JPH10267872A - Method for evaluating characteristic of substance based on programmed temperature desorption spectral method and method for forming semiconductor insulating film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and easily evaluate a structural characteristic of a substance by forming models of a diffusion process from the interior of the substance of chemical species to the vicinity of a surface and a surface desorption process, e.g. stripping, accumulation, gas phase emission, etc., and combining the models with a programmed temperature desorption spectrum. SOLUTION: Models of a diffusion process and a surface desorption process are represented respectively by formulae I and II wherein T is a temperature, (t) is a time, (x) is a distance in a thicknesswise direction, (c) is a concentration of chemical species, D is a diffusion coefficient, Do ,i is a prediffusion exponential term, Ed ,i is a diffusion activation energy, kB is a Boltzmann factor, (k) is a desorption reaction speed constant, cs is a surface accumulation amount, (n) is a desorption reaction degree, fj is a surface coverage rate, Ao ,j is a predesorption exponential term, and Ea ,j is a desorption activation energy. A sample 11 is heated by a heater 14. The temperature T obtained by a temperature control device 16 and the amount of chemical species in a generated gas which is detected by a quadruple mass spectrometer 21 are stored as an actually measured programmed temperature desorption spectrum in a memory device 33. A calculator 34 carries out fitting with the use of the spectrum according to the method of least squares, determines each parameter of the formulae I, II and displays at a display device 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating material properties, and more particularly to a method for analyzing a thermal desorption spectrum and a method for forming a semiconductor insulating film using the analysis method.

[0002]

2. Description of the Related Art In the thermal desorption spectroscopy method, the amount of desorption at each temperature is determined for each mass number of a chemical species contained in a substance by performing one experiment in which the temperature of the substance is increased. You can know. Further, the surface desorption characteristics (desorption activation energy on the surface of the substance) of the chemical species can be obtained from the desorption amount of the chemical species contained in the substance at each temperature.

[0003] From the results of the thermal desorption spectroscopy method, the following applications have conventionally been used.

(1) Ease of gas desorption is estimated from the temperature at which a peak appears.

The peak of the thermal desorption spectrum indicates the temperature at which the chemical species desorbs most, and the temperature at which the peak appears indicates the magnitude of the desorption activation energy. The higher the temperature at which the peak appears, the less likely the species is to occur at lower elimination reactions, ie, it has a higher elimination activation energy. Therefore, the ease of desorption of the gas of the chemical species can be qualitatively estimated from the temperature at which the peak appears.

(2) Estimating the desorption activation energy of a gas from the desorption temperature.

The elimination reaction on the surface is regarded as the n-th elimination reaction, and the elimination activation energy is estimated from the elimination rate equation. However, it is necessary to carry out a plurality of experiments at different heating rates to determine the pre-exponential term of the elimination reaction and make an assumption in advance.

[0008]

In the above (1), the easiness of desorption of chemical species can be known only qualitatively. Also, (2)
Then, if the actual exponential term is significantly different from the assumed value, the desorption activation energy may be erroneously specified.

In (1) and (2), since the diffusion of the chemical species or the precursor of the chemical species inside the substance is not taken into account, the activation energy of diffusion and the pre-exponential term cannot be obtained. . Therefore, in order to determine the activation energy of diffusion and the exponent term, it was necessary to separately measure the diffusion rate under various temperature environments.

[0010] It is an object of the present invention to rapidly improve material structural characteristics such as diffusion activation energy and pre-diffusion exponent in a substance and desorption activation energy and pre-desorption exponent on a substance surface for each chemical species. And to find it easily.

Another object of the present invention is to provide a method for forming a semiconductor insulating film, which can reduce the time required for film formation compared to the prior art.

[0012]

A feature of the present invention that achieves the above object is that, in using a thermal desorption spectroscopy method, a diffusion process in which a chemical species diffuses from a substance to near a surface thereof by heating and has been diffused. Chemical species are captured and accumulated,
Modeling the surface desorption process released into the gas phase,
It is to evaluate the material structure characteristics based on the model and the measured thermal desorption spectrum.

According to this feature, by combining the model with the actually measured thermal desorption spectrum, the diffusion activation energy, the pre-diffusion exponent term, and the substance The constants such as the desorption activation energy of the chemical species on the surface and the exponent before desorption can be easily obtained, and the structural characteristics of the substance can be evaluated.

Further, by using a single thermal desorption spectrum measurement, each constant can be easily and easily obtained, and the structural characteristics of the substance can be evaluated.

Another feature of the present invention to achieve the object is to form a semiconductor insulating film and determine the amount of chemical species desorbed from the formed semiconductor insulating film. Evaluating the structural characteristics of the semiconductor insulating film depending on the amount of the chemical species obtained by using the measurement, and forming the insulating film under conditions different from the conditions under which the semiconductor insulating film was formed based on the evaluation. It is in. Thus, the semiconductor insulating film can be quickly and easily evaluated, and a high-quality semiconductor insulating film can be formed in a short time. Further, the time required for developing a process for forming a semiconductor insulating film can be shortened.

In addition, when a semiconductor insulating film is formed and a thermal desorption spectroscopy method is used, a diffusion process in which a chemical species diffuses from a substance to the vicinity of the surface by heating, and the diffusion of the chemical species is carried out. Model the surface desorption process that is accumulated and released into the gas phase, evaluate the material structure characteristics based on the model and the measured thermal desorption spectra, and based on the evaluation, evaluate the semiconductor insulating film. When the insulating film is formed under conditions different from the conditions under which the film is formed, the above-described effects and the effect of fluctuation can be obtained.

Further, the amount of the chemical species desorbed from the formed semiconductor insulating film after the formation of the semiconductor insulating film, the amount of the chemical species determined by using a single temperature-programmed desorption spectrum measurement. The same effect as described above can also be obtained by evaluating the structural characteristics of the semiconductor insulating film depending on the amount and forming the insulating film under the same conditions as those under which the semiconductor insulating film was formed based on the evaluation. As a result, the quality of the semiconductor insulating film can be maintained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A material property evaluation method according to a first embodiment of the present invention will be described with reference to FIG.

The method for evaluating material properties according to the present embodiment uses the chemical species (atoms, molecules, ions, radicals, etc.) contained in the material.
The thermal desorption mechanism of the surface is modeled into a diffusion process that diffuses from the inside of the material to the surface of the material, and a surface desorption process that is captured and accumulated on the surface and released into the gas phase. By combining information obtained from measured thermal desorption spectra, constants and factors incorporated into the model as unknowns in modeling are obtained, and the structural characteristics of the substance are evaluated.

In this embodiment, a model of the diffusion process is represented by (Equation 1), and a model of the surface detachment process is represented by (Equation 2).

[0021]

(Equation 1)

[0022]

(Equation 2)

Here, T: temperature, t: time, x: distance in the thickness direction of the substance, c: concentration of chemical species, D: diffusion coefficient,
D _{0, i} : exponent before diffusion, E _{d, i} : diffusion activation energy,
k _B : Boltzmann factor, k: desorption reaction rate constant, c _s :
Surface accumulation amount, n: Desorption reaction order, f _j : Surface coverage ratio,
A _{0, j} : exponential term before desorption, E _{a, j} : desorption activation energy.

The amount dq / dt of chemical species reaching the surface per unit time can be obtained from (Equation 1). This (Equation 2) substituted for by equation (1) by solving the equation (2) obtained the value of the left side k · c _s ^n. Since the left side k in (Equation 2) represents the desorption rate, the temperature rising desorption spectrum can be reproduced by plotting the value on the left side while changing the temperature (Equation 2). Here, if the parameters in (Equation 1) and (Equation 2) are determined so as to reproduce the measured thermal desorption spectrum,
The diffusion activation energy E _{d, i} , the pre-diffusion index term D _{0, i} , the desorption activation energy E _{a, j} , and the pre-desorption index term A _{0, j} can be obtained.

FIG. 2 shows a material property evaluation apparatus 100 for performing the material property evaluation method of this embodiment.

The material property evaluation apparatus 100 includes a sample unit 10 for storing a sample 11 for which material structure characteristics are to be obtained, a mass spectrometer 20 for measuring the amount of chemical species desorbed from the sample, and an analysis for obtaining the material structure characteristics. It is composed of a unit 30.

The sample section 10 includes a vacuum vessel 12 for containing the sample 11, a vacuum pump 13 connected to the vacuum vessel 12 and maintaining the inside of the vacuum vessel 12 at a low pressure of 1 × 10 to ⁶ Torr or less.
It comprises a heater 14 for heating the sample 11, a thermocouple 15 for measuring the temperature near the sample 11, and a temperature controller 16 for controlling the temperature of the heater 14. The temperature control device 16 can arbitrarily adjust the time change of the temperature at which the sample 11 is heated, and can determine the temperature of the sample 11 based on the temperature measured by the thermocouple 15.

The mass spectrometer 20 includes a quadrupole mass spectrometer 21
And a tube 22 that carries the gas in the vacuum vessel 12 to the quadrupole mass spectrometer 21. The gas generated from the sample 11 by being heated is conveyed to the quadrupole mass spectrometer 21 where the type and amount are measured.

The analyzing section 30 comprises a data analyzing device 31 and a display device 32. The data analyzing device 31 has a storage device 33 and a calculator 34. The storage device 33 stores (Equation 1) and (Equation 2) of the model and the initial values of the parameters which have been input in advance. When the measurement is performed by the thermal desorption spectrum method, the temperature control device is used. From 16, the temperature of the sample and the amount of the chemical species for each type from the quadrupole mass spectrometer 21 are input.

Next, a method for evaluating the sample 11 using the material property evaluation apparatus 100 will be described.

First, the amount of desorbed gas is measured by a thermal desorption spectroscopy method. The sample 11 is heated by the heater 14. The temperature T determined by the temperature controller 16 and the amount of the chemical species contained in the gas generated from the sample determined by the quadrupole mass spectrometer 21 at this temperature T indicate the measured thermal desorption spectra. Is stored in the storage device 33.

After completion of the measurement, the calculator 34 determines the parameters of (Equation 1) and (Equation 2) by using the measured thermal desorption spectrum. The calculator 34 performs fitting by the least squares method.

The flow of the fitting program executed by the calculator 34 will be described with reference to FIG.

(1) Initial values are set for each parameter of (Equation 1) and (Equation 2). The initial value is previously selected from a database (not shown) in which previous measurement results are collected and stored in the storage device 33. At the start of the calculation, (Equation 1) and (Equation 2) and the initial value of each parameter are output from the storage device 33, and the
Then, the initial values are set to the parameters of (Equation 1) and (Equation 2).

(2) Actual measured data of a thermal desorption spectrum,
That is, the temperature, the time, and the amount of desorbed gas are output from the storage device 33, and are fitted to (Equation 1) and (Equation 2) in the calculator 34. At this time, about 100 to 200 points of the measured data may be selected as the representative points.

(3) (Equation 2) The value of the left side k · c _s ⁿ is obtained. Then, a least squares fit is performed. That is, the square of the difference between the calculated value and the measured value at each temperature is taken to obtain a sum at all points, and the calculation is repeated while changing the parameters until the sum becomes equal to or less than the set allowable value. (4) When the sum of squares of the error finally falls below the allowable value,
The value of each parameter is stored in the storage device 33.

Although the number of fitting parameters is automatically prepared by the number of peaks of the thermal desorption spectrum, the number of fitting parameters may be changed to an arbitrary number by changing the program of the calculator 34. (5) After the fitting is completed, the values of the parameters are displayed on the display device 32. The data analyzer 31 compares the diffusion activation energy, the pre-diffusion exponential term, the desorption activation energy and the pre-desorption exponent term with the data in the storage device 33, and lists the permissible diffusion and desorption reactions. Display device 32
To be displayed.

As described above, according to the material property evaluation apparatus 100 of the present embodiment, the diffusion activation energy E _d, which could not be obtained without performing the thermal desorption spectrum measurement many times conventionally _{. i} , the pre-diffusion exponent D _{0, i} , the desorption activation energy E _{a, j} , and the pre-desorption exponent A _{0, j} can be determined by a single thermal desorption spectrum measurement. Therefore, the structural characteristics of the substance can be quickly and easily evaluated.

(Embodiment 2) A method for forming a semiconductor insulating film according to a second embodiment of the present invention will be described below.

In this embodiment, an SiO ₂ insulating film is deposited on a Si wafer 41 provided with metal wiring by a plasma CVD method, and a fluorine-added SiO ₂ film is further formed on the SiO ₂ insulating film.
Taking the method of forming a semiconductor insulating film to form _two films as an example, the desorption activation energy, pre-desorption exponent, diffusion activation energy, and diffusion of water in the insulating film are used as indices for evaluating the semiconductor insulating film. The exponent term is clarified, and the thickness of the semiconductor insulating film is determined.

Since the fluorine-added SiO ₂ film has high water permeability, the SiO ₂ insulating film is also a protective film for metal wiring. Si
Activation energy of desorption of water from O ₂ insulating film, exponential term before desorption, energy of activation for diffusion of water in SiO ₂ insulating film, exponential term of diffusion before, diffusion activity of water in fluorine-added SiO ₂ film If the activation energy and the pre-diffusion exponent term become clear, the time required for water to pass through the fluorine-added SiO ₂ film and the SiO ₂ insulating film and reach the underlying metal wiring can be determined. Therefore, the thickness of the SiO ₂ insulating film required as the protective film can be determined according to the water resistance required of the semiconductor insulating film.

The semiconductor manufacturing apparatus 200 used in this embodiment will be described with reference to FIG.

The semiconductor manufacturing apparatus 200 comprises the material property evaluation apparatus 100 of the first embodiment, a film forming system 40, and a sample transport system 50.

The film forming system 40 includes a film forming device 42, a gas supply system 43, a gas discharge system 44, and a control device 45.

In the film forming apparatus 42, a plurality of Si wafers 41
Next, a SiO ₂ insulating film and a fluorine-added SiO ₂ film are formed. The film forming apparatus 42 is connected to a gas supply system 43 for supplying a film forming gas and a gas discharging system 44 for discharging extra gas in the film forming apparatus 42.

The control device 45 includes a material property evaluation device 100
Activation energy, pre-desorption exponent, diffusion activation energy, pre-diffusion exponent, and the pre-input assumptions (what percentage of water is The thickness of the semiconductor insulating film is determined based on whether or not it is necessary to prevent the period, and the amount of the film forming gas supplied from the gas supply system 43 to the film forming apparatus 42 is adjusted by controlling the opening and closing of the valve 46. And has a function of determining a film formation time.

The sample transport system 50 transports the Si wafer 41 from the film forming device 42 to the material property evaluation device 100.

A method for forming a semiconductor insulating film using the semiconductor manufacturing apparatus 200 will be described.

(1) First, a metal wiring is applied to the S
Regarding the sample in which the SiO ₂ insulating film is deposited on the i-wafer 41 by the plasma CVD method, the deactivation activation energy of water in the SiO ₂ insulating film, the exponent before desorption, the diffusion activation Find the energy and pre-diffusion exponential terms. If the material property evaluation device 100 is used, 5 to 10
You can find these constants in minutes.

(2) Next, a fluorine-added SiO ₂ film having high water permeability is formed on the SiO ₂ insulating film on the Si wafer 41 on which the metal wiring and the SiO ₂ insulating film have been formed by the film forming apparatus 42. .

(3) The sample loading system 80 is made of fluorine-added Si
A part of the Si wafer 41 on which the O ₂ film is formed is sent to the material property evaluation device 100.

(4) The material property evaluation apparatus 100 obtains the diffusion activation energy and the pre-diffusion exponent term of the water in the fluorinated SiO ₂ film of the Si wafer 41 sent thereto.

(5) The control unit 45 sets the desorption activation energy, pre-desorption exponent, diffusion activation energy, pre-diffusion exponent, and assumed conditions of water in the insulating film output from the material property evaluation unit 100. Based on this, the thickness of the SiO ₂ insulating film is determined.

In the material property evaluation apparatus 100, the diffusion activation energy of the SiO ₂ insulating film was about 18 to 20 kcal / mol, and the exponent before diffusion was 2.5 × 10 to ⁹ m ² / s. In addition, the desorption speed was sufficiently higher than the diffusion speed, and it was found that the influence of desorption was negligible.

(6) The controller 45 controls the opening and closing of the valve 46 based on the thickness of the SiO ₂ insulating film to adjust the amount of the film forming gas supplied from the gas supply system 43 to the film forming apparatus 42. Then, the film formation time is determined, and the SiO ₂ insulating film is formed again.

As described above, the evaluation of a semiconductor insulating film, which could not be obtained without performing the thermal desorption spectrum measurement many times in the past, is described in the present embodiment. Can be obtained by Therefore, the structural characteristics of the insulating film can be quickly and easily evaluated, and a high-quality insulating film can be formed quickly and easily.

By using such a semiconductor manufacturing apparatus 200 to form a film while checking the properties of the semiconductor insulating film, a constant change in process conditions (pressure, temperature, gas flow rate, etc.) can be maintained. A high-quality semiconductor insulating film can be formed.

In this embodiment, each constant was checked for water in the semiconductor insulating film. However, since water, hydrogen fluoride, and fluorine are considered to be the cause of wiring corrosion, fluorine-added SiO 2 was used.
_{When two} films are used as insulating films, material property evaluation device 1
If the chemical species to be evaluated are water, hydrogen fluoride, and fluorine at 00, the thickness of the high-quality semiconductor insulating film can be determined more accurately.

Conventionally, in order to obtain the diffusion activation energy and the pre-diffusion exponential term, it has been necessary to repeat a plurality of thermal desorption spectrum measurements. In this embodiment, the diffusion activation energy and the pre-diffusion exponent term can be simultaneously determined for a plurality of chemical species by a single thermal desorption spectrum measurement.
The time required for the evaluation requires only a small amount of calculation time in the analysis system, and an increase in the entire time including the time for measuring the temperature-programmed desorption spectrum can be suppressed to 10% or less. Therefore, by applying the present invention to the process development of a semiconductor insulating film, the development period can be significantly reduced.

In this embodiment, the semiconductor insulating film was evaluated by the material characteristic evaluation device 100 in the process of forming the fluorine-added SiO ₂ film. If you perform an evaluation with 100,
A higher quality semiconductor device can be manufactured.

[0061]

According to the present invention, each constant such as the diffusion activation energy of a chemical species in a substance, a pre-diffusion exponent, and the desorption activation energy of a chemical species on a substance surface, a pre-desorption exponent term, etc. Can be easily obtained, and the structural characteristics of the substance can be evaluated.

Also, by using a single thermal desorption spectrum measurement, each constant can be easily and quickly obtained, and the structural characteristics of the substance can be evaluated.

Further, the semiconductor insulating film can be evaluated quickly and easily, and a high-quality semiconductor insulating film can be formed in a short time. Further, the time required for developing a process for forming a semiconductor insulating film can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a material property evaluation method according to a first embodiment.

FIG. 2 is a diagram illustrating a material property evaluation device 100 according to a first embodiment.

FIG. 3 is a flowchart of a fitting program executed by a calculator 34;

FIG. 4 is a diagram illustrating a semiconductor manufacturing apparatus 200 according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... sample part, 11 ... sample, 12 ... vacuum container, 13 ... vacuum pump, 14 ... heater, 15 ... thermocouple, 16 ... temperature controller, 20 ... mass spectrometer, 21 ... quadrupole mass spectrometer, 22 ... pipe, 30 ... analysis unit, 31 ... data analysis device,
32 display device, 33 storage device, 34 calculator, 40
... film forming system, 41 ... Si wafer, 42 ... film forming device, 43 ...
Gas supply system, 44 ... Gas discharge system, 45 ... Control device, 46
… Valve, 50… sample transport system, 100… material property evaluation device, 200… semiconductor manufacturing device.

Claims (5)

[Claims] In a method for evaluating a material structure using a thermal desorption spectroscopy method as a method for analyzing a substance structure, when the thermal desorption spectroscopy method is used, a chemical species diffuses from a substance to near a surface thereof by heating. Model the diffusion process that occurs and the surface desorption process in which the diffused species are captured and accumulated and released into the gas phase, and evaluate the material properties based on the model and the measured thermal desorption spectra. A material property evaluation method. 2. The method according to claim 1, wherein the activation energies for diffusion and desorption are determined by a single thermal desorption spectrum measurement. 3. The step of forming a semiconductor insulating film and the amount of a chemical species desorbed from the formed semiconductor insulating film, the amount being determined using a single thermal desorption spectrum measurement. Evaluating the structural characteristics of the semiconductor insulating film depending on the amount of the chemical species, and forming an insulating film under conditions different from the conditions under which the semiconductor insulating film was formed based on the evaluation. A method for forming a semiconductor insulating film, comprising: 4. A step of forming a semiconductor insulating film, and a diffusion process in which a chemical species is diffused from a substance to near a surface thereof by heating when a thermal desorption spectroscopy method, which is a technique for analyzing a substance structure, is used. Modeling the surface desorption process in which the diffused species are captured and accumulated, and released into the gas phase, and evaluating the material structural characteristics based on the model and the measured temperature-programmed desorption spectrum; Forming an insulating film under conditions different from the conditions under which the semiconductor insulating film was formed based on the evaluation. 5. The step of forming a semiconductor insulating film and the amount of chemical species desorbed from the formed semiconductor insulating film, which is determined by using a single thermal desorption spectrum measurement. Evaluating the structural characteristics of the insulating film depending on the amount of molecules, and forming a semiconductor insulating film under the same conditions as those for forming the semiconductor insulating film based on the evaluation. A method for forming a semiconductor insulating film, comprising: