WO1997013157A1

WO1997013157A1 - Ic tester and method of locating defective portions of ic

Info

Publication number: WO1997013157A1
Application number: PCT/JP1995/002053
Authority: WO
Inventors: Masayuki Kuribara; Akira Goishi; Koshi Ueda
Original assignee: Advantest Corporation
Priority date: 1994-04-08
Filing date: 1995-10-06
Publication date: 1997-04-10

Abstract

An apparatus for analyzing failures of an IC chip and locating defective portions by irradiating the surface of an IC with an ion beam and displaying a potential contrast image of a wiring conductor on the surface of the chip, which provides improved handling and better image quality. To this end, means for setting a plurality of patterns for stopping an updating operation of the patterns is provided in a test pattern generator, the pattern updating operation of the test pattern generator is stopped wherever this stop pattern is generated, and a stop signal is sent to an ion beam tester so as to acquire image data. When acquisition of the image data is completed, signal generation means transmits an acquisition completion signal, and the test pattern generator again starts the pattern updating operation. As a result, different test patterns can be applied alternately to the chip under test, and image quality can be improved by adding and subtracting the image data. A method of locating defective portions of the IC comprises turning off a power supply of the chip at the time of a first test pattern (r) so as to fix the logic of the wiring conductor at the (r) pattern to LOW so that a difference always occurs in a potential contrast image when any difference of the logic exists between acceptable and defective chips by the acquisition of the image data at the second test pattern (n).

Description

Specification

Ic test apparatus and method for identifying defective part of ic using this apparatus

The present invention irradiates an IC under test with an ion beam, measures the amount of secondary electrons generated from the irradiated point, displays the potential distribution in the IC as a potential contrast image, and displays the defect portion. The present invention relates to an IC test apparatus used for specifying an IC, an ion beam tester used therefor, and a method for specifying a defective portion of an IC to be measured. Background art

Conventionally, the chip of the IC under test is swept and irradiated with an ion beam (irradiating while scanning), and the amount of secondary electrons generated from each irradiation point is measured for each irradiation point. By taking this measured amount as an electrical signal, an IC test device that displays the potential distribution in the IC as a potential contrast image and uses it for analysis of defective parts has been put into practical use. I have.

Fig. 13 shows the schematic configuration of this type of conventional IC test equipment. In the figure, 1Q0 indicates the entire IC test apparatus. The IC test apparatus 100 is roughly divided into a test device, a turn generator 200, and an ion beam tester 300.

The test pattern generator 200 gives a test pattern signal to the device under test DUT mounted on the ion beam tester 300. The conventional test pattern generator 200 includes a start switch 201 for starting the generation of a test pattern and a stop switch used for stopping the generation of the test pattern at an arbitrary time. When the specified test pattern occurs, the test pattern Pattern setting means 203 for stopping the update of the pattern, and a pattern for detecting the occurrence of the test pattern set in the stop pattern setting means 203 and stopping the update of the test pattern. It comprises a holding means 204 and a stop signal generating means 205 for transmitting a signal indicating that the updating of the test pattern has been stopped. The control for stopping the update operation of the test pattern in the test pattern is performed.

On the other hand, the ion beam test 300 is provided with a lens barrel 301 for irradiating the device under test with an ion beam and a lower portion of the lens barrel 301, and the device under test DUT is placed in a vacuum. And a stage provided inside the chamber and moving the position of the device under test DUT in the X-Y direction, and a device under test DUT Sensor 304 for measuring the amount of secondary electrons generated from the image, an image data acquisition device 3005 for capturing the electric signal detected by the sensor 304 as image data, and image data A monitor 306 that displays the image data processed by the acquisition device 305 as a potential contrast image, emission of the ion beam and its emission amount (current value), acceleration voltage, scanning speed, and scanning The lens barrel controller 307 controls the area and the like.

When the test pattern generator 200 detects that the test pattern generator 200 has generated the test pattern set in the stop pattern setting means 203, the pattern holding means 204 suspends the update operation of the test pattern. The test pattern set in the stop pattern setting means 203 continues to be output. At the same time, a stop signal indicating that the update operation of the test pattern has been stopped is supplied from the stop signal generation means 205 to the image data acquisition device 300 and the lens barrel controller 300. The mirror controller 307 controls the emission of the ion beam in response to the supply of the stop signal. At the same time, the image data acquisition device 300 starts to acquire image data. You.

The method of specifying the defective part of the IC is to confirm the test pattern that generates the defect of the defective product tested in advance with the IC tester, and set the test pattern that causes the defect in the stop pattern setting means 203. Do. When the test pattern generator 200 detects that a test pattern that causes a failure has been set in the stop pattern setting means 203, the test pattern update operation is paused and the stop pattern is set. Continue to output the test pattern set in means 203. The lens barrel controller 307 controls the firing of the ion beam in response to the supply of the stop signal. At the same time, the image data acquisition device 305 starts capturing image data. The above image data is taken in for non-defective and non-defective products, and a comparison operation is performed by the image data acquisition device 305, and a difference between the two is specified as a defective portion.

In this type of conventional IC test apparatus, the stop time of the test pattern is set to be slightly longer than the time required for capturing the image data overnight. For this reason, if it is attempted to change the image data capture conditions, the stop time of the test pattern must also be changed, which has the disadvantage of poor operability. Force for setting ion beam acceleration voltage, scanning speed, scanning area, number of scans, etc .; changing these settings will change the time required to capture image data. For this reason, if the conditions for capturing image data are changed, the stop time of the test pattern must be changed accordingly. As a result, since both the test pattern generator 200 and the ion beam tester 300 must be operated, the operation is troublesome.

—On the other hand, it is necessary to change the conditions for capturing image data according to the purpose of the test. In particular, the device under test DUT is already covered with an insulating film as a protective layer. In the IC chip used, the X-ray of the wiring conductor buried under this insulating film will be observed. However, it is difficult to extract the potential distribution of the wire conductor of an IC chip having an insulating film adhered on the surface as a potential contrast image. In other words, when the surface of the insulating film is irradiated with an ion beam, the potential distribution gradually disappears due to the accumulation of electric charges on the insulating film in proportion to the irradiation time, and the potential contrast image originally required is obtained. There is a disadvantage that it is not possible to obtain Figure 14 shows the situation. Figure 14A shows the potential contrast image when the potentials of L logic, H logic, L logic, and H logic are given to the conductors under the insulating film, L2, La, and L, respectively. Is shown. As shown in the figure, the potential contrast image is white (a large amount of secondary electrons reach sensor 304) by applying the L logic potential (voltage close to OV or negative potential). Is displayed as. When the potential of H logic (voltage more positive than 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 the L logic and the H logic, and is displayed in gray.

Fig. 14B shows the state immediately after the irradiation and scanning of the ion beam (after 0.1 to 0.3 seconds). A few seconds after the start of ion beam irradiation, the potential contrast rapidly decreases as shown in Fig. 14C, and the potential contrast disappears. Therefore, the capture of image data is effective only in the state shown in Fig. 14A. Even if the image data is captured in the image memory due to the short time in which the potential contrast exists, only one time is required. It is difficult to obtain clear images simply by capturing image data.

Because of this phenomenon of potential contrast reduction, the frequency of changing the image data acquisition conditions (ion beam scanning area, ion beam current value, etc.) is high. Therefore, every time the image data capture conditions are changed, the setting of the time during which the test panel is stopped must be changed, and operation is not performed at this point. There is an inconvenience with poor workability.

An object of the present invention is to improve the operability of this type of IC test apparatus, to obtain a clear potential contrast image even when a potential contrast reduction phenomenon exists, and It seeks to provide a way to identify defective parts of an IC.

Another object of the present invention is to improve the quality of a potential contrast image representing a potential distribution of a wiring conductor in an IC chip in a state where a desired test pattern is applied. A brief supplementary description of this purpose is provided.

The potential contrast image is obtained by applying a desired test pattern to the DUT under test, irradiating a partial area of the DUT under test with an ion beam, and measuring the amount of secondary electrons generated. As described above, in the case of an IC chip where the surface of the device under test is covered with an insulating film, the force is proportional to the irradiation amount of the ion beam. There is a phenomenon that the potential distribution formed on the insulating film disappears. For this reason, the acquisition of image data is limited to only the first surface sweep of ion beam irradiation. Image data is captured only during this one-time sweep irradiation of the ion beam, and this image data is repeatedly read out and displayed even if the potential contrast image on the monitor 310 is displayed. There is a drawback that details are unclear due to the small amount of data.One way to solve this drawback is to continuously update the test patterns and continue until a specific test pattern n is reached. A method of continuing the ion beam sweep irradiation is considered. By adopting this method, while the test pattern is changing at a high speed, the ion beam is swept and irradiated, so the potential of the insulating film covering the top surface of the IC chip is the average of the potential change of the wiring conductor. Value, that is, an intermediate value between the H logic and the L logic, and when the pattern update operation stops at the target test pattern n, the potential determined by the test pattern n The distribution can be captured as a potential contrast image. After retrieving the image data, the test pattern update operation is resumed, and in this state, if the irradiation of the ion beam is continued, the potential of the insulating film returns to an intermediate value between H logic and L logic.

Therefore, by repeating this, a potential contrast image in a state where a desired test pattern is applied can be repeatedly obtained, the image data amount can be increased, and an average value processing or the like is performed. This provides an advantage that the quality of the potential contrast image can be improved.

However, this method also has the following disadvantages. That is, when the pattern update operation is stopped with the desired test pattern, the wiring conductor that appears as a potential contrast image based on the immediately preceding potential and the potential contrast image as the potential contrast image There are mixed wiring conductors that do not appear, resulting in a potential contrast image that is not suitable for failure analysis. The reason why a conductor appearing as a potential contrast image and a conductor not appearing as a mixture will be understood from the operation description of this application. Disclosure of the invention

The present invention proposes a device capable of improving the operability and the image quality of a potential contrast image, and a particularly effective method for specifying a defective portion of an IC to be measured. In other words, an ion beam tester that sweeps and irradiates the device under test with an ion beam, measures the amount of secondary electrons generated from each irradiation point, and reproduces the potential distribution inside the device under test as an image. A test pattern generator for providing a test pattern to the device under test, a stop pattern setting means for setting a test pattern to be stopped in the test pattern generator; Means for temporarily stopping the test pattern update operation when the test pattern set by the means has been generated, and a pattern indicating that the test pattern update operation has stopped. A stop signal generating means for outputting a pattern stop signal, and a release means for releasing the holding state of the pattern holding means by receiving an acquisition completion signal indicating completion of image data acquisition from the ion beam tester. The image data acquisition means which starts the image data acquisition in response to the pattern stop signal generated by the stop signal generation means, and indicates that the image data acquisition means has acquired the required image data. An acquisition completion signal generating means for generating an acquisition completion signal is provided.

According to this configuration, when the image data acquisition unit acquires the required image data, the acquisition completion signal generation unit generates an acquisition completion signal indicating the completion of the acquisition of the image data. The pattern generator starts the test pattern update operation in response to the acquisition completion signal.

Therefore, according to this configuration, it is not necessary to set a test pattern stop time in the test pattern generator, and the acquisition of image data and the automatic start and stop of the test pattern are repeated, so that no manual operation is required. There is no need. In addition, by setting the test pattern generation to the repetition generation mode, it is possible to repeatedly acquire image data in a state where the same test pattern is applied.

Another object of the present invention is to improve the image quality by compensating for the phenomenon of lowering the potential contrast. For this reason, the present invention is configured so that at least two test patterns can be 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 of. Simultaneously, ion beam irradiation 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 difference between the image data with a different test pattern applied is obtained.

Thus, both when the first test pattern and the second test pattern occur, By performing ion beam sweep irradiation and acquiring image data, the potential is obtained by calculating the difference between the image data obtained when the first test pattern is applied and the image data obtained when the second test pattern is applied. Only the changed part can be displayed as a potential contrast image.

In this case, since the difference between the two image data is obtained, the potential contrast at the portion where the potential is inverted when the first test pattern and the second test pattern are applied is emphasized, and the image quality is improved. You can get clear images

As a special method of specifying the defective part of IC, the power of the device under test is turned off (disconnected) at the time of the first test pattern r. As a result, the logic of the wiring conductor in the r pattern is forcibly fixed to the L logic, and the image is captured. In the second test pattern n, the power is turned on (connected) and the image is captured. In this way, if there is a difference in logic between a good product and a defective product, a difference image must appear in the potential contrast image. In other words, the IC defective portion can be identified by the difference image between the potential contrast images of the non-defective product and the defective product. BRIEF DESCRIPTION OF THE FIGURES

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

FIG. 2 is a waveform chart for explaining the operation of the embodiment shown in FIG. FIG. 3 is another waveform chart for explaining the operation of the embodiment shown in FIG.

FIG. 4 is a waveform chart for explaining the operation of the method invention.

FIG. 5 is another waveform diagram for explaining the operation of the method invention. FIG. 6 is a plan view for explaining the potential applied to the wiring in the device under test when the test pattern r of FIG. 1 is applied.

Fig. 7 shows the wiring in the device under test when the test pattern n in Fig. 1 is applied. FIG. 3 is a plan view for explaining potentials given to the thyristor.

FIG. 8 is a front view showing a potential contrast image obtained when the test pattern r is applied after the test patterns r and n in FIG. 1 are alternately applied. FIG. 9 is a front view showing a potential contrast image obtained when test patterns n are applied after patterns r and n are alternately applied. FIG. 10 is a front view showing a potential contrast in which the polarity of the potential contrast shown in FIG. 8 is inverted.

FIG. 11 is a front view showing a result calculated by the calculating means of FIG. 1 as a potential contrast.

FIG. 12 is a waveform diagram illustrating the reason why the potential contrast of a portion to which a potential of the same polarity is applied disappears when the test patterns r and n in FIG. 1 are alternately applied.

FIG. 13 is a block diagram for explaining a conventional technique.

FIG. 14 is a front view showing an example of a potential contrast image for explaining a drawback of the conventional technique. BEST MODE FOR CARRYING OUT THE INVENTION

Figure 1 shows a block diagram of the IC test equipment used in the present invention. Parts corresponding to those in FIG. 13 are denoted by the same reference numerals. The structure of the IC test apparatus 100 is characterized in that the ion beam tester 300 is provided with acquisition completion signal generating means 310 for transmitting an acquisition completion signal indicating the completion of the acquisition of image data. There are provided a plurality of means of 305 A and 305 B, and a calculation means 309 for obtaining the difference between the image data obtained by the image data obtaining means 305 A and 305 B. It is a point.

In this embodiment, the acquisition completion signal generating means 308 is an image data acquiring means. It detects that the acquisition of the image data has been completed in 305A and 305B, and transmits 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 to the test pattern generator 200 to release the stop of the test pattern when the acquisition completion signal is input. The test pattern generator 200 starts the update operation of the test pattern released from the stop state.

In other words, according to this apparatus, if, for example, the stop patterns r and n are set in the stop pattern setting means 203, the pattern holding means 2 is generated each time the stop patterns r and n are generated. 04 operates to stop the update operation of the test pattern of the test pattern generator 200, and maintains the state where the test pattern r or n is output. Figure 2 shows the situation. Figure 2A shows the start signal, and Figure 2B shows the test pattern signal. When the pattern of the test pattern signal reaches r or n (generally indicates the address indicating the pattern generation order), the pattern holding means 204 temporarily updates the pattern of the test pattern generator 200. Stop and maintain the state where pattern r or n is output. At the same time, a stop signal is output from the stop signal generating means 205, and the stop signal is input to the image data capturing device 30δ to start capturing image data. FIG. 2F shows the operation period for acquiring image data.

Completion of image data capture can be known, for example, by detecting a vertical retrace signal indicating that the ion beam sweep irradiation has reached one screen. By transmitting an acquisition completion signal when one or any number of vertical retrace signals are detected, an acquisition completion signal is output when the ion beam scans one to several screens for any screen. Can be sent. Figure 2G shows the acquisition completion signal.

A test is performed by giving an acquisition completion signal to the pattern holding means 204. The pattern signal generator 200 is released from the stop state, and updates the test pattern as r + l, r + 2, ... or n + l, n + 2 ... as shown in Fig. 2B. Output up to the last pattern Last. If the test pattern generation is set to one time, the operation stops with the last pattern last generated. If the test pattern generation is set to be continuous and the restart after image data acquisition is set back to the first pattern, the test pattern r is automatically stopped when a test pattern r is generated as shown in Fig. 3. When the acquisition of image data is completed, it returns to the first pattern and restarts, the next time it stops at test pattern n, and returns to the first test pattern after image data acquisition, and repeats pattern generation . With this setting, the image data with the specified test patterns r and n applied can be automatically acquired multiple times. The end can be stopped by operating the stop switch 202.

As described above, according to this apparatus, when the potential contrast image is observed or the test pattern n and the reference pattern r are set in the stop pattern setting means 203, the test pattern generator 20 Since the start and stop operations of 0 are linked to the image data acquisition operation of the ion beam tester 300, the test pattern generator 200 and the ion beam test device 300 even if the image data acquisition conditions are changed. There is no need to change the side settings. This simplifies operation and improves operability.

The invention of this application is to obtain a method of comparing the potential contrast between a good product and a defective product by using the IC test apparatus with improved operability and specifying a defective portion of the IC. As shown in FIG. 1, image data obtained by applying different test patterns to a plurality of image data acquisition means 300A and 300B are captured. That is, image data in a state where the test pattern r is given to the device under test DUT is taken into the image data acquisition means 3◦5A. Also get image data overnight The image data in a state where the test pattern n is given to the device under test DUT is taken into the means 3 05 B.

The image data acquired by the image data acquisition means 300 A is inverted in polarity and applied to the arithmetic means 309, and the image data acquired by the image data acquisition means 305 B is directly used by the arithmetic means 309. 0 9 is given. The calculating means 309 adds the image data given from the image data obtaining means 305A and 305B, and displays the result of the addition on the monitor 306. By displaying the calculation result of the calculating means 309 on the monitor 306, the potential contrast image becomes a clear image.

The reason will be described below. Fig. 6 shows the potential applied to the wiring conductors ₁ , ₂ , ₃ , and ₃ in the device under test 011 when the test pattern r is applied. Conductor in the example of means that FIG 6 L, to L logic, H logic conductor L _2, conductors to L logic, the conductor L ₄ shows a case of giving the H logic. While Figure 7 shows the potential applied to the wiring conductor ~L ₄ of the device under test in the DUT when applying a test pattern n. L logic to the conductor L> in the example of FIG. 7, the conductor L ₂ illustrates logic, H logic conductor L _3, the conductor L ₄ a case of giving the H logic.

Figures 8 and 9 show these potential contrast images. Fig. 8 shows a potential contrast image when test pattern r is applied, and Fig. 9 shows a potential contrast image when test pattern n is applied. In the potential co emissions trusses IMAGING shown in FIG. 8, the potential co emissions trusses bets the conductor is lost, only the potential co emissions trusses DOO conductor L ₂ and L ₃ are left. In the potential co emissions trusses IMAGING shown in FIG. 9, the potential co down trusts conductor and L ₄ are disappeared, only the potential co emissions trusses DOO conductor L z and L ₃ are left. The reason is that the potentials applied to the conductors L 1 and L 4 are the same both when the test pattern r is applied and when the test pattern n is applied.

Figure 12 shows how the potential contrast disappears. Figure 12 A shows the test pattern. The periods during which the turns r and η are applied and the ion beam irradiation period are shown. Figure 1 2 beta are potential co emissions trusses event to occur in the insulating film existing on the surface of the conductor, Fig. 1 2 C is ¾ position co emissions trusses event to occur in the insulating film existing on the surface of the conductor L _2, FIG. 1 2 D potential co emissions trusses event to occur in the insulating film existing on the surface of the conductor L _3, FIG. 1 2 E represents a potential co emissions trusses event to occur on the surface of the conductor L _4.

As shown in Fig. 12B and Fig. 12E, the first time the test pattern r was applied, the potential contrast generated a force.Then, when the test pattern n was applied, the same potential was applied. It is because, rather than the occurrence of potential co-down truss door, I Ri potential con trusses door to the irradiation of Lee Onbimu is strange turned into the direction to disappear, to converge to the equilibrium potential V _s. Then the test patterns r and n conductors be marked pressurized alternately L, and potential co emissions trusses DOO the insulating film existing on the surface of L ₄ are not generated.

In contrast, because the insulating film existing on the surface of the conductor L ₂ and L ₃ are opposite polarity potential is applied to each of the test patterns r and n is applied, the test patterns r and n are applied Each time, a reverse potential contrast occurs.

I can understand why I Ri potential co emissions trusses DOO conductor and L ₄ disappears the foregoing description. In this example, the polarity of either one of the potential contrasts left in this case and the image data (same as the potential contrast) acquired by the image data acquisition means 300A is inverted. The result is given to the calculating means 309, and added to the image data obtained by the image data obtaining means 305 B by the calculating means 309.

FIG. 10 shows image data obtained by inverting the polarity of the image data (potential contrast) acquired by the image data acquisition means 305A. The image data shown in FIG. 11 is obtained by adding the image data shown in FIG. 10 and the image data shown in FIG. Image data shown in FIG. 1 1 is a conductor L ₂ It has been added and emphasized about the potential contrast of this. As a result, the quality of the image is improved, and a potential contrast image with good resolution can be obtained.

Next, a description will be given of an invention of a method for specifying a defective portion of the measured IC by using the above-mentioned ion beam tester 300.

First, Table 1 shows the correspondence table between the logic signals of non-defective ICs and defective ICs and the potential contrast images.

PC

Fifteen

[Table 1] Correspondence between non-defective products and defective products and word contrast and potential contrast images

Good product Defective product Good product /

Descent r n * J

TA ηη-turn Potential:! ン Γ ',:

Item ·-/ n ',' turn potential] no R IU

Above question SS Tiger Image Truss Sun IS

1 Η α し I I White m

9 gray

Gray

H H II gray ">,

4 LI 3 Ι (Π

Black &

5 White Yes

6 Li Gray Yes

Shiri H

7 i black

1 ri H ri gray having iut

8 LS process Η1¾ϊΙ m color m

9 H i

1 0 Gray Yes «", m White

1 1 i Gray Yes

1 2 Shi H H

1 3 m Li White Yes M

1 4 gray

him gray

1 5 G

1 6 H 2 ^ 11 黑 with color

The logic signal pattern is a combination of H logic and L logic.If the same potential is applied to the first test pattern r and the second test pattern n, a gray potential contrast image is obtained. When L logic is given at the first test pattern r and H logic is given at the second test pattern n, a black potential contrast image is obtained.H logic is given at the first test pattern r, and the second test pattern is given. When logic is given at time n, a white potential contrast image is obtained.

By utilizing this fact, it is possible to identify the defective portion of the IC by comparing the potential contrast images of the logic signals of the good product and the defective product. Table 1 shows the combination of logical patterns that can occur between good and defective products, and shows whether there is a difference in potential contrast images between good and defective products, and whether there is a problem in fault detection. Item 3, item 8, item 9, and item 14 in Table 1 have the same image because the logical signals of good and defective products are the same. The problems in fault detection are item 2 and item 15. In other words, it does not appear as a difference even though the logic level of each test pattern is different between good and defective products. The present invention is a method for solving this problem in fault detection.

FIG. 5 is a waveform chart for explaining the operation of the present invention. This feature is that the power of the device under test is turned off (turned off) at the time of the first test pattern r, and in that state the image data is acquired by irradiating and scanning the ion beam. When the first test pattern is r, the logic is always low because the power is off. At the end of the first test pattern r and then at the second test pattern n, the power is turned on (contacted), the ion beam is irradiated and scanned, and image data acquisition is performed. FIG. 4 shows an example of a method of performing measurement by repeatedly turning off and on the power supply. Table 2 shows whether there is a difference between the potential contrast images of good and defective products and whether there is a problem in fault detection using the method of the present invention. / 13157

1 7

[Table 2] Responses of non-defective and defective products and potential contrast images

(Power off at r pattern)

As shown in Table 2, there is no problem in detecting the position of the defective site, the difference between the image of the good product and the image of the bad product can be reliably obtained, and the defective parts of the IC can be determined by comparing the top contrast. Can be specified reliably. Industrial applicability

As described above, according to the present invention, different test patterns, for example, r and n are alternately applied, and a difference in potential contrast generated by the test patterns is displayed. Alternatively, the quality of the image can be improved as compared with a potential contrast image in a state in which one of n is applied. As a result, the potential distribution of the wiring conductor in the IC chip can be analyzed with higher accuracy, so that there is an advantage that a defective portion can be specified in a short time.

In addition, if another test pattern is selected for the test pattern r in sequence while the test pattern n is left as it is, a potential contrast image of another conductor that cannot be seen by the combination of the test pattern r and n can be seen. . Furthermore, by applying the same test pattern, for example, n repeatedly, and changing, for example, the power supply voltage applied to the device under test DUT for each application, abnormal operation is caused alternately every time the test pattern is stopped. As a result, a potential contrast can be generated only in a portion where an abnormal operation occurs. Therefore, in this case, there is an advantage that the defective portion can be directly specified.

When performing ion beam irradiation scanning and image data acquisition during the first test pattern r, the power of the device under test is turned off to change the logic of the wiring conductor in the first test r pattern to L. The logic is fixed and the image can be captured by turning on the power in the second test pattern n. By comparing the non-defective product with the non-defective one in this image, if there is a difference between the two, a difference image will appear in the potential contrast image, so it is possible to identify the defective part of the IC. it can Advantages can be obtained, which can be very effective in analyzing the failure of the IC under test.

Claims

The scope of the claims

1. The surface of the device under test is swept and irradiated with an ion beam, and the secondary electrons generated from each irradiation point! : An ion beam tester (300) for measuring the potential distribution on the surface of the device under test as an image, and a test pattern generator (300) for sequentially updating the test pattern signal to the device under test. In an IC test apparatus (100) comprising:

On the test pattern generator (200) side, a stop pattern setting means (200) for setting at least two test patterns for temporarily stopping the pattern update operation of the test pattern generator (200). Each time the test pattern generator (200) generates each test pattern set in the stop pattern setting means (203), the test pattern updating operation is temporarily performed in that state. A pattern holding means (204) for stopping and a stop signal generating means (205) for outputting a pattern stop signal representing the updating operation of the test pattern every time the updating operation of the test panel is stopped,

The ion beam tester (300) captures image data in response to the pattern stop signals supplied by the stop signal generating means (205) respectively in the two stop patterns to the ion beam tester (300). Two image data acquisition means (305A, 305B), an arithmetic means (309) for calculating a difference between the image data acquired by the two image data acquisition means, and an arithmetic means (309) An IC test apparatus comprising: a monitor (306) for displaying the image data of the difference calculated in (309).

2. In the IC test apparatus (100) described in claim 1, the ion beam test apparatus (300) is connected to each of the image data acquisition means (305A,

The acquisition completion signal indicating the completion of the acquisition of the image data Means for generating an image completion signal (308), and the pattern holding means (204) includes an acquisition completion signal indicating completion of image data acquisition from the ion beam test (300). An IC tester configured to restart the pattern update of the test pattern generator (200) upon receiving the supply of the test pattern.

3. Construct an IC test apparatus (100) together with a test pattern generator (200) for applying a test pattern to the device under test. Sweep irradiate the surface of the device under test with an ion beam, In the ion beam test (300), which measures the amount of secondary electrons generated from the surface and displays the potential distribution on the surface of the device under test as an image,

The test pattern generator (200) captures image data acquired in response to the pattern stop signals supplied in at least two stop patterns, respectively, and at least two image data acquisition means (300) 5A, 305B), calculating means (309) for obtaining the difference between the image data obtained by the two image data obtaining means (305A, 305B), and the calculating means (309) A monitor (306) for displaying the image data of the difference calculated in (309), and an ion beam tester provided with.

4. At the ion beam test (300) described in claim 3, each time the image data acquisition means (305A, 300B) completes the acquisition of the required image data, it is displayed. An ion beam test device characterized by comprising an acquisition completion signal generating means (308) for generating an acquisition completion signal and supplying the acquisition completion signal to the test pattern generator (200).

5. A test pattern generator (2) that applies a test pattern to the device under test Together with an IC test apparatus (100), sweeping and irradiating the surface of the device under test with an ion beam, measuring the amount of secondary electrons generated from each irradiation point, and measuring the amount of secondary electrons An ion beam tester (300) that displays the potential distribution on the surface as an image in a measurement method that captures the image data in the first test pattern r and the second test pattern n by at least two stop patterns. ,

At least at the time of the first test pattern r, the power of the device under test is turned off, and the first image is captured by irradiating an ion beam.

At least for the second test pattern n, the power of the device under test is turned on, and an ion beam is irradiated to acquire a second image.

Calculating an image of a difference between the first image and the second image,

A position where the image of the difference of the device under test is different from the image of the difference of the non-defective IC is specified as a defective portion of the measured IC.

How to identify defective parts of IC.