US 9,436,099 B2 · Lithographic focus and dose measurement using a 2-D target

Abstract

In order to determine whether an exposure apparatus is outputting the correct dose of radiation and its projection system is focusing the radiation correctly, a test pattern is used on a mask for printing a specific marker onto a substrate. This marker is then measured by an inspection apparatus, such as a scatterometer, to determine whether there are errors in focus and dose and other related properties. The test pattern is configured such that changes in focus and dose may be easily determined by measuring the properties of a pattern that is exposed using the mask. The test pattern may be a 2D pattern where physical or geometric properties, e.g., pitch, are different in each of the two dimensions. The test pattern may also be a one-dimensional pattern made up of an array of structures in one dimension, the structures being made up of at least one substructure, the substructures reacting differently to focus and dose and giving rise to an exposed pattern from which focus and dose may be determined.

Claims11

Dependent claims

A method comprising:

printing a marker on a substrate using an exposure apparatus and a mask, the mask including a pattern for creating the marker, wherein the marker comprises a two-dimensional array of structures formed by repeated exposure of the pattern, such that the structures along an x direction of the two-dimensional array are sensitive to dose variations, but are not sensitive to focus variations, and the structures along a y direction of the two-dimensional array are sensitive to both dose and focus variations;
and
measuring a property of the substrate that has been exposed by the exposure apparatus and the mask, the measuring comprising:
projecting a radiation beam onto the marker on the substrate;
detecting radiation reflected from the marker on the substrate;
and
determining, from the properties of the reflected radiation, at least one of the focus and the dose of the exposure apparatus.

4 more elements

A lithographic cell comprising:

a coater arranged to coat a substrate with a radiation sensitive layer;
an exposure apparatus configured to expose an image onto the radiation sensitive layer of the substrate coated by the coater;
a developer configured to develop the image exposed by the exposure apparatus;
and
an inspection apparatus configured to measure a property of a substrate on which a marker has been printed by the exposure apparatus using a mask containing a pattern, the pattern comprising a two-dimensional array of structures arranged such that the marker includes repeating structures formed by repeated exposure of the pattern, such that the structures along an x direction of the two-dimensional array are sensitive to dose variations, but are not sensitive to focus variations, and the structures along a y direction of the two-dimensional array are sensitive to both dose and focus variations, the inspection apparatus comprising,
a radiation source,
a projection system configured to direct radiation from the radiation source onto the marker,
a detector configured to detect radiation reflected from the marker, and
a processor configured to determine properties of the reflected radiation and, from the properties of the reflected radiation, determine at least one of focus and dose related properties of the exposure apparatus used to print the marker.

6 more elements

Dependencies are inferred from the claim text.

Lithographic focus and dose measurement using a 2-D target

Life of this patent

Lithographic focus and dose measurement using a 2-D target

Life of this patent

Abstract

Claims11