JP3209220B2 - Exposure method and semiconductor element manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for exposing a reticle pattern to a photosensitive substrate and a method for manufacturing a semiconductor device using such an exposure method.

[0002]

2. Description of the Related Art Conventionally, in an exposure apparatus for manufacturing a semiconductor element, particularly a semiconductor element having a high degree of integration such as a super LSI, a lighting apparatus having an optical integrator (a so-called fly-eye integrator) comprising a fly-eye lens has been used. Have been. One example of such a lighting device is a light source, an elliptical mirror, a cold mirror, a divergent collimating lens, two fly-eye lenses and a convergent collimating lens, as disclosed, for example, in US Pat. No. 3,296,923. It illuminates the illuminated object surface with substantially uniform illuminance. By using the fly-eye lens in this manner, a number of secondary light sources corresponding to the number of fly-eye lenses are formed, and these can illuminate the illuminated object surface in a plurality of directions in a superimposed manner. The non-uniformity of the illuminance distribution on the object plane can be reduced to several percent or less.

[0003] Recently, with higher integration of VLSI and the like, illumination light required for good printing exposure of a circuit pattern is required to have better illuminance uniformity. Therefore, Japanese Patent Application Laid-Open No. Sho 64-42821 proposes a lighting device that can obtain better illuminance uniformity by using a so-called patterned filter and can maintain an optimum lighting state according to a reticle or a wafer to be used. Have been.

FIG. 7A shows a main part of an illumination device using a conventional patterned filter. In FIG. 7A, reference numeral 1 denotes a fly-eye integrator, and fly-eye integrator 1 is a lens element. 2-1 and 2-
2, 2-3, ‥‥ are formed by bundling. A patterned filter plate 3 is arranged on the light source side of the fly-eye integrator 1, and a light-shielding portion 4 is formed in the patterned filter plate 3, for example, in the center of a region corresponding to the lens element 2-2.

[0005] Illumination light IL composed of substantially parallel light beams emitted from a light source (not shown) passes through the patterned filter plate 3 and is incident on the fly-eye integrator 1, where the rear side of the fly-eye integrator 1 ( Light from a number of secondary light sources formed on the focal plane corresponding to each lens element on the focal plane
Are irradiated onto the illuminated object surface 6 such as the pattern forming surface of the reticle. In this case, if the Z-axis is taken in a direction parallel to the plane of the paper of FIG. Illuminance distribution I on surface 6
D becomes, for example, distributions 7A and 7C in FIG. 7B, respectively.

On the other hand, since the light shielding portion 4 is formed in front of the lens element 2-2 at the center of the fly-eye integrator 1, the illumination light from the lens element 2-2 on the object surface 6 to be illuminated. The illuminance distribution ID is, for example, as shown in FIG.
As shown in the distribution 7B of FIG. 7B, the vicinity of the optical axis has a characteristic of dropping. Therefore, the three lens elements 2-1 to 2-3
The overall illuminance distribution of the illumination light from is, for example, a flat distribution 8 in FIG. That is, in the patterned filter system, the uniformity of the illuminance distribution as a whole is improved by appropriately changing the illuminance distribution of the illumination light from a predetermined lens element of the fly-eye integrator 1.

[0007]

However, in the prior art as described above, the light-shielding portion is provided only on a very small part of a large number of lens elements constituting the fly-eye integrator. Although effective for improving the illuminance uniformity, there is a disadvantage that the coherence degree of the illumination light changes depending on the illumination position of the illuminated object. Specifically, in the example of FIG. 7A, normal illumination light is irradiated in the illumination area ZB on the illuminated object surface 6, but in the illumination area ZA, the light shielding section 4 on the patterned filter plate 3 The illumination light from the lens element 2-2 is blocked.
Therefore, illumination close to annular illumination is performed in the illumination area ZA, and the coherence degree of the illumination light is different between the illumination areas ZA and ZB.

If the image of the pattern on the illuminated object surface 6 is projected onto a photosensitive substrate by a projection optical system (not shown), if the degree of coherence of the illumination light changes in such a manner, the incident light of the projection optical system Since the light amount distribution in the pupil plane (Fourier transform plane) changes, there is a disadvantage that the imaging characteristics change depending on the pattern of the light shielding unit 4 of the patterned filter plate 3.

In this regard, there has been proposed an illumination device in which fly-eye integrators are arranged in multiple stages in the optical axis direction of the illumination device to further improve the uniformity of the illuminance and the coherence degree. With such a configuration, there is an inconvenience that the lighting device becomes large as a whole. In view of the foregoing, the present invention has been made to improve the uniformity of illuminance on the illuminated object surface without increasing the size of the entire apparatus and without deteriorating the uniformity of the coherence degree on the illuminated object surface. The purpose is to do.

[0010]

A first exposure method according to the present invention includes an illumination step of illuminating a reticle with illumination light via an optical integrator, and a step of transferring a pattern of the reticle to a photosensitive substrate. In the method, the illumination step includes a variable step of changing a distribution of illumination light on an incident side of the optical integrator, and a member that uniforms an illuminance distribution according to the change of the illumination light distribution by the variable step. And an adjustment step of adjusting the illuminance distribution by exchanging the member.

Next, a second exposure method according to the present invention is directed to an exposure method having an illumination step of illuminating illumination light onto a reticle via an optical integrator and a step of transferring a pattern of the reticle to a photosensitive substrate. The illumination step is a wavelength selection step of using the interference filter plate to make illumination light of a desired wavelength range on the incident side of the optical integrator, and a variable step of changing the distribution of illumination light on the incidence side of the optical integrator, Adjusting the illuminance distribution according to a change in the distribution of the illumination light due to the variable step. Further, the method of manufacturing a semiconductor device according to the present invention is to manufacture a semiconductor device by transferring the pattern of the reticle onto the photosensitive substrate using the exposure method of the present invention.

[0012]

The principle of the present invention will be described with reference to FIG. FIG. 1A shows a main part of a lighting device used as an example in the present invention. As shown in FIG. 1A, a fly-eye integrator 16 corresponding to an optical integrator of the present invention has three fly-eye integrators. It is assumed that it is constituted by lens elements 17-1 to 17-3.
Lens elements 17-1 to 17-1 in the transmittance distribution adjusting member 14 corresponding to the member for uniforming the illuminance distribution of the present invention disposed on the light source side of the fly-eye integrator 16
In the region immediately before 7-3, filter elements 15-1 to 15-3 each having a predetermined transmittance distribution are formed.

In this case, according to the present invention, first, the transmittance distribution of the filter element 15-1 is such that the lens element 17-1 is transmitted through the filter element 15-1.
The illuminance distribution of the illumination light emitted from the irradiating object surface 20 corresponding to the reticle of the present invention by the condenser lens 19 is determined so as to be uniform as a distribution 21A in FIG. Similarly, the lens element 17
-2 and condenser lens 1 emitted from 17-3
9 so that the illuminance distribution of the illuminating light illuminated on the illuminated object surface 20 by the filter element 9 becomes uniform like the distributions 21B and 21C in FIG.
2 and 15-3 are determined. Thus, the illuminance distribution of the entire illumination light on the illuminated object surface 20 is as shown in FIG.
As shown by the distribution 22 in FIG. Moreover, in FIG. 1A, in different observation areas ZA and ZB on the illuminated object plane 20, the same amount of illumination light is received from the lens elements 17-1 to 17-3, respectively, so that the coherence degree is also high. Are equal.

That is, by correcting all the lens elements constituting the fly-eye integrator 16, the object plane 2 to be illuminated from each lens element is corrected.
The illuminance distribution of the illumination light toward zero is made uniform.
In this case, the contribution of the illumination light from each lens element of the fly-eye integrator 16 to different image height positions on the illuminated object plane 20 is equal. Therefore, assuming that the image of the illuminated object plane 20 is projected onto the photosensitive substrate via the projection optical system, the change in the light amount distribution in the entrance pupil plane (Fourier transform plane) of the projection optical system with respect to the image height displacement is: A small change in the coherence degree on the image plane, which contributes to imaging without increasing the size of the apparatus, can be suppressed to a small value.

In the present invention, the illuminance distribution is adjusted according to the change in the distribution of the illumination light on the incident side of the fly-eye integrator 16. Thereby, for example, when replacing the mercury lamp that supplies the illumination light with another mercury lamp,
Even in the case where the distribution of the illumination light on the incident side of the fly-eye integrator 16 changes, the illumination can be performed without increasing the size of the entire apparatus and without deteriorating the coherence degree on the object surface 20 to be illuminated. Illuminance uniformity on the object plane 20 can be improved.

[0016]

FIG. 2 to FIG. 4 show a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 2 shows a schematic configuration of the illumination device of the present embodiment. In FIG. 2, reference numeral 9 denotes an ultra-high pressure mercury lamp, and illumination light IL from the mercury lamp 9 is an elliptical mirror 10.
After being reflected by the cold mirror 11, the light is focused on the second focal point of the elliptical mirror 10. After that, the diverging illumination light is converted into a parallel light beam by the collimation lens 12, and then enters the fly-eye integrator 16 via the interference filter plate 13 and the patterned filter plate 14. The interference filter plate 13 allows only the luminous flux of a desired wavelength range of the illumination light IL emitted from the collimation lens 12 to pass through to the patterned filter plate 14 side. The patterned filter plate 14 is formed by forming a large number of filter elements corresponding to the respective lens elements constituting the fly-eye integrator 16 on a transparent parallel plane plate made of quartz glass or the like (details will be described later).

In the vicinity of the focal plane on the rear side (condenser lens side) of the fly-eye integrator 16, a number of secondary light sources equal to the number of lens elements constituting the fly-eye integrator 16 are formed. The light beams from these secondary light sources are reflected by the reflection mirror 18 and then condensed by the converging condenser lens 19 to be superimposed and guided on the illuminated object surface 20 corresponding to the pattern forming surface of the reticle. Then, a reticle pattern arranged on the illuminated object surface 20 is projected onto the wafer surface by a projection optical system (not shown).

Next, the configurations of the patterned filter plate 14 and the fly-eye integrator 16 of this embodiment will be described. First, as shown in FIG. 2, the fly-eye integrator 16 has a large number of lens elements 17 each having a rectangular cross section.
-3, 17-8, 17-14,... Are bundled, and the rear focal point of the incident light side lens surface 16a is almost at the position of the exit light side lens surface 16b. The front focus of 16b is located at the incident light side lens surface 16a. For this reason, the parallel light beam incident on the fly-eye integrator 16 is condensed near the exit-side lens surface 16b of each lens element, and is equal to the number of lens elements near the exit surface of the fly-eye integrator 16. A number of secondary light sources are formed.

Exit lens side 1 of each lens element
6b functions as a field lens for each secondary light source, and the incident surface of the fly-eye integrator 16 is configured to be substantially conjugate with the illuminated object surface 20 by the condenser lens 19. Therefore, the luminous fluxes from a number of secondary light sources formed in the vicinity of the exit surface of the fly-eye integrator 16 illuminate the illuminated object surface 20, respectively, so that the illuminated object surface 20 is uniformly illuminated in a superimposed manner. You.

Also, images of a number of secondary light sources formed near the exit surface of the fly-eye integrator 16 are projected onto the entrance pupil plane of a projection optical system (not shown) by a condenser lens 19, and the wafer is subjected to so-called Koehler illumination. Even on the surface, uniform illumination is performed. FIG. 3 is a front view of the patterned filter 14 and the fly-eye integrator 16 as viewed from the interference filter plate 13 side (incident light side). In FIG. The filter element 15 is located in the area immediately before each lens element 16.
-1, 15-2, 15-3, ‥‥. The transmittance distributions of these filter elements 15-1, 15-2,...
The illuminance distribution above is set to be uniform.
Therefore, the filter elements 15-1, 15-2,.
The transmittance distribution of ‥ is independently set according to the characteristics of the corresponding lens element in the fly-eye integrator 16 and the distribution characteristics of the illumination light from the mercury lamp 9.

More specifically, in a direction crossing the fly-eye integrator 16 in a direction parallel to the plane of FIG.
Take the axis and move the fly-eye integrator 16 in FIG.
Lens elements 17-3, 17-8 and 17-1
4, each of the patterned filter plates 1 of FIG.
4. Filter elements 15-3, 15-8 and 1 in 4
5-14 are located. In this case, as an example, the filter elements 15-3, 15-8, and 15
The distribution of transmittance T along the Z axis of −14 is shown in FIG.
(A), (b) and (c). Thereby, the illuminance distribution of the illumination light emitted from the lens elements 17-3, 17-8 and 17-14 of the fly-eye integrator 16 of FIG. Independently uniform.

Similarly, the fly-eye integrator 16
The illuminance distribution of the illumination light emitted from the other lens elements and emitted onto the illuminated object surface 20 by the condenser lens 19 also becomes uniform. Thus, the illumination target object surface 20 is illuminated by the illumination light from the fly-eye integrator 16 with a uniform illuminance distribution as a whole. Moreover, at different points on the illuminated object surface 20, the illumination light from each lens element of the fly-eye integrator 16 is received by an approximately equal amount, so that the coherence degree of the illuminated light on the illuminated object surface 20 is increased. Is uniform. As a result, the imaging characteristics of the projection optical system are favorably maintained.

The illumination light from each lens element of the fly-eye integrator 16 may be made uniform in the illuminance distribution on the object surface 20 to be illuminated. Of course, it is not necessary to arrange the filter element. However, needless to say, a filter element having no change in light amount (a constant transmittance distribution) may be arranged on the incident side of the lens element having no illuminance unevenness.

In FIG. 2, the patterned filter plate 14 is supported so as to be movable by a driving device (not shown), and the distance D between the patterned filter plate 14 and the fly-eye integrator 16 is defined by the optical path of the illumination light IL. May be variable along the line. By moving the patterned filter plate 14 to change the interval D, the transmittance distribution of each filter element of the patterned filter plate 14 is deformed to some extent by a kind of defocus effect. For example, by fixing the interval D where the uniformity of the illuminance distribution and the uniformity of the coherence degree on the illuminated object plane 20 are in the best state, the imaging characteristics can be further improved.

Further, for example, when the light amount of the mercury lamp 9 is reduced and the mercury lamp 9 is replaced with another mercury lamp, the illumination light on the incident light side of each lens element of the fly-eye integrator 16 is used. May change. Therefore, the patterned filter plate 14 is arranged, for example, by a turret plate system so that it can be replaced with a patterned filter plate having another characteristic, and when the mercury lamp 9 is replaced, the patterned filter plate is also replaced with a new mercury lamp. It is desirable to replace it with a filter plate having characteristics corresponding to the lamp.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a projection exposure apparatus to which the illumination device of this embodiment is applied. In FIG. 5, the illumination light from the mercury lamp 9 is converted into a substantially parallel light beam through an elliptical mirror 10, a cold mirror 11, and a collimation lens 12. By providing a shutter 23 near the second focal point of the elliptical mirror 10 and closing the shutter 23 by the drive motor 24, the supply of the illumination light to the collimation lens 12 is stopped at any time. As the light source of the lighting device, for example, an excimer laser light source that generates KrF laser light or the like can be used in addition to the mercury lamp 9. When an excimer laser light source is used, a beam expander or the like is used instead of the optical system from the elliptical mirror 10 to the collimation lens 12.

Then, in order from the collimation lens 12, a first polyhedral prism 25 having a quadrangular pyramid (pyramid) concave portion and a second polyhedral prism 26 having a quadrangular pyramid (pyramid) convex portion are arranged. . The illumination light emitted from the second polyhedral prism 26 is divided into four light beams at equal angles around the optical axis with the optical axis as the center.

The light beams thus divided into four light beams are respectively applied to the patterned filter plates 27A, 27B, 27C and 27C.
D through the fly-eye integrators 28A, 28
B, 28C and 28D. FIG. 5 shows only the patterned filter plates 27A and 27B and the fly-eye integrators 28A and 28B.
The two patterned filter plates 27C and 27D and the two fly-eye filters sandwich the optical axis AX in a direction perpendicular to the paper surface of FIG.
Integrators 28C and 28D are arranged. The patterned filter plates 27A to 27D of the present embodiment also include filter elements corresponding to the respective lens elements constituting the fly-eye integrators 28A to 28D. Those fly-eye integrators 28
A, 28B, 28C, and 28D are 90 ° around the optical axis AX.
° are arranged at intervals.

Fly-eye integrators 28A-28
A number of secondary light sources are formed on the reticle-side focal plane of D, respectively, and variable aperture stops 29A to 29D are arranged near the formation surfaces of these secondary light sources. In FIG. 5, only the variable aperture stops 29A and 29B appear. The illumination light passing through these variable aperture stops 29A to 29D is
The reticle 3 is condensed through the auxiliary condenser lens 30, the mirror 31 and the main condenser lens 32, respectively.
3 is illuminated with uniform illuminance. The pattern of the reticle 33 is transferred by the projection optical system 34 onto the wafer 35 on the wafer stage 36 at a predetermined reduction magnification β.

In this case, the patterned filter plate 27A
Are set such that the illuminance distribution of the illumination light emitted from the corresponding lens element of the fly-eye integrator 28A and irradiated onto the reticle 33 becomes uniform. Similarly, the transmittance distributions of the individual filter elements of the patterned filter plates 27B to 27D are the same as the illuminance distributions of the illumination light emitted from the corresponding lens elements of the fly-eye integrators 28B to 28D and irradiated onto the reticle 33, respectively. Set to be uniform. Thereby, the illuminance uniformity of the illumination light in the pattern area of the reticle 33 is good, and the uniformity of the coherence degree is also good.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a schematic configuration of the illumination device of the present embodiment. As shown in FIG. 6, the patterned filter plate 14 of FIG. The other configuration is the same as that of FIG. 2, and in FIG. 6, portions corresponding to FIG. 2 are denoted by the same reference numerals and detailed description thereof will be omitted.

In the embodiment shown in FIG.
As a result, the distribution of the illumination light incident on the individual lens elements constituting the fly-eye integrator 16 is made substantially uniform, and as a result, the illumination light is emitted from the individual lens elements and irradiated on the illuminated object surface 20 by the condenser lens 19. The illuminance distribution of the illumination light is made substantially uniform. In addition, since the amount of illumination light received from each lens element of the fly-eye integrator 16 at each point on the illuminated object plane 20 is substantially the same, it is possible to maintain good uniformity of the coherence degree without increasing the size of the apparatus. .

In place of the ground glass plate 38, for example, a phase type diffraction grating having a random pitch can be used. Also, the same effect can be obtained by using a transmission type pattern in which the pitch is random and the pitch is fine about the wavelength. It should be noted that the present invention is not limited to the above-described embodiments, but can take various configurations without departing from the gist of the present invention. For example, FIGS. 2, 5, and 6 show examples in which a light source image is formed at an infinite position by the collimation lens 12 and a parallel light beam enters the fly-eye integrators (16, 28A to 28D). The image is a fly-eye integrator (16, 28A-2
8D). Also in this case, the fly-eye integrator (16, 28A-
It is considered that a secondary light source is formed on the exit side of 28D).

[0034]

According to the present invention, for example, when the light amount of a mercury lamp for supplying illumination light is reduced and the mercury lamp is replaced with another mercury lamp, the illumination light on the incident side of the optical integrator is used. Even if the distribution changes, the illuminance distribution is adjusted according to the change in the distribution of the illuminating light, so that the coherence degree uniformity on the reticle is deteriorated without increasing the size of the entire apparatus. Irradiation uniformity on the reticle can be improved without causing the illuminance to be uniform.

[Brief description of the drawings]

FIG. 1A is an optical path diagram for explaining the principle of the present invention,
FIG. 2B is a distribution diagram illustrating an example of the illuminance distribution on the illuminated object surface in FIG.

FIG. 2 is a configuration diagram schematically illustrating a lighting device according to a first embodiment of the present invention.

FIG. 3 is a front view of the patterned filter plate 14 and the fly-eye integrator 16 of FIG. 2 viewed from the interference filter plate 13 side.

4 (a) to 4 (c) are distribution diagrams each showing an example of characteristics of transmittance distribution of each filter element of the patterned filter plate 14 of FIG.

FIG. 5 is a configuration diagram schematically showing a projection exposure apparatus to which an illumination device according to a second embodiment of the present invention is applied.

FIG. 6 is a configuration diagram schematically showing a lighting device according to a third embodiment of the present invention.

7A is an optical path diagram showing a main part of an illumination device using a conventional patterned filter plate, and FIG. 7B is an example of an illuminance distribution on an object surface 6 to be illuminated in FIG. 7A; FIG.

[Explanation of symbols]

 Reference Signs List 9 super high pressure mercury lamp 10 elliptical mirror 11 cold mirror 12 collimation lens 13 interference filter plate 14 patterned filter plate 16 fly-eye integrator 18 reflection mirror 19 condenser lens 20 illuminated object surface 27A, 27B patterned filter plate 28A, 28B FlyEye Integrator 38 Ground glass plate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521 H01S 3/101

Claims (7)

(57) [Claims] 1. An exposure method comprising: an illuminating step of illuminating illumination light onto a reticle via an optical integrator; and a step of transferring a pattern of the reticle to a photosensitive substrate, wherein the illuminating step is performed on an incident side of the optical integrator. A variable step of changing the distribution of the illumination light, and adjusting the illuminance distribution by replacing a member that makes the illuminance distribution uniform according to the change in the distribution of the illumination light by the variable step with a member having another characteristic. And an exposure method. 2. The exposure method according to claim 1, wherein said illuminating step includes a wavelength selecting step of using an interference filter plate to illuminate light in a desired wavelength range on the incident side of the optical integrator. 3. The adjusting step includes replacing a mercury lamp that supplies the illumination light with another mercury lamp.
3. The exposure method according to claim 1, wherein a distribution of illumination light on an incident side of the optical integrator is changed. 4. The exposure method according to claim 1, wherein the illuminating step includes a step of causing a substantially parallel light beam to enter the optical integrator as the illuminating light. 5. An exposure method comprising: an illuminating step of illuminating illumination light onto a reticle via an optical integrator; and a step of transferring a pattern of the reticle to a photosensitive substrate, wherein the illuminating step uses an interference filter plate. A wavelength selection step of making illumination light of a desired wavelength range on the incident side of the optical integrator, a variable step of changing the distribution of illumination light on the incident side of the optical integrator, and a change of the distribution of the illumination light due to the variable step An adjusting step of adjusting the illuminance distribution in accordance with the method. 6. The exposure method according to claim 5, wherein the adjusting step adjusts on an incident side of the optical integrator. 7. A method for manufacturing a semiconductor device, comprising: transferring a pattern of the reticle onto the photosensitive substrate by using the exposure method according to claim 1. .