Reflection-type photoetching projection objective

[0024] Specific embodiments of the present invention will be described in detail below with reference to the drawings.

[0025] The structure of the projection objective optical system of the present invention is as follows figure 2 As shown, after the mask surface 1 is irradiated by the illuminating light, the light passing through the mask is reflected by the plane mirror 2 and then enters the spherical mirror 3. The plane mirror 2 makes the chief rays of each object point reflect at 90 degrees. The concave spherical mirror 3 has a positive refractive power, so that the light falling on it can be partially converged and reflected. The light reflected from the spherical reflector 3 enters the spherical reflector 4, and the spherical reflector 4 has a negative refractive power, so that the reflected light can be incident on the spherical reflector 5 in a divergent form. After the light from each object point passes through the above-mentioned optical components, a pupil surface is formed on the spherical mirror 5. The spherical mirror 5 has a positive refractive power and reflects the divergent incident light in a convergent form. The reflected light reflected from the spherical mirror 5 enters the spherical mirror 4 again. The divergent light reflected by the spherical mirror 4 with negative refractive power, after being reflected by the spherical mirror 3, is incident on the plane mirror 6 in a convergent form. The plane mirror 6 makes the principal rays of each object point at 90 degrees. The reflection forms an image point on the image plane 7.

[0026] In essence, the objective lens structure provided by the present invention is a coaxial reflective objective lens structure, except for the plane reflector 2 and the plane reflector 6, the spherical reflector 3, the spherical reflector 4, and the spherical reflector 5 are all rotationally symmetrical about the optical axis 8. . If tracing to the image surface along the light propagation direction of the mask surface, the structure of the objective lens is symmetrical about the pupil surface (spherical mirror 5), which provides the objective lens with advantages such as no coma and small distortion.

[0027] The key point of the lithographic projection objective with the three-sided mirror structure proposed in the present invention is that it introduces an extra mirror to make the light reflection twice more than the traditional offner structure, which essentially makes The optical power distribution of the optical system has many possibilities, and the optical power of each reflector is reasonably allocated, so that the optical power of each reflector is weakened, and it is easy to correct field curvature and astigmatism.

[0028] The refractive power of the spherical mirror 3 is Ф1, the refractive power of the spherical mirror 4 is Ф2, and the refractive power of the spherical mirror 3 is Ф5. The following conditions should be met between them to obtain better image quality:

[0029] 2*Ф1+2*Ф2+2*Ф3 <1*e-6

[0030] -0.8 <-0.4

[0031] -1.7 <-1.2

[0032] The sum of the distance L1 between the mask surface 1 and the mirror 2 and the distance L2 between the mirror and the spherical mirror 3, that is, the object distance L. The larger the value, the better the image quality of the objective lens, but at the same time it will increase the diameter of the spherical mirror 3. Big.

[0033] The objective lens of the present invention adopts wide-band exposure, and the wide-wave band combined by g (435.83 nm) h (404.65 nm) i (365.01 nm) lines can report patterns with good image quality. The object side numerical aperture NA is 0.08.

[0034] The objective field of view of the objective lens of the present invention is a circular arc shape, such as image 3 As shown, the field of view length in the non-scanning direction is 500 mm, the sagittal height is 134 mm, the arc width is 4 mm, and the imaging magnification is positive 1 times.

[0035] The structure data of this embodiment is as follows:

[0036] surface radius thickness glass semi-aperture object infinity 884.31387 1 infinity 800 mirror 546.2946 2 -1696.77 -555.508 mirror 432.6765 3 -1126.94 574.47152 mirror 192.5238 STO -1676.11 -574.4715 mirror 138.4456 5 -1126.94 555.50805 mirror 192.5675 6 -1696.77 -800 mirror 432.737 7 infinity -884.3139 mirror 373.0039 image infinity

[0037] The RMS value of wave aberration of the present invention is as Figure 4 As shown, the maximum is 0.0477λ, and λ is the h-line wavelength (404.65nm).

[0038] The descriptions in this specification are only preferred specific embodiments of the present invention, and the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the present invention. All technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention should fall within the scope of the present invention.