JPH0417248A - Electron beam device and image obtaining method thereof - Google Patents

Abstract

PURPOSE:To always control a beam irradiation quantity per unit irradiation area of an observation area constantly by providing a control means for performing thinned-out irradiation of electron beam on the basis of observation magnification of an object to be irradiated. CONSTITUTION:A control means 15 for performing thinned-out irradiation of an electron beam 11a on the basis of an observation magnification alpha of an object 17 to be irradiated is provided. For example, at the time of testing an object 17 to be irradiated, which is covered with an insulating film, and at the time of judging a failure, in the case that an observation magnification alphathereof is enlarged, irradiation control for enlarging a thinned-out space of the electron beam 11a is performed, and in the case that an observation magnification alpha thereof is reduced, irradiation control for reducing a thinned-out space reversely is performed. An observation magnification alpha is set on the basis of an image element of a display means 16. Even if an observation magnification alpha is changed, a beam irradiation quantity per unit irradiation area of the electron beam 11a, which is irradiated in an observation area of an object 17 to be irradiated, can thereby always constantly be controlled.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figs. 6 and 7) Problems to be solved by the invention Means for solving the problems (Figs. 1 and 2) Effects Embodiments (Figures 3 to 5) Effects of the invention [Summary] An electron beam device, especially an object covered with an insulating film, is irradiated with an electron beam and used for fault diagnosis, voltage measurement, etc. Regarding the beam scanning function of the device, we devised a method for irradiating the object with the electron beam.
The purpose is to obtain stable reflected electrons or secondary electrons and display an SEM image of the object even if the observation magnification changes, and at least emit an electron beam to the irradiated object. an electron gun, a deflection means for deflecting and scanning the electron beam, a detection means for detecting reflected electrons or secondary electrons from the irradiated object, and a signal processing means for performing signal processing of the reflected electrons or secondary electrons. a display means for displaying an image of the object to be irradiated based on the signal-processed image data; and the electron gun.

The apparatus includes a deflection means, a signal processing means, and a control means for controlling input and output of the display means, and the control means thins out the electron beam and irradiates the object based on the observation magnification of the object to be irradiated.

[Industrial application field]

The present invention relates to an electron beam device and an image acquisition method thereof. More specifically, the present invention relates to an electron beam device and an image acquisition method thereof. More specifically, the present invention relates to an electron beam device that irradiates an irradiated object covered with an insulating film with an electron beam to perform failure diagnosis, voltage measurement, etc. It relates to the beam scanning function and scanning method of the device used.

In recent years, electron beam devices such as scanning electron microscopes and electron piece testers have been used that acquire images by deflecting and scanning an electron beam on an irradiated object protected by an insulating film.

According to this, since the sample surface is covered with an insulating film, charging occurs due to beam irradiation. Furthermore, the charging state on the insulating protective film changes as the observation magnification changes. Therefore, it is necessary to readjust the optical parameters every time the magnification is changed.

Therefore, by devising a method for irradiating an object with an electron beam, even if the observation magnification changes, it is possible to obtain stable reflected electrons or secondary electrons and measure voltage waveforms, etc. An electron beam device is desired.

[Conventional technology]

FIG. 6.7 is an explanatory diagram of a conventional example.

FIG. 6 shows a configuration diagram of a conventional electron beam device.

In the figure, an electron beam device such as a scanning electron microscope device includes an electron gun 1, a deflection means 2, and a secondary electron detector 3 provided in a lens barrel, and externally connected to the secondary electron detector 3. a signal processing circuit 4 that processes signals of the reflected electrons and secondary electrons 1b; a monitor 6 that displays an image based on the signal-processed data; and the electron gun 1. Deflection means 2. It is composed of a signal processing circuit 4 and a control computer 5 that controls input and output of a monitor 6.

The function of this apparatus is that first, an electron beam 1a is deflected and irradiated onto an irradiated object 7 through an electron optical system such as a deflection means 2.

Next, the reflected electrons and secondary electrons 1b from the irradiated object 7 are detected by the secondary electron detector 3. Thereafter, the reflected electrons and secondary electrons 1b are subjected to signal processing by the signal processing circuit 4. Based on this signal-processed image data, an SEM (Scanning Elect
ron Microscope) image is displayed on the monitor 6.

With this, it is possible to observe the wiring position of a fine pattern of an LSI (semiconductor integrated circuit device), its voltage waveform, etc.

[Problems that the invention attempts to solve]

By the way, according to the conventional example, when testing or diagnosing a failure of an LSI, the insulating film on the surface of the chip is removed and the wiring of the LSI is directly irradiated with an electron beam lb.

However, removing the insulating film may lead to complete destruction of LSIs, which are becoming more highly integrated and ultra-fine. There is a tendency to

Further, the electron beam 1a is subjected to rast scanning on the irradiated object 7, as shown in FIG.

That is, an image is generated by continuously irradiating an electron beam 1a along a position corresponding to each pixel and sampling reflected electrons and secondary electrons emitted from the electron beam 1a. At this time, since the sample surface is covered with an insulating film, charging occurs due to the beam irradiation.

This charging state changes as the observation magnification changes. For example, when the observation magnification is increased, the amount of electron beams irradiated to the observation area increases, making it easier for the insulating M film to be charged. This is because the amount of beam irradiation per unit irradiation area increases as the observation magnification increases.

This effect appears greatly when sampling backscattered electrons and secondary electrons 1b. In particular, when the magnification is changed from high to low, the acquired SEM image becomes a dark screen, and when the magnification is changed from low to high, On the contrary, the screen becomes white and shining.

This poses a problem in that the optical parameters of the secondary electron detection system must be readjusted every time the observation magnification is changed.

The present invention was created in view of the problems of the prior art, and by devising a method for irradiating an object with an electron beam, it is possible to obtain stable reflected electrons or An object of the present invention is to provide an electron beam device and an image acquisition method thereof that can acquire secondary electrons and display a SEM image of the object.

[Means to solve the problem]

FIG. 1 is a principle diagram of an electron beam device according to the present invention, and FIG.
Figures (a) and (b) each show a principle diagram of an image acquisition method of an electron beam device according to the present invention.

The device includes at least an electron gun 11 that emits an electron beam 11a to an object 17 to be irradiated, and the electron beam 11a.
a deflecting means 12 for deflecting and scanning the irradiated object 1;
a detection means 13 for detecting reflected electrons or secondary electrons 11b from 7; a signal processing means 14 for signal processing the reflected electrons or secondary electrons 11b; a display means 16 for displaying an image of an object 17; and the electron gun 11. Deflection means 12. It is equipped with a control means 15 for controlling the input and output of the signal processing means 14 and the display means 16, and the control means 15 controls the irradiation object 17.
The method is characterized in that the electron beam 11a is thinned out based on the observation magnification α of
First, in step PI, a plurality of irradiation areas A1, A2...An are set on the irradiation target object 17, and further, in step P2, the irradiation areas A1, A2...An are set to m.
unit irradiation areas a1. Divide into a2...am,
Next, in Step 71P3, the electron beam 11a is applied to each similar area ai of the divided m unit irradiation areas a1, a2...am, and then, in Step P
In step 4, image processing of the irradiated object 17 is performed based on the reflected electrons or secondary electrons 11b obtained by the irradiation process, thereby achieving the above object.

[Effect]

According to the apparatus of the present invention, the observation magnification α of the irradiated object 17
A control means 15 is provided which thins out and irradiates the electron beam 11a based on the following.

For example, when the observation magnification α is increased when testing or fault diagnosing the irradiated object 17 covered with an insulating film, irradiation control is performed to increase the thinning interval of the electron beam 11a. , when the observation magnification α is reduced, conversely, irradiation control is performed to reduce the thinning interval. Here, the observation magnification α is assumed to be based on the pixels of the display means 16.

Therefore, even if the observation magnification α changes, the electron beam 21a that is irradiated onto the observation area M of the irradiated object 17
The beam irradiation amount per unit irradiation area can always be controlled to be constant.

As a result, even if the observation magnification α of the irradiated object F is increased, it is possible to reduce the occurrence of charging on the insulation protection crotch as much as possible compared to the conventional example.

Further, according to the method of the present invention, a plurality of irradiation areas A1, A2...An are set on the irradiation target object 17,
The irradiated areas A1, A2...An are further divided into m unit irradiated areas a1, a2...am, and the m unit irradiated areas a1, a2... a
An interlaced irradiation process is performed with the electron beam 11a for each m open area ai, and image processing of the irradiated object 17 is performed based on the reflected electrons or secondary electrons 11b obtained by the irradiation process.

For this reason, even if the observation magnification α changes due to a user's usage request, etc., the beam irradiation amount per unit irradiation area of the electron beam 11a irradiated onto the observation area of the irradiated object 17 is always controlled to be constant. This makes it possible to acquire stable reflected electrons or secondary electrons 11b and display an SEM image of the object. for example,
Even when the observation magnification is changed from high to low magnification,
The acquired SEM image will no longer appear as a dark screen, or vice versa, even when the magnification is changed from a low magnification to a high magnification, the screen will no longer shine white.

As a result, every time the observation magnification changes as in the conventional example,
It becomes possible to omit the process of readjusting the electro-optical parameters.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

3 to 5 are diagrams for explaining an electron beam device and its image acquisition method according to an embodiment of the present invention, and FIG.
1 shows a configuration diagram of an electron beam device according to an embodiment of the present invention.

In the figure, for example, a scanning electron microscope device that acquires an image of a sample LSI 30, which is an example of the irradiation object 16, includes an electron gun 21 that emits an electron beam 21a to the LSI 30 in a lens barrel 20, and an electron gun 21 that emits an electron beam 21a to the LSI 30. A pulse gate 22D, a deflection coil 22B, and a L
An analyzer 27 that analyzes the energy of the reflected electrons and secondary electrons 21b from the SI 30, and a secondary electron detector 23 that detects the secondary electrons 21b are provided.

Also, externally there are a pulse generator 22A, a gate circuit 22B, and a pulse gate driver 22C that irradiate the electron beam 21a in a pulsed manner, a D/A converter 26 that supplies an analysis voltage to the analyzer 27, and a next electron 21
A sampling A/D circuit 24A, an averaging circuit 24B, a memory device 22c, and an LSI 30
an LSI driver 28 that supplies sample voltage E to the wiring of
Electron gun 21. Pulse generator 22A, deflector coil 22E
, memory device 22C, D/A converter 26 and LSI
The control computer 25 controls the input and output of the driver 2.

The control computer 25 is an electron gun control circuit 2 that controls the electron gun.
5A, a change drive control circuit 25B that controls the deflector coil 22E, and an LSI drive control circuit 25C that controls the LSI driver 28, which stores signal-processed image data and temporarily stores data related to observation magnification α. An MPU 25E performs arithmetic processing based on input/output data from each circuit, and an I10 circuit 25F inputs and outputs data such as observation magnification α input from the outside.

25G is a system bus that transfers various data. 29 is a monitor, which displays the image of LSi30 (S
EM image).

In this manner, the electron microscope device according to the embodiment of the present invention is provided with a control calculation jIJ, 25 that thins out and irradiates the electron beam 21a based on the observation magnification α of the sample LSI 30.

For example, when testing or diagnosing a sample LSI 30 covered with an insulating film, if the observation magnification α of the LSr 30 is increased, irradiation control is performed to increase the thinning interval of the electron beam 21a, When the observation magnification is reduced to the observation magnification α, conversely, irradiation control is performed to reduce the thinning interval.

Here, when the observation magnification α is based on the pixels of the monitor 29, when the magnification α is increased, an enlarged image of the sample LSI 30 is displayed on the monitor 29.On the other hand, when the observation magnification α is decreased, Sample L reduced on monitor 29
An image of SI30 is displayed.

Therefore, when the observation magnification α is changed, the sample LSI
The amount of beam irradiation per unit irradiation area of the electron beam 21a irradiated onto the 30 observation areas can be controlled to be constant at all times.

As a result, even if the observation magnification α of the sample LSI 30 is increased, it is possible to reduce the occurrence of charging on the insulating protective film as much as possible compared to the conventional example.

Next, the image acquisition method of the device will be explained with supplementary explanation of its operation.

FIG. 4 is an operation flowchart of the electron beam apparatus according to the embodiment of the present invention, and FIGS. 5(a) to 5(c) are supplementary explanatory diagrams thereof.

In FIG. 4, for example, when acquiring an image of the sample LSI 30 whose wiring is protected by an insulating protective film, first, in step PI, the observation magnification α is specified by the user as preprocessing.
Observation area X+*axXYmax related to sample LSI30
(see FIG. 5(a)). Thereafter, as shown in FIG. 5(a), the observation area (Xmax) of the sample LSI 30.

'1'max) = (+pixels x j lines), n irradiation areas A1 to An are set.

Furthermore, one irradiation area An is defined as, for example, 4 pixels x 4 pixels.
Division processing is performed into unit irradiation areas (1) to [phase] of line = 16. Here, k is an offset value between pixels, and indicates the respective differences between the unit irradiation area (■) and (2), the region color (2), and the region color (2). Further, l is an offset value between lines, and indicates the difference between the unit irradiation areas (■) and (2), the upper area (2), the Vi area (2), and [phase], respectively.

In addition, step is the observation area X and the number of thinnings in the
It shows the number that jumps over the line. In the embodiment of the present invention, 5 steps=4 pixels in the X direction and 4 lines in the Y direction.

Then, in step P2, 1=j==/! =0 processing. At this time, the electron beam 21a is applied to the irradiated wI area A1.
is moved to the unit irradiation area ■. The electron beam 21a is
It is controlled by a pulse generator 22A, a gate circuit 22B, a pulse gate driver 22C, and a pulse generator 22D via a control calculation fi25, and is moved by a deflection coil 22E and the like via a deflection drive control circuit 25B.

Next, in step P3, the sampling data of the (Xi, Yj) coordinates is stored. At this time, reflected electrons and secondary electrons 21b from the LSI 30 are detected by the secondary electron detector 23. Also, the analyzer 27 is connected to the D/A converter 26.
The analysis voltage is supplied to the These reflected electrons and secondary electrons 21
b is converted into a digital signal by the sampling A/D circuit 24A, subjected to averaging processing, and stored in the storage circuit 25D shown in FIG. The memorization method at this time is j!, as shown in FIG. 5(c). X5tep=0 stored in the buffer memory area with 16 unit irradiation areas ■~[phase] as one unit.For example, observation w4\R(Xmax.

Image data related to a unit irradiation area (2) of n irradiation areas A1 to An set to Ymax) - (ilii elements x j lines) are sequentially stored in the memory area allocated to the area (2). Further, the image data related to the unit irradiation area (2) is sequentially stored in the memory area allocated to the area (2) in the same way. Based on this, the observation area (Xsax,
Ymax) = (i pixels x j lines) all image data is stored, and image display data is later generated by the MPU 25H.

Next, in step P4, the process of i=i+5tep is performed. This is a state in which the electron beam 21a is moved from the unit irradiation area (2) of the irradiation area AI to the unit irradiation area (2) of the irradiation area A2. As a result, the secondary electrons 21b and the like are detected as in step P3, and are subjected to signal processing.

Thereafter, in step P5, it is determined whether i<Xmax. In this case, if i < Xmax (YES).

That is, if the electron beam 21a does not reach the end Xmax of the observation area in the X direction, the process returns to step P3 and steps P3 to P5 are sequentially repeated.

If i>Xma) (No), that is, if the electron beam 21a reaches X111aX, the process moves to step P6.

Therefore, in step P6, i=, j=j+steρ
process. This is from the irradiated area A1 to the irradiated area fJ
J! Electron beam 2 is applied to the unit irradiation area of IiA i +1.
1a has been moved. This allows step P
Similarly to 3, secondary electrons 21b and the like are detected and subjected to signal processing.

Thereafter, in step P7, a process is performed to determine whether j<Ymax. In this case, if j < Y+wax (YES).

That is, if the electron beam 21a does not reach the end Ywax of the observation area in the Y direction, the process returns to step P3 and steps P3 to P7 are sequentially repeated.

If j>Ymax (No), that is, if the electron beam 21a reaches Ymax, the process moves to step P8.

Therefore, in step P8, j=1 and +1 are processed. This is a state in which the electron beam 21a is moved from the unit irradiation area (2) of the irradiation area AI to the unit irradiation area (2) of the irradiation area A2. As a result, the secondary electrons 21b and the like are detected as in step P3, and are subjected to signal processing.

Thereafter, in step P9, a determination process of k<5tep is performed. At this time, if k<5tep (YES), that is, if the offset value k between pixels does not exceed the thinning number stepρ-4 pixels, the process moves to step PIO and i
= to process. After that, the process returns to step P3 and repeats steps P3 to P9.

Further, if l(>5tep (No), that is, if the offset value k between pixels exceeds the thinning number 5tep=4 pixels, the process moves to step pH.

At step pH, k=0. Process l-1, +1. This is a state in which the electron beam 21a is moved from the unit irradiation area (2) of the irradiation area AI to the unit irradiation area (2) of the irradiation area A2. As a result, the secondary electrons 21b and the like are detected as in step P3, and are subjected to signal processing.

Thereafter, in step P12, it is determined whether ffi<5tep. At this time, if l<5tep (YES),
That is, the offset value r between lines is the thinning number s t
If it does not exceed ep=4 lines, the process moves to step P13 and processes j=1. Then step P3
Return to step P3 and repeat steps PI2. Also 1
, [>5tep (No), that is, if the offset value l between lines exceeds the thinning number 5tep=4 lines, the process moves to step P14.

As a result, image data for one screen of the sample LSI 30 is stored in the storage circuit 25D.

Next, display processing is performed in step P14.

At this time, the MP025E reads out one screen worth of image data stored in the storage circuit 25D and displays it on the monitor 29 as image display data. For example, observation magnification α
Even when changing from a high magnification to a low magnification, the obtained S
The EM image will no longer appear as a dark screen, or vice versa, even when the magnification is increased from low to high.

As a result, the sample LSI with the observation magnification α specified by the user
It is possible to acquire images of 30 wirings, etc.

In this way, according to the image acquisition method according to the embodiment of the present invention, the sample LSI 30 has a plurality of irradiated areas A1 and A2.
. . . The setting process of An is performed, and the irradiation target MUA1. A
2...An further has 16 unit irradiation areas ■, ■
...■, and 2 electron beams are applied to each of the divided 16 unit irradiation areas ■, and open areas ■ of ■...■.
1a is subjected to interlaced irradiation treatment, and the sample LSI is
30 image processes are performed.

Therefore, if the observation magnification α changes due to a user's usage request, etc., the observation area X*aXY of the sample LSI 30
The amount of beam irradiation per unit irradiation area of the electron beam 21a irradiated to +max can be controlled to always be constant. From this, stable reflected electrons or secondary electrons 21
b can be acquired and a SEM image of the wiring etc. of the LSI 30 can be displayed.

This makes it possible to omit the process of readjusting the optical parameters of the signal processing system every time the observation magnification α changes as in the conventional example.

〔Effect of the invention〕

As explained above, according to the apparatus of the present invention, a control means is provided for thinning and irradiating the electron beam based on the observation magnification of the object to be irradiated.

Therefore, since the electron beam can be thinned out, the amount of beam irradiation per unit irradiation area of the observation area can be controlled to be constant at all times. As a result, even if the observation magnification of the object to be irradiated is increased, it is possible to reduce the occurrence of charging on the insulating wire Wi as much as possible compared to the conventional example.

Further, according to the method of the present invention, an object to be irradiated is subjected to interlaced irradiation processing with an electron beam, and image processing is performed based on reflected electrons or secondary electrons obtained by the irradiation processing.

Therefore, even if the observation magnification changes due to a user's usage request or the like, the beam irradiation amount can always be controlled to be constant. This makes it possible to observe a high-resolution SEM image that is not affected by observation magnification.

This greatly contributes to the manufacture of high-performance, high-reliability scanning electron microscope devices, electron beam testers, and the like.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of an electron beam device according to the present invention. FIG. 2 is a principle diagram of an image acquisition method of an electron beam device according to the present invention. FIG. 3 is a principle diagram of an electron beam device according to an embodiment of the present invention. FIG. 4 is a flowchart of an image acquisition method according to an embodiment of the present invention; FIG. 5 is a supplementary explanatory diagram of an image acquisition method according to an embodiment of the present invention; FIG. 6 is a conventional example FIG. 7 is a block diagram of an electron beam apparatus according to the present invention, and is a time for explaining an image acquisition method according to a conventional example. (Explanation of symbols) 11... Electron gun, 12... Deflection means, 13... Detection means, 14... Signal processing means, 15... Control means, 16... Display means, 11a. ...Electron beam, 11b... Backscattered electrons or secondary electrons, A1-An... Irradiated area, 81-am... Unit irradiated area.

Claims (2)

[Claims] (1) At least an electron gun (11) that emits an electron beam (11a) to an object to be irradiated (17), a deflection means (12) that deflects and scans the electron beam (11a), and an object to be irradiated. (17) Reflected electrons or secondary electrons (1
1b), and a signal processing means (13) for signal processing the reflected electrons or secondary electrons (11b).
14), and display means (16) for displaying an image of the irradiated object (17) based on the signal-processed image data.
and a control means (15) for controlling input and output of the electron gun (11), the deflection means (12), the signal processing means (14) and the display means (16), the control means (15) comprising: An electron beam device characterized in that an electron beam (11a) is thinned out and irradiated based on an observation magnification (α) of an object to be irradiated (17). (2) Multiple irradiation areas (A1
, A2...An), and the irradiation area (
A1, A2...An) are divided into m unit irradiation areas (a1,
a2...am), and the same area (a
i) Perform interlaced irradiation treatment with the electron beam (11a) for each time,
The reflected electrons or secondary electrons (
11b) An image acquisition method for an electron beam device, characterized in that image processing of an irradiated object (17) is performed based on the method.