Abstract: Methods of determining an optimal focus height are disclosed. In one arrangement, measurement data from a plurality of applications of the metrology process to a target are obtained. Each application of the metrology process includes illuminating the target with a radiation spot and detecting radiation redirected by the target. The applications of the metrology process include applications at different nominal focus heights. The measurement data includes, for each application of the metrology process, at least a component of a detected pupil representation of an optical characteristic of the redirected radiation in a pupil plane. The method includes determining an optimal focus height for the metrology process using the obtained measurement data.

Abstract: Disclosed is a method of optimizing within an inspection apparatus, the position and/or size (and therefore focus) of a measurement illumination spot relative to a target on a substrate. The method comprises detecting scattered radiation from at least the target resultant from illuminating the target, for different sizes and/or positions of said illumination spot relative to the target; and optimizing said position and/or size of the measurement illumination spot relative to the target based on a characteristic of the detected scattered radiation for the different sizes and/or positions of said illumination spot relative to the target.

Abstract: Methods of determining an optimal focus height are disclosed. In one arrangement, measurement data from a plurality of applications of the metrology process to a target are obtained. Each application of the metrology process includes illuminating the target with a radiation spot and detecting radiation redirected by the target. The applications of the metrology process include applications at different nominal focus heights. The measurement data includes, for each application of the metrology process, at least a component of a detected pupil representation of an optical characteristic of the redirected radiation in a pupil plane. The method includes determining an optimal focus height for the metrology process using the obtained measurement data.

Abstract: Disclosed is a method of optimizing within an inspection apparatus, the position and/or size (and therefore focus) of a measurement illumination spot relative to a target on a substrate. The method comprises detecting scattered radiation from at least the target resultant from illuminating the target, for different sizes and/or positions of said illumination spot relative to the target; and optimizing said position and/or size of the measurement illumination spot relative to the target based on a characteristic of the detected scattered radiation for the different sizes and/or positions of said illumination spot relative to the target.

Abstract: A scatterometer for measuring a property of a substrate includes a focus sensing arrangement including an arrangement (65) that directs a first beam of radiation onto a focusing arrangement, to be detected by a focus sensor arrangement (61). A focus controller (67) provides control signals representative of the relative positions of the focusing arrangement (15, 69) and the substrate (W), which are required to focus the first beam of radiation on the substrate. An actuator arrangement adjusts the position of the focusing arrangement dependent on the control signals. An irradiation arrangement directs a second beam of radiation onto the substrate using the focusing arrangement, a measurement detector (18) detecting the second radiation beam after reflection from the substrate. A focus offset arrangement adjusts the focus produced by the focusing arrangement to compensate for an offset between the focusing of the first beam of radiation and the second beam of radiation.

Abstract: A scatterometer for measuring a property of a substrate includes a focus sensing arrangement including an arrangement (65) that directs a first beam of radiation onto a focusing arrangement, to be detected by a focus sensor arrangement (61). A focus controller (67) provides control signals representative of the relative positions of the focusing arrangement (15, 69) and the substrate (W), which are required to focus the first beam of radiation on the substrate. An actuator arrangement adjusts the position of the focusing arrangement dependent on the control signals. An irradiation arrangement directs a second beam of radiation onto the substrate using the focusing arrangement, a measurement detector (18) detecting the second radiation beam after reflection from the substrate. A focus offset arrangement adjusts the focus produced by the focusing arrangement to compensate for an offset between the focusing of the first beam of radiation and the second beam of radiation.

Abstract: A focus sensor comprises a confocal sensor. Within the confocal sensor there are a plurality of aperture plates positioned in front of a plurality of detectors. Rather than a conventional pinhole aperture shape there is a central aperture surrounded by a plurality of outer aperture portions.

Abstract: A scatterometer has a focus sensor arranged to detect whether the target being measured is in a correct focal plane. A modulation is applied to a component of the focus sensor or the scatterometer such that a defocus as measured by the focus sensor varies according to a certain function. From knowledge of the modulation, the gain of the sensor can be calibrated.

Abstract: A method of exposing a substrate (e.g. in a lithographic apparatus comprising a substrate table to support a substrate) according to one embodiment of the invention includes performing first and a second height measurement of a part of at least one substrate with a first and second sensor, generating and storing an offset error map based on a difference between the measurements; generating and storing a height map of portions of the substrate (or another substrate that has had a similar processing as the part) by performing height measurements with the first sensor and correcting this height map by means of the offset error map; and exposing the substrate (or the other substrate).

Abstract: A scatterometer has a focus sensor arranged to detect whether the target being measured is in a correct focal plane. A modulation is applied to a component of the focus sensor or the scatterometer such that a defocus as measured by the focus sensor varies according to a certain function. From knowledge of the modulation, the gain of the sensor can be calibrated.