JPH06324123A - Electron beam tester - Google Patents

Abstract

(57) [Abstract] [Purpose] Electron beam tester for non-contact measurement of voltage and timing of internal wiring of integrated circuit by using electron beam, especially strobe secondary image for visually confirming operating state of integrated circuit Regarding the electron beam tester that can obtain
An object of the present invention is to provide an electron beam tester capable of speedily acquiring an integrated circuit image and at the same time visually confirming the operating state of the integrated circuit. An electronic circuit in which an electron beam in which a reference timing serving as a reference is minutely changed for a predetermined number of frames and the timing control means outputs the change timing, and the irradiation means is pulsed based on the reference timing and the change timing is integrated circuit. It was designed to irradiate the laser and to acquire the image of the integrated circuit based on the secondary electrons detected from the integrated circuit.
Image acquisition is performed without changing the irradiation timing of the electron beam within one frame, and thus image acquisition can be speeded up. Further, the operation of the integrated circuit and the wiring continuity inspection can be easily performed based on the image acquired at high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam tester which uses an electron beam to measure the voltage and timing of internal wiring of an integrated circuit in a non-contact manner, and more particularly to a stroboscope capable of visually confirming the operating state of the integrated circuit. The present invention relates to an electron beam tester capable of acquiring the next image.

[0002]

2. Description of the Related Art Generally, when detecting a voltage waveform in an internal wiring of an integrated circuit, an electron beam tester acquires an image near a measurement point in the integrated circuit and measures the voltage waveform based on this image. This image is displayed on a monitor through a two-dimensional scanning of a pulsed electron beam on the surface of the integrated circuit, captures secondary electrons emitted therefrom, an amplifier and a signal processing circuit. Secondary electrons emitted from the integrated circuit display contain wiring voltage information. In other words, the amount of secondary electrons emitted from the high voltage portion is small and the secondary electron amount is large from the low voltage portion, so the analysis voltage of the energy analyzer disposed between the surface of the integrated circuit and the secondary electron detector should be set appropriately. If selected, an image with potential contrast is displayed on the monitor.

The waveform measurement is carried out by irradiating a specific point on the image with an electron beam, and shifting the irradiation timing while analyzing the energy of the emitted secondary electrons with an energy analyzer.

A conventional electron beam tester in which the timing is changed and shifted will be described with reference to FIGS. FIG. 5 is an operation timing chart of wirings A to E of the integrated circuit and a phase image at timings T _{0 to} T ₄ , FIG. 6 is an operation flowchart of a conventional electron beam tester, and FIG. 7 is each timing chart of FIG. It is each image corresponding to.

In each of the above figures, the conventional electron beam tester displays the images at a plurality of phases in the same frame by shifting the irradiation timing when the surface of the integrated circuit of the sample is two-dimensionally scanned by the electron beam. , Is configured to confirm the operating state of the integrated circuit based on the displayed phase image.

The operation of the conventional electron beam tester based on this configuration will be described. First, the signals of the timing chart shown in FIG. 5A are repeatedly applied to the wirings A to E in the integrated circuit. An area of wirings A to E of the integrated circuit is irradiated with an electron beam pulsed at reference timings T _{0 to} T _{4 at} predetermined intervals using an arbitrary point of this signal as a phase reference point.

In such an electron beam irradiation state, the phase of the electron beam irradiation timing is initialized and set to the reference timing T ₀ (PH = 0) (step 1).
0). Secondary electrons emitted from the integrated circuit are detected with respect to the electron beam emitted at the reference timing T ₀ , and an image is acquired based on the detected secondary electrons (step 11). When this image is acquired, the number of images N (corresponding to the reference timing number) captured in one frame set in advance = 5 is sequentially subtracted (step 12). It is determined whether or not this subtraction result is "0" (step 1
3) If the subtraction result is diagnosed as "0", the detection of the phase image is completed and the process ends.

It has been determined that the subtraction result is not "0".
If the reference tanming T₀Is T ₁(T₁To T₂，
T₂To T₃, T₃To T_Four) To the
14). Reference timing T after this transition₁(Or T
₂~ T_Four) Further image acquisition (step 11)
It will be repeated. That is, one frame of the displayed image
Images of multiple timings are acquired in the game.
The wiring that the integrated circuit is operating is in one frame of the image.
Changes from white to black and from black to white. Power and ground
The brightness does not change in the wiring where the voltage does not change.

In this way, all reference timings T ₀
Each image corresponding to ~ T ₄ is stored in one frame, and
As shown in (b), it is possible to confirm the instantaneous operating state in various fields of view.

Further, as a conventional electron beam tester, DF
Some use I (Dinamic Fault Image) technology,
This schematic structure is shown in FIG. This other technique has a large number of image memories M ₁ , M ₂ , ..., M _m and changes the irradiation tamming for each frame to sequentially store images I ₁ ,
Although I ₂ , ..., I _m are stored, the temporal change of each wiring is recorded as an image in the depth direction (M ₁ → M _m ) of the memory. Then, once the strobe image is acquired, the image is used to verify the defective bending and the operation.

[0011]

Since the conventional electron beam tester is configured as described above, a plurality of timings are changed in one frame, so that the scanning time for one frame becomes long. There is. When the scanning time becomes long, there is a problem that the tracking of the moving mechanism and the image deteriorates when trying to look at the wiring at another position.

Further, in another electron beam tester using a DIF, there is a problem in that the operation state cannot be instantaneously confirmed in various visual fields because only the image is acquired by changing the irradiation timing in the same visual field.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electron beam tester capable of speedily acquiring an image of an integrated circuit and at the same time visually confirming the operating state of the integrated circuit. And

[0014]

An electron beam tester according to the present invention comprises an electron beam irradiating means for irradiating an integrated circuit with a pulsed electron beam synchronized with repetition of a test pattern of the integrated circuit, and an electron beam irradiating means. A secondary electron detection means for detecting a signal of secondary electrons emitted from the integrated circuit irradiated with the beam, and an electron beam tester for testing the operation of the integrated circuit based on the detected secondary electron signal. The timing of the electron beam emitted from the electron beam irradiating means is output as a reference timing for each frame with reference to the repetition of the test pattern of the integrated circuit, and a minute time is elapsed from the reference timing every time the frame is repeated a predetermined number of times. It is provided with a timing control means for changing and outputting as a change timing.

[0015]

According to the present invention, the reference timing serving as a reference is minutely changed for each predetermined number of frames, and the timing control means outputs the change timing, and the irradiation means is pulsed based on the reference timing and the change timing. Since the integrated circuit is irradiated with the beam and the image of the integrated circuit is acquired based on the secondary electrons detected from the integrated circuit, the image can be acquired within one frame without changing the irradiation timing of the electron beam. Will be done,
Image acquisition can be speeded up. Furthermore, the operation confirmation and wiring continuity inspection of the integrated circuit can be easily performed based on the image acquired at high speed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electron beam tester according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic block diagram of the electron beam tester of this embodiment, FIG. 2 is an operation flowchart of the embodiment shown in FIG. 1, and FIG. 3 is an operation timing of a signal input to the integrated circuit in the embodiment shown in FIG. FIG. 4 shows a display image at each timing in the operation timing chart shown in FIG.

In each of the above figures, the electron beam tester according to this embodiment includes a timing control circuit 21 for pulsing the electron beam emitted from the electron gun 1 onto the surface of the integrated circuit 10 of the sample and controlling the irradiation at a predetermined timing. , A scanning deflector driving circuit 2 for driving and controlling a scanning deflector 6 for scanning and deflecting the irradiated electron beam to a predetermined area of the integrated circuit 10.
2 and secondary electrons emitted from the integrated circuit 10 irradiated with the electron beam are the secondary electron detector 7 and the energy analyzer 8.
The signal processing circuit 23 that performs arithmetic processing on the detection signal that is detected and analyzed by the device and is output, and the moving mechanism control unit 30 that controls the moving mechanism 14 that moves the mounting table on which the integrated circuit 10 is mounted.
A vacuum evacuation control unit 40 that brings the sample chamber 11 and the electron beam lens barrel 13 into a vacuum state, a lens barrel control unit 50 that controls each optical system and the like in the electron beam lens barrel 13, and controls the entire apparatus. A central processing unit 60 that performs a calculation operation and a display unit 70 that displays an image of the integrated circuit 10 acquired at each irradiation timing based on the calculation result are provided.

The timing control circuit 21, the scanning deflector drive circuit 22, and the signal processing circuit 23 are provided in the electron beam control unit 2.
Configures 0. Next, the operation of this embodiment based on the above configuration will be described.

First, the central processing unit 60 initializes the phase of the irradiation timing of the electron beam, and the reference timing T
_It is set to ₀ (PH = 0) (step 1). The number of phase changes C = N of this irradiation timing is set (step 2). Further, the electron beam is deflected in a predetermined direction by the sub-blanker 3 and the main blanker 4 controlled by the timing control circuit 21 based on the reference timing T ₀ , and becomes a pulsed electron beam by shifting to the objective aperture. The pulsed electron beam is irradiated onto a predetermined area on the integrated circuit 10 via the scanning deflector 6 under the control of the scanning deflector driving circuit 22. Integrated circuit 1 irradiated with this electron beam
Secondary electrons are emitted from 0, the secondary electrons are detected by the secondary electron detector 7 and analyzed by the energy analyzer 8, and the signal of the detected / analyzed secondary electrons is processed by the signal processing circuit 23.
Will handle. The processed signal is input to the central processing unit 60, and a predetermined calculation process is performed to obtain an image (see FIG. 4A) at the reference timing T ₀ (see FIG. 3) (step 3). . This image is displayed on the display unit 70 in real time under the control of the central processing unit 60.

Further, the central processing unit 60 judges whether or not all the preset number N of all images have been acquired (step 4). If it is judged that all images have not been acquired,
Every time an image is acquired, "1" is subtracted from the preset number N of all images (step 5). Based on the result of this subtraction, it is determined whether or not the number C of phase changes is "0" (step 6). If it is determined by this determination that the number of phase changes C is not "0", the phase PH is set to T _{m + 1} (step 7). That is, in the case of the reference timing, T ₀ to T ₁
The image acquisition is repeated by sequentially shifting to T _{2 and then} to T ₂ and returning to step 3.

On the other hand, when the number of phase changes is judged to be "0" in step 6, the reference timing T
₀ (or T ₁ , T ₂ ) is changed for a minute time and the phase PH
= T ₀ + t ₁ (or T ₀ + t ₂ , T ₁ + t ₁ , T ₁ + t
₂ , T ₂ + t ₁ , T ₂ + t ₂ ), which is output as the change timing (step 8). When the B change timing T ₀ + t ₁ is output, the process returns to step 2 again,
Image acquisition (step 3) is repeated based on this change timing T ₀ + t ₁ .

In this way, the reference timing T₀, T₁, T
₂Change time after changing the image acquisition
Ming T₀+ T₁, T₁+ T₁, T₂+ T₁Image acquisition with
And change timing by changing the time in minute increments
T₀+ T₂, T₁+ T₂, T ₂+ T₂Change like
Then, an image is acquired based on each of the change timings.
This reference timing T₀~ T₂And change timing T₀
+ T₁~ T₂+ T₂The image acquired based on
It shows in (a)-(i). This change timing T₀+ T₁
~ T₂+ T₂Drive a minute pulse signal
To check the operating status even with a moving wiring pattern
It is possible to visually detect and track wiring abnormalities.

In the prior art shown in FIGS. 5A and 6, during the reference timings T _{0 to} T ₄ (T ₀ -T).
₁ , T ₁ -T ₂ , T ₂ -T ₃ , T ₃ -T ₄ ), even though the voltage input to each wiring is changing.
For example, the wiring C is observed as if it has not changed. On the other hand, in the case of the present embodiment, the operation state can be confirmed at any of the change timings T ₀ + t _{1 to} T ₂ + t ₂ for any signal change of the wirings A, B, and C.

In order to see the operation of the integrated circuit from which this image was acquired with white and black contrast, the analysis voltage of the energy analyzer 8 was changed and set so far during the image acquisition. This is made to perform the waveform measurement of the wiring which is operating in advance, and automatically obtain the analysis voltage V _rL of the power failure portion and the analysis voltage V _rH of the high potential portion, and set the analysis voltage V _rS between them. It is the one.

V _rS = V _rL + (V _rL + V _rH ) / 2

[0027]

As described above, in the present invention,
The timing control means outputs the reference timing, which is the reference, for each predetermined number of frames by a minute time as the change timing, and the irradiation means irradiates the integrated circuit with the pulsed electron beam based on the reference timing and the change timing. Since the image of the integrated circuit is acquired based on the secondary electrons detected from the integrated circuit, the image acquisition is performed without changing the irradiation timing of the electron beam within one frame. Can speed up.
Further, there is an effect that the operation confirmation / wiring continuity inspection of the integrated circuit can be easily performed based on the image acquired at high speed.

[Brief description of drawings]

FIG. 1 is a schematic block configuration diagram of an electron beam tester according to an embodiment of the present invention.

FIG. 2 is an operation flowchart of the embodiment described in FIG.

FIG. 3 is an operation timing chart of signals input to the integrated circuit in the embodiment shown in FIG.

FIG. 4 is a display image at each timing in the operation timing chart shown in FIG.

FIG. 5 is an operation timing chart of wirings A to E of an integrated circuit as a sample of a conventional electron beam tester and phase images at timings T _{0 to} T ₄ .

FIG. 6 is an operation flowchart of a conventional electron beam tester.

7A to 7C are images corresponding to the timing charts of FIGS.

FIG. 8 is a schematic configuration diagram of another conventional electron beam tester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... 1st lens 3 ... Sub blanker 4 ... Main blanker 5 ... 2nd lens 6 ... Scan deflector 7 ... Secondary electron detector 8 ... Energy analyzer 9 ... 3rd lens 10 ... Integrated circuit 11 ... Sample chamber 13 ... Electron beam lens barrel 14 ... Integrated circuit moving mechanism 20 ... Electron beam control unit 21 ... Timing control circuit 22 ... Scan deflector drive circuit 23 ... Signal processing circuit 30 ... Moving mechanism control unit 40 ... Vacuum exhaust control unit 50 ... Lens barrel control unit 60 ... Central processing unit 70 ... Display unit

Claims (4)

[Claims] 1. An electron beam irradiation means for irradiating an integrated circuit with a pulsed electron beam synchronized with repetition of a test pattern of the integrated circuit, and a secondary beam emitted from the integrated circuit irradiated with the electron beam. An electron beam tester having secondary electron detection means for detecting an electron signal and testing the operation of an integrated circuit based on the detected secondary electron signal, wherein the electron beam emitted from the electron beam irradiation means is The timing control means outputs the timing as a reference timing for each frame with reference to the repetition of the test pattern of the integrated circuit, and outputs the change timing as a change timing by changing a minute time from the reference timing every time the frame is repeated a predetermined number of times. An electron beam tester characterized by that. 2. The electron beam tester according to claim 1, further comprising moving means for changing a position for two-dimensionally scanning the surface of the integrated circuit while repeating the image acquisition by the secondary electron detecting means. An electron beam tester characterized by that. 3. The electron beam tester according to claim 1 or 2, wherein the timing control unit repeatedly outputs a plurality of timings designated in advance as change timings. 4. The electron beam tester according to any one of claims 1 to 3, wherein the timing control means repeatedly outputs a change timing in response to a signal change in a test pattern of an integrated circuit. Beam tester.