Abstract: A method to reduce sensitivity of a level sensor, arranged to measure a height of a substrate, to variations of a property of an optical component in the level sensor includes directing a beam of radiation toward a diffractive element and directing the beam, via an optical system, to a first reflective element at a first angle of incidence. The beam has a first polarization and a second polarization that is perpendicular to the first polarization. The first reflective element reflects the beam toward a second reflective element at a second angle of incidence causing the beam to impinge on the substrate. The first and second angles of incidence are selected to reduce variations of a ratio of intensities of the first polarization to the second polarization of the beam imparted by a property of a layer of at least one of the first and second reflective elements.

Abstract: A method to reduce sensitivity of a level sensor, arranged to measure a height of a substrate, to variations of a property of an optical component in the level sensor includes directing a beam of radiation toward a diffractive element and directing the beam, via an optical system, to a first reflective element at a first angle of incidence. The beam has a first polarization and a second polarization that is perpendicular to the first polarization. The first reflective element reflects the beam toward a second reflective element at a second angle of incidence causing the beam to impinge on the substrate. The first and second angles of incidence are selected to reduce variations of a ratio of intensities of the first polarization to the second polarization of the beam imparted by a property of a layer of at least one of the first and second reflective elements.

Abstract: According to one embodiment, a prism system is provided. The prism system includes a polarizing beam splitter (PBS) surface. The PBS surface is configured to generate first and second sub-beams having corresponding first and second polarization information from a received beam, the second polarization information being different than the first polarization information. A first optical path of the first sub-beam within the prism system has substantially same length as a second optical path of the second sub-beam within the prism system. Additionally or alternatively, the first sub-beam achieves a predetermined polarization extinction ratio.

Abstract: An optical inspection apparatus, including: an optical metrology tool configured to measure structures, the optical metrology tool including: an electromagnetic (EM) radiation source configured to direct a beam of EM radiation along an EM radiation path; and an adaptive optical system disposed in a portion of the EM radiation path and configured to adjust a shape of a wave front of the beam of EM radiation, the adaptive optical system including: a first aspherical optical element; a second aspherical optical element adjacent the first aspherical optical element; and an actuator configured to cause relative movement between the first optical element and the second optical element in a direction different from a beam axis of the portion of the EM radiation path.

Abstract: According to one embodiment, a prism system is provided. The prism system includes a polarizing beam splitter (PBS) surface. The PBS surface is configured to generate first and second sub-beams having corresponding first and second polarization information from a received beam, the second polarization information being different than the first polarization information. A first optical path of the first sub-beam within the prism system has substantially same length as a second optical path of the second sub-beam within the prism system. Additionally or alternatively, the first sub-beam achieves a predetermined polarization extinction ratio.

Abstract: According to one embodiment, a prism system is provided. The prism system includes a polarizing beam splitter (PBS) surface. The PBS surface is configured to generate first and second sub-beams having corresponding first and second polarization information from a received beam, the second polarization information being different than the first polarization information. A first optical path of the first sub-beam within the prism system has substantially same length as a second optical path of the second sub-beam within the prism system. Additionally or alternatively, the first sub-beam achieves a predetermined polarization extinction ratio.

Abstract: An inspection apparatus includes an inspection optical system configured to a direct an inspection beam onto a surface of a substrate, the inspection optical system having an objective, a focus measurement optical system configured to receive a focus measurement beam, redirected by the substrate, from the objective, the focus measurement optical system having a movable reflective element configured to receive the focus measurement beam, and a control system configured to cause movement of the reflective element with a direction component along a beam path of the focus measurement beam and configured to determine whether the substrate surface is in the focus of the objective based on the focus measurement beam.

Abstract: A beam homogenizer for homogenizing a beam of radiation and an illumination system and metrology apparatus comprising such a beam homogenizer as provided. The beam homogenizer comprises a filter system having a controllable radial absorption profile and configured to output a filtered beam and an optical mixing element configured to homogenize the filtered beam. The filter system may be configured to homogenize the angular beam profile radially and said optical mixing element may be configured to homogenize the angular beam profile azimuthally.

Abstract: According to one embodiment, a prism system is provided. The prism system includes a polarizing beam splitter (PBS) surface. The PBS surface is configured to generate first and second sub-beams having corresponding first and second polarization information from a received beam, the second polarization information being different than the first polarization information. A first optical path of the first sub-beam within the prism system has substantially same length as a second optical path of the second sub-beam within the prism system. Additionally or alternatively, the first sub-beam achieves a predetermined polarization extinction ratio.

Abstract: An inspection apparatus including: a substrate holder configured to hold a substrate; an aperture device; and an optical system configured to direct a first measurement beam of radiation onto the substrate, the first measurement beam having a first intensity distribution, and configured to direct a second focusing beam of radiation onto the substrate at a same time as the first measurement beam is directed on the substrate, the second focusing beam having a second intensity distribution, wherein at least part of the second intensity distribution is spatially separated from the first intensity distribution at least at the substrate and/or the aperture device.

Abstract: An inspection apparatus includes an inspection optical system configured to a direct an inspection beam onto a surface of a substrate, the inspection optical system having an objective, a focus measurement optical system configured to receive a focus measurement beam, redirected by the substrate, from the objective, the focus measurement optical system having a movable reflective element configured to receive the focus measurement beam, and a control system configured to cause movement of the reflective element with a direction component along a beam path of the focus measurement beam and configured to determine whether the substrate surface is in the focus of the objective based on the focus measurement beam.

Abstract: An inspection apparatus may determine precise OV measurements of a target on a substrate using an optical pupil symmetrizer to reduce the inspection apparatus's sensitivity to asymmetry and non-uniformity of the illumination beam in the pupil plane. The inspection apparatus includes an illumination system that forms a symmetrical illumination pupil by (1) splitting an illumination beam into sub-beams, (2) directing the sub-beams along different optical branches, (3) inverting or rotating at least one of the sub-beams in two dimensions, and recombining the sub-beams along the illumination path to symmetrize the intensity distribution. The illumination system is further configured such that the first and second sub-beams have an optical path difference that is greater than a temporal coherence length of the at least one beam and less than a depth of focus in the pupil plane of the objective optical system.

Abstract: An optical inspection apparatus, including: an optical metrology tool configured to measure structures, the optical metrology tool including: an electromagnetic (EM) radiation source configured to direct a beam of EM radiation along an EM radiation path; and an adaptive optical system disposed in a portion of the EM radiation path and configured to adjust a shape of a wave front of the beam of EM radiation, the adaptive optical system including: a first aspherical optical element; a second aspherical optical element adjacent the first aspherical optical element; and an actuator configured to cause relative movement between the first optical element and the second optical element in a direction different from a beam axis of the portion of the EM radiation path.

Abstract: A beam homogenizer for homogenizing a beam of radiation and an illumination system and metrology apparatus comprising such a beam homogenizer as provided. The beam homogenizer comprises a filter system having a controllable radial absorption profile and configured to output a filtered beam and an optical mixing element configured to homogenize the filtered beam. The filter system may be configured to homogenize the angular beam profile radially and said optical mixing element may be configured to homogenize the angular beam profile azimuthally.

Abstract: An inspection apparatus including: a substrate holder configured to hold a substrate; an aperture device; and an optical system configured to direct a first measurement beam of radiation onto the substrate, the first measurement beam having a first intensity distribution, and configured to direct a second focusing beam of radiation onto the substrate at a same time as the first measurement beam is directed on the substrate, the second focusing beam having a second intensity distribution, wherein at least part of the second intensity distribution is spatially separated from the first intensity distribution at least at the substrate and/or the aperture device.

Abstract: An inspection apparatus may determine precise OV measurements of a target on a substrate using an optical pupil symmetrizer to reduce the inspection apparatus's sensitivity to asymmetry and non-uniformity of the illumination beam in the pupil plane. The inspection apparatus includes an illumination system that forms a symmetrical illumination pupil by (1) splitting an illumination beam into sub-beams, (2) directing the sub-beams along different optical branches, (3) inverting or rotating at least one of the sub-beams in two dimensions, and recombining the sub-beams along the illumination path to symmetrize the intensity distribution. The illumination system is further configured such that the first and second sub-beams have an optical path difference that is greater than a temporal coherence length of the at least one light source and less than a depth of focus in the pupil plane of the objective optical system.

Abstract: A system and method are used to direct a radiation beam to illuminate non-perpendicularly a patterning array of individually controllable elements used for patterning the radiation beam. The individually controllable elements can change a telecentricity of the radiation beam. Projection of the radiation beam onto the individually controllable elements can be by a concave mirror or use a folding mirror placed in an object field of the individually controllable elements. Alternatively, the individually controllable elements can change the optical axis of the radiation beam.

Abstract: An off-axis catadioptric projection optical systems for use in lithography tools for processing modulated light used to form an image on a substrate is provided. The optical system includes an off-axis mirror segment, a fold mirror, a relay, an aperture stop and a refractive lens group. Modulated light is transmitted through the system to form an image on a substrate. The projection system includes an off-axis mirror segment, an aperture stop and a refractive lens group. Alternatively, the projection system includes an off-axis mirror segment, a negative refractive lens group, a concave mirror, a relay, an aperture stop, and a refractive lens group.

Abstract: The present invention is directed to off-axis catadioptric projection optical systems for use in lithography tools for processing modulated light used to form an image on a substrate, such as a semiconductor wafer or flat panel display. In one embodiment the optical system includes an off-axis mirror segment, a fold mirror, a relay, an aperture stop and a refractive lens group. Modulated light is transmitted through the system to form an image on a substrate. In a second embodiment the projection system includes an off-axis mirror segment, an aperture stop and a refractive lens group. In a third embodiment the projection system includes an off-axis mirror segment, a negative refractive lens group, a concave mirror, a relay, an aperture stop, and a refractive lens group. A method to produce a device using a lithographic apparatus including a projection system with an off-axis mirror segment as the first element in a projection optics system is also provided.

Abstract: An off-axis catadioptric projection optical systems for use in lithography tools for processing modulated light used to form an image on a substrate is provided. In one embodiment the optical system includes an off-axis mirror segment, a fold mirror, a relay, an aperture stop and a refractive lens group. Modulated light is transmitted through the system to form an image on a substrate. In a second embodiment the projection system includes an off-axis mirror segment, an aperture stop and a refractive lens group. In a third embodiment the projection system includes an off-axis mirror segment, a negative refractive lens group, a concave mirror, a relay, an aperture stop, and a refractive lens group. A method to produce a device using a lithographic apparatus including a projection system with an off-axis mirror segment as the first element in a projection optics system is also provided.