JP6022759B2 - Catadioptric projection optical system and projection exposure apparatus having the same - Google Patents

Description

  The present invention relates to a projection exposure apparatus that projects and exposes a pattern onto a substrate or the like using a projection optical system, and more particularly to a configuration of a catadioptric projection optical system.

  As a projection optical system used in a projection exposure apparatus, a catadioptric projection optical system combining a reflective optical system such as a concave mirror and a refractive optical system is known, and in particular, a polarizing element for suppressing ghost and flare light. There has been proposed a catadioptric projection optical system of full area exposure provided with (see Patent Document 1).

  There, a polarizing beam splitter and a quarter-wave plate are disposed between the refractive optical system and the concave mirror, and one polarized light separated by the polarizing beam splitter is reflected by the concave mirror, and the polarizing beam splitter is used. Re-enter the beam. Then, the polarized light emitted from the polarization beam splitter is imaged on the substrate by the imaging optical system.

  Also, a catadioptric projection optical system that reflects both light beams divided by a polarizing beam splitter is known in order to prevent a decrease in illuminance of pattern light (see Patent Document 2). There, both polarized lights split by the polarizing beam splitter are re-entered into the polarizing beam splitter by two concave mirrors, respectively.

JP-A-3-282527 Japanese Patent Laid-Open No. 6-181161

  A conventional catadioptric projection optical system is configured on the premise that it is equipped in a reduction projection exposure apparatus used mainly in the preceding process of the wafer process. Since the substrate size is very large in the subsequent process of pattern formation on the liquid crystal substrate and printed circuit board and wafer process, it is necessary to enlarge the area size that can be projected at one time as much as possible. Is required to be used.

  However, even if the conventional catadioptric projection optical system based on reduced projection is incorporated into the catadioptric projection optical system at the same magnification, it maintains high resolution, ensures constant illumination, and expands the projection area at the same time. It is difficult to realize.

  Therefore, there is a need for a catadioptric projection optical system that can suppress a decrease in illuminance and aberrations and can realize a wide exposure area while maintaining high resolution.

  The projection optical system of the present invention is an equal magnification projection optical system combining a reflection optical system and a refractive optical system, and is applied to a projection exposure apparatus provided with an illumination optical system in addition to the projection optical system.

  The projection optical system is disposed on the optical path of one light separated by the first optical system that forms an image of the pattern light on the object surface, a folding prism that polarization-separates light from the first optical system, and the folding prism. A second optical system and a first concave mirror that reflects the light transmitted through the second optical system and re-enters the folding prism via the second optical system are provided.

  Further, the projection optical system reflects the light transmitted through the third optical system and the third optical system disposed on the optical path of the other light separated by the folding prism, and returns to the folding prism via the third optical system. A second concave mirror for incidence; and a fourth optical system disposed on an optical path between the folding prism and the image plane.

  The folding prism of the present invention guides the reflected light from the first and second concave mirrors to the image plane side, and the fourth optical system forms an image of the reflected light emitted from the folding prism on the image plane. Further, the marginal ray from the object plane is substantially perpendicularly incident on the folding prism.

Here, “substantially normal incidence” means that marginal rays are incident in parallel along the optical axis within a range that can be regarded as normal incidence in terms of optical design with respect to the incident surface of the folding prism. For example, when it is 0.5 degrees or less, more specifically, 0.3 degrees or less, and further limited is 0.2 degrees, 0.1 degrees, 1 × 10 ⁻² , 1 × 10 ⁻³ or less, It can be considered that it is perpendicularly incident on the.

Preferably, the lens power combining the second optical system and the first concave mirror and the lens power combining the third optical system and the second concave mirror are set to 1 × 10 ⁻⁴ or less. It is desirable that the maximum field angle h and the optical path length L from the object plane to the first and second concave mirrors satisfy the following conditional expression.

k × h × L ^−m ≦ β

Here, k and m represent coefficients determined by the characteristics of the projection optical system. Also, β represents the maximum incident angle to the folding prism that can correct the illuminance of the illumination optical system.

For example, the maximum field angle h and the optical path length L satisfy the following conditional expression.

98.065 × h × L ^−1.0305 ≦ 6.5

  A polarization beam splitter can be configured for the folding prism. For example, a first quarter-wave plate disposed between the polarization beam splitter and the second optical system, and a second quarter-wave plate disposed between the polarization beam splitter and the third optical system. And can be provided.

  When the light source is a mercury lamp or the like that emits illumination light in a wide wavelength range, the first and second quarter-wave plates can polarize light at wavelengths of at least 400 nm in the wavelength range of 350 nm to 450 nm. It can be configured to be.

  A projection optical system having other features of the present invention is disposed in the front stage optical system that forms an image of the pattern light on the object surface, the folding prism that polarizes and separates the light from the front stage optical system, and the optical path behind the folding prism. An intermediate optical system, a concave mirror that reflects light transmitted through the intermediate optical system and re-enters the folding prism via the intermediate optical system, and a rear-stage optical system disposed on the optical path between the folding prism and the image plane The folding prism guides the reflected light from the concave mirror to the image plane side, the rear optical system forms an image on the image plane of the reflected light emitted from the folding prism, and the marginal ray from the object plane is It is substantially perpendicularly incident on the folding prism.

  According to the present invention, a projection exposure apparatus can form a highly accurate pattern while ensuring a wide exposure area.

It is the internal block diagram which showed typically the projection exposure apparatus which is this embodiment. It is the figure which showed the optical system arrangement configuration in a projection optical system. It is the figure which showed the projection optical system equivalent to the projection optical system of FIG. 2, and an optical path. It is the graph which showed the relationship between the synthetic power of a 2nd lens group and a concave mirror, and the incident angle of a marginal ray. It is a graph showing the relationship between the optical path length and the maximum incident angle for different maximum angles of view. It is the graph which showed the relationship between the maximum angle of view and the coefficient of each approximate curve. It is the graph which showed the illumination intensity nonuniformity when the illumination intensity nonuniformity with respect to the incident angle to a polarizing beam splitter, and the illumination intensity correction by an illumination system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an internal configuration diagram schematically showing a projection exposure apparatus according to the present embodiment.

  The projection exposure apparatus 10 is an exposure apparatus that forms a pattern on a substrate SW such as a semiconductor substrate such as a silicon wafer or a printed wiring board for an electronic circuit board, and the pattern drawn on the photomask PM is transferred to the substrate SW. Project against.

  The projection exposure apparatus 10 includes an illumination optical system 20, a projection optical system 30, and a light source unit 50, and a photomask PM is disposed on the imaging surface of the illumination optical system 20. The light source unit 50 includes a discharge lamp 52 that emits light in a wavelength range of 350 to 450 nm, and the light emitted from the lamp 52 is guided to the illumination optical system 20 by an elliptical mirror 54.

  The illumination optical system 20 includes a mirror 22, a collimator lens 24, a fly-eye lens 26, and a condenser lens 28. The light incident on the illumination optical system 20 is guided to the collimator lens 24 by the mirror 22 and is converted into a parallel light beam. Then, the light is uniformly corrected by the fly-eye lens 26.

  The light condensed by the condenser lens 28 irradiates the photomask PM. A pattern to be drawn on the substrate SW is formed on the photomask PM, and the pattern light of the photomask PM is projected onto the substrate SW through the projection optical system 30.

  The projection optical system 30 is a 1 × -magnification catadioptric projection optical system including a first lens group 32, a second lens group 34, a third lens group 36, and a fourth lens group 38. A polarization beam splitter 40 is disposed between the second and third lens groups 34 and 36.

  The light incident on the projection optical system 30 is polarized and separated by the polarization separation surface 40A of the polarization beam splitter 40, and is transmitted straight in the direction of the second lens group 34 and reflected by the polarization separation surface 40A, and is reflected by the second lens group. The light is divided into light traveling in the direction of the third lens group 36 perpendicular to 34.

  Concave mirrors 42 and 44 are respectively arranged behind the second and third lens groups 34 and 36, and light that has passed through the second and third lens groups 34 and 36 is again transmitted by the concave mirrors 42 and 44. The light enters the polarization beam splitter 40.

  The light re-entered from the third lens group 36 side passes through the polarization beam splitter 40 and travels straight toward the substrate SW as it is, while the light re-entered from the second lens group 34 side is transmitted to the substrate by the polarization beam splitter 40. Reflects in the SW direction. As a result, the entire pattern light that has passed through the mask PM is guided to the fourth lens group 38, and the pattern light is imaged on the substrate SW by the fourth lens group 38.

  The moving stage 11 mounted on the gantry 13 that supports the substrate SW can move and rotate the substrate SW in a direction perpendicular to and parallel to the optical axis. The substrate SW is fixed to the stage 11 by vacuum suction or the like. During the exposure, the mask pattern is exposed on the entire substrate SW as the substrate SW stage 11 moves by the step & repeat method.

  Next, the internal configuration of the projection optical system 30 will be described in detail with reference to FIGS.

  FIG. 2 is a diagram showing an optical system arrangement configuration in the projection optical system 30. FIG. 3 is a diagram showing a projection optical system having an optical path equivalent to the projection optical system 30 of FIG.

  The first lens group 32 includes a meniscus lens 32A having a concave first surface, positive lenses 32B and 32C, a negative lens 32D having concave surfaces, and a positive lens 32E, and has a positive refractive power as a whole optical system.

  The cube-shaped polarization beam splitter 40 is a prism arranged so that its incident surface 40S is perpendicular to the optical axis E, and a polarization separation surface 40A is formed on a joint slope where two right angle prisms are bonded together. Yes. The normal line of the polarization separation surface 40A is inclined 45 degrees with respect to the optical axis E.

  The light that has entered the polarization beam splitter 40 from the first lens group 32 is separated into p-polarized light that is transmitted through the polarization separation surface 40A and s-polarized light that is reflected by the polarization separation surface 40A. The p-polarized light exits from the polarization beam splitter 40 along the optical axis E as it is, and enters the second lens group 34 having negative refractive power.

  The second lens group 34 includes a quarter-wave plate 34a, a positive lens 34B, and a double-sided concave negative lens 34C. The p-polarized light is converted into circularly polarized light by the quarter wavelength plate 34a, and then reaches the concave mirror 42 through the positive lens 34B and the negative lens 34C.

  The concave mirror 42 has a spherical reflecting surface symmetrical with respect to the optical axis E, and collects and reflects p-polarized light. The reflected p-polarized light is converted into s-polarized light when entering the quarter-wave plate 34a again. Then, the s-polarized light re-entering the polarization beam splitter 40 is reflected by the polarization separation surface 40A and is emitted in the direction of the fourth lens group 38.

  On the other hand, the s-polarized light polarized and separated by the polarization separation surface 40A exits from the polarization beam splitter 40 in the orthogonal direction in which the third lens group 36 is located. Similar to the second lens group 34, the third lens group 36 is an optical system having a negative refractive power and includes a quarter-wave plate 36A, a positive lens 36B, and a double-sided concave negative lens 36C. A concave mirror 44 having a refractive power of 1 is disposed.

  The s-polarized light emitted from the polarization beam splitter 40 is polarized into circularly polarized light by the quarter wavelength plate 36A, and then reaches the concave mirror 44 through the positive lens 34B and the negative lens 34C. The circularly polarized light reflected by the concave mirror 44 is converted into p-polarized light by the quarter-wave plate 36A, and then enters the polarization beam splitter 40 again. Since the light incident on the polarization beam splitter 40 is p-polarized light, the incident light passes through the polarization separation surface 40A as it is and exits toward the fourth lens group 38.

  The fourth lens group 38 has the same lens arrangement as that of the first lens group 32, and includes a meniscus lens 38A having a concave first surface, positive lenses 38B and 38C, a negative lens 38D having both sides concave, and a positive lens 38E. , Has a positive refractive power.

  The surface of the substrate SW coincides with the image plane of the projection optical system 30. Therefore, both of the lights divided by the polarization beam splitter 40 are imaged on the surface of the substrate SW by the fourth lens group 38, and the entire pattern light contributes to the exposure as it is.

  The quarter-wave plates 34a and 36A are broadband wavelength plates capable of polarizing light in the wavelength range of 350 to 450 nm, and correspond to the entire wavelength range of illumination light emitted from the light source 50 and suppress chromatic aberration. In addition, you may comprise so that it may respond | correspond to the light of a 400 nm or more wavelength range.

  The first lens group 32 and the fourth lens group 38 have the same optical system configuration and optical characteristics, and the second lens group 34 and the third lens group 36 also have the same optical system configuration and optical characteristics. Further, the optical path length of light traveling back and forth through the second lens group 34 to the substrate SW is equal to the optical path length of light traveling back and forth through the third lens group 36.

  Therefore, the equal magnification projection optical system 30 shown in FIG. 2 is equivalent in optical path to the projection optical system shown in FIG. 3, and the first lens group 32 (fourth lens group 38), the polarization beam splitter 40, and the second lens group. The degree of illuminance, resolution, and aberration are determined by optical characteristics including the mutual arrangement interval of 34 (third lens group 36) and concave mirror 42 (concave mirror 44), refractive power, and the like.

  In the present embodiment, the marginal rays ML1 and ML2 of the light emitted from the first lens group 32 are parallel to the optical axis and perpendicularly incident on the incident surface 40S of the polarization beam splitter 40. However, the marginal rays ML1 and ML2 represent rays at the end of the entrance pupil of the first lens group 32 among the light emitted from the optical axis point of the object (here, the mask PM).

  The projection optical system 30 is not configured to correct the pattern light into a parallel light beam and enter the entire incident surface of the polarization beam splitter as in the reduction projection optical system, but to the marginal rays M1 and M2 from the object point on the optical axis of the mask PM. Only imposes a normal incidence condition on the polarizing beam splitter 40. The first to fourth lens groups 32 to 38 are configured so that this condition is satisfied.

In the present embodiment, the lens power P between the second lens group 34 and the concave mirror 42 (= the third lens group 36 and the concave mirror 44) satisfies the following expression. However, the lens power P represents the reciprocal of the focal length obtained by combining the second lens group 34 and the concave mirror 42 (= the third lens group 36 and the concave mirror 44).

P ≦ 1 × 10 ⁻⁴ (1)

  The lens power P is extremely close to 0 and very small. Here, the optical characteristics are determined so that the minus power of the second lens group 34 and the plus power of the concave mirror 42 are offset. The lens power P in the third lens group 36 and the concave mirror 44 is also the same.

  Since the optical system having such a lens power P is disposed behind the polarizing beam splitter 40, the pupil positions of the first and fourth lens groups 32 and 38 need to be at infinity, but marginal rays M1 and M2 Infinitely parallel to the optical axis and incident on the polarization beam splitter 40, it is possible to arrange an optical system having such a lens power P.

Furthermore, in the present embodiment, in addition to the above-described conditions of the marginal rays M1 and M2 and the combined lens power P, the maximum field angle h in the mask PM (substrate SW) and the optical path length L from the mask PM to the concave mirrors 42 and 44 are obtained. (Mm) satisfies the following conditional expression.

k × h × L ^−m ≦ β (2)

  However, the maximum field angle h represents the longest distance from the optical axis of the exposure area on the image plane. m is a coefficient obtained from an approximate expression representing the relationship between the optical path length L for each maximum field angle h and the incident angle θ to the polarization beam splitter 40, and here, m is set to 1.035.

  On the other hand, k is a coefficient obtained from an approximate expression for each maximum angle of view h, which will be described later. Here, k is set to 98.065. Furthermore, β represents a limit incident angle that can correct the illuminance distribution of the illumination optical system 20 described later. Here, β is set to 6.5 degrees.

  By constructing the projection optical system 30 that satisfies the parallel incidence of the marginal rays M1 and M2 and the above expressions (1) and (2), high resolution is maintained without lowering the illuminance, and a wider exposure area is secured. be able to. Hereinafter, the reason why the equations (1) and (2) are derived will be described.

  FIG. 4 is a graph showing the relationship between the combined power P of the second lens group 34 and the concave mirror 42 and the incident angle of the marginal ray. The third lens group 36 and the concave mirror 44 also show the same relationship.

A plurality of plots shown in FIG. 4 indicate a plurality of projection optical systems having different combined powers P and corresponding incident angles (in this case, Θ) of marginal rays. The vertical axis of the graph represents the incident angle Θ of the marginal ray, and the horizontal axis represents the combined power P. Based on the coordinates of these plots, an approximate curve T1 represented by the following equation can be defined.

Θ = −694940P ² + 2938.7P (3)

As is clear from the graph of FIG. 4 and the above approximate expression, when the combined power P is 1 × 10 ⁻⁴ or less, the incident angle Θ of the marginal ray is 0.29 degrees at the maximum, and the marginal ray is substantially the optical axis. Parallel to E. On the other hand, when the combined power P is a larger value, the incident angle Θ deviates from a state substantially parallel to the optical axis E. For example, when Θ = 2 × 10 ⁻⁴ is exceeded, the incident angle of the marginal ray is 0.56 degrees or more.

  In the case of a projection optical system of the same magnification, if the irradiation area of the concave mirror affects the exposure area size and the marginal ray is not parallel to the optical axis E, it is difficult to ensure a wide angle of view, that is, a wide exposure area. Therefore, the configurations of the second and third lens groups 34 and 36 and the concave mirrors 42 and 44 of the projection optical system 30 are determined so that the combined power P satisfies the expression (1).

  Next, the reason for using condition (2) as a condition will be described. When the size of the projection optical system 30 is reduced, it is desirable to make the optical path length L from the object plane (mask PM) to the concave mirrors 42 and 44 as short as possible. On the other hand, when the optical path length L is shortened, the incident inclination angle when the pattern light is incident on the polarization beam splitter 40 is increased. This affects the illuminance distribution non-uniformity in the entire exposure area, that is, the occurrence of uneven illuminance.

  Therefore, the maximum incident angle θ of light when the optical path length L was changed was investigated for the same-magnification catadioptric projection optical system having a different maximum field angle h, and the relationship was clarified. However, it is assumed that the catadioptric projection optical system satisfies the conditions of the normal incidence of the marginal light beam and the combined power P shown in the equation (1). The maximum incident angle θ represents the maximum incident angle among the incident angles of light incident on the polarizing beam splitter 40.

  FIG. 5 is a graph showing the relationship between the optical path length L and the maximum incident angle θ for different maximum angles of view h. FIG. 6 is a graph showing the relationship between the maximum angle of view h and the coefficient of each approximate curve.

In FIG. 5, the maximum incident angle θ when the optical path length L is changed is plotted. It can be seen that the shorter the optical path length L, the larger the incident angle θ, which is associated with an approximate exponential function. Here, an approximate curve for each angle of view h is represented by the following equation.

θ = 468.1L ^-1.030 (angle of view h = 5 mm)
θ = 938.9L ^-1.030 (angle of view h = 10 mm)
θ = 11415.2L− ^1.031 (angle of view h = 15 mm)
θ = 1900.3L ^-1.032 (angle of view h = 20 mm)
θ = 2398.0L ^-1.033 (view angle h = 25mm)
θ = 2912.3L− ^1.035 (angle of view h = 30 mm)
θ = 3451.6L ^−1.037 (angle of view h = 35 mm)
θ = 4025.5L− ^1.039 (angle of view h = 40 mm)

.... (4)

When the relationship between the maximum angle of view h and the coefficient of each approximate curve is examined, the relationship is linear as shown in FIG. Therefore, it is possible to adopt an approximate line format as shown by the following expression.

k = 98.05 × h (5)

On the other hand, the average of the exponent part of the approximate curve represented by the equation (4) is -1.035 here. Therefore, the following expressions for obtaining the maximum incident angle θ are derived from the expressions (4) and (5).

θ = 98.065 × h × L ^−1.0305 (6)

  This indicates that the maximum incident angle θ to the polarization beam splitter 40 can be calculated from the maximum field angle h and the optical path length L within a range that satisfies the condition of the combined power P in the expression (1). The maximum incident angle θ does not depend on the numerical aperture NA of the projection optical system 30.

  As described above, if the size reduction of the projection optical system 30 is taken into consideration, it is preferable to shorten the optical path length L as much as possible. However, when the maximum incident angle θ is increased, it becomes impossible to maintain the uniform illuminance distribution as a whole. Therefore, it was examined how much the maximum incident angle θ would become difficult to maintain constant illuminance, and the maximum maximum incident angle at which illuminance instability could not be avoided was determined.

  FIG. 7 is a graph showing the illuminance unevenness with respect to the incident angle to the polarization beam splitter and the illuminance unevenness when the illumination system corrects the illuminance. The plot shows the illuminance unevenness with respect to the incident angle θ on the polarization beam splitter 40 and the illuminance unevenness when the illumination optical system 20 performs illuminance correction. However, the incident angle parallel to the optical axis is 0 degree, the upward incident angle from the optical axis is positive, and the opposite is negative.

  In general, even when light is uniformly irradiated onto a mask, an illuminance distribution centered on the optical axis is generated according to the angle of incidence on the polarization beam splitter. The ratio between the illuminance of light incident on the modified beam splitter and the illuminance of light finally emitted from the polarizing beam splitter via the concave mirror (herein referred to as optical efficiency) decreases as the incident angle of light increases. . For example, in the case of the polarizing beam splitter 40, the optical efficiency decreases as shown in Table 1 below.

  In FIG. 7, the illuminance unevenness when the incident angle is changed from −7.5 degrees to 7.5 degrees is shown as a plot, which is approximately a value along a quadratic curve. However, the reference is when the incident angle is 0 degree.

  On the other hand, the illumination optical system 20 can correct the illuminance to be uniform, and the bending that changes the declination (radius of curvature) of the condenser lens 28 in the illumination optical system 20 without changing the focal length. The illuminance distribution can be adjusted by applying the technique. Illuminance unevenness when the illuminance distribution is changed is plotted in FIG. However, the illuminance unevenness due to this correction indicates the change in illuminance relative to the reference illuminance when the illuminance distribution is changed.

  However, there is a limit to the illuminance correction by such an illumination optical system, and if the incident angle exceeds a predetermined angle, the correction cannot be practically performed. The difference between the illuminance unevenness due to the polarizing element and the corrected illuminance unevenness due to the illumination optical system is shown in Table 2 below. However, here, the polarizing beam splitter is described as a polarizing element.

  The illuminance unevenness based on the illumination correction of the illumination optical system 20 and the illuminance unevenness depending on the incident angle can be represented by different approximate curves F1 and F2, respectively. When the incident angle is 6.5 degrees or less, the value of the approximate curve F1 is lower than the approximate curve F2, and the illuminance unevenness caused by the incident angle can be covered by the illuminance correction of the illumination optical system 20.

However, if it exceeds 6.5 degrees, the value of the approximate curve F1 exceeds the value of the approximate curve F2, and even if the illumination optical system 20 is corrected to the limit, the illuminance unevenness cannot be offset. . Therefore, by setting the maximum incident angle θ (absolute value) to the polarizing beam splitter 40 to 6.5 degrees or less, it becomes possible to maintain a constant illuminance, and the following expression is derived from the expression (6).

98.065 × h × L ^−1.0305 ≦ 6.5 (7)

  If the incident angle limit value of 6.5 degrees is set to a value determined based on the optical characteristics of the illumination optical system 20, it is possible to define the limit incident angle according to the illumination optical system 20 to be used. Each approximate expression of the curve shown in FIG. 5 can be defined according to the optical characteristics of the optical system. Then, expression (2) is derived by expressing the limit incident angle by β and the coefficient of each approximate expression by k.

  Thus, according to the present embodiment, the projection optical system 30 of the projection exposure apparatus 10 includes the first lens group 32, the second lens group 34, the third lens group 36, and the fourth lens group 38, and includes the first lens group. A polarizing beam splitter 40 is disposed between the group 32 and the second and third lens groups 34 and 36. The optical characteristics (refractive power, etc.) of the first lens group 32 are determined so that the marginal rays M1 and M2 from the point on the optical axis of the mask PM are perpendicularly incident on the incident surface 40A of the polarization beam splitter 40. Yes.

  With such a projection optical system, it is possible to secure a maximum exposure area in the equal-magnification catadioptric optical system and realize a full exposure area with a high angle of view. Then, it is possible to project a pattern with a constant illuminance with respect to the entire area, and it is possible to realize highly accurate pattern formation.

  In the conventional reduction projection optical system, the light from the entire object surface is configured to be a parallel light beam with respect to the folding prism. However, in the present invention, such a configuration is not adopted, and from an on-axis object point. Strict normal incidence is defined for the marginal ray, which is the light ray of. Unlike the conventional projection optical system, it does not adopt such a rule that the expansion of the exposure area that is almost parallel to the optical axis cannot be expected. Thereby, the function of the equal magnification projection optical system of maximizing the exposure area can be fully exhibited.

  In addition, by newly deriving a relational expression between the optical path length and the angle of view, the size of the entire optical system of the exposure apparatus including the illumination optical system can be made compact and downsizing can be satisfied. The maximum angle of view can be easily derived according to the optical characteristics.

  In the present embodiment, the two concave mirrors are arranged behind the optical axis of the polarizing beam splitter, but a configuration with one concave mirror is also possible. Further, the folding prism may be constituted by means other than the polarizing beam splitter. Furthermore, the present invention is not limited to the same magnification, and can be applied to a reduction projection optical system.

  In the following, an equal magnification catadioptric optical system as an example will be described.

  The projection optical system according to the present embodiment is an equal reflection / refraction optical system capable of exposing an area having a maximum field angle h = 125 mm and a diameter of 250 mm and having an optical path length L of 1523.476 mm. The lens configuration is shown in Table 3 below.

In this embodiment, the incident angle of the marginal ray is 0.001 degrees, is substantially parallel to the optical axis, and is perpendicularly incident on the incident surface of the polarizing beam splitter. The combined lens power P is 2.226 × 10 ⁻⁴ and satisfies the expression (1). Further, according to the maximum angle of view h = 125 mm and the optical path length L = 1522.476 mm, the maximum incident angle θ is 6.40, which satisfies the conditions of the expressions (2) and (7).

  With respect to the equal-magnification catadioptric optical system of this example, the incident angle θ when the numerical aperture was changed was examined. Table 4 below shows values of incident angles at different angles of view and numerical apertures.

  As shown in Table 4, it is clear that the maximum incident angle θ does not depend on the numerical aperture and is derived from the equation (2).

DESCRIPTION OF SYMBOLS 10 Projection exposure apparatus 20 Illumination optical system 30 Projection optical system 32 1st lens group (1st optical system, front | former stage optical system)
34 Second lens group (second optical system, intermediate optical system)
34a 1/4 wavelength plate (first 1/4 wavelength plate)
36 Third lens group (third optical system, intermediate optical system)
36A 1/4 wavelength plate (second 1/4 wavelength plate)
38 Fourth lens group (fourth optical system, rear optical system)
40 Polarizing beam splitter (folding prism)
42 Concave mirror (first concave mirror)
44 Concave mirror (second concave mirror)
PM mask SW substrate

Claims (5)

1 × catadioptric projection optical system,
A first optical system that forms an image of pattern light on the object surface;
A folding prism for polarizing and separating light from the first optical system;
A second optical system disposed on an optical path of one light separated by the folding prism;
A first concave mirror that reflects light transmitted through the second optical system and re-enters the folding prism via the second optical system;
A third optical system disposed on the optical path of the other light separated by the folding prism;
A second concave mirror that reflects the light transmitted through the third optical system and re-enters the folding prism via the third optical system;
A fourth optical system disposed on the optical path between the folding prism and the image plane,
The folding prism guides reflected light from the first and second concave mirrors to the image plane side;
The fourth optical system forms an image of reflected light emitted from the folding prism on an image plane;
Optical characteristics of the first optical system are determined so that marginal rays from the object plane are substantially perpendicularly incident on the folding prism ,
The lens power combining the second optical system and the first concave mirror, and the lens power combining the third optical system and the second concave mirror are 1 × 10 ⁻⁴ (1 / mm) or less,
A catadioptric magnification optical projection system characterized in that a maximum field angle h (mm) and an optical path length L (mm) from the object surface to the first and second concave mirrors satisfy the following conditional expression:

k × h × L ^−m ≦ β

Here, k and m represent coefficients determined by the characteristics of the projection optical system. Β represents the maximum incident angle (°) to the folding prism capable of correcting the illuminance of the illumination optical system, the lens power represents the reciprocal of the focal length, and the maximum field angle h represents the exposure area on the image plane. Represents the longest distance from the optical axis. 2. The catadioptric equal magnification projection optical system according to claim 1 , wherein the maximum field angle h and the optical path length L satisfy the following conditional expression.

98.065 × h × L ^−1.0305 ≦ 6.5
The folding prism has a polarizing beam splitter;
A first quarter-wave plate disposed between the polarizing beam splitter and the second optical system;
The catadioptric unit magnification according to any one of claims 1 to 2 , further comprising a second quarter-wave plate disposed between the polarizing beam splitter and the third optical system. Projection optics. 4. The catadioptric type according to claim 3 , wherein the first and second quarter-wave plates are capable of polarizing light at a wavelength of at least 400 nm in a wavelength range of 350 nm to 450 nm. 1X projection optical system. Projection exposure apparatus having a catadioptric magnification projection optical system according to any one of claims 1 to 4.

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