Electric charged particle beam microscopy, electric charged particle beam microscope, critical dimension measurement and critical dimension measurement system

• US 7,372,051 B2
• Filed: 07/27/2005
• Issued: 05/13/2008
• Est. Priority Date: 08/23/2004
• Status: Active Grant

• Current Assignee: Hitachi High-Tech Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Inventors: Tsuneta, Ruriko, Koguchi, Masanari, Inada, Hiromi, Hashimoto, Takahito
• Primary Examiner(s): Vanore; David A.
• Assistant Examiner(s): SOUW, BERNARD E
• Application Number:
  US11/189,897
• Publication Number:
  US 20060038125A1
• Time in Patent Office: 1,021 Days
• Field of Search: 250/306, 250/492.3
• US Class Current: 250/492.3
• CPC Class Codes: G01N 23/22 by measuring secondary emission from the material
• CPC Class Codes: H01J 2237/223 Fourier techniques
• CPC Class Codes: H01J 2237/24592 Inspection and quality control of devices
• CPC Class Codes: H01J 2237/2823 Resolution
• CPC Class Codes: H01J 2237/2826 Calibration
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube
• CPC Class Codes: H01J 37/263 Contrast, resolution or power of penetration
• 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

Abstract

Magnification errors are reduced in the required range of magnification in electric charged particle beam application apparatuses and critical dimension measurement instruments. To achieve this, a first image, whose magnification for the specimen is actually measured, is recorded, a second image, whose magnification for the specimen is unknown, is recorded, and the magnification of the second image for the first image is analyzed by using image analysis. Thereby, the magnification of the second image for the specimen is actually measured. Then, magnification is actually measured in the whole range of magnification by repeating the magnification analysis described above by taking the second image as the first image. Actually measuring the magnification of images for the specimen in the whole range of magnification and calibrating the same permits a reduction of magnification errors by a digit.

Claims

1. An electric charged particle beam microscopy wherein a specimen is irradiated with a charged particle beam, and secondary charged particles generated by the specimen are detected to thereby obtain an image of the specimen, the microscopy comprising:

a step of taking a first image with a known magnification relative to the specimen by irradiating the specimen with the charged particle beams under a first control condition;

a step of taking a second image having a common field of view with the first image by irradiating the specimen with the charged particle beam under a second control condition;

a step of image processing for analyzing a magnification of the second image relative to the first image from the common field of view;

a step of calculating the magnification of the second image relative to the specimen from the magnification of the first image relative to the specimen, and the magnification of the second image relative to the first image; and

a step of recording the magnification of the second image relative to the specimen along with the second control condition.

2. The electric charged particle beam microscopy according to claim 1, further comprising:

when the magnification of the second image to the first image cannot be analyzed in the step of image processing,

a step of taking a third image having a common field of view with the first image by irradiating a specimen with electric charged particle beam under a third control condition requiring that the magnification is between magnification of the first image and magnification of the second image;

a step of image processing for analyzing the magnification of the third image relative to first image;

a step of image processing for analyzing the magnification of the second image relative to the third image; and

a step of calculating the magnification of the second image relative to the specimen from the magnification of the previous first image to the specimen, the magnification of the third image relative to the first image, and the magnification of the second image relative to the third image.

3. The electric charged particle beam microscopy according to claim 2, wherein the image processing step includes a step of calculating the Fourier transform image of an image and a step of calculating the coordinate transformed image of the Fourier transformed image, the coordinate transformed image serving as the basis of calculating magnification.

4. The electric charged particle beam microscopy according to claim 3 wherein the first control condition is a condition that enables to measure the interval between crystal lattice surfaces from the image acquired and the magnification for specimen is a magnification actually measured from the interval between lattice surfaces.

5. An electric charged particle beam application device comprising:

an electric charged particle source for generating a first electric charged particle beam;

a first electromagnetic field generator that leads the first electric charged particle beam to a specimen;

a specimen stage for setting a position of a specimen with respect to the first electric charged particle beam;

a detector for detecting secondary charged particles;

a second electromagnetic field generator that leads the secondary charged particles radiating from the specimen to the detector;

a unit for image formation for forming an image of specimen structure based on the detector output; and

a controller for setting image magnification by using the electromagnetic field generator;

wherein

the controller has a unit for magnification calibration, and

the unit for magnification calibration records a first image with a known magnification relative to the specimen by irradiating the specimen with an electric charged particle beam under a first control condition, records a second image having a common field of view with the first image by irradiating the specimen with the electric charged particle beam under a second control condition, calculates a magnification of the second image relative to the first image recorded, calculates a magnification of the second image relative to the specimen from the magnification of the first image relative to the specimen and the magnification of the second image relative to the first image, and records the magnification of the second image relative to the specimen together with the second control condition.

6. The electric charged particle beam application device according to claim 5, wherein the controller sets magnification by using a deflector that constitutes the first electromagnetic field generator.

7. The electric charged particle beam application device according to claim 5, wherein the controller sets a magnification by using lens that constitute the electromagnetic field generator.

8. A critical dimension measurement method for measuring the critical dimensions of a specimen to be measured by irradiating the specimen to be measured with an electric charged particle beams, detecting electrically charged particles secondarily generated from the specimen caused by the irradiation, and inputting the image data acquired into a computer, wherein the method comprises:

a step of inputting first image data including at least a standard specimen for magnification calibration into the computer;

a step of calculating a magnification of the first image relative to the specimen by comparing an actual length of the standard specimen and a length on the first image;

a step of inputting second image data including at least a specimen to be measured for critical dimension measurement into the computer;

a step of calculating a magnification of the second image relative to the specimen by analyzing the magnification of the second image relative to the first image; and

a step of converting a length of the specimen to be measured for critical dimension measurement on the second image into an actual length.

9. A critical dimension measurement system comprising:

a specimen stage for putting a specimen to be measured and a standard specimen for calibration;

an irradiation optical system for irradiating the specimen to be measured for critical dimension measurement or the standard specimen with an electric charged particle beam;

a detector for detecting electric charged particles generated secondarily from the specimen to be measured for critical dimension measurement or the standard specimen as a result of irradiation by the electric charged particle beam;

a unit for acquiring image signals from the detector;

a magnification controller for setting a magnification of an image by an adjustment of an electron optical system;

a user interface for inputting a magnification of an image to be taken; and

a critical dimension measurement unit for measuring a length of a specimen from the image signal,

wherein

the magnification controller sets the electron optical system at the first and second magnification conditions in response to the image magnification inputted by the user interface, and

wherein

the critical dimension measurement unit

calculates a magnification of the first image relative to the specimen by comparing an actual length of the standard specimen and a length on a first image by using the first image of the standard specimen taken under the first magnification condition,

analyzes the magnification of a second image taken under the second magnification condition relative to the first image to thereby calculate a magnification of the second image relative to the specimen, and

uses the magnification information to estimate a length of the specimen to be measured for critical dimension measurement.

10. A critical dimension measurement system comprising:

a unit for image signal formation for acquiring image signals for a specimen to be measured for critical dimension measurement by irradiating the specimen with an electric charged particle beam from an electric charged particle beam source, and detecting electric charged particles generated secondarily from the specimen; and

a unit for data processing for inputting image signals formed at the unit for image signal formation, processing image, and measuring a critical dimension of the specimen based on a result of the image processing; and

wherein

the unit for data processing

calculates a magnification of a first image relative to a specimen by comparing an actual length of a standard specimen and a length in the first image based on the first image of the standard specimen taken with a magnification of under a first irradiation condition,

analyzes a magnification of a second image taken under a second irradiation condition relative to the first image to thereby calculate a magnification of the second image relative to the specimen; and

estimates a length of the specimen to be measured by using the magnification information.