JPH07287055A - Ion beam tester, ic testing device using it, and method for specifying failed part of ic using ic testing device - Google Patents

Abstract

PURPOSE:To provide a new ion beam tester and an IC testing device where the operability of the device and picture quality can be improved and a method for measuring an element to be tested. CONSTITUTION:A stop signal generation means 205 is newly provided at a test pattern generator 200 and an acquisition completion signal generation means 308 is provided at an ion beam tester. Image data start to be acquired by the stop signal and the stop state is canceled when the image data are completely acquired and updating is resumed. This repetition enables a desired potential contrast image to be repeatedly acquired. Also, by providing a mode switching means at the side of a charged particle ray device 300 to obtain a clearer potential contrast image. Measurement methods for achieving a clear potential contrast include a method for executing the acquisition of image data at each other time, that for inverting and then adding one of two image data, and that for acquiring image data by applying a charged particle ray 320 to the same screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates an IC under test with a charged particle beam, measures the amount of secondary electrons generated from the irradiation point, and displays the potential distribution in the IC as a potential contrast image. The present invention relates to an ion beam tester used to identify a portion, an IC testing apparatus using the same, and a method of identifying a defective portion of an IC using this apparatus.

[0002]

2. Description of the Related Art Conventionally, a chip of an IC to be tested is swept irradiated with a charged particle beam (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.

Regarding these technologies, the applicant of the present application has previously mentioned in Japanese Patent Application No. 5-190449 "Electron beam tester and IC tester using the same" and Japanese Patent Application No. 5-257625.
"A method for identifying a defective portion of an IC" is disclosed. After that, in the process of pursuing the disclosed technique, it was confirmed that the invention can be applied not only to the electron beam tester but also to all charged particle beam devices including the ion beam tester, and is an effective invention. The details will be described below.

FIG. 18 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 device 100 is roughly divided into a test pattern generator 200 and a charged particle beam device 300. Here, the charged particle beam device 300 refers to an ion beam tester and an electron beam tester, but in this specification, the ion beam tester is referred to as a charged particle beam device 300.
Further, the ion beam is referred to as a charged particle beam.

The test pattern generator 200 gives a test pattern signal to the device under test DUT mounted on the charged particle beam device 300. The conventional test pattern generator 200 includes a start switch 201 for starting the generation of a test pattern,
The stop switch 202 used to stop the generation of the test pattern at an arbitrary time, the stop pattern setting means 203 for stopping the update of the test pattern when the specified test pattern occurs, and the stop pattern setting means 203. A pattern holding means 204 for detecting the occurrence of the set test pattern and stopping the update of the test pattern, and a stop signal generating means 205 for transmitting a signal indicating that the update of the test pattern has stopped are provided. The pattern signal generation start control, the stop control, and the control for stopping the test pattern update operation in a specific test pattern can be performed.

On the other hand, the charged particle beam apparatus 300 includes a lens barrel portion 301 for irradiating the device under test DUT with a charged particle beam, and a chamber provided under the lens barrel portion 301 for arranging the device under test DUT in a vacuum. 302, a stage 303 provided inside the chamber 302 for moving the position of the device under test DUT in the XY direction, and a sensor 304 for measuring the amount of secondary electrons generated from the device under test DUT.
An image data acquisition device 305 that captures an electrical 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; and emission of a charged particle beam and its emission. Amount (current value), acceleration voltage, scanning speed,
The lens barrel controller 307 controls the 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, the test pattern updating operation is temporarily stopped, and 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
Receives the supply of the stop signal and controls the firing of the charged particle beam. 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 which causes a defect in the stop pattern setting means 203. The test pattern that causes a defect is
It is confirmed in advance by a general IC tester. When the test pattern generator 200 detects that the test pattern that causes the failure set in the stop pattern setting unit 203 is generated, the test pattern updating operation is temporarily stopped and the test pattern set in the stop pattern setting unit 203 is stopped. Keep issuing. The lens barrel controller 307 receives the supply of the stop signal and controls to emit the charged particle beam. At the same time, 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.

[0009]

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 of the charged particle beam, the scanning speed, 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. Will be done. For this reason, if you change the image data acquisition conditions,
The test pattern stop time must also be changed to accommodate this. As a result, the test pattern generator 200
Since it is necessary to operate both the charged particle beam device 300 and the charged particle beam device 300, the operation is 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. In other words, when the surface of the insulating film is irradiated with a charged particle beam, the potential distribution gradually disappears due to the accumulation of charges on the insulating film in proportion to the irradiation time, and the originally desired potential contrast image cannot be obtained. FIG. 19 shows the situation. FIG. 19A shows a 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 (the amount of secondary electrons reaching the sensor 304 is large) 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 electrons reaching the sensor 304 is small). Here, the insulating substrate PB has an intermediate potential between L logic and H logic and is displayed in gray.

FIG. 19B shows the state immediately after the irradiation and scanning of the charged particle beam (when 0.1 to 0.3 seconds have elapsed). As can be seen from this figure, when irradiation of the charged particle beam is started, the potential contrast rapidly decreases and disappears after a few seconds as shown in FIG. 19C. Therefore, capturing of image data is effective only in the state shown in FIG. 19A, and since the time during which the potential contrast exists is short, even if the image data is captured in the image memory, it is possible to obtain a clear image only by capturing the image data once. Difficult to get.

Due to the phenomenon of the decrease in the potential contrast, the image data acquisition condition (the scanning area of the charged particle beam, the current value of the charged particle beam, etc.) is 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 improve the operability of this type of IC test device and to obtain a clear potential contrast image even if there is a phenomenon of potential contrast reduction. Ion beam tester (charged particle beam device) Another object of the present invention is to provide an IC tester using the same and a method for identifying a defective part of a new IC.

Another object of the present invention is to improve the image quality of a potential contrast image representing the potential distribution of wiring conductors in an IC chip in a state where a desired test pattern is applied, in an IC chip covered with an insulating film. Is to let.
A brief supplementary explanation will be given to the points of this purpose. The potential contrast image is obtained by sweeping and irradiating a partial area of the device under test DUT with a charged particle beam in a state where a desired test pattern is applied to the device under test DUT, and capturing the generation amount of secondary electrons as image data. As described above, in an IC chip in which the surface of the device under test is covered with an insulating film, the potential distribution formed on the insulating film disappears in proportion to the dose of the charged particle beam as described above. There is. Therefore, the acquisition of image data is limited to the first one-time surface scanning of the charged particle beam irradiation. Image data is taken in only during this one-time sweep irradiation of the charged particle beam, the image data is stored in a screen memory or the like, the stored image data is repeatedly read, and a potential contrast image is displayed on the monitor 306. However, the amount of image data is small, so that there is a drawback that the details are unclear.

As a method of solving this drawback, a method of sequentially updating the test pattern and continuing the sweep irradiation of the charged particle beam until the specific test pattern n is reached can be considered. By adopting this method, since the charged particle beam is swept and irradiated while the test pattern is changing at high speed, the potential of the insulating film covering the upper surface of the IC chip is the average value of the potential change of the wiring conductor, that is, H logic. When the update activity of the target test pattern n is stopped, the potential distribution determined by the test pattern can be captured as a potential contrast image. After the capture of the image data, the test pattern update operation is restarted again, and if the charged particle beam sweep irradiation is continued even in this state, the potential of the insulating film becomes an intermediate value between H logic and L logic again.

Therefore, by repeating this, the potential contrast image with the desired test pattern applied can be repeatedly obtained, the amount of image data can be increased, and the image quality of the potential contrast image can be improved. Benefits are obtained. However, this method also has the following drawbacks. In other words, when the pattern update operation is stopped with a desired test pattern, a wiring conductor that appears as a potential contrast image due to the potential immediately before that and a wiring conductor that does not appear as a potential contrast image coexist, and potential contrast unsuitable for defect analysis. Become a statue. The reason why the conductors that appear as the potential contrast image and the conductors that do not appear as the potential contrast image coexist will be understood from the description of the operation of the second invention of this application.

[0017]

The first invention of this application proposes a device capable of improving operability. That is, the charged particle beam device sweeps and irradiates the device under test, measures the amount of secondary electrons generated from each irradiation point, and displays the potential distribution in the device under test as an image, and the device under test. In an IC test apparatus configured to include a test pattern generator for giving a test pattern, a stop pattern setting means for setting a test pattern for stopping the update of the test pattern in the test pattern generator, and the stop pattern setting means. The pattern holding means for stopping the test pattern update operation in the state where the test pattern set in 1. is generated, the stop signal generation means for outputting the pattern stop signal indicating that the test pattern update operation is stopped, and the charged particle beam device. And a release means for releasing the holding state of the pattern holding means in response to the supply of the acquisition completion signal indicating the completion of the acquisition of the image data from , An image data acquisition means for starting the acquisition of image data in response to a pattern stop signal generated by the stop signal generation means in the charged particle beam device, and an acquisition indicating that this image data acquisition means has acquired the required image data An acquisition completion signal generating means for generating a completion signal is provided.

According to the structure of the first aspect of the present invention, 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. .

The second invention of this application aims to improve the image quality by compensating for the decrease phenomenon of the potential contrast. For this reason, in the second invention, at least two test patterns are set in the stop pattern setting means provided in the test pattern generator, and the test pattern is generated every time the first test pattern and the second test pattern are generated. Stop the update operation. At the same time, when the first test pattern is generated, only the charged particle beam sweep irradiation is executed without acquiring the image data, and when the second test pattern is generated, the charged particle beam irradiation and the image data acquisition are executed. In other cases, by not irradiating the charged particle beam, the image obtained by irradiating the second test pattern has a large change in the signal at the portion where the internal potential changes as compared with the case of the first test pattern. Detected.

As described above, by only irradiating the charged particle beam when the first test pattern is generated, the potential contrast on the surface of the device under test is displayed as the potential distribution when the second test pattern is applied to actually acquire an image. can do. 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.

As an invention of a method of identifying a defective portion of an IC,
The first test pattern and the second test pattern are made to be the same test pattern by using the apparatus of the above invention, and the measuring method for changing the operating condition given to the device under test DUT at the time of applying each test pattern, the first test pattern and the second test A different test pattern is used, image data is acquired at the time of applying each test pattern, and a measurement method for displaying the image data of the difference and a first method at the time of applying the first test pattern and the second test pattern
We propose a method of acquiring image data during the second irradiation and irradiating the same screen multiple times to make the surface potential of the device under test equilibrium potential. As a result, a clear potential contrast image can be obtained at the failure location.

[0022]

FIG. 1 shows an embodiment of the first invention of this application.
Portions corresponding to those in FIG. 18 are designated by the same reference numerals. The characteristic structure of this IC test apparatus is the charged particle beam apparatus 300.
The point is that the acquisition completion signal generating means 308 is provided. The acquisition completion signal generating means 308 is the image data acquisition device 30.
Detected that the acquisition of image data was completed in 5,
An acquisition completion signal is transmitted 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.

Upon receiving the acquisition completion signal, the pattern holding means 204 gives the test pattern generator 200 a command for canceling the stop of the test pattern. The test pattern generator 200 is released from the stopped state and starts the test pattern update operation. In other words, according to the present invention, assuming that the stop pattern n is set in the stop pattern setting means 203, the pattern holding means 204 operates every time the stop pattern n occurs and the test pattern generator 2
The test pattern update operation of 00 is stopped, and the state in which the test pattern n is output is maintained. The situation is shown in FIG. 2A shows a start signal and FIG. 2B shows a test pattern signal. When the pattern of the test pattern signal reaches n (generally indicating an address indicating the pattern generation order), the pattern holding unit 204 stops the pattern update operation of the test pattern generator 200 and maintains the state in which the pattern n is output. . At the same time, a stop signal is output from the stop signal generating means 205, and this stop signal is input to the image data capturing device 305 to start capturing image data. FIG. 2D shows an image data fetching operation period.

Completion of image data acquisition can be known by detecting, for example, a vertical retrace signal indicating that the sweep irradiation of the charged particle beam has reached one screen. By transmitting the acquisition completion signal when one or an arbitrary number of vertical blanking signals are detected, the acquisition completion signal can be transmitted when the charged particle beam scans one screen to several screens of arbitrary screens. . The acquisition completion signal is shown in FIG. 2E.

The test pattern signal generator 200 is supplied with the acquisition completion signal by the pattern holding means 204.
Is released from the stopped state, the test pattern is updated to n + 1, n + 2 ... As shown in FIG. 2B, and the final pattern Last is output. When the test pattern is generated once, the test pattern is stopped in the state where the final pattern Last is generated.

When the test pattern generation is set to be continuous, the test pattern n is automatically stopped each time the test pattern n is generated, as shown in FIG. 3, and restarted when the acquisition of the image data is completed, and the final pattern Last is set. After the occurrence, the test pattern returns to the beginning and the pattern is repeated. However, after the image data is acquired, the generation of the test pattern can be returned to the beginning as shown in FIG. In any case, the image data in the state in which the specified test pattern n is applied can be automatically acquired a plurality of times. For termination, generation of the test pattern can be stopped by operating the stop switch 202.

By setting the test pattern in the stop pattern setting means 203 in this way, the test pattern generator 200
Since the start and stop operations of are linked to the image data acquisition operation on the charged particle beam device 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 second invention of this application intends to improve the image acquisition performance by utilizing the IC test apparatus proposed in the first invention. The second part of this application is shown in FIG.
An example of the invention will be described. In the second invention, the stop pattern setting means 203 is configured so that the first test pattern r and the second test pattern n can be set, and the charged particle beam device 3 is also provided.
00 is provided with a mode switching means 309. When the first test pattern r is generated and the test pattern generator 200 stops the test pattern update operation, the mode switching unit 309 causes the lens barrel controller 307 to perform the sweep irradiation of the charged particle beam, and the image data acquisition device 305. Does not perform image capture 1st
Operation mode and when the second test pattern n is generated and the test pattern generator 200 stops the test pattern update operation, it is switched to the second operation mode in which both the lens barrel controller 307 and the image data acquisition device 305 are operated. Take control.

6 and 7 show the states of the first operation mode and the second operation mode. FIG. 6 shows a case where the test pattern is continuously generated from the first address to the last address Last. Further, FIG. 7 shows a case where the first operation mode and the second operation mode are executed to return to the head address. 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 a charged particle beam, the device under test DU
The potential on the surface of T 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 will be described with reference to FIGS. 8, 9, 11 and 14. FIG. 8 shows the potentials applied to the conductors L ₁ , L ₂ , L ₃ , and L ₄ when the first test pattern r is applied. The example of FIG. 8 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. 9 is the second
The electric potentials given to the conductors L _{1 to} L ₄ when the test pattern n is applied are shown. The example of FIG. 9 shows a state in which the L logic is applied to the conductors L ₁ and L ₂ and the H logic is applied to L ₃ and L ₄ .

In the state shown in FIG. 8, the area including the conductors L _{1 to} L ₄ is swept-irradiated with the charged particle beam, and in the state where the second test pattern n shown in FIG. At that time, by capturing the image data, the potential contrast image shown in FIG. 11 can be obtained. As is apparent from the potential contrast image shown in FIG. 11, 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. First
Since the L logic is given to the conductors L ₁ and L ₃ when the test pattern r is applied, the potential of the insulating film on the surface of these conductors L ₁ and L ₃ is also equal to the equilibrium potential V _S (insulator (Equivalent to the potential of)) is biased to a lower potential. Also the conductor L
Since the ₂ and L ₄ are given H logic, the potential of the insulating film covering the upper surface of these L ₂ and L ₄ it is being biased than the equilibrium potential V _S in the forward direction.

When the charged particle beam 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 charged particle beam, but when the irradiation of the charged particle beam stops, the potential change stops. Although some test patterns are applied during the time from the first test pattern r to the second test pattern n, the potential V changed as a result of sweep irradiation with the charged particle beam.
The values _a , _Vb , _Vc , and _Vd are maintained at the values when the irradiation of the charged particle beam was stopped.

When the second test pattern n is generated, the second test pattern n is applied and the irradiation of the charged particle beam is restarted, when the potentials applied 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 at the portions of the conductors L ₁ and L ₄ is already the equilibrium potential V.
And the potential change starts from the potential approaching the _S, further since it is already close to the equilibrium potential V _S, a short time at a potential contrast image because it would reach the equilibrium potential V _S is hardly 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 changes start from the potentials V _e and V _f which are greatly separated from the equilibrium potential V _S. As a result, a potential contrast image can be obtained as in the initial state. Therefore, according to the second aspect of the present invention, by applying the second test pattern n after applying the first test pattern r, the second test pattern n is applied.
A potential contrast image can always 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 test pattern n is applied.

Therefore, the image data can be accumulated by taking in the potential contrast image as image data every time, and a clear potential contrast image can be obtained by performing the 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.

Next, the invention of a method of identifying a defective portion of an IC will be described. As a first measurement method invention, the device of the present invention is used, and the first test pattern and the second test pattern are set to the same test pattern n, and a failure occurs by changing the operating condition given to the device under test DUT when each test pattern is applied. Discover the place. That is, the first test pattern is n, the second test pattern is also n, and when applying the first test pattern n, the operating voltage is given a voltage outside the specified voltage range of 4.5 to 5.5 V, for example, 3 V, A prescribed voltage of 5 V is applied when the second test pattern is applied. If the operation is normal when the first test pattern n is applied and when the second test pattern n is applied, no potential contrast image is obtained when the second test pattern n is applied.

On the other hand, when an abnormality occurs in the operation either when the first test pattern n is applied or when the second test pattern n is applied, a conductor whose applied voltage has a reverse polarity is generated and the potential contrast is increased. You can get a statue. 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.

As an operating condition, there is also a method in which the operating voltage is kept constant and the clock rate of each test pattern is changed for measurement. For example, it is a method in which the clock rate in the first test pattern is set to a standard, for example, 10 MHz, and is changed to 15 MHz in the second test pattern for measurement. In this measurement method, if any one of the operations is abnormal,
A potential contrast image can be obtained, and failure analysis such as margin failure can be quickly performed.

In the second method invention, the polarity of the image data captured at the time of applying the first test pattern r is inverted and stored, and
The image data acquired at the time of applying the test pattern n is added, and the addition result is used as a potential contrast image on the monitor 3
00 is displayed. Also in this second measuring method, the potential contrast image becomes a clear image.

The reason will be described again with reference to FIGS. 8 to 14. FIG. 8 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 L logic conductor L ₁ in the example of FIG. 8,
The case where the H logic is given to the conductor L ₂ , the L logic is given to the conductor L ₃ , and the H logic is given to the conductor L ₄ is shown. On the other hand, FIG. 9 shows the wiring conductors L _{1 to} L ₄ in the device under test DUT when the test pattern n is applied.
Indicates the potential applied to. In the example of FIG. 9, the conductor L ₁ is given L logic, the conductor L ₂ is given L logic, the conductor L ₃ is given H logic, and the conductor L ₄ is given H logic.

FIG. 10 and FIG. 11 show these potential contrast images. FIG. 10 shows a potential contrast image when the test pattern r is applied, and FIG. 11 shows a potential contrast image when the test pattern n is applied. In the potential contrast image shown in FIG. 10, 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. 11, the potential contrast between the conductors L ₁ and L ₄ disappears, and only the potential contrast between 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. 14 shows how the potential contrast disappears. FIG. 14A shows a period during which the test patterns r and n are applied and a period during which the charged particle beam is irradiated. 14B is a potential contrast generated on the insulating film present on the surface of the conductor L ₁ , FIG. 14C is a potential contrast generated on the insulating film present on the surface of the conductor L ₂ , and FIG. 14D is an insulation present on the surface of the conductor L ₃ . FIG. 14E shows the potential contrast generated on the film, and FIG. 14E shows the potential contrast generated on the surface of the conductor L ₄ .

As shown in FIGS. 14B and 14E, 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, the potential contrast changes in the direction of disappearing by the irradiation of the charged particle beam, and converges to the equilibrium potential V _S. After that, even if the test patterns r and n are alternately applied, the conductors L ₁ and L
_No potential contrast occurs in the insulating film existing on the surface of ₄ .

On the other hand, the test patterns r and n are applied to the insulating films present on the surfaces of the conductors L ₂ and L _{3 because} potentials of opposite polarities are applied each time 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.

FIG. 12 shows image data (potential contrast) of the image data obtained in the first test pattern, which is obtained by reversing the polarity of FIG. By adding the image data shown in FIG. 12 and the image data shown in FIG.
The image data shown in 3 is obtained. The image data shown in FIG. 13 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 polarity-inverted image data of one test pattern and the image data of the other test pattern,
The image quality is improved, and a potential-contrast image with good resolution can be obtained.

In the third method invention, when the first test pattern r and the second test pattern n are applied, only the charged particle beam irradiation scanning is performed a plurality of times on the same screen after the first image data acquisition. This is shown in FIGS. 15 and 16.

FIG. 17 shows how the potential contrast disappears in this embodiment. As shown in FIGS. 17B and 17E, the potential contrast is first generated when the first test pattern r is applied, but converges to the equilibrium potential V _S during the irradiation scanning of the charged particle beam a plurality of times. Even if the first test pattern r and the second test pattern n are applied alternately thereafter, the potentials in the same direction are applied to the conductors L ₁ and L ₄ , so that a potential contrast is generated in the insulating film existing on the surface thereof. do not do.

On the other hand, since the insulating film existing on the surfaces of the conductors L ₂ and L ₃ is applied with a potential of opposite polarity every time the first test pattern r and the second test pattern n are applied, the test pattern Each time r and n are applied, the opposite potential contrast occurs. In this method, irradiation scanning with the charged particle beam is performed a plurality of times on the same screen, so that 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.

[0052]

According to the present invention, compared with the conventional device,
By providing the acquisition completion signal generating means, the operability was greatly improved and the system could be automated. Next, by providing the mode switching means, the irradiation method of the charged particle beam and the image data acquisition method at the time of a plurality of test patterns can be switched to various kinds, and the flexibility of the measurement method is increased. Further, the potential contrast image can be clearly displayed by the new measuring method, and the abnormal operation of the device under test can be generated as the potential contrast.
Therefore, there is also 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 block diagram showing an embodiment of a first invention of this application.

FIG. 2 is a waveform chart for explaining the operation of the embodiment shown in FIG.

FIG. 3 is a waveform chart for explaining the operation of the embodiment shown in FIG.

4 is a waveform chart for explaining the operation of the embodiment shown in FIG.

FIG. 5 is a block diagram showing an embodiment of the second invention of this application.

6 is a waveform chart for explaining the operation of the embodiment shown in FIG.

7 is a waveform diagram for explaining the operation of the embodiment shown in FIG.

FIG. 8 is a plan view for explaining the potential applied to the wiring in the device under test when the test pattern r of the example is applied.

FIG. 9 is a plan view for explaining the potential applied to the wiring in the device under test when the test pattern n of the example is applied.

FIG. 10 is a front view showing a potential contrast image obtained in a state where the test pattern r is applied after alternately applying the test patterns r and n of the example.

FIG. 11 is a front view showing a potential contrast image obtained by applying the test pattern n after alternately applying the test patterns r and n of the example.

12 is a front view showing a potential contrast obtained by inverting the polarity of the potential contrast shown in FIG. 10 of the example.

FIG. 13 is a front view showing the calculation result of the embodiment as potential contrast.

FIG. 14 is a waveform diagram illustrating the reason why the potential contrast disappears in a portion to which a potential having the same polarity is applied when test patterns r and n of the example are applied alternately.

FIG. 15 is a waveform chart for explaining the operation of the measurement method embodiment.

FIG. 16 is a waveform chart for explaining the operation of the measurement method embodiment.

FIG. 17 is a waveform diagram illustrating the reason why the potential contrast disappears in a portion to which a potential having the same polarity is applied when the test patterns r and n of the example are applied alternately.

FIG. 18 is a block diagram for explaining a conventional technique.

FIG. 19 is an explanatory diagram 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 Charged particle beam apparatus 301 Lens barrel section 302 Chamber 303 Stage 304 Sensor 305 Image data acquisition apparatus 306 Monitor 307 Lens barrel control section 308 Acquisition completion signal generating means 309 Mode switching means 320 Charged particle beam

Claims (9)

[Claims] 1. An ion beam tester for sweeping and irradiating the surface of a device under test with a charged particle beam, measuring the amount of secondary electrons generated from each irradiation point, and displaying the potential distribution in the device under test as an image. (300) and a test pattern generator (2) for sequentially updating and applying a test pattern signal to the device under test.
00) and an IC test apparatus (100) configured to include
In the test pattern generator (200) side, a stop pattern setting means (203) for setting a test pattern for stopping the update of the test pattern, and the stop pattern setting for the test pattern generator (200). Means (203)
The test pattern update operation is stopped while the generation of the test pattern set to is held, and the test pattern generator () receives the acquisition completion signal indicating the completion of the acquisition of the image data from the ion beam tester (300). Pattern holding means (204) for restarting the pattern update of (200)
And a stop signal generating means (20) for outputting a pattern stop signal indicating that the test pattern update operation has stopped.
5) is provided, and the ion beam tester (300) receives the pattern stop signal generated by the stop signal generation means (205) and starts capturing image data, and the image data acquisition means (305). An IC test apparatus, comprising: an acquisition completion signal generating means (308) for generating the acquisition completion signal indicating that the data acquisition means (305) has acquired the required image data. 2. An ion beam tester for sweeping and irradiating the surface of a device under test with a charged particle beam, measuring the amount of secondary electrons generated from each irradiation point, and displaying the potential distribution in the device under test as an image. (300) and a test pattern generator (2) for sequentially updating and applying a test pattern signal to the device under test.
00) and an IC test apparatus (100) configured to include
In the test pattern generator (200) side, stop pattern setting means (203) for setting at least two test patterns, that is, a first test pattern and a second test pattern, for which updating of the test pattern should be temporarily stopped, For the test pattern generator (200), the stop pattern setting means (2
Pattern holding means (204) for stopping the update operation of the test pattern while holding the generation of the test pattern set in (03), and a stop signal for outputting a pattern stop signal indicating that the update operation of the test pattern is stopped. And an image data acquisition means (305) for providing the ion beam tester (300) with the pattern stop signal generated by the stop signal generation means (205) to start capturing image data. , In the state where the first test pattern is generated and the test pattern update operation is temporarily stopped, the acquisition of image data is prohibited in response to the pattern stop signal, and only the charged particle beam sweep irradiation is performed on the device under test. In the first operation mode, the second test pattern is generated, and the test pattern update operation is temporarily stopped. The second that performs image data acquisition operation while sweeping irradiation of the secondary line
An IC test apparatus comprising: a mode switching means (309) for switching between operation modes and executing the mode. 3. The IC test device (10) according to claim 2.
0), the ion beam tester (300) includes acquisition completion signal generation means (308) for generating the acquisition completion signal indicating that the image data acquisition means (305) has completed acquisition of image data, and The pattern holding means (204) is configured to receive an acquisition completion signal indicating completion of acquisition of image data from the ion beam tester (300) and restart pattern updating of the test pattern generator (200). Test equipment. 4. The amount of secondary electrons generated from each irradiation point by sweeping and irradiating the surface of the device under test, to which the test pattern generated by sequentially updating from the test pattern generator (200) is given, with the charged particle beam. And an ion beam tester (30) for displaying the surface potential distribution of the device under test as an image.
In 0), the image data acquisition means (305) for receiving the pattern stop signal from the test pattern generator (200) and starting the acquisition of the image data, and the image data acquisition means (3).
05) generates an acquisition completion signal indicating that necessary image data has been acquired, and supplies an acquisition completion signal generating means (308) for supplying the acquisition completion signal to the test pattern generator (200). Ion beam tester. 5. The amount of secondary electrons generated from each irradiation point by sweeping and irradiating the surface of the device under test, to which the test pattern generated by sequentially updating from the test pattern generator (200) is given, with the charged particle beam. And an ion beam tester (30) for displaying the surface potential distribution of the device under test as an image.
0), an image data acquisition unit (305) that starts capturing image data in response to a pattern stop signal generated by the test pattern generator (200), and a first test pattern in the test pattern generator (200). And a first operation mode in which the acquisition of image data is prohibited in response to the pattern stop signal and only the charged particle beam is swept to the device under test in response to the pattern stop signal.
A second test pattern is generated in the test pattern generator (200), and an operation of acquiring image data is performed while sweeping and irradiating the device under test with a charged particle beam in a state where a test pattern updating operation is temporarily stopped. An ion beam tester comprising: a mode switching unit (309) for switching between operation modes and executing the mode. 6. The ion beam tester (300) according to claim 5, wherein the image data acquisition means (30).
When 5) completes the acquisition of the required image data, it generates an acquisition completion signal indicating that, and the test pattern generator (20
0) acquisition completion signal generating means (308)
Ion beam tester including. 7. An ion beam tester for irradiating the surface of the device under test with a charged particle beam by sweeping, measuring the amount of secondary electrons generated from each irradiation point, and displaying the potential distribution on the surface of the device under test as an image. (300) and a test pattern generator (200) for sequentially updating and applying a test pattern signal to the device under test, the test pattern generator (20)
In the method for measuring the device under test of the IC test apparatus (100) configured to set two test patterns in the stop pattern setting means (203) provided on the (0) side, a first test pattern and a second test are provided. The same test pattern n is used as the pattern, and the operating conditions given to the device under test at the time of application of the first test pattern n and the second test pattern n are set to different operating conditions. When the second test pattern n is executed, the sweep irradiation of the charged particle beam and the acquisition of the image data are executed without acquiring the image data. Display a contrast image,
A method for identifying a defective portion of an IC. 8. An ion beam tester for sweeping and irradiating the surface of a device under test with a charged particle beam, measuring the amount of secondary electrons generated from each irradiation point, and displaying the potential distribution on the surface of the device under test as an image. (300) and a test pattern generator (200) for sequentially updating and applying a test pattern signal to the device under test, the test pattern generator (20)
In the method of measuring the device under test of the IC test apparatus (100) configured to set two test patterns in the stop pattern setting means (203) provided on the (0) side, the electron beam at the time of the first test pattern r Sweep irradiation and image data acquisition are performed, electron beam sweep irradiation and image data acquisition are performed at the second test pattern n, and the image data obtained at the first test pattern r and the second test pattern are performed. The difference from the image data obtained at time n is obtained, and the potential contrast image on the surface of the device under test is displayed.
A method for identifying a defective portion of an IC. 9. An ion beam tester for irradiating the surface of a device under test with a charged particle beam by sweeping irradiation, measuring the amount of secondary electrons generated from each irradiation point, and displaying the potential distribution on the surface of the device under test as an image. (300) and a test pattern generator (200) for sequentially updating and applying a test pattern signal to the device under test, the test pattern generator (20)
In the measuring method of the device under test of the IC test apparatus (100) configured to set two test patterns in the stop pattern setting means (203) provided on the (0) side, charged particles are generated at the time of the first test pattern r. The surface of the device under test is repeatedly irradiated with the charged particle beam several times on the same screen even when the surface potential of the device under test is set to the equilibrium potential by repeating the sweep irradiation of the same line multiple times on the same screen. The potential is set to the equilibrium potential, and the image data is acquired for the first screen portion during the irradiation of the charged particle beam sweep in the first test pattern r or the second test pattern n, and the potential contrast of the surface of the device under test is acquired. Displaying a statue,
A method for identifying a defective portion of an IC.