JPH0792240A - Method for specifying defective part of ic - Google Patents

Abstract

PURPOSE:To generate a contrast image at an abnormal point by performing solely sweeping of electron beams when a first test pattern is generated, and not only casting electron beams, but taking image data when a second test pattern is generated. CONSTITUTION:A setting means 203 for setting a stopping pattern is so constituted as to be able to set two test patterns. When a test pattern gamma which is the same as a test pattern eta, but has a different operating condition to be given to a to-be-tested element DUT is generated and a test pattern generator 200 stops updating of test patterns, a switching means 309 makes a controller 307 for a barrel conduct only sweeping of electron beams EB. When the test pattern etais generated and the generator 200 stops updating of test patterns, the switching means 309 switches both the controller 307 to conduct casting of beams EB and a device 305 to take image data. Accordingly, a potential contrast at a surface of the element DUT can be displayed as a potential distribution when the test pattern eta aimed to actually take an image is applied. An abnormal action is generated as a potential contrast, so that a defective point can be quickly specified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to irradiate an IC to be tested with an electron beam, measure the amount of secondary electrons generated from the irradiation point, and display the potential distribution in the IC as a potential contrast image. The present invention relates to a method of identifying a defective portion of an IC.

[0002]

2. Description of the Related Art Conventionally, an electron beam is swept onto a chip of an IC to be tested (irradiated while scanning), and the amount of secondary electrons generated from each irradiation point is measured at each irradiation point.
An IC test apparatus has been put into practical use in which the potential distribution in the IC is displayed as a potential contrast image by taking in this measured amount as an electric signal and utilized for analysis of a defective portion.

FIG. 22 shows a schematic structure of a conventional IC test apparatus of this type. In the figure, 100 indicates the entire IC test apparatus. The IC test apparatus 100 is roughly divided into a test pattern generator 200 and an electron beam tester 300. The test pattern generator 200 gives a test pattern signal to the device under test DUT mounted on the electron beam tester 300. The conventional test pattern generator 200 includes a start switch 201 for starting the generation of a test pattern, a stop switch 202 used for stopping the generation of the test pattern at an arbitrary time point, and a test pattern when the specified test pattern is generated. Pattern setting means 203 for stopping the update of the test pattern and the pattern holding means 2 for detecting the occurrence of the test pattern set in the stop pattern setting means 203 and stopping the update of the test pattern.
04, and a stop signal generation means 205 for transmitting a signal indicating that the update of the test pattern has stopped. The test pattern signal generation start control, the stop control, and the test pattern update operation in a specific test pattern are performed. It is configured so that it can be controlled to stop.

On the other hand, the electron beam tester 300 includes a lens barrel portion 301 for irradiating the device under test DUT with the electron beam EB.
The device under test DUT is provided below the lens barrel 301.
And a chamber 302 for arranging the
No. 02, and the position of the device under test DUT is X-
The stage 303 to be moved in the Y direction and the device under test DU
Sensor 3 for measuring the amount of secondary electrons generated from T
04, an image data acquisition device 305 that captures the electric signal detected by the sensor 304 as image data, a monitor 306 that displays the image data processed by the image data acquisition device 305 as a potential contrast image, the emission of the electron beam EB, and the emission thereof. The lens barrel controller 307 controls the emission amount (current value), accelerating voltage, scanning speed, scanning area, and the like.

When the pattern holding means 204 detects that the test pattern generator 200 has generated the test pattern set in the stop pattern setting means 203, it suspends the test pattern updating operation and stops the stop pattern setting means 20.
Continue to issue the test pattern set to 3. At the same time, a stop signal indicating that the test pattern updating operation has stopped is given from the stop signal generating means 205 to the image data acquisition device 305 and the lens barrel controller 307. Lens barrel controller 307
Controls the emission of the electron beam EB in response to the supply of the stop signal. At the same time, the image data acquisition device 305 starts capturing image data.

A method of identifying a defective portion of an IC is performed by setting a test pattern that causes a defect in the stop pattern setting means 203. When the test pattern generator 200 detects that a test pattern that causes a failure, which is set in the stop pattern setting means 203, is generated, the test pattern updating operation is temporarily stopped and the stop pattern setting means 20.
Continue to issue the test pattern set to 3. Lens barrel controller 3
07 receives the supply of the stop signal and controls to emit the electron beam EB. Along with this, the image data acquisition device 305
Starts capturing image data. The above-described image data acquisition is performed for the non-defective product state and the defective product state, and the image data acquisition device 305 performs a comparison calculation to identify the difference between the two as the defective part.

[0007]

Conventionally, the stop time of the test pattern is set to be a little longer than the time required to capture the image data. For this reason, if an attempt is made to change the conditions for capturing image data, the stop time of the test pattern also has to be changed, which has the drawback of poor operability.

That is, the acceleration voltage scanning speed of the electron beam, the scanning area, the number of times of scanning, etc. must be set in order to take in the image data, but if these settings are changed, the time required to take in the image data changes. become. For this reason, if the image data acquisition condition is changed, the stop time of the test pattern must be changed accordingly. As a result, both the test pattern generator 200 and the electron beam tester 300 have to be operated, which makes the operation troublesome.

On the other hand, it is necessary to change various conditions for capturing image data according to the purpose of the test. Especially the device under test DU
The surface of T is already covered with an insulating film as a protective layer I
In the C chip, the potential of the wiring conductor buried under this insulating film will be observed. However, it is difficult to extract the potential distribution of the wiring conductor of an IC chip having an insulating film deposited on the surface as a potential contrast image. That is, when the surface of the insulating film is irradiated with the electron beam, the potential gradient due to the distribution of charges on the insulating film gradually disappears in proportion to the irradiation time, and there is a disadvantage that the originally desired potential contrast image cannot be obtained. This is shown in FIG. FIG. 23A shows the conductor L existing under the insulating film.
The potential contrast images when L, H, L, and H logic potentials are respectively applied to ₁ , L ₂ , L ₃ , and L ₄ are shown. As shown in the figure, the potential contrast image is displayed as white (large amount of secondary electron emission) by applying an L logic potential (a voltage close to 0 V or a negative potential). When an H logic potential (a voltage on the positive side of 0 V) is applied, it is displayed in black (the amount of secondary electron emission is small). Here, the insulating substrate PB has an intermediate potential between L logic and H logic and is displayed in gray.

FIG. 23B shows a state immediately after irradiation and scanning with the electron beam EB (at a time point when 0.1 to 0.3 seconds have elapsed). As can be seen from this figure, when the irradiation of the electron beam EB is started, the potential contrast rapidly decreases and disappears after a few seconds as shown in FIG. 23C. Therefore, the acquisition of the image data is effective only in the state shown in FIG. 23A, and since the time during which the potential contrast exists is short, even if the image data is acquired in the image memory, it is possible to obtain a clear image only by acquiring the image data once. Difficult to get.

Due to the phenomenon of the decrease in the potential contrast, the conditions for capturing the image data (electron beam scanning area, electron beam current value, etc.) are frequently changed. Therefore, the setting of the time for stopping the test pattern must be changed every time the image data acquisition condition is changed, which is disadvantageous in terms of operability. An object of the present invention is to invent a method for improving the operability of an IC test apparatus of this type and identifying a defective portion of an IC even if there is a phenomenon of a decrease in potential contrast, and a clear potential contrast image therefor. Is to get.

[0012]

In order to obtain a clear potential contrast image capable of identifying a defective portion of an IC, which is one of the objects of the present invention, it is necessary to propose an IC test apparatus with improved operability. is there. In other words, an electron beam tester that sweeps and irradiates the device under test with an electron beam, measures the amount of secondary electrons generated from each irradiation point, and reproduces the potential distribution in the device under test as an image, and a test pattern for the device under test. In a IC test apparatus configured to include a test pattern generator for giving a test pattern generator, a stop pattern setting means for setting a test pattern to be stopped in the test pattern generator and a test pattern set by the stop pattern setting means are generated. Pattern holding means for stopping the update operation of the test pattern in this state, a stop signal generating means for outputting a pattern stop signal indicating that the update operation of the test pattern has stopped, and the completion of acquisition of image data from the electron beam tester. A release means for releasing the holding state of the pattern holding means in response to the supply of the acquisition completion signal is provided. The image data acquisition means for starting the acquisition of the image data in response to the pattern stop signal generated by the stop signal generation means, and the acquisition completion signal indicating that the image data acquisition means has acquired the required image data And an acquisition completion signal generating means.

According to this structure, when the image data capturing means acquires the required image data, the acquisition completion signal generating means generates the acquisition completion signal indicating the completion of the acquisition of the image data. The pattern generator starts the test pattern update operation by the acquisition completion signal. Therefore, according to this configuration, it is not necessary to set the test pattern stop time in the test pattern generator, the acquisition of image data, the automatic start and stop of the test pattern are repeated, and no human labor is required. .

By setting the generation of the test pattern to the repetitive generation mode, it is possible to repeatedly acquire the image data in the state in which the same test pattern is applied.
In order to identify the defective portion of the IC, it is necessary to compensate for the phenomenon of the decrease in potential contrast and obtain a clear potential contrast image with improved image quality. Therefore, in the first embodiment, the stop pattern setting means provided in the test pattern generator is configured so that at least two test patterns can be set, and the test pattern is updated every time the first test pattern and the second test pattern are generated. Stop the operation. At the same time, when the first test pattern is generated, only the electron beam sweep irradiation is executed without acquiring the image data, and when the second test pattern is generated, the electron beam irradiation and the image data acquisition are executed.

As described above, by only irradiating the electron beam when the first test pattern is generated, the potential contrast of the surface of the device under test is displayed as the potential distribution when the second test pattern for which an image is actually desired is applied. be able to. As a result, a potential contrast image can be obtained every time in a portion where the potential when the first test pattern is applied and the potential when the second test pattern is applied have opposite polarities.
As a result, the effect of improving the image quality can be obtained.

In the second embodiment, electron beam irradiation and image data acquisition are performed both when the first test pattern is generated and when the second test pattern is generated, and the image data obtained when the first test pattern is applied is inverted. , The sum with the image data obtained when applying the second test pattern is obtained. As a result, only the portion where the potential has changed can be displayed as a potential contrast image. In this case, since the sum of the two image data is obtained, the potential contrast of the portion where the potentials are reversed when the first test pattern and the second test pattern are applied is emphasized and obtained, the image quality of the image is improved, and a clear image is obtained. Can be obtained.

In the third embodiment, the electron beam irradiation is performed for several frames both when the first test pattern is generated and when the second test pattern is generated, so that the potentials at the time when the test patterns are finished reach the equilibrium potentials. As a result, when a potential change occurs at the time of generating the first test pattern and at the time of generating the second test pattern, a larger displacement amount with respect to the equilibrium potential is obtained, the potential contrast is emphasized, and the potential contrast with good resolution is obtained. You can get a statue.

As a method of identifying the defective portion of the IC, the first test pattern and the second test pattern are made the same pattern,
The operating conditions given to the device under test DUT at the time of applying each test pattern are changed. As a result, a potential contrast image can be obtained at the failure location.

[0019]

【Example】

(Embodiment 1) FIG. 2 shows an embodiment of an IC test apparatus with improved operability. The parts corresponding to those in FIG. 22 are designated by the same reference numerals. The characteristic structure of this IC test apparatus is that the electron beam tester 300 is provided with an acquisition completion signal generating means 308. The acquisition completion signal generating means 308 detects that the image data acquisition device 305 has completed the acquisition of the image data, and sends an acquisition completion signal at the time of this detection. This acquisition completion signal is input to the pattern holding means 204 provided on the test pattern generator 200 side.

The pattern holding means 204 gives a command for canceling the stop of the test pattern to the test pattern generator 200 by receiving the acquisition completion signal. The test pattern generator 200 is released from the stopped state and starts the test pattern update operation. By setting the test pattern in the stop pattern setting means 203 in this way, the start and stop operations of the test pattern generator 200 are performed by the electron beam tester 30.
Since it is linked to the image data acquisition operation on the 0 side, it is not necessary to change the setting on the test pattern generator 200 side even if the image data acquisition condition is changed. Therefore, the operation is simplified and the operability can be improved.

The invention of this application improves the image acquisition performance by utilizing this IC test apparatus having improved operability.
To obtain a clear potential contrast image that can identify the defective portion of C. FIG. 3 shows an embodiment of this application. In this embodiment, the stop pattern setting means 203 is configured to set the first test pattern r and the second test pattern n, and the electron beam tester 300 is provided with the mode switching means 309. When the test pattern generator 200 stops the test pattern updating operation by the generation of the first test pattern r, the mode switching unit 309 causes the lens barrel controller 307 to perform the sweep irradiation of the electron beam EB, and the image data acquisition device 305. Is a first operation mode in which image acquisition is not executed,
The second test pattern n is generated and the test pattern generator 20 is generated.
When 0 stops the test pattern update operation, control is performed to switch to the second operation mode in which both the lens barrel controller 307 and the image data acquisition device 305 operate.

4 and 5 show the states of the first operation mode and the second operation mode. FIG. 4 shows a case where test patterns are continuously generated from the first address to the last address Last. Further, FIG. 5 shows a case where the first operation mode and the second operation mode are returned to the head address each time they are executed. As described above, by causing the image data to be acquired in the second operation mode after the first operation mode, it is possible to remove the influence of the reduction in the potential contrast on the surface (insulating film) of the device under test DUT.

That is, the device under test DU in the first operation mode
By irradiating T with the electron beam EB, the potential of the surface of the device under test DUT is set to the potential contrast based on the test pattern. Since the test pattern n is generated in the state where the potential contrast is given, only the portion where the wiring conductor to which the potential of the opposite polarity is given in the state where the test pattern r is applied and the state where the test pattern n is applied is present. , The potential contrast image is repeatedly obtained. Therefore, a clear potential contrast image can be obtained by accumulating the potential contrast image.

This is shown in FIGS. 6 to 8. FIG. 6 shows conductors L ₁ , L ₂ and L when the first test pattern r is applied.
₃ shows the potential applied to L ₄ . The example of FIG. 6 shows a state in which L ₁ is given L logic, L ₂ is given H logic, L ₃ is given L logic, and L ₄ is given H logic. FIG. 7 shows the potentials applied to the conductors L _{1 to} L ₄ when the second test pattern n is applied.
In the example of FIG. 7, conductors L ₁ and L ₂ are L logic, and L ₃ and L ₄ are H logic.
Indicates the state of giving logic.

In the state shown in FIG. 6, the area including the conductors L _{1 to} L ₄ is swept and irradiated with the electron beam EB, and the electron beam EB is swept and irradiated in the state where the second test pattern n shown in FIG. 7 is given, At that time, by capturing the image data, the potential contrast image shown in FIG. 8 can be obtained. As is clear from the potential contrast image shown in FIG. 8, only the conductor having the opposite polarity between the state in which the first test pattern r is applied and the state in which the second test pattern n is applied is the potential contrast image. appear. That is, in this example, the conductors L ₂ and L ₃ correspond thereto, and the conductors L ₁ and L ₄ are not displayed as a potential contrast image because the same potential is applied.

The reason will be described with reference to FIG. When the first test pattern r is applied, the conductors L ₁ and L ₃ have L
Since the logic is given, the potential of the insulating film on the surface of these conductors L ₁ and L ₃ is also biased to a potential lower than the equilibrium potential V _S (equivalent to the potential of the insulator) shown by the dotted line in the figure. Also the conductor L ₂
Since H logic is given to L and L ₄ , these L ₂ and L
The potential of the insulating film covering the upper surface of ₄ is biased in the positive direction from the equilibrium potential V _S.

When the electron beam EB is swept and irradiated in this state, the potential of the insulating film temporarily changes toward the equilibrium potential V _S. The potential on the insulating film changes during the period of sweep irradiation with the electron beam EB, but when the irradiation of the electron beam EB stops, the potential change stops. Although some test patterns are applied during the period from the first test pattern r to the second test pattern n, the changed potentials V _a , V _b , V _c , and V _d are as a result of sweep irradiation with the electron beam EB. The value at the time when the irradiation of the electron beam EB is stopped is maintained.

When the second test pattern n is generated, the second test pattern n is applied, and the irradiation of the electron beam EB is restarted, when the potentials given to the conductors L _{1 to} L ₄ have opposite polarities. The potential change starts from a potential greatly separated from the equilibrium potential V _S, and the potential changes start from the potentials V _a and V _d approaching the equilibrium potential V _S in the portion to which the potential having the same polarity as the previous time is applied. Therefore, the second test pattern n is applied and the voltage of the same polarity as that of the previous time is applied. In this example, the potential of the insulating film in the portions of the conductors L ₁ and L ₄ is changed from the potential that has already approached the equilibrium potential V _S. Since the potential change starts and the equilibrium potential V _S has already been approached, the equilibrium potential V _S is reached in a short time, so that almost no potential contrast image can be obtained.

On the other hand, in the portions of the conductors L ₂ and L ₃ to which the voltages of opposite polarities are applied, the potential starts to change from the potentials V _e and V _f which are far from the equilibrium potential V _S. As a result, a potential contrast image can be obtained as in the initial state. Therefore, according to this embodiment, by applying the second test pattern n after applying the first test pattern r, a voltage having a polarity opposite to the voltage applied to the first test pattern r when the second test pattern n is applied. A potential contrast image can always be obtained on a conductor to which is given.

Therefore, the image data can be accumulated by taking in this potential contrast image as image data every time, and a clear potential contrast image can be obtained by performing an averaging process of the image data. By sequentially changing the first test pattern r, when the test pattern n to be observed is applied, the conductors having opposite polarities can be sequentially changed. This makes it possible to observe almost all states of existing conductors.

According to the present invention, a potential contrast image can be obtained on a conductor to which a voltage having a polarity opposite to that of the voltage applied to the first test pattern r is applied when the second test pattern n described above is applied. It is possible to specify the defective portion of the IC. In other words, the failure location can be found by making the first test pattern and the second test pattern the same and changing the operating conditions given to the device under test DUT when each test pattern is applied. The first test pattern is n,
The second test pattern is also n, and when the first test pattern n is applied, the operating voltage is given a voltage outside the specified voltage range of 4.5 to 5.5 V, for example, 3 V, and when the second test pattern is applied, it is specified. The voltage of 5V is applied. If the operation is normal when the first test pattern is applied and when the second test pattern is applied, the second
No potential contrast image is obtained when the test pattern is applied.

On the other hand, when an abnormality occurs in the operation either when the first test pattern is applied or when the second test pattern is applied, a conductor whose applied voltage has a reverse polarity is generated, and a potential contrast image is displayed. Obtainable. Therefore, this potential contrast image includes a portion where the operation is abnormal, and a failure such as a defective margin can be analyzed quickly.

(Embodiment 2) FIG. 9 shows an embodiment of an IC test apparatus for enhancing the potential contrast. The characteristic structure of this embodiment is that the electron beam tester 300 is provided with a plurality of image data acquisition means 305A and 305B, and an arithmetic means 310 for obtaining the sum of the image data acquired by these image data acquisition means 305A and 305B. That is the point.

The acquisition completion signal generating means 308 detects that the image data acquisition means 305A and 305B have completed the acquisition of the image data, and sends an acquisition completion signal at the time of this detection. This acquisition completion signal is input to the pattern holding means 204 provided on the test pattern generator 200 side.
The pattern holding means 204 gives a command for canceling the stop of the test pattern to the test pattern generator 200 when the acquisition completion signal is input. Test pattern generator 2
00 starts the update operation of the test pattern released from the stopped state.

In other words, according to this embodiment, assuming that the stop patterns r and n are set in the stop pattern setting means 203, the pattern holding means 204 operates every time the stop patterns r and n are generated to generate a test pattern. Bowl 200
The test pattern update operation is stopped and the test pattern r
Alternatively, the state in which n is output is maintained. This is shown in FIG. 10A shows a start signal and FIG. 10B shows a test pattern signal. The pattern of the test pattern signal is r or n
Upon reaching (generally indicating an address indicating the pattern generation order), the pattern holding unit 204 stops the pattern updating operation of the test pattern generator 200 and maintains the state of outputting the pattern r or n. At the same time, a stop signal is output from the stop signal generation means 205, and this stop signal is input to the image data acquisition device 305 to start the acquisition of image data. FIG. 10F shows an image data acquisition operation period.

When the test pattern is continuously generated and the restart after the image data acquisition is set to return to the first pattern, the test pattern r is set as shown in FIG.
Automatically occurs, and when the acquisition of the image data is completed, it returns to the first pattern and restarts. Next time, it stops at the test pattern n, and after the acquisition of the image data, it returns to the first test pattern again and the pattern Is repeated. The test patterns r and n specified by setting in this way
It is possible to automatically acquire the image data in the state in which is applied multiple times. For termination, generation of the test pattern can be stopped by operating the stop switch 202.

As described above, according to this embodiment, by observing the potential contrast image and setting the test pattern n and the reference pattern r in the stop pattern setting means 203, the test pattern generator 200 is started and stopped. Since the operation is linked to the image data acquisition operation on the electron beam tester 300 side, it is not necessary to change the setting on the test pattern generator 200 side even if the image data acquisition condition is changed. Therefore, the operation is simplified and the operability can be improved.

The invention of this application improves the image acquisition performance by using this IC test apparatus with improved operability.
To obtain a clearer potential contrast image that can identify the defective portion of C. As shown in FIG. 9, image data in a state in which different test patterns are applied to the plurality of image data acquisition units 305A and 305B is captured. That is, the test pattern r is applied to the device under test DU in the image data acquisition means 305A.
The image data in the state given to T is taken in. The test pattern n is added to the device under test DUT in the image data acquisition means 305B.
Capture the image data in the state given to.

The polarity of the image data taken in by the image data acquisition means 305A is inverted and given to the arithmetic means 310, and the image data taken in by the image data acquisition means 305B is given as it is to the arithmetic means 310. The calculation means 310 adds the image data given from the image data acquisition means 305A and 305B, and displays the addition result on the monitor 300. By displaying the calculation result of the calculation means 310 on the monitor 306, the potential contrast image becomes a clear image.

The reason will be described below. FIG. 12 shows the potentials applied to the wiring conductors L ₁ , L ₂ , L ₃ and L ₄ in the device under test DUT when the test pattern r is applied. That is, the example of the drawing shows a case where the conductor L ₁ is given L logic, the conductor L ₂ is given H logic, the conductor L ₃ is given L logic, and the conductor L ₄ is given H logic.
On the other hand, FIG. 13 shows the potentials applied to the wiring conductors L _{1 to} L ₄ in the device under test DUT when the test pattern n is applied. In the illustrated example, the conductor L ₁ has L logic, and the conductor L ₂ has L logic.
H logic conductor L _3, the conductor L ₄ shows a case of giving the H logic.

14 and 15 show these potential contrast images. 14 shows a potential contrast image when the test pattern r is applied, and FIG. 15 shows a potential contrast image when the test pattern n is applied. In the potential contrast image shown in FIG. 14, the potential contrasts of the conductors L ₁ and L ₄ disappear, and only the potential contrast of the conductors L ₂ and L ₃ remains. In the potential contrast image shown in FIG. 15, the potential contrasts of the conductors L ₁ and L ₄ disappear, and only the potential contrast of the conductors L ₂ and L ₃ remains. The reason is that the potentials applied to the conductors L ₁ and L ₄ are the same when the test pattern r is applied and when the test pattern n is applied.

FIG. 18 shows how the potential contrast disappears. FIG. 18A shows a period in which the test patterns r and n are applied and an electron beam irradiation period. 18B is a potential contrast generated on the insulating film present on the surface of the conductor L ₁ , FIG. 18C is a potential contrast generated on the insulating film present on the surface of the conductor L ₂ , and FIG. 18D is an insulation present on the surface of the conductor L ₃ . FIG. 18E shows the potential contrast generated on the film, and FIG. 18E shows the potential contrast generated on the surface of the conductor L ₄ .

As shown in FIGS. 18B and 18E, the potential contrast is generated at the first application of the test pattern r, but when the test pattern n is subsequently applied, the potentials in the same direction are applied, so that the potential contrast is increased. Is not generated, and the potential contrast is changed to disappear by the irradiation of the electron beam EB, and converges to the equilibrium potential V _S. After that, even if the test patterns r and n are alternately applied, the conductor L ₁
No potential contrast is generated in the insulating film existing on the surfaces of L ₄ and L ₄ .

On the other hand, the insulating films on the surfaces of the conductors L ₂ and L ₃ are applied with potentials of opposite polarities each time the test patterns r and n are applied, so that the test patterns r and n are applied. Each time, the opposite potential contrast is generated. From the above description, the reason why the potential contrast between the conductors L ₁ and L ₄ disappears can be understood. In this embodiment, either one of the potential contrasts left in this way, in this example, the image data acquired by the image data acquisition unit 305A (synonymous with the potential contrast) is inverted in polarity, and the calculation unit 310 is operated.
To the image data acquisition means 305B by the calculation means 310.
It is added to the image data acquired in.

FIG. 16 shows image data obtained by inverting the polarity of the image data (potential contrast) acquired by the image data acquisition means 305A. By adding the image data shown in FIG. 16 and the image data shown in FIG.
The image data shown in 7 is obtained. The image data shown in FIG. 17 are added together and emphasized with respect to the potential contrast of the conductors L ₂ and L ₃ . As a result, the quality of the image is improved and a potential contrast image with good resolution can be obtained.

As described above, the test pattern r is applied to the conductor.
When an electric potential of opposite polarity is applied each time when the test patterns r and n are applied, a reverse electric potential contrast is generated every time the test patterns r and n are applied. Furthermore,
In this embodiment, the potential contrast is emphasized by adding the image data whose polarities are inverted, the image quality is improved, and a potential contrast image with good resolution can be obtained. From this feature, it becomes possible to identify the defective portion of the IC according to the present invention. That is, by making the test patterns r and n the same and changing the operating conditions given to the device under test DUT at the time of applying each test pattern, it is possible to quickly analyze a failure such as a margin failure in the potential contrast image of the first or more embodiments. You can

(Embodiment 3) This embodiment is one of the methods for enhancing the potential contrast, and the same IC test apparatus as that of Embodiment 2 is used. The difference from the second embodiment is that after image data is acquired in the test patterns r and n,
This is to execute only beam irradiation scanning for several frames (one frame or more). This is shown in FIGS. 19 and 20.

FIG. 21 shows how the potential contrast disappears in this embodiment. As shown in FIG. 21B and FIG. 21E, the potential contrast is generated at the beginning when the test pattern r is applied, but it is focused on the equilibrium potential V _S during irradiation scanning of r for several frames. Even if the test patterns r and n are alternately applied thereafter, no potential contrast is generated in the insulating films present on the surfaces of the conductors L ₁ and L ₄ because the potentials in the same direction are applied.

On the other hand, the insulating films present on the surfaces of the conductors L ₂ and L ₃ are applied with potentials of opposite polarities each time the test patterns r and n are applied, so that the test patterns r and n are applied. Each time, the opposite potential contrast is generated. In this method, since the electron beam irradiation scanning is performed for several frames, the potentials at the end of the test pattern reach the equilibrium potentials. As a result, when a potential change occurs like L ₂ and L ₃ , a larger displacement amount with respect to the equilibrium potential can be obtained, and a potential contrast image with high resolution in which the potential contrast is emphasized can be obtained. it can.

As described above, the test pattern r is applied to the conductor.
When an electric potential of opposite polarity is applied each time when the test patterns r and n are applied, a larger amount of displacement with respect to the equilibrium potential is applied to the insulating film existing on the surface of the test pattern r and n in the opposite direction. It is possible to obtain a high-resolution potential contrast image in which the potential contrast is emphasized. From this feature, it becomes possible to identify the defective portion of the IC according to the present invention. That is, by making the test patterns r and n the same and changing the operating conditions given to the device under test DUT at the time of applying each test pattern, it is possible to quickly analyze a failure such as a margin defect in the potential contrast image of Example 1 or more. You can

[0051]

By applying the same test pattern, for example, n repeatedly, and changing the power supply voltage applied to the device under test DUT with each application, an abnormal operation can be generated as a potential contrast. Therefore, there is an advantage that a defective portion can be directly specified immediately, and a great effect can be exerted in analyzing a failure such as a margin failure.

[Brief description of drawings]

FIG. 1 is a waveform diagram for explaining the operation of the present invention (Example 1).

FIG. 2 is a block diagram showing an embodiment of an IC test apparatus with improved operability.

FIG. 3 is a block diagram showing a first embodiment.

FIG. 4 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 5 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 6 is a plan view for explaining the operation of the first embodiment.

FIG. 7 is a plan view for explaining the operation of the first embodiment.

FIG. 8 is a front view showing a display result according to the first embodiment.

FIG. 9 is a block diagram showing a second embodiment.

FIG. 10 is a waveform diagram for explaining the operation of the second embodiment.

FIG. 11 is a waveform diagram for explaining the operation of the second embodiment.

FIG. 12 is a plan view for explaining the potential applied to the wiring in the device under test when the test pattern r of Example 2 is applied.

FIG. 13 is a plan view for explaining the potential applied to the wiring in the device under test when the test pattern n of Example 2 is applied.

FIG. 14 is a front view showing a potential contrast image obtained in a state where the test pattern r is applied after the test patterns r and n of Example 2 are alternately applied.

FIG. 15 is a front view showing a potential contrast image obtained in a state where the test pattern n is applied after the test patterns r and n of Example 2 are alternately applied.

16 is a front view showing a potential contrast obtained by inverting the polarity of the potential contrast shown in FIG. 14 of Example 2. FIG.

FIG. 17 is a front view showing the result of calculation by the calculation means of the second embodiment as potential contrast.

FIG. 18 is a waveform diagram illustrating the reason why the potential contrast disappears in the portion to which the potentials of the same polarity are applied when the test patterns r and n of Example 2 are applied alternately.

FIG. 19 is a waveform chart for explaining the operation of the third embodiment.

FIG. 20 is a waveform chart for explaining the operation of the third embodiment.

FIG. 21 is a waveform diagram illustrating the reason why the potential contrast disappears in a portion to which a potential of the same polarity is applied when test patterns r and n of Example 3 are applied alternately.

FIG. 22 is a block diagram for explaining a conventional technique.

FIG. 23 is a front view showing an example of a potential contrast image for explaining the drawbacks of the conventional technique.

[Explanation of symbols]

 100 IC test apparatus 200 Test pattern generator 201 Start switch 202 Stop switch 203 Stop pattern setting means 204 Pattern holding means 205 Stop signal generating means 300 Electron beam tester 301 Lens barrel section 302 Chamber 303 Stage 304 Sensors 305, 305A, 305B Image data Acquisition device 306 Monitor 307 Lens barrel control unit 308 Acquisition completion signal generation means 309 Mode switching means 310 Computing means

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[Procedure amendment]

[Submission date] April 15, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

By setting the generation of the test pattern to the repetitive generation mode, it is possible to repeatedly acquire the image data in the state in which the same test pattern is applied.
In order to identify the defective portion of the IC, it is necessary to compensate for the phenomenon of the decrease in potential contrast and obtain a clear potential contrast image with improved image quality. Therefore, in the first embodiment, the stop pattern setting means provided in the test pattern generator is configured to be able to set at least two test patterns, and the test pattern is updated every time the first test pattern and the second test pattern are generated. Stop the operation. At the same time, when the first test pattern is generated, only the electron beam sweep irradiation is executed without acquiring the image data, and when the second test pattern is generated, the electron beam irradiation and the image data acquisition are executed. Except when this second test pattern occurs, the electronic bee
By not irradiating the
The image data by irradiation is used for the first test pattern and the second test.
Only the part where the internal potential changed during the test pattern is clear
It is detected as the image data of contrast.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

In the second embodiment, electron beam irradiation and image data acquisition are performed both when the first test pattern is generated and when the second test pattern is generated, and the image data obtained when the first test pattern is applied is inverted. , The sum with the image data obtained when applying the second test pattern is obtained. As a result, only the portion where the potential has changed can be displayed as a potential contrast image. In this case, the difference between the two image data
Since it is obtained, the potential contrast of the portion where the potentials are reversed when the first test pattern and the second test pattern are applied is emphasized and obtained, the image quality of the image is improved, and a clear image can be obtained.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

In the third embodiment, since the electron beam irradiation is performed for several frames (a plurality of times on the same screen) both when the first test pattern is generated and when the second test pattern is generated, the potentials at the end of the test pattern are different. Reach equilibrium potential.
As a result, when a potential change occurs when the first test pattern is generated and when the second pattern is generated,
A larger displacement amount can be obtained, and a potential-contrast image with high resolution in which the potential contrast is emphasized can be obtained.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

(Embodiment 3) This embodiment is one of the methods for enhancing the potential contrast, and the same IC test apparatus as that of Embodiment 2 is used. The difference from the second embodiment is that after image data is acquired in the test patterns r and n,
Only a few beam irradiation scans ( multiple times on the same screen )
Is to do. This is shown in FIGS. 19 and 20.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Correction target item name] Fig. 22

[Correction method] Change

[Correction content]

FIG. 22

Claims (3)

[Claims] 1. A device under test is swept and irradiated with an electron beam,
An electron beam tester for measuring the amount of secondary electrons generated from each irradiation point and reproducing the potential distribution in the device under test as an image, and a test pattern generator for giving a test pattern signal to the device under test are provided. In the IC test apparatus configured as described above, the stop pattern setting means provided in the test pattern generator has two
Two test patterns can be set, only the electron beam sweep irradiation is executed without acquiring image data when the first test pattern is generated, and the electron beam irradiation and image data are generated when the second test pattern is generated. Are displayed, and the potential contrast on the surface of the device under test is displayed as a potential distribution when the second test pattern for which an image is to be actually obtained is applied, and the first test pattern and the second test pattern are set to the same pattern, and each test is performed. A method of identifying a defective portion of an IC, which is performed by changing an operating condition given to a device under test DUT when a pattern is applied and thereby obtaining a potential contrast image at a defective portion. 2. Irradiation with an electron beam and acquisition of image data are performed both when the first test pattern is generated and when the second test pattern is generated, and the image data obtained when the first test pattern is applied is inverted, The sum of the image data obtained when applying the test pattern is calculated, and only the part where the potential has changed is displayed as a potential contrast image, and the potential contrast is emphasized to obtain the image quality of the image, and a clear image is obtained. The method for identifying a defective portion of an IC according to claim 1, wherein 3. The electron beam irradiation is performed for several frames both when the first test pattern is generated and when the second test pattern is generated,
When the potential at the end of the test pattern is reached to the equilibrium potential and the potential change occurs when the first test pattern is generated and the second test pattern is generated, a larger displacement amount is obtained with respect to the equilibrium potential. 2. The method for identifying a defective portion of an IC according to claim 1, which is performed by obtaining a potential-contrast image with high resolution in which the potential contrast is emphasized.