JP2017152494A - Piezoelectric body evaluation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus capable of evaluating characteristics of a piezoelectric body at a stage before a structure (sandwich structure) in which an upper electrode and a lower electrode are formed on a surface of the piezoelectric body.SOLUTION: The piezoelectric body evaluation device includes: a temperature changing section that changes the temperature of the piezoelectric body by acting on a sample including the piezoelectric body; and a surface potential measuring section that measures the surface potential of the piezoelectric body. The surface potential measuring section measures a change in the surface potential of the piezoelectric body corresponding to the temperature change of the piezoelectric body caused by the temperature changing section.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric body evaluation apparatus.

  Conventionally, various piezoelectric body evaluation apparatuses and piezoelectric body evaluation methods for measuring characteristics (dielectric characteristics, pyroelectric characteristics, etc.) of piezoelectric bodies are known.

  For example, as a method for measuring the pyroelectric coefficient, a “method for measuring the pyroelectric coefficient of fine ceramics” described in JIS R 1651: 2002 is known. In this method, electrodes are formed on both surfaces of a ceramic sample, a temperature change is applied, and a current generated at that time is measured to obtain a pyroelectric coefficient.

  In addition, the pyroelectric body having electrode pairs on the surface is sequentially held at two different temperatures, the pyroelectric charge generated at that time is accumulated in a capacitor, and the pyroelectric coefficient is obtained from the voltage value between the capacitor electrodes. A simple coefficient measuring device is also known (Patent Document 1).

  Further, as a measurement of dielectric characteristics, it is widely known that an electrode pair is provided on the surface of a piezoelectric body and the capacitance is measured with a commercially available electric measuring instrument such as an LCR meter or an impedance analyzer.

  However, as described above, in the conventional piezoelectric body evaluation apparatus and evaluation method, an element having a structure in which upper and lower electrodes are formed on both surfaces of a piezoelectric body (sandwich structure) is prepared, and current and voltage between the electrodes are measured. Thus, the characteristics of the piezoelectric body are measured. Therefore, the conventional apparatus or method cannot measure the dielectric characteristics, piezoelectric characteristics, pyroelectric characteristics, etc. of the piezoelectric body before the formation of the sandwich structure element. Therefore, when there is a defect in the element, it has not been possible to determine whether the defect is due to the piezoelectric body or the electrode.

  The present invention has been made in view of the above points, and can measure the characteristics of a piezoelectric body without preparing a structure (sandwich structure) in which an upper electrode and a lower electrode are formed on both surfaces of the piezoelectric body. It is an object of the present invention to provide a piezoelectric body evaluation apparatus capable of performing the above.

  In order to solve the above problems, the present invention includes a temperature changing unit that changes the temperature of the piezoelectric body by acting on a sample including the piezoelectric body, and a surface potential measuring unit that measures the surface potential of the piezoelectric body. There is provided a piezoelectric body evaluation apparatus, wherein the surface potential measurement unit measures a change in surface potential of the piezoelectric body corresponding to a temperature change of the piezoelectric body caused by the temperature change section. It is characterized by doing.

  According to the present invention, there is provided a piezoelectric body evaluation apparatus capable of measuring characteristics of a piezoelectric body without preparing a structure (sandwich structure) in which an upper electrode and a lower electrode are formed on the surface of the piezoelectric body.

It is a figure which shows roughly the structure of the piezoelectric material evaluation apparatus by 1 aspect of this invention. It is a figure which shows roughly the structure of the piezoelectric material evaluation apparatus by 1 aspect of this invention. It is a figure which shows roughly the structure of the piezoelectric material evaluation apparatus by 1 aspect of this invention. It is a figure showing the mode of a rise and fall of surface potential.

[1] Piezoelectric Evaluation Apparatus and Piezoelectric Evaluation Method According to First Aspect The piezoelectric evaluation apparatus according to the first aspect of the present invention is a temperature change that acts on a sample including a piezoelectric body to change the temperature of the piezoelectric body. And a surface potential measuring unit that measures a surface potential of the piezoelectric body, wherein the surface potential measuring unit responds to a temperature change of the piezoelectric body caused by the temperature changing unit. The change of the surface potential of the piezoelectric body is measured.

  In the piezoelectric body evaluation method according to the first aspect of the present invention, a sample including a piezoelectric body is prepared, the temperature of the piezoelectric body is changed, and the change in the surface potential of the piezoelectric body corresponding to the temperature change is detected. Measure.

  With such a piezoelectric evaluation device, it is possible to measure the pyroelectric characteristics of the piezoelectric body without the need to prepare a structure (sandwich structure) in which the upper electrode and the lower electrode are formed on the surface of the piezoelectric body. Can be evaluated. The pyroelectric characteristic refers to, for example, a pyroelectric coefficient.

  Since the characteristics of the piezoelectric body can be evaluated without preparing a structure (sandwich structure) in which an upper electrode and a lower electrode are formed on the surface of the piezoelectric body, a piezoelectric element (an element provided with an upper electrode and a lower electrode on the surface of the piezoelectric body) ) Can be measured at a stage before completion of the process, that is, in an intermediate product in the process of manufacturing the piezoelectric element. For example, the characteristics of the piezoelectric body can be measured in a laminated body of the lower electrode and the piezoelectric body that is not provided with the upper electrode. Even at the stage after the sandwich structure is obtained, the piezoelectric body can be measured if the surface of the piezoelectric body has an exposed portion that can measure the surface potential. It is.

(Pyroelectric characteristics measurement principle)
Hereinafter, the measurement principle of pyroelectric characteristics according to one embodiment of the present invention will be described using measurement of the pyroelectric coefficient as an example.

  Some piezoelectric bodies have spontaneous polarization, and such piezoelectric bodies have pyroelectric characteristics in which spontaneous polarization (surface charge) changes due to temperature changes. It is known that the pyroelectric coefficient p is defined by the following equation.

p = dPs / dT (1)
dPs: change in spontaneous polarization dT: change in temperature

  From the equation (1), the following equation is derived.

p = Ip / (A · dT / dt) (2)
Ip: Pyroelectric current A: Pyroelectric electrode area dT / dt: Temperature gradient

  In the conventional pyroelectric coefficient measurement, a pyroelectric body having an electrode pair on the surface is heated or cooled at a constant temperature increase or cooling rate dT / dt, and the pyroelectric charge generated on the electrode at that time is converted into a current Ip. Take out as. And a pyroelectric coefficient is calculated | required based on Formula (2).

  On the other hand, in the measurement of the pyroelectric coefficient according to an aspect of the present invention, the temperature change unit changes the temperature of the surface of the piezoelectric body by heating or cooling the piezoelectric body, thereby giving a temperature change dT. The change in spontaneous polarization dPs corresponding to is measured. The dPs can be obtained based on a value obtained by measuring a change dV in the surface potential of the piezoelectric body. The following formula (3) is used for the calculation.

dPs = Q ₂ −Q ₁ = C (V ₂ −V ₁ ) = C · dV (3)
dPs: change in spontaneous polarization dV: change in surface potential Q ₁ , Q ₂ : charge amount before and after temperature change V ₁ , V ₂ : surface potential before and after temperature change C: capacitance

  And the pyroelectric coefficient p can be calculated | required by applying the obtained value to Formula (1).

  As described above, according to one aspect of the present invention, the surface potential measurement unit measures the change in surface potential, and the pyroelectric characteristics are measured based on the change, thereby evaluating the piezoelectric body. Unlike conventional evaluation apparatuses and evaluation methods, it is not necessary to prepare a piezoelectric element in which upper and lower electrodes are provided on a piezoelectric body and measure the current and voltage between the electrodes.

(Device configuration)
FIG. 1 schematically shows a basic configuration of a piezoelectric body evaluation apparatus according to a first aspect of the present invention. A piezoelectric body evaluation apparatus 100 according to an aspect of the present invention includes a temperature change unit 2 that can change the temperature of a piezoelectric body 12 by acting on a sample 1 including the piezoelectric body 12 that is an evaluation target, and the surface of the piezoelectric body. And a surface potential measuring unit 3 capable of measuring a potential.

  The temperature changing unit 2 is not particularly limited as long as it can change the temperature of the piezoelectric body 12, specifically, the temperature of the surface of the piezoelectric body 12. The temperature changing unit 2 may be a means that acts to increase the temperature of the piezoelectric body 12, or may be a means that acts to decrease the temperature of the piezoelectric body 12.

  Examples of the temperature changing unit 2 that acts to increase the temperature of the piezoelectric body 12 include those using laser light irradiation and those using flash lamp condensing. Among these, a semiconductor laser (LD) is preferable because of high response (high response speed). When a semiconductor laser is used as the temperature changing portion 2, it is easy to irradiate a desired area by using a pinhole or the like. In that case, the shape of the laser irradiation region may be arbitrary. Moreover, if a shape is circular, the diameter of the irradiation area can be adjusted to 0.5-3 mm, for example.

  When a semiconductor laser is used as the temperature changing portion 2, the sample including the piezoelectric body is heated by laser light irradiation. By this heating, the temperature of the piezoelectric body 12 rises and a temperature change ΔT occurs. This temperature change ΔT can be measured by a temperature measuring unit (not shown) described later.

  When using the temperature change part 2 using laser light irradiation, as shown in FIG. 1, a sample 1 including a substrate 10, a lower electrode 11, and a piezoelectric body 12 is used. It is preferable to irradiate the laser beam from the surface on the side where the piezoelectric body 12 is not provided. This is because 100% of the laser light may not be supplied to the irradiation region when light irradiation is performed from the front surface of the substrate. For example, when PZT (lead zirconate titanate) is used as the piezoelectric body, interference depending on the thickness of the piezoelectric body may occur. In this case, the temperature change of the piezoelectric body 12 depends on the thickness. .

  Further, when the temperature changing unit 2 is a means that acts to lower the surface temperature of the piezoelectric body 12, for example, cooling by conduction from a refrigerant such as dry ice or a Peltier element can be cited.

  As the surface potential measuring unit 3, for example, a surface potential evaluation device disclosed in Japanese Patent Application Laid-Open No. 2007-64835, a surface potential meter such as model 323, model 325 manufactured by TREK, or the like can be used. The surface potential measuring unit 3 measures a change in surface potential ΔV of the piezoelectric body corresponding to the temperature change ΔT of the piezoelectric body caused by the temperature changing unit 2.

  The temperature change ΔT can be set to an arbitrary range within a range from room temperature to the Curie point temperature of the piezoelectric body, for example. Preferably, ΔT ≧ 30 ° C. is preferred in order to increase the S / N (SN ratio) of the surface electrometer output. In addition, although the term of the temperature change per unit time (namely, speed) is not included in the expression (3), in the actual measurement, the temperature equivalent to the response speed is used as a method for obtaining the S / N of the surface electrometer. It is preferable to provide a rate of change.

  Based on the temperature change ΔT and the surface potential change ΔV, the pyroelectric coefficient can be calculated by the equations (1) and (3). This calculation may be performed by a data processing unit (not shown) provided in the piezoelectric body evaluation apparatus 100 and the data processing unit.

  At least one of the temperature change unit 2 and the surface potential measurement unit 3 is preferably a non-contact type, and more preferably both the temperature change unit 2 and the surface potential measurement unit 3 are non-contact types. This is because it is not necessary to consider the electrode lead-out part, so that there is no restriction on the sample size.

  As shown in FIG. 1, the temperature change unit 2 and the surface potential measurement unit 3 are preferably provided on opposite sides of the sample 1 including the piezoelectric body 12. That is, the temperature change unit 2 and the surface potential measurement unit 3 may be provided on the front and back of the sample 1 at positions corresponding to each other. With this configuration, it becomes easy to measure a temperature change and a surface potential change at an arbitrary location on the surface of the piezoelectric body 12. The temperature change unit 2 and the surface potential measurement unit 3 can be arranged on the same side of the sample 1 in parallel, for example, above the sample 1. In that case, the surface potential measuring unit 3 is disposed above a predetermined region of the piezoelectric body whose temperature is to be changed, and the temperature changing unit 2 is to act on the predetermined region whose temperature is to be changed from an oblique direction. Has been placed.

  In one aspect of the present invention, a temperature measuring unit (not shown) that measures a temperature change of the piezoelectric body 12 is further provided. The temperature measuring unit may be a non-contact type thermometer, for example, a pyrometer.

  In addition, it is preferable that the temperature changing unit 2 and the surface potential measuring unit 3 and the temperature measuring unit are all non-contact type because there is no need to consider the electrode extraction unit, and thus there is no restriction on the sample size. .

  In one aspect of the present invention, the piezoelectric body evaluation apparatus 100 may include a sample stage 5 on which the sample 1 is placed. 2 and 3 are schematic views of the piezoelectric body evaluation apparatus 100 including the sample stage 5. 2 is a view of the piezoelectric body evaluation apparatus 100 as viewed from above, and FIG. 3 is a view of the piezoelectric body evaluation apparatus 100 as viewed from the side. The sample stage 5 is movable relative to the temperature change unit 2 and the surface potential measurement unit 3. Thereby, it is easy to measure the surface potential at a plurality of locations on the surface of the piezoelectric body 12 (multi-point measurement), and it is possible to evaluate variation in characteristics on the surface of the piezoelectric body 12. In the multipoint measurement, the pyroelectric characteristics of the piezoelectric body can be measured at the number of points corresponding to the distance that is the spatial resolution of the surface electrometer. For example, when the Trek model 323 is used, the spatial resolution is 5 mm. Therefore, if the sample is a 6-inch wafer size, the pyroelectric characteristics of the piezoelectric body should be measured at 400 to 600 points. Can do.

  The variation in characteristics can be evaluated by obtaining a standard deviation with respect to the center value. In this case, the center value does not need to be an absolute value and may be obtained as a relative value.

  As shown in FIGS. 2 and 3, if the sample stage is rotatable around the center point O of the sample stage 5, the above multipoint measurement is further facilitated. The sample stage 5 may be movable in a linear direction relative to the temperature change unit 2 and the surface potential measurement unit 3, or in any direction on the plane in which the surface of the sample stage 5 extends. It may be movable. In this case, the sample stage 5 may have a rectangular shape, for example, and may include a mechanism that reciprocates in the linear direction.

(sample)
In one embodiment of the present invention, a sample including a piezoelectric body to be evaluated is used. In the case of using a temperature changing portion that utilizes laser light irradiation, a sample including a piezoelectric body and a lower electrode is preferable. When a heating unit using laser beam irradiation is used as the temperature changing unit, the laser beam is absorbed by the lower electrode and converted into heat. Thereby, thermal energy can be supplied to the piezoelectric body without depending on the thickness of the piezoelectric body.

  The sample may include a substrate. For example, a sample including a substrate, a lower electrode formed on the substrate, and a piezoelectric body formed on the lower electrode can be used. In addition, if the surface of the piezoelectric body has an exposed portion that can measure the surface potential of the piezoelectric body, a sample in which some layer is provided on the piezoelectric body of the sample is used. It can be used as a sample for a piezoelectric body evaluation apparatus according to an aspect of the invention.

  The lower electrode may be a lower electrode of an element obtained through a later manufacturing process, or may be a temporary lower electrode for measurement instead of the lower electrode actually used in the element.

  Examples of the piezoelectric body include inorganic or organic piezoelectric bodies such as lead zirconate titanate, lanthanum-doped lead zirconate titanate, lithium niobate, sodium potassium niobate, and polyvinylidene fluoride resin.

  There is no particular limitation on the thickness of the piezoelectric body evaluated by the piezoelectric body evaluation apparatus according to one aspect of the present invention. If it is a piezoelectric body used for the element of PIEZO MEMS (piezoelectric MEMS), the thickness is about 0.5-10 micrometers.

  The piezoelectric body included in the sample can be formed by a sputtering method, a CSD (Chemical Solution Deposition) method, or the like. When a piezoelectric material is formed by sputtering, spontaneous polarization occurs due to the introduction of crystal lattice defects. Therefore, the piezoelectric body formed by the sputtering method does not need to be polarized. On the other hand, when the CSD method is used, since the spontaneous polarization of the film after film formation is not uniform, a polarization process or the like is required. The polarization process can be performed by the charging unit 4 shown in FIGS. Examples of the charging unit 4 include a corona charger. The charging unit 4 adjusts the discharge of electric charges so as to align the spontaneous polarization of the surface of the piezoelectric body 12.

  As the substrate, silicon can be used. When silicon (Si) is used and a laser is used as the temperature change unit 2, it is necessary to select a wavelength that does not absorb light with respect to silicon. A preferred laser wavelength is about 900-1400 nm. Light having such a wavelength passes through the silicon substrate, is absorbed by the lower electrode, and is converted into heat.

[2] Piezoelectric evaluation apparatus and piezoelectric body evaluation method according to the second aspect of the present invention The piezoelectric evaluation apparatus according to the second aspect of the present invention includes the piezoelectric body in addition to the configuration according to the first aspect of the present invention. The surface potential measuring unit measures a change with time of the surface potential that decreases due to self-discharge after the surface potential of the piezoelectric body reaches saturation. . Note that a piezoelectric body evaluation apparatus according to an aspect of the present invention is a piezoelectric body evaluation apparatus including a charging unit that applies a charge to a piezoelectric body and a surface potential measurement unit that measures a surface potential of the piezoelectric body. The surface potential measuring unit may measure a change with time of the surface potential that decreases due to self-discharge after the surface potential of the piezoelectric body reaches saturation.

  In the piezoelectric body evaluation method according to the second aspect of the present invention, a sample including a piezoelectric body is prepared, the piezoelectric body is charged until the surface potential of the piezoelectric body reaches saturation, and the surface potential reaches saturation. The time-dependent change of the surface potential that decreases due to self-discharge after the measurement is measured.

  With such a piezoelectric body evaluation apparatus, the dielectric characteristics of the piezoelectric body can be measured without preparing a structure (sandwich structure) in which an upper electrode and a lower electrode are formed on the surface of the piezoelectric body. Specifically, the dielectric characteristics of the piezoelectric body indicate capacitance, dielectric constant, relative dielectric constant, insulation resistance, dielectric loss, and the like.

(Measurement principle of dielectric properties)
The principle of measuring dielectric characteristics according to one embodiment of the present invention will be described below as a main example of measuring capacitance.

  In the measurement of electrostatic capacity, first, electric charges are supplied to the surface area of the piezoelectric body to be charged until the surface potential is sufficiently saturated. As represented by the following equation, a surface potential V proportional to the charge amount Q appears in the charged piezoelectric body.

Q = C ・ V (4)
Q: Charge amount C: Capacitance V: Surface potential

Based on the above equation (4), if the value of the amount of charge Q given until the surface potential reaches saturation and the value of the surface potential V (V _max ) reaching saturation, the capacitance C can be obtained. it can. The surface potential V is measured by a surface potential measuring unit.

Here, after the charge is applied by the charging unit, in order to measure the surface potential by the surface potential measuring unit, the time when the surface potential of the piezoelectric body reaches saturation and becomes the maximum, and the time when the surface potential is measured Then there will be a time difference. During that time, spontaneous discharge occurs and the surface potential of the piezoelectric body decreases. Therefore, it is difficult to surface potential of the piezoelectric body to accurately measure the surface potential (true maximum surface potential) V _max at the point of reaching saturation. Therefore, when the surface potential of the piezoelectric body reaches saturation, charging by the charging unit is stopped, and a change with time of the surface potential that decreases due to subsequent self-discharge is measured. That is, a plurality of surface potential values corresponding to a predetermined time are recorded. FIG. 4 shows an increase in the surface potential of the piezoelectric body until the surface potential reaches saturation, and a decrease in the surface potential of the piezoelectric body due to self-discharge after charging is stopped.

Then, the capacitance is obtained based on the change of the measured surface potential with time. Specifically, the logarithm (logt) of the time t that has elapsed after the surface potential of the piezoelectric body reaches saturation and reaches its maximum is plotted on the horizontal axis and the surface potential is plotted on the vertical axis. Substantially since a linear relationship is obtained by plotting, the value when the logt of abscissa extrapolated to 0, it can be a true maximum surface potential V _max. The calculation of the capacitance may be performed by a data processing unit (not shown) provided in the piezoelectric body evaluation apparatus 100.

Thus the true maximum surface potential V _max obtained and a charge amount Q given by the charging unit by applying the expression (3), it is possible to obtain the electrostatic capacitance C.

  Further, from the obtained capacitance value, it is possible to obtain the dielectric constant, and hence the relative dielectric constant. Furthermore, the discharge time constant, insulation resistance, and relative dielectric loss can also be obtained.

The discharge time constant τ can be obtained by approximation of the above semilogarithm. The discharge time constant τ generally refers to the time that elapses until 37% of the maximum surface potential V _max is discharged (see FIG. 4). However, when examining the relative change in characteristics due to the position of the sample (i.e. when assessing the homogeneity of the product) the like, as the time when 37% of the maximum surface potential V _max has elapsed until discharged It is not necessary to obtain the discharge time constant τ.

  After the charging is turned off, the surface potential of the region indicated as the discharge time constant in FIG. 4 is composed of an initial sharply decreasing region and a gradually decreasing region thereafter. The initial sharply decreasing region can be separated and analyzed as a component of relative dielectric loss, and the slowly decreasing region can be separated and analyzed as an insulation resistance component.

The insulation resistance R can be obtained as follows. The potential at the time when 37% of V _max is discharged is defined as the initial potential V ₀ . When the charge Q (unit coulomb) existing in the material at the surface potential V ₀ flows to the ground potential as a leakage current, ΔQ is reduced. In that case, the current I corresponding to ΔQ per unit time is measured. A value obtained by dividing the current I by the initial surface potential V ₀ corresponds to a direct current insulation resistance.

  In order to quantify the dielectric property and conductivity of the piezoelectric material in the piezoelectric material sample sandwiched between the upper and lower electrodes (sandwich structure), the relative dielectric constant and the electric conductivity are important. On the other hand, generally, dielectric loss is used in theoretical handling. The dielectric loss corresponds to the ratio between the real part and the imaginary part of a complex number representing the dielectric constant with respect to the alternating electric field frequency. Usually, such characteristics can be measured with an existing measuring instrument such as an LCR meter or an impedance analyzer. However, it cannot be performed when at least one electrode is not formed as in the sample of one embodiment of the present invention.

  The relative dielectric loss can be obtained using the discharge time constant. Specifically, a discharge time constant is obtained for a material having a known dielectric loss, and the dielectric loss of the piezoelectric body is quantified as a relative value thereof. As a material having a known dielectric loss, an organic material sheet such as PVDF or polypropylene is suitable.

  As described above, according to one aspect of the present invention, the surface potential measurement unit measures the change in the surface potential with time, and the dielectric characteristics are measured based on the change to evaluate the piezoelectric body. Unlike conventional evaluation apparatuses and evaluation methods, it is not necessary to prepare a piezoelectric element in which upper and lower electrodes are provided on a piezoelectric body and measure the current and voltage between the electrodes.

(Device configuration)
2 and 3 show a schematic configuration of the piezoelectric body evaluation apparatus 100 according to the second aspect of the present invention. FIG. 2 is a view of the piezoelectric body evaluation apparatus according to the second aspect of the present invention as viewed from above, and FIG. 3 is a view of the piezoelectric body evaluation apparatus 100 as viewed from the side. The basic configuration of the piezoelectric body evaluation apparatus 100 according to the second aspect is the same as that of the piezoelectric body evaluation apparatus 100 according to the first aspect described above with reference to FIGS.

  The piezoelectric body evaluation apparatus according to the second aspect of the present invention includes a temperature change unit 2, a surface potential measurement unit 3, and a charging unit 4. The surface potential measuring unit 3 and the charging unit 4 are arranged on the side of the sample 1 where the piezoelectric body 12 is provided.

  The charging unit 4 may be capable of discharging electric charges to the piezoelectric body 12 so that the electric charges are saturated. For example, the charging unit 4 using corona charging can be used.

  In one aspect of the present invention, the piezoelectric body evaluation apparatus 100 may include a sample stage 5 on which the sample 1 is placed. The sample stage 5 is movable relative to the surface potential measuring unit 3 and the charging unit 4. Thereby, it is easy to measure the surface potential at a plurality of locations on the surface of the piezoelectric body 12 (multi-point measurement), and it is possible to evaluate variation in characteristics on the surface of the piezoelectric body 12.

  As shown in FIGS. 2 and 3, when the sample stage 5 is rotatable about the center point O of the sample stage 5, the above-described multipoint measurement is further facilitated. The sample stage 5 may be movable in a linear direction relative to the temperature change unit 2 and the surface potential measurement unit 3, or in any direction on the plane in which the surface of the sample stage 5 extends. It may be movable. In this case, the sample stage 5 may have a rectangular shape, for example, and may include a mechanism that reciprocates in the linear direction.

  Note that the piezoelectric body evaluation apparatus and the piezoelectric body evaluation method according to an aspect of the present invention are particularly useful in the field of PIEZO MEMS (piezoelectric MEMS), which has recently been on the market.

  The foundry undertaking the manufacture of PIEZO MEMS delivers the product ("piezoelectric film / lower electrode / substrate") in which the electrode film (lower electrode) and the piezoelectric film are formed in order on the wafer substrate to the user (purchaser) as a product. To do. However, as described above, according to the conventional apparatus and method, the measurement of the characteristics of the piezoelectric body is first performed when a structure (sandwich structure) in which the upper electrode and the lower electrode are formed on the surface of the piezoelectric body is obtained. It becomes possible. In other words, conventionally, there has been no way to measure the characteristics of a piezoelectric body for a product without an upper electrode. Therefore, the founder cannot measure the characteristics (dielectric characteristics, pyroelectric characteristics, etc.) of the piezoelectric film in the structure “piezoelectric film / lower electrode / substrate” before shipment and provide the information to the user. It was. Further, it is difficult for the user (purchaser) to determine whether or not the piezoelectric film itself satisfies a sufficient performance before providing the upper electrode in the delivered product.

  According to the piezoelectric body evaluation apparatus and the piezoelectric body evaluation method of the present invention, without preparing the structure (sandwich structure) in which the upper electrode and the lower electrode are formed on the surface of the piezoelectric body, that is, the stage before providing the upper electrode Even so, since the characteristics of the piezoelectric body can be measured, the above problem can be solved.

Example 1
A platinum film having a thickness of 200 nm was deposited on the silicon substrate on which the thermal oxide film was disposed via an adhesion film to form a first electrode (lower electrode). Subsequently, lead zirconate titanate (PZT) was formed on the first electrode so as to have a thickness of 2 μm by sputtering.

  Light irradiation with a semiconductor laser was performed from the back side of the obtained sample. The wavelength of the laser irradiation light was 980 nm. A pyrometer (manufactured by Chino, Digital Radiation Thermometer IR-AHT0) was used to measure the temperature of the PZT film surface. The pyroelectric coefficient was determined based on the temperature change of the surface of the piezoelectric body and the accompanying change in surface potential.

(Comparative Example 1)
A platinum film having a thickness of 100 nm was deposited as an upper electrode on the sample manufactured in Example 1. About the element containing this upper electrode, the pyroelectric coefficient was calculated | required by "the measuring method of the pyroelectric coefficient of a fine ceramics" described in JISR1651: 2002.

  The measured pyroelectric coefficient was almost the same between Example 1 and Comparative Example 1.

(Example 2)
The PZT film of the sample prepared in Example 1 was charged by a self-made corona charger, and the charger was stopped when the surface potential reached saturation. Thereafter, using a surface potentiometer (model 323, manufactured by Trek), the surface potential was measured over time by self-discharge of the PZT film, and V _max was determined as described above. The value of the electrostatic capacity was obtained from Equation (3).

(Comparative Example 2)
About the sample of the comparative example 1, the electrostatic capacitance was calculated | required using the HIOKI impedance analyzer IM3750 apparatus.

  The measured capacitance was almost the same between Example 2 and Comparative Example 2.

1 Sample 10 Substrate 11 Lower electrode (first electrode)
12 Piezoelectric material (piezoelectric film)
2 Temperature change unit 3 Surface potential measurement unit 4 Charging unit 5 Sample stage 100 Piezoelectric evaluation apparatus

JP-A-6-160193

Claims (20)

A temperature changing section that changes the temperature of the piezoelectric body by acting on a sample including the piezoelectric body;
A piezoelectric body evaluation apparatus comprising a surface potential measurement unit that measures the surface potential of the piezoelectric body,
The piezoelectric body evaluation apparatus, wherein the surface potential measuring unit measures a change in surface potential of the piezoelectric body corresponding to a temperature change of the piezoelectric body caused by the temperature changing section. A first data processing unit,
The piezoelectric body evaluation apparatus according to claim 1, wherein the first data processing unit measures pyroelectric characteristics of the piezoelectric body based on the temperature change and the surface potential change.   The piezoelectric body evaluation apparatus according to claim 1, wherein the sample includes a substrate, a lower electrode formed on the substrate, and the piezoelectric body formed on the lower electrode.   The piezoelectric body evaluation apparatus according to claim 1, further comprising a temperature measurement section, wherein the temperature measurement section measures a temperature change of the piezoelectric body.   The piezoelectric body evaluation apparatus according to any one of claims 1 to 4, wherein the temperature change unit and the surface potential measurement unit are provided on opposite sides of the sample.   The piezoelectric body evaluation apparatus according to any one of claims 1 to 5, further comprising a charging unit that applies an electric charge to the piezoelectric body.   The piezoelectric body evaluation apparatus according to claim 6, wherein the charging unit performs polarization processing of the piezoelectric body. A sample stage on which the sample is placed;
The piezoelectric body evaluation apparatus according to claim 6, wherein the sample stage is movable relative to the temperature change unit and the surface potential measurement unit.   The surface potential measuring unit measures a change with time of the surface potential which is decreased by self-discharge after the surface potential of the piezoelectric body reaches saturation due to the application of electric charge by the charging unit. Piezoelectric evaluation apparatus. A second data processing unit,
The piezoelectric body evaluation apparatus according to claim 9, wherein the second data processing unit measures dielectric characteristics of the piezoelectric body based on a change with time of the surface potential.   The piezoelectric body evaluation apparatus according to claim 8, wherein the sample stage is movable relative to the temperature change unit, the surface potential measurement unit, and the charging unit. Prepare a sample containing a piezoelectric body,
Acting on the sample to change the temperature of the piezoelectric body;
A piezoelectric body evaluation method for measuring a change in surface potential of the piezoelectric body corresponding to the temperature change.   The piezoelectric body evaluation method according to claim 12, further comprising measuring pyroelectric characteristics of the piezoelectric body based on the temperature change and the surface potential change.   The piezoelectric body evaluation method according to claim 12 or 13, wherein the sample includes a substrate, a lower electrode formed on the substrate, and the piezoelectric body formed on the lower electrode.   The piezoelectric body evaluation method according to claim 12, further comprising measuring the temperature change. Measuring the change in surface potential from the front side of the sample;
The piezoelectric body evaluation method according to claim 12, wherein acting on the sample to change the temperature of the piezoelectric body is performed from a back surface of the sample.   The piezoelectric body evaluation method according to claim 12, wherein a polarization process is performed by charging the piezoelectric body before changing a temperature of the piezoelectric body.   The piezoelectric body evaluation method according to claim 17, wherein changing the temperature of the piezoelectric body, measuring a change in surface potential of the piezoelectric body, and charging the piezoelectric body are performed in a non-contact manner. Prepare a sample containing a piezoelectric body,
Charging the piezoelectric body until the surface potential of the piezoelectric body reaches saturation,
A piezoelectric material evaluation method for measuring a change with time of the surface potential which decreases due to self-discharge after the surface potential reaches saturation.   The piezoelectric body evaluation method according to claim 19, further comprising measuring dielectric characteristics of the piezoelectric body based on a change in the surface potential with time.

Images