JP2917869B2 - An EB tester that limits the scanning range of the electron beam - Google Patents

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 ("EB") used for test and failure analysis of a semiconductor integrated circuit.
In particular, the present invention relates to a technique for acquiring a potential waveform of an EB tester.

[0002]

2. Description of the Related Art Conventionally, when a fault location of a semiconductor integrated circuit device (hereinafter referred to as "LSI") is specified using an EB tester, a potential image of a good product and a potential image of a defective product are acquired and then compared. The fault location is specified by obtaining a potential waveform.

[0003] A conventional EB tester will be briefly described below. FIG. 5 shows a schematic configuration of the EB tester.

Referring to FIG. 5, an EB tester mounts an electron beam (EB) lens barrel 11, an electron beam generator 12, an LSI 13 to be tested, and a terminal of the LSI 13 and an LS.
A test board 14 provided with a predetermined jig for making an electrical connection with the I tester 17, an XY stage 15 that makes the LSI 13 movable in the XY directions, and secondary electrons generated from the LSI 13 when the LSI 13 is irradiated with an electron beam. The secondary electron detector 16 for detecting lines and the test board 1
4, an LSI tester 17 for supplying a power supply voltage and a test pattern via an XY stage driving device 18 for driving and controlling the XY stage 15, and a beam pulse control device 1 A for controlling the generation of an electron beam from the electron beam generating unit 12. A CP that processes the secondary electrons into image information or waveform information, stores this information, and controls the beam pulse control device 1A and the XY stage drive device 18 from the image data.
U19 and CR for displaying the obtained potential image and various information
T1B is provided.

Next, a procedure for obtaining a potential waveform at a probing point using the EB tester will be described.

FIG. 4 shows a CRT 1B for displaying a potential image and the like.
As shown in (A), the XY stage 15 and the like are controlled to include a probing point which is a measurement point for observing a potential waveform, and a potential image enlarged to a required magnification is displayed.

[0007] Assuming that the number of display pixels in the horizontal direction of the potential image at this time is X0 and the number of display pixels in the vertical direction is Y0, the number of horizontal acquisition pixels X2 and the number of vertical acquisition pixels Y2 of the potential image at the time of acquiring the potential waveform. Are equal to X0 and Y0, respectively.

[0008] Further, as shown in FIG.
The potential image in B is formed by arranging a plurality of pixels in a matrix. The number of pixels does not change even when the magnification is changed, so that it is irrelevant to the measurement time of the potential waveform.

FIG. 3A schematically shows an example of an obtained potential waveform (relative voltage value). FIG. 3A shows a voltage change at the time when the time has elapsed from 0 to t0, 2t0, 3t0,.

When this is measured in a measurement range that is doubled in the time axis direction, the result is as shown in FIG.

In a predetermined memory area of the CPU 19 of the EB tester, sampled voltage value data is stored in the form of a table. The potential waveform displayed on the EB tester is processed by the CPU 19 to process the data. This is output as a waveform image above.

The memory area for storing the voltage value data is constant irrespective of the time unit (referred to as "time division") T0 on the observed time axis, so that the number of measurement points in the time axis direction is fixed. However, when the image is enlarged in the time axis direction (the resolution is increased in the time axis direction), it takes a measurement time according to the enlarged time magnification.

This is because the repetition time of the test pattern given to the observed LSI 13 and the time division T0
This is because the measurement time is determined by the ratio of.

For example, time division T0 = 1 μs
If the measurement time is 10 s (second) at (microsecond), the measurement time is 20 s at time division T0 = 500 ns (nanosecond). Therefore, if the time division T0 is set to the ns order, very large measurement Time.

In a failure analysis, for example, when a malfunction occurs due to a time relationship between a clock of a flip-flop as a device under test and a data input, etc.
In general, the time division T0 is set to a high time resolution of the order of ns, and a few to about ten points are measured for both non-defective products and defective products, and a very large measurement time is required.

[0016]

As described above, in the above-described conventional EB tester, the time division T0
When the time is reduced (the time magnification is increased, that is, the time resolution is increased), there is a problem that the observation time of the potential waveform becomes longer.

Therefore, the present invention solves the above problems,
When acquiring a potential waveform using an EB tester, by limiting the scanning range and reducing the number of acquired pixels,
The purpose is to reduce the potential waveform observation time.

[0018]

In order to achieve the above object, the present invention comprises a means for irradiating an integrated circuit device with an electron beam; a means for detecting a secondary electron beam generated from the integrated circuit device; Means for displaying a secondary electron beam two-dimensionally as a potential image on a monitor screen, and temporally displaying the secondary electron beam at a measurement point for observing an arbitrary potential waveform on the integrated circuit device on the monitor screen. Means for limiting the vertical and / or horizontal scanning range with respect to the normal potential image scanning range when obtaining the potential waveform at the measurement point in the EB tester having at least
Scanning per unit time for the measurement point
An EB tester characterized by increasing the number of times is provided.

In the EB tester of the present invention, it is preferable that a normal voltage is obtained when the potential waveform at the measurement point is obtained.
The scanning in the vertical and / or horizontal direction
When the scanning range is limited, when the scanning range is not
Means for switching time-sharing
It is characterized in that the waveform observation time is shortened .

[0020] In addition, in the EB tester of the present invention, before
Scanning range of the two-dimensional display on the monitor screen in the vertical direction
Enclosure limits, horizontal scan range limits, and vertical and horizontal
At least one of the limits of the scanning range in both directions
Thus, the case where the scanning range is limited and the case where the scanning range is not limited may be switched in a time-sharing manner to shorten the potential waveform observation time.

According to the EB tester of the present invention, unlike the conventional example in which the potential image area is specified by scanning all the pixels (full scan) of the potential image area and a desired potential waveform is obtained, the potential waveform at the measurement point is obtained. When acquiring the image, the scanning range is limited only to a predetermined predetermined neighboring area including the measurement point, thereby reducing the number of acquired pixels per scan and shortening the time required per scan ( That is, by increasing the number of scans of the measurement point per unit time), the potential waveform observation time can be shortened even when a high time resolution is set.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. It is assumed that the basic configuration of the EB tester is as shown in FIG. 5 referred to in the description of the conventional example.

[0023]

Embodiment 1 FIG. 1A is a diagram showing a scanning range of a potential image at the time of acquiring a waveform in one embodiment of the present invention.

The number of pixels Y obtained in the vertical direction of the potential image at the time of waveform acquisition
1 is selected so as to include a measurement point (referred to as "probing point") for observing an arbitrary potential waveform on the LSI, and Y1 <Y0 (where Y0 is the number of pixels in the vertical display of the potential image). To choose.

By limiting the scanning range in this way, the number of times of scanning the probing point per unit time increases. This is because the number of scans is proportional to the reciprocal of the number of pixels to be scanned.

More specifically, the number of scans per unit time is Z / (X0 × Y0) (where Z is a predetermined coefficient) in the conventional example of the all-pixel scanning type. In this case, Z / (X0 × Y1), the ratio of the number of scans to the conventional example is Y0 / Y1, and since Y1 <Y0,
In the present embodiment, the number of scans per unit time is set to be larger than in the conventional example.

The increase in the number of scans per unit time with respect to the probing point increases the potential waveform observation time. For example, Y0
When / Y1 = 2, the potential waveform observation time is half of the conventional potential waveform observation time.

[0028]

Embodiment 2 FIG. 1B is a diagram showing a scanning range of a potential image at the time of acquiring a waveform according to a second embodiment of the present invention.

Referring to FIG. 1 (B), the number of pixels X1 in the horizontal direction of the potential image at the time of waveform acquisition is selected so as to include the probing point, and X1 <X0 (where X0 is the horizontal direction of the potential image). (Direction display pixels).

By limiting the scanning range in this way, the number of times of scanning the probing point per unit time increases. This is because the number of scans is proportional to the reciprocal of the number of pixels to be scanned. More specifically, the number of scans per unit time is Z / (X0
× Y0), which is Z / (X1 × Y0) in the present embodiment, and the ratio is X0 / X1. Since X1 <X0, the ratio X0 / X1 is larger than 1; In the embodiment, the number of scans per unit time is set to be larger than in the conventional example.

That is, an increase in the number of scans shortens the potential waveform observation time. According to the present embodiment, for example, when X0 / X1 = 2, it is half the conventional potential waveform observation time.

[0032]

Third Embodiment FIG. 1C is a diagram showing a scanning range of a potential image when acquiring a waveform according to a third embodiment of the present invention.

The number of pixels X obtained in the horizontal direction of the potential image at the time of waveform acquisition
1 and the number Y1 of pixels obtained in the vertical direction of the potential image are selected so as to include the probing point, and X1 <X0 and Y1 <Y0.

By limiting the scanning range in this way, the number of times of scanning the probing point per unit time increases. This is because the number of scans is proportional to the reciprocal of the number of pixels to be scanned.
(X0 × Y0), in this embodiment, Z / (X1 × Y1), and the ratio is X0 × Y0 / (X1 × Y1), where X1 <X0,
Since Y1 <Y0, X0 × Y0 / (X1 × Y1) is 1
In this embodiment, the number of scans per unit time is larger than in the conventional example.

That is, an increase in the number of scans shortens the potential waveform observation time. According to the present embodiment, for example, X0 / X1 = 2 and Y0 / Y1
= 2, it is 1/4 of the conventional potential waveform observation time.

[0036]

Embodiment 4 FIG. 2A is a time chart for explaining a fourth embodiment of the present invention.

In the present embodiment, one of the methods (types A to C in the figure) for acquiring the potential waveform while limiting the scanning range according to the first to third embodiments (type A in the figure) ) And the conventional method of acquiring a potential waveform without limiting the scanning range (type D) is switched to a time-sharing (time-division) method, thereby shortening the potential waveform observation time.

[0038]

[Fifth Embodiment] FIG. 2B is a time chart for explaining a fifth embodiment of the present invention.

In the present embodiment, the potential waveform acquisition method (types A and B in the figure) for limiting the two scanning ranges of the first to third embodiments is switched in a time-sharing manner. , The potential waveform observation time is shortened.

[0040]

Sixth Embodiment FIG. 2C is a time chart for explaining a sixth embodiment of the present invention.

In this embodiment, the method of acquiring a potential waveform (Types A, B, and C) for limiting the scanning range of the first to third embodiments and the conventional method of acquiring a potential waveform without limiting the scanning range are used. (Type D) is switched in a time-sharing manner to reduce the potential waveform observation time.

[0042]

As described above, according to the EB tester of the present invention, the potential waveform observation time can be shortened by reducing the number of pixels acquired at the time of potential waveform observation.

[Brief description of the drawings]

FIG. 1A is a diagram illustrating a relationship between the number of pixels for acquiring a potential image and the number of display pixels when acquiring a waveform in an EB tester according to an embodiment of the present invention. (B) is a diagram showing the relationship between the number of pixels for acquiring a potential image and the number of display pixels when acquiring a waveform in the EB tester according to the second embodiment of the present invention. (C) is a diagram showing the relationship between the number of pixels for acquiring a potential image and the number of display pixels when acquiring a waveform in the EB tester according to the third embodiment of the present invention.

FIG. 2A is a timing chart for explaining a fourth embodiment of the present invention. (B) It is a timing chart for explaining a 5th embodiment of the present invention. (C) is a timing chart for explaining the sixth embodiment of the present invention.

FIG. 3A is a waveform diagram showing a potential waveform acquired by an EB tester. (B) The potential waveform shown in FIG.
FIG. 6 is a waveform diagram when the observation is made by multiplying by two.

FIG. 4A is a diagram showing a relationship between the number of pixels for acquiring a potential image and the number of display pixels when acquiring a waveform in a conventional EB tester. FIG. 4B is an enlarged view of FIG.

FIG. 5 is a diagram showing a typical configuration of an EB tester.

[Explanation of symbols]

 11 EB Barrel 12 EB Generator 13 LSI 14 Test Board 15 XY Stage 16 Secondary Electron Detector 17 LSI Tester 18 XY Stage Drive 19 CPU 1A Beam Pulse Controller 1B CRT

Claims (4)

(57) [Claims] A means for irradiating the integrated circuit device with an electron beam; a means for detecting a secondary electron beam generated from the integrated circuit device; and a two-dimensionally applying the secondary electron beam to a monitor screen as a potential image. An EB tester having at least: a display unit; and a unit that temporally displays the secondary electron beam at a measurement point for observing an arbitrary potential waveform on the integrated circuit device as a potential waveform on a monitor screen. When obtaining the potential waveform at the point, the scanning range in the vertical and / or horizontal direction is
A unit for the measurement point, comprising means for limiting the enclosure
E characterized by increasing the number of scans per hour
B tester. 2. A means for irradiating an integrated circuit device with an electron beam.
And detecting a secondary electron beam generated from the integrated circuit device
Means, and a potential image of the secondary electron beam two-dimensionally on a monitor screen.
Means for displaying as an arbitrary potential on the integrated circuit device
The secondary electron beam at the measurement point where the waveform is observed
Means for displaying as a potential waveform on the monitor screen
When the potential waveform at the measurement point is obtained by the EB tester having the
Vertical and / or horizontal scan range
There are two cases: one is to limit the
Equipped with means for switching in an imsharing manner,
An EB tester characterized by shortening the observation time . 3. A two-dimensional display on the monitor screen,
Limit the scan range in the direction, limit the scan range in the horizontal direction,
And the limits of the scanning range in both the vertical and horizontal directions
When the scanning range is limited by at least one
Time-sharing between the case where the range is not limited
In other words, the potential waveform observation time is shortened.
The EB tester according to claim 1 . 4. A two-dimensional display on the monitor screen,
Limit the scan range in the direction, limit the scan range in the horizontal direction,
And the limits of the scanning range in both the vertical and horizontal directions
Small and if Kutomo limiting two by scanning range, EB of claim 1 or 2, wherein switching between a case that does not limit the scanning range time-sharing manner, characterized in that to shorten the potential waveform observation time Tester.