JP2013054286A - Projection optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system that has achieved reduction in manufacturing costs and size although both-side telecentric is achieved as well as a sufficient exposure area and a large numerical aperture, while restricting an increase in the number of composing lenses.SOLUTION: A projection optical system for projecting an image of a first object onto a second object comprises, in order from the first object side toward the second object: a first lens group having positive refractive power; a second lens group having negative refractive power and having a pair of negative lenses forming a pair of concave faces facing each other; a third lens group having positive refractive power; an aperture stop; a fourth lens group having positive refractive power; a fifth lens group having negative refractive power and having a pair of negative lenses forming a pair of concave faces facing each other; and a sixth lens group having positive refractive power. The projection optical system satisfies the following conditions: 0.3<f1/fa<1.3, -0.36<f2/fa<-0.08, and 0.13<f3/fa<0.5.

Description

  The present invention relates to a projection optical system for projecting a pattern of a first object onto a substrate or the like as a second object, and in particular, a semiconductor-use liquid crystal formed on a reticle (mask) as a first object. The present invention relates to a projection optical system suitable for projecting and exposing a pattern for a touch panel, a touch panel or a printed board on a substrate (wafer, plate, etc.) as a second object.

  In recent years, projection exposure machines have been widely used in the manufacture of semiconductor substrates, liquid crystal substrates, touch panel substrates, printed circuit boards, and the like, and projection optical systems used for these projection exposure machines are also widely known. In such a projection exposure apparatus, exposure is performed using a light source that supplies exposure light from g-line (436 nm) to i-line (365 nm). The performance required for projection optical systems is also becoming increasingly severe. In this projection optical system, it is particularly important to have high resolution and good optical characteristics by correcting aberrations such as distortion and curvature of field. In this case, if an attempt is made to suppress the number of constituent lenses, the image area for exposure becomes smaller. In order to cope with this, a projection optical system has been proposed in which a sufficiently large image area can be obtained by increasing the numerical aperture NA (numerical aperture) mainly for the manufacture of liquid crystal substrates. (For example, see Patent Documents 1 to 4).

JP 2000-1999850 A JP 2002-72080 A JP 2006-267383 A JP 2007-79015 A

In the projection optical systems described in Patent Documents 1 to 4, an image area (exposure area) having sufficient resolution and optical characteristics for manufacturing a product and having a sufficiently large size for practical use is obtained. However, in any projection optical system, since a large number of lenses exceeding 30 are required as constituent lenses, the total length of the projection optical system is increased, the weight is increased, and the manufacturing cost is increased. In addition, since the number of lenses is large, production errors are large, and high lens manufacturing accuracy is required, which further increases the cost.
Therefore, the object of the present invention is to solve the above-mentioned problems and suppress the increase in the number of constituent lenses, while exposing an exposure area and resolution sufficient to manufacture a semiconductor substrate, a liquid crystal substrate, a touch panel substrate, a printed circuit board, and the like. It is another object of the present invention to provide a compact projection optical system capable of obtaining optical characteristics.

In order to solve the above problem, a projection optical system according to one embodiment of the present invention includes:
Projecting an image of a first object onto a second object,
In order from the first object side toward the second object,
A first lens group having a positive refractive power;
A second lens group having a pair of negative lenses having negative refractive power and forming a pair of concave surfaces facing each other;
A third lens group having a positive refractive power;
An aperture stop,
A fourth lens group having a positive refractive power;
A fifth lens group having a pair of negative lenses having negative refractive power and forming a pair of concave surfaces facing each other;
The sixth lens unit has a positive refractive power.
According to the preferable aspect of this invention, it is comprised so that the following conditions may be satisfied.
0. 3 <f1 / fa <1.3
−0.36 <f2 / fa <−0.08
0.13 <f3 / fa <0.5
However,
f1: focal length of the first lens group,
f2: focal length of the second lens group,
f3: focal length of the third lens group,
fa: the focal length of the front group consisting of the first, second and third lens groups,
It is.
Moreover, according to another preferable aspect of this invention, it is comprised so that the following conditions may be satisfied.
0.45 <| β | <2.2
0. 3 <f6 / fb <1.3
−0.36 <f5 / fb <−0.08
0.13 <f4 / fb <0.5
However,
β: lateral magnification of the projection optical system,
f4: focal length of the fourth lens group,
f5: focal length of the fifth lens group,
f6: focal length of the sixth lens group,
fb: the focal length of the rear group consisting of the fourth, fifth and sixth lens groups,
It is.

According to still another preferred embodiment of the present invention, the following conditions are satisfied.
−1.8 <r1 / r2 <−0.6
1.0 <r3 / r2 <1.8
However,
r1: radius of curvature of the concave surface on the first object side in the concave surface set of the second lens group facing each other r2: radius of curvature of the concave surface on the second object side in the concave surface set of the second lens group facing each other ,
r3: The smallest value of the absolute value of each radius of curvature in each lens surface of the third lens group,
It is.

Moreover, according to the preferable aspect of this invention, it is comprised so that the following conditions may be satisfied.
1.0 <r4 / r5 <1.8
−1.8 <r6 / r5 <−0.6
However,
r4: The smallest absolute value of each radius of curvature in each lens surface of the fourth lens group,
r5: radius of curvature of the concave surface on the first object side in the concave surface group of the fifth lens group facing each other,
r6: radius of curvature of the concave surface on the second object side in the concave surface group of the fifth lens group facing each other,
It is.

Projecting the image of the second object onto the first object has the same effect.

  The projection optical system of the present invention is characterized in that the total number of constituent lenses is 10 or more and 20 or less.

  Furthermore, the first object side and the second object side are both telecentric optical systems.

The first lens group is composed of one or more positive refractive index lenses,
The sixth lens group includes one or more positive refractive index lenses.

The first lens group has two or more curved surfaces having the same absolute value of the radius of curvature.
The sixth lens group is characterized in that there are two or more curved surfaces having the same absolute value of the radius of curvature.
The present invention is characterized by comprising a front group and a rear group arranged substantially symmetrically with respect to the aperture stop, and a projection magnification between the first object and the second object is -1.

In the projection optical system of the present invention, although it is telecentric on both sides, an increase in the number of constituent lenses is suppressed, and various aberrations, particularly astigmatism and field curvature, can be corrected well in a wider exposure area than in the past. As a result, a compact projection optical system with sufficient exposure area, resolution, and optical characteristics as a projection optical system for an exposure apparatus can be used as a projection optical system for various types of printed circuits and at a low cost. Can be realized.

It is the schematic which shows 1st Embodiment of the projection optical system of this invention. It is the schematic which shows 2nd Embodiment of the projection optical system of this invention. It is the schematic which shows 3rd Embodiment of the projection optical system of this invention. It is the schematic which shows 4th Embodiment of the projection optical system of this invention. It is a figure which shows the astigmatism and distortion of the projection optical system in 1st Embodiment. It is a figure which shows the coma aberration of the projection optical system in 1st Embodiment. It is a figure which shows the astigmatism and distortion aberration of the projection optical system in 2nd Embodiment. It is a figure which shows the coma aberration of the projection optical system in 2nd Embodiment. It is a figure which shows the astigmatism and distortion of the projection optical system in 3rd Embodiment. It is a figure which shows the coma aberration of the projection optical system in 3rd Embodiment. It is a figure which shows astigmatism and distortion of the projection optical system in 4th Embodiment. It is a figure which shows the coma aberration of the projection optical system in 4th Embodiment.

  The projection optical system according to one embodiment of the present invention employs positive / negative / positive / aperture stop / positive / negative / positive refractive power arrangement, and has as much symmetry as possible with respect to the aperture stop. Thus, it is possible to correct asymmetric aberrations, particularly coma aberration and distortion aberrations very well.

The first lens group having a positive refractive power mainly contributes to correction of distortion while maintaining the telecentricity on the first object side. The sixth lens group having a positive refractive power also contributes mainly to correction of distortion while maintaining the telecentricity on the second object side. Specifically, these first and sixth lens groups generate distortion and correct the distortion generated from the second to fifth lens groups in a well-balanced manner.

The second lens group and the fifth lens group having negative refractive power mainly have a function of correcting the Petzval sum of the entire system, and aim to flatten the image plane over a wide exposure area. The third lens group having a positive refractive power mainly contributes to correction of spherical aberration and also to correction of astigmatism and field curvature. Here, the second lens group having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface, and generates a negative Petzval sum from the positive lens component in the third lens group. It has a function of correcting Petzval sum and correcting negative spherical aberration generated from the third lens unit having positive refractive power.

Further, the fourth lens group having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the fifth lens group having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and generates a negative Petzval sum from the positive lens component in the fourth lens group. It has a function of correcting the Petzval sum and correcting negative spherical aberration generated from the fourth lens unit having positive refractive power.

In the projection optical system as described above, it is preferable that the following conditions (1) to (3) are satisfied.
(1) 0. 3 <f1 / fa <1.3
(2) −0.36 <f2 / fa <−0.08
(3) 0.13 <f3 / fa <0.5
However,
β: lateral magnification of the projection optical system,
f1: focal length of the first lens group,
f2: focal length of the second lens group,
f3: focal length of the third lens group,
fa: Focal length of the front group consisting of the first, second and third lens groups.

When the upper limit of the above condition (1) is exceeded, the telecentricity on the first object side is broken, and negative distortion is greatly generated. Furthermore, the outer diameters of the second and third lens groups are increased, which increases the manufacturing cost. On the contrary, when the lower limit of the condition (1) is exceeded, the telecentricity on the first object side collapses and a large positive distortion occurs, which is not preferable.
The above condition (2) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (2) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (2) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (3) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (3) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (3) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, in the projection optical system as described above, it is preferable that the following conditions (4) to (7) are satisfied.
(4) 0.45 <| β | <2.2
(5) 0. 3 <f6 / fb <1.3
(6) −0.36 <f5 / fb <−0.08
(7) 0.13 <f4 / fb <0.5
However,
f4: focal length of the fourth lens group,
f5: focal length of the fifth lens group,
f6: focal length of the sixth lens group,
fb: focal length of the rear group consisting of the fourth, fifth and sixth lens groups.
In the condition (4), since the front group and the rear group of the projection optical system have as much symmetry as possible with respect to the aperture stop, an optimum magnification range for correcting asymmetric aberration, particularly coma aberration and distortion aberration, is extremely good. It prescribes. When the magnification range of condition (4) is exceeded, it becomes difficult to correct the asymmetric aberrations of the front group and the rear group, particularly coma and distortion, which is not preferable.
When the upper limit of the above condition (5) is exceeded, the telecentricity on the second object side is broken and a large positive distortion is generated. Further, the outer diameters of the fourth and fifth lens groups are increased, which increases the manufacturing cost. On the contrary, when the lower limit of the condition (5) is exceeded, the telecentricity on the second object side is broken, and negative distortion is greatly generated, which is not preferable.
The above condition (6) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (6) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (6) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (7) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (7) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (7) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

In the projection optical system as described above, it is preferable that the following conditions (8) to (9) are satisfied (8) −1.8 <r1 / r2 <−0.6.
(9) 1.0 <r3 / r2 <1.8
However,
r1: the radius of curvature of the concave surface on the first object side in the concave group facing each other of the second lens group,
r2: the radius of curvature of the concave surface on the second object side in the concave surface group of the second lens group facing each other,
r3: The smallest absolute value of each radius of curvature in each lens surface of the third lens group.
The condition (8) defines the optimum shape of the concave surfaces facing each other in the second lens group. Here, when the condition is outside the range of condition (8), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, correction of spherical aberration and Petzval sum is difficult, which is not preferable.
The condition (9) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (9) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (9) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, in the projection optical system as described above, it is preferable that the following conditions (10) to (11) are satisfied.
(10) 1.0 <r4 / r5 <1.8
(11) −1.8 <r6 / r5 <−0.6
However,
r4: The smallest absolute value of each radius of curvature in each lens surface of the fourth lens group,
r5: radius of curvature of the concave surface on the first object side in the concave surface group of the fifth lens group facing each other,
r6: the radius of curvature of the concave surface on the second object side in the concave surface group of the fifth lens group facing each other.
Above condition (10)
This is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (10) is exceeded, negative spherical aberration and upper coma aberration are greatly generated. Conversely, when the lower limit of the condition (10) is exceeded, positive spherical aberration and lower side aberration are generated. This is not preferable because the coma aberration is greatly generated.
The condition (11) defines the optimum shape of the concave surfaces facing each other in the second lens group. Here, if it is outside the range of the condition (11), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, it is difficult to correct spherical aberration and Petzval sum, which is not preferable.

In the projection optical system as described above, even when the image of the second object is projected onto the first object, the correction amount of various aberrations is the same and the same effect is brought about.

In the projection optical system as described above, the total number of constituent lenses is 10 or more and 20 or less.
As in the projection optical systems described in Patent Documents 1 to 4, if the number of lenses is increased, the numerical aperture NA can be increased and the exposure area can be increased, but the total length of the optical system is increased and the weight is increased. The optical system is very expensive to manufacture. In addition, since the number of lenses is large, production errors are large, and high lens manufacturing accuracy is required, which further increases the cost. Further, the transmittance of the entire optical system is lowered, and a problem of heat generation from the lens also occurs. On the other hand, when the number of constituent lenses is less than 10, the aberration cannot be corrected to a level necessary for exposure of a printed circuit board or the like.
Therefore, in this projection optical system, it is considered preferable that the total number of constituent lenses is 10 or more and 20 or less.

  The projection optical system of the present invention is further characterized in that both the object side and the image side are telecentric optical systems.

  In this embodiment, a telecentric optical system in which the optical axis and the principal ray are considered to be parallel is formed on both the object side and the image side of the projection optical system. In a projection exposure apparatus, it is required to faithfully project an image of a pattern on a reticle onto a substrate at an arbitrary set magnification. In particular, it is necessary to prevent a magnification error from occurring. On the other hand, in general, an optical system forms a good image within the depth of focus range. Therefore, if the image side is not a telecentric optical system, a magnification error may always occur. Further, when the object side is not a telecentric optical system, there is always a fear of pattern position error on the reticle.

  The projection optical system of the present invention is characterized in that the first lens group includes one or more positive refractive index lenses, and the sixth lens group includes one or more positive refractive index lenses. Since the first and sixth lens groups are relatively large lenses, the lens group composed of positive refractive index lenses reduces the number of large lenses, reduces production errors, and further reduces cost. It becomes a factor. Further, the transmittance of the entire optical system is improved, and the problem of heat generation from the lens can be reduced.

  In the projection optical system of the present invention, the first lens group has two or more curved surfaces with the same absolute value of the radius of curvature, and the sixth lens group has two or more curved surfaces with the same absolute value of the radius of curvature. It is characterized by having. Since the first and sixth lens groups are relatively large lenses, a lens configured with a curved surface having the same absolute value of the radius of curvature causes a reduction in manufacturing cost. The lens manufacturing accuracy can be easily improved.

Another embodiment of the projection optical system of the present invention is characterized in that the projection magnification between the first object and the second object is -1. It consists of a front group and a rear group that are arranged symmetrically with respect to the aperture stop, and it is preferable that coma aberration, distortion aberration, and chromatic aberration of magnification can be corrected to zero, and the manufacturing cost is reduced.

[First Example] FIG. 1 is a diagram showing a lens configuration of a projection optical system according to the first example of the present embodiment. The projection optical system according to the first example includes a first lens group G1 having a positive refractive power composed of one lens L1 and two lenses in order from the first object side P1 to the second object side P2. Second lens group G2 having negative refractive power composed of L2 to L3, third lens group G3 having positive refractive power composed of two lenses L4 to L5, aperture stop AS, and two lenses L6 To L7, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power composed of two lenses L8 to L9, and a positive refraction composed of one lens L10. And a sixth lens group G6 for power. A pair of concave surfaces facing each other is formed on the pair of negative lenses L2 to L3 of the second lens group G2, and a pair of concave surfaces facing each other is formed on the pair of negative lenses L8 to L9 of the fifth lens group G5. As described above, the first embodiment of the projection optical system includes a total of ten lenses.
Next, the values of the specifications of the projection optical system are shown in the following table. The positive, negative, positive, aperture stop, positive, negative, and positive refractive power arrangement is adopted, and the aperture diaphragm has symmetry as much as possible, so that asymmetric aberrations, especially coma and distortion, are extremely good. It can be corrected.
The first lens group G1 having a positive refractive power mainly contributes to correction of distortion while maintaining the telecentricity on the first object side P1 side. The sixth lens group G6 having a positive refractive power also contributes mainly to correction of distortion while maintaining the telecentricity on the second object side P2.
The second lens group G2 and the fifth lens group G5 having negative refractive power mainly have a function of correcting the Petzval sum of the entire system, and aim to flatten the image plane over a wide exposure area. The third lens group G3 having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the second lens group G2 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens component in the third lens group G3. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the third lens group G3 having a positive refractive power.

The fourth lens group G4 having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the fifth lens group G5 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens components in the fourth lens group G4. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the fourth lens group G4 having a positive refractive power.

According to said result, the following conditions (1)-(3) are satisfied.
(1) 0. 3 <f1 / fa <1.3
(2) −0.36 <f2 / fa <−0.08
(3) 0.13 <f3 / fa <0.5
When the upper limit of the above condition (1) is exceeded, the telecentricity on the first object side P1 side is broken, and negative distortion is greatly generated. Further, the outer diameters of the second and third lens groups G3 are increased, and the manufacturing cost is increased. On the contrary, when the lower limit of the condition (1) is exceeded, the telecentricity on the first object side P1 side is broken and a large positive distortion is generated, which is not preferable.
The above condition (2) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (2) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (2) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (3) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (3) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (3) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (4) to (7) are satisfied.
(4) 0.45 <| β | <2.2
(5) 0. 3 <f6 / fb <1.3
(6) −0.36 <f5 / fb <−0.08
(7) 0.13 <f4 / fb <0.5
In the condition (4), since the front group and the rear group of the projection optical system have as much symmetry as possible with respect to the aperture stop, an optimum magnification range for correcting asymmetric aberration, particularly coma aberration and distortion aberration, is extremely good. It prescribes. When the magnification range of condition (4) is exceeded, it becomes difficult to correct the asymmetric aberrations of the front group and the rear group, particularly coma and distortion, which is not preferable.
When the upper limit of the condition (5) is exceeded, the telecentricity on the second object side P2 side is broken, and a large positive distortion is generated. Further, the outer diameters of the fourth and fifth lens groups G5 are increased, and the manufacturing cost is increased. Conversely, when the lower limit of the above condition (5) is exceeded, the telecentricity on the second object side P2 side is broken and negative distortion is greatly generated, which is not preferable.
The above condition (6) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (6) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (6) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (7) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (7) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (7) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Further, the following conditions (8) to (9) are satisfied (8) −1.8 <r1 / r2 <−0.6
(9) 1.0 <r3 / r2 <1.8
The condition (8) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, when the condition is outside the range of condition (8), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, correction of spherical aberration and Petzval sum is difficult, which is not preferable.
The condition (9) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (9) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (9) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (10) to (11) are satisfied.
(10) 1.0 <r4 / r5 <1.8
(11) −1.8 <r6 / r5 <−0.6
Above condition (10)
This is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (10) is exceeded, negative spherical aberration and upper coma aberration are greatly generated. Conversely, when the lower limit of the condition (10) is exceeded, positive spherical aberration and lower side aberration are generated. This is not preferable because the coma aberration is greatly generated.
The condition (11) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, if it is outside the range of the condition (11), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, it is difficult to correct spherical aberration and Petzval sum, which is not preferable.

As described above, the first embodiment of the projection optical system includes a total of ten lenses.
If the number of lenses is increased, the numerical aperture NA can be increased and the exposure area can be increased, but the overall length of the optical system is increased and the weight is increased, resulting in an optical system that is very expensive to manufacture. In addition, since the number of lenses is large, production errors are large, and high lens manufacturing accuracy is required, which further increases the cost. Further, the transmittance of the entire optical system is lowered, and a problem of heat generation from the lens also occurs. On the other hand, when the number of constituent lenses is less than 10, the aberration cannot be corrected to a level necessary for exposure of a printed circuit board or the like.

As described above, in the first embodiment of the projection optical system, a telecentric optical system in which the optical axis and the principal ray can be regarded as parallel is formed on both the object side and the image side. In a projection exposure apparatus, it is required to faithfully project an image of a pattern on a reticle onto a substrate at an arbitrary set magnification. In particular, it is necessary to prevent a magnification error from occurring. On the other hand, in general, an optical system forms a good image within the depth of focus range. Therefore, if the image side is not a telecentric optical system, a magnification error may always occur. Further, when the object side is not a telecentric optical system, there is always a fear of pattern position error on the reticle.

  The first lens group G1 is composed of one positive refractive index lens, and the sixth lens group G6 is composed of one positive refractive index lens. Since the first and sixth lens groups G6 are relatively large lenses, the lens group composed of positive refractive index lenses reduces the number of large lenses, reduces production errors, and further reduces costs. It becomes a factor of. Further, the transmittance of the entire optical system is improved, and the problem of heat generation from the lens can be reduced.

As described above, in the first embodiment of the projection optical system, the projection magnification between the first object side P1 and the second object side P2 is -1. It consists of a front group and a rear group that are arranged symmetrically with respect to the aperture stop, and it is preferable that coma aberration, distortion aberration, and chromatic aberration of magnification can be corrected to zero, and the manufacturing cost is reduced.

FIG. 5 is a diagram showing astigmatism and distortion of the projection optical system in the first embodiment. FIG. 6 is a diagram showing coma aberration of the projection optical system in the first embodiment. In each aberration diagram, Y represents the image height. The line indicated by T in the astigmatism diagram indicates the field curvature of the tangential image plane, and the line indicated by S indicates the field curvature of the sagittal image plane. In addition, the vertical scale of the coma aberration diagram indicates 50 microns at 5 scales. As is apparent from the respective aberration diagrams, in the projection optical system of the first example, various aberrations are well corrected over the entire large projection field (effective diameter 204 mm), and good optical performance is ensured. In particular, referring to the astigmatism diagrams, it can be seen that the flatness of the image surface is ensured satisfactorily.
In the first embodiment of the projection optical system according to the present invention, it is possible to satisfactorily correct the aberration of the projection optical system, and the exposure area, resolution, and optical characteristics sufficient to manufacture various substrates. And a compact projection optical system in which the outer diameters of the second, third, fourth, and fifth lenses G2 to G5 are suppressed, and can be realized at low cost.

[Second Example] FIG. 2 is a diagram showing a lens configuration of a projection optical system according to a second example of the present embodiment. The projection optical system according to the second example includes a first lens group G1 having a positive refractive power composed of two lenses L1 and L2 and two lenses in order from the first object side P1 to the second object side P2. The second lens group G2 having negative refractive power composed of the lenses L3 to L4, the third lens group G3 having positive refractive power composed of the two lenses L5 to L6, the aperture stop AS, and two lenses Consists of a fourth lens group G4 having positive refractive power composed of lenses L7 to L8, a fifth lens group G5 having negative refractive power composed of two lenses L9 to L10, and two lenses L11 to L12. And a sixth lens group G6 having positive refractive power. In addition, a pair of concave surfaces facing each other is formed on the pair of negative lenses L3 to L4 of the second lens group G2, and a pair of concave surfaces facing each other is formed on the pair of negative lenses L9 to L10 of the fifth lens group G5. As described above, the second embodiment of the projection optical system includes a total of 12 lenses.
Next, the values of the specifications of the projection optical system are shown in the following table. The positive, negative, positive, aperture stop, positive, negative, and positive refractive power arrangement is adopted, and the aperture diaphragm has symmetry as much as possible, so that asymmetric aberrations, especially coma and distortion, are extremely good. It can be corrected.
The first lens group G1 having a positive refractive power mainly contributes to correction of distortion while maintaining the telecentricity on the first object side P1 side. The sixth lens group G6 having positive refractive power also contributes mainly to correction of distortion while maintaining the telecentricity on the second object side P2.
The second lens group G2 and the fifth lens group G5 having negative refractive power mainly have a function of correcting the Petzval sum of the entire system, and aim to flatten the image plane over a wide exposure area. 3rd with positive refractive power
The lens group G3 mainly contributes to correction of spherical aberration and also to correction of astigmatism and field curvature. Here, the second lens group G2 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens component in the third lens group G3. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the third lens group G3 having a positive refractive power.

The fourth lens group G4 having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the fifth lens group G5 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens components in the fourth lens group G4. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the fourth lens group G4 having a positive refractive power.

According to said result, the following conditions (1)-(3) are satisfied.
(1) 0. 3 <f1 / fa <1.3
(2) −0.36 <f2 / fa <−0.08
(3) 0.13 <f3 / fa <0.5
When the upper limit of the above condition (1) is exceeded, the telecentricity on the first object side P1 side is broken, and negative distortion is greatly generated. Further, the outer diameters of the second and third lens groups G3 are increased, and the manufacturing cost is increased. On the contrary, when the lower limit of the condition (1) is exceeded, the telecentricity on the first object side P1 side is broken and a large positive distortion is generated, which is not preferable.
The above condition (2) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (2) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (2) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (3) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (3) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (3) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (4) to (7) are satisfied.
(4) 0.45 <| β | <2.2
(5) 0. 3 <f6 / fb <1.3
(6) −0.36 <f5 / fb <−0.08
(7) 0.13 <f4 / fb <0.5
In the condition (4), since the front group and the rear group of the projection optical system have as much symmetry as possible with respect to the aperture stop, an optimum magnification range for correcting asymmetric aberration, particularly coma aberration and distortion aberration, is extremely good. It prescribes. When the magnification range of condition (4) is exceeded, it becomes difficult to correct the asymmetric aberrations of the front group and the rear group, particularly coma and distortion, which is not preferable.
When the upper limit of the condition (5) is exceeded, the telecentricity on the second object side P2 side is broken, and a large positive distortion is generated. Further, the outer diameters of the fourth and fifth lens groups G5 are increased, and the manufacturing cost is increased. Conversely, when the lower limit of the above condition (5) is exceeded, the telecentricity on the second object side P2 side is broken and negative distortion is greatly generated, which is not preferable.
The above condition (6) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (6) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (6) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (7) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (7) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (7) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Further, the following conditions (8) to (9) are satisfied (8) −1.8 <r1 / r2 <−0.6
(9) 1.0 <r3 / r2 <1.8
The condition (8) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, when the condition is outside the range of condition (8), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, correction of spherical aberration and Petzval sum is difficult, which is not preferable.
The condition (9) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (9) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (9) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (10) to (11) are satisfied.
(10) 1.0 <r4 / r5 <1.8
(11) −1.8 <r6 / r5 <−0.6
The condition (10) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (10) is exceeded, negative spherical aberration and upper coma aberration are greatly generated. Conversely, when the lower limit of the condition (10) is exceeded, positive spherical aberration and lower side aberration are generated. This is not preferable because the coma aberration is greatly generated.
The condition (11) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, if it is outside the range of the condition (11), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, it is difficult to correct spherical aberration and Petzval sum, which is not preferable.

As described above, the second embodiment of the projection optical system includes a total of 12 lenses.
If the number of lenses is increased, the numerical aperture NA can be increased and the exposure area can be increased, but the overall length of the optical system is increased and the weight is increased, resulting in an optical system that is very expensive to manufacture. In addition, since the number of lenses is large, production errors are large, and high lens manufacturing accuracy is required, which further increases the cost. Further, the transmittance of the entire optical system is lowered, and a problem of heat generation from the lens also occurs. On the other hand, when the number of constituent lenses is less than 10, the aberration cannot be corrected to a level necessary for exposure.

As described above, in the second embodiment of the projection optical system, a telecentric optical system in which the optical axis and the principal ray are regarded as parallel is formed on both the object side and the image side. In a projection exposure apparatus, it is required to faithfully project an image of a pattern on a reticle onto a substrate at an arbitrary set magnification. In particular, it is necessary to prevent a magnification error from occurring. On the other hand, in general, an optical system forms a good image within the depth of focus range. Therefore, if the image side is not a telecentric optical system, a magnification error may always occur. Further, when the object side is not a telecentric optical system, there is always a fear of pattern position error on the reticle.

  The first lens group G1 is composed of one positive refractive index lens, and the sixth lens group G6 is composed of one positive refractive index lens. Since the first and sixth lens groups G6 are relatively large lenses, the lens group composed of positive refractive index lenses reduces the number of large lenses, reduces production errors, and further reduces costs. It becomes a factor of. Further, the transmittance of the entire optical system is improved, and the problem of heat generation from the lens can be reduced.

As described above, in the second embodiment of the projection optical system, the first lens group G1 has two or more curved surfaces having the same absolute value of the curvature radius, and the sixth lens group G6 has an absolute curvature radius. Curved surfaces having the same value have two or more surfaces. Since the first and sixth lens groups G6 are relatively large lenses, a lens configured with a curved surface having the same absolute value of the radius of curvature causes a reduction in manufacturing cost. The lens manufacturing accuracy can be easily improved.
As described above, in the second embodiment of the projection optical system, the projection magnification between the first object side P1 and the second object side P2 is -1. It consists of a front group and a rear group that are arranged symmetrically with respect to the aperture stop, and it is preferable that coma aberration, distortion aberration, and chromatic aberration of magnification can be corrected to zero, and the manufacturing cost is reduced.

FIG. 7 is a diagram showing astigmatism and distortion of the projection optical system in the second embodiment. FIG. 8 is a diagram showing coma aberration of the projection optical system in the second embodiment. In each aberration diagram, Y represents the image height. The line indicated by T in the astigmatism diagram indicates the field curvature of the tangential image plane, and the line indicated by S indicates the field curvature of the sagittal image plane. In addition, the vertical scale of the coma aberration diagram indicates 50 microns at 5 scales. As is clear from each aberration diagram, in the projection optical system of the second example, various aberrations are well corrected over the entire large projection field (effective diameter: 204 mm), and good optical performance is ensured. In particular, referring to the astigmatism diagrams, it can be seen that the flatness of the image surface is ensured satisfactorily.
In the second embodiment of the projection optical system according to the present invention, it is possible to satisfactorily correct the aberration of the projection optical system, and the exposure area, resolution, and optical characteristics sufficient to manufacture various substrates. And a compact projection optical system in which the outer diameters of the second, third, fourth, and fifth lenses G2 to G5 are suppressed, and can be realized at low cost.

[Third Example] FIG. 3 is a view showing the lens arrangement of a projection optical system according to the third example of the present embodiment. The projection optical system according to the third example includes a first lens group G1 having a positive refractive power composed of two lenses L1 and L2 in order from the first object side P1 to the second object side P2, and two lenses. The second lens group G2 having negative refractive power composed of the lenses L3 to L4, the third lens group G3 having positive refractive power composed of the two lenses L5 to L6, the aperture stop AS, and two lenses Consists of a fourth lens group G4 having positive refractive power composed of lenses L7 to L8, a fifth lens group G5 having negative refractive power composed of two lenses L9 to L10, and two lenses L11 to L12. And a sixth lens group G6 having positive refractive power. In addition, a pair of concave surfaces facing each other is formed on the pair of negative lenses L3 to L4 of the second lens group G2, and a pair of concave surfaces facing each other is formed on the pair of negative lenses L9 to L10 of the fifth lens group G5. As described above, the third embodiment of the projection optical system includes a total of 12 lenses.
Next, the values of the specifications of the projection optical system are shown in the following table. The positive, negative, positive, aperture stop, positive, negative, and positive refractive power arrangement is adopted, and the aperture diaphragm has symmetry as much as possible, so that asymmetric aberrations, especially coma and distortion, are extremely good. It can be corrected.
The first lens group G1 having a positive refractive power mainly contributes to correction of distortion while maintaining the telecentricity on the first object side P1 side. The sixth lens group G6 having positive refractive power also contributes mainly to correction of distortion while maintaining the telecentricity on the second object side P2.
The second lens group G2 and the fifth lens group G5 having negative refractive power mainly have a function of correcting the Petzval sum of the entire system, and aim to flatten the image plane over a wide exposure area. 3rd with positive refractive power
The lens group G3 mainly contributes to correction of spherical aberration and also to correction of astigmatism and field curvature. Here, the second lens group G2 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens component in the third lens group G3. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the third lens group G3 having a positive refractive power.

The fourth lens group G4 having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the fifth lens group G5 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens components in the fourth lens group G4. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the fourth lens group G4 having a positive refractive power.

According to said result, the following conditions (1)-(3) are satisfied.
(1) 0. 3 <f1 / fa <1.3
(2) −0.36 <f2 / fa <−0.08
(3) 0.13 <f3 / fa <0.5
When the upper limit of the above condition (1) is exceeded, the telecentricity on the first object side P1 side is broken, and negative distortion is greatly generated. Further, the outer diameters of the second and third lens groups G3 are increased, and the manufacturing cost is increased. On the contrary, when the lower limit of the condition (1) is exceeded, the telecentricity on the first object side P1 side is broken and a large positive distortion is generated, which is not preferable.
The above condition (2) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (2) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (2) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (3) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (3) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (3) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (4) to (7) are satisfied.
(4) 0.45 <| β | <2.2
(5) 0. 3 <f6 / fb <1.3
(6) −0.36 <f5 / fb <−0.08
(7) 0.13 <f4 / fb <0.5
In the condition (4), since the front group and the rear group of the projection optical system have as much symmetry as possible with respect to the aperture stop, an optimum magnification range for correcting asymmetric aberration, particularly coma aberration and distortion aberration, is extremely good. It prescribes. When the magnification range of condition (4) is exceeded, it becomes difficult to correct the asymmetric aberrations of the front group and the rear group, particularly coma and distortion, which is not preferable.
When the upper limit of the above condition (5) is exceeded, the telecentricity on the second object side P2 side is broken and a large positive distortion is generated. Further, the outer diameters of the fourth and fifth lens groups G5 are increased, and the manufacturing cost is increased. Conversely, when the lower limit of the above condition (5) is exceeded, the telecentricity on the second object side P2 side is broken and negative distortion is greatly generated, which is not preferable.
The above condition (6) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (6) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (6) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (7) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (7) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (7) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Moreover, the following conditions (8) to (9) are satisfied (8) −1.8 <r1 / r2 <−0.6
(9) 1.0 <r3 / r2 <1.8
The condition (8) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, when the condition is outside the range of condition (8), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, correction of spherical aberration and Petzval sum is difficult, which is not preferable.
The condition (9) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (9) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (9) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (10) to (11) are satisfied.
(10) 1.0 <r4 / r5 <1.8
(11) −1.8 <r6 / r5 <−0.6
The condition (10) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (10) is exceeded, negative spherical aberration and upper coma aberration are greatly generated. Conversely, when the lower limit of the condition (10) is exceeded, positive spherical aberration and lower side aberration are generated. This is not preferable because the coma aberration is greatly generated.
The condition (11) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, if it is outside the range of the condition (11), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, it is difficult to correct spherical aberration and Petzval sum, which is not preferable.

As described above, the third embodiment of the projection optical system includes a total of 12 lenses.
If the number of lenses is increased, the numerical aperture NA can be increased and the exposure area can be increased, but the overall length of the optical system is increased and the weight is increased, resulting in an optical system that is very expensive to manufacture. In addition, since the number of lenses is large, production errors are large, and high lens manufacturing accuracy is required, which further increases the cost. Further, the transmittance of the entire optical system is lowered, and a problem of heat generation from the lens also occurs. On the other hand, when the number of constituent lenses is less than 10, the aberration cannot be corrected to a level necessary for exposure.

As described above, in the third embodiment of the projection optical system, a telecentric optical system in which the optical axis and the principal ray can be regarded as parallel is formed on both the object side and the image side. In a projection exposure apparatus, it is required to faithfully project an image of a pattern on a reticle onto a substrate at an arbitrary set magnification. In particular, it is necessary to prevent a magnification error from occurring. On the other hand, in general, an optical system forms a good image within the depth of focus range. Therefore, if the image side is not a telecentric optical system, a magnification error may always occur. Further, when the object side is not a telecentric optical system, there is always a fear of pattern position error on the reticle.

  The first lens group G1 is composed of one positive refractive index lens, and the sixth lens group G6 is composed of one positive refractive index lens. Since the first and sixth lens groups G6 are relatively large lenses, the lens group composed of positive refractive index lenses reduces the number of large lenses, reduces production errors, and further reduces costs. It becomes a factor of. Further, the transmittance of the entire optical system is improved, and the problem of heat generation from the lens can be reduced.

As described above, in the third embodiment of the projection optical system, the first lens group G1 has two or more curved surfaces having the same absolute value of the curvature radius, and the sixth lens group G6 has an absolute curvature radius. Curved surfaces having the same value have two or more surfaces. Since the first and sixth lens groups G6 are relatively large lenses, a lens configured with a curved surface having the same absolute value of the radius of curvature causes a reduction in manufacturing cost. The lens manufacturing accuracy can be easily improved.

As described above, in the third embodiment of the projection optical system, the projection magnification between the first object side P1 and the second object side P2 is -1. It consists of a front group and a rear group that are arranged symmetrically with respect to the aperture stop, and it is preferable that coma aberration, distortion aberration, and chromatic aberration of magnification can be corrected to zero, and the manufacturing cost is reduced.

FIG. 9 is a diagram showing astigmatism and distortion of the projection optical system in the third embodiment. FIG. 10 is a diagram illustrating coma aberration of the projection optical system according to the third embodiment. In each aberration diagram, Y represents the image height. The line indicated by T in the astigmatism diagram indicates the field curvature of the tangential image plane, and the line indicated by S indicates the field curvature of the sagittal image plane. In addition, the vertical scale of the coma aberration diagram indicates 50 microns at 5 scales. As is apparent from each aberration diagram, in the projection optical system of the third example, various aberrations are well corrected over the entire large projection field (effective diameter 204 mm), and good optical performance is ensured. In particular, referring to the astigmatism diagrams, it can be seen that the flatness of the image surface is ensured satisfactorily.
In the third embodiment of the projection optical system according to the present invention, it is possible to satisfactorily correct the aberration of the projection optical system, and the exposure area, resolution, and optical characteristics sufficient to manufacture various substrates. And a compact projection optical system in which the outer diameters of the second, third, fourth, and fifth lenses G2 to G5 are suppressed, and can be realized at low cost.

[Fourth Example] FIG. 4 is a view showing the lens arrangement of a projection optical system according to the fourth example of the present embodiment. The projection optical system according to the fourth example includes a first lens group G1 having a positive refractive power composed of two lenses L1 and L2 and two lenses in order from the first object side P1 to the second object side P2. The second lens group G2 having negative refractive power composed of the lenses L3 to L4, the third lens group G3 having positive refractive power composed of the two lenses L5 to L6, the aperture stop AS, and two lenses Consists of a fourth lens group G4 having positive refractive power composed of lenses L7 to L8, a fifth lens group G5 having negative refractive power composed of two lenses L9 to L10, and two lenses L11 to L12. And a sixth lens group G6 having positive refractive power. In addition, a pair of concave surfaces facing each other is formed on the pair of negative lenses L3 to L4 of the second lens group G2, and a pair of concave surfaces facing each other is formed on the pair of negative lenses L9 to L10 of the fifth lens group G5. As described above, the fourth embodiment of the projection optical system includes a total of 12 lenses.
Next, the values of the specifications of the projection optical system are shown in the following table. The positive, negative, positive, aperture stop, positive, negative, and positive refractive power arrangement is adopted, and the aperture diaphragm has symmetry as much as possible, so that asymmetric aberrations, especially coma and distortion, are extremely good. It can be corrected.
The first lens group G1 having a positive refractive power mainly contributes to correction of distortion while maintaining the telecentricity on the first object side P1 side. The sixth lens group G6 having positive refractive power also contributes mainly to correction of distortion while maintaining the telecentricity on the second object side P2.
The second lens group G2 and the fifth lens group G5 having negative refractive power mainly have a function of correcting the Petzval sum of the entire system, and aim to flatten the image plane over a wide exposure area. The third lens group G3 having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the second lens group G2 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens component in the third lens group G3. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the third lens group G3 having a positive refractive power.

The fourth lens group G4 having a positive refractive power mainly contributes to correction of spherical aberration, and also contributes to correction of astigmatism and field curvature. Here, the fifth lens group G5 having a pair of negative lenses forming a pair of concave surfaces facing each other generates a positive Petzval sum by this concave surface and is generated from the positive lens components in the fourth lens group G4. It has a function of correcting the negative Petzval sum and correcting the negative spherical aberration generated from the fourth lens group G4 having a positive refractive power.

According to said result, the following conditions (1)-(3) are satisfied.
(1) 0. 3 <f1 / fa <1.3
(2) −0.36 <f2 / fa <−0.08
(3) 0.13 <f3 / fa <0.5
When the upper limit of the above condition (1) is exceeded, the telecentricity on the first object side P1 side is broken, and negative distortion is greatly generated. Further, the outer diameters of the second and third lens groups G3 are increased, and the manufacturing cost is increased. On the contrary, when the lower limit of the condition (1) is exceeded, the telecentricity on the first object side P1 side is broken and a large positive distortion is generated, which is not preferable.
The above condition (2) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (2) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (2) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (3) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (3) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (3) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (4) to (7) are satisfied.
(4) 0.45 <| β | <2.2
(5) 0. 3 <f6 / fb <1.3
(6) −0.36 <f5 / fb <−0.08
(7) 0.13 <f4 / fb <0.5
In the condition (4), since the front group and the rear group of the projection optical system have as much symmetry as possible with respect to the aperture stop, an optimum magnification range for correcting asymmetric aberration, particularly coma aberration and distortion aberration, is extremely good. It prescribes. When the magnification range of condition (4) is exceeded, it becomes difficult to correct the asymmetric aberrations of the front group and the rear group, particularly coma and distortion, which is not preferable.
When the upper limit of the above condition (5) is exceeded, the telecentricity on the second object side P2 side is broken and a large positive distortion is generated. Further, the outer diameters of the fourth and fifth lens groups G5 are increased, and the manufacturing cost is increased. Conversely, if the lower limit of the above condition (5) is exceeded, the second
This is not preferable because the telecentricity on the object side P2 side is broken and negative distortion is greatly generated.
The above condition (6) is mainly for satisfactorily correcting the Petzval sum and spherical aberration of the entire system. When the upper limit of the condition (6) is exceeded, positive curvature of field and positive spherical aberration occur greatly. Conversely, when the lower limit of the condition (6) is exceeded, negative curvature of field is obtained. Since negative spherical aberration is greatly generated, it is not preferable.
The condition (7) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (7) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (7) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Further, the following conditions (8) to (9) are satisfied (8) −1.8 <r1 / r2 <−0.6
(9) 1.0 <r3 / r2 <1.8
The condition (8) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, when the condition is outside the range of condition (8), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, correction of spherical aberration and Petzval sum is difficult, which is not preferable.
The condition (9) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (9) is exceeded, positive spherical aberration and positive curvature of field aberration are greatly generated. Conversely, when the lower limit of the condition (9) is exceeded, negative spherical aberration is caused. Since negative curvature of field aberration is greatly generated, it is not preferable.

Furthermore, the following conditions (10) to (11) are satisfied.
(10) 1.0 <r4 / r5 <1.8
(11) −1.8 <r6 / r5 <−0.6
The condition (10) is mainly for satisfactorily correcting spherical aberration and field curvature aberration. When the upper limit of the condition (10) is exceeded, negative spherical aberration and upper coma aberration are greatly generated. Conversely, when the lower limit of the condition (10) is exceeded, positive spherical aberration and lower side aberration are generated. This is not preferable because the coma aberration is greatly generated.
The condition (11) defines the optimum shape of the concave surfaces facing each other in the second lens group G2. Here, if it is outside the range of the condition (11), the symmetry of the shape of the gas lens is lost, and coma aberration is generated. In addition, it is difficult to correct spherical aberration and Petzval sum, which is not preferable.

As described above, the fourth embodiment of the projection optical system includes a total of 12 lenses.
If the number of lenses is increased, the numerical aperture NA can be increased and the exposure area can be increased, but the overall length of the optical system is increased and the weight is increased, resulting in an optical system that is very expensive to manufacture. In addition, since the number of lenses is large, production errors are large, and high lens manufacturing accuracy is required, which further increases the cost. Further, the transmittance of the entire optical system is lowered, and a problem of heat generation from the lens also occurs. On the other hand, when the number of constituent lenses is less than 10, the aberration cannot be corrected to a level necessary for exposure.

As described above, in the fourth embodiment of the projection optical system, a telecentric optical system in which the optical axis and the principal ray are regarded as parallel is formed on both the object side and the image side. In a projection exposure apparatus, it is required to faithfully project an image of a pattern on a reticle onto a substrate at an arbitrary set magnification. In particular, it is necessary to prevent a magnification error from occurring. On the other hand, in general, an optical system forms a good image within the depth of focus range. Therefore, if the image side is not a telecentric optical system, a magnification error may always occur. Further, when the object side is not a telecentric optical system, there is always a fear of pattern position error on the reticle.

  The first lens group G1 is composed of one positive refractive index lens, and the sixth lens group G6 is composed of one positive refractive index lens. Since the first and sixth lens groups G6 are relatively large lenses, the lens group composed of positive refractive index lenses reduces the number of large lenses, reduces production errors, and further reduces costs. It becomes a factor of. Further, the transmittance of the entire optical system is improved, and the problem of heat generation from the lens can be reduced.

As described above, in the fourth embodiment of the projection optical system, the first lens group G1 has two or more curved surfaces having the same absolute value of the curvature radius, and the sixth lens group G6 has an absolute curvature radius. Curved surfaces having the same value have two or more surfaces. Since the first and sixth lens groups G6 are relatively large lenses, a lens configured with a curved surface having the same absolute value of the radius of curvature causes a reduction in manufacturing cost. The lens manufacturing accuracy can be easily improved.

FIG. 11 is a diagram showing astigmatism and distortion of the projection optical system in the fourth embodiment. FIG. 12 is a diagram showing coma aberration of the projection optical system in the fourth embodiment. In each aberration diagram, Y represents the image height. The line indicated by T in the astigmatism diagram indicates the field curvature of the tangential image plane, and the line indicated by S indicates the field curvature of the sagittal image plane. In addition, the vertical scale of the coma aberration diagram indicates 50 microns at 5 scales. As is apparent from the respective aberration diagrams, in the projection optical system of the fourth example, various aberrations are well corrected over the entire large projection field (effective diameter 204 mm), and good optical performance is ensured. In particular, referring to the astigmatism diagrams, it can be seen that the flatness of the image surface is ensured satisfactorily.
In the fourth embodiment of the projection optical system according to the present invention, it is possible to satisfactorily correct the aberration of the projection optical system, and the exposure area, resolution, and optical characteristics sufficient to manufacture various substrates. And a compact projection optical system in which the outer diameters of the second, third, fourth, and fifth lenses G2 to G5 are suppressed, and can be realized at low cost.

P1 First object side P2 Second object side AS Aperture stop

Claims (10)

In a projection optical system for projecting an image of a first object onto a second object,
In order from the first object side toward the second object,
A first lens group having a positive refractive power;
A second lens group having a pair of negative lenses having negative refractive power and forming a pair of concave surfaces facing each other;
A third lens group having a positive refractive power;
An aperture stop,
A fourth lens group having a positive refractive power;
A fifth lens group having a pair of negative lenses having negative refractive power and forming a pair of concave surfaces facing each other;
A sixth lens unit having a positive refractive power,
0. 3 <f1 / fa <1.3
−0.36 <f2 / fa <−0.08
0.13 <f3 / fa <0.5
Projection optical system characterized by satisfying
However,
f1: focal length of the first lens group,
f2: focal length of the second lens group,
f3: focal length of the third lens group,
fa: the focal length of the front group consisting of the first, second and third lens groups, In the projection optical system,
0.45 <| β | <2.2
0. 3 <f6 / fb <1.3
−0.36 <f5 / fb <−0.08
0.13 <f4 / fb <0.5
The projection optical system according to claim 1, wherein:
However,
β: lateral magnification of the projection optical system,
f4: focal length of the fourth lens group,
f5: focal length of the fifth lens group,
f6: focal length of the sixth lens group,
fb: focal length of rear group consisting of the fourth, fifth and sixth lens groups, The second and third lens groups are
−1.8 <r1 / r2 <−0.6
1.0 <r3 / r2 <1.8
The projection optical system according to claim 1, wherein:
However,
r1: the radius of curvature of the concave surface on the first object side in the concave group facing each other of the second lens group,
r2: the radius of curvature of the concave surface on the second object side in the concave surface group of the second lens group facing each other,
r3: The smallest value of the absolute value of each radius of curvature in each lens surface of the third lens group, The fourth and fifth lens groups are
1.0 <r4 / r5 <1.8
−1.8 <r6 / r5 <−0.6
The projection optical system according to claim 3, wherein:
However,
r4: The smallest absolute value of each radius of curvature in each lens surface of the fourth lens group,
r5: radius of curvature of the concave surface on the first object side in the concave surface group of the fifth lens group facing each other,
r6: radius of curvature of the concave surface on the second object side in the concave surface group facing each other of the fifth lens group   The projection optical system according to claim 3, wherein an image of the second object is projected onto the first object.   6. The projection optical system according to claim 5, wherein the total number of constituent lenses of the projection optical system is 10 or more and 20 or less.   The projection optical system according to claim 6, wherein both the first object side and the second object side are telecentric optical systems. The first lens group includes one or more positive refractive index lenses,
The projection optical system according to claim 6, wherein the sixth lens group includes one or more positive refractive index lenses. The first lens group has two or more curved surfaces having the same absolute value of the radius of curvature.
The projection optical system according to claim 7, wherein the sixth lens group has two or more curved surfaces having the same absolute value of the radius of curvature. The projection magnification between the first object and the second object is -1, which is composed of a front group and a rear group that are arranged symmetrically with respect to the aperture stop. Projection optics.

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