. The exposure device according to claim 1, which has a shielding unit disposed on the conjugate plane to define the illumination range of the original plate. A method of manufacturing an article, comprising: A procedure for exposing a substrate using the exposure apparatus according to any one of claims 1 to 8, and A procedure for developing the aforementioned exposed substrate, An article is manufactured from the substrate obtained by the aforementioned development.

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