JP2002075818A - Method of computing absorbed-energy distribution of charged-beam exposure, simulator, charged-beam exposure method, manufacturing method of semiconductor device and mask and recording medium for recording program for computation of absorbed- energy distribution of charged-beam exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of computing the absorbed-energy distribution of charged beams, by which process prediction having high accuracy in charged-beam exposure is realized. SOLUTION: The irradiation conditions of a plurality of substances constituting an irradiated substrate and charged beams are input, and the first substance is specified from the substances. Monte Carlo computing method is conducted when there is only the first substance, and the first energy distribution in the first substance is obtained. When this distribution is functionally approximated, the first scattering parameter can be computed accurately. Monte Carlo computing method is conducted regarding the irradiated substrate, and the second energy distribution in the first substance is obtained. When a third energy distribution is obtained by subtracting the first distribution from the second distribution, and functionally approximating the third distribution, the second scattering parameter can also be computed accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exposure using a charged beam of electrons or ions, and more particularly, to a method of calculating an absorption energy distribution in a resist in charged beam exposure, a simulator, a charged beam exposure method, and a method of exposing a semiconductor device or mask. The present invention relates to a manufacturing method and a recording medium on which a program for calculating an absorption energy distribution of charged beam exposure is recorded.

[0002]

2. Description of the Related Art With the recent miniaturization of exposure patterns in the manufacture of semiconductor devices, higher precision is required for electron beam exposure. In particular, it is an issue to increase the fidelity of the pattern shape and the process latitude. In order to solve this problem, a computer performs exposure simulation. By using the exposure simulation, the pattern shape and the process allowance can be predicted. Recently, lithography designs that optimize process conditions, mask dimensions and shapes, and exposure methods have been performed based on these simulation results.

In electron beam exposure, the irradiated electrons are scattered in the resist and lose energy. Conversely, the resist gains energy from the electrons and is exposed when the amount of energy exceeds a predetermined amount.

[0004] As shown in FIG.
The scattering of electrons in a substance such as a resist during the exposure is classified into forward scatter 92 and back scatter 93.

[0005] Forward scattering 92 refers to a phenomenon in which incident electrons are slightly scattered due to interaction with matter. For example,
The electrons incident on the resist surface gradually spread in the lateral direction as they proceed in the film thickness direction. Forward scatter 92
Strongly affects the cross-sectional shape of the resist pattern.

On the other hand, the backscattering 93 refers to a phenomenon in which electrons that have entered the substrate 21 as deeply as scattered and scattered are incident on the resist 21 again while spreading in the plane direction. The backscattered electrons incident on the resist again expose the resist again. For this reason, the surface distribution T of the amount of energy absorbed by the resist 21 is, as shown in FIG. 21B, the absorption energy distribution F due to the energy given by the forward scattering of the electrons and the absorption energy distribution F due to the electrons. It is expressed as the sum with the absorbed energy distribution B resulting from the energy provided by the backscattering.

In lithography design, it is necessary to predict the resist shape and dimensions of a complicated design pattern. Since the calculation load is very large, approximating the absorption energy distribution of the electrons in the resist by a specific function is indispensable for speeding up the calculation of the exposure simulation. Generally, a plurality of Gaussian functions are used for this approximation.

In the exposure simulation, when the pattern size is predicted, or when the size / shape is corrected by predicting the thinning or shortage of the size, the scattering radius of forward scattering becomes important. Further, if the beam blur amount is introduced as a parameter, it is possible to predict the process margin. Specifically, by approximating the beam blur amount by a Gaussian function and superimposing the beam blur amount on the scattering radius of forward scattering, it becomes possible to predict the process margin when the exposure amount and the focal position are changed. The scattering radius of the forward scattering can be easily obtained from the absorption energy distribution F due to the forward scattering approximated by the Gaussian function.

As described above, it is understood that the simulation of the absorption energy distribution of the electron beam exposure forms the core of the exposure simulation. Further, it is also used to determine important proximity effect correction parameters in electron beam exposure. For example, in order to perform an efficient process design, an exposure margin or the like is calculated in advance. Also,
In the proximity effect correction of a batch transfer mask, which has been actively studied recently, the ratio of the dimensional change due to the proximity effect is predicted in advance by simulation, and the mask size is corrected.

The simulation of the absorbed energy distribution uses Monte Carlo calculation and is performed as follows.

(1) First, in step S31 of FIG. 22, a target substrate structure, an acceleration voltage of incident electrons, and the like are input.

(2) Next, in step S32, 1
The Monte Carlo calculation of the absorption energy distribution T in the resist is performed on the electron beam of the point incidence.

(3) In step S33, the distribution T is approximated by a plurality of Gaussian functions or other functions,
An approximate distribution Ta is obtained.

(4) Further, when performing an exposure simulation, the absorbed energy distribution Ta expressed by an approximate expression
Is used to calculate the absorption energy distribution in the resist for the desired pattern.

(5) Based on the absorbed energy distribution obtained in (4), a development calculation or the like is performed to obtain a pattern dimension.

[0016]

As described above, a basic parameter in lithography design of electron beam exposure is to determine an approximate expression of an absorption energy distribution of forward scattering and back scattering of electrons in a substance. (Expansion and strength). When obtaining these coefficients, the absorption energy distribution T of the electron beam in the resist is divided into an energy distribution F caused by forward scattered electrons and an energy distribution B caused by back scattered electrons. For this separation, (1) an operator separates, or (2) an approach is approximated as forward scattering by focusing only on a certain distance from the beam incident position, and the rest is approximated as backscattering. .

In these methods, the accuracy of approximating the distribution T, which is the result of the Monte Carlo calculation, with a plurality of Gaussian functions or other functions was not sufficient.

Further, since the distribution F of the forward scattering greatly affects the resolution of the resist, the following problems may occur due to the inability to make an accurate estimation.

(1) The estimation of the proximity effect correction parameter becomes inaccurate.

(2) The accuracy of calculation of an exposure margin, which is important for lithography design, and the accuracy of process margin prediction deteriorate.

(3) The accuracy of dimension correction depending on the pattern dimension is degraded.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for calculating a distribution of absorbed energy of a charged beam which realizes highly accurate process prediction in charged beam exposure. It is.

It is another object of the present invention to provide a simulator for a charged beam absorption energy distribution which realizes highly accurate process prediction in electron beam exposure.

An object of the present invention is to provide a charged beam exposure method that enables highly accurate patterning in electron beam exposure.

An object of the present invention is to provide a method of manufacturing a semiconductor device or a mask which enables highly accurate patterning in charged beam exposure.

An object of the present invention is to provide a recording medium in which a program for calculating a charged beam absorption energy distribution for realizing highly accurate process prediction in charged beam exposure is recorded.

[0027]

Means for Solving the Problems To achieve the above object, a first feature of the present invention is a step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam; A step of designating a first substance from among them, a step of generating a first parameter file based on a plurality of substances and irradiation conditions, and a case where only the first substance is present based on the first parameter file A method of performing a Monte Carlo calculation to obtain a first energy distribution in a first substance, and a step of approximating the first energy distribution as a function to extract a first scattering parameter; In the method of calculating the energy distribution. Here, the “charged beam” refers to an electron beam and an ion beam. This makes it possible to determine the accurate forward scattering radii of the charged particles in the first substance. Then, it becomes possible to improve the accuracy of proximity effect correction and various exposure simulations. This is the first
Is caused by the energy obtained only by forward scattering of the charged particles.

A first feature of the present invention is that a Monte Carlo calculation is performed on an irradiated substrate based on a first parameter file to obtain a second energy distribution in a first substance, and a second energy distribution is obtained from the second energy distribution. It is more effective to further include a step of subtracting one energy distribution to obtain a third energy distribution and a step of approximating the third energy distribution by a function to extract a second scattering parameter. Here, "subtract the first energy distribution from the second energy distribution" means to subtract the first energy from the second energy for each portion in the first substance. This makes it possible to determine the exact backscattering radius of the charged particles in the first substance. Then, it becomes possible to improve the accuracy of proximity effect correction and various exposure simulations.

A first feature of the present invention is that the step of obtaining the first energy distribution includes the step of generating a second parameter file for a case where only the first substance exists based on a plurality of substances and irradiation conditions. And performing a Monte Carlo calculation based on the second parameter file to obtain a first energy distribution in the first substance. Thus, the respective Monte Carlo calculations can be performed in parallel based on the two parameter files, so that the calculation time can be reduced.

According to a first feature of the present invention, the step of obtaining a third energy distribution includes the steps of: approximating the first energy distribution with a plurality of Gaussian functions to obtain a fourth energy distribution; Subtracting the fourth energy distribution from the distribution to obtain a third energy distribution. In addition, the step of obtaining the third energy distribution includes the step of approximating the first energy distribution with a plurality of Gaussian functions to obtain a fourth energy distribution, and the step of approximating the second energy distribution with a plurality of Gaussian functions. It is even more effective to include a step of obtaining a fifth energy distribution and a step of subtracting the fourth energy distribution from the fifth energy distribution to obtain a third energy distribution. As a result, it is possible to average the calculation variation caused by the Monte Carlo calculation, and it is possible to improve the calculation accuracy.

A first feature of the present invention is more effective in that the step of extracting the first scattering parameter includes the step of approximating the first energy distribution with a plurality of Gaussian functions. Further, the step of extracting the second scattering parameter includes a step of approximating the third energy distribution with a plurality of Gaussian functions, which is more effective. As a result, the accuracy of proximity effect correction and various exposure simulations can be improved.

A first feature of the present invention resides in a step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam, a step of designating a first substance from the substances, and a step of specifying the plurality of substances. Generating a first parameter file based on the irradiation conditions, performing a Monte Carlo calculation on the irradiated substrate based on the first parameter file, and setting the traveling direction of the charged beam to the first substance in the first direction A step of selectively accumulating the energy absorbed from the charged beam to obtain a first energy distribution in the first substance, and extracting a first scattering parameter by function approximation of the first energy distribution. It is more effective to include the steps of: Thus, the first energy distribution can be calculated without performing the Monte Carlo calculation assuming the structure of only the first substance.

A first feature of the present invention is that when the traveling direction of the charged beam with respect to the first substance is not the first direction, the energy absorbed from the charged beam is selectively accumulated, and the energy within the first substance is reduced. It is more effective to include the step of obtaining the third energy distribution and the step of extracting the second scattering parameter by function approximation of the third energy distribution. Thus, the third energy distribution can be calculated without subtracting the energy distribution.

A first feature of the present invention is that the range in the first direction is a range in which a plurality of substances other than the first substance do not exist on the extension line from the end point to the start point. It is. Here, the "end point" and the "start point" are the end point and the start point when the first direction is regarded as an arrow.
Thus, it can be determined that the charged particles do not pass through a plurality of substances other than the first substance.

A second feature of the present invention is that a step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam, a step of designating a first substance from the plurality of substances, Generating a first parameter file based on the substance and the irradiation conditions, and performing a Monte Carlo calculation on the case where only the first substance is present based on the first parameter file to perform the first Obtaining an energy distribution; extracting a first scattering parameter by function approximation of the first energy distribution;
Calculating the second energy distribution in the first substance by performing Monte Carlo calculation on the irradiated substrate based on the parameter file of the above, and obtaining the third energy distribution by subtracting the first energy distribution from the second energy distribution A charged beam exposure method includes a step of extracting a second scattering parameter by function approximation of the third distribution, and a step of determining a proximity effect correction parameter based on the second scattering parameter. This makes it possible to obtain accurate forward and backward scattering radii of the charged particles in the first substance, thereby improving the accuracy of proximity effect correction and various exposure simulations. .

A third feature of the present invention is that a step of inputting a plurality of substances constituting the irradiation substrate and irradiation conditions of a charged beam, a step of designating a first substance from the plurality of substances, Generating a first parameter file based on the substance and the irradiation conditions, and performing a Monte Carlo calculation on the case where only the first substance is present based on the first parameter file to perform the first A step of obtaining an energy distribution, a step of extracting a first scattering parameter by approximating the first energy distribution as a function, and a step of performing a development calculation based on the first scattering parameter to correct a mask dimension. And a method for manufacturing a mask. This makes it possible to accurately determine the forward and backward scattering radii of the charged particles in the first substance, so that the accuracy of proximity effect correction and various exposure simulations can be improved. Dimensional accuracy can be improved.

A fourth feature of the present invention is that a step of inputting a plurality of substances constituting the irradiation substrate and irradiation conditions of a charged beam, a step of designating a first substance from the plurality of substances, Generating a first parameter file based on the substance and the irradiation conditions, and performing a Monte Carlo calculation on the case where only the first substance is present based on the first parameter file to perform the first A computer readable program recorded with a program for calculating an absorption energy distribution of charged beam exposure, including a step of obtaining an energy distribution and a step of extracting a first scattering parameter by function approximation of the first energy distribution. It is on a recording medium. Here, the “recording medium” includes, for example, a medium such as a semiconductor memory, a magnetic disk, an optical disk, and a magnetic tape on which a program can be recorded. This makes it possible to accurately determine the forward and backward scattering radii of the charged particles in the first substance, so that the accuracy of proximity effect correction and various exposure simulations can be improved. Dimensional accuracy can be improved.

A fifth feature of the present invention resides in that a parameter file recording section for recording a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam, and a first section for obtaining an absorption energy distribution from the plurality of substances. And a Monte Carlo calculation for calculating the first and second energy distributions in the first material by performing a Monte Carlo calculation on the case where only the first material is present and on the irradiated substrate when only the first material is present Unit, an absorption energy distribution calculating unit for subtracting the first energy distribution from the second energy distribution to obtain a third energy distribution, and a distribution function approximating unit for approximating the first and third energy distributions as a function. And a scattering radius calculator for calculating a first scattering parameter and a second scattering parameter from the first and third energy distributions approximated by a function. In the regulator. This makes it possible to determine the exact scattering radius of the forward scattering of electrons in the desired substance. Then, it becomes possible to improve the accuracy of proximity effect correction and various exposure simulations.

[0039]

Embodiments and examples of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and different from actual ones. In addition, it goes without saying that portions having different dimensional relationships and ratios are included between the drawings.

As shown in FIG. 1, the simulator of the absorbed energy distribution of the charged beam exposure according to the embodiment of the present invention comprises a computing unit 1, an input / output unit 11, a parameter file recording unit 12, an absorbed energy distribution It has a recording unit 14 and an absorption energy recording unit 15 approximated by a distribution function.

The operation unit 1 includes a parameter file generation unit 2
And a generation unit 3 for a backscattering elimination structure, and an absorption energy distribution calculation unit 4. The calculation unit 4 includes a Monte Carlo calculation unit 5, a difference absorption energy distribution calculation unit 6, an incident angle determination unit 7, and a data processing unit 8. The data processing unit 8 has a distribution function approximation unit 9 and a scattering radius calculation unit 10.

In the input / output unit 11, various data necessary for calculating the absorption energy distribution, such as the energy of incident electrons, the type of material of the irradiated object, the composition and constituent atoms of each irradiated object, the density of each irradiated object, The properties of each atom, the structure of the irradiated object,
Set the calculation area and input the mesh size of the calculation area.

The parameter file generator 2 generates a parameter file from various data necessary for calculating the input absorbed energy distribution. The parameter file is a set of data that can be subjected to Monte Carlo calculation in the calculation of the absorption energy distribution described below.
The generated parameter file is recorded in the parameter file recording unit 12. Note that the parameter file contains pattern data, which is recorded in the pattern data recording unit.

The generation unit 3 of the backscattering elimination structure generates a virtual structure based on the structure input to the parameter file, in which only forward scattering is generated and no backscattering is considered to occur. The virtual structure is a structure in which only the member for which the absorption energy distribution is to be obtained is left, and all other members are replaced with a vacuum. The reason for replacing with a vacuum is that the charged particles do not scatter in a vacuum, and the vacuum is not limited to the vacuum as long as the scattering radius is extremely small as compared with the replaced member or the remaining member. For example, an air or hydrogen atmosphere can be considered. The generated virtual structure is recorded in the parameter file recording unit 12. This allows
A desired substance, for example, a resist portion can be designated as the member for which the absorption energy distribution is to be obtained. Based on the input data, a first parameter file including a silicon substrate and a resist unit and a second parameter file for only the designated resist unit are generated.

The Monte Carlo calculator 5 performs a Monte Carlo calculation on each of the generated first and second parameter files. The scattering of the electron beam and the energy applied to each mesh when the electron beam is incident on the irradiation object are calculated. As a result, the trajectory of the electrons and the energy given to each mesh can be obtained. From the file 1, an absorption energy distribution T obtained by combining forward scattering and back scattering in the substrate and the resist is obtained.
From the second file, an absorption energy distribution F due to forward scattering in the resist is obtained. Distributions T and F found
Is recorded in the absorption energy distribution recording unit 14.

In the difference absorption energy distribution calculation section 6,
Absorption energy distribution T combining forward scattering and backscattering
Then, the amount of absorbed energy at the same position is subtracted from the absorbed energy distribution F due to forward scattering to obtain the absorbed energy distribution B due to back scattering. Distribution B found
Is recorded in the absorption energy distribution recording unit 14.

The incident angle discriminating section 7 discriminates whether or not the charged particles are backscattered according to the direction of the charged particles incident on the mesh, and accumulates the energy imparted to the mesh for each.

In the distribution function approximation unit 9 of the data processing unit 8,
The absorption energy distributions T, F, and B in the resist, which are the calculation results of the scattering of the electron beam and the applied energy in each mesh, are approximated by a Gaussian function or the like, and the approximated distributions Ta, Fa, and Ba are obtained. The approximated distributions Ta, Fa and Ba are recorded in the absorption energy distribution recording unit 15 approximated by the distribution function. The scattering radius calculation unit 10 calculates a scattering radius Rf for forward scattering and a scattering radius Rb for back scattering from the approximated absorption energy distributions Fa and Ba.
Ask for.

By using this simulator, it is possible to obtain the accurate forward scattering radii of electrons in a desired substance. Then, it becomes possible to improve the accuracy of proximity effect correction and various exposure simulations.

[0050]

Embodiment 1 Silicon (Si) as shown in FIG.
A method of calculating the absorption energy distribution in the resist 21 in a structure in which the resist 21 is disposed on the substrate 22 will be described. This calculation method is a method of calculating the absorption energy distribution of an electron beam for a substrate to be irradiated composed of a plurality of substances such as a resist 21 and a silicon substrate 22. And the like, a step of specifying a desired substance or site such as the resist 21, a step of generating a first parameter file of the substrate to be irradiated based on the inputted data, and a step of generating the first parameter. Performing a Monte Carlo calculation based on the file to obtain an absorption energy distribution T in the case where an irradiated substrate including a desired substance or site is present, and performing a Monte Carlo calculation based on the first parameter file to obtain a desired substance or A step of obtaining an absorption energy distribution F in the case where only a part exists; Subtracting the distributions F, a step of determining the energy distribution B, energy distribution F
And B to analyze and extract scattering parameters.

(1) In step S1 of FIG. 2, assuming a target substrate structure, data such as an irradiation target substrate composed of a plurality of substances including a resist 21 and electron beam irradiation conditions are shown in FIG. Input from the input / output unit 11. The calculation region is divided into meshes of several nanometers, and information on the constituent atoms and density of the resist 21 and the silicon substrate 22 is input. Based on the input data, resist 2
A first parameter file of the irradiated substrate including the substrate 1 and the substrate 22 is generated.

(2) In step S2, the Monte Carlo calculator 5 shown in FIG.
FIG. 3 shows a result of performing a Monte Carlo calculation based on the parameter file 1 and absorbing the irradiated substrate including the resist 21.
An absorption energy distribution T as shown in FIG.

In the Monte Carlo calculation, electron scattering and energy loss in a material can be obtained by a mathematical model and random numbers. The process of energy loss includes elastic scattering and elastic scattering. Also, models of elastic scattering include partial wave expansion, screened Ruther, and Ford scattering models, and models of elastic scattering include models of internal electron excitation, valence electron excitation, plasmon excitation, and phonon scattering.

The calculation of the scattering of electrons in the material is as follows:
The processing is performed based on the algorithms (d) to (d).

(A) Find the differential scattering cross section for each scattering process. The scattering cross section is determined by an equation from the energy of the electrons and the properties of the target material.

(B) The free process of each scattering process is obtained from the differential scattering cross section and random numbers.

(C) The mean free path in one scattering is determined from the free steps of each scattering step.

(D) At the position moved by the mean free path, return to (b) and perform the scattering calculation again.

When a plurality of materials exist, the material is determined at each scattering location. Further, the energy and the angle change for each scattering are maintained. By repeating the above-mentioned scattering calculation, it is possible to obtain a trajectory of electrons in the material and an energy amount map of the electrons applied to the material.

FIG. 4 shows the result of Monte Carlo calculation in the case where the substrate 22 exists for the two incident electrons 31 and 41. The first incident electrons 31 enter the mesh 24 in the resist 21 in the row L1 and the column R1 with the energy amount 1. The incident first electrons 32 are scattered forward and give half of the energy they have to the mesh in row L1 and column R1. Hereinafter, in order to make the description easy to understand, it is assumed that the incident electrons 31, 41, etc., give energy to the mesh at a constant rate of 1/2 for each scattering as a process of energy loss.

In FIG. 5A, the mesh 2 of each row and column is
The energy absorbed and accumulated by the meshes 24 and 25 corresponding to 4 and 25 is recorded in the area 26. The region 26 in each row and each column has an energy amount of 0 before the first electron 31 is incident.
Is set to An energy amount １ ／ is applied to the region 26 in the row L1 and the column R1.

Further, the first incident electrons 32 enter the mesh 24 in the row L1 and the column R2 with an energy amount of ２. The incident first electrons 33 are scattered forward, and give an energy amount of 1/4 to the mesh of the row L1 and the column R2. FIG.
In the area 26 of the row L1 and the column R2 in FIG.
Is added. The first incident electron 33 has an energy amount 1 /
4 enters the mesh 25 in the substrate 22 in the row L2 and the column R3. The incident first electrons 34 are backscattered and give an energy amount １ ／ to the mesh 25 in the row L2 and the column R3. An energy amount of 1/8 is applied to the region 26 of the row L2 and the column R3 in FIG. The first incident electrons 34 enter the mesh 24 in the resist 21 in the row L3 and the column R2 with an energy amount of 1/8. The incident first electrons 35 are backscattered and give an energy amount 1/16 to the mesh 24 in the row L3 and the column R2. Region 26 at row L3 and column R2 in FIG.
1/16 of the energy.

Next, the second incident electron 41 also has the energy amount 1 and the mesh 2 in the resist 21 in the row L1 and the column R1.
4 is incident. The incident second electrons 42 scatter forward,
Half of the energy held is given to the mesh in row L1 and column R1. In FIG. 5B, meshes 24 and 25 when the second electrons 41 are scattered after the first electrons 31 are scattered.
The energy that is absorbed and accumulated in the area is recorded in the area 26. The energy amount １ ／ is added to the region 26 in the row L1 and the column R1, and the accumulated value becomes 1.

Further, the second incident electrons 42 enter the mesh 24 in the row L2 and the column R2 with an energy amount of １ ／. The incident second electrons 43 are scattered forward and give an energy amount of 1/4 to the mesh of the row L2 and the column R2. FIG.
In the area 26 of the row L2 and the column R2 in FIG.
Is added. The second incident electron 43 has an energy amount 1 /
4 enters the mesh 24 in the row L3 and the column R2. The incident second electrons 44 are scattered forward, and the energy amount 1 /
8 is given to the mesh 24 in the row L3 and the column R2. FIG. 5 (b)
Is added to the region 26 in the row L3, column R2, and the accumulated value becomes 3/16. The second incident electrons 44 enter the mesh 25 in the substrate 22 in the row L3 and the column R3 with an energy amount of 1/8. The incident second electrons 45 are scattered forward and give an energy amount 1/16 to the mesh 25 in the row L3 and the column R3. Region 2 at row L3 and column R3 in FIG. 5B
An energy amount of 1/16 is added to 6.

In the region 27 shown in FIG.
The distribution T in the row direction of the energy absorbed in is obtained.

(3) In step S5 in FIG. 2, a resist 21 is designated from the input / output unit 11 in FIG. As shown in FIG. 3B, only the desired substance or site, that is, only the resist 21 is extracted from the irradiation substrate from the designated resist 21 and the first file by the generation unit 3 of the backscattering elimination structure in FIG. A second parameter file is generated. That is,
Data is input assuming that the object to be irradiated is only the resist 21 and there is no substrate 22. The calculation area is divided into meshes in units of several nm, and information on constituent atoms and density of the resist 21 is input.

(4) In step S6 of FIG.
The Monte Carlo calculator 5 performs a Monte Carlo calculation on the irradiation target of only the resist 21 based on the second parameter file, and obtains the resist 21 as shown in FIG.
To obtain the absorption energy distribution F due to the forward scattering of.

FIG. 6 shows the result of Monte Carlo calculation for the two incident electrons 31 and 41 when there is no substrate 22. A vacuum 23 is arranged below the resist 21. For the sake of simplicity, the path from entering the resist 21 to once releasing it is the same as in FIG. The difference between the behavior of the first incident electron 31 and the behavior of the second incident electron 41 as compared with FIG.
No scattering occurs when 1 is released into the vacuum 23. As a result, the first incident electrons 35 in FIG. 4 due to back scattering do not exist in FIG.

In FIG. 7A, the energy absorbed by the mesh 24 in each row and each column in FIG. 6 due to the first incident electrons 31 is recorded in the area 26. In FIG. 7B, the energy that is absorbed by the mesh 24 in each row and column of FIG. 6 due to the second incident electrons 41 and accumulated with respect to FIG. In a region 28 in FIG. 7C, a distribution F in the row direction of the energy absorbed in the resist 21 is obtained.

(5) In step S3 of FIG.
The distribution F is subtracted from the distribution T in the absorption energy distribution calculator 6 of the difference to obtain an absorption energy distribution B due to backscattering as shown in FIG. Area 29 in FIG.
Then, from the distribution T of the absorption energy recorded in the area 27 in the row direction, the distribution F of the absorption energy recorded in the area 28 in the row direction is subtracted for each row to obtain the distribution B of the absorption energy in the row direction. ing.

(6) In step S4, the distribution B is approximated by the distribution function approximation unit 9 in FIG. 1 with a plurality of Gaussian functions or other functions to obtain an approximated distribution function Ba. The scattering radius calculator 10 calculates the scattering radius Rb of back scattering of electrons in the distribution function Ba resist.

(7) In step S7, the distribution F is approximated by the distribution function approximating unit 9 with a plurality of Gaussian functions or other functions, and an approximated distribution function Fa is obtained. The scattering radius calculation unit 10 obtains a scattering radius Rf of forward scattering of electrons in the resist.

As described above, as shown in step S8,
Approximate absorption energy distributions Fa and Ba, which are the result of the calculation method of the absorption energy distribution in the resist 21, are obtained.

(8) Further, when performing proximity effect correction calculation, in step S10 in FIG. 8, as shown in the approximate expression obtained in step S8 in FIG. 2 and the patterns 51 to 53 in FIG. The proximity effect correction parameter is calculated using the desired desired pattern data. First, pattern 51
Beams having constant beam intensities 55 to 57 are set as shown in FIG. FIG. 9B shows the beam intensity corresponding to the position of AA ′ in FIG. 9A. Next, the beam irradiation pattern 55
To 57, the absorbed energy distributions Fa and B in step S8.
When a is applied, absorption energy distributions F1 to F3 and B1 to B3 as shown in FIG. 9C can be obtained. In other words, the calculation is performed by regarding each of the patterns 55 to 57 as a one-point incident electron beam flux. The distributions corresponding to the pattern 55 are the distributions F1 and B1, and the same applies to the patterns 56 and 57. Next, the sum 58 of the distributions B1 to B3 is obtained. Then, the electron beam irradiation pattern 59 shown in FIG. 10A is calculated so that the energy distribution becomes a constant value when added to the sum 58. This pattern 5
9 is a so-called proximity effect correction parameter. In the proximity effect correction, a correction parameter is obtained from the distribution of backscattered electrons.

(9) In step S10, a proximity effect correction calculation is performed based on the correction parameter 59 to create a drawing pattern. Specifically, patterns 55 to 57
The beam irradiation pattern 60 corrected by adding the correction parameter 59 to the beam pattern is obtained. This pattern 60 becomes the drawing data. The distribution of absorbed energy based on the drawing data is shown as a distribution 61 in FIG. From this, it can be seen that a pattern similar to the patterns 55 to 57 can be developed by appropriately setting the amount of energy required for development.

(10) Further, when performing a process simulation, in step S11 of FIG.
12 using the approximate expressions Fa and Ba in step S8.
With respect to the desired pattern 62 as shown in (a), the absorption energy distribution in the resist is calculated. First, pattern 6
2 is divided into absorption energy distribution approximation units 63, and FIG.
The beam intensity is set for each unit 63 as in 2 (b). For example, the intensity of each unit 63 may be fixed to one.
Next, the energy distributions F4 to F6 due to forward scattering in FIG. 12C are obtained for each unit 63 using the approximate expression Fa, and the sum 65 of the superposition is calculated. In FIG. 12C, the distribution at the position AA ′ in FIG.
Similarly, for the BB ′ position and the CC ′ position, the sum of the energy distribution due to forward scattering and the superposition is obtained, and FIG.
Contour lines 66 to 6 of the amount of absorbed energy as shown in 2 (d)
Calculate 8.

(11) In step S12 of FIG. 11, development calculations and the like are performed to determine the pattern dimensions. For example, when the development occurs at the boundary of the amount of energy absorbed by the contour line 66, the shape of the contour line 66 becomes the development pattern. However, it is different from the desired pattern 62. Therefore,
Returning to step S11, the development pattern can be corrected. In the calculation of the process margin, a change in the pattern dimension is obtained using the development characteristics and development time of the resist, blurring of the beam, and the like as parameters. In the dimension correction of the collective transfer mask described above, a change in the pattern dimension based on the proximity effect is calculated, and the mask dimension is corrected.

First, the beam irradiation pattern corresponding to the position CC ′ in FIG. 12A is changed from FIG. 12B to FIG.
Change as shown in (a). Then, energy distributions F5, F7, and F8 due to forward scattering are obtained for each of the units 63 and 69, and the sum of the superposition is calculated. Similarly, FIG.
The setting as shown in FIG. 13C is also performed for the position BB ′ of FIG. 13A, and the calculation as shown in FIG. 13D is performed. And
Contour lines 71 to 73 of the corrected absorbed energy amount as shown in FIG.

According to this method, since the substrate itself is not considered, backscattered electrons from the substrate can be excluded from the calculation result. That is, the magnitude of forward scattering of electrons in pure resist can be obtained. In addition, the magnitude of the backscatter can be similarly accurately obtained.

As a result, it is possible to accurately determine the scattering radius Rf of the forward scattering and the scattering radius Rb of the back scattering of electrons in a desired material such as the resist 21. As a result, the following becomes possible.

(1) The accuracy of the proximity effect correction can be improved.

(2) The accuracy of the exposure simulation can be improved, and the productivity is improved.

(3) It is possible to improve the mask transfer accuracy with respect to the dimensional correction of the batch transfer mask.

According to the present invention, as a step of generating a parameter file, not only a first parameter file for performing calculations on a substrate to be irradiated on the basis of input data, but also only a desired substance or site from the substrate to be irradiated. Then, a second parameter file for performing the calculation in the case of extracting is generated. That is, when creating input data, by designating a resist as a desired substance or site, it is possible to create a second parameter file using Monte Carlo calculation in which the object to be irradiated is only the resist and there is no substrate. By individually calculating using the first and second parameter files created in this way, it becomes possible to calculate the absorbed energy distributions T and F.

[0085]

[Embodiment 2] FIG. 14 is a flowchart showing a method of calculating an absorption energy distribution in charged beam exposure according to Embodiment 2 of the present invention. The difference from the flowchart of FIG. 2 of the first embodiment is that step S21 is newly added after step S2, and that step S3 is different from step S22.
It is a point that has been replaced. Thus, in the subtraction processing in step S22, the distributions Ta and Fa in which the Monte Carlo calculation deviation is reduced by the approximate expression can be used, and the resultant distribution B deviation can be reduced.
More accurate distribution Ba can be obtained.

Further, according to the present invention, the absorption energy distribution F is approximated by a plurality of Gaussian functions, and the absorption energy distribution Fa is subtracted from the absorption energy distribution T by using the approximated absorption energy distribution Fa. The energy distribution B may be obtained.

Since the absorption energy distribution T is represented by a plurality of Gaussian functions, even if the distribution T is approximated by a function, an error is large and the accuracy cannot be improved. On the other hand, the absorption energy distribution F, which is a calculation result of only forward scattering, does not include backscattered electrons, and can be accurately approximated by a Gaussian function. By approximating the absorption energy distribution F, which can be approximated with relatively high accuracy, by a Gaussian function or the like, it is possible to average the calculation variation at the time of Monte Carlo calculation, and to obtain a highly accurate distribution Fa. Distribution Fa
Can be improved, the distribution B obtained by the subtraction process using the distribution Fa and further the distribution Ba can be improved. Then, since the absorbed energy distributions F and B can be represented by a high-precision approximate expression, it is possible to use this approximate expression for calculation,
High-speed calculation becomes possible.

[0088]

Third Embodiment FIG. 15 is a flowchart showing a method of calculating an absorption energy distribution in charged beam exposure according to a third embodiment of the present invention. In the calculation method according to the third embodiment, the energy absorbed by the resist layer is determined based on the angle of the incident electrons with respect to the mesh as to whether the energy is due to forward scattering or backscattering, and the energy is separately accumulated. A distribution F and an absorption energy distribution B due to backscattering are calculated. That is, in the step of obtaining the absorption energy distributions F, B, and T, the step of obtaining the absorption energy distributions F and B is performed by the absorption energy distribution T.
, And is characterized in that an absorption energy distribution corresponding to the absorption energies F and B is created according to the electron incident direction.

The calculation method of the third embodiment will be described below.

(1) First, in step S1, a substrate structure, an acceleration voltage, and the like are input. In step S2, Monte Carlo calculation of the absorption energy distribution is performed. The steps up to this point are the same as steps S1 and S2 in FIG. 2 of the first embodiment. Therefore, in the case of all angles for which the angle determination is not performed, the distribution T is obtained as in FIG.

(2) Next, in step S23, the angle is determined. The angle formed by the directions 75 and 76 of the electrons incident on the mesh 79 with respect to the initial incident beam direction 74 of the electrons incident on the substrate in FIG.
7 and 78. For example, when the incident direction is the same as the direction 74, the incident angle is 0 degree. 180 for reverse direction
It becomes degree.

The principle will be described with reference to FIG. In FIG. 17, the substrate configuration including the resist 21 and the substrate 22, the arrangement of the meshes 24 and 25, the trajectories of the first incident electrons 31 to 35 and the second incident electrons 41 to 45, and the energy of the incident electrons to the mesh The way of giving is the same as that of FIG. 4 of the first embodiment for convenience of explanation. Substrate 22
When electrons 31 are incident on the resist 21 and the substrate 22, they are scattered. At this time, the backscattered electrons 35 are
Incident angle 83 is-
It has an angle in the range of not more than 90 degrees and not less than -180 degrees and in the range of not less than 90 degrees and not more than 180 degrees. On the other hand, the incident angles 81, 82, 8 of the forward scattered electrons 32 to 34, 42 to 45
Nos. 4 to 86 have angles in the range from -90 degrees to 90 degrees. As described above, it is possible to determine whether or not the incident electrons have been backscattered based on the incident angle of the incident electrons.

FIG. 18A is a view showing a calculation result of an absorption energy distribution by the first incident electrons 31 in FIG. The recording area corresponding to each mesh 24 and 25 has an absorption energy distribution recording area 87 due to forward scattering and an absorption energy distribution recording area 88 due to back scattering. For example, the electron 33 in FIG. 17 has an incident angle 81 in the range of not less than -90 degrees and not more than 90 degrees, so it is determined to be a forward scattered electron, and the energy amount of 1 / 4 is added. On the other hand, the electron 35 in FIG.
Since it is in the range of not less than 90 degrees and the range of not less than 90 degrees and not more than 180 degrees, it is determined as backscattered electrons, and an energy amount of 1
/ 16 is added. The distribution of the total absorbed energy in the resist 21 and the substrate 22 is determined by the recording areas 87 and 88 of these two.
Is the sum of the energy amounts recorded in. That is, if the determination based on the angle is not performed, the absorbed energy distribution T in the resist can be obtained.

FIG. 18B shows a calculation result obtained by accumulating the absorption energy distribution by the second incident electrons 41 in FIG. 17 on the calculation result of the absorption energy distribution by the first incident electrons 31 in FIG. FIG. FIG. 18C is based on the accumulated absorption energy distribution of FIG.
The distribution of absorbed energy due to forward and backward scattering in the plane of the resist layer shown in FIG. In particular,
For example, the amount of energy due to forward scattering in the in-plane L1 of the resist layer (the amount of energy recorded in the L1 row of the region 28) is recorded in the R1 column and R2 column region 87 of the L1 row in FIG. 18B. It is obtained by adding the energy amounts 1 and 1/4. The amount of energy due to backscattering in the in-plane L3 of the resist layer (the amount of energy recorded in the L3 row of the area 29) was recorded in the R1 column and the R2 column area 88 of the L3 row in FIG. 18B. Energy amount 0 and 1 /
It is determined by adding 16. Finally, the energy amount recorded in the area 27 is determined by the rows L1 to L3 of the areas 28 and 29.
It is obtained by taking the sum of the energy amounts for each. Note that the energy amounts recorded in these areas 27 to 29 correspond to the areas 27 to 29 in FIG.

In the third embodiment, the angles of the electrons incident on the mesh are determined to determine the forward scattered electrons and the back scattered electrons. However, the third embodiment differs from the first embodiment in the subtraction processing (FIG. 2). May be applied. That is, as shown in FIG. 19, the absorption energy distribution F of the forward scattered electrons is obtained by the angle discrimination in step S23, and the absorption energy distribution F is subtracted from the absorption energy distribution T simultaneously obtained in step S3.
May be required. Further, as shown in FIG. 20, the absorption energy distribution B of the backscattered electrons is obtained by the angle discrimination in step S23, and the absorption energy distribution B is subtracted from the absorption energy distribution T obtained at the same time.
Is also possible.

As described above, when the Monte Carlo calculation is performed to determine the absorption energy distribution, it is possible to determine the absorption energy distributions A, B, and C almost simultaneously by determining the angle of the electrons incident on the mesh. .
Thereby, the calculation speed can be improved and the accuracy can be increased.

That is, according to the method of the present invention, since the substrate itself is not considered, it is possible to exclude the backscattered electrons themselves from the substrate from the calculation result. That is, by using this method, it is possible to obtain the magnitude of forward scattering of electrons in pure resist. In addition, the magnitude of the backscatter can be similarly accurately obtained.

[0098]

As described above, according to the present invention, it is possible to provide a method for calculating the absorption energy distribution of a charged beam that realizes highly accurate process prediction in charged beam exposure.

Further, according to the present invention, it is possible to provide a simulator for a distribution of a absorbed energy of a charged beam which realizes highly accurate process prediction in electron beam exposure.

According to the present invention, it is possible to provide a charged beam exposure method which enables highly accurate patterning in electron beam exposure.

According to the present invention, it is possible to provide a method of manufacturing a semiconductor device or a mask which enables highly accurate patterning in charged beam exposure.

According to the present invention, it is possible to provide a recording medium in which a program for calculating a distribution of absorbed energy of a charged beam for realizing highly accurate process prediction in charged beam exposure is recorded.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a simulator of an absorbed energy distribution of charged beam exposure according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a calculation method of an absorption energy distribution in charged beam exposure according to the first embodiment of the present invention.

FIG. 3 is a conceptual diagram of a procedure of a calculation method of an absorption energy distribution in charged beam exposure according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a calculation result of a Monte Carlo calculation in a case where there is a substrate according to the calculation method according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a calculation result of an absorption energy distribution in a case where a substrate is present, by the calculation method according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a calculation result of a Monte Carlo calculation in a case where there is no substrate in the calculation method according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a calculation result of an absorption energy distribution in a case where there is no substrate in the calculation method according to the first embodiment of the present invention.

FIG. 8 is a flowchart illustrating an exposure method (part 1) according to the first embodiment of the present invention.

FIG. 9 is a conceptual diagram (part 1) of a procedure of an exposure method (part 1) according to the first embodiment of the present invention.

FIG. 10 is an exposure method according to the first embodiment of the present invention (part 1);
FIG. 7 is a conceptual diagram (No. 2) of the procedure of FIG.

FIG. 11 is an exposure method according to the first embodiment of the present invention (part 2);
It is a flowchart which shows.

FIG. 12 is an exposure method according to the first embodiment of the present invention (part 2);
FIG. 4 is a conceptual diagram (No. 1) of the procedure of FIG.

FIG. 13 is an exposure method according to the first embodiment of the present invention (part 2);
FIG. 7 is a conceptual diagram (No. 2) of the procedure of FIG.

FIG. 14 is a flowchart illustrating a method of calculating an absorption energy distribution in charged beam exposure according to the second embodiment of the present invention.

FIG. 15 is a flowchart illustrating a method of calculating an absorbed energy distribution in charged beam exposure according to the third embodiment of the present invention.

FIG. 16 is a diagram for explaining an incident angle.

FIG. 17 is a diagram illustrating a calculation result of Monte Carlo calculation by a calculation method according to the third embodiment of the present invention.

FIG. 18 is a diagram illustrating a calculation result of an absorption energy distribution by a calculation method according to the third embodiment of the present invention.

FIG. 19 is a flowchart illustrating a calculation method of an absorbed energy distribution in charged beam exposure according to the first application example of the third embodiment of the present invention.

FIG. 20 is a flowchart illustrating a calculation method of an absorbed energy distribution of charged beam exposure according to a second application example of the third embodiment of the present invention.

FIG. 21 is a conceptual diagram of an absorption energy distribution in charged beam exposure.

FIG. 22 is a flowchart showing a conventional method of calculating an absorption energy distribution in charged beam exposure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Operation part 2 Exposure parameter file generation part 3 Generation part of backscattering elimination structure 4 Absorption energy distribution calculation part 5 Monte Carlo calculation part 6 Difference absorption energy distribution calculation part 7 Incident angle discrimination part 8 Data processing part 9 Distribution function approximation part 10 Scattering radius calculation unit 11 Input / output unit 12 Parameter file recording unit 13 Pattern data recording unit 14 Absorption energy distribution recording unit 15 Absorption energy distribution recording unit approximated by distribution function 21 Resist 22 Substrate 23 Vacuum 24, 25 mesh 26 Absorption energy distribution Recording area 27 Absorption energy distribution recording area in the plane of resist layer 28 Absorption energy distribution recording area due to forward scattering in the plane of resist layer 29 Absorption energy distribution recording area due to back scattering in the plane of resist layer 31 to 35 first Incident electrons 41 to 45 2 incident electrons 51 to 53 pattern 54 mesh 55, 56, 57 beam irradiation pattern F1 to F10 absorption energy distribution due to forward scattering B1 to B3 absorption energy distribution due to back scattering 58 superposition of absorption energy distribution due to back scattering 59 proximity effect correction Parameter 60 Corrected beam irradiation pattern 61 Corrected absorption energy distribution 62 Pattern 63, 69, 70 Approximate unit of absorption energy distribution 64 Beam irradiation pattern 65 Superposition of absorption energy distribution by forward scattering 66 to 68, 71 to 73 Absorption energy Contour of quantity 74 Incident beam direction 75 Incident direction of forward scattered beam only 76 Incident direction of back scattered beam 77, 78, 81 to 86 Incident angle 79 Mesh 87 Absorbed energy by forward scattering Distribution recording area 88 Absorption energy distribution recording area due to backscattering 91 Trace of incident electrons 92 Trace of electrons due to forward scattering only 93 Trace of electrons due to forward scattering and backscattering

 ──────────────────────────────────────────────────の Continued on front page (54) [Title of Invention] Calculation method of absorbed energy distribution of charged beam exposure, simulator, charged beam exposure method, manufacturing method of semiconductor device and mask, calculation of absorbed energy distribution of charged beam exposure Storage medium storing the program to be executed

Claims (14)

[Claims] 1. A step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam; a step of designating a first substance from among the substances; Generating a first parameter file, and performing Monte Carlo calculation on the case where only the first substance is present based on the first parameter file;
Determining a first energy distribution in the first material; and extracting a first scattering parameter by approximating the first distribution as a function, wherein the absorption of the charged beam exposure is performed. Calculation method of energy distribution. 2. a step of performing a Monte Carlo calculation on the irradiation substrate based on the first parameter file to obtain a second energy distribution in the first substance; and calculating the first distribution from the second distribution. 2. A calculation method according to claim 1, further comprising: a step of obtaining a third energy distribution by subtracting a second energy distribution; and a step of extracting a second scattering parameter by approximating the third distribution with a function. . 3. The step of obtaining the first energy distribution includes: a step of generating a second parameter file for a case where only the first substance is present, based on the substance and the irradiation conditions; And performing a Monte Carlo calculation based on the parameter file of (1) to obtain a first energy distribution in the first substance. 4. The step of obtaining the third energy distribution, the step of approximating the first distribution with a plurality of Gaussian functions to obtain a fourth energy distribution, and the step of obtaining the fourth energy distribution from the second distribution. Calculating the third energy distribution by subtracting the distribution. 5. The step of obtaining the third energy distribution, the step of: approximating the first distribution with a plurality of Gaussian functions to obtain a fourth energy distribution; 3. A step of obtaining a fifth energy distribution by approximating with a function, and a step of subtracting the fourth distribution from the fifth distribution to obtain a third energy distribution. Or the calculation method according to claim 3. 6. The method according to claim 1, wherein the step of extracting the first scattering parameter includes the step of approximating the first distribution with a plurality of Gaussian functions. Calculation method. 7. The method according to claim 2, wherein the step of extracting the second scattering parameter includes the step of approximating the third distribution with a plurality of Gaussian functions. Calculation method. 8. A step of inputting a plurality of substances constituting the irradiation substrate and irradiation conditions of a charged beam; a step of designating a first substance from among the substances; Generating a first parameter file, performing Monte Carlo calculation on the irradiated substrate based on the first parameter file, and when the traveling direction of the charged beam with respect to the first substance is the first direction. Selectively accumulating the energy absorbed from the charged beam to obtain a first energy distribution in the first material; and extracting a first scattering parameter by approximating the first distribution as a function. And calculating the absorbed energy distribution of the charged beam exposure. 9. When the traveling direction of the charged beam with respect to the first substance is not the first direction, energy absorbed from the charged beam is selectively accumulated, and a third energy in the first substance is accumulated. The method according to claim 8, further comprising: obtaining an energy distribution; and extracting a second scattering parameter by function approximation of the third distribution. 10. The method according to claim 8, wherein the range in the first direction is a range in a direction in which the substance other than the first substance does not exist on an extension line from the end point to the start point. 9. The calculation method according to 9. 11. A step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam, a step of designating a first substance from among the substances, and a step of specifying a first substance from among the substances. Generating a first parameter file; and performing Monte Carlo calculation on the case where only the first substance exists based on the first parameter file;
A step of obtaining a first energy distribution in the first substance; a step of extracting a first scattering parameter by approximating the first distribution as a function; and a step of extracting the irradiation substrate based on the first parameter file. Calculating a second energy distribution in the first material by performing a Monte Carlo calculation on the first material; subtracting the first distribution from the second distribution to obtain a third energy distribution; 3. A charged beam exposure method, comprising: extracting a second scattering parameter by function approximation of the distribution of No. 3; and determining a proximity effect correction parameter based on the second scattering parameter. 12. A step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam; a step of designating a first substance from among the substances; Generating a first parameter file; and performing Monte Carlo calculation on the case where only the first substance exists based on the first parameter file;
Obtaining a first energy distribution in the first substance; extracting a first scattering parameter by function approximation of the first distribution; and performing a development calculation based on the first scattering parameter. And correcting the mask dimensions. And a method of manufacturing a mask. 13. A step of inputting a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam; a step of designating a first substance from the substances; and a step of specifying a first substance from the substances and the irradiation conditions. Generating a first parameter file; and performing Monte Carlo calculation on the case where only the first substance exists based on the first parameter file;
Determining a first energy distribution in the first substance; and extracting a first scattering parameter by approximating the first distribution with a function, thereby absorbing a charged beam exposure. A computer-readable recording medium on which a program for calculating an energy distribution is recorded. 14. A parameter file recording unit for recording a plurality of substances constituting an irradiation substrate and irradiation conditions of a charged beam; A Monte Carlo calculation unit that performs Monte Carlo calculation on the case where only the first substance is present and on the irradiated substrate to obtain first and second energy distributions in the first substance; A difference absorption energy calculation unit for subtracting the first distribution from the distribution to obtain a third energy distribution; a distribution function approximation unit for approximating the first and third distributions as a function; A simulator comprising: a scattering radius calculator for calculating a first scattering parameter and a second scattering parameter from first and third distributions.