JPH11297263A - Electron beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the wide-ranged inspection of a sample in a short time even for a large sample. SOLUTION: A primary electron beam 5 is deflected clockwise in the drawing by a magnetic field type deflector 9 generating a magnetic field vertical to the paper surface, and thinly focused on a wafer sample 11 by an electron lens 10. A decelerating electric field to the primary electron beam is formed on the front surface of the sample 11. The secondary electron or reflected electron generated from the sample 11 is accelerated by this decelerating electric field, and taken out to the upper part. The electron 16 passed through the opening of an electrode 12 is deflected clockwise on the paper surface by a deflector 9. Therefore, the optical path of the electron 16 is separated from the optical path of the primary electron beam 5 by the deflector 9. The electron 16 deflected by the deflector 9 is detected by a detection system consisting of a MCP 18, a phosphor screen 90 and a position corresponding detector 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electron beam apparatus suitable for inspecting a wafer sample for defects or foreign matter in a process of manufacturing a semiconductor device or the like.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, a pattern is formed on a wafer. However, if this pattern is not formed as designed or if dust or the like adheres to the wafer, that part becomes a defect and the final part is formed. The typical device becomes defective.

For this reason, it is important to detect a defective portion in the process of manufacturing a device and to investigate the cause thereof in order to improve the yield of device manufacturing. For this defect inspection, a scanning electron microscope is often used as a pattern formed on a device is miniaturized.

That is, an electron beam is irradiated on a wafer sample by two.
2D generated by electron beam irradiation
Detecting secondary electrons and reflected electrons, observing the scanning electron image of the sample, and comparing the obtained pattern image with the designed pattern to detect defective parts, observe foreign matter,
Analyzing.

[0005]

In the above-described ordinary scanning electron microscope, a finely focused electron beam is two-dimensionally scanned on a sample.
A lot of time is required. This problem becomes more remarkable as the size of the wafer becomes larger and the pattern formed on the wafer becomes finer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to realize an electron beam apparatus capable of inspecting a large area of a large sample in a short time.

[0007]

According to the first aspect of the present invention, there is provided an electron beam apparatus configured to form a primary electron beam into a line, irradiate a sample with a linear primary electron beam, A position-corresponding detector arranged in a line for detecting electrons generated by the irradiation of the primary electron beam, and a moving means for moving the sample two-dimensionally.

In the first invention, a linear primary electron beam is irradiated on a sample, and electrons generated from the sample are detected by a position-corresponding detector arranged in a line.
An electron beam apparatus according to a second aspect of the present invention comprises a means for shaping a primary electron beam into a line, a deflecting means for deflecting the linear primary electron beam to irradiate the sample almost vertically, and Decelerating means for decelerating before, a position correspondence detector arranged in a line for detecting electrons generated by irradiation of the primary electron beam to the sample, accelerated by the decelerating means, and deflected by the deflecting means, Moving means for moving the sample two-dimensionally.

In the second aspect of the invention, the linear primary electron beam is deflected to irradiate the sample perpendicular to the sample, decelerate in front of the sample, accelerate the electrons generated from the sample, take out the electrons upward, and extract the electrons. It is detected by the position correspondence detector arranged in a line.

An electron beam apparatus according to a third aspect of the present invention inspects a sample for defects based on an output signal of a position correspondence detector. An electron beam apparatus according to a fourth aspect is the electron beam apparatus according to the first or second aspect, wherein the two-dimensional movement of the sample is performed by a linear movement in a first direction perpendicular to the linear electron beam. , By a linear movement in a second direction perpendicular to the first direction.

According to a fifth aspect of the present invention, in the electron beam apparatus according to the first or second aspect, the sample is two-dimensionally moved by rotating the stage on which the sample is mounted and moving the rotary stage linearly. By doing it.

According to a sixth aspect of the present invention, in the electron beam device according to the first or second aspect, the position correspondence detector detects a screen that emits electrons multiplied by the microchannel plate, and detects light emission of the screen. Linear PI
It consisted of an N photodiode array.

According to a seventh aspect of the present invention, in the electron beam apparatus according to the first or second aspect, the linear primary electron beam irradiated on the sample is deflected in a direction perpendicular to the longitudinal direction of the line.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of an electron optical system of a defect inspection apparatus according to the present invention, where 1 is an electron gun. An acceleration voltage is applied from an acceleration power supply 4 between the emitter 2 and the acceleration electrode 3 in the electron gun 1. Note that the emitter 2 has a shape that is elongated in a direction perpendicular to the paper surface. The electron gun 1 is provided with control electrodes and the like, but these are removed from the drawing.

The primary electron beam 5 generated from the electron gun 1
Are collected by the electronic lens 6. The light is emitted to a slit 7 having a line-shaped opening elongated in a direction perpendicular to the paper surface. The primary electron beam 5 having a linear cross section that has passed through the opening of the slit 7 is converted into a parallel light beam by the electron lens 8 and enters the magnetic field type deflector 9.

The magnetic field deflector 9 generates a magnetic field B perpendicular to the plane of the drawing, and the electron beam 5 is deflected clockwise in the figure. The primary electron beam 5 deflected by the deflector 9 is
It is narrowly focused on the wafer sample 11 by the electron lens 10.

A ground potential electrode 12 is provided between the electron lens 10 and the sample 11, and the electron beam passes through the opening of the ground potential electrode 12 and irradiates the wafer sample 11 vertically.

A negative voltage is applied from the power supply 13 to the sample 11, and a deceleration electric field is formed on the front surface of the sample 11 with respect to the primary electron beam. An auxiliary electrode 14 having a potential equal to the sample potential is provided between the sample 11 and the electrode 12. The electrode 14 also has an aperture through which an electron beam passes. The openings of the electrodes 12 and 14 are formed in a rectangular shape whose longitudinal direction is perpendicular to the plane of the drawing in accordance with the cross-sectional shape of the electron beam. It is desirable.

The sample 11 is placed on a moving stage 15. The stage 15 is moved in the X direction perpendicular to the longitudinal direction of the linear primary electron beam and in the Y direction perpendicular to the X direction (perpendicular to the plane of the drawing).

Electrons (secondary electrons, reflected electrons) generated by the irradiation of the sample 11 with the primary electron beam are accelerated by an accelerating electric field between the sample 11 and the electrode 12, and are taken out upward. The electrons 16 that have passed through the opening of the electrode 12 are made parallel by the electron lens 10 and are deflected clockwise by the deflector 9 on the page. Therefore, the optical path of the electrons 16 is separated from the optical path of the primary electron beam 5 by the deflector 9.

The electrons 16 deflected by the deflector 9 are
It is converged in a line on an MCP (micro channel plate) 18 by an electron lens 17. MCP18
In this example, a number of channel plates are arranged in a direction perpendicular to the plane of the paper, and the electrons 16 are multiplied by each channel plate. A voltage is applied to both ends of the MCP 18 from a power supply 19. The MCP 18 may be a two-dimensionally arranged matrix type.

The electrons multiplied by the MCP 18 collide with the fluorescent screen 20 and cause the screen 20 to emit light according to the amount. The output terminal of the MCP 18 and the screen 2
Between 0 and 0, an acceleration voltage is applied from the acceleration power supply 21.
As a result, the electrons from the output end of the MCP 18 are accelerated and collide with the screen 20.

Behind the screen 20, a position correspondence detector 22 is arranged. As the position correspondence detector 22, for example, a linear PIN photodiode array is used.

FIG. 2 shows an example of a signal processing circuit of the defect inspection apparatus according to the present invention. Each detection signal from the linear PIN photodiode array 22 as a position correspondence detector is amplified by an operational amplifier 23 provided for each detection element, and each amplified signal is converted into a digital signal by an AD converter 24. Is converted.
The gain of each operational amplifier 23 can be finely adjusted.

The signal converted by the AD converter 24 is
The data is supplied to the dual port memory 25 and written at a high speed. The signal written in the memory 25 is extracted and supplied to the pattern recognition engine 26. The pattern recognition engine 26, based on the content learned in advance,
It detects a defect portion of the sample and foreign matter, and outputs the position and size of the defect and the foreign matter portion. The operation of such a configuration will now be described.

Electrons generated from the emitter 2 in the electron gun 1 are accelerated by an acceleration voltage applied between the emitter 2 and the acceleration electrode 3 from an acceleration power supply 4. Here, the emitter 2 is elongated in a direction perpendicular to the plane of the drawing, and as a result, a primary electron beam 5 having an elongated cross section is generated.

Primary electron beam 5 generated from electron gun 1
Are collected by the electronic lens 6. The light is emitted to a slit 7 having a line-shaped opening elongated in a direction perpendicular to the paper surface. The primary electron beam 5 having a linear cross section that has passed through the opening of the slit 7 is converted into a parallel light beam by the electron lens 8 and enters the magnetic field type deflector 9.

Although a linear emitter 2 and a linear slit 7 are used to produce a primary electron beam having an elongated cross section, a general point-like emitter is used, and a linear slit is used. A primary electron beam having an elongated cross-sectional shape may be formed by using only the primary electron beam, and the means for forming the primary electron beam in a line shape can be appropriately changed.

The primary electron beam 5 has a magnetic field B perpendicular to the paper surface.
The wafer sample 1 is deflected clockwise by a magnetic field deflector 9 that generates the
1 is narrowly focused.

Here, a ground potential electrode 12 is provided between the electron lens 10 and the sample 11, and a negative voltage is applied to the sample 11 from a power supply 13.
As a result, a deceleration electric field is formed on the front surface of the sample 11 with respect to the primary electron beam. For example, when the acceleration voltage of the primary electron beam 5 by the acceleration power source 4 is -10 kV,
When -9 kV is applied to sample 11 from
An electron beam having an energy of kV is irradiated.

Irradiation of the sample 11 with the primary electron beam generates secondary electrons and reflected electrons from the sample 11, and an electric field between the sample 11 and the electrode 12 acts as an acceleration electric field for these electrons. Therefore, electrons 16 from the sample
Is accelerated by this accelerating electric field and is taken out upward.

An auxiliary electrode 14 having a potential equal to the sample potential is provided between the sample 11 and the electrode 12. Is a distribution in which electrons from the sample diverge, and the electrons from the sample are absorbed by the electrode 12.

On the other hand, by providing the auxiliary electrode 14 having a potential equal to the sample potential, an electric field distribution for focusing the electrons from the sample is formed above the sample 11, and the electrons from the sample are efficiently transferred to the electrode 12. Can be taken out at the top.

As described above, the sample 11 is irradiated with the linear primary electron beam 5, and the sample 11 is mounted on the moving stage 15, and the stage 15 is arranged on the longitudinal side of the linear primary electron beam. It is moved in the X direction (perpendicular to the paper surface) perpendicular to the direction and the Y direction perpendicular to the X direction (perpendicular to the paper surface).

As a result, the observation surface of the sample
Is scanned by the primary electron beam. At this time, the movement of the stage in the Y direction is intermittently performed every length of the primary electron beam in the longitudinal direction.

Electrons (secondary electrons, reflected electrons) generated by the irradiation of the sample 11 with the primary electron beam are accelerated by an accelerating electric field between the sample 11 and the electrode 12, and are taken out upward. The electrons 16 that have passed through the opening of the electrode 12 are made parallel by the electron lens 10 and are deflected clockwise by the deflector 9 on the page. Therefore, the optical path of the electrons 16 is separated from the optical path of the primary electron beam 5 by the deflector 9.

The electrons 16 deflected by the deflector 9 are
The light is focused on the MCP 18 in a line by the electronic lens 17. The electrons multiplied by the MCP 18 collide with the fluorescent screen 20 and cause the screen 20 to emit light according to the amount. The light emission of the screen 20 is detected by the position corresponding detector 22.
Is detected by

Each detection signal from the linear PIN photodiode array 22 as a position correspondence detector is
Each signal amplified by an operational amplifier 23 provided for each detection element and amplified
Is converted into a digital signal.

The signal converted by the AD converter 24 is
The data is supplied to the dual port memory 25 and written at a high speed. The signal written in the memory 25 is extracted and supplied to the pattern recognition engine 26.

The writing and taking out of signals to and from the memory 26 are performed in synchronization with the movement of the stage 15,
Are supplied to the pattern recognition engine 26. The pattern recognition engine 26 detects a defective portion or a foreign substance of the sample based on the content learned in advance, and outputs the position and size of the defect or the foreign substance part.

The operation of the pattern recognition engine 26 includes, for example,
Extract the contour of the defective part. The outline is, for example, an enclosed portion determined by a certain threshold value with respect to the signal amount of each pixel.

The feature amount of the portion surrounded by the outline (ie, foreign matter or defect portion) obtained by the above processing is
Calculate coefficients such as size, shape, signal amount, and signal variation. This is compared with a predetermined identification coefficient or a coefficient obtained by learning, and a defective portion such as a foreign substance or a missing part is specified.

The above is an example of the operation of the pattern recognition engine 26.
Can also be performed. That is, the signal amount is actually measured from a sample having no foreign matter or defect and a foreign matter or defect having a known size and content, and stored as a reference value.

Next, the fetched image data is compared with the above-mentioned reference value to determine the presence or absence of a foreign substance or a defective portion, and to obtain position and size information at the same time. As described above, in the above-described embodiment, the sample is irradiated with the linear primary electron beam, and the sample surface can be scanned with the linear primary electron beam. In comparison, it is possible to inspect a wide sample surface at high speed.

In the above-described embodiment, the deflector 9 is provided to separate the irradiation axis of the primary electron beam from the axis of the generated electrons.
2. The power supply 13 and the auxiliary electrode 14 are omitted, and a through-hole through which the primary electron beam passes is formed in the detection system such as the MCP 18, the screen 20, and the detector 22, so that the irradiation axis of the primary electron beam and the axis of the electron generated by it are adjusted It can be coaxial. Of course, at this time, it is necessary to make the through hole through which the primary electron beam passes through the detection system as small as possible to reduce the influence on the detection signal.

The AD-converted signal is written to the dual port memory 25 at a high speed. By forming a double buffer in this way, while data is being written to one buffer, another buffer is simultaneously written. , And can be processed by the pattern recognition engine 26. Therefore, even when the stage is moved at a high speed, it is possible to sufficiently cope with it.

In the above-described embodiment, the position where the linear primary electron beam is irradiated moves with the linear movement of the stage, so that the resolution of the image is somewhat deteriorated. In order to prevent the resolution from deteriorating, a deflector is provided in the optical path of the primary electron beam, and the linear electron beam is moved by one pixel of the image according to the moving speed of the stage by the deflector. May be deflected in the moving direction of the stage at the same speed as the moving speed of the stage.

That is, by deflecting the primary electron beam with the sawtooth wave in synchronization with the movement of the stage, the linear primary electron beam can be stopped at one point on the sample for the time of the deflection. Therefore, it is possible to maintain high image resolution.

The image on the detector moves in the vertical direction (direction in which no pixels are adjacent) due to the deflection of the linear primary electron beam. However, since the movement width is at most one pixel, it is sufficiently smaller than the size of each detection element, so that the influence of the movement of the image on the detector side can be ignored.

In the embodiment shown in FIG. 1, the stage is moved linearly in the X and Y directions to scan a linear electron beam on the sample surface. However, the rotational movement of the stage may be used. it can. FIG. 3 shows an embodiment using a rotary stage.

In FIG. 3, reference numeral 30 denotes a rotary stage on which, for example, three wafer samples 31, 32, 33 to be inspected are mounted. The rotating stage 30 is configured to be able to rotate around a rotating shaft 34, and the entire rotating stage 30 is, for example,
The rotary stage 30 is configured to be moved in the vertical direction in the figure, and is arranged so that the radial direction of the rotary stage 30 coincides with the direction perpendicular to the paper surface of FIG. This makes it easier to increase the speed of the rotary stage 30 as compared with the case where the stage 15 is driven by reciprocating motion in the X direction. In this rotary stage system, the defect coordinate position is R-θ
Although it is obtained by coordinates, it may be appropriately converted to XY coordinates.

[0052]

As described above, in the first aspect of the present invention, the sample is irradiated with the linear primary electron beam, and the electrons generated from the sample are detected by the position-corresponding detectors arranged in a line. As a result, scanning of the sample surface over a wide area by the electron beam can be performed at high speed.

In the second aspect of the present invention, the linear primary electron beam is deflected to irradiate the sample perpendicular to the sample, decelerate in front of the sample, accelerate the electrons generated from the sample, take out the electrons upward, and extract the electrons. Since the detection is performed by the position-corresponding detectors arranged in a line, a wide area of the sample surface can be scanned with the electron beam at a high speed.

In the electron beam apparatus according to the third invention, the defect of the sample is inspected based on the output signal of the position correspondence detector, so that the defect inspection of the sample can be performed at a high speed.

According to a fourth aspect of the present invention, in the electron beam apparatus according to the first or second aspect, the two-dimensional movement of the sample is performed in a linear manner in a first direction perpendicular to the linear electron beam. And a linear movement in a second direction perpendicular to the first direction, so that the same effect as in the first invention can be obtained.

According to a fifth aspect of the present invention, in the electron beam apparatus according to the first or second aspect, the sample is moved two-dimensionally by rotating the stage on which the sample is mounted and moving the rotary stage linearly. By doing so, the same effect as in the first invention can be obtained.

According to a sixth aspect of the present invention, in the electron beam apparatus according to the first or second aspect, the position correspondence detector detects a screen for emitting the electrons multiplied by the microchannel plate and light emission of the screen. Linear PI
Since it is configured with the N photodiode array, the same effect as that of the first invention can be obtained. .

According to a seventh aspect of the present invention, in the electron beam apparatus according to the first or second aspect, the linear primary electron beam irradiated on the sample is deflected in a direction perpendicular to the linear longitudinal direction. Therefore, the same effect as that of the first or second invention can be obtained, and the resolution of the acquired image can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an electron optical system of an electron beam defect inspection device according to the present invention.

FIG. 2 is a diagram showing an example of a signal processing circuit of the electron beam defect inspection device according to the present invention.

FIG. 3 is a diagram showing an embodiment in which a stage of a wafer sample is rotated and moved.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron gun 2 Emitter 3 Acceleration electrode 5 Electron beam 6, 8, 10, 17 Electron lens 7 Slit 9 Deflector 11 Wafer sample 12 Electrode 14 Auxiliary electrode 15 Stage 16 Electron 18 MCP 20 Screen 22 Detector

Claims (7)

[Claims] 1. A means for shaping a primary electron beam into a line, a means for irradiating a sample with a linear primary electron beam, and a means for detecting electrons generated by irradiation of the sample with the primary electron beam. An electron beam apparatus comprising: a position correspondence detector arranged in a line; and a moving means for moving a sample two-dimensionally. 2. A means for shaping a primary electron beam into a line, a deflecting means for deflecting the linear primary electron beam to irradiate the sample almost vertically, and a deceleration means for decelerating the electron beam in front of the sample. A position-corresponding detector arranged in a line for detecting electrons generated by irradiation of the primary electron beam onto the sample, accelerated by the deceleration means, and deflected by the deflecting means; An electron beam device comprising: a moving unit that moves the electron beam. 3. The electron beam apparatus according to claim 1, wherein a defect of the sample is inspected based on an output signal of the position correspondence detector. 4. A two-dimensional movement of the sample includes a straight movement in a first direction perpendicular to the linear electron beam and a straight movement in a second direction perpendicular to the first direction. The electron beam apparatus according to claim 1, wherein the electron beam apparatus is moved by a shape movement. 5. The electron beam apparatus according to claim 1, wherein the two-dimensional movement of the sample is performed by rotating a stage on which the sample is mounted and moving the rotary stage linearly. 6. A position correspondence detector comprising: a screen for emitting electrons multiplied by a microchannel plate;
3. The electron beam apparatus according to claim 1, further comprising a linear PIN photodiode array for detecting light emission of a screen. 7. The electron beam apparatus according to claim 1, wherein the linear primary electron beam applied to the sample is deflected in a direction perpendicular to the longitudinal direction of the line.