JPH085796A - X-ray projection aligner - Google Patents

Abstract

PURPOSE:To provide an X-ray aligner to improve the efficiency of mass production in the semiconductor manufacturing technology (lithography) for copying minute patterns. CONSTITUTION:A condenser mirror 1 and a mask 2 are laid out in such a configuration as the condenser mirror 1 with a rotary elliptic face is divided into areas 4 and 5 and X rays reflected on the areas 4 and 5 of each rotary elliptic face overlap at the illuminating position of the mask 2 to condense the rays. Therefore, this makes it possible to use a set of two mirrors in an imaging optical system used for an X-ray projection aligner and to make an effective use of illumination light, thereby making an effect for improving the throughput of the aligner. Moreover, it has a secondary effect for making it possible to make incoherent the illumination to improve the quality of images in the imaging optical system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an X-ray projection exposure apparatus, and more specifically in a semiconductor manufacturing technique (lithography) for transferring a fine pattern, and collects X-rays emitted from a light source by a condenser mirror. The present invention relates to an X-ray projection exposure apparatus for illuminating a mask having a pattern to be projected, projecting and exposing reflected light or transmitted light from the mask onto a substrate through an imaging optical means to transfer the pattern. is there.

[0002]

2. Description of the Related Art In an X-ray projection exposure apparatus, it is possible to transfer a pattern with high accuracy and increase the proportion of X-rays from a light source that actually contributes to exposure, thereby improving the number of transfers per unit time, that is, the throughput. is important.

In the X-ray projection exposure apparatus, the exposure wavelength is 13n.
Since the light in the soft X-ray region of about m is used, the image-forming optical means of the X-ray projection exposure apparatus is constructed of a reflecting mirror because the transmission type lens cannot be used. The surface of the reflecting mirror is composed of a multilayer film for reflecting the light having the exposure wavelength in the soft X-ray region, but the reflectance is about 60% at the most. Therefore, in order to improve the throughput, it is desirable to reduce the number of condenser mirrors and the number of reflecting mirrors forming the imaging optical system.

As an X-ray projection exposure apparatus for the purpose of improving the throughput with high transfer accuracy, as described in Japanese Patent Laid-Open Publication No. 4-225215, a spheroidal mirror 1 is used as a condenser mirror. It is known that a combination of three aspherical mirrors is used as the image forming optical system. In the above-mentioned conventional technique, in order to effectively utilize the light intensity of the light source, the mask illumination area is formed into an arc shape by using a condenser mirror having one spheroidal reflecting surface. That is, as shown in FIG. 9, when the pattern of the mask 2 is transferred to the wafer 9 by the imaging optical system 10 of the three reflective mirrors 10-1, 10-2 and 10-3, the imaging optical system is used. The respective reflection type mirrors constituting 10 form a shadow and block the exposure light, so that an effective image forming area (mask illumination area) becomes an arc shape. Therefore, in order to effectively use the X-ray beam of the light source, a condenser mirror having a spheroidal reflecting surface is used to make the irradiation area of the illumination light on the mask into the arc shape.

Further, as another X-ray projection exposure apparatus, even if there is a defect in the mirror forming the imaging optical system, in order to reduce the adverse effect due to the defect, a condenser mirror is combined with two mirrors. In addition, the irradiation area of the illumination light on the mask is formed into the arc shape, and the X-ray from the light source is masked at the vertical image forming position and the horizontal image forming position of the X-ray image at the light source position. Has been proposed in which the light is focused near an entrance pupil of the reduction imaging optical system (Japanese Patent Laid-Open No. 4-225).
215).

[0006]

An X using a spheroidal mirror as the conventionally known condenser mirror described above.
The line projection exposure apparatus has the following two problems. The first problem is that the light from the light source is used effectively, so if the spheroid of the condenser mirror is widened, as shown in FIG.
The beam from the light source 3 in the plane including the beam has a divergence v, and the beam reflected by the condenser mirror 1 converges on a focal point on the optical axis z. Therefore, when the mask 2 is away from the focus, the mask illumination width on the mask 2 is widened,
The peripheral portion becomes an ineffective beam, which reduces the beam utilization efficiency and the resolution. The second problem is that, in order to reduce the loss of the reflecting mirror of the imaging optical system and further improve the throughput, the reflecting mirror may be composed of a minimum of two reflecting mirrors that can form the imaging optical system. In the case of an imaging optical system composed of two sets of reflecting mirrors, the object point height (the distance from the optical axis of the imaging optical system to the position of the irradiation beam on the mask) will be described in detail later. There is an unavoidable problem that it becomes difficult to correct the magnification variation (image distortion) due to.

In order to reduce the influence of this image distortion, the mask illumination width may be narrowed, but the effective illumination width of the two-lens image forming optical system is narrower than that of the three-lens image forming optical system. However, there is a problem that the light condensed by the condenser mirror cannot be effectively used, and eventually the throughput cannot be improved by using either the two-lens group or the three-lens group imaging optical system.

Further, in the conventional X-ray projection exposure apparatus in which the influence of the defects of the mirrors constituting the reduction image-forming optical system is reduced, a condenser mirror is a toroidal mirror,
It is configured by a combination of two or more mirrors such as two toroidal mirrors and one plane mirror, or two cylindrical mirrors. Therefore, the condenser mirror reflects the light more than once, and the reflection loss is not improved even though the imaging optical system is composed of two reflection mirrors. Therefore, this is a cause of a decrease in throughput.

Therefore, the main object of the present invention is to realize an X-ray projection exposure apparatus capable of improving the throughput by improving the ratio of the X-ray beam from the light source to the image formation without lowering the resolution of the projection mapping. It is to be.

[0010]

In order to achieve the above object, one form of an X-ray projection exposure apparatus of the present invention is one in which a condenser mirror collects light to illuminate a mask, and light reflected or transmitted from the mask is transmitted. In an exposure apparatus for projecting light onto a substrate (wafer) through an image forming optical means to transfer the pattern on the mask onto the substrate, a reflecting surface constituting the condenser mirror is exposed to an X-ray only once. It is composed of a plurality of reflecting spheroids, and one of each of the plurality of spheroids is reflected.
One focal point coincides with the position of the light source, and the X-rays reflected by the plurality of spheroids are arranged so as to overlap and irradiate in the object point height direction on the mask. That is, the configuration and position of the spheroidal surface were specified so that the spheroidal surface of the plurality of mirrors narrows the width of the mask illumination area on the mask. The plurality of spheroidal reflecting surfaces may be formed of a single solid or a plurality of condenser mirrors. Further, moving means may be provided to move the condenser mirror. Although it is desirable that the above-mentioned overlap completely overlaps, it may be partially overlapped.

Another form of the X-ray projection exposure apparatus of the present invention is
A single ellipse has a cross section of a reflecting surface that constitutes the condenser mirror, and the light source is arranged at one focus of the ellipse,
The condenser mirror in which the other focal point of the ellipse is the center of the irradiation area of the mask and the reflective surface is a rotational surface whose rotational center is the axis connecting the one focal point and the pupil position of the imaging optical system. Use and configure.

[0012]

When the light source is a sheet-like beam which is evenly diverged in the horizontal direction and has a small thickness, a spheroidal surface is used as a condenser mirror for condensing the sheet-like beam, and the light source is generated from an elliptical focus. The light focused by the condenser mirror is focused on the other focus. Therefore,
If the mask is between the condenser mirror, the imaging optics and the other focal point, the illuminated area on the mask is arcuate, and if the mask is at the other focal point, the illuminated area on the mask is a point. become. The ellipse rotates around the optical axis of the imaging optical system arranged so that the light source passes through. By making the rotating surface obtained at that time a reflecting surface, the illumination area on the mask can be made into a linear arc.

According to the first embodiment of the present invention, as shown in FIG. 1, the reflecting surface of the condenser mirror 1 is divided into a plurality of regions 4 and 5 in the light traveling direction, and the respective regions 4 and 5 are divided. One of the focal points of the spheroid is aligned with the light source 3, and the other is distributed on the optical axis z, such as 14 and 15, and the focal point of the spheroid is changed stepwise, and the outer peripheral rays of each region are 11-
Since 4 and 11-5 irradiate the effective illumination area of the mask 2 overlappingly, even if the opening angle v from the light source 3 is increased, the mask illumination width ΔH can be narrowed, so that the image distortion is increased. The illumination light from the light source 3 can be effectively used even in a two-image forming optical system in which the effective illumination area of the mask 2 is narrow.

According to the second aspect of the present invention, the cross section including the optical axis of the imaging optical system of the condenser mirror 1 is a single ellipse, one of the ellipses has a light source and the mask has the other focal point. It is placed in the vicinity. Further, the illuminated area on the mask is the width in the moving direction of the mask by making the rotating surface obtained when the above-mentioned cross section is rotated around the optical axis of the imaging optical system arranged so as to pass through the light source. Becomes a linear arc that is further narrowed. Therefore, the image distortion is small, the number of reflections of X-rays from the light source to the wafer is minimized by the condenser mirror once and the image forming optical system twice, and the light source opening angle can be increased. Effective use of light becomes possible.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic view of the essential parts showing the construction of an embodiment of an X-ray projection exposure apparatus according to the present invention. In this embodiment, the reflecting surface of the condenser mirror 1 is composed of a plurality of spheroidal surfaces as described with reference to FIG. 1, and the mask is arranged at a position away from the focus position of the ellipse. The X-rays from the light source 3 become the X-rays 11 condensed by the condenser mirror 1 and irradiate the mask 2. The X-ray reflected by the mask 2 transfers and projects the pattern of the mask 2 onto the wafer 9 by the image forming optical means 8 of the mirrors 8-1 and 8-2 of the two sets. Mask 2
The wafer 9 is synchronously scanned by the scanning drive means in the direction indicated by the arrow, that is, in the direction perpendicular to the optical axis. When the imaging optical means 8 has a reduction magnification, the mask 2 and the wafer 9 are synchronously scanned while changing the speeds by the reduction magnification.

As described with reference to FIG. 1, the reflecting surface of the condenser mirror 1 is divided into a plurality of areas in the X-ray traveling direction, and one focal point of the spheroidal surface of the light source 3 is in each area. The other focal points correspond to the positions, and the other focal points are composed of different reflecting surfaces. That is, the X-ray reflected in each region is
As described above, the mask illumination width in the mask scanning direction overlaps. The light source 3 is arranged on the optical axis of the imaging optical means 8. The light source 3 is a synchrotron, and its radiated light is a sheet-like beam whose cross-sectional shape is uniformly diverged in the horizontal direction and whose thickness is thin. Therefore, when the sheet-like beam is reflected by the spheroidal reflecting surface, an arcuate (annular zone) illumination area is formed on the mask 2. The height of the object point (the distance from the optical axis of the imaging optical unit 8 to the illumination position of the mask) is 60 mm, the reduction ratio of the imaging optical unit 8 is 1/5, and the width of the arc-shaped illumination region is 1.
If it is 00 mm, it is 12 mm downward from the nip axis of the wafer 9.
The pattern of the arcuate illumination area having a width of 20 mm is transferred there. Although the above embodiment uses the reflected light from the mask 2, it is clear from the description of FIG. 1 that the transmitted light may be used. In this embodiment, the light source may be synchrotron radiation light or a laser plasma X-ray source. Further, the exposure wavelength is preferably 3 nm to 20 nm from the viewpoint of manufacturing technology and materials of the multilayer film forming the mirror.

As described in the section of the operation, the mask illumination width can be narrowed by increasing the opening angle v from the light source 3 by combining the spheroidal surfaces of the condenser mirror 1. Even when the optical system 8 is used, the light from the light source 3 can be efficiently used for exposure without increasing the image distortion, and it is possible to realize an improvement in throughput that has never been seen before. In the above description, the light source 3 is associated with the points 14 and 15 on the optical axis, but it is obvious that the point associated with the light source 3 is not limited to this. For example,
As shown in FIG. 3, if the spheroidal surface of the condenser mirror 1 is composed of a plurality of spheroidal surfaces 6 and 7 so as to take a corresponding point on the entrance pupil plane of the imaging optical system, the imaging optical system is formed. In the meridional direction of (1), it is possible to approach incoherent illumination, and as a result, the image quality is improved.

Further, as shown in FIG. 4, by swinging the condenser mirror 1 in the x-axis direction, incoherent illumination in the sagittal direction of the image forming optical system becomes possible. As shown in FIG. 4, the swing trajectory is preferably an arc trajectory with the mask 2 illumination position (the point where the center line of the arc illumination region intersects the axis perpendicular to the optical axis) as the rotation center.
Besides, it is obvious that the same effect can be obtained even if the condenser mirror 1 is divided into each region and a plurality of condenser mirrors are used.

The improvement of image distortion according to this embodiment will be described with reference to FIGS. FIG. 5 is a diagram showing the relationship between the object height and the image distortion in the case where two sets of image forming optical means are used. As shown in the figure, in the vicinity of the object height of 60 mm, -0.26%
It has a degree of image distortion E. This is an aberration caused by the fact that the image distortion cannot be corrected because the image forming optical system 8 is composed of the double mirror as described above. Fig. 6 shows how this aberration affects
It will be explained by.

FIG. 6 is a diagram for explaining the relationship between the mask illumination area and the exposure area on the wafer. Note that the exposure area on the wafer is shown in an enlarged and inverted direction for easy comparison with the mask illumination area. As shown in FIG. 6, when there is a change in reduction magnification due to image distortion due to the height of an object point, the transferred image causes lateral shift s depending on the scanning position, which leads to blurring of the transfer pattern. Where 0.1μ
The size tolerance of the transfer pattern sufficient to transfer m is within 10%, the center value H of the object point height is 60 mm, and the reduction ratio m of the imaging optical system is 1/5 as shown in FIG. If the width W of the arcuate mask illumination area is 50 mm, the size shift S due to transfer is given by the following equation.

[0021]

[Equation 1]

Further, the mask illumination width ΔH can be defined by the following equation.

[0023]

[Equation 2]

Here, H1 and H2 are the upper and lower limits of the illumination width of the mask illumination area as shown in FIG. (1) and (2)
Using the formula, the effective dimension shift amount is 0.1 μm of 10% of 1
Assuming 0 nm, the width of the height of the object point (mask illumination width) ΔH
Is only 35 μm. At this time, the reflected (or transmitted) light is shaped like an arc at the mask position.
As described with reference to FIG. 1, in the first embodiment of the present invention, 2
The X-rays from the two spheroidal reflecting surfaces 4 and 5 irradiate the same area on the mask 2, that is, the mask illumination width ΔH, so that the shift S can be reduced and the image distortion can be reduced.

FIG. 7 is a block diagram showing the configuration of another embodiment of the X-ray projection exposure apparatus according to the present invention. In this embodiment, as shown in the drawing, the cross section including the optical axis of the imaging optical system is an ellipse, and the rotation that can be performed when the cross section of the ellipse is rotated around the optical axis of the imaging optical system arranged so as to pass through the light source. With respect to the condenser mirror 1 whose surface is a reflecting surface, the light source 3 is arranged at one first focus of the ellipse, and the mask is arranged so that the irradiation position of the mask 2 is located at the other second focus of the ellipse. ing. Also in this embodiment, the condenser mirror 1 may be configured to have a plurality of spheroids each having one reflection in the X-ray traveling direction. In this embodiment, since the irradiation position of the mask is located at the focal point of the ellipse, the irradiation region width ΔH can be extremely narrowed, so that the image distortion in the lateral direction can be reduced and at the same time the utilization efficiency of the light beam can be improved, thus improving the throughput. Can be improved. Further, since the condenser mirror 1 has a single reflecting surface, the throughput improving effect is extremely high and the manufacturing is easy as compared with the condenser mirror which performs a plurality of reflections in the traveling direction of the X-rays.

FIG. 8 is a characteristic diagram for explaining the throughput improving effect of the other embodiment. In the figure, the horizontal axis shows the resist sensitivity of the wafer, and the horizontal axis shows the throughput of the X-ray projection exposure apparatus (the number of wafers subjected to exposure processing per time). If the resist sensitivity is Smj / cm ² , the exposure area of the wafer is A, the X-ray intensity reaching the wafer surface is P, and the overhead time due to movement of the stage is t ₀ ,

[0027]

(Equation 3)

It is represented by Where X is the X-ray intensity

[0029]

[Equation 4]

It is represented by Ps is the brightness of the light source, θ is the horizontal acquisition angle of the beam, I is the beam current, Rc is the reflectance of the condenser mirror, the transmittance of the filter used for cutting long-wavelength light, Rm is the reflectance of the multilayer film surface, and n is n. The number of reflections of the multilayer film, Δλ / λ, is the bandwidth.

As shown by the shaded area in FIG. 8, the practical sensitivity of the chemically amplified resist is 3 to 5 mJ / cm ² . Also,
The throughput that can be used in the X-ray exposure apparatus is 20 sheets / hr or more in consideration of the effect of mass production. Based on the expressions (3) and (4), the characteristic according to the embodiment of the present invention shown in FIG. 7 and the conventional imaging optical system are configured by two mirrors, and two mirrors are combined as a condenser mirror. The characteristics of the conventional device are shown by curves a and b, respectively. As is apparent from the figure, in the embodiment of the present invention, the throughput is remarkably improved, and in the practical resist sensitivity range of 3 to 5 mJ / cm ² , 20 to 30 sheets / hr which is practical can be realized.

[0032]

According to the present invention, the reflection from the light source to the wafer is minimized by using three sets of mirrors to reduce the loss due to the mirrors, thereby improving the throughput of the X-ray projection exposure apparatus and rotating the condenser mirror. It is possible to reduce the lateral distortion of the image caused by the elliptical surface. In addition, there is a secondary effect that illumination can be made incoherent to improve the image quality of the imaging optical system.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a principle of a main part of an X-ray projection exposure apparatus according to the present invention.

FIG. 2 is a diagram showing the configuration of an embodiment of an X-ray projection exposure apparatus according to the present invention.

FIG. 3 is a diagram showing a main part configuration of another embodiment of the X-ray projection exposure apparatus according to the present invention.

FIG. 4 is a diagram showing a main part configuration of still another embodiment of the X-ray projection exposure apparatus according to the present invention.

FIG. 5 is a diagram illustrating image distortion characteristics of a pair of imaging optical systems.

FIG. 6 is a diagram showing a relationship between a mask illumination area and a projected image of a pair of imaging optical systems.

FIG. 7 is a diagram showing the configuration of an embodiment of an X-ray projection exposure apparatus according to the present invention.

FIG. 8 is a diagram showing throughput characteristics of an example of an X-ray projection exposure apparatus according to the present invention and a conventional example.

FIG. 9 is a diagram showing a configuration of an imaging optical system of a conventional X-ray projection exposure apparatus.

FIG. 10 is a diagram showing a configuration of a condenser mirror unit of a conventional X-ray projection exposure apparatus.

[Explanation of symbols]

 1: Condenser mirror 2: Mask 3: Light source 4: Illumination area A 5: Illumination area B 6: Illumination area C 7: Illumination area D 8: 2-image forming optical system 9: Wafer 10: 3-piece combination Image optical system 11: Mask illumination light 12: Mask pattern 13: Pattern being transferred onto the wafer by synchronous scanning 14: Pattern transferred onto the wafer

Claims (11)

[Claims] 1. A mask which illuminates a mask by condensing X-rays emitted from a light source by a condenser mirror, and projects reflected light or transmitted light from the mask onto a substrate through an image forming optical means to expose the mask. In the exposure device that transfers the pattern above,
The condenser mirror is a spheroidal surface, the reflecting surface of the spheroidal surface is divided into a plurality of regions, and the X-ray reflected in each region irradiates the same region of the mask. X-ray projection exposure apparatus. 2. The X-ray projection exposure apparatus according to claim 1, wherein the focal positions of the respective regions of the condenser mirror are distributed in the entrance pupil plane of the imaging optical means.
Line projection exposure system. 3. The X-ray projection exposure apparatus according to claim 1, wherein the focal positions of the respective regions of the condenser mirror are distributed on the optical axis of the image forming optical means. 4. An X-ray projection exposure apparatus according to claim 1, 2 or 3, further comprising drive means for reciprocating the condenser mirror. 5. The X-ray projection exposure apparatus according to claim 4, wherein the condenser mirror is arranged in an arcuate path whose center of rotation is a point where a centerline of the arcuate illumination area of the mask intersects an axis perpendicular to the optical axis. An X-ray projection exposure apparatus, characterized in that a driving means for reciprocating movement is provided. 6. An X-ray diverging from a light source is condensed by a condenser mirror to illuminate a mask, and reflected light or transmitted light from the mask is projected and exposed on a substrate through an imaging optical means to expose the mask. In the exposure device that transfers the pattern above,
One cross section including the optical axis of the imaging optical system of the reflecting surface that constitutes the condenser mirror is a single ellipse, the light source is arranged at one focus of the ellipse, and the condenser mirror is the other focus of the ellipse. Is the center of the irradiation area of the mask,
An X-ray projection exposure apparatus comprising: the condenser mirror having a shape in which the reflection surface is a rotation surface rotated around the ellipse. 7. The X-ray projection exposure apparatus according to any one of claims 1 to 6, wherein the light source is a synchrotron X-ray source. 8. The X-ray projection exposure apparatus according to any one of claims 1 to 6, wherein the light source is a laser plasma X-ray source. 9. An X-ray projection exposure apparatus according to any one of claims 1 to 6, wherein the image forming optical means comprises two reflecting mirrors. 10. The X-ray projection exposure apparatus according to claim 1, further comprising means for synchronously scanning the mask and the substrate. 11. The X-ray projection exposure apparatus according to claim 1, wherein the light source is a light source that emits light having a wavelength in the range of 3 nanometers to 20 nanometers. Projection exposure device.