JP4373857B2 - Electrical property measurement method - Google Patents

Description

  The present invention relates to an electrical property value measurement method, and in particular, an electrical property value measurement for measuring the electrical conductivity or resistivity of an interface between a conductor layer and a dielectric in an electronic component or circuit board used in a millimeter wave region. It is about the law.

  In general, in the microstrip line, strip line, coplanar line, etc. used for circuit boards and semiconductor device packages, the conductivity at the interface between the conductor layer and the dielectric has become an important parameter in designing the circuit loss. ing. For example, in recent years, in-vehicle radars and millimeter-wave wireless LANs have been developed, but measurement values of the conductivity at the interface between the conductor layer and the dielectric in the millimeter-wave region are required for circuit design. I came. In particular, in the millimeter wave region, it is known that the conductivity rapidly deteriorates due to the surface roughness of the inner layer conductor, and the evaluation of the conductivity at the frequency at which the system is constructed is required.

In recent years, a method using a both-end short-circuited dielectric cylindrical resonator as shown in FIG. 8 has been proposed as a method for measuring the conductivity at the interface between the conductor layer and the dielectric. In this double-end short-circuited dielectric cylindrical resonator, the dielectric substrate 3a and 3b provided with conductor layers 5a and 5b on one side are placed on the upper and lower sides of the dielectric cylinder 10 so that the dielectric substrate 3a and 3b are in contact with the dielectric cylinder 10. There is known a method of sandwiching the electrodes so as to be in contact with each other and obtaining the interface conductivity from the unloaded Q. As the dielectric cylinder 10, a low-loss sapphire cylinder is used. This method realizes measurement with good accuracy in the microwave band by excitation with a loop antenna. In addition, measurement results using NRD guide excitation have also been reported in the millimeter wave band (see, for example, Patent Document 1).
JP-A-10-216795

  However, when the double-end short-circuited dielectric cylinder resonator method is used in the millimeter wave band, there is a problem that the size of the sapphire cylinder used as the dielectric cylinder 10 becomes small and it is difficult to configure the resonator.

In the double-end short-circuited dielectric cylindrical resonator method, the dielectric cylinder 10 is sandwiched by the conductor layers 5a and 5b to form a resonator, but the upper and lower conductor layers 5a and 5b are parallel to each other. There is a precondition. However, if the sample measured in the microwave band is applied as it is, there is a problem that the diameter of the conductor layers 5a and 5b becomes too large with respect to the dielectric cylinder 10 and the parallelism of the upper and lower conductors 5a and 5b is deteriorated. It was. For example, in the 13 GHz band measurement using the TE ₀₁₁ mode, the dimensions of the sapphire cylinder are a diameter D = 10 mm and a height H = 5 mm, whereas in the 60 GHz band measurement using the TE ₀₂₁ mode, sapphire The dimensions of the cylinder are a diameter D = 3.1 mm and a height H = 2.25 mm.

  At this time, the size required for the conductor layers 5a and 5b is not less than 30 mm in diameter in the 13 GHz band, but may be not less than 10 mm in the 60 GHz band. Since it is difficult to install a conductor with a diameter of 30 mm measured in the 13 GHz band above and below a sapphire cylinder with a diameter of 3 mm, currently, a conductor with a small size is used. For this reason, in the millimeter wave band, more time is spent on the preparation time for the resonator than on the measurement time.

  The present invention can measure a conductor layer of any size to some extent in the millimeter wave band, and has a measurement accuracy equivalent to the conventional one, and easily measures the conductivity at the interface between the conductor layer and the dielectric. An object of the present invention is to provide an electrical property value measuring method capable of achieving the above.

An electrical property value measuring method of the present invention is a cylindrical cavity resonator in which both end openings of a cylindrical conductor are closed by first and second shields, and the first and second shields are made of conductors. A first step of measuring a resonance frequency f1 and no-load Q1 of the cylindrical cavity resonator, and determining an electrical property value and dimensions of the cylindrical cavity resonator from the resonance frequency f1 and no-load Q1;
At least one of the first and second shields is composed of a dielectric substrate having a conductor layer as an inner layer, or a dielectric substrate having a conductor layer provided on one surface, and the shield side is a cylindrical cavity on the dielectric side. The cylindrical conductor is provided on the cylindrical conductor so as to be on the side, and the resonance frequency f2 and no-load Q2 of the cylindrical cavity resonator are measured. The resonance frequency f2, the no-load Q2, and the first And a second step of obtaining an electrical property value of the interface between the conductor layer and the dielectric from the electrical property value and dimensions of the cylindrical cavity resonator obtained in the step.

The electrical property value measuring method of the present invention has a cylindrical cavity resonator structure as shown in FIG. 1, and has a TE ₀₁₁ mode electric field intensity distribution. The electric field strength of the TE ₀₁₁ mode of this cylindrical cavity resonator becomes maximum at the center plane in the height direction of the cavity resonator and becomes zero at both ends. In the electrical property value measuring method of the present invention, as shown in FIG. 2, since the conductor is disposed at a position where the electric field is zero at both ends, the influence of the dielectric constant and dielectric loss tangent of the dielectric can be reduced. .

  In the electrical property value measuring method of the present invention, the conductor layer is circular, and the diameter thereof is larger than the diameter of the cylindrical cavity. In such a measuring method, the specific conductivity or resistivity of the conductor can be obtained.

Furthermore, the electrical property value measuring method of the present invention is characterized in that the thickness of the dielectric interposed between the opening of the cylindrical conductor and the conductor layer is 0.3 mm or less. In such a measurement method, the thickness of the dielectric interposed between the opening of the cylindrical conductor and the conductor layer is set to 0.3 mm or less, so that the sample (dielectric) between the conductor layer and the opening is reduced. The influence of the dielectric constant and dielectric loss tangent of the body can be reduced. In particular, in the millimeter wave band, for example, when used at a frequency of 30 to 100 GHz, it is desirable that the dielectric thickness between the conductor layer and the opening is reduced to a thickness of 0.3 mm or less. By making the dielectric between the conductor layer and the opening thinner, the electric field energy accumulated in the dielectric substrate can be reduced, and the decrease in the resonance frequency of the TE ₀₁₁ mode can be mitigated.

Furthermore, the electrical property value measuring method of the present invention measures the TE mode resonance frequency f and no-load Q of the cylindrical cavity resonator, and determines the interface between the conductor layer and the dielectric from the resonance frequency f and no-load Q. It is characterized in that the electrical property value of is obtained. In particular, it is desirable to measure the resonance frequency f and unloaded Q of the TE ₀₁₁ mode of the cylindrical cavity resonator to determine the electrical property value of the sample conductor interface. Thus, by using the TE-mode resonance frequency f and the no-load Q of the cylindrical cavity resonator, radiation in the radial direction from the dielectric end can be eliminated.

  The electrical property value measuring method of the present invention is characterized in that a dimensional ratio D / H of a height H to a diameter D of a cylindrical cavity is 1 or more.

  In such an electrical property value measurement method, the measurement accuracy can be increased by setting the dimensional ratio D / H of the height H to the diameter D of the cylindrical cavity to 1 or more. FIG. 7 shows a ratio of the conductor loss of the cylindrical cavity and the conductor loss of the upper and lower shielding plates to the dimension ratio D / H of the height H to the diameter D of the cylindrical cavity when the resonance frequency is constant. By setting the dimensional ratio such that the conductor loss ratio of the shielding plate is larger than the conductor loss ratio of the cylindrical cavity in the ratio of the total loss, the measurement accuracy of the interface conductivity can be improved. In addition, as shown in FIG. 6, it can be seen that the measurement accuracy is improved by using a cylindrical cavity having a higher conductivity than the measurement sample.

  Furthermore, the electrical property value measuring method of the present invention changes the temperature of the cylindrical cavity resonator, measures the temperature dependence of the resonance frequency f and no load Q of the cylindrical cavity resonator, and It is characterized by determining the temperature dependence of the physical property value. In such an electrical property value measurement method, the temperature of the cylindrical cavity resonator is changed, the temperature dependence of the resonance frequency f and no load Q of the cylindrical cavity resonator is measured, and the electrical conductivity of the specific conductivity or resistivity is measured. The temperature dependence of the physical property value can be determined.

  According to the present invention, in the millimeter wave band of 30 GHz or higher, which has not been able to be measured stably in the past, it is possible to easily measure the conductivity of the interface between the conductor layer and the dielectric using a cavity resonator, and the measurement time. Can be greatly shortened.

  FIG. 1 is a structural diagram and electric field distribution of a cylindrical cavity resonator used in the first step of the electrical property value measuring method of the present invention. The cylindrical cavity resonator has a structure in which the opening portions at both ends of the cylindrical conductor 2 are shielded by the first and second shields 1a and 1b made of a conductor. The cylindrical conductor 2 and the first and second shields 1a and 1b are made of a metal such as Cu, Fe, Ag, Au, Mo, or W. If the thickness is thicker than the skin depth at the measurement frequency, no problem occurs.

  Although not shown in the figure, excitation and detection of the resonator are usually performed by magnetic coupling through a loop antenna at the tip of the coaxial line with an excitation hole formed in the cylindrical conductor 2. This evaluation method has already been established in JIS R 1641, and the method may be followed. Further, this first step need not be performed once the conductivity is once determined.

  FIG. 2 is a structural diagram of a cylindrical cavity resonator used in the second step. This cylindrical cavity resonator is configured by shielding the upper and lower sides of a cylindrical conductor 2 with dielectric substrates 3a and 3b (first and second shields) in which conductor layers 4a and 4b as measurement samples are provided as inner layers. . That is, the dielectric constituting the dielectric substrates 3a and 3b faces the cylindrical cavity side, and the dielectrics 3a1 and 3b1 are interposed between the cylindrical cavity and the conductor layers 4a and 4b. . It is necessary to use dielectrics 3a1 and 3b1 having sufficient parallelism. Also in the second step, the excitation and detection of the resonator may be performed in the same manner as in the first step.

The conductor layers 4a and 4b are circular and have a diameter larger than the diameter of the cylindrical cavity. Thereby, the TE ₀₁₁ mode electromagnetic field can be confined inside the cavity resonator. In particular, the diameter of the conductor layers 4a and 4b is particularly preferably 1.5 times or more larger than the diameter D of the cavity because the electromagnetic field is not radiated from the end of the dielectric in the radial direction. Further, there is no problem if the thickness of the conductor layers 4a and 4b is greater than the skin depth at the measurement frequency.

  Furthermore, the thickness of the dielectrics 3a1, 3b1 interposed between the opening of the cylindrical conductor 2 and the conductor layers 4a, 4b is set to 0.3 mm or less. Thereby, the influence of the dielectric constant and dielectric loss tangent of the dielectrics 3a1, 3b1 between the conductor layers 4a, 4b and the opening can be reduced, and more accurate interface conductivity of the conductor layers 4a, 4b can be obtained. Can do. In particular, in the millimeter wave band, for example, when used at a frequency of 30 to 100 GHz, the thickness of the dielectrics 3a1 and 3b1 between the conductor layers 4a and 4b and the opening portion particularly concentrates the electric field on the dielectric. It is desirable that it is 0.3 mm or less because it is not allowed to occur.

  In addition, as shown in FIG. 3, you may comprise the upper opening part of the cylindrical conductor 2 with a bottomed cylinder by shielding with the dielectric substrate 3b by which the conductor layer 4b was inner-layered. In this case, there is an advantage that the structure is simpler and only one sample is required.

  FIG. 4 shows another structure of the cylindrical cavity resonator used in the second step. In FIG. 4, the upper and lower openings of the cylindrical conductor 2 are provided with conductor layers 5a and 5b on one surface. The dielectric substrates 6a and 6b (first and second shields) are shielded. That is, the dielectric substrates 6a and 6b face the cylindrical cavity side. In other words, the dielectric substrates 6a and 6b are interposed between the cylindrical cavity and the conductor layers 5a and 5b.

  Further, as shown in FIG. 5, the upper opening of the cylindrical conductor 2 having a bottomed cylindrical shape may be shielded by a dielectric substrate 6b having a conductor layer 5b provided on one surface. In this case, there is an advantage that the structure is simpler and only one sample is required.

  The conductivity of the conductor layers 4a and 4b or the conductor layers 5a and 5b is calculated by performing numerical calculation such as a finite element method or a mode matching method. Using the axially symmetric finite element method, the accuracy of the resonant electromagnetic field distribution, resonant frequency, and no-load Q from the size, shape, relative dielectric constant, and dielectric loss tangent to the axially symmetric resonator used in the present invention. Can be calculated in a short time. Therefore, if this is applied, the conductivity of the sample can be obtained from the resonance frequency and the no-load Q.

  Next, the electrical property value measuring method of the present invention will be described. First, the dimensions and conductivity of the cavity resonator (FIG. 1) are evaluated. Usually, this evaluation method has already been established in JIS R 1641: 2002, and the method may be followed.

  Further, the specific conductivities of the first and second shields 1a and 1b and the cylindrical conductor 2 can be evaluated separately. For example, the evaluation method of the shields 1a and 1b is established in JIS R 1627 and is calculated according to the method. Two resonators for 60 GHz band and 40 GHz band were prepared. For these two resonators, the resonance frequency and the no-load Q are measured using a network analyzer, and the specific conductivity σ (pl) of the shields 1a and 1b is evaluated. Subsequently, the cavity resonator is measured by the evaluation method according to JIS R 1641, and the specific conductivity σ (cl) of the cylindrical conductor 2 can be calculated from the measurement result and the measurement results of the shields 1a and 1b. This calculation is described in JIS R 1641.

Next, the conductivity of the interface between the dielectrics 3a1 and 3b1 and the conductors 4a and 4b, which is the second step, is measured using the measured cavity resonator (FIG. 2). First, the resonance frequency f and no-load Q are measured using a network analyzer, and the specific conductivity at the interface between the dielectrics 3a1, 3b1 and the conductors 4a, 4b is measured. There is the following relationship between the TE ₀₁₁ mode Q _u used for measurement and Q, Q _d due to dielectric loss and Q, Q _c due to conductor loss.

Where W is the total stored energy inside the resonator, W ₁ and W ₂ are stored energy in the cylindrical cavity and stored in the dielectric, tan δ is the dielectric loss tangent, P _c1 and P _c2 are the loss energy in the cylindrical conductor and It is the loss energy in the sample conductor. W and P are obtained by integrating the electromagnetic field components of the resonator. As an electromagnetic field calculation method, it is necessary to perform numerical calculation by a finite element method, a mode matching method, an FDTD method, or the like. The specific conductivity can be obtained from the measured value of the no load Q using the relationship of the expression (1) after performing these predetermined calculations.

  The electrical property value measuring method of the present invention is most effective particularly in the millimeter wave band, and can be suitably used for measuring the interfacial conductivity of a conductor formed by metallization or vapor deposition in an insulator, for example, ceramic. .

  The first step is performed to evaluate the cavity resonator used in the measurement. The dimensions and conductivity of the cavity resonator (FIG. 1) were evaluated. Usually, this evaluation method is already established in JIS R 1641: 2002, and this method can be followed. However, this time, the specific conductivities of the first and second shields 1a and 1b and the cylindrical conductor 2 are separately set. Was evaluated.

  First, the evaluation method of the 1st, 2nd shield 1a, 1b was established by JISR1627, and followed the method. Two resonators for the 60 GHz band and 40 GHz band are prepared, and the resonance frequency f and no-load Q are measured for each of these two resonators using a network analyzer. The specific conductivity σ (pl) of the bodies 1a and 1b was evaluated. The results are shown in (plate) in Table 1.

  Subsequently, the cavity resonator is measured by the evaluation method according to JIS R 1641, and the specific conductivity σ (cl) of the cylindrical conductor 2 is calculated from the measurement result and the measurement results of the first and second shields 1a and 1b. Is done. This calculation was obtained by the above method. The results are shown in (clinder) in Table 1.

  Next, the conductivity of the interface between the dielectric and the conductor layer, which is the second step, is measured using the measured cavity resonator. The sample used for this measurement is inner layer metallization (Cu) in LTCC (low temperature fired substrate) having a dielectric thickness of 0.3 mm. The thickness was 0.01 mm, and the diameter was twice that of the cylindrical cavity.

The type of resonator shown in FIG. 3 was used. Table 1 shows the results obtained by measuring the resonance frequency f ₀ and the no-load Qu using a network analyzer and determining the specific conductivity σr at the interface between the dielectric and the metallized layer (conductor layer).

Here, analysis was performed using a mode matching method based on measured values of dielectric constant ε ′ and dielectric loss tangent tan δ of a dielectric having resonance frequencies f ₀ of about 37 GHz and about 63 GHz and the conductivity σ (pl) of the cylindrical cavity. In addition, when the resonance frequency f ₀ was about 31 GHz, the measurement for the same sample was performed by the conventional cylindrical resonator method (FIG. 8). The results are also shown in Table 1.

  From the results in Table 1, it can be seen that the value of the specific conductivity of the oxygen-free copper cavity resonator also decreases as the frequency increases.

  Moreover, the dependence of the specific conductivity on the frequency is shown in FIG. 7 from these results. From this result, it was possible to actually measure that the specific conductivity of the sample was decreased due to the influence of the surface roughness and the like as the resonance frequency increased.

1 shows the structure of a cylindrical cavity resonator used in the first step of the present invention and the electric field distribution. The structure of the cylindrical cavity resonator used for the 2nd process of this invention is shown, (a) is sectional drawing, (b) is a top view. It is sectional drawing which shows the structure of the other cylindrical cavity resonator used for the 2nd process of this invention. It is sectional drawing which shows the structure of the further another cylindrical cavity resonator used for the 2nd process of this invention. It is sectional drawing which shows the structure of the further another cylindrical cavity resonator used for the 2nd process of this invention. It is a chart used when designing the dimension of the cylindrical cavity resonator of this invention. It is a measurement result of the specific conductivity (interface electrical conductivity) of LTCC and inner layer metallization with respect to the frequency by this invention. It is sectional drawing which shows an example of the structure of the conventional both ends short circuit type dielectric cylinder resonator.

Explanation of symbols

1a, 1b ... 1st, 2nd shielding board 2 ... Cylindrical conductor 3a, 3b, 6a, 6b ... Dielectric substrate 4a, 4b, 5a, 5b ... Conductor layer

Claims (7)

A cylindrical cavity resonator in which openings at both ends of a cylindrical conductor are closed by first and second shields, and the resonance frequency of the cylindrical cavity resonator when the first and second shields are made of a conductor. a first step of measuring f1 and no-load Q1, and determining an electrical property value and dimensions of the cylindrical cavity resonator from the resonance frequency f1 and no-load Q1;
At least one of the first and second shields is composed of a dielectric substrate having a conductor layer as an inner layer, or a dielectric substrate having a conductor layer provided on one surface, and the shield side is a cylindrical cavity on the dielectric side. The cylindrical conductor is provided on the cylindrical conductor so as to be on the side, and the resonance frequency f2 and no-load Q2 of the cylindrical cavity resonator are measured. The resonance frequency f2, the no-load Q2, and the first A second step of obtaining an electrical property value of the interface between the conductor layer and the dielectric from the electrical property value and dimensions of the cylindrical cavity resonator obtained in the step. Value measurement method. 2. The electrical property value measuring method according to claim 1, wherein the conductor layer is circular and has a diameter larger than that of the cylindrical cavity. The method for measuring an electrical property value according to claim 1 or 2, wherein the thickness of the dielectric interposed between the opening of the cylindrical conductor and the conductor layer is 0.3 mm or less. A TE-mode resonance frequency f and no-load Q of a cylindrical cavity resonator are measured, and an electrical property value of an interface between a conductor layer and a dielectric is obtained from the resonance frequency f and no-load Q. Item 4. An electrical property value measuring method according to any one of Items 1 to 3. 5. The electrical property value according to claim 4, wherein the TE ₀₁₁ mode resonance frequency f and no-load Q of the cylindrical cavity resonator are measured to determine an electrical property value at the interface between the conductor layer and the dielectric. Measurement method. 6. The electrical property value measuring method according to claim 1, wherein a dimensional ratio D / H of a height H to a diameter D of the cylindrical cavity is 1 or more. The temperature dependence of the resonance frequency f of the cylindrical cavity resonator and the unloaded Q is measured by changing the temperature of the cylindrical cavity resonator, and the temperature dependence of the electrical property value at the interface between the conductor layer and the dielectric is obtained. The electrical property value measuring method according to any one of claims 1 to 6.

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