Lithographic apparatus and method

Patent metadata

Field	Value
Publication number	US-10996567-B2
Application number	US-201816622250-A
Country	US
Kind code	B2
Filing date	May 31, 2018
Priority date	Jun 14, 2017
Publication date	May 4, 2021
Grant date	May 4, 2021

Abstract

A method for quantifying the effect of pupil function variations on a lithographic effect within a lithographic apparatus is disclosed. The method comprises: determining a discrete, two-dimensional sensitivity map in a pupil plane of the lithographic apparatus, wherein the lithographic effect is given by the inner product of said sensitivity map with a discrete, two-dimensional pupil function variation map of a radiation beam in the pupil plane. The pupil plane of a lithographic apparatus generally refers to the exit pupil of a projection system of the lithographic apparatus. Pupil function variations may comprise: relative phase variations within the pupil plane and/or relative intensity variations within the pupil plane.

First claim

The invention claimed is:

1. A method comprising:
determining a discrete, two-dimensional sensitivity map in a pupil plane of a lithographic apparatus, wherein a lithographic effect within the lithographic apparatus is given by an inner product of the sensitivity map with a discrete, two-dimensional pupil function variation map of a radiation beam in the pupil plane, and wherein the determining the sensitivity map in the pupil plane comprises:
determining a plurality of pixels comprising a pixel of the sensitivity map in the pupil plane, wherein determining the pixel of the sensitivity map in the pupil plane comprises:
determining an image that results from a pixel of the pupil function variation map corresponding to the pixel of the sensitivity map in the pupil plane having a non-nominal value and all other pixels of the pupil function variation map having nominal values;
determining the lithographic effect from the determined image; and
determining the pixel of the sensitivity map in the pupil plane based on the determined lithographic effect and the non-nominal value.

2. The method of claim 1 , wherein prior to the determination of the plurality of pixels, the method further comprises:
determining nominal partial images that result from pixels of the of the pupil function variation map having nominal values, wherein an image with no pupil function variations is given by a sum of the nominal partial images; and
storing the nominal partial images for use during determination of the plurality of pixels.

3. The method of claim 2 , further comprising:
determining a total image with no pupil function variations based on the nominal partial images; and
storing the total image prior to determination of the plurality of pixels.

4. The method of claim 2 , wherein:
the determining the pixel of the pupil function variation map further comprises determining non-nominal partial images that result from the pixel of the pupil function variation map having the non-nominal value and all other pixels of the pupil function variation map having nominal values; and
the determining the image that results from the one pixel of the pupil function variation map having the non-nominal value and all other pixels of the pupil function variation map having nominal values is based on a sum of the non-nominal partial images the partial images that result from the pixels of the pupil plane function variation map having nominal values.

5. The method of claim 4 , wherein the determining the image that results from the pixel of the pupil function variation map having the non-nominal value and all other pixels of the pupil function variation map having nominal values comprises:
subtracting the nominal partial images from a stored total image; and
adding the non-nominal partial images to the stored total image.

6. The method of claim 1 , wherein the sensitivity map is determined for a portion of the pupil plane which contributes to an image formed by the lithographic apparatus.

7. The method of claim 1 , wherein the sensitivity map in a first portion of the pupil plane is determined and the sensitivity map in a second portion of the pupil plane is determined from the sensitivity map in the first portion of the pupil plane.

8. A method comprising:
selecting one or more parameters of a lithographic process in dependence on a sensitivity map determined by:
determining a discrete, two-dimensional sensitivity map in a pupil plane of a lithographic apparatus, wherein a lithographic effect within the lithographic apparatus is given by an inner product of the sensitivity map with a discrete, two-dimensional pupil function variation map of a radiation beam in the pupil plane, and wherein the determining the sensitivity map in the pupil plane comprises:
determining a plurality of pixels, the plurality of pixels comprising a pixel of the sensitivity map in the pupil plane, wherein determining the pixel of the sensitivity map in the pupil plane comprises:
determining an image that results from a pixel of the pupil function variation map corresponding to the pixel of the sensitivity map in the pupil plane having a non-nominal value and all other pixels of the pupil function variation map having nominal values;
determining the lithographic effect from the determined image; and
determining the pixel of the sensitivity map in the pupil plane based on the determined lithographic effect and the non-nominal value.

9. The method of claim 8 , wherein the one or more parameters of the lithographic process comprises an illumination mode.

10. The method of claim 9 , wherein a rotationally symmetric illumination mode is selected, such that an intensity of radiation in an illuminator pupil plane is dependent on a radial coordinate.

11. The method of claim 8 , wherein the one or more parameters of the lithographic process comprises a reticle pattern.

12. The method of claim 8 , wherein the method uses a non-linear least squares procedure which involves a minimization of a merit function from a starting condition, the merit function having a set of tunable parameters.

13. The method of claim 8 , wherein the one or more parameters of the lithographic process are selected such that, for a selected lithographic effect, the sensitivity map is substantially sensitive to only one or more Zernike contributions to be measured.

14. A method comprising:
forming an image of a patterning device on at least one target region of a resist covered substrate;
processing the substrate;
inspecting the image formed on the at least one target region; and
determining one or more aberrations based on the inspecting,
wherein the image of the patterning device is formed using one or more parameters of a lithographic process selected by:
determining a discrete, two-dimensional sensitivity map in a pupil plane of a lithographic apparatus, wherein a lithographic effect within the lithographic apparatus is given by an inner product of the sensitivity map with a discrete, two-dimensional pupil function variation map of a radiation beam in the pupil plane, and wherein the determining the sensitivity map in the pupil plane comprises:
determining a plurality of pixels, the plurality of pixels comprising a pixel of the sensitivity map in the pupil plane, wherein determining the pixel of the sensitivity map in the pupil plane comprises:
determining an image that results from a pixel of the pupil function variation map corresponding to the pixel of the sensitivity map in the pupil plane having a non-nominal value and all other pixels of the pupil function variation map having nominal values;
determining the lithographic effect from the determined image; and
determining the pixel of the sensitivity map in the pupil plane based on the determined lithographic effect and the non-nominal value.

15. The method of claim 14 , further comprising correcting for the one or more aberrations.

16. A lithographic apparatus configured to carry out a method for quantifying an effect of pupil function variations on a lithographic effect within a lithographic apparatus, the lithographic apparatus comprising:
an illumination system configured to illuminate a pattern of a patterning device; and
a projection system configured to project an image of the patterning device onto a substrate, wherein:
the lithographic apparatus is further configured to determine a discrete, two-dimensional sensitivity map in a pupil plane,
a lithographic effect within the lithographic apparatus is given by an inner product of the sensitivity map with a discrete, two-dimensional pupil functio

Assignees

• Asml Netherlands Bv

Inventors

• Baselmans Johannes Jacobus Matheus
• Smeets Bart
• Toma Cristina Ioana

Classifications

• G03F7/705

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title

• G03F7/706 Primary

  Aberration measurement · CPC title

• G03F7/70491 Primary

  Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes · CPC title