Patent Application
20080164410
This US non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application No. 10-2006-0131080 filed in the Korean Intellectual Property Office on Dec. 20, 2006, the entirety of which is hereby incorporated herein by reference.
The present invention relates to failure analysis systems and failure analysis methods. More specifically, the present invention is directed to an emission detecting analysis system and a method of detecting emission on an object.
An emission analysis method is an analysis method for analyzing photons emitted from a test target to detect failure positions of the test target. That is, fail positions may be detected by analyzing photons generated by charge migration or concentration when wiring of an electronic circuit is abnormally opened or shorted.
As shown in
Referring to
Conventionally, an image of a test target and an emission image may be obtained by means of an optical microscope. However, the limitation in magnification of the optical microscope causes low resolution for identifying a failure position of a micro circuit. This results in the inefficiency that after detecting an emission point at a micro circuit such as a semiconductor device, a test target is carried to a separately installed scanning electron microscope (SEM) to detect a failure position. In addition, the limitation in resolving power makes it difficult to determine what portion of a pattern corresponds to the detected failure position. Furthermore, an emission point detecting and failure analysis system is a separate system, resulting in difficulty in detecting an emission point.
Exemplary embodiments of the present invention are directed to an mission analysis system and an emission analysis method.
According to a first aspect, the present invention is directed to an mission analysis system, which may include: a chamber; a rotatable stage inside the chamber on which a test target is placed; a scanning electron microscope (SEM) column for obtaining an image of the test target; and an emission detector column for detecting a light emission of the test target.
In one embodiment, the rotatable stage has a rotation axis parallel with a stage surface.
In one embodiment, the SEM column and the emission detector column are disposed in front of the stage, and an axis of the emission detector column is inclined relative to an axis of the SEM column. An angle of the stage surface can be controllable relative to the axis of the SEM column and the axis of the emission detector column.
In one embodiment, the rotatable stage has a rotation axis perpendicular to a stage surface.
In one embodiment, the stage is parallel-movable along an orthogonal coordinate parallel with a stage surface.
In one embodiment, the emission detector column comprises an objective lens unit including a plurality of objective lenses having different magnifications.
In one embodiment, the system further comprises: an image processor for processing a detected emission image at the emission detector to adjust a magnification; an image filter for filtering an enlarged emission image to increase an accuracy of an emission point; and a superimposor for overlapping the SEM image with the emission image to mark an emission point on the SEM image.
In one embodiment, the system further comprises a focused ion beam (FIB) column installed at the chamber to etch an emission point. The FIB column can be installed in front of the stage, and an axis of the FIB column can be inclined relative to the axis of the SEM column and the axis of the emission detector column. An angle of the stage surface can be controllable relative to the axis of the FIB column, the axis of the SEM column, and the axis of the emission detector column. The rotatable stage can have a rotation axis parallel with the stage surface and a rotation axis perpendicular to the stage surface and can be parallel-movable along an orthogonal coordinate parallel with the stage surface.
According to another aspect, the invention is directed to an emission analysis method including: obtaining a scanning electron microscope (SEM) image of a test target; obtaining a failed image, where an emission point detected at the test target is marked, by means of an emission detector; and overlapping the failed image with the SEM image to mark the emission point on the SEM image.
In one embodiment, an SEM column and an emission detector column are installed to be inclined in front of a stage on which the test target is placed. An angle of the stage is controlled to make an axis of the SEM column perpendicular to a stage surface to obtain the SEM image and is controlled to make an axis of the emission detector column perpendicular to the stage surface to detect the emission point.
In one embodiment, the method further comprises: adjusting a magnification of the failed image to be equivalent to that of the SEM image for the test target. The failed image and the SEM image can overlap each other to mark a failure point on the SEM image. The method may further comprise: filtering an emission point of a failed image enlarged with a higher magnification than a failed image obtained at the emission detector to increase a position accuracy of an emission point. Luminance of the enlarged emission point can be filtered to be eliminated.
In one embodiment, the method further comprises etching the emission point of the test target using focused ion beam (FIB) to analyze a physical structure of a failure. In one embodiment, the FIB column, the SEM column, and the emission detector column are installed to be inclined in front of the stage on which the test target is placed. An angle of the stage can be controlled to make an axis of the SEM column perpendicular to a stage surface to obtain an SEM image and is controlled to make an axis of the emission detector column perpendicular to the stage surface to detect an emission point. The angle of the stage can be controlled to make the axis of the FIB column perpendicular to the stage surface to etch the test target.
The foregoing and other features and advantages of the invention will be apparent from the more particular description of preferred aspects of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
The emission detector column 118 includes an objective lens unit including a plurality of objective lenses 116 having different magnifications. The stage 110 is configured to be rotatable and includes a rotation axis A3 that is parallel with a stage surface and a rotation axis A4 that is perpendicular to the stage surface. Also, the stage 110 is configured to be parallel-movable along orthogonal coordinates D1 and D2 of the stage surface.
The surface of the stage 110 and the axis A1 of the SEM column 114 may be perpendicularly disposed at a step of obtaining a scanning electron microscope (SEM) image. The stage 110 rotated about the axis A3 at a predetermined angle is identified as stage 110′. The surface of the stage 110′ may be disposed to be perpendicular to the axis A2 of the emission detector column 118 during the emission detection. When an SEM image is obtained and an emission is detected, the stage 110 may be parallel-translated in directions D1 and D2 parallel with the stage surface, respectively, and may rotate on the axis A4 to change the position of the test target 112.
In the present invention, an image processor 120, an image filter 130, and a superimposor 140 are provided at the emission detector column 118. The image processor 120 enlarges or reduces an emission-detected image. The image filter 130 filters and eliminates luminance lower than emission point luminance to increase accuracy of an emission-detected point. The superimposor 140 overlaps a final failed image filtered at the image filter 130 with an image obtained at the SEM column 114 to mark an emission point on an SEM image.
The emission detector column 218 includes an objective lens unit including a plurality of objective lenses 216 having different magnifications. The stage 210 is configured to be rotatable and includes a rotation axis A3 that is parallel with a stage surface and a rotation axis A4 that is perpendicular to the stage surface. Also the stage 210 is configured to be parallel-movable along orthogonal coordinates D1 and D2 of the stage surface.
The surface of the stage 210 may be disposed to be perpendicular to the axis A1 of the SEM column 214 at a step of obtaining a scanning electron microscope (SEM) image. The stage 210 rotated about the axis A3 at predetermined angles is identified as stage 210′ and 210″, respectively. The surface of the stage 210′ may be disposed to be perpendicular to the axis A2 of the emission detector column 218 during the emission detection. The surface of the stage 210″ may be disposed to be perpendicular to the axis A3 of the FIB column 222 during an FIB etching. When the SEM image is obtained, the emission is detected, and the FIB etching is conducted, the stages 210, 210′, and 210″ may be parallel-translated in directions D1, D2, and D3 parallel with the stage surfaces, respectively, and may rotate on the axis A4 to change the position of the test target 212.
In the present invention, an image processor 220, an image filter 230, and a superimposor 240 are provided at the emission detector column 218. The image processor 220 enlarges or reduces an emission-detected image. The image filter 230 filters and eliminates luminance lower than emission point luminance to increase accuracy of an emission-detected point. The superimposor 240 overlaps a final failed image filtered at the image filter 230 with an image obtained at the SEM column 214 to mark an emission point on an SEM image. Further, a focused ion beam (FIB) controller 250 is provided at the emission detector column 218. The FIB controller 250 detects an emission point marked on the SEM image to control an FIB etching.
Referring to
Referring to
Since a scanning electron microscope (SEM) may have a higher magnification than an emission detector, the SEM image 320 may have a higher magnification than the failed image 330. The present invention may further include a step of processing the failed image 330 to be enlarged (S13). Due to the enlargement of the failed image 330, the emission point is also enlarged to lower its accuracy. For this reason, the present invention includes a step of filtering the enlarged emission point to increase its accuracy (S14). Since luminance of an emission point varies with the intensity of emitted photons or heat, a portion having a lower intensity than a predetermined intensity (hereinafter referred to as “predetermined luminance”) is filtered and eliminated at an enlarged emission point to increase an accuracy of the emission point. The failed image 330 and the SEM image 320 overlap each other to mark an emission point on the SEM image (S15), as illustrated in
Referring to
With reference to the overlapped image of the SEM image and the failed image, an emission point of the test target is detected (S24). The emission point of the test target is etched using focused ion beam (FIB) to analyze a physical structure of a failure 342 in an FIB image 340 (S25), as illustrated in
In the present invention, after an emission point is etched using FIB, an image of the etched portion is obtained by means of a scanning electron microscope (SEM) installed at an emission analysis system according to the present invention to analyze a physical structure. Further, the stage rotates at a predetermined angle to analyze a structure of an FIB-etched section.
According to the present invention, it is possible to perform high-magnification emission analysis and accurately detect an emission point at a test target. A physical structure of the emission point is analyzed at the test target to reduce time required for analyzing a failure.
Although the present invention has been described in connection with the embodiment of the present invention illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitutions, modifications and changes may be made without departing from the scope and spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0131080 | Dec 2006 | KR | national |
