Lithographic apparatus and device manufacturing method
View Patent ↗A lithographic apparatus includes a support structure configured to hold a patterning device, the patterning device configured to pattern a beam of radiation according to a desired pattern, a substrate table configured to hold a substrate and a projection system configured to project the beam as patterned onto a target portion of the substrate. The lithographic apparatus further includes a polarization modifier disposed in a path of the beam. The polarization modifier comprises a material having a linear polarization.
1. A lithographic apparatus, comprising:
a support structure configured to hold a patterning device, the patterning device configured to pattern a beam of radiation;
a substrate table configured to hold a substrate;
a projection system configured to project a beam as patterned onto a target portion of the substrate; and
a linear birefringence material polarization modifier disposed in a path of the beam, wherein the modifier comprises a material having a radially and quadratically varying magnitude of linear birefringence so as to increase a depth of focus of a lithographic process projection.
2. The apparatus according to claim 1 , wherein the magnitude of birefringence of the material is larger at greater radial distances from a center of the modifier.
3. The apparatus according to claim 1 , wherein the magnitude of birefringence of the material is smaller at greater radial distances from a center of the modifier.
4. The apparatus according to claim 1 , wherein the polarization modifier is disposed in a pupil plane of the projection system or in a vicinity of the pupil plane.
5. The apparatus according to claim 1 , wherein the polarization modifier is disposed between the patterning device and the projection system.
6. A lithographic apparatus, comprising:
a support structure configured to hold a patterning device, the patterning device configured to pattern a beam of radiation;
a substrate table configured to hold a substrate;
a projection system configured to project a beam as patterned onto a target portion of the substrate; and
a linear birefringence material polarization modifier disposed in a path of the beam,
wherein the modifier comprises a material having a radially varying linear birefringence, and
wherein a variation of a refractive index of the material, Δn, as a function of pupil coordinates p and q is given by an equation:
Δ
n
=
exp
{
ⅈ
Δφ
0
p
2
+
q
2
NA
2
}
wherein i is the imaginary number, NA is a numerical aperture of the projection system, and Δφ 0 is a value of a retardance at a rim of an aperture of the projection system.
7. A lithographic apparatus, comprising:
a support structure configured to hold a patterning device, the patterning device configured to pattern a beam of radiation;
a substrate table configured to hold a substrate;
a projection system configured to project a beam as patterned onto a target portion of the substrate; and
a linear birefringence material polarization modifier disposed in a path of the beam, wherein the modifier comprises a material having a radially varying magnitude of linear birefringence so as to increase a depth of focus of a lithographic process projection,
wherein a variation of a refractive index of the material, Δn, as a function of pupil coordinates p and q is given by an equation:
Δ
n
=
exp
{
ⅈ
Δφ
0
p
2
+
q
2
NA
2
}
wherein i is the imaginary number, NA is a numerical aperture of the projection system, and Δφ 0 is a value of a retardance at a rim of an aperture of the projection system.