LARGE FIELD PROJECTION OBJECTIVE FOR LITHOGRAPHY
A lithography projection objective ( 30 ) for focusing and imaging a pattern of a reticle onto a wafer including, from the reticle and along an optical axis: a first lens group G 31 having a positive refractive power; a second lens group G 32 having a positive refractive power; a third lens group G 33 having a positive refractive power; and a fourth lens group G 34 having a positive refractive power. These four lens groups form a 2× magnification design which has a partial field of view of not smaller than 100 mm; a wavelength band of I-line±5 nm can ensure a sufficient exposure light intensity. Moreover, the present invention also achieves, with a relatively simple structure, the demanded millimeter-level resolution as well as the correction of distortions, field curvatures, astigmatisms and chromatic aberrations in a large field.
1 . A lithography projection objective for focusing and imaging a pattern of a reticle onto a wafer comprising, from the reticle and along an optical axis:
a first lens group G 31 having a positive refractive power;
a second lens group G 32 having a positive refractive power;
a third lens group G 33 having a positive refractive power; and
a fourth lens group G 34 having a positive refractive power,
wherein the following formulae are satisfied:
1. 8<| f G32 /f G31|<5.4
0.57<| f G33 /f G34 |<0.97
0.19<| f G33 /f G32 |<0.5
where f G31 is a focal length of the first lens group G 31 , f G32 is a focal length of the second lens group G 32 , f G33 is a focal length of the third lens group G 33 , and f G34 is a focal length of the fourth lens group G 34 .
2 . The lithography projection objective according to claim 1 , wherein:
the first lens group G 31 comprises at least four lenses;
the second lens group G 32 comprises at least six lenses which includes at least two pairs of lenses each consisting of a positive lens and a negative lens adjacent to the positive lens;
the third lens group G 33 comprises at least four lenses and includes a sub-lens group G 33 - 1 n having a positive refractive power, the sub-lens group G 33 - 1 n including at least two adjacent lenses of the third lens group G 33 both of which have a positive refractive power;
the fourth lens group G 34 comprises at least six lenses and includes a sub-lens group G 34 - 1 n having a positive refractive power, the sub-lens group G 34 - 1 n including at least three directly successively arranged lenses of the fourth lens group G 34 all of which have a positive refractive power; and
the following formulae are satisfied:
1.03<| f el — max /f G31 |<1.95
0.34<| f G33-1n /f G33 |<0.87
0.21<| f G34-1n /f G34 |<0.47
where f el — max is a focal length of a lens of the first lens group G 31 which has a greatest refractive power in the first lens group G 31 , f G33-1n is a focal length of the sub-lens group G 33 - 1 n of the third lens group G 33 , and f G34-1n is a focal length of the sub-lens group G 34 - 1 n of the fourth lens group G 34 .
3 . The lithography projection objective according to claim 2 , wherein the second lens group G 32 includes at least a positive lens and a negative lens directly adjacent to the positive lens, and wherein the following formula is satisfied:
1.23< V G32-P /V G32-N <1.85
where V G32-P is an Abbe number of the positive lens of the second lens group G 32 , and V G32-N is an Abbe number of the negative lens of the second lens group G 32 that is directly adjacent to the positive lens.
4 . The lithography projection objective according to claim 2 , wherein the second lens group G 32 includes at least a positive lens and a negative lens directly adjacent to the positive lens, and wherein the following formula is satisfied:
1.59 <V G32-P /V G32-N <2.65
where V G32-P is an Abbe number of the positive lens of the second lens group G 32 , and V G32-N is an Abbe number of the negative lens of the second lens group G 32 that is directly adjacent to the positive lens.
5 . The lithography projection objective according to claim 1 , wherein among the two adjacent positive lenses of the sub-lens group G 33-1n of the third lens group G 33 , the one disposed downstream in a direction from the reticle to the wafer has a greater focal length, and wherein the focal lengths of the two adjacent positive lenses are both within a range of 0.75 to 1.
6 . The lithography projection objective according to claim 2 , wherein the projection objective is made of at least two groups of high refractive index mateirals and at least two groups of low refractive index mateirals.
7 . The lithography projection objective according to claim 6 , wherein:
the high refractive index mateirals are mateirals having a refractive index of higher than 1.55 at I-line, including a first material group whose materials have refractive indices which are higher than 1.55 at I-line and Abbe numbers which are higher than 45 and a second material group whose materials have refractive indices which are higher than 1.55 at I-line and Abbe numbers which are higher than 50;
the low refractive index mateirals are mateirals having a refractive index of lower than 1.55 at I-line, including a third material group whose materials have refractive indices which are lower than 1.55 at I-line and Abbe numbers which are lower than 55 and a fourth material group whose materials have a refractive indices which are lower than 1.55 at I-line and Abbe numbers which are higher than 60.
8 . The lithography projection objective according to claim 7 , wherein each of the first, second, third and fourth lens groups includes at least one lens made of a material of the first or second material group.
9 . The lithography projection objective according to claim 7 , wherein each of the first, second, and fourth lens groups includes at least one lens made of a material of the first material group.
10 . The lithography projection objective according to claim 9 , wherein both of a first lens of the first lens group G 31 and a last lens of the fourth lens group G 34 are made of a material of the first material group.
11 . The lithography projection objective according to claim 7 , wherein the third lens group includes at least one lens made of a material of the second material group.
12 . The lithography projection objective according to claim 7 , wherein:
the second lens group includes at least one pair of lenses which have convace surfaces facing each other;
the third lens group includes at least one meniscus lens which has a concanve surface facing an image plane; and
the fourth lens group includes at least one meniscus lens which has a concanve surface facing an object plane.