JPH07128409A - Charged particle test device and semiconductor integrated circuit test device - Google Patents

Abstract

PURPOSE:To surely detect the change of inner condition of an IC without being affected by the electrostatic charge of a protective film by a method wherein when receiving a condition signal from a test signal generator, the acquisition of a prescribed picture of an image is executed. CONSTITUTION:A test pattern signal from a test pattern generator 18 is applied to an IC 15 via a lead wire 19 so that the IC 15 is activated. A trigger signal from a trigger signal generator 22 is supplied to a delay circuit 25 in synchronism with the test pattern signal and a pulse generator 26 is driven in accordance with the output, and the IC 15 is irradiated with a pulsating electron beam 14. The acquisition of an image is started every time when an operation condition of the test signal generator 12 is changed. That is, when the operation condition is set to the test signal generator 12, a condition signal corresponding to that is generated by a condition signal generator 28 to be transmitted to a controller 32. In the above embodiment, when acquiring a picture of an image, a completion signal is supplied to the generator 12 from the controller 32 and the next testing is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates a semiconductor integrated circuit with a charged particle beam such as an electron beam or an ion beam, measures the amount of secondary electrons generated, and displays the potential distribution of the semiconductor integrated circuit as a grayscale image. The present invention relates to a semiconductor integrated circuit test device used for displaying and determining a defective portion.

[0002]

2. Description of the Related Art For example, a semiconductor integrated circuit (hereinafter referred to as an IC) which is operating in an electron beam test apparatus is irradiated with an electron beam, the amount of secondary electrons generated at that time is measured, and the same test is performed. For the pattern, the electron beam irradiation position is sequentially shifted to display a grayscale image according to the amount of secondary electrons. In the display image in this case, for example, as shown in FIG. 7A, the wiring pattern images 1 to 4 of the IC appear, but there are few secondary electrons from the wiring to which the high level potential is applied, and the pattern image 1 in the display image is displayed. , 2 is displayed in black. On the other hand, many secondary electrons from the wiring to which the low-level potential is applied are displayed in white in the display image like the pattern images 3 and 4, and the portion 1 other than the wiring 1
5, the generated secondary electrons are in the middle of each secondary electron in the high level part and the low level part and are displayed in gray.

Since the application test pattern corresponding to this display image is known, that is, the potential at the time of normal operation of each wiring is known, whether or not the IC is operating correctly by looking at this display image, It is possible to judge which part is abnormal.

[0004]

A protective layer of an insulating film is usually formed on the surface of an IC chip. Therefore, if the above-mentioned test by electron beam irradiation is repeated under the same conditions, the protective film is charged and the potential difference on the IC disappears, and for example, as shown in FIG.
Becomes thin, the low-level wiring pattern images 3 and 4 become whitish gray, it becomes difficult to distinguish the potential distribution, and finally the IC surface becomes a substantially uniform potential, and as shown in FIG.ゞ It becomes a uniform gray display and it becomes impossible to know the potential distribution.

[0005]

According to the first aspect of the present invention, a charged particle test apparatus has means for receiving a trigger signal from a test signal generator, and a charged particle beam pulse is generated based on the received trigger signal. Means and a test signal generator from the I
A unit for receiving a condition signal indicating that the operating condition of C, that is, an operating power supply voltage, an operating clock speed, and the like have been changed, and a unit for executing the acquisition of a predetermined screen image when the condition signal is received.

Further, there is provided means for generating a completion signal and transmitting it to the test signal generator when the image acquisition for the predetermined screen is completed. When the completion signal is received by the test signal generator, the test signal generator is provided with means for changing the operating condition of the IC to generate the test signal. Alternatively, there is provided means for automatically changing the operating condition and generating a test signal after a sufficient time has elapsed to acquire a predetermined screen without generating a completion signal.

According to the second invention, means for receiving a trigger signal from the test signal generator in the charged particle test apparatus, means for generating a charged particle beam pulse on the basis of the received trigger signal, and each time an image is acquired. And means for changing the generation timing of the charged particle beam pulse with respect to the trigger signal. According to the third aspect of the present invention, the charged particle test apparatus has means for receiving the trigger signal from the test signal generator, and the charged particle beam pulse is generated at a plurality of timings which are deviated in time with respect to the received trigger signal. Means are provided.

In any of the first to third inventions, the difference between the two images thus obtained can be displayed, or a specific one image can be displayed. To be done.

[0009]

FIG. 1 shows an embodiment of the present invention. When an electron beam test apparatus is used as the charged particle test apparatus 11, the test signal generator 12 is connected to this. In the electron beam test apparatus 11, the electron beam 14 is generated in a pulse shape in the vacuum chamber 13 and is irradiated on the IC 15 in the chamber 13. Secondary electrons generated by the irradiation are detected by the secondary electron detector 16 and taken into the memory 17.

The test pattern signal from the test pattern generator 18 in the test signal generator 12 is passed through the lead wire 19,
Further, it is applied to the IC 15 via the connector 21 and IC1
5 works. In synchronization with the test pattern signal, the trigger signal from the trigger signal generator 22 is passed through the lead wire 23 and further to the connector 24, and the electron beam test apparatus 11
Is supplied to the internal delay circuit 25. The pulse generator 26 is driven by the output of the delay circuit 25, a pulse is generated, and the electron beam 14 is pulsed by the pulse by the IC 15
Irradiate.

For example, as shown in FIGS. 3A and 3B, a pattern in which "1" is written as a test pattern signal, a pattern in which "0" is written, a high impedance input pattern, and the like are repeated, and a read pattern generated between these patterns. (FIG. 3B) is applied to the IC 15, and a trigger signal is generated as shown in FIG. 3C in agreement with the leading edge of each specific pattern, for example, a “1” write pattern, and the delay circuit 25 is generated as shown in FIG. 3D. A pulse is generated from the pulse generator 26 with a delay of ΔT. In this way, electron beam irradiation is performed for each specific pattern, secondary electron measurement is performed, and data for one pixel is taken in. Data for adjacent positions is taken in by the next electron beam irradiation.
By sequentially operating in the same manner, data for a certain area designated by the IC 15 is taken in as one screen. The captured data is stored in the memory 17, and the stored content is displayed as an image on the display unit 27 from the beginning of the data capture.

According to the first aspect of the invention, each time the operating condition of the IC 15 is changed, image capturing is started. That is, the test signal generator 12 is provided with means for sequentially changing the operating conditions, and when one operating condition is set, a condition signal corresponding to the condition is generated from the condition signal generating unit 28, which is the lead wire 29, It is transmitted to the control unit 32 in the electron beam test apparatus 11 through the connector 31. Further, in this example, when the image for one screen is acquired, the completion signal is generated from the control unit 32 and is supplied to the test signal generator 12 through the connector 33 and the lead wire 34. Upon receiving this completion signal, the test signal generator 12 shifts to the test under the next operating condition. Electron beam test apparatus 11 and test signal generator 12
Is operated by a controller using a CPU.

The operation flow of the test signal generator 12 is shown in FIG. 2A.
Shown in. First, the operating condition for setting the operating condition of the IC is set (S ₁ ). A condition signal corresponding to this operating condition is generated (S ₂ ), a drive signal, that is, a test pattern signal is generated, and these condition signal and test pattern signal are transmitted to the electron beam test apparatus 11 (S ₃ ). Trigger signal when the specific pattern occurs is generated and transmitted to the electron beam test apparatus (S _4). Checks next completion signal has been received (S _5), if not received continues the generation of the test pattern returns to step S _3, it repeats the same thing.

On the other hand, when the completion signal is received in step S ₅ , the generation of the test pattern signal is stopped (S ₆ ), the operating condition is changed by one step in a predetermined order (S ₇ ), and the process proceeds to step S ₁ . Returning, the changed operating condition is set, the condition signal and the test pattern signal are generated in the same manner as above, and the electron beam test apparatus 11 acquires the image under the changed operating condition. become.

The flow of operation of the electron beam test apparatus 11 is shown in FIG. 2B. First, image capturing conditions such as electron beam scanning speed, scanning area, electron beam acceleration speed, and scanning position are set (S ₁ ). In this state, it waits for the condition signal to be received from the test signal generator (S ₂ ). When the condition signal is received, the contents of the condition signal are judged, and in which area in the memory 17 the image data is to be taken is set according to the contents (S ₃ ), and the taking of the image is started ( S ₄ ).
That is, each time the trigger signal is received, data is taken in for each pixel as described above. 1 of the image data of screen uptake has checks completed (S _5), and transmits the generating a completion signal to end the test signal generator 12 (S _6).

Since the operating condition is changed every time one screen image is taken in this way, the potential changes even in the same portion of the IC 15, especially in the case of the potential change based on the change of the logical value. The effect of charging on the protective film is eliminated,
You can know the state of the change. For example, when the operation condition is changed when the image obtained without any charging is shown in FIG. 4A, wiring pattern images 1 and 4 are obtained as shown in FIG. 4B.
The potential is the same as in FIG. 4A, but the wiring pattern image 2 changes from a high potential to a low potential, and the wiring pattern image 3 changes from a low potential to a high potential. When images are captured by repeating these two operating conditions, the acquired image under the operating conditions corresponding to the image shown in FIG. 4A is shown in FIG.
As shown in C, the wiring pattern images 2 and 3 clearly appear, the former is high potential, the latter is low potential, the wiring pattern images 1 and 4 are gray, and no potential change occurs. Is understood. When captured under operating conditions corresponding to the image of FIG. 4B, the wiring pattern image 2 appears white and the wiring pattern image 3 appears clearly as black, as shown in FIG. 4D.

In the above, the electron beam test apparatus 11 is used.
When 1 image is taken in, the completion signal is sent to the test signal generator 1.
However, omitting this, allow sufficient time for the electron beam test apparatus 11 to take in one screen of data in the test signal generator 12, and change the operating condition every time a predetermined time elapses. Good. That is, as shown with the same reference numerals to the steps corresponding to FIG. 2A in Figure 5A, it is checked whether or not a predetermined time has elapsed in step S ₇ instead of step S _5, while not passed the test pattern signal The generation is continued, and when a predetermined time elapses, the generation of the test pattern signal is stopped and the operation condition is changed.

Only when the condition signal received in the electron beam test apparatus 11 is a specific one (which can be freely set), the image data obtained at that time is displayed, and the other cases are not displayed. You can also For example, when there are two operation conditions and the images of FIGS. 4C and 4 are alternately repeated, one of them can be displayed by designating the condition signal, and the potential distribution corresponding to the condition can be observed slowly. It should be noted that when there are two operating conditions in this way, the condition signal may simply be a signal indicating that the operating conditions have been changed, and when there are three or more operating conditions, a condition signal for distinguishing between them is used.

Next, embodiments of the inventions of claims 2 and 5 will be described. In this case, changing the operating condition is not a condition. Therefore, in FIG. 1, the condition signal generator 28, the completion signal generator, etc. are omitted. In this case, in the electron beam test apparatus 11, the generation time of the electron beam pulse with respect to the trigger signal is changed every time one screen of data is fetched. For example, as shown in FIG. 6A, a test pattern signal is generated, and in response thereto, a trigger signal shown in FIG. 6B is generated, and in the first image data import, as shown in FIG. 6C, ΔT ₁ is added to the trigger signal. An electron beam pulse is generated with a delay. When importing the data on the next screen,
As shown in FIG. 6D, an electron beam pulse is generated with a delay of ΔT _{2 with} respect to the trigger signal. As described above, the image data may be alternately captured by generating the electron beam pulse at two different timings, or the image data may be sequentially captured by generating the electron beam pulse at more different timings. .

The operation flow of the electron beam test apparatus in this case is as shown in FIG. 5B, for example. That is, the image capture condition is set in the same manner as step S _{1 in} FIG. 2B (S ₁ ). Then set whether taken up which area in the memory 17 (S _2), further to set the irradiation pulse generation time for the trigger signal (S _3). For this irradiation pulse generation time, sequentially select a plurality of preset times,
Try to set one of them. Therefore, the delay circuit 25 in FIG. 1 is a variable delay circuit, and the control unit 32 can set the delay amount.

After the irradiation pulse generation time is set, the import of image data is started (S ₄ ). When the image data is captured for one screen (S ₅ ), the process returns to step S ₂ to change the image data storage area, change the irradiation pulse generation time, and capture the image data again. Hereinafter, the same thing is repeated. In this way, by changing the irradiation pulse generation time with respect to the trigger signal, the IC1 before the change is changed.
When the state of the IC 15 after the change is changed with respect to the state of 5, the state before and after the response to the applied test pattern is detected, and in this case also, as described with reference to FIG. 4, the changed wiring pattern. The statue appears clearly,
You can definitely know this.

In the third aspect of the invention, when the trigger signal is received, the irradiation pulse is generated at a plurality of different timings as shown in FIG. 6E, for example. Figure 6E
Then, the irradiation pulse is generated with a delay of ΔT ₁ and ΔT ₂ with respect to the trigger signal. Image data is taken in for each irradiation pulse, but these are stored in different areas, and the image data taken in at ΔT ₁ and the image data taken in at ΔT ₂ are alternately or in parallel displayed on the display unit 27. Is displayed. That is, when the test pattern signal speed is relatively slow, this can be done, and when the test pattern signal is fast, the same test can be performed by performing as described with reference to FIG. 5B.

When image data is taken in at a plurality of different timings in one test cycle T as described above, it is possible to set the take-in timing and display only the taken-in one image data. Further, in any of the above cases, it is also possible to select any two of the plurality of captured image data and add them differentially to obtain a display in which the influence of charging is further eliminated. Further, it is preferable that the delay amount of the delay circuit 25 can be freely set. Instead of setting the delay amount, the test signal generator 12 may freely set the timing of generating the trigger signal. Transmission and reception of signals between the electron beam test apparatus 11 and the test signal generator 12 may be performed using a bus.

[0024]

As described above, according to the present invention, the operating condition is changed and the irradiation pulse generation timing is changed every time a predetermined image is acquired. Therefore, the internal state of the IC is changed based on the change. Can be reliably detected without being affected by the charging of the protective film.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the invention of claim 4;

FIG. 2A is a flowchart showing an operation example of a test signal generator 12, and B is a flowchart showing an operation example of an electron beam test apparatus.

FIG. 3 is a time chart showing an example of the relationship among a test pattern signal, a trigger signal, and an irradiation pulse.

FIG. 4 is a diagram showing an example of an image.

FIG. 5A is a flowchart showing another operation example of the test signal generator, and B is a flowchart showing another operation example of the electron beam test apparatus.

FIG. 6 is a time chart showing another example of the relationship between the test pattern signal, the trigger signal, and the irradiation pulse.

FIG. 7 is a diagram showing an image for explaining a problem in the conventional apparatus.

Front page continuation (72) Inventor Yusuke Kawamoto 1-32-1, Asahimachi, Nerima-ku, Tokyo Within Advantest, Inc.

Claims (13)

[Claims] 1. A charged particle test apparatus for obtaining an image of a potential distribution of the semiconductor integrated circuit by irradiating an operating semiconductor integrated circuit with a charged particle beam in a pulsed manner and detecting secondary electrons thereof. Means for receiving a trigger signal from a test signal generator that supplies an operation test signal to an integrated circuit; means for generating the charged particle beam pulse with the received trigger signal as a reference; and the semiconductor from the test signal generator. A charged particle, comprising: a unit that receives a condition signal indicating that the operating condition of the integrated circuit has been changed; and a unit that, when receiving the condition signal, executes a unit for acquiring a predetermined screen of the image. Test equipment. 2. A charged particle test apparatus which obtains an image of a potential distribution of the semiconductor integrated circuit by irradiating the operating semiconductor integrated circuit with a charged particle beam in a pulsed manner and detecting secondary electrons thereof. Means for receiving a trigger signal from a test signal generator that supplies an operation test signal to an integrated circuit; means for generating the charged particle beam pulse based on the reception trigger signal; and the trigger signal for each acquisition of the image. A means for changing the generation timing of the charged particle beam pulse with respect to, and a charged particle test apparatus. 3. A charged particle test apparatus for obtaining an image of potential distribution of the semiconductor integrated circuit by irradiating the operating semiconductor integrated circuit with a charged particle beam in a pulsed manner and detecting secondary electrons thereof. Means for receiving a trigger signal from a test signal generator that supplies an operation test signal to the integrated circuit; and means for generating the charged particle beam pulse at a plurality of timings that are temporally shifted with respect to the reception trigger signal. A charged particle test apparatus, comprising: 4. A test signal generator and a charged particle test apparatus, wherein an operation test signal is supplied from the test signal generator to a semiconductor integrated circuit in the charged particle test apparatus, and the semiconductor integrated circuit is provided. A semiconductor integrated circuit which is operated and in which the charged particle test device irradiates the semiconductor integrated circuit in a pulsed manner with a charged particle beam, detects secondary electrons thereof, and obtains an image of the potential distribution of the semiconductor integrated circuit. In the circuit test device, when the test signal generator causes the test signal generator to generate the test signal, the condition signal indicating the change is transmitted to the charged particle test device. Means for transmitting a trigger signal indicating a generation reference of a particle beam pulse to the charged particle test apparatus, means for receiving the trigger signal in the charged particle test apparatus, and reception thereof And a means for generating the charged particle beam pulse with the trigger signal as a reference, a means for receiving the condition signal, and a means for executing acquisition of a predetermined screen of the image when the condition signal is received, A semiconductor integrated circuit test device characterized by the above. 5. A test signal generator and a charged particle test apparatus are provided, and an operation test signal is supplied from the test signal generator to a semiconductor integrated circuit in the charged particle test apparatus to operate the semiconductor integrated circuit. During the operation, the charged particle beam is radiated to the semiconductor integrated circuit in a pulsed manner by the charged particle test apparatus, and secondary electrons thereof are detected to obtain an image of the potential distribution of the semiconductor integrated circuit. In the test apparatus, the test signal generator includes means for transmitting a trigger signal indicating a generation reference of the charged particle beam pulse to the charged particle test apparatus, and the charged particle test apparatus receives the trigger signal. Means for generating the charged particle beam pulse based on the received trigger signal, and generation of the charged particle beam pulse for the trigger signal every time the image is acquired. A semiconductor integrated circuit test apparatus comprising: means for changing raw timing. 6. A test signal generator and a charged particle test apparatus, wherein an operation test signal is supplied from the test signal generator to a semiconductor integrated circuit in the charged particle test apparatus to operate the semiconductor integrated circuit. During the operation, the charged particle beam is radiated to the semiconductor integrated circuit in a pulsed manner by the charged particle test apparatus, and secondary electrons thereof are detected to obtain an image of the potential distribution of the semiconductor integrated circuit. In the test apparatus, the test signal generator includes means for transmitting a trigger signal indicating the generation reference of the charged particle beam pulse to the charged particle test apparatus, and the charged particle test apparatus for receiving the trigger signal. And a means for generating the charged particle beam pulse at a plurality of timings which are temporally shifted with respect to the received trigger signal as a reference. Integrated circuit test equipment. 7. The variable delay means for delaying the received trigger signal by a desired time to change the generation time of the charged particle beam pulse is provided.
The test apparatus according to any one of 1. 8. A means for making a difference between a plurality of acquired images and displaying the difference is provided.
7. The test apparatus according to any one of 1 to 6. 9. A means for detecting a specific condition from the condition signal, and a means for displaying an acquired image corresponding to the specific condition only when the specific condition is detected. The charged particle test device according to claim 1. 10. The semiconductor integrated circuit test apparatus according to claim 4, wherein the test signal generator includes means for changing the operating condition at predetermined time intervals. 11. The test apparatus according to claim 1, further comprising means for transmitting a completion signal indicating the completion of image acquisition to the test signal generator when the image acquisition is completed. 12. The semiconductor integrated circuit test circuit according to claim 11, wherein said test signal generator is provided with means for changing an operating condition when receiving said completion signal. 13. A selected one of a plurality of acquired images
7. The semiconductor integrated circuit testing device according to claim 2, 3, 5, or 6, further comprising means for displaying only the display.