EXPOSURE METHOD AND STORAGE MEDIUM

• US 20120075614A1
• Filed: 09/02/2011
• Published: 03/29/2012
• 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
• Granted Patent: US 9,268,239 B2
• Time in Patent Office: Days
• US Class Current: 355/77
• 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. An exposure method of exposing a substrate to light using an illumination optical system which illuminates a mask, and a projection optical system which projects a pattern of the mask onto the substrate, the method comprising:

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

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

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

a fourth step of setting a plurality of different aberration states which are expected to exist in the projection optical system;

a fifth step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, an optical image of the pattern of the mask, which is formed in the evaluation area set in the second step when one aberration state selected from the plurality of aberration states set in the fourth 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 third step;

a sixth step of determining, based on the optical images calculated in the fifth step, a weight to be applied to each of the plurality of element light sources such 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, thereby 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;

a seventh step of illuminating the mask with light emitted by the illumination optical system which forms the light intensity distribution determined in the sixth step; and

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

wherein the first step to the six step are performed by a computer.

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

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

wherein

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

in the sixth 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 such 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, thereby 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 third step includes a step of 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 fifth step, an optical image of the pattern of the mask, which is formed at a position corresponding to the evaluation area set in the second step, is calculated for each of the element light sources for intensity evaluation as well, and

in the sixth 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 such 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, thereby 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 sixth step, mathematical programming is used to determine a light intensity distribution to be formed on the pupil plane of the illumination optical system such 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 fourth 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. An exposure method of exposing a substrate to light using an illumination optical system which illuminates a mask, and a projection optical system which projects a pattern of the mask onto the substrate, the method comprising:

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

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

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

a fourth step of setting a plurality of different aberration states which are expected to exist in the projection optical system;

a fifth step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, an optical image of the temporary pattern of the mask, which is formed in the evaluation area set in the second step when one aberration state selected from the plurality of aberration states set in the fourth 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 third step;

a sixth step of determining, based on the optical images calculated in the fifth 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 such 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, thereby determining, as the pattern of the mask, and a 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;

a seventh step of illuminating the mask, on which the determined pattern of the mask is formed, with light emitted by the illumination optical system which forms the light intensity distribution determined in the sixth step; and

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

wherein the first step to the sixth step are performed by a computer.

8. A computer-readable storage medium storing a program for causing 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 which illuminates a mask in an exposure apparatus including the illumination optical system and a projection optical system which projects a pattern of the mask onto a substrate,

the program causing the computer to execute:

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

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

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

a fourth step of setting a plurality of different aberration states which are expected to exist in the projection optical system;

a fifth step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, an optical image of the pattern of the mask, which is formed in the evaluation area set in the second step when one aberration state selected from the plurality of aberration states set in the fourth 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 third step; and

a sixth step of determining, based on the optical images calculated in the fifth step, a weight to be applied to each of the plurality of element light sources such 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, thereby 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 computer-readable storage medium storing a program for causing a computer to execute a determination method of determining a pattern of a mask used in an exposure apparatus including an illumination optical system which illuminates the mask, and a projection optical system which 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,

the program causing the computer to execute:

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

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

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

a fourth step of setting a plurality of different aberration states which are expected to exist in the projection optical system;

a fifth step of calculating, for each of all combinations of the plurality of aberration states and the plurality of element light sources, an optical image of the temporary pattern of the mask, which is formed in the evaluation area set in the second step when one aberration state selected from the plurality of aberration states set in the fourth 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 third step; and

a sixth step of determining, based on the optical images calculated in the fifth 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 such 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, thereby 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.