JP2009049305A - Oxide film thickness estimating method and device, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxide film thickness estimating device capable of precisely obtaining the thickness of a film deposited by a plasma film deposition device during a deposition process. <P>SOLUTION: The oxide film thickness estimating device includes: a database 11 which stores and holds as a template the relation between plasma light emission intensity obtained by a previous experiment and generated through a plasma oxidation process and oxidation seed density; an oxidation seed density estimation unit 12 which acquires two of light emission intensities measured by a spectroscope 4 during execution of a process to be monitored and obtains oxidation seed density from the light emission intensity ratio obtained from the acquired the light emission intensities and a template read out of the database 11; and a film thickness estimation unit 13 which obtains an oxidation film thickness by substituting the obtained oxidation seed density for a previously set oxidation film growth model. The oxidation seed density estimation unit corrects the light emission intensity ratio on the basis of process conditions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oxide film thickness estimation method, apparatus, and program for estimating a film thickness formed by a plasma oxidation process.

  Measuring the film thickness of products and intermediate products manufactured by a film-forming process such as a plasma film-forming device is not only for direct use, such as judging the quality of products and evaluating the quality, but also plasma. Indirect use such as diagnosing the presence or absence of abnormality in the equipment constituting the manufacturing process including the film forming apparatus can also be performed. This indirect use is based on the premise that if the equipment that constitutes the manufacturing process operates normally, the manufactured product will also be good, and if a defective product is manufactured, something will be done to the equipment. It is estimated that an abnormality or failure has occurred.

As a technique for measuring the film thickness, there is a method of directly measuring using a measuring instrument such as an ellipsometer. The ellipsometer measures changes in the polarization state of incident light and reflected light on the surface of a thin film, which is a measurement object, and calculates the film thickness and refractive index of the thin film from data obtained therefrom. As a technique for indirectly measuring the film thickness, there is a method for estimating the film thickness formed by sputtering or CVD using light intensity (Patent Document 1).
JP 2003-188150 A

  In order to measure the film thickness using an ellipsometer, a light emitting unit that emits light to irradiate the surface of the object to be measured and a light receiving unit that receives the reflected light reflected on the surface of the chamber are formed. It is necessary to attach a part, and the apparatus configuration becomes large. In addition, there must be a chamber window at a position where the light emitting unit, light receiving unit, and wafer are properly positioned, but since there are few such film forming apparatuses, it is necessary to modify the chamber, and the modification affects the film formation. There is a risk of giving. Further, since the ellipsometer obtains the film thickness based on the change in the polarization state of the incident light and the reflected light, it is affected by the plasma emission generated during execution of the film forming process in the plasma film forming apparatus, and the measurement accuracy is lowered. Therefore, the film thickness is not measured in real time during the film formation process, and is often measured after the film formation. Therefore, when an ellipsometer is used, the film thickness cannot be measured during the film forming process, and feedback control for the film forming apparatus cannot be performed based on the measurement result, and the presence or absence of abnormality cannot be estimated.

  Since the film thickness monitoring technique based on the light emission intensity disclosed in Patent Document 1 is an invention that assumes an etching process, it is easy to use the correlation between the two parameters of the light emission intensity and the plasma processing time and the film thickness. However, in plasma oxidation, the relationship between emission intensity, plasma processing time, and film thickness is complicated, and the film forming speed varies with time. Therefore, the technique disclosed in Patent Document 1 cannot be applied.

  The present invention provides an oxide film thickness estimation method capable of accurately obtaining a film thickness to be formed by a plasma film formation apparatus during execution of the film formation process and that does not affect the film formation process of the plasma film formation apparatus, and An object is to provide an apparatus and a program.

  The oxide film thickness estimation method according to the present invention stores (1) the relationship between the plasma emission intensity generated by the plasma oxidation process and the oxidation species density as a template. Then, the plasma emission intensity measured during the execution of the process to be monitored is acquired, the step of obtaining the oxidized species density from the acquired plasma emission intensity and the relationship stored as the template, and the obtained oxidized species density are preset. And substituting in an oxide film growth model to obtain an oxide film thickness.

  (2) The plasma oxidation process uses oxygen and krypton or oxygen and argon, and the emission intensity can be a ratio of two plasma emission intensity.

  (3) The emission intensity may be corrected by the oxygen partial pressure.

  (4) The emission intensity is preferably corrected by the microwave power.

  (5) The oxide film thickness estimation apparatus according to the present invention includes a storage unit that stores and holds, as a template, the relationship between the plasma emission intensity generated during the plasma oxidation process and the density of the oxidized species as a template, and is measured during execution of the process to be monitored The oxidized plasma density is obtained from the acquired plasma emission intensity and the relationship read from the storage unit, and the oxidized species density is obtained by setting the obtained oxidized species density in advance. And a film thickness estimating means for obtaining an oxide film thickness by substituting into the growth model.

  (6) The program of the present invention acquires a plasma emission intensity measured during execution of a process to be monitored by a computer, and the generated plasma emission intensity and a plasma generated in association with a plasma oxidation process stored in a storage means Based on the relationship between the emission intensity and the oxidized species density, the oxidized species density estimating means for obtaining the oxidized species density, and the film for obtaining the oxidized film thickness by substituting the obtained oxidized species density into a preset oxide film growth model This is a program for functioning as thickness estimation means.

  Templates can be created for the relationship between emission intensity and oxidation species by determining the relationship between emission intensity and oxide thickness from the results of previous experiments and by determining the relationship between oxide thickness and oxidation species from the above calculation results. it can. The oxide film growth model can be defined by, for example, a differential equation based on a reaction mechanism on the wafer.

  When a disturbance occurs during the execution of the plasma film formation process, the emission intensity fluctuates with the density of the oxidized species. Therefore, by monitoring the emission intensity, it is possible to accurately estimate the oxidized species density reflecting the influence of disturbance that cannot be understood only by the process conditions. And the film thickness which considered the influence of a disturbance can be calculated | required by calculating | requiring the film growth estimation using the differential equation of film growth from the estimated oxidation seed density. Therefore, the present invention can reflect fluctuations in the process that cannot be obtained only by the physicochemical model based on the process conditions.

  Unlike the other methods, the film thickness estimation process of the present invention uses the intensity of light emission generated with the execution of the plasma film formation process, so that the plasma state can be measured without disturbing the plasma state. Therefore, the film thickness can be estimated in real time during the process execution. A process with high reproducibility can always be performed by diagnosing the process abnormality based on the obtained film thickness, or by adjusting the process conditions by feeding back the monitored film thickness. Also, as a system configuration, it is only necessary to attach a spectroscope for measuring the emission intensity of plasma, so that the film thickness can be obtained with a simple configuration.

  Further, by performing the correction process, it is possible to estimate the oxidized species density using the same template (relation between plasma emission intensity and oxidized species density) even under different process conditions. In other words, if a template set based on the same process conditions obtained in a prior experiment is used, the oxidation species density and the film thickness can be estimated without correction.

  According to the present invention, the film thickness formed by the plasma film forming apparatus can be accurately obtained during the film forming process without affecting the film forming process. Of course, the present invention does not prevent the film thickness from being obtained after the film formation process is performed.

  FIG. 1 shows a manufacturing system including an oxide film thickness estimation apparatus according to a preferred embodiment of the present invention. As shown in FIG. 1, the plasma film forming apparatus includes a process chamber 1 serving as an area where film forming processing by a plasma oxidation process is performed, an apparatus controller 2 that controls the operation of a process executed in the process chamber 1, It has. The apparatus controller 2 controls the process by giving instructions such as gas flow rate and microwave power to the process chamber 1. In this embodiment, the plasma film forming apparatus is a microwave-excited high-density plasma apparatus using krypton and oxygen.

The plasma oxidation mechanism in the process chamber 1 is as follows. As shown in FIG. 2, a predetermined gas is supplied into the chamber 1 with the silicon wafer 5 set in the process chamber 1. In this state, by applying a microwave, plasma is generated, the surface of the silicon wafer 5 is oxidized by oxygen atoms excited in the plasma, and the SiO ₂ film 6 is formed.

  At this time, a gas phase reaction and a surface reaction occur inside the process chamber 1. The gas phase reaction is (a) a reaction for generating oxidized species in plasma. This generation reaction of oxidizing species consists of more than 30 elementary reactions. The surface reaction includes (b) deactivation of oxidized species on the inner wall of the chamber 1 and (c) oxidation reaction of silicon generated on the surface of the silicon wafer 5. The amount obtained by subtracting the amount lost in (b) from the amount produced in (a) contributes to the oxidation reaction in (c).

  Therefore, the oxide film growth is estimated and predicted by simulating these reactions on a personal computer. For the simulation, a commercially available chemical reaction simulator such as CHEMKIN can be used. FIG. 3 shows the result of simulating the state of oxide film growth. As shown in the figure, the oxide film grows immediately immediately after the start, and thereafter the oxide film grows gradually.

  Returning to FIG. 1, the overall configuration will be described. In this embodiment, one end of the optical fiber 7 is attached to the measurement window of the process chamber 1 and the other end of the optical fiber 7 is connected to the spectrometer 3. A part of the plasma emission generated in the process chamber 1 during the plasma oxidation process is guided to the spectroscope 3 through the optical fiber 7, and the emission intensity is obtained there. The obtained emission intensity is input to the oxide film thickness estimation apparatus 10. Since the plasma film forming apparatus of this embodiment is a microwave-excited high-density plasma apparatus using krypton and oxygen, the spectroscope 3 obtains and outputs the luminescence intensity of krypton and oxygen.

  The process conditions output from the apparatus controller 2 are also input to the oxide film thickness estimation apparatus 10. The process conditions are also referred to as recipes, and there are indicated values such as a gas flow rate and a microwave power given to the process chamber 1 by the creation condition apparatus controller 2. In this embodiment, there are oxygen partial pressure, microwave power, process time and chamber pressure.

  Further, the ellipsometer 10 measures the oxide film thickness of the silicon wafer 5 oxidized in the process chamber 1 during the preliminary experiment. The film thickness data obtained by the ellipsometer 4 is given to the oxide film thickness estimation apparatus 10.

  The oxide film thickness estimation apparatus 10 performs a process for obtaining the relationship between the light emission intensity and the oxidation species density in a preliminary experiment, and performs a process for estimating the film thickness from the light emission intensity and process conditions during operation. The film thickness monitoring by the plasma emission intensity in the oxide film thickness estimation apparatus 10 is as follows.

  In the plasma oxidation process, oxidation species that are the main cause of oxidation are generated by plasma, and the oxidation species react with silicon on the silicon wafer 6 to generate an oxide film. Therefore, if the density of the oxidized species is known, the oxide film thickness can be estimated.

  As shown in the simulation results in FIG. 3, a physicochemical model based on process conditions such as microwave power can be used to estimate the oxide film thickness generated when the process conditions are given. However, in an actual oxide film formation process, fluctuations and disturbances that cannot be specified under process conditions occur. The density of the oxidized species closely related to the oxide film thickness is affected by the disturbance. On the other hand, the estimation of the oxide film thickness using the above-mentioned simulation has low accuracy because the influence of disturbance cannot be reflected in the simulation.

  Therefore, in the present embodiment, the processing for estimating the density of oxidized species in consideration of disturbance is performed, and then the oxide film thickness is estimated based on the estimated density of oxidized species. The density of the oxidized species was estimated using process conditions and plasma emission intensity. This causes the emission intensity to fluctuate together with the density of oxidized species due to disturbance, so that the influence of disturbance not reflected only by the process conditions is reflected by using the emission intensity. Further, the estimation of film growth is obtained from the estimated oxidation species density using a differential equation for film growth.

In order to obtain the relationship between the emission intensity and the oxidized species density, the following processing is performed as a preliminary experiment. The user changes the process conditions as appropriate to execute the plasma film forming process. The process conditions and the emission intensity obtained using the spectroscope 3 during the execution of the process are given to the oxide film thickness estimation apparatus 10. The emission intensity can be, for example, an average value obtained during process execution. The result of measuring the oxide film thickness of the SiO ₂ film 6 formed on the silicon wafer 5 by the ellipsometer 4 after the execution of the process is input to the oxide film thickness estimating apparatus 10.

The process conditions to be changed were oxygen partial pressure, microwave power, process time, and chamber pressure. An example of specific conditions is as shown in Table 1 below. Moreover, although the value of each condition is an instruction value called a recipe, an actual measurement value may be used.

  The oxide film thickness estimation apparatus 10 stores and holds the given data in association with each other. This association can be a table structure in which, for example, each process condition shown in Table 1 is associated with the corresponding emission intensity and film thickness.

ただし、
Ｌ：酸化膜厚
Ｃ_０：ＳｉＯ_２表面の酸化種密度
Ｃ_１：ＳｉＯ_２生成に必要な単位体積当たりの酸化種の数
Ｄ：ＳｉＯ_２中の酸化種の拡散係数
ｋ：酸化反応の速度定数
ｔ：時間
α：定数
である。 Prior to explaining the specific function of the oxide film thickness estimation apparatus 10, the plasma oxidation mechanism will be described in detail. Oxide species react on a silicon wafer to form an oxide film. In thermal oxidation, a deal-grove model is known in which oxidized species diffuse in the SiO ₂ film and react at the Si interface to generate SiO ₂ . In the Deal-Grove model, the state of oxide film growth is expressed by the following differential equation.

However,
L: Oxide film thickness C ₀ : Oxidized species density on SiO ₂ surface C ₁ : Number of oxidized species per unit volume necessary for SiO ₂ production D: Diffusion coefficient of oxidized species in SiO ₂ k: Rate constant of oxidation reaction t: time α: constant.

However, since the Deal-Grove model does not agree well with experimental data in plasma oxidation, an oxide film growth model in which the differential equation is modified is used here as follows.

However, a, b, and c are constants, and [O ^* ] is the density of oxidized species generated by the plasma.

As shown in FIG. 4, some of the oxidized species generated by the plasma emit light when falling from a high energy state (upper level) to a lower state (lower level). The plasma emission intensity I at this time has the following relational expression.

  As shown in the above relational expression, since the emission intensity depends on the particle density, it is conceivable to estimate the particle density related to the emission by measuring the emission intensity. Actinometry is known as a method for estimating particle density from emission intensity. Actinometry is a method for obtaining the particle density by taking the ratio of the emission intensity caused by two types of particles. However, the emission intensity ratio (uses 777 nm as the emission intensity of oxygen and 893 nm as the emission intensity of krypton) and the oxidation species density obtained by performing the process using oxygen and krypton under the process conditions shown in Table 1 were obtained by simulation. When the values were plotted, the results shown in FIG. 5 were obtained. As is clear from FIG. 5, there is no relationship between the two as expected in actinometry. This is considered because the conditions for using actinometry are not satisfied. In order to be able to use actinometry, the following conditions a to c need to be satisfied.

a. Plasma emission is represented by a corona equilibrium model.
b. The energy required for excitation of each particle is equal.
c. The collision cross section of each particle is similar.

  Since the high-density plasma is used in the plasma film forming apparatus which is the subject of the present invention, it is considered that the above condition a is not satisfied.

  Therefore, in this embodiment, the oxidation species density and the emission intensity are associated by correcting the emission intensity ratio using a parameter other than the emission intensity. Specifically, a conversion coefficient depending on the oxygen partial pressure as shown in FIG. 6 is obtained. Then, the relationship between the light emission intensity ratio corrected by multiplying the light emission intensity ratio by the conversion coefficient and the density of oxidized species is as shown in FIG. As shown in FIG. 7, when this corrected data is used, it is plotted on almost one curve. Therefore, using this relationship as a template, the oxidized species density can be estimated from the emission intensity ratio and the oxygen partial pressure.

  The graph of the conversion coefficient with respect to the oxygen partial pressure shown in FIG. 6 is obtained by experiment. In other words, when looking at FIG. 5, when focusing on the same oxygen partial pressure and looking at the correlation between the emission intensity and the oxidized species density, it can be seen that each is plotted along a certain curve (or straight line). Therefore, one oxygen partial pressure (for example, 1.75%) is set as the reference oxygen partial pressure, and the oxidized species density of the other oxygen partial pressure is on or near the curve of the reference oxygen partial pressure. Find the correct conversion factor. For example, when the experimental data with an oxygen partial pressure of 0.5% is the emission intensity ratio A1 and the oxidized species density B, the oxidized species density B on the curve showing the correlation of the reference oxygen partial pressure (1.75%). If the emission intensity ratio of A2 is A2, the conversion coefficient is A2 / A1. The conversion coefficient for each data is obtained by the user, and the obtained value may be input to the oxide film thickness estimation apparatus 10, or when the curve of the reference oxygen partial pressure can be specified by an arithmetic expression, The oxide film thickness estimation apparatus 10 may be automatically obtained using the arithmetic expression.

  In this way, the respective conversion coefficients that are placed on the curve indicating the correlation of the reference oxygen partial pressure are obtained for some or all of the other oxygen partial pressure data, and the obtained values are shown in FIG. Plot on a graph showing the correlation between oxygen partial pressure and conversion coefficient. Then, the coefficient in the characteristic equation defining the “oxygen partial pressure-conversion coefficient characteristic” shown in FIG. 6 is determined by using the least square method or the like so as to best fit the plotted values. This coefficient is determined by the oxide film thickness estimating apparatus 10.

  In accordance with the characteristic formula thus determined, a graph is re-created in which the horizontal axis represents a value obtained by multiplying the emission intensity ratio by the conversion coefficient with respect to data other than the reference oxygen partial pressure, and the vertical axis represents the oxidized species density. Then, based on each point in the re-created graph, a coefficient in an arithmetic expression that prescribes “a value obtained by multiplying the light emission intensity ratio by the conversion coefficient—oxidized species density characteristic” shown in FIG. 7 using a least square method or the like. By determining, a template is obtained. A series of processing until these coefficients are determined is executed by the oxide film thickness estimation apparatus 10. Of course, the user may execute part or all of the result, and the result may be input to the oxide film thickness estimation apparatus 10.

  The oxide film thickness estimation apparatus 10 stores in the database 11 a characteristic formula for obtaining the conversion coefficient thus obtained and an arithmetic expression for obtaining the oxidation species density as a template. The oxide film thickness estimation apparatus 10 obtains the oxidation species density estimation unit 12 that estimates the oxidation species density using the template from the emission intensity and process conditions acquired at the time of actual process execution, and the oxidation species density estimation unit 12. A film thickness estimation unit 13 that estimates the oxide film thickness based on the oxidized species density.

  The oxidized species density estimation unit 12 reads a template obtained by preliminary experiments and stored in the database 11, and uses the template (a characteristic equation for obtaining the conversion coefficient) to calculate a conversion coefficient corresponding to the oxygen partial pressure of the process condition. Determine (substitute the oxygen partial pressure for x in the characteristic equation to obtain the conversion coefficient y). Next, the oxidized species density estimation unit 12 calculates a light emission intensity ratio from the two given light emission intensities, and obtains a corrected light emission intensity ratio by multiplying the calculated light emission intensity ratio by the conversion coefficient obtained previously. The corrected emission intensity ratio is substituted into x in the arithmetic expression for obtaining the oxidized species density to calculate the oxidized species density. The oxidized species density estimation unit 12 gives the obtained oxidized species density to the film thickness estimation unit 13 at the next stage.

ただし、
ａ=２．３６×１０^１１
ｂ＝−３．５４×１０^１２
ｃ＝１．３９×１０^１３
とし、初期膜厚を５オングストロームとした。
The film thickness estimation unit 13 calculates the oxide film thickness by substituting the obtained oxidized species density into (Equation 2) and calculating.

However,
a = 2.36 × 10 ¹¹
b = −3.54 × 10 ¹²
c = 1.39 × 10 ¹³
The initial film thickness was 5 angstroms.

  FIG. 8 shows a comparison between the oxide film thickness obtained using the oxide film thickness estimation apparatus 10 of the present embodiment and the actually measured value obtained by the ellipsometer 4. As is apparent from FIG. 8, the measured value and estimated value of the oxide film thickness are good, and it has been confirmed that the film thickness can be estimated correctly considering the influence of disturbance.

  Based on the film thickness obtained by the oxide film thickness estimation apparatus 10, process abnormality diagnosis is performed, or the process conditions are adjusted by feeding back the monitoring film thickness, so that a process with high reproducibility is always performed. be able to.

  FIG. 9 and subsequent figures are diagrams for explaining a second embodiment of the present invention. In the first embodiment, the emission intensity ratio is associated with the oxidation species density by multiplying the conversion coefficient depending on the oxygen partial pressure. However, the present invention is not limited to this, and other than the oxygen partial pressure. These parameters (microwave power, process chamber pressure) can also be used for the correspondence.

  Therefore, in this embodiment, the light emission intensity ratio is associated with the oxidized species density by multiplying the coefficient depending on the oxygen partial pressure and the coefficient depending on the microwave power. FIG. 9 shows conversion coefficients for microwave power. This conversion coefficient is created for the process conditions shown in Table 1, and is created by the same procedure as that for obtaining the oxygen partial pressure conversion coefficient in the first embodiment described above. Then, when the coefficient of the expression for specifying the conversion coefficient is determined as shown in FIG. 9, it is stored in the database 11 as a template. Similarly, as shown in FIG. 10, the coefficient of the formula for obtaining the conversion coefficient by the oxygen partial pressure is determined and stored in the database.

  FIG. 11 shows the correspondence between the value obtained by multiplying the light emission intensity ratio by these two conversion coefficients and the density of oxidized species. The coefficient of the arithmetic expression for estimating the oxidation species density is also created in the same procedure as in the first embodiment and stored in the database 11.

  During actual process execution, the oxidized species density estimation unit 12 estimates the oxidized species density from the given emission intensity, oxygen partial pressure, and microwave power using each template stored in the database 11, and estimates the film thickness. The unit 13 calculates the oxide film thickness. FIG. 12 shows a comparison between the oxide film thickness obtained using the apparatus of the second embodiment and the measured value. As is clear from FIG. 12, the measured value and estimated value of the oxide film thickness are good, and it was confirmed that the film thickness can be estimated correctly considering the influence of disturbance.

  In each of the above embodiments, the plasma film forming apparatus is a microwave-excited high-density plasma apparatus using krypton and oxygen. However, the present invention is not limited to this, for example, argon is used instead of krypton. Can do.

(A) is a figure which shows an example of the system containing an oxide film thickness estimation apparatus, (b) is the blocks which show the internal structure of an oxide film thickness estimation apparatus. It is a figure which shows an example of a process chamber. It is a figure which shows a simulation result. It is a figure explaining the mechanism of light emission. It is a figure which shows the relationship between luminescence intensity ratio and oxidation seed density. It is a figure which shows the conversion coefficient by oxygen partial pressure. It is a figure which shows the relationship between the value which converted the luminescence intensity ratio, and oxidation seed density. It is a figure which shows the comparison of an oxide film thickness actual value and an estimated value. It is a figure which shows the conversion coefficient by microwave power. It is a figure which shows the conversion coefficient by oxygen partial pressure. It is a figure which shows the relationship between the value which converted the luminescence intensity ratio, and oxidation seed density. It is a figure which shows the comparison of an oxide film thickness actual value and an estimated value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Process chamber 2 Apparatus controller 3 Spectrometer 4 Ellipsometer 10 Oxide film thickness estimation apparatus 11 Database 12 Oxidation seed density estimation part 13 Film thickness estimation part

Claims (6)

The relationship between the plasma emission intensity generated during the plasma oxidation process and the density of oxidized species is stored and retained as a template,
Obtaining the plasma emission intensity measured during the process being monitored, and obtaining the oxidized species density from the acquired plasma emission intensity and the relationship stored as the template;
Substituting the obtained oxide species density into a predetermined oxide film growth model to obtain an oxide film thickness,
An oxide film thickness estimation method comprising:   The method of claim 1, wherein the plasma oxidation process uses oxygen and krypton or oxygen and argon, and the emission intensity is a ratio of two plasma emission intensity.   3. The method for estimating an oxide film thickness according to claim 1, wherein the emission intensity is corrected by an oxygen partial pressure.   4. The method for estimating an oxide film thickness according to claim 3, wherein the emission intensity is corrected by microwave power. A storage unit that stores and holds the relationship between the plasma emission intensity generated in accordance with the plasma oxidation process and the density of oxidized species as a template,
An oxidized species density estimating means for obtaining the plasma emission intensity measured during execution of the process to be monitored, and obtaining the oxidized species density from the acquired plasma emission intensity and the relationship read from the storage unit;
Film thickness estimation means for substituting the determined oxidation species density into a predetermined oxide film growth model to obtain an oxide film thickness,
An oxide film thickness estimation apparatus comprising: Computer
The plasma emission intensity measured during the execution of the monitored process is acquired, the acquired plasma emission intensity, and the relationship between the plasma emission intensity generated by the plasma oxidation process stored in the storage means and the density of the oxidized species. Based on the oxidized species density estimation means for obtaining the oxidized species density,
Film thickness estimating means for substituting the determined oxidation species density into a predetermined oxide film growth model to obtain an oxide film thickness,
Program to function as.

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