JPH06102318A - Probe device - Google Patents

Abstract

PURPOSE:To provide a probe device which can measure the fine wiring of a sub-micron width at high speed without increasing the size of a device and has a function to apply voltage to wirings, related to an inspection device for testing an electronic circuit in its operating condition and particularly related to the measuring device for the voltage applied to a fine wiring formed on a plane. CONSTITUTION:A probe device comprises a conductive needle 1 which can come into contact with a wiring, a conductive cantilever 2 connected to the conductive needle 1, a photoconductor film for forming a photoconductive gate part 3, a first conductor 4 which comes into contact with a part of the photoconductor film and is connected to the cantilever 1, and a second conductor 5 which is opposite to the first conductor 4 and comes into contact with a part of the photoconductor film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection device for testing an electronic circuit in an operating state, and more particularly to a device for measuring a voltage applied to a fine wiring formed on a plane.

[0002] It is often required to measure the voltage of wiring formed in electronic circuits. In particular,
In the manufacture of semiconductor integrated circuits (ICs), it is indispensable to test the device characteristics and investigate the cause of malfunctions (fault analysis).

However, with the high integration of ICs such as LSIs in recent years, the number of I / O pins has become enormous and I / O
It is becoming difficult to perform accurate failure analysis only by measuring the pin signal. Therefore, it is necessary to measure the voltage of the fine wiring in the IC. However, due to the high integration and high speed of ICs, the measurement accuracy is insufficient with conventional measurement methods, and the development of new measurement methods with high accuracy is desired.

[0004]

2. Description of the Related Art A device using an electron beam or a light beam has been studied or put into practical use in order to measure the voltage of a fine wiring in an IC and its time variation.

A device using an electron beam is a device that measures the voltage at the irradiation point by irradiating the internal wiring of the IC with a narrowed electron beam and performing energy analysis of secondary electrons emitted from the irradiation point. Is. Short voltage (
For example, in order to measure the change of 1 ns or less), a sampling method in which the electron beam is pulsed is used.

With this device using an electron beam, it is possible to measure the voltage of fine wiring with a submicron width. However, by narrowing the electron beam, the number of electrons in the electron beam is reduced, so that the voltage measurement resolution is reduced. Is reduced. Therefore, long-term measurement is required to secure sufficient resolution. Also, when measuring the voltage change over time, a long time measurement is required as in the case above, when the electron beam pulse width is shortened in order to increase the time resolution. On the other hand, due to the transit time effect of secondary electrons, it is theoretically difficult to realize a time resolution higher than 5 ps, for example.

As one voltage measurement method using a light beam, a minute electro-optic crystal is placed in the vicinity of the internal wiring of the IC, and the voltage is measured by utilizing the electro-optic effect induced by the wiring voltage in the crystal ( EO sampling method). (For example, Valdmanis JA, Electron. Lett. 23, 1308-131
0, 1987) The voltage resolution is higher than the method using electron beam. However, due to the spatial resolution determined by the wavelength of light, it is theoretically difficult to measure the voltage of fine wiring of 1 μm or less. Moreover, a resolution of 0.5 ps or more was obtained in the measurement of voltage change over time.

As another voltage measuring method using a light beam,
There is a method of utilizing a photoconductive gate. Photoconductive gate
The conductivity is extremely low when light is not irradiated (gate off state), but the conductivity increases for a short time when light is irradiated. (Gate-on state) By utilizing this effect to detect the current of the photoconductive gate, the voltage applied to the gate, that is, the wiring voltage can be measured.

In this method, a photoconductive material having a high-speed photoresponse characteristic is used, and a sampling method is used in which incident light is pulsed to obtain a time resolution as high as ps. Also, by selecting an appropriate photoconductive material, it is possible to obtain a measurement sensitivity that is 10 times higher than the voltage measurement sensitivity when the electro-optic effect is used.

When light is irradiated with a bias voltage applied to the photoconductive gate, a voltage is generated in the cantilever and the voltage can be applied to the object to be measured. However, when forming a photoconductive gate by radiation damage to SOS (Silicon On Sapphier), the photoconductive gate had to be built in advance on the LSI chip to be measured. LS to be measured
In some cases, the photoconductive gate is not prefabricated on the I-chip in advance, but in that case, there was a problem in that it was impossible to probe fine wiring because the electrode pads that made electrical contact were large. Moreover, even if the contact electrode could be made minute, it was not possible to accurately probe the contact electrode for fine wiring of submicron width.

As described above, in order to overcome the difficulty that there is no general method for measuring fine wiring of submicron width at high speed, the inventors of the present invention have developed a small conductive wire whose tip diameter is about 0.1 μm. We proposed a probe equipped with a sex needle, a conductive cantilever, and an electro-optic crystal, and a voltage measuring device using them. (See Japanese Patent No. 03-324696 Specification)

[0012]

However, according to the disclosure of 91P11279, a semiconductor laser is used as a light source for voltage measurement. It is possible that the signal waveform inside the VLSI can be measured in less than 1/10 of the time of the equipment using an electron beam, but it still takes tens to hundreds of seconds to measure one waveform. is there.

According to the disclosure, AFM (Atomic Force)
Light reflected by the cantilever and light reflected by the electro-optic crystal (voltage measurement) used for Microscopy operation
Since it is necessary to measure each of the two lights of the above by separate detectors, there is a problem that the device configuration becomes complicated and large.

Further, in general, the probe device may require a function of applying a voltage to the wiring in addition to the voltage measurement of the wiring, but the disclosed probe device does not have the function.

Therefore, an object of the present invention is to provide a probe device capable of measuring fine wiring of submicron width at high speed without increasing the size of the device and having a function of applying a voltage to the wiring. And

[0016]

The above problems can be solved by the following device. That is, a conductive needle capable of contacting the wiring, a conductive cantilever connected to the conductive needle, a photoconductor film forming a photoconductive gate portion, and a part of the photoconductor film are contacted. The first to connect to the cantilever
And a second conductor facing the first conductor and contacting a part of the photoconductor film.

FIG. 1 is a diagram for explaining the principle of the present invention. In the figure, 1 is a conductive needle, 2 is a conductive cantilever, 3 is a photoconductive gate, 4, 5 are conductors, 6 is a substrate, 7 is wiring, 8, 9
Is the incident beam and 10 is the reflected beam.

The structure and function of the conductive needle 1 and the conductive cantilever 2 are the same as those disclosed in 91P11279. Using the atomic force acting between the conductive needle 1 and the surface of the wiring 7 (acting at a distance of the order of 1 nm to 10 nm),
High resolution of sample surface height (sub nm to 1 nm
Can be measured).

Further, based on the function of finely moving the sample in the vertical direction with respect to the wiring contact portion (in the order of nm), and the bending of the cantilever by feedback based on the measured bending of the cantilever (conductive needle 1 and wiring surface It has a function to keep (distance) constant. In addition, it also has a function to scan the sample horizontally with respect to the wiring contact area in two-dimensional steps with minute increments (nm order).

With the above functions, the sample surface nm ~ μm
It is possible to measure the minute shape of. It is also possible to fix the sample and scan the entire voltage measuring device two-dimensionally.

Further, it is possible to obtain a concavo-convex image (or line profile) due to the wiring on the sample surface. The wiring 7 to be measured is found by changing the scanning position while observing this. After moving the probe to the target point on the target wiring (for example, the center of the wiring width),
By bringing the conductive needle 1 into contact with the target point on the wiring,
Wire 7 to conductive needle 1 (and therefore conductive cantilever 2)
To conduct. The photoconductive gate 3 formed on the substrate 6 of the probe is a conductive cantilever 2 and thus a conductive needle.
Connected with 1.

With this structure, in the voltage measurement, the time required to measure the voltage signal waveform of the wiring with a constant resolution can be shortened and the apparatus can be further improved, as compared with the case where the electro-optic effect is used. Miniaturization is realized. Further, it is also possible to apply a voltage (continuous / pulse) to the fine wiring with which the conductive needle 1 is in contact.

[0023]

In the present invention, the photoconductive gate is connected to the conductive cantilever having the conductive microneedles for realizing the AFM function.

Since the photoconductive gate has a higher sensitivity than the electro-optical effect, it enables measurement in a short time. Also, the optical system for detecting the reflected light is not required as in the case of using the electro-optical effect to measure the voltage by detecting the current in the gate 0N state (proportional to the voltage). Therefore, the device can be simplified and downsized.

Furthermore, by applying a bias voltage to the photoconductive gate and irradiating it with laser light (continuous, pulse), it is possible to apply a voltage (continuous, pulse) to the fine wiring.

[0026]

Embodiments Four embodiments of the present invention will be described with reference to the drawings. In the figure, the same reference numerals represent the same members and the same devices. First Example FIG. 2 is a diagram schematically showing the structure of a probe according to the first example. Figure 2 (a) shows the plan view and Figure 2 (b) shows the elevation view. A photoconductive gate 3 made of photoconductive material such as ion-irradiated silicon (Si) crystal, amorphous Si, or damaged gallium arsenide crystal is formed on an insulating substrate 6 such as sapphire. Metal electrodes 4, 5 are formed on the top of the parallel gap 15. The width of the electrode is, for example, 50 μm, and the width of the gap 15 is, for example, 10 μm. Also, in order to increase the voltage measurement sensitivity, a gap 13 having a shape as shown in FIG. 2 (c) is possible instead of the parallel gap.

The load of the conductive needle 1 is, for example, 10 ⁻⁸ N, and the spring constant of the conductive cantilever 2 is, for example, 1 N / m. A current detector 11 or a bias power source is connected to the electrode 5 which is not directly connected to the conductive cantilever 2.

FIG. 3 is a diagram schematically showing the device configuration of an example in which the probe according to the first embodiment is applied to a wiring inspection device. In the figure, 21 is the XYZ stage, 22 is the XYZ stage.
Z actuator, 23 is a position detection light receiver, 24 is a wiring detection control unit, 25 is a voltage waveform measurement control unit, 26 is an LSI drive device, 27 is a photoconductive gate irradiation laser, 28 is a conductive cantilever irradiation laser, 29 is an optical fiber, 30 is an LSI
It's a chip.

The laser beam 9 is made incident on the conductive cantilever 2 by the laser 28 through the fiber 29. Position detection receiver 23 for reflected light 10 from the conductive cantilever 2
Wiring on the surface of the LSI 30 is detected by the AFM function that controls the XYZ actuator 22 by the wiring detection control unit 24.
An uneven image (or line profile) can be obtained by. The wiring 7 to be measured is found by changing the scanning position while observing this. After moving the probe to the target point on the wire of interest (for example, the center of the wire width), bring the conductive needle 1 into contact with the target point on the wire to move the wire 7 to the conductive needle 1 (thus Conductive cantilever 2). Probe board 6
The photoconductive gate 3 formed on is connected to the conductive cantilever 2, and thus the conductive needle 1. In synchronization with the LSI drive device 26 that drives the LSI 30, the laser light pulse 8 is transmitted via the fiber 29 by the laser 27 to the photoconductive gate 3
Incident on. The voltage at the target point is detected by the current detector 11 and stored as data in the voltage waveform measurement control unit. The voltage waveform data is obtained by performing the above operation while scanning the timing of the laser light pulse 8 by the timing control unit 31. Second Embodiment This embodiment is a modification of the first embodiment. FIG. 4 is a schematic diagram for explaining the present embodiment, and FIG. 5 is a diagram schematically showing the structure of the probe. FIG. 5 (a) shows the elevation view and FIG. 5 (b) shows the plan view.

A photoconductive gate 3 and electrodes 4 and 5 are formed on the back surface (the surface opposite to the incident light 8) of a transparent substrate 14 such as sapphire. This structure has an advantage in manufacturing technology that it is not necessary to form the electrode 4 connecting the conductive cantilever 2 and the photoconductive gate 3 also on the side surface of the transparent substrate 14. Third Embodiment In general, the narrower the gap between the electrodes, the higher the voltage measurement sensitivity (and therefore the higher the voltage measurement resolution), but the lower the breakdown voltage at which the photoconductive gate is destroyed by the electric field. Therefore, it is necessary to control the gap between the electrodes in the order of μm in order to form a photoconductive gate with the highest possible sensitivity and withstand voltage. For that purpose, a high resolution exposure apparatus is required.

FIG. 6 is a diagram schematically showing the structure of the probe. FIG. 6 (a) shows the elevation view and FIG. 6 (b) shows the plan view. As shown in the figure, the two electrodes and the photoconductive film are
For example, the transparent substrate 14 has a structure in which the back surface (the surface opposite to the incident light 8) is laminated in the incident light 8 direction. The electrode 5'closer to the substrate is a transparent electrode such as ITO. It is not so difficult to control the thickness of the photoconductive film 3 with submicron accuracy. Therefore, in this structure, the voltage measurement sensitivity and the withstand voltage can be changed depending on the thickness of the photoconductive film 3, so that the voltage measurement sensitivity and the withstand voltage can be controlled with high accuracy without using a high resolution exposure apparatus. Fourth Embodiment This embodiment is a modification of the third embodiment.

FIG. 7 is a diagram schematically showing the structure of the probe. FIG. 7 (a) shows the elevation view and FIG. 7 (b) shows the plan view. As shown in Fig. 7 (a), a transparent cantilever 2'made of a silicon nitride film or a silicon oxide film is formed in place of the conductive cantilever 2, and the photoconductive gate 3, the electrode 4, and the transparent electrode 5 are further formed thereon. 'Is a formed structure.

In this embodiment, there is an advantage that the transparent cantilever 2 ′ having a small spring constant can be formed by controlling the silicon nitride film or the silicon oxide film.

[0034]

EFFECTS OF THE INVENTION The present invention provides a probe device capable of measuring the voltage of a fine wiring of submicron width at high speed without increasing the size of the device and having a function of applying a voltage to the wiring. . As a result, it greatly contributes to the high efficiency of inspection in the operating state of high-speed and highly integrated ICs.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a diagram schematically showing the structure of the probe of the first embodiment.

FIG. 3 is a diagram schematically showing a device configuration of an example in which the probe according to the first embodiment is applied to a wiring inspection device.

FIG. 4 is a schematic diagram illustrating a second embodiment.

FIG. 5 is a diagram schematically showing the structure of the probe of the second embodiment.

FIG. 6 is a diagram schematically showing the structure of the probe of the third embodiment.

FIG. 7 is a diagram schematically showing the structure of the probe of the fourth embodiment.

[Explanation of symbols]

 1 conductive needle 2 conductive cantilever 2'transparent cantilever 3 photoconductive gate 4, 5 conductive electrode 5'transparent electrode 6 substrate 7 wiring 8, 9 incident light 10 reflected light 11 current detector 12 bias power supply 13 gap 14 transparent substrate 15 Parallel gap 21 XYZ stage 22 XYZ actuator 23 Position detection light receiver 24 Wiring detection control unit 25 Voltage waveform measurement control unit 26 LSI driving device 27 Photoconductive gate irradiation laser 28 Conductive cantilever irradiation laser 29 Optical fiber 30 LSI chip 31 Timing controller

Claims (6)

[Claims] 1. Contacting fine wiring formed on a plane,
In a probe device that measures the applied voltage,
A conductive needle capable of contacting the wiring, a conductive cantilever connected to the conductive needle, a photoconductive film forming a photoconductive gate portion, and a part of the photoconductive film, A probe device comprising: a first conductor connected to the cantilever; and a second conductor facing the first conductor and contacting a part of the photoconductor film. . 2. The probe according to claim 1, wherein the first conductor and the second conductor are formed to face each other on the photoconductor film formed on a substrate. apparatus. 3. The probe according to claim 2, wherein the photoconductor film, the first conductor, and the second conductor are formed only on one surface of a transparent substrate. apparatus. 4. The photoconductive gate portion has a laminated structure of the first conductor, the photoconductor film, and the second conductor, and one conductor is a transparent conductor. The probe device according to claim 1, wherein: 5. The probe device according to claim 1, wherein the conductive cantilever includes a transparent insulating film and a conductive film. 6. A wiring inspection device for inspecting an IC wiring in an operating state, wherein a conductive needle is moved to a specific point position on the wiring, and the conductive needle is brought into contact with a specific point on the wiring.
A conductive cantilever connected to the conductive needle, a photoconductor film forming a photoconductive gate portion, and a first conductor contacting a part of the photoconductor film and connected to the cantilever,
A second conductor facing the first conductor and contacting a part of the photoconductor film; a light irradiating device for irradiating the conductive gate in conjunction with an IC driving device; 2. A wiring inspection apparatus comprising: a switch unit connected to the second conductor; and a current detection unit and a bias power supply unit which are switched by the switch unit.