JPS5976441A - Diagnostic apparatus for integrated circuit - Google Patents

Abstract

PURPOSE:To facilitate detection of defective point and discovery of cause by storing coordinates of a plurality of diagnostic points in the IC and by measuring and displaying voltages of nodes through sequential irradiation of electron beam at the diagnostic points for each driving of IC with an input data. CONSTITUTION:An IC3 is scanned by electron beam, the secondary electron is detected 1-7 and stored 18, and the secondary electron picture corresponding to data is displayed 20 through a control circuit 8. At this time, a picture 29 indicates contrast, designates diagnostic point 30 and stores 13 the coordinate. A voltage of diagnostic point 30 designated by reading stored coordinate 13 is measured with an energy analyzer 2. A series of input/output data train is read in accordance with the driving sequence from the auxiliry storage 10. It is then applied step-by-step to an IC3 by the driving circuit for the purpose of diagnosis. A result is repeatedly displayed 20 as a voltage map. An abnormal point for an input data can be detected accurately by observing said map.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an apparatus for diagnosing an integrated circuit using an electron beam, and in particular, for diagnosing an integrated circuit driven by a diagnostic input data string. Regarding equipment.

(2) Background of the Technology In recent years, the degree of integration of integrated circuits in semiconductor devices has increased dramatically, and their patterns have become extremely fine. As a result, diagnosing integrated circuits (testing to see if the integrated circuit is working properly, and if it is defective, clarifying whether the cause is somewhere inside the integrated circuit) is extremely important in product development. Although it is important, conventional integrated circuit testing equipment that performs the above-mentioned diagnosis, which is important, but has become very difficult, ■ provides various diagnostic input signals to the integrated circuit and determines whether the resulting output signal is normal or not. We are testing whether the product is good or bad. In the case of a defect, the content of the abnormal output signal is further analyzed to estimate where within the integrated circuit the cause of the defect is.

■If this estimation is insufficient, remove the top plate of the integrated circuit pancage, expose the integrated circuit chip, and measure the voltage by touching a metal needle with a minute tip to a specific point on the chip. The cause of the defect is being identified. However, this mechanical stylus has problems such as the risk of destroying the integrated circuit, insufficient spatial resolution, and the time it takes to reach the top of the furnace, making it unsuitable for large-scale integrated circuits. Can not.

■Therefore, as an alternative method for diagnosing the inside of integrated circuits, methods using electron beam probes have been actively researched and developed in recent years. For details, see ``Electron Beam Blobbing as a Powerful Tool for LSI Diagnosis'' by Furukawa, Gosei, and Inagaki.

Nikkei Electronics, March 15, 1982 issue.

PP, 172-201.

This method utilizes the fact that secondary electrons generated when an operating integrated circuit is irradiated with an electron beam contain information about the surface voltage.

In other words, in the secondary electron signal obtained by detecting these secondary electrons with a secondary electron detector, the signal of secondary electrons generated from a high voltage area is small, and the signal of secondary electrons generated from a low voltage area is small. The signal has the property of being large. Therefore, like a scanning electron microscope (SEM), a secondary electron signal obtained by two-dimensionally scanning an operating integrated circuit with a narrowly focused electron beam is used to transmit a secondary electron signal to the two axes (luminance modulation axes) of a cathode tube display device CRT. ) and input scanning signals of the electron beam to the X and Y axes, an image of the integrated circuit can be obtained on the display device CRT in which areas of high voltage are dark and areas of low voltage are bright. . This is well known as a voltage contrast image of a scanning electron microscope SEM.

On the other hand, 2 is emitted from the integrated circuit irradiated with the electron beam.
The energy of the secondary electron changes depending on the surface voltage. When the energy of these secondary electrons is analyzed using an energy analyzer, the higher the surface voltage, the lower the energy of the secondary electrons.

Therefore, by positioning an electron beam at a specific point on the chip surface of an integrated circuit and analyzing the energy of the secondary electrons, the voltage can be measured without contact.

By using the two methods described above, it is possible to understand the voltage state on the surface of an integrated circuit chip two-dimensionally, and it is also possible to measure the voltage at specific points, making it a powerful weapon for diagnosing integrated circuits. .

However, when diagnosing a very large-scale integrated circuit, the diagnostic input data string required for functional testing from external input/output pins becomes enormous, and it is impossible to exhaust all of it. . For this reason, defects are often discovered during the packaging of integrated circuits.

Furthermore, the diagnostic data for functional tests is not always complete, and the defective states discovered in these tests do not necessarily represent the state at the time when the integrated circuit malfunctions.

Therefore, for diagnosis aimed at identifying defective locations and causes of defects, there is a need for a diagnostic device that can accurately identify the location of failure in an integrated circuit.

(3) Prior art and problems Conventionally, devices that diagnose integrated circuits using electron beams use the external input/output pins of the integrated circuit to detect diagnostic inputs that have been found to be abnormal in the functional test. The integrated circuit was driven with data, and in this state voltage images of various parts of the integrated circuit were displayed and voltage measurements were performed. In addition, there are other diagnostic devices that drive an integrated circuit periodically at high speed to obtain a voltage waveform of one cycle (for example, a strobe scanning microscope).

In the former method, voltage images of integrated circuits and high-precision voltage measurements at diagnostic nodes can be measured in a relatively short period of time, but only integrated circuits in a specific state, such as an abnormal state appearing at an external input/output pin, can be handled.

For this reason, it is not possible to accurately grasp malfunctions of integrated circuits that do not appear on external input/output pins due to incomplete input data for functional tests, and it tends to be difficult to identify defective semiconductor elements or clarify the cause of defects. there were.

In the latter method, the diagnostic node voltage of an integrated circuit operating periodically can be determined with high time resolution, but it requires high-speed periodic driving of the integrated circuit, and the I! There are drawbacks such as the long time required and the measurable time range being short.

(First Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a method for measuring and understanding voltage changes at a diagnostic node of an integrated circuit that does not require periodic driving and is driven by a long sequence of input data strings. The present invention aims to provide a diagnostic device for integrated circuits that is capable of diagnosing integrated circuits.

(5) Structure of the Invention In order to achieve the above object, the present invention provides a driving circuit for driving an integrated circuit, a storage device storing an input data string for providing a signal to the driving circuit, and an electron beam. An electron beam device equipped with an optical lens barrel for irradiation is provided with a storage device for storing the coordinates of a plurality of diagnostic node points in the integrated circuit, and each time the integrated circuit is driven by the input data. This is a diagnostic device for integrated circuits having a function of successively irradiating an electron beam to a diagnostic node of an integrated circuit driven by an integrated circuit to measure and display the voltage at the diagnostic node. It is equipped with an energy analyzer to analyze the energy of secondary electrons from a point, and a function to calculate the voltage of the integrated circuit from the results of this energy analysis. It also includes a dedicated electron beam frame scanning signal generation circuit for obtaining a secondary electron image of the integrated circuit, an image data storage device, an image display device, and a coordinate system of an arbitrary node point on the image on the image display device. The measured voltage at each diagnostic node point is displayed in a graph as a voltage map in sequence with respect to the input data of the integrated circuit.

Further, there is provided a storage device for storing standard voltage values corresponding to input data of the main node points, and a storage device for displaying the standard voltage values in a format corresponding to the voltage map of the main node points.

(6) Examples of the invention Next, one embodiment of the present invention will be described based on FIG.

The integrated circuit 3 to be diagnosed is mounted on a sample stage 4 provided within the sample chamber of the electron optical column 1. Secondary electrons 1-6 from integrated circuit 3 irradiated with electron beam 1-5
passes through the energy analyzer 2 to the secondary electron detector 1-
7, it is converted into a secondary military signal S, passes through the amplifier 5, and is sent to the AD
The data is converted into digital data by a converter 6 or an AD converter 7.

The analysis voltage Va of the energy analyzer 2 is given by digital data from the control circuit 8 via the DA converter 9. The integrated circuit 3 is driven through a drive circuit 11 based on a diagnostic input data string stored in an auxiliary storage device 10. Movement of the sample stage 4 is performed by a stage drive circuit 2 based on stage movement data output from a control circuit 8.

The positioning of the electron beams 1-5 is performed via the DA converter 16 using deflection signals 14 and 15 output from the control circuit 8 or the storage device 13.

Also, under the control of a dedicated scanning signal generation circuit 17, frame scanning of the electron beam 1-5 is performed using a frame scanning signal 17-1, secondary electron signal data is stored in the frame memory 18, and data is transferred to the video RAM 9. A secondary electronic image is displayed on the display device 20 by transferring frame memory data. A cross mark that can be freely moved by a mark moving circuit is always displayed on the display device 20.
The coordinates of this cross mark can be read by the control device 8.

In addition, the electron beam 1 that is constantly illuminated by the electron mirror 1-1
-5 is designed to be cut off except when necessary for the blanker 1-2, and the blanking signal 22-1 or 22-2 input to the blanker drive circuit 22 is used in this embodiment. The operation will be explained based on FIGS. 1 to 5.

1. In order to obtain a secondary electron image of the area including the node point to be diagnosed in the integrated circuit 3 in FIG. )10■, and the control circuit 8 gives the start signal 17-2 to the frame scanning signal generation circuit 17. The frame scanning signal generation circuit 17 generates a frame scanning signal 17-1 to be applied to the deflector 1-4, and sends a control signal 17-3 synchronized with this to the blanker drive circuit 22, AD converter 6. is applied to the frame memory 18. Therefore, the secondary electron signal detected by the secondary electron detector 1-7 in synchronization with the frame constant distortion signal is stored in the frame memory 8 by the amplifier 5. The data is stored as digital data via the AD converter 6. When one frame scanning is completed, the secondary electronic image data stored in the frame memory 18 is transferred to the video camera via the control circuit 8.

A secondary electron image corresponding to the secondary electron image data is transferred to and stored in the Otum 19 and displayed on the display device 20. This secondary electron image is shown in FIG. The open areas are brightly lit by integrated circuit wiring. Therefore, a mark moving circuit is used to indicate the diagnostic node point on the secondary electronic image. For example, when points 30-1 to 30-4 on the secondary electron image 29 are specified, the coordinates of the specified plurality of node points 30-1 to 30-4 are read by the control circuit 8, respectively. , are stored in the storage device 13.

After this, all switches 23, 24, 25 are pushed down.

After that, the coordinate information is sequentially read out from the memory device @ 13 and given to the deflector 1-4 via the DA converter 16, and the voltage measurement at the designated diagnostic node points 30-1 to 30-4 is performed. This is performed sequentially by the energy analyzer 2. The principle of voltage measurement by this energy analyzer 2 will be explained with reference to FIG.

The horizontal axis of the figure shows the analysis voltage Va, and the vertical axis shows the voltage of the secondary electron signal S.

Here, when the analysis voltage Va of the energy analyzer 2 is changed, the signal S caused by the secondary electrons 1-6 emitted by the irradiation with the electron beam 1-5 changes according to the applied voltage of the given wiring section. It changes as shown by curves 31 to 32 in FIG.

At this time, when the applied voltage at the deuteron beam irradiation point is 0 (v), the analysis curve 32 is obtained at the 131.5th analysis car, and the analysis curve 32 is 5 (v) for the analysis car 131.
The curve that has been translated to the right by just that.

Therefore, the unknown voltage node points 30-1 to 30-4
The analytical curve 33 at
According to the analysis curve 31 for ), the node voltage becomes Vn (V) when VJ is moving in parallel.

On the other hand, an example of a diagnostic input/output data string given to the integrated circuit 3 is shown in FIG.

This is an input/output data string of a collector circuit having 64 input/output pins, the horizontal axis shows the output knob pin number, and the vertical axis shows the drive order of the input/output data string.

Here, °゛1'''I O,n P'l means input data, respectively, logic 1'HJ, logic η1orL''.

"Positive pulse") 9, H, L, Z mean the expected value data of the output, and each is promoted by "H".

logic IFrLJ, r positive pulse. These input data strings are read from the auxiliary storage device 10 in accordance with the driving order and applied to the W rero path 3 by the driving circuit 11 one unit at a time.

The drive circuit 11 inputs the control signal 11-1 to the storage device 13 every time the circuit 3 is driven by one step of "4% T+".

By inputting the control signal 11-1, the coordinates of the diagnostic node points 30-1 to 31)-4 are read out one by one from the pupil device 13, and the electron beam 1-5 is applied to the node point of the 6th clinic. is positioned. Then, at the diagnostic node point, the analysis curve is determined by the operation of the energy analyzer 2,
The voltage at each diagnostic node is measured. If all indicated diagnostic node points! When the setting is completed, the storage device 13
Control is returned to the drive device 11 by the control signal 11-2 issued from the control signal 11-2, and the next step of drive is performed.

After repeating the above steps, you can confirm that the measurement results are as follows.
It is displayed on the graph display device 26 as a city and pressure map.

FIG. 5 shows a display example of this voltage map.

This corresponds to the ``node point'' within each clinic shown in Figure 9'S2.
The voltage map is I), (C), 0)
are %y-do points 30-1, 30-2, 30-3 respectively.
, 411j for 30-4, the vertical axis of each map is the measured node point pressure Vn, and the horizontal axis is the number of the data string (step) for integrated circuit diagnosis shown in FIG. is.

Therefore, the voltage map of this graph display device
By doing x E-=, it is possible to accurately grasp what kind of input data and where the abnormality is occurring.

Here, if a location where voltage map data during normal operation corresponding to the input data is stored in the auxiliary storage device 27 is selected as a diagnostic node point, this is displayed on the graph display device 28 as a reference voltage map. Diagnosis can be performed by comparing and checking the measured voltage map.

Therefore, we will use a concrete example of a high-accumulation circuit to improve this diagnosis.
To clarify, it is the following j angle.

In the integrated circuit 35 shown in FIG. 6, let us take as an example the case where there is a short circuit with the data at the defective location 34. Note that 38.39 is a NAND circuit, and 37-1 to 3
7-3 indicates an input pin, and 37-4 indicates an output pin.

In this circuit, diagnostic input data shown in FIG. 7 is applied to input pins 37-1 to 37-3 at each step.

That is, 1 to 3 in FIG. 7 are input pins 37-1 to 37-, respectively.
3 shows the data given to output pin 37-4, and 4 shows the data to be obtained at output pin 37-4 at that time. Therefore,
If a functional test is carried out using only such data example, it will be found that an abnormality has occurred in the integrated circuit 35 only when the data of the fifth step is provided. However, according to the embodiment of the present invention, the voltage map shown by the solid line in FIG. 8 is obtained for the diagnostic node point 36.

That is, the horizontal axis in FIG. 8 shows the steps of the input data, and the thread/child axis (d node voltage is shown.) As you can see, it is easy to see that an abnormal state occurs even for the data of the t?J1st step. Therefore, in integrated circuits that have become more complex and diverse in recent years, when correct data cannot be obtained from the output pin, that is, when an abnormality is detected, it is possible to detect it at the actual location of the abnormality. Although there are many places where the signal status has returned to the same state as normal, it is very useful for detecting such abnormality locations.

In the above embodiment, the voltage map is displayed after the measurement for all input data is completed, but the measurement results for each input data are displayed in the graph display device 26 as a voltage map in order. It may also be added and displayed.

(7) Effects of the Invention According to the present invention, in diagnosing an integrated circuit, it is possible to accurately grasp a defective part at a stage earlier than a defective part discovered from an external input/output pin from a voltage map of a diagnostic node point. ,
Diagnosis, such as discovering defective parts and elucidating the cause of the defect, becomes part of the service.

[Brief explanation of the drawing]

FIG. 1 shows an example of the present invention, FIG. 2 shows an example of a secondary electronic image displayed on the display device of FIG. 1, and FIG.
4 and 7 are examples of diagnostic input data stored in the auxiliary storage device shown in FIG. 1, and FIGS. FIG. 6 shows an example of the voltage map displayed on the graph display device shown in the figure, and FIG. 6 shows an example of the configuration of the integrated circuit to be diagnosed. Here, 1 is an electron optical lens barrel, 1-1 is an electron gun, 1-2 is a blanker, 1-3 is an electron lens, 1-4 is a deflector, and 1-5
is an electron beam, 1-6 is a secondary electron, 1-7 is a secondary electron detector, 2 is an energy analyzer, 3 is an integrated circuit, 4 is a sample stage, 6.7 is an AD converter, and 8 is a control circuit , 11 is an integrated circuit driving circuit, 13 is a storage device, 17 is a frame scanning signal generation circuit, 18 is a frame memory, 19 is an ID video ram, 26.28 is a graph display device, 29 is a secondary electron image of Hayabusa f and the circuit. , 30-1 to 30-4 are diagnostic node points, 31+32. 33 is an analysis curve, 35 is an integrated circuit, and 37-1 to 37-4 are input/output pins of the integrated circuit. 61i3 30 7th old vision E ''-'171

Claims (1)

[Scope of Claims] (1) A drive circuit for driving an integrated circuit, a storage device for storing an input data string for providing a signal to the drive circuit, and an optical lens barrel for emitting electron beams. In the electron beam device, a storage device is provided for storing the coordinates of a plurality of diagnostic node points in the integrated circuit, and a function is provided to measure and display the voltage that drives the integrated circuit based on the input data. An integrated circuit diagnostic device characterized by: (2. Claim 1 provides an energy analyzer for analyzing the energy of secondary electrons from the diagnostic node point, and a function for calculating the voltage of the integrated circuit based on the result of this energy analysis. A device for diagnosing integrated circuits, characterized in that: (3) A dedicated electron beam frame scanning signal generation circuit for obtaining a secondary electron image of an integrated circuit according to claims 1 and 2; An integrated circuit diagnostic device comprising an image data storage device, an image display device, and a function for inputting the coordinates of an arbitrary node point on the image on the image display device. (4) Scope of Claims An integrated circuit Ω diagnostic device characterized by having a function of sequentially displaying the voltages at each diagnostic node point measured in items 1 to 3 in a graph as a voltage map with respect to input data of the integrated circuit. (5) In claims 1 to 3, there is provided a storage device for storing standard voltage values corresponding to the input data of the main nodes, and a graph of the standard voltage values in a format corresponding to the voltage map of the main nodes. A diagnostic device for integrated circuits, characterized by having a display function.