JPH118278A - Device and method for inspecting semiconductor wafer by charged particle beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an electrical inspection in a halfway stage through manufacturing by comparing the measurement value of a secondary electron observation quantity with a threshold and perform classification, depending on whether the measurement value is larger or smaller than the threshold. SOLUTION: A wafer stage 2 has a reverse side electrode 3 that touches the reverse side of a wafer 8 and a counter electrode 4 so that it faces opposite a wafer 10. A voltage generator 5 is connected between the reverse side electrode 3 and the counter electrode 4 by an electric wire 6 for controlling a potential. Electron beam 11 is emitted from an electron gun 1 towards the wafer 10, electric charges are injected to the wafer 10, and then secondary electrons 12 are detected by a secondary electron observation equipment 7, thus observing a secondary electron image. At this time, the threshold of the secondary electron observation quantity to be detected is determined by a threshold-determining device 8, and the secondary electron observation quantity according to a secondary electron comparison device 9 is compared with its threshold for classification, thus obtaining a semiconductor wafer inspection method for performing an electrical, defect inspection without any contact, without making contact even at a halfway stage in the manufacture of an LSI.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI inspection method for performing an electrical inspection of element formation in a non-contact manner during a manufacturing process.

[0002]

2. Description of the Related Art As a method for inspecting an element formed on a substrate in a non-contact manner, there is a method of optically inspecting an LSI pattern to detect a shape defect. According to this method, a shape abnormality occurring during the LSI manufacturing process can be detected, and when an abnormality occurs, its cause can be removed at a relatively early stage.

As a method of detecting an electrical defect, there is a method of performing an electrical inspection by physical contact with an electrode after manufacturing an LSI. The one using a tester is a typical example. Generally, in an LSI manufacturing process, an electrical inspection is performed in a final process to confirm a normal operation of the LSI.

As an inspection method using an electron beam, there are a method of observing a shape by a scanning electron microscope and a method of examining a wiring potential during LSI operation by an electron beam tester after completion of the LSI as a potential contrast.

[0005]

However, the pattern inspection by the optical method has a problem that the detected shape abnormality is not always linked to the final electrical failure of the LSI. That is, even if the cause of the shape abnormality is removed, the normal electrical function of the LSI is not guaranteed. In addition, there is a limit to the resolution to be detected, and it is difficult to detect a defect caused by a three-dimensional structure because it is a planar inspection. Further, it is difficult to detect a leak failure or the like to the thin film.

On the other hand, the electrical function test involves physical contact with the LSI element, and the element is destroyed by the contact. Also, since it is necessary to manufacture pads for making contact, wiring and the like are required. Inspection is not possible until the final step.

[0007] In shape observation with a scanning electron microscope, shape inspection does not always detect electrical failure.

Further, in an inspection method using an electron beam tester, a secondary electron image is more likely to obtain a contrast due to the potential of the sample than a general scanning electron microscope.
There is a drawback that the period from the creation of the defect to the detection is lengthened because the LSI is put into an operating state and the defect is inspected after manufacturing.

SUMMARY OF THE INVENTION An object of the present invention is to realize an electrical inspection in the middle of manufacturing, and to provide a method for applying an effective potential to a device to be inspected even in a non-contact manner and judging a defect. That is.

[0010]

According to the present invention, there is provided a semiconductor wafer inspection apparatus using a charged particle beam, comprising: a first conductive layer, a second insulating film and a third element formed on a semiconductor wafer; In an apparatus for inspecting electrical contact between the third elements, a scanning charged particle microscope equipped with a wafer stage in which a potential contrast of a secondary electron image is obtained according to a magnitude of a secondary electron observation amount of a secondary electron detector. A back electrode in contact with the back surface of the wafer, a counter electrode having at least a portion of the wafer surface facing the back electrode with a space, and a device for controlling the potential difference between the potential of the back electrode and the counter electrode potential, Apparatus for determining the threshold of the secondary electron observable, and comparing the measured value of the secondary electron observable with the threshold, and classifying according to whether the measured value of the secondary electron observable is larger or smaller than the threshold. And a device.

Further, according to the method for inspecting a semiconductor wafer by a charged particle beam of the present invention, of the first conductive layer, the second insulating film and the third element formed on the semiconductor wafer, the first conductive layer and the third In a method of inspecting electrical contact between elements, a back surface of a scanning charged particle microscope equipped with a wafer stage in which a potential contrast of a secondary electron image is obtained according to a magnitude of a secondary electron observation amount, the back surface contacting the back surface of the wafer An electrode, a counter electrode having at least a portion of the wafer surface facing the back electrode with a space therebetween, and a device for controlling the potential difference between the back electrode potential and the counter electrode potential, using a back electrode potential. By irradiating the charged particle beam onto the wafer with the potential lower than the counter electrode potential, electric charges are injected into at least the second insulating film and the third element formed on the wafer. Then, depending on whether there is electrical contact between the third element and the first conductive layer, different potentials are formed on the third element, and secondary electrons generated by irradiating the third element with a charged particle beam are generated. The amount is compared with a threshold value, the secondary electron observation amount in the third element is larger than the threshold value, it is determined that there is electrical contact between the third element and the first conductive layer, and the back electrode potential is set to the counter electrode. The potential is made larger than the potential, and a charged particle beam is irradiated on the wafer to inject electric charge into at least the second insulating film and the third element formed on the wafer, so that a charge is injected between the third element and the first conductive layer. A different potential is formed on the third element depending on whether or not there is electrical contact with the third element, and the amount of secondary electrons generated by irradiating the third element with the charged particle beam is compared with a threshold value. If the amount of secondary electron observation is smaller than the threshold, It is determined that there is electrical contact between the one conductivity layer.

Next, the principle of the present invention will be described.

Elements formed on the wafer include an insulating layer, an element electrically connected to the conductive layer of the wafer, and an element electrically insulated from the conductive layer of the wafer. Examples of the insulating layer include a gate oxide film and an interlayer insulating film, and examples of an element connected to the conductive layer of the wafer include a contact hole and an electrode embedded in the contact hole. Elements that are electrically insulated from the conductive layer of the wafer include a gate electrode and the like.

When electric charge is injected into these elements and the electric charge flows into the conductive layer of the wafer, the potential of the element becomes equal to the potential of the wafer. However, when the element is insulated from the conductive layer of the wafer, the element is charged by the wafer. A different potential from that of the conductive layer is generated. As a means for controlling the potential formed by the charge injection, the potential is selected by selecting the potentials of the back electrode and the counter electrode on the wafer. Since the energy of the secondary electrons generated by the irradiation of the charged particle beam is several eV or less, it is possible to selectively control the case of re-injection into the wafer and the case of escaping in the direction of the counter electrode by the potential difference between the back electrode and the counter electrode. it can. That is, the secondary charging process for re-injecting the secondary electrons is controlled.

If re-injection on the wafer is selected, the element insulated from the insulating layer on the wafer or the conductive layer on the wafer is negatively charged. However, in the opposite case, it is positively charged. At this time, in order to obtain a positive charge, it is necessary to make the primary charge by primary injection charge and secondary electron emission positive. However, even if a Ga ion beam or an electron beam is used, the acceleration energy is increased. Is set to around 1 keV, the primary charging can be in the positive direction.

In this manner, the potential difference between the non-defective product and the non-defective product is reduced due to a leak failure to the wafer, such as a gate electrode, which must be originally insulated from the wafer, or a poor insulation of a contact hole, which must be insulated from the wafer. give. The secondary electron image obtained as a result has a large amount of secondary electron observables in places where the potential is low, a high potential contrast of white and high brightness is obtained, and a small amount of secondary electron observables in places where the potential is high and black and low brightness. Potential contrast is obtained. A defect is detected based on the amount of observed secondary electrons or the potential contrast of the secondary electron image.

In the method of the present invention, whether a defect is determined by using the observed amount of secondary electrons or a defect is determined by using the potential contrast produces the same result. , Which means that it includes both methods.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a semiconductor wafer inspection apparatus using a charged particle beam according to the present invention, and FIG.
FIG. 3A is a graph showing the relationship between the electron beam acceleration voltage and the secondary electron emission ratio, FIG. 3A is an explanatory diagram in the case where the insulating film on the wafer is positively charged by secondary electrons, and FIG. FIG. 7 is an explanatory diagram in the case of negative charging.

In FIG. 1, a back surface electrode 3 is provided on a wafer stage 2 to be in contact with the back surface of a wafer 8.
The counter electrode 4 is provided so as to face 0. A voltage generator 5 is connected between the back surface electrode 3 and the counter electrode 4 by an electric wire 6, and controls a potential.

After irradiating the electron beam 11 from the electron gun 1 to the wafer 10 and injecting charges into the wafer 10, the secondary electrons 12 are detected by the secondary electron observation device 7, and the secondary electron image is observed. . At this time, the threshold value of the secondary electron observation amount to be detected is determined by the threshold value determination device 8, and the secondary electron observation amount by the secondary electron comparison device 9 is compared with the threshold value to perform classification.

Here, a method for controlling the charged potential of an insulating film formed on a wafer, for example, will be described.

As shown in FIG. 2, when the acceleration voltage is 1 keV, the secondary electron emission ratio is larger than 1, so that the primary charging of the insulating film by the electron beam injection and the secondary electron emission is in the positive direction.

In this state, the potential of the insulating film can be controlled by the back electrode and the counter electrode.

Referring to FIG. 3, the control of the charging potential of the insulating film on the wafer 30 will be described. As shown in FIG. 3A, the potential of the back electrode 23 is changed from the potential of the counter electrode 24 by the voltage generator 25. If the distance is also reduced, the secondary electrons are accelerated in the direction of the counter electrode, so that the insulating film is charged with positive charges.

However, as shown in FIG. 3B, when the potential of the back electrode 23 is made higher than the potential of the counter electrode 24, the secondary electrons having a small energy are pulled back toward the wafer 30, and the secondary charge in the negative direction is generated. Occur. As a result, the insulating film is negatively charged.

Thus, the potential of the insulating film can be controlled.

The charge potential is similarly controlled for elements other than the insulating film formed on the wafer 30.

In this case, if the element is originally insulated from the diffusion layer or the like of the wafer 30, the potential is obtained by charging as described above. It has the same potential as the 30 diffusion layers. Since a potential is applied to the diffusion layer of the wafer 30 by the back electrode 23, a potential difference occurs between a normal element and a defective element, and a low-potential portion is white by observing a secondary electron image after the potential difference has occurred, and a high potential The potential contrast can be observed at a black spot, and the defective spot can be specified.

(Second Embodiment) Next, with reference to FIG. 4, a method of determining a threshold value for determining whether an electrode is electrically connected to a conductive layer of a wafer in the present invention will be described.

FIG. 4 is an explanatory view of the second, third, and fourth embodiments of the present invention. FIG. 4A is a structural diagram for explaining selection of a threshold value in the inspection of the present invention. (B) is a diagram showing the potential of each part and the amount of observed secondary electrons for the same explanation.

A second insulating film 42 is formed on the first wafer conductive layer 41 in order from the bottom, and a third non-conductive electrode 43 which is not in electrical contact with the wafer conductive layer 41, and a wafer conductive layer. A conductive electrode (A) 44 in electrical contact is formed.

Here, for example, when the back electrode potential is made smaller than the counter electrode potential and the electron beam is irradiated at 1 keV, the potential of each element becomes electrically connected to the wafer conductive layer 41 as shown in FIG. The potential of the element in contact is relatively low, but the potential of the element and the insulating film not in electrical contact with the wafer conductive layer 41 is relatively high.

Here, as a threshold value for determining whether or not the conductive electrode (A) 44 is normally electrically in contact with the wafer conductive layer 41, the amount of the secondary electrons observed in the insulating film 42 is used as a threshold value. ) 44 compared with the observed secondary electron quantity. That is, the threshold (1) in FIG. 4B is selected as the threshold.

When the amount of observed secondary electrons at the conductive electrode (A) 44 is larger than the threshold value (1), the conductive electrode (A)
Since the potential of 44 is lower than the potential of the insulating film 42, it can be determined that the conductive electrode (A) 44 is normally in electrical contact with the wafer conductive layer 41.

Conversely, when the amount of secondary electrons observed at the conductive electrode 44 is substantially equal to the threshold value (1), the conductive electrode (A) 44
Is equal to the potential of the insulating film 42, and is insulated from the wafer conductive layer 41 and can be determined to be defective.

In this example, an example in which the amount of observed secondary electrons is used as a criterion for determination is shown, but the same applies when the potential contrast of a secondary electron image is used as a criterion for determination. That is, the conductive electrode (A)
Comparing the potential contrast at 44 with the potential contrast at the insulating film 42, if the potential contrast at the conductive electrode (A) 44 is higher in brightness and white, the conductive electrode (A) 44
Can be determined to be normally in electrical contact with the wafer conductive layer 41.

(Third Embodiment) Referring to FIG. 4, similarly to the second embodiment, an average value of the electron beam irradiation area indicated by threshold 2 in FIG. 4B is selected as the threshold. .

In this case, when the insulating film 42 and the non-conducting electrode 43, which are elements that are not in electrical contact with the wafer conductive layer 41, are normal, the amount of secondary electrons observed becomes smaller than the threshold value (2). , The potential is greater than the wafer conductive layer.

On the contrary, when the conduction electrode (A) 44 which is in electrical contact with the wafer conductive layer is normal, the observed secondary electron quantity becomes larger than the threshold value (2), and the potential becomes lower than the threshold value (2). Will be the same.

In this manner, by setting the average value of the observed amount of secondary electrons in the electron beam irradiation area to the threshold value (2), the elements electrically connected to the wafer conductive layer and the elements not connected to the wafer conductive layer are detected. be able to.

(Fourth Embodiment) Referring to FIG. 4 in the same manner as in the second embodiment, a device to be inspected manufactured on the same layer as the device to be inspected within the electron beam scanning range as a threshold value Select the amount of secondary electrons observed when the element located at a different location from the element is irradiated with the electron beam.

That is, when the conductive electrode (A) 44 is used as the device to be inspected, the observed amount of secondary electrons at the conductive electrode (B) 45 is used as the threshold. In this case, the threshold (3) corresponds to this in FIG.

When inspecting whether the conductive electrode (A) 44 is normally in electrical contact with the wafer conductive layer 41, the amount of secondary electrons observed when the conductive electrode (A) 44 is irradiated with an electron beam. Is smaller than the threshold value (3). If the conduction electrode (A) 44 is smaller than the threshold value (3),
In the case of No. 1, the electrical contact has been cut off, and it can be determined that it is defective.
Conversely, if the amount of secondary electrons observed is about the same as the threshold value (3), it can be determined that the wafer electrically contacts the wafer conductive layer 41 normally.

(Fifth Embodiment) In this embodiment,
An example of detecting a contact hole defect will be described with reference to FIG.

FIGS. 5A and 5B are explanatory diagrams of the fifth and sixth embodiments of the present invention. FIG. 5A shows a case where a defect is detected after an electrode is buried in a contact hole according to the present invention. FIG. 3B is an explanatory diagram in a case where a defect of a contact hole is detected after the contact hole is opened according to the present invention.

By using the method of the first embodiment, the back electrode potential is set to, for example, 5 V lower than the counter electrode potential.
When the defective contact 53 and the insulating film 52 are irradiated with an electron beam, secondary electrons are emitted and positive charges are charged, but the normal contact 54 has the same potential as the substrate 51.

Since the potential of the substrate 51 is the same as the potential of the back electrode, the potential of the defective electrode 53 and the insulating film 52 becomes higher than those of the substrate 51 and the normal contact 54.
The amount of secondary electrons observed is small for the bad contact 53 and large for the normal contact 54.

The potential contrast of the secondary electron image obtained as a result is such that the defective contact 53 is black and the normal contact 54 is white, so that the defective contact 53 can be detected.

(Sixth Embodiment) An example in which a contact hole defect is detected after opening the contact hole shown in FIG. 5B will be described.

As in the previous example, the potential of the back electrode is made lower than the potential of the counter electrode by using the method of the first embodiment. Positive charges are charged in the insulating film 52 and the defective contact 56 in which the insulating film remains on the bottom, but the potential of the contact bottom is the potential of the substrate 51 in the normal contact 57, so that the potential contrast of the secondary electron image is poor. The bottom of the contact 56 is black and the bottom of the normal contact 57 is white, and the defective contact 56 can be detected.

(Seventh Embodiment) FIG. 6 is an explanatory diagram of a gate oxide film inspection according to a seventh embodiment of the present invention.

In this embodiment, an example in which a leak defect of a gate oxide film is inspected will be described with reference to FIG. A gate electrode 63 or 64 is formed on a gate oxide film 62 formed on a substrate 61. There is a normal gate electrode 63 formed on a normal gate oxide film and a defective gate electrode 64 formed on a gate oxide film having insulation failure.

Using the method of the first embodiment, the back electrode potential is set to, for example, 5 V lower than the counter electrode potential.
The normal gate electrode 63 is charged with a positive charge, but the defective gate electrode 64 has the same potential as the substrate 61, and the resulting secondary electron image shows that the normal gate electrode 63 is black and the defective gate electrode 64 is A white potential contrast can be obtained, and the gate electrode 64 formed on the defective gate oxide film can be detected.

(Eighth Embodiment) FIG. 7 is an explanatory diagram of a measurement of a dielectric strength of a gate oxide film according to an eighth embodiment of the present invention.

As shown in FIG. 7, a gate oxide film is formed on a substrate, and the withstand voltage of the gate oxide film between the substrate and the gate electrode of the sample having the gate electrode formed thereon is measured. In this method, the potential difference between the counter electrode and the back electrode is gradually increased with time. In this example, the potential of the counter electrode is fixed, and the potential of the back electrode is gradually increased in the positive direction. As shown in FIG. 7, when the back electrode potential is increased in the positive direction, the gate electrode potential is shifted in the positive direction, but when the potential formed on the gate electrode is higher than the counter electrode potential. Since the secondary electrons are re-injected into the gate electrode, the potential of the gate electrode is kept almost equal to the potential of the counter electrode although there is a slight shift.

Therefore, the potential difference between the gate electrode potential and the substrate potential increases, and breakdown occurs at a level exceeding the withstand voltage of the gate oxide film, and the gate electrode potential becomes equal to the substrate potential. The withstand voltage of the gate oxide film is the potential difference between the substrate potential and the gate electrode potential immediately before this breakdown occurs, and is measured as a value obtained by subtracting a slight shift amount from the potential difference between the back electrode potential and the counter electrode potential. can do.

(Ninth Embodiment) Referring to Table 1, two types of electron beam irradiation for charging and electron beam irradiation for potential measurement according to the ninth embodiment of the present invention will be described. An example of performing irradiation will be described.

[0059] First, as Step 1, an area to be observed is irradiated with an acceleration voltage of 10 kV, a beam current of 50 nA, and a back electrode potential of +10 V. Next, in step 2, secondary electrons are observed while irradiating an electron beam at an acceleration voltage of 1 kV, a beam current of 500 pA, and a back electrode potential of +10 V. In the present embodiment, the sample can be sufficiently charged in a short time in step 1, and the charged potential can be precisely observed in step 2.

(Tenth Embodiment) FIG. 8 is an explanatory diagram of potential contrast inversion according to a tenth embodiment of the present invention.

The tenth embodiment will be described with reference to FIG. 8. In the inspection of the wafer after the contact hole is opened, the potential image (1) is obtained with the back electrode potential at +10 V. Next, a potential image (2) is obtained at a back electrode potential of -10V. In the potential image (1), a normal contact hole is black and a potential contrast is obtained, but a defective contact hole is gray. Next, in the potential image (2), a normal contact hole is white and a potential contrast is obtained, but a defective contact hole is gray.

That is, in the potential images (1) and (2), the potential contrast of the normal contact hole is inverted, but the potential contrast of the defective contact hole does not change much.

By detecting the inversion of the contrast, a normal contact hole and a defective contact hole can be easily distinguished.

In this embodiment, the difference image between the potential image (1) and the potential image (2) is taken to extract only the portion where the contrast is inverted.

(Eleventh Embodiment) FIG. 9 is an explanatory diagram of an example of detecting a defect of a gate oxide film formed on a wafer according to an eleventh embodiment of the present invention. )
FIG. 3B is a diagram in which a voltage is applied to the back electrode in a pulsed manner, and FIG.

Referring to FIG. 9, an eleventh embodiment will be described. An example of detecting a defect of a gate oxide film of a sample having a gate electrode formed on a wafer is shown. In this embodiment, an oxide film or a wafer is formed on the back surface of the wafer. A method for obtaining a good potential contrast even when multiple wells are formed will be described.

In general, in such a sample, since the back electrode and the wafer conductive layer are insulated, there is a leak defect that not only the wafer surface insulating film and the normal gate electrode but also the wafer itself is charged by electron beam irradiation. The gate electrode is similarly charged, making it difficult to obtain a potential contrast between a normal gate electrode and a defective gate electrode. This embodiment provides a method for solving this problem and forming a good potential contrast.

As shown in FIG. 9A, the back electrode potential is pulsed from +5 V to 0 V and from 0 V to +5 V. At this time, the potential of the gate electrode formed on the wafer fluctuates due to capacitive coupling from the back electrode potential and becomes uniform due to charging of electron beam irradiation, and changes as shown in FIG. 9B. .

The normal gate electrode insulated from the wafer changes as shown by the solid line, and the defective gate electrode leaking to the wafer changes as shown by the broken line because of its large electric capacity. Here, for a while after the back electrode fluctuates,
A period occurs in which the potential of the normal gate electrode is different from the potential of the defective gate electrode. By activating the image acquisition gate during this period and acquiring an image only during this period, a potential contrast between a normal gate electrode and a defective gate electrode can be obtained.

[0070]

As described above, the present invention irradiates a charged particle beam onto a wafer by controlling the potential difference between the back electrode potential and the counter electrode potential of a scanning charged particle microscope equipped with a wafer stage. In this method, electric charge is injected into the device formed on the wafer, and the secondary observation amount is compared with a threshold value to determine a defective electrical contact. There is an effect that it is possible to provide a semiconductor wafer inspection method capable of performing inspection without contact.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a semiconductor wafer inspection apparatus using a charged particle beam according to the present invention.

FIG. 2 is a graph showing a relationship between an electron beam acceleration voltage and a secondary electron emission ratio.

FIG. 3A is an explanatory diagram in a case where an insulating film on a wafer is positively charged by secondary electrons, and FIG. 3B is an explanatory diagram in a case where the insulating film is negatively charged.

FIGS. 4A and 4B are explanatory diagrams of second, third, and fourth embodiments of the present invention, wherein FIG. 4A is a structural diagram for explaining selection of a threshold value in an inspection of the present invention, and FIG. FIG. 7 is a diagram showing the potential of each part and the amount of secondary electrons observed for the same explanation.

FIGS. 5A and 5B are explanatory views of fifth and sixth embodiments of the present invention, wherein FIG. 5A is an explanatory view of detecting a defect after an electrode is buried in a contact hole according to the present invention. ,
FIG. 3B is an explanatory diagram in a case where a defect of the contact hole is detected after the contact hole is opened according to the present invention.

FIG. 6 is an explanatory view of a gate oxide film inspection according to a seventh embodiment of the present invention.

FIG. 7 is an explanatory diagram of a dielectric strength measurement of a gate oxide film according to an eighth embodiment of the present invention.

FIG. 8 is an explanatory diagram of potential contrast inversion according to a tenth embodiment of the present invention.

FIG. 9 is an explanatory diagram of an example of detecting a defect of a gate oxide film formed on a wafer according to an eleventh embodiment of the present invention. Figure,
(B) is a diagram showing normal and defective gate electrodes.

[Description of Signs] 1 Electron gun 2 Wafer stage 3,23 Back electrode 4,24 Counter electrode 5,25 Voltage generator 6 Electric wire 7 Secondary electron observation device 8 Threshold determination device 9 Threshold comparison device 10,30 Wafer 11,55 , 65 electron beam 12 secondary electron 41 wafer conductive layer 42, 52 insulating film 43 non-conductive electrode 44 conductive electrode (A) 45 conductive electrode (B) 51, 61 substrate 53, 56 defective contact 54, 57 normal contact 62 gate oxidation Film 63 Normal gate electrode 64 Bad gate electrode

Claims (12)

[Claims] An apparatus for inspecting an electrical contact between the first conductive layer and the third element among a first conductive layer, a second insulating film, and a third element formed on a semiconductor wafer, The potential contrast of the secondary electron image of the scanning charged particle microscope equipped with the wafer stage obtained by the magnitude of the secondary electron observation amount of the secondary electron detector, the back electrode contacting the back surface of the wafer, at least the surface of the wafer A counter electrode having a portion facing the back electrode with a space therebetween, a device for controlling a potential difference between the potential of the back electrode and the potential of the counter electrode, and a device for determining a threshold value of a secondary electron observation amount A device for comparing the measured value of the secondary electron observable amount with the threshold value and classifying the measured value of the secondary electron observable value according to whether the measured value of the secondary electron amount is larger or smaller than the threshold value. Over inspection apparatus. 2. A method of inspecting an electrical contact between the first conductive layer and the third element among a first conductive layer, a second insulating film, and a third element formed on a semiconductor wafer, The back surface electrode of the scanning charged particle microscope equipped with a wafer stage in which the potential contrast of the secondary electron image is obtained according to the magnitude of the observed secondary electrons,
Using a counter electrode having at least a portion of the wafer surface with a space facing the back electrode and a device for controlling the potential difference between the back electrode potential and the counter electrode potential, using the back electrode potential Is smaller than the counter electrode potential, by injecting charge into at least the second insulating film and the third element formed on the wafer by irradiating the wafer with a charged particle beam, the third element and Depending on whether or not there is an electrical contact between the first conductive layers, different potentials are formed on the third element, and a secondary electron observation amount generated by irradiating the third element with a charged particle beam is a threshold. Compared with, it is determined that the amount of secondary electrons observed in the third element is larger than the threshold value and that there is an electrical contact between the third element and the first conductive layer, the back electrode potential the Opposite The potential is greater than the pole potential, and a charged particle beam is irradiated on the wafer to inject charges into at least the second insulating film and the third element formed on the wafer, and the third element and the first conductive element are charged. Depending on whether or not there is electrical contact between the layers, different potentials are formed on the third element, and a secondary electron observation amount generated by irradiating the third element with a charged particle beam is compared with a threshold, A method for inspecting a semiconductor wafer, comprising: judging that the amount of observed secondary electrons in the third element is smaller than the threshold value, that there is an electrical contact between the third element and the first conductive layer. 3. The semiconductor wafer inspection according to claim 2, wherein a secondary electron observation amount obtained by irradiating the insulating film with a charged particle beam is used as a threshold for judging a secondary electron observation amount in the third element. Method. 4. The semiconductor wafer inspection method according to claim 2, wherein an average value of the observed amount of secondary electrons in a charged particle beam scanning range is used as a threshold for judging the amount of observed secondary electrons in the third element. 5. An element located at a different position from the third element manufactured on the same layer as the third element within a charged particle beam scanning range, as a threshold for judging a secondary electron observation amount in the third element. 3. The semiconductor wafer inspection method according to claim 2, wherein an observed amount of secondary electrons is used when the charged particle beam is irradiated on the semiconductor wafer. 6. A method for electrically inspecting an opening in said wafer, said insulating hole having a contact hole formed in said insulating film and said insulating film on a semiconductor wafer, wherein a secondary electron is observed in another contact hole. The threshold value is determined based on the amount of secondary electrons in the insulating film or the amount of secondary electrons observed in the insulating film. The potential of the back electrode is made smaller than the potential of the counter electrode. Judgment as a hole, those smaller than the threshold are judged as defective contact holes, the back electrode potential is set higher than the counter electrode potential, and the secondary electron observation amount in the contact hole to be inspected is larger than the threshold. A contact hole that is determined to be a defective contact hole and a hole smaller than the threshold value is determined to be a normal contact hole. The method for inspecting a semiconductor wafer according to claim 2. 7. A method for inspecting the continuity of a contact of a semiconductor wafer having an electrode formed in a contact hole, wherein a threshold value of a secondary electron observation amount at the electrode portion is determined by using a secondary electron observation amount or insulation at another electrode. Determined by the amount of secondary electrons observed in the film, the back electrode potential is made smaller than the potential of the counter electrode, and the one where the amount of secondary electrons observed in the contact electrode to be inspected is larger than the threshold value is determined as a normal contact. A contact smaller than the threshold is determined to be a defective contact, the back electrode potential is set to be higher than the counter electrode potential, and a secondary electron observation amount in the contact electrode to be inspected that is larger than the threshold is determined to be a defective contact. And determining a contact smaller than the threshold value as a normal contact.
The semiconductor wafer inspection method according to the above. 8. A method for inspecting the insulating property of a gate oxide film of a semiconductor wafer having a gate electrode formed on the gate oxide film, the method comprising: Determined by the amount of secondary electrons observed in the film, the back electrode potential is made smaller than the potential of the counter electrode, and the one where the amount of secondary electrons observed in the gate electrode to be inspected is larger than the threshold value is determined as a defective gate oxide film. The one smaller than the threshold value is determined as a normal gate oxide film, the back electrode potential is set higher than the counter electrode potential, and the one where the amount of secondary electrons observed at the gate electrode to be tested is larger than the threshold value is determined as normal. 3. The semiconductor wafer inspection method according to claim 2, wherein a gate electrode is determined, and a gate electrode smaller than the threshold is determined as a defective gate electrode. 9. A method for inspecting a semiconductor wafer having a gate electrode formed on a gate oxide film, the method comprising: irradiating a charged particle beam onto the wafer while gradually increasing a potential difference between a back electrode and a counter electrode. 3. The semiconductor wafer inspection method according to claim 2, wherein a potential difference when the potential contrast of the gate electrode portion becomes maximum or minimum is measured to determine the dielectric strength of the gate oxide film. 10. The semiconductor wafer inspection method according to claim 2, wherein the irradiation of the charged particle beam includes first irradiation for applying a potential to the device and second irradiation for observing secondary electrons. 11. A first secondary electron image is obtained by setting the potential of the back electrode to the potential of the counter electrode or lower, and a second secondary electron image is obtained by setting the potential of the back electrode higher than the potential of the counter electrode. 3. The semiconductor wafer inspection method according to claim 2, wherein the first secondary electron image and the second secondary electron image are used to check for inversion of potential contrast, and to detect an element whose potential contrast is not inverted as a defect. Method. 12. The secondary electrode potential is changed from a first potential to a second potential while continuously irradiating a charged particle beam, and the secondary electrode is changed only for a predetermined period after the rear electrode changes to a second potential. 3. The semiconductor wafer inspection method according to claim 2, wherein the electronic image is obtained by a gate that obtains a secondary electron image only for a selected period, and the element defect is determined based on the secondary electron image.