JP2003142541A - Analysis method of particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analysis method of particles for analyzing even extremely fine metal and organic-family impurity particles that are less than 2 μm and exist on the surface of an object to be analyzed such as a semiconductor wafer. SOLUTION: Coordinates of particles that are detected by a particle counter are measured (1), and the coordinates data of the particles and coordinates at the outer periphery of a wafer that are measured by a laser marker are converted to coordinates data for marking by an external computer (2, 3, and 4). Based on the coordinates data for marking, peripheries of the particles are marked (5 and 6). Additionally, according to the coordinates data of the particles and the coordinates of the wafer outer periphery that are measured by an analyzer (TOF-SIMS), conversion to coordinates data for analysis is made by the external computer (7 and 8). Based on the coordinates data for analysis, the mark is detected by the analyzer, and the particles are analyzed with the mark as a guide (9 and 10).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing particles, and more particularly to a method for analyzing minute particles scattered on the surface of a semiconductor wafer by a time-of-flight mass spectrometer or the like.

[0002]

2. Description of the Related Art Conventionally, it has been required to analyze particles of metal or organic impurities adhering to the surface of a semiconductor wafer. There are various analysis methods according to the content to be analyzed, and one of them is the method of using a time-of-flight mass spectrometer (TOF-SIMS). In TOF-SIMS, the primary ions are applied to the object to be analyzed to generate secondary ions, and the secondary ions arrive at the detector from the light secondary ions, so that the identification can be performed by the arrival time. TO like this
By F-SIMS analysis, for example, a spectrum as shown in FIG. 8 is obtained, and it is possible to analyze particles of metal or organic impurities.

As a procedure for analyzing particles on the surface of a semiconductor wafer by using the conventional TOF-SIMS, first, particles on the surface of the wafer are detected as bright spots by a particle counter such as a laser scattering type foreign matter inspection device,
Measure the coordinates of these bright spots. Next, this wafer is set in TOF-SIMS equipped with a coordinate conversion function to perform coordinate conversion, and based on the converted coordinate data, particles are confirmed and analyzed by an optical microscope attached to the device. be able to. As an apparatus for analyzing particles, there is also an apparatus capable of analyzing extremely small metal particles, such as SEM-EDX.

[0004]

However, when the TOF-SIMS is used, the optical microscope attached to the apparatus can see only the actual particle size of about 2 μm. In addition, the coordinate transformation performed in TOF-SIMS picks up particles with large particle sizes as shown in FIG. 9, and among these, three points (particles) 1 apart from each other by the optical microscope attached to TOF-SIMS 1, Searching for 2 and 3, alignment (3 point alignment) is performed based on these points, and coordinate correspondence measurement is performed. Therefore, if particles with a size of 2 μm or more that can be seen with the attached optical microscope do not adhere to distant positions on the wafer surface, the above three-point alignment cannot be performed, and coordinate conversion must be performed. I can't.

For these reasons, it is not possible to accurately grasp the position of particles smaller than 2 μm, which cannot be seen in the optical microscope attached to TOF-SIMS, and therefore it is necessary to analyze these minute particles with TOF-SIMS. I couldn't. Also, due to the play of the holder that sets the wafer, a slight deviation when the wafer is placed causes a deviation of several hundreds of μm when performing the analysis, so it is 2 μm.
Sometimes particles larger than m cannot be found.

On the other hand, if SEM-EDX is used, coordinate correspondence measurement can be performed even for particles of less than 2 μm, but identification of particles is limited to metal, and organic particles cannot be identified.

It is an object of the present invention to provide a particle analysis method capable of analyzing even extremely minute metal or organic impurity particles of less than 2 μm existing on the surface of an analyte such as a semiconductor wafer. And

[0008]

In order to achieve the above object, the present invention provides a method for analyzing particles on the surface of an analyte, wherein particles on the surface of the analyte are radiated by a particle counter. The coordinate data measured for the position of the bright spot is input to an external computer having a coordinate conversion function, and the analyte is set on a marking device capable of marking a mark around particles, The coordinates measured about the outer peripheral position of the analyte are input to the external computer, the coordinate data by the particle counter is converted into marking coordinate data corresponding to the marking device, and in the marking device, the marking coordinate data is obtained. Mark around the particle detected based on the above, and analyze the marked analyte. Set the location, type the coordinates measured for the peripheral position of 該被 analyte to the external computer,
The coordinate data by the particle counter is converted into analysis coordinate data corresponding to the analysis device, and in the analysis device, the mark provided by the marking device is detected based on the analysis coordinate data, and the mark is detected. There is provided a method of analyzing particles, wherein the particles are analyzed as a mark.

As described above, the coordinates of the particles detected as the bright spots by the particle counter are coordinate-converted by the external computer, and based on this, the marking device can mark marks around the particles. Then, even if the particles are extremely minute things that cannot be seen with the microscope attached to the analyzer, if a mark attached to the periphery of the particle is found, the particles in the vicinity of the mark are analyzed using this as a mark. be able to.

A laser marker can be preferably used as the marking device (claim 2). With the laser marker, it is possible to accurately mark a desired position on the surface of the analyte, that is, the periphery of the particle to be analyzed, based on the converted marking coordinates.

Further, according to the present invention, there is also provided an analysis method in which the detection of particles and the marking on the periphery thereof are performed by the same device. That is, particles on the surface of the analyte are detected as bright spots by a particle counter having a marking function, coordinate data is measured for the positions of the bright spots, and a mark is placed around the bright spots. Coordinate data of particles is input to an external computer having a coordinate conversion function, the analyte with the mark is set in an analyzer, and the coordinates measured for the outer peripheral position of the analyte are input to the external computer. Input, converting the coordinate data by the particle counter to analysis coordinate data corresponding to the analysis device, in the analysis device, based on the analysis coordinate data, to detect the mark provided by the particle counter, Party characterized by analyzing the particles using the mark as a mark Analysis method of Le is provided (claim 3).

If a particle counter having a marking function is used, a mark can be accurately placed around the particle without coordinate conversion. Particles in the vicinity of the mark can be analyzed by using as a mark.

As the analyzer used in the present invention, a time-of-flight mass spectrometer can be preferably used (claim 4). In a generally used time-of-flight mass spectrometer (TOF-SIMS), microscopic particles of less than 2 μm can hardly be confirmed with an attached microscope, but if a mark is put around the particles according to the present invention, ,
Since this mark can be confirmed with the microscope attached to TOF-SIMS, the position of the particle can be accurately grasped by using this mark as a mark, and the particle can be analyzed.

As the analyte to be analyzed in the present invention, a semiconductor wafer having an orientation flat or a notch can be preferably used (claim 5). For these semiconductor wafers, it is strongly desired to evaluate fine particles of metal or organic material scattered on the surface thereof, and according to the present invention, it is possible to easily analyze these particles. Further, the orientation flats and notches formed on the semiconductor wafer are convenient for measuring the coordinates of the outer peripheral position of the analyte in the present invention, and the coordinates of the particles detected by the particle counter are accurately converted. It can be reflected in the coordinates of the marking device or analysis device.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the accompanying drawings. The analyzer and the analyte in the present invention are not particularly limited, but a case where TOF-SIMS is used to analyze the particles on the surface of the silicon wafer will be described as a preferred embodiment.

FIG. 1 shows an example of a particle analyzing method according to the present invention. As shown here, when analyzing the particles on the surface of the silicon wafer in the present invention, the coordinates of the particles detected by the particle counter are measured (1), and the coordinate data of the particles and the laser marker are used. The coordinates of the measured outer circumference of the wafer are converted into marking coordinate data by an external computer (2, 3, 4). Next, based on the marking coordinate data, a laser marker is used to put marks around the particles (5, 6). Further, the coordinate data of the particles and the coordinates of the outer circumference of the wafer measured by the analyzer (TOF-SIMS) are converted into analysis coordinate data by an external computer (7, 8). Then, based on the analysis coordinate data, the analyzer detects the mark,
Particles can be analyzed using this mark as a mark (9, 10).

The steps will be described in detail below. First, particles on the surface of the wafer are detected as bright spots by a particle counter, and coordinate data is measured for the positions of the bright spots (1). Since the particle counter detects particles and the like with scattered light caused by them, it is possible to detect extremely small particles of, for example, about 0.1 μm and measure the coordinates of the position. The particle referred to in the present invention is used as a generic term for those detected as a bright spot by a particle counter, and not only when it is actually a particle,
It also includes protrusions, depressions (pits), and foreign matter that has adhered.

Next, the particle coordinate data measured as described above is input to an external computer having a coordinate conversion function (2). As this external computer, it is possible to use a computer in which coordinate conversion software capable of converting the coordinates of the particle position measured by the particle counter into the coordinates corresponding to the laser marker and TOF-SIMS, respectively. If software that can be converted to other coordinate systems is also used, it can be used when performing analysis with an analyzer other than TOF-SIMS.

Next, the wafer is set on the stage of a laser marker capable of marking marks around the particles, the coordinates of the outer peripheral position of the wafer are measured, and the coordinates are input to the computer (3). The measurement of the coordinates of the outer peripheral position of the wafer includes, for example, two points at the left and right corners of the notch portion 4 of the edge of the wafer W as shown in FIG.
The outer peripheral position of the point can be found by an optical microscope attached to the laser marker to measure the coordinates.

It should be noted that the five points to be measured here may be located at appropriate distances (angle intervals between points from the center) on the outer circumference of the wafer, but they should be points at equal intervals and equal distances. Is preferred. Further, in the case of the wafer W having the orientation flat 5 formed as shown in FIG.
It suffices to find the outer peripheral positions of five points including the points and measure the coordinates.

By inputting the coordinates of the outer peripheral position of the wafer to the external computer as described above, the coordinate data of the particles already input to the computer can be converted into the coordinate data for marking (4). Specifically, the coordinates of the positions of the five points on the outer circumference of the wafer measured as described above are converted to an external computer having the coordinate conversion function (a computer in which the coordinate conversion software is installed).
By inputting to the outer circumference, the center of the wafer on the stage can be detected, and the coordinate data by the particle counter can be converted into the marking coordinate data corresponding to the laser marker.

The calculation itself of the coordinate transformation performed by the external computer of the present invention is not particularly limited, and the following calculation formulas can be applied, for example. First, among the coordinates of 5 points including the corners of 2 points on the left and right of the notch portion as shown in FIG. 2A, the coordinates of 3 points other than the notch portion (x1, y1), (x2, y2), ( The values of (x3, y3) are substituted into the following formulas to determine α, β, r. As a result, the coordinates of the center point of the wafer (circle) are determined, and by further determining the directions of the X axis and the Y axis from the position of the notch, new coordinates can be determined.

[0023]

[Equation 1]

After the conversion into the marking coordinate data as described above, a particle is detected by the laser marker based on the marking coordinate data, and a mark is put around the particle (5, 6). Regarding the marking method, first, the position of the particle is specified based on the marking coordinate data, but the detected bright spots include pits, protrusions, mounds, etc. on the wafer surface in addition to the particles. Therefore, the marker can be moved to the coordinates of the object to be analyzed based on the marking coordinate data, particles can be searched for with the attached optical microscope, and marking can be performed. The microscope of the laser marker has a higher magnification than the microscope attached to the TOF-SIMS and can confirm the particles to be analyzed. Specifically, it is preferable that the particles of less than 2 μm can be confirmed.

The shape, number, size, etc. of the marks are not particularly limited as long as they can be seen with the optical microscope attached to the TOF-SIMS. For example, as shown in FIG. Mark 7 on all sides of point 6
By adding 4 points, it becomes easier to confirm the mark 7 when the optical microscope attached to the TOF-SIMS detects it later. Further, even if the particles themselves cannot be confirmed with the TOF-SIMS microscope, the particles 6 are present at the centers of the four marks 7, so the centers of these marks 7 may be analyzed.

Next, the coordinate data of the particles are converted into TOF-
The coordinates are converted into analysis coordinate data for particle analysis by SIMS, and this procedure is basically the same as the above-mentioned coordinate conversion into laser marker coordinate data. That is, the wafer with the mark is set on the TOF-SIMS stage, and the outer peripheral position of the wafer is measured. The method of measuring such an outer peripheral position is similar to the case of measuring with a laser marker.

Then, the coordinates of the outer peripheral position of the wafer measured by TOF-SIMS are input to the external computer (7). Since the coordinate data of the particles to be analyzed are input to the computer (2), the coordinate data of the particles can be converted into the coordinate data for analysis corresponding to the coordinates when performing the analysis by TOF-SIMS. You can (8).

In the TOF-SIMS, a mark provided by a laser marker is detected based on the analysis coordinate data obtained as described above, and particles are analyzed using this mark as a mark (9, 10).

Specifically, the TOF-with the wafer set
Move the SIMS stage to the analysis coordinates of the marked particles. Here, there is an error in the coordinate conversion, and it is not possible to completely specify the position of an extremely minute particle to be analyzed, for example, 0.1 μm, only with the coordinate for analysis. Look for the mark with the optical microscope attached to the device. At this time, if the size of the particles to be analyzed is less than 2 μm, the particles themselves cannot be seen with the attached optical microscope, but the marks around them can be seen with the optical microscope. Perform an analysis. For example, when four marks are provided around the particles as shown in FIG. 3, the particles existing there can be analyzed by scanning in accordance with the central portions of the four marks.

In the above-described analysis method, marking is performed by using the particle counter and the laser marker and performing coordinate conversion between these devices, but instead of this, a particle counter having a marking function may be used. it can. That is, a particle counter having a marking function (for example, MAGI manufactured by Lasertec Co., Ltd.
CS: Multiple image Acquisition for Giga-bit patter
n Inspection with Confocal System), particles on the surface of the wafer can be detected as bright spots, coordinate data can be measured for the positions of the bright spots, and marks can be placed around the particles located at the bright spots. it can. Therefore, it is possible to perform from the detection of particles to the marking with one device without performing coordinate conversion.

The flow after marking is the same as above. That is, the coordinate data of particles by the particle counter is input to an external computer having a coordinate conversion function (2), the marked analyte is set in the analyzer, and the outer peripheral position of the analyte is measured. The coordinates are input to the external computer (7). This allows
Since the coordinate data by the particle counter can be converted into the coordinate data for analysis corresponding to the analyzing device (8), the mark attached by the particle counter is detected in the analyzing device based on the coordinate data for analyzing, The particles are analyzed using this mark as a mark (10).

[0032]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. (Example 1) A silicon wafer having a diameter of 200 mm with a notch formed was examined for particles and the like adhering to the surface thereof with a particle counter (MAGICS) having a marking function. A point has been detected. The coordinate data of the positions of these bright spots are input to a computer in which coordinate conversion software is incorporated, and as shown in FIG. 5, 4 μm marks with a diameter of 5 μm are provided around the particles of the analysis target particle. I attached it (the particle is visible in the center).

Next, the wafer with the mark is subjected to TOF-SI.
It was set on the MS stage, and in addition to the coordinates of the left and right corners of the notch of the wafer, three points on the outer circumference of the wafer were combined to measure a total of five coordinates. These coordinates were input to the above computer, and the coordinate data of the position of the bright spot measured by the particle counter was converted into the coordinate data for analysis corresponding to TOF-SIMS. Based on the analytical coordinate data obtained in this way, the stage is moved and
Two marks were detected with an optical microscope.

Particles could not be confirmed with the TOF-SIMS optical microscope, but the four marks around it could be confirmed, and the position of the particles to be analyzed could be accurately specified. It was Therefore,
When the center of each of the four marks was analyzed by TOF-SIMS, hydrocarbon fragments were obtained, and it was found that the particles were organic particles.

(Embodiment 2) A silicon wafer having a diameter of 150 mm on which an orientation flat (orientation flat) is formed is subjected to Bernoulli chucking so that the wafer surface A
Contaminated with l. When a bright spot on the surface of the Al-contaminated wafer was detected by a particle counter, a bright spot was detected on the surface of the wafer as shown in FIG. The coordinate data of the positions of these bright spots were input to a computer incorporating coordinate conversion software.

Next, the wafer was set on the stage of the laser marker, and in addition to the coordinates of the left and right corners of the orientation flat of the wafer, three coordinates on the outer circumference of the wafer were combined to measure a total of five coordinates. These coordinates were input to the above computer, and the coordinate data of the position of the bright spot measured by the particle counter was converted into the marking coordinate data corresponding to the laser marker. On the basis of the obtained coordinate data for marking, particles were detected with a high-power microscope attached to the laser marker, and four marks having a diameter of 5 μm were attached to the four sides of the particle in the same manner as in Example 1.

After marking as above, TOF-SIMS
The wafer was set on the stage, and the coordinates of five points on the outer circumference of the wafer were measured using the attached optical microscope in the same manner as the coordinate measurement with the laser marker, and the coordinates were input to the computer. Then, the computer can use the coordinate data of the particles to be analyzed that have already been measured by the particle counter.
It was converted to the coordinate data for analysis corresponding to TOF-SIMS. The stage was moved based on the thus obtained coordinate data for analysis, and the four marks made by the marking device were detected by an optical microscope.

Particles could not be confirmed with the TOF-SIMS optical microscope, but the four marks around the particles could be confirmed, and the position of the particles to be analyzed could be accurately specified. It was And TO
When the central portions of the four marks were analyzed by F-SIMS, spectra as shown in FIG. 7 were obtained, and aluminum could be detected. When the size of the aluminum particles was measured by other means, it was 0.47 μm.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has any similar effect to the present invention. It is included in the technical scope of the invention.

For example, in the above-described embodiment, the case where the particles on the surface of the silicon wafer are analyzed by TOF-SIMS has been described, but the analyte in the present invention is not limited to the silicon wafer, and the TOF is also applicable to the analyzer. -Other than SIMS can be preferably used.

[0041]

As described above, according to the present invention, a coordinate conversion is used, a mark is attached around the particle, and the particle is analyzed using this mark as a mark. Therefore, the particles are extremely small, and even for the minute particles that could not be analyzed because the position of the particles could not be accurately specified with the analyzer,
Based on the coordinate conversion data, it is possible to accurately specify the position of the particle using the mark as a mark for analysis.

For example, 2 scattered on the surface of the semiconductor wafer.
TOF-SIMS for metal and organic impurities particles less than μm
It has been difficult to analyze in the past, but in the present invention, TOF-SIMS was used as an analysis device, and by combining this with a marking device having a microscope with high magnification,
It is also possible to analyze particles of metal or organic impurities less than m.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of an analysis method according to the present invention.

FIG. 2A is a diagram showing an example of an outer peripheral position to be measured of a wafer having a notch formed therein. (B) It is the figure which showed an example of the outer peripheral position which should be measured of the wafer in which the orientation flat was formed.

FIG. 3 is a diagram showing an example of marking.

4 is a bright spot detected in Example 1. FIG.

5A and 5B are marks attached to particles in Example 1. FIG.

6 is a bright spot detected in Example 2. FIG.

FIG. 7 is a spectrum obtained by analyzing particles by TOF-SIMS in Example 2.

FIG. 8 is an example of a spectrum obtained when a particle is analyzed by TOF-SIMS.

FIG. 9 is an example showing positions of three particles selected by three-point alignment performed by coordinate conversion in TOF-SIMS.

[Explanation of symbols]

1, 2, 3, ... Bright points used for 3-point alignment, 4 ... Notch, 5 ... Orientation flat, 6 ... Particle, 7 ... Mark, W ... Wafer.

Claims (5)

[Claims] 1. A method for analyzing particles on the surface of an analyte, wherein particles on the surface of the analyte are detected as bright spots by a particle counter, and coordinate data measured at the positions of the bright spots are used. ,, input to an external computer having a coordinate conversion function, set the analyte to a marking device that can put a mark around the particles, the coordinates measured for the outer peripheral position of the analyte to the external computer The coordinate data by the particle counter is converted into marking coordinate data corresponding to the marking device, and a mark is attached around the particle detected based on the marking coordinate data in the marking device. Set the analyte marked with on the analyzer and measure the outer peripheral position of the analyte. The coordinate data is input to the external computer, the coordinate data by the particle counter is converted into analysis coordinate data corresponding to the analysis device, and in the analysis device, based on the analysis coordinate data, added by the marking device. A particle analysis method, which comprises detecting the formed mark and analyzing the particles using the mark as a mark. 2. The particle analysis method according to claim 1, wherein a laser marker is used as the marking device. 3. A method for analyzing particles on the surface of an analyte, wherein particles on the surface of the analyte are detected as bright spots by a particle counter having a marking function,
While measuring the coordinate data for the position of the bright spot,
With a mark around it, the particle coordinate data by the particle counter is input to an external computer having a coordinate conversion function, and the analyte with the mark is set in an analyzer.
The coordinates measured about the outer peripheral position of the analyte are input to the external computer, the coordinate data by the particle counter is converted into analysis coordinate data corresponding to the analyzer, and the analysis coordinate data is converted by the analyzer. Based on the above, the mark attached by the particle counter is detected, and the particle is analyzed using the mark as a mark. 4. The particle analysis method according to claim 1, wherein a time-of-flight mass spectrometer is used as the analyzer. 5. The particle analysis method according to claim 1, wherein a semiconductor wafer having an orientation flat or a notch is used as the analyte.