RU2463554C1 - Method of determining thickness of thin transparent film - Google Patents

Method of determining thickness of thin transparent film Download PDF

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RU2463554C1
RU2463554C1 RU2011118830/28A RU2011118830A RU2463554C1 RU 2463554 C1 RU2463554 C1 RU 2463554C1 RU 2011118830/28 A RU2011118830/28 A RU 2011118830/28A RU 2011118830 A RU2011118830 A RU 2011118830A RU 2463554 C1 RU2463554 C1 RU 2463554C1
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powder
ψ
metal
measurement results
thickness
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RU2011118830/28A
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Лев Александрович Акашев (RU)
Лев Александрович Акашев
Владимир Григорьевич Шевченко (RU)
Владимир Григорьевич Шевченко
Виктор Анатольевич Кочедыков (RU)
Виктор Анатольевич Кочедыков
Николай Александрович Попов (RU)
Николай Александрович Попов
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Учреждение Российской академии наук Институт химии твердого тела Уральского отделения РАН
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Abstract

FIELD: physics.
SUBSTANCE: method involves measuring ellipsometric parameters Δ and Ψ and then recording the measurement results in a plane in form of a curve, wherein ellipsometric parameters Δ and Ψ of a metal powder pressed in advance are determined, the measurement results of which are recorded on a plane in which there are curves, having the recorded measurement results of the ellipsometric parameters Δ and Ψ of the powder of the corresponding metal which is pressed in advance, with predetermined optical parameters, obtained using several values of given optical parameters of said powder, set by varying the volume ratio of the active metal with a certain increment.
EFFECT: invention enables to determine an oxide film formed on the surface of a metal powder, as well as volume ratio of the active metal.
4 dwg

Description

The invention relates to measuring technique, to methods of optical-physical measurements based on ellipsometry, and is intended to determine the thickness of thin transparent films.

A known method for determining the thickness of thin transparent films in the process of forming the layer structure by measuring the ellipsometric parameters Δ and Ψ with subsequent calculation of the derivative, while one of the ellipsometric parameters is chosen as a function, and another ellipsometric parameter is taken as an argument, the calculation results are fixed in the plane of the derivative ellipsometric parameter - an ellipsometric parameter in the form of a curve by which optical constants are determined, a change in the composition of the layer material , as well as its thickness (patent RU 2396545, MKI G01N 21/17, 2010) (prototype).

However, the known method provides the ability to determine the thickness of only a monolithic continuous sample, in particular a film, the optical parameters of which remain unchanged over time. The method does not provide the ability to measure the thickness of the oxide film formed on the surface of the metal powder, and, as a consequence, the proportion of the active component (metal) at each time point.

Thus, the authors were faced with the task of developing a method for measuring the thickness of a thin transparent, in particular oxide film, formed on the surface of a metal powder, as well as the fraction of the active component (metal) at each time point.

The problem is solved in the proposed method for determining the thickness of a thin transparent film by measuring the ellipsometric parameters Δ and Ψ with subsequent fixation of the measurement results in the plane in the form of a curve in which ellipsometric parameters Δ and определяют are determined for the pre-pressed metal powder, the measurement results of which are applied to the plane, in which there are curves containing fixed results of measuring the ellipsometric parameters Δ and Ψ of the powder of the corresponding metal, p compressed, with predetermined optical parameters, obtained using a number of values of the specified optical parameters of the powder, specified by changing the volume fraction of the active metal with a certain step.

Currently, there is no known method for measuring a thin transparent oxide film formed on the surface of a metal powder, with the simultaneous determination of the volume fraction of the active metal at any time.

The authors of the proposed technical solution using ellipsometry have developed not only a method for determining the thickness of an oxide film formed on the surface of a metal powder particles, but also a fraction of the active component (metal) corresponding to it. When developing the method, the authors had to take into account the fact of the physicochemical state of the metal powder, which is a collection of particles of different sizes and different configurations (from spherical to fragmentation, etc.). The particle size distribution of the powder is characterized by its specific surface, which is the sum of the outer surfaces of all particles per unit volume. Therefore, the process of formation of an oxide film is fundamentally different from the process of its formation on the surface of a continuous monolithic sample (see figure 1-A). The optical parameters (refractive index and absorption coefficient) are constantly changing during the oxidation process, while the volume fraction of the active metal is constantly decreasing. In this connection, the nomograms characterizing the formation of the structure in time have fundamental differences. If in the case of a solid surface the optical parameters remain constant for a film of a fixed thickness, then in the case of a metal powder, the optical parameters change in time, the "floating" values of the optical parameters also determine the unconventional form of the ellipsometric nomogram (see Fig. 2). To ensure the technological feasibility of performing ellipsometry, the initial powder is pre-pressed at a pressure sufficient to obtain a monolithic sample (see Fig. 1-B).

Figure 1 schematically shows the reflection systems: Figure 1-A - monolithic substrate - a transparent film; figure 1-B is a metal powder before pressing; figure 1-B - pressed powders.

The proposed method can be implemented as follows. To build a nomogram in a plane with coordinates Δ and Ψ, the surface of a metal powder pre-compressed in the form of tablets under a pressure of 300-310 kg / cm 2 is irradiated with laser radiation with a wavelength of λ = 0.6328 μm on a laser ellipsometer LEF-3M at a known angle fall. Then, a series of values of the optical parameters of the compressed powder is determined by setting changes in the volume fraction of the active metal with a certain step by solving the Maxwell-Garnet equation:

Figure 00000001

where: N = n-ik; n, k are the optical constants (or parameters) of the pressed powder;

N 1 = n 1 -ik 1 ; n 1 , k 1 - optical constants of aluminum;

n ok - the refractive index of aluminum oxide;

q is the volume fraction of the active metal; (1-q) is the volume fraction of alumina.

The resulting optical constants are introduced into the basic ellipsometry equation:

Figure 00000002

where: r 01p and r 12p are the Fresnel reflection coefficients for the p-component of the electric field, corresponding to the boundaries between the media ε 0 and ε 1 and ε 1 and ε 2 , respectively; r 01s and r 12s are the Fresnel reflection coefficients for s - components related respectively to the same boundaries as r 01p and r 12p , where the Fresnel reflection coefficients are written as:

Figure 00000003

Figure 00000004

Figure 00000005

Figure 00000006

Figure 00000007

Figure 00000008

ε 2 , ε 1 , ε 0 - dielectric constant of the substrate, film and medium (air or vacuum), respectively; n 2 , n 1 , n 0 are the refractive indices; k 2 , k 1 , k 0 - absorption coefficients (usually k 0 = 0); ω is the frequency of light, c is the speed of light in vacuum; d is the thickness of the surface film. Based on the solution of the basic ellipsometry equation, a nomogram is built, for which the calculation results are fixed in the plane Δ and плоскости in the form of a series of radial curves (see Fig. 2). q is the volume fraction of the active metal, the numbers on the curves (left and right) are the thickness of the oxide film in nanometers, the radial lines are lines of equal thickness. The resulting nomogram is used to determine the thickness of the oxide film, as well as the fraction of the active metal of any experimental sample. Why metal powder is pre-pressed under a pressure of 300-310 kg / cm 2 , then the ellipsometric parameters Δ and определяют are determined, the measurement results are applied as experimental points on the nomogram and the thickness of the oxide film, as well as the fraction of the active metal, are determined. The proposed method is illustrated by the following example.

Example 1. An aluminum powder prepared by mechanical grinding of monolithic aluminum containing 99.999% of the main component is pressed into tablets under a pressure of 300 kg / cm 2 . Then, the initial ellipsometric parameters Δ and Ψ from the surface of the powder are measured on a LEF-3M laser ellipsometer at an angle of incidence of the light beam on the sample φ = 65 °. Next, the tablets are placed in a muffle furnace heated to a temperature of 873 K, kept at this temperature for 5 minutes, 15 minutes, 25 minutes, 40 minutes, 55 minutes and 75 minutes. After each exposure, the tablets are cooled to room temperature and the ellipsometric parameters Δ and ψ are measured. The measurement results were applied to Δ-ψ nomogram (figure 2). Using the nomogram, the fraction of the active metal q and the thickness of the oxide film d are determined. Figure 3 and figure 4 presents the dependence of the fraction of the active metal of aluminum powder and the thickness of the oxide film on the surface of the powder on the time of stepwise oxidation in air at T = 873 K. After 75 minutes of oxidation under these conditions, the proportion of the active metal decreases to q = 0.62, and the thickness of the oxide film reaches d = 96 nm.

Thus, the authors propose a method for determining the thickness of a thin transparent film using ellipsometry, which allows you to determine the thickness of the oxide film formed on the surface of the metal powder, as well as the volume fraction of the active metal.

Claims (1)

  1. A method for determining the thickness of a thin transparent film by measuring the ellipsometric parameters Δ and Ψ followed by fixing the measurement results in a plane in the form of a curve, characterized in that the pre-pressed metal powder determines the ellipsometric parameters Δ and Ψ, the measurement results of which are applied to the plane in which curves containing fixed results of measuring the ellipsometric parameters Δ and Ψ of the powder of the corresponding metal, previously pressed, with predetermined optical parameters obtained using a number of values of the specified optical parameters of the powder, specified by changing the volume fraction of the active metal with a certain step.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2558645C1 (en) * 2014-01-17 2015-08-10 Открытое акционерное общество "Научно-производственное предприятие "Пульсар" Method to determine thickness of metal films
RU2650833C1 (en) * 2016-12-27 2018-04-17 федеральное государственное бюджетное образовательное учреждение высшего образования "Московский государственный технический университет имени Н.Э. Баумана (национальный исследовательский университет)" (МГТУ им. Н.Э. Баумана) Method of non-destructive quality control of thermoelectric module thermal contact
RU2659873C1 (en) * 2017-05-22 2018-07-04 Федеральное государственное бюджетное учреждение науки Институт химии твердого тела Уральского отделения Российской академии наук Method for determining optical constants of films of chemically active metals or their alloys

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SU1226042A1 (en) * 1984-08-18 1986-04-23 Предприятие П/Я В-2892 Method of measuring thickness of film on bases
US6465265B2 (en) * 2000-03-16 2002-10-15 Therma-Wave, Inc. Analysis of interface layer characteristics
US6515746B2 (en) * 1997-07-11 2003-02-04 Therma-Wave, Inc. Thin film optical measurement system and method with calibrating ellipsometer
US6731386B2 (en) * 2001-01-04 2004-05-04 Agere Systems Inc. Measurement technique for ultra-thin oxides
RU2396545C1 (en) * 2008-12-31 2010-08-10 Учреждение Российской академии наук Институт физики полупроводников им. А.В. Ржанова Сибирского отделения РАН Method of inspecting composition of material during structure formation

Patent Citations (5)

* Cited by examiner, † Cited by third party
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SU1226042A1 (en) * 1984-08-18 1986-04-23 Предприятие П/Я В-2892 Method of measuring thickness of film on bases
US6515746B2 (en) * 1997-07-11 2003-02-04 Therma-Wave, Inc. Thin film optical measurement system and method with calibrating ellipsometer
US6465265B2 (en) * 2000-03-16 2002-10-15 Therma-Wave, Inc. Analysis of interface layer characteristics
US6731386B2 (en) * 2001-01-04 2004-05-04 Agere Systems Inc. Measurement technique for ultra-thin oxides
RU2396545C1 (en) * 2008-12-31 2010-08-10 Учреждение Российской академии наук Институт физики полупроводников им. А.В. Ржанова Сибирского отделения РАН Method of inspecting composition of material during structure formation

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2558645C1 (en) * 2014-01-17 2015-08-10 Открытое акционерное общество "Научно-производственное предприятие "Пульсар" Method to determine thickness of metal films
RU2650833C1 (en) * 2016-12-27 2018-04-17 федеральное государственное бюджетное образовательное учреждение высшего образования "Московский государственный технический университет имени Н.Э. Баумана (национальный исследовательский университет)" (МГТУ им. Н.Э. Баумана) Method of non-destructive quality control of thermoelectric module thermal contact
RU2659873C1 (en) * 2017-05-22 2018-07-04 Федеральное государственное бюджетное учреждение науки Институт химии твердого тела Уральского отделения Российской академии наук Method for determining optical constants of films of chemically active metals or their alloys

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