US 6,114,681 A · Automatic focus control method and automatic focus control system having in focus and out of focus states detection

Abstract

An automatic focus control system comprises an electron beam lens column 1, a device control apparatus 2, and a host computer 3. In the host computer 3, an image processing section 32 and so on are provided. In case of measuring the critical dimension of the patterns in the wafer, after performing the global alignment adjustment, the power spectrum is calculated based on the SEM image of each measuring point in the wafer. After that, in case that the high-frequency component is included more than a prescribed standard value, without performing the automatic focus adjustment, the process for the pattern recognition is performed, and in case that the high-frequency component is included less than the standard value, the process for pattern recognition is performed just before the automatic focus adjustment. Therefore, it is possible to decrease the frequency (times) which performs the process for automatic focus adjustment; as a result, the throughput for measuring is improved.

Claims12

Dependent claims

An automatic focus control method capable of selecting whether or not to perform a process for an automatic focus adjustment for a measuring object set to a microscope;

wherein:
whether or not the measuring object set to said microscope is in focus is detected;
in case of having determined to be in focus, a process for pattern recognition of said measuring object without performing automatic focus adjustment of the measuring object is performed;
in case of having determined to be out of focus, after the automatic focus adjustment has been performed at that non-focal point, the process for pattern recognition is performed.

1 more element

An automatic focus control system including an automatic focus adjustment means for performing automatic focus adjustment for a measuring object set to a microscope, and a pattern recognition means for performing a process for pattern recognition of said measuring object, comprising:

a frequency component analyzing means for calculating a power spectrum based on the result performed one-critical dimensional or two-critical dimensional Fourier transform process for image of said measuring object taken in said microscope;
an automatic focus control means for if the ratio of frequency component equal to or higher than a prescribed frequency in the power spectrum is equal to or larger than a standard value at each of a plurality of points of said measuring object, performing the process for pattern recognition by said pattern recognition means without performing the automatic focus adjustment by said automatic focus adjustment means, and if the ratio is smaller than said standard value, performing the process for pattern recognition by said pattern recognition means after having performed the process for automatic focus adjustment.

Dependencies are inferred from the claim text.

Automatic focus control method and automatic focus control system having in focus and out of focus states detection

Life of this patent

Automatic focus control method and automatic focus control system having in focus and out of focus states detection

Life of this patent

Abstract

Claims12