JPH1126350A - Exposure equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To collect a large divergence angle of SR light in the horizontal direction to increase the intensity of irradiation on a required exposure surface, and at the same time irradiate the required exposure surface with substantially the same intensity. An exposure apparatus capable of accurately transferring a fine pattern. SOLUTION: A mirror is used for a first mirror 72 for condensing and reflecting radiation light 71 emitted at a large divergence angle, and a mask for receiving the reflected radiation light and transferring a pattern to a wafer. And a second mirror 73 for irradiation. The reflecting surface shape of the first mirror 72 is concave in the x-axis direction and concave in the y-axis direction, and the reflecting surface shape of the second mirror 73 is convex in the y-axis direction. The shape of the reflecting surfaces of the first and second mirrors such that the emitted radiation irradiates the entire exposed area 76 of the wafer with substantially the same intensity via the first and second mirrors; The first mirror, the second mirror and the mask are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure apparatus,
In particular, the present invention relates to an exposure apparatus that irradiates radiated light from a light source such as an SR light source using a mirror and exposes and transfers a mask pattern onto a wafer.

[0002]

2. Description of the Related Art An SR (synchrotron radiation) light source is
In the direction within the R orbital plane (usually, the SR orbital plane is set to coincide with the horizontal plane and is hereinafter referred to as the horizontal direction), it has a large divergence angle, and the direction perpendicular to the SR orbital plane (also the vertical direction) ) Is a light source of radiated light (hereinafter referred to as SR light) that emits sheet-like electromagnetic waves (including X-rays and vacuum ultraviolet rays) having a small divergence angle. Since the divergence angle in the vertical direction is small, when radiated light is irradiated as it is, it is irradiated only in a small range in the vertical direction. Therefore, in an exposure apparatus using an SR light source, some method is required to expand the exposure area of the X-ray irradiated from the SR light source in the vertical direction.

As a method for this, (1) a method in which an oblique incidence mirror is arranged between an SR light source and an exposure surface and vibrated at an angle of several mrad (RP Haelbich et al.
J. Vac. Sci. & Technol. Bl
(4), Oct. -Dec. 1983; 1262
~ 1266), (2) SR oblique incidence mirror with curved surface
A method in which the divergence angle of an X-ray beam in the vertical direction is enlarged by reflection between a light source and an exposure surface and reflection on a curved mirror surface (Warren D. Grobman, handbook)
k on Synchrotron Radiatio
n, Vol. 1, chap. 13, p. 1135, No
rth-Holland Publishing C
O. , 1983). Also, (3)
As an improvement method of (2), the mirror shape is shifted from the cylindrical shape, and the curvature of the peripheral portion is continuously reduced, thereby increasing the vertical divergence angle of the X-ray beam while achieving uniform intensity ( JP-A-1-2440
0). FIG. 12 is a schematic perspective view of a conventional exposure apparatus (3), in which reference numeral 120 denotes a light emitting point, 122 denotes a mirror, and 129 denotes a mask. The divergence angle of the SR light from the light emitting point 120 is expanded in the vertical direction by a mirror 122 having a special shape, and is irradiated on the mask 129. Then, the pattern formed on the mask is exposed and transferred to a wafer substrate (not shown).

[0004]

SUMMARY OF THE INVENTION Among these methods,
In (1), an irradiation area narrower than the area to be exposed is scanned on the mask surface, so that only a part of the exposure area is instantaneously irradiated, and the exposure mask and the wafer are partially Thermally expands. The effect of this thermal expansion cannot be eliminated unless the oscillation period of the mirror is short enough,
It becomes difficult to transfer a fine pattern accurately. On the other hand, in order to shorten the oscillation period sufficiently, a large drive power is required, which may not be practically realized.
The loss time during acceleration / deceleration reduces the throughput.

On the other hand, the method (2) can be said to be one of the measures for covering the above-mentioned drawback (1) because the required exposure area can be collectively irradiated. However, in the above document, since the mirror shape is cylindrical (cylindrical surface), it is necessary to sufficiently expand the beam in order to make the irradiation intensity uniform, resulting in a significant loss of energy. On the other hand, if the irradiation intensity is not reduced, the irradiation intensity will not be uniform in the required exposure area, and a supplementary exposure amount control mechanism such as a shutter, which is not disclosed in the above document, will be required. Further, a large divergence angle of the sheet-like electromagnetic wave in the horizontal direction cannot be collected, and therefore, only the angle at which the exposure area extends from the light emitting point in the horizontal direction can be used.

(3) solves the disadvantage of (2) that the energy is lost due to the beam expansion and that the irradiation intensity is not uniform in the required exposure area. As in (2), only the angle at which the exposure area extends from the light emitting point can be used. Therefore, the intensity applied to the required exposure area is
(2) Although it has been greatly improved,
It was necessary to improve the exposure throughput by taking measures to increase the light source intensity or to increase the sensitivity of the resist. This leads to an increase in the cost of the SR light source, an increase in the scale of the SR light source, or an increase in cost due to development of a resist.

On the other hand, in terms of condensing a large divergence angle in the horizontal direction of a sheet-like electromagnetic wave, as an improvement of (1), an obliquely incident mirror is applied to a direction perpendicular to the optical axis of the SR light (x
Irradiating the mirror with a concave curvature in the direction and forming an irradiation area narrower in the vertical direction than the area to be exposed on the mask while converging the SR light, and oscillating the mirror at an angle of several mrad. There is also a method of vibrating the narrow irradiation area in the vertical direction on the mask, thereby substantially enlarging the irradiation area. However, only a part of the exposure area is momentarily irradiated with the beam, and it is difficult to accurately transfer the fine pattern without sufficiently shortening the oscillation period of the mirror. It is.

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to condense a large divergence angle in the horizontal direction of SR light, which is a sheet-like electromagnetic wave, to thereby increase the required exposure without increasing the light source intensity. An object of the present invention is to provide an exposure apparatus capable of simultaneously increasing the intensity of irradiation on a surface and simultaneously irradiating a required exposure surface with substantially the same intensity to accurately transfer a fine pattern and improve throughput. .

[0009] Further, the shape error of the mirror or the X-ray window, scratches on the mirror surface, dust and foreign matter adhering to the surface of the mirror or the X-ray window, and differences in the distribution of surface roughness on the mirror surface, etc. An exposure apparatus having a method for solving exposure unevenness caused by the above.

[0010]

According to the present invention, there is provided an exposure apparatus comprising:
An exposure device that reflects the radiation emitted from the R light source with a mirror and exposes and transfers the pattern of the mask onto the wafer.
A first mirror for converging and reflecting the radiation emitted from the SR orbital plane at a large divergence angle; and a second mirror for reflecting the radiation reflected by the first mirror and irradiating the mask with the radiation. 2
It consists of a mirror. The reflection surface shape of the first mirror is concave in the x-axis direction and concave in the y-axis direction.
The reflection surface shape of the mirror is convex in the y-axis direction, and the radiated light emitted from the light source in the horizontal direction is reflected by the first mirror and the second mirror.
The shape of the reflecting surfaces of the first mirror and the second mirror, and the first mirror, the second mirror, the mask, and the like are used to irradiate the entire exposed area of the wafer through the mirrors with substantially the same intensity. This is the arrangement of wafers. However, the area where the pattern of the mask is transferred to the wafer is defined as an exposure area, the emission light emitted from the emission point of the emission light and reaching the center of the exposure area is defined as the principal ray, and the principal ray is reflected on the first mirror. The point of reflection is taken as the center of the first mirror, the point at which the principal ray is reflected on the second mirror is taken as the center of the second mirror, and the normal of each mirror drawn from the center of each mirror at each mirror Is the z-axis, the direction from the reflecting surface of the mirror toward the outside of the mirror is the positive direction of the z-axis, and the axis perpendicular to the plane formed by the principal ray incident on each mirror and the z-axis of each mirror is And the axis perpendicular to both the x-axis and the z-axis of each mirror is the y-axis of each mirror, and the y product of each mirror whose inner product with the vector in the traveling direction of the principal ray emitted from each mirror is positive The direction of the axis is defined as a positive direction, and the unit vector in the positive direction of the y-axis is Cross product of the positive direction of the unit vector of the axis defines a direction of x-axis of each mirror such that the positive direction of the unit vector in the x-axis as a positive direction.

In addition, of the radiation emitted from the SR light source, the radiation near the principal ray emitted in a direction perpendicular to the SR orbital plane is reflected by the first mirror toward the second mirror. After that, it is preferable that a concave radius of curvature in the y-axis direction near the center of the reflection surface of the first mirror is set so that the light is condensed to almost one point before entering the second mirror. .

The distance between the light emitting point and the center of the first mirror is l ₁
The distance between the center of the first mirror and the center of the second mirror is l ₂ , the distance between the center of the second mirror and the mask is l _3, and the oblique incidence angles on the first and second mirrors are θ. When the radii of curvature in the x and y directions near the center of the first mirror are r _1x and r _1y , respectively, the radius of curvature r in the y direction
_1y is r _1y > _2/11 × l ₁ × l ₂ / (l ₁ + l ₂ ) / si
nθ is preferably set, and y
The radius of curvature r _{1y in the} direction is _2/11 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin θ <r
_1y <2 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin θ
The radius of curvature r _{1x in the} direction is set so that r _1x <2 sin θ / (1 / l ₁ + 3/2 / l ₂ ) or r _1x > 2 sin θ / (1 / l ₁ + 2/3 / l ₂ ). Is preferred.

Further, the second mirror may be rotatable, and at least one of rotational vibration and linear vibration may be possible.

In this case, the area where the radiation reflected by the second mirror irradiates the mask is larger than the exposure area of the wafer, and the maximum value of the irradiation intensity in the exposure area is less than twice the minimum value. The first mirror and the second
It is preferable that the shape and processing accuracy of the reflecting surface of the mirror and the arrangement of the first mirror, the second mirror, the mask, and the wafer are the same.

The first mirror is concave in both the x and y directions and the second mirror is convex in the y direction. The first mirror converges the SR light emitted from the light source with a large divergence angle in the horizontal direction to a narrow divergence angle. Since the SR light in the vertical direction is condensed on the second mirror before being incident on the second mirror, it is diffused and irradiated on the mask surface by the second mirror, so that the entire exposure area can be irradiated with almost uniform intensity and the throughput is improved.

The vertical SR light from the first mirror is
Since the light is condensed before the mirror, the length of the second mirror in the irradiation direction can be reduced, and the size and weight of the second mirror can be reduced. Thereby, the processing accuracy of the mirror can be improved, and the minute vibration can be easily performed.

Further, by micro-vibrating the mirror,
Eliminates irregularities in the shape of the mirror or X-ray window, scratches on the mirror surface, dust and foreign matter adhering to the surface of the mirror and X-ray window, and uneven exposure due to differences in the distribution of surface roughness on the mirror surface. Further, by irradiating the entire exposed area with substantially uniform intensity, the line width uniformity can be improved in lithography.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1A and 1B are schematic layout views showing the configuration and arrangement of an optical system of an exposure apparatus according to a first embodiment of the present invention, wherein FIG. 1A is a side view and FIG. 1B is a top view.
In the figure, reference numeral 10 denotes a light emitting point, 11 and 15 denote SR light, 12 denotes a first mirror, and 13 denotes a second mirror.

In FIG. 1, SR light 11 is emitted in a tangential direction when an electron orbit is bent by a bending magnet at a light emitting point 10. In the present embodiment, the SR light 11 emitted from the light emitting point 10 at a large angle is reflected by the first mirror 12 and then reflected by the second mirror 13.
The SR light 15 reflected by the second mirror 13 is
It is directed in the direction of a mask (not shown).

FIG. 2 is a schematic perspective view showing the concept of the principal ray, the center of the mirror, and the coordinate system in the embodiment of the present invention. In FIG.
2 is the first mirror, 22a is the center of the first mirror, 23 is the second mirror, 23a is the center of the second mirror, 25, 26, 2
7 is a principal ray, 29 is a mask, and 29a is the center of the mask.

From the light emitting point 20a of the SR ring 20, which is a light source of radiation such as X-rays and vacuum ultraviolet rays, SR light emitted as wide as several tens mrad in the horizontal direction and as narrow as about 1 mrad in the vertical direction is generated. A region (referred to as an irradiation region) of the mask 29 including at least a region (referred to as an exposure region) where the pattern continuously reflected by the first mirror 22 and the second mirror 23 and transferred onto the wafer is drawn on the mask 28. Irradiated. Of the SR light diverging in the horizontal and vertical directions and emitted from the light emitting point, the center 2 of the mask 29
The SR light that reaches 9a is referred to as principal rays 25, 26, and 27, and the point at which principal ray 25 is reflected by first mirror 22 is referred to as first ray.
The point at which the center 22a of the mirror and the principal ray 26 are reflected by the second mirror 23 is called the center 23a of the second mirror. The normal of each mirror drawn from the mirror centers 22a and 23a is the z-axis, the direction from the mirror to the outside of the mirror is the positive direction of the z-axis, and the principal ray incident on each mirror and the z-axis of each mirror The axis perpendicular to the plane created by x is the x axis of each mirror, the axis perpendicular to both the x axis and z axis of each mirror is the y axis of each mirror, and the vector of the traveling direction of the principal ray emitted from each mirror A unit vector in the positive direction of the y-axis such that the direction of the y-axis of each mirror whose inner product is positive is the positive direction, and the positive direction of the x-axis of each mirror is the xyz axis forming a left-handed system The direction of the x-axis in which the cross product of the x-axis and the unit vector in the positive direction of the z-axis becomes the unit vector in the positive direction of the x-axis is defined as the positive direction.

The SR light is directed in the horizontal direction (in the plane of the SR orbit).
Has a large divergence angle and a small divergence angle in the vertical direction (perpendicular to the SR orbital plane).
Line, including vacuum ultraviolet rays). The “SR light having a large divergence angle in the horizontal direction” is not strictly emitted from one light emitting point, but is emitted tangentially from each point on the electron trajectory of the SR. Here, SR light emitted from an SR electron trajectory having a length small enough to be regarded as a sufficient point is regarded as SR light emitted from a single light emitting point with a divergence angle corresponding to the length of the electron trajectory. ing.

FIG. 3 is a schematic perspective view showing an optical path of SR light emitted in the vertical direction according to the embodiment of the present invention. In the figure, reference numeral 30 denotes a light source, 31 denotes SR light emitted in the vertical direction, and 3 denotes a light source.
Reference numeral 2 denotes a first mirror, 33 denotes a second mirror, 34 and 35 denote virtual planes, 34a and 35a denote intersections between the SR light emitted in the vertical direction and the virtual plane, and 36 denotes a condensing position.

The SR light 31 emitted vertically from the light source 30 with a divergence angle of about 1 mrad is, as shown in FIG. 3, a first mirror having a concave shape in the x-axis direction and a concave shape in the y-axis direction. 32, and is particularly concave at the y-axis direction.
At 6, the light is converged to almost one point. The second mirror 33 is installed downstream of the focal point. The second mirror 33 has a convex shape in the y-axis direction, further spreads the SR light spreading from the focused point 36, and emits the SR light in the mask direction. The virtual plane 34 between the light source 30 and the first mirror 32 and the second
Intersecting lines 34a and 35a between the virtual plane 35 between the mirror 33 and the mask and the SR light emitted in the vertical direction are vertical lines.

FIG. 4 is a schematic perspective view showing an optical path of SR light emitted in the horizontal direction according to the embodiment of the present invention. In the figure, reference numeral 40 denotes a light source, 41 denotes SR light emitted in the horizontal direction,
2 is a first mirror, 42a is a line of intersection between the SR light emitted in the horizontal direction and the first mirror, 44, 45, 46, and 47 are virtual planes, and 44a, 45a, 46a, and 47a are emitted in the horizontal direction. The line of intersection of the SR light and the virtual plane, 48 is the SR light emitted from the first mirror.

As shown in FIG. 4, the SR light 41 emitted from the light source 40 in the horizontal direction with a divergence angle of about several tens mrad has a concave shape in the x-axis direction and a concave shape in the y-axis direction. The light enters one mirror 42. Of the SR light emitted in the horizontal direction, an imaginary plane 44 perpendicular to the light (principal ray) incident on the center of the mask and the intersection line 44a of the SR light emitted in the horizontal direction are straight lines. SR emitted in the horizontal direction with the first mirror 42
The intersection line 42a with the light 41 has a shape close to a parabola because the first mirror 42 is mainly concave in the x-axis direction.
The intersection of the SR light 48 emitted from the first mirror 42 and the virtual plane perpendicular to the principal ray is the virtual plane 4 immediately after the first mirror.
In 5, the intersection line 45a is concave as in the direction of the concave surface of the first mirror 42 in the x-axis direction (the concave surface is upward in FIG. 4). On the other hand, since the first mirror 42 is concave in the y-axis direction, the virtual plane 4
6 becomes a straight line at an intersection 46a, and becomes further convex at an intersection 47a with an imaginary plane 47 further away.

The S emitted from the second mirror in the vertical direction in FIG.
It is installed farther from the light source than the position 33 where the R light converges to almost one point, and the light source is located at a point closer to the light source than at a point 46 where the line of intersection between the SR light 41 emitted in the horizontal direction and the virtual plane perpendicular to the principal ray becomes straight. By setting it near, the SR light is almost condensed in the vertical direction at the second mirror position, and the light in the horizontal direction is almost straight. As a result, the width of the SR light in the projection direction at the position where it is projected on the second mirror is sufficiently small, and even if the length of the second mirror in the incidence direction is reduced, all the incident light can be reflected. It becomes possible. That is, SR
The size of the second mirror can be sufficiently reduced without lowering the light use efficiency.

Since the wavelength of light used in an exposure apparatus using SR light is around 1 nm, the required mirror shape needs to be almost as accurate as the wavelength. It goes without saying that, when processing mirrors with the same precision, the smaller the mirror size, the easier the processing.
However, since the size of the first mirror is several hundred mm and the shape does not have a target axis, it is difficult at present to process with a precision of several nm. When the mirror shape is ideal, the intensity is completely uniform. However, in practice, intensity unevenness occurs due to a mirror processing error or the like. Similarly, the X-ray window used at the boundary of the vacuum region in the SR light irradiation path is mainly made of a Be film,
Since there is a rolling step in the process of thinning, a processing error occurs in the X-ray window, which further causes uneven strength.

The processing error of this mirror or X-ray window is
SR having a period of several tens μm to several mm in an exposure area on a mask
Appears as uneven light intensity. Therefore, 10
By slightly vibrating the mirror so that the SR light fluctuates by about mm, unevenness caused by a processing error of the mirror or the X-ray window is reduced. In the embodiment of the present invention, the length of the second mirror, which is farther from the light source than the first mirror, can be reduced to 100 to 300 mm to reduce the weight. Processing errors of the mirror or X-ray window, scratches on the mirror surface, dust and foreign matter adhering to the surface of the mirror, X-ray window, and uneven exposure caused by differences in the distribution of surface roughness on the mirror surface, etc. Can be relaxed.

Next, embodiments including specific numerical examples will be described with reference to the drawings. In FIG. 2, the distance l ₁ = 28 between the light emitting point 20a and the center 22a of the first mirror.
00 mm, the distance l ₂ = 3200 mm between the center 22a of the first mirror and the center 23a of the second mirror, the distance l ₃ = 5000 mm between the center 23a of the second mirror and the mask 29, the first
Oblique incidence angle θ to mirror 22 and second mirror 23 = 18 mr
set as ad, 4500 closer to the mask than the second mirror 23
A Be film having a thickness of 18 μm / mm is provided as a vacuum partition. He is 150 To on the mask side of the vacuum partition.
It is filled at a pressure of rr. The mask 29 has a pattern made of an absorber mainly containing tungsten on a 2 μm thick membrane made of SiC. There is a wafer at a gap of 20 μm from the mask membrane.

The first mirror 22 has a concave shape in the x-axis direction and a concave shape in the y-axis direction. The radius of curvature in the x direction is r _x = 89.9 mm−0.0062 × ymm, and the radius of curvature in the y direction is near the center. r _y = 82284 mm was set. Radius of curvature r _x
Is changed in the y direction, so that the radius of curvature of the mirror is slightly smaller in the direction away from the light emitting point near the center of the mirror. The second mirror has a particularly convex shape in the y-axis direction, and has a radius of curvature of 1332 mm in the x direction and a radius of curvature of 34,800 mm in the y direction. FIG. 5 shows the mirror shape of this embodiment. FIGS. 5A and 5B are three-dimensional views showing the shape of the mirror of the embodiment, wherein FIG. 5A shows a first mirror and FIG. 5B shows a second mirror.

As shown in FIG. 3, the SR light emitted in the vertical direction is reflected by the first mirror 32 and is collected at a position 1 = 1007 mm from the center of the first mirror. Since the distance from the first mirror 32 to the second mirror 33 is l ₂ = 3200 mm, the distance from the focal point 36 to the second mirror 33 is 2193 mm, and the light rays near the second mirror 33 have a similar relationship. The width in the direction perpendicular to
2193/1007 compared to the width near the first mirror 32
The width is approximately 2.18 times. This is the first
If the light that has reached the mirror proceeds without being reflected by the first mirror as it is, 6000/2800 = 2.14 times. Therefore, when the width of the SR light is not at the second mirror position and there is no first mirror. In comparison, it means that it is not particularly large.

Further, as shown in FIG. 4, the position of the virtual plane 46 where the intersection line between the SR light 41 emitted in the horizontal direction and the virtual plane perpendicular to the light entering the center of the mask becomes a straight line is the second position. When there is no mirror, 3 from the center of the first mirror 42
Since the position is 560 mm, the position of the second mirror is closer to the light source than the position, and is very close to the position, so that the size of the second mirror can be reduced as a result.

FIG. 6 shows the distribution of the reflected light from the first mirror at the center position of the second mirror. FIG. 6 is a plan view showing the distribution of reflected light from the first mirror at the center position of the second mirror in the example, and -13.5 mr in the x direction.
1.35 mrad at an angle of ad to 13.5 mrad, and -0.28 mrad to 0.28 mra in the y direction
It represents the distribution of light rays at the center position of the second mirror when a total of 105 light rays are emitted from the light source at an angle of d and at intervals of 0.14 mrad.

First mirror and SR emitted on SR orbital plane
Since the line of intersection with light is almost a parabola as shown by the line of intersection 42a of the first mirror in FIG. 4, the effective area of the first mirror 42 needs to be 540 mm even though the effective length of the second mirror is required. The length of the area is about 280 mm. In order to eliminate shape deterioration such as surface drooping during mirror processing or deformation due to deformation due to a pressing force, the thickness of the mirror is required to be at least in proportion to the length of the mirror. The width direction is substantially the same for both the first mirror and the second mirror, so that the second mirror is about 1 /
It weighs 3.7. If the configuration according to the present invention is not implemented, the length of the second mirror is expected to be at least as large as that of the first mirror.
This means that the weight of the mirror can be reduced to about 1/4. Since the mirror size can be reduced, not only can the processing accuracy of the second mirror be improved, but also it is easy to make micro-vibration to reduce unevenness in intensity due to the processing error of the first mirror and the processing error of the X-ray window. I have.

FIG. 7 is a schematic perspective view showing an irradiation area and an exposure area formed by SR light on a mask in the embodiment. In the figure, reference numeral 70 denotes a light source, 71 denotes SR light, 72 denotes a first mirror, 73 Is the second mirror, 75 is the irradiation area on the mask,
Reference numeral 76 denotes an exposure area on the mask, and the exposure area is indicated by oblique lines.

In this embodiment, the exposure area 76 is 4 Gb
It is 50 mm square which is required for the itDRAM generation. The SR light reflected from the second mirror irradiates an irradiation area 75 of about 60 mm square on the mask.

As shown in FIG. 4, when the SR light 41 emitted in the horizontal direction is reflected only by the first mirror 42, the SR light 41 is converted into a chief ray at a position 3560 mm behind the first mirror 42 (virtual plane 46). The line of intersection with the vertical plane is a straight line, but the curvature radius 13 in the x direction is closer to the light source 40 than this plane.
With the second mirror having a radius of curvature of 32800 mm and a radius of curvature of 34800 mm in the y direction, the SR light reflected by the second mirror and emitted in the horizontal direction connects a substantially straight line of intersection on the mask surface at the position of the mask surface. .

FIG. 8 is a plan view showing the distribution of light rays at the mask position in the embodiment, and -13.5 in the x direction.
1.35 mrad at an angle between mrad and 13.5 mrad
At intervals of -0.28 mrad to 0.28 m in the y direction
A total of 441 at an interval of 0.028 mrad at an angle of rad
The distribution of the light beam at the mask position when this light beam is emitted from the light source is shown. The black square represents the position where the light beam reaches when the emission angle in the y direction is 0, and it can be seen that it is almost a straight line.

When the SR light 41 emitted in the horizontal direction from the light source 40 is continuously reflected by the first mirror 42 and the second mirror, and is not linear on the mask surface or on the wafer, In addition, the intensity distribution becomes two-dimensional on the mask or the wafer, and it becomes difficult to control the exposure amount. As described above, in the case of the scan exposure method, even when there is a slight intensity distribution, the intensity is averaged by scanning and the influence is relatively small, but in the case of the collective exposure method, the intensity distribution is two-dimensional. In this case, it becomes quite difficult to control the exposure amount.

FIG. 9 is a schematic three-dimensional view showing the power absorbed by the resist in the embodiment, and the power absorbed by the resist can be made substantially constant in a region of about 60 mm square.

By the way, the distance between the emission point and the center of the first mirror and l _1, the distance between the centers of the second mirror of the first mirror and l _2, the distance between the center and the mask of the second mirror Let l ₃ be the angle of oblique incidence on the first mirror and the second mirror, and let r _1x and r _1y be the radii of curvature in the x and y directions near the center of the first mirror, respectively. The focal lengths f _1x and f _1y near the center are respectively expressed as f _1x = r _1x / (2 sin θ)) f _1y = r _1y × sin θ / 2.

Light emitted from the light emitting point in the direction perpendicular to the SR orbital plane diverges with a small spread. Assuming that the angle representing the spread of the light is δ, when there is no first mirror, 2 × (l ₁ + l ₂ ) × tan (δ / 2) in the direction perpendicular to the SR orbital plane at the center position of the second mirror. Only spread. On the other hand, when the first mirror is present, it spreads by 2 × l ₁ × tan (δ / 2) × (l ₂ −b) / b in the direction perpendicular to the SR orbital plane at the center position of the second mirror. Here, b = 1 / (1 / f _1y −1 / l ₁ ).

By installing the first mirror, the light emitted in the direction perpendicular to the SR orbital plane can be expanded by 10 times or more at the second mirror position as compared with the case without the first mirror. It is not preferable because it will be too much. Therefore, 2 × l ₁ × tan (δ / 2) × (l ₂ −b) / b <10
× 2 × (l ₁ + l ₂ ) × tan (δ / 2). Therefore, it is necessary that b> l ₁ × l ₂ / (11 × l ₁ + 10 × l ₂ ). Therefore, the _{f 1y> l 1 × l 2} /11 / (l 1 + l 2).

That is, in the present embodiment, the radius of curvature of the first mirror in the y direction satisfies the following condition: r _1y > _2/11 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin θ (1) Is preferred.

In order to reduce the size of the second mirror, it is preferable that the light is converged to almost one point before entering the second mirror, and b <l ₂ , and thus 1 / (1 / f _1y −1 / l ₁ ) <l _2, that is, f _1y <l ₁ × l ₂ / (l ₁ + l ₂ ).

If this is represented by r _1y , it is more preferable in the present embodiment that the following upper limit value is satisfied in addition to the lower limit value defined by the above equation (1).

R _1y <2 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin θ (2) Further, in order to collect the SR light spread in the SR orbital plane,
The mirror has a concave curvature in the x direction. However, when the collected SR light may converge to almost one point on the second mirror due to the curvature, the second mirror is heated and deformed. The deformation of the mirror is
It is not preferable because the non-uniformity of the intensity of the SR light irradiated on the mask is increased.

In order to avoid this, it is necessary to focus light sufficiently before the second mirror, or to focus light sufficiently far away. This is achieved by making the spread of the light in the x direction on the second mirror less than twice the spread of the light in the x direction on the first mirror.

Therefore, is the position where the light spread in the SR orbital plane is almost condensed closer to the first mirror than the position ２ of the first mirror between the first mirror and the second mirror? Alternatively, it is sufficient if the distance is at least half the distance between the first mirror and the second mirror from the second mirror.

That is, when c = 1 / (1 / f _1x −1 / l ₁ ), it is necessary that c <2/3 × l ₂ or c> 3/2 × l _2. . That is, f _1x <1 / (1 / l ₁ + 3/2 / l ₂ ) or f _1x > 1 / (1 / l ₁ + 2/3 / l ₂ ).

Therefore, in the present embodiment, r _1x <2 sin θ / (1 / l ₁ + 3/2 / l ₂ ) or r _1x > 2 sin θ / (1 / l ₁ + 2/3 / l ₂ ) (3) It is more preferable that the above condition is satisfied.

In this embodiment, l ₁ = 2800 mm,
l ₂ = 3200 mm, l ₃ = 5000 mm, θ = 18 m
rad, and from the above equation (1), r
_1y > 15085 mm From the above equation (2), 15085 mm <r _1y <1659
35 mm From the above equation (3), r _1x <43.6 mm or r
_1x > 63.7 mm, and in the apparatus of the present embodiment, by setting r _1x = 89.9 mm−0.0062 × y mm r _1y = 82284 mm as specific numerical values satisfying these, a very excellent X A line illumination optical system has been realized.

FIG. 10 is a schematic perspective view showing a state in which the second mirror is micro-rotated and vibrated in the embodiment. In FIG. 10, reference numeral 100 denotes a light source, and 101 denotes an SR emitted in a vertical direction.
Light, 102 is a first mirror, 103 is a second mirror, 104
Is a rotation x-axis, 105 is an irradiation area, and 106 is an exposure area. FIGS. 11A and 11B are schematic diagrams illustrating the concept and embodiment of the concept of micro-vibration. FIG. 11A shows the irradiation intensity on the mask surface before the mirror micro-scan, and FIG. Movement, (c) shows the irradiation intensity on the mask surface after the mirror minute scan.

There is a shape error of the mirror or the X-ray window, a scratch on the mirror surface, dust or foreign matter adhered to the surface of the mirror or the X-ray window, and a difference in distribution of surface roughness on the mirror surface. Otherwise, the power absorbed by the resist is constant in the irradiated area, especially in the exposed area. However, with respect to X-rays or vacuum ultraviolet rays, a minute mirror shape error or uneven thickness of the X-ray window causes uneven irradiation intensity of the X-rays or vacuum ultraviolet rays. Therefore, as shown in FIG. 11A, irradiation intensity unevenness occurs in the irradiation region. As shown in FIG. 10, when the second mirror 103 is rotationally oscillated about the rotation x-axis 104 and is slightly oscillated within a range where the end of the irradiation area 105 does not enter the exposure area 106, FIG. As shown in ()), the irradiation intensity unevenness moves within the exposure area. As a result, as shown in FIG. 11C, the average of the irradiation intensity becomes substantially uniform in the exposure region. Outside the exposure area, the averaged irradiation intensity decreases continuously.
When the rotational vibration is increased so that the end of the irradiation area enters the exposure area, a portion where the irradiation intensity continuously decreases enters the exposure area, which is not preferable.

On the other hand, when the mirror is shaken under the condition that the end of the irradiation intensity does not enter the exposure region, if the irradiation intensity unevenness in the exposure region is large, the unevenness of the irradiation intensity can be made uniform by the minute vibration of the second mirror. Is no longer enough. The unevenness is remarkably uniformed by the minute vibration of the second mirror when the period of the unevenness is smaller than the distance over which the unevenness moves. When the period of the irregularity is about twice as long as the distance over which the irregularity moves, the irregularity becomes about 1 / π. When the maximum value of the irradiation intensity is twice the minimum value and the average of the irradiation intensity has an intermediate value, the irradiation intensity unevenness is ± 0.5 / 1.5, that is, ± 33%. In this case, the unevenness is 1
/ Π, the irregularity is about ± 10.5 at ± 33 / π.
%. In the exposure, since the unevenness must be ± 10% or less, the maximum value of the irradiation intensity must be less than twice the minimum value. When the period of the irregularity is twice or more as compared with the distance over which the irregularity moves, the effect of making the irradiation intensity irregularity uniform by the minute vibration becomes extremely small.

As described above, the micro-rotational vibration causes the shape error of the mirror or the X-ray window, the scratches on the mirror surface, the dust adhered to the mirror and the surface of the X-ray window, the foreign matter, and the surface roughness. Irradiation intensity unevenness generated due to a difference in distribution on the mirror surface can be made uniform. Further, in the present embodiment, since the size of the second mirror is reduced, minute vibration is facilitated.

Here, as means for moving the irradiation intensity unevenness within the exposure area, the second mirror has a minute rotational vibration. However, a minute linear vibration or a combination thereof may be used.
Needless to say, the rotation may be minute rotation of the first mirror or linear vibration. When the SR light reaching the wafer vibrates in the vertical direction due to those vibrations, scratches on the optical element, exposure unevenness generated due to shape errors, etc. are removed, and the axis for rotating and oscillating the mirror,
It is desirable that the axis is substantially in the x direction, and it is desirable that the vibration direction of the linear vibration is substantially in the y direction. Further, the same effect can be obtained by rotating the mirror about a straight line having an angle deviated from the normal line of the mirror as an axis.

In the embodiment, the exposure apparatus of the one-shot exposure system has been described, but the present invention is naturally applicable to a scan exposure system.

[0060]

As described above, in the present invention, the entire surface of the exposure area can be irradiated with substantially uniform intensity by making the first mirror concave in both the x and y directions and making the second mirror convex in the y direction.

Also, the shape error of the mirror or the X-ray window,
If there are scratches on the mirror surface, dust on the mirror, dust adhering to the surface of the X-ray window, and differences in the distribution of surface roughness on the mirror surface, etc., the mirror is further vibrated by micro-vibration. It is possible to irradiate the entire exposed area with uniform intensity, and it is possible to improve the line width uniformity in lithography.

Further, since the SR light in the vertical direction from the first mirror is converged before the second mirror, the length of the second mirror in the irradiation direction can be reduced, and the second mirror can be reduced in size and weight. As a result, the processing accuracy of the mirror can be increased,
There is an effect that minute vibration can be easily performed.

Furthermore, by collecting the SR light emitted from the light source at a large divergence angle in the horizontal direction, the intensity of irradiation on the mask can be increased, and the throughput can be improved.

Further, the radius of curvature of the first mirror in the y direction is given by r _1y > _2/11 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin
By satisfying the condition of θ, the light emitted in the direction perpendicular to the SR orbital plane is prevented from spreading too much at the position of the second mirror, and further, r _1y <2 × l ₁ × l ₂ / (l ₁ + l ₂₎ ) / Sin θ, or the radius of curvature of the first mirror in the x direction is r _1x <2 sin θ / (1 / l ₁ + 3/2 / l ₂ ) or r _1x > 2 sin θ / (1 / l ₁₎ By satisfying the condition of + 2/3 / l ₂ ), a more preferable exposure apparatus can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram showing a configuration and an arrangement of an optical system of an exposure apparatus according to a first embodiment of the present invention. (A) is a side view. (B) is a top view.

FIG. 2 is a schematic perspective view showing the concept of a principal ray, a center of a mirror, and a coordinate system in the embodiment of the present invention.

FIG. 3 shows an SR emitted in a vertical direction according to the embodiment of the present invention.
FIG. 3 is a schematic perspective view illustrating an optical path of light.

FIG. 4 shows an SR emitted in the horizontal direction according to the embodiment of the present invention.
FIG. 3 is a schematic perspective view illustrating an optical path of light.

FIG. 5 is a three-dimensional view showing the shape of the mirror according to the embodiment.
(A) is a first mirror. (B) is a second mirror.

FIG. 6 is a plan view showing distribution of light reflected from a first mirror at a center position of a second mirror in the embodiment.

FIG. 7 is a schematic perspective view showing an irradiation area and an exposure area formed on a mask by SR light in an example.

FIG. 8 is a plan view showing a distribution of light rays at a mask position in the example.

FIG. 9 is a schematic three-dimensional view showing power absorbed by a resist in an example.

FIG. 10 is a schematic perspective view showing a state in which a second mirror is vibrated minutely in the embodiment.

FIG. 11 is a schematic diagram illustrating the concept and an embodiment of the concept of micro-vibration. (A) is the irradiation intensity on the mask surface before the mirror minute scan. (B) shows the movement of the irradiation intensity unevenness on the mask surface by the mirror minute scan. (C) is the irradiation intensity on the mask surface after the mirror minute scan.

FIG. 12 is a schematic perspective view of an exposure apparatus of a conventional example (3).

[Explanation of symbols]

10, 20a, 120 Emission point 11, 15 SR light 12, 22, 32, 42, 72, 102 First mirror 13, 23, 73, 103 Second mirror 20 SR ring 22a Center of first mirror 23a Second mirror Center 25, 26, 27 Principal ray 29, 129 Mask 29a Center of mask 30, 40, 70, 100 Light source 31, 101 SR light emitted in the vertical direction 34, 35, 44, 45, 46, 47 Virtual plane 34a, 35a Intersecting line between the SR light emitted in the vertical direction and the virtual plane 36 Focused position 41 SR light emitted in the horizontal direction 42a Intersecting line 44a between the SR light emitted in the horizontal direction and the first mirror 44a, 45a, 46a, 47a The intersection line 48 between the SR light emitted in the horizontal direction and the virtual plane 48 is the SR light emitted from the first mirror 71 SR light 75 Irradiation on the mask Area 76 Exposure area on mask 104 Rotation x-axis 105 Irradiation area 106 Exposure area 122 Mirror

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshiaki Fukuda 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shunichi Uzawa 3- 30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Non Corporation

Claims (12)

[Claims] 1. An exposure apparatus for reflecting, by a mirror, radiation emitted from an SR light source and exposing and transferring a mask pattern onto a wafer, wherein the mirror emits radiation with a large divergence angle in an SR orbit plane. A first mirror for condensing and reflecting the light, and a second mirror for reflecting the radiation reflected by the first mirror and irradiating the mask with the first mirror. An area to be transferred is an exposure area, a point where the emitted light emitted from the emission point of the emitted light and reaches the center of the exposed area is a principal ray, and the principal ray is reflected on the first mirror. Is the center of the first mirror, the point at which the chief ray is reflected on the second mirror is the center of the second mirror, and the normal of each mirror drawn from the center of each mirror is z Axis and the mirror's reflective surface The direction toward the outside of the Luo mirror z
The axis is set to the positive direction, and the axis perpendicular to the plane formed by the principal ray incident on each mirror and the z-axis of each mirror is set as the x-axis of each mirror. The axis perpendicular to both the x-axis and z-axis of each mirror Is the y axis of each mirror, the direction of the y axis of each mirror whose inner product with the vector of the traveling direction of the principal ray emitted from each mirror is positive is the positive direction, and the unit vector of the positive direction of the y axis is When the direction of the x-axis of each mirror is defined as a positive direction such that the cross product with the unit vector of the positive direction of the z-axis becomes a unit vector of the positive direction of the x-axis, the reflection surface shape of the first mirror Are concave in the x-axis direction and concave in the y-axis direction, the reflecting surface shape of the second mirror is convex in the y-axis direction, and the radiated light emitted from the light source in the horizontal direction is the first mirror. And the same intensity over the entire exposed area of the wafer via the second mirror. Such as irradiation,
An exposure apparatus comprising: a shape of a reflection surface of the first mirror and the second mirror; and an arrangement of the first mirror, the second mirror, the mask, and the wafer. 2. The radiation near the chief ray emitted in a direction perpendicular to the SR orbital plane, of the radiation emitted from the SR light source, is transmitted to the second mirror by the first mirror. The concave radius of curvature in the y-axis direction near the center of the reflecting surface of the first mirror is set so that after being reflected toward the second mirror, the light is condensed to substantially one point before entering the second mirror. The exposure apparatus according to claim 1, wherein: 3. The distance between the light emitting point and the center of the first mirror is l ₁ , the distance between the center of the first mirror and the center of the second mirror is l _2, and the center of the second mirror is The distance between the first mirror and the mask is l ₃ , the oblique incidence angles on the first mirror and the second mirror are θ, and the radii of curvature in the x and y directions near the center of the first mirror are r _1x ,
_Assuming that r _1y , the radius of curvature r _1y in the y direction is given by: r _1y > _2/11 × l ₁ × l ₂ / (l ₁ + l ₂ ) / si
The exposure apparatus according to claim 1, wherein the exposure apparatus is set to be nθ. 4. Further, the radius of curvature r _{1y in the} y direction is _2/11 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin θ <r
_4. The exposure apparatus according to claim 3, wherein the setting is made so that _1y <2 × l ₁ × l ₂ / (l ₁ + l ₂ ) / sin θ. 5. The exposure apparatus according to claim 3, wherein the radius of curvature r _{1x in the} x direction is set to satisfy r _1x <2 sin θ / (1 / l ₁ + 3/2 / l ₂ ). 6. The exposure apparatus according to claim 3, wherein the radius of curvature r _{1x in the} x direction is set so that r _1x > 2 sin θ / (1 / l ₁ + 2/3 / l ₂ ). 7. The system according to claim 2, wherein said second mirror is rotatable.
3. The exposure apparatus according to claim 1. 8. The exposure apparatus according to claim 2, wherein the second mirror is capable of at least one of rotational vibration and linear vibration. 9. The exposure apparatus according to claim 8, wherein a rotational vibration axis of the rotational vibration of the second mirror is substantially an x-axis. 10. The exposure apparatus according to claim 8, wherein the vibration direction of the linear vibration of the second mirror is substantially the y direction. 11. A region in which the radiation reflected by the second mirror irradiates the mask is larger than an exposure region of the wafer, and a maximum value of irradiation intensity in the exposure region is twice a minimum value. The following are the shapes and processing accuracy of the reflecting surfaces of the first mirror and the second mirror, and the arrangement of the first mirror, the second mirror, the mask, and the wafer, as follows. The exposure apparatus according to any one of claims 7 to 10. 12. The exposure apparatus according to claim 1, wherein a method of exposing the wafer by the exposure apparatus is a batch exposure method.