Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1999-12-01
2001-12-04
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S1540PB, C324S501000, C250S310000, C250S311000
Reexamination Certificate
active
06326798
ABSTRACT:
This patent application claims priority based on a Japanese patent application, H10-342227 filed on Dec. 1, 1998, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric beam tester which tests electric components such as a semiconductor. In particular, the present invention relates to an electric beam tester which has a means of correcting an image scanned by an electric beam.
2. Description of the Related Art
If a magnetic field is generated in an electric component, which is an object being measured by an electric beam tester, an error is generated at the landing point of the primary electron. Distortion therefore occurs in the measuring results of the voltage waveform. To correct this distortion, Logic State Mapping image, LSM image is used. The LSM image is an image obtained by providing a test pattern to electric components such as semiconductors and at the same time scanning the electric components. The error of the landing point of the primary electron can be measured by measuring the change of the LSM image with time. By previously measuring the error of the landing point of the primary electrons, the necessary correction can be made to each phase of the test signal, even in the case of measuring the voltage waveform of the electric component.
FIG. 1
shows an example of the LSM image. It is desirable to automatically calculate the magnitude of the landing point error of the primary electron based on the LSM image. However, there is an area in the LSM image in which the secondary electron is not detected as shown in the black areas in FIG.
1
. Furthermore, because a pattern or wiring such as GND and power supply, are cut off in the upper and lower edges of the LSM image, it is difficult to calculate the degree of deviation just using the simple operation method. Additionally, because the signal to noise ratio, SN ratio, of the LSM image data is low, it is difficult to calculate the degree of deviation just using the simple operation method. Therefore, it is difficult to automatically calculate the magnitude of the landing point error of the primary electron.
Thus, the operator of the electric beam tester detects the degree of deviation by referring to the LSM image, and corrects the landing point of the primary electrons according to the degree of deviation. Therefore, the problem can occur where the degree of deviation cannot be accurately detected, and a complicated operation has to be undertaken for the correction.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an electric beam tester which can overcomes the above issues in the related art. This object is achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, an electric beam tester which tests an electric component can be provided. The electric beam tester comprises a signal generating apparatus which provides a signal to the electric component; an electric gun which scans an electric beam onto the electric component to which the signal generated by the signal generating apparatus is provided; a detector which detects secondary electrons radiated from the electric component, by irradiating the electric beam onto the electric component; an image generating means which generates a scanned image of the electric component using the secondary electrons detected by the detector; a selecting means which selects a part of an image of the scanned image generated by the image generating means; and a correcting means which corrects the scanned image using the part of an image selected by the selecting means.
According to the second aspect of the present invention, an image processing apparatus, which processes a scanned image is provided. This scanned image is obtained by scanning an electric beam on a specific straight line in an electric component to which a signal is provided from a signal generating apparatus. The scanned image may show an electric potential on the specific straight line within a prescribed time range. The image processing apparatus may comprise a selecting means which selects a range of the straight line and time range in the scanned image; and a correcting means which corrects the entire scanned image so that changes over time in an image selected by the selecting means decreases.
The scanned image may show a change of electric potential in the electric component over time; and the selecting means may select a time range in the scanned image. The scanned image may show a change of electric potential over time on a specific straight line in the electric component; and the selecting means may select a prescribed range on the straight line. The selecting means may select the part of an image from a plurality of places. In this case, the part of an image may be selected from a plurality of places so that at least an image of one area is selected at all times.
The correcting means may correct the entire scanned image so that any change over time in the part of an image selected by the selecting means decreases. The image processing apparatus may further comprise a display device which displays the scanned image corrected by the correcting means. The selecting means may select as the part of an image, an image from the scanned image of an area having a greater level of contrast than a prescribed reference value in the scanned image, and an image nearby this selected area.
The selecting means may select as the part of an image an image of an area where secondary electrons greater than a prescribed reference value are detected in the scanned image, and an image nearby the selected image. The image processing apparatus may further comprise a display device which displays the scanned image generated by the image generating means; wherein the selecting means may select as the part of an image, a region designated by a user within a region of the scanned image displayed in the display device.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.
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Advantest Corporation
Metjahic Safet
Nguyen Jimmy
Rosenthal & Osha L.L.P.
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