JPH09326425A - Method of defect inspection and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a failure through the measurement of a local electrical characteristics of microstructure devices. SOLUTION: By observing with scanning electronic microscope and with the aid of probe movement mechanism 14, 15, 16, and 17 controlled by the probe movement control circuit 18, a plurality of sharp tipped probe 1, 2, 3, and 4 are made to approach until their contact current saturate and contacted tightly the sample electrodes 5, 6, 7, and 8 respectively. When the contact of all probes used for the measurement are completed, the current-voltage characteristics among the probes is measured by the measuring circuit of electrical characteristics 19 and the local electrical characteristics of the device is obtained. Since the specific local position of the device is directly probed by the probe, the defective position is easily identified.

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 the performance of an electronic element or analyzing a failure.

[0002]

2. Description of the Related Art Conventionally, the characteristics of electronic devices have been evaluated using a prober or an electron beam tester. For example, the electron beam tester method is described in Journal of Applied Physics, No. 63.
Volumes, No. 6, pp. 608-611, examples of which are described respectively.

In a conventionally known prober, a probe is brought into contact with a position where the electrical characteristics of an inspection sample are to be measured while observing with an optical microscope in the atmosphere. With this device, 2
It is possible to use a book-like probe, which makes it possible to evaluate device characteristics such as current-voltage characteristics of a specific portion of the circuit. Further, in this apparatus, it is possible to perform processing such as wiring cutting with a YAG laser, and it is possible to measure characteristics by isolating part of the element.

The electron beam tester obtains the wiring potential of the electronic element in the operating state from the contrast of the scanning electron microscope image. This is because it is possible to obtain a potential contrast with an accuracy of 10 mV by using an energy filter, so it is possible to detect a failure and identify its location by comparing it with the reference data obtained from a non-defective electronic element. it can.

[0005]

In the first method (prober) described above, since an optical microscope is used for observing a sample, there is a limit in observing submicron wiring, and an electronic element of 0.1
When the line width becomes μm, it becomes impossible to observe, so it becomes impossible to contact the probe with such fine wiring. Also,
Since a YAG laser is used for processing electronic elements,
The laser wavelength (0.355μ
m) becomes difficult. Also, when the wiring of the electronic element to be contacted becomes finer such as 0.1 μm, it is necessary to make the tip of the probe thin in order to make contact with this,
There is a problem in that the probe is easily damaged, and the wiring is fine, so that the probe is easily broken. For this reason, in order to make reliable contact without damaging the probe or the wiring, the contact method requires much higher accuracy than the conventional method. Further, when a large contact area can be taken as in the conventional case, the relative drift between the probe and the sample did not pose a problem, but with the miniaturization of the contact area, the change in the contact state due to the drift is large. It becomes a problem. However, the conventional method does not take such measures against drift. Further, in the conventional method, since the probe and the wiring are contacted in the atmosphere, if the contact area becomes finer in the future,
Contact resistance due to oxide films on the wiring and the tip of the probe and contaminants becomes a big problem. In addition, not only cutting and peeling processing for measuring the electrical characteristics of the element, but also metal processing such as pad formation and wiring formation is required. It was not possible with the conventional method that uses the processing described in 1.

On the other hand, in the second method (electron beam tester), since the electron beam is used, surface potential information can be obtained with high surface resolution, but the input pattern given to the circuit is from the input terminal of the electronic element. Therefore, it was not possible to apply an arbitrary voltage to a specific local position. For this reason, it was not possible to measure the electrical characteristics of only a specific position, such as current-voltage characteristics. Therefore, it is necessary to try many test patterns for failure analysis by the electron beam tester, and it is difficult to identify the cause of the failure even if the location can be identified.

[0007]

In order to solve the above-mentioned problems, firstly, electron irradiation is used as a microscopic means for observing a tip of a probe and a specific position in a sample to which the probe is brought into contact. A microscopic means composed of a system or an ion irradiation system and a secondary electron detection system is provided. This microscopic means has a resolution of nm level.

Further, a moving mechanism for positioning and an approaching mechanism are provided to bring the tip of the probe into contact with the sample. here,
It is necessary to ensure electrical contact between the probe and the sample and prevent damage to the probe and the sample. Therefore, in the present invention, as a contact method, contact confirmation is performed by saturating the contact current between the probe and the sample, and reliable electrical conduction is realized. Here, in order to prevent damage to the probe and the sample, it is necessary to reduce the approach speed at the time of contact, so in the present invention, the position immediately before contact is detected by detecting the tunnel current or the atomic force. , Only the approach speed from that position can be made small. Further, for contact with a place where no contact current flows, such as a gate electrode, contact confirmation by force detection, saturation of effective contact current value by AC bias application, or the like can be used for contact confirmation. Further, in the present invention, accurate contact confirmation can be performed by monitoring the potential of the position on the sample surface where the probe should come into contact. In other words, with a bias applied between the probe and the sample,
When contacting the probe with the sample, if there is contact resistance between the probe and sample, a voltage drop will occur due to this contact resistance, so the sample potential at the position where the probe comes into contact is detected by this voltage drop. It becomes smaller than the needle potential (when the probe side is positive). Therefore, it can be determined that the contact resistance is reduced by making the sample potential at the position where the probe comes into contact equal to the voltage applied to the probe within a certain error range. Thus
Contact confirmation can be performed. In the present invention, a secondary electron detector having an energy filter is used for the sample potential monitor, but since charged particles such as electrons and ions are used for observation in the present invention, the probe and the sample Since the potential of the sample surface changes at the time of contact, this primary charged particle beam is bent by a change in the electric field, which causes a problem that the observation position shifts. In order to correct this, in the present invention, the probe tip position immediately before contact is recorded in the memory as pattern information of the microscopic image, and if the observation position shift occurs due to the probe contact, the observation region is expanded and the pattern information of the memory is stored. Pattern matching is performed to find the position of the tip of the probe and return to high-magnification observation centered on that position.

Further, in order to prevent the change in the contact state due to the relative drift between the probe and the sample, it is necessary to compensate for the shift due to the drift or to shorten the time from the contact to the end of the electrical characteristic measurement. Therefore, as one method, it is considered that the probe has a spring effect to absorb the displacement. Conventionally, there has been a probe having a spring effect in the vertical direction. However, this conventional purpose is to alleviate the impact at the time of contact with the probe, and has not been intended to compensate for minute displacement such as drift. Further, the conventional method does not have a spring effect in the lateral direction (direction parallel to the sample surface), and therefore cannot cope with drift in this direction at all. In the present invention, by using a probe having a spring effect in both the vertical and horizontal directions as the probe, the spring structure portion can absorb the deviation due to the drift in all directions. Also,
Immediately start electrical property measurement by temporarily holding all the probes used for electrical characteristic measurement in the state immediately before contact (tunnel current or atomic force detection state), and then contacting all the probes at the same time. Therefore, the contact time can be shortened and the influence of drift can be minimized.

To solve the problem of contact resistance due to oxide films or contaminants on the wiring or on the tip of the probe which increases with the miniaturization of the contact area between the probe and the sample, in the present invention, the measurement is performed in vacuum. The pollution can be reduced. Further, by irradiating the surface of the probe or the sample with an ion beam, an electron beam, or light before the contact with the probe, it is possible to remove these oxide films, contaminants, and the like.

The electrical characteristics can be obtained by measuring the current-voltage characteristics between the probes brought into contact with the sample. In the present invention, since the probe is used, it is possible to apply a voltage to an arbitrary position on the sample surface, which is not possible with the electron beam tester. Here, the charged particle beam (electron,
Or an ion beam) affects the current-voltage characteristics, it has an irradiation system that can block the charged particle beam only during the measurement of the electrical characteristics. In addition, since the present invention is equipped with a charged particle irradiation system and a secondary electron detection system, by adding an energy filter to this secondary electron detection system, the sample surface potential distribution can be calculated like an electron beam tester. Can be observed. Therefore, it is possible to measure the sample surface potential distribution at that time while applying a voltage to an arbitrary position on the sample surface with the probe.

In the sample processing before the device characteristic measurement, in the present invention, by using the focused ion beam, fine processing of 0.1 μm or less can be performed. Even in the case of electron beam, fine processing is possible by combining with reactive assist gas. Therefore, a part of the electronic element can be isolated, so that the defective position can be easily identified. Further, in the present invention, since the processing is performed in a vacuum, it is possible to deposit a metal film by using a deposition gas and an irradiation beam (ion, electron, or laser). Can be formed. Also, if you want to make a probe contact to the lower layer element or wiring that is not exposed,
Even if the upper surface is not peeled off as in the conventional case, in the present invention, after opening a contact hole to the wiring from the surface,
By filling the holes with metal as described above using the deposition gas and the irradiation beam, electrical contact from the surface becomes possible.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to identify a defective position of an electronic element and measure a local electric characteristic of the electronic element to measure its characteristic. In the present invention, the tip of the probe is brought into contact with a minute region to be brought into contact with the probe while observing with a microscopic device having a resolution on the order of nm such as a scanning electron microscope. Here, accurate contact confirmation is performed by saturation of the contact current. Then, by measuring the current-voltage characteristics between these probes, the local information of the element can be obtained. In this way, the defective position can be identified. Further, by adding a discriminating circuit to this electric characteristic measuring system, it is possible to select good products and defective products.

Specific examples are shown below in <Example 1> to <Example 9>.

<Embodiment 1> FIG. 1 shows the entire system of the present invention. Here, the purpose is to measure the electrical characteristics between the electrodes 5, 6, 7, and 8 by using the four probes 1, 2, 3, and 4. These probes 1, 2, 3, and 4 are 0.1 of the sample 9
It is desirable that the radius of curvature of the tip be 0.1 μm or less so that it can be contacted with a minute region of the μm level. First, the surface of the sample 9 and the probes 1, 2, 3, and 4 are observed with a scanning electron microscope. This scanning electron microscope is composed of an electron source 10, a deflection lens 11, and a secondary electron detector 13.
Is a primary electron beam, and 21 is a secondary electron emitted from the sample surface. While observing in this way, the tips 1, 2, 3, 4
Are moved above the electrodes 5, 6, 7, 8 to be brought into contact with each other. This movement is performed by controlling the probe movement mechanism 14, 15, 16, 17 of each of the probes 1, 2, 3, 4 by the probe movement control circuit 18. Here, in this embodiment, the probe moving mechanisms 14, 15, 16 and 17 use piezoelectric elements having a high positional resolution.

Next, the contact method will be described with reference to FIG. In this figure, only the contact of the probe 1 is taken up for description. What is important in this contact is to make sure that the probe 1 and the electrode 5 are in contact with each other and that the contact between the probe 1 and the electrode 5 is a minimum so as not to damage them. In order not to damage both,
It is necessary to reduce the approach speed of the probe. However, if the approaching speed is reduced as a whole, the problem that the approaching time becomes too long occurs. In order to solve this, it is sufficient to detect the position immediately before the contact, increase the approach speed to this position, and decrease only the approach speed from the immediately preceding position to the contact completion position. For this purpose, a method of detecting the position immediately before contact is required. For example, there is a method of detecting a tunnel current as used in FIG. FIG.
Reference numeral 50 in (a) is a preamplifier for detecting a tunnel current, which can normally detect a current of about pA to nA. Reference numeral 51 denotes a changeover switch, which is a preamplifier 50 for detecting a tunnel current.
And the ammeter 30 for contact current detection are switched. 52, 5
Reference numeral 3 is a switch for switching the closed loop between when the probe approaches and when the electrical characteristics are measured. FIG. 2B is a diagram showing the relationship between the approach distance Zt and the current (tunnel current, contact current) I when the probe 1 is approached. First, the changeover switch 51 is on the preamplifier 50 side, 52 is on the power supply 31 side, and
When 3 is connected to the changeover switch 51 side and a bias is applied between the probe 1 and the sample 9 by the power supply 31 to bring the probe 1 closer to the electrode 5, a tunnel current flows at Z ₅₁ . At this time, the distance between the probe 1 and the electrode 5 is about 1 nm or less. As a result, the position immediately before contact can be detected. However, if the approach is simply stopped at the tunnel current detection position Z ₅₁ , the probe 1 may approach the electrode 5 and come into contact with the electrode 5 due to the response speed of the probe moving mechanism 14 and the creep phenomenon. Therefore, it is better to apply feedback from the probe movement control circuit 18 to the probe moving mechanism 14 so that the tunnel current becomes constant. After that, the changeover switch 51 is connected to the side of the ammeter 30 to reduce the approaching speed and bring the probe 1 closer to the electrode 9. Then, a contact current starts to flow when the probe 1 and the electrode 5 come into contact with each other (Z ₅₂ ). When the probe 1 is moved closer to this state, the contact current I increases as shown in FIG. 5B due to an increase in the contact area. When the contact current I is no longer affected by the change in the contact state, that is, when the contact current is saturated, the contact is considered to be completed, and the probe 1 is moved at the approach distance Z ₅₃ to move the probe shown in FIG. The mechanism 14 is stopped by the control of the probe movement control circuit 18. By doing so, the probe 1 and the electrode 5 can be surely brought into contact with each other.

When the contact of all the probes 1, 2, 3, 4 is completed in this way, the sample 9 and the probe 1 are connected to the electrical characteristic measuring circuit 19 by the changeover switches 52, 53, and the probes 1, 2, The current-voltage characteristic between 3 and 4 is measured. By doing so, local electrical characteristics of the device can be obtained.

FIG. 3A shows an example of probe contact when a MOS device is used as a measurement sample. Here, three probes 1,
Only two or three are used and brought into contact with the source electrode 35, the gate electrode 36, and the drain electrode 37, respectively. For example, when measuring output characteristics, the source electrode 3 is moved by the probe 1.
5 to the ground level, the probe 2 swings the voltage V _G of the gate electrode 36 as a parameter, and the probe 3
The drain voltage V applied to the drain electrode 37 by
By measuring and _D, between the probe 1 and 3 (source, drain) of the relationship between the drain current I _D flowing through, it is possible to obtain an output characteristic of the MOS. For example, if this is an n-channel MOS and is a non-defective product, the characteristics shown in FIG. 3B will be measured.

In this way, the defective position can be identified by bringing the probe into contact with the sample and comparing the local element characteristics measured from that portion between the good product and the defective product. In this method, the electrical characteristics can be obtained by directly applying a voltage to the position considered to be defective, so the defective position can be identified by comparing with the method of inputting a test pattern from the input terminal of the electronic element to identify the defective position. Is easy, and the defective state can be measured in detail.

<Embodiment 2> In the present embodiment, 2 from the sample is used.
A method of obtaining the sample surface information by the next electron will be described. Although only the probe 1 is shown here for simplification, a plurality of probes is actually used as shown in FIG. FIG.
100 is an energy filter, and 101 is a potential measuring device. Here, first, a contact method using this detection system will be described. The contact confirmation by the contact current saturation described with reference to FIG. 2 in the first embodiment is a contact method for the purpose of stabilizing the contact state, and lowers the contact resistance to the error range with respect to the element characteristics. I do not guarantee that.
That is, with the contact method of FIG. 2, it is possible to relatively compare the characteristics of a non-defective product and a defective product to detect defects, but it is clear whether the obtained device characteristics are absolute or not. Can't judge. Therefore, in order to perform the measurement in which the absolute characteristics are important, it is necessary to use the contact confirmation as described with reference to FIG. 4 in this embodiment. Here, only the contact of the probe 1 will be extracted and described. First, the primary electron beam 20 emitted from the electron source 10 is applied to the electrode 5 to be contacted by the probe 1 by the deflection lens 11. At this time, the secondary electrons 21 emitted from the electrode 5 are transferred to the energy filter 1
00 through the secondary electron detector 13. The potential V of the electrode 5 can be known by the potential measuring device 101 from the energy distribution information of the secondary electrons. For example, when the probe 1 is biased with a potential Vt to be brought close to it, the relationship between the approach distance Zt and the potential V of the electrode 5 is as shown in FIG. 4B.
Z ₁₀₁ corresponds to the position where the probe 1 comes into contact with the electrode 5, but since the voltage drop due to contact resistance is large in this vicinity, the potential has not yet risen to the probe voltage Vt, and the contact is still poor. It shows that the contact resistance is in a state that cannot be ignored with respect to the element resistance. That is, in order to make a reliable contact, the potential of the electrode 5 is set to a certain error level V
When the position reaches the position Z ₁₀₂ which is equal to or more than t ', the contact is completed and the approach is stopped. This means that when the voltage drop due to the contact resistance has an error below a negligible level (for example, 1%), it is judged that the contact is completed. In this way, it becomes possible to perform reliable contact confirmation.

Further, by using the apparatus of FIG. 4A, the wiring potential can be monitored by the energy filter 100 like the conventional electron beam tester. Therefore, the sample surface potential distribution obtained by this can be observed. It is also possible to use this for failure analysis. However,
Unlike the conventional electron beam tester, in this case, since the probe is provided, it is possible to obtain the sample surface potential distribution while locally applying a voltage at the probe, which facilitates defective position identification.

By the way, when the probe and the sample come into contact with each other, the following problems occur in the observation. Although the electron beam is used in the present embodiment, the biased probe 1 comes into contact with the electrode 5 and the electrode potential V changes as described with reference to FIG. The primary electron beam 110 is bent, and the displacement of the observed image occurs.
In this case, if the contact of the other probes 2, 3 and 4 is not completed, the contact position of these probes cannot be observed and correct contact cannot be performed. Further, as described above, this image shift becomes fatal when performing the failure analysis by the wiring potential monitor. Therefore, a method for correcting this image shift is necessary. This will be described with reference to FIG. Reference numeral 131 in FIG. 6A is an area to be originally observed, and 1
Reference numeral 32 is an observation region that is displaced due to the contact of the probe 1 with the electrode 5. 6B to 6G are observed images. FIG. 6 (b)
Is a low-magnification observation image immediately before the probe 1 comes into contact with the electrode 5. The observation image is stored in the image memory 133 and the pattern of the probe is recognized. Next, high magnification observation is performed in order to bring the probe 1 into accurate contact with the electrode 5 (FIG. 6C). This figure 6
The observation area of (c) corresponds to the area 131 of FIG.
Here, when the probe 1 comes into contact with the electrode 5, the observation area becomes
Since it shifts like the region 132 in (a), the observed image is shown in FIG.
As in (d), neither the probe nor the electrode can be seen. Therefore, by the image shift correction circuit 130 of FIG. 6A, the deflection lens 11 switches the primary electron beam 20 to the wide area scan,
Observe (Fig. 6 (e)). Here, the initial image (FIG. 6B) stored in the image memory 133 and the current image (FIG. 6E) are collated by the image shift correction circuit 130, and the initial center position is determined from the pattern recognition. An offset is added to the deflection lens 11 by the image shift correction circuit 130 by the amount of the calculated shift of the center position, and the primary electron beam 20
Is corrected and returned to the initial center position (FIG. 6 (f)). In this way, the image shift can be corrected by returning to the high-magnification observation centering on the corrected position (FIG. 6 (g)).

In the above method, the capture of the probe shape by pattern recognition was used, but a method of simply capturing the probe shape will be described with reference to FIG. A power source 102 applies a voltage between the probe 1 and the sample 9 and can be modulated. That is, when the probe 1 is not in contact with the sample yet, the potential of the probe 1 changes due to the modulation by the power source 102, but the surface potential of the sample 9 does not change. Therefore, when an observation image of secondary electrons is obtained during this modulation, only the probe contrast changes as shown in FIGS. 7B and 7C. In this way, the probe shape can be stored in the image memory 133.

In the apparatus used in this embodiment, since the secondary electron detection system has an energy filter, it is possible to confirm the probe contact accurately by monitoring the potential of the contact position.
Further, it is possible to perform defect analysis by measuring the sample surface potential distribution in combination with voltage application by a probe, which facilitates defect position identification. Further, the image shift correction makes it possible to keep the observation location constant.

<Embodiment 3> In this embodiment, an apparatus having a processing means for processing a measurement sample before the electrical characteristic measurement (probe contact) will be described with reference to FIG. In this device,
Instead of the electron irradiation system of FIG. 1, an ion beam irradiation system composed of an ion source 150, electrostatic lenses 151 and 153, and a deflector 152 is provided, and an ion beam 154 is applied to the sample 9.
Can be irradiated.

In order to detect defects by using the LSI as a measurement sample, it is not possible to obtain the electrical characteristics of that portion by merely bringing the probe into contact with the wiring or electrode to be measured. This is because these wirings form closed loops at various places and include electrical characteristics other than the portion to be actually measured (for example, one MOSFET). Therefore, in order to obtain the electrical characteristics of only the portion to be actually measured, it is necessary to isolate that portion. For this reason, a sample processing means is required. An apparatus shown in FIG. 8 has an ion beam irradiation system added as the processing means. In this case, the ion beam 154 is used not only for processing but also as an observation means. That is,
By scanning the ion beam 154 on the surface of the sample 9 and detecting the secondary electrons emitted from the sample 9 by the secondary electron detector 13, it can be observed as a so-called scanning ion microscope. Of course, in this case, in order to prevent the surface of the sample 9 from being damaged as much as possible, it is necessary to reduce the amount of ion current more than in the case of processing. Even if the damage due to the ion beam is still a problem, the electron irradiation system is removed and the ion irradiation system is introduced in FIG.
An electron irradiation system can also be provided for observation with an electron beam.

From here, FIG. 9 shows the types of sample processing.
This will be described below. When it is desired to measure the electrical characteristics of the element 160 of FIG. 9A, the wiring connected to the element 160, for example, 161 is connected to the ion beam 154 so that the measurement portion does not form a closed loop at other places as described above. The trench 162 is used to cut off the circuit so that only this element 160 is isolated. Thus, by measuring the electrical characteristics with the probe, it is possible to obtain the characteristics of only the element 160. In addition, the element to be measured does not always appear on the sample surface. For example, there may be a case where a protective film is formed, or a case where the protective film is buried in a lower layer. However, since the probe cannot be brought into contact with this state as it is, in this case, as shown in FIG. 9B, the layer above the element 163 to be measured is covered with the ion beam 15
It is necessary to grind away with 4 and process so that the probe can contact the element 163. When it is difficult to directly contact the probe with the wiring, as shown in FIG. 9C, the ion beam 154 is irradiated while introducing the deposition gas 166 by the gas nozzle 165 to irradiate the metal film. Since it can be formed, it is possible to form the probe contact pad 164 that can be electrically connected to the wiring 167. In addition, FIG.
If it is desired to measure the lower layer device 163 as shown in FIG. 9D without removing the wide area as shown in FIG. 9B, the wiring 168 is contacted with the ion beam 154 to the contact hole 16
9 is opened, and as in FIG. 9C, the contact hole 169 is filled with the metal film 170 as shown in FIG. 9D ′, and the probe is brought into contact with the embedded metal portion 170, so that the characteristics of the element 163 are improved. It is also possible to measure

Although the processing by the ion beam is described here, it is also possible to use a laser for the processing. However, in this case, the processing accuracy determined by the laser wavelength (for example,
The limit is about 0.4 μm for a YAG laser. Therefore, the focused ion beam is more effective for fine processing. Further, if the reactive assist gas is used, the processing speed can be increased even in the case of an ion beam or a laser beam, and it becomes possible to perform processing with an electron beam.

Further, in FIG. 8, the device having the processing function has been described, but the processing means and the electric characteristic measuring device by the probe do not necessarily have to be one device, and another processing device is used as shown in FIG. It is also possible to perform the processing as shown and perform the measurement with the defect inspection apparatus shown in FIG.

By performing the sample processing as described in the present embodiment, it is possible to measure the electrical characteristics of only a specific portion of the device and narrow down the defective position of the device, so that the defect identification becomes easy.

<Embodiment 4> In this embodiment, a cleaning process before contacting a probe with a sample will be described with reference to FIG. Most of the poor contact between the probe and the sample is caused by mixing of an insulating substance between them. For example, oxide films and contaminants cause this. In the conventional tester, since the probe is brought into contact with a large electrode such as a bonding pad, the contact area can be made large, and therefore these insulating substances do not cause much problems. However, when the wiring becomes minute like the current element and it becomes necessary to directly contact the probe with this wiring, the contact area cannot be made large. It will have an impact. Unlike the prior art, the present invention measures electrical characteristics in a vacuum. Therefore, if the surface of the sample or the probe is cleaned before the contact with the probe, such contact failure can be suppressed.

For example, as shown in FIG.
When the contaminant 172 is present on the wiring 167 to which the probe is to be contacted to measure the ion beam, the ion beam 154 is irradiated by an apparatus as shown in FIG.
It is possible to remove contaminants as in 3.

Further, as shown in FIG. 10B, also in the case of contaminants on the surface of the probe, the ion beam 1 is used as in the case of FIG. 10A.
By irradiating 54, it can be removed as in 175. Further, in the case of the probe, when various samples are measured, there is a possibility that the sample substance measured previously is attached, and therefore it is necessary to clean the probe every time by this method.

The cleaning can be performed not only by ion beam but also by irradiation with electron beam or light.

In this embodiment, by cleaning in vacuum, the probe and sample can be brought into reliable contact with each other, and accurate device characteristics can be measured.

<Embodiment 5> In the electric characteristic measuring method using the probe, the most important thing is to surely maintain the contact between the probe and the sample. However, in the usual case, there is a thermal or mechanical drift between the probe and the sample,
Since the relative position changes, it is difficult to keep the contact state constant. To compensate for this, for example, a probe having a spring effect as shown in FIG. 11 may be used. With the probe 40 in contact with the electrode 43, the probe holder 42
Even if the relative position of the electrode 43 and the electrode 43 changes by Δx as shown in FIG. 11A to FIG. 11B, the U-shaped spring structure portion 4
1 absorbs this relative displacement due to the spring effect, and good contact can be maintained. In addition, the probes 44 and 45 having the shapes shown in FIGS. 4C and 4D can similarly absorb the drift by the spring structure portions 46 and 47. in this case,
Since the tip of the probe 40 and the electrode 43 need to have a frictional force, the spring structure portion 41 is made to contact with each other while being compressed by a small force. FIG. 12 shows the relationship between the probe approach distance Zt and the contact current Ic flowing between the probe samples. In the contact method up to the above, the position Z where the contact current is saturated
_{Although the} contact of ₂₃ is completed, this spring probe further approaches Z ₂₄ so that the tip of the probe 40 and the electrode 43 have a frictional force. This probe stop position Z ₂₄ is, of course,
It is necessary that the probe 1 and the electrode 4 are not damaged.
In the case of this spring probe, since it has a spring effect in the vertical direction as well, compared to a probe that does not have a spring effect, the approach area where the probe, sample, etc. are not damaged is wider, so the setting of Z ₂₄ is set. Is easy. Also, when estimated from the time required for measurement and the drift velocity, the displacement distance Δx is at most about 1 μm,
The spring structure portion 41 can be sufficiently deformed by elastic deformation. Also,
Since this spring structure portion 43 can also absorb the drift in the direction perpendicular to the sample surface, the contact state can be kept constant.

According to this embodiment, the change in relative position due to the drift of the probe and the sample can be absorbed by the spring structure, and good contact can be maintained.

<Embodiment 6> Since an electron beam is used as the observation means in the above embodiment, the irradiated electrons are absorbed by the electrodes and the probe. It does not matter if the element current flowing in the measurement of the voltage-current characteristics between the probes is large enough to ignore this electron beam current, but if the element current is small and the electron beam current cannot be ignored, this observation It is necessary to block the electron beam for. In this case,
A blanking electrode 140 and a shield plate 141 may be added to the primary electron beam irradiation system as shown in FIG. That is, at the time of observation for contacting with the probe, the primary electron beam 20 is passed through without operating the blanking electrode 140 as shown in FIG.
As shown in (b), a voltage is applied to the blanking electrode 140 to bend the primary electron beam 20 so that it is shielded by the shield plate 141.

According to this embodiment, correct electric characteristics can be obtained without being affected by electron irradiation.

<Embodiment 7> In the present embodiment, a method will be described in which even if an image shift occurs when the probe comes into contact as shown in the second embodiment, the probe is surely brought into contact without depending on the image shift correction. This contact method is shown in FIG. Here, for the sake of simplicity, only two probes 1 and 2 are extracted. Initially, the probe needles 1 and 2 are separated from the electrodes 5 and 6 to be in contact with each other (FIG. 14A). First, the probe 1 is brought close to the tunnel current detection state (FIG. 14B). Here, the probe 1 is kept in a feedback control state by a constant tunnel current. Next, the probe 2 is moved closer to the tunnel current detection state (FIG. 14C). After keeping both of them in the tunnel state in this way, the two probes 1 and 2 are simultaneously approached and brought into contact with the electrodes 5 and 6, respectively. As a result, even if the observation images are displaced and the contact positions of the tips of the probes 1 and 2 and the electrodes 5 and 6 are no longer visible, they can be correctly contacted. Although the case of using two probes has been described here, even when using more than one probe, all the probes are once kept in a tunnel state, and then all the probes are brought close to each other to make contact. By doing so, it is possible to make a correct contact without being affected by the image movement as well.

Further, in this case, since all the probes are brought into contact with each other at the same time, the time from the probe contact to the measurement of the electrical characteristics can be shortened. Therefore, the contact state due to the drift as described in the sixth embodiment can be achieved. The advantage is that changes in

According to this embodiment, since all the probes are brought into contact with each other at the same time, they can be brought into contact with each other without being affected by the image shift of the observed image, and the influence of drift can be suppressed.

<Embodiment 8> In Embodiment 1, the tunnel current detection is used as the position just before the contact, but as described in this embodiment, the position immediately before the contact is detected between the tip of the probe 1 and the electrode 5. There is also a method that uses the atomic force that acts on. Figure 15 (a)
60 is a cantilever for detecting an atomic force, and the voltmeter 64 detects the piezoelectric electromotive force of the piezoelectric elements 62 and 63 which receives a force due to the deformation of the cantilever 60 due to the atomic force. That is, from the electromotive force measured by the voltmeter 64, the probe 1
The atomic force between the electrode and the electrode 5 can be known. FIG.
(b) is the approach distance Zt when the probe 1 is approached and the probe 1
FIG. 6 is a diagram showing a relationship of an interatomic force Fa acting between the electrode 5 and the electrode 5. First, when the changeover switch 65 is connected to the voltmeter 64 side and the probe 1 is moved closer to the electrode 5, the atomic force Fa increases rapidly from Z ₆₁ . Here, when a certain force F ₆₂ is reached, the approach is stopped at Z ₆₂ . As a result, the position immediately before contact can be detected. However, the atomic force detection position Z
If the approach is simply stopped at ₆₂ , the probe 1 may approach the electrode 5 and come into contact with the electrode 5 due to the response speed of the probe moving mechanism 14 and the creep phenomenon, as described in FIG. Therefore, it is better to apply feedback from the probe movement control circuit 18 to the probe moving mechanism 14 so that the atomic force becomes constant at F ₆₂ . After that, the changeover switch 65 is connected to the side of the ammeter 30 to reduce the approaching speed so that the probe 1 approaches the electrode 5. FIG. 15C is a diagram showing the relationship between the approach distance Zt and the contact current Ic when the probe 1 is approached. Thereafter, the same as described in FIG. 2, the position Z ₆₄ that the probe 1 and the electrode 5 is in contact with Z _63, the contact current is saturated
Stops the approach of the probe 1 and completes the contact.

In the contact method of the present embodiment, even if the tip of the probe accidentally approaches the insulator, since the immediately preceding position detection by the atomic force is used, the tip of the probe is not damaged.

<Embodiment 9> As described in the above embodiments, the contact current does not always flow through the electrodes or the like to be contacted. For example, if the electrode is an electrode such as a gate, the contact current cannot be detected because it is basically insulated from the sample substrate. In this case, the contact method as described below is used.

Even through an insulator, an AC current can be passed by applying an AC bias. A method using this AC bias application will be described with reference to FIG. First, an AC voltage is applied between the probe 1 and the sample 9 by the AC power supply 80, and the effective value of the AC current flowing by contact is measured by the ammeter 30 (FIG. 16A). At this time,
FIG. 16B shows the relationship between the approach distance Zt and the contact current effective value Ic. When the approach distance is Z ₈₁ , the probe 1 and the electrode 5 come into contact with each other, and when the approach distance is Z ₈₂ , the current flows. Ic is saturated. With this saturation as contact confirmation, the probe movement control circuit 18 stops the probe movement mechanism 14 by the approach distance Z ₈₂ . In this way, the contact can be completed. When using this alternating current, it is also possible to make contact via tunneling current detection.

Further, as shown in FIG. 17, the contact can be confirmed by using the force acting between the probe 1 and the electrode 5 instead of the contact current. In this case, unlike the case of measuring the atomic force in FIG. 15, the leaf spring 90 detects the force due to the contact, so it is necessary to measure a force sufficiently larger than the nN order force normally used for the atomic force measurement. 15
A cantilever having a higher rigidity than the cantilever 60 of (a) is used. When the probe 1 is approached in this way, the relationship between the approach distance Zt and the force F acting between the probe 1 and the electrode 5 becomes as shown in FIG. 17 (b), so that at a specific force F _91. Contact can be made by stopping the probe moving mechanism 14 according to a command from the probe movement control circuit 18. Where this contact force F
Is determined by the shape of the tip of the probe, the material (strength) of the probe tip, the size of the contact electrode, the material of the contact electrode, and the like. For example,
Below Fmin in FIG. 17B, there are problems that the contact is weak, the contact resistance is large, and the ohmic contact is not established. Further, if the force exceeds Fmax, problems such as breakage of the probe and collapse of the wiring occur. In other words, in order to make reliable contact, Fmin, Fmax
It is necessary to approach the distances Zmin and Zmax corresponding to.

According to this embodiment, the probe can be properly brought into contact with an electrode such as a gate electrode via an insulator.

[0049]

EFFECTS OF THE INVENTION According to the present invention, since it has a microscopic means by high-resolution charged particle irradiation and a probe moving mechanism having a high positional accuracy, it is possible to set an arbitrary position even in an electronic device having a fine structure of 0.1 μm or less. Since the probe can be brought into contact with, the electrical characteristics at any position can be measured.
In addition, since accurate contact can be performed by using contact confirmation or the like by bringing the probe close until the contact current is saturated through detection immediately before contact by tunnel current or the like, accurate element characteristics can be measured. Further, since the contaminants and the like on the probe and the sample surface can be removed by the cleaning device using the ions in vacuum, the element characteristics can be accurately measured. Further, in the processing using an ion beam or the like, fine processing of 0.1 μm or less is possible, and the specific position of the electronic element can be isolated, so that the defective position can be easily identified. Further, in the present invention, since the processing is performed in a vacuum, it is possible to deposit a metal film by using a deposition gas and an ion beam, and the electrode pad formation facilitates probe contact,
Further, by forming the contact hole, it is possible to make electrical contact with the lower layer wiring. Therefore, it becomes possible to measure the local electrical characteristics inside the electronic element.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a probe current detection system.

FIG. 3 is a diagram showing an example of measurement with an actual device.

FIG. 4 is a diagram showing a sample potential detection system.

FIG. 5 is a diagram showing an electron beam that is bent by a change in sample potential due to contact with a probe.

FIG. 6 is a diagram showing a method of correcting an observation image shift.

FIG. 7 is a diagram showing a probe marking method.

FIG. 8 is a diagram showing a defect inspection apparatus having an ion beam irradiation system.

FIG. 9 is a view showing sample processing.

FIG. 10 is a diagram showing a cleaning method.

FIG. 11 is a view showing a probe having a spring effect.

FIG. 12 is a diagram showing a contact state of a spring probe.

FIG. 13 is a diagram showing an electron beam blocking method.

FIG. 14 is a diagram showing a simultaneous contact method for a plurality of probes.

FIG. 15 is a diagram showing a contact method via atomic force detection.

FIG. 16 is a diagram showing a method of contacting a gate electrode by applying an AC voltage.

FIG. 17 is a diagram showing a method of contacting a gate electrode by force detection.

[Explanation of symbols]

1, 2, 3, 4 ... Probe, 5, 6, 7, 8 ... Electrode, 9 ... Sample, 10 ... Electron source, 11 ... Deflection lens, 13 ... Secondary electron detector, 14, 15, 16, 17 ... Probe moving mechanism, 18
... Probe movement control circuit, 19 ... Electrical characteristic measurement circuit, 20 ...
Primary electron beam, 21 ... Secondary electron, 30 ... Ammeter, 31
... power supply, 35 ... source electrode, 36 ... gate electrode, 37 ...
Drain electrode, 40 ... Probe, 41 ... Spring structure part, 42 ...
Probe holder, 44, 45 ... Probes, 46, 47 ... Spring structure part, 50 ... Preamplifier, 51, 52, 53 ... Changeover switch, 60 ... Cantilever, 62, 63 ... Piezoelectric element, 6
4 ... Voltmeter, 65 ... Changeover switch, 70 ... Insulating layer, 7
1 ... Switch, 80 ... AC power supply, 90 ... Leaf spring, 100
... Energy filter, 101 ... Potential measuring device, 102 ...
AC power supply, 110 ... Bent electron beam, 130 ... Image shift correction circuit, 131 ... Initial observation region, 132 ... Image shift observation region, 133 ... Image memory, 140 ... Blanking electrode, 141 ... Shielding plate, 150 ... Ion source, 151
... electrostatic lens, 152 ... deflector, 153 ... electrostatic lens,
154 ... Ion beam, 160 ... Measuring element, 161 ... Wiring, 162 ... Machining groove, 163 ... Lower layer measuring element, 164 ...
Electrode pad, 165 ... Nozzle, 166 ... Depositive gas, 1
67, 168 ... Wiring, 169 ... Contact hole, 17
0 ... Embedded metal part, 172 ... Pollutant, 173 ... Removed pollutant, 174 ... Pollutant, 175 ... Removed pollutant.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01R 31/26 G01R 31/26 J 31/302 H01L 21/304 341D 31/319 G01R 31/28 L H01L 21/3065 R 21/304 341 H01L 21/302 E (72) Inventor Fumiko Arakawa 5-20-1 Kamimizumotocho, Kodaira-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor, Seiichiro Asayama 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd. (72) Inventor Yasuhiro Mitsui 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Inside the Central Research Laboratory of Hitachi Ltd. ( 72) Inventor Hitoshi Nakahara 1-280, Higashi Koikekubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd. (72) Yoshimi Kawanami, Toin love, Kokubunji, Tokyo Kubo chome 280 address Hitachi, Ltd. center within the Institute

Claims (31)

[Claims] 1. A vacuum container, a probe in the vacuum container, a mechanism for moving the probe, a sample stage on which a sample is placed, a charged particle source, and an irradiation means for irradiating a beam from the charged particle source. A defect inspection apparatus having a detector for detecting charged particles from a sample, a means for applying a voltage between the probe and the sample, or a means for applying a voltage between the probes, and a means for measuring an electrical characteristic of the sample. 2. A vacuum container, a probe in the vacuum container, a mechanism for moving the probe, a sample stage on which a sample is placed, a charged particle source, and irradiation means for irradiating a beam from the charged particle source. A detector for detecting charged particles from the sample, a means for applying a voltage between the probe and the sample, or a means for applying a voltage between the probes, a means for measuring the electrical characteristics of the sample, and a measurement value from the measuring means A defect inspection apparatus having a determination means for determining a defect based on the above. 3. The means for measuring the electrical characteristics of the sample comprises:
The defect inspection apparatus according to claim 1, wherein a current-voltage characteristic between an arbitrary combination of the probe and the sample is measured. 4. The means for measuring the electrical characteristics of the sample comprises:
3. The defect inspection device according to claim 1, wherein the potential measurement is performed on the sample surface by a detector having an energy filter for detecting the charged particles. 5. A vacuum container, a probe in the vacuum container, a mechanism for moving the probe, a sample stage on which a sample is placed, a charged particle source, and an irradiation unit for irradiating a beam from the charged particle source. A detector for detecting charged particles from a sample, a mechanism for correcting the irradiation position deviation of the probe or charged particles due to a potential change of the sample, and a voltage application between the probe and the sample or between the probes. A defect inspection apparatus having means for measuring and electrical characteristics of a sample. 6. A mechanism for correcting the irradiation position deviation of the charged particles includes an image memory for recording an observation image immediately before contact between the probe and the sample, and a mechanism for switching to wide area observation when the observation image deviation occurs. The wide area observation image and the observation image recorded in the image memory are collated, the movement amount of the observation image center position is calculated, and the deviation is corrected by moving the observation area by the movement amount. The defect inspection apparatus according to claim 5. 7. In the collation of the observation image, a modulation voltage is applied to the probe, and the probe shape is obtained from a signal synchronized with the modulation from image information detected by a charged particle detector. The defect inspection device according to claim 6. 8. A vacuum container, a probe in the vacuum container, a mechanism for moving the probe, a sample stage on which a sample is placed, a charged particle source, and an irradiation unit for irradiating a beam from the charged particle source. , A detector for detecting charged particles from a sample, a means for applying a voltage between the probe and the sample, or a means for applying a voltage between the probe and the probe by saturating a contact current flowing between the probe and the sample. A defect inspection device having a mechanism for confirming contact between a needle and a sample, and means for measuring the electrical characteristics of the sample. 9. The defect inspection apparatus according to claim 8, wherein the contact confirmation mechanism makes contact between the probe and the sample through detection of a tunnel current flowing between the probe and the sample. 10. In the defect inspection apparatus, different current detectors are used for detecting a contact current and a tunnel current between the probe and the sample, and when the probe and the sample are further brought closer to each other after the tunnel current is detected. The defect inspection apparatus according to claim 9, further comprising a changeover switch for changing over the current detector. 11. In the defect inspection apparatus, a closed circuit is formed between the probe and the sample when a contact current between the probe and the sample is detected, and a closed circuit is formed between the probes when measuring the electrical characteristics of the sample. 11. The defect inspection apparatus according to claim 8, further comprising a changeover switch for changing over so as to form a defect. 12. A vacuum container, a probe and a probe moving mechanism in the vacuum container, a sample stage on which a sample is placed, a charged particle source,
Irradiation means for irradiating a beam from the charged particle source, a detector for detecting charged particles from the sample, and between the probe and the sample,
Alternatively, the means for applying a voltage between the probes and the potential at the position on the surface of the sample to be inspected to contact the probe become the potential defined by the probe applied voltage, so that the probe contacts the sample. A defect inspection device having a confirmation mechanism and means for measuring the electrical characteristics of a sample. 13. A probe for contacting a sample surface with a sample, wherein the probe is in a direction parallel to the sample surface when the probe is in contact with the sample. A probe having a structure in which a change in relative position is absorbed by a spring structure. 14. The defect inspection apparatus according to claim 1, wherein the probe has the probe according to claim 13. 15. The defect inspection apparatus according to claim 14, wherein, as the probe moving mechanism, the probe support portion and the sample are brought closer to each other by a predetermined distance after the probe comes into contact with the sample. 16. The defect inspection apparatus according to claim 1, further comprising a light irradiation unit in the defect inspection apparatus. 17. The defect inspection apparatus according to claim 1, wherein said charged particle irradiation means has a mechanism for interrupting said charged particle beam during the measurement of said electric characteristics. 18. The defect inspection apparatus according to claim 1, wherein in the probe moving mechanism, all of the probes used for the electrical characteristics are brought into contact with the sample surface at the same time. 19. The defect inspection apparatus according to claim 1, further comprising a mechanism for confirming contact between the probe and the sample by detecting a force acting between the probe and the sample. Defective inspection device. 20. In the defect inspection apparatus, an AC voltage is applied between the probe and the sample to saturate an effective value of a contact current flowing between the probe and the sample to confirm contact between the probe and the sample. The defect inspection apparatus according to claim 1, further comprising a mechanism for performing the inspection. 21. The contact confirmation mechanism makes contact between the probe and the sample through detection of an atomic force acting between the probe and the sample. Defective inspection device. 22. The probe moving mechanism further brings the probe and the sample closer to each other by 1 nm or more from a detection position of a tunnel current flowing between the probe and the sample.
~ The defect inspection device according to 7. 23. In the probe, the radius of curvature of the tip of the probe is 100 nm or less.
Defect inspection device described. 24. A fine movement mechanism including a piezoelectric element is provided in the probe movement mechanism.
Defect inspection device described. 25. Using a charged particle beam or a laser, cutting a circuit of a sample, forming a wiring, burying a trench, forming an electrode pad, or removing a protective layer,
Alternatively, after removing the upper layer of the inspection element, the probe is brought into contact with the sample while observing the sample by using a microscopic means having a charged particle irradiation system, and between the probe and the sample, or between the probes. A defect inspection method that evaluates the device characteristics of a sample by measuring the electrical characteristics of. 26. Using a charged particle beam or a laser, cutting a circuit of a sample, forming a wiring, filling a trench, forming an electrode pad, or removing a protective layer,
Alternatively, after removing the upper layer of the inspection element, the probe is brought into contact with the sample while observing the sample by using a microscopic means having a charged particle irradiation system, and between the probe and the sample, or between the probes. A defect inspection method for evaluating device characteristics of a sample from information on the sample surface potential distribution obtained by applying a voltage to the sample and spectrally detecting charged particles from the sample surface. 27. A microscopic means having a charged particle irradiation system after performing a surface cleaning treatment by removing an insulating thin film on the surface of a probe or a sample or a contaminant by using a charged particle beam or light. A defect inspection method for evaluating element characteristics of a sample by observing the sample using the probe and bringing the probe into contact with the sample and measuring electrical characteristics between the probe and the sample or between the probe. 28. A microscopic means having a charged particle irradiation system after performing a surface cleaning treatment by removing an insulating thin film on the surface of a probe or a sample or a contaminant by using a charged particle beam or light. By contacting the probe with the sample while observing the sample using a voltage is applied between the probe and the sample, or between the probes, and spectrally detecting charged particles from the surface of the sample. A defect inspection method for evaluating device characteristics of a sample from the obtained surface potential distribution information of the sample. 29. In the contact between the probe and the sample, the contact between the probe and the sample is confirmed by saturating the contact current flowing between the probe and the sample.
Defect inspection method described. 30. The contact between the probe and the sample is detected by detecting the force acting between the probe and the sample when the probe and the sample are in contact with each other. Defective inspection device. 31. When the probe and the sample are brought into contact with each other, a voltage is applied between the probe and the sample, and the charged particles are spectroscopically detected from a position on the sample surface where the probe should come into contact. 29. The defect inspection method according to claim 25, wherein the contact confirmation between the probe and the sample is performed when the sample surface potential information becomes a potential defined by the probe applied voltage.