Electron beam irradiation method, electron beam irradiation apparatus, and computer readable non-transitory storage medium

1. An electron beam irradiation method comprising:

calculating a charge amount distribution in a case where a substrate is irradiated with an electron beam, by using an index indicating complexity of a shape boundary of a pattern to be formed on the substrate, wherein an area density U of a pattern and a perimeter distance W of a pattern per unit area are used as the index indicating complexity of the shape boundary of the pattern;

calculating a positional deviation amount of an irradiation pattern to be formed due to irradiation with the electron beam, by using the charge amount distribution having been calculated;

correcting an irradiation position by using the positional deviation amount having been calculated; and

applying an electron beam to the irradiation position having been corrected.

2. The method according to claim 1 , wherein the charge amount distribution is calculated using a function depending on the area density U of the pattern.

3. The method according to claim 1 , wherein the charge amount distribution is calculated by a model equation of a(U)·W/U+b(U){1−exp(−c·W/U)} which uses the area density U of the pattern, the perimeter distance W of the pattern per unit area, a function a(U) depending on the area density U of the pattern, a function b(U) depending on the area density U, where the function b(U) is different from the function a(U), and a coefficient c.

4. The method according to claim 1 , wherein the charge amount distribution is calculated using, in addition to the index indicating complexity, an exposure intensity distribution, a fogging electron amount distribution, and a charge decay amount along with passage of time.

5. An electron beam irradiation apparatus comprising:

a charge amount distribution calculation circuit programmed to calculate a charge amount distribution in a case where a substrate is irradiated with an electron beam, by using an index indicating complexity of a shape boundary of a pattern to be formed on the substrate, wherein an area density U of a pattern and a perimeter distance W of a pattern per unit area are used as the index indicating complexity of the shape boundary of the pattern;

a positional deviation amount calculation circuit programmed to calculate a positional deviation amount of an irradiation pattern to be formed due to irradiation by the electron beam, by using the charge amount distribution having been calculated;

a correction circuit programmed to correct an irradiation position by using the positional deviation amount having been calculated; and

an electron beam irradiation mechanism including an emission source which emits the electron beam and a deflector which deflects the electron beam to apply an electron beam to the irradiation position having been corrected.

6. The apparatus according to claim 5 , wherein the charge amount distribution calculation circuitry calculates the charge amount distribution by using a function depending on the area density U of the pattern.

7. The apparatus according to claim 5 , wherein the charge amount distribution calculation circuitry calculates the charge amount distribution by a model equation of a(U)·W/U+b(U){1−exp(−c·W/U)} which uses the area density U of the pattern, the perimeter distance W of the pattern per unit area, a function a(U) depending on the area density U of the pattern, a function b(U) depending on the area density U, where the function b(U) is different from the function a(U), and a coefficient c.

8. A non-transitory computer readable storage medium storing a program for causing a computer, which controls an electron beam irradiation apparatus for applying an electron beam, to execute processing comprising:

calculating a charge amount distribution in a case where a substrate is irradiated with an electron beam, by using an index, which indicates complexity of a shape boundary of a pattern to be formed on the substrate, read from a storage device, wherein an area density U of a pattern and a perimeter distance W of a pattern per unit area are used as the index indicating complexity of the shape boundary of the pattern; and

calculating a positional deviation amount of an irradiation pattern to be formed due to irradiation by the electron beam, by using the charge amount distribution having been calculated.

9. The method according to claim 1 , wherein the charge amount distribution is calculated using WV obtained by dividing the perimeter distance W by the area density U.

10. The apparatus according to claim 5 , wherein the charge amount distribution is calculated using W/U obtained by dividing the perimeter distance W by the area density U.