Scanning electron microscope and system for inspecting semiconductor device

• US 20060108525A1
• Filed: 11/08/2005
• Published: 05/25/2006
• Est. Priority Date: 11/10/2004
• Status: Active Grant

• Current Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Inventors: Honda, Toshifumi, Nakagaki, Ryo
• Granted Patent: US 7,834,317 B2
• Time in Patent Office: Days
• US Class Current: 250/310
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: H01J 2237/24592 Inspection and quality control of devices
• CPC Class Codes: H01J 2237/2817 Pattern inspection
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube
• CPC Class Codes: H01J 37/265 Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence

Abstract

A scanning electron microscope has an electron source for illuminating a primary electron beam on a specimen wafer, an accelerating electrode, a condenser lens, a deflector, an objective lens, a detector for acquiring a digital image by sampling a signal of emissive electrons generated from the specimen wafer, a digitizing means, an image memory for storing, displaying or processing the acquired digital image, an input/output unit, an image creation unit and an image processor. The scanning electron microscope is provided with a sampling unit for sampling the emissive electron signal at intervals each smaller than the pixel size of the digital image to be stored, displayed or processed and an image creation process means for enlarging the pixel size on the basis of the sampled emissive electron signal to create a digital image.

Claims

1. A scanning electron microscope comprising:

electron beam illumination means for irradiating a focused electron beam on a desired region of a specimen while scanning the beam thereon;

digital image acquisition means for detecting secondary charged particles generated from the desired region of said specimen under scanning irradiation of the electron beam by said electron beam illumination means and digitizing a detected signal at a predetermined sampling clock to obtain a digital image of the surface of said specimen;

image processing means for processing the digital image acquired by said digital image acquisition means; and

control means for controlling said electron beam illumination means, said digital image acquisition means and said image processing means,

wherein said control means controls said electron beam illumination means and/or said digital image acquisition means to scan the electron beam plural times on said specimen so as to obtain image signals of a plurality of frames for which timing of said sampling clock is shifted and applies to the plural frame image signals for which timing of said sampling clock is shifted an image process including a frame addition process, thereby obtaining a digital image, which is reduced in noise component, of the surface of said specimen.

2. A scanning electron microscope according to claim 1, wherein in obtaining the plural frame image signals for which timing of said sampling clock is shifted, the timing of said sampling clock is shifted by a smaller interval than that of said sampling clock.

3. A scanning electron microscope according to claim 1, wherein said image process inclusive of said frame addition process includes a densification process for synthesizing said plurality of frame image signals into a densified image having a large number of pixels, a picture quality improvement process for restoring a degraded signal and a process for thinning out pixels of an image applied with an image quality improvement process.

4. A scanning electron microscope according to claim 1, wherein said scanning electron microscope is any one of a SEM for measuring dimensions of a pattern formed on the specimen, a SEM for detecting defects of a pattern formed on the specimen and a SEM for reviewing defects of a pattern formed on the specimen.

5. A scanning electron microscope comprising:

electron beam illumination means for irradiating a focused electron beam on a desired region of a specimen while scanning the electron beam thereon;

digital image acquisition means for detecting secondary charged particles generated from the desired region under scanning irradiation of the electron beam by said electron beam illumination means and digitizing a detected signal to obtain a digital image of the surface of said specimen;

image processing means for processing the digital image acquired by said digital image acquisition means; and

control means for controlling said electron beam illumination means, said digital image acquisition means and said image processing means,

wherein said control means controls said electron beam illumination means and/or said digital image acquisition means to scan the electron beam plural times on said specimen so that image signals of a plurality of frames may be obtained for which a photographing region on said specimen is displaced by a distance corresponding to one pixel or less of said digital image signal and controls said image processing means to apply an image process inclusive of a frame addition process to the plural frame image signals subject to displacement by the distance corresponding to the one pixel so that a digital image, which is reduced in noise component, of the surface of said specimen may be obtained.

6. A scanning electron microscope according to claim 5, wherein said image process inclusive of said frame addition process includes a densification process for synthesizing said plurality of frame image signals into a densified image having a large number of pixels, an image quality improvement process for restoring a degraded signal and a process for thinning out pixels of an image applied with the image quality improvement process.

7. A scanning electron microscope according to claim 5, wherein said scanning electron microscope is any one of a SEM for measuring dimensions of a pattern formed on the specimen, a SEM for detecting defects of a pattern formed on the specimen and a SEM for reviewing defects of a pattern formed on the specimen.

8. A method of acquiring an electron beam image of a specimen by using a scanning electron microscope, comprising the steps of:

irradiating a focused electron beam on a desired region of a specimen while scanning the beam thereon;

detecting secondary charged particles generated from the desired region of said specimen under scanning irradiation of the focused electron beam and digitizing a detected signal at a predetermined sampling clock to obtain a digital image of the surface of said specimen; and

processing the obtained digital image,

wherein in the step of obtaining the digital image of the specimen surface, image signals of a plurality of frames are obtained by scanning the electron beam plural times on said specimen and shifting timing of said sampling clock and in the step of processing the digital image, an image process inclusive of a frame addition process for adding the plural frame image signals for which timing of said sampling clock is shifted is conducted, thereby obtaining a digital image, which is reduced in noise component, of the surface of said specimen.

9. A specimen electron beam image acquisition method using scanning electron microscope according to claim 8, wherein in obtaining the plural frame image signals for which timing of said sampling clock is shifted, the timing of the sampling clock is shifted by a smaller interval than that of said sampling clock.

10. A specimen electron beam image acquisition method using scanning electron microscope according to claim 8, wherein said image process inclusive of said frame addition process includes a densification process for synthesizing said plurality of frame image signals into a densified image having a large number of pixels, an image quality improvement process for restoring a degraded signal and a process for thinning out pixels of an image applied with the image quality improvement process.

11. A specimen electron beam image acquisition method using scanning electron microscope according to claim 8, wherein said scanning electron microscope is any one of a SEM for measuring dimensions of a pattern formed on the specimen, a SEM for detecting defects of a pattern formed on the specimen and a SEM for reviewing defects of a pattern formed on the specimen.

12. A method of acquiring an electron beam image of a specimen by using a scanning electron microscope, comprising the steps of:

irradiating a focused electron beam on a desired region of a specimen while scanning the beam thereon;

detecting secondary charged particles generated from the desired region of said specimen under scanning irradiation of the focused electron beam;

acquiring a digital image of the surface of said specimen by digitizing the signal obtained through detection; and

processing the obtained digital image,

wherein in the step of obtaining the digital image of specimen surface, the electron beam is scanned on said specimen plural times to obtain image signals of a plurality of frames for which a photographing region on said specimen is displaced by a distance corresponding to one pixel or less of said digital image signal and in the step of processing the obtained digital image, an image process inclusive of a process for adding the obtained plural frame image signals is conducted to obtain a digital image, which is reduced in noise component, of the surface of said specimen.

13. A specimen electron beam image acquisition method using scanning electron microscope according to claim 12, wherein said image process inclusive of the process for adding the frame image signals includes a densification process for synthesizing said plurality of frame image signals into a densified image having a large number of pixels, an image quality improvement process for restoring a degraded signal and a process for thinning out pixels of an image applied with the image improvement process.

14. A specimen electron beam image acquisition method using scanning electron microscope according to claim 12, wherein said scanning electron microscope is any one of a SEM for measuring dimensions of a pattern formed on the specimen, a SEM for detecting defects of a pattern formed on the specimen and a SEM for reviewing defects of a pattern formed on the specimen.