JP2005034843A - Calculation method of reaction mechanism and recording medium with the calculation method recorded thereon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calculation method of a reaction mechanism capable of easily calculating a reaction process and to provide a process simulation method using thereof. <P>SOLUTION: In the calculation method of the reaction mechanism, the reaction process of chemical species is estimated by making atoms consisting of one or more chemical species dynamically move respectively and by dynamically calculating, many times or until an intended chemical species is obtained, to determine their state after a fixed time. In the process simulation, an optical design of the process is carried out using the above calculation method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a reaction mechanism calculation method. More specifically, the present invention simulates a mechanism in which one molecule undergoes a decomposition reaction or a mechanism in which a plurality of molecules react while interacting with each other by a dynamic calculation in consideration of the movement of atoms constituting the molecule. The present invention relates to a reaction mechanism calculation method.

In the manufacturing process, process simulation is often studied in order to improve productivity and the like.

For example, in the manufacturing process using chemical reaction, how the reaction occurs,
It is studied how to improve the yield and reaction rate. In order to perform such a process simulation, details of the reaction mechanism, a rate equation of the elementary process, and the like are necessary, and these are often determined experimentally.

It has also been attempted to optimize the structure of the transition state using the molecular orbital method and to calculate the reaction rate equation using absolute reaction kinetics. As another method, Japanese Patent Application Laid-Open No. 9-279340 discloses a method for calculating the material of an amorphous silicon thin film and the speed for forming the thin film using molecular dynamics. (Patent Document 1) As another method, JP-A-7-
Japanese Patent No. 37821 discloses a method of optimizing a process to satisfy a predetermined specification based on a chemical reaction formula and a reaction time prediction. (Patent Document 2)
Japanese Patent Laid-Open No. 9-279340 JP-A-7-37821

However, even when trying to obtain the reaction rate experimentally, it is often impossible to elucidate the reaction process. For example, when trying to clarify the reaction mechanism of a system that measures the decomposition rate by flowing a raw material gas into a reaction tube, the overall rate such as the reduction rate of the raw material gas is not even if the reaction mechanism is examined by experiment. Although it is required, it is often not known until all the intermediate processes that occur after flowing the raw material gas, that is, the reactant processes.

On the other hand, the calculation of the velocity using the molecular orbital method examines the elementary process assumed in advance based on the energy level, so it is highly likely that an important unexpected elementary process is overlooked, Even if the elementary process can be accurately predicted, it takes time to optimize the structure of the transition state, and the transition state cannot often be found accurately.

As described above, conventional methods for searching or calculating reaction mechanisms lack accuracy and certainty.

With respect to such a problem, the present invention intends to provide an efficient method for calculating a reaction mechanism using a computer.

[Summary of Invention]
In the present invention, the reaction of the chemical species is simulated by moving the atoms kinetically by a computer, and the reaction process of the chemical species (reactive element process that may occur) is estimated from multiple dynamic calculations. This makes it possible to estimate the reaction mechanism. The reaction process can be displayed on a display means such as a display. The display content is not limited to the reaction process, and may be a reaction product in the reaction process. In addition, the reaction process and reaction product can be recorded on an optical disk or a magnetic recording medium.

<Summary>
The reaction mechanism calculation method of the present invention includes a step of simulating the dynamic motion of each atom constituting one or a plurality of chemical species that cause a chemical reaction, and a plurality of states of the system after a certain period of time. And a step of estimating a reaction process of the chemical species from the calculation result.

Further, the reaction mechanism calculation method of the present invention is a computer-readable recording medium storing a program for operating a computer, wherein the program is used to calculate atoms of one or more chemical species that cause a chemical reaction. A procedure for simulating each dynamic motion, a procedure for calculating the state of the system after a certain period of time a plurality of times, and a procedure for estimating the reaction process of the chemical species from the calculation result, To do.

<Effect>
According to the present invention, it is possible to easily estimate a reaction process in a chemical reaction, and to optimize a process in a manufacturing process or the like based on an understanding of the estimated reaction process.

According to the present invention, it is possible to easily estimate a reaction process and optimize a process based on an understanding of the reaction process.

[Detailed Description of the Invention]
The details of the present invention will be described below with reference to the illustrated embodiments. In addition, the same code | symbol is attached | subjected to the same component over all the drawings.

In the first reaction mechanism calculation method of the present invention, what kind of reaction, that is, what kind of reaction is caused by one or more chemical species, and what kind of transition state when the reaction occurs, It is for estimating whether such a reaction product is formed. This reaction mechanism calculation method will be described below with reference to the flowchart shown in FIG.

The chemical species of interest in the present invention is arbitrary and most typically is a molecule composed of a plurality of atoms, but any chemical species such as monoatomic molecules, ions, radicals, and others. Good. Therefore, chemical species such as CF ₃ ⁺ , CF ₃ ⁻ , CF ₃ or electrons can also be used in the calculation. In addition, a chemical species electronically excited by light can be used. Most typically, a reaction mechanism is examined by a kinetic method for a molecule composed of a plurality of atoms.

The chemical species generally consists of a plurality of atoms. In the present invention, the type of a raw material chemical species to be examined for reaction is input. For example, if the name of a chemical species is input, the three-dimensional coordinates of the chemical species are read from the database. The potential energy of the stable structure of the chemical species may be stored in a database, or may be sequentially calculated from the read structure by a molecular orbital method or the like. Examples of molecular orbital methods used for calculating energy include semi-empirical molecular orbital methods, molecular mechanics methods, ab initio methods, and density functional methods (for example, Explorin).
g Chemistry With Electronics Structure Me
thods, 2nd ed. Ed. James B.B. Foresman &
Aeleen Frisch, Chap. 1, Computation Mode
ls & Model Chemistries, pp. 3-11). Also,
The level of kinetic energy given to a plurality of molecules is also input (101 in FIG. 1).

Next, the binding information of the read chemical species is stored as data. The structure of the chemical species is randomly changed as long as the read bonds are not broken. In addition, a vibration speed is given to each atom of the chemical species and a rotational speed is given to the chemical species so as to substantially satisfy the arbitrarily input kinetic energy.
When performing dynamic calculation of a plurality of chemical species, the chemical species are arranged at appropriate intervals and oriented in a random direction. Provides translational speed in the direction in which chemical species interact. The translational energy substantially satisfies the input kinetic energy. The translation vector is generally directed in the direction in which the center of gravity of the chemical species collides, but may be deviated from this direction (102 in FIG. 1).

The dynamic reaction calculation is performed using the initial structure of the chemical species thus determined and the initial velocity of each atom as the initial state. The force acting on each atom is determined by the molecular orbital method, and according to the force, New
Ton dynamically moves each atom at an appropriate time step. The atoms are moved so as to keep the sum of the potential energy and kinetic energy of the chemical species constant, but the kinetic energy can be scaled by an appropriate method (103 in FIG. 1).

In particular, when calculating the reaction between a plurality of chemical species, the molecular orbital calculation before and after the collision of the plurality of chemical species should be performed in detail. At this time, it is necessary to take into account the Coulomb force generated by the charge or acceleration by an external force such as an electric field or a magnetic field for chemical species having a charge such as ions, and more complicated calculation is required to calculate the mechanism. It is normal to become. For example, a semi-empirical molecular orbital method can be used as a molecular orbital calculation when a plurality of chemical species collide, and a molecular mechanics method can be used before and after the chemical species collide. In this case, the entire calculation time can be shortened. Of course, all reactions between chemical species can be performed by the same calculation method, for example, by a semi-empirical molecular orbital method.

In addition, by simulating a solid surface based on clusters and periodic boundary conditions, it is possible to investigate the reactive process on the surface using the same dynamic technique. When simulating a solid surface, the degree of freedom of translation and rotation of the chemical species simulating the surface is zero. By this setting, it is possible to continuously collide the raw material and the reaction product with the surface and to simulate the surface reaction. When simulating a solid surface, the coordinates of some atoms may be fixed so as not to move during dynamic reaction calculation.

Furthermore, the reaction in a solvent can be simulated. In this case, the kinetic calculation can be performed using the potential in consideration of the solvent effect, that is, the solvation potential. As such a technique, for example, the COSMO method (Conductor-like Score) is used.
ening Model) (for example, Fujitsu MOPAC 93 M).
annual, Revision Number 2, by James J. et al. P.
Stewart, 1993 8. 26 COSMO at p217). Or you may arrange | position a solvent molecule | numerator and may perform the kinetic calculation also including a solvent molecule | numerator.

By these molecular orbital calculations, for example, what kind of change occurs in a chemical species when a certain chemical species collides with another chemical species is calculated.

ＳｉＨ_４とＳｉＨ_４とが反応する場合を例に取ると、ＳｉＨ_４とＳｉＨ_４が離れて存在
している場合には、Ｓｉ１にＨ１〜Ｈ４が、Ｓｉ２にＨ５〜Ｈ８が結合している。マトリ
ックス中の１は原子と原子の結合がある場合、０は無い場合を示している。マトリックス
の上三角部分は、下三角部分と同一なので省略してある。 In such a case, typically, after collision, either a different chemical species passes through a transition state, or the structural change of the chemical species does not occur upon collision. The presence or absence of such a structural change, that is, whether or not a reaction has occurred is determined. The bond information of the chemical species after performing the dynamic calculation for a certain time is calculated and compared with the stored bond information of the chemical species. If there is a change in the bond, it is determined that a reaction has occurred. An example of the combined information is as shown in Table 1.

Taking the case where SiH ₄ and SiH ₄ react as an example, when SiH ₄ and SiH ₄ exist apart from each other, H1 to H4 are bonded to Si1, and H5 to H8 are bonded to Si2. In the matrix, 1 indicates that there is an atom-to-atom bond and 0 does not exist. The upper triangular part of the matrix is omitted because it is the same as the lower triangular part.

このように計算前後の結合マトリックスを比較することにより、反応の有無を判定する
ことができる。結合マトリックスは、分子軌道法により結合次数を計算し、結合次数があ
る値（例えば０．４）より大きければ結合があると判断して、作成する。結合があると判
断する次数は原子の種類によって変化させてもよい。 As a result of calculation after a certain time, it is assumed that the binding is as shown in Table 2. H1 to H3 and Si2 are bonded to Si1, and Si1 and H5 to H7 are bonded to Si2. On the other hand, H4 and H8
Are joined. That is, Si ₂ H ₆ and H ₂ are generated.

Thus, the presence or absence of reaction can be determined by comparing the binding matrices before and after the calculation. The bond matrix is created by calculating the bond order by the molecular orbital method, and determining that there is a bond if the bond order is larger than a certain value (for example, 0.4). The order in which it is determined that there is a bond may be changed depending on the type of atom.

Further, if the distance between two atoms is smaller than a value (for example, 1.5) obtained by multiplying the sum of the atomic radii of each atom by a certain value, it may be determined that there is a bond.

The presence / absence of reaction may be determined not only by binding information but also by changes in potential energy of chemical species and kinetic energy. For example, when SiH ₄ and SiH ₄ collide,
Translation energy of ₄ molecules, in the case of simply reflected simply crash, translation energy is reduced upon impact, after the collision, vibrations and rotational kinetic energy or translational energy of the SiH ₄ molecules collided partner, The energy is exchanged with each other, and although there is a slight change in the energy level, it has a translational energy almost equal to the translational energy before the collision. However, when the reaction occurs, or combined with other SiH ₄ molecules, to or forming a constituent atom and new molecules other SiH ₄ molecules constitute a SiH ₄ before collision atoms The translational energy with reference to changes greatly after a collision. Such a point where the translational energy is minimal or close to 0 is likely to have a structure close to the transition state of the reaction. When the transition state structure optimization is performed, the structure at this point can be adopted as the initial structure of the transition state structure optimization.

If it becomes another chemical species after collision, it can be cited as one of the reactant processes in the system. Another species that occurs after the collision is identified as a reaction product. The stable structure of the identified chemical species can be calculated, for example, by the molecular orbital method. When the initial state of chemical species, the conditions in collision, etc. are changed, the reactive element process required dynamically is also changed. Therefore, there are usually many kinds of reactive element processes as a whole. The reaction element structure and the structure of the reaction product when the reaction occurs can be stored in a recording medium one by one, and can also be displayed on a display means such as a display. The display of the record information can be performed by, for example, an appropriately designed user interface. When a reaction occurs, by designating this reaction product as an input chemical species, the reaction between the reaction products and the reaction between the reaction product and the raw material can be calculated.

Therefore, in order to clarify the reaction mechanism, it is important to clarify all these reactant processes. For this purpose, it is preferable to perform dynamic calculation repeatedly by changing the initial conditions. More preferably, the number of times that a certain conclusion can be derived is calculated by processing based on statistics. That is, the first reaction mechanism calculation method of the present invention is completed by repeating the kinetic calculation a specific number of times. The initial conditions are also important, and it is preferable to provide the specific initial conditions, for example, translation, rotation, or vibrational energy of the chemical species as a function of temperature. At this time, it is preferable to determine various energies according to temperature based on thermodynamics.

In addition, the initial chemical species are the raw materials of the reaction system that is most easily clarified, but the product estimated by the above method is also treated as the initial chemical species in the kinetic calculation. be able to. Treating the product as an initial species is important to reveal the actual complex reaction mechanism.

The result of calculating such a reaction process is displayed by an appropriate display means or recorded on a recording medium by an appropriate recording means and used. Although the display means and the recording means are not particularly limited, they are generally displayed on various displays, printed on an appropriate support, or recorded on an optical disk or magnetic recording medium.

Another embodiment of the reaction mechanism calculation method according to the present invention is described below with reference to FIG.

The method is the same as that described above until a predetermined number of times, in this case, n times of dynamic calculations are performed. It is assumed that the number of times that the reaction has occurred in n dynamic calculations is only a specific number of times, for example, L times. When the number of times of reaction occurs less than L times, the kinetic energy given in the initial condition is small. Therefore, the kinetic energy is increased by ΔT1, and the dynamic calculation is performed a predetermined number of times again. By appropriately setting the temperature with reference to the reaction probability indicated by the broken line in FIG. 6, the kinetic energy is increased and the reaction probability is increased. In addition, when the reaction occurs more than a specific number of times, for example, m times, the kinetic energy is too large and the reaction occurs too much, making it difficult to evaluate the elementary reaction. In this case, the kinetic energy is reduced by reducing the kinetic energy by ΔT2, and the dynamic calculation is performed again a predetermined number of times. In this way, reaction analysis can be performed with appropriate kinetic energy.

By using the information of the reactive element process data and the calculation process data, the structure of the product and the transition state can be optimized. Since the information on what kind of product is generated is obtained from the reactant process data, a stable structure and potential energy can be obtained using the structure of the obtained product as an initial structure. In order to obtain the transition state, the structure of the transition state may be estimated from the structure of the raw material and the product, and it may be used as the initial structure of the structure optimization. Also, the structure close to the transition state of the reaction is extracted from the calculation process data. Thus, it can be used for the initial structure of the structure optimization of the transition state. In order to calculate the reaction rate, activation energy, such as ab initio method or density functional method,
It is desirable to use a method that is said to have a good agreement between the heat of reaction and the experimental value.

単分子分解の場合には、反応速度定数に圧力依存性が現れるので、ＲＲＫＭ（Ｒｉｃｅ
−Ｒａｍｓｐｅｒｇｅｒ−Ｋａｓｓｅｌ−Ｍａｒｃｕｓ）モデル（例えばＣｈｅｍｉｃａ
ｌ Ｋｉｎｅｔｉｃｓ， ３ｒｄ Ｅｄ． ｂｙ Ｋｅｉｔｈ Ｊ．Ｌａｉｄｌｅｒ，
Ｈａｒｐｅｒ Ｃｏｌｌｉｎｓｍ １９８７， Ｓｅｃｔ． ５．３．５ ａｔ ｐ１６
４を参照）などに基づいた、圧力依存を考慮した反応速度式とするべきである。 The reaction rate k, for example, the reaction rate k when raw materials A and B react, is Q ^* for the transition state partition function, Q _A and Q _B for the partition function of _A and _B , E _{0 for the} activation energy, and Boltzmann constant Where k _B , Planck's constant is h, gas constant is R, absolute temperature is T, gas volume is V, and terms for translation, rotation, and vibration are trans, rot, and vib, respectively, as follows: Indicated.

In the case of monomolecular decomposition, pressure dependence appears in the reaction rate constant, so RRKM (Rice
-Ramsperger-Kassel-Marcus) model (eg Chemica)
l Kinetics, 3rd Ed. by Keith J.M. Laidler,
Harper Collinsm 1987, Sect. 5.3.5 at p16
The reaction rate formula should be based on the pressure dependence and the like.

In the same manner, the product can be automatically designated as the initial chemical species, and the calculation can be performed as many times as the number of times specified for the reaction between the raw material and the product. In this case, when there are a plurality of products, a molecule having a large number of atoms can be selected from the plurality of products. Moreover, the chemical species used as the raw material may be the same, or may be selected randomly from a plurality of raw materials with an appropriate probability.

On the other hand, when a specific substance is to be synthesized from known raw materials, the synthesis method may be unknown. The second reaction mechanism calculation method of the present invention clarifies a reaction process for obtaining a target chemical species from a given raw material in such a case.

This reaction mechanism calculation method will be described with reference to FIG.

First, a target chemical species, a group of chemical species as a raw material (for example, A, B, C...), And a reaction path number k are input as necessary (301 and 302 in FIG. 3).

For the chemical species randomly selected from the group of the raw material chemical species, as in the reaction mechanism calculation method described above, the displacement, orientation, and translation, vibration, and rotation speed of each atom are determined.
Dynamic calculation is performed (303 in FIG. 3). As a result of the calculation, if the possibility of reaction is recognized through a display or the like, it is recorded as an elementary process (310 in FIG. 3), and a reaction product is added as a chemical species as a raw material (308 in FIG. 3). . In addition to the data obtained by the method of the present invention, known data may be recorded in advance for the data of these reactant processes or reaction products. Further, how the reaction product reacts may be searched by searching a reaction database, and the product may be added.

On the other hand, if a reaction product is generated, it is determined whether or not the reaction product matches the target chemical species (305 in FIG. 3), and if they match, the recorded reaction data is used to go back to the raw material. The reaction route is determined (311 in FIG. 3).

By repeating such calculation until the number of paths reaches k, a desired number of combined paths can be calculated.

In addition, when examining what kind of reaction product is produced at what ratio by the actual process, from the raw material concentration of process conditions, temperature, pressure, and other conditions,
It is also possible to determine initial conditions for dynamic calculations. For example, if the concentration ratio of the source gases is 2: 1, the number of calculations for each combination of A + A, A + B, and B + B is 4/9, 4/9, and 1 depending on the collision occurrence probability of each combination. / 9. Conversely, the concentration of the reaction product can be estimated according to the probability of collision after performing the reaction calculation at an equal rate. For example, after calculating each combination of A + A, A + B, and B + B equally, B +
What is necessary is just to make the generation | occurrence | production ratio of the reaction product produced | generated by B 1/4.

The kinetic energy can also be sampled according to the Maxwell distribution of process temperature. As will be described later, since the reaction process can be found more efficiently when the reaction calculation is performed under the condition of large kinetic energy, the reaction rate at the process temperature is determined from the existing rate in the Maxwell distribution of energy to be studied. Can also be converted to

It is also possible to perform dynamic calculations by generating raw material and carrier molecules according to the process pressure. For example, in a cube with a side of 100 angstroms, chemical species are generated according to process conditions, and the generated molecules are dynamically moved under periodic boundary conditions to examine what kind of reaction occurs. can do. Here, when the pressure is low, the probability of a three-body collision is low, so that it is more efficient to perform the dynamic calculation for a combination of any two chemical species.

The reaction mechanism calculation method of the present invention can be recorded on any recording medium. Specific recording media are floppy disk (R), CD-ROM, MD (Mini Disk).
, MO (Magneto-Optical disk), PD (Phase-chang)
e Disk), DVD (Digital Versatile Disk), and others. A semiconductor chip may be used to store and execute the reaction mechanism calculation method of the present invention.

FIG. 8 is a bird's-eye view illustrating an overview of a simulation apparatus in which the simulation apparatus including the reaction mechanism calculation unit described above is realized by hardware.

The main body of the simulation apparatus 801 includes a reaction mechanism calculation means, and further includes a floppy disk (R) apparatus (floppy disk (R) drive) 802 and an optical disk apparatus (optical disk drive) 803. A floppy disk (R) 804 is inserted into the floppy disk (R) drive 802 and a CD-ROM 805 is inserted into the optical disk drive 803 from the insertion slot, and these are read out. A program stored in a recording medium can be installed in the system. Further, by connecting a predetermined drive device, for example, a ROM 806 as a memory device used for a game pack or the like, or a cassette tape 807 as a magnetic tape device can be used.

By giving a random rotation and vibration mode to the molecule as an initial state and moving the molecule in a random direction dynamically, it is possible to simulate a state close to an actual reaction in a computer. By performing such a calculation a plurality of times, preferably the number of times that a conclusion is derived based on statistical theory, it is possible to select what occurs as a reaction process.

分子の安定構造のエネルギをＥ_０、安定構造からある構造へ変位したときのエネルギを
Ｅ’とする。ポテンシャルエネルギと振動エネルギとの和は一定であるので、ポテンシャ
ルエネルギと振動エネルギとの保存を考慮した振動温度Ｔ_ｖｉｂ’は下式の通りとなる。

目的とする温度に相当する、並進、回転、および振動のエネルギを、分子構造の平衡状
態からの変位と、原子の速度であたえ、各原子に作用する力を分子軌道法により求め、そ
の力に従って、原子をニュートン力学的に動かす操作を行う。 Mass of atoms i in the molecule, coordinates, and velocity, respectively _m i, assumed to be _{x i,} and _{v i.} Here, x _i and v _i are vectors. Also, _let ν _trans , ν _rot , and ν _vib be the degrees of freedom of translation, rotation, and vibration of the molecule, respectively. At this time, the temperatures T _tran , T _rot , and T _vib corresponding to the translation, rotation, and vibration of the molecule are k _B
If Boltzmann's constant is used, it is expressed by the following equation.

The energy of the stable structure of the molecule is E ₀ , and the energy when displaced from the stable structure to a certain structure is E ′. Since the sum of the potential energy and the vibration energy is constant, the vibration temperature T _vib ′ considering the preservation of the potential energy and the vibration energy is expressed by the following equation.

The translational, rotational, and vibrational energy corresponding to the target temperature is given by the displacement from the equilibrium state of the molecular structure and the velocity of the atoms, and the force acting on each atom is determined by the molecular orbital method. , Do the operation to move the atom Newton mechanically.

An example of the calculation result when the translation speed is given in the direction in which two SiH ₄ molecules collide when such an operation is performed is as shown in FIGS.

In the example shown in FIG. 1, they simply collide and move away (that is, no intermolecular reaction takes place). First, each initial SiH ₄ molecule approaches in a state in which each atom has its own energy, and becomes a state close to a transition state. Here, the next state is determined from the energy of each atom, but in the case of FIG. 4, it does not react and leaves as the original molecule.

On the other hand, in the example shown in FIG. 5, two molecules collide and become a state close to a transition state. As calculated from the energy of each atom in this state, it can be seen that Si ₂ H ₆ and H ₂ are generated at the next stage, and two molecules are reacted. At this time, the calculation time of the dynamic calculation is longer than the time required for the collision calculated by the distance between the two molecules of the initial structure (SiH ₄ ) and the translation speed.

In this example, the force acting on each atom was obtained by using the PM3 method which is a semi-empirical molecular orbital method. You can ask more.

Further, the direction of collision can be selected at random, and the temperature of translation, rotation, or vibration can also be selected at random. Further, the collision directions do not have to be opposed to each other, and the number of colliding molecules may be more than two. When two or more molecules collide, the molecular orbital method is preferably used, and when the molecular mechanics method is used, it is necessary to select an appropriate parameter necessary for the calculation.

A reaction of only one molecule, for example, a decomposition reaction, can also be calculated by the same method as described above.

By repeating such operations a plurality of times, preferably a number of times that a conclusion can be drawn by statistical processing, what kind of chemical species are generated by what kind of chemical reaction, for example, by reaction of a specific molecule It becomes possible to estimate.

It is also possible to investigate a more detailed reaction mechanism by further calculating the product and raw material molecules estimated by such a method, or the products by a similar method.

The transition state can be obtained by setting the structure close to the transition state of the reaction in FIG. 5 as an initial structure for transition state structure optimization by a normal molecular orbital method. By optimizing the structure of the transition state, it is possible to obtain the raw material system, the partition function of the transition state, and the energy difference, and to obtain the reaction rate from the absolute reaction kinetics.

The calculation process of dynamics can be stored at an appropriate sampling interval, but it may be difficult to store all of a large number of calculation results as the number of calculations increases. In such a case, it is possible to investigate what kind of reaction has occurred by storing only the initial condition of the dynamic calculation and the final structure within the calculation time.

It is also possible to extract only those having a final structure different from the initial molecular structure and save only the data. Further, only the transition state of data determined to have a final structure different from the initial molecular structure, or a structure close thereto, and the final structure may be stored.

The determination of whether or not a reaction has occurred can be made by examining whether the final structure is different from parameters indicating the bonding of the initial structure, such as distance, angle, bond order information, and others.

In the case of general thermal energy, the energy distribution of gas molecules has a Boltzmann distribution (shown by a solid line) as shown in FIG.

For example, molecules having an average energy of 1000K include molecules having different intrinsic energies. Some molecules have energy of several thousand degrees, and those having such high energy are highly reactive.

In the case of a reaction having a reaction probability as shown in FIG. 6 (shown by a broken line), the integral value of the product of the reaction probability and the Boltzmann distribution indicates the reactivity of the molecule at that temperature. When reacting kinetically, it is possible to investigate the reaction efficiently by focusing on the molecule at a temperature corresponding to the high energy of the Boltzmann distribution and performing reaction simulation.

Such a change in the reaction probability due to the energy difference can also be confirmed by the reaction mechanism calculation method of the present invention.

For example, when calculation is performed 500 times when two molecules of SiH ₄ collide, the number of reactions increases as the energy applied to the initial molecule increases. FIG. 7 shows the result.

The reaction rate can be estimated from the proportion of molecules according to the Boltzmann distribution at the kinetic reaction temperature and the reaction probability.

The temperature applied at the time of dynamic calculation may be different for a plurality of molecules, and may be different for each energy of rotation, vibration, and translation.

Specifically, SiH ₂ Cl ₂ and NH ₃ are used as raw material gases for forming a silicon nitride film by a CVD method (for example, a thermal CVD method). When this raw material gas is used, NH ₄ Cl is generated as a reactive product, which is considered to contribute to particles on the wafer, which is a cause of device yield reduction. SiH ₂ Cl by the method of the present invention
_When the gas phase reaction process between ₂ and NH ₃ was examined, it was found that the following reaction occurred.

SiH ₂ Cl ₂ + NH ₃ → H ₂ NSiH ₂ Cl + HCl
H ₂ NSiH ₂ Cl ₂ + NH ₃ → H ₂ NSiH ₂ NH ₂ + HCl
H ₂ NSiH ₂ Cl + SiH ₂ Cl ₂ → H ₂ ClSiNHSiH ₂ Cl + HCl
2H ₂ NSiH ₂ Cl → H ₂ NSiH ₃ + H ₂ NSiHCl ₂
... (Omitted)
By using a gas containing no Cl gas, such as H ₂ NSiH ₂ NH _2, as a source gas among those generated by these reactions, it was possible to form a silicon nitride film that does not generate NH ₄ Cl. As described above, the CVD reaction mechanism is simulated by the method of the present invention, the film formation species is examined, and the film formation species capable of obtaining the desired film formation characteristics are directly supplied to greatly improve the process. It becomes possible.

From the structural optimization of these elementary processes using the ab initio method, the activation energy and frequency factor of the reaction are calculated, the film formation simulation in the apparatus is performed, and the film formation conditions such as the raw material gas flow rate, pressure, or temperature Can be optimized. In general, the gas flow, temperature, and pressure in the system are analyzed by numerical analysis methods, etc., and the mass balance is calculated according to the calculated reaction rate equation to calculate the concentration distribution in the system, and the film formation rate and other components are achieved. Calculate membrane properties.

A specific example of finding the synthesis route from the raw material to the target chemical species by the second reaction mechanism calculation method of the present invention is as follows.

Consider the case of finding a route for synthesizing SiH ₂ (NH ₂ ) ₂ as the target chemical species. First, SiH ₄ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , and NH ₃ are listed as raw materials in a group of raw material chemical species. According to the method of the present invention, a chemical species to be reacted at random is selected from the list, and kinetic calculation is performed.

Select SiH ₂ Cl ₂ and NH ₃ and add them to the initial species group as SiH ₂ ClNH ₂ results from kinetic reaction calculations when they collide. At this time, Si
Information that SiH ₂ ClNH ₂ is generated from H ₂ Cl ₂ and NH ₃ is stored as information. In the course of the repeated _{calculations, SiH} from SiH ₂ ClNH 2 and NH ₃ Metropolitan _{2 (NH 2)} 2
Is generated. This SiH ₂ (NH ₂ ) ₂ is added to the initial group of chemical species, and the synthesis route is also stored as information. Since this SiH ₂ (NH ₂ ) ₂ is the target chemical species, its synthesis route is output retroactively until the raw material of the reactant process matches that in the initial chemical species list.

SiH ₂ (NH ₂ ) ₂ ← SiH ₂ ClNH ₂ + NH ₃
SiH ₂ ClNH ₂ ← SiH ₂ Cl ₂ + NH ₃
Since SiH ₂ Cl ₂ and NH ₃ are included in the group of the initial raw material chemical species, the output ends at this stage, and the synthesis route is determined.

In this reaction mechanism calculation method, the reaction process can be used by previously registering a known reaction in addition to the one obtained by calculation. At this time, the reaction product obtained by the registered known reaction may be automatically used as an additional raw material chemical species.

For example, it is known that SiH ₂ Cl ₂ decomposes into SiCl ₂ and H ₂ . Therefore,
If SiH ₂ Cl ₂ is present in the group of source chemical species, SiCl ₂ and H ₂ may be automatically added to the group of source species.

The case of executing the reaction mechanism calculation procedure recorded on such a recording medium will be described as follows.

First, the reaction mechanism calculation procedure program is recorded in a recording medium such as a floppy disk (R) drive 802, an optical disk drive 803, or a semiconductor chip in FIG. Subsequently, the program is read from the recording medium and sequentially executed by the CPU of the computer 801 connected to the reading device.

In addition, the processing in the embodiment of the present invention is realized by a computer executable program,
This program can be recorded on a computer-readable recording medium.

The recording medium in the present invention includes a magnetic disk, floppy disk (R), hard disk, optical disk (CD-ROM, CD-R, DVD, etc.), magneto-optical disk (
The storage form may be any form as long as the storage medium can store a program and can be read by a computer.

Further, an OS (operating system) operating on the computer based on an instruction of a program installed in the computer from the recording medium, database management software, MW (middleware) such as a network, and the like for realizing the present embodiment A part of each process may be executed.

Furthermore, the recording medium in the present invention is not limited to a medium independent of a computer,
In addition, a recording medium in which a program transmitted via the Internet or the like is downloaded and stored or temporarily stored is also included.

Further, the number of recording media is not limited to one, and even when the processing in the present embodiment is executed from a plurality of media, it is included in the recording media in the present invention, and the configuration of the media may be any configuration.

The computer according to the present invention executes each process according to the present embodiment based on a program stored in a recording medium, and a single device such as a personal computer or a plurality of devices are connected to a network. Any configuration such as a system may be used.

In addition, the computer in the present invention is not limited to a personal computer, and includes an arithmetic processing device, a microcomputer, and the like included in an information processing device, and is a generic term for devices or devices that can realize the functions of the present invention by a program. is doing.

The flowchart which shows an example of the reaction mechanism determination by the 1st reaction mechanism calculation method of this invention. The flowchart which shows an example of the reaction mechanism determination by the 1st reaction mechanism calculation method of this invention. The flowchart which shows an example of the reaction mechanism determination by the 2nd reaction mechanism calculation method of this invention. According to the reaction mechanism calculation method of the present invention, when the colliding two SiH _4, illustrates a calculation result when the reaction did not occur. According to the reaction mechanism calculation method of the present invention, when the colliding two SiH _4, shows the calculation results when the reaction occurs. The figure which shows the energy distribution and reaction probability of a molecule | numerator whose average energy is 1000K. It was determined by dynamic calculation, shows the frequency with which the reaction occurs when the SiH ₄ was 2 molecule collisions. It is a bird's-eye view which shows the external appearance of the apparatus for enforcing the reaction mechanism calculation method of this invention.

Explanation of symbols

801 Simulation device 802 floppy disk (R) device (floppy disk (R) drive)
803 Optical disk device (optical disk drive)
804 Floppy disk (R)
805 CD-ROM
806 ROM
807 cassette tape

Claims (15)

Simulating the dynamic motion of each of the atoms constituting one or more species that cause a chemical reaction;
A step of calculating the state of the system after a certain time over pluralizations;
Estimating a reaction process of the chemical species from the calculation result;
The reaction mechanism calculation method characterized by having. The reaction mechanism calculation method according to claim 1, wherein the reaction process or a reaction product in the reaction process is displayed. The reaction mechanism calculation method according to claim 1, wherein the reactant process or a reaction product in the reactant process is recorded on a predetermined recording medium. The reaction mechanism calculation method according to any one of claims 1 to 3, wherein a force acting on each atom is obtained by a molecular orbital method, and the atom is moved according to the force. Giving translational, rotational, and vibrational energy to a chemical species at random, and performing dynamics calculations with atomic displacement, atomic velocity, and chemical species orientation in the chemical species determined by the initial state,
The reaction mechanism calculation method of any one of Claims 1-4. 6. The reaction mechanism calculation method according to any one of claims 1 to 5, wherein the energy of translation, rotation, and vibration randomly given to the chemical species is selected as a function of temperature. 7. The reaction process is estimated by extracting a calculation result having a state in which a state of a chemical species after a certain time is different from an initial chemical species from a plurality of kinetic calculation results. The reaction mechanism calculation method of description. The reaction mechanism calculation method according to any one of claims 1 to 7, wherein a reaction rate equation of a reaction element process is calculated by processing a plurality of kinetic calculation results based on statistical theory. The reaction mechanism calculation method according to claim 1, wherein a transition state of a reaction element process is extracted from a result of kinetic calculation, and a reaction rate is calculated based on statistical mechanics. The reaction mechanism calculation method according to any one of claims 1 to 9, wherein the initial chemical species is a reaction product generated in a reaction element process obtained by an arbitrary kinetic calculation. The reaction mechanism calculation method according to any one of claims 1 to 10, wherein a reaction rate is calculated by calculating a reaction rate based on probability theory from a result of kinetic calculation. The molecule is moved so that other chemical species continuously collide with the specific chemical species.
The reaction mechanism calculation method according to any one of 1 above. In a computer-readable recording medium recording a program for operating a computer,
The program is
A procedure for simulating the dynamic motion of each of the atoms constituting one or more chemical species that cause a chemical reaction;
A procedure for calculating the state of the system after a certain time multiple times;
A procedure for estimating the reaction process of the chemical species from the calculation result;
A recording medium on which a reaction mechanism calculation method is recorded. The recording medium according to claim 13, wherein the reactive element process or a reaction product in the reactive element process is displayed. The recording medium according to claim 13 or 14, wherein the reactant process or a reaction product in the reactant process is recorded on a predetermined recording medium.

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