JP2002324826A - High frequency probing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems of the mismatching of characteristic impedance, increase of the reflection of signals and insufficient propagation of a high frequency signal because the shape of a contact part with the wafer probe of a high frequency probing pad is restricted. SOLUTION: The high frequency probing pad is constituted of a pad part 11 wherein a signal conductor 1 and a ground conductor 2 formed on the upper face of a dielectric substrate contacts a wafer probe, a leading line part 13 led out from an object to be measured, a matching line part 14, and a connection line part 12 connecting between the pad part 11 and the matching line part 14 and between the leading line part 13 and the matching line part 14. The characteristic impedance of the pad part 11 is larger than that of the wafer probe, the characteristic impedance of the matching line part 14 is smaller than that of the wafer probe, and the high frequency probing pad is made a quarter of the free space wavelength of the high frequency signal of the maximum frequency applying electric length combining the connection line part 12 and the matching line part 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency probing pad used for measuring electrical characteristics of a semiconductor device, a package or a circuit board for accommodating the semiconductor device at a high frequency such as a microwave band or a millimeter wave band. The present invention relates to a low-reflection high-frequency probing pad with improved reflection characteristics in a pad portion that contacts a probe.

[0002]

2. Description of the Related Art In the measurement and evaluation of electrical characteristics of semiconductor devices and semiconductor device storage packages and circuit boards in a high frequency band such as a microwave band or a millimeter wave band, a coplanar line structure is provided on a measuring instrument side. In addition, a wafer probe that enables high-accuracy measurement by contact with a measurement object is used. On the other hand, a probing pad for high frequency for making a measurement by bringing the wafer probe into contact with the object to be measured is formed and used.

[0003] This high-frequency probing pad is formed by forming a signal conductor and a ground conductor on a dielectric substrate.
The shape and dimensions are set within a range that can be manufactured under the condition that the shape of the contact part required for electrical connection with the signal conductor and the ground conductor of the wafer probe is limited. Therefore, the characteristic impedance of the probing pad may not match the characteristic impedance of the wafer probe depending on the permittivity of the substrate used and the shapes of the signal conductor and the ground conductor.

For example, for a high-frequency probing pad, a conductor is formed on almost the entire lower surface of a dielectric substrate having a relative dielectric constant of 3.4 to form a grounded lower surface conductor, and a conductor thickness of 20 mm is formed on the upper surface.
The frequency characteristic of the characteristic impedance of the pad portion corresponding to the dimensions required by the wafer probe by forming a signal conductor having a width of 0.20 mm and a ground conductor at a distance of 0.10 mm on both sides of the signal conductor, When the frequency characteristics of the characteristic impedance of the lead-out line portion having the width of the signal conductor of 0.30 mm are extracted with the same configuration, the characteristic curves of the frequency characteristics shown in the diagram in FIG. 13 are obtained.

In FIG. 13, the horizontal axis is frequency (unit: GH)
z), the vertical axis indicates the characteristic impedance (unit: Ω), and the characteristic curves P and F indicate the frequency characteristics of the characteristic impedance of the pad portion and the lead line portion, respectively. The characteristic impedance of the corresponding wafer probe is 50Ω. From this result, the characteristic impedance of the transmission line in the pad portion corresponding to the size required by the wafer probe is larger than the characteristic impedance of the transmission line in the lead-out line portion, and matching of the characteristic impedance with the wafer probe can be realized. I understand that there is no.

In such a case, in the conventional connection between the pad portion and the lead-out line, a high-frequency probing pad is formed by connecting the pad portion with a transmission line whose line width is linearly changed.

For example, FIG. 3 is a plan view showing an example of the structure of a conventional high-frequency probing pad.
Conductor is formed on almost the entire lower surface of the dielectric substrate of 4 to form a lower surface ground conductor, and the upper surface has a conductor thickness of 20 μm and a width of 0.20 m
The signal conductor 1 and the ground conductor 2 are formed on both sides of the signal conductor 1 at a distance of 0.10 mm to form a pad portion 11 corresponding to the size required by the wafer probe, and to reduce the width of the signal conductor by the same configuration. A lead-out line portion 13 of 0.30 mm, and a connection portion 12 between the pad portion 11 and the lead-out line portion 13 which is linearly connected at an angle of 45 ° with an interval of 0.1 mm between the signal conductor and the ground conductor. And a probing pad. When the electrical characteristics of this conventional high-frequency probing pad are extracted by electromagnetic field simulation,
A characteristic curve of frequency characteristics as shown in the diagram in FIG. 14 is obtained.

In FIG. 14, the horizontal axis is frequency (unit: GH)
z), the vertical axis indicates the reflection coefficient (unit: dB) as an evaluation index of the amount of reflection in the input high-frequency signal, and the characteristic curve indicates the frequency characteristic of the reflection coefficient. From this result, it can be seen that as the frequency increases, the reflection coefficient increases, and reflection occurs due to mismatching of characteristic impedance. Therefore, in this case, it can be seen that it can be used only in the low frequency band where the reflection is relatively small.

[0009]

However, in the above-mentioned conventional high-frequency probing pad,
Probing pads consisting of signal conductors and ground conductors formed on a dielectric substrate can be manufactured under conditions where the shape of the contact parts required for electrical connection with the signal conductors and ground conductors of the wafer probe is limited In this case, characteristic impedance mismatch occurs between the probe and the wafer probe. As a result, the reflection of the incident signal increases. Is insufficient and accurate measurement of high-frequency characteristics cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to perform impedance matching with a wafer probe even at a high frequency even when the shape setting of a probing pad is limited. It is an object of the present invention to provide a high-frequency probing pad capable of accurately measuring high-frequency characteristics.

[0011]

According to the present invention, there is provided a high-frequency probing pad having a lower surface grounding conductor formed on a lower surface of a substrate made of a dielectric material, and a signal conductor and a lower surface grounding conductor formed on the upper surface facing the lower surface grounding conductor. The signal conductor and the ground conductor,
A pad portion for contacting a signal conductor and a ground conductor of a wafer probe having a coplanar line structure, and a lead line portion electrically connected to and pulled from the device under test,
A matching line portion provided between the pad portion and the lead-out line portion is electrically connected to the pad portion and the matching line portion, and between the lead-out line portion and the matching line portion. The characteristic impedance of the pad portion is larger than that of the wafer probe, and the characteristic impedance of the matching line portion is smaller than that of the wafer probe. The electric length including the line portion is set to be equal to or less than one-fourth of the free space wavelength of the high frequency signal of the highest applied frequency.

In the above structure, the high frequency probing pad of the present invention may further comprise a dielectric film made of a dielectric material formed on the upper surface of the substrate so as to cover the signal conductor and the ground conductor. A dielectric film-free area for contacting the signal conductor and the ground conductor of the wafer probe is provided on the dielectric film on the signal conductor and the ground conductor.

[0013] Further, the high frequency probing pad of the present invention, in the above configuration, is characterized in that the dielectric constant of the dielectric film is larger than the dielectric constant of the substrate.

Further, in the high frequency probing pad of the present invention, in each of the above-described configurations, the geometric mean value of the characteristic impedance of the pad portion and the characteristic impedance of the matching line portion is divided by the characteristic impedance value of the lead line portion. The value is 0.75 or more and 1.02 or less.

[0015]

According to the high frequency probing pad of the present invention, a lower surface ground conductor is formed on the lower surface of a substrate made of a dielectric material, and the upper surface is opposed to the lower surface ground conductor. The signal conductor and the ground conductor are connected to a pad portion for contacting the signal conductor and the ground conductor of the wafer probe having the coplanar line structure, respectively, and a lead electrically connected to and pulled from the device under test. A line portion, a matching line portion provided between the pad portion and the lead-out line portion, and a connection for electrically connecting the pad portion and the matching line portion and between the lead-out line portion and the matching line portion, respectively; The characteristic impedance of the pad part is larger than that of the wafer probe, and the characteristic impedance of the matching line part is larger than that of the wafer probe. And the electrical length of the combined line and matching line is less than one-fourth of the free-space wavelength of the highest frequency signal applied. In the range of the electrical length that is sufficiently short for the free space wavelength of the high frequency signal of the highest frequency, the presence of a part having a large characteristic impedance and a part having a small characteristic impedance match the impedance seen from the wafer probe by their interaction. As a result, it is possible to solve the problem that the reflection of the incident signal increases and the problem that the propagation of the high-frequency signal becomes insufficient as the frequency increases.

In such a high-frequency probing pad of the present invention, the width and length of the signal conductor or the distance between the signal conductor and the ground conductor are determined by adjusting the width of the pad portion, the connection line portion, the lead-out line portion and the matching line portion. In the section, the wafer probe can be probed and set in a range where there is no difficulty in manufacturing, but the characteristic impedance is set as close to the characteristic impedance of the wafer probe as possible as much as possible in order to perform impedance matching. The characteristic impedance of the matching line part will be closer to the characteristic impedance of the wafer probe, and the characteristic characteristics of the pad part and the matching line part and the leading line part will change with respect to the frequency. More reliably done On, it becomes possible to shorten the length of the connecting line part, in order to further applicable frequency is that high, it is desirable that the setting of the characteristic impedance of the pad portion to the aforementioned setting.

The characteristic impedance of the matching line portion is such that the value obtained by dividing the geometric mean value of the characteristic impedance of the pad portion and the characteristic impedance of the matching line portion by the characteristic impedance value of the drawing line portion is 0.75 or more and 1.02 or less. It is good to set.

Further, if the combined electrical length of the connection line portion and the matching line portion exceeds one-fourth of the free space wavelength of the highest frequency high-frequency signal to be applied, the impedance of the length for the high-frequency signal is not sufficient. It acts as a circuit element that does not require continuity, and tends to make impedance matching difficult.

According to the high frequency probing pad of the present invention, in the above structure, a dielectric film made of a dielectric material is formed on the upper surface of the substrate so as to cover the signal conductor and the ground conductor. When a dielectric film non-formed area for contacting the signal conductor and the ground conductor of the wafer probe is provided on the dielectric film on the conductor, when the dielectric film is not formed when viewed in the cross section of the transmission line, Means that the electric field distributed inside the substrate increases at higher frequencies than at low frequencies, and the impedance tends to be low due to the increase in capacitance.However, the distribution of the electric field at low frequencies and high frequencies by forming a dielectric film , The change in characteristic impedance with respect to frequency can be reduced. Because it is good, it can be a high-frequency probing pads can be applied to measurements in higher frequency as compared with the prior art.

In this case, the material and the thickness of the dielectric film are determined by using a glass cloth resin-based material such as PTFE as the dielectric substrate.
When using a resin such as (polytetrafluoroethylene), PPE (polyphenylene ether), BT (bismaleide triazine) resin, fluorine, cyanate ester, phenol, epoxy, or a glass cloth resin-based / ceramic composite material, for example, epoxy It may be formed by applying a dielectric material such as polyimide or polyimide, and its thickness is within a range that does not cause difficulty in application, and may be about the conductor thickness or more. When a ceramic material is used for the dielectric substrate, the dielectric film is not limited to a material such as epoxy or polyimide, and may be formed as a dielectric film by forming a ceramic layer by a printing method and firing it simultaneously with the substrate.

When a region where a dielectric film is not formed is provided,
It may be set within a range that does not cause difficulties in probing.However, by forming a dielectric film between the signal conductor and the ground conductor constituting the pad portion and also on the upper surface, the capacitance is increased, and the wafer probe is further improved. Since the above-described effect is obtained because the characteristic impedance approaches the characteristic impedance, it is desirable that the region where the dielectric film is not formed is as small as possible.

According to the high-frequency probing pad of the present invention, when the dielectric constant of the dielectric film is larger than the dielectric constant of the substrate in the above-described configuration, when viewed in a cross section of the transmission line, The distribution of the electric field at the low frequency and the high frequency becomes closer because the distribution of the electric field increases near the signal conductor and the ground conductor on the upper surface of the substrate. Since the change can be made smaller, the matching of the characteristic impedance is good even at a high frequency, so that a high-frequency probing pad that can be applied to measurement at a higher frequency than the conventional one can be obtained. .

According to the high-frequency probing pad of the present invention, in each of the above-described structures, the value obtained by dividing the geometric mean value of the characteristic impedance of the pad portion and the characteristic impedance of the matching line portion by the characteristic impedance value of the extraction line portion is 0.75. If it is not less than 1.02, the characteristic impedance of the matching line section can be maintained in the vicinity of the element value necessary for impedance matching. High frequency probing pad.

If this value is less than 0.75, the characteristic impedance of the matching line portion becomes too low, which deviates from the element value required for impedance matching, and the matching tends to become insufficient at higher frequencies. , 1.02
When the ratio exceeds, the effect of impedance matching tends to be reduced because the shape approaches the shape of a conventional high-frequency probing pad.

Hereinafter, the high-frequency probing pad of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of a high-frequency probing pad according to the present invention. In FIG. 1, reference numeral 1 denotes a signal conductor, and 2 denotes ground conductors located on both sides of the signal conductor 1, each of which is formed on an upper surface of a substrate (not shown) made of a dielectric material. A conductor is formed on, for example, substantially the entire lower surface of the dielectric substrate so as to face the signal conductor 1 and the ground conductor 2 to form a lower surface ground conductor (not shown). The upper surface ground conductor 2 is a through-hole conductor or the like. Are electrically connected through a through conductor (not shown).

The signal conductor 1 and the ground conductor 2 are formed by changing their shapes in the transmission direction of the high-frequency signal as shown in FIG. 1, for example, so that the signal conductor and the ground conductor of the wafer probe (not shown) are formed. A pad portion 11 which is brought into contact with and electrically connected to the dimensions required by the device, a lead-out line portion 13 which is electrically connected and drawn from a device under test (not shown), and A matching line section 14 provided between the pad section 11 and the leading line section 13 for performing impedance matching, and further between the pad section 11 and the matching line section 14, and between the pad section 11 and the leading line section 13. And a connection line section 12 for electrically connecting between the two.

The signal conductor 1 and the ground conductor 2 are
The characteristic impedance of the pad section 11 is larger than the characteristic impedance of the wafer probe, the characteristic impedance of the matching line section 14 is smaller than that, and the characteristic impedance of the lead line section 13 is set to be substantially equal to that. ing.

Further, the signal conductor 1 and the ground conductor 2
The electrical length of the line including the matching line portion 14 and the connection line portions 12 before and after the matching line portion is set to be not more than ４ of the free space wavelength of the high frequency signal of the highest applied frequency.

[0030] With such a configuration, when there is a portion having a large characteristic impedance and a portion having a small characteristic impedance in a range of an electrical length sufficiently short with respect to the wavelength as viewed from the wafer probe, the interaction between the portions is large. This causes the characteristic impedance seen from the wafer probe to be matched, thereby increasing the reflection of the incident signal due to the mismatch of the characteristic impedance, and impairing the propagation of the high-frequency signal especially as the frequency becomes higher. This eliminates the problem of being sufficient.

FIG. 2 is a plan view showing another embodiment of the high-frequency probing pad according to the present invention. In FIG. 2, the same portions as those in FIG. 1 are denoted by the same reference numerals, 1 is a signal conductor, 2 is a ground conductor, 11 is a pad portion, 12 is a connection line portion, 13 is a lead line portion, and 14 is a matching line. Department. Reference numeral 3 denotes a dielectric film made of a dielectric material formed on the upper surface of a substrate (not shown) so as to cover the signal conductor 1 and the ground conductor 2. Reference numeral 4 denotes a signal conductor 1 and a ground conductor 2 of the pad portion 11. This is a dielectric film non-formation area provided on the dielectric film 3 for abutting the signal conductor and the ground conductor of the wafer probe.

By forming the dielectric film 3 and providing the dielectric film non-formation region 4 in this manner, a change in the characteristic impedance of the probing pad with respect to the frequency can be reduced, and the characteristic impedance of the probing pad can be reduced even at a high frequency. Good matching can be achieved.

In this example, the shape, size, and position of the dielectric film non-forming region 4 are such that a slit (rectangle) having a width of 0.15 mm is aligned with the center of the signal conductor and the center of the slit, and similar slits are formed on both sides thereof. Is provided at intervals of 0.10 mm to correspond to the center interval (pitch) between the signal conductor and the ground conductor of the wafer probe of 0.25 mm. The shape may be circular, elliptical, square, or a combination thereof.

[0034]

Next, a specific example of the high-frequency probing pad of the present invention will be described.

Example 1 First, as an example of the high-frequency probing pad of the present invention, the applied frequency was DC to 70 GHz.
In order to function as a conductor, a conductor is formed on almost the entire lower surface of the dielectric substrate having a relative dielectric constant of 3.4 to form a lower surface ground conductor, and the upper surface is opposed to this, and the thickness is set to 20 μm. Is 0.20 mm and the distance to the ground conductor is 0.10 mm, and the signal line width is 0.55 mm and the distance to the ground conductor is 0.10 mm.
0.10 mm long matching line section and a signal line width of 0.1 mm.
The distance between the signal conductor and the ground conductor, which is 30 mm and is between 0.15 mm and the pad and the matching line and between the matching line and the drawing line, is 0.10 mm. and a linear connection line portion having an angle of 45 ° secured in each mm, and a high-frequency signal is propagated through the pad portion by a length of 0.05 mm from the tip of the wafer probe. The length up to the end opposite to the wafer probe was set to 1.00 mm, and a sample A of the high-frequency probing pad of the present invention having the shape as shown in FIG. 1 was obtained.

When the characteristic impedances of the pad portion, the matching line portion, and the lead-out line portion of the sample A are extracted by electromagnetic field simulation, FIG.
The characteristic curve of the frequency characteristic as shown in the same diagram as in FIG. In FIG. 5, P added to the characteristic curve of the characteristic impedance (unit: Ω) indicates a pad portion, M indicates a matching line portion, and F indicates a lead line portion. Also,
C indicates a geometric mean value of characteristic impedance values of the pad portion and the matching line portion.

From the results shown in FIG. 5, the frequency characteristic of the characteristic impedance in each line portion is smaller at high frequencies than at low frequencies, and the tendency is more remarkable for lines having a small characteristic impedance. It can be seen that the geometric mean value (characteristic curve C) of the characteristic impedance value with the section is kept smaller than the characteristic impedance (characteristic curve F) of the lead line section.

As another example of the high-frequency probing pad of the present invention, in order to make the applied frequency function from DC to 70 GHz, the relative permittivity is set to 3.
A conductor is formed on substantially the entire lower surface of the dielectric substrate 4 to form a lower surface ground conductor.
A pad section with a signal line width of 0.20 mm and a distance of 0.10 mm from the ground conductor, and a matching line section with a signal line width of 0.45 mm and a distance of 0.10 mm from the ground conductor, set to 20 μm. The signal line width is 0.28 mm and the distance between the ground conductor is 0.
A 45 ° angled straight line that secures 0.10 mm between the signal conductor and the ground conductor, connecting between the 10 mm lead line section, the pad section and the matching line section, and between the matching line section and the lead line section. Each of the connection line portions is formed, so that the high frequency signal propagates through the pad portion by a length of 0.05 mm from the tip of the wafer probe, from the tip of the wafer probe to the end of the lead line on the side opposite to the wafer probe. Is formed to a length of 1.00 mm, and a dielectric film having a relative dielectric constant of 4.4 is deposited over substantially the entire upper surface at a thickness of 20 μm, and a dielectric film is formed on the signal conductor and the ground conductor of the pad portion. A sample B as shown in FIG. 2 was obtained by providing a non-formation region.

When characteristic impedances of the pad portion, the matching line portion, and the lead line portion of the sample B are extracted by electromagnetic field simulation, a characteristic curve of frequency characteristics as shown in FIG. 6 as a diagram similar to FIG. 5 is obtained. Was. In FIG. 6, P added to the characteristic curve of the characteristic impedance (unit: Ω) represents a pad portion, M represents a matching line portion,
F indicates a lead line portion, and C indicates a geometric mean value of characteristic impedance values of the pad portion and the matching line portion.

From the results shown in FIG. 6, the frequency characteristic of the characteristic impedance in each line portion is smaller at high frequencies than at low frequencies, and the tendency is more remarkable for lines having small characteristic impedance. It can be seen that the geometric mean value (characteristic curve C) of the characteristic impedance value with the section is kept smaller than the characteristic impedance (characteristic curve F) of the lead line section.

Further, as a comparative example, a conductor is formed on substantially the entire lower surface of a dielectric substrate having a relative dielectric constant of 3.4 to form a grounded lower surface conductor.
m, a pad part with a signal line width of 0.20 mm and a distance of 0.10 mm from the ground conductor, a lead line part with a signal line width of 0.30 mm and a distance of 0.10 mm from the ground conductor, a pad part and a lead line To form a linear connection line section at an angle of 45 ° that secures a distance of 0.10 mm between the signal conductor and the ground conductor, and the pad section has a high frequency signal of 0.05 mm from the tip of the wafer probe. A conventional high-frequency probing pad having a shape as shown in FIG. 3 is formed to have a length of 1.00 mm from the tip of the wafer probe to the end of the lead-out line opposite to the wafer probe so as to propagate the length. Of Sample C was obtained.

When the characteristic impedance of the pad portion and the lead line portion of the sample C was extracted by electromagnetic field simulation, a characteristic curve of frequency characteristics as shown in the diagram of FIG. 13 was obtained. As described above, P added to the characteristic curve of the characteristic impedance (unit: Ω) indicates a pad portion, and F indicates a lead line portion.

Further, a shape similar to that of the sample B is formed symmetrically with respect to a straight line perpendicular to the transmission direction of the high-frequency signal on the opposite side of the dielectric substrate, and the lead-out lines are connected to each other so that the length of the lead-out line is 7.48. mm, and a sample D as shown in FIG. 4 was obtained.

When the electrical characteristics of the samples A to C were extracted by electromagnetic field simulation, the characteristic curves of the frequency characteristics as shown in the diagram of FIG. 8 were obtained. In FIG. 8, the horizontal axis indicates frequency (unit: GHz), the vertical axis indicates reflection coefficient (unit: dB) as an evaluation index of the amount of reflection in the input signal, and the characteristic curve indicates the reflection coefficient of the reflection coefficient. 9 shows frequency characteristics. In addition, A ·
B and C indicate characteristic curves of samples A, B, and C, respectively.

From this result, it can be seen that, in Sample C, which is a conventional high-frequency probing pad, as the frequency increases, the reflection coefficient increases, and reflection occurs due to mismatching of characteristic impedance. On the other hand, it is understood that the samples A and B, which are the high-frequency probing pads of the present invention, have low reflection even at high frequencies and are high-frequency probing pads having good electrical characteristics. In particular, in sample B, the dielectric film deposited on the upper surface of the substrate can reduce the frequency change of the characteristic impedance of the transmission line as can be seen from FIG. It can be seen that it functions as a high frequency probing pad having good electrical characteristics. In order to reduce the change in the characteristic impedance with respect to the frequency, it was confirmed that the effect was more remarkable when the dielectric constant of the dielectric film was set to be about 1.5 times higher than the dielectric constant of the substrate.

According to FIG. 8, the reflection of the sample B near 80 GHz is large. This is because the electrical length of the matching line portion and the connection line portion of the sample B is changed by the free space wavelength of the high frequency signal. This is because the quarter frequency is set to 79 GHz, and at higher frequencies, the reflection becomes large due to insufficient matching of the characteristic impedance. Accordingly, by setting the combined electrical length of the matching line portion and the connection line portion to be equal to or less than one-fourth of the free space wavelength of the highest frequency high-frequency signal to be applied in accordance with the applied frequency, a high-reflection high-frequency signal with low reflection can be obtained. It can be understood that it can be realized as a probing pad for use.

When the electrical characteristics of the sample D were extracted by electromagnetic field simulation and measurement by a network analyzer, a characteristic curve of frequency characteristics was obtained as shown by the diagram in FIG. In FIG. 9, the horizontal axis represents frequency (unit: GHz), the vertical axis represents reflection coefficient (unit: dB) as an evaluation index of the amount of reflection in the input signal, and the characteristic curve represents the reflection coefficient. 9 shows frequency characteristics. Further, S added to the characteristic curve indicates a value extracted by simulation of the sample D, and M indicates a value extracted by measurement.

From these results, it was confirmed that the electromagnetic field simulation and the measurement were in good agreement, and that the probing pad of the present invention could be realized as a high-frequency probing pad with low reflection.

Further, of the frequency characteristics of the reflection coefficient obtained by the measurement, the characteristics of 50 GHz or less are converted as time axis characteristics and extracted as step response characteristics. A characteristic curve was obtained.

In FIG. 10, the horizontal axis represents the time (unit: ps (picoseconds)) in which the reflected wave was observed, the vertical axis represents the resistance value (unit: Ω) of the reflected wave, and the characteristic curve represents the time of the resistance. The axis characteristics are shown. From this result, it is understood that the change in the resistance value is suppressed to be small by the effect of the matching line portion.
It was confirmed that the high-frequency probing pad of the present invention functions as a high-frequency probing pad having low reflection characteristics.

Thus, the high-frequency probing pad of the present invention can provide good matching of the characteristic impedance even at a high frequency by providing the matching line portion even when the setting of the shape of the probing pad is limited by the wafer probe. It was confirmed that it was possible.

[Example 2] In the same high-frequency probing pad as the sample A of [Example 1], the signal line width of the matching line portion was set to 0.40 mm, and the distance from the ground conductor was set to 0.1 mm, and the connection line portion was adjusted. Thus, a sample E was obtained.

Further, in the same high-frequency probing pad as that of the sample A of [Example 1], the signal line width of the matching line portion was reduced.
Sample F was obtained by adjusting the connection line portion with 0.70 mm and an interval of 0.1 mm with the ground conductor.

For these samples E and F, the pad portion
The characteristic impedance of the matching line section and the lead line section is extracted by electromagnetic field simulation, and the value obtained by dividing the geometric mean value of the characteristic impedance of the pad section and the matching line section by the characteristic impedance value of the lead line section is extracted as an impedance ratio. Then, a characteristic curve of frequency characteristics as shown by the diagram in FIG. 11 was obtained. In FIG. 11, the horizontal axis represents frequency (unit: GHz), the vertical axis represents impedance ratio, and the characteristic curve represents frequency characteristics of the impedance ratio. A, E, and F added to the characteristic curves indicate that they are characteristic curves of the samples A, E, and F, respectively.

With respect to these samples EF, the electric characteristics were extracted by electromagnetic field simulation and illustrated together with the samples A and C of [Example 1]. As shown in FIG. Obtained. In FIG. 12, the horizontal axis represents the frequency (unit: GHz), and the vertical axis represents the reflection coefficient (unit: d) as an evaluation index of the amount of reflection in the input signal.
B), and the characteristic curve shows the frequency characteristic of the reflection coefficient. A, C, E, and F added to the characteristic curves indicate that they are characteristic curves of samples A, C, E, and F, respectively.

From these results, it is found that the sample E having the largest value of the impedance ratio of 1.02 in the applicable frequency band has slightly inferior characteristics to the sample A, but the sample using the conventional high-frequency probing pad. It can be seen that the reflection is smaller than C and the characteristics are good. On the other hand, the sample F has a reflection frequency of about 65 GHz, which is substantially equal to the reflection coefficient of the sample C using the conventional high-frequency probing pad, and the impedance ratio at this frequency is 0.75. Below this frequency, the reflection is smaller than that of the sample A, and the sample A has good characteristics.

Therefore, when the value obtained by dividing the geometric mean value of the characteristic impedance of the pad portion and the characteristic impedance of the matching line portion by the characteristic impedance value of the extraction line portion is 0.75 or more and 1.02 or less, the matching is more reliably performed. We can see that we can do it. Further, the characteristic impedance of the matching line portion most suitable for impedance matching is determined by the components of the transmission line (substrate permittivity, substrate thickness, conductor thickness, dielectric constant of dielectric film, dielectric film thickness, signal conductor of pad portion). It depends on the width and the distance between the signal conductor and the ground conductor of the pad part), but it can be regarded as the value obtained by dividing the geometric mean value of the characteristic impedance of the pad part and the characteristic impedance of the matching line part by the characteristic impedance value of the lead line part. Since the values are distributed almost close to each other, it has been confirmed that when the value is in the range of about 0.80 to 0.95, the impedance matching is good, and it can be realized as a high-frequency probing pad with low reflection.

Thus, the high-frequency probing pad of the present invention can provide a good matching of the characteristic impedance even at a high frequency by providing the matching line portion even when the setting of the shape of the probing pad is limited by the wafer probe. It was confirmed that it was possible.

The above is merely an example of the embodiment of the present invention, and the present invention is not limited to the embodiment. Various changes and improvements may be made without departing from the gist of the present invention. No problem.

For example, a connecting line portion having a signal line width changed linearly between a pad portion and a matching line portion or a matching line portion and a leading line portion may not be provided, but may be directly connected to form a connecting line portion. The connection part in this case is formed in a step shape, and becomes a component as a connection line part.

Further, for example, the matching line portion may be formed as an open-end stub line branched from the signal line, and in this case, the impedance of the signal line is reduced, so that the connection line portion is equivalent.

[0062]

As described above, according to the high-frequency probing pad of the present invention, the signal conductor and the signal conductor are formed by forming the lower surface ground conductor on the lower surface of the substrate made of a dielectric material and facing the lower surface ground conductor on the upper surface. The signal conductor and the ground conductor are formed by forming ground conductors located on both sides, and the signal conductor and the ground conductor are electrically connected to and pulled out from a pad portion for contacting the signal conductor and the ground conductor of the wafer probe having the coplanar line structure, respectively. And a matching line portion provided between the pad portion and the drawing line portion, between the pad portion and the matching line portion, and between the drawing line portion and the matching line portion. And the connection line section connected to the wafer probe, and the characteristic impedance of the pad section is larger than that of the wafer probe, and the characteristic impedance of the matching line section is Is smaller than that of the wafer probe, and the electrical length of the connection line and the matching line is less than one-fourth of the free-space wavelength of the highest-frequency signal applied. The characteristic impedance seen from the wafer probe by the interaction between the part with large characteristic impedance and the part with small characteristic impedance in the electrical length range short enough for the free space wavelength of the high frequency signal of the highest frequency Since the matching can be performed, as a result, the problem that the reflection of the incident signal increases and the problem that the propagation of the high-frequency signal becomes insufficient as the frequency becomes higher can be solved.

According to the high frequency probing pad of the present invention, in the above structure, a dielectric film made of a dielectric material is formed on the upper surface of the substrate so as to cover the signal conductor and the ground conductor, and the signal conductor of the pad portion is formed. When a dielectric film non-formation region for contacting the signal conductor and the ground conductor of the wafer probe is provided on the dielectric film on the ground conductor, the dielectric film is not formed when viewed in the cross section of the transmission line. In this case, the electric field distributed inside the substrate at a higher frequency than at the low frequency increases, and the impedance tends to be low due to an increase in the capacitance. However, the electric field at the low frequency and the high frequency is formed by forming the dielectric film. Of the characteristic impedance with respect to frequency can be reduced, and the characteristic impedance can be reduced even at higher frequencies. Since if it is good, it can be a high-frequency probing pads can be applied to measurements in higher frequency as compared with the prior art.

Further, according to the high frequency probing pad of the present invention, in the above configuration, when the dielectric constant of the dielectric film is larger than the dielectric constant of the substrate, when viewed in a cross section of the transmission line, Since the electric field distributed inside the substrate is reduced and the electric field distribution is increased near the signal conductor and the ground conductor on the upper surface of the substrate, the distribution of the electric field at low frequency and high frequency becomes closer, so the characteristic with respect to frequency A high-frequency probing pad that can be applied to measurements at higher frequencies compared to conventional ones, because the characteristic impedance can be matched well even at higher frequencies because the change in impedance can be made smaller. Can be.

Further, according to the high-frequency probing pad of the present invention, in each of the above-described configurations, the value obtained by dividing the geometric mean value of the characteristic impedance of the pad portion and the characteristic impedance of the matching line portion by the characteristic impedance value of the extraction line portion. Is not less than 0.75 and not more than 1.02, the characteristic impedance of the matching line portion can be maintained in the vicinity of the element value required for impedance matching. A high-frequency probing pad with low reflection characteristics can be obtained.

As described above, according to the present invention, even when the setting of the shape of the probing pad is limited, impedance matching with the wafer probe can be performed even at a high frequency, and accurate measurement of high-frequency characteristics can be performed. A probing pad for high frequency could be provided.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of an embodiment of a high-frequency probing pad of the present invention.

FIG. 2 is a plan view showing another example of the embodiment of the high-frequency probing pad of the present invention.

FIG. 3 is a plan view showing an example of a conventional high-frequency probing pad.

FIG. 4 is a plan view showing another example of the embodiment of the high-frequency probing pad of the present invention.

FIG. 5 is a diagram showing frequency characteristics of characteristic impedance of each line portion in an example of the high-frequency probing pad of the present invention.

FIG. 6 is a diagram showing frequency characteristics of characteristic impedance of each line portion in another example of the high-frequency probing pad of the present invention.

FIG. 7 is a diagram comparing the frequency change characteristics of the characteristic impedance of the lead-out line portion of the high-frequency probing pad of the present invention.

FIG. 8 is a diagram comparing the frequency characteristics of the reflection coefficient of the high-frequency probing pad.

FIG. 9 is a diagram comparing the frequency characteristics of the reflection coefficient by simulation and measurement in another example of the high-frequency probing pad of the present invention.

FIG. 10 is a diagram showing a time-base characteristic (step response characteristic) of a resistance value extracted by measurement in another example of the high-frequency probing pad of the present invention.

FIG. 11 is a diagram comparing frequency characteristics of impedance ratios in a high-frequency probing pad.

FIG. 12 is a graph comparing the frequency characteristics of the reflection coefficient of a high-frequency probing pad.

FIG. 13 is a diagram showing frequency characteristics of characteristic impedance of each line portion of a conventional high frequency probing pad.

FIG. 14 is a diagram showing a frequency characteristic of a reflection coefficient of a conventional high-frequency probing pad.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Signal conductor 2 ... Ground conductor 3 ... Dielectric film 4 ... Dielectric film non-formation area 11 ... Pad line Section 12 Connection line section 13 Lead line section 14 Matching line section

Claims (4)

[Claims] 1. A signal conductor comprising: a lower surface ground conductor formed on a lower surface of a substrate made of a dielectric material; and a signal conductor and ground conductors located on both sides thereof formed on the upper surface so as to face the lower surface ground conductor. And the grounding conductor includes a pad portion that makes contact with a signal conductor and a grounding conductor of a wafer probe having a coplanar line structure, an extraction line portion electrically connected and extracted from the device under test, and the pad portion and the extraction portion. From a matching line portion provided between the pad portion and the matching line portion, and from a connection line portion electrically connecting between the lead line portion and the matching line portion. Is composed of
And the characteristic impedance of the pad portion is larger than that of the wafer probe, and the characteristic impedance of the matching line portion is smaller than that of the wafer probe.
The free space wavelength of the high frequency signal of the highest frequency to which the electric length of the connection line portion and the matching line portion is applied is 4
A high-frequency probing pad characterized in that the probing pad is less than one-half. 2. A dielectric film made of a dielectric material is formed on an upper surface of the substrate so as to cover the signal conductor and the ground conductor, and the dielectric film on the signal conductor and the ground conductor of the pad portion is formed. 2. The high frequency probing pad according to claim 1, further comprising a dielectric film non-forming region for contacting a signal conductor and a ground conductor of the wafer probe. 3. The high frequency probing pad according to claim 2, wherein the dielectric constant of said dielectric film is higher than that of said substrate. 4. A value obtained by dividing a geometric mean value of a characteristic impedance of the pad portion and a characteristic impedance of the matching line portion by a characteristic impedance value of the lead line portion is 0.75 or more and 1.02 or less. Item 1
The high-frequency probing pad according to claim 3.