Four-mirror extreme ultraviolet (EUV) lithography projection system

Patent · Sat Jan 01 00:00:00 EST 2000

OSTI ID:873351

Cohen, Simon J ^[1]; Jeong, Hwan J ^[2]; Shafer, David R ^[3]

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1. Pleasonton, CA
2. Los Altos, CA
3. Fairfield, CT

The invention is directed to a four-mirror catoptric projection system for extreme ultraviolet (EUV) lithography to transfer a pattern from a reflective reticle to a wafer substrate. In order along the light path followed by light from the reticle to the wafer substrate, the system includes a dominantly hyperbolic convex mirror, a dominantly elliptical concave mirror, spherical convex mirror, and spherical concave mirror. The reticle and wafer substrate are positioned along the system's optical axis on opposite sides of the mirrors. The hyperbolic and elliptical mirrors are positioned on the same side of the system's optical axis as the reticle, and are relatively large in diameter as they are positioned on the high magnification side of the system. The hyperbolic and elliptical mirrors are relatively far off the optical axis and hence they have significant aspherical components in their curvatures. The convex spherical mirror is positioned on the optical axis, and has a substantially or perfectly spherical shape. The spherical concave mirror is positioned substantially on the opposite side of the optical axis from the hyperbolic and elliptical mirrors. Because it is positioned off-axis to a degree, the spherical concave mirror has some asphericity to counter aberrations. The spherical concave mirror forms a relatively large, uniform field on the wafer substrate. The mirrors can be tilted or decentered slightly to achieve further increase in the field size.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• DOE Contract Number: W-7405-ENG-48
• Assignee: Ultratech Stepper, Inc. (San Jose, CA); Regents of University of California (Oakland, CA)
• Patent Number(s): US 6142641
• OSTI ID: 873351
• Country of Publication: United States
• Language: English

Related Subjects

four-mirror
extreme
ultraviolet
euv
lithography
projection
directed
catoptric
transfer
pattern
reflective
reticle
wafer
substrate
light
path
followed
dominantly
hyperbolic
convex
mirror
elliptical
concave
spherical
positioned
optical
axis
opposite
mirrors
relatively
diameter
magnification
hence
significant
aspherical
components
curvatures
substantially
perfectly
shape
off-axis
degree
asphericity
counter
aberrations
forms
uniform
field
tilted
decentered
slightly
achieve
increase
size
wafer substrate
spherical concave
spherical shape
optical axis
extreme ultraviolet
concave mirror
spherical mirror
convex mirror
reflective reticle
uniform field
light path
mirror forms
convex spherical
elliptical concave
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