Four-mirror extreme ultraviolet (EUV) lithography projection system

Patent · Sat Jan 01 04:00:00 EST 2000

OSTI ID:873351

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

---

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
• 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

/359/
aberrations
achieve
aspherical
asphericity
axis
catoptric
components
concave
concave mirror
convex
convex mirror
convex spherical
counter
curvatures
decentered
degree
diameter
directed
dominantly
elliptical
elliptical concave
euv
extreme
extreme ultraviolet
field
followed
forms
four-mirror
hence
hyperbolic
increase
light
light path
lithography
magnification
mirror
mirror forms
mirrors
off-axis
opposite
optical
optical axis
path
pattern
perfectly
positioned
projection
reflective
reflective reticle
relatively
reticle
shape
significant
size
slightly
spherical
spherical concave
spherical mirror
spherical shape
substantially
substrate
tilted
transfer
ultraviolet
uniform
uniform field
wafer
wafer substrate