Exposure method and storage medium

• US 9,268,239 B2
• Filed: 09/02/2011
• Issued: 02/23/2016
• Est. Priority Date: 09/28/2010
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Gyoda, Yuichi, Tsujita, Kouichirou
• Primary Examiner(s): Kim, Peter B
• Application Number:
  US13/224,488
• Publication Number:
  US 20120075614A1
• Time in Patent Office: 1,635 Days
• Field of Search: 355/77, 355/53, 355/67
• US Class Current: 1/1
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G03F 7/706 Aberration measurement

Abstract

The present invention provides an exposure method including the steps of generating a plurality of element light sources formed on a pupil plane of an illumination optical system, setting a plurality of aberration states which are expected to exist in a projection optical system, calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, an optical image of a pattern of a mask, which is formed in an evaluation area when one aberration state among the plurality of aberration states is produced in the projection optical system, and the pattern of the mask is illuminated with one element light source among the plurality of element light sources, determining, based on the calculated optical images, as a light intensity distribution to be formed on the pupil plane, a light source obtained by combining the plurality of element light sources applied with weights.

Claims

1. A method of determining a light intensity distribution to be formed on a pupil plane of an illumination optical system that illuminates a mask of an exposure apparatus including the illumination optical system, and a projection optical system that projects a pattern of the mask onto a substrate, and setting the determined light intensity distribution to the illumination optical system of the exposure apparatus, the method comprising:

a pattern setting step of setting a pattern of a mask to be placed on an object plane of the projection optical system;

an evaluation area setting step of setting an evaluation area used to evaluate an optical image of the pattern of the mask set in the pattern setting step, which is formed on the image plane of the projection optical system;

a generating step of generating a plurality of element light sources formed on the pupil plane of the illumination optical system;

an aberration state setting step of setting a plurality of different aberration states that are expected to exist in the projection optical system;

a calculating step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, the optical image of the pattern of the mask, which is formed in the evaluation area set in the evaluation area setting step when one aberration state selected from the plurality of aberration states set in the aberration state setting step is produced in the projection optical system, and the pattern of the mask is illuminated with one element light source selected from the plurality of element light sources generated in the generating step; and

a determining step of determining, based on the optical images calculated in the calculating step, a weight to be applied to each of the plurality of element light sources so that an edge position, in the evaluation area, of each of the optical images of the pattern of the mask comes close to a target edge position, and determining, as the light intensity distribution to be formed on the pupil plane of the illumination optical system, a light source obtained by combining the plurality of element light sources applied with the weights,

wherein the pattern setting step, the evaluation area setting step, the generating step, the aberration state setting step, the calculating step, and the determination step are performed by a computer.

2. The method according to claim 1, further comprising:

a defocus plane setting step of setting a plurality of defocus planes defocused from the image plane of the projection optical system,

wherein, in the calculating step, the optical image of the pattern of the mask, which is formed at a position corresponding to the evaluation area set in the evaluation area setting step, is calculated for each of the plurality of defocus planes as well, and

wherein, in the determining step, based on the optical image calculated for each of the plurality of defocus planes as well, a weight to be applied to each of the plurality of element light sources is determined so that an edge position, in the evaluation area, of each of the optical images of the pattern of the mask comes close to a target edge position, and determining, as a light intensity distribution to be formed on the pupil plane of the illumination optical system, a light source obtained by combining the plurality of element light sources applied with the weights.

3. The method according to claim 1, wherein:

the generating step includes generating element light sources for intensity evaluation, which are obtained by proportionally multiplying intensities of the plurality of element light sources by a given factor,

in the calculating step, the optical image of the pattern of the mask, which is formed at a position corresponding to the evaluation area set in the evaluation area setting step, is calculated for each of the element light sources for intensity evaluation as well, and

in the determining step, based on the optical image calculated for each of the element light sources for intensity evaluation as well, a weight to be applied to each of the plurality of element light sources is determined so that an edge position, in the evaluation area, of each of the optical images of the pattern of the mask comes close to a target edge position, and determining, as a light intensity distribution to be formed on the pupil plane of the illumination optical system, a light source obtained by combining the plurality of element light sources applied with the weights.

4. The method according to claim 1, wherein, in the determining step, mathematical programming is used to determine a light intensity distribution to be formed on the pupil plane of the illumination optical system so that an edge position, in the evaluation area, of each of the optical images of the pattern of the mask comes close to a target edge position.

5. The method according to claim 1, wherein, in the aberration state setting step, each of the plurality of aberration states is set so as to include at least a coma aberration.

6. The method according to claim 1, wherein the pattern of the mask includes a pattern of a mask used for an ion implantation process.

7. A method of determining a pattern of a mask used in an exposure apparatus including an illumination optical system that illuminates the mask, and a projection optical system that projects the pattern of the mask onto a substrate, and a light intensity distribution to be formed on a pupil plane of the illumination optical system, setting the mask having the determined pattern in the exposure apparatus, and setting the determined light intensity distribution to the illumination optical system of the exposure apparatus, the method comprising:

a pattern setting step of setting a temporary pattern of a mask to be placed on an object plane of the projection optical system;

an evaluation area setting step of setting an evaluation area used to evaluate an optical image of the temporary pattern of the mask set in the pattern setting step, which is formed on the image plane of the projection optical system;

a generating step of generating a plurality of element light sources formed on the pupil plane of the illumination optical system;

an aberration state setting step of setting a plurality of different aberration states that are expected to exist in the projection optical system;

a calculating step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, the optical image of the temporary pattern of the mask, which is formed in the evaluation area set in the evaluation area setting step when one aberration state selected from the plurality of aberration states set in the aberration state setting step is produced in the projection optical system, and the temporary pattern of the mask is illuminated with one element light source selected from the plurality of element light sources generated in the generating step; and

a determining step of determining, based on the optical images calculated in the calculating step, a parameter used to define a shape of a pattern of the mask, and a weight to be applied to each of the plurality of element light sources so that an edge position, in the evaluation area, of each of the optical images of the temporary pattern of the mask comes close to a target edge position, and determining, as the pattern of the mask and the light intensity distribution to be formed on the pupil plane of the illumination optical system, a pattern defined by the determined parameter and a light source obtained by combining the plurality of element light sources applied with the weights, respectively,

wherein the pattern setting step, the evaluation area setting step, the generating step, the aberration state setting step, the calculating step, and the calculating step are performed by a computer.

8. A non-transitory computer-readable storage medium storing a program executable by a computer to execute a determination method of determining a light intensity distribution to be formed on a pupil plane of an illumination optical system that illuminates a mask of an exposure apparatus including the illumination optical system and a projection optical system that projects a pattern of the mask onto a substrate, and setting the determined light intensity distribution to the illumination optical system of the exposure apparatus, the method comprising:

a pattern setting step of setting a pattern of a mask to be placed on an object plane of the projection optical system;

an evaluation area setting step of setting an evaluation area used to evaluate an optical image of the pattern of the mask set in the pattern setting step, which is formed on the image plane of the projection optical system;

a generating step of generating a plurality of element light sources formed on the pupil plane of the illumination optical system;

an aberration state setting step of setting a plurality of different aberration states that are expected to exist in the projection optical system;

a calculating step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, the optical image of the pattern of the mask, which is formed in the evaluation area set in the evaluation area setting step when one aberration state selected from the plurality of aberration states set in the aberration state setting step is produced in the projection optical system, and the pattern of the mask is illuminated with one element light source selected from the plurality of element light sources generated in the generating step; and

a determining step of determining, based on the optical images calculated in the calculating step, a weight to be applied to each of the plurality of element light sources so that an edge position, in the evaluation area, of each of the optical images of the pattern of the mask comes close to a target edge position, and determining, as the light intensity distribution to be formed on the pupil plane of the illumination optical system, a light source obtained by combining the plurality of element light sources applied with the weights.

9. A non-transitory computer-readable storage medium storing a program executable by a computer to execute a determination method of determining a pattern of a mask used in an exposure apparatus including an illumination optical system that illuminates the mask, and a projection optical system that projects the pattern of the mask onto a substrate, and a light intensity distribution to be formed on a pupil plane of the illumination optical system setting the mask having the determined pattern in the exposure apparatus, and setting the determined light intensity distribution to the illumination optical system of the exposure apparatus, the method comprising:

a pattern setting step of setting a temporary pattern of a mask to be placed on an object plane of the projection optical system;

an evaluation area setting step of setting an evaluation area used to evaluate an optical image of the temporary pattern of the mask set in the pattern setting step, which is formed on the image plane of the projection optical system;

a generating step of generating a plurality of element light sources formed on the pupil plane of the illumination optical system;

an aberration state setting step of setting a plurality of different aberration states that are expected to exist in the projection optical system;

a calculating step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, the optical image of the temporary pattern of the mask, which is formed in the evaluation area set in the evaluation area setting step when one aberration state selected from the plurality of aberration states set in the aberration state setting step is produced in the projection optical system, and the temporary pattern of the mask is illuminated with one element light source selected from the plurality of element light sources generated in the generating step; and

a determining step of determining, based on the optical images calculated in the calculating step, a parameter used to define a shape of a pattern of the mask, and a weight to be applied to each of the plurality of element light sources so that an edge position, in the evaluation area, of each of the optical images of the temporary pattern of the mask comes close to a target edge position, and determining, as the pattern of the mask and the light intensity distribution to be formed on the pupil plane of the illumination optical system, a pattern defined by the determined parameter and a light source obtained by combining the plurality of element light sources applied with the weights, respectively.

10. An exposure method of exposing a substrate to light, the method comprising:

a light intensity distribution determining step of determining a light intensity distribution to be formed on a pupil plane of an illumination optical system that illuminates a mask;

an illuminating step of illuminating the mask with light emitted by the illumination optical system that forms the light intensity distribution determined in the light intensity distribution determining step; and

a projecting step of projecting an image of a pattern of the mask onto the substrate via a projection optical system,

wherein the light intensity distribution determining step includes;

a pattern setting step of setting a pattern of a mask to be placed on an object plane of the projection optical system;

an evaluation area setting step of setting an evaluation area used to evaluate an optical image of the pattern of the mask set in the pattern setting step, which is formed on the image plane of the projection optical system;

a generating step of generating a plurality of element light sources formed on the pupil plane of the illumination optical system;

an aberration state setting step of setting a plurality of different aberration states that are expected to exist in the projection optical system;

a calculating step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, the optical image of the pattern of the mask, which is formed in the evaluation area set in the evaluation area setting step when one aberration state selected from the plurality of aberration states set in the aberration state setting step is produced in the projection optical system, and the pattern of the mask is illuminated with one element light source selected from the plurality of element light sources generated in the generating step; and

a determining step of determining, based on the optical images calculated in the calculating step, a weight to be applied to each of the plurality of element light sources so that an edge position, in the evaluation area, of each of the optical images of the pattern of the mask comes close to a target edge position, and determining, as the light intensity distribution to be formed on the pupil plane of the illumination optical system, a light source obtained by combining the plurality of element light sources applied with the weights, and

wherein the light intensity determining step is performed by a computer.

11. An exposure method of exposing a substrate to light, the method comprising:

a pattern and light intensity distribution determining step of determining a pattern of a mask used in an exposure apparatus including an illumination optical system that illuminates the mask, and a light intensity distribution to be formed on a pupil plane of the illumination optical system;

an illuminating step of illuminating the pattern of the mask determined in the pattern and light intensity distribution determining step, with light emitted by the illumination optical system that forms the light intensity distribution determined in the pattern and light intensity distribution determining step; and

a projecting step of projecting an image of the pattern of the mask onto the substrate via a projection optical system, and

wherein the pattern and light intensity distribution determining step includes;

a pattern setting step of setting a temporary pattern of a mask to be placed on an object plane of the projection optical system;

an evaluation area setting step of setting an evaluation area used to evaluate an optical image of the temporary pattern of the mask set in the pattern setting step, which is formed on the image plane of the projection optical system;

a generating step of generating a plurality of element light sources formed on the pupil plane of the illumination optical system;

an aberration state setting step of setting a plurality of different aberration states that are expected to exist in the projection optical system;

a calculating step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, the optical image of the temporary pattern of the mask, which is formed in the evaluation area set in the evaluation area setting step when one aberration state selected from the plurality of aberration states set in the aberration state setting step is produced in the projection optical system, and the temporary pattern of the mask is illuminated with one element light source selected from the plurality of element light sources generated in the generating step; and

a determining step of determining, based on the optical images calculated in the calculating step, a parameter used to define a shape of a pattern of the mask, and a weight to be applied to each of the plurality of element light sources so that an edge position, in the evaluation area, of each of the optical images of the temporary pattern of the mask comes close to a target edge position, and determining, as the pattern of the mask and the light intensity distribution to be formed on the pupil plane of the illumination optical system, a pattern defined by the determined parameter and a light source obtained by combining the plurality of element light sources applied with the weights, respectively, and

wherein the pattern and light intensity distribution determining is performed by a computer.