JP2004048059A - Defect inspection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the localized electrical characteristic of a device having a fine structure, and to detect defects. <P>SOLUTION: A plurality of point probes having sharp tips 1, 2, 3 and 4 access sample electrodes 5, 6, 7 and 8 respectively until contact currents saturate and contact with them securely, while observing through a scanning electron microscope, by the control of a point probe moving control circuit 18 by using point probe moving mechanisms 14, 15, 16 and 17. When contacts of all the point probes used for measuring are completed, a current-voltage characteristic between point probes is measured by an electrical characteristic measurement circuit 19, and the localized electrical characteristic of an element is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an apparatus for evaluating the performance of an electronic element or analyzing a failure.

Conventionally, characteristics of electronic devices have been evaluated using a prober or an electron beam tester. For example, an example of the electron beam tester method is described in Journal of Japan Society of Applied Physics, Vol. 63, No. 6, pages 608 to 611, respectively.

(4) With a conventionally known prober, a probe is brought into contact with a position at which an electrical property of a test sample is to be measured while observing the sample with an optical microscope in the atmosphere. In this device, it is possible to use two probes, and thereby, it is possible to evaluate element characteristics such as current-voltage characteristics of a specific portion of the circuit. In this apparatus, processing such as wiring cutting can be performed with a YAG laser, and characteristics can be measured while isolating a part of the element.

An electron beam tester obtains the wiring potential of an operating electronic device from the contrast of a scanning electron microscope image. This is because, by using an energy filter, a potential contrast with an accuracy of 10 mV can be obtained.Therefore, it is possible to detect a failure and identify the location by comparing it with reference data obtained from a good electronic device. it can.

Journal of Japan Society of Applied Physics, Vol. 63, No. 6, pp. 608 to 611

In the first method (prober), since an optical microscope is used for sample observation, there is a limit in observing submicron wiring. If the electronic element has a line width of 0.1 μm in the future, observation becomes impossible. Contact of the probe to the wiring becomes impossible. In addition, since a YAG laser is used for processing an electronic element, fine processing of 0.1 μm or less becomes difficult due to the laser wavelength (0.355 μm in this apparatus). In addition, when the wiring of the electronic element to be contacted becomes finer, such as 0.1 μm, the tip of the probe needs to be thinner in order to make contact with it, so that the probe is easily damaged, Since the wiring is also fine, there is a problem that the wiring is easily broken. For this reason, in order to ensure reliable contact without damaging the probe or wiring, the contact method requires much higher accuracy than before. In addition, when a large contact area can be obtained as in the conventional case, the relative drift between the probe and the sample did not matter much, but with the miniaturization of the contact area, the change in the contact state due to the drift was large. It becomes a problem. However, such a countermeasure against drift is not implemented in the conventional method. In addition, in the conventional method, since the probe and the wiring are brought into contact in the atmosphere, if the contact area becomes finer in the future, the contact resistance due to an oxide film or contaminants on the wiring or at the tip of the probe becomes a serious problem. It is becoming. In addition, processing for measuring the electrical characteristics of the element requires not only cutting and peeling, but also processing for depositing a metal, such as forming a pad and forming a wiring, but it is necessary to perform processing in the air. It was not possible with the conventional method using the processing in the above.

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

In order to solve the above problems, first, as a microscopic means for observing a specific position in a sample to be brought into contact with the tip of the probe, an electron irradiation system or an ion irradiation system is used. Microscopic means constituted by an electron detection system is provided. This microscope has a resolution of nm level.

In addition, a moving mechanism for positioning and an approach mechanism are provided for bringing the tip of the probe into contact with the sample. Here, it is necessary to ensure that the contact between the probe and the sample is electrically conducted and that the probe and the sample are not damaged. For this reason, in the present invention, as a contact method, contact is confirmed 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 the contact is detected by detecting the tunnel current and the atomic force. , Only the approach speed from that position can be reduced.
Further, for a contact with a place where a contact current does not flow, such as a gate electrode, contact confirmation by force detection or saturation of a contact current effective value by application of an AC bias can be performed. Further, in the present invention, accurate contact confirmation can be performed by monitoring the potential at the position where the probe on the sample surface is to be brought into contact. In other words, if the probe and the sample are brought into contact with each other with a bias applied between the probe and the sample, if there is a contact resistance between the probe and the sample, this contact resistance causes a voltage drop. Is lower than the probe potential by the amount of this voltage drop (when the probe side is positive). Therefore, when the sample potential at the position where the probe contacts the probe is equal to the voltage applied to the probe within a certain error range, it can be determined that the contact resistance has decreased. 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. However, in the present invention, charged particles such as electrons and ions are used for observation. Since the potential of the sample surface changes at the time of contact, the primary charged particle beam is bent by the change in the electric field, causing a problem that the observation position is shifted. In order to correct this, in the present invention, the tip position of the probe immediately before the contact is recorded in the memory as pattern information of the microscope image, and when the displacement of the observation position occurs due to the contact with the probe, the observation area is expanded to match the pattern information of the memory. Is used to determine the tip position of the probe and return to high-magnification observation with that position as the center.

Also, in order to prevent a 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 contact to the end of the electrical characteristic measurement. Therefore, as one method, it is conceivable to make the probe have a spring effect to absorb the displacement. Conventionally, there has been a probe having a spring effect in a vertical direction. However, this conventional purpose is to alleviate the impact at the time of contact with the probe, and is not intended to compensate for minute displacement such as drift. Further, the conventional method has no spring effect in the lateral direction (the direction horizontal to the sample surface), and thus cannot cope with drift in this direction at all. In the present invention, a probe having a spring effect in both the vertical and horizontal directions is used as the probe, so that the displacement due to drift in all directions can be absorbed by the spring structure. In addition, after temporarily holding all the probes used for electrical property measurement in the state immediately before contact (tunnel current or atomic force detection state), contact all the probes at the same time to immediately measure electrical properties. As a result, the contact time can be shortened, and the influence of drift can be minimized.

In the present invention, since the measurement is performed in a vacuum, the contamination is reduced due to the problem of contact resistance due to an oxide film or a contaminant on the wiring or the tip of the probe which increases with the miniaturization of the contact area between the probe and the sample. It can be kept low. 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, the oxide film, the contaminants, and the like can be removed.

Electrical characteristics can be obtained by measuring the current-voltage characteristics and the like between the probes brought into contact with the sample. In the present invention, since a probe is used, it is possible to apply a voltage to an arbitrary position on the sample surface, which is impossible with an electron beam tester. Here, when the charged particle beam (electron or ion beam) used for the microscopic means affects the current-voltage characteristics, there is provided an irradiation system that can block the charged particle beam only during the measurement of the electric characteristics. In addition, in the present invention, since a charged particle irradiation system and a secondary electron detection system are provided, by adding an energy filter to the secondary electron detection system, the sample surface potential distribution can be reduced as in an electron beam tester. Can be observed. Therefore, it is possible to measure the potential distribution of the sample surface at that time while applying a voltage to an arbitrary position on the sample surface with the probe.

試 料 In the sample processing before measuring the element characteristics, in the present invention, fine processing of 0.1 μm or less can be performed by using a focused ion beam. In the case of an electron beam, fine processing becomes possible by combining with a reactive assist gas. For this reason, since a part of the electronic element can be isolated, the defect position can be easily identified. In addition, in the present invention, since the processing is performed in a vacuum, a metal film can be deposited by using a deposition gas and an irradiation beam (ion, electron, or laser), and an electrode pad for probe contact can be formed. Formation is possible. In addition, when it is desired to make a probe contact with a lower layer element or wiring that is not exposed on the surface, a contact hole to the wiring is opened from the surface in the present invention without removing the entire upper surface as in the related art. After that, the holes are filled with a metal using a deposition gas and an irradiation beam as described above, so that electrical contact from the surface becomes possible.

According to the present invention, a microscopic means by charged particle irradiation with high resolution and a probe moving mechanism with high positional accuracy are provided, so that even in an electronic element having a fine structure of 0.1 μm or less, the probe is brought into contact with an arbitrary position. Therefore, the electrical characteristics at an arbitrary position can be measured. In addition, accurate contact characteristics can be obtained by using contact confirmation or the like by approaching the probe until the contact current is saturated through detection immediately before contact by a tunnel current or the like, so that accurate element characteristics can be measured. In addition, a cleaning device using ions or the like in a vacuum can remove contaminants and the like on the probe and the sample surface, so that accurate element characteristics can be measured. Further, in processing using an ion beam or the like, fine processing of 0.1 μm or less is possible, and a specific position of an electronic element can be isolated, so that defective position identification becomes easy. Further, in the present invention, since the processing is performed in a vacuum, a metal film can be deposited by using a deposition gas and an ion beam, etc., a probe contact can be easily formed by forming an electrode pad, and a lower layer can be formed by forming a contact hole. Electrical contact to the wiring is also possible. For this reason, local electric characteristics inside the electronic element can be measured.

An object of the present invention is to measure a local electric characteristic of an electronic element for identifying a defective position of the electronic element and measuring its characteristic. In the present invention, the tip of the probe is brought into contact with a minute area to be brought into contact with the probe while observing with a microscopic means having a resolution on the order of nm, such as a scanning electron microscope. Here, accurate contact confirmation is performed by the saturation of the contact current or the like. Then, by measuring the current-voltage characteristics between these tips, local information of the element can be obtained. Thus, defective position identification can be performed. In addition, by adding a discriminating circuit to the electrical characteristic measuring system, it is possible to sort out non-defective products and defective products.

Hereinafter, specific examples are shown in <Example 1> to <Example 9>.

Fig. 1 shows the overall system of the present invention. Here, the purpose is to measure the electrical characteristics between the electrodes 5, 6, 7, 8 using the four probes 1, 2, 3, 4. The tips 1, 2, 3, and 4 preferably have a tip with a radius of curvature of 0.1 μm or less so as to be able to contact a minute region of the sample 9 at a level of 0.1 μm. 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 includes an electron source 10, a deflecting lens 11, and a secondary electron detector 13, where 20 is a primary electron beam and 21 is secondary electrons emitted from the sample surface. While observing in this manner, the probes 1, 2, 3, and 4 are moved to above the electrodes 5, 6, 7, and 8 to be contacted, respectively. This movement is performed by controlling the probe movement mechanisms 14, 15, 16, 17 of the probes 1, 2, 3, 4 respectively by the probe movement control circuit 18. Here, in this embodiment, a piezoelectric element having a high position resolution is used for the probe moving mechanisms 14, 15, 16, and 17.

Next, the contact method will be described with reference to FIG. In this figure, only the contact of the probe 1 will be described. 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 to minimize the contact so as not to damage both. In order to prevent damage to both, it is necessary to reduce the approach speed of the probe. However, if the approach speed is reduced as a whole, there is a problem that the time required for the approach becomes too long. To solve this, the position immediately before the contact is detected, the approach speed is increased up to this position, and only the approach speed from the immediately preceding position to the contact completion position is decreased. For this purpose, a method for detecting the position immediately before the contact is required. For example, there is a method based on tunnel current detection as used in FIG. Reference numeral 50 in FIG. 2A denotes 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 for switching between the preamplifier 50 for detecting a tunnel current and the ammeter 30 for detecting a contact current. Reference numerals 52 and 53 denote switches for switching between closed loops when the probe approaches and when 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 approaching the probe 1. First, the changeover switch 51 is connected to the preamplifier 50 side, 52 is connected to the power supply 31 side, 53 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 so that the probe 1 is connected. As you brought close to the electrode 5, a tunnel current flows Z _51. At this time, the distance between the probe 1 and the electrode 5 is about 1 nm or less. Thereby, the position immediately before the contact can be detected. However, merely stopping the approaching the tunnel current detection position Z _51, since the response speed and creep phenomena of the probe moving mechanism 14, which may probe 1 will be freely contacted close to the electrode 5 Therefore, it is better to apply feedback from the probe movement control circuit 18 to the probe movement mechanism 14 so that the tunnel current becomes constant. Thereafter, the changeover switch 51 is connected to the ammeter 30 side, the approach speed is reduced, and the probe 1 approaches the electrode 9. Then, when the probe 1 and the electrode 5 come into contact (Z ₅₂ ), a contact current starts to flow. When the probe 1 is moved closer in this state, the contact current I increases as shown in FIG. Then, a state in which the contact current I is no longer affected by the contact state changes, that is, as the contact completed by a state in which the contact current is saturated, the probe moves in FIG 1 the probe 1 at the position of the approach distance Z ₅₃ The mechanism 14 is stopped under the control of the probe movement control circuit 18. In this way, the probe 1 and the electrode 5 can be reliably contacted.

When the contact of all the probes 1, 2, 3, 4 is completed, 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, 3, 4, A current-voltage characteristic is measured. In this way, local electrical characteristics of the element can be obtained.

FIG. 3A shows an example of probe contact when a MOS device is used as a measurement sample. Here, only three probes 1, 2, and 3 are used, and are brought into contact with the source electrode 35, the gate electrode 36, and the drain electrode 37, respectively. For example, when measuring the output characteristics, applying the source electrode 35 by the probe 1 down to the ground level, waving a voltage V _G of the gate electrode 36 by the probe 2 as a parameter, the probe 3 to the drain electrode 37 The output characteristics of this MOS can be obtained by measuring the relationship between the drain voltage V _D to be applied and the drain current I _D flowing between the probes 1 and 3 (between the source and the drain). For example, if this is an n-channel MOS and is a non-defective product, the characteristics shown in FIG. 3B are measured.

(4) As described above, the defective position can be identified by bringing the probe into contact with the sample and comparing the local element characteristics measured from the portion between the good product and the bad product. In this method, the electrical characteristics can be obtained by directly applying a voltage to a position considered to be defective, so that the identification of the defective position is compared with the method of inputting a test pattern from the input terminal of the electronic element to identify the defective position. And the defective state can be measured in detail.

In this embodiment, a method for obtaining sample surface information from secondary electrons from a sample will be described. Here, only the probe 1 is shown for simplicity, but actually, as shown in FIG. 1, a plurality of probes are used. 4 is an energy filter, and 101 is a potential measuring device. Here, a contact method using this detection system will be described first. The contact confirmation based on 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 reduces the contact resistance to an error range with respect to the element characteristics. I do not guarantee that. In other words, it is possible to perform the defect detection by comparing the characteristics of non-defective products and defective products with the contact method shown in FIG. 2, but it is not clear whether the obtained device characteristics are absolute. Can not judge. Therefore, in order to perform a measurement in which absolute characteristics are important, it is necessary to use contact confirmation as described with reference to FIG. 4 in this embodiment. Here, only the contact of the probe 1 will be described. First, a primary electron beam 20 emitted from an electron source 10 is irradiated by a deflection lens 11 onto an electrode 5 to be brought into contact with a probe 1. At this time, the secondary electrons 21 emitted from the electrode 5 are detected by the secondary electron detector 13 through the energy filter 100. 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, if the probe 1 is approached by applying a bias of the potential Vt, the relationship between the approach distance Zt and the potential V of the electrode 5 is as shown in FIG. Z ₁₀₁ is equivalent to the position where the probe 1 is in contact with the electrode 5, has a large voltage drop due to contact resistance in this vicinity, yet the potential not fully up to the tip voltage Vt, is still contact bad, This indicates that the contact resistance is not negligible with respect to the element resistance. That is, to take reliable contact, the electrodes 5 potential, stop approach as a contact completion by coming to a position Z ₁₀₂ be more than a certain error level Vt '. That is, when the voltage drop due to the contact resistance becomes an error equal to or less than a negligible level (for example, 1% or the like), it is determined that the contact is completed. Thus, reliable contact confirmation can be performed.

Further, by using the apparatus shown in FIG. 4A, the wiring potential can be monitored by the energy filter 100 in the same manner as in the conventional electron beam tester, so that the distribution of the sample surface potential obtained by this can be observed. Yes, this can be used for failure analysis. However, unlike a conventional electron beam tester, in this case, since a probe is provided, a sample surface potential distribution can be obtained while locally applying a voltage with the probe, thereby facilitating defect position identification.

By the way, at the time of contact between the probe and the sample, the following problems occur in the observation. Although an electron beam is used in this 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 observed image is displaced. In this case, if the contact of the other probes 2, 3, and 4 is not completed, the contact positions of these probes cannot be observed, and correct contact cannot be made. Further, as described above, when a failure analysis is performed by the wiring potential monitor, this image shift is fatal. For this reason, a method for correcting this image shift is required. This will be described with reference to FIG. In FIG. 6A, reference numeral 131 denotes an area to be originally observed, and reference numeral 132 denotes an observation area shifted due to the contact of the probe 1 with the electrode 5. (B) to (g) of FIG. 6 are observation images. FIG. 6B shows a low-magnification observation image immediately before the probe 1 comes into contact with the electrode 5. This observation image is taken into the image memory 133, and the pattern of the probe is recognized.
Next, high-magnification observation is performed to accurately bring the probe 1 into contact with the electrode 5 (FIG. 6C). The observation area in FIG. 6C corresponds to the area 131 in FIG. Here, when the probe 1 comes into contact with the electrode 5, the observation area shifts as shown by the area 132 in FIG. 6A, and the observation image is in a state in which neither the probe nor the electrode is visible as shown in FIG. become. Thus, the primary electron beam 20 is switched to wide area scanning by the deflection lens 11 by the image shift correction circuit 130 in FIG. 6A, and observation is performed (FIG. 6E). Here, the initial image (FIG. 6B) captured 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 applied to the deflecting lens 11 by the image shift correction circuit 130 by an amount corresponding to the shift of the center position thus determined, and the shift of the primary electron beam 20 is corrected to return to the initial center position (FIG. 6 (f)). . In this way, by returning to the high-magnification observation centering on the corrected position (FIG. 6G), the image shift can be corrected.

In the above method, the acquisition of the probe shape by pattern recognition was used, but a method of easily acquiring the probe shape will be described with reference to FIG. Reference numeral 102 denotes a power supply for applying a voltage between the probe 1 and the sample 9, which can be modulated. That is, in a state where the probe 1 is not yet in contact with the sample, the modulation by the power supply 102 changes the potential of the probe 1 but does not change the surface potential of the sample 9. For this reason, if an observation image by 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, accurate contact confirmation of the probe can be performed by monitoring the potential at the contact position. In addition, failure analysis can be performed by measuring the surface potential distribution of the sample in combination with voltage application by the probe, and the failure position can be easily identified. Further, the observation place can be kept constant by the image shift correction.

In this embodiment, an apparatus having processing means for a measurement sample to be performed before electrical characteristic measurement (contact with a probe) will be described with reference to FIG. This apparatus has an ion beam irradiation system including an ion source 150, electrostatic lenses 151 and 153, and a deflector 152 instead of the electron irradiation system of FIG. 1, and can irradiate the sample 9 with the ion beam 154. it can.

In order to detect a defect using an LSI as a measurement sample, it is not possible to obtain the electrical characteristics of the portion simply by bringing the probe into contact with the wiring or electrode to be measured. This is because these wirings form closed loops in various places and include electrical characteristics other than the part (for example, one MOSFET or the like) to be actually measured. For this reason, in order to obtain the electrical characteristics of only the part that is actually measured, it is necessary to isolate that part. For this purpose, a sample processing means is required. FIG. 8 shows an apparatus to which an ion beam irradiation system is added as a processing means. In this case, the ion beam 154 is used not only for processing but also for observation.
That is, by scanning the surface of the sample 9 with the ion beam 154 and detecting the secondary electrons emitted from the sample 9 by the secondary electron detector 13, it is possible to observe as a so-called scanning ion microscope. Of course, in this case, in order to minimize the damage on the surface of the sample 9, it is necessary to reduce the amount of ion current as compared with the case of processing. If the damage caused by the ion beam is still a problem, the electron irradiation system is removed and the ion irradiation system is introduced in FIG. 8, but observation using the electron beam can also be performed with the electron irradiation system.

The types of sample processing will now be described with reference to FIG. When it is desired to measure the electrical characteristics of the element 160 shown in FIG. 9A, a wiring connected to the element 160, for example, 161 is formed with an ion beam 154 so that the measurement portion does not form a closed loop at another place as described above. By digging the groove 162 using this, the circuit is cut off and only the 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. Further, 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 by a multilayer wiring.
However, in this case, the probe cannot be brought into contact. In this case, as shown in FIG. 9B, the layer above the element 163 to be measured is scraped off with the ion beam 154, and the probe is attached to the element 163. Need to be processed so that they can contact each other. When it is difficult to bring the probe directly into contact with the wiring, as shown in FIG. 9C, the metal film is irradiated with the ion beam 154 while introducing the deposition gas 166 by the gas nozzle 165. 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, if it is desired to measure the lower element 163 as shown in FIG. 9D without cutting off a wide area as shown in FIG. 9B, a contact hole 169 is opened with an ion beam 154 to the wiring 168. 9C, the contact hole 169 is buried with the metal film 170 as shown in FIG. 9D, and the probe is brought into contact with the buried metal portion 170 to measure the characteristics of the element 163. It becomes possible.

加工 Here, the processing using the ion beam has been described, but a laser can be used for the processing. However, in this case, the processing accuracy determined by the laser wavelength (for example, about 0.4 μm for a YAG laser) is limited. For this reason, the focused ion beam is more effective for fine processing. If a reactive assist gas is used, the processing speed can be increased even in the case of an ion beam or a laser beam, and processing can be performed by an electron beam.

In FIG. 8, an apparatus having a processing function has been described. However, the apparatus for measuring electrical characteristics using a processing means and a probe does not necessarily have to be one apparatus, and another processing apparatus is used as shown in FIG. 9. It is also possible to perform various processing and perform measurement using the defect inspection apparatus shown in FIG.

試 料 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 element and to narrow down the defective position of the element, thereby facilitating the defect identification.

In the present embodiment, a cleaning process before bringing a probe into contact with a sample will be described with reference to FIG. Many of the contact failures between the probe and the sample are caused by mixing of an insulating substance between them. For example, oxide films and contaminants cause this. In the conventional tester, since the probe was brought into contact with a large electrode such as a bonding pad, the contact area could be increased. Therefore, these insulating materials did not cause much problems. However, if the wiring becomes smaller as in the current element and it becomes necessary to directly contact the probe with this wiring, the contact area cannot be increased, and such an insulating substance may cause a poor contact. Will have an effect. According to the present invention, unlike the related art, the electrical characteristics are measured in a vacuum. Therefore, if the surface of the sample or the probe is cleaned before the probe contacts, such a contact failure can be suppressed.
For example, as shown in FIG. 10A, when a contaminant 172 is present on a wiring 167 to be contacted with a probe for measuring the element 160, an ion beam 154 is used by an apparatus as shown in FIG. Irradiation can remove contaminants like 173.

Also, as shown in FIG. 10B, the contaminants on the surface of the probe can be removed as shown by 175 by irradiating the ion beam 154 as in FIG. 10A. Further, in the case of a probe, when various samples are measured, there is a possibility that the previously measured sample substance may be attached, and therefore, it is necessary to clean the probe by this method every time.

清浄 In addition, this cleaning can be performed not only with an ion beam but also with an electron beam or light irradiation.

In the present embodiment, the probe is cleaned in a vacuum, so that the probe and the sample can be surely contacted with each other, so that accurate element characteristics can be measured.

The most important thing in the method of measuring electrical characteristics using a probe is to keep the contact between the probe and the sample reliably. However, in a normal case, it is difficult to maintain a constant contact state because a relative position changes due to thermal or mechanical drift between the probe and the sample. 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, even if the relative position between the probe holder 42 and the electrode 43 changes from Δx as shown in FIG. 11A to FIG. The spring structure portion 41 absorbs the relative displacement by a spring effect, and can maintain good contact. In addition, the probes 44 and 45 having the shapes shown in FIGS. 4C and 4D can also absorb the drift by the spring structures 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 41 is brought into contact in a state of 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 described above, the contact Z _{23 at} which the contact current is saturated is determined to be in contact. However, in this spring probe, the contact is further moved to Z ₂₄ so that the tip of the probe 40 and the electrode 43 have a frictional force. The probe stop position Z ₂₄ is, of course, it must be a position where the probe 1 and the electrode 4 is not damaged, in the case of the spring probe is to have a spring effect in a vertical direction , as compared to the probe without a spring effect, since the probe, the approach region sample or the like is not damaged wide set of Z ₂₄ is easy. When the displacement distance Δx is at most about 1 μm when estimated from the time required for the measurement and the drift speed, the displacement can be sufficiently followed by the elastic deformation of the spring structure 41. The spring structure 43 can also absorb a drift in the direction perpendicular to the sample surface, so that the contact state can be kept constant.

According to the present embodiment, the relative position change due to the drift between the probe and the sample can be absorbed by the spring structure, and the contact can be kept good.

(4) In the above embodiment, since the electron beam is used for the observation means, the irradiated electrons are absorbed by the electrodes and the probe. This is not a problem if the element current flowing in the measurement of the voltage-current characteristics between the tips is so large that the current due to the electron beam can be ignored. It is necessary to cut off the electron beam. In this case, a blanking electrode 140 and a shielding plate 141 may be added to the primary electron beam irradiation system as shown in FIG. That is, at the time of observation for contact with the probe, the primary electron beam 20 is passed without operating the blanking electrode 140 as shown in FIG. 13A, and as shown in FIG. As described above, the voltage is applied to the blanking electrode 140 to bend the primary electron beam 20 so that the primary electron beam 20 is shielded by the shielding plate 141.

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

In the present embodiment, a method will be described in which even when an image shift occurs at the time of contact with the probe as shown in the second embodiment, the probe is surely brought into contact without relying on the image shift correction. This contact method is shown in FIG. Here, only two probes 1 and 2 are extracted for simplicity. At first, the probe is away from the electrodes 5 and 6 that should still be in contact with the probes 1 and 2 (FIG. 14A). First, the probe 1 is brought close to the tunnel current detection state (FIG. 14B). Here, the probe 1 is maintained in a feedback control state by a constant tunnel current. Next, the probe 2 is moved closer to the same, and the tunnel current is similarly maintained (FIG. 14C).
After the two probes are thus kept in the tunnel state, the two probes 1 and 2 are simultaneously approached and brought into contact with the electrodes 5 and 6, respectively. Thus, even if the observation images are shifted and the contact positions of the tips 1 and 2 and the electrodes 5 and 6 become invisible, they can be brought into correct contact. Here, the case of two probes has been described. However, even when more than two probes are used, once all the probes are once kept in a tunnel state, all the probes are brought into close contact at the same time. By doing so, it is possible to make a correct contact similarly without being affected by the image movement.

In this case, since all the probes are brought into contact at the same time, the time from probe contact to measurement of electrical characteristics can be shortened. There is an advantage that it does not easily occur.

According to the present embodiment, since all the probes are brought into contact at the same time, the contact can be made without being affected by the image shift of the observation image, and the influence of the drift can be suppressed.

In the first embodiment, the detection of the tunnel current is used as the position immediately before the contact, but as described in the present embodiment, the method of using the atomic force acting between the tip of the probe 1 and the electrode 5 for the position just before the contact. There is also. Reference numeral 60 in FIG. 15A denotes a cantilever for detecting an atomic force, and the voltmeter 64 detects the piezoelectric electromotive force of the piezoelectric elements 62 and 63 which receive a force due to the deformation of the cantilever 60 due to the atomic force. That is, the atomic force between the probe 1 and the electrode 5 can be known from the electromotive force measured by the voltmeter 64. FIG. 15B is a diagram showing the relationship between the approach distance Zt when the probe 1 is approached and the atomic force Fa acting between the probe 1 and the electrode 5.
First, by connecting the switch 65 to the voltmeter 64 side and gradually brought close to the probe 1 to the electrode 5, an atomic force Fa increases sharply from Z _61. Here, to stop approaching with Z ₆₂ was turned to a force F _62. Thereby, the position immediately before the contact can be detected. However, simply stop the approaching atomic force detection position Z _62, as described with reference to FIG 2, because of the response speed and creep phenomena of the probe moving mechanism 14, the probe 1 is close to the electrode 5 because it may result in freely contact, it is better to atomic force multiplied by feedback from the probe movement control circuit 18 to the probe moving mechanism 14 so as to be constant at F _62. Thereafter, the changeover switch 65 is connected to the ammeter 30 side, the approach speed is reduced, and the probe 1 approaches the electrode 5. FIG. 15C is a diagram illustrating a relationship between the approach distance Zt and the contact current Ic when the probe 1 is approached. After that, the procedure is the same as that described with reference to FIG. 2. The probe 1 and the electrode 5 come into contact with each other at Z ₆₃ , and the approach of the probe 1 is stopped at the position Z ₆₄ where the contact current is saturated, and the contact is completed.

接触 In the contact method of this embodiment, even if the tip of the probe accidentally approaches the insulator, the position immediately before the detection by the atomic force is used, so that the tip of the probe is not damaged.

As described in the above embodiment, a contact current does not always flow through an electrode or the like to be brought into contact. For example, if the electrode is an electrode such as a gate, the contact current cannot be detected because the electrode is basically insulated from the sample substrate. In this case, a contact method as described below is used.

An AC current can be passed through an insulator even if an AC bias is applied. A method using the 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 through the contact is measured by the ammeter 30 (FIG. 16A). In this case, the approach distance Zt and shows the relationship between the contact current effective value Ic is FIG. 16 (b), the approach distance the probe 1 and the electrode 5 in contact when Z _81, approach distance Z ₈₂ , The current Ic is saturated. The saturated and contact confirmation, the probe movement control circuit 18 stops the probe movement mechanism 14 approach distance Z _82. Thus, the contact can be completed. In the case of using this alternating current, the contact can also be made through tunnel current detection.

Further, as shown in FIG. 17, the contact can be confirmed 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 contact, so that it is necessary to measure a force sufficiently larger than the force of the order of nN normally used for measuring the atomic force. Therefore, the one having higher rigidity than the cantilever 60 of FIG. 15A is used. Thus, when the approach of the probe 1, the relationship between the force F acting between the approach distance Zt and the probe 1 electrode 5, since as shown in FIG. 17 (b), upon reaching a certain 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. Here, the contact force F is determined by the shape of the tip of the probe, the material (strength) of the tip of the probe, the size of the contact electrode, the material of the contact electrode, and the like. For example, below Fmin in FIG. 17 (b), there is a problem that the contact is weak, the contact resistance is large, and the ohmic contact is not formed. Further, when the force is equal to or higher than Fmax, problems such as breakage of the probe and falling down of the wiring arise. In other words, in order to make reliable contact, it is necessary to approach between the approach distances Zmin and Zmax corresponding to Fmin and Fmax.

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

The figure which shows one Example of this invention. The figure which shows a probe current detection system. The figure which shows the example of a measurement in an actual device. The figure which shows a sample potential detection system. The figure which shows the electron beam bent by the sample electric potential change by probe contact. The figure which shows the correction method of observation image shift. The figure which shows a probe marking method. The figure which shows the defect inspection apparatus which has an ion beam irradiation system. The figure which shows sample processing. The figure which shows a cleaning method. The figure which shows the probe which has a spring effect. The figure which shows the contact state in a spring probe. The figure which shows the blocking method of an electron beam. The figure which shows the simultaneous contact method of a several probe. The figure which shows the contact method via an atomic force detection. The figure which shows the contact method with the gate electrode by application of an alternating voltage. The figure which shows the contact method with the gate electrode by force detection.

Explanation of reference numerals

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 ······································································································································ Gate electrode, 37 drain electrode, 40 probe, 41 spring structure, 42 probe holder, 44, 45 probe, 46, 47 spring structure, 50 preamplifier, 51, 52, 53 ... Changeover switch, 60: cantilever, 62, 63: piezoelectric element, 64: voltmeter, 65: changeover switch, 70: insulating layer, 71: switch, 80: AC power supply, 90: leaf spring, 100: energy filter, 101 ... Potential measurement device, 102 AC power supply, 110 Bent electron beam, 130: Image shift correction circuit, 131: Initial observation area, 132: Observed area with image shift, 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: processing groove, 163: lower layer measuring element, 164: electrode pad, 165: nozzle, 166 .. Deposition gas, 167, 168 wiring, 169 contact hole, 170 embedded metal part, 172 contaminant, 173 removed contaminant, 174 contaminant, 175 removed contaminant.

Claims (31)

A vacuum container, a probe and the probe moving mechanism on the vacuum container, a sample table on which a sample is placed, a charged particle source, an irradiation unit for irradiating a beam from the charged particle source, and a charge from the sample. A defect inspection apparatus comprising: a detector for detecting particles; a means for applying a voltage between the probe and the sample or between the probes; and a means for measuring an electrical property of the sample. A vacuum container, a probe and the probe moving mechanism on the vacuum container, a sample table on which a sample is placed, a charged particle source, an irradiation unit for irradiating a beam from the charged particle source, and a charge from the sample. A detector for detecting particles, a means for applying a voltage between the probe and the sample, or between the probes, a means for measuring the electrical characteristics of the sample, and determining a defect based on a measurement value from the measuring means. A defect inspection device having a determination unit. 3. The defect inspection apparatus according to claim 1, wherein the means for measuring the electrical characteristics of the sample measures current-voltage characteristics between any combination of the probe and the sample. 3. The defect inspection apparatus according to claim 1, wherein the means for measuring the electrical characteristics of the sample is a potential measurement on the surface of the sample by a detector having an energy filter for detecting the charged particles. A vacuum container, a probe and the probe moving mechanism on the vacuum container, a sample table on which a sample is placed, a charged particle source, an irradiation unit for irradiating a beam from the charged particle source, and a charge from the sample. A detector for detecting particles, the probe, or a mechanism for correcting a displacement of the irradiation position of charged particles due to a change in the potential of the sample, and a means for applying a voltage between the probe and the sample or between the probes, A defect inspection device having means for measuring the electrical characteristics of a sample. The mechanism for correcting the displacement of the irradiation position of the charged particles includes an image memory for recording an observation image immediately before the contact between the probe and the sample, a mechanism for switching to wide area observation when an observation image shift occurs, and a mechanism for switching to the wide area observation. 6. The image processing apparatus according to claim 5, wherein an image is compared with an observation image recorded in the image memory, a movement amount of an observation image center position is determined, and a shift is corrected by moving the observation region by the movement amount. Defect inspection equipment. In the collation of the observation image, a modulation voltage is applied to the probe, and a probe shape is acquired from a signal synchronized with the modulation from image information detected by a charged particle detector. Item 7. The defect inspection device according to Item 6. A vacuum container, a probe and the probe moving mechanism on the vacuum container, a sample table on which a sample is placed, a charged particle source, an irradiation unit for irradiating a beam from the charged particle source, and a charge from the sample. A detector for detecting particles, a means for applying a voltage between the probe and the sample or between the probes, and a contact between the probe and the sample due to saturation of a contact current flowing between the probe and the sample. A defect inspection device having a mechanism for checking and a means for measuring the electrical characteristics of a 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. In the defect inspection apparatus, different current detectors are used for the detection of the contact current between the probe and the sample and the detection of the tunnel current, and after the tunnel current is detected, when the probe and the sample are further approached, the current detection is performed. 10. The defect inspection apparatus according to claim 9, further comprising a changeover switch for changing over the unit. In the defect inspection device, a closed circuit is formed between the probe and the sample when the contact current between the probe and the sample is detected, and a closed circuit is formed between the probe and the probe when measuring the electrical characteristics of the sample. The defect inspection apparatus according to claim 8, further comprising a changeover switch for changing over. A vacuum container, a probe and the probe moving mechanism on the vacuum container, a sample table on which a sample is placed, a charged particle source, an irradiation unit for irradiating a beam from the charged particle source, and a charge from the sample. A detector for detecting particles, a means for applying a voltage between the probe and the sample or between the probes, and a potential at a position on the surface of the sample to be contacted with the probe, which is determined by the applied voltage of the probe. A defect inspection apparatus having a mechanism for confirming contact between the probe and the sample when the potential becomes a specified potential, and means for measuring electrical characteristics of the sample. The probe is brought into contact with the surface of the sample, and as a probe of the device for measuring the characteristics of the sample, when the probe is in contact with the sample, the probe in a direction parallel to the sample surface and the relative position change between the sample are measured by a spring. A probe characterized by having a structure that absorbs by its structure. The defect inspection apparatus according to any one of claims 1 to 12, wherein the probe includes the probe according to claim 13. 15. The defect inspection apparatus according to claim 14, wherein the probe moving mechanism further moves the probe support portion and the sample closer to each other by a certain distance after the probe comes into contact with the sample. 13. The defect inspection device according to claim 1, wherein the defect inspection device includes a light irradiation unit. The defect inspection apparatus according to any one of claims 1 to 3, wherein the charged particle irradiation means has a mechanism for interrupting the charged particle beam during the measurement of the electrical characteristics. 13. The defect inspection apparatus according to claim 1, wherein in the probe moving mechanism, all the probes used for the electrical characteristics are simultaneously brought into contact with a sample surface. The defect inspection apparatus according to any one of claims 1 to 7, wherein the defect inspection apparatus has a mechanism for confirming contact between the probe and the sample by detecting a force acting between the probe and the sample. In the defect inspection device, a mechanism is provided for confirming contact between the probe and the sample by applying an AC voltage between the probe and the sample and saturating an effective value of a contact current flowing between the probe and the sample. The defect inspection apparatus according to claim 1, wherein: 13. The defect inspection apparatus according to claim 1, wherein 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. 8. The defect inspection apparatus according to claim 1, wherein the probe moving mechanism further moves 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. 13. The defect inspection apparatus according to claim 1, wherein a radius of curvature of a tip of the probe is 100 nm or less. 13. The defect inspection apparatus according to claim 1, wherein the probe moving mechanism has a fine movement mechanism using a piezoelectric element. After using a charged particle beam or laser to cut the circuit of the sample, or form a wiring, or bury a trench, or form an electrode pad, or remove a protective layer, or remove an upper layer of a test element, a charged particle irradiation system is provided. A defect inspection in which a probe is brought into contact with the sample while observing the sample using a microscopic means, and the electrical characteristics between the probe and the sample or between the probes are measured to evaluate the element characteristics of the sample. Method. After using a charged particle beam or laser to cut the circuit of the sample, or form a wiring, or bury a trench, or form an electrode pad, or remove a protective layer, or remove an upper layer of a test element, a charged particle irradiation system is provided. While observing the sample using a microscopic means, a probe is brought into contact with the sample, a voltage is applied between the probe and the sample, or between the probes, and a charged particle from the sample surface is spectrally detected. A defect inspection method for evaluating the element characteristics of the sample from the sample surface potential distribution information obtained thereby. Using a charged particle beam or light, a probe or an insulating thin film on the surface of the sample, or after performing a surface cleaning treatment by removing contaminants, the sample is cleaned using a microscopic means having a charged particle irradiation system. A defect inspection method in which the probe is brought into contact with the sample while observing, and the electrical characteristics between the probe and the sample or between the probes are measured to evaluate the element characteristics of the sample. Using a charged particle beam or light, a probe or an insulating thin film on the surface of the sample, or after performing a surface cleaning treatment by removing contaminants, the sample is cleaned using a microscopic means having a charged particle irradiation system. While observing, the probe is brought into contact with the sample, a voltage is applied between the probe and the sample, or between the probes, and a sample surface potential obtained by spectrally detecting charged particles from the sample surface. A defect inspection method for evaluating element characteristics of the sample from distribution information. 29. The defect inspection method according to claim 25, wherein in contact between the probe and the sample, the contact between the probe and the sample is confirmed by saturating a contact current flowing between the probe and the sample. 29. The defect inspection apparatus according to claim 25, wherein in contact between the probe and the sample, contact between the probe and the sample is confirmed by detecting a force acting between the probe and the sample. In the contact between the probe and the sample, a voltage is applied between the probe and the sample, and the sample surface potential information obtained by spectrally detecting the charged particles from the position on the sample surface where the probe should contact is obtained. 29. The defect inspection method according to claim 25, wherein the contact between the probe and the sample is confirmed by reaching a potential defined by a voltage applied to the probe.

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