JPS60168116A - Reflecting optical system - Google Patents

Abstract

PURPOSE:To increase a wafer printing quantity per time by constituting a titled system so that emitted light roughly parallel to an optical axis is reflected by a concave mirror, and thereafter, made incident on the vicinity of an intersection point of a convex mirror and the optical axis, and reflected light from the intersection point of the convex mirror and the optical axis is reflected by the concave mirror, and emitted roughly in parallel to the optical axis. CONSTITUTION:An astigmatism and a curvature of image are corrected by an aspherical lens L1. As for the shape of the aspherical lens L1, it is determined so that all beams of main light parallel to an optical axis O of each image height in a correcting area are made incident on a center 02 of a convex mirror M2, and each main light reflected from the center 02 of the convex mirror M2 is all made incident in parallel to an image picture. The shape of an aspherical surface of the concave mirror M2 is constituted so that the aspherical surface quantity becomes the maximum by 70%-80% of an effective diameter, and thereafter, it is reduced. When the shape of the aspherical lens L1 is selected so that aspherical aberrations of positive and negative are negated each other by each image height of the correcting area, the main light parallel to the optical axis O of each image height is made incident on the center 02 of this optical system. The astigmatism of the whole reflecting optical system is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflective optical system suitable for application to, for example, a projection type scanning exposure apparatus, particularly an optical system for an aligner used in the manufacture of LSI and the like.

Conventional reflective optical systems of this type include, for example, reflective optical systems that use concentric or non-concentric concave mirrors and convex mirrors, and nearly concentric reflective systems that use concave mirrors and convex mirrors, as well as negative meniscus lenses and chromatic aberration correction mechanisms. Various types of optical systems are known.

These reflective optical systems have a good image area formed in an off-axis semi-arc-shaped area, and a partial image of the mask corresponding to this good image area is formed on the wafer, and the mask and wafer are integrated into the reflective optical system. Aligners are known that scan relative to a system to form an entire image of a mask on a wafer. However, all of the conventional reflective optical systems have large astigmatism and field curvature, so the width of the good image area is extremely narrow, for example, about 1 mm, and when adapted to an aligner, many scans are required. This method requires time, that is, exposure time, and has the disadvantage that the amount of wafers printed per hour is relatively small.

The purpose of the present invention is to improve the drawbacks of the conventional example, to sufficiently correct astigmatism and field curvature by introducing an aspherical lens, and to expand the good image area of the corrected image height. The object of the present invention is to provide a reflective optical system that increases the amount of wafer printing per hour, and its gist is to make the reflective surfaces of a concave mirror and a convex mirror face each other, and to provide a first optical member in front of the reflective surface side of the concave mirror. An optical means having a second optical member is disposed, a subject is disposed on the opposite side of the concave mirror with respect to the optical means, a light beam from the subject passes through the first optical member, and the concave mirror, the The light is reflected in the order of the convex mirror and the concave mirror, and the second
A reflective optical system that forms an image after passing through an optical member of the object, wherein light rays emitted from a region outside the optical axis of the reflective optical system of the object substantially parallel to the optical axis are directed to the first optical member. After passing through and reflecting on the concave mirror, the light ray is incident near the intersection of the convex mirror and the optical axis, or the light ray reflected from the intersection of the convex mirror and the optical axis is reflected on the concave mirror,
At least one of the first optical member or the second optical member and the convex mirror are provided with an aspheric surface so that the light is emitted substantially parallel to the optical axis after passing through the second optical member. This is a characteristic feature.

Next, the present invention will be explained in detail based on illustrated embodiments.

In the first embodiment shown in FIG. 1, a concave mirror Ml and a convex mirror M2 having an aspherical surface with a smaller radius are arranged so that their optical axes O coincide with each other, and their centers of curvature are aligned. The mirror surfaces are arranged to face each other so as to face in the same direction. Then, an aspherical lens Ll is provided between the object Sl and the convex mirror M2, and between the object St and the image plane S2 and the convex mirror M2, which are located symmetrically about the point O1 on the optical axis 0.
are arranged in a symmetrical shape around the optical axis O. The light flux emitted from the object S1 is transmitted through the concave mirror M2 and the convex mirror M2.
, the concave mirror and the concave mirror, the object height PI is reflected three times between these two mirror surfaces M1 and M2, and then is imaged at the same magnification at the point ρ2 on the image plane S2, and this reflection The convex mirror M2 plays the role of an aperture in the optical system. Since this reflective optical system is arranged symmetrically with respect to the center 02 of the effective diameter of the convex mirror M2, coma aberration and distortion aberration, which are asymmetric aberrations, do not occur when the light beam enters this center 02. , the occurrence of astigmatism and field curvature is inevitable.

Therefore, in this reflective optical system, astigmatism and field curvature are corrected by the aspheric lens L1. For this reason, the shape of the aspherical lens L1 is such that all principal rays parallel to the optical axis O at each image height within the correction area shown in the astigmatism diagram in FIG. 2 enter the center 02 of the convex mirror M2. , and the shape of the aspherical lens L1 is determined so that each principal ray reflected from the center 02 of the convex mirror M2 is all incident parallel to the image plane. The shape of the aspherical surface of the concave mirror M2 is such that the amount of aspherical surface is maximum at 70% to 80% of the effective diameter, and then decreases. Note that the astigmatism in Fig. 2 is (a) to (j
) shows cases in which the combinations of the aspherical shapes of the aspherical lens L1 and the convex mirror M2 are different.

As long as the aberration can be well corrected, even if all of the principal rays are slightly off-center, some of the principal rays may be off-center, and all of the principal rays may be incident on the image plane. The shape of the aspherical lens Ll may be determined so that the principal rays are incident somewhat non-parallelly or some principal rays are incident somewhat non-parallelly.

In such a case, for example, it is possible to provide an aspherical surface on the object S1 side of the lens L1 and use a meniscus lens member on the image plane S2 side. However, since it is easier to manufacture and explain the case where both sides are provided with an aspherical surface than with only one side provided with an aspherical surface, the case where both sides are provided with an aspherical surface will be described below.

In this case, the concave lens barrel functions as a convex lens, so that the concave mirror M1 has a positive spherical aberration that occurs at each incident height of the concave mirror M1 corresponding to each half-arc image height in the correction area. Negative spherical aberration is generated in the corresponding incident light of the spherical lens L1. Therefore, if the shape of the aspherical lens L1 is selected so that the positive and negative spherical aberrations cancel each other out at each image height in the correction area, the chief ray parallel to the optical axis 0 at each image height will be at the center of this optical system. It will be incident on 02. In other words, when the infinity chief ray of each image height within the correction area is corrected so that it always converges on the center 02 of the optical system, the astigmatism of the entire reflective optical system due to the symmetry at the center 02 will be corrected.

The correction area shown in Fig. 2 is determined by the relationship between the inclination of the sagittal image surface S and the meridional image surface m and the permissible depth. In order to eliminate the distance difference and reduce the field curvature at each image height within the correction area, an aspherical lens L1 is adopted.
This makes it possible to expand the correction area and increase the slit width. However, if even higher performance is required, other aberrations caused by the introduction of the aspherical lens L1 cannot be ignored. Therefore, by making the convex mirror M2 even more aspherical, it was possible to correct the lateral aberration caused by the introduction of the aspherical lens Ll.

In Figure 1, due to the action of the aspherical lens L1, the chief ray parallel to the optical axis O at each image height within the correction area is always directed to the convex mirror M.
2, even if the convex mirror M2 is aspherical, the upper ray UR and the lower ray L are not affected at all by principal ray-related aberrations, that is, astigmatism and field curvature.
R aberration can be corrected.

In this first embodiment shown in FIG. 1, the concave mirror Ml and the convex mirror M2 are non-concentric, and the aspherical lens L1 is a slightly convex lens, and the convex surface of the old concave mirror is an aspherical surface, and each principal ray within the correction area passes through. As the image height increases, the aspherical part becomes
It is designed to form a more negative component than the reference sphere.

Note that the number of the aspherical lenses 1 is not just one, but there is no problem even if there are a plurality of them. In addition, Fig. 2(a)
~(f) is the astigmatism diagram as described above, and FIG. 3(a)
) to (f) are lateral aberration diagrams.

Figure 4, Figure 5 (a) to (e), Figure 6 (a) to (e)
2 shows a configuration diagram, an astigmatism diagram, and a lateral aberration diagram of the second embodiment, respectively. In this second embodiment, a concave mirror'
Ml and the aspherical convex mirror film are concentric, and the aspherical lens L
2 has a parallel plane plate with aspherical surfaces on both sides. The aspherical surface portion through which the chief ray of each image height passes within the correction area is formed to have a more negative component than the reference spherical surface as the image height increases, that is, as the refractive power of the concave lens barrel increases. ing. In addition, the concave mirror liver is similar to the first embodiment,
The amount of aspherical surface increases as it moves away from the optical axis, and then decreases.

FIG. 7 shows the configuration of the third embodiment, and FIG. 8(a) to
9(e) and FIGS. 9(a) to 9(e) show an astigmatism diagram and a lateral aberration diagram, respectively. In this third embodiment, a negative meniscus lens is used to cancel the positive effect of the concave lens barrel, and this is made into an aspherical lens L3, and the convex mirror M2 is made aspherical, and the concave mirror M1 and the convex mirror M2 is non-concentric. Note that the shape of the aspherical part of the old concave mirror of the aspherical lens L3 is that the negative meniscus lens is the same as the concave mirror M1.
Since the refractive power is stronger than that of the reference spherical surface, the range through which the chief ray of each image height passes within the correction area is composed of components more positive than that of the reference spherical surface. The aspherical amount of the concave mirror M2 is formed such that the negative refractive power component increases with respect to the reference plane as the distance from the optical axis increases.

Fig. 10 is a configuration diagram of the fourth embodiment, - Fig. 11 (
a), (b), (e)' ((c), (d
), (f) not shown), Figures 12(a) to (e)
are an astigmatism diagram and a lateral aberration diagram, respectively. The concave mirror old and the aspherical convex mirror M2 are concentric, and the aspherical lens L4 is a slightly convex lens whose surface on the concave mirror Ml side is aspherical, and the aspherical part through which each chief ray in the correction area passes has a high image height. As the surface becomes more negative, it forms a more negative component than the reference spherical surface. Correction of chromatic aberration caused by the introduction of this aspherical lens L4 is performed by a positive component chromatic aberration correcting lens L5.

In other words, by using the aspherical lens L4, astigmatism is corrected, and as mentioned above, due to the symmetry of the optical system, no comatic aberration or distortion aberration occurs, but due to the glass thickness of the aspherical lens L4, The resulting chromatic aberration and other aberrations cannot be ignored. Therefore, by making the convex mirror M2 aspherical and using the chromatic aberration correction lens L5, the aspherical lens L4
This made it possible to correct lateral aberrations and chromatic aberrations caused by the introduction of the lens. That is, the lateral aberration generated by the aspherical lens L4 is corrected by the aspherical refractive surface of the convex mirror M2, and the chromatic aberration is corrected by the chromatic aberration correcting lens L5, which is a mildly convex lens.

In the above-described embodiment, the number of the aspherical lens L4 and the chromatic aberration correction lens L5 is one, but there is no particular problem even if there are a plurality of these. Further, these refractive members are not made of glass, but may be made of other transparent materials.

13 and 14 show astigmatism diagrams and lateral aberration diagrams when the convex mirror M2 in the first embodiment shown in FIG. As is clear from the above, the aspheric surface of the convex mirror M2 greatly contributes to improving the lateral aberration.

Next, numerical examples of the optical configuration in each of the first, second, third, and fourth embodiments are listed as Tables 1, 2, 3, and 4, respectively. Further, Table 5 shows numerical examples when an aspherical surface is not used for the convex mirror M2 in the configuration shown in FIG. In addition, in FIGS. 1, 4, 7, and 10, Ri is the radius of curvature of the surface of the i-th optical member according to the order in which the light travels, and Di is the axial thickness or thickness of the i-th optical member. It is an air interval, and the positive and negative signs are positive when it progresses from left to right.

Table 1 R1=oo D1=14. Ei5 Fused silica water'
R2=-13882,0e D2=488. Air R3
=-500,03=-246,45 mirror* 2R4=
-247,37D4= 248.45 Mirror R5=
−500,05=−488−,−air*” R13=
-6882,0606= -14,,85 Fused quartz R?
= (X) D? = -The mirror * is an aspherical surface, and is symmetrical about the optical axis, and the deviation X from the plane at the distance from the optical axis is expressed as
/[14(1-(h/R) 21-2]+Bh4+Ch
6+Dh8+Eh12 Letting the aspherical amount of the aspherical lens be AH (including AH1 and AH2) and the aspherical amount of the convex mirror M2 be ΔX, the following values will be obtained.

(1) In the case of Figure 2 (a) and Figure 3 (a), this 1R snow-8
882,06 B=4.59302-10"j C=-2,3280
9-1O-12D=-1,19195-10" E=
5.58425-10-"ΔH-5,58・10'2*2 R=-247,37 B=-5,80383・10-" C=3.83848
・1O-130=-4,35184-10-20E-3
,00619-to'.

Δx=2.47・1O-6 (2) In the case of Fig. 2(b) and Fig. 3(b), water' R=-
8882,06 B=4.59302-10" C=-2,328H-
10-”D=-1,191E15-lo-sgE=
5.56425-10-22ΔH=5.58Φ1O-2*2 R=-247,37 B=-3,4822・10'OC=2.3038-1
0-13D=-2,8111-10-2° E=-
1,8037-1O-20A x= 1.53-10-
' (3) In the case of Figure 2 (C) and Figure 3 (C) * ' R
=-8882,08 B=4.59302-1O-8C=-2,32808
-1O-1zD=-1,19195・10-' E=
5.58425・lo−22ΔH=5.58・1O−2 4C2R=−247,37 B=−8,12504・10−1° G=5.373
8?・1O-13D=-fl, 0!1250・10-2
° E=-4,20868・10-2°, l! l'X=
3.41 ・10-et al. (4) Figure 2 (d), Figure 3 (
In case of d) *' R=-6882,0f(B=4.82287・10-8 C-2,44240
・10-12D=-1,25155・10-' E=
5.84246・lo-22-H=5.88・10-2 *2R=-247,37 B=-3,48220・10-1° G=2.303
08-10-'3D=-2.61110・10-"E
=-4,20888・Ig-20Δx=1.53・10
4 (5) In the case of Fig. 2 (e) and Fig. 3 (e) * l R=
-6882,0G B=4.82287 dispute 10-% C=-2,442
40・1O-120=-1,25155Φ1O-18
E=5.84246Φ10(2ΔH=5.88・1
0'2 *2 RI! -247,37 B=-8,12500・10" C=5.37387
-10"D--8,09250・1040 E=-4,
20888・10-2゜A x= 3.41- 10-
(8) In the case of Fig. 2 (f) and Fig. 3 (f) * 1 'R
=-13882.06 B-4,3833,7@1O-1IC=-2,2097
9・1O−120=−1,13235・10−11 E
child5.28fi03・10(2Att=5.3o・
lO″2 * 2 R=-247,37 B=-3,48220・10-1° G-2,3030
8010-130=-2,81110010-13E lightning-1,80370・10'2゜Δx-1,53s 10
-” Table 2 *' R1= 00 01= 15. Fused quartz *2R
2= 00 02= 489.1188 Air R3=-
500,03=-244,8448 mirror*3R4=
-255,155204=244.8448 Mirror R5=-500,05=-489,988 mirror*2
R6= country D6= -15, fused silica*' R7=
00 07=-Air (1) In the case of Figures 5 (a) and 6 (a) *IR = Flash B = 1.43 fl? 0.10-”C=5.l[14
59・Io−IBI]=1.38587・10−
1 et al. E=-1,480113-1o-20A H,=
5.25・10-2 *2 R=■ B= 8.51818-10" C= 2.05182
-10-120--8.82781・1O-17E-3
,58277・10″ΔH2-4,93010″2 Zero 3 R--255,1552 B--1207B20・10-1' G-11,458
78・10-”D--8,813771@10-21
E--5,74418・10"217X-3,53
Fist 1O-7 (2) In the case of Fig. 5 (b) and Fig. 6 (b') *I R=
■ B'= 1.50853・10" C-5,42280
・to-”D-1,455113・10-”E-1,
55497・10′2゜ΔHr =5.55” 10
Admiration *2 R=■ B= 8. ! 3440?・10-9 G-2, 1545
1・1O−120=−9,058!3i3−10”'
E-3,78190・1041A H2=5.21・
10'2 Tree 3 R=L255.1552 B=-1,81143・10-" C-1,41881
-1O-13D--1,03015・10” E-8,
81827・1041A x= 5.88 10-7 (3) In the case of Fig. 5 (C) and Fig. 6 (c) *1 B=1.50853-10-" C=5.422800
10-130= 1.45516 ・10-1 et al. E
=-1,55487・10η0ΔH1=5.55・
10-2 *2R=oo- B= 8.94407・10-” C=2.15451
Conflict 1O-12D=J, 05898・10-'7 E=-
3,76190φ1O-21A H2=5.21 ・1
O-2 Wood 3R=-255,1552 B=-8,03810・10-"C-4,72938
・10-140=-3,43385010-1' E
= -2, 872090IO-21Δx= 1.18*
1O-7 (4) In the case of Figure 5 (d) and Figure 6 (d) *IR = Prisoner B = 1.3f (481 (・10" C = 4.9063
8 fists 10-130 = 1.31858・10-1 et al. E
=-1,401388・10-2°ΔH+ =4. f1
5 elo-2 B-8,09225-10-1' C= 1.8483
2-10'λD=-8,18E123-10-17E
=-3,40383-10-21ΔH2=4.65 0
10-2*3 R='-255,1552 B=-6,03810-10" C=4.72938
-1O-140='-3,43385-10"l E=
-2,87208-10-”Δ x= 1.18* 1
O-7 (5) In the case of Fig. 5 (e) and Fig. 6 (e), water I R = ■ B = 1.50853-10-” C = 5.4228
0-10”D=1.4551B-1O-1bE=-1
, 55497-10-20ΔH, = 5.55 ・lO'
2 *2R=o.

B=8.8440? -10-qC=2.15451-1
0”D=-9,058913-1O-17E=-3,7
8190-1[)-217H2=5.21 ・1O-2 *3 R= -255,1552 B=-8,03810・10-"I C= 4.729
38010-”4D--3,43385・10-”
E-2,87208・1 g-21Δx=1.18
・ 10-7 Table 3 R1=-141,81DI=11.03 Fused silica water' R2=-148,5802=3!34.47 Air R3=,-551,1503=-279,0? mirror*
2 R4=-287,1804=279.07 Mirror R5=-551,1505=-394,47 mirror* ” R[l=-148,58[]8=-11,
03 Fused quartz R7=-141,91D7=-Air (1) In the case of Fig. 8(a) and Fig. 9(a)
148,58 B 8.22051◆1f)-” C= 1.089
12-1O-I3D=-7, fi91?2・10"E
= 2.41287・10-22ΔH= 1.88 meeting
1O-4 * 2 R=-287,18 B= 4.06158Φ 10-12 C= 1.23
208・l 0-140--6.801731110
-2sE=-9,04580-10-2zΔx=
2.35 a 10-' (2) In the case of Fig. 8 (b) and Fig. 9 (b) * ” R-
-148,58 B=-8,22051・1O-1° G=1.08
1112・1O-IRD=-7,89172-10-
1” E= 2.41287- 1O-2zΔH1 interest,
98 ・1O-4 *2 R--287,18 B= 9.13855- 10'2 C= 2.772
20- to-” ID=-1,5303+3・10-
21 E=-2,03531・10″21Δ x=3
．． 53・ 104 (3) In the case of Fig. 8 (C) and Fig. 9 (c) *' R=
-148,58 B=-6,53152@10-1' C=1.14
358- 1O-13D=-8,07831Φ 1O-
Ill E-2, 53351・10-22ΔH-1,
98010-4 * 2 R=-287, 18 B= 9.13855・10-12 G= 2.772
20・1o −140=−1,53038・10−21
E=-2,03531-10-20Δ x=3.53
Φ 1O-1 (4) In the case of Fig. 8 (d) and Fig. 9 (d) * ” R=
-148,58 B=-8,06498・1O-10G= 1.0818
8・1O-IRD--7,4i3900-10-' E
= 2J5254-10'2"ΔH= 1.93・10
-4 * 2R=-2137,18 B= 9.13855Φ1O-12G= 2.7?22
0・10-'4D=-1,53039 dispute 10-"E
=-2,03531・H)-21Δx= 3.53#
10-" (5) In the case of Fig. 8 (e) and Fig. 9 (e) * " R=
-148,58 B=-Ei, 08498φ10-1° G= 1.08
1813-10-”n=-7,as9oo-to-+
8E-2, 35254-to-”ΔH-1, 93Φ10
-4 *2 R=-287,18 B-2,03079-to-+: C= 7.9870
0-xo-'! 'n= 3.4ooee・10-2
2 E=-4,52292・10-27Δx=1
．． 18・ 10-7 Table 4 R1= o3DI= 15. Fused quartz *I R2=1
3874.2 02-180. Air R3= 00 0
3-, 11.5 Fused quartz R4-4105,404=2
70. Air R5=-500,05 days-244,844
8 mirror tree 2R8 knee 255.1552 DB-244
, 8448 Mirror R? =-500,07=-270,Mirror R8=-4105,4D8=-11,5 Fused silica R
8-■ 09-180. Air *I RIO-13874, 2[110-15, Fused quartz R11=(X) Dll--Air (1) In the case of Fig. 11 (a) and Fig. 12 (a) * 1
1? -13874,2 B=7.397013・10-' C=2.4485
8・10°1″D=-4,8i110132・10
-5” E-1,11358・10riAH=2.02
・10*2 R=-255,1552 B--8,38331・10-" C=-fi, 91
182・10-1 momme n=-1,3213f(2・10
-19 E・-2,2f149B-10"'ΔX=8
．． 41-10-' (2) In the case of Figures 11(b) and 12(b), the CI
R=13874.2 B-8,13677・10-'I C-2,6834
4. 10-”n=-5,158f38・10-17
E=1.22505・10-21Δ H=2.28-
1O-2 * 2 R=-255,1552 B--6,38331・10-" C=-8,911
82・10-IsD--1,328B2・10-1
” E = −2, 2841118・lOｽΔ x
-8,41*'l0-7 (3) In the case of Fig. 11(c), tree' RJ3874.2 B-8,136? ? Jar to-9C-2, 811344
・10-130--5.15968 ・IO°1A E-1,22505-10-"ΔH-2,28・1
04 * 2 R-255,1552 B--5,42581-1O-II C-5,8750
5-10-"D・-1, 127E13φ10-' E-
1,132523・10′.

Δx-8,23-10-' (4) In the case of Fig. 11 (d)
・1O-130=-5,151168・10-17 E
-1,22505・lO<1ΔH= 2.29-10'
2 *2 R-255,1552 B-7,8511!38・10-1' C-8,211
418・to-”D--'1.591114・10-'
E-2,71798・1o-20Δ x-1,18-
10-Also (5) In the case of Fig. 11 (e) and Fig. 12 (e) *'
R-13874,2 B= 8.82378, jO” C= 2.258
81-10-'D=-4.32708-10" E=
1.02737-10-21ΔH= 1.813・l
O'2 *2 R-'255.1552 B=-8,38331-10-110=-6,8118
2-10-”D=-1,321382-10”E=
-2,28498-10-”A x = !1.41
Conflict 1O-7 (6) In the case of Fig. 11 (f) * ” R = 13874.2 B = fi, 823? 8-1O-qC = 2.2588
1-10-'D=-4.32708-to"E=
1.02737-10-2'ΔH-1,88-10-2*2 R=-255,1552 B=-7, [1599B-1O-11G=-8,29
418-10-1'D=-1,591114-10"'
, E=-2,71798-10"A x=1.18・
10-'= Table 5 R1= oo D1= 14.85 Fused quartz*I
R2=-13882,0802=488. Air R3
=-500,03=-24B,45 Mirror R4=-2
47,3704-248,45 mirror R5=-500,
05-488, Air*' Re=-8882, 0Ei Dfl=-14,
85 fused silica R7=ooD? = -Mirror*' R=-6882,08 B=4.5!11302-10-" C=-2,3
2fiO8-10-”D=-1,191!35-10-
'E=5.58425-10-27ΔH=5.58
-10'2 In these tables, the aspherical amount ΔH (including ΔH1 and ΔH2) of the aspherical lens L is AH=(ΔRH2−Δ
RHI)/A h.

Here, Ah indicates the semi-arc shaped good image area given by R2 - old by the aspherical lens L as shown in Fig. 15(a), and ARHI and ΔRH2 indicate the good image area as shown in Fig. 15(b'). It represents the amount of aspherical surface from the reference spherical surface at height R2. In addition, in (b), the solid line A indicates a reference plane centered on point 03, and the dotted line B indicates an aspherical surface.

As can be seen from these tables, the aspherical amount AH is 1/
104 and 1/10, and when ΔH is smaller than 1/104, the amount of change in the aspherical surface decreases, the effect of the aspherical surface weakens, and a wide slit width cannot be obtained. Moreover, when the aspherical surface amount ΔH becomes larger than 1/10, the amount of change in the aspherical surface increases, and the sagittal image surface S and the meridional image surface m
The slits move apart, making it impossible to obtain a wide slit width.

As can be seen from these tables, the allowable value of the aspherical amount ΔH changes depending on the size of the reference spherical surface. That is, the reference sphere I
When RI is larger than 1000mm, the aspherical amount ΔH is 1
It is between /103 and 1/10, and if these lower and upper limits are exceeded, the same disadvantages as mentioned above will occur. Furthermore, when the reference spherical surface IRI is 200 mm or less, the aspherical amount AH is between 1/104 and 1/l 03. occurs.

Further, the aspherical amount ΔX of the convex mirror M2 is defined as ΔX=ΔX/D, where ΔX is the aspherical amount from the reference spherical surface of the convex mirror at a height of 70% of one effective radius of the convex mirror M2.

Here, it is desirable that ΔX be larger than 1/109 and smaller than 1/10'. If the lower limit value is exceeded, the correction of the 7 rare light will not be sufficient, and if the upper limit value is exceeded, the amount of aspherical surface will become large and the correction of the flare light will be excessive, which is not preferable.

Furthermore, the second optical member constituting the aspherical lenses L1 to L4 and the glass temperature of the second optical member are respectively j
If l, ν2, then 60 ν, <io.

It is desirable to satisfy the following condition: 60<ν2×100. 7-tube number ν1, ν
If 2 is smaller than 60, the occurrence of chromatic aberration increases and the usable wavelength range is very narrowly limited. In addition, the Atsbe number ν1
, ν2 larger than 100 does not currently exist.

As explained above, the reflective optical system according to the present invention allows the sagittal image plane S and the meridional image plane m to coincide over a wide range at each image height in the correction area by introducing an aspherical lens and making the convex mirror aspherical. In addition to correcting the lateral aberration caused by the aspherical lens, it becomes possible to expand the good image area of the corrected image height. Furthermore, by expanding the good image area, that is, by increasing the slit width, it is possible to shorten the exposure time in the exposure device. In particular, it is not limited by the concentricity of the concave mirror and the convex mirror, and unlike a lens configuration with only a spherical system, it is possible to focus only on the correction of the aspherical surface without being restricted in the position where these are placed. This has the advantage of providing a high-performance reflective optical system. According to the example, the image height is 100 to 90 mm, that is, the slit width is about LO mm.
The good image area has been expanded. Further, by using the chromatic aberration correcting lens, it becomes possible to correct the chromatic aberration caused by the aspherical lens and expand the good image area of the corrected image height.

Next, an example in which the reflective optical system according to the present invention is applied to a semiconductor printing apparatus will be explained with reference to FIGS. 16 and 17. FIG. 16 shows the optical arrangement of the printing device, in which 1 is an optical system for mask illumination, along the horizontal optical axis are a spherical mirror 2, a light source 3 consisting of an arcuate mercury lamp, a lens 4, and a filter 5.45.
A degree mirror 6 and a lens 7 are arranged. Note that the filter 5 removes light that is photosensitive to the wafer, and is inserted into the illumination optical path during mask-wafer alignment. The mask illumination optical system 1 illuminates the mask in an arc or a semi-arc, thereby limiting the imaging area of the reflective optical system to an arc or a semi-arc. Reference numeral 8 denotes a mask placed on the upper horizontal plane, and this mask 8 is held by a known mask holder (not shown). A reflective optical system 1O according to the present invention is arranged below this mask 8 to form an image of the mask 8 on a wafer 9.

Note that the object side S1 is symmetrical about the optical axis O of the aspherical lens L.
and the image plane S2 side are separated, unlike the previous embodiment,
The light beams are deflected and used by mirrors 11 and 12, respectively. The wafer 9 is held by a known wafer holder, and the wafer holder is
, Y, and θ directions.

A microscope optical system 13 is inserted as an illumination optical system between the mask 8 and the mask 8 during alignment, and it is determined whether the mask 8 and the wafer 9 have a predetermined positional relationship. If the mask 8 and wafer 9 are not in a predetermined positional relationship, the wafer 9 is adjusted and moved relative to the mask 8 using the X, Y, and θ adjustment members of the wafer holder described above to bring them into a predetermined relationship.

Next, FIG. 17 showing the external appearance of this printing apparatus will be explained. In FIG. 17, 20 is a lamp house in which the illumination optical system l shown in FIG. 11 is built. 21 is a unit in which the alignment microscope optical system 13 is arranged, and this unit 21 is supported so as to be movable back and forth.

22 is a mask support, and 23 is a wafer support. These supports 22 and 23 are connected by a coupling member 24 so that they can move together.

Here, the supports 22 and 23 move together, but the wafer 9 can move minutely relative to the supports 23.

25 is an arm fixed to the coupling member 24, and this arm 25 is supported by a guide 26. Then, by the horizontal movement mechanism included in the guide 26, the supports 22, 23 are moved together horizontally and linearly.

27 is a tube that houses the reflective imaging optical system; 28 is a base; 29
is a turntable, and 30 is an auto feeder. The auto feeder 30 automatically feeds the wafer 9 onto the wafer support 23 via the turntable 29.

Next, the operation of this apparatus will be explained. First, the mutual positional relationship between the mask 8 and the wafer 9 is aligned. During this alignment, the aforementioned filter is inserted into the illumination optical system l, and a semi-arc shaped light source image is formed on the mask 8 by the lens 4.7 using non-photosensitive light. At this time, the microscope optical system 13 is also inserted between the lens 7 and the mask 8. This microscope optical system 13 allows the mask 8
, the alignment marks on the wafer 9 are observed, and both alignment marks are adjusted by operating the wafer support 23. After the alignment of the mask 8 and wafer 9 is completed, the aforementioned filter and microscope optical system 13 are retracted from the optical path.

At the same time, the light source 3 is turned off or blocked by a shutter means (not shown), and then a photosensitive semi-arc shaped light source image is formed on the mask 8 by turning on the light TA3 or opening the shutter. At the same time, the arm 25 starts moving the guide 26 in the horizontal direction.

This horizontal movement causes an image of the entire mask 8 to be printed onto the wafer 9.

[Brief explanation of the drawing]

The drawings show an embodiment of the reflective optical system according to the present invention, and FIG. 1 is a configuration diagram of the first embodiment of the present invention, and FIGS. 2 and 3 are its astigmatism diagram, lateral aberration diagram, and diagram. Figure 4 is a configuration diagram of the second embodiment, Figures 5 and 6 are its astigmatism diagram, lateral aberration diagram, and Figure 7.
The figure is a configuration diagram of the third embodiment, FIGS. 8 and 9 are astigmatism diagrams and lateral aberration diagrams, and FIG. 10 is a configuration diagram of the fourth embodiment.
Figures 11 and 12 are the astigmatism diagram, lateral aberration diagram, and the first
Figures 3 and 14 are astigmatism diagrams and lateral aberration diagrams when an aspherical surface is not used for the convex mirror in the configuration of Figure 1. Figure 15 is an explanatory diagram of the aspherical amount ΔH, and Figures 16 and 17. 1 is a configuration diagram of a printing apparatus using a reflective optical system according to the present invention. Old code is concave mirror, M2 is convex mirror, Ll, L2, L3, L
4 is an aspherical lens, L5 is a chromatic aberration correction lens, h is a correction area, 02 is the center of the convex mirror, Δh is a good image area, S is a sagittal image surface, m is a meridional image surface, l is an illumination optical system, 8 9 is a mask, 9 is a wafer, 10 is a reflective optical system, 13
' is the microscope optical system. Patent applicant: Canon Co., Ltd. Drawing Figure 1 - (J, 20 0.20-0.20 020-020
0.20° and 12 Figure 3 CG) Figure 3 (b) (C) (d) Figure 3 (e) (, f) Figure 5 6th (Q) (b) (c) Figure 6 (d) (e). (f) Figure 7 (a) (b) (c) -0,200,20-0,200,20-0,2002
0 Fig. 8 (d) (e) Fig. 9 (O) Fig. 9 (b) (C) (d) Fig. 9 (e) @ Fig. 10 Fig. 12 - λ = 365 mm Day person = 290 mm (O ), -, =435.8 mm Fig. 12 (b) (C) (d) Fig. 12 (, e) (f) -〇 U0.2U Fig. 14 Fig. 15 ((1) Fig. 16 99 Procedural amendment (voluntary) - March 26, 1980 1. Indication of the case 1982 Patent Application No. 24613 2. Name of the invention Reflective optical system 3. Person making the amendment Relationship to the case Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (10
0) Canon Co., Ltd. Representative Ryu Kaku Sanbu 4, Agent Address: C-104 Umejima High Town, 2-17-3 Umejima, Adachi-ku, Tokyo 121 5, Detailed description of the invention and drawings in the specification subject to amendment (1) "Air" on page 17, line 9 of the specification is corrected to "mirror." (2) Correct “mirror” in the 11th line of the same page to “air”. (3) Correct “E l, t'z J to r” in the 15th line of the same page.
Eh” J. (4) Figure 16 of the drawing is amended to reflect that the attached copy has not been distributed.

Claims (1)

[Scope of Claims] 1. An optical means having a first optical member and a second optical member is disposed in front of the reflective surface side of the concave mirror, with the reflective surfaces of a concave mirror and a convex mirror facing each other, and the optical means A subject is placed on the opposite side of the concave mirror, and the light beam from the subject passes through the first optical member, is reflected in the order of the concave mirror, the convex mirror, and the concave mirror, and is reflected on the second optical member. A reflective optical system that forms an image after passing through the reflective optical system, in which light rays emitted from an area outside the optical axis of the reflective optical system of the subject substantially parallel to the optical axis pass through the first optical member and form an image on the concave mirror. After being reflected by the concave mirror, the light beam is incident near the intersection of the convex mirror and the optical axis, or the light beam reflected from the intersection of the convex mirror and the optical axis is reflected by the concave mirror and passes through the second optical member. The present invention is characterized in that at least one of the first optical member or the second optical member and the convex mirror are provided with an aspheric surface so that the light is emitted substantially parallel to the optical axis. Reflective optical system. 2. The reflective optical system according to claim 1, wherein each of the first optical member and the second optical member is provided with at least one aspherical surface. 3. The reflective optical system according to claim 1, wherein the first optical member and the second optical member each have one aspherical surface. 4. The reflective optical system according to claim 3, wherein the aspheric surfaces of the first optical member and the second optical member have the same shape and are arranged symmetrically with respect to the optical axis. 5. Both the aspherical surface formed on at least one of the first optical member or the second optical member and the aspherical surface of the convex mirror have a shape in which a negative refractive power component increases as the distance from the optical axis increases. A reflective optical system according to claim 1. 8. The reflective optical system according to claim 4, wherein the first optical member and the second optical member are constituted by the same aspherical lens. 7. 2. The reflective optical system according to claim 1, wherein the region outside the optical axis has a semi-arc shape. 8. The aspherical surfaces of the first optical member and the second optical member each have a shape in which a negative refractive power component increases as the distance from the optical axis increases. Reflective optical system as described. 8. A patent claim that satisfies the following conditions: 60 x ν, < 100 60 x ν2 x 100, where the Abbe numbers of the glasses of the first optical member and the second optical member are ν1 and ν2, respectively. The reflective optical system according to item 3. 10. The height of the subject from the optical axis is Hl and H2.
The direction in which the aspheric amount from the reference spherical surface of the aspheric surface applied to the first optical member or the second optical member increases the negative refractive power is indicated by a positive sign. When the sum of the aspherical surface amounts at the height old and the height H2 from the optical axis are respectively ΔRHI and ΔRH2, 1/104≦1 (ΔRH2−ΔRHI)/Δh
The reflective optical system according to claim 1, which satisfies the condition: 1≦1/10. 11. The first optical member is provided with an aspherical surface, the radius of curvature of the lens surface to which the aspherical surface is provided is R, and - the object is placed within an area Ah surrounded by a height 1 and a height H2 from the optical axis. , and the aspherical amount of the aspherical surface from the reference spherical surface at the height old and the height H2 from the optical axis is respectively ΔRHI
, ΔRH2, IRI>1000 1/103<l(ΔRH2-ΔRH1)/Δh1<l/
10. A reflective optical system according to claim 1, which satisfies the following conditions. 12. Claim 12, wherein the second optical member has the same aspherical shape as the first optical member.
Reflective optical system as described in Section. 13. The first optical member is provided with an aspherical surface, the radius of curvature of the lens surface to which the aspherical surface is provided is R, and the subject is placed within an area Ah surrounded by a height 1 and a height H2 from the optical axis. , and the aspherical amount of the aspherical surface from the reference spherical surface at the height old and the height H2 from the optical axis is respectively ΔRHI
, ΔRH2, IRI<200 1/104< + (ΔR)+2−ΔRHI)/Δh1
The reflective optical system according to claim 1, which satisfies the conditional expression <l/103. 14. Claim 14, wherein the second optical member has the same aspherical shape as the first optical member.
Reflective optical system as described in Section. 15. The shape of the aspherical surface of the convex mirror is configured such that the amount of aspherical surface from the reference spherical surface increases as the distance from the optical axis increases within the effective surface, and then decreases thereafter. Reflective optics. 18. Both the first optical member and the second optical member have a meniscus-shaped lens portion with a convex surface facing the concave mirror side, and the shape of the four-sided aspherical surface has a large weight within the effective surface. 2. The reflective optical system according to claim 1, wherein the negative refractive power component increases with increasing distance from the optical axis with respect to the q-sphere surface. 17. When the effective diameter of the convex mirror is D, and the aspheric amount of the convex mirror from the reference sphere at a height of 70% of the effective radius of the convex mirror from the optical axis is ΔX, 1/109<JXlo, The reflective optical system according to claim 1 or 12, which satisfies the conditional expression <1/104. 18. The reflective optical system according to claim 1, wherein each of the first optical member and the second optical member constitutes a plurality of lenses. 18. The reflective optical system according to claim 18, wherein the plurality of lenses are made of the same glass.