Calibration methods, calibration substrates, lithographic apparatus and device manufacturing methods

A method of calibrating an alignment system in a lithographic apparatus capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an optical system, the method comprising:

• providing a substrate having a pair of first reference markers on a first surface thereof;
• performing a first alignment to the pair of first reference markers using the optical system,
• performing a first exposure of a pair of second reference markers on a second surface of the substrate;
• performing a first rotation of the substrate by 180° about a first axis;
• performing a second alignment to the pair of second reference markers using the optical system;
• performing a second exposure of a pair of third reference markers on the first surface of the substrate;
• and
• measuring the relative positions of the first and third reference markers to calibrate the alignment system.

A method of calibrating a lithographic apparatus including an alignment system capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an optical system, the method comprising:

• providing a calibration substrate having first and second opposite surfaces and being transparent to the radiation of the alignment beam, the calibration substrate having a reference marker on a first surface thereof, the reference marker being detectable from both the first and second surfaces;
• performing a first alignment to the reference marker with the alignment beam directed onto the first surface;
• performing a second alignment to the reference marker with the alignment beam directed onto the second surface and propagating through the calibration substrate to the first surface, while a plane plate is interposed into the alignment beam so that a focal position of the alignment system is displaced to the position of the first marker, wherein the first and second alignments may be performed in any order;
• providing a substrate having a pair of first reference markers on a first surface thereof;
• performing a first alignment to the pair of first reference markers using the optical system,
• performing a first exposure of a pair of second reference markers on a second surface of the substrate;
• performing a first rotation of the substrate by 180° about a first axis;
• performing a second alignment to the pair of second reference markers using the optical system;
• performing a second exposure of a pair of third reference markers on the first surface of the substrate;
• and
• measuring the relative positions of the first and third reference markers to calibrate the alignment system.

A method of calibrating an alignment system in a lithographic apparatus capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an optical system, the method comprising:

• providing a substrate having a pair of first reference markers on a first surface thereof and a pair of second reference markers on a second surface thereof;
• performing an alignment to the first reference marks with the alignment beam directed onto the surface;
• performing an alignment to the second reference marks using the optical system;
• performing a first rotation of the substrate by 180° about a first axis;
• performing an alignment to the second reference marks with the alignment beam directed onto the surface, performing an alignment to the first reference marks using the optical system;
• and
• comparing the alignments, wherein the alignments may be performed in any order.

A method of calibrating a lithographic apparatus including an alignment system capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an optical system, the method comprising:

• providing a calibration substrate having first and second opposite surfaces and being transparent to the radiation of the alignment beam, the calibration substrate having a reference marker on a first surface thereof, the reference marker being detectable from both the first and second surfaces;
• performing a first alignment to the reference marker with the alignment beam directed onto the first surface;
• performing a second alignment to the reference marker with the alignment beam directed onto the second surface and propagating through the calibration substrate to the first surface, while a plane plate is interposed into the alignment beam so that a focal position of the alignment system is displaced to the position of the first marker, wherein the first and second alignments may be performed in any order;
• providing a substrate having a pair of first reference markers on a first surface thereof and a pair of second reference markers on a second surface thereof;
• performing an alignment to the first reference marks with the alignment beam directed onto the surface;
• performing an alignment to the second reference marks using the additional optical system;
• performing a first rotation of the substrate by 180° about a first axis;
• performing an alignment to the second reference marks with the alignment beam directed onto the surface, performing an alignment to the first reference marks using the system;
• and
• comparing the alignments, wherein the alignments may be performed in any order.

A method of calibrating a lithographic apparatus including an alignment system capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an optical system, the method comprising;

• providing a substrate having a pair of first reference markers on a first surface thereof and a pair of second reference markers on a second surface thereof;
• performing a first alignment to the pair of first reference markers using the optical system,
• performing a first exposure of the pair of second reference markers on the second surface of the substrate;
• performing a first rotation of the substrate by 180° about a first axis;
• performing a second alignment to the pair of second reference markers using the optical system;
• performing a second exposure of a pair of third reference markers on the first surface of the substrate;
• measuring the relative positions of the first and third reference markers to calibrate the alignment system;
• performing an alignment to the first reference marks with the alignment beam directed onto the surface;
• performing an alignment to the second reference marks using the optical system;
• performing a first rotation of the substrate by 180° about a first axis;
• performing an alignment to the second reference marks with the alignment beam directed onto the surface, performing an alignment to the first reference marks using the optical system;
• and
• comparing the alignments, wherein the alignments may be performed in any order.

A method of calibrating an alignment system in a lithographic apparatus capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an additional optical system, the method comprising:

• providing a calibration substrate having a first pair of rows of three or more reference markers on a first surface thereof, and a second pair of rows of three or more reference markers on a second surface thereof;
• performing an alignment to the first pair of rows of reference marks using the directly incident alignment radiation, and performing an alignment to the second pair of rows of reference marks using the optical system;
• performing a first rotation of the substrate by 180° about a first axis;
• performing an alignment to the second pair of rows of reference marks using the directly incident alignment radiation, and performing an alignment to the first pair of rows of reference marks using the additional optical system;
• and
• comparing the alignments, wherein the alignments may be performed in any order.

A method of calibrating a lithographic apparatus an alignment system in a capable of aligning to alignment markers on opposite sides of a substrate, the alignment system directing an alignment beam of radiation directly onto one side and directing the alignment beam onto the other side via an additional optical system, the method comprising:

• providing a calibration substrate having a first pair of rows of three or more reference markers on a first surface thereof, and a second pair of rows of three or more reference markers on a second surface thereof;
• performing an alignment to the first pair of rows of reference marks using the directly incident alignment radiation, and performing an alignment to the second pair of rows of reference marks using the optical system;
• performing a first rotation of the substrate by 180° about a first axis;
• performing an alignment to the second pair of rows of reference marks using the directly incident alignment radiation, and performing an alignment to the first pair of rows of reference marks using the additional optical system;
• comparing the alignments, wherein the alignments may be performed in any order;
• providing a substrate having a pair of first reference markers on a first surface thereof;
• performing a first alignment to the pair of first reference markers using the optical system;
• performing a first exposure of a pair of second reference markers on a second surface of the substrate;
• performing a first rotation of the substrate by 180° about a first axis;
• performing a second alignment to the pair of second reference markers using the optical system;
• performing a second exposure of a pair of third reference markers on the first surface of the substrate;
• and
• measuring the relative positions of the first and third reference markers to calibrate the alignment system.

A lithographic projection apparatus comprising:

• a radiation system constructed and arragned to supply a projection beam of radiation;
• a patterning device constructed and arranged to pattern the projection beam according to a desired pattern;
• a substrate table constructed and arranged to hold a substrate;
• a projection system constructed and arranged to image the patterned beam onto a target portion on a first side of the substrate;
• an alignment system employing an alignment beam of radiation to which the substrate is transparent constructed and arranged to align a reference marker on the support system or the patterning device to an alignment marker provided on a first surface of the substrate onto which the patterned beam is to be imaged;
• a plane plate selectively interposable into the path of the alignment beam such that the alignment beam is focused onto a second surface of the substrate opposite to the first surface.

A device manufacturing method, comprising:

• providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
• providing a projection beam of radiation using a radiation system;
• using a patterning device to endow the projection beam with a pattern in its cross-section;
• using an alignment system to align a reference marker on the support system or the patterning means with a first alignment marker provided on a first surface of the substrate onto which the patterned beam is to be imaged by illuminating the alignment marker with a beam of radiation to which the substrate is transparent;
• interposing a plane plate into the path of the alignment beam such that the alignment beam is focused onto a second surface of the substrate opposite to the first surface and aligning the reference marker with a second alignment marker provided on a second surface of the substrate opposite the first surface;
• and
• projecting the patterned beam of radiation onto a target area of the layer of radiation-sensitive material on a first side of the substrate.