JP4835874B2 - Data processing method for scanning beam device - Google Patents

Description

  The present invention relates to a scanning beam apparatus that forms a scanned image by two-dimensionally scanning a charged particle beam such as an electron beam or an ion beam on a sample, and more particularly to data processing of a scanned image of the scanning beam apparatus.

  In a scanning beam apparatus, a charged particle beam is scanned two-dimensionally on a sample to obtain a scanned image. In this scanning beam apparatus, the charged particle beam and the sample stage are relatively moved in the X-axis direction and the Y-axis direction for two-dimensional scanning.

Acquiring a scanned image efficiently is demanded with an increase in the size of a frame formed on a substrate as a sample and the accompanying increase in the size of the substrate itself.
As a configuration that satisfies this requirement, a configuration is known in which a plurality of charged particle beam sources are used and a scanned image is acquired by the plurality of charged particle beams.

  FIG. 6 is a diagram for explaining the outline of the scanning beam device. FIG. 6 shows a case where a scanning image is acquired by two-dimensionally scanning a TFT array substrate as a sample using an electron beam as a charged particle beam.

  FIG. 6 (a) schematically shows the TFT array substrate 1. On the substrate 1, a TFT array panel 2, a connector pad 3 for supplying current from the outside to the gate and source of the TFT array, and the like are formed. ing. FIG. 6 (b) shows an outline of a prober frame 11 for inspecting the TFT array substrate 1. The prober frame 11 is in contact with the connector pad 3 and the opening 12 formed in accordance with the panel 2. Connector pins 13 for supplying current to the TFT array are provided. The connector pin 13 is formed on the back surface side of FIG. 6 (b), and the prober frame 11 is brought into contact with the connector pad 3 on the prober frame 11 side by superimposing the prober frame 11 on the TFT array substrate 1. Is supplied.

  FIG. 6C shows a state in which the prober frame 11 is overlaid on the TFT array substrate 1, and the TFT array panel 2 can be seen through the opening 12.

  By irradiating the TFT array substrate 1 with an electron beam from an electron beam source (not shown) and scanning the panel 2, the secondary electrons emitted from the panel 2 are detected by a detector (not shown). A scanning image of the TFT array is acquired.

  Since the signal intensity of the acquired scan image changes depending on the state of the pixel of the TFT array, the defect inspection of the pixel of the TFT array can be performed by detecting the signal intensity of the scan image.

  FIG. 7 shows an example in which scanning is performed using a plurality of electron beam sources (GUNa, GUNb,...). A plurality of electron beam sources (GUNa, GUNb,...) Divide the TFT array substrate 1 into several regions and scan each region to obtain a scanned image. Scanning in each region can be performed by a plurality of passes (for example, pass 1 to pass 4).

  As described above, when a plurality of electron beam sources are used, there is a variation in each electron beam source, and thus the signal intensity acquired using each electron beam source may vary. Thus, if there is a variation in the signal intensity of the detection signal, it affects the accuracy of the defect inspection of the TFT array pixel.

  Therefore, conventionally, a predetermined material such as Al (aluminum) is provided at a predetermined position on the prober frame 11 as shown in FIGS. The signal intensity of secondary electrons obtained by irradiating the reference region 14 with an electron beam is used as a reference.

   When performing a defect inspection of a pixel of the TFT array, for example, an average intensity is obtained from the signal intensity obtained from the reference region 14 provided in addition to the pixel, and a calibration curve is formed using this as the reference intensity. The defect inspection is performed by setting the signal intensity of the defective portion based on the above.

  FIG. 8 is a diagram for explaining a case where a calibration curve is formed using the reference intensity and defect inspection is performed based on the calibration curve.

   FIG. 8A shows the intensity distribution A1 of the scanned image obtained by scanning the panel A with the electron beam source GUNa, and FIG. 8B shows the scan obtained by scanning the panel B with the electron beam source GUNb. An intensity distribution B1 of the image is shown.

  When the detection signal intensity shown in FIG. 8 (a) is compared with the detection signal intensity shown in FIG. 8 (b), each standard intensity (reference intensity) is different. Since this standard intensity (reference intensity) is a signal intensity obtained from the same intensity region 14, the same signal intensity is expected, but the signal intensity varies depending on variations in electron beam sources.

  For this reason, when the intensity distribution A1 shown in FIG. 8 (a) and the intensity distribution B1 shown in FIG. In some cases, defect inspection is not performed correctly. Therefore, the distribution curve is deformed using the distribution centers and standard intensities of the intensity distributions A1 and B1, and a calibration curve shown in FIG. 8C is formed. Based on the calibration curve, the signal intensities of the defective portions a and b are obtained. Determining and performing defect inspection.

  The method described above is based on the premise that the reference intensity obtained by a plurality of electron beam sources is stable. However, the inventor of the present application does not always stabilize the reference intensity itself obtained by irradiating the reference region 14, and the reference intensity itself obtained by each electron beam source fluctuates. We found that the nature is low.

  Therefore, in the method in which the signal intensity obtained from the reference area provided on the prober frame is used as the reference intensity, there is a problem that the signal intensity of the scanned image obtained by a plurality of charged particle beam sources varies. There is also a problem that high inspection accuracy cannot be obtained in defect inspection.

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-described conventional problems and reduce variations in signal intensity of scanning images acquired by a plurality of charged particle beam sources without using a reference intensity. It is another object of the present invention to improve the accuracy of defect inspection by reducing variations in scanned images acquired by a plurality of charged particle beam sources without using a reference intensity.

  The present invention relates to a scanning beam apparatus that forms a scanned image by two-dimensionally scanning a charged particle beam from a plurality of charged particle beam sources on a sample to form a signal intensity of each scanned image obtained by each charged particle beam. The first step for obtaining the signal intensity distribution for each, the second step for adjusting the distribution shape of each signal intensity distribution to be the same distribution shape, and the distribution shape of each signal intensity distribution being the same distribution shape And a third step of obtaining the signal intensity of each scanned image at the time.

  Attention is paid to the distribution shape of the intensity distribution of the scanning image obtained from the region to be measured of the sample, and the distribution shape of the intensity distribution is matched with the scanning image obtained from each charged particle beam source. This reduces variations in the signal intensity of the scanned image acquired by the plurality of charged particle beam sources without using the reference intensity.

  The charged particle beam of the present invention can be an electron beam or an ion beam, and the charged particle beam source that irradiates the sample with the charged particle beam can be an electron beam source or an ion beam source.

  The sample to be scanned by the scanning beam apparatus of the present invention can be, for example, a TFT array substrate. When using a TFT array substrate as a sample, obtain pixel data of the TFT array as a scanned image, and perform a defect inspection to determine whether the pixel is a normal pixel or a defective pixel from the signal intensity of this pixel data. Can do.

  The second step is a step of matching the standard deviation of the signal intensity distribution of each scanned image with the reference standard deviation. For the signal intensity distribution of each scanned image with different charged particle beam sources obtained in the first step, a standard deviation is obtained from the signal intensity. Since the signal intensity distribution of each scanned image is assumed to have the same distribution characteristic (for example, normal distribution), this standard deviation is a distribution shape caused by variations in the charged particle beam source or the like regarding the distribution characteristic. Represents.

  Therefore, in the present invention, in the second step, this standard deviation is matched with each scanning image to obtain a signal intensity distribution that eliminates the variation of the charged particle beam source, etc., and in the third step, each signal intensity distribution The signal intensity of each scanned image is obtained when the distribution shape is the same.

  In the process of the present invention, since the conventional reference intensity is not used, there is no variation in the signal intensity of the scanned image due to instability of the reference intensity.

  In the second step, the standard deviation of the signal intensity distribution of each scanned image can be matched with the standard deviation by multiplying the standard deviation by a coefficient. As the standard deviation of the reference, one of a plurality of scanned images is selected and set as the standard deviation of the selected scanned image, or a preset standard deviation of the scanned image may be used.

  By multiplying the coefficient, the standard deviation of each scanned image becomes the same. In the third step, a coefficient for matching with the standard deviation obtained in the second step is used, and correction is performed by multiplying the signal intensity of each scanned image by the coefficient.

  The standard deviation of the signal intensity distribution of the scanned image obtained by multiplying this coefficient is the same, and the distribution shape is the same.

  By comparing the signal intensity of each scanned image corrected in the third step with the same threshold value, the defect of the sample is determined. According to this defect determination, since the signal intensity level is not adjusted using the reference intensity as in the prior art, there is no variation in the signal intensity of the scanned image due to the instability of the reference intensity, and the accuracy of the defect inspection is improved. Can be improved.

  In the scanning beam scanning according to the present invention, a TFT array is used as a sample, and an electron beam is used as a charged particle beam applied to the TFT array, thereby making it possible to determine a defect of a pixel included in the TFT array.

  According to the present invention, it is possible to reduce variations in the signal intensity of a scanned image acquired by a plurality of charged particle beam sources without using a reference intensity.

  In addition, it is possible to reduce variations in scanned images acquired by a plurality of charged particle beam sources without using a reference intensity.

5 is a flowchart for explaining a data processing method by the scanning beam apparatus of the present invention. It is a figure for demonstrating standardization of the signal strength distribution of this invention. It is a flowchart for demonstrating an example of standardization of the distribution shape of invention. It is a figure of signal intensity distribution for explaining an example of standardization of the distribution shape of the present invention. It is a figure of signal intensity distribution for explaining an example of standardization of the distribution shape of the present invention. It is a figure for demonstrating the outline of a scanning beam apparatus. It is a figure which shows the example which scans with several electron beam sources (GUNa, GUNb, ...). It is a figure for demonstrating the case where a defect inspection is performed based on a calibration curve.

Explanation of symbols

1 ... TFT array substrate, 2 ... Panel, 3 ... Connector pad, 11 ... Prober frame, 12 ... Opening, 13 ... Connector pin, 14 ... Reference area.

   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a flowchart for explaining a data processing method by the scanning beam apparatus of the present invention.

  The present invention relates to data processing in a scanning beam apparatus that forms a scanned image by two-dimensionally scanning a sample with charged particle beams from a plurality of charged particle beam sources. An example of detecting secondary electrons obtained by irradiating a TFT array with this electron beam using an electron beam as a beam will be explained.

  The electron beam is scanned on the TFT array by moving the electron beam and / or the TFT array while irradiating the TFT array with the electron beam from the electron beam source (Sl).

  When the electron beam is irradiated onto the TFT array, secondary electrons are emitted from the TFT array. The scanning beam device detects this secondary electron by the detector (S2).

  On the TFT array, secondary electrons emitted from normal pixels and secondary electrons emitted from defective pixels have different signal intensity distribution states. The distribution state of the signal intensity can be represented by the signal intensity and quantity (the number of pixels having the intensity in the panel).

Secondary electrons emitted from normal pixels exhibit distribution characteristics with a certain signal intensity as the distribution center.
This distribution characteristic corresponds to the characteristics of an electron beam source, a TFT array, or the like. Further, secondary electrons emitted from the defective pixel appear at a signal intensity position deviating from the distribution characteristics of the normal pixel.

  A signal intensity distribution is obtained for the signal intensity of the secondary electrons detected by the detector and the number (quantity) of pixels having this signal intensity. FIGS. 2A to 2D schematically show signal intensity distributions obtained by irradiating panels A to D of the TFT array with electron beams from the electron beam sources GUNa to GUNd. The numerical values shown here are tentatively shown for convenience of explanation, and do not represent actual values. For the convenience of explanation, the signal intensity distribution is also exaggerated from the actual signal intensity distribution center and distribution shape (S3).

  As shown in FIGS. 2 (a) to (d), the signal intensity distribution as detected by the detector has a different signal intensity distribution shape, so the signal intensity is not the same even for defective pixels of the same type. The signal intensity of the defective pixel cannot be compared with the same threshold value.

  In the data processing of the present invention, these signal intensity distributions having different distribution shapes are standardized by matching the distribution shapes with the standard deviation as a reference. 2 (e) to 2 (h) show a state in which the distribution shapes are matched by matching the standard deviations of the signal intensity distributions shown in FIGS. 2 (a) to 2 (d).

   For example, when the standard deviations of the signal intensity distributions in FIGS. 2 (a) to 2 (d) are σa, σb, σc, and σd, the standard deviation of these signal intensity distributions is set to a common σ0. As shown in FIGS. 2E to 2H, the distribution shapes of the signal intensity distributions are matched. The common standard deviation σ0 may be selected from standard deviations σa, σb, σc, and σd, or a standard deviation set in advance may be used (S4).

  Next, the signal intensity of the defective portion is obtained based on the distribution shape standardized in the step of S4, and defect determination is performed based on this signal intensity (S5).

  The flowchart shown in FIG. 3 shows an example of standardization (standardization) of the distribution shape of S4 described above.

  A standard deviation is obtained for acquired data detected from each panel by irradiation of each electron beam source. According to the example of FIG. 2, standard deviations σa, σb, σc, and σd are obtained from each signal intensity distribution (S41).

  Each standard deviation σa, σb, σc, σd can be matched with the standard deviation σ0 by multiplying by a coefficient k. The coefficient ka for making the standard deviation σa coincide with the standard deviation σ0 can be obtained by, for example, ka = σ0 / σa. The coefficients ka to kd are calculated for the standard deviations σa to σd of each signal intensity distribution. Note that, here, an example of four signal intensity distributions obtained by four electron beam sources GUNa to GUNd is shown, but the number of signal intensity distributions is not limited to four, and the charged particle beam provided in the scanning beam device The number of signal intensity distributions obtained according to the number of sources (electron beam sources) can be obtained (S42).

  Next, the signal strength is corrected by multiplying the raw data of each signal strength distribution by the coefficients ka to kd obtained in step S42. By the correction of this data, the standard deviation of any signal intensity distribution becomes the same σ0, and the signal intensity distributions match (S43).

   4 and 5 show the electron beam source GUNa. The signal intensity distribution obtained by GUNb (Fig. 4 (b), Fig. 5 (b)) and the signal intensity distribution obtained by multiplying this signal intensity distribution by predetermined coefficients ka and kb (Fig. 4 (c), Fig. 4) 5 (c)).

FIG. 4A shows the intensity distribution A1 of the signal intensity and its quantity (number of pixels having the intensity in the panel) obtained by emitting secondary electrons from the electron beam source GUNa, and FIG. ) Shows the average value μa and the standard deviation σa of the intensity distribution.
Here, a distribution example in which the distribution center and the average value μa coincide is shown.

  FIG. 4 (c) shows a signal intensity distribution obtained by multiplying a predetermined coefficient ka of the signal intensity to obtain a standard deviation σ0. In this signal intensity distribution, the intensity at the center of the distribution is used as a reference point (for example, 100), and the intensity at the 0 point position is obtained by extrapolation using the standard deviation σ 0 from the reference point at the center of the distribution.

  By adjusting the standard deviation σa to the standard deviation σ0 and obtaining the zero point position, the defect inspection can be performed from the signal intensity on the intensity distribution.

  For example, the signal intensity of the defective part a in FIG. 4 (a) is obtained as the signal intensity of the defective part a in FIG. 4 (c) by obtaining the zero point position with the standard deviation as σ0. Defect determination is performed by comparing the signal intensity with a preset threshold value. Note that, as described above, the threshold for performing defect determination is based on the intensity scale formed by the reference point of the distribution center and the 0 point obtained by extrapolation in the intensity distribution with the standard deviation of σ0. Set it.

  Similarly, Fig. 5 (a) shows the intensity distribution B of the signal intensity and its quantity obtained by detecting secondary electrons from the electron beam source GUNa, and Fig. 5 (b) shows the average value of this intensity distribution. μb and standard deviation σb are shown. Here, a distribution example in which the distribution center and the average value μb coincide is shown.

   FIG. 5 (c) shows a signal intensity distribution obtained by multiplying a predetermined coefficient kb of the signal intensity to obtain a standard deviation σ0. As in FIG. 4 (c), in this signal intensity distribution, the intensity at the center of the distribution is used as a reference point (for example, 100), and the standard deviation σ0 from the reference point at the center of the distribution is used. Strength is determined by extrapolation.

  In FIG. 5 (c), by aligning the standard deviation σb with the standard deviation σ0 and obtaining the 0 point position, by comparing the signal intensity of the defect part b in the intensity distribution with a preset threshold value, Defect determination is performed.

   The signal intensity distribution of the electron beam source GUNa shown in FIG. 4 (c) and the signal intensity distribution of the electron beam source GUNb shown in FIG. 5 (c) are both the same standard deviation σ0 and the distribution shape is the same. Therefore, the signal intensity of each defective part can also be compared on the same intensity scale, and defect inspection can be determined based on the same standard.

  Further, in this defect determination, since the signal intensity detected from the reference area is not used as a reference as in the prior art, it is possible to prevent a decrease in defect inspection accuracy due to the instability of the signal intensity.

  The scanning beam apparatus of the present invention can be applied to an electron beam microanalyzer, a scanning electron microscope, an X-ray analyzer, and the like.

Claims (3)

In a scanning beam apparatus that forms a scanned image by two-dimensionally scanning a sample with charged particle beams from a plurality of charged particle beam sources,
A first step of obtaining a signal intensity distribution for each signal intensity of each scanned image obtained by each charged particle beam;
A second step of calculating a coefficient for standardizing the distribution shape of the signal intensity distribution of each scanned image based on the standard deviation of the signal intensity distribution of each scanned image;
A third step of performing defect determination based on the signal intensity of the defect portion obtained based on the standardized signal intensity distribution shape of each scanned image,
The third step includes
Standardizing the signal intensity distribution shape of each scanned image by multiplying the signal intensity of each scanned image by the coefficient calculated in the second step,
In the standardized signal intensity distribution shape of each scanned image, the signal intensity at the center of the distribution is used as a reference point, and the same for each scanned image from the reference point and the 0 point position obtained using the standard deviation of the reference from the reference point. Forming an intensity scale of
Find the signal intensity of each scanned image and the threshold common to each scanned image on the intensity scale,
A data processing method for a scanning beam apparatus, wherein a defect of a sample is determined by comparing the signal intensity obtained in each scanning image with the same threshold value. The coefficient is determined by the ratio of the standard deviation of the signal intensity distribution of each scanned image and the standard deviation of the reference ,
2. The data processing method for a scanning beam apparatus according to claim 1, wherein the standardization is performed by multiplying the signal strength of each scanned image by the obtained coefficient to correct the signal strength of each scanned image . The data processing method for a scanning beam apparatus according to claim 1 or 2 , wherein the sample is a TFT array, the charged particle beam is an electron beam, and defect determination of an image provided in the TFT array is performed. .

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