JPH0926436A - Electronic element evaluation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the characteristics of a specific element circuit which is formed at a submicron region of an actual device by arranging a plurality of probes with a sharp tip on a sample surface at a specific inclination and interval. SOLUTION: For example, the center axes of probes 2-4 are deviated from the normal direction of the surface of the surface of a measurement sample 1 and the deviation θ is set to a range of 30-60 deg.. Also, the probes 2-4 are arranged with an interval exceeding an azimuth angle with the sample 1 as the center, namely at least 30 deg. from a reference line when the probes 2-4 are projected on the surface of the sample 1. By setting the azimuth angle to 2π/n, the distance between contacts among the probes can be minimized. By deviating the center axes of the probes 2-4 from the normal line of the surface of the measurement sample 1 and arranging the probes 2-4 with an interval exceeding an azimuth angle of at least 30 deg., the probes cannot be in contact with one another and a plurality of probes can be brought into contact with a small region on the surface of the sample 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating characteristics of electronic devices.

[0002]

2. Description of the Related Art Conventionally, the characteristics of electronic devices have been evaluated by using a device called a prober. For example, the example is described on page 544 of the Semiconductor Measurement and Evaluation Encyclopedia (Science Forum). In this method, a probe called a probe is applied to an electrode called a bonding pad formed on the surface of a sample to make electrical contact with a specific portion of an electronic element. For example, by using two probes, element characteristics such as current-voltage characteristics of a specific portion of a circuit can be evaluated. In this method, it was necessary to prepare in advance a sample for evaluation (Test Element Group: TEG) in which a bonding pad having a side of about 100 μm was formed on the surface.

[0003]

SUMMARY OF THE INVENTION In the above conventional method,
It was necessary to previously form a bonding pad having a side of about 100 μm for measurement on the surface of the sample. That is, a measurement electrode (bonding pad) that can be easily aligned with an optical microscope and can be surely brought into electrical contact simply by mounting a probe was required. However, with the progress of miniaturization of electronic devices (for example, a microfabrication technique of 0.5 μm line width is used in 16-mega DRAM), defects caused by the miniaturization have become remarkable.

Such defects often appear due to subtle differences in the conditions of the element forming process. However, TEG
Since it is necessary to form a bonding pad having a side of about 100 μm, the formation process and structure itself do not completely match those of the actual device. Therefore, a defect to be analyzed may not appear. That is, in the conventional prober,
Since the actual device cannot be measured, there has been a problem that the intended failure analysis cannot be performed. In order to solve this, a small area (~ 0.
It was necessary to bring a plurality of probes into contact with 1 μm).

[0005]

In order to solve the above-mentioned problems, it is only necessary to make the tip of the probe sharp in the conventional prober (the radius of curvature is about 10 nm to 1 μm).
In the conventional prober, the probe 31 installed at the tip of the support member 30 is brought into contact with the bonding pad. By sharpening the tip of this probe, it is possible to bring the tip of one probe into contact with a minute region. However, when trying to bring a plurality of probes into contact with a minute area, the probes come into contact with each other first in a portion other than the tip portion. as a result,
It was not possible to bring a plurality of probes into contact with the minute area of the sample. It was found that the conventional method had a problem in that the blunt probe was brought into contact with the surface of the sample almost vertically from the problems of operability and reliability described above. That is, the present invention has revealed that the following means are required to bring a plurality of probes into contact with a minute region of a sample.

In the present invention, the central axis of the probe is shifted from the direction normal to the surface of the sample to be measured. The deviation θ is 30
The range was set to -60 °.

Further, a plurality of (n) probes are arranged at intervals of an azimuth angle of 30 ° or more around the sample.
When the azimuth angle is 2π / n, the distance between the contact points between the probes can be minimized.

The normal line is a line perpendicular to the sample surface, and the azimuth angle φ is an angle from a reference line when the probe is projected on the sample surface (see FIG. 3). .

[0009]

In the present invention, the central axis of the probe is displaced from the normal line of the surface of the sample to be measured, and the probes are arranged at intervals of 30 ° or more in azimuth. A plurality of probes can be brought into contact with the minute area of the.

[0010]

An embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a diagram of a main part of the present invention viewed from directly above. Around the measurement sample 1, the three probes 2 to 4 have an azimuth angle of 120.
They are arranged at an interval of ° (2π / 3 radians). Each probe is moved by the probe moving mechanism 5-7,
The tip of the probe can be brought into contact with the target position of the sample. Each probe is electrically coupled to the evaluation / measurement unit 8 so that application of voltage and measurement of current flowing between each probe can be performed.

FIG. 2 is a side view of the main part of the present invention (a view from the side of the probe 2 in FIG. 1, the probe 2 is omitted). It can be seen that the two probes 3 and 4 are in contact with a specific location of the sample 1 obliquely with respect to the sample. In the present invention, the central axes 9 and 10 of the probe having such a sharp tip are
Is set in an oblique direction with respect to the sample, so that a plurality of probes can be brought into contact with the minute region.

The reason why such a probe is arranged will be described below. No matter how sharp the tip of the probe is, it has a finite size at the nanometer level. Further, the size (diameter) increases as the distance from the tip end increases. Even if the tip of the probe is brought into contact with the sample surface, the probe is not damaged, so that the root diameter r of the probe must be at least on the order of microns. For example, if the probe is arranged perpendicularly to the surface as shown in FIG.
No matter how sharp 0 or 21 is, the distance between the probes 22 and 23 cannot be less than the diameter r of the root of the probe. That is, the distance d between contact points does not fall below r. Since the root diameter r of the probe must be at least on the order of microns, the contact point distance does not become smaller than the order of microns when the probe is brought into contact with the sample perpendicularly. Therefore, FIG.
It is necessary to bring the probe into contact with the sample from an oblique direction, as shown in.

Even in the conventional method, due to operational problems, the probe is contacted with the sample from an oblique direction, which is the portion 30 (see FIG. 5) that supports the probe. Note that it is not the tip 31.

Although the probe has been described as macroscopically described above, the importance of the present invention becomes more significant when a plurality of probes are to be brought into contact with a region of about 0.1 μm.

No matter how sharp the tip of the probe is, at the atomic level, the tip of the probe has a shape close to a sphere (see FIG. 6).
A probe (see FIG. 7) in which atoms are piled up in a line does not actually exist, and even if there is, there is a problem in strength to bring the tip of the probe into contact with the sample surface.

For the sake of simplicity, the shape of the tip of the probe will be described below assuming a parabola. It has been explained above that the probes cannot be brought close to each other by aligning the central axis of the probes with the normal line of the sample. Therefore, in the present invention, as shown in FIG. 8, the central axes 40 and 41 of the probe are inclined from the normal line 47 of the sample surface 46.
At this time, the probe does not come into contact with the sample at the tip portions 42 and 43, but comes into contact with the other portions 44 and 45.
For this reason, if it is tilted too much, the contact portion becomes farther from the tip end portion, and as a result, the distance d between the probe contact points increases.

FIG. 9 shows the inclination of the center axis of the probe from the sample normal when two probes are used (both are common, see FIG. 8).
FIG. 3 is a diagram showing a minimum distance between contact points between each probe and a sample. When the central axis of the probe coincides with the normal line, the minimum contact point distance becomes large because it depends on the diameter of the root of the probe. On the other hand, if the central axis is tilted too much, the contact point is separated from the tip of the probe, and the minimum distance between contact points becomes large. Therefore, in the present invention, the inclination of the central axis from the sample normal line is set in the range of 30 to 60 °. It will be understood from FIGS. 8 and 9 that the minimum contact point distance can be reduced in this range.

Next, the azimuth angle will be described. First, 2
In the case of a probe, it is good to install the probes so as to face each other. FIG.
[Fig. 6] is a view of the two probes seen from directly above. FIG. 10a is a view when two probes are installed facing each other, and FIG. 10b is a view when they are installed at an azimuth angle of 120 °. It is assumed that the inclination of the central axis from the normal line is 30 °, and the point of contact with the sample surface is indicated by x. The minimum distance between contact points when the azimuth angle is 120 ° is
It is about 1.5 times that at 180 °. When using two probes, if the azimuth angle is set to 180 °,
Minimum distance between contact points can be minimized. For the same reason, the azimuth angle may be set to 120 ° when three probes are used (see FIG. 11) and the azimuth angle may be set to 90 ° when four probes are used (see FIG. 12). ).

The azimuth angle to be set has been described with reference to FIGS. As described above, when using n probes, the distance between the contact points between the probes and the sample can be minimized by setting the azimuth angle to 2π / n.

FIG. 13 is a diagram showing the relationship between the azimuth angle between the probes and the distance between the minimum contact points. It can be seen that the distance between the minimum contact points increases as the azimuth angle decreases. Particularly, when the angle is 30 ° or less, the roots of the probes come into contact with each other, and the distance between the minimum contact points suddenly increases (see the description in FIG. 9). Therefore, in the present invention, the azimuth angle is set to 30 ° or more.

The azimuth angle 2π / n is a standard when using n probes. In some cases, it is better to set the azimuth angle to be smaller than 2π / n due to the device configuration. For example, when confirming the contact point with a scanning electron microscope, as shown in FIG. 14, the secondary electron detector 60 is not interrupted by the probes 61 to 64 so that the contact point between the sample and the probe can be desired. There is a need to. In such a case, the azimuth angle between the four adjacent probes is smaller than 90 ° (2π / 4).

FIG. 15 is a diagram showing an embodiment in which the present invention is applied to actual electronic element characteristic evaluation. The probe 50 is in contact with the gate electrode 51, the probe 52 is in contact with the source electrode 53, and the probe 54 is in contact with the drain electrode 55. The gate voltage can be manipulated by changing the voltage applied to the probe 50. At this time, the device characteristics can be evaluated by measuring the current flowing between the probes 52 and 54, that is, the current flowing between the source and the drain. Since such an element is formed in the submicron region, it was not possible to perform such a measurement by directly contacting the probe with the electrode by the conventional method. Therefore, it was necessary to form a TEG for measurement. However, the use of the present invention makes it possible to measure the local element characteristics on the actual device.

Furthermore, according to the present invention, it is possible to measure the electrical characteristics of a minute region of less than 0.1 μm.
Not only device characteristics on the device but also basic material properties such as electric conductivity of thin film materials can be measured.
For example, the electrical conductivity of an atomic layer order thin film formed on a substrate is affected by the unevenness of the substrate as well as the electrical conductivity of the thin film itself. There is always a step of atomic layer height on the substrate when viewed in μm order, so even if the electric conductivity of a macro region is measured using a conventional prober,
It is not possible to measure the electrical conductivity properties of the thin film itself. By using the present invention, it is possible to measure the electrical characteristics of a minute region,
The electrical characteristics of the thin film itself can be measured without being affected by the unevenness of the substrate. In the future, in order to develop a device using a nanostructure such as a quantum effect device, elucidation of the electrical characteristics of such a microstructure will be indispensable, and the usefulness of the present invention can be seen.

[0024]

According to the present invention, in order to evaluate the characteristics of the electronic element formed in the minute area, not only the sharp tip of the tip is used, but the central axis of the tip is set to the surface of the sample. Since a plurality of (n) probes are tilted (30 to 60 °) from the normal line and arranged at intervals of azimuth angles of 30 ° or more, the plurality of probes should be brought into contact with the submicron region at the same time. You can Therefore, the element characteristics on the actual device formed in the submicron region can be evaluated, and there is no need to form a TEG for measurement as in the conventional case.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a principle configuration of the present invention.

FIG. 2 is a side view of the main part of FIG.

FIG. 3 is an explanatory diagram of a normal line and an azimuth angle.

FIG. 4 is an explanatory view when a probe is brought into contact with the surface of a sample perpendicularly.

FIG. 5 is an explanatory view of a conventional probe and a probe supporting portion.

FIG. 6 is a schematic view showing a tip end portion of a probe seen at a nanometer level.

FIG. 7 is a schematic diagram showing probes formed by stacking atoms in a row.

FIG. 8 is an explanatory diagram showing a distance between contact points between the probe and the sample surface.

FIG. 9 is an explanatory diagram showing the angle dependence of the distance between the minimum contact points.

FIG. 10 is an explanatory diagram of an azimuth angle with two probes.

FIG. 11 is an explanatory diagram of an azimuth angle with a three-probe.

FIG. 12 is an explanatory diagram of an azimuth angle with a four-point probe.

FIG. 13 is an explanatory diagram showing the azimuth angle dependency of the minimum contact point distance.

FIG. 14 is an explanatory diagram showing an example in which a secondary electron detector is installed.

FIG. 15 is a plan view showing a measurement example of an actual device.

[Explanation of symbols]

1 ... Sample, 2,3,4 ... probe, 5,6,7 ... probe moving mechanism, 8 ... evaluation / measurement part, 9,10 ... probe center axis, 2
0, 21 ... Tip tip, 22, 23 ... Tip, 30 ... Tip support part, 31 ... Tip tip, 40, 41 ... Central axis of the tip,
42, 43 ... Tip part, 44, 45 ... Contact part with sample surface, 46 ... Sample, 47 ... Normal line, 50 ... Probe, 51 ... Gate electrode, 52 ... Probe, 53 ... Source electrode, 54 ... Probe, 55 ... Drain electrode, 60 ... Secondary electron detector, 6
1, 62, 63, 64 ... Probes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Makiko Kono 1-280, Higashi Koikekubo, Kokubunji City, Tokyo Metropolitan Research Laboratory, Hitachi, Ltd. (72) Satoshi Tomimatsu 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Center

Claims (8)

[Claims] 1. An electronic element evaluation apparatus having a plurality of probes, wherein a central axis of the probes is tilted from a normal line of a sample surface to be measured, and a point on the sample surface to be measured is measured. An electronic element evaluation apparatus, which is arranged with an azimuth angle of 30 ° or more as a center. 2. The electronic element evaluation apparatus according to claim 1, wherein an angle formed by a central axis of the probe and a normal line of the sample surface is in a range of 30 to 60 °. 3. The electronic element evaluation apparatus according to claim 1, wherein the two probes are arranged at an azimuth angle of 30 ° or more. 4. The electronic device evaluation apparatus according to claim 3, wherein the azimuth angle is 120 °. 5. The electronic element evaluation apparatus according to claim 1, wherein the three probes are arranged at intervals of an azimuth angle of 30 ° or more around a point to be measured on the sample surface. 6. The electronic device evaluation apparatus according to claim 5, wherein the azimuth angle is 120 °. 7. The electronic element evaluation apparatus according to claim 1, wherein the four probes are arranged at intervals of an azimuth angle of 30 ° or more around a point to be measured on the sample surface. 8. The electronic device evaluation apparatus according to claim 7, wherein the azimuth angle is 90 °.