JP2009042038A - Evaluation method and evaluation device for physical property of thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable pressure/temperature polarization analysis/measurement method aimed at finding physical properties such as the film thickness L, refractive index n, extinction coefficient k, etc. of a thin-film specimen at specific pressure and temperature by measuring polarization parameters (Ψ, Δ) of the specimen while continuously changing the temperature of the thin-film specimen in a wide range, thereby evaluating the quantity, size, specific surface area, and thermal expansion coefficient, of nano-holes, and thermo-optical characteristics, etc. accompanying decomposition/desorption. <P>SOLUTION: As to a polarization analyzer, a specimen is disposed in a specimen evaluation chamber provided with an optically transparent window. The window is provided with an optical surface which remains vertical to incident light applied to the specimen mounted on a specimen table even if the pressure and temperature of gas are changed in the evaluation chamber, and an optical surface which remains vertical to reflected light reflected from the specimen even if temperature is changed. It is thereby made possible to find the refractive index, extinction coefficient, or film thickness of the specimen at various temperatures in a prescribed atmosphere having various pressures. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is directed to a thin film sample having a submicron film thickness, and the thin film sample installation space is set to a pressure in the range of vacuum to atmospheric pressure (about 1013 hPa) or higher, preferably in the range of 1 Pa to 1020 hPa. The thin film sample is in a temperature range from extremely low temperature to very high temperature, preferably in a low temperature range (-196 ° C. or higher and lower than 0 ° C.), middle temperature range (0 ° C. or higher and lower than 200 ° C.) A method of measuring the film thickness and refractive index of the thin film sample by controlling to a predetermined temperature in the temperature range, and measuring the temperature dependence of the film thickness and refractive index while changing the temperature range at a specific speed. This method analyzes the measurement results and evaluates the adsorption and desorption characteristics of gas molecules depending on the pore structure, the thermal expansion related to the coefficient of linear expansion and the decomposition and desorption behavior of the thin film sample. The present invention relates to a technique that can be applied to the evaluation of physical properties such as nanoporosity and nanostructure change related to the functional expression of semiconductor thin film materials and the like.

  In the development of next-generation semiconductor ULSI, it is indispensable to reduce the dielectric constant (low-case) of the insulating film in order to reduce the parasitic capacitance that causes signal delay. It is important to evaluate the high-sensitivity properties of thin film materials that can be used as low dielectric constant films (low-Ke films) produced by various film forming methods such as sol-gel spin coating and plasma chemical vapor deposition.

  The dielectric constant can be related to the refractive index based on Maxwell's equation, where the electric flux density is equal to the product of the dielectric constant and the electric field, and the magnetic flux density is equal to the product of the magnetic permeability and the strength of the magnetic field.

  The ellipsometric measurement method is used to measure the refractive index of the thin film, but the ellipsometric measurement method has long been known as a representative method for analyzing the film thickness with a thin film quality and an error of one atomic layer or less. It is a technique.

In the ellipsometry measurement method, light of a specific polarization state is incident on a thin film sample deposited on a substrate, and the electric field of the component reflected from the sample is parallel to the incident surface (p component: p polarization). reflectance R _p and an electric field component perpendicular to the plane of incidence: by measuring the ratio [rho = R _p / R _s of the reflectivity R _s of (s component s-polarized), the refractive index n of the sample, extinction This is a technique for obtaining an attenuation coefficient k (referred to as a complex refractive index by combining n and k), a film thickness L, and the like.

  The measurement result is generally a complex number, and can be expressed as ρ = tanΨexp (iΔ) using the imaginary unit i. Here, Ψ (Psi) and Δ (Delta) are parameters representing the polarization state of the light to be measured (reflected light), and Ψ is an amplitude reflectance ratio between the p component and the s component, Δ Indicates the phase difference between the p component and the s component, respectively. Since ρ is a value that depends on the refractive index n, the extinction coefficient k, and the film thickness L of the thin film sample, the polarization state of the reflected light, that is, the polarization parameters (Ψ, Δ ), And by applying an appropriate model, the refractive index, extinction coefficient, and film thickness of the sample can be obtained.

One effective measure for reducing the dielectric constant of the insulating film is a method of reducing the dielectric constant by forming holes having a dielectric constant of 1 in the insulating material. For this reason, in the semiconductor industry, development of technology for introducing pores (nanopores) at a molecular size level into an insulating material has been actively promoted. Nanopores in a substance are classified as micropores with a size of 2 nm or less, mesopores with 2 nm-50 nm, and macropores with a thickness of 50 nm or more, depending on the pore diameter. One method for forming nanopores in a thin film material is the porogen method.
In the porogen method, a precursor composite film is prepared from a mixed raw material of a thermally unstable organic raw material and another organic or inorganic raw material that is relatively stable, and a nanocomposite is formed in the precursor composite film. The porogen (unstable organic phase) dispersed as metric-scale aggregates is thermally decomposed, and voids are formed as spaces left after the porogen is decomposed.

  In relation to the porous thin film using the porogen method, the known porogen-containing thin film sample prepared by sol-gel spin coating is cured and analyzed for pore formation process, thermal stability, and moisture absorption characteristics by surface modification. There is research.

  Chang et al. Conducted a temperature-programmed desorption gas analysis method for the porogen decomposition reaction when a sol-gel spin-coated thin film deposited on a silicon substrate using an organomethylsilsesquioxane precursor was cured at a temperature of 450 ° C or lower ( TDS) (Non-Patent Document 1). In this study, the relationship between the dielectric constant and the porogen desorption temperature was discussed by evaluating the refractive index of the sample rapidly cooled to room temperature after confirming that the porogen had completely desorbed by 250 ° C. ing.

  In addition, research on the heat resistance of plasma-polymerized low dielectric constant films using hexamethyldisiloxane as the main raw material has been conducted (Non-patent Document 2). Although the conclusion that heat resistance is good based on the TDS evaluation results has not been obtained in this document, knowledge about the inherent thermal stability of the film has not been obtained. .

  In addition, research on the moisture absorption characteristics of the low dielectric constant film was also conducted (Non-patent Document 3). Bonding state of adsorbed water in low dielectric constant film obtained by surface treatment with tetramethylcyclotetrasiloxane (TMCTS) on sol-gel spin coat film using ethyl orthosilicate (TEOS) as main raw material As a result of TDS evaluation, it was reported that water molecules adsorbed in the vacancies desorbed at 400 ° C. The measurement was performed based on the measurement results of the refractive index and the dielectric constant obtained in the above.

  As described above, in all studies, the refractive index of the raw material for the low-K film has been measured in a non-contact and highly sensitive manner by the ellipsometry measurement method, but it could not be measured in a wide temperature range. With reference to the evaluation results, the refractive index of a thin film sample obtained by rapidly cooling a thin film treated at a specific temperature to near room temperature was evaluated. For this reason, there has been a problem that detailed examination on the vacancy formation temperature and the thermal decomposition temperature in the curing process cannot be made by in-situ observation of the refractive index accompanying the temperature change.

  A method of manufacturing a semiconductor device and an apparatus for manufacturing the same have been invented for performing appropriate oxide film removal according to the removal state of the oxide film when removing the oxide film on the substrate (Patent Document 1). In the present invention, a technique has been developed in which polarization parameters (Ψ, Δ) up to 800 ° C. can be measured and in-situ analysis of the state change of the substrate accompanying a temperature rise can be made. Although this invention was expected to be applicable to the refractive index measurement of the above-mentioned wax film material, an infrared heating method without a cooling device was adopted as a temperature control method, and the thin film sample to be measured Is rapidly heated to a high temperature, so the polarization parameters (Ψ, Δ) are obtained as a function of time rather than temperature. For this reason, there has been a problem that knowledge about the temperature dependence of the refractive index and film thickness required for characteristic evaluation cannot be obtained.

  Further, in the invention, since the polarization parameters (Ψ, Δ) are measured while the sample is held in vacuum, there is a problem that the thin film material cannot be evaluated under a desired atmosphere and pressure conditions.

In next-generation semiconductor development, as the circuit density in the device increases, the distance between wirings tends to be shorter, and the minimum wiring pitch adopted for next-generation semiconductors has decreased to 45 nm or less. It is necessary to reduce the size of the vacancies in the wax film for adapting to the highly miniaturized next generation semiconductor as much as possible.
The vacancies introduced into the vacancy-introducing waxy film material are micropores and mesopores, and an ultrasensitive measurement method capable of evaluating the micropores and mesopores in the thin film is required.

A general-purpose gas adsorption method is used to evaluate micropores and mesopores present in bulk materials such as powder (Non-patent Document 4). In this measurement method, the specific surface area of the sample powder and the size of the pores are determined from the amount of adsorption of gas molecules (usually nitrogen, krypton, etc.) whose surface area is known to the surface of the powder maintained at a low temperature. is there.
A typical analytical model for evaluating the specific surface area is called the Brunauer-Emmet-Teller (BET) method. The relative pressure P / P _{0 of} the introduced gas (P is the pressure of the gas, P ₀ is the gas This is a method for determining the specific surface area (BET specific surface area) by measuring the adsorption amount of monomolecules from the relationship between the saturated vapor pressure and the adsorption amount q.

In addition, under the isothermal condition with the sample temperature kept constant, the adsorption isotherm can be obtained by observing the adsorption amount q while gradually changing the pressure P of the adsorbed molecules from the vacuum state to the saturated vapor pressure P ₀ or less. Obtainable. It is known that the adsorption isotherm is related to the size of nanopores.
In the case of mesopores having a pore diameter of 2 nm or more, the pore diameter distribution can be obtained from the relative pressure dependence of the adsorption amount based on the Kelvin equation. For micropores with a pore size of 2 nm or less, the pore size distribution can be obtained by applying the Dubinin-Astakhov (DA) method or the like.

  However, since the general-purpose gas adsorption method has low sensitivity, there is a problem that a large amount of specimen sample needs to be prepared for each measurement in order to apply it to a thin film material.

  In order to apply the gas adsorption measurement method to a small amount of porous thin film sample, a method using an organic solvent or water having a low vapor pressure as an adsorbent was invented (Patent Document 2). However, since it is limited to measurement at room temperature, a substance that can be used as an adsorbed molecule is limited to water having a low vapor pressure and a strong interaction with an organic solvent having a relatively large molecular weight and many materials. For this reason, when an adsorbed molecule having a large molecular diameter is used, there is a problem in that it is limited to measurement of vacancies larger than the adsorbed molecule. More seriously, there is a principle problem that the swelling effect cannot be ignored for adsorbed molecules having strong interaction with the sample.

In order to use a gas such as nitrogen or argon as an adsorbed molecule that has a small interaction with many substances and can detect smaller vacancies, the sample should have a boiling point temperature of the adsorbed gas, for example, in the case of nitrogen. There is a problem that it has to be cooled to an extremely low temperature of −196 ° C., which is not solved by the invention of Patent Document 2.
Japanese Patent No. 3253932 US Pat. No. 6,319,736 SY Chang, et al., Journal of the Electrochemical Society, vol.151 (6), pp.F146F152 (2004). Y. Shioya, et al., Journal of the Electrochemical Society, vol. 151 (1), pp. C56C61 (2004). Y. Uchida, et al., MicroelectronicEngineering, vol.83, pp.2126-2129 (2006). SM Gregg and KS Sing: Adsorption, Surface Area and Porosity (Academic Press, London, 1982).

  The object of the present invention is to set the temperature of the thin film sample in a low temperature range (less than 0 ° C.) and a medium temperature range (0 ° C. or more and less than 200 ° C.), with the environment of the thin film sample being a vacuum or a gas atmosphere having a specific pressure of atmospheric pressure or less To measuring the polarization parameters (Ψ, Δ) of the thin film sample while continuously changing in the range from high temperature to 200 ° C. While changing the temperature, obtain physical properties such as the film thickness L, refractive index n, extinction coefficient k, etc., and analyze the measurement results obtained by changing the pressure and temperature to determine the amount and size of the nanopores and the specific surface area. Another object of the present invention is to provide a pressure-variable and temperature-variable ellipsometric measurement method for the purpose of evaluating the coefficient of thermal expansion, thermo-optical characteristics associated with decomposition and desorption. In the present specification, “changing temperature or pressure” means changing at least one of temperature and pressure.

  The environment of the thin film sample to be measured is set to a vacuum condition or a specific atmospheric condition different from the atmosphere, and the polarization parameters (Ψ, Δ) of the thin film sample are measured under the above conditions to determine the refractive index n, the extinction coefficient k, and the film In order to be able to determine the thickness L, a sample evaluation chamber provided with an optical window was developed, and a temperature variable ellipsometry measurement apparatus equipped with the sample evaluation chamber was developed.

  FIG. 1 shows an outline of the temperature variable ellipsometry measuring apparatus. The function of each part will be described below.

  The sample evaluation chamber provided with the optical window provided in the temperature variable ellipsometry measuring device has an optical window (1) in a housing (sample evaluation chamber: 5) provided with a stage (4) on which a thin film sample (3) is arranged. The optical window (1) is coupled and has an optical surface installed so that the incident light (11) and the reflected light (12) from the sample surface pass vertically.

The sample stage (4) is provided with a metal pipe for transporting the refrigerant introduced from the refrigerant inlet (23) using a heater and a refrigerant introduction pump not shown in FIG. By controlling the output of the refrigerant introduction pump and the heater with the temperature controller while monitoring the sample temperature with the installed temperature sensor, the thin film sample (3) is heated from the refrigerant temperature to the temperature that can be raised by the heater. It can be kept at an arbitrary temperature in the range up to.
A low-temperature liquid such as liquid helium, liquid hydrogen, liquid nitrogen, liquid argon, or liquid oxygen can be used as the refrigerant.
The controllable temperature range can be a range of the lower limit temperature and the upper limit temperature shown below. The lower limit temperature can be determined depending on the boiling point of the refrigerant liquid used, for example, liquid helium temperature (-269 ° C), liquid hydrogen temperature (-253 ° C), liquid nitrogen temperature (-196 ° C), liquid Argon temperature (-186 ° C), liquid oxygen temperature (-183 ° C), etc. The upper limit temperature can be determined depending on the output of the heater. For example, it can be several hundred degrees Celsius, preferably 600 degrees Celsius.

  The sample evaluation chamber provided with the optical window is sufficiently airtight and after the valve (19) is closed, the environment of the thin film sample (3) is kept in a vacuum state of 1 Pa or less by the exhaust pump (22). can do. The degree of vacuum in the sample evaluation chamber can be monitored with a vacuum gauge (18).

  By holding a predetermined gas in the atmosphere adjustment gas cylinder (16) and introducing it into the sample evaluation chamber, an arbitrary pressure in a pressure range from vacuum to about atmospheric pressure, preferably in a pressure range of 1 Pa to 1020 hPa The atmosphere can be maintained. The pressure in the sample evaluation chamber can be monitored with a pressure gauge (17).

  Further, by switching the three-way valve (21) to the gas discharge port (25) side, measurement can be performed while the gas in the atmosphere adjustment gas cylinder (16) is flowed into the sample evaluation chamber at a predetermined flow rate. The flow rate can be monitored with a flow meter (20).

  A polarization parameter measurement system including a light source (9), a detection unit (10), and an ellipsometric measurement controller (8) converts white light output from the light source (9) into linearly polarized light by a polarizer and converts incident light (11 The reflected light (12) that is incident at an angle θ with respect to the direction perpendicular to the substrate surface and reflected by the sample thin film is reflected in the sample surface as elliptically polarized light in the detector (10). After passing through the analyzer, the intensity of the light is measured to obtain the polarization parameters (Ψ, Δ). However, the axis of linear polarization of incident light is in the p direction (the direction of the intersection of the plane perpendicular to the optical axis and the plane containing the incident light and reflected light) and the s direction (p direction in the plane perpendicular to the optical axis). In a direction perpendicular to

  Method of obtaining refractive index n, extinction coefficient k, and film thickness L from polarization parameters (Ψ, Δ) obtained by ellipsometry measurement and complex reflectance of polarization component (HG Tompkins and WA McGahan, Spectroscopic Ellipsometry and Reflectmetry: A User's Guide, John Wiley & Sons, Inc., New York, 1999.)

The relationship between the complex refractive index N = n−ik of the sample and the polarization parameters (ψ, Δ) at each wavelength λ will be described, where θ is the angle formed between the incident light and the normal of the sample surface. As described above, by measuring the Ψ (or tan Ψ) and Δ (or cos Δ) of the reflected light, each thin film placed in a rare gas (refractive index ˜1) in a vacuum or atmospheric pressure is measured. The refractive index n and the extinction coefficient k at the wavelength λ are obtained from the following equations.

The film thickness L is obtained by using the optical interference effect in the thin film sample on the substrate. More specifically, the film thickness L of each polarization component subjected to multiple reflections between the interface 1 on the thin film surface and between the thin film and the substrate interface 2. It is obtained from the relationship between the reflectance and the Fresnel reflection coefficient r.

  Here, β = 2πλLNcosφ, and each r corresponds to the reflection at the interface indicated by the subscript for the polarization component indicated by the superscript, and φ represents the angle of the incident light within the film with respect to the normal of the sample surface As shown, the relationship of nsinφ = sinθ is established from Snell's law for a thin film having a refractive index n.

  By analyzing the measurement result of the polarization parameter using a model based on Equations 1 to 4, the refractive index n, the extinction coefficient k, and the film thickness L of the sample thin film can be obtained.

  By using the temperature variable ellipsometry measuring device described above, the sample chamber is set to a pressure in the range from vacuum to atmospheric pressure or higher, preferably in the range from 1 Pa to 1020 hPa, and from extremely low to very high temperature. Set the sample temperature within a wide temperature range, preferably the low temperature range (-196 ° C or higher and lower than 0 ° C), middle temperature range (0 ° C or higher and lower than 200 ° C), and high temperature range (200 ° C or higher and lower than 600 ° C). A thin film sample at a specific temperature and a specific pressure is measured by ellipsometry by raising or lowering the temperature at a predetermined speed or both, and the temperature of the refractive index n, extinction coefficient k, and film thickness L of the thin film sample is measured. Dependence, and the refractive index n, extinction coefficient k, and film thickness L under different pressure conditions at a specific temperature can be observed, and the temperature difference of the refractive index n, extinction coefficient k, and film thickness L Calculate the coefficient of thermal expansion and the thermo-optic coefficient from Each temperature dependency can be evaluated.

を導き出した。Aは物質に固有の定数である。 <Relation between refractive index and density>
Dutch theoretical physicist Hendrik-Lorenz leaves the medium ether that transmits light out of the idea that it is purely electromagnetic, and in terms of the refractive index and density ρ of light in a transparent material, Lorentz-Lorenz Formula of

Derived. A is a constant specific to the substance.

ここで下付の添え字、sk、filmは、薄膜試料を構成する骨格部分の屈折率および空孔を含んだ膜全体の屈折率にそれぞれ対応する。この式から膜中の空孔量が増加すると膜の屈折率n_filmは減少する。 <Relation between refractive index and porosity>
ρ and the porosity V _p are related by the equation V _p = (ρ ₀ −ρ) / ρ ₀ = 1−ρ / ρ ₀ . Here, ρ ₀ is a skeleton density corresponding to zero porosity. From the Lorentz-Lawrence relationship according to Equation 5, the relationship between the refractive index n and the porosity V _p is expressed as follows.

Here, the subscripts sk and film respectively correspond to the refractive index of the skeleton part constituting the thin film sample and the refractive index of the entire film including the holes. From this equation, as the amount of pores in the film increases, the refractive index n _film of the _film decreases.

ここでΔLは伸び、ΔTは温度上昇である。
＜熱光学係数＞
公知の文献（Z. Zhang, et al., Polymer, vol.47, pp.4893-4896 (2006).）によると、屈折率nの温度依存性から求められる熱光学係数dn/dTには以下の関係がある。

<Coefficient of thermal expansion>
The coefficient of thermal expansion is defined by a value indicating the rate at which the length and volume of an object expand with increasing temperature per 1 ° C. The rate at which the length changes in response to an increase in temperature is called the linear expansion coefficient. The length Lx at the temperature x ° C. and the linear expansion coefficient α have the following relationship.

Here, ΔL is elongation and ΔT is temperature rise.
<Thermo-optic coefficient>
According to a known document (Z. Zhang, et al., Polymer, vol. 47, pp. 4893-4896 (2006)), the thermo-optic coefficient dn / dT obtained from the temperature dependence of the refractive index n is There is a relationship.

In the above formula, ξ represents a volume expansion coefficient (= 3α), and (∂n / ∂T) _ρ represents a term when the density is constant. Since Utilizing Lawrence equation refractive index n can be replaced with the density ρ, - (ρ∂n / ∂ρ) T but is a value determined from the density dependence of the refractive index, the Lorentz by Equation 5 It can be read as a term that depends only on the temperature change of density. That is, it is clear that the absolute value of the left side (-dn / dT) shows a larger value when the amount of density decrease per unit temperature, in other words, the amount of increase in porosity per unit temperature, is large.

For thin-film samples with relatively small variations in thermal expansion coefficient and (∂n / ∂T) _ρ , such as silica and other inorganic oxides and organic insulating film candidate materials, the empty space for the left-hand side term -dn / dT in the above equation is used. The contribution due to the variation in porosity increases, and by measuring the temperature dependence of the left-hand side term -dn / dT, it becomes possible to analyze the temperature change of the porosity with high sensitivity.

の関係を用いて測定できる。 <Refractive index and adsorption of gas molecules at low temperatures>
When the film composition of the thin film sample is constant, when the refractive index is decreased the refractive index n _film of the entire membrane by pore formation of 1, the molecules of the refractive index n _ad the pores is adsorbed, the amount of adsorbed molecules Accordingly, the refractive index _nob of the observed film increases. Here, the void volume V _f filled with adsorbed molecules is

It can be measured using the relationship.

The amount of holes V _f filled with adsorbed molecules is proportional to the adsorbed amount q of adsorbed molecules. Based on Equation 9, the difference between the refractive index of the adsorbed molecule and the refractive index of the vacancy (= 1) is calculated by ellipsometry in order to calculate the void volume V _f filled with the adsorbed molecule from the observed refractive index. It must be sufficiently large compared to the measurement error (about 1 / (100n)) in the method. Heptane (refractive index at room temperature: 1.38579), liquid nitrogen (refractive index at -195.35 ° C: 1.1985), liquid argon (refractive index at -187.61 ° C: 1.2312), liquid krypton (refractive index: 1.3), liquid hydrogen (refractive index) : The refractive index of each gas molecule used in the gas adsorption method such as 1.112) is sufficiently larger than the refractive index of the pores (= 1), so the gas can be applied as an adsorbed molecule to the porous thin film sample. it can.

で表されることが知られている。ここで、P₀は吸着分子の飽和蒸気圧、q₀は全空孔に吸着したときの最大吸着量、βは吸着分子および試料に依存する定数である。 The relationship between the amount q of adsorbed gas molecules in the vacancies and the pore diameter D has been studied in detail in known studies. According to known literature (RZWang, et al., Int. J. Energy Res., Vol.23, pp.887-898 (1999)), under the isobaric condition of pressure P, molecular adsorption to the pores The relationship between quantity q, hole diameter D and absolute temperature T _K is

It is known that Here, P ₀ is the saturated vapor pressure of the adsorbed molecule, q ₀ is the maximum adsorption amount when adsorbed in all the vacancies, and β is a constant depending on the adsorbed molecule and the sample.

  From the relationship of Equation 10, it is clear that when the temperature is lowered under the isobaric condition of the predetermined pressure P, the adsorption amount starts to increase on the higher temperature side as the sample has pores with smaller pore diameters. is there. The relationship of Equation 9 is based on a known study (X. Zhao, et al., Science, vol. 306, pp. 1012-1015 (2004).) Concerning hydrogen storage materials containing micropores or mesopores. It has been applied and its usefulness has been experimentally supported.

  As described in detail so far, paying attention to the fact that the thermo-optic coefficient depends on the density of the thin film sample, that is, the porosity, a temperature variable ellipsometer capable of measuring in the temperature range from 0 ° C to 600 ° C Has been developed to enable non-contact and in-situ observation of the formation of vacancies in low dielectric constant insulating film materials.

  Further, by extending the lower limit temperature to an extremely low temperature such as liquid helium temperature or liquid nitrogen temperature, gas adsorption ellipsometry measurement performed at room temperature so far is performed at an extremely low temperature such as liquid nitrogen temperature. It became possible. A gas such as nitrogen, argon or krypton can be selected as the atmosphere in the sample installation chamber equipped with the measuring apparatus according to the present invention, and the apparatus according to the present invention is applied by using the gas as an adsorbed molecule. Enabled gas adsorption measurement. In addition, it became possible to observe the pore size distribution including micro pores with smaller pore sizes, which could not be measured by solvent adsorption.

  The best mode for carrying out the invention will be described with reference to the drawings.

As an example according to the present invention, a silica sputtered thin film pretreated by annealing at 600 ° C. for 30 minutes under a stream of dry nitrogen was normalized by dividing by (a) film thickness L ₂₀ = 1.0 [μm] at 20 ° C. FIG. 2 shows the film thickness L / L ₂₀ and the temperature dependency of (b) the refractive index n with respect to light having a wavelength of 630 nm in the middle temperature range and the high temperature range. The silica-sputtered film was prepared using a high-frequency magnetron sputtering deposition apparatus under the following conditions as process parameters: high-frequency discharge output 450 W, coexisting argon gas pressure 0.1 Pa, sputter target SiO ₂ , deposition time 120 minutes.

As is clear from the results shown in FIG. 2, the refractive index near room temperature is in agreement with the literature value of 1.45 for nonporous silica. The linear expansion coefficient α and the thermo-optic coefficient −dn / dT in the measurement temperature range (0 ° C.-600 ° C.) are calculated from the gradient of the measured refractive index and film thickness in the measurement temperature range shown in FIG. It was shown in 1.

  Table 1 also shows the linear expansion coefficient α and the thermo-optic coefficient −dn / dT of a polysiloxane thin film (hereinafter “siloxane thin film”) produced by plasma enhanced chemical vapor deposition (PECVD). The siloxane thin film is prepared by diluting a mixed raw material of 4: 1 relative amount of hexamethyldisiloxane and cyclohexene oxide with a mixed gas of a relative amount of 12: 8 of argon and oxygen, high frequency discharge output 200 W, reactor pressure 150 Pa, It was obtained by annealing a thin film produced on a silicon substrate under conditions of a substrate temperature of 250 ° C. and a deposition time of 5 minutes at 600 ° C. in a dry nitrogen stream.

  As another embodiment of the present invention, an analysis result of vacancy formation accompanying pyrolysis and desorption due to temperature rise of porogen in an organic-inorganic composite thin film produced by PECVD will be described.

  FIG. 3 shows the temperature dependence of the refractive index of a porogen-containing silica thin film prepared by PECVD with respect to light having a wavelength of 630 nm.

  The porogen-containing silica thin film is prepared by diluting a mixed raw material of 5: 3 relative amount of normal ethyl silicate (TEOS) and cyclohexane with a relative amount of argon gas 10, high-frequency discharge output 200 W, reactor pressure 150 Pa, substrate temperature 80 It was obtained by fabricating on a silicon substrate under the conditions of ° C. and deposition time of 12 minutes. The film thickness at room temperature is 0.8 [μm].

  FIG. 4 shows the temperature dependence of the porogen-containing siloxane thin film prepared by PECVD with respect to light having a wavelength of 630 nm.

  The porogen-containing siloxane thin film is prepared by diluting a 4: 3 relative mixed raw material of hexamethyldisiloxane and cyclohexane with a relative amount of argon gas 12, high-frequency discharge output 200 W, reactor pressure 150 Pa, substrate temperature 100 ° C., deposition It was obtained by producing on a silicon substrate under each condition for 15 minutes. The film thickness at room temperature is 0.5 [μm].

  As shown in FIG. 3 and FIG. 4, the refractive index of the thin film heated to 600 ° C. and then cooled to room temperature is greatly reduced compared to the refractive index of the thin film before heating, and empty due to the pyrolytic desorption of the porogen. It shows that holes were formed and the porosity increased.

  Using Equation 6 and the refractive index of the skeletal component forming each thin film sample (silica thin film: 1.45, siloxane thin film: 1.49), the porosity determined from the refractive index at 20 ° C. of the heated thin film is 33% and 30% respectively.

  The temperature dependence of the thermo-optic coefficient -dn / dT at the time of temperature rise of these thin film samples is shown in FIG.

  Compared to the thermo-optic coefficients of the silica thin film and siloxane thin film shown in Table 1, the thermo-optic coefficient of each thin film containing porogen is sufficiently large in the measurement temperature range, and the change in the thermo-optic coefficient of the porogen-containing thin film is the heat of the porogen. It shows that the fluctuation of porosity with the formation of pores due to decomposition is dominant.

  When the results of the respective thin film samples shown in FIG. 5 are examined in detail, in the measurement results of the porogen-containing silica thin film, the peaks due to rapid vacancy formation accompanying porogen desorption are about 150 ° C. and about 280 ° C. In the measurement results of the porogen-containing siloxane thin film, a slightly broad peak was observed at about 400 ° C. due to vacancy formation. From this result, it is clear that the measured pore formation temperatures of the two types of porogen-containing thin films are different. According to the present invention, it was shown that in-situ observation of the vacancy formation process by the porogen method is possible.

FIG. 6 shows the results showing still another embodiment of the present invention. A micropore-containing silica-based thin film and a mesopore-containing silica-based thin film, each having a pore diameter determined by the slow positron lifetime measurement method of 1.7 nm and 4.0 nm, were used as thin film samples. After the thin film sample was placed in the sample evaluation chamber, the sample evaluation chamber was preliminarily annealed at 120 ° C. for several minutes under a vacuum of 1 Pa or less, and then dry argon was introduced so that the sample evaluation chamber was 1013 hPa. Ellipsometric measurement was performed while decreasing the sample temperature while maintaining the argon pressure at 1013 hPa. FIG. 6 shows the temperature dependence of the difference Δn = n−n ₁₂₀ between the refractive index n of light at a wavelength of 630 nm of each thin film sample measured at each temperature and the refractive index n ₁₂₀ of light at a wavelength of 630 nm measured at 120 ° C. showed that.

FIG. 7 shows the sample temperature dependency of V _f obtained by applying Equation 9 to the temperature dependency of the refractive index measured for each thin film sample shown in FIG. As described above, V _f reflects the amount of gas molecules adsorbed in the vacancies. As the result of FIG. 7 shows, when the temperature is decreased, the mesopore-containing silica-based thin film having a large pore diameter has a vacancy around −40 ° C., which is higher than the temperature at which V _f starts to increase. V _f of a microporous silica-based thin film having a small pore diameter has begun to increase. From this result, it was shown that the nanopore structure analysis is possible by applying the present invention.

  In the development of next-generation semiconductors in the semiconductor industry, it is indispensable to lower the dielectric constant of the insulating film in order to reduce the parasitic capacitance that causes signal delay. Nanospace is introduced into insulating materials such as silica. Development of a porous ultra-low K film with a significantly reduced dielectric constant is underway. The present invention provides a physical property evaluation method that is indispensable for the development of a void-introducing type wax-like film material.

  The organic thin film material used in the production of a semiconductor device is a viscoelastic body, and the thermal residual stress and warpage deformation of the material have serious consequences such as peeling at the interface with the metal wiring in the device. The present invention provides a method capable of highly sensitive evaluation of the glass transition temperature and the coefficient of thermal expansion (thermal expansion coefficient) that are closely related to these physical properties.

  Measurement of the thermo-optic coefficient is indispensable for athermal materials, optical switching materials, and the like that are being studied for application to optical communication media. By applying the temperature variable ellipsometry measurement method according to the present invention, it is possible to perform highly sensitive measurement of the thermo-optic coefficient in a wide temperature range. It can also be applied to thin films with sub-micron thickness that cannot be measured by the prism coupling method, and can contribute to the research and development of optical thin film materials.

The development of porous thin films applicable to optical waveguides, high-sensitivity gas sensors, molecular separation membranes, etc. has been carried out, and measurement techniques for non-destructive and microscopic cavities of nano vacancies in the thin films are important. The pore structure evaluation method provided by the ultrasensitive gas adsorption amount measuring technique according to the present invention contributes to the research and development of functional porous thin film materials.
Research results have shown that storage properties can be improved by thinning a material with hydrogen storage properties. By applying the present invention, it is possible to evaluate the adsorption characteristics of the thin film with respect to hydrogen with high sensitivity. For this reason, it contributes to the development of new materials for storing hydrogen, which is expected as an alternative clean energy for fossil fuels that are considered to be the cause of greenhouse gases.

  Applicable to the analysis of thermal properties of device-related materials such as ferroelectrics, low dielectric constant films, sealants, and glass transition analysis of polymer thin films used in organic EL and next-generation integrated circuits. .

1 is a schematic view of a temperature variable ellipsometry measuring apparatus that is capable of pressure adjustment and includes a sample evaluation chamber having an optical window. Silica sputtered thin film pretreated by annealing at 600 ° C for 30 minutes in a dry nitrogen stream (a) Film thickness normalized by dividing by 20 ° C, and (b) Light with a wavelength of 630 nm Refractive index n with respect to is shown in the temperature dependence in the middle temperature range and the high temperature range under a dry nitrogen stream at a flow rate of 0.5 L / min. Using the porogen-containing silica thin film prepared by the PECVD method as a sample, the temperature dependence of the refractive index with respect to light having a wavelength of 630 nm was measured in a dry nitrogen stream at a flow rate of 0.4 L / min. The arrows in the figure indicate the direction of temperature change. Using the porogen-containing siloxane thin film prepared by PECVD method as a sample, the temperature dependence of the refractive index with respect to light having a wavelength of 630 nm was measured in a dry nitrogen stream at a flow rate of 0.4 L / min. The arrows in the figure indicate the direction of temperature change. The temperature dependence of the thermo-optic coefficient calculated from the temperature minute difference in the temperature rising process of each refractive index shown in FIGS. 3 and 4 is shown. It shows the temperature dependence of the difference Δn between the refractive index measured under an argon atmosphere at atmospheric pressure (about 1013 hPa) and the argon flow rate being zero and the refractive index at 120 ° C. under the same condition. FIG. 6 shows the temperature dependence of V _f calculated from the results of FIG.

Explanation of symbols

1: Optical window 2: Sample evaluation chamber 3: Thin film sample 4: Sample stage with heater and temperature sensor 5: Connecting line 6 of heater / temperature sensor and temperature controller 6: Temperature controller 7: Control computer 8: Polarization Analysis measurement controller 9: Light source 10: Detection unit 11: Incident light 12: Reflected light 13: Connection line 14 of light source and polarization analysis measurement controller 14: Connection line 15 of polarization analysis measurement controller and control computer 15: Temperature controller And control computer connection line 16: atmosphere adjusting gas cylinder 17: pressure gauge 18: vacuum gauge 19: valve 20: flow meter 21: three-way valve 22: exhaust pump 23: refrigerant liquid supply port 24: refrigerant liquid discharge Outlet 25: Gas outlet

Claims (4)

  In the ellipsometry method, a sample is placed in a sample evaluation chamber provided with an optically transparent window, and incident light irradiating the sample is changed even if the gas pressure or temperature in the sample evaluation chamber is changed. By providing an optical surface that is perpendicular to the sample and an optical surface that is perpendicular to the reflected light reflected by the sample, the refractive index, extinction coefficient, or film thickness of the sample at various pressures and temperatures can be obtained. An ellipsometry method characterized by being capable.   The polarization analysis method according to claim 1, wherein the temperature is in a range of −196 ° C. to 600 ° C.   The polarization analysis method according to claim 1, wherein the pressure is a pressure in a range of 1 Pa to 1020 hPa.   In the ellipsometer, the apparatus includes a sample evaluation chamber, and the chamber includes a window, a sample table is disposed in the chamber, and a gas pressure in the sample evaluation chamber or An optical surface perpendicular to the incident light irradiated on the sample placed on the sample stage and an optical surface perpendicular to the reflected light reflected from the sample are provided even when the temperature is changed. Ellipsometer.

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