JP2009068909A - Method for measuring thin-film thermophysical property, and device for measuring the thin-film thermophysical property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film thermal diffusivity measuring device of a surface heating/surface temperature measuring type, into which an analysis model that takes into consideration the film thickness is incorporated. <P>SOLUTION: When the surface of a thin film 2 formed on a substrate 1 is heated instantaneously by using heating pulsed light 3, such as, laser pulsed beam to the substrate 1, the surface temperature rises instantaneously. Then, the heat diffuses to the inside of the thin film 2 and penetrates into the substrate 1, and the surface temperature of the thin film 2 is attenuated. Temperature-measuring pulsed light 4 (P2) is irradiated to the same domain as for the heating pulsed light 3 (P3). Light intensity of its reflected light (4b) changes slightly, depending on the surface temperature of the thin film 2. The intensity of the reflected light is detected by a detector 5, and the temperature change of the thin film 2 surface is detected. The detector 5 is equipped with a light intensity sensor 5a for measuring the intensity of the reflected light, and an information processing device 5b for determining and recording the actual temperature and its change, based on a signal from the light intensity sensor 5a. An operation part for calculating a thermal diffusivity of the thin film from the analysis model that takes into consideration the film thickness is integrated into the information processing device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film thermophysical property measurement technique, and more particularly, to a technique applicable to all measuring devices that measure a thin film thermophysical property value from a temperature history curve generated when pulse heating is periodically performed on a thin film surface.

  The thermophysical property value of a thin film is an important parameter in the thermal design of the advanced electronics field where fine structures and high integration such as optical disks, hard disks and semiconductor devices are progressing. Many thin films are formed on substrates of various materials such as metals, semiconductors, and insulators. A technique for quantitatively measuring the thermophysical value of a thin film formed on an arbitrary substrate is required.

  Eesley, Paddock et al. Heated the thin film sample surface with a picosecond pulse laser, and calculated the thermal diffusivity of the single layer thin film formed on the substrate from the temperature decay curve of the sample surface and the absorption coefficient with respect to the wavelength of the heating pulse light of the thin film. Although it was calculated from the temperature history curve when it was assumed that the thin film by one-pulse heating was semi-infinitely thick, it was difficult to measure quantitatively because it was sensitive to the uncertainty of the absorption coefficient and the surface condition (see Non-Patent Document 1). ).

  Capinski, Cahill, Norris, et al. Have developed a similar surface heating and surface temperature measurement type thin film thermophysical property measurement device, and analyzed by adding numerically the contribution of repeated irradiation of heating pulses (Patent Literature). 1, see Non-Patent Documents 2, 3, and 4). At that time, a metal film is formed on the surface of the object, and the thermal conductivity of the base thin film is calculated from heat penetration from the metal thin film to the base film assuming that the heat capacity and film thickness of the metal thin film are known. The range of objects that can be applied by attaching a metal film to the surface is wide, but it is difficult to tell which part of the temperature history curve the contribution of thermal diffusion inside the thin film, the contribution of the thermal resistance between the metal film and the thin film and the inside of the thin film It is also difficult to separate the thermal diffusion contributions.

  Baba and Taketoshi et al. Developed a backside heating / surface temperature measuring system (see Patent Documents 2 and 3). Although this method can directly observe thermal energy transfer across the film, it is restricted that the substrate is transparent to heating light and temperature measuring light, and cannot be measured for any substrate.

US Patent Publication: US 7,182,510 B2 Japanese Patent No. 3252155 JP 2003-322628 A C.A.Paddock and G.A.Eesley, “Transient thermoreflectance from thin metal films”, J.Appl.Phys. (1986), vol.60, p.285 W.S.Capinski, H.J.Maris, “Improved apparatus for picosecond pump-and-probe optical measurements”, Rev. Sci. Instrum. (1996), vol.67, p.388 D.G.Cahill, “Analysis of heat flow in layered structures for time-domain thermoreflectance”, Rev. Sci. Instrum., (2004), vol.75, p.5119 R.J. Stevens, A.N. Smith and P.M.Norris, “Signal analysis and characterization of experimental setup for the thermoreflectance technique”, Rev. Sci. Instrum., (2006), vol. 77, 084901.

  However, in the conventional analysis method, it is difficult to extract only the thermal diffusion inside the thin film because the thickness of the film is not considered even though the contribution due to repeated heating is taken into consideration.

  An object of the present invention is to construct a surface heating / surface temperature measurement type thin film thermal diffusivity measuring apparatus incorporating an analysis model in consideration of the film thickness. It is to try to realize the measurement easily.

  According to the present invention, by incorporating the thickness of the film into the analysis, even in the surface heating / surface temperature measurement type high-speed temperature measurement, the film is formed in the same manner as the thin film thermal diffusivity measurement method of the back surface heating / surface temperature measurement type. It is possible to take into account the contribution of thermal energy transfer across, and quantitative thermal diffusivity measurement can be realized even in surface heating / surface temperature measurement type arrangements.

That is, according to one aspect of the present invention, the step of heating the surface of the thin film formed on the substrate with a periodic pulse train, and the step of detecting the temperature change of the heated heating area of the surface of the thin film; Obtaining a periodic surface temperature change of the thin film as a function of time;
Calculating the thermal diffusivity of the thin film from an analysis model that takes into account the film thickness of the target thin film based on the obtained temporal change in the surface temperature of the thin film and the film thickness of the thin film. A thin film thermophysical property measurement method is provided.

  The step of calculating the thermal diffusivity of the thin film is based on the temperature history curve in the heating region, the film thickness, and the penetration depth of the heating light. It is preferable to include a step of calculating the thermal diffusivity of the thin film from an analysis model considering the above. In the heating step, by repeatedly heating the surface of the thin film, by subtracting from the observed temperature history curve the temperature decay component that occurs because the heating region is constantly hot relative to the surroundings, It is preferable to have a step of calculating a thermal diffusivity after converting a temperature history curve by periodic pulse heating into a temperature history curve by single pulse heating. In order to convert the temperature history curve by the periodic pulse heating into the temperature history curve by the single pulse heating, it is preferable to have a step of subtracting a linearly temperature decay component from the temperature history curve. Without converting to a temperature history curve by single pulse heating, the temperature history curve by periodic pulse heating is divided into a temperature history curve by the single pulse heating and a component that linearly attenuates temperature from the temperature history curve. Means for analyzing from the model considered at the same time may be provided. The heating step preferably includes a step of heating using a pulsed laser that periodically oscillates. It should be noted that the step of detecting the temperature change of the heated region has a step of irradiating the heated region using a cw laser and obtaining a temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity. Anyway. In addition, the step of irradiating the heating region with another pulse laser that oscillates synchronously with the same repetition period as the heating pulse laser and obtains the temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity You may make it have.

  Note that the present invention may be a program that causes a computer to execute control of devices related to the above steps, or may be a computer-readable recording medium that records such a program.

  According to another aspect of the present invention, a heating means for heating a thin film surface formed on a substrate with a periodic pulse train, a temperature detection means for detecting a temperature change in a heated region of the thin film surface, and a thin film A means for obtaining a periodic surface temperature change as a function of time, and a means for calculating a thermal diffusivity based on the obtained time change of the surface temperature and the film thickness of the thin film. An apparatus for measuring thin film thermophysical properties is provided. There may be means for storing periodic surface temperature changes of the thin film as a function of time.

  There may be provided means for calculating the thermal diffusivity of the thin film based on the temperature history curve, the film thickness and the penetration depth of the heating light in the region to be heated. In addition, by subtracting from the observed temperature history curve the temperature decay component that occurs because the heating area is constantly hot relative to the surroundings due to repeated heating, a single temperature history curve due to periodic pulse heating is obtained. You may make it have a means to calculate a thermal diffusivity after converting into the temperature history curve by pulse heating. Furthermore, it is preferable to have a calculation unit that subtracts a component that linearly attenuates temperature from the temperature history curve in order to convert the temperature history curve by single pulse heating. Without converting to a temperature history curve by single pulse heating, the temperature history curve by periodic pulse heating is divided into a temperature history curve by the single pulse heating and a component that linearly attenuates temperature from the temperature history curve. You may have the calculating part analyzed from the model considered simultaneously. A pulsed laser that periodically oscillates may be used as the heating means. As a means for detecting a temperature change in the heated region, it is preferable to irradiate the heated region using a cw laser and obtain a temperature history curve on the film surface from the surface temperature dependence of the reflected light intensity. It is preferable to irradiate the heating region with another pulse laser that oscillates synchronously with the same repetition period as the heating pulse laser, and obtains a temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity.

  In the prior art, slight changes in the decay portion of the temperature history curve are easily reflected in the thermal diffusivity results, and it is difficult to quantitatively determine the thermal diffusivity. By introducing a temperature history curve model that takes into account and subtracting the contribution specific to heating by repetitive pulses, it is possible to fit the entire temperature history curve with high reliability and to improve measurement accuracy .

Hereinafter, a thin film thermophysical property measurement technique according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing the principle of a surface heating / surface temperature measurement type high-speed pulse heating thermoreflectance method, which is a thin film thermophysical property measurement technique according to the present embodiment. As means for heating the substrate 1 in a pulsed manner, the surface of the thin film 2 provided (for example, formed) on the substrate 1 is instantaneously applied by using, for example, heating pulse light 3 such as laser pulse light. Can be heated. Due to the heating, the temperature at the surface of the thin film 2 rises instantaneously. Thereafter, the heat diffuses into the thin film 2 and penetrates into the substrate 1, so that the surface temperature of the thin film 2 is attenuated.

  The temperature measuring pulse light 4 (P2) is irradiated to the same region as the heating pulse light 3 (P1) (4a). The light intensity of the reflected light (4b) slightly changes depending on the surface temperature of the thin film 2 (this phenomenon is referred to as thermoreflectance). By detecting the temperature-dependent change in the intensity of the reflected light (4b) with the detector 5, the temperature change on the surface of the thin film 2 can be detected. The detector 5 includes a light intensity sensor 5a that measures the intensity of the reflected light (4b), and an information processing device 5b that obtains and records the actual temperature and its change based on a signal from the light intensity sensor 5a. Yes.

  FIG. 2 is a functional block diagram of the thin-film thermophysical property measuring apparatus A used for actual measurement. The thin-film thermophysical property measuring apparatus A shown in FIG. 2 obtains heating (excitation) pulsed light L2 and probe light L3 from separate light sources, and uses an electrical signal to determine the timing of both lights L2 and L3 when the pulsed light is oscillated. It is configured to control with.

  Specifically, the light source includes picosecond TiS (titanium sapphire) lasers 21 and 23 that generate laser pulses, and controllers 15 and 17 that stably and stably control the repetition period of the pulses. Yes.

  The picosecond TiS laser (1) 21 shown in FIG. 2 is used as the sample heating light L1 and L2, and the picosecond TiS laser (2) 23 is used as the probe light L3. The pulse width of the pulsed light is 2 ps each, and the oscillation frequency is 76 MHz (repetition period 13.2 ns). In order to maintain the oscillation frequency of the picosecond TiS laser (1) 21 at 76 MHz, the resonator length of the picosecond titanium sapphire laser (1) 21 is controlled to be constant by the controller (1) 15. A 76 MHz reference signal for control is supplied from the controller (1) 15. Similarly, in order to maintain the oscillation frequency of the picosecond TiS laser (2) 23 at 76 MHz, the controller (2) 17 controls the resonator length of the picosecond TiS laser (2) 23 to be constant. A 76 MHz reference signal for control is supplied from the controller (2) 17. The relationship between the reference signal and the pulse oscillation phase is kept constant for each laser. The phase difference between the outputs of the controller (1) 15 and the controller (2) 17 can be remotely controlled by a setting panel for setting the signal waveform of the controller (2) 17 or the personal computer 11 or the like.

  In the configuration shown in FIG. 2, two picosecond titanium sapphire lasers 21 and 23 are used. However, the light source is not limited to the above-described light source as long as the light source oscillates a pulse with an equal period. Is optional.

  The heating light L1 is intensity-modulated at a frequency of 1 MHz when passing through the acoustic light modulator 25. The signal S2 for intensity modulation of 1 MHz is supplied by a signal generator (1) 47. The signal S2 for intensity modulation is also used as an input for the reference signal S5 to the lock-in amplifier 41. As an example of the modulation method, the acoustic light modulation element 25 is used in the present embodiment. However, for example, a mechanical chopper or an electro-optic crystal element may be used.

  The modulation frequency used here is a signal of 1 MHz, but it must be slower than the pulse repetition frequency. For example, when the pulse oscillates at a repetition rate of 76 MHz, about 500 kHz to 10 MHz. A modulation frequency between is suitable. The heating light L <b> 2 modulated by the acoustic light modulation element 25 is condensed on the interface between the thin film 2 and the substrate 1. The probe light L3 is condensed on the same surface of the thin film 2 as the heated region.

  The probe lights L6 and L7 reflected by the surface of the sample 1 are detected by a detector 37 that can be constituted by, for example, a silicon photodiode. The electric signal S1 based on the detected light is sent to the signal input terminal 41a of the lock-in amplifier 41. Since the surface temperature of the sample 1 has a component that changes at 1 MHz due to the intensity modulation of the heating light L2, the probe light L6 reflected by the sample 1 also includes a periodic component of 1 MHz although it is minute. The AC component of the probe light synchronized with the intensity modulation frequency of 1 MHz is detected by the lock-in amplifier 41.

  The time change of the reflectance change (thermoreflectance) proportional to the temperature change can be recorded on a hard disk or the like of the computer by controlling the delay of the sample arrival time of the probe light with respect to the heating light by using the computer 11. it can. The computer 11 incorporates an arithmetic processing unit for calculating the thermal diffusivity of the thin film from the recorded temperature history curve and the analysis model and analysis procedure taking into consideration the film thickness of the thin film as shown in Example 1 below. ing.

[Example 1]
Below, the measurement result obtained by said structure is demonstrated.
FIG. 3 is a diagram showing a temperature history curve by periodic heating pulses as a solid line, where the vertical axis represents the thermoreflectance signal and the horizontal axis represents time. The sample to be measured has a structure in which a molybdenum thin film 2 is formed on a glass substrate 1, and the film thickness of the molybdenum thin film 2 is about 400 nm. As shown in FIG. 3, the time range that appears to decrease linearly before the rapid temperature rise is assumed to be a steady heat escape to the surroundings and is approximated and subtracted with a straight line. A straight line f (t) = at + b for subtraction is observed at t <t ₀ (here, t ₀ = 3.68 × 10 ⁻⁹ s determined experimentally) earlier than time t ₀ when the heating pulse light arrives. The temperature history curve was determined (see FIG. 4).

  A temperature history curve indicated by a solid line in FIG. 5 is obtained by subtracting a chain line from the solid line in FIG. 4 and can be regarded as a temperature history curve by single pulse heating.

Next, the temperature history curve shown by the solid line in FIG. 5 is _converted into the entire range or a part of the range included in t ₀ <t <t ₀ + t _rep using the following equation (1) of the temperature history curve for a single pulse. On the other hand, curve fitting is performed. However, when fitting in a part of the range, both the initial steeply decaying temperature region and the region where the temperature decays slowly due to the heat reaching the substrate are included. desirable.

Here, t ₀ = 3.68 × 10 ⁻⁹ s determined experimentally is used as the time t ₀ when the heating pulse light arrives. In FIG. 5, curve fitting was performed in the range of t−t ₀ > 0 for the theoretical curve calculated up to n = ± 4. The unknown parameters are the temperature amplitude ΔT, the absorption coefficient (reciprocal of the penetration depth of the heating light pulse) α and the film thickness d α · d, and the thermal diffusion time τ _f = d ² / κ _f . Here, κ _f is a thermal diffusivity. γ is a temperature amplitude coefficient of the mirror image of the heating source, and is a value that varies between −1 and 1, and can be described using the thermal permeability of the thin film and the substrate. When γ = 1, heat is insulated at the interface between the thin film and the substrate.

If the film thickness and the absorption coefficient are known, the unknown parameters are the temperature amplitude ΔT and the thermal diffusivity κ _{f of the} thin film, and two unknown parameter fittings. The film thickness d was determined by fitting two unknowns using the measured value of 4.059 × 10 ⁻⁷ m and the measured value of the absorption coefficient α of 4.82 × 10 ⁷ m ^−1. The rate is 3.3 × 10 ⁻⁵ m ² s ⁻¹ , which is almost the same as the value of 3.0 × 10 ⁻⁵ m ² s ⁻¹ when the back surface heated surface temperature measurement type is performed on the same sample. To do. The actual curve fitting result is a curve that reproduces the experimental result well, as shown by the solid line and the dotted line. It is more effective that the thermal permeability of the substrate is smaller than that of the thin film and is closer to adiabatic conditions.

  When the absorption coefficient is unknown, three unknowns may be determined by curve fitting using the product of the absorption coefficient and the film thickness as an unknown parameter.

  When the reciprocal of the absorption coefficient α (the penetration depth of the heating light) can be ignored as compared with the film thickness d, the following formula (2) may be used instead of the above formula (1).

If it is possible to consider that γ = 1 under the condition that the expression (2) holds, T (t) at a certain time or more is constant. The time _t1.5 which is 1.5 times the constant value may be determined in the data converted into the temperature history curve of single pulse heating, and the thermal diffusivity of the thin film may be calculated from the following equation.

  If the temperature decay curve always has a downward convex curvature and it is difficult to determine the linear region, use the following formula to analyze it by including it in the linear contribution fitting. Also good. In contrast to the observed raw data in Figure 3,

としてｔ_０＜ｔ＜ｔ_０＋τ_rに含まれる全域または一部の範囲でＳ（ｔ）をカーブフィットすることもできる。ここでτ_ｒは加熱パルスの周期である。

As _{t 0 <t <t 0 +} τ in the range of the whole or a part contained in _r can be curve fit to S (t). Here, τ _r is the period of the heating pulse.

A method for deriving the slope of the second term on the right side of Equation (4) will be described below. Here, in order to simplify the expression, the calculation is made assuming that the time t ₀ = 0 when the heating pulse is irradiated for convenience. The observed temperature history curve S (t) is expressed by the following equation as a superposition of past components of the single pulse temperature history curve.

Let S (τ _r ) be an offset and subtract from the observed signal S (t) to examine the difference from the temperature response due to single pulse heating.

式（６）の右辺第２項をｔについて一次までテーラー展開すると

When the second term on the right side of equation (6) is Taylor-expanded to the first order with respect to t

式（７）の右辺の微分を以下の式（８）で近似すると、以下のように式（４）に示した傾きが得られる。

When the derivative on the right side of Equation (7) is approximated by Equation (8) below, the slope shown in Equation (4) is obtained as follows.

  In this way, the slope of the linear contribution can also be calculated from the model representing the temperature history curve of single pulse heating, but the measurement signal has drifts due to causes other than heat conduction (for example, slight deviation of the irradiation position). If it is included, it is difficult to separate the inclination shown by the equation (8) from the inclination due to drift, so the coefficient of the inclination may also be curve-fitted as an unknown parameter. In the experimental example shown here, a temperature history curve is obtained by using pulsed light for temperature measurement and performing delay time control on the heated pulsed light. However, if the observation time scale is 100 ns or more, the cw laser It is also possible to use observation means using a radiation thermometer. Further, the present invention can be applied to an apparatus using a contact type probe using a probe, such as SPM (Scanning Probe Microscope). In the conventional technique, a slight change in the decay portion of the temperature history curve is easily reflected in the thermal diffusivity result, and it is difficult to discuss the quantitative thermal diffusivity, but the technique according to the present embodiment is used. By introducing a temperature history curve model that takes into account the contribution of film thickness, and subtracting the contribution specific to heating by repeated pulses, the thermal diffusivity of the thin film can be calculated with high reliability over the entire temperature history curve. Is possible.

  The present invention can be used in thermal design in the advanced electronics field where fine structures and high integration are progressing such as optical disks, hard disks, and semiconductor devices.

It is a principle figure of surface heating and surface temperature measurement by one embodiment of the present invention. It is a functional block diagram which shows one structural example of the surface heating and surface temperature measuring apparatus by this Embodiment. It is a figure which shows the example of the temperature history curve of the repetition pulse heating obtained using the said apparatus. It is a figure which shows the temperature history curve example of repeated pulse heating. It is a figure which shows the example analyzed in consideration of the film thickness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Thin film, 3 ... Heating pulse light, 4 ... Temperature measurement pulse light, 5 ... Detector.

Claims (18)

Heating the surface of the thin film deposited on the substrate with a periodic pulse train;
Detecting a temperature change in a heated region on the surface of the thin film; and
Obtaining a periodic surface temperature change of the thin film as a function of time;
Calculating the thermal diffusivity of the thin film from an analysis model that takes into account the thickness of the target thin film, based on the obtained temporal change in the surface temperature of the thin film and the film thickness of the thin film. A method for measuring thin film thermophysical properties. Calculating the thermal diffusivity of the thin film,
Based on the temperature history curve in the heating region, the film thickness and the penetration depth of the heating pulse, the thermal diffusion of the thin film from the analysis model considering the thickness of the target thin film and the penetration depth of the heating pulse in the film The thin film thermophysical property measurement method according to claim 1, further comprising a step of calculating a rate.   In the heating step, by repeatedly heating the surface of the thin film, by subtracting from the observed temperature history curve the temperature decay component that occurs because the heating region is constantly hot relative to the surroundings, The thin film thermal diffusivity measurement according to claim 1, further comprising a step of calculating a thermal diffusivity after converting a temperature history curve by periodic pulse heating into a temperature history curve by single pulse heating. Method.   A step of subtracting a linearly temperature-decaying component from the temperature history curve in order to convert the temperature history curve due to the periodic pulse heating into the temperature history curve due to the single pulse heating. Item 4. The method for measuring thin-film thermophysical properties according to Item 3.   3. The step of analyzing the temperature history curve by the periodic pulse heating from a model that simultaneously considers a component that linearly attenuates the temperature with the temperature history curve by the single pulse heating. The thin film thermophysical property measuring method described in 1.   The thin film thermophysical property measuring method according to any one of claims 1 to 5, wherein the heating step includes a step of heating using a pulse laser that periodically oscillates.   The step of detecting the temperature change of the heated region has a step of irradiating the heated region using a cw laser and obtaining a temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity. The thin film thermophysical property measuring method according to claim 6.   A step of irradiating the heating region with another pulse laser that oscillates synchronously with the same repetition period as the heating pulse laser and obtains a temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity. The thin film thermophysical property measuring method according to claim 6. Heating means for heating the surface of the thin film formed on the substrate with a periodic pulse train;
Temperature detecting means for detecting a temperature change in the heated area of the thin film surface;
Means for obtaining a periodic surface temperature change of the thin film as a function of time;
Thin-film thermophysical property measurement, comprising means for calculating thermal diffusivity from an analytical model that takes into account the thickness of the target thin film based on the obtained time variation of the surface temperature and the film thickness of the thin film apparatus.   Based on the temperature history curve in the region to be heated, the film thickness, and the penetration depth of the heating light, the heat of the thin film is obtained from an analysis model that takes into account the thickness of the target thin film and the penetration depth of the heating pulse in the film. The thin film thermophysical property measuring apparatus according to claim 9, further comprising means for calculating a diffusivity.   By subtracting from the observed temperature history curve the temperature decay component that occurs because the heating area is constantly hot relative to the surroundings due to repeated heating, the temperature history curve due to periodic pulse heating is heated by a single pulse. The thin film thermophysical property measuring apparatus according to claim 9 or 10, further comprising means for calculating a thermal diffusivity after conversion into a temperature history curve according to claim 11.   The thin-film thermophysical property measuring apparatus according to claim 11, further comprising a calculation unit that subtracts a linearly decaying component from the temperature history curve in order to convert the temperature history curve by single pulse heating.   11. The apparatus according to claim 9, further comprising means for analyzing the temperature history curve due to the periodic pulse heating from a model that simultaneously takes into account the temperature decay curve linearly with the temperature history curve due to the single pulse heating. Thin film thermophysical property measuring apparatus according to 1.   The thin film thermophysical property measuring apparatus according to any one of claims 9 to 13, wherein a pulsed laser that periodically oscillates is used as the heating means.   A means for detecting a temperature change in a heated region is to irradiate the heated region using a cw laser and obtain a temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity. Item 15. The thin-film thermophysical property measuring apparatus according to Item 14.   It is characterized by irradiating the heating region with another pulse laser that oscillates in synchronization with the same repetition period as the heating pulse laser, and obtains the temperature history curve of the film surface from the surface temperature dependence of the reflected light intensity. The thin film thermophysical property measuring apparatus according to claim 14. Heating the surface of a thin film of known thickness formed on a substrate with a periodic pulse train;
Detecting a temperature change in a heated region on the surface of the thin film; and
Obtaining a periodic surface temperature change of the thin film as a function of time;
Calculating the thermal diffusivity of the thin film from an analytical model considering the thickness of the target thin film based on the obtained temporal change in the surface temperature of the thin film and the film thickness of the thin film, By subtracting the measured value of the thermoreflectance signal during the period before the rapid temperature rise from the measured value of the thermoreflectance signal of the temperature history curve due to a simple heat pulse, a single temperature history curve due to a periodic heat pulse is obtained. A method of measuring a thermal property of a thin film, comprising the step of calculating a thermal diffusivity of the thin film by converting into a temperature history curve by pulse heating. Heating the surface of a thin film of known thickness formed on a substrate with a periodic pulse train;
Detecting a temperature change in a heated region on the surface of the thin film; and
Obtaining a periodic surface temperature change of the thin film as a function of time;
A step of calculating the thermal diffusivity of the thin film from an analysis model that takes into account the thickness of the target thin film based on the obtained temporal change in the surface temperature of the thin film and the film thickness of the thin film, The temperature at which a model curve is observed, which is the sum of the temperature history curve by pulse heating and the temperature decay component that occurs because the surface of the thin film is repeatedly heated to the surroundings by repeatedly heating the surface of the thin film. And a step of calculating a thermal diffusivity of the thin film so as to fit the hysteresis curve.

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