Construction method and system of photoresist secondary electron generation model

Abstract

The invention discloses a construction method and system of a photoresist secondary electron generation model, and relates to the technical field of photoetching processes. The method comprises the following steps: determining a simulated photoresist formula, and constructing a photoresist system model according to the photoresist formula; simulating the thin film density of the photoresist system model, and outputting the center-of-mass coordinates of molecules in the thin film; determining the number of photons in the photoresist film, and obtaining photon coordinates; determining the molecular type of molecular ionization caused by the photons according to the distance from the photons to the centroid coordinates, and obtaining the energy of the photoelectrons by combining the ionization energy of the molecules; and carrying out secondary electron generation Monte Carlo simulation on all photon positions in the photoresist film by combining the energy of the photoelectrons and the photon coordinates to obtain the distribution of the secondary electrons in the photoresist film, and outputting the coordinates of the secondary electrons. Parameters such as ionization energy are introduced into the calculation model, and through Monte Carlo simulation, the distribution of secondary electrons in the exposed film of photoresists of different types and proportions can be simulated.

Description

Technical Field

[0001] The present invention relates to the field of photolithography technology, and more specifically to a method and system for constructing a photoresist secondary electron generation model. Background Art

[0002] In the photoresist reaction mechanism, the photoresist absorbs photons to generate high-energy photoelectrons. These high-energy photoelectrons are distributed in the photoresist film, undergo elastic and inelastic scattering processes, and cause further ionization and generate several secondary electrons. These secondary electrons will be adsorbed by the photoacid generator (PAG) and then dissociate and produce photoacid. Therefore, the size of the ionization energy determines the generation efficiency of secondary electrons and their movement path, and the distribution of secondary electrons in the film has a very large impact on the dissociation of PAG to generate photoacid. The disadvantage of existing photolithography software is that the current simulation research on secondary electrons is mainly aimed at electron beam lithography, and only the ionization process caused by a single electron or photon is studied, and there is a lack of simulation of the distribution of secondary electrons in the film. Therefore, for those skilled in the art, how to simulate the distribution of secondary electrons in the photoresist film is a problem that needs to be solved urgently. Summary of the invention

[0003] In view of this, the present invention provides a method and system for constructing a photoresist secondary electron generation model to solve the problems raised in the background technology.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: a method for constructing a photoresist secondary electron generation model, the specific steps include the following:

[0005] S1. Determine a simulated photoresist formula, and construct a photoresist system model according to the photoresist formula;

[0006] S2, performing molecular dynamics simulation on the photoresist system model to obtain the density of the photoresist film after relaxation, and outputting the center of mass coordinates of the molecules in the film;

[0007] S3, determining the number of photons in the photoresist film, and randomly distributing them in the film to obtain the photon coordinates;

[0008] S4, determining the type of molecule ionized by the photon according to the distance from the photon to the center of mass coordinate, and obtaining the energy of the photoelectron in combination with the ionization energy of the molecule;

[0009] S5. Perform a Monte Carlo simulation of secondary electron generation on all photon positions in the photoresist film in combination with the energy of the photoelectrons and the photon coordinates to obtain the distribution of secondary electrons in the photoresist film and output the secondary electron coordinates.

[0010] Optionally, the number of photons in the photoresist film is determined based on a simulated exposure dose and a photon absorption efficiency.

[0011] Optionally, the energy of the photoelectron is the photon energy minus the molecular ionization energy, wherein the ionization energy of different types of molecules is calculated by first principle software.

[0012] Optionally, a photoelectron is generated at the photon, and the photoelectron undergoes elastic scattering and inelastic scattering. The inelastic scattering causes the energy of the photoelectron to be lost and a secondary electron is generated. By tracing the photoelectron after energy loss and the generated secondary electron, a cascade process of the secondary electron is obtained.

[0013] Optionally, the energy loss of inelastic scattering is calculated by Bethe's law:

[0014]

[0015] Where s is the electron free path, Z i is the atomic number of the ith element, A i is the atomic weight of the target, J i is the ionization energy, E is the electron instantaneous energy, and ρ is the photoresist film density.

[0016] Optionally, the energy of the secondary electron is obtained using a uniform random number R:

[0017]

[0018]

[0019] Where φ is the work function, is the average binding energy of the outer shell electrons, E c is the parameter that limits the secondary electron energy, E s is the energy of the secondary electron.

[0020] Optionally, the specific steps of obtaining the secondary electron coordinates are:

[0021] Monte Carlo simulation is performed on the generation of secondary electrons by a single photon to obtain the free path, scattering angle and azimuth parameters in each elastic or inelastic scattering process;

[0022] The simulation results of different photons are substituted into the photon coordinates to obtain the secondary electron distribution and secondary electron coordinates in the entire photoresist film.

[0023] On the other hand, a system for constructing a photoresist secondary electron generation model is provided, comprising a photoresist model construction module, a first calculation module, a photon distribution module, a photoelectron energy calculation module, and a secondary electron distribution calculation module; wherein,

[0024] The photoresist model building module is used to determine a simulated photoresist formula and build a photoresist system model according to the photoresist formula;

[0025] The first calculation module is used to perform molecular dynamics simulation on the photoresist system model to obtain the density of the photoresist film after relaxation and output the center of mass coordinates of the molecules in the film;

[0026] The photon distribution module is used to determine the number of photons in the photoresist film and randomly distribute them in the film to obtain the photon coordinates;

[0027] The photoelectron energy calculation module is used to determine the type of molecule ionized by the photon according to the distance from the photon to the center of mass coordinate, and obtain the energy of the photoelectron in combination with the ionization energy of the molecule;

[0028] The secondary electron distribution calculation module is used to perform Monte Carlo simulation of secondary electron generation on all photon positions in the photoresist film in combination with the energy of the photoelectrons and the photon coordinates, obtain the distribution of secondary electrons in the photoresist film, and output the secondary electron coordinates.

[0029] It also includes a molecular ionization energy calculation module, which is used to calculate the ionization energy of different types of molecules through first-principles software.

[0030] It can be seen from the above technical scheme that, compared with the prior art, the present invention discloses a method and system for constructing a photoresist secondary electron generation model, which has the following beneficial technical effects: the calculation model of the present invention introduces parameters such as ionization energy, and obtains the generation and distribution of secondary electrons during the exposure process of the extreme ultraviolet photoresist through Monte Carlo simulation. By calculating the movement path of the secondary electrons in the extreme ultraviolet photoresist, the distribution of secondary electrons in the film of photoresists of different types and proportions after exposure can be simulated, thereby achieving accurate and efficient simulation of the distribution of secondary electrons in the extreme ultraviolet photoresist film. It should be noted that the secondary electron generation model in the present invention can not only be applied to extreme ultraviolet lithography, but also to other lithography fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0032] Figure 1 is a flow chart of the method of the present invention;

[0033] Figure 2 is a system structure diagram of the present invention;

[0034] Figure 3 A diagram showing the movement path of secondary electrons according to an embodiment of the present invention;

[0035] Figure 4 A molecular distribution diagram in a photoresist film simulated in an embodiment of the present invention;

[0036] Figure 5 4 is a secondary electron coordinate diagram in the photoresist film in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The embodiment of the present invention takes extreme ultraviolet lithography as an example and discloses a method for constructing a secondary electron generation model of an extreme ultraviolet photoresist, such as Figure 1 As shown, the specific steps include the following:

[0039] S1. Determine a simulated photoresist formula and construct a photoresist system model according to the photoresist formula;

[0040] S2. Perform molecular dynamics simulation on the photoresist system model to obtain the density of the photoresist film after relaxation, and output the center of mass coordinates of the molecules in the film;

[0041] S3, determining the number of photons in the photoresist film, and randomly distributing them in the film to obtain the photon coordinates;

[0042] S4. Determine the type of molecule ionized by the photon based on the distance from the photon to the center of mass coordinates, and obtain the energy of the photoelectron based on the ionization energy of the molecule;

[0043] S5. Perform a Monte Carlo simulation of secondary electron generation on all photon positions in the photoresist film in combination with the energy of the photoelectrons and the photon coordinates, obtain the distribution of secondary electrons in the photoresist film, and output the secondary electron coordinates.

[0044] Furthermore, in step S3, the number of photons in the photoresist film is determined according to the simulated exposure dose and the absorption efficiency of photons.

[0045] Furthermore, the energy of the photoelectron is the photon energy minus the molecular ionization energy, wherein the ionization energy of different types of molecules is calculated using first-principles software.

[0046] Furthermore, photoelectrons are generated at the photons, and the photoelectrons undergo elastic scattering and inelastic scattering. The inelastic scattering causes the energy of the photoelectrons to be lost and a secondary electron is generated. By tracing the photoelectrons after energy loss and the generated secondary electrons, a cascade process of the secondary electrons is obtained.

[0047] Photons will ionize the photoresist to produce photoelectrons, and the energy of the photoelectrons is the photon energy minus the ionization energy. Photoelectrons will undergo elastic scattering and inelastic scattering. Elastic scattering is related to the interaction between electrons and atomic nuclei. The direction of electron movement changes, but no energy loss occurs. Inelastic scattering is the interaction between the incident electron and the electron of the target atom. Energy is transferred from the incident electron to the orbital electron of the target atom and secondary electrons are generated. Each elastic or inelastic scattering process includes three parameters: free path, scattering angle and azimuth angle. These parameters are obtained through Monte Carlo simulation, and finally the complete electron movement path is obtained.

[0048] Furthermore, the specific steps of obtaining the secondary electron coordinates in step S5 are:

[0049] Monte Carlo simulation is performed on the generation of secondary electrons by a single photon to obtain the free path, scattering angle and azimuth parameters in each elastic or inelastic scattering process;

[0050] The simulation results of different photons are substituted into the photon coordinates to obtain the secondary electron distribution and secondary electron coordinates in the entire photoresist film.

[0051] Specifically, the calculation process of the secondary electron motion trajectory is as follows:

[0052] Elastic scattering: The secondary electron trajectory model includes elastic scattering, which only changes the electron's motion angle but not its energy, and inelastic scattering, which causes electron energy loss and produces secondary electrons. Elastic scattering is related to the interaction between high-energy electrons and atomic nuclei. In this process, the direction of the electron's motion changes, but its energy remains unchanged. Elastic scattering uses the Mott cross section fitted by Browning:

[0053]

[0054] Where Z is the atomic number and E is the electron instantaneous energy (eV). Then the average distance between consecutive elastic scattering events is calculated, i.e., the elastic scattering mean free path Λ el , determined by the following formula:

[0055]

[0056] Where n is the atomic density, and a random number R (0-1) is used to calculate the electron free path Δs of the current elastic scattering event: Δs = -Λ·ln(R); (3)

[0057] Elastic scattering angle θ el Determined by the following formula:

[0058]

[0059] Azimuth

[0060] Inelastic scattering: Inelastic scattering involves the interaction between the incident electron and the orbital electrons of the target atom, with energy transferred from the incident electron to the target atom and its orbital electrons. The energy loss of the incident electron is caused by electron, proton and phonon excitation, ionization and other processes. The inelastic scattering model used in this embodiment is based on the continuous energy loss method (continuous deceleration approximation, CSDA) and is expressed in terms of energy loss per unit length. The inelastic mean free path of the secondary electron is calculated using the empirical formula for organic compounds:

[0061]

[0062] Where ρ is the density and the inelastic scattering cross section is derived using the following formula:

[0063]

[0064] The energy loss at each step is calculated using Bethe's law:

[0065]

[0066] Where s is the electron free path, Z i is the atomic number of the ith element, A i is the atomic weight of the target, J i is the ionization energy, E is the electron instantaneous energy, and ρ is the photoresist film density.

[0067] The energy of the secondary electron is obtained using a uniform random number R:

[0068]

[0069]

[0070] Where φ is the work function (HOMO energy level is used here for approximation), is the average binding energy of the outer shell electrons (here the value of ionization energy is taken), E c is the parameter that limits the secondary electron energy, E s is the energy of the secondary electron.

[0071] By simulating the generation process of secondary electrons and subsequent electrons, the movement path of EUV photoresist and the number of secondary electrons generated can be obtained. inel for

[0072]

[0073] Secondary electron scattering angle θ se Determined by the loss energy and the electron energy:

[0074]

[0075] Among them, ΔE is the energy lost in the inelastic scattering process, and the azimuth angle between the initial electron and the secondary electron is can be calculated by different random numbers R:

[0076] The probability of elastic or inelastic scattering is determined by the cross sections of elastic and inelastic scattering, which are:

[0077] The model of the method of the present invention can be used in the field of extreme ultraviolet lithography simulation. Taking the generation of secondary electrons by BPA-6BOC photoresist as an example, the ionization energy of the photoresist is 8.3eV, and the energy of the generated photoelectrons is 84.7eV. The density of the film is 1.2g / cm3 obtained by molecular dynamics simulation. The movement paths of the photoelectrons and the generated secondary electrons are as follows: Figure 3 The molecular distribution in the simulated photoresist film is shown in Figure 4 As shown, the blue dots are photoresist molecules, the red dots are PAGs, and the green dots are alkaline neutralizers.

[0078] Determine the distance between the photon and the surrounding molecules, confirm the type of molecule that will cause ionization, and combine the ionization energy of the molecule to obtain the energy of the photoelectron. Figure 3 As an example), substitute it into the photon position and finally get the coordinates of the secondary electrons in the photoresist film, such as Figure 5 shown.

[0079] On the other hand, a system for constructing a secondary electron generation model of an extreme ultraviolet photoresist is provided, such as Figure 2 As shown, it includes a photoresist model building module, a first calculation module, a photon distribution module, a photoelectron energy calculation module, and a secondary electron distribution calculation module; wherein,

[0080] A photoresist model building module, used to determine a simulated photoresist formula and build a photoresist system model according to the photoresist formula;

[0081] The first calculation module is used to perform molecular dynamics simulation on the photoresist system model to obtain the density of the photoresist film after relaxation and output the center of mass coordinates of the molecules in the film;

[0082] The photon distribution module is used to determine the number of photons in the photoresist film and randomly distribute them in the film to obtain the photon coordinates;

[0083] The photoelectron energy calculation module is used to determine the type of molecule ionized by the photon based on the distance from the photon to the center of mass coordinates, and to obtain the energy of the photoelectron based on the ionization energy of the molecule;

[0084] The secondary electron distribution calculation module is used to perform Monte Carlo simulation of secondary electron generation for all photon positions in the photoresist film by combining the energy of the photoelectrons and the photon coordinates, obtain the distribution of secondary electrons in the photoresist film, and output the secondary electron coordinates.

[0085] It also includes a molecular ionization energy calculation module, which is used to calculate the ionization energy of different types of molecules through first-principles software.

[0086] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for constructing a photoresist secondary electron generation model, characterized in that: The specific steps include the following: S1. Determine a simulated photoresist formula, and construct a photoresist system model according to the photoresist formula; S2, simulate the film density of the photoresist system model and output the center of mass coordinates of the molecules in the film; S3, determining the number of photons in the photoresist film and obtaining the photon coordinates; S4, determining the type of molecule ionized by the photon according to the distance from the photon to the center of mass coordinate, and obtaining the energy of the photoelectron in combination with the ionization energy of the molecule; S5. Perform a Monte Carlo simulation of secondary electron generation on all photon positions in the photoresist film in combination with the energy of the photoelectrons and the photon coordinates to obtain the distribution of secondary electrons in the photoresist film and output the secondary electron coordinates.

2. The method for constructing a photoresist secondary electron generation model according to claim 1, characterized in that: The number of photons in the photoresist film is determined based on the simulated exposure dose and the absorption efficiency of the photons.

3. The method for constructing a photoresist secondary electron generation model according to claim 1, characterized in that: The energy of the photoelectron varies with the ionization energy of the molecule, wherein the ionization energy of different types of molecules is calculated using first principle software.

4. The method for constructing a photoresist secondary electron generation model according to claim 1, characterized in that: Photoelectrons are generated at the photons, and the photoelectrons are subjected to elastic scattering and inelastic scattering, simulating the scattering process of the photoelectrons to obtain a cascade process of photoelectrons and secondary electrons.

5. The method for constructing a photoresist secondary electron generation model according to claim 4, characterized in that: The energy loss of inelastic scattering is calculated by Bethe's law: Where s is the electron free path, Z i is the atomic number of the ith element, A i is the atomic weight of the target, J i is the ionization energy, E is the electron instantaneous energy, and ρ is the photoresist film density.

6. The method for constructing a photoresist secondary electron generation model according to claim 4, characterized in that: The energy of the secondary electron is obtained using a uniform random number R: Where φ is the work function, is the average binding energy of the outer shell electrons, E c is the parameter that limits the secondary electron energy, E s is the energy of the secondary electron.

7. The method for constructing a photoresist secondary electron generation model according to claim 1, characterized in that: The specific steps of obtaining the secondary electron coordinates are: The Monte Carlo simulation results of different photons are substituted into the photon coordinates to obtain the secondary electron distribution and secondary electron coordinates in the entire photoresist film.

8. A system for constructing a photoresist secondary electron generation model, characterized in that: It includes a photoresist model building module, a first calculation module, a photon distribution module, a photoelectron energy calculation module, and a secondary electron distribution calculation module; wherein, The photoresist model building module is used to determine a simulated photoresist formula and build a photoresist system model according to the photoresist formula; The first calculation module is used to simulate the film density of the photoresist system model and output the center of mass coordinates of the molecules in the film; The photon distribution module is used to determine the number of photons in the photoresist film and obtain the photon coordinates; The photoelectron energy calculation module is used to determine the type of molecule ionized by the photon according to the distance from the photon to the center of mass coordinate, and obtain the energy of the photoelectron in combination with the ionization energy of the molecule; The secondary electron distribution calculation module is used to perform Monte Carlo simulation of secondary electron generation on all photon positions in the photoresist film in combination with the energy of the photoelectrons and the photon coordinates, obtain the distribution of secondary electrons in the photoresist film, and output the secondary electron coordinates.

9. A system for constructing a photoresist secondary electron generation model according to claim 8, characterized in that: It also includes a molecular ionization energy calculation module, which is used to calculate the ionization energy of different types of molecules through first-principles software.

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