JP2000180391A - Electron microscope and flaw shape confirming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electron microscope capable of enhancing the accuracy of alignment while shortening the time required in the observation of a flaw and accurately confirming the shape of the flaw. SOLUTION: In an SEM constituted of an electron gun 1, converging lenses 2, 3, a scanning coil 4, an object lens 5, an XY stage 6, a reflected electron sensor 7, a secondary electron sensor 8, an amplifier 9, a scanning signal generator 10 and a cathode ray tube (CRT) 11, a laser marker 12 is provided on the peripheral part of the electron gun 1. In the confirmation of the shape of the flaw on the surface of a wafer, at first, the inspection data formed by observing the surface of the wafer by a flaw inspecting device is converted to coordinates for the SEM and, before the alignment of the wafer is performed in the SEM, marks are formed on the surface of the wafer, for example, at two places by a laser marker 12 and, thereafter, a position is confirmed by using the marks when the alignment of the wafer is performed and the correction of the origin is performed. Subsequently, the shape of the surface flaw of the wafer is confirmed in the SEM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron microscope and a method for confirming a defect shape, and more particularly to a method suitable for use in confirming the shape of a defect on a wafer surface using a scanning electron microscope (SEM). It is.

[0002]

2. Description of the Related Art Conventionally, an SEM has been used as an apparatus for observing the shape of a defect on a wafer surface. Also,
The wafers for which the shape of a defect is confirmed using the SEM include a wafer on which a pattern is formed and a wafer on which a pattern is not formed (a blank wafer, a blank wafer).
fer). Below, these two
A method of confirming the shape of a defect in each type of wafer will be described.

First, a case will be described in which the shape of a defect on a wafer on which a pattern is formed is confirmed. That is, first, in a defect inspection apparatus using an image comparison method, alignment is performed in accordance with an alignment point existing at a predetermined position on a wafer, and then defects on the wafer surface are confirmed. As a result, inspection data including position coordinate data of the defect is created.

Thereafter, the inspection data obtained by the above-described defect inspection apparatus is supplied to an SEM linked to the defect inspection apparatus. On the other hand, the wafer on which the pattern is formed is also transferred to the SEM. The supplied inspection data is S
A coordinate conversion process is performed in the EM, and the EM is adjusted to coordinates that match the SEM. Next, in the SEM, after performing alignment at the same position as the alignment point used when performing the defect inspection by the defect inspection apparatus, the shape of the defect on the wafer surface is confirmed.

As described above, since a link can be made between the defect inspection apparatus and the SEM, there is no need to perform correction between them. Therefore, the shape of the defect on the wafer surface confirmed by the defect inspection apparatus can be easily and accurately observed by the SEM. The detection accuracy at this time is as good as several to several tens of μm.

Next, a case where the shape of a defect in a blank wafer is confirmed will be described. That is, first,
In a defect inspection apparatus using a laser scattering method, alignment is performed using a total of five marks provided in advance at three locations on the outer periphery of the wafer and at two locations on the orientation flat (orientation flat). This defect inspection apparatus is used only for a sample on which no pattern is formed. Then, the actual defect on the wafer surface is inspected by the defect inspection apparatus. As a result, inspection data including position coordinate data of the defect is created. The inspection data created by this defect inspection apparatus is recorded on a storage medium such as a floppy disk.

After that, the storage medium and the blank wafer are transferred to the SEM. Then, coordinate conversion processing is performed on the inspection data recorded in the storage medium, and SE
It is adjusted to coordinates that match M. Next, in the SEM, after alignment is performed at the same position as the above-described five marks, the shape of a defect on the surface of the blank wafer is confirmed.

[0008]

However, the above-described defect inspection apparatus based on the laser scattering method has a poorer coordinate accuracy than the SEM coordinate accuracy. Some samples have only minute defects. Even if the position coordinates of the minute defects on the sample surface are to be specified by the above-described defect inspection apparatus, the position of the defect having the minute particle size becomes unclear. However, the position coordinates of the defect are not specified. As a result, it is difficult to confirm the shape of the defect in the SEM, and there is a problem that a defect (a minute defect) to be confirmed may not be confirmed.

Further, the shape of the defect on the sample surface is determined by SEM.
Even when the defect is confirmed by the method, when the defect whose shape is confirmed is processed by an external device such as a focused ion beam (FIB) analyzer, the position of the defect needs to be specified. However, at present, the defect whose shape has been confirmed by the SEM must be searched again by a device such as an optical microscope other than the SEM. Therefore, extra time is required until analysis.

Accordingly, an object of the present invention is to improve the alignment accuracy in an electron microscope when checking defects on a substrate on which a pattern is not formed by using an electron microscope, and to reduce the time required for checking defects. An object of the present invention is to provide an electron microscope and a defect shape confirmation method capable of shortening and easily confirming the shape of a defect.

[0011]

In order to achieve the above object, a first aspect of the present invention is to provide an electron microscope which irradiates a sample with an electron beam and confirms a defect of the sample using the electron beam. And a mark forming means for forming a mark at a predetermined position of the sample.

According to a second aspect of the present invention, there is provided a defect shape confirming method for confirming the shape of a defect on a sample surface using an electron microscope, wherein the electron microscope forms a mark at a predetermined position on the sample. A mark forming means for forming a mark on the sample before confirming the shape of the defect.

In the second aspect of the invention, typically, the origin of the sample is corrected using the mark on the surface of the sample formed by the mark forming means.

In the second aspect of the present invention, in order to form a temporary defect when observing the shape of a defect with an electron microscope, typically, the position of the defect on the sample surface confirmed by the electron microscope is A mark is formed by a mark forming means.

In the present invention, typically, the mark forming means is provided in a portion around an electron gun of an electron microscope, or provided between an objective lens of the electron microscope and a sample.

In the present invention, typically, the mark forming means comprises a laser. Also, the laser
Specifically, for example, a yttrium aluminum garnet (YAG) laser is used. In addition, in the present invention, typically, a mark is formed on the surface of the sample by irradiating the sample with laser light extracted from a laser to cut the surface of the sample.

In the present invention, typically, the mark forming means is configured to be movable in a direction perpendicular to the emission direction of the electron beam.

In the present invention, typically, the sample is
It is a semiconductor wafer with no pattern formed,
Other samples can be used.

In the present invention, the electron microscope is specifically a scanning electron microscope (SEM), a scanning transmission electron microscope (Scanning Transmission Electron Microscope,
STEM), Transmission Electron Microscope (Transmission Electron Microscope)
nMicroscope, TEM, reflection electron microscope (Reflecti)
on Electron Microscope (REM), High Resolution Transmission Electron Microscope
croscope, HR-TEM), Ultra-High Voltage Transmission Electron Microsc
ope, UHV-TEM), analytical electron microscope (Analytical
Electron Microscope (AEM), Ultra-High Vacuum Transmission Electron Micr
A predetermined electron microscope is selected from these electron microscopes according to the type and thickness of the sample to be subjected to the defect inspection.

According to the present invention constructed as described above, since the electron microscope has the mark forming means for forming a mark on the sample on which no pattern is formed, the substrate surface confirmed by the electron microscope can be confirmed. Since a mark can be formed on the mark, the mark can be detected as a temporary defect, and the position coordinates of the defect can be easily corrected.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

First, a scanning electron microscope (SEM) according to an embodiment of the present invention will be described. FIG. 1 shows the overall configuration of the SEM according to this embodiment.

As shown in FIG. 1, in the SEM according to this embodiment, an electron gun 1, focusing lenses 2, 3, a scanning coil 4, an objective lens 5, an XY stage 6,
It comprises a backscattered electron sensor 7, a secondary electron sensor 8, an amplifier 9, a scanning signal generator 10, and a cathode ray tube (CRT) 11. Further, a laser marker 12 is provided in a portion around the electron gun 1.

The electron gun 1 is for emitting an electron beam EB for irradiating a sample (not shown) on the XY stage 6. In this embodiment, the XY stage 6 is controlled by an XY stage controller (not shown). Further, the converging lenses 2 and 3
Are for converging the emitted electron beams EB.

The scanning coil 4 is used to systematically sweep the electron beam EB in a predetermined area. The sweep of the electron beam EB is controlled by a scanning signal supplied from a scanning signal generator 10 described later.

The objective lens 5 is for narrowing the converged electron beam EB to a minute spot. The backscattered electron sensor 7 detects reflected electrons in the electron beam EB applied to the sample on the XY stage 6, and sends a backscattered electron detection signal corresponding to the detected amount of electrons to the amplifier 9. It is for supply. Here, the reflected electrons have energy equal to or higher than about 50 eV of the electron beam EB incident on the sample. The secondary electron sensor 8 detects secondary electrons generated when the sample is irradiated with the electron beam EB, and outputs a secondary electron detection signal corresponding to the detected amount of secondary electrons to the amplifier 9. It is for supplying to.
Here, the secondary electrons have an energy of about 2 to 5 eV. In addition, electron beam induced currents (EBIC, Electr
On Beam Induced Current) is also supplied to the amplifier 9.

The amplifier 9 receives the backscattered electron detection signal,
The secondary electron detection signal and the EBIC signal are amplified, and the CRT 1
This is for supplying to one electron gun 11a. Also,
The scanning signal generator 10 supplies a scanning signal for sweeping the electron beam EB applied to the surface of the sample to the scanning coil 4 for scanning, and controls the scanning coil 4 for scanning. This is for supplying a signal corresponding to the signal to the deflection yoke 11b of the CRT 11.

The CRT 11 is for displaying image information observed in the sample. CRT11
Is a signal corresponding to the scanning signal supplied from the scanning signal generator 8 to the deflection yoke 11a, and a signal from the amplifier 9 to the electron gun 1
1b based on the amplified reflected electron detection signal, secondary electron detection signal, and EBIC signal, the C corresponding to the position on the sample where the electron beam EB is irradiated.
The image information of the sample surface is displayed at a position on the screen of the RT 11.

The laser marker 12 is configured to be movable in the horizontal direction, and irradiates the sample surface with a laser beam having a predetermined energy through the converging lenses 2 and 3 and the objective lens 5 described above. The sample is irradiated with a laser beam having a predetermined energy extracted from the laser marker 12, and the sample surface is minutely cut (for example, about 0.5 to 1.0 μm) to perform marking. ing.

As described above, the SEM according to the embodiment is configured.

Next, a method of confirming the shape of a defect on a blank wafer using the SEM configured as described above will be described. That is, first, in a defect inspection apparatus using a laser scattering method, 3.
Alignment is performed using a total of five marks provided at two locations and at the orientation flat.

Next, actual defects on the wafer surface are inspected by the defect inspection apparatus. As a result, inspection data including position coordinate data of the defect is created. Thereafter, the inspection data created by the defect inspection device is recorded on a storage medium such as a floppy disk.

Next, this storage medium is transferred to the SEM.
Then, in the SEM, coordinate conversion processing is performed on the recorded inspection data, and the inspection data is adjusted to coordinates that match the SEM. Also, as shown in FIG. 2, marks 22a and 22b are formed by cutting, for example, two portions on the blank wafer 21 with the laser marker 12. The size of these marks 22a and 22b is, for example, 0.1 mm. Several to several μm, preferably, for example, 0.5 to 1.0 μm
It is. In order to minimize dust generation during the formation of the marks 22a and 22b, the two positions where the marks are formed are set at the outer peripheral portion in the wafer.

Next, in the SEM shown in FIG. 1, alignment is performed at the same positions as the five marks used as alignments when the defect inspection is performed by the defect inspection apparatus. At this time, the positions of the marks 22a and 22b on the blank wafer 21 shown in FIG. 2 are confirmed. Then, origin correction is performed using these marks 22a and 22b. Then, based on the inspection data subjected to the coordinate conversion processing and the marks 22a and 22b, the defect shapes on the surface of the blank wafer are checked, and those defect shapes are determined on the CRT1.
1 is displayed on the screen. Thereby, the shape of the defect on the surface of the blank wafer 21 using the SEM is confirmed.

As described above, the shape of the defect on the surface of the blank wafer 21 is confirmed by the SEM. Then, as is conventionally known, the blank wafer 21 is
The data is transferred to an external analyzer such as an analyzer, and a predetermined analysis is performed in the analyzer. Further, processing such as repair of the observed defect is performed as necessary.

As described above, according to this embodiment, the laser marker 1 is located near the electron gun 1 in the SEM.
2, the marks 22a and 22b are formed at two places on the blank wafer 21 when observing the shape of the defect on the surface of the blank wafer, that is, the wafer on which the pattern is not provided. Thus, the marks 22a and 22b can be recognized as temporary defects, so that the origin correction conventionally performed using an actual defect at an arbitrary position can be performed at a predetermined position (the position of the marks 22a and 22b). Can be done with
Therefore, even when there is only a minute defect on the blank wafer, the origin can be corrected.
The actual confirmation of the shape of the minute defect using the SEM can be performed with higher accuracy. Further, coordinate conversion for converting inspection data obtained by inspecting the position coordinates of a defect performed before confirmation of the shape of the defect by the SEM into coordinates suitable for the SEM can be efficiently performed. Also, SEM
The accuracy of coordinates between the defect inspection apparatus and the defect inspection apparatus can be improved, and the work efficiency of confirming the shape of a defect can be improved.

Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. is there.

For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as needed.

For example, in the above-described embodiment, the position of the mark formed by the laser marker 12 is
Although the predetermined position is set on the blank wafer, a mark may be formed on any defect on the surface of the blank wafer 21. As a result, the position of the defect can be specified more clearly. Therefore, when observing the defect shape with an SEM and analyzing it in detail using an external analyzer,
In an apparatus other than the SEM, such as an optical microscope, the work of reconfirming the defect position can be reduced. Further, the state around the defect can be confirmed by both the SEM and the optical microscope, and useful defect information for subsequent analysis can be obtained.

Further, for example, in the above-described embodiment, the laser marker 12 is provided near the electron gun 1, but as shown in FIG. 3, the laser marker 12 is provided between the objective lens 5 and the XY stage 6. May be provided.

Further, for example, in the above-described embodiment, the laser marker 12 is configured to be movable in a direction perpendicular to the emission direction of the electron beam EB. However, the laser marker 12 is fixed at a predetermined position, and the XY stage 6 is fixed. The upper sample may be configured to be moved, whereby the blank wafer 21 of the sample may be moved and a desired position may be irradiated with laser to form the marks 22a and 22b.

[0042]

As described above, according to the present invention, the electron microscope has the mark forming means for forming a mark at a predetermined position on the surface of the sample. By forming a mark at a predetermined position on the front surface, when confirming a defect on a substrate on which a pattern is not formed, alignment accuracy in an electron microscope can be improved, and the time required for confirming the defect can be reduced. And the shape of the defect can be easily confirmed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an entire configuration of an SEM according to an embodiment of the present invention.

FIG. 2 is a plan view showing a formation position of a mark on a wafer by a laser marker according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating another example of the overall configuration of the SEM according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Electron gun, 4 ... Scanning scan coil, 5 ...
..Objective lens, 10 ... scanning signal generator, 11 ...
CRT, 11a: deflection yoke, 11b: electron gun, 12: laser marker

Claims (11)

[Claims] 1. An electron microscope which irradiates a sample with an electron beam and checks a defect of the sample using the electron beam, wherein the electron microscope has a mark forming means for forming a mark at a predetermined position of the sample. Characteristic electron microscope. 2. An electron microscope according to claim 1, wherein said mark forming means is provided at a portion around an electron gun of said electron microscope. 3. The electron microscope according to claim 1, wherein the mark forming means is provided between the objective lens of the electron microscope and the sample. 4. The electron microscope according to claim 1, wherein said mark forming means comprises a laser. 5. By irradiating the sample with laser light extracted from the laser and shaving the surface of the sample,
5. The electron microscope according to claim 4, wherein a mark is formed on said surface. 6. The electron microscope according to claim 1, wherein said mark forming means is configured to be movable in a direction perpendicular to an emission direction of said electron beam. 7. The electron microscope according to claim 1, wherein the sample is a semiconductor wafer on which no pattern is formed. 8. A defect shape confirmation method for confirming the shape of a defect on a sample surface using an electron microscope, wherein the electron microscope has a mark forming means for forming a mark at a predetermined position on the sample. A defect shape confirming method, wherein a mark is formed on the sample by the mark forming means before confirming the shape of the defect. 9. The method according to claim 8, wherein the origin of the sample is corrected using the mark on the surface of the sample formed by the mark forming means. 10. The method according to claim 8, wherein a mark is formed by the mark forming means at a position of the defect on the surface of the sample confirmed by the electron microscope. 11. The method according to claim 8, wherein the mark is formed in at least two places on the surface of the sample.